摘要
Existing methods for examining the friction parameters in metal forming all have advantages and disadvantages.Based on the theory of plasticity,the current study established quantitative correlations among friction coefficient/factor,yield stress of the workpiece material,load and die geometry in the forward extrusion with a conical die,and then designed a procedure for testing the friction parameters in forming processes using the correlations.A series of extrusion experiments along with the numerical simulations,using AA 7050 specimens under various lubricating conditions,were carried out.The results proved that the method can obtain the friction coefficient/factor with an acceptable precision.Theoretically,since the effects of material properties,forming velocity,temperature and surficial condition,etc.,on the deformation can be directly considered in the operation,this method is applicable to a wide range of material types and forming conditions.To avoid the occurrence of "barreling phenomenon" under large load which may lead to failure of the operation,it is recommended that half angle of the conical die ranges from 5 to 10 degrees.
基金
the National Natural Science Foundation of China(No.51575066),the Natural Science Foundation of Chongqing(No.cstc2018jcyjAX0159)。
