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research-article

Thermally Induced Mechanical Response of Metal Foam During Laser Forming

[+] Author and Article Information
Tizian Bucher

Advanced Manufacturing Laboratory, Department of Mechanical Engineering, Columbia University, New York, NY 10027
tb2430@columbia.edu

Adelaide Young

Advanced Manufacturing Laboratory, Department of Mechanical Engineering, Columbia University, New York, NY 10027
agy2107@columbia.edu

Min Zhang

ASME Member, Laser Processing Research Center, School of Mechanical and Electrical Engineering, Soochow University, Suzhou, Jiangsu 215021, China
mzhang@aliyun.com

Changjun Chen

ASME Member, Laser Processing Research Center, School of Mechanical and Electrical Engineering, Soochow University, Suzhou, Jiangsu 215021, China
chjchen2001@aliyun.com

Y. Lawrence Yao

ASME Fellow, Advanced Manufacturing Laboratory, Department of Mechanical Engineering, Columbia University, New York, NY 10027
yly1@columbia.edu

1Corresponding author.

ASME doi:10.1115/1.4038995 History: Received March 31, 2017; Revised January 04, 2018

Abstract

To date, metal foam products have rarely made it past the prototype stage. The reason is that few methods exist to manufacture metal foam into the shapes required in engineering applications. Laser forming is currently the only method with a high geometrical flexibility that is able to shape arbitrarily sized parts. However, the process is still poorly understood when used on metal foam, and many issues regarding the foam's mechanical response have not yet been addressed. In this study, the mechanical behavior of metal foam during laser forming was characterized by measuring its strain response via digital image correlation. The resulting data was used to verify whether the temperature gradient mechanism (TGM), well established in solid sheet metal forming, is valid for metal foam, as has always been assumed without experimental proof. Additionally, the behavior of metal foam at large bending angles was studied, and the impact of laser-induced imperfections on its mechanical performance was investigated. The mechanical response was numerically simulated using models with different levels of geometrical approximation. It was shown that bending is primarily caused by compression-induced shortening, achieved via cell crushing near the laser irradiated surface. Since this mechanism differs from the traditional TGM, where bending is caused by plastic compressive strains near the laser irradiated surface, a modified temperature gradient mechanism (MTGM) was proposed. The densification occurring in MTGM locally alters the material properties of the metal foam, limiting the maximum achievable bending angle, without significantly impacting its mechanical performance.

Copyright (c) 2018 by ASME
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