Experimental Study On Dynamic Tensile Mechanical Properties And Fracture Behavior Of Sintered Nd-Fe-B

The dynamic tensile properties and fracture behavior of Sintered Nd-Fe-B were studied by means of a split Hopkinson pressure bar(SHPB)device and separate Hopkinson tensile bar(SHTB)device.The sintered Nd-Fe-B was tested using SHPB test system under dynamic Brazilian test.The deformation and fracture processes of the specimen was recorded and analyzed according to high-speed camera and digital image correlation(DIC)technology.The tensile strength of the specimen was obtained according to the elastic theory when the load applied on the specimen reached the maximum.It was found that cracks along the loading diameter appeared on the surface of the specimen under the special load before the maximum load combined with high-speed camera and DIC technology.The local fracture strain at the typical location of the failure area was given by DIC.In the dynamic Brazilian test,DIC technology was used to obtain the width of the failure area on the surface of the specimen under the maximum load.The fracture energy corresponding to the specimen under the maximum load was given,which can be used as the energy criterion for the fracture of the sintered Nd-Fe-B specimen.The results show that the sintered Nd-Fe-B specimen has a certain strain rate effect,and the tensile strength and fracture energy of the sintered Nd-Fe-B increase with the increase of the strain rate.In addition,obvious transgranular fracture can be seen in the SEM diagram of the recovered specimen under high strain rate.The sintered Nd-Fe-B in the uniaxial tensile test was tested using SHTB test system.Using the experimental method combined with high-speed camera and DIC technology obtains the photos of fracture process and stress-strain curves of sintered Nd-Fe-B under quasi-static condition.And analyzing the tensile strength and fracture strain of sintered Nd-Fe-B.The SHTB device was used to conduct the uniaxial tensile experiment under dynamic loading to study the stress-strain behavior of sintered Nd-Fe-B with high strain rate.According to SHTB experiment,the stress-strain curves was obtained under high strain rate.The results show that the tensile strength increases with the increase of the strain rate.In addition,it was found that the transgranular fracture became obvious with the increase of strain rate by analyzing the SEM diagram of recovered specimens.