Probabilistic finite element analysis of fatigue life of additively manufactured clasp

Abstract

The present study was aimed to develop a probabilistic finite element method (FEM) that predicts the variability in the fatigue life of additively manufactured clasp so that it can be used as a virtual test in the design phase before manufacturing. Titanium alloy (Ti-6Al-4V) clasp with integrated chucking part, which was designed for experimental fatigue test to validate the computational method, was investigated. To predict the lower bound, an initial spherical defect was assumed in the region where stress concentration was predicted. The Smith-Watson-Topper (SWT) method, Bäumel & Seeger rule, elasto-plastic FEM, and zooming FEM were used. The influence of assumed initial defect on the fatigue life was significant, and the large variability in the fatigue life was predicted. This study demonstrated that the proposed practical computational method can simulate the large variability in the fatigue life of titanium alloy clasp, which is useful in its design before manufacturing.

Comparison of the fatigue life of pure titanium and titanium alloy clasps manufactured by laser powder bed fusion and its prediction before manufacturing

“…In addition to the static properties of CPTi, we demonstrated the merit of CPTi in terms of a high-cycle fatigue life. Note that the properties of Ti64 are discussed in our previous paper on FEA [20].…”

“…Wang et al [31] discussed the support structures of partial dentures. In the next step of the present study, the same building orientation as that of a clinical clasp [20] without the cylindrical chucking part would be used by developing a geometry compensation methodology [32] for the chucking part.…”

“…FEA can predict the fatigue life before manufacturing, as shown in Figure 8. To analyze the variability, novel numerical studies have considered the initial defects in probabilistic FEA [18][19][20]38]. However, the variability in the fatigue life can be expressed by calibrating the fatigue parameters in the SWT method, in a similar manner as that performed for the averaged fatigue life in Figure 8 and Table 3.…”

“…where N f is the fatigue life, and E is the Young's modulus. The calculated maximum principal stress was used for determining σ max , and the maximum principal strain was used for estimating Δε [20]. Based on the rule of Baumel and Seeger [23], σ' f = 1.67σ u and ε' f = 0.35 were used, where σ u is the ultimate strength.…”

“…In addition to the experimental study, a numerical approach using finite element analysis (FEA) is presented to predict the fatigue life of CPTi and Ti64 clasps before manufacturing. The need for numerical studies using FEA is increasing owing to the demand for the quality assurance of AM products [18][19][20] and for the design of new medical devices [21]. In the Materials and methods section, the design of the clasp specimens is presented, followed by the fatigue test method and the numerical strategy using the elastoplastic material model, finite element model, and fatigue life prediction method.…”