单 位：
南京林业大学生物质材料国家地方联合工程研究中心
关键词：
重组竹;扩展有限元法(XFEM);内聚区模型;尺寸效应;断裂韧度;数值模拟
摘 要：
重组竹作为一种高强度复合材料正被逐渐用于建筑领域,但其工艺特点决定了重组竹构件是带裂纹工作的。以ABAQUS有限元软件为平台,结合扩展有限元法(XFEM)和内聚区模型(CZM)对重组竹I型断裂进行数值模拟。三维双悬臂梁(DCB)模型采用基于牵引分离法则的内聚行为描述裂纹的启裂和扩展,得到裂纹扩展全过程的可视结果和外荷载-裂纹张开口位移曲线(P-δ曲线),并对比模拟曲线和试验曲线,考虑峰值荷载存在差异的合理性。再进一步处理荷载-位移曲线,得到裂纹扩展阻力曲线(R曲线),并通过对比R曲线再次验证了该数值方法的有效性,为工程实际应用提供参考。在此基础上,又对比了5种不同厚度和3种不同初始裂纹长度条件下的重组竹I型断裂能量释放率,分析了厚度和初始裂纹长度2种尺寸参数对重组竹断裂韧性的影响。结果表明:薄试件具有较大的断裂韧度,随着厚度增大,双悬臂构件由平面应力状态转为平面应变状态,双悬臂梁的能量释放率趋于一个恒定的较低值,其中,厚度大于40 mm的试件模拟准确度较高。对于处于平面应变状态下的双悬臂梁,其初始裂纹长度对断裂韧度的模拟结果影响较小。
译 名：
Numerical simulation analysis of parallel strand bamboo type Ⅰfracture using extended finite element method
作 者：
LIU Mingkai;ZHOU Aiping;LIU Yanyan;SHENG Baolu;National-provincial Joint Engineering Research Center of Biomaterials,Nanjing Forestry University;
关键词：
bamboo scrimber;;extended finite element method(XFEM);;cohesive zone model;;size effect;;fracture toughness;;numerical simulation
摘 要：
Due to the limited wood resources and the increasing demand for wood products,bamboo as a short-term renewable resource can be used for replacing wood to effectively alleviate the shortage of wood resources.Parallel strand bamboo(PSB) is a new building material,which is made of original bamboo and recombined by a series of processing technology.The existing research showed that,compared with the general engineering wood,PSB had higher strength,superior mechanical properties,and larger bearing capacity in bending and compression.As a kind of highstrength composite material,PSB is gradually used in the field of construction,but PSB components have its technological characteristic drawbacks,e.g.,cracks during its service caused by its inherent defects.There was the stress concentration around micro cracks,and the material was easy to be damaged under the yield stress,which will lead to component failure or even structural collapse.Therefore,for materials with micro cracks,the prediction of fracture toughness can effectively prevent the occurrence of fracture failure.This study used ABAQUS finite element software as a platform and combined with the extended finite element method(XFEM) and the cohesive zone model(CZM)to simulate the PSB I-hype fracture.The three-dimensional double cantilever beam(DCB) model was used to investigate the cohesive behavior based on the traction separation law to describe the crack initiation and propagation.The visual results of the whole process of crack propagation and the external load crack tension opening displacement curve(P-δ curve) were obtained.The simulation curve and the experimental curve were compared by considering the rationality of the difference between the peak loads.The crack growth resistance curve(R curve) was obtained through further process of the load-displacement curve.The comparison of the R curves verified the effectiveness of the numerical method again,which provided a reference for the practical application of engineering.On this basis,the energy release rate of I-type fracture of PSB under the condition of five different thicknesses and three different initial crack lengths were compared,and the influences of two size parameters,thickness and initial crack length on the fracture toughness of PSB were analyzed.The results showed that the thin specimens had a large fracture toughness.With the increase of thickness,the double cantilever components changed from plane stress state to plane strain state,and the energy release rate of DCB tended to a constant low value.Among them,the simulation accuracy of specimens with a thickness greater than 40 mm was higher.For the double cantilever beam under plane strain,the initial crack length had a small effect on the simulation results of fracture toughness.
