Critical crack tip opening displacement (CTODc) of concrete using experimental and analytical evaluation with seven different compressive strengths ranging from 30 up to 150 MPa was studied based on two types of fract...Critical crack tip opening displacement (CTODc) of concrete using experimental and analytical evaluation with seven different compressive strengths ranging from 30 up to 150 MPa was studied based on two types of fracture tests:three-point bending (TPB) and wedge splitting (WS).In the tests,the values of CTODc were experimentally recorded using a novel technique,in which fiber Bragg grating (FBG) sensors were used,and two traditional techniques,in which strain gauges and clip gauges were deployed.The values of CTODc of tested concrete were also predicted using two existing analytical formulae proposed by JENQ & SHAH and XU,respectively.It is found that the values of CTODc obtained by both experimental measurements and analytical formulae exhibit a negligible variation as the compressive strength of concrete increases,and the test geometry adopted has little impact on the value of CTODc.Regarding the experimental measurement of CTODc,the clip gauge method generally leads to a larger value of CTODc and shows a more significant scatter as compared with the other two methods,while the strain gauge method leads to a slightly lower CTODc as compared with the FBG sensor method.The analytical formula proposed by JENQ and SHAH is found to generally lead to an overestimation,while the analytical formula proposed by XU shows a good accuracy.展开更多
依据BS7448标准对DH36药芯焊丝气保焊接头进行了裂纹尖端张开位移(crack tip opening displacement,CTOD)试验,通过对接头进行组织、断口分析,同时对预制疲劳裂纹过程进行有限元模拟分析,研究不同预制疲劳裂纹最大载荷对CTOD值的影响....依据BS7448标准对DH36药芯焊丝气保焊接头进行了裂纹尖端张开位移(crack tip opening displacement,CTOD)试验,通过对接头进行组织、断口分析,同时对预制疲劳裂纹过程进行有限元模拟分析,研究不同预制疲劳裂纹最大载荷对CTOD值的影响.结果表明,预制疲劳裂纹最大载荷对CTOD试验结果影响很大.当预制疲劳裂纹最大载荷远小于BS7448标准规定的最大值时,试验过程易出现突跃,即pop-in现象,从而得到较小的CTOD值;反之,当预制疲劳裂纹最大载荷接近或超过BS7448标准规定的最大值时,pop-in现象减弱、延迟或者消失,得到较大的CTOD值.故而为了保证试验结果的可靠性,标准中应对预制疲劳裂纹载荷敏感的接头更严格的规定其最大值.展开更多
以船用A36钢板为试验材料,开展紧凑拉伸试验裂纹尖端张开位移δ(crack tip opening displacement,CTOD)的双引伸计测试方法研究。结果显示,采用双引伸计方法可直接测定旋转因子r及δ,计算得到名义应力σ与裂纹尖端张开位移塑性分量δp(p...以船用A36钢板为试验材料,开展紧凑拉伸试验裂纹尖端张开位移δ(crack tip opening displacement,CTOD)的双引伸计测试方法研究。结果显示,采用双引伸计方法可直接测定旋转因子r及δ,计算得到名义应力σ与裂纹尖端张开位移塑性分量δp(plastic component of CTOD)的相关性曲线。与国标GB/T 21143—2007测试方法相比,双引伸计法对δp的测试精度更高;与EPRI(Electronic Power Research Institute)计算方法相比,双引伸计法对σ—δp关系曲线的确定更为直接可靠。展开更多
基金Project(50438010) supported by the Key Program of the National Natural Science Foundation of ChinaProject(JGZXJJ2006-13) supported by the Research and Application Programs of Key Technologies for Major Constructions in the South-North Water Transfer Project Construction in China
文摘Critical crack tip opening displacement (CTODc) of concrete using experimental and analytical evaluation with seven different compressive strengths ranging from 30 up to 150 MPa was studied based on two types of fracture tests:three-point bending (TPB) and wedge splitting (WS).In the tests,the values of CTODc were experimentally recorded using a novel technique,in which fiber Bragg grating (FBG) sensors were used,and two traditional techniques,in which strain gauges and clip gauges were deployed.The values of CTODc of tested concrete were also predicted using two existing analytical formulae proposed by JENQ & SHAH and XU,respectively.It is found that the values of CTODc obtained by both experimental measurements and analytical formulae exhibit a negligible variation as the compressive strength of concrete increases,and the test geometry adopted has little impact on the value of CTODc.Regarding the experimental measurement of CTODc,the clip gauge method generally leads to a larger value of CTODc and shows a more significant scatter as compared with the other two methods,while the strain gauge method leads to a slightly lower CTODc as compared with the FBG sensor method.The analytical formula proposed by JENQ and SHAH is found to generally lead to an overestimation,while the analytical formula proposed by XU shows a good accuracy.
文摘依据BS7448标准对DH36药芯焊丝气保焊接头进行了裂纹尖端张开位移(crack tip opening displacement,CTOD)试验,通过对接头进行组织、断口分析,同时对预制疲劳裂纹过程进行有限元模拟分析,研究不同预制疲劳裂纹最大载荷对CTOD值的影响.结果表明,预制疲劳裂纹最大载荷对CTOD试验结果影响很大.当预制疲劳裂纹最大载荷远小于BS7448标准规定的最大值时,试验过程易出现突跃,即pop-in现象,从而得到较小的CTOD值;反之,当预制疲劳裂纹最大载荷接近或超过BS7448标准规定的最大值时,pop-in现象减弱、延迟或者消失,得到较大的CTOD值.故而为了保证试验结果的可靠性,标准中应对预制疲劳裂纹载荷敏感的接头更严格的规定其最大值.
文摘以船用A36钢板为试验材料,开展紧凑拉伸试验裂纹尖端张开位移δ(crack tip opening displacement,CTOD)的双引伸计测试方法研究。结果显示,采用双引伸计方法可直接测定旋转因子r及δ,计算得到名义应力σ与裂纹尖端张开位移塑性分量δp(plastic component of CTOD)的相关性曲线。与国标GB/T 21143—2007测试方法相比,双引伸计法对δp的测试精度更高;与EPRI(Electronic Power Research Institute)计算方法相比,双引伸计法对σ—δp关系曲线的确定更为直接可靠。
