断裂相场法在材料失效分析中的应用:界面断裂的超剪切转变

Phase-Field Fracture Method Applied in Material Failure Analysis:Supershear Transition of Interfacial Fracture

Ⅱ型裂纹界面断裂速率可以超越材料的剪切波速已经在理论和实验中被证明,这种界面断裂的跨声速转变被普遍认为受“Burridge-Andrews”机制(也称“子-母”裂纹机制)控制。然而,对于这种跨声速转变机制,子裂纹的直接证据很少被报道,甚至有些报道中并没有在裂纹跨声速转变过程中观察到子裂纹。近期,中国科学技术大学李良彬教授课题组开展了Ⅱ型裂纹界面跨声速转变的数值模拟研究,“子-母”裂纹扩展过程首次在相场断裂模拟中被重现。他们的工作揭示了一个跨声速裂纹发生的临界预应力水平值,并提出了子裂纹出现的定量化预测准则。

Crack propagation velocity is a crucial discussion for understanding dynamic fracture.Classical dynamic fracture theory predicts a“forbidden velocity zone”for modeⅡcracks,i.e.,the velocity between the Rayleigh and shear wave speeds.However,supershear transition has been demonstrated theoretically and experimentally for mode-Ⅱcrack constrained to weak interfaces.Such transition is commonly accepted to be governed by the Burridge-Andrews mechanism(also known as“mother-daughter”crack),which predicts direct nucleation of a secondary intersonic daughter crack induced at the Rayleigh wave speed.Nevertheless,to our knowledge,“mother-daughter”crack pairs are rarely reported with visual observations,and the supershear rupture without the daughter crack forming has also been found in some previous reports.Recently,Prof.Liangbin Li’s group at University of Science and Technology of China and the coworkers reported the Sub-Rayleigh to supershear transition of dynamic mode-Ⅱcracks based on numerical simulations.Their numerical experiments successfully reproduced the“mother-daughter”cracks for the first time in phase-field fracture modeling,as well as the supershear transition without the daughter crack.Given that,a crack tip blunting-tearing hypothesis was presented to explain that cracks comply with different mechanisms from Sub-Rayleigh to supershear regimes,and a critical prestress level was revealed below which no supershear transition can be accomplished from the Sub-Rayleigh propagation.Furthermore,the criteria were also proposed for predicting the occurrence of the daughter crack through systematic simulations.This paper briefly presents their progress in the studying of the Sub-Rayleigh to supershear transition for dynamic mode-Ⅱinterfacial fracture.