用平台巴西圆盘实验确定金属粉末压坯的力学性能参数

Flattened Brazilian Disc Test for Determining Mechanical Properties of Green P/M Compacts

为确定金属粉末压坯的力学性能,本文采用平台型加载方式的巴西圆盘实验对铜、铁两种不同相对密度的金属粉末压坯进行直径压缩。利用同步实验图像记录,研究了圆盘中心裂纹的生长和金属粉末压坯的拉伸断裂过程。通过压缩实验获得了金属粉末压坯的位移-载荷曲线,结合弹性力学理论和数值分析方法,确定了压坯的三个力学性能参数:由直线段确定弹性模量E、由线性段与非线性段的转折点确定抗拉强度σ_t和由局部最小载荷确定张开型断裂韧度K_(Ic),它们与相对密度的关系均符合幂指数函数变化规律。

With the purpose of determining mechanical parameters of green P/M compacts,Brazilian disc specimen was employed.Two flats were introduced to the Brazilian disc to improve stress state.Metal powder discs of iron and copper with different relative densities were investigated by flattened Brazilian disc test.Through the images captured by the camera in real time,central crack initiation and the tensile fracture process of the pressed metal powder discs were studied in detail.Displacement-load curves of 5-stages were recorded during the experiments.By combining the theory of elastic mechanics and numerical calculation,mechanical parameters were determined from the displacement-load curves.E can be determined by slope of the linear region,σt by the turning point between the linear region and nonlinear region,K（Ic） by the minimum load subsequent to the maximum load.It is concluded that E、σt and K（Ic） are power function relationships with relative density.