Johnson Joseph, Kujawski Daniel
Mechanical and Aerospace Engineering, Western Michigan University, Kalamazoo, MI 49008, USA.
Materials (Basel). 2023 Oct 18;16(20):6740. doi: 10.3390/ma16206740.
This study was completed in effort to characterize the notch sensitivity of additively manufactured (AM) Inconel 718 produced by laser powder bed fusion (L-PBF). Three different root radii on V-notched test specimens and smooth specimens were evaluated under tensile conditions for specimens built in vertical and horizontal orientations. Both the total axial strain and localized notch diametral strain were measured. Finite element analysis (FEA) was completed on each specimen geometry to confirm the actual strain measurements near the notch. Test results showed the tensile strength of the notched specimens were larger than the tensile strength values of the smooth specimens. These tensile results equate to a notch-sensitivity ratio () greater than one, indicating that the L-PBF Inconel 718 material is a notch-strengthened material. It is suspected that the notch strengthening is a result of increased triaxial stress produced near the notch tip causing added material constraints, resulting in higher strength values for the notched specimens. Fractography analysis was completed on the various fracture surfaces and identified a dominate ductile failure mode within all of the specimens; however, the amount of ductility reduced with smaller notch root radii. While this study provides the initial notch responses of the L-PBF Inconel 718, further research must be completed in regard to the impact of notches on more complex loading behaviors, such as fatigue and stress-rupture conditions.
本研究旨在表征通过激光粉末床熔融（L-PBF）增材制造的Inconel 718的缺口敏感性。对V型缺口试样和光滑试样上三种不同的根部半径进行了评估，这些试样在垂直和水平方向构建，并在拉伸条件下进行测试。测量了总轴向应变和局部缺口直径应变。对每个试样几何形状进行了有限元分析（FEA），以确认缺口附近的实际应变测量值。测试结果表明，缺口试样的抗拉强度大于光滑试样的抗拉强度值。这些拉伸结果等同于缺口敏感性比率（）大于1，表明L-PBF Inconel 718材料是一种缺口强化材料。据推测，缺口强化是由于缺口尖端附近产生的三轴应力增加导致材料约束增加，从而使缺口试样的强度值更高。对各种断口表面进行了断口分析，并确定了所有试样中主要的韧性失效模式；然而，随着缺口根部半径减小，韧性降低。虽然本研究提供了L-PBF Inconel 718的初始缺口响应，但关于缺口对更复杂加载行为（如疲劳和应力断裂条件）的影响，还必须完成进一步的研究。
