The Effect of Stress Intensity Factor on Fatigue Life of AM Parts Made from Polymer

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Date

2021

Authors

El Fazani, H.H.
Coil, J.D.A.
Shah, R.R.
Laliberte, J.F.

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University of Texas at Austin

Abstract

The fatigue characteristics of additively manufactured specimens was investigated. A commercial acrylonitrile-butadiene-styrene (ABS) polymer (P430) was selected to manufacture AM fatigue coupons due to its low cost and wide applications. A total of 30 fatigue coupons were built on flat and on edge using a Stratasys SST 1200es fused deposition machine. The AM samples were manufactured at different build orientations of 0°, 22.5°, 45°, 67.5°, and 90°. The objective of this experiment is to investigate the influence of stress intensity factor on fatigue life of AM polymer parts. The specimens were tested under low sinusoidal tension-tension fatigue loading. The fatigue crack behaviour was monitored using a travelling microscope method. The stress intensity factor was investigated as the cycles accumulated. The effect of stress intensity factor on fatigue life was examined. The investigation of fatigue crack growth as a function of the number of fatigue cycles was discussed. It was found the fatigue coupons manufactured at 0° build orientation have a better fatigue life compared with the other build orientations. More investigation is required for other AM parameters such as layer thickness, infill density, manufacturing process to help better understand the fatigue performance of AM part made by polymer material. The Scanning Electron Microscope (SEM) technology was used to characterize the fractured surfaces and void distribution of AM fatigue parts. The void percentage was estimated. The results showed that AM fatigue parts built on flat has a higher void percentage compared to the AM parts manufactured on edge.

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