United States Department of Transportation
i
Finite element estimation of the residual stresses in roller-straightened rail
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2004-11-13
[PDF-370.03 KB]
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Abstract:The purpose of this paper is to develop models to accurately predict
the residual stresses due to the roller straightening of railroad rails.
Several aspects of residual stress creation in rail due to roller
straightening are addressed. The effect of the characteristics of the
loads applied by the roller-straightener on the stress profile is
examined. In addition, the analysis attempts to discern the relative
influence of bending and contact on the residual stresses. The last goal
is to determine how the heat treatment of rail alters the predicted
roller-straightening residual stress field.
The loads for the simulation are estimated from available data. To
identify the most credible values, a baseline loading case is defined
and modeled. These straightening loads are parameterized by
considering alternative loading scenarios. Residual stresses and
deformations are calculated using these loads.
To separate the effects of bending and contact on the residual stress
induced by the roller loads, each credible load case is analyzed with
two models. One is a 2-dimensional generalized plane strain (GPS)
model that accounts only for the flexural stresses. The other is a fully
3-dimensional analysis that includes roll-on-rail contact to make
estimates of the true residual stress field. Comparison of the residual
stress results from both models reveals the relative influence of local
roll-rail contact and bending on the final profile.
Comparison of the 2- and 3-dimensional residual stress results reveals
that the magnitude of the contact loads is a decisive influence on the
stress field, even in portions of the rail web located far from the
contact interface. Therefore, it is critical to obtain accurate estimates
of the straightening loads to make accurate roller straightening
residual stress estimates.
Heat treatment of the rail prior to roller straightening primarily affects
the longitudinal residual stress in the web, causing a positive shift in
the stress values.
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