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Variation simulation model for pre-stress effect on welding distortion in multi-stage assemblies
Choi, Wooyoung,Chung, Hyun Elsevier 2018 Thin-Walled Structures Vol.127 No.-
<P><B>Abstract</B></P> <P>In the shipbuilding industry, steel plates are assembled and joined to construct a block, and dozens of blocks are erected to build a ship. The major joining process used to assemble the steel plates is welding. Because the welding process causes strong non-uniform heating of the parts being joined, the local heating and subsequent cooling of welded pieces induce volumetric changes, producing transient and residual stresses as well as plastic deformation. This welding distortion is the main factor causing geometrical imperfections in the steel plate assembly process. These non-nominally shaped parts need to be clamped before the following joining process, which in turn causes pre-stress in the parts being joined. The pre-stresses due to welding and clamping significantly affect the subsequent welding processes. This paper proposes a variation simulation model of compliant assemblies to analyze the propagation of geometrical variations through multiple assembly stages, including the welding distortion under the effect of the pre-stress state. This research extends the mechanical variation simulation model to include the effects of clamping stresses by expressing the pre-stress terms in the form of an additional stiffness matrix. The result helps in confirming the effect of the pre-stress state on the subsequent welding distortion in the multi-stage assembly process. The proposed model can be used to predict the propagation of assembly variation in steel plate assemblies considering the pre-stress effect and welding distortion.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A variation simulation model of compliant assemblies is proposed. </LI> <LI> The model assesses the effect of the pre-stress states on multi-stage welding processes. </LI> <LI> The welding distortion is considered under the effect of the pre-stress state. </LI> <LI> The pre-stress terms are expressed as an additional stiffness matrix. </LI> <LI> This model can predict the propagation of assembly variation in steel plate assemblies. </LI> </UL> </P>
최우영(Wooyoung Choi),정현(Hyun Chung) (사)한국CDE학회 2013 한국 CAD/CAM 학회 학술발표회 논문집 Vol.2013 No.1
Welding is the primary joining process in manufacturing marine structures. As a way to improve the dimensional quality of products in shipyard during the production process, the welding distortion and their estimation have been studied rigorously. The welding distortion accounts for major geometrical variations in the intermediate products in shipbuilding processes and greatly affects the downstream assembly processes. The residual stresses, caused by the non-nominally shaped intermediate products, affect the magnitude of welding distortions as well. In previous research, an initial variation and welding distortion of the nominal parts are described as a linear superposition by the modified method of influence coefficient. However this research neglects the effects of the welding variations and residual stress to the final assembly spring-back deviation shape and only considers the mean deviation of welding distortion. This paper suggests a compliant assembly theory which includes the welding deformation using method of influence coefficient. The proposed model is based on the sources of variation and sensitivity matrix, which effectively represent the patterns of welding distortion of non-nominal plate parts. This suggested model is validated using the experimental data of thin plate welding.