ABSTRACT
Objective To investigate the biomechanical characteristics of the human pelvis-femur complex under lateral pelvic impacts during sideways falls using three dimensional (3D) finite element (FE) method. Methods Based on the model database of China Mechanical Virtual Human, a 3D FE model of the pelvis femur soft tissue complex was created, including cortical bone, cancellous bone and soft tissue capsule. A rigid plane model was also constructed for ground simulation and constrained in all freedoms. The average hip lateral impact velocity of 2 m/s was applied to the model and the time for simulation analysis was set at 20 ms. The stress and strain distribution on the pelvis-femur complex were obtained by the 3D FE calculation and analysis. ResultsOn the contact surface, the peak impact load reached to 7 656 N at 13 ms, while the maximum Von Mises stress on the soft tissue was 2.64 MPa. Simultaneously, the peak Von Mises stress of 142.64 MPa on the cortical bone occurred in the region of pubic symphysis, which was approximate to the yield stress on the cancellous bone. The Von Mises stress level was higher in the region of the femur neck and greater trochanter. At 13 ms, the peak Von Mises stress on the cortical bone of the femur neck was 76.49 MPa and that on the cancellous bone was 8.44 MPa with the peak compressive principal strain being 0.94%. The peak Von Mises stress on the cancellous bone of greater trochanter was 8.50 MPa, while the peak compressive principal strain was 0.93%. Conclusions Bone fractures of the pelvis-femur complex tend to occur in the region of the femur neck, greater trochanter and pubic symphysis under deceleration impacts during sideways falls.
ABSTRACT
Purpose: Set up a new technique to reproduce the cavitation effect in the process of brain deceleration impact Methods: A transparent physical brain model with tiny air bubbles was built and loaded on an upright brain deceleration impacting moveable platform. Then, in the high strength lighting circumstance, the moveable platform was made to free fall from a height of 40cm and impacted on a fixed platform, and the whole deceleration impacting process was recorded by a high-speed video camera. Using the serial pictures analysing software, the volume and mean pressure change of the air bubbles were calculated and the cavitation effect of the brain tissue during the impact was studied. Results: The volume of the air bubble in the contrecoup site increased obviously in the impacting process, the volume of the air bubble in the coup site decreased in the impacting process and the volume change of the air bubble in the middle site was not evident enough in the impacting process. Conclusion: The results proved the negative pressure and the cavitation phenomenon in the contrecoup site. The experiments explicitly and directly showed the cavitation effect in the contrecoup site during the decelerating impact It was helpful to better understand the distribution characters of the dynamic stress of the brain tissue in the brain decelerating impact in a certain extent, and it could also provide some methods and experimental foundation to clarify the mechanical mechanism of the brain contrecoup injury which was often taken place in traffic accidental injury. Besides, the methods were of significance to research the biomechanism, diagnosis and prevention of the brain deceleration impacting injury.
ABSTRACT
Objective to research the mechanical style(compressive or tensile force)of the key site of brain tissue in brain deceleration impact.Method a transparent physical brain model with air bubbles was built and loaded on an upright brain decaler ation impacting expedmentel platform.Then,the moveable platform was made a free fall from a height of 400mm and impacted on the fixed platform,and the whole deceleration impacting process was recorded by a high-speed video camera.Using the serial pictures analyzing Software,the length change of the long ads(vertical to the impacting direction)and the short axis(in the impacting di-rection)of the air bubbles were analyzed and calculated.Result the length change of the long axis of air bub-ble with in site coup was smallerthan the absolute value of that of the short axis;while with the air bubble in the contrecoup site,the length change of the long axis was bigger than the absolute value of the short axis.Conclusions the results showed that the air bubble in the coup site mainly suffered from the tensile force vertical to the impacting direction and the air bubble in the contrecoup site mainly suffered from the compres-sive force in the impacting direction.Since the propeny of tensile resistance of the brain tissue is inferior to the property of compressive resistance of the brain tissue, the injury is often easier to occur in the contrecoup site than in coup site. The results were of significance to the research of biomechanical mechanism, diagnosis and prevention of the brain deceleration impacting injury.
ABSTRACT
Objective to research the mechanical style(compressive or tensile force)of the key site of brain tissue in brain deceleration impact.Method a transparent physical brain model with air bubbles was built and loaded on an upright brain decaler ation impacting expedmentel platform.Then,the moveable platform was made a free fall from a height of 400mm and impacted on the fixed platform,and the whole deceleration impacting process was recorded by a high-speed video camera.Using the serial pictures analyzing Software,the length change of the long ads(vertical to the impacting direction)and the short axis(in the impacting di-rection)of the air bubbles were analyzed and calculated.Result the length change of the long axis of air bub-ble with in site coup was smallerthan the absolute value of that of the short axis;while with the air bubble in the contrecoup site,the length change of the long axis was bigger than the absolute value of the short axis.Conclusions the results showed that the air bubble in the coup site mainly suffered from the tensile force vertical to the impacting direction and the air bubble in the contrecoup site mainly suffered from the compres-sive force in the impacting direction.Since the propeny of tensile resistance of the brain tissue is inferior to the property of compressive resistance of the brain tissue, the injury is often easier to occur in the contrecoup site than in coup site. The results were of significance to the research of biomechanical mechanism, diagnosis and prevention of the brain deceleration impacting injury.
ABSTRACT
Objective to research the mechanical style(compressive or tensile force)of the key site of brain tissue in brain deceleration impact.Method a transparent physical brain model with air bubbles was built and loaded on an upright brain decaler ation impacting expedmentel platform.Then,the moveable platform was made a free fall from a height of 400mm and impacted on the fixed platform,and the whole deceleration impacting process was recorded by a high-speed video camera.Using the serial pictures analyzing Software,the length change of the long ads(vertical to the impacting direction)and the short axis(in the impacting di-rection)of the air bubbles were analyzed and calculated.Result the length change of the long axis of air bub-ble with in site coup was smallerthan the absolute value of that of the short axis;while with the air bubble in the contrecoup site,the length change of the long axis was bigger than the absolute value of the short axis.Conclusions the results showed that the air bubble in the coup site mainly suffered from the tensile force vertical to the impacting direction and the air bubble in the contrecoup site mainly suffered from the compres-sive force in the impacting direction.Since the propeny of tensile resistance of the brain tissue is inferior to the property of compressive resistance of the brain tissue, the injury is often easier to occur in the contrecoup site than in coup site. The results were of significance to the research of biomechanical mechanism, diagnosis and prevention of the brain deceleration impacting injury.