An experimental-numerical method for measuring dynamic crack propagatingvelocities under stress wave loading is established in this paper. The experiments of thethree-point bend specimen are done on the improved Hopki...An experimental-numerical method for measuring dynamic crack propagatingvelocities under stress wave loading is established in this paper. The experiments of thethree-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point,dynamic load and instantaneous crack length are measured, then crack propagating velocities arecalculated. Experiments on 40Cr steel show that the results given by this method have a goodagreement with that obtained by the resistance fracture gage method. Therefore this method isfeasible for measuring crack propagating velocities under high loading rate and will have wideapplication.展开更多
A real-time quantitative optical method to characterize crack propagation in colloidal photonic crystal film（CPCF）is developed based on particle deformation models and previous real-time crack observations. The crac...A real-time quantitative optical method to characterize crack propagation in colloidal photonic crystal film（CPCF）is developed based on particle deformation models and previous real-time crack observations. The crack propagation process and temperature dependence of the crack propagation rate in CPCF are investigated. By this method, the crack propagation rate is found to slow down gradually to zero when cracks become more numerous and dense. Meanwhile, with the temperature increasing, the crack propagation rate constant decreases. The negative temperature dependence of the crack propagation rate is due to the increase of van der Waals attraction, which finally results in the decrease of resultant force. The findings provide new insight into the crack propagation process in CPCF.展开更多
Using the complex variable function method and the technique of conformal mapping, the anti-plane shear problem of an elliptic hole with asymmetric colfinear cracks in a one-dimensional hexagonal quasi-crystal is solv...Using the complex variable function method and the technique of conformal mapping, the anti-plane shear problem of an elliptic hole with asymmetric colfinear cracks in a one-dimensional hexagonal quasi-crystal is solved, and the exact analytic solutions of the stress intensity factors （SIFs） for mode Ⅲ problem are obtained. Under the limiting conditions, the present results reduce to the Griffith crack and many new results obtained as well, such as the circular hole with asymmetric collinear cracks, the elliptic hole with a straight crack, the mode T crack, the cross crack and so on. As far as the phonon field is concerned, these results, which play an important role in many practical and theoretical applications, are shown to be in good agreement with the classical results.展开更多
By using the dynamic photoelastic method and our technique of fabricating an internal crack in solid , the scattered waves of incident grazing longitudinal ultrasonic wave pulse by a ribbon-type crack are ob-served an...By using the dynamic photoelastic method and our technique of fabricating an internal crack in solid , the scattered waves of incident grazing longitudinal ultrasonic wave pulse by a ribbon-type crack are ob-served and analyzed . In particular, the distribution of the intensity of the scattered head wave is measured quantitatively . The experimental results fairly agree with the theoretical ones given in ref. [ 1 ] .展开更多
API SPEC5D标准规定的材料性能指标不能反映钻杆抵抗疲劳及腐蚀疲劳的性能。对4个厂家的S135钢级钻杆的材料进行了腐蚀疲劳寿命试验、拉伸性能试验及成分分析。试验结果表明,虽然4种钻杆的化学成分及材料性能都符合标准要求,且材料的拉...API SPEC5D标准规定的材料性能指标不能反映钻杆抵抗疲劳及腐蚀疲劳的性能。对4个厂家的S135钢级钻杆的材料进行了腐蚀疲劳寿命试验、拉伸性能试验及成分分析。试验结果表明,虽然4种钻杆的化学成分及材料性能都符合标准要求,且材料的拉伸强度基本相同,但腐蚀疲劳寿命相差很大。腐蚀疲劳断口观察及断裂机理分析表明,腐蚀疲劳裂纹扩展机理是阳极溶解与氢致开裂共存,氢致开裂加快了疲劳裂纹扩展。材料低倍组织酸洗检验、显微组织分析表明,4种钻杆的金属组织特别是低倍组织有明显差别。低倍组织反映了成分偏析程度、夹杂物含量及分布等。成分偏析及夹杂物导致材料的阳极溶解、特别是氢致开裂速度加快,所以是腐蚀疲劳寿命减少的主要原因。油田数据验证,钻杆材料的低倍组织酸洗检验可作为间接评定钻杆材料腐蚀疲劳性能的方法。展开更多
文摘An experimental-numerical method for measuring dynamic crack propagatingvelocities under stress wave loading is established in this paper. The experiments of thethree-point bend specimen are done on the improved Hopkinson bar. Deflection of loading point,dynamic load and instantaneous crack length are measured, then crack propagating velocities arecalculated. Experiments on 40Cr steel show that the results given by this method have a goodagreement with that obtained by the resistance fracture gage method. Therefore this method isfeasible for measuring crack propagating velocities under high loading rate and will have wideapplication.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB932903 and 2012CB932904)the National Natural Science Foundation of China(Grant Nos.51372270,11474333,and 21173260)
文摘A real-time quantitative optical method to characterize crack propagation in colloidal photonic crystal film（CPCF）is developed based on particle deformation models and previous real-time crack observations. The crack propagation process and temperature dependence of the crack propagation rate in CPCF are investigated. By this method, the crack propagation rate is found to slow down gradually to zero when cracks become more numerous and dense. Meanwhile, with the temperature increasing, the crack propagation rate constant decreases. The negative temperature dependence of the crack propagation rate is due to the increase of van der Waals attraction, which finally results in the decrease of resultant force. The findings provide new insight into the crack propagation process in CPCF.
基金supported by the National Natural Science Foundation of China (Grant No 10761005)the Inner Mongolia Natural Science Foundation of China (Grant No 200607010104)
文摘Using the complex variable function method and the technique of conformal mapping, the anti-plane shear problem of an elliptic hole with asymmetric colfinear cracks in a one-dimensional hexagonal quasi-crystal is solved, and the exact analytic solutions of the stress intensity factors （SIFs） for mode Ⅲ problem are obtained. Under the limiting conditions, the present results reduce to the Griffith crack and many new results obtained as well, such as the circular hole with asymmetric collinear cracks, the elliptic hole with a straight crack, the mode T crack, the cross crack and so on. As far as the phonon field is concerned, these results, which play an important role in many practical and theoretical applications, are shown to be in good agreement with the classical results.
文摘By using the dynamic photoelastic method and our technique of fabricating an internal crack in solid , the scattered waves of incident grazing longitudinal ultrasonic wave pulse by a ribbon-type crack are ob-served and analyzed . In particular, the distribution of the intensity of the scattered head wave is measured quantitatively . The experimental results fairly agree with the theoretical ones given in ref. [ 1 ] .
