Residual stress analysis for additive manufactured large automobile parts by using neutron and simulation 2020-01-1071
Metal additive manufacturing has high potential to produce automobile parts, due to its shape flexibility and unique material properties. On the other hand, residual stress which is generated by rapid solidification causes deformation, cracks and failure under building process. To avoid these problems, understanding of internal residual stress distribution is necessary. However, from the view point of measureable area, conventional residual stress measurement methods such as strain gages and X-ray diffractometers, is limited to only the surface layer of the parts. Therefore, neutron which has a high penetration capability was chosen as a probe to measure internal residual stress in this research. By using time of flight neutron diffraction facility VULCAN at Oak Ridge National Laboratory, residual stress for mono-cylinder head, which were made of aluminum alloy, was measured non-distractively. From the result of precise measurement, interior stress distribution was visualized. According to the result, bottom area where was just above a base plate showed higher stress gradient than top where was the farthest side from a base plate. This trend came from restriction of a base plate. Comparing actual stresses to simulation predictions, the stress distributions along to building direction showed completely opposite tendency. For instance, simulated stress for building direction suggested tensile, even though measured stress was compression. As opposed to building direction, measured and predicted stress for inter layer directions showed similar trend. These results might suggest lack of some simulation parameters especially related to the building direction and/or incompleteness of its theory. These results could provide valuable insights not only for improving additive manufacturing process itself but also simulation technique.
Tomohiro Ikeda, Satoshi Hirose, Hisao Uozumi, Ke An, Yan Chen, Alan Seid, Tatsuya Okayama, TAKASHI KATSURAI
Honda R&D Co., Ltd., Oak Ridge National Laboratory, Honda R & D Americas Inc