提出了焊接接头预充氢拉伸法评价焊接接头氢致裂纹敏感性的新方法,以30Cr Mn Si Ni2钢TIG焊接接头为研究对象,对此方法进行了试验验证.结果表明,预充氢后的拉伸试样断裂位置由未充氢时的母材区转变为HAZ粗晶区,预充氢电流对屈服强度影...提出了焊接接头预充氢拉伸法评价焊接接头氢致裂纹敏感性的新方法,以30Cr Mn Si Ni2钢TIG焊接接头为研究对象,对此方法进行了试验验证.结果表明,预充氢后的拉伸试样断裂位置由未充氢时的母材区转变为HAZ粗晶区,预充氢电流对屈服强度影响不大,随预充氢电流密度增加抗拉强度下降,断后伸长率和断面收缩率减小.同时,随着预充氢电流的增加,断裂方式由准解理断裂和韧窝断裂组成的混合型断裂逐渐向穿晶准解理断裂和沿晶准解理混合断裂过渡.预充氢拉伸试验结果表明该方法能够方便地确定焊接接头临氢环境时的薄弱环节,有效评价焊接接头氢致裂纹敏感性.展开更多
In order to evaluate the accumulative of tensile strain in the process of fatigue failure, the digital image correlation（DIC） method was utilized to characterize the tensile strain development of asphalt mixtures in...In order to evaluate the accumulative of tensile strain in the process of fatigue failure, the digital image correlation（DIC） method was utilized to characterize the tensile strain development of asphalt mixtures in the indirect tensile（IDT）fatigue test. Three typical hot mix asphalt（HMA） mixtures with varying nominal maximum aggregate sizes were tested at four stress levels. During the tests, a digital camera was mounted to capture the displacement/strain fields on the surface of the specimen by recording the real-time change of speckle position. The results indicate that the vertical deformation curve can barely evaluate the fatigue performance accurately due to the non-negligible local deflection near the loading point. However, based on the analysis of strain fields,the optimal fatigue cracking zone is determined as a 40mm×40mm rectangle in the middle of the specimens. Also, a reasonable fatigue model based on the tensile strain curves calculated by DIC is proposed to predict the fatigue lives of asphalt mixtures.展开更多
In order to numerically simulate the failure process of rock and concrete under uniaxial tension,an improved method of selecting the mechanical properties of materials was presented for the random mechanic parameter m...In order to numerically simulate the failure process of rock and concrete under uniaxial tension,an improved method of selecting the mechanical properties of materials was presented for the random mechanic parameter model based on the mesoscopic damage mechanics.The product of strength and elastic modulus of mesoscale representative volume element was considered to be one of the mechanical property parameters of materials and assumed to conform to specified probability distributions to reflect the heterogeneity of mechanical property in materials.With the improved property parameter selection method,a numerical program was developed and the simulation of the failure process of the rock and concrete specimens under static tensile loading condition was carried out.The failure process and complete stress-strain curves of a class of rock and concrete in stable fracture propagation manner under uniaxial tension were obtained.The simulated macroscopic mechanical behavior was compared with the available laboratory experimental observation,and a reasonable agreement was obtained.Verification shows that the improved parameter selection method is suitable for mesoscopic numerical simulation in the failure process of rock and concrete.展开更多
Three characteristic points in the deformation history of a fractured tensile specimen are selected tocalculate two values of n( n1 and n2 ) to represent the hardening ability of material during the homogeneous plas-t...Three characteristic points in the deformation history of a fractured tensile specimen are selected tocalculate two values of n( n1 and n2 ) to represent the hardening ability of material during the homogeneous plas-tic deformation and the following large plastic deformation. Experimental results obtained with mild streel andred copper show that n determined using the three-point method proposed is better to describe the hardening a-bility of material. It is therefore concluded that three-point method can be used to describe the hardening prop-erty of material during both homogeneous deformation and large plastic deformation.展开更多
文摘提出了焊接接头预充氢拉伸法评价焊接接头氢致裂纹敏感性的新方法,以30Cr Mn Si Ni2钢TIG焊接接头为研究对象,对此方法进行了试验验证.结果表明,预充氢后的拉伸试样断裂位置由未充氢时的母材区转变为HAZ粗晶区,预充氢电流对屈服强度影响不大,随预充氢电流密度增加抗拉强度下降,断后伸长率和断面收缩率减小.同时,随着预充氢电流的增加,断裂方式由准解理断裂和韧窝断裂组成的混合型断裂逐渐向穿晶准解理断裂和沿晶准解理混合断裂过渡.预充氢拉伸试验结果表明该方法能够方便地确定焊接接头临氢环境时的薄弱环节,有效评价焊接接头氢致裂纹敏感性.
文摘In order to evaluate the accumulative of tensile strain in the process of fatigue failure, the digital image correlation（DIC） method was utilized to characterize the tensile strain development of asphalt mixtures in the indirect tensile（IDT）fatigue test. Three typical hot mix asphalt（HMA） mixtures with varying nominal maximum aggregate sizes were tested at four stress levels. During the tests, a digital camera was mounted to capture the displacement/strain fields on the surface of the specimen by recording the real-time change of speckle position. The results indicate that the vertical deformation curve can barely evaluate the fatigue performance accurately due to the non-negligible local deflection near the loading point. However, based on the analysis of strain fields,the optimal fatigue cracking zone is determined as a 40mm×40mm rectangle in the middle of the specimens. Also, a reasonable fatigue model based on the tensile strain curves calculated by DIC is proposed to predict the fatigue lives of asphalt mixtures.
基金Project(50679006) supported by the National Natural Science Foundation of ChinaProject(NCET-06-0270) supported by the Program for New Century Excellent Talents in University
文摘In order to numerically simulate the failure process of rock and concrete under uniaxial tension,an improved method of selecting the mechanical properties of materials was presented for the random mechanic parameter model based on the mesoscopic damage mechanics.The product of strength and elastic modulus of mesoscale representative volume element was considered to be one of the mechanical property parameters of materials and assumed to conform to specified probability distributions to reflect the heterogeneity of mechanical property in materials.With the improved property parameter selection method,a numerical program was developed and the simulation of the failure process of the rock and concrete specimens under static tensile loading condition was carried out.The failure process and complete stress-strain curves of a class of rock and concrete in stable fracture propagation manner under uniaxial tension were obtained.The simulated macroscopic mechanical behavior was compared with the available laboratory experimental observation,and a reasonable agreement was obtained.Verification shows that the improved parameter selection method is suitable for mesoscopic numerical simulation in the failure process of rock and concrete.
文摘Three characteristic points in the deformation history of a fractured tensile specimen are selected tocalculate two values of n( n1 and n2 ) to represent the hardening ability of material during the homogeneous plas-tic deformation and the following large plastic deformation. Experimental results obtained with mild streel andred copper show that n determined using the three-point method proposed is better to describe the hardening a-bility of material. It is therefore concluded that three-point method can be used to describe the hardening prop-erty of material during both homogeneous deformation and large plastic deformation.
