Multiaxial fatigue behavior of wrought and additive manufactured Ti-6Al-4V including surface finish effect
Multiaxial fatigue behavior of wrought and additive manufactured Ti-6Al-4V including surface finish effect
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DOI：
10.1016/j.ijfatigue.2017.03.044
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发表时间：
2017-07-01
影响因子：
6
通讯作者：
Shamsaei, Nima
中科院分区：
文献类型：
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作者：
Fatemi, Ali;Molaei, Reza;Shamsaei, Nima
增材制造（AM）技术已经能够有效地制造具有复杂几何形状的部件，并且基于激光的粉末床熔合（L-PBF）是最常用的AM制造工艺之一。在许多应用中，AM零件的载荷条件是多轴的。即使在单轴加载条件下，由于几何形状的复杂性或残余应力的相互作用，应力状态仍然可能是多轴的。因此，了解AM材料在多轴应力状态下的循环变形和疲劳行为对此类部件的预期性能至关重要。在这项研究中，使用薄壁管试样的Ti-6Al-4V合金制成的一个共同的PBF过程中，这些行为进行了研究。为了与常规材料的性能进行比较，还研究了变形Ti-6Al-4V合金。所考虑的载荷包括轴向、扭转、同相轴向扭转和90个异相轴向扭转载荷。表面粗糙度的影响也进行了研究，同时考虑建成和加工和抛光的表面条件的AM标本。AM材料的延展性被认为是显着低于锻造材料由于马氏体微观结构以及缺陷的存在。AM标本有显着较短的寿命相比，锻造标本在所有的负载条件下，无论表面光洁度。然而，机械加工改善了AM试样的疲劳性能。在所有加载条件下，AM试样的脆性断裂均发生在最大拉伸面，而锻造试样的韧性断裂均发生在剪切面。因此，疲劳试验结果的锻造材料的相关使用基于剪切的临界平面模型，而AM试样的测试数据相关的最大主应力标准的基础上。(C)2017爱思唯尔有限公司版权所有
Additive manufacturing (AM) technology has enabled efficient fabrication of parts with complex geometries and laser-based powder bed fusion (L-PBF) is one of the most commonly used AM fabrication process. In many applications, the loading condition of AM parts is multiaxial. Even under uniaxial loading conditions, due to the geometry complexity or interaction of residual stresses, the stress state may still be multiaxial. Therefore, an understanding of cyclic deformation and fatigue behaviors of AM materials under multiaxial stress states is critical to the expected performance of such parts. These behaviors were investigated in this study using thin-walled tubular specimens of Ti-6Al-4V alloy made of a common PBF process. To compare with the conventional material performance, wrought Ti-6Al-4V alloy was also investigated. The loadings considered included axial, torsion, in-phase axial-torsion, and 90 out-of phase axial-torsion loads. The surface roughness effect was also studied by considering both the as built and the machined and polished surface conditions of the AM specimens. The ductility of the AM material was found to be significantly lower than the wrought material due to the martensitic microstructure as well as the presence of defects. AM specimens had significantly shorter lives compared to the wrought specimens under all loading conditions and regardless of the surface finish. However, machining improved the fatigue performance of AM specimens. For all loading conditions brittle fracture of AM specimens was observed with cracking on maximum tensile plane, and ductile fracture of wrought specimens with shear cracking. Consequently, fatigue test results of the wrought material were correlated using a shear-based critical plane model, while the AM specimen test data were correlated based on the maximum principal stress criterion. (C) 2017 Elsevier Ltd. All rights reserved.