PSI - Issue 28

Yuichi Otsuka et al. / Procedia Structural Integrity 28 (2020) 1018–1023 Y.Otsuka et al. / Structural Integrity Procedia 00 (2020) 000–000

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IR camera

Cyclic load

Specimen

(a) Cyclic compression test

(b) A supported hole for IR measure ment

Fig. 1. Cyclic compression test apparatus of the acetabular cup with AE and IR

loading cycles were set as 1 × 10 6 cycles. The displacement of the acetabular cup using a cantilever system. AE and IR measurement was simultaneously applied.

3. Results and Discussions

3.1. Damages in porous simulated bone by cyclic compression

Figure 2 shows the damage behavior of porous simulated bone at low stress amplitude σ a = -0.75 [MPa], R = 10. The specimen did not show any visible inelastic displacement and then no damages in both AE(Fig. 2(a)) and IR(Fig. 2(b)) were observed. On the other hand, when the su ffi ciently higher loading σ a = -1.8 [MPa] was applied, the specimen showed accumulated increase of its temperature due to internal friction by inelastic damages due to cyclic loading (Fig. 3). This behavior can also be confirmed continuous AE signals relating to fracture of trunks in the porous simulated bone. The result clearly demonstrated that IR could determine the accumulated damages in porous simulated bone. Figure 4 shows e ff ects of damages on loosening behavior of acetabular cup by cyclic loading. IR could identify accumulated damages and heating by friction at interface between porous simualted bone and acetabular cup after de lamination (Figure 4(a,b)). Both normal and rotational displacement was accumulated by cyclic loading (Fig. 4(c,d)), and the extent of those values were compatible with previous study [8] and clinical reports [4]. The result suggested that the observation hole of IR did not a ff ect at all on the displacement behavior of the acetabular cup because the sti ff ness of the lost porous simulated bone was completely compensated by a supporting acrylic resin tube, which can validate the result of (Fig. 4(c,d)). Temperature changes detected by IR, which suggests inelastic damages in porous simulated bone, could be associated with normal displacement of the acetabular cup (Fig. 4(e)). Furthermore, AE signals relating to delamination of HAp coating or interfaces between porous simulated bone with HAp coating could also be correlated with rotational displacement of the acetabular cup (Fig. 4(f)). Both results clearly demonstrated that loss in mechanical fixation could directly induce the displacement of the acetabular cup, which can eventually led to 3.2. Loosening behavior of acetabular cup by cyclic compression