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Fatigue Crack Growth in Additive Manufactured

Release date:2020-11-04

Additive Manufacturing technology of large scale and high-performance metallic integral structures is a significant milestone and a leading direction in the 3-D printing field, applying it to aircraft is a perfect way to reduce structural weight and cost. However, the difference in material microstructure between the AM alloys and conventional wrought or casting alloys sets new challenges to the damage tolerance evaluation, consequently, restricts the wide application of AM components in the primary load-bearing aircraft structures.

CAE Aircraft Strength Research Institute (ASRI) has used experimental investigations and numerical simulations to research the crack growth behavior and the corresponding mechanical parameters under the fatigue loading for samples manufactured by the Laser Metal Deposition (LMD) process. There are three key techniques in the present research, which are as follows, experimental investigation on crack path change due to material micro structure, crack tip measurements on crack tip strain field, crack closure, etc. to understand the loading effect and material factors on crack growth dominating parameters, peridynamic simulations considering the material micro structure and fatigue degradation. The key found in the present research are as follows: the LMD Ti-alloy microstructures has respective impacts on fatigue crack growth behavior, and in specific, the impacts of α laths on the crack path is particularly significant, the variations of crack-tip strain fields can be used to predict retardation effects and fatigue lifetime more accurately, the proposed peridynamic fatigue model can reflects the effects of both microstructure and loading sequence on fatigue crack growth.

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Fig1  Material-structure characteristics of additive manufacturing structure

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Fig2  Fatigue crack growth rate predictions under simple variableamplitude loading

 

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