This paper presents a system for treating of the actual measured data for load histories. The approach consists of two steps: stress analysis and fatigue damage prediction. Finite element analysis is conducted for the component in question to obtain detailed stress-strain responses. A significant number of failures occurred in a brake end beam which led to economic losses and disruption of service. The cracks appeared to be fatigue cracks caused by the dynamic load produced in the loaded bogie frame. Strain gauge data were analyzed, and fatigue cycles were calculated from this data. Rainflow cycle counting was used to estimate cumulative damage of the end beam under in-service loading conditions. The fatigue life calculated with the rainflow cycle counting method, the P-S-N curve, and the modified Miner's rule agreed well with actual fatigue life within an error range of 2.7%~31%.
Residual stress occurs in almost every processing such as casting, rolling, molding, welding, and mechanical processing. A high residual stress level can significantly increase the risk of unexpected product failure from various boundary conditions. In particular, cyclic-dependent fatigue damage is much affected by the residual stress of components. Hence, accurately monitoring the residual stress will be very useful to maintain safety and to predict the repair period and the remaining life of products. X-ray diffraction is a common nondestructive technique that can be used to determine the levels of residual stress in near-surface layers of a component. Therefore, in this study, residual stress distribution in plate-type specimens of rolled steel sheets was measured by the X-ray stress measurement method. The degrees of elastic and plastic deformations were estimated by using Cr-K α and Mo-K α1 characteristic X-rays on SPHD and SPCD steels.
The present work submits an investigation about the optimum process parameters and quality improvement of mill scale recycling. With increasing concerns on environmental issues, the recycling of materials of all types has become an important issue. In this paper, an optimization method is developed to improve quality in mill scale recycling. The optimum configuration of process parameters to achieve high metallization efficiency was determined by experiments. The Taguchi method, the signal-to-noise (S/N) ratio, the analysis of variance (ANOVA) and rsponse surface optimization are employed to find the main effects and to determine their optimum process parameters. The significant process parameters were identified and their effects on mill scale recycling were studied. Finally, a confirmation experiment with the optimal levels of the process parameters was carried out to demonstrate the effectiveness of the Taguchi method.
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