To investigate microstructure failure in ferrite-martensite dual phase steel,in-situ observations were performed on multiple plate DP800 specimens during uniaxial tensile tests. Microstructure evolution of the observe...To investigate microstructure failure in ferrite-martensite dual phase steel,in-situ observations were performed on multiple plate DP800 specimens during uniaxial tensile tests. Microstructure evolution of the observed region was investigated in details. The experimental data showed that micro-cracks in various regions differed in the initiation time,and micro-failures mainly occurred from the locations with typical characteristics of stress concentration（ i. e. ferrite interiors,the interfaces of ferrite-martensite grains and the martensite-martensite interfaces）. Growth of micro-crack generally experienced the following stages： cracking from martensite boundaries,tiny particles in ferrite interiors,or martensite interiors,propagating in ferrite,bypassing martensite boundaries,or passing through martensite-martensite interfaces,finally ending on martensite boundaries. Martensite was one important source of micro-failure and changed the propagation of micro-cracks significantly. Microstructure deformation was inhomogeneous in the stage of plastic deformation.展开更多
Total 72 lapped specimens including six different kinds of CR340 steel structures were prepared to study the influence of the spot welding technology on their fatigue characteristics.Fatigue test and group method were...Total 72 lapped specimens including six different kinds of CR340 steel structures were prepared to study the influence of the spot welding technology on their fatigue characteristics.Fatigue test and group method were employed and performed on each sample to obtain the fatigue experimental data of each structure under four stress levels.The results show that the spot welding technology had a notable impact on the fatigue performance of both the shear and tensile joints.It can significantly improve the fatigue strength of the structure,the consistency and repeatability of experimental data,as well as the stability and reliability of the structure under dynamic load environment.The shear spot welding structure demonstrates the best fatigue performance which is very important for wide application in engineering of this method.展开更多
基金supported by the National Natural Science Foundation of China(51375307 )the Anhui University Provincial Natural Science Research Project(KJ2016A181 )+1 种基金the Key Discipline Team(AKZDXK2015C03)High Level Talent Research Project of Anhui Science and Technology University(ZRC2014464)
文摘To investigate microstructure failure in ferrite-martensite dual phase steel,in-situ observations were performed on multiple plate DP800 specimens during uniaxial tensile tests. Microstructure evolution of the observed region was investigated in details. The experimental data showed that micro-cracks in various regions differed in the initiation time,and micro-failures mainly occurred from the locations with typical characteristics of stress concentration（ i. e. ferrite interiors,the interfaces of ferrite-martensite grains and the martensite-martensite interfaces）. Growth of micro-crack generally experienced the following stages： cracking from martensite boundaries,tiny particles in ferrite interiors,or martensite interiors,propagating in ferrite,bypassing martensite boundaries,or passing through martensite-martensite interfaces,finally ending on martensite boundaries. Martensite was one important source of micro-failure and changed the propagation of micro-cracks significantly. Microstructure deformation was inhomogeneous in the stage of plastic deformation.
基金Item Sponsored by National Natural Science Foundation of China(51375307,51275296)Key Discipline Team of China(AKZDXK2015C03)University Provincial Natural Science Research Project of Anhui Province of China(KJ2016A181)
文摘Total 72 lapped specimens including six different kinds of CR340 steel structures were prepared to study the influence of the spot welding technology on their fatigue characteristics.Fatigue test and group method were employed and performed on each sample to obtain the fatigue experimental data of each structure under four stress levels.The results show that the spot welding technology had a notable impact on the fatigue performance of both the shear and tensile joints.It can significantly improve the fatigue strength of the structure,the consistency and repeatability of experimental data,as well as the stability and reliability of the structure under dynamic load environment.The shear spot welding structure demonstrates the best fatigue performance which is very important for wide application in engineering of this method.
