Shamir Muhammad, Zhang Xiang, Syed Abdul Khadar, Sadler Wayne
Centre for Manufacturing and Materials, Coventry University, Coventry CV1 5FB, UK.
Materials (Basel). 2023 Jul 30;16(15):5355. doi: 10.3390/ma16155355.
This paper reports the effect of as-deposited surface conditions on the fatigue strength of an additively manufactured titanium alloy, Ti-6Al-4V (WAAM Ti64). First, the local stress concentration caused by the surface waviness was quantified using a metrology technique and computer modelling. Fatigue tests were conducted under bending loads at a cyclic load ratio of 0.1. The applicability of two predictive methods was the focus of this study. The traditional notch stress method was unable to predict the correct S-N curve trend slope, which could be attributed to the early crack initiation from the troughs on the as-built surface, with crack propagation being the dominant failure mechanism. By treating the troughs as small cracks, the fracture mechanics approach delivered good predictions at every applied stress level. Surface machining and polishing may not always be practical or required; it depends on the applications and service load levels. This research demonstrated that the fracture mechanics approach can be used for predicting the fatigue life of WAAM titanium alloys in as-built conditions and, hence, can be a tool for decision making on the level of surface machining.
本文报道了增材制造钛合金Ti-6Al-4V（WAAM Ti64）沉积态表面条件对疲劳强度的影响。首先，使用计量技术和计算机建模对由表面波纹引起的局部应力集中进行了量化。在循环载荷比为0.1的弯曲载荷下进行了疲劳试验。本研究的重点是两种预测方法的适用性。传统的缺口应力方法无法预测正确的S-N曲线趋势斜率，这可能归因于在增材制造表面的波谷处早期裂纹萌生，裂纹扩展是主要的失效机制。通过将波谷视为小裂纹，断裂力学方法在每个施加应力水平下都给出了良好的预测。表面加工和抛光可能并不总是可行或必要的；这取决于应用和服役载荷水平。本研究表明，断裂力学方法可用于预测增材制造条件下WAAM钛合金的疲劳寿命，因此可作为决定表面加工水平的工具。
