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Technology

Deep Rolling and Roll Straightening Technology

03-2004

Deep Rolling Technology

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Technology

Deep Rolling • • • generates internal stresses increases the surface hardness improves surface roughness

Result: increase in fatigue strength

03-2004

Deep Rolling Technology

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Technology

Increase of Fatigue Strength of Crankshafts Material

M E A S U R E SIncrease strength

Reduction of stress

Design

Heavier webs Overlapping of pins Optimization of surface quality

Surface

Generating of compressive residual stress in the fillet radii

03-2004

Deep Rolling Technology

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Technology

Comparison between deep rolling and induction heat treating
Fatigue strength improvement An optimum deep rolling process provides higherfatigue strength than induction hardening Fatigue strength variation is 0.2 mm possible with variation on heat treated crankshafts with the disadvantage of longer grinding cycle times and risk of wheel/crankshaft collision: Longer fine feed travel distances due to higher run-out and higher variation Greater stock removal required to compensate for higher run-out and higher variation The deeprolling process has the advantage of straightening hardened crankshafts.
03-2004 Deep Rolling Technology 6

Technology

Comparison between deep rolling and induction heat treating
New-generation crankshafts with narrow counterweights Deformation of the counterweights can be avoided by optimizing rolling forces and their circumferential distribution No controllable corrections are possible usingthe induction heat treatment process. Additional process advantages of deep rolling in comparison to induction heat treatment The deep rolling process is environmentally advantageous compared to heat treatment The deep rolling process consumes less energy than heat treatment The deep rolling process emits no emissions The deep rolling process requires less floor space than heat treatment equipmentReduced grinding wheel wear – less stock removal, radii not ground
03-2004 Deep Rolling Technology 7

Technology

Comparison between deep rolling and induction heat treating
Additional process advantages (cont’d) The deep rolling process emits less noise than the heat treatment process The deep rolling process permits automatic part changeover for multiple crankshaft types on one productionline Changeover for multiple crankshaft types on one production line is not possible with induction heat treatment equipment without manual intervention Deep rolling process set-up times between crankshafts of the same family are < 10 minutes and < 30 minutes for crankshafts of a different family (bearing diameters and journal widths) Set-up times for heat treatment equipment are highHegenscheidt-MFD‘s latest deep rolling technology enables real time in-process verification of deep rolling penetration on every rolled journal.
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Technology

Stress distribution during deep rolling (FEM calculation)

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Deep Rolling Technology

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Technology

Stress distribution after deep rolling (FEM calculation)

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Deep Rolling Technology10

Technology

Tangential residual stresses in a deep rolled shaft FEM Calculation
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Technology

Pin left

Pin right

Measured (x-ray) tangential residual stresses in a deep rolled radius Source VW 2003

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Deep Rolling Technology

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Technology

Increasing deep rolling force

Distance from surface

Calculated axialresidual compressive stresses Source:Schaal 2002
Increasing load

Distance from surface (mm)

Axial residual stresses for one deep rolling force and different external load
03-2004 Deep Rolling Technology 13

Technology

Influence of Residual Stresses by Bending Load During Engine Run

Residual stresses after deep rolling

Bending stresses Summary of the stresses

Overlapping of the...
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