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Influence of grain size on the small fatigue crack initiation and propagation behaviors of a nickel-based superalloy at 650℃
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作者 Xumin Zhu Congyang Gong +5 位作者 Yun-Fei Jia Runzi Wang Chengcheng Zhang Yao Fu Shan-Tung Tu Xian-Cheng Zhang 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第8期1607-1617,共11页
GH4169 at 650℃ in atmosphere was investigated by using single edge notch tensile specimens. The number of main cracks and crack initiation mechanisms at the notch surface strongly depended on the grain size. The crac... GH4169 at 650℃ in atmosphere was investigated by using single edge notch tensile specimens. The number of main cracks and crack initiation mechanisms at the notch surface strongly depended on the grain size. The crack initiation life accounted for more percentages of the total fatigue life for the alloy with smaller grain size. The fatigue life generally increased with increasing crack initiation life. The small crack transited to long crack when its length reached 10 times the grain size. 展开更多
关键词 Fatigue CRACK INITIATION SMALL CRACK CRACK growth rate GRAIN size effect High temperature
Slow Quasi-Periodic Curves and Spiral Cracks in Chalcogenide Glass Thin Films 预览
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作者 Myroslav Kozak Vladimir Zhikharev +1 位作者 Vasyl Loya Vasyl Fedelesh 《材料科学与工程:中英文A版》 2019年第3期109-115,共7页
In the paper,thin films(1.5÷2.5μm thick)of As2S3 and As2Se3 chalcogenide glasses were investigated.The propagation of slow curves cracks in real time was observed,as well as circular Hertz cracks,the growth of w... In the paper,thin films(1.5÷2.5μm thick)of As2S3 and As2Se3 chalcogenide glasses were investigated.The propagation of slow curves cracks in real time was observed,as well as circular Hertz cracks,the growth of which is an increase in the diameter of the crack in time.All crack patterns known in the literature were observed.Research shows the spiral crack is a consequence of the superposition of the Hertz crack and the straight crack.The principle of coordination of stress relieving during the formation of patterns is formulated.Authors have done a lot of research work.And authors have drawn some meaningful conclusions. 展开更多
关键词 CHALCOGENIDE glasses CRACK patterns SPIRAL CRACK Hertz CRACK
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Edge crack growth of mortar plate specimens under uniaxial loading tests 预览
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作者 Zhenghong Huang Shouchun Deng +1 位作者 Haibo Li Hong Zuo 《岩石力学与岩土工程学报:英文版》 CSCD 2019年第2期300-313,共14页
In this paper,a compression-to-tension conversion technique is developed by applying predominant mode I loading test,using a servo-controlled compression system.The technique is applied to thin mortar plate specimens ... In this paper,a compression-to-tension conversion technique is developed by applying predominant mode I loading test,using a servo-controlled compression system.The technique is applied to thin mortar plate specimens of different widths that include a prefabricated crack on either a single side to facilitate unilateral crack propagation,or prefabricated cracks positioned on both sides asymmetrically with respect to the specimen midpoint to facilitate bilateral crack propagation under direct tensile stress with a loading rate of 0.001 mm/s.The results show that the main pathways of unilateral crack propagation governing specimen failure are fluctuated locally,but present an approximately straight line overall in the absence of pre-existing internal defects.However,the pathways of bilateral crack propagation are relatively complex,although they present similar characteristics.Analysis results suggest that bilateral crack propagation can be basically divided into three stages,i.e.a stage of linear propagation,a stage representing deviation from the other crack,and a stage where one crack approaches either the other crack or approaches the opposite edge of the specimen,and thereby forming a continuous crack through the specimen.In addition,the stressestrain curves of bilateral crack specimens do not vary significantly around the point of peak stress prior to specimen failure,which means that the specimens do not fail instantaneously. 展开更多
关键词 MORTAR PLATE SPECIMEN Direct tension test Interaction CRACK CRACK path CRACK PROPAGATION Stressestrain CURVE
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直齿圆柱齿轮分度圆的裂纹损伤机理研究 预览
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作者 翁武燕 吴育仁 《机电工程》 CAS 北大核心 2019年第6期555-561,共7页
针对齿轮分度圆位置长期处于交变载荷状态容易产生疲劳裂纹的问题,综合考虑齿轮、转子和轴承之间的耦合关系,建立了十二自由度齿轮—转子—轴承弯扭耦合非线性动力学模型,并分析了分度圆裂纹对齿轮副时变啮合刚度的影响。采用Runge-kutt... 针对齿轮分度圆位置长期处于交变载荷状态容易产生疲劳裂纹的问题,综合考虑齿轮、转子和轴承之间的耦合关系,建立了十二自由度齿轮—转子—轴承弯扭耦合非线性动力学模型,并分析了分度圆裂纹对齿轮副时变啮合刚度的影响。采用Runge-kutta法求解了齿轮传动系统的运动微分方程,获得了分度圆裂纹损伤状态下系统的动态响应,研究了系统动态响应中的无量纲参数指标。研究结果表明:当分度圆处存在裂纹损伤时,齿轮系统时—频域上均呈现相应的损伤特征,振动信号序列中的峭度指标、裕度因子、峰值因子和脉冲因子均随裂纹的加深而增大;研究可为分度圆处裂纹损伤的演化机理分析和齿轮故障诊断研究提供理论基础。 展开更多
关键词 直齿轮 裂纹 时-频特性 裂纹损伤
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Deformation field and crack analyses of concrete using digital image correlation method
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作者 Yijie HUANG Xujia HE +1 位作者 Qing WANG Jianzhuang XIAO 《结构与土木工程前沿:英文版》 EI CSCD 2019年第5期1183-1199,共17页
The study on the deformation distribution and crack propagation of concrete under axial compression was conducted by the digital image correlation (DIC) method. The main parameter in this test is the water-cement (fT/... The study on the deformation distribution and crack propagation of concrete under axial compression was conducted by the digital image correlation (DIC) method. The main parameter in this test is the water-cement (fT/C) ratio. The novel analysis process and numerical program for DIC method were established. The displacements and strains of coarse aggregate, and cement mortar and interface transition zone (ITZ) were obtained and verified by experimental results. It was found that the axial displacement distributed non-uniformly during the loading stage, and the axial displacements of ITZs and cement mortar were larger than that of coarse aggregates before the occurrence of macrocracks. The effect of W/C on the horizontal displacement was not obvious. Test results also showed that the transverse and shear deformation concentration areas (DCAs) were formed when stress reached 30%-40% of the peak stress. The transverse and shear DCAs crossed the cement mortar, and ITZs and coarse aggregates. However, the axial DCA mainly surrounded the coarse aggregate. Generally, the higher W/C was, the more size and number of DCAs were. The crack propagations of specimens varied with the variation of W/C. The micro-crack of concrete mainly initiated in the ITZs, irrespective of the W/C. The number and distribution range of cracks in concrete with high W/C were larger than those of cracks in specimen adopting low W/C. However, the value and width of eraeks in high W/C specimen were relatively small. The W/C had an obvious effect on the characteristics of concrete deterioration. Finally, the characteristics of crack was also evaluated by comparing the calculated results. 展开更多
关键词 DEFORMATION filed distribution CRACK development digital image CORRELATION method mechanical properties water-cement RATIO characteristics of DEFORMATION and CRACK
40Mn2圆钢热顶锻开裂原因分析 预览
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作者 文承 《福建冶金》 2019年第6期38-40,共3页
本文针对40Mn2圆钢1/3热顶锻严重开裂问题,运用高倍显微镜、扫描电镜、能谱仪等检测设备,结合钢坯低倍酸洗,从坯到材系统分析,综合分析发现造成圆钢表面裂纹的重要原因是钢坯存在皮下裂纹、柱状晶较发达等低倍缺陷。为冶炼生产工艺优化... 本文针对40Mn2圆钢1/3热顶锻严重开裂问题,运用高倍显微镜、扫描电镜、能谱仪等检测设备,结合钢坯低倍酸洗,从坯到材系统分析,综合分析发现造成圆钢表面裂纹的重要原因是钢坯存在皮下裂纹、柱状晶较发达等低倍缺陷。为冶炼生产工艺优化提供依据,从而实现40Mn2批量稳定生产。 展开更多
关键词 40Mn2 热顶锻 裂纹 皮下裂纹
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High-temperature fracture behavior of MnS inclusions based on GTN model
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作者 Xin-gang Liu Can Wang +1 位作者 Qing-feng Deng Bao-feng Guo 《钢铁研究学报:英文版》 SCIE EI CAS CSCD 2019年第9期941-952,共12页
The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image a... The influence of the MnS plastic inclusion on the accumulation of internal damage was considered, and the Gurson– Tvergaard–Needleman (GTN) model was calibrated based on the finite element inverse method and image analysis method using ABAQUS and GTN models. The modified GTN damage model was used to simulate the initiation and propagation of cracks in an as-cast 304 stainless steel with MnS inclusions at 900 C. The simulation results agreed well with the experimental results, indicating that the model can be effectively applied to examine the high-temperature fracture behavior of MnS inclusions. The simulation and high-temperature tensile test results revealed that MnS inclusions increased the number of holes initiation and the probability of hole polymerization, reduced the crack propagation resistance, accelerated the occurrence of material fracture behavior, and were closely related to the stress state at high temperatures. When the stress triaxiality was low, the plastic strain in the metal matrix was high, and the MnS plastic inclusions accelerated the polymerization of the pores, making metal fracture failure more likely. On the other hand, when the stress triaxiality was high, the stress state in the metal matrix was biased to the tensile state, the plastic strain in the metal matrix was low, and the influence of MnS plastic inclusions on the fracture behavior was not evident. 展开更多
关键词 MNS inclusion GTN model Tension High-temperature fracture behavior CRACK INITIATION CRACK propagation Stress
树种及背面裂隙对多层实木复合地板表板开裂的影响
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作者 余康 徐耀飞 +1 位作者 李星 李黎 《木材加工机械》 2019年第1期8-12,共5页
为了探究多层实木复合地板常用树种、背面裂隙对多层实木复合地板表板开裂的影响,以不同树种、背面裂隙度为影响因素,采用冷热循环试验,以表板裂隙条数为衡量标准讨论了多层实木复合地板表板开裂情况。结果表明:试验采用的三个树种均会... 为了探究多层实木复合地板常用树种、背面裂隙对多层实木复合地板表板开裂的影响,以不同树种、背面裂隙度为影响因素,采用冷热循环试验,以表板裂隙条数为衡量标准讨论了多层实木复合地板表板开裂情况。结果表明:试验采用的三个树种均会产生背面裂隙,黑胡桃表板的裂隙度最小,山核桃表板的裂隙度最大;所用单板背面裂隙度越大,表板开裂越严重。 展开更多
关键词 树种 裂隙 表板开裂
动态加载率对巷道内裂纹扩展速度及动态起裂韧度的影响 预览
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作者 周磊 朱哲明 +2 位作者 董玉清 应鹏 王磊 《振动与冲击》 EI CSCD 北大核心 2019年第4期129-136,共8页
在巷道的钻爆法掘进过程中,巷道围岩周围将诱发较多的径向裂隙。为了研究不同冲击载荷作用下巷道内裂纹扩展速度及起裂韧度的变化规律,采用落锤冲击试验机对裂纹巷道模型试件进行冲击加载,模型试件选用青砂岩制作;试验中,采用裂纹扩展... 在巷道的钻爆法掘进过程中,巷道围岩周围将诱发较多的径向裂隙。为了研究不同冲击载荷作用下巷道内裂纹扩展速度及起裂韧度的变化规律,采用落锤冲击试验机对裂纹巷道模型试件进行冲击加载,模型试件选用青砂岩制作;试验中,采用裂纹扩展计进行裂纹扩展速度及起裂时间的测定,对不同冲击高度下裂纹扩展速度及起裂时间进行分析;随后采用ABAQUS有限元程序结合试验-数值法计算巷道模型试样在不同动态加载率作用下的动态起裂韧度,并对起裂韧度的变化规律进行统计分析。得出如下结论:①巷道内预制裂纹的扩展速度随着动态加载高度的增加而增大,随后逐渐趋于稳定,实测裂纹扩展速度略小于0.38倍砂岩纵波波速;②巷道内预制裂纹的起裂时间,随着动态加载率的增加呈缓慢下降的趋势,降低幅度范围约为50μs;③随着动态加载率的增加,巷道内裂纹的动态起裂韧度逐渐增大,上升趋势也逐渐加大。 展开更多
关键词 巷道 裂纹 动态加载率 裂纹扩展速度 起裂韧度
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多层界面相陶瓷基复合材料裂纹偏转机制模拟
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作者 方光武 高希光 宋迎东 《航空动力学报》 EI CAS CSCD 北大核心 2019年第8期1805-1812,共8页
针对多层界面相陶瓷基复合材料(CMCs)裂纹偏转机制进行了有限元模拟。在圆柱单胞模型中,按照界面相各亚层的实际厚度建立多层界面相几何模型,然后赋予各亚层对应的组分材料参数,获取轴对称有限元模型。在此基础上,采用虚拟裂纹闭合技术(... 针对多层界面相陶瓷基复合材料(CMCs)裂纹偏转机制进行了有限元模拟。在圆柱单胞模型中,按照界面相各亚层的实际厚度建立多层界面相几何模型,然后赋予各亚层对应的组分材料参数,获取轴对称有限元模型。在此基础上,采用虚拟裂纹闭合技术(VCCT)分别计算基体裂纹在界面相处偏转与穿透两种情形的能量释放率Gd和Gp,根据断裂力学准则实现对裂纹在多层界面相内部偏转机制的分析。可以看出:各向异性界面相比各向同性界面相内部的Gd/Gp比值更大,更利于裂纹偏转的发生;总厚度相同的多层界面相与单层界面相相比,其内部的Gd/Gp比值更高,裂纹在其内部发生偏转的机会更多,且五层界面相(PyC/SiC/PyC/SiC/PyC)比三层界面相(PyC/SiC/PyC)更利于裂纹发生偏转。 展开更多
关键词 陶瓷基复合材料 多层界面相 裂纹 偏转 虚拟裂纹闭合技术(VCCT)
基于能量释放率的Ⅱ型裂纹分叉研究
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作者 多依丽 谢禹钧 +2 位作者 海军 刘明 孙麟 《力学季刊》 CSCD 北大核心 2019年第1期167-174,共8页
裂纹尖端存在奇异应力场,该类奇异应力场所具有的高度应力集中将导致裂纹开裂.本文应用典型的J积分理论来划分裂纹尖端的积分路径,基于能量释放率理论对Ⅱ型裂纹尖端的复杂分叉情况进行研究.通过所建立的断裂模型求解出Ⅱ型裂纹多种分... 裂纹尖端存在奇异应力场,该类奇异应力场所具有的高度应力集中将导致裂纹开裂.本文应用典型的J积分理论来划分裂纹尖端的积分路径,基于能量释放率理论对Ⅱ型裂纹尖端的复杂分叉情况进行研究.通过所建立的断裂模型求解出Ⅱ型裂纹多种分叉形式的能量释放率的解析解;导出了各种分叉构型的能量驱动力;提出了各种分叉构型的K-型开裂准则;给出了裂纹分叉的临界开裂角;确定了裂纹的分叉韧性与断裂韧性之间的关系.通过本文研究方法得出的裂纹分叉形式及裂纹分叉临界开裂角与已有实验结果十分吻合. 展开更多
关键词 裂纹 裂纹分叉 J积分 断裂韧性 能量释放率
Effects of microstructure on fatigue crack propagation behavior in a bi-modal TC11 titanium alloy fabricated via laser additive manufacturing
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作者 Yafei Wang Rui Chen +3 位作者 Xu Cheng Yanyan Zhu Jikui Zhang Huaming Wang 《材料科学技术学报:英文版》 SCIE EI CAS CSCD 2019年第2期403-408,共6页
In this study, the crack propagation behaviors in the equiaxed and equiaxed-columnar grain regions of a heat-treated laser add让ive manufacturing (LAM) TC11 alloy w让h a special bi-modal microstructure are investigate... In this study, the crack propagation behaviors in the equiaxed and equiaxed-columnar grain regions of a heat-treated laser add让ive manufacturing (LAM) TC11 alloy w让h a special bi-modal microstructure are investigated. The results indicate that the alloy presents a special bi-modal microstructure that comprises a fork-like primary α(αρ) phase surro un ded by a sec on dary a colony (as) in the β phase matrix after the heat treatment is completed. The samples demonstrate a fast crack growth rate with larger da/dN values through the equiaxed grain sample versus across the equiaxed-columnar grain sample at low AK values (<13.8). The differences that are observed between the crack propagation behaviors (in the crack initiation stage) of the samples can be mostly attributed to the different size and morphology of the ap lamellae and as colony within the grains in the equiaxed and columnar grain regions rather than the grain boundaries. The cracks prefer to grow along the a/p boundary with a smooth propagation route and a fast propagation rate in the equiaxed grain region, where the ap and a clusters have a large size. However, in the columgrain region, small and randomly distributed ap lamellae generate a zigzagshaped propagation path with a reduction in the da/dN value. Additionally, the change in the size of the ap lamellae in the equiaxed grains (heat affected bands, HAB) is also observed to influence the propagation behavior of the crack during the crack initiation stage. 展开更多
关键词 LASER additive manufacturing TC11 titanium alloy MICROSTRUCTURE FATIGUE CRACK propagation path FATIGUE CRACK growth rate
圆形杂质对裂纹扩展的影响 预览
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作者 邢帅兵 王强胜 +1 位作者 生月 江晓禹 《应用数学和力学》 CSCD 北大核心 2019年第2期189-199,共11页
在单轴拉伸载荷作用下,运用分布位错方法对无限大平面内含有一个裂纹和一个任意方向的杂质问题进行求解,得到了裂纹尖端的应力强度因子、应力场以及应变能密度.利用最小应变能密度因子准则来判断裂纹扩展方向.结果显示:软杂质对裂纹尖... 在单轴拉伸载荷作用下,运用分布位错方法对无限大平面内含有一个裂纹和一个任意方向的杂质问题进行求解,得到了裂纹尖端的应力强度因子、应力场以及应变能密度.利用最小应变能密度因子准则来判断裂纹扩展方向.结果显示:软杂质对裂纹尖端应力强度因子、应变能密度和应力场有增强作用,而硬杂质则具有屏蔽作用.在-30°<θ<30°范围内,杂质对裂纹扩展方向的影响较小,而在-90°<θ<-30°或30°<θ<90°范围内,杂质对裂纹扩展方向的影响较大.软杂质对裂纹扩展有吸引作用,而硬杂质具有排斥作用. 展开更多
关键词 杂质 裂纹 分布位错方法 裂纹扩展
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原岩应力对裂纹动态断裂行为的影响规律研究
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作者 邓帅 朱哲明 +3 位作者 王磊 牛草原 周磊 应鹏 《岩石力学与工程学报》 EI CAS CSCD 北大核心 2019年第10期1989-1999,共11页
深地岩体赋存于高原岩应力环境,常常受到动力扰动。为了研究原岩应力对裂纹动态断裂行为的影响,使用侧向加压设备赋予岩石初始应力以模拟原岩应力,利用中低速落锤冲击设备实施冲击实验。在冲击实验中使用裂纹扩展计(CPG)获取裂纹起裂时... 深地岩体赋存于高原岩应力环境,常常受到动力扰动。为了研究原岩应力对裂纹动态断裂行为的影响,使用侧向加压设备赋予岩石初始应力以模拟原岩应力,利用中低速落锤冲击设备实施冲击实验。在冲击实验中使用裂纹扩展计(CPG)获取裂纹起裂时刻和裂纹扩展速度,同时使用AUTODYN有限差分法软件和ABAQUS有限元软件实施数值模拟研究。实验和数值模拟结果显示,垂直于裂纹面的原岩应力改变了裂纹起裂时间、裂纹扩展速度和裂纹扩展长度,但是对临界动态应力强度因子没有影响。垂直于裂纹面的原岩应力使得裂纹起裂时间出现滞后现象,并且原岩应力越大裂纹扩展速度越低,裂纹扩展长度越短。 展开更多
关键词 岩石力学 原岩应力 裂纹 起裂时刻 扩展速度 临界动态应力强度因子
锚具失效后后张法预应力简支梁试验研究 预览
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作者 周凌宇 薛宪鑫 尹国伟 《中南大学学报:自然科学版》 EI CAS CSCD 北大核心 2019年第1期100-107,共8页
为研究后张法预应力混凝土简支梁桥拆除锚具后残余预应力对结构抗力的贡献,通过2根切除锚具试验梁和1根对照梁的静载试验,研究拆除锚具后预应力梁的受力性能。研究结果表明:拆除锚具后,预应力钢束通过灌浆材料对混凝土具有纵向压缩作用... 为研究后张法预应力混凝土简支梁桥拆除锚具后残余预应力对结构抗力的贡献,通过2根切除锚具试验梁和1根对照梁的静载试验,研究拆除锚具后预应力梁的受力性能。研究结果表明:拆除锚具后,预应力钢束通过灌浆材料对混凝土具有纵向压缩作用,混凝土与普通钢筋对结构的贡献从端部到跨中逐渐减小;切除锚具只影响开裂荷载和裂缝开展宽度,并不影响梁体最后的裂缝分布形式和跨中混凝土破坏形态,但会降低极限荷载;达到屈服荷载后,试验梁的预应力钢束与孔道灌浆开始脱离,试验梁承载能力降低,试验梁的抗裂性能以及结构延性明显降低;开裂后,在同样荷载增量下,试验梁中预应力钢束承担更多的荷载。建议在实际拆桥工程中,当拆除锚具后,在达到结构屈服荷载之前可按正常状态考虑预应力钢束对结构的作用. 展开更多
关键词 后张法 预应力简支梁 锚具失效 裂缝 承载力 抗裂性能 延性
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钢-UHPC轻型组合桥面结构试验及裂缝宽度计算研究
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作者 邵旭东 罗军 +2 位作者 曹君辉 樊伟 王衍 《土木工程学报》 EI CSCD 北大核心 2019年第3期61-75,共15页
为研究钢-UHPC轻型组合桥面结构的裂缝特征,并评估现有规范公式对钢-UHPC轻型组合桥面结构裂缝宽度计算的适用性,综合考虑配筋率、保护层厚度、UHPC层厚度和栓钉间距4个因素,对40个钢-UHPC组合板进行正交试验。试验结果表明:未配筋钢-U... 为研究钢-UHPC轻型组合桥面结构的裂缝特征,并评估现有规范公式对钢-UHPC轻型组合桥面结构裂缝宽度计算的适用性,综合考虑配筋率、保护层厚度、UHPC层厚度和栓钉间距4个因素,对40个钢-UHPC组合板进行正交试验。试验结果表明:未配筋钢-UHPC组合构件裂缝数量较少,且开裂后裂缝发展较快,密集配筋钢-UHPC组合构件裂缝细而密,在裂缝宽度为0.15mm之前,荷载-最大裂缝宽度曲线大致呈直线,钢筋屈服后,裂缝发展较快,当裂缝宽度达到0.2mm以后,裂缝数量基本趋于不变;配筋率和保护层厚度对开裂应力和平均裂缝间距的影响较大,UHPC层厚度对其影响不大。根据现有规范公式计算钢-UHPC组合结构裂缝宽度过于保守,文中根据钢-UHPC组合桥面结构的特点和裂缝扩展特征,提出钢筋应力的计算方法,计算结果和试验实测结果吻合较好;在现有规范公式的基础上,对平均裂缝间距计算公式和钢筋应变不均匀系数计算公式进行了修正,给出钢-UHPC轻型组合结构最大裂缝宽度建议公式,建议公式的计算值和试验值吻合较好。 展开更多
关键词 超高性能混凝土(UHPC) 轻型组合桥面 受弯性能 裂缝 裂缝宽度计算
Numerical Simulation and Experimental Studies on Elastic-Plastic Fatigue Crack Growth 预览
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作者 Jie Wang Wei Jiang Qi Wang 《工程与科学中的计算机建模(英文)》 2019年第2期377-395,共19页
A elastic-plastic fatigue crack growth(FCG)finite element model was developed for predicting crack growth rate under cyclic load.The propagation criterion for this model was established based on plastically dissipated... A elastic-plastic fatigue crack growth(FCG)finite element model was developed for predicting crack growth rate under cyclic load.The propagation criterion for this model was established based on plastically dissipated energy.The crack growth simulation under cyclic computation was implemented through the ABAQUS scripting interface.The predictions of this model are in good agreement with the results of crack propagation experiment of compact tension specimen made of 304 stainless steel.Based on the proposed model,the single peak overload retardation effect of elastic-plastic fatigue crack was analyzed.The results shows that the single peak overload will reduce the accumulation rate of plastic energy dissipation of elements at crack tip plastic zone,so that crack growth will be arrested.The crack growth rate will not recover until the crack tip exceed the affected region.Meanwhile,the crack growth rate is mainly determined by the amplitude rather than the mean load under the condition of small scale yielding.The proposed model would be helpful for predicting the growth rate of mode I elastic-plastic fatigue crack. 展开更多
关键词 Plastic dissipation energy elastic-plastic fatigue crack finite element model crack growth rate.
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CFRP板加固含I型裂纹混凝土的断裂扩展规律 预览
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作者 韩艳 王龙龙 刘志浩 《材料导报》 EI CAS CSCD 北大核心 2019年第S02期304-308,共5页
制作两个含Ⅰ型预制裂缝的混凝土试件并进行三点弯曲试验,在其中一个试件底面粘贴碳纤维板进行加固,以CCD相机为观测系统,用数字散斑技术对混凝土试件预制裂缝尖端的扩展特征、裂缝尖端张开位移及应力强度因子等进行分析,研究了碳纤维... 制作两个含Ⅰ型预制裂缝的混凝土试件并进行三点弯曲试验,在其中一个试件底面粘贴碳纤维板进行加固,以CCD相机为观测系统,用数字散斑技术对混凝土试件预制裂缝尖端的扩展特征、裂缝尖端张开位移及应力强度因子等进行分析,研究了碳纤维复合材料(CFRP)板的加固效果。结果表明:外贴CFRP板加固能增加混凝土的抗弯刚度,显著提高混凝土的抗弯承载力,延缓裂缝开展;在相同荷载作用下,外贴CFRP板加固可以减小试件预制裂缝扩展宽度和距离;外CFRP板加固含Ⅰ型预制裂缝混凝土试件的裂缝尖端应力强度因子增加速度小于相同的未粘贴CFRP板混凝土试件。 展开更多
关键词 散斑 碳纤维复合材料(CFRP) 裂缝 裂尖张开位移 应力强度因子
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碳纤维复材筋增强混凝土梁受剪性能试验研究
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作者 陈科 张春涛 王磊 《建筑科学》 CSCD 北大核心 2019年第1期57-63,共7页
为研究碳纤维复材(CFRP)筋增强混凝土梁的受剪性能,以配箍率和剪跨比为试验变量,进行了3根两点集中荷载作用下的CFRP筋简支梁受剪试验,对CFRP筋梁的裂缝发展、破坏形态、斜向开裂荷载、跨中挠度、受剪承载力等进行了观察和测量。试验结... 为研究碳纤维复材(CFRP)筋增强混凝土梁的受剪性能,以配箍率和剪跨比为试验变量,进行了3根两点集中荷载作用下的CFRP筋简支梁受剪试验,对CFRP筋梁的裂缝发展、破坏形态、斜向开裂荷载、跨中挠度、受剪承载力等进行了观察和测量。试验结果表明:CFRP筋梁的剪切破坏由贯通斜裂缝所致,配箍率和剪跨比对斜向开裂荷载和极限承载力影响显著。将本次试验值与我国《纤维增强复合材料建设工程应用技术规范》(GB 50608-2010)、美国规范ACI 440. 1R-06和英国规范BISEI-1999规范的计算值进行对比分析,结合此次试验结果和国内外搜集的70组已有试验数据,对我国GB 50608-2010的受剪承载力计算公式的准确性和安全性进行探讨,提出了一种计算CFRP筋梁抗剪承载力的建议公式。 展开更多
关键词 碳纤维复材筋混凝土梁 受剪承载力 裂缝 静力试验
熔覆材料对高速钢刀具激光熔覆断屑台裂纹及硬度的影响 预览
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作者 吴毛朝 于爱兵 +3 位作者 魏金龙 陈秋洁 孙磊 袁建东 《中国机械工程》 CAS CSCD 北大核心 2019年第13期1607-1612,1620共7页
应用激光粉末熔覆技术,在高速钢车刀的前刀面上制备出断屑台。通过切削实验,对比普通高速钢车刀和含激光熔覆断屑台车刀的断屑效果,观察激光粉末熔覆断屑台的金相组织和形貌,测试激光粉末熔覆断屑台的热膨胀系数、物相和显微硬度。研究... 应用激光粉末熔覆技术,在高速钢车刀的前刀面上制备出断屑台。通过切削实验,对比普通高速钢车刀和含激光熔覆断屑台车刀的断屑效果,观察激光粉末熔覆断屑台的金相组织和形貌,测试激光粉末熔覆断屑台的热膨胀系数、物相和显微硬度。研究结果表明:具有激光熔覆断屑台的高速钢车刀,在切削过程中能够减小切屑的卷曲半径,从而使切屑更容易折断,实现有效断屑。用M2/WC-12Co粉末制作激光熔覆断屑台,能够实现激光熔覆层与高速钢基体的良好冶金结合,熔覆层无熔覆裂纹缺陷,熔覆层的硬度与高速钢车刀基体相近。M2/WC-12Co激光熔覆粉末适于制作高速钢刀具的激光熔覆断屑台。 展开更多
关键词 激光熔覆 刀具 断屑 裂纹 熔覆粉末
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