基于Johnson-Cook模型对金属粉末高速压制温升影响因素的研究

Study on Influencing Factors of Temperature Rise of Metal Powder in High Speed Pressing Based on Johnson-Cook Model

高速压制中粉末颗粒在微秒级的时间内发生大变形和微摩擦而产生大量的热,导致颗粒表面接触处温度急剧上升。为了研究颗粒间温升的影响因素,通过MSC.MARC软件对铝粉建立了离散密排球堆积简化模型,对金属粉末温升机理进行了研究。通过对比不同摩擦系数下压制速度对温升的影响,发现提高压制速度能提高颗粒间温升,其原因是摩擦力变大。对不同参数Johnson-Cook模型模拟发现,材料的屈服应力和应变硬化模量对高速压制过程的温升有较大的影响,其中屈服应力影响最大。对大部分金属粉末而言,在一定的压制速度和摩擦系数下,粉末压制和烧结的同步进行是可实现的。以铝粉为例,在摩擦系数0.3,压制速度80 m/s时,局部区域最高温度为678℃,达到熔点以上。

The powder particle at the microsecond level time in high speed pressing produces the large deformation and micro-friction, and it generates a lot of heat to cause rapid temperature rise at particle surface contacts. In order to research the influential factors of the temperature rise among the particles, the simplified model of discrete dense accumulation of volleyball for the aluminium powder was established by using MSC. MARC software. And the temperature rise mechanism of the metal powders was studied. By comparing the influence of the pressing speed on the temperature rise under different friction coefficients, it is found that improving the pressing speed can improve the temperature rise between particles,and the reason is that the friction becomes larger. After the simulation used different parameters of Johnson-Cook model, it is found that the yield stress and strain hardening modulus of the material have great influence on the temperature rise in high velocity compaction process, in which the effect of yield stress is maximum. For most metal powder, under certain suppression rate and friction coefficient, the synchronization of pressing and sintering is achievable. Taking aluminum powder as an example, the local maximum temperature is 678 ℃ when the friction coefficient is 0.3, and pressing speed is 80 m/s.