Constitutive equation for metal plastic forming reflects the relationships among the parameters of stress, strain and strain rate. The accuracy of constitutive equation is a key factor in the research of material mechanism, finite element simulation accuracy and forming failure. The commonly used establishment methods of constitutive equation are summarized. Those methods include experiment method, theory analysis method, neural network method, regression method and inverse finite element method. The advantages and disadvantages of those methods are discussed, and application scope of those methods is summarized simultaneously.
Friction at the interface of die and workpiece plays an important role in metal forming. This paper introduces measurement methods of friction coefficient at curved surface in recent years, and divides the friction coefficient measurement methods into direct measurement methods and indirect measurement methods. Furthermore, the working principles and technical characteristics of these methods are explained.
The thin metal plastic forming is an indispensable metal forming technology. Wrinkling is one of the common defects in plastic forming. If this kind of defects can be used properly, the formability of metal will be better. In this paper, the recent researches on the methods of identifying wrinkles, distinction of the useful wrinkles and harmful wrinkles, control and application of the wrinkles are summarized. The useful wrinkles are expected to improve the forming property.
Due to its advantages over the spot welding technique, clinch joining technique is applied extensively in the automobile, electrical apparatus, etc. The quality and strength of the joints are the hot issues of the technique, which are severely affected by the processing parameters and die structure parameters. Clinch joining experiments of aluminous sheetsL5 were carried out under various blank holder forces and die structure parameters, and the influence of the parameters on the failure mode, section quality and strength of the joints were analyzed. The results show that the failure of the joints is mainly the shearing and a good section quality and high shearing strength of the joints can be obtained by reasonable processing parameters and die structure parameters.
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