Plate Residual Stress Effects on Dimensional Accuracy in Thermal Cutting

Abstract

Dimensional inaccuracies induced by thermal cutting processes have not received sufficient attention in the open literature. A series of recent research initiatives, including this one, have demonstrated that thermal cutting can contribute significantly to dimensional inaccuracies in the form of two major mechanisms:thermally induced part distortions andplate movements as the residual stresses in the original plate are relieved to achieve new equilibrium conditions during cutting. For the former, laser cutting and managing heat sink conditions are effective in minimizing the cutting-induced distortions. For the latter, considerations must be given to the residual stress conditions in the plates to be cut so that a proper cutting sequence and layout plan can be developed to mitigate the plate residual stress effects on part/plate movements during cutting. In this paper, a major research program recently completed under the auspices of the Gulf Coast Regional Maritime Technology Center will be summarized. Some of the major findings are as follows:Although steel mill processes and parameters vary significantly from mill to mill, the important residual stress features that are relevant to cutting accuracy are dominated by only a few mill process parameters.Localized short-range residual stresses are not detrimental to cutting accuracy, even if the short-range residual stress magnitude can be high. Long-range residual stress distributions that achieve equilibrium conditions at a length scale of plate width are most important for cutting sequence planning purposes.As a result, a generalized residual stress distribution (long range) has been established for cutting planning purposes, although the detailed features may vary from mill to mill.Through a detailed series of parametric analyses using advanced modeling techniques, it was found that cutting sequencing is very important in mitigating the plate residual stress effects.It is important and practical to ensure the consistency in steel conditions so that a set of cutting procedures can be developed for mitigating plate residual stress effects on cutting accuracy, rather than trying to eliminate residual stresses in mill plates.