【文章內(nèi)容簡介】 ild stress is 22Mpa higher than parallel yield stress,tensile strength is 26Mpa higher,which demostrates particular size and distribution of grains is regular from further research in ,grian sizes of the suface is larger than center grains (). secondly,there are certain grain orientation in the center of the material().Part of the grain in the axis along the rolling direction is obviously larger than the other two axises,which proved that grain refinement along the thickness direction varies in rolling the following aneal and artificial aging,there are certain preferred orientation in the refined grains after grain growth or recrytalization,and these factors lead material with certain anisotropic. pares smooth tensile test with notch tensile test,the notch radius is 4mm,the test showed that the deformation resistance increased at notch the same deformtion,load of smooth test is is bigger at the foot of notch under geometry the simple tensile process,larger additional stress derived from the thickness and width direction,and then triaxis tensile stress shear stress or equivalent Mises stress that ductile deformation needed decreased,which would lead to ductile the mcro aspect,minish the notch radius,stress triaxiality of ponent increased,stress concertration increased at the foot of the notch,ductilty decreased,and fracture strain decreased engineering strain of the notch specimen is %,which is only 35% of the engineering strain of smooth tensile specimen. From the experiment analysis,it’s clear that stress condition is not related to yielding obviously,but it matters badly to losing effectiveness of fracture. Dynamic tensile test Experiment equipment and measurement principle Car accidents mostly happens at the velocity of 50Km per hour, the impact kinetic energy of midweight car can be up to the strain rate of these similar impact accidents is about 100s1 ,but the limitation of local strain rate is within 1*,the strain of dynamic test is in the scale of 102~103s1 on the basis of safe impact design. Currently,the applied test equipment are as follows:1 Falling weight device Different heights of falling hammer acquire various kinetic energy, experiment data are collected and processed by using signal processing device such as of such devices are simple structure,easy operation and low fits impact tests of the level of 10m/s. Previously, there have been such devices such as Tinghua university。State Key Laboratory of Auotmotive Safety and Energy and Haribin institute of technology throughout the nation. experiment devices There are vertical type and horizontal type,it gains great speed by exploded high energy ballon, the specimens are fastened on data acquisition board with piezoelectric sensor,specimens are impacted with hammer loaded with different masses,while record the impact process with highspeed digital shooting technology can acquire video image of 10000 frames per second,and the frequency of impact data reach up to present,all the advance insitute are capable of this test,such as Cambridge,Kaiserslautern university and Fraunhofer IWM machanical institute ,who use this device to test impact responses of ponents. Hopkinson draw(press) poles test devices This method is first proposed in 1914,it’s the earliest method of testing transient state pulse ,many researchers changed and developed this method,in which the improved discret Hopkinson draw poles by Koisky is the most typical one,that has bee major testing tool of dynamic property of kind of experiment is taken in metallic large defomation dynamic machinsm respose of strain rate within 102~104s1. The key point of Hopkinson’s testing technology is to assure that separate the stress wave effect with dynamic buckling effect within the impact ,the incidence pole and test pole of the test device are designed to be longer,in order to sepperate the infunce from reflex waves of press pole,so the equipment would take much space. On the other hand,due to the strict restriction of specimen size,which could make sure ductile stress wave in the ponent take small proportion in structure buckling response time,press stress is well distributed in ponents. Key physical qualities need to be determined in this experiment are as follows.(1) input response of impact load(2) response,value and distribution of structural load(3) response,value and distribution of structural displacement(4) strain rate of material,the key formula are