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| Forming Limit of FSW Aluminum Alloy Blank Based on a New Constitutive Model |
Guannan CHU1,Yanli LIN1( ),Weining SONG2,Lin ZHANG1 |
1 School of Materials Science & Engineering, Harbin Institute of Technology at Weihai, Weihai 264209, China;
2 Weihai Northern Electric Group Company Limited, Weihai 264209, China |
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Cite this article:
Guannan CHU,Yanli LIN,Weining SONG,Lin ZHANG. Forming Limit of FSW Aluminum Alloy Blank Based on a New Constitutive Model. Acta Metall Sin, 2017, 53(1): 114-122.
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Abstract Automobile lightweight can effectively save fuel consumption and reduce CO2 emissions. Aluminum and its alloys are desirable for the automotive industry due to their excellent high-strength to weight ratio. However, due to the introduction of the welding seam, it has brought new changes to the forming process, especially to the forming limit. To establish a reasonable forming limit curve (FLC) analysis method of friction stir welding (FSW) aluminum alloy blank, a new theoretical model was proposed based on the new second order function constitutive model. The main idea is using the differences in mechanical property between the welding and heat affected zone substitution for the hypothesis of geometry groove in the classic M-K theoretical model. The new second order function constitutive model was applied to M-K theoretical model. Eventually, a new FLC theoretical model for FSW aluminum alloy blank was established. Such theoretical model also overcomes the low strain hardening exponent of aluminum alloy material, which leads to a poor regression accuracy by power-exponent function model. The forming limit test for FSW aluminum alloy blank was performed, and the real-time strain was measured by three-dimensional digital speckle strain measurement system (XJTUDIC). Finally, the results of experiments and the theoretical analysis are compared. Compared with the traditional power law, the regression result of the new second order function constitutive model on the stress-strain curve no matter in the initial yield stage or in late deformation stage has a good fitting precision. The maximum fitting error of the power law on the stress-strain curve is more than 12%, but the fitting error of the new second order function constitutive model is less than 1%. The theoretical prediction based on the new second order function constitutive model is significantly better than the theoretical predictions based on power law in predicting the forming limit of FSW aluminum alloy blank. The prediction error of the first principal strain based on the new second order function constitutive model is less than 0.01. While the maximum prediction error of the first principal strain based on the power law is 0.14.
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Received: 10 May 2016
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| Fund: Supported by National Natural Science Foundation of China (Nos.51405102 and 51475121), China Postdoctoral Science Foundation (No.2015M570286), Fundamental Research Funds for the Central Universities of China (No.HIT.NSRIF.2016093), and the Scientific Research Foundation of Harbin Institute of Technology at Weihai (No.HIT(WH)201414) |
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