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Residual Stress Measurement Techniques for Additive Manufacturing Applications



Author(s)

Adi Ben-Artzy¹, Kahraman Demir², Jack Peterson³, Stuart Maloy⁴, Grace X. Gu² and Peter Hosemann^3,4

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DOI:10.17265/2161-6213/2022.1-3.001

1. Ben-Gurion university, PO Box 653, Beer-Sheva 84105, Israel
2. Department of Mechanical Engineering, University of California Berkeley, Berkeley, CA 94720, USA
3. Department of Nuclear Engineering, University of California Berkeley, Berkeley,CA 94720, USA
4. Lawrence Berkeley National Laboratory, Material Science Division, Berkeley, CA 94720, USA

RSs (Residual stress) in engineering components can lead to dimensional instability, distortion during life cycle or in some cases catastrophic failure. RSs in AM (additive manufacturing) parts are a consequent of thermal expansion during heating, thermal contraction during solidification of each laser pass, and volume change due to phase transformations. Currently, most RS measurement techniques are destructive or semi-DT (destructive tests) based on releasing the RS by drilling or slitting the sample while X-ray or neutron diffraction techniques are considered as nondestructive techniques but require the use of powerful beams and slicing a small sample of the detected part. In this paper, a novel nondestructive RS measuring technique is presented, using fs (Femto-Second) laser trenching up to 250 μm depth. The fs-laser trenching relaxes surface stresses violating the stress balance that is measured by a bidirectional SG (strain gauge). In this work, RSs induced in low carbon steel samples using an IPG Photonics YLR500-AC-Y14 500 W YAG laser (simulating the last pass of SLM) were directly measured by proposed method. The results show the precision and accuracy of the fs-laser trenching and SG technique, that can be applied to evaluate RS in wrought and cast metals as well. This novel method still needs to be validated and be supported by a model.

AM, RS, fs laser, SG, laser.