| The occupant's pelvis is one of the most vulnerable organs to the striking vehicle.Pelvic injury contributes significantly to traffic fatalities because of the comparatively small gap between the occupant and the intruding door.These days,automotive industries are significantly concerned with the protection of vehicle occupant against the lateral impacts in a side collision.According to has long-term consequences on the society,economic aspects,human life,and high mortality during the pelvic fracture in China and another developed countries such as USA,importance this issue should not be ignored.Therefore,it is very necessary to design and create a kind of dynamic model of the pelvic impactor system and pelvic complex model that can be used to simulate the biomechanical response of the pelvic complex under lateral impact load with least possible time,acceptable accuracy,and high flexibility.At present,understanding about the pelvic compression(PC)under the lateral impact is not enough.Most of the previous study was conducted based on the statistical analysis of clinical cases and anatomy study rather than biomechanical research.Moreover,almost all of the previous pelvic models were developed with excessive simplifications.Most of the previous models included materials such as bone,ligament,and cartilage,whereas muscles and fatty tissue wrapped around the bone,also have a great influence on the dynamic response characteristics of the pelvic under the lateral impact load.Hence,it is necessary to consider the soft tissue for the pelvic model.Under such context,we propose to investigate the mechanism of PC under lateral impact from a biomechanical stand,trying to providing associated a dynamic model of pelvic side-impactor support for predicting PC,pelvic impact force,and effectiveness of pelvic protector in lateral impact with different materials and thicknesses.The detailed work is listed as follows:1.The pelvis flexible model was extracted from the computed tomography(CT)images information of the Outer skin contours and pelvic bone of Chinese female volunteer.Based on the contour construction and characteristics of the anatomical structure was developed geometry complex model of the pelvic-femoral by using the techniques of reverse engineering.And the finite element model of the pelvic-femoral was created in Hypermesh software.The 3D finite element(FE)model of the pelvic-femoral system was developed using a wide range of mechanical properties in the complex bone and soft tissue in order to get a realistic biomechanical response under lateral impact load.The pre-processing module of pelvic finite element model was transformed to the MSC-Adams flexible body(mnf)by the Abaqus software.The dynamic model of the pelvic side-impactor system was developed in the MSC-ADAMS software.And finally,dynamic model of pelvic side-impactor system was completed through coupling with the complex flexible model of pelvic.2.The dynamic simulation of pelvic side-impactor and the pelvic complex model was verified through comparing the simulation results under the same condition with the experimental results reported in the literature.The time duration of maximum impact forces appeared close to the reported data.The maximum compressive strain region was matched with the fracture position reported in the literature.Moreover,the main biomechanical criteria such as the maximum compression,impact force appeared for the response of the pelvic model.The peak time of impact force was close to the average reported in the literature.The compression ratio,impact force was in the range of between the upper bound and lower bound.Therefore,the model can be effective,in order to study pelvic injury mechanism under the lateral impact load.Because of the complex structure and the variety material properties,dynamic simulation of the finite element model of femoral-pelvic for computing often needs to a long time.While computing time of the femoral-pelvic dynamic simulation using the MSC-ADAMS software with the same hardware was no more than 15 minutes.So,MSC-Adams dynamic simulation can reduce to computing cost,greatly.And also can obtain impact force,compression and other important dynamic response parameters3.The dynamic response characteristics of the pelvic complex under different impact velocity were studied.The deformation curve of the lateral impact was produced due to the initial acceleration between pelvic and impactor.And the second deceleration was produced due to the position of pelvic between lateral support and the impactor.The dynamic model analysis revealed that the risk of pelvic injury increased with the increasing of the impacting force.The peak impact force increases linearly while the maximum compression was exponentially increasing.The peak impact force due to 5.5m/s velocity of the impactor shows the evidence of bone fracture occurrence.The maximum compression was increased to 32% and the peak time was reduced to 24.28 ms because of peak impact force.4.Another aim of this study was to investigate the effectiveness of the hip protectors.According to the 4 m/s impact velocity,the force attenuation provided by the various hip protectors ranged between 10.7% and 40.6%.The protector with the combination of hard/soft material(hip protection type D)provided greater force attenuation at all velocities.Hip protector with soft material(hip protection type B)provided lower force attenuation and also demonstrated greater time duration due to the force attenuation.Based on the results analysis,the protection mechanism of lateral impact was discussed.In this thesis,the numerical model of femoral-pelvic was real enough to simulate the dynamic response of pelvis,the result of this study will be helpful for the deep understanding of the injury mechanism of the pelvic under lateral impact loads and provide guidance for design pelvic lateral impact protector.In addition,the dynamic model of the pelvic-impactor system can be used to investigate the biomechanical response from other organs of the human body such as thorax and lower leg under lateral impact. |
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