design of a cargo fastening device for heavy cargo...

Design of a cargo fastening device with a load indicator for heavy cargo

Konstruktion av lastspänningsanordning med lastindikator för tung last

Niklas Stenqvist

Fakultet: Fakulteten för hälsa, natur- och teknikvetenskap

Kurs: Examensarbete för civilingenjörsexamen i maskinteknik

Omfattning: 30 hp

Handledare: Anders Gåård

Examinator: Jens Bergström

2014-05-23

Serial number

Abstract

The aim of this thesis was to develop a new turnbuckle for fastening containers on cargo

ships. The design was supposed to indicate whether the turnbuckle could be re-used,

i.e. it hadn’t plastically deformed. This indication could reduce the risk of a turnbuckle

breaking during transport, since turnbuckles that have been exposed to a load above

their safe working load would indicate this.

In total 25 different concepts were developed and put through two different elimination

matrices which were evaluated against a requirement specification. The final design had

calculated stress of 630 MPa at breaking load and 472 MPa proof load, the loads are

defined by Germanischer Lloyd [16]. A concept for measurement of the deformation of

the turnbuckle was developed, however it is in need of further development and testing

before it can be implemented. A suggestion of manufacturing method, material and

surface treatment has been given, but prototype testing is required to verify the design

and ensure adequate corrosion protection.

Sammanfattning

Malet med detta examensarbete var att utveckla en ny spannare till containrar pa last-

fartyg. Den fardiga konstruktionen skulle indikera om spannaren kunde anvandas for

ytterligare en resa; d.v.s. den hade inte plastiskt deformerats. Denna typ av indikation

kan reducera risken att en spannare gar sonder under transport, eftersom spannare som

har utsatts for en last over strackgransen indikerar detta.

Totalt 25 koncept togs fram och utvarderades, genom tva olika elimineringsmatriser, mot

en kravspecifikation. Den slutgiltiga konstruktionen hade en hogsta beraknad spanning

pa 630 MPa vid ”breaking load” och 472 MPa vid ”proof load”, laster som definieras

av Germanischer Lloyd [16]. Ett koncept for matning av deformationen av spannaren

togs fram, men den kraver ytterligare utveckling och testning innan den ar redo for

anvandning. Forslag pa tillverkningsmetod, material och ytbehandling har presenterats,

men testning av en prototyp kravs for att verifiera att konstruktionen ar tillfredsstallande

och att den har adekvat korrosionsskydd.

Acknowledgements

First and foremost I want to thank my supervisor at Technogarden Engineering, Mr

Martin Niklasson, for all the help, guidance and valuable discussions during this thesis

work.

I would also like to thank Mr. Anders Gaard for his guidance on how to write the report

and the discussions around the thesis work.

Thanks to Ms. My Andersson, Mr. Alexander Jonsson, Mr. Rickard Akerfalk, Mr.

Johan Sandgren and Mr. Martin Ostberg for their valuable input during concept eval-

uation and elimination.

Thanks to Mr. Lars Jacobsson for helping me with printing printing a prototype in the

3D-printer.

Lastly I want to thank Mr. Jon Hogblad for his input and help with all the calculations

in Ansys and for the valuable discussions around the results. Without the help and

discussions this thesis work would not have been possible.

iii

Contents

Abstract i

Sammanfattning ii

Acknowledgements iii

Contents iv

List of Figures vii

List of Tables viii

Abbreviations ix

1 Introduction 1

1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.1 Technogarden Engineering Resources AB . . . . . . . . . . . . . . 1

1.1.2 Problem description . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1.3 Current equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Project specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.1 Definition of problem . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.2 Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

1.2.3 Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2 Method 5

2.1 Project planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.1 Work Breakdown Structure . . . . . . . . . . . . . . . . . . . . . . 5

2.2 Problem refinement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2.1 Requirement specification . . . . . . . . . . . . . . . . . . . . . . . 6

2.3 Concept generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.4 Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.5 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.5.1 Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.5.2 Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.5.3 Constraints and applied forces . . . . . . . . . . . . . . . . . . . . 11

iv

Contents v

3 Results 12

3.1 Problem Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.1.1 Identified sub-problems . . . . . . . . . . . . . . . . . . . . . . . . 12

3.1.2 Requirement specification . . . . . . . . . . . . . . . . . . . . . . . 13

3.2 Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.1 The body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.1.1 Concept 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.1.2 Concept 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.2.1.3 Concept 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.2.1.4 Concept 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.2.2 Concepts for rod holder . . . . . . . . . . . . . . . . . . . . . . . . 17

3.2.3 Concepts for measuring of the force . . . . . . . . . . . . . . . . . 18

3.2.4 Concepts for transferring the force to the container corner . . . . . 18

3.2.5 Combined concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.2.5.1 Elimination of combined concepts . . . . . . . . . . . . . 19

3.2.6 Additional concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.3 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.3.1 Force measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.4 Material selection and manufacturing . . . . . . . . . . . . . . . . . . . . . 23

3.5 Chosen concept and its functionality . . . . . . . . . . . . . . . . . . . . . 25

4 Discussion 28

4.1 General discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.1.1 Initial goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.1.2 Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2 Discussion about the concepts . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.1 Pros and cons of body concepts . . . . . . . . . . . . . . . . . . . . 30

4.2.1.1 Concept 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.1.2 Concept 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.1.3 Concept 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.1.4 Concept 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.2.2 Rod holders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.2.3 Force measurements . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.2.4 Transmitting the load from the turnbuckle . . . . . . . . . . . . . . 33

4.3 Elimination matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

4.4 Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.4.1 Mesh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.5 Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.6 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

4.7 Manufacturing and material selection . . . . . . . . . . . . . . . . . . . . . 36

4.8 Further development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

5 Conclusion and recommendations 38

A Project Plan 39

Contents vi

B Elimination Matrix 41

Bibliography 43

List of Figures

1.1 Schematic drawing of standardized container sizes . . . . . . . . . . . . . 2

1.2 How some of the lashing equipment is used[7]. . . . . . . . . . . . . . . . . 2

1.3 The different movements of a ship[9]. . . . . . . . . . . . . . . . . . . . . . 3

2.1 The half model used in calculations . . . . . . . . . . . . . . . . . . . . . . 9

2.2 The different bodies of the turnbuckle . . . . . . . . . . . . . . . . . . . . 10

2.3 Constraints and forces acting on the body and rod . . . . . . . . . . . . . 11

3.1 The first concept for the body . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2 The second concept for the body . . . . . . . . . . . . . . . . . . . . . . . 16

3.3 The first concept for the body . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.4 The fourth concept for the body . . . . . . . . . . . . . . . . . . . . . . . 17

3.5 Concepts for the rodholder . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.6 The sliding axis within the cylinder . . . . . . . . . . . . . . . . . . . . . . 18

3.7 Concept A, the additional concept . . . . . . . . . . . . . . . . . . . . . . 21

3.8 The mesh of the simulated turnbuckle . . . . . . . . . . . . . . . . . . . . 22

3.9 Stresses in concept A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.10 Stresses in the two different versions of concept A at breaking load . . . . 23

3.11 Deformation along the Y-axis at breaking load . . . . . . . . . . . . . . . 23

3.12 Stresses of the final design at SWL & BL . . . . . . . . . . . . . . . . . . 25

3.13 A 3D printed plastic prototype of the final design . . . . . . . . . . . . . . 26

3.14 A 3D printed plastic prototype of the final design . . . . . . . . . . . . . . 27

B.1 Example of elimination matrix based on Pahl and Beitz[15] . . . . . . . . 42

vii

List of Tables

2.1 The main tasks of the project and the estimated time taken to finish eachtask . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 The aspects of the different categories . . . . . . . . . . . . . . . . . . . . 7

2.3 Detailed concept evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.1 Requirement specification . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.2 A matrix over the different sub-solutions . . . . . . . . . . . . . . . . . . . 19

3.3 Elimination matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.4 Detailed concept evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.5 Required impact strengths . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.6 Mechanical characteristics of untreated 42CrMo4 steel.[19] . . . . . . . . 25

A.1 Work breakdown structure . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

viii

Abbreviations

TEU Twenty-foot Equivalent Unit

FFE Forty Foot Equivalent (Also known as FEU)

GL Germanischer Lloyd

SWL Safe Working Load

PL Proof Load

BL Breaking Load

ix

Chapter 1

Introduction

1.1 Background

1.1.1 Technogarden Engineering Resources AB

Technogarden Engineering Resources AB is a technical consultant company and the

work in this thesis was carried out in their office in Karlstad, Sweden. They are a

part of the Norconsult AS group, which has their main office in Norway. Technogarden

Engineering Resources AB was founded in 2003 and specializes in technical advising,

developing organisations and recruiting.

1.1.2 Problem description

In 2012 about 600 million twenty-foot equivalent unit (TEU1) of goods were transported

on ships [1]. A schematic figure of these containers can be seen in figure 1.1. The average

value of a forty-foot equivalent (FFE2)container , which is the same as two TEU, was

USD 2.678 according to Maersk Line [2]. The new tripple-E class ships of Maersk Line

are capable of carrying 18340 TEU, giving a full shipment a value of about 49 million

USD [3].

The containers are loaded in port and stacked onto each other, sometimes as high as

1A twenty-foot equivalent unit is 20’ x 8’ x 8’6” (Length x width x height) according to ISO 668:2013.2A forty-foot equivalent is 40’ x 8’ x 8’6” (Length x width x height) according to ISO 668:2013.

1

Chapter 1. Introduction and specification of problem 2

Figure 1.1: Schematic drawing of standardized container sizes

Figure 1.2: How some of the lashing equipment is used[7].

10 tiers and over 20 containers in width. To secure the containers onto the ship sev-

eral different types of lashing equipment is used, a schematic view of how some of the

equipment is used can be seen in figure 1.2.

According to a small survey conducted by the World Shipping Council among their

members, between 350 and 675 containers on average are lost to the sea each year[4].

These accidents happens without the one in charge, the captain, getting a warning that

they’re about to happen. Loss of tension in, failure of or too high compressional loads

can lead to lost cargo or injuries to the working staff [5], [6].


Figure 1.3: The different movements of a ship[9].

However, even though safety precautions are taken and the cargo is secured by profes-

sionals, the wind force in combination with the ship movements (defined in figure 1.3)

can overstress the lashings and lead to failure. In bad conditions a phenomenon called

parametric rolling can occur, producing large roll amplitudes [8]. Parametric rolling is

a phenomenon were the ship experience large rolling amplitudes, inducing high stresses

on both the hull of the ship as well as the equipment securing the containers on deck

[10]-[13]. While the ship is moving with either pure head or following seas or at a small

angle (<5 degrees), with a low encounter frequency of waves, the buoyancy forces will

further develop the rolling instead of dampening it [14]. In some cases the roll angles

have been as high as 40 degrees combined with wind speeds of up to 30 m/s, with loss

of containers as a consequence [8].

1.1.3 Current equipment

The currently used equipment, which the new design should be compatible with, consist

of twist-locks placed in the corner of the containers and lashing rods/bars that are

fastened next to the twist-locks. The turnbuckle in this thesis should be compatible

with the lashing bars used today and with the threaded corer fitting that connects to

the opposite corner of the lashing bar.


1.2 Project specification

While securing heavy cargo on for instance a ship, a truck or on trains there is a risk

that the fastening device might break or lose tension. This can result in loss of cargo,

damage to property or, in a worst case scenario, injury to people. There are currently

no cargo-fastening devices that indicate if the tension is above the appropriate level or

if the tension is lost completely.

1.2.1 Definition of problem

Secure heavy cargo with adequate force and maintain it until it’s time for unloading.

While the cargo is secured, the force should be observable at all times to make sure it

is adequate.

1.2.2 Purpose

To find a solution that ensures adequate tension of cargo until unloading.

1.2.3 Goal

The goal of this project is to deliver several concepts and a working design for a new

kind of fastening devices for heavy cargo. The device should be fit for trucks as well

as trains and ships. The device should also indicate when the tension is higher than

intended or when the tension is lost through a sensor.

Chapter 2

Method

2.1 Project planning

The first step of the project was to identify which work packages should be included and

which dependencies there was between them. This work breakdown structure (WBS)

can be seen in appendix A. Following this a time estimation of each task was performed

in order to fit the allotted time for this thesis, which is 30 ECTS credits or 800 hours of

work.

2.1.1 Work Breakdown Structure

The project was divided into the main tasks of a design process, as defined by Johannes-

son et. al.(2004) in their book [15]. The main tasks of the WBS can be seen in table 2.1

and each of these main tasks are divided into subtasks. Some additional main tasks were

identified, such as patent preparation/application and three different presentations, one

held for the receiver of the project, Technogarden Engineering Resources AB, and two

for the project advisor and examiner at Karlstad University. A quarter of the time of

the project was spent on writing the report and the second largest entry, Evaluation of

design, included a ’design-loop’ to ensure that the final design met the criteria listed in

the requirement specification.

5

Chapter 2 Method and theory 6

Table 2.1: The main tasks of the project and the estimated time taken to finish eachtask

Task Name Work

Start-up 36 hrsPre-study 98 hrs

Report 204 hrsConcept development 80 hrs

Patent preparations 12 hrsDesign phase 72 hrs

Half time presentations 12 hrsFinalization of design 84 hrs

Preparation for manufacturing 68 hrsEvaluation of design 104 hrs

Final presentation 30 hrs

Sum 808 hrs

2.2 Problem refinement

The initially identified (see chapter 1) problem was reviewed to achieve a more accurate

and detailed description of the problem. This was done by first expanding the problem

and generalize it to fit all kinds of lashings of goods, ranging from heavy containers on

ships to securing of small boats at a pier. It was then divided into two main categories

of interest and each of these was further divided into detailed areas. The reason for this

was to make sure that the correct problem was solved, as changes in the definition of

the problem late in the design phase will be costly compared to changes in the start

according to Johannesson et. al.(2004) [15]. This eased the task of identifying potential

stakeholders and people to interview that could help narrowing down the problem even

further.

2.2.1 Requirement specification

The identified requirements of the part were divided into Demands and Wishes. The

wishes were weighted between 1 to 5, where 5 was the most important wish and 1

was the least important. The criterias were also divided into five different categories

including Design, Operation, Function, Manufacturing and Life cycle. The different

aspects included in each category are presented in table 2.2 below.


Table 2.2: The aspects of the different categories

Category Aspects included

Design Mechanical properties, environmental conditionsOperation Customers’ use of product

Function The function of the productManufacturing Includes environmental effects and cost

Life cycle Recyclability

2.3 Concept generation

In order to ensure that the final product meets the requirements listed in the requirement

specification the concept generation process was divided into five different steps, as

suggested by Johannesson et. al.(2004) [15].

• Formulate the problem in a broader, abstract, solution-neutral form

• Conduct a function analysis, which divides the main function of the product into

sub-functions

• Seek solutions to the sub-functions

• Combine the alternatives to the sub-functions into a solution

• Sort out potential final solutions

When the sub-problems, which the sub-functions should solve, have been identified and

given several solutions all the different sub-problems are placed in a matrix. In this

matrix, the first column represents the sub-functions of the final product and the rest

of the columns are filled with different proposed solutions to each sub-function. The

next step is to combine the different solutions into a potential final solution and to sort

out the unreasonable combinations and through that reduce the potential solutions to

a smaller number.

The next step is to make use of an elimination matrix and for this thesis Pahl and Beitz

elimination matrix was chosen as initial method for sorting and evaluation of concepts

[15]. An example of this elimination matrix is shown in appendix B.1. The concepts

were then given a plus or minus sign, depending on if they were believed to fulfil the

criteria or not. A plus sign gave a value of +1 and a negative sign gave a value of -1


and all of the concepts with a total value of four or above were put through to the next

round for another, more detailed elimination matrix.

The detailed elimination matrix was evaluated with the help of a reference group and

an example of the matrix can be seen in table 2.3.

Table 2.3: Detailed concept evaluation

Concept → 1 2 3 (ref) 4 5 6

Demands ↓

Design - robust 0 0

DA

TE

0 0 0Design - ergonomic + + 0 - -

Operation 0 + + 0 +Manufacturing 0 0 0 + +

Function + + 0 - -Storing - - 0 0 0

Sum + 2 3 1 1 2

Sum 0 3 2 5 3 2

Sum - 1 1 0 2 2

Net value 1 2 0 1 -1 0

Rank 2 1 4 2 6 4

Further development No Yes No No No No

The limit for passing to the next round was set to a net value of 2 by the reference

group.

2.4 Standards

For the design of the turnbuckle standard ISO-3874 and the Germanischer Lloyd (GL)

classification has been used [16]. Both ISO-3874 and GL has explicit loads to be used

in calculations regarding the strength of the turnbuckle, however the loads from GL are

higher and therefore they’ve been used in calculations in this report.


2.5 Calculations

To ensure structural integrity of the final design, a Finite Element Analysis was carried

out in Ansys. Two parts were included in the analysis, the turnbuckle and a represen-

tational model of a lashing bar. To allow for a finer mesh, while keeping the computing

time at a low level, a symmetrical model was used. The entire model was divided along

a plane intersecting the centre axis, as can be seen in figure 2.1.

Figure 2.1: The half model used in calculations

2.5.1 Mesh

The use of a plane-symmetric method resulted in 231943 elements and 936235 nodes.

The different colors in figure 2.1 represent the sliced bodies used for meshing. Each

body has its own meshing strategy, to allow the mesh to be optimized for each part of

the body since they have different difficulties while meshing. In total there are thirteen

different bodies, which can be seen in figure 2.2. The different techniques used are:

1. Swept with 20 elements in the Z-direction, 2mm face sizing

2. Swept with 10 elements in the X-direction, 3mm face sizing

3. Body sizing of 1mm, hex dominated mesh












Figure 2.2: The different bodies of the turnbuckle

2.5.2 Contacts

Two different setups were used regarding the contacts of the parts. In the first setup all

contacts were modelled as bonded, meaning that they’re treated as a single body.

In the second setup, all those bodies which are part of the turnbuckle were modelled

as bonded. The contacts between the rod and turnbuckle, however, were modelled as

frictionless contacts, with augmented lagrange formulation and the interface treatment

was set to adjust to touch.


2.5.3 Constraints and applied forces

During the simulations the force was applied on the end surface of the rod, 3 in figure

2.3. It was scaled to half of the real value since the model is symmetrical. To ensure

that the force was only acting in the Z-direction a remote displacement was put on the

entire surface area of the rod. The remote displacement locked the rod in all directions

and all rotations except for the Z-direction. A fixed support was added to the threaded

part of the turnbuckle, 1 in figure 2.3, acting as the connection between the turnbuckle

and the container.

Figure 2.3: Constraints and forces acting on the body and rod

Chapter 3

Results

3.1 Problem Identification

During the pre-study and literature study phase of the project the problem was slightly

altered and re-redefined from the previously presented. It was then defined as:

Identification of turnbuckles which have been exposed to a load above their yield

strength.

3.1.1 Identified sub-problems

As mentioned in chapter 2, the problem was divided into smaller, manageable problems.

These were identified from evaluating the current lashing equipment and through the

study of incident reports regarding container ships. The sub-problems that were found

are presented below:

• A body designed to withstand tensional loads

• Transfer load from lashing rod to turnbuckle

• Transfer load from turnbuckle to corner fitting of container

• Measure pre-tensioning force

• Measure if the SWL (Safe working load) has been exceeded

12

Chapter 3. Results 13

These were then concretized and described with two words, a predicate and a subject,

as described by Johannesson et. al.(2004) [15]. The two last sub-problems were then

combined into one single problem, since they can make use of the same solution. The

two-word problems are listed below:

• Withstand load

• Transmit load (turnbuckle to rod)

• Transmit load (turnbuckle to container corner)

• Measure force

3.1.2 Requirement specification

The requirement specification, divided into the five categories mentioned in chapter 2,

totalled 22 criteria. The requirement specification, and the weights of the wishes, is

presented in table 3.1.


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3.2 Concepts

Following the methodology described in section 2.3 and the identified sub-problems from

section 3.1.1 several different concepts were generated for each problem. They were then

combined to create a working concept for the main problem.

3.2.1 The body

Four different concepts were created for the body of the turnbuckle, each with its own

pros and cons and they are all presented below.

3.2.1.1 Concept 1

The first concept for the body of the turnbuckle is an elliptical, egg-shaped, body de-

signed with the force measurement in mind. The idea was to be able to measure the

decreasing distance between the two sides and therefore know the elongation in the

turnbuckle. A model of this can be seen in figure 3.1 below.

Figure 3.1: The first concept for the body


3.2.1.2 Concept 2

The second concept is of a closed, rectangular shape. This simple geometry ensures

easier manufacturing compared to concept 1 and it’s easy to adjust according to each

customers’ wishes. A figure of this design is shown in figure 3.2 below.

Figure 3.2: The second concept for the body

3.2.1.3 Concept 3

Concept 3 is similar to concept 2, with the difference that it’s thinner and instead has

wider parts on the sides to ensure enough stiffness is achieved. The wider parts also

ensures that a good grip can be achieved while tensioning the turnbuckle. It’s shown in

figure 3.3.

Figure 3.3: The first concept for the body


3.2.1.4 Concept 4

The fourth and last concept of the body is a combination of the first and third concepts,

it has an elliptical shape with thin (relatively), rectangular segments connecting the two

ends of the turnbuckle. There are 3 segments connecting the both ends, as seen in figure

3.4, and it’s possible to use two of these to place the force measuring devices on.

Figure 3.4: The fourth concept for the body

3.2.2 Concepts for rod holder

In order to achieve tension between the rod and the opposing corner of the container, a

part of the turnbuckle has to hold the rod in place. Three different concepts for this part

of the turnbuckle are presented below in figure 3.5. The three concepts are somewhat

similar, but with a difference in how to connect the rod.

The first concept for the rod holder has four connecting half-circles on one side of the

turnbuckle, which ensures easy fitting of the rod to the turnbuckle. The second concept

(a) Concept A (b) Concept B (c) Concept C

Figure 3.5: Concepts for the rodholder


has two half-circles on each side of the turnbuckle and four in total. This will make

sure that the turnbuckle stays in place without the users having to hold it in place. The

third concept has every other half-circle on one side and every other on the other side.

This complicates the mounting of the rod to the turnbuckle, but when it’s mounted it

has the best support out of the three concepts.

3.2.3 Concepts for measuring of the force

Two different concepts for the measurement of the force in the turnbuckle have been

developed. One is pure mechanical and the other one is based on electronics and strain

gauges. The idea behind the mechanical concept is to get rid of the sensitive electric

equipment to make the final product more robust. The mechanical concept is based on

an axis sliding within a cylinder, which moves as the body deforms. This requires a good

knowledge of the stiffness of the design, whereas the use of strain gauges measure the

actual strain in the body. The axis will have three different color markings (see figure

3.6) to tell the user when the turnbuckle isn’t pre-tensioned enough, a part where the

pre-tensioning force is adequate and a part where it indicates that the SWL has been

exceeded. The colors chosen are according to Arbetsmiljoverkets regulations, to ensure

that they’re easy for the user to understand[18].

Figure 3.6: The sliding axis within the cylinder

3.2.4 Concepts for transferring the force to the container corner

The concept for transferring the force from the turnbuckle to the corner of the container

is based on the current equipment. It has a heel that fits into the space of the corner

and in the other end there is a threaded part that fits the turnbuckle.


3.2.5 Combined concepts

With all of the above described concepts, a matrix of possible solutions can be generate,

seen in table 3.2 below. The amount of total solutions that can be generated with these

sub-solutions are 24 and they are put into an elimination matrix, appendix B.1, for

further narrowing down of the concepts.

Table 3.2: A matrix over the different sub-solutions

Sub-problem Sub-solution #1 Sub-solution #2

Withstand load Egg-shaped RectangularTransmit load (turnbuckle to rod) All up Half up, half down

Measure force Axis-cylinder Strain gaugesTransmit load(turnbuckle to container) Threaded part

Sub-problem Sub-solution #3 Sub-solution #4

Withstand load Wide rectangle Elliptical shapeTransmit load (turnbuckle to rod) Every other up

Measure forceTransmit load(turnbuckle to container)

3.2.5.1 Elimination of combined concepts

The elimination matrix had six different criteria to evaluate which concepts that were

thought to be possible solutions to the problem. The elimination matrix, and explana-

tions of the concepts, can be seen in table 3.3 below.

Every concept has been given a two letter abbreviation and they’re listed below:

• EG - Egg-shaped body

• RE - Rectangular body

• TR - Thin rectangular body

• EL - Elliptical body

• AU - All rod-connectors under

• HU - Half of the rod-connectors under

• EO - Every other rod-connector under


• AC - Axis-cylinder measuring

• SG - Strain gauges

• TH - Threaded part with heel

Table 3.3: Elimination matrix

Version: 1.0

Concepts: Solv

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1 EG + AU + AC + TH + + + + + + +

2 EG + HU + AC + TH + + + + + + +

3 EG + EO + AC + TH + - + + + - -

4 EG + AU + SG + TH + - + + - + -

5 EG + HU + SG + TH + - + + - + -

6 EG + EO + SG + TH + - + + - - -

7 RE + AU + AC + TH + + + + + + +

8 RE + HU + AC + TH + + + + + + +

9 RE + EO + AC + TH + - + + + - -

10 RE + AU + SG + TH + - + + - + -

11 RE + HU + SG + TH + - + + - + -

12 RE + EO + SG + TH + - + + - - -

13 TR + AU + AC + TH + + + + + + +

14 TR + HU + AC + TH + + + + + + +

15 TR + EO + AC + TH + - + + + - -

16 TR + AU + SG + TH + - + + - + -

17 TR + HU + SG + TH + - + + - + -

18 TR + EO + SG + TH + - + + - - -

19 EL + AU + AC + TH + + + - + - -

20 EL + HU + AC + TH + + + - + - -

21 EL + EO + AC + TH + + + - + - -

22 EL + AU + SG + TH + - + - - - -

23 EL + HU + SG + TH + - + - - - -

24 EL + EO + SG + TH + - + - - - -

After the general selection of the initial concepts, a more detailed concept evaluation

was conducted which ended in concept 7 being chosen for further development. The

evaluation of the six concepts can be seen in table 3.4 below.


Table 3.4: Detailed concept evaluation

Concept → 1 2 7 (ref) 8 13 14

Demands ↓

Design - robust 0 0

201

4-0

4-1

5

0 0 0Design - ergonomic + + 0 - -

Operation 0 + + 0 +Manufacturing 0 0 0 + +

Function + + 0 - -Storing - - 0 0 0

Sum + 2 3 1 1 2

Sum 0 3 2 5 3 2

Sum - 1 1 0 2 2

Net value 1 2 0 1 -1 0

Rank 2 1 4 2 6 4

Further development No Yes No No No No

3.2.6 Additional concept

During the analysis of the chosen concept, another concept was developed. It was a

combination of concepts 2 and 8 which makes use of the two strengths of each concept.

From concept 2 the egg-shaped part was taken and from concept 8 the rectangular body,

with rectangular cross-sections was taken. They were combined into a single concept

where the part that connects the rod to the turnbuckle was from concept 8 and the

opposite end is from concept 2. A figure of this concept, from here on called concept A,

can be seen below, figure 3.7.

Figure 3.7: Concept A, the additional concept


3.3 Calculations

As mentioned in 2.5.1, 231943 elements and 936235 nodes were used in the calculations.

The areas with highest stresses had a higher concentration of elements, see figure 3.8a.

However in the contact area between the innermost knob and the turnbuckle some

singularities arose. These elements are shown in figure 3.8b.

(a) Mesh concentration in the high-stress area

(b) Some of the singular elements in the contactarea between the knob and the turnbuckle

Figure 3.8: The mesh of the simulated turnbuckle

During the calculations, concept 7 did not meet the requirements listed by GL [16]

without modifications. This contributed to an increased weight to the point where it

did not meet the weight requirement. However, the combined concept, concept A showed

good potential both for withstanding the required forces and measuring the deformation.

Therefore, this concept was further developed and an arc was added connecting the two

sides where the bending force was at its largest. A picture of the stresses in concept A

with focus on the bending stresses can be seen in figure 3.9.

Figure 3.9: Stresses in concept A


From figure 3.9 it can be clearly seen that the stresses in the first body are above the yield

strength of the chosen material (see chapter 3.4). To solve this problem two different

solutions were tested and analysed. The first involved an arc that was added on both

sides of the body to decrease the bending stresses, causing the problems. The results of

this solution can be seen in figure 3.10a. The second geometry had a thicker wall where

the bending stresses were at their highest. The result from the changed geometry can

be seen in figure 3.10b.

(a) Stresses of concept A with the arc

(b) Stresses of concept A with thicker wall

Figure 3.10: Stresses in the two different versions of concept A at breaking load

3.3.1 Force measurement

To measure the deformation, the axis-cylinder concept was placed where the deformation

was at its highest, see figure 3.11. The deformation of the part in the Y-direction was

simulated to 0,73mm at breaking load and 0,55mm at proof load.

Figure 3.11: Deformation along the Y-axis at breaking load

3.4 Material selection and manufacturing

The demands of the material in the turnbuckle, as described by the Germanischer Lloyd

classification [16] states that material must be made out of steel and fulfill the re-

quiremets listed below.


• The steels shall be killed, i.e. completely deoxidized, and fine grain treated

• All products shall be heat treated, that means normalised or quenched and tem-

pered.

• The steels shall fulfil the requirements for impact strength mentioned in the Stan-

dards and approved specifications respectively, at least fulfil the requirements men-

tioned in Table 3.5.

• Unalloyed steels intended for welding shall not have a higher carbon content than

0.22 % (ladle analysis)

• If the type of product requires it, additional non-destructive test can be required.

The table mentioned in the requirements (table 3.5) is regarding the impact strength

of the material at certain temperatures. Since the turnbuckle is to be used above deck,

the lower working temperature to be expected is −20 ◦C [16]. Furthermore the material

Table 3.5: Required impact strengths

Product from

Impact energy

KV 1[J]

minlongitudinal transverse

Rolled products Remin ≥ 235N/mm2 27 (19) 20 (14)

Rolled products Remin ≥ 355N/mm2 34 (24) 24 (17)

Forged steels 27 (19)Cast steels 27 (19)

should be able to withstand corrosion, as specified in the requirement specification (table

3.1). There are several different ways of ensuring corrosion resistance of the final product,

but for this project two different concepts were evaluated. The first concept was having

a corrosion resistant bulk material (e.g. stainless steel) and the second was having a

non-corrosion resistant material in the bulk and then applying a surface treatment in

order to protect the material. However, since no stainless steels are recommended in

GL’s rules for their classification of lashing devices [16], a cast steel was favoured. The

chosen alloy was EN 10083 (42CrMo4) as it is a high-strength steel with good castability.

The final design of the turnbuckle was done with casting as manufacturing method, in


mind. This was to comply with the requirement that the product should be suitable for

mass-production.

3.5 Chosen concept and its functionality

From the FEA-simulations it was concluded that concept A with the additional walls

fulfilled the requirements specified in table 3.1. The highest stress in the part when the

breaking load of 490 kN was applied was 630 MPa, which is below the ultimate yield

strength of the material, see table 3.6. The highest stresses at SWL and PL were 316

MPa and 472 MPa respectively, this can be seen in figures 3.12a and 3.12b.

Table 3.6: Mechanical characteristics of untreated 42CrMo4 steel.[19]

Tensile characteristics Hardness

Yield strength RP0.2 (MPa) Tensile strength Elongation Young’s modulus HV0.1RP0.2 (MPa) Rm (MPa) At (%) E (GPa)

978 1050 16.5 201 356

(a) Stresses at safe working load

(b) Stresses proof load

Figure 3.12: Stresses of the final design at SWL & BL

The final weight of the turnbuckle, including the axis and cylinder was 12.5 kg which is

within AMV’s recommendations for lifting by persons in unnatural positions. The final

design is shown in figures 3.13 and 3.14.


Figure 3.13: A 3D printed plastic prototype of the final design

Figure 3.14: A rendered picture of the final design with all its function

The deformation measuring concept of an axis going into a cylinder can be seen in

figure 3.14, however this was not included in the first prototype as it complicated the


manufacturing process. The idea behind this concept is explained in chapter 3.2.3, but

in short the idea is to push a colored cylinder with the axis. When the cylinder is pushed

a certain, pre-determined, length, the user will be able to see a green marking in the

small window of the bigger cylinder. If the cylinder is pushed too far, i.e. the turnbuckle

has deformed more than it’s allowed to, the window will instead show red. This allows

for easy recognition of over-strained turnbuckles which are not safe to use.

Chapter 4

Discussion

4.1 General discussion

4.1.1 Initial goal

The initial goal of the project (see chapter 1.2.3) was to design a device that would fit

trucks as well as trains and ships. However, during the project this goal was revised

to only include large cargo/container ships. This was done in order to narrow down

the problem, making it possible to finish the project within the allotted time. It also

enabled time to be taken to do a thorough pre-study and to produce a single prototype

in plastic, which wouldn’t have been possible if the device was to be compatible with all

three vehicles. It was also decided, early on, that the turnbuckle should be compatible

with the current equipment. This was to ease the introducing of this product on the

market. It was thought that if the users of the turnbuckle had to buy completely new

rods and container connections to be able to use the new turnbuckle, the market would be

reduced. Therefore, compatibility with current lashing equipment was deemed necessary

in order to make sure that there’s a market for the product when it was finished.

4.1.2 Problem

The next step was to identify the main problem with the current equipment and one of

the main problems, since there are several reasons for loss of cargo, was the identification

of faulty / over-strained equipment[6]. With the short times the ships are allowed to

28

Chapter 4. Discussion 29

spend in port, since longer turn-around times in ports means less money earned, the

equipment might not always be inspected thoroughly enough. This can lead to inappro-

priate equipment being used for another trip to save some time while in port.

When the main-problem had been identified and defined (see chapter 3.1) formulating

the sub-problems were the next step of the project. Five different sub-problems were

identified (3.1.1) and these eased the task of solving the main problem. This approach

is solely based on the procedure described by Johannesson et. al.(2004) [15], which is

thought to be a good way to avoid the problem of jumping to conclusions before iden-

tifying the main problem.

The first sub-problem was identified as A body designed to withstand tensional loads and

was written this way to emphasize that the body shouldn’t have to experience com-

pressional loads if compatible with today’s lashing equipment. If using a design of the

turnbuckle and the lashing rod that is capable of resisting compressional loads it would

be possible to relieve the turnbuckle on the other side of the container of some stress.

However, it might induce a problem with bending in the rod, since they’re quite thin

compared to their length. This would introduce several new sub-problems to take into

account while designing the turnbuckle and would at least require a change in the con-

nection between the turnbuckle and the rod.

The second sub-problem concerns the transfer of the load from the lashing rod, which

is connected to the container corner, to the turnbuckle. Three different concepts were

developed for solving this problem, where the one with two semi-circles up and one down

was favoured. This was to ease the task of connecting the rod with the turnbuckle as

having all of the semi-circles on the same side of the turnbuckle would require the user

to hold both the rod and the turnbuckle until some tensioning had been reached. The

concept where every other semi-circle is up and every other is down was not deemed

applicable to the design since it would’ve required a loose fitting between the rod and the

turnbuckle. Without this loose fitting, it would be impossible to attach the rod to the

turnbuckle. A loose fitting between the two parts would also decrease the contact area

between the rod and the turnbuckle as the semi-circles would become smaller. With the

decrease in contact area, the contact pressure would increase. Without reinforcement

of the contact areas, or a material with a relatively, even for steels, high compressional

strength, the contact pressure would lead to large deformations.


4.2 Discussion about the concepts

Early on in the thesis it was decided that focus was to be put upon developing a new

body with the ability to measure forces acting on the fastening device. The idea of con-

structing a additional part to be put upon the current equipment was discarded since it

was believed to be hard to implement. The decision to design a new body also enabled

the body to be adapted to a mechanical strain measurement, removing the eletronics

such a strain gauges etc. The urge to remove the electronics existed because there oper-

ational environment above deck on a ship crossing a sea are harsh in terms of electronics.

Since the turnbuckle only has to account for tension, considering the design of the cur-

rent lashing bars, a body consisting of long, thin rods were the first idea to come to

mind. Both concept 2 and 3 were inspired by this idea and the dimensions of them

could’ve been adapted to the required loads. However, since there’s only tensional loads

in them, the force measurement have to be along the axis of the force. This was thought

to complicate the mechanical measurement of the deformation, therefore focus was put

upon developing a body where the largest deformations would be somewhere easier to

measure. This is what originated the ideas for concept 1 and 4, a curved body where

the strain could be measured between the arms.

4.2.1 Pros and cons of body concepts

4.2.1.1 Concept 1

The strength of the first concept comes in its curved outer body and the large cross-

sectional area required to withstand the loads. The curved arms enables the use of a

mechanical strain measurer, as earlier mentioned. Its soft edges, with some additional

rounding, would also make it suitable for e.g. casting.

However, to keep the radii of the outer curves at a value where the deformation is enough

to measure, the body would have to either be wide and long or thin and short. A wide

body would be bulky for the operators to handle and it would increase the weight of

the turnbuckle. The thin and short body would introduce a problem with attaching

the rod to the turnbuckle. It would only be possible to use the first two knobs on the

rod, restricting the usable length of the rod. The reason for this that the rod and the


threaded part, connecting the turnbuckle to the container corner, would collide in the

middle while tensioning the device.

4.2.1.2 Concept 2

The second concept makes use of a thin body with long, thin rectangular rods to with-

stand the tensional loads. In figure 3.2 there’s only a single holder for the rod, but with

space available between the rod connector and the threaded end it would be possible

to add several holders to the body. The body could also be changed depending on the

customers’ choice, a long body could have several holders allowing the operator to have

more contact points or adapt the connection depending on the length of the rod.

As earlier mentioned, the use of straight rods for force measurement was considered

problematic as either drilled holes would have to be put in the middle of the area where

the highest stresses are or a device connecting to both ends would have to be used.

Drilled holes in the middle of the load bearing area might introduce a problem with

stress concentrations and be a fracture initiation point. A device connecting on the

outside of both ends would require the movement to be reversed in order to indicate

the deformation in the part. If it wasn’t reversed the whole idea of the colored cylinder

getting stuck when the turnbuckle has been overstrained, falls.

4.2.1.3 Concept 3

This body shares some of the pros with concept 2; it has long thin rods connecting both

ends but they’re wider and thinner than in concept 2. The profit of this are a better

grip for the operator while tensioning the device as the wide flat parts are easy to grip

and that the turnbuckle can be made thinner, which eases storages while it’s not in use.

However, it suffers from the same cons as concept 2 regarding the measurement of the

strain in the component.

4.2.1.4 Concept 4

Concept 4 is the most original concept, with its’ 3 curved arms connecting the two

cylinders. This concept has a obvious path of deformation, so it’s well adapted to the

force measurement.


The cons are however several and severe; it’s hard to manufacture in one piece, it’s bulky

and takes up a lot of space during storage. To manufacture it, the arms would have to

be welded to the cylinders introducing several difficulties with alignment of the threaded

part and the rod holder as well as the strength and fatigue properties of the weld.

4.2.2 Rod holders

The three concepts for the rod holder are quite similar, this is due to the requirement

that it has to be compatible with the current lashing equipment. The only difference

between them is how they’re placed, where the concept having half of the half-circles

was favoured. This was because it gives the operator stability and the ability to let go

of the rod once it’s connected to the turnbuckle. This eases the task of tensioning the

device since the operator can use both hands to turn the turnbuckle.

4.2.3 Force measurements

The idea of measuring the instantaneous force in real-time, as specified in section 1.2.1,

was revised and changed to ”Identification of turnbuckles which have been exposed to a

load above their yield strength.”. This changes the requirements of the force measuring

equipment and simplifies the problem since no real-time data has to be transmitted and

processed. The pros of having a mechanical measuring device instead of using electronics

such as strain gauges, are that they’re less sensitive to the harsh environment above deck

on a ship.

To ensure the functionality of the axis-cylinder concept, some further development and

testing is required. Since the ship will experience both roll and pitch (see figure 1.3)

the friction between the colored cylinder and the hole where it slides has to be enough

for it to not move during ship movement. Furthermore, to make sure that the colored

cylinder doesn’t return to its original position when the tension is released, two springed

barbs should be added. These will stop the colored cylinder and show a red color to

the operator, indicating that the turnbuckle should be replaced. Since the deformations

are small (0,55mm at PL and 0,73mm at BL) a magnification of this might have to

used. It can either be in form of a gear ratio, increasing the movement of the cylinder

or a magnifying glass placed above the cylinder in the housing. The gear idea will

however introduce several new problem and an entire design, with many mechanisms


would have to be developed. This will increase the manufacturing cost of the part, which

will reduce the attractiveness of the product. Instead focus should be put upon testing

a magnifying glass with the appropriate zoom. This can help make the coloring more

clear to the inspector.

4.2.4 Transmitting the load from the turnbuckle

To transmit the load from the turnbuckle to the container corner, only one concept was

brought forth. This is because the threaded end of the turnbuckle enables the user to

adapt the connection between the turnbuckle and the container corner through the use

of different existing equipment. The connection can be done through using two shorter

rods where one of the rods have a hook in the end and a jaw, with a threaded rod in the

other end, or it can be done through using a part that is designed to fit in the container

corner. This part is a currently used part and is considered to be included in the current

equipment (see chapter 1.1.3).

4.3 Elimination matrices

While putting the concepts through an elimination matrix and grading each of the con-

cepts, a level of subjectiveness is always present. This will influence the weighting of

each concept, possibly leading to a worse concept passing to the next round of elimi-

nation. By using a reference group and discussions while grading the concept, a higher

level of objectiveness was achieved.

During these discussions the problems with the use of strain gauges as force measuring

method was brought forth. The harsh environment on a ship was believed to add a lot

of complexity to the design of the electronics. This was the reason that all concepts

with strain gauges were given a negative value in terms of fulfilling all the demands and

reliability.

In the second, more detailed, elimination matrix, concept number seven was chosen as

reference and the other concepts were weighed against it. All the design were believed

to be equally robust since none of them had any sensitive electronics and were made out

of steel. The ergonomics of the concepts however differed, where concept 1 and 2 with

their egg-shaped body were believed to be more well-suited for the operator than the


rectangular body. This was because the rectangular had thinner faces for the operator

to put his hand while tightening the turnbuckle. The thin rectangular body was believed

to be the worst of the bodies. This was because the thin edges was thought to be hard

to grip and might become slippery when wet or covered with ice.

With regard to the operation criteria, the concepts having at least one semi-circle on

the opposite side of the others were favored since it was thought to ease the fastening

procedure, as mentioned in 4.2.2. This also influenced the rating of the function criteria,

where the operator is in focus. If the turnbuckle is easier to fasten, the time taken to

fasten the containers can be reduced, reducing the total time needed in port. The only

negative values that concept 2, the concept that were further developed and that the

final design is based upon, received was under the criteria storing. The egg-shaped outer

of concept 2 will require some more storing space than e.g. the thin rectangular body.

4.4 Calculations

The chosen concept, concept 2, was discarded early on in the calculations when a

new concept was developed, concept A. The new concept was thought to combine the

strengths of concepts 2 and 8, making use of the long, thin part of concept 8 and the

egg-shaped part of concept 2. In the simulations, during the first part where only

bonded contacts were used (see chapter 2.5.2), concept 2 alone required the addition of

more material than the weight requirement allowed. Therefore some weight was saved

by removing half the body and adding half of concept 8’s body. This quickly showed

potential and the decision was taken to move on to frictionless contacts. The most

problematic part of the body was in the connection between the egg and the rectangular

parts, where large bending stresses arose. Two different ideas was brought forth, an

arc and an addition to the wall thickness. Making use of an arc in the final design,

however, would increase the manufacturing complexity and it would also increase the

storing space needed for the turnbuckle. Thereforce, the thicker wall was favored and

adapted to the calculated stresses. In the final design, the weight ended up at 12,15 kg,

which was within the limits specified by AMV [17].


4.4.1 Mesh

The preferred method of meshing was slicing the part into sweepable bodies. This was

because the sweep makes use of hexagonal elements and a sweepable body will have

fewer distorted elements. However, this proved problematic with the radii close to the

semi-circles. Therefore, a hex-dominated mesh was chosen with small elements in order

to mesh the complex geometries. After the calculations were done only the contact areas

between the rod and the turnbuckle proved to be problematic and giving rise to singular

stresses. Some singularities could be seen in the contact, accounting for the high values

of the legend seen in figures 3.8b. The singularities were located at the end of a radius

on the edge of the material and this might explain why they appeared. It would be

possible to refine the mesh even further in the problematic area, but the stresses were

believed to be singular and therefore no effort was put into removing them.

4.5 Contacts

The initial approach to the contacts between the rod and the turnbuckle was to define

all contacts as bonded, i.e. behaving as a single part. This was preferred since bonded

contacts are linear thus easier to solve, reducing the computing time needed. The shorter

computing time enables more simulations to be done, giving a chance to test the setup

for errors or misbehaviour. It was during these tests that the idea of adding a remote

displacement came up, locking the rod in all degrees of freedom except for the Z-axis in

order to come closer to the real case.

When the setup was satisfactory the bonded contacts between the rod and the turnbuckle

were changed to non-linear, frictionless contacts. All other contacts between the sliced

bodies were still defined as bonded. The frictionless contacts allows motions normal

to the contact area, but does not allow tension to be transferred between the contacts.

This however, increased the computing time by about 11 hours, showing the need for

usage of linear, bonded contacts to test the setup.


4.6 Results

Even though some of the stresses were higher than the ultimate yield strength during

simulations of BL, they are believed to be singular and were excluded from the analysis.

The highest, simulated and non-singular, stresses at BL were 632 MPa, which is below

the yield strength of 978 MPa. Since it is a simulated value, the highest simulated stress

had to be lower than the yield strength in order to be certain no plastic deformation

occurs.

4.7 Manufacturing and material selection

To meet the requirement of having a final design that was suitable for mass-production,

focus was put upon adapting the design for casting. However, in order to make the

turnbuckle fully suitable for casting, further development is needed with regards to the

draft angles of the sides.

It would also be possible to use laser cutting to cut the outline of the turnbuckle and

then machine the semi-circles and the thread in a mill. The choice between laser cutting

and casting the turnbuckle have to be further examined, as the final price of the two

methods depends heavily on production volume. The machining of the part is required

whichever way of manufacturing the body that is chosen, as the semi-circles and the

thread has to be done in a machine in order for the dimensions of the part to be within

the required tolerances. The chosen material was EN 10083 (42CrMo4) since it’s suitable

for both casting and hot-dip galvanizing. Furthermore, it’s mechanical properties allows

weight to be saved since it’s a high-strength steel. The weight saving is crucial in order

to make the turnbuckle easy to handle.

The galvanization of the turnbuckle has to be tested in order to be sure that it provides

adequate protection against the salt water on the ships. This could be done through

acquiring small parts of the material and then galvanize and test them.


4.8 Further development

In order to finalize the part and prepare it for being put into production, some further

development is needed. Several of the aspects that need development have been men-

tioned earlier, but the most critical is the axis-cylinder measurement. The resolution on

the current solution is believed to be too small for it to be visible to the inspector/oper-

ator. This solution has to be tested, possibly while performing a proof-test, as defined

by the American Bureau of Shipping , of the turnbuckle.

Chapter 5

Conclusion and recommendations

The final design of the turnbuckle meet the requirements specified by GL according

to calculations, having a highest stress of 630 MPa at BL and 472 MPa at PL. A

concept for the measurement of the force has been developed, but it is in need of further

development before it can be tested. The choice of material and manufacturing method

has to be further considered, taking the market demand into account while choosing

manufacturing method. The surface treatment of the turnbuckle, hot-dip galvanizing,

has to be thoroughly tested to ensure that it will withstand the harsh environment above

deck on a ship.

38

Appendix A

Project Plan

39

Appendix A. Project plan 40

Table A.1: Work breakdown structure

WBS Task Name

1 Start-up

1.1 Specification1.2 Time schedule

2 Pre-study

2.1 Problem identification2.2 Interviews2.3 Research of existing and similar products2.4 Requirement specification

3 Report

3.1 Report structure3.2 Report

4 Concept development

4.1 Concept4.2 Acquire similar products4.3 Product analysis of similar products

5 Patent preparations

5.1 Patent application preparations5.2 Patent application

6 Design phase

6.1 3D-modelling6.2 Development towards DFA / DFM

7 Half time presentations

7.1 Concept presentation7.2 Half-time presentation preparations7.3 Half-time presentation

8 Finalization of design

8.1 Material selection8.2 Structural calculations (FEM)

9 Preparation for manufacturing

9.1 2D-modelling

10 Evaluation of design

10.1 Prototype production10.2 Testing of prototype10.3 Evaluation of results

11 Final presentation

11.4 Opposition11.1 Final presentation of project11.2 Presentation

Appendix B

Elimination Matrix

41

Appendix B. Elimination Matrix 42

Ver

sio

n:

1.0

Concept

Criteria 1

Criteria 2

Criteria 3

Criteria 4

Criteria 5

Criteria 6

Criteria 7

Criteria 8

De

cisi

on

A B C D E F G Sho

rt d

esc

rip

tio

n o

f co

nce

pts

:

A B(+

)(+

)

C(-

)(-

)

D(?

)(?

)

E F G

Elim

inat

ion

cri

teri

a:D

eci

sio

n:

Pro

cee

d w

ith

so

luti

on

Elim

inat

e s

olu

tio

n

Acq

uir

e m

ore

info

Yes

No

Mo

re in

fo n

eed

ed

Elim

inat

ion

mat

rix

Elim

inat

ion

mat

rix

for:

Tu

rnb

uck

le

Co

mm

ents

Figure B.1: Example of elimination matrix based on Pahl and Beitz[15]

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