The effect of loading rate on ductile fracture toughness and fracture surface roughness
The effect of loading rate on ductile fracture toughness and fracture surface roughness
复制标题
加载速率对韧性断裂韧性和断裂表面粗糙度的影响
DOI：
10.1016/j.jmps.2014.11.007
复制
发表时间：
2015
影响因子：
5.3
通讯作者：
A. Needleman
中科院分区：
文献类型：
--
作者：
Shmuel Osovski;A. Srivastava;L. Ponson;E. Bouchaud;V. Tvergaard;K. Ravi;A. Needleman
在I型平面应变、小尺度屈服条件下，模拟了韧性裂纹扩展阻力和断口表面粗糙度随加载速率的变化规律。三维计算采用弹粘塑性本构关系的逐步空化固体与两个种群的孔洞成核的第二相颗粒。较大的包裹体在早期导致空洞成核，被建模为离散的空洞成核点，而较小的颗粒需要较大的应变才能使空洞成核，被建模为均匀分布。计算了较大夹杂物的密度为3.6%和7.1%，规定的加载速率K (I)为1× 10 5 MPa m s−1 ~ 5× 10 7 MPa m s−1。研究发现，在较低加载速率下，韧性断裂模式可以看作是主裂纹的主导扩展，而在较高加载速率下，韧性断裂模式可以看作是先于主裂纹的损伤形核和微裂纹的主导扩展。随着加载速率的增加，jic、撕裂模量、tr、总塑性耗散和断裂过程区塑性耗散值均增大。随着规定加载速率的增加，断裂过程区塑性耗散占总塑性耗散的比例减小。断口表面表现出两种自仿射状态，在小长度尺度上的Hurst指数β≈0.60，在大长度尺度上的β≈0.45。多重分形谱在大多数情况下显示多仿射行为，但在加载速率和长度尺度范围内也显示单仿射行为。表征断口统计的参数，包括从幂律尾向指数尾过渡的长度尺度，与裂纹扩展/损伤积累模式有关。当K < 3× 10 7 MPa m s−1时，表面粗糙度相关函数的饱和值与jic值和tr值呈线性关系。
The variation of ductile crack growth resistance and fracture surface roughness with loading rate is modeled under mode I plane strain, small scale yielding conditions. Three-dimensional calculations are carried out using an elastic–viscoplastic constitutive relation for a progressively cavitating solid with two populations of void nucleating second phase particles. Larger inclusions that result in void nucleation at an early stage are modeled as discrete void nucleation sites while smaller particles that require large strains to nucleate voids are homogeneously distributed. The calculations are carried out for two values of density of the larger inclusions, 3.6% and 7.1%, and for prescribed loading rates K ̇̇ I ranging from 1× 10 5 MPa m s− 1 to 5× 10 7 MPa m s− 1. The ductile fracture mode is found to undergo a transition from one that can be regarded as growth of a dominant main crack at the lower loading rates to one dominated by damage nucleation and micro-cracking ahead of the main crack at the higher loading rates. The values of J IC, the tearing modulus, T R, the total plastic dissipation and the plastic dissipation in the fracture process region are all found to increase with increasing loading rate. However, the ratio of plastic dissipation in the fracture process region to total plastic dissipation decreases with increasing prescribed loading rate. The fracture surfaces are found to display two self-affine regimes, with a Hurst exponent β≈ 0.60 at small length scales and with β≈ 0.45 at larger length scales. The multi-fractal spectra indicate multi-affine behavior in most cases but a range of loading rates and length scales exhibiting mono-affine behavior is also found. Parameters characterizing the fracture surface statistics, including the length scale at which a transition from a power law tail to an exponential tail occurs, are related to the mode of crack growth/damage accumulation. A linear relation is found between the values of J IC and T R and the saturation value of the correlation function of the surface roughness for K ̇̇ I< 3× 10 7 MPa m s− 1.