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Strain Age ControlM.Meleddu

Amsterdam 22-06-2016

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External actions

TENSILE + BENDING STRESS(load, D/d ratio, cycles)

INCREASE OF TEMPERATURE

(load, friction, AHC, cycles)

Today we speck about these 2 main influencing parameters

Which elements are in common in all the applications?

Did you ever happen?

Basic concepts on wire fatigue

Bending moment M M

sa

s

t

Alternate Stress

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Basic concepts on wire fatigue

T T

s

sm

t

Tensile stress

But we are not satisfied: we want to stress more our wire…

Medium Stress

sa

s

t

T T

s

sm

t

T Tsm

sa

s

t

Bending moment

Tensile stress

M M

M M

Basic concepts on wire fatigue

If we combined the 2 actions

• The axial load generates sliding planes on

45°• The bending moment generates high

surface tensions inducing crystal plane

protrusion

T, M

Sliding planes

T, M

T, MT, M

Sliding planes

Basic concepts on wire fatigueWhat’s the process behind the wire break for fatigue?

Hardening effect on Ductil – Brittle transition after cyclic

alternate loads

Drawn wire Stress-Strain curve

Cumulate Energy before

failure

sm

sa

s

t

If tensile stress +

Bending stress are

applied

TENSILE +

BENDING

STRESS

High Hardening

Softening

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s

t

s

t

Hardening effect on Ductil – Brittle transition after cyclic alternate loads

High Hardening

Softening

What about the rope?

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T

D: Sheave Diameter

d: Rope diameter

sm

sa

sm medium Stress

T

sm

sa

s

t

if D decreases:

sa increases

sa =

D sheave

d rope

E

TENSILE + BENDING STRESS(load, D/d ratio, cycles)

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?

External actions

How many of you think the temperature monitoring is important?

And why?

Maybe because of the lubricant preservation?

Not exactlyWhat about the steel properties?

INCREASE OF TEMPERATURE

(load, friction, AHC, cycles)

If Temperature increases

s

e

Agt: Elongation

What if heating acts on wire?

High RP02 – Rm difference

Low RP02 – Rm difference

Equivalent RP02,Rm

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What if heating acts on wires?

1500

1600

1700

1800

1900

2000

2100

2200

0 25 50 75 100 125 150 175

RP

02

-R

m M

Pa

T° C

RP02-Rm

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What if heating acts on Strands?

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What if heating acts on Strands?

Still convinced we can extend the life time of the ropes just developing high temperature resistance lubricant?

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What’s important in all of this?

Few furthers considerations:We can develop• continuous monitoring systems (no matter is the Technology)• Diagnostic systems (MRT, LMA)• High temperature lubricant resistance

But

If we do not keep in mind what is the limit of utilization of

the raw material we can just wait until some problem to

occur before we can detect it

Redaelli Development STAY TUNEDThermal status of the rope under given

conditions

- Thermal gradient acquisition

inside/outside the rope

- Correlation between the 2 values in

transient and steady state status

- Definition of Redaelli Mathematical

model

- Devices

GrazieThank you

M.Meleddu