共查询到20条相似文献,搜索用时 46 毫秒
1.
Study on the Relationship Between J-Integral and COD 总被引:1,自引:0,他引:1
J-integral and crack opening displacement δ (COD) were important parameters for characterization of fractures in engineering materials. The relationship between J-integral and COD has been investigated for a long time and was generally represented as J = m σyδ, where σy is the yield strength and m is a function of specimen geometry and material properties. To determine the value of m, extensive studies and experiments have been performed. The method that used the fracture-surface topography analysis (FRASTA) for determining J-integral from fracture surfaces of materials was introduced. On the basis of the relationship between COD and fracture surface average profile, the relationship between J-integral and COD was deduced and compared with the generally used equation. The method was experimentally confirmed to be able to provide a new way to determine the relationship between J-integral and COD. 相似文献
2.
DEVELOPMENT OF FRASTA SIMULATION SOFTWARE 总被引:1,自引:0,他引:1
Y.G. Cao K. Tanaka 《金属学报(英文版)》2006,19(3):165-170
Fracture-surface topography analysis (FRASTA) was successfully used to simulate the process of crack and calculate parameters of crack such as the crack opening angle (COA) and crack-tip opening angle (CTOA). But because the amount of calculation is large, errors are often made during the course of calculation. FRASTA simulation software, namely fracture surface analyst (FSA ) is developed and a series of center-cracked tension (CCT) and double edge notched (DEN) specimens of different materials with different sizes are tested, their fracture surfaces are scanned by non-contact 319 scanning system and the elevation data of the fracture surfaces is recorded. FSA used the recorded elevation data of fracture surfaces to simulate the process of crack based on the principle of FRASTA. Results show that FSA can accurately simulate the process and calculate the parameters of crack. 相似文献
3.
Y. G. Cao K. Tanaka 《金属学报(英文版)》2005,18(5):594-602
A new method, using the fracture-surface topography analysis (FRASTA), of determining the parameters of rotation factor and CTOA is provided. The fracture surfaces are scanned by laser microscope and the height data is recorded to analyze. By comparing the crack extension, plastic rotation factor and COA obtained by the method of double clip gauge and by this new method respectively, the validity of it is verified. It is then used to determine the CTOA. .The critical CTOA is well determined in this paper. Also by the new method, the variation of crack opening deformation (COA and CTOA) through specimen thickness can be obtained which can't be obtained by the usual methods. It also can provide much information of crack extension such as direction and ratio. 相似文献
4.
5.
分别采用常规和超声疲劳的试验方法,结合断裂力学理论以及FRASTA仿真,开展了GCr15钢超高周疲劳破坏行为的研究。结果表明,根据裂纹萌生位置的不同,疲劳破坏分为表面和内部破坏两种,其中内部破坏伴有granular bright facet(GBF)现象的产生,整个内部裂纹具有Fish-eye形貌特征。材料的疲劳S-N曲线呈现持续下降的趋势,ΔKGBF(4~4.2MPa·m1/2)是控制内部裂纹扩展的临界参数,超声疲劳试验提高了材料的疲劳强度,高强度钢的超高周疲劳行为的研究应采用常规试验为主,超声为辅的试验方法。 相似文献
7.
8.
利用爆炸焊及电子束焊接方法制备了含不同厚度中间纯铝层的LY12/Al/LY12四点弯曲试样,并在纯铝层中预制了平行于界面的疲劳裂纹,加载后裂纹尖端侧剖形貌的金相观察和对应断口表面的微区成分的能谱分析均确认了裂纹在纯铝层内的扩展,实验结果表明:在双界面强约束下,随着中间纯铝层厚度的减小,所测定的预裂纹试样的载荷/位移曲线表现出明显的差异;以其临界J积分表征的断裂韧性值显著降低,即纯铝层发生了韧脆转变;试样断口表面出现局部准解理花样等脆化特征,其所占比例逐渐增加;对这种约束下纯铝韧脆转变的微观机理进行了初步的探讨。 相似文献
9.
F.Q.Tian D.Y.He X.Y.Li Y.W.Shi D.Zhang 《金属学报(英文版)》2004,17(6):934-939
Welded joint is a mechanical heterogeneous body, and mechanical heterogeneity has great effect on dynamic fracture behaviour of welded joints. In the present investigation, dynamic response curve and dynamic J-integral of practical undermatched welded joint and whole base and whole weld three-point-bend (TPB) models containing longitudinal crack are computed. Dynamic J-integral is evaluated using virtual crack extension (VCE) method and the computation is performed using MARC finite element code. Because of the effect of inertia,dynamic load response curve of computed model waves periodically. Dynamic J-integral evaluated by VCE method is path independent. The effect of inertia has little influence on dynamic J-integral curve. The value of dynamic J-integral of undermatched welded joint is lower than that of whole base metal and higher than that of whole weld metal. The results establish the foundation of safety evaluation for dynamic loaded welded structures. 相似文献
10.
通过试验、理论分析和有限元模拟对工业纯钛TA2室温蠕变条件下裂纹尖端应力应变场的参量表征及估算进行了研究。试验研究表明,在室温条件下,工业纯钛TA2存在明显的第1阶段蠕变现象。理论分析和有限元模拟表明,对TA2裂纹体进行保载时,裂纹尖端的应力应变场为HRR场,提出采用与时间相关的J积分来表征,并给出了估算方法。通过有限元计算,获得了TA2室温蠕变条件下CT试样的时间相关J积分值,论证了采用J积分来表征室温蠕变条件下TA2裂纹尖端应力应变场的合理性。将有限元计算与估算方法获得的J积分进行了比较,验证了估算方法的有效性和准确性。 相似文献
11.
通过断裂实验、二维有限元分析(2-D FEA)、三维有限元分析(3-D)以及EPRI解等4种方法获得了工业纯钛(CP Ti)紧凑拉伸试验(CT)的J积分。结果表明,EPRI解获得的J积分与2-D FEA结果吻合,但是它们明显低于实验结果,而3-D FEA获得的J积分更接近于实验值。为了提高J积分的估算精度,提出了基于3-D FEA改进的EPRI解,并用实验结果进行了验证。此外,将由原EPRI解和改进的EPRI解获得的J积分建立的CP Ti失效评定曲线(FAC)与实验结果进行比较,发现EPRI解的改进不仅提高了J积分的估算精度,而且提高了FAC的可靠性。 相似文献
12.
V. M. A. Leitao M. H. Aliabadi D. P. Rooke R. Cook 《Journal of Materials Engineering and Performance》1998,7(3):352-360
Two boundary element methods of simulating crack growth in the presence of residual stress fields are presented, and the results
are compared to experimental measurements. The first method utilizes linear elastic fracture mechanics (LEFM) and superimposes
the solutions due to the applied load and the residual stress field. In this method, the residual stress fields are obtained
from an elastoplastic BEM analysis, and numerical weight functions are used to obtain the stress intensity factors due to
the fatigue loading. The second method presented is an elastoplastic fracture mechanics (EPFM) approach for crack growth simulation.
A nonlinear J-integral is used in the fatigue life calculations. The methods are shown to agree well with experimental measurements
of crack growth in prestressed open hole specimens. Results are also presented for the case where the prestress is applied
to specimens that have been precracked. 相似文献
13.
基于裂纹尖端钝化能的断裂韧性估算方法 总被引:1,自引:0,他引:1
基于裂纹尖端塑性钝化能,从平面应力状态和平面应变状态分析KIc入手,建立了金属材料平面应变断裂韧性KIc值的能量估算方法,同时考虑了应力松弛和材料强化的影响,以及塑性钝化区形状和裂纹尖端应力状态的分布,并由此推导出了一个基于常规力学性能的断裂韧性KIc值的计算公式。利用LZ50车轴钢的试验数据进行了对比分析,标定出LZ50车轴钢的形状因子Z参数,并对比分析了KIc试验概率值分布与计算概率值分布规律,讨论了各影响因素对KIc值的影响规律。计算结果表明,所建立的KIc公式能够反映常规力学性能与平面应变断裂韧性间的关系。 相似文献
14.
MA Weidian Tsinghua University Beijing ChinaZHANG Shicheng TIAN Xitang Haribin Institute of Technology Harbin China Dept.of Mechanical Engineering Tsinghua University Beijing China 《金属学报(英文版)》1989,2(7):48-54
The effects of material inhomogeneity and weld width of the overmatched welded joints with alongitudinal crack or flaw upon the J-interal,a characterizing parameter for elastoplasticfracture,have been studied.The overmatched weld is idealized to be a parallelly cracked andsandwiched hard layer,the yieht stress of which is higher than that of the base metal.Numeri-cal solutions were obtained by using elastoplastic finite element method under the assumptionof plane stress.The resuits show that the values of J-integral are remarkably affected by thematerial inhomogeneity ant the weld width especially when the nominal stress or nominalstrain is comparatively high,which,therfore,should be taken into account when evaluatingthe crack driving force for an overmatched joint. 相似文献
15.
系列示波冲击断口三维形貌几何特征和断裂性能 总被引:2,自引:0,他引:2
应用示波冲击试验技术测量了P460NL1钢不同温度系列下的动态断裂性能。利用扫描电镜立体对技术,图像处理与分析和计算视觉方法对示波冲击断口形貌进行了三维重建和定量分析。 相似文献
16.
本文用再结晶法测定了中心裂纹拉伸试件裂纹尖端强应变区的塑性应变分布,求得了强应变区参数与J积分及裂纹尖端张开位移COD的定量关系,并用三维弹塑性有限元法进行了计算。实验和计算结果表明,用再结晶法研究三维弹塑性裂纹问题是一种很有效的方法。 相似文献
17.
金属断裂表面的分形(Fractal)与断裂韧性 总被引:25,自引:0,他引:25
本文借助于图象分析技术使用Slit island方法研究了两种高强度钢不同热处理制度和不同试验温度条件下平面应变断裂表面的分形维数.结果表明,断裂表面是一种分形结构,断裂韧性K_(IC)值的对数随分形维数D_F增加成单调下降的直线关系.这种关系反映了不同热处理制度所引起的材料微观结构变化和不同试验温度所引起的断裂机制变化,D_F可以做为金属断裂韧性的一种度量。最后,用临界裂纹扩展力与不规则断裂表面真实面积之间的关系对结果进行了理论分析. 相似文献
18.
19.
20.
本文应用环状裂纹受拉圆棒试样的尺寸效应于测定中低强度钢的平面应变断裂韧度K_(IC)。所用试样的尺寸比标准试样小很多。用J积分分析了尺寸效应,并通过有限元计算和断口分析探讨了允许用较小尺寸的圆棒试样测定K_(IC)的原因。 相似文献