An Integrated Analysis Method of Service Life Based on the 3D Heterogeneous Material Model with Casting Defects
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JMEPEG https://doi.org/10.1007/s11665-020-04937-0
An Integrated Analysis Method of Service Life Based on the 3D Heterogeneous Material Model with Casting Defects Kai You, Lei Rao, Xue Bai, and Tianyu Miao (Submitted July 12, 2019; in revised form May 13, 2020) Based on the heterogeneous material model, an integrated analysis method was introduced to predict the service life of propeller. The morphology and distribution characteristic of non-continuous defects (porosity & inclusion) were calculated and mapped into the finite element model by 3D-mapping algorithm, and the fatigue life was predicted based on the heterogeneous material model. In this paper, the coupling analysis of casting process and fatigue prediction of marine propeller was done. The results show that porosity and mass inclusions in blade roots of propeller form serious heterogeneous characteristics in those parts, which increased the maximum stress of the propeller and decreased its theoretical fatigue life by 1/2, indicating that the effect of non-continuous defects on the service performance of casting is notable and cannot be ignored. Based on the integrated analysis method, the inference of the pouring temperature and gating system on the service life of propeller was studied further. The integrated analysis method brings the influence of the casting defects into structural analysis and fatigue analysis, which can improve the accuracy of the fatigue life prediction significantly. Keywords
3D-mapping algorithm, fatigue life, heterogeneous model, integrated analysis method, non-continuous defects
1. Introduction Casting defects are a basic issue in regard to fatigue life of castings, which has attracted much attention in recent years. As the quality of casting is closely related to casting process and production condition, and the alloy materials have complex solidification behavior and structure morphology, it is liable to bring a variety of casting defects such as shrinkage cavity, sand holes, shrinkage porosity, pore and inclusions. These casting defects can destroy the continuity and weaken the mechanical strength of the metal matrix, which are also called noncontinuous defects. Non-continuous defects are often the region of stress concentration and eventually become the origin of fatigue crack initiation (Ref 1, 2). The influence of noncontinuous defects on the fatigue life of casting has been widely discussed, and a general consensus has been obtained: the size, location and quantity of defects are closely related to their fatigue life. According to Gerard et al. (Ref 3), fatigue cracks are easier to initiate from larger holes. Wang discovered that large defects near the surface are often the initial origin of fatigue cracks, while internal defects far from the surface have little effect on their service life (Ref 4). Sigl K M et al. discovered that the mechanical strength of materials will not be weakened when the voids ratio is less than 10%, but the fatigue Kai You, Lei Rao, Xue Bai, and Tianyu Miao, College of Mechanics and materials, Hoh
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