PSI - Issue 17

Feiyang He et al. / Procedia Structural Integrity 17 (2019) 72–79 Feiyang He/ Structural Integrity Procedia 00 (2019) 000 – 000

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exhibited anisotropic behaviour with a huge impact of raster orientations. Patel and Patel (2015) analysed the impact of infill parameter on ABS fracture. Padzi et al. (2017) compared the fatigue characteristics of 3D printing ABS and moulding ABS specimens, and the results indicated that 3D printed part has a lower fatigue life, which may not be suitable for industrial applications. Therefore, some researchers focused on the performance of fibre reinforced ABS. Zhong et al. (2001) found that glass fibres significantly improved the strength of the ABS filament at the expense of reduced flexibility and handleability. Moreover, composite filament, prepared by extrusion, was found to work well with the 3D printer. However, the recent paper presents the opposite conclusion. Zai et al. (2019) compared the capacity to resist the fatigue of Aluminum and ABS beam. The paper replaced the residual cycle number and crack depth with the dimensionless residual fatigue life and fractional frequency drop due to the difference of specimen specifications. As Figure 3 showed, specimens which are manufactured by FDM are found to have more residual fatigue life at same frequency drop under cyclic loading during some stages.

Figure 4 Residual fatigue life trend of different materials (Zai et al., 2019)

5. Conclusion

With the review presented on the research about structural fatigue and fracture, many types of research focused on the impact of thermo-mechanical loads to structural damage, some of them performed the TMF test. For TMF tests, they used the experimental method to emphasise the relation between fatigue cycle number and loads. However, they did not consider the variable crack growth rate during crack propagation. It means the non-linear increase in crack length under cyclic loads is not fully studied. On the other hand, some researchers also performed the thermo-mechanical fatigue crack growth test and proposed empirical models between crack growth rate and load conditions. However, due to lack of analytical relations and mathematical models, their applications are limited. In terms of the analytical relation between thermo-mechanical load and fracture, only one study proposed that the numerical fracture analysis under temperature varies with the energetic method. However, they did not consider applying energetic analysis in crack growth. Also, compared with the complexity of thermo-mechanical loads in practice, the load's condition in TMF tests applied in the research only considered the impact of a few parameters, i.e. the phase difference between thermal and mechanical loads, the frequency of loads, the temperature difference and load ratio. Existing research still requires a systematic model to include all parameters. Therefore, for structures under complicated loading conditions, it will be a key contribution to develop a more detailed mathematical model between loads and crack propagation.