The Dynamic Responses Of The Pig’s Lower Limb Materials Under Impact Loadings

Underwater explosion can produce enormous shock acceleration in a very short duration,resulting in severe human injuries,and human lower extremities and soft tissue are prone to be injured by the shock acceleration.Landmine explosions cause mine-impact damage to personnel in armored vehicles,whose main performance is the comminuted fracture,limb off and so on.The degree of injury is closely related to the mechanical properties of the lower limb bone under impact compression.For this reason,the study of dynamic mechanics performance of the lower limb bone under high-speed impact can provide certain references for different types of evaluation about personal injury and design for protective devices.Compared to traditional metal materials in engineering,testing the performance of the lower limb bone becomes comparatively difficult because of its attribute of life and the more brittle physical characteristics.Specific to the situation that mentioned above,a feasible and effective method of sample preparation and preservation has been put forward in this paper,it makes the specimen retains the original cross-sectional shape of the bone and remain active as much as possible.Once the program of sample preparation and sample preservation was determined,the quasi-static experiment of bone tissue would be conducted.Then the stress-strain curve of the material was obtained,and the distribution of ultimate strength was analyzed.Based on the existing Split Hopkinson Pressure Bar(SHPB)experimental technology,the shaper was used to improved it in the paper,which could ensure constant strain rate loading and uniform stress-strain during the measurement.This paper has made some exploratory studies on the dynamic mechanical properties of bone under high strain rates,and obtained numerous data of dynamic compression test,which shows femur and shank have highly dependency on strain rate and they also exhibit a strong central distribution along with weak ends.Then compared with the data in the quasi-static experiment;finally,it found that the lower limb bone has significant strain rate effect under a wide range of strain rates.Some of the further researches have described the model of bone used creep and relaxation model which were used to describe the viscoelastic material.In this paper,the nonlinear viscoelastic constitutive model ZWT was used,and some parameters were fitted.Finally,the model of bone was established in this paper.