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RISS 인기검색어
- 검색키워드
- 저자 : Daw-Kwei Leu (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Springback prediction of the vee bending process for high-strength steel sheets
Daw-Kwei Leu,Zhi-Wei Zhuang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.3
The precise prediction of springback is a key to assessing the accuracy of part geometry in sheet bending. A simplified approach is developed by considering the thickness ratio, normal anisotropy, and the strain-hardening exponent to estimate the springback of vee bending based on elementary bending theory. Accordingly, a series of experiments is performed to verify the numerical simulation. The calculation of the springback angle agrees well with the experiment, which reflects the reliability of the proposed model. The effects of process parameters such as punch radius, material strength, and sheet thickness on the springback angle are experimentally tested to determine the dominant parameters for reducing the springback angle in the sheet bending process for high-strength steel sheets. Moreover, the effects of the thickness ratio, normal anisotropy, and the strain-hardening exponent on the springback angle in the vee bending process for high-strength steel sheets are theoretically studied. Therefore, improving understanding on and control of the springback reduction of the vee bending process in practical applications is possible.
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Daw-Kwei Leu 대한기계학회 2010 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.24 No.8
This work evaluates the friction coefficient using the model of plastic hemispherical contact against a rigid flat. The fractional profile of an ellipsoid is utilized to describe the deformed hemispherical shape, and simultaneously define the contact area ratio. Particularly, an adhesion factor is defined to assess the junction ability of asperity adhesion under compressive loading. Additionally, the complex process of contact is assumed as a series of contact states changing from fracture to shearing. The friction coefficient, which obeys the constant friction law, is then derived as a function of interference and strain hardening exponent via adhesion theory. Finally, a comparison of friction coefficient is made with the published experiment, showing that the calculated value is larger than the experimental value. Some practical conclusions are presented and a conceptual understanding of contact friction is provided.
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Daw-Kwei Leu 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.6
This work presents an indentation model of the Brinell hardness test, which is a rigid ball-deformable plane contact model (RB-DP model), to elucidate the sliding friction mechanism of sheet metal forming. In the proposed model, the friction force can be defined as a combination of shear (shearing effect) and plough (ploughing effect) forces. The real contact area ratio α is determined from the RBDP model under sliding condition. Moreover, the lateral contact area ratio / A_c A_r can be specified as a function of the real contact area ratio α . Based on Meyer’s law and Hertz contact problem, the maximum contact area ratio α_u , a limiting condition of the real contact area ratio α , can be described as a function of the strain hardening exponent n. Additionally, a limiting condition applies: the strain hardening exponent n must be less than 0.64 in the present model. The present friction model reveals that the friction coefficient μ_d is a function of strain hardening exponent n, the real contact area ratio α and the maximum contact area ratio α_u . The calculated friction coefficient μ_d agrees with the published experimental results.
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Daw-Kwei Leu 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1
In this study, a series of experiments are performed to characterize the asymmetric V-die bending process for a High-strength steel(HSS) sheet. The main challenge in asymmetric V-die bending is positional deviation of the bending point during bending, given by amagnitude and a direction of deviation of the bending point. The effects of process parameters, such as radii of the punch head and thedie shoulder, on the positional deviation of the bending point were experimentally examined to identify those that govern the deviation ofthe bending point in an asymmetric bending process. This work improves our understanding of deviations of the bending point, and canbe used for developing process design guidelines for asymmetric bending of high-strength steel sheets to produce precise, asymmetricallybent parts.
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