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
Focused on the girth weld of a φ762 x 28.6 mm （X65） offshore UOE pipe, the fracture toughness properties at different weld joint positions were tested. Meanwhile,the largest size of different cracks under service c...Focused on the girth weld of a φ762 x 28.6 mm （X65） offshore UOE pipe, the fracture toughness properties at different weld joint positions were tested. Meanwhile,the largest size of different cracks under service condition was calculated by using CRACKWISE. The service life of the UOE pipe with postulated crack-like flaws was calculated by considering various fatigue factors, such as vibrations caused by ocean current and fluctuations of inner pressure. The assessment process and results can be used to direct the repair of weld flaws laid in pipes or to assess the reliability of in-serving pipes.展开更多
根据BSI 7448 Part Ⅰ标准,测定了海洋平台用钢E36以裂纹尖端张开位移(CTOD)为表征的韧脆转变温度曲线.通过改变试样厚度,研究面外拘束对韧脆转变温度区间的影响并分析了其变化规律.结果表明,E36钢具有典型的韧脆转变特征,其韧脆转变温...根据BSI 7448 Part Ⅰ标准,测定了海洋平台用钢E36以裂纹尖端张开位移(CTOD)为表征的韧脆转变温度曲线.通过改变试样厚度,研究面外拘束对韧脆转变温度区间的影响并分析了其变化规律.结果表明,E36钢具有典型的韧脆转变特征,其韧脆转变温度曲线可以用Boltzmann函数进行拟合,具有良好的相关性;试样厚度越大,韧脆转变温度越高,断裂性能下降.通过有限元模拟分析三维裂纹尖端应力状态,选择了面外拘束参数T_z,用来阐述厚度效应对韧脆转变温度的影响,具有良好的相关性.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Focused on the girth weld of a φ762 x 28.6 mm （X65） offshore UOE pipe, the fracture toughness properties at different weld joint positions were tested. Meanwhile,the largest size of different cracks under service condition was calculated by using CRACKWISE. The service life of the UOE pipe with postulated crack-like flaws was calculated by considering various fatigue factors, such as vibrations caused by ocean current and fluctuations of inner pressure. The assessment process and results can be used to direct the repair of weld flaws laid in pipes or to assess the reliability of in-serving pipes.
文摘根据BSI 7448 Part Ⅰ标准,测定了海洋平台用钢E36以裂纹尖端张开位移(CTOD)为表征的韧脆转变温度曲线.通过改变试样厚度,研究面外拘束对韧脆转变温度区间的影响并分析了其变化规律.结果表明,E36钢具有典型的韧脆转变特征,其韧脆转变温度曲线可以用Boltzmann函数进行拟合,具有良好的相关性;试样厚度越大,韧脆转变温度越高,断裂性能下降.通过有限元模拟分析三维裂纹尖端应力状态,选择了面外拘束参数T_z,用来阐述厚度效应对韧脆转变温度的影响,具有良好的相关性.
