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1.
The definition of J-integral of interfacial crack was introduced. The three-point bending tests were carried out to obtain the critical loading
values when the interfacial crack initiation occurred between coatings and substrates. The finite element analysis (FEA) was
adopted to analyze the stress distribution in the specimens and compute the J-integral of the interfacial crack between LX88A coating and Chinese Q345 steel. The results showed that the average value
of critical J-integral is 0.70 N/m, which can be taken as the fracture parameter to evaluate the interfacial fracture behavior for the
three-point bending specimens of LX88A coating/Q345 steel system.
Supported by Tianjin Natural Science Foundation (No.08JCYBJC09100), New Teacher Research Fund for the Doctoral Program of
Higher Education of China (No.20070056096) and New Century Outstanding Talented Person Plan of China.
XU Lianyong, born in 1975, male, Dr. 相似文献
2.
基于柔度测试方法,提出了J积分增量算式;对CT试样,提出了裂纹嘴张开位移V0和加载线裂纹张开位移VLL之间的V0~VLL转换算式,裂纹长度a与弹性模量E计算的简化算式。基于适合同时测试V0和VLL的CT试样设计,对45#钢CT试样进行了多级加-卸载,对CT试样的V0~VLL转换算式进行了试验验证。计算与试验结果表明,新公式具有良好精度。 相似文献
3.
采用反射式焦散线方法对水泥石中添加玻璃纤维后的强度变化问题进行了实验研究.首先,制作了不添加与添加玻璃纤维的2种水泥石试件,并采用镜面移植方法在试件的表面进行反射镜面的制作与加工.然后,采用多火花式高速摄影系统对试件在冲击断裂过程中的裂纹扩展和裂纹尖端焦散线的情景进行记录.最后,对2种试件的裂纹起裂时间、动态应力强度因子和裂纹扩展速度等参数进行计算和对比分析.分析发现,玻璃纤维提高了水泥石的断裂韧度、延迟了裂纹的起裂时间,对水泥石具有明显的强化效应.实验结果对研究水泥石的断裂力学属性特征具有一定意义. 相似文献
4.
利用大型有限元软件ANSYS/LS-DYNA的模拟功能,对轧辊的裂纹尖端开裂模式进行了模拟分析。在将裂纹尖端区域细化的基础上,得出含表面裂纹的热轧工作辊两个裂纹尖端的开裂模式是不同的,并且随着轧制深入以及裂纹扩展规律的影响,出现了裂纹尖端局部塑性区以及材料局部的卸载情况,使应力强度因子K以及J积分之间不再满足在线弹性过程中的换算关系形式。 相似文献
5.
Xian-kui Zhu 《浙江大学学报(A卷英文版)》2009,10(11):1541-1560
In this paper a critical review is presented ofthe history and current state of the art of J-integral resistance curve testing and experimental evaluation methods in conjunction with a discussion of the development of the plane strain fracture toughness test standard ASTM E 1820 developed by American Society for Testing and Materials （ASTM）. Early research efforts on this topic are reviewed first, These include the J-integral concept, experimental estimates of the J-integral for stationary cracks, load line displacement （LLD） and crack mouth opening displacement （CMOD） based ηfactor equations, different formulations of J-integral incremental equations for growing cracks, crack growth corrected .JR curve determination, and experimental test methods. Recent developments in J-R curve testing and evaluation are then described, with emphasis on accurate J-integral incremental equations, a normalization method, a modified basic method, a CMOD direct method with use of incremental equations, relationships of plastic geometry factors, constraint-dependent J-R curve testing and correction approaches. An overview of the present fracture toughness test standard ASTM E1820-08a is then presented. The review shows that after more than 40 years of investigation and development, the J-integral resistance curve test methods in ASTM E1820 have become simpler, more cost-effective and more accurate. 相似文献
6.
CUI Hong-bin 《实验室研究与探索》2007,(10)
由于高强度钢在疲劳断裂过程中很难产生辉纹,给裂纹扩展的研究带来一定的困难。本文在对接焊平板的疲劳断裂试验中,采用降载勾线法制造出"海滩状花纹",借此对裂纹扩展过程中裂纹前缘形状和裂纹扩展速率进行分析,并与Newman-Raju公式的计算结果进行比较。 相似文献
7.
某汽车配件公司生产汽车油管发生折弯开裂现象,采用金相显微镜和扫描电镜等对油管进行观察并分析开裂原因。结果表明:原双层卷焊管表面存在细小裂纹,在折弯过程中,裂纹在外力作用下发生了扩展,最终导致开裂。 相似文献
8.
The fracture behavior of a ceramic reinforced metal-base coating prepared by high velocity arc spraying (HVAS)technology in three-point bending test was studied.Moreover,finite element analysis(FEA)was adopted to analyze the stress distribution in the crack front.It can be found that the crack norrnal to the interface in the coatings occurred at the location where a fixed moment of force was reached.So the critical moment can be taken as thecoating cracking criterion,which was confirmed by FEA results.In addition,the stress levels at three different locations where cracks occurred near the interface are almost the same.The results will provide reference for the design of coatings and the structure integrity evaluation of coating/substrate systems. 相似文献
9.
The mechanism and criterion of crack initiation and propagation of rocks were investigated by many researchers,And the creep behaviour of rocks was also theoretically and experimentally studied by some scientists and engineers.The characteristics of crack initation and propagation of rocks under creep condition.however,are very improtant for rock engineering and still not paid enough attention by researchers,In this paper,the criterion and mechanism of crack initiation and propagation under creep condition were investigated using specimens collected from sandstone rock formations outcropping in the Emei Mountain,the Sichuan Province of China.Cuboid specimens under three point bending were used in this investigation.All specimens were classified into four sorts and used for Mode-I fracutre of creep frcture tests.The experimental result shows that due to creep deformation.rock crack will inevitably initialt and propagate under a load of KI,which is less than fracture toughness KIC but not less than a constant(marked as KIC2),KIC2 indicates the ability of rock to resist crack initiation and propagation under creep conditions and is less than fracture tough ness KIC.defined as creep fracture toughness in this paper,KIC2 should be considered as an importnat parameter on design and computation of rock engineering.The microstructureal mechanism for crack initiation and propagation of rock materials under creep condition was introduced based on competitive model between softening effect and hardening effect,and the validity of test result was explained.The test result was also verified in rheological theory.When KI is more than KIC2 but less than KIC,rock crack will initiate and propagate after a time interval of sustained loading under creep condition.In order to find the relation between duration of sustained lading.which can lead to crack initiation and propagation,and the initial stress intensity factor KI,an unequal0interval time sequence forecasting and predicting model was introduced,and the relation was obtained for homogeneous and isotropic fine-grained red sandstone.Finally a modified fracture toughness formula was given,in which the influence of fracture process zone(FPZ) was fully considered. 相似文献
10.
郑如杰毕贤顺 《福建工程学院学报》2017,(3):224-228
利用断裂力学方法对含有裂纹混凝土试件的断裂韧度进行了研究。通过预制不同裂纹深度的混凝土试件,采用三点弯曲试验方法对含裂纹混凝土梁的断裂韧度进行实验,同时利用ABAQUS软件,采用最大主应力牵引损伤开裂准则与线性软化损伤模型进行数值模拟。结果表明,实验结果和数值模拟比较一致,最大误差不超过15%,当初始缝纹长度为40~120 mm时,起裂断裂韧度KiniIC变化幅度较小,失稳断裂韧度KunIC有明显的减小趋势。 相似文献
11.
Through the experiments of 7 T-section composite beams, steel fiber reinforced self-stressing concrete （SFRSC） as the composite beam in the composite layer was studied under the hogging bending. The tests simulated composite layer tensile strain under the hogging bending of inverted loading composite beams, giving the relationship under the different fatigue stress ratios between fatigue cycles and steel bar’s stress range, crack width, stiffness loss and damage, etc., in composite layer. This article established fatigue life equation, and analyzed SFRSC reinforced mechanism to crack width and stiffness loss. The results show that SFRSC as the composite beam concrete has excellent properties of crack resistance and tensile, can reinforce the fatigue crack width and stiffness loss of composite beams, and improve the durability and in normal use of composite beams in the hogging bending zone. 相似文献
12.
By using semisolid joining technique,the bonding of stainless steel and semisolid aluminum alloy is successfully realized.The relationships between interracial shear strength and solid fraction of aluminum alloy,bonding pressure and time of keeping pressure were studied by the method of orthogonal experiment.The interfacial structure and the fracture structure of the bonding plate are studied by means of optical microscope (OM) and scanning electron microscope (SEM).The results show that there is the best solid fraction between the solid phase line and the liquid phase line of the semisolid aluminum alloy,with the increase of bonding pressure and pressure time,the interfacial shear strength increases rapidly,and then with further increase of bonding pressure and pressure time,the shear strength rises little.Along the interface,solid phase and liquid phase bond with stainless steel by turns because of the different diffusion ability.So,a new type of non-equilibrium diffusion interfacial structure is constructed at the interface of stainless steel and aluminum alloy,compound mechanism of plastic and brittle fracture interface was formed at the shear fracture interface. 相似文献
13.
为研究钢管高性能混凝土界面黏结性能,进行了包括钢管壁厚、截面形式、钢材类型和钢管内表面状态4 个参数的推出试验研究,分析了试件的试验现象、荷载-滑移曲线和界面黏结强度。 结果表明,仅当试件壁厚较薄时,钢管中下部会出现45°剪切滑移线;不同钢管壁厚试件的荷载-滑移曲线共有3 种增长模式,均包括胶结滑移段、滑移段和摩阻段3 个阶段;增大钢管壁厚、使钢管内表面锈蚀可以提高界面黏结强度;采用方形钢管代替圆形钢管、不锈钢管代替普通钢管对界面黏结强度有不利影响。 相似文献
14.
Calculation Model of Equivalent Strength for Induced Crack Based on Double-K Fracture Theory and Its Optimizing Setting in RCC Arch Dam 总被引：2，自引：0，他引：2
By means of fracture testing on roller-compacted concrete (RCC) three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KIC^ini,KIC^un, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer‘s optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice. 相似文献
15.
Fatigue and fracture behavior of nickel-based superalloy Inconel 718 up to the very high cycle regime 总被引：2，自引：0，他引：2
Xian-feng Ma Zheng Duan Hui-ji Shi Ryosuke Murai Eiichi Yanagisawa 《浙江大学学报(A卷英文版)》2010,11(10):727-737
The fatigue and fracture behavior of nickel-based superalloy Inconel 718 was investigated up to the very high cycle regime under rotary bending tests at room temperature. It was found that this superalloy can still fracture after exceeding 107 cycles. Fractographic analysis revealed that there was a transition from fatigue crack initiation at multi-sites to single initiation with decreasing stress levels. The fracture surface can be divided into four areas according to the appearance, associated with fracture mechanics analysis of the corresponding stress intensity factors. The fracture mechanism dominant in each area was disclosed by scanning electron microscope examination and analyzed in comparison with those obtained from the crack growth tests. Subsequently, life prediction modeling was proposed by estimating the crack initiation and propagation stage respectively. It was found that Chan （2003）＇s model for initiation life and the Paris law for growth life can provide comparable predictions against the experimental life. 相似文献
16.
钢桥面环氧沥青铺装的界面行为 总被引：2，自引：0，他引：2
通过引入一个新参数膜劲度,在部分共同作用原理的基础上,建立了描述钢桥面环氧沥青混凝土铺装复合梁在负弯矩作用下的界面行为模型,用以分析钢-环氧沥青混凝土之间的界面滑移与应变.推导了弹性工作状态下复合梁的界面滑移与应变的表达式,编制了数值计算程序并用2根复合梁进行了校核.然后采用该程序分析了界面滑移与应变沿复合梁纵向的分布特征,以及铺装层中的最大拉应力、层间剪应力对材料参数的敏感性.结果表明,界面效应削弱了钢桥面铺装复合梁的整体抗弯刚度;中低温条件下,采用劲度更大的粘结层材料有利于改善沥青铺装层的受力;粘结层的损伤累积将加剧沥青铺装层的破坏. 相似文献
17.
A new type of green reactive powder concrete (GRPC) with compressive strength of 200 MPa is prepared by utilizing composite mineral admixtures, natural fine aggregates, and short and fine steel fibers. The quasi-static mechanical properties (mechanical strength, toughness, fracture energy and interfacial bonding strength) of GRPC specimens, cured in three different types of regimes, are investigated. The experimental results show that the mechanical properties of the C200 GRPC made with the powder binders that is composed of 40% of Portland cement, 25% of ultra fine slag, 25% of ultra fine fly ash and 10% of silica fume are better than the others'. The corresponding compressive strength, flexural strength and fracture energy are more than 200 MPa, and 30 000 J/ m2 respectively. The dynamic tensile behavior of the C200 GRPC is also investigated through the split Hopkinson pressure bar (SHPB) according to the spalling phenomenon. The dynamic testing results demonstrate that strain rate has an important effect on the dynamic tensile behavior of GRPC. With the increase of strain rate, its peak stress and relevant strain increase. The GRPC exhibits an excellent strain ratio stiffening effect under the dynamic tensile load with high strain ratio, resulting in a significant change of the fracture pattern. 相似文献
18.
对调质42CrMo钢进行室温下各种应力循环和对称应变循环的低周疲劳实验,揭示材料的循环软化特性,棘轮变形和低周疲劳特性以及棘轮-疲劳交互作用。结果表明,调质42CrMo钢体现出明显的循环软化;在应力幅值或平均应力较高时,试样的棘轮变形较大,其破坏形式为延性破坏,而在应力水平较低时,材料的破坏由疲劳裂纹扩展所致的脆性断裂引起;材料在应力循环下的低周疲劳寿命由于有棘轮变形的产生而受到平均应力、应力幅值、最大应力和应变比等多种因素的影响。 相似文献
19.
The failure mode and adhesion of thermal barrier coating (TBC) 8YSZ (ZrO2+8% (w/w) Y2O3) deposited on NiCoCrAlTaY bond coat by atmospheric plasma spraying were investigated. A grooved modified three-point bending specimen that can generate a single interface crack to facilitate the control of crack growth was adopted for testing, which was conducted at the ambient temperature of 100 °C. The morphology and composition of fractured surfaces were examined by means of a scanning electron microscopy (SEM) and an energy disperse spectroscopy (EDS). Images and spectrum show that cracks are initiated and propagated exclusively within YSZ layer adjacent to top/bond coat interface. The load-displacement curves obtained exhibit similar shapes that indicate two distinct stages in crack initiation and stable crack growth. Finite element analyses were performed to extract the adhesion strength of the TBCs. The delamination toughness of the plasma-sprayed 8YSZ coatings at 100 °C, in terms of critical strain energy release rate Gc, can be reliably obtained from an analytical solution. 相似文献
20.
JU Jian-hua XIA Yi-ben ZHANG Wei-li LU Yu WANG Lin-jun SHI Wei-min School of Material Science Engineering Shanghai University Shanghai China National Lab for Infrared Physics. Shanghai Institute of Technical Physics Chinese Academy of 《上海大学学报(英文版)》2000,(Z1)
l IntroductionDLC film is one of coating materials that has highhardness and good wear-resisbot PrOPerlies. When thefilm is deposited on low haulness substrates with thedifferent YOung's model and expansion coefficient, ahigh stress occurs in the film, which resulted in thedecrement of the adherence of the film and the filmspliting or carking['~4]. In order to improve theadherence of DLC film on the soft subside, the mostcommon method is tO colltrol the iIYIPurities, such as H,St, N and… 相似文献