sterss calculation in bolted joint

8/9/2019 Sterss Calculation in Bolted Joint

1/39

Overview of VDI 2230

An Introduction to the

Calculation Method forDetermining the Stress in aBolted oint


2/39

Im!ortant "ote

This summary of the VDI 2230 Standard isintended to provide a basic understanding ofthe method. Readers who wish to put the

standard to use are urged to refer to thecompete standard that contains ainformation! "gures! etc.


3/39

De#nitions

Covers high$dut% &olted 'oints withconstant or alternating loads

Bolted 'oints are se!ara&le 'oints&etween two or more com!onentsusing one or more &olts

oint must ful#ll its function andwithstand wor(ing load


4/39

Aim of Calculation

Determine &olt dimension allowing for)

Strength grade of the &olt

*eduction of !reload &% wor(ing load *eduction of !reload &% em&edding

Scatter of !reload during tightening

+atigue strength under an alternatingload

Com!ressive stress on clam!ed !arts


5/39

,- *ange of Validit%

Steel Bolts

M. to M3/

*oom em!erature


6/39

2- Choice of CalculationA!!roach

De!endent u!on geometr%

C%lindrical single &olted 'oint

Beam connection

Circular !late

*otation of 1anges

+langed 'oint with !lane &earing face


7/39

C%lindrical Single Boltedoint

Aial force #$

ransverse force #%

Bending moment &'


8/39

Beam 4eometr% 5- ,

Aial force #$

ransverse force #%

Moment of the !lane of the &eam &(


9/39

Beam 4eometr% 5- 2

Aial force #$

ransverse force #%

Moment of the !lane of the &eam &(


10/39

*otation of +langes

Aial force #$6!i!e force7

Bending moment &'

Internal !ressurep


11/39

+langed oint with 8laneBearing +ace 5- ,


orsional moment &T

Moment &'


12/39

+langed oint with 8laneBearing +ace 5- 2


ransverse force #%

orsional moment &T Moment &'


13/39

+langed oint with 8laneBearing +ace 5- 3


ransverse force #%

orsional moment &T Moment &'


14/39

3- Anal%sis of +orce andDeformation

O!timi9ed &% means of thorough andeact consideration of forces anddeformations including)

5lastic resilience of &olt and !arts

:oad and deformation ratio for !arts inassem&led state and o!erating state


15/39

.- Calculation Ste!s

Begins with eternal wor(ing load #'

;or(ing load and elastic

deformations ma% cause) Aial force #$

ransverse force#%

Bending Moment &'

or


16/39

Determining BoltDimensions

Once wor(ing load conditions are(nown allow for)

:oss of !reload to em&edding

Assem&l% !reload reduced &% !ro!ortionof aial &olt force

"ecessar% minimum clam! load in the

'oint 8reload scatter due to assem&l% method


17/39

Calculation Ste! *,

5stimation of &olt diameter d

5stimation of clam!ing length ratio

)*d 5stimation of mean surface !ressure

under &olt head or nut areap+

Ifp+is eceeded 'oint must &emodi#ed and )*dre$determined


18/39

Calculation Ste! *2

Determination of tightening factor$ allowing for)

Assem&l% method

State of lu&rication

Surface condition


19/39

Calculation Ste! *3

Determination of re


20/39

Calculation Ste! *.

Determination of load factor

, including)

Determination of elastic resilience of &olt S

5valuation of the !osition of loadintroduction n-)

Determination of elastic resilience ofclam!ed !arts

Calculation of re


21/39

Calculation Ste! *=

Determination of loss of !reload #(

due to em&edding

Determination of total em&edding


22/39

Calculation Ste! *>

Determination of &olt si9e and grade

+or tightening within the elastic rangeselect &olt for which initial clam!ing load is

e


23/39

Calculation Ste! *@

If changes in &olt or clam!ing lengthratio )*d are necessar% re!eat

Ste!s *. through *>


24/39

Calculation Ste! *

Chec( that maimum !ermissi&le&olt force is not eceeded


25/39

Calculation Ste! */

Determine alternating stress endurance of&olt

Allow for &ending stress in eccentric load

a!!lications O&tain a!!roimate value for !ermissi&le

stress deviation from ta&les

If not satisfactor% use &olt with larger

diameter or greater endurance limit

Consider &ending stress for eccentric loading


26/39

Calculation Ste! *,0

Chec( surface !ressure under &olthead and nut &earing area

Allow for chamfering of hole indetermining &earing area

a&les !rovide recommendations formaimum allowa&le surface !ressure

If using tightening to or &e%ond %ieldmodif% calculation


27/39

=- In1uencing +actors

Allow for factors de!ending u!on)

Material and surface design of clam!ed!arts

Sha!e of selected &olts and nuts

Assem&l% conditions


28/39

Strength of the Bolt

Stress caused &%)

orsional and aial stresses duringtightening

;or(ing load

Should not eceed %ield load


29/39

Minimum hread5ngagement

De!ends u!on)

hread form !itch tolerance and diameter

+orm of the nut 6wrenching width7

Bolt hole

Strength and ductilit% of &olt and nutmaterials

%!e of stress 6tensile torsional &ending7 +riction coecients

"um&er of tightenings


30/39

hread Shear Strength

Bolt$"ut Strength Matching

"um&er for strength grade of nut ise


31/39

Calculation of *e


32/39

Bolt ead eight

5nsures that failure will occur in freeloaded thread section or in the shan(

ighest tensile stress in thread Eighest tensile stress in &olt head


33/39

Surface 8ressure at Boltead "ut Bearing Areas

Calculation determines surface!ressure ca!a&le of causing cree!resulting in loss of !reload

Surface !ressure due to maimumload should not eceed com!ressive%ield !oint of clam!ed material


34/39

ightening +actor Al!ha A

Allowance must &e made for torsionalstress caused &% !itch and threadfriction and aial tensile stress

Scatter in friction coecients anderrors in method of controlling !reloadcreate uncertaint% in level of tensile

and torsional stress ightening factor $ re1ects amount of

re


35/39

+atigue Strength

Design modi#cations to im!roveendurance limit of 'oint

Increase !reload

*educe !itch of screw thread

*eduction of modulus of nut materialelasticit%

Increase thread engagement


36/39

+atigue Strength $Continued

Design modi#cations to im!roveendurance limit of 'oint

Change form of nut

*educe strength of nut material

Increase elastic resilience of &olt lowerelastic resilience of !arts

Shift introduction of load towardinterface


37/39

5m&edding

Caused &% 1attening of surfaceirregularities

AHects forces in 'oint

*educes elastic deformation and!reload


38/39

Self$:oosening and8revention

8reload dro!s due to)

*elaation as a result of em&edment orcree!

*otational loosening due to relativemovements &etween mating surfaces


39/39

>- Calculation 5am!les

5- , Concentric Clam!ing andConcentric :oading

5- 2 ransverse Shearing +orce

5- 3 orsional Shearing :oad

5- . 5ccentric Clam!ing and

5ccentric :oading 5- = 5ccentric Clam!ing and

:oading

sterss calculation in bolted joint

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