平板冲击加载下对双相钢动态损伤演变的研究

利用一级轻汽炮以一击二的方式对2种不同热处理状态的双相钢进行加载,采用多普勒测速系统对加载过程中样品的自由面粒子速度进行测量,通过金相显微分析、纳米压痕分析对样品进行表征,探讨了双相钢的层裂损伤演变。结果表明:孔洞并没有像准静态损伤理论一样在相界面处优先形核长大,而是在马氏体内部形核,然后长大贯通形成微裂纹贯穿整个马氏体,形成穿晶断裂; 由于相界面对冲击波具有反射与透射作用,冲击波从高阻抗的相传入低阻抗的相内时会在高阻抗相内形成拉伸脉冲,从而引起层裂损伤; 相界面越多,在高阻抗相内产生拉应力并形成孔洞的几率越大,样品层裂强度也越低。

Dynamic Damage Evolution in Dual-Phase Steels Under Plate Impact Loading

The dual-phase steel samples with two different treatment conditions were loaded by using one stage light gas gun. During the loading process, the free-surface particle velocity of the samples was measured by using a Doppler velocity sensor. Then, the sample was characterized by using metallographic microscope, nanoindentation testing, for discussing the damage evolution of the spallation in the dual-phase steel. Results show that the void nucleation and growth are not found to preferentially occur at the phase interface as quasi-static damage evolution. Instead, the voids are nucleated in the martensite, and then grow and coalesce to form microcracks that run throughout the whole martensite, leading to the formation of transgranular fracture. Due to reflection and transmission of shock wave by the phases interface, a tensile pulse will be generated in the phase with high impedance when a shock wave is transmitted from martensite with high impedance to ferrite with low impedance, leading to the spallation damage. And, more phase interfaces will lead to the greater probability of tensile stress generated in the high impedance phase and more void nucleation, resulting in the reduction in the spallation strength.