This laboratory was designated as Na-tional Laboratory in 1988 and is subordi-nate to the Institute of Metal Research(IMR),Academia Sinica.It is nowwell-equipped after rebuilding under a spe-cial grant-in-aid program ...This laboratory was designated as Na-tional Laboratory in 1988 and is subordi-nate to the Institute of Metal Research(IMR),Academia Sinica.It is nowwell-equipped after rebuilding under a spe-cial grant-in-aid program from the centralgovernment.According to the policy of“Opening,Flowing and Serving the WholeCountry”for the national laboratories,vis-iting research fellows at home and fromabroad are welcome to join common re-search projects in this lab.展开更多
Samples prepared from as-extruded magnesium alloy Mg-3%Al-1%Zn （AZ31） billets were utilized in low-cycle fatigue tests in order to investigate the frequency-dependent fatigue life. Fully reversed strain-controlled t...Samples prepared from as-extruded magnesium alloy Mg-3%Al-1%Zn （AZ31） billets were utilized in low-cycle fatigue tests in order to investigate the frequency-dependent fatigue life. Fully reversed strain-controlled tension-compression fatigue tests were carried out at frequencies of 1 Hz and 10 Hz in air. The microstructures were examined by optical microscopy （OM） and scanning electron microscopy （SEM）.When the strain amplitude was lower than 0.2%, the fatigue life exhibited a positive correlation with loading frequency, and the activity of twinning was increased at 10 Hz. When the strain amplitude was higher than 0.2%, significant twinning was observed both at these two frequencies, and the fatigue life was found to be independent of frequency. The possible reasons for this frequency-related fatigue lifetime may be due to the dependence of twinning upon loading frequency and strain amplitude.展开更多
The principles for lifecycle safety guarantee of engineering structures areproposed, and the conception is developed for developing the safety guarantee system by integratingthe monitoring system, analysis system and ...The principles for lifecycle safety guarantee of engineering structures areproposed, and the conception is developed for developing the safety guarantee system by integratingthe monitoring system, analysis system and maintenance system together on the basis of multi-sensor,distribution-measurement, data fusion and digital-signal-processor (DSP) technologies as well asthree-dimensional (3D) fatigue fracture unified theory. As all the systems should work in situs andin real-time, micromation and integration are important. Damage detectability is introduced toclarify the relationship of life prediction and healthy monitoring or faulty diagnosis. The researchwork to realize the lifecycle safety guarantee system is summarized and perspectives for futureefforts are outlined.展开更多
A general model of fatigue crack growth(FCG) in ductile alloys under variable amplitude loading is proposed based on the passivation-lancet theory and the crack closure concept.The model can capture the interactions o...A general model of fatigue crack growth(FCG) in ductile alloys under variable amplitude loading is proposed based on the passivation-lancet theory and the crack closure concept.The model can capture the interactions of single cycle overloading and underloading,sequential loading and spectrum loading effectively.Moreover,the retardation effect due to overloads and the acceleration effect due to underloading can be described quantitatively by a transition function of crack opening stress.The fatigue test data in 2024-T351,2024-T3 and 7075-T6 aluminum alloys under different types of variable amplitude loading and spectrum loading are used to validate the general model and the predictions by the general model are in good agreement with the test data.Furthermore,the predictions are also compared with the existing models,including FASTRAN,AFGROW and the state-space model,and the comparison results show that the general model predicts the FCG process more accurately.展开更多
文摘This laboratory was designated as Na-tional Laboratory in 1988 and is subordi-nate to the Institute of Metal Research(IMR),Academia Sinica.It is nowwell-equipped after rebuilding under a spe-cial grant-in-aid program from the centralgovernment.According to the policy of“Opening,Flowing and Serving the WholeCountry”for the national laboratories,vis-iting research fellows at home and fromabroad are welcome to join common re-search projects in this lab.
基金the National Natural Science Foundation of China(No.50901042)NUST Research Funding(No.2011YBXM156)
文摘Samples prepared from as-extruded magnesium alloy Mg-3%Al-1%Zn （AZ31） billets were utilized in low-cycle fatigue tests in order to investigate the frequency-dependent fatigue life. Fully reversed strain-controlled tension-compression fatigue tests were carried out at frequencies of 1 Hz and 10 Hz in air. The microstructures were examined by optical microscopy （OM） and scanning electron microscopy （SEM）.When the strain amplitude was lower than 0.2%, the fatigue life exhibited a positive correlation with loading frequency, and the activity of twinning was increased at 10 Hz. When the strain amplitude was higher than 0.2%, significant twinning was observed both at these two frequencies, and the fatigue life was found to be independent of frequency. The possible reasons for this frequency-related fatigue lifetime may be due to the dependence of twinning upon loading frequency and strain amplitude.
基金This project is supported by National Natural Science Foundation of China (No.50275073)Space Science Foundation of China (No.03B52011).
文摘The principles for lifecycle safety guarantee of engineering structures areproposed, and the conception is developed for developing the safety guarantee system by integratingthe monitoring system, analysis system and maintenance system together on the basis of multi-sensor,distribution-measurement, data fusion and digital-signal-processor (DSP) technologies as well asthree-dimensional (3D) fatigue fracture unified theory. As all the systems should work in situs andin real-time, micromation and integration are important. Damage detectability is introduced toclarify the relationship of life prediction and healthy monitoring or faulty diagnosis. The researchwork to realize the lifecycle safety guarantee system is summarized and perspectives for futureefforts are outlined.
基金supported by the Gas Turbine Establishment of China (Grant No. GTE022006084)
文摘A general model of fatigue crack growth(FCG) in ductile alloys under variable amplitude loading is proposed based on the passivation-lancet theory and the crack closure concept.The model can capture the interactions of single cycle overloading and underloading,sequential loading and spectrum loading effectively.Moreover,the retardation effect due to overloads and the acceleration effect due to underloading can be described quantitatively by a transition function of crack opening stress.The fatigue test data in 2024-T351,2024-T3 and 7075-T6 aluminum alloys under different types of variable amplitude loading and spectrum loading are used to validate the general model and the predictions by the general model are in good agreement with the test data.Furthermore,the predictions are also compared with the existing models,including FASTRAN,AFGROW and the state-space model,and the comparison results show that the general model predicts the FCG process more accurately.
