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TECHNICAL PAPERS

Investigation of Effect of Phase Transformations on Mechanical Behavior of AISI 1010 Steel in Laser Forming

[+] Author and Article Information
Yajun Fan

Department of Mechanical Engineering,  Columbia University, New York, NY 10027yf2121@columbia.edu

Zhishang Yang, Keith Egland

Technical Center,  Caterpillar, Inc., Peoria, IL

Peng Cheng, Lawrence Yao

Department of Mechanical Engineering,  Columbia University, New York, NY 10027

J. Manuf. Sci. Eng 129(1), 110-116 (Nov 07, 2005) (7 pages) doi:10.1115/1.2162911 History: Received July 01, 2004; Revised November 07, 2005

In laser forming, phase transformations in the heat affected zone take place under steep cooling rates and temperature gradients, and have a significant affect on the laser forming process and final mechanical properties of products. In this work, phase transformations during laser forming of AISI 1010 steel are experimentally and numerically investigated and the transient volume fraction of each available phase is calculated by coupling the thermal history from finite element analysis with a phase transformation kinetic model. Consequently, the flow stresses of material are obtained from the constitutive relationship of the phases, and the laser forming process is modeled considering the effect of work hardening, recrystallization and phase transformation. A series of carefully controlled experiments are also conducted to validate the theoretically predicted results.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Flow chart of the coupled thermal-microstructural-mechanical modeling approach

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Figure 2

Schematic of straight-line laser bending of AISI1010 steel sheet: s0 is sheet thickness, W sheet width, L sheet length, and d laser spot diameter

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Figure 3

The heat affected zone (HAZ) after laser scan, etched in 3% nital solution: (a) 400W and 25mm∕s; (b) 800W and 50mm∕s

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Figure 4

The boundary of the HAZ at 400W and 25mm∕s. The grain refinement in the HAZ can be observed.

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Figure 5

Microstructural observations at different locations in the HAZ after laser scanning, 400W and 25mm∕s: (a) top of the HAZ; (b) middle of the HAZ, and (c) bottom of the HAZ. Etched in saturated picral solution.

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Figure 6

The typical thermal cycles at different thickness depths on the scanning path (X=20mm, Y=0mm) from FEM thermal modeling of laser forming of AISI 1010 steel

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Figure 7

The volume fraction of transformed austenite at the end of heating: (a) P=400W, V=25mm∕s; and (b) P=800W, V=50mm∕s

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Figure 8

The transformed austenite distribution at the end of heating along the thickness on the scan path (Y=0mm)

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Figure 9

The phase constitution after cooling, P=400W, V=25mm∕s: (a) martensite and (b) ferrite

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Figure 10

The measured Vickers microhardness along thickness on the scanning path (Y=0mm): test load=25g and duration time=10s. An evident hardness drop is in the bottom of the HAZ, where the volume fraction of martensite drops quickly to zero.

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Figure 12

Y-component of plastic strain along thickness on the scanning path (X=20mm and Y=0mm) from FEM mechanical modeling of laser forming of AISI 1010 steel

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Figure 11

The comparison between numerically predicted bending angles and experimentally obtained bending angles at various locations along scanning path (Y=0mm)

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