Upload
others
View
7
Download
0
Embed Size (px)
Citation preview
© MAPS Technology Ltd
Measurement of
Residual Stress in
Automotive
Components
John McCarthy
Technical Director, MAPS Technology Ltd
© 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?
© MAPS Technology Ltd
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?
© MAPS Technology Ltd
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
• Factory 2 assembly
+50% life
© MAPS Technology Ltd
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
© MAPS Technology Ltd
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 Technology Ltd
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
© MAPS Technology Ltd
Applications
Automotive Components
© MAPS Technology Ltd
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
• Factory 2 assembly
+50% life
© MAPS Technology Ltd
Case Study: Rear Suspension Arm
Prototype
Factory 1 (–50% life)
Factory 2 (+50% life)
© MAPS Technology Ltd
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
© MAPS Technology Ltd
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 Technology Ltd
MAPS Measurements on
Crossmember
© MAPS Technology Ltd
Chassis Crossmember
Peened:
Stresses to 0.15mm
Peened:
Stresses to 0.5mm
© MAPS Technology Ltd
Chassis Crossmember
Peened:
Stresses to 0.15mm
Unpeened:
Stresses to 0.15mm
© MAPS Technology Ltd
Chassis Crossmember
Unpeened:
Stresses to 0.15mm
RHS
Unpeened:
Stresses to 0.15mm
LHS
© MAPS Technology Ltd
Effect of fatigue on residual stress
© MAPS Technology Ltd
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