The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics ...The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.展开更多
Hierarchical defects are defined as adjacent defects at different length scales.Involved are the two scales where the stress field distribution is interrelated.Based on the complex variable method and conformal mappin...Hierarchical defects are defined as adjacent defects at different length scales.Involved are the two scales where the stress field distribution is interrelated.Based on the complex variable method and conformal mapping,a multiscale framework for solving the problems of hierarchical defects is formulated.The separated representations of mapping function,the governing equations of potentials,and the stress field are subsequently obtained.The proposed multiscale framework can be used to solve a variety of simplified engineering problems.The case in point is the analytical solution of a macroscopic elliptic hole with a microscopic circular edge defect.The results indicate that the microscopic defect aggregates the stress concentration on the macroscopic defect and likely leads to global propagation and rupture.Multiple micro-defects have interactive effects on the distribution of the stress field.The level of stress concentration may be reduced by the coalescence of micro-defects.This work provides a unified method to analytically investigate the influence of edge micro-defects within the scope of multiscale hierarchy.The formulated multiscale approach can also be potentially applied to materials with hierarchical defects,such as additive manufacturing and bio-inspired materials.展开更多
Through comparing the measured data of dynamic strains due to loading and temperature by the stain gauge and temperature sensor at the same location,the information in the strain data was divided into three parts in t...Through comparing the measured data of dynamic strains due to loading and temperature by the stain gauge and temperature sensor at the same location,the information in the strain data was divided into three parts in the frequency domain by using the defined index named power spectral density(PSD)-ratio index.The three parts are dominated respectively by temperature varying,stresses,and noises and thus can be distinguished from the determined the separatrix frequencies.Also,a simple algorithm was developed to separate the three types of information and to extract the strain caused mainly by structural stresses.As an application of the proposed method,the effect of strain deformation and noises on the fatigue assessment was investigated based on the separated data.The results show that,the determined values of separatrix frequencies are valuable for the monitoring data from other bridges.The algorithm is a multiresolution and hierarchical method,which has been validated as a simple and effective method for data analyses,and is suitable for the compression and preprocessing of the great amount monitoring data and easy to be integrated into the structural health monitoring(SHM)soft system.The strain due to temperature varying attributes a little to the errors of fatigue assessment;however,the noises or random disturbance existed in the monitoring data have much responsibility for the errors,and the main reason is that the random disturbance shifts the real strain/stress amplitude picked up by real structural stress or strain.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52204092 and 52274203).
文摘The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.
基金the National Natural Science Foundation of China(No.51878154)the National Program on Major Research Project of China(No.2016YFC0701301)。
文摘Hierarchical defects are defined as adjacent defects at different length scales.Involved are the two scales where the stress field distribution is interrelated.Based on the complex variable method and conformal mapping,a multiscale framework for solving the problems of hierarchical defects is formulated.The separated representations of mapping function,the governing equations of potentials,and the stress field are subsequently obtained.The proposed multiscale framework can be used to solve a variety of simplified engineering problems.The case in point is the analytical solution of a macroscopic elliptic hole with a microscopic circular edge defect.The results indicate that the microscopic defect aggregates the stress concentration on the macroscopic defect and likely leads to global propagation and rupture.Multiple micro-defects have interactive effects on the distribution of the stress field.The level of stress concentration may be reduced by the coalescence of micro-defects.This work provides a unified method to analytically investigate the influence of edge micro-defects within the scope of multiscale hierarchy.The formulated multiscale approach can also be potentially applied to materials with hierarchical defects,such as additive manufacturing and bio-inspired materials.
文摘Through comparing the measured data of dynamic strains due to loading and temperature by the stain gauge and temperature sensor at the same location,the information in the strain data was divided into three parts in the frequency domain by using the defined index named power spectral density(PSD)-ratio index.The three parts are dominated respectively by temperature varying,stresses,and noises and thus can be distinguished from the determined the separatrix frequencies.Also,a simple algorithm was developed to separate the three types of information and to extract the strain caused mainly by structural stresses.As an application of the proposed method,the effect of strain deformation and noises on the fatigue assessment was investigated based on the separated data.The results show that,the determined values of separatrix frequencies are valuable for the monitoring data from other bridges.The algorithm is a multiresolution and hierarchical method,which has been validated as a simple and effective method for data analyses,and is suitable for the compression and preprocessing of the great amount monitoring data and easy to be integrated into the structural health monitoring(SHM)soft system.The strain due to temperature varying attributes a little to the errors of fatigue assessment;however,the noises or random disturbance existed in the monitoring data have much responsibility for the errors,and the main reason is that the random disturbance shifts the real strain/stress amplitude picked up by real structural stress or strain.
