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
Based on a digital image correlation（DIC）method with the measurements of a high speed crack＇s displacement and strain fields,a technique to accurately and automatically locate its crack tip has been developed.The c...Based on a digital image correlation（DIC）method with the measurements of a high speed crack＇s displacement and strain fields,a technique to accurately and automatically locate its crack tip has been developed.The crack tip is identified by finding the abrupt jump on the opening（or dislocation）curve of a point on the trace of the crack propagation,while the opening is measured through a virtual extensometer technique and the abrupt jump is identified by finding the peak on the curve.The method was verified using a specially designed experiment and applied to measure the critical crack tip opening angle of a rock sample.Because the involvement of analytical models has been avoided and then the good performance could be ensured for low resolution speckle images,this technique is expected to be very useful in the quantitative study of high speed cracks in experiments using high speed cameras.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
为了寻求更为简单、准确的临界裂纹尖端张开角(CTOAc)测量方法以推广CTOA准则的应用,本文对材料CTOAc的测量方法进行了研究。根据CTOA的性质及Gteborgs Kungliga Segel Sllskap(GKSS)提出的CTOAc估算方法导出了两种不同裂纹尖端张...为了寻求更为简单、准确的临界裂纹尖端张开角(CTOAc)测量方法以推广CTOA准则的应用,本文对材料CTOAc的测量方法进行了研究。根据CTOA的性质及Gteborgs Kungliga Segel Sllskap(GKSS)提出的CTOAc估算方法导出了两种不同裂纹尖端张开位移(CTOD)定义之间的关系,并进一步得到一种基于准静态拉伸试验的CTOAc测量方法,该方法与GKSS提出的估算方法相等效但更加简单。为了验证准静态拉伸试验法的准确性,对7B04 M(T)试样进行了静态拉伸试验,并使用上述两种方法估算7B04的CTOAc,结果表明两种方法估算出的CTOAc仅相差1%。同时分别采用平面应变核模型、平面应力模型对试样进行了弹塑性有限元模拟,模拟结果与试验结果相吻合。展开更多
老龄飞机中由于多裂纹的产生将导致结构剩余寿命大幅削减。针对如飞机机舱上布有沿纵向铆钉接头的隔板结构,文中给出一种分析多部位损伤结构剩余强度的方法。裂纹扩展模型是分析的基础,文中对两类(单参量和三参量)扩展模型进行讨论,给...老龄飞机中由于多裂纹的产生将导致结构剩余寿命大幅削减。针对如飞机机舱上布有沿纵向铆钉接头的隔板结构,文中给出一种分析多部位损伤结构剩余强度的方法。裂纹扩展模型是分析的基础,文中对两类(单参量和三参量)扩展模型进行讨论,给出裂纹在增量载荷下萌生与稳定扩展的处理方法。基于Irwin和Dugdale裂尖张开位移模型与Swift准则,给出较为完整的分析多部位损伤(multiple site damage,MSD)结构剩余强度的方法。最后,通过对飞机压力舱上的沿纵向铆钉接头的模拟计算,对文中方法进行验证。由分析结果可知,采用文中方法计算得到的剩余强度值与试验值符合得较好,该方法能较为准确有效地对复杂MSD结构的剩余强度进行分析。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.
基金Supported by the National Natural Science Foundation of China(11172039,11402023)the Fundamental Research Funding of BIT(20120142021)the State Key Laboratory of Earthquake Dynamics(LED2011B03)
文摘Based on a digital image correlation（DIC）method with the measurements of a high speed crack＇s displacement and strain fields,a technique to accurately and automatically locate its crack tip has been developed.The crack tip is identified by finding the abrupt jump on the opening（or dislocation）curve of a point on the trace of the crack propagation,while the opening is measured through a virtual extensometer technique and the abrupt jump is identified by finding the peak on the curve.The method was verified using a specially designed experiment and applied to measure the critical crack tip opening angle of a rock sample.Because the involvement of analytical models has been avoided and then the good performance could be ensured for low resolution speckle images,this technique is expected to be very useful in the quantitative study of high speed cracks in experiments using high speed cameras.
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.
文摘为了寻求更为简单、准确的临界裂纹尖端张开角(CTOAc)测量方法以推广CTOA准则的应用,本文对材料CTOAc的测量方法进行了研究。根据CTOA的性质及Gteborgs Kungliga Segel Sllskap(GKSS)提出的CTOAc估算方法导出了两种不同裂纹尖端张开位移(CTOD)定义之间的关系,并进一步得到一种基于准静态拉伸试验的CTOAc测量方法,该方法与GKSS提出的估算方法相等效但更加简单。为了验证准静态拉伸试验法的准确性,对7B04 M(T)试样进行了静态拉伸试验,并使用上述两种方法估算7B04的CTOAc,结果表明两种方法估算出的CTOAc仅相差1%。同时分别采用平面应变核模型、平面应力模型对试样进行了弹塑性有限元模拟,模拟结果与试验结果相吻合。
文摘老龄飞机中由于多裂纹的产生将导致结构剩余寿命大幅削减。针对如飞机机舱上布有沿纵向铆钉接头的隔板结构,文中给出一种分析多部位损伤结构剩余强度的方法。裂纹扩展模型是分析的基础,文中对两类(单参量和三参量)扩展模型进行讨论,给出裂纹在增量载荷下萌生与稳定扩展的处理方法。基于Irwin和Dugdale裂尖张开位移模型与Swift准则,给出较为完整的分析多部位损伤(multiple site damage,MSD)结构剩余强度的方法。最后,通过对飞机压力舱上的沿纵向铆钉接头的模拟计算,对文中方法进行验证。由分析结果可知,采用文中方法计算得到的剩余强度值与试验值符合得较好,该方法能较为准确有效地对复杂MSD结构的剩余强度进行分析。
