制动盘热机开裂机理的模拟研究

SIMULATION STUDY ON OPENING MECHANISM OF THERMALMECHANICAL CRACK OF BRAKE DISC

综合考虑灰铸铁物理属性随温度变化规律、拉/压各向力学性能差异和弹塑性应变应力关系,采用有限元计算方法,研究灰铸铁制动盘在不同制动工况下的温度场、应力场、应变场以及热机裂纹强度,揭示制动盘热机开裂原因及裂纹分布规律。热机耦合计算结果表明制动盘在初始制动速度为180 km/h下,最大温度为360℃、径向压/拉应力275MPa/85 MPa、周向压/拉应力为374 MPa/100 MPa、径/周向塑性应变为-4.6×10^(-5)/-6.75×10^(-5)。热机开裂计算结果表明径向裂纹尖端应力强度因子ΔK为6.69MPa·m^(1/2)大于周向裂纹尖端应力强度因子5.49 MPa·m^(1/2),径向裂纹张开距离大于周向裂纹张开距离,证明制动盘表面裂纹分布以径向裂纹为主且径向裂纹尺寸大于周向裂纹。

Considering physical properties variation of gray cast iron with temperature,difference mechanical behavior of material between compression and tension,relationship of elastic and plastic stress-strain of material,synthetically studied the temperature field,stress field,strain field and thermal crack strength of brake disc under different braking conditions,and revealed the opening mechanism of thermomechanical crack and crack distribution. Results of thermomechanical coupling simulation show the maximum temperature is 360℃ with initial speed of 180km/h,radial compression/tension stress are275Mpa/85 Mpa,circumferential compression/tension stress are 374 MPa/100 MPa,radial/circumferential plastic deformation are-4. 6 × 10^-5/-6. 75 × 10^-5. Results of thermomechanical opening calculation show stress intensity factor of radial crack ΔK6. 69 MPa·m^1/2 is larger than ΔK 5. 49 MPa·m^1/2 of circumferential crack,opening displacement of radial crack is larger than that of circumferential crack,which indicating radial cracks are mainly distributed on brake disc,and the sizes of radial crack are larger than that of circumferential crack.