Measurement of Residual Stress in Automotive Components · Measurement of Residual Stress in Automotive Components John McCarthy Technical Director, MAPS Technology Ltd ... • Residual

© MAPS Technology Ltd

Measurement of

Residual Stress in

Automotive

Components

John McCarthy

Technical Director, MAPS Technology Ltd


Stress

• Stress is the metric most commonly used by engineers to judge

– how hard a material is working

– how close to failure the material is

– how long a material might last

– how severe the effects of an external agent might be on a material

– whether there may be some distortion in a material

• In automotive a knowledge of total stress can improve crash

performance, durability and manufacture

• How do we determine stress?


Some issues

• Residual stresses can affect low speed impact performance

– how can we control these?

• Residual stresses exist in fatigue samples

– how do they affect my fatigue data?

• Residual stresses in supplied steels are unknown and

uncontrolled

– how do we ensure that we have compressive stresses where we want them?

• Peening the surface of a component improves durability

– how can we be sure in production that the peening is adequate?


Case Study: Rear Suspension Arm

• Three components

– One prototype assembly

– One assembly from production at Factory 1

– One assembly from production in Factory 2

• Steel from same

supplier and factory

• Factory 1 assembly

–50% life


+50% life


MAPS system

• Patented magnetic method of stress measurement

� non-destructive, rapid

� absolute biaxial stress

� stress depth profiling

� accurate to a few MPa

• Standard MAPS instrument

� laboratory tool

� verified against laboratory methods:X-ray & neutron diffraction, synchrotron x-ray


Centre of Plate

-250

-200

-150

-100

-50

0

50

100

150

200

0 2 4 6 8 10 12

Depth / mmS

tre

ss

/M

Pa

s11 MAPS

s11 XRD

Upper plate surface Lower plate surface

Does MAPS Work?

Comparisons with other techniques

• Neutron diffraction

– weldments & surface treatments

• X-ray diffraction

– on aerospace bearing & rail heads

• Hole drilling

– weldments & rail

• Strain gauges

– Aerospace components and rail

-45

0

45

90

0 100 200 300 400 500

X / mm

Mo

st

Te

ns

ile

Ax

is /

°

Hole Drilling 'near'

Hole Drilling 'far'

MAPS

W

e

l

d


MAPS – Independent Testing

67.7Load case D

48.9Load case C

19.6Load case B

48.9Load case A

(MPa)(MPa)

MAPS

result

Applied stress

(from strain gauges)

48.1

18.9

49.8

68.2


Applications

Automotive Components



• Three components

– One prototype assembly

– One assembly from production at Factory 1

– One assembly from production in Factory 2

• Steel from same

supplier and factory


–50% life


+50% life



Prototype

Factory 1 (–50% life)

Factory 2 (+50% life)


MAPS Bearing Scanner

• Aerospace bearing inspection

• surface compressive stresses desirable to improve wear

• time available allowed X-ray diffraction measurement at 3 points on surface/bearing

• MAPS on-line measurement

• dynamic measurement at 7m/s

• entire surface inspected in less time than for 3 XRD points

• non-intrusive depth profiling


Stress mapping on bearing

raceway

Hoop stress Cross-track stress

Stress measurement by X-ray diffraction at 180°, 45° was -535 MPa

Stress measurement by X-ray diffraction at 180°, 45° was -336 MPa


MAPS Measurements on

Crossmember


Chassis Crossmember

Peened:

Stresses to 0.15mm

Peened:

Stresses to 0.5mm


Chassis Crossmember

Peened:

Stresses to 0.15mm

Unpeened:

Stresses to 0.15mm


Chassis Crossmember

Unpeened:

Stresses to 0.15mm

RHS

Unpeened:

Stresses to 0.15mm

LHS


Effect of fatigue on residual stress


Effect of fatigue on material

XM1037 2300 Hz Data

-10

-5

0

5

10

15

20

1 2 3 4 5 6 7 8 9 10

Position

Da

mag

e

unclamped

0 cycles

75k cycles

210k cycles

349k cycles

353k cycles

371k cycles

372.5k cycles

392.5k cycles

415.6k cycles

Measurement of Residual Stress in Automotive Components · Measurement of Residual Stress in Automotive Components John McCarthy Technical Director, MAPS Technology Ltd ... • Residual

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