In this paper， the validated TUST injury bionic model of Chinese three-year-old child occupant （TUST IBMs 3YO-O） with detailed anatomical structure features is used to build a simulation model， according to two dynamic frontal crash test specifications specified in C-NCAP （2001 version）. A simulation is conducted to analyze the kinematic and biomechanical responses of the head， neck and chest and study the injury mechanism and the injury discrepancy of three-year-old child occupant in different conditions during frontal crash evaluation test. The results show that in the aspect of kinematic response， the injury risk of three-year-old child occupant in the frontal 50% overlap mobile progressive deformable barrier （MPDB） crash test is higher than that in the frontal 100% overlap rigid barrier （FRB） crash test， and the child farther away from the impact point has more serious injuries. In the aspect of biomechanical response， the three-year-old child occupant may suffer a mild concussion due to the lower jaw contacting the chest in the FRB crash test， while in the MPDB crash test， the child moves transversely toward left with the lower jaw contacting the right side of chest， leading to a larger peak biomechanical response， and may inducing minor concussion， rib fracture， lung contusion and other injuries.
In order to enhance the laser welding quality of AZ31B magnesium alloy， the surfaces of specimen are cleaned by nanosecond pulsed laser before welding. The surface morphologies and chemical compositions with different ways of cleaning are analyzed by scanning electron microscope and energy spectrometer. The dynamic processes of laser welding are observed via high-speed photography to analyze the effects of the different ways of cleaning and parameters on the surface cleaning effect and welding quality. The results show that the oxide film on magnesium alloy surface can be effectively removed by nanosecond pulsed laser cleaning， with the surface of specimen exhibiting fine microstructure features. Compared with the untreated or steel-brushed processes， laser cleaning process has a positive effect on the stabilities of the keyhole and molten pool during laser welding of magnesium alloy： the scale-like ripples on weld surface are uniform and fine， the microstructure of the joint is evenly distributed along the direction of plate thickness， with few defects of pores and cracks. Furthermore， the pre-weld laser cleaning can significantly increase the elongation rate of the laser weld joint of magnesium alloy. Compared with the untreated or steel-brushed processes， its joint elongation increases by 50.3% and 16.4% respectively. Appropriate laser cleaning can effectively remove the oxide film on the magnesium alloy surface， improve the surface microstructure， and obtain a higher tensile strength and elongation rate of the weld joints.
After the promulgation of C-NCAP 2021， 6 seconds pressure maintaining requirement poses a challenge to the design and development of curtain airbag （CAB）. This paper aims to conduct a study on inflator， as one of the key components of CAB. Based on heat transfer theory with the knowledge of thermodynamics， the deployment process of CAB is divided into three sub-processes， the effects of inflator on the pressure maintaining process of CAB are expounded， and the role and influence of inflator’s key parameters are summed up in detail. It is concluded by theoretical analysis and case study that the pyrotechnic inflator is not suitable to pressure maintaining CAB， cold-gas inflator is weak in product competitiveness， while the hybrid inflator with competitive price can possibly meet the requirements of CAB in pressure maintaining as long as its temperature is lower than the critical one such as 450 K.
Based on the plane motion theory， a theoretical analysis method for the slide mode of the vehicle in small-overlap frontal crash is proposed， and the relationship between the slide value and the impact forces is revealed and verified by experiments and tests. The impact area is divided into six parts and the sixth-order impact force characteristic curves are put forward. Based on the characteristic curves and the uniform design method， the sample space of vehicle slide value and different characteristic curves is obtained by using the theoretical method proposed. Furthermore， the BP neural network is established to conduct a sensitivity analysis of the impact forces and the vehicle slide value in the six regions of characteristic curves， with the critical impact region under that working condition identified. The theoretical method proposed and the sensitivity analysis conducted provide a theoretical support for the structural design for small-overlap frontal crash.
On the base of traditional simulation and combined with deep learning， a rapid prediction method of seat’s anti-whiplash injury performance is proposed. Firstly， a series material level， component level， subassembly level and seat level static and dynamic physical experiments are carried out on a Shanghai VW’s vehicle seat. Then using the results of experiments to calibrate the existing simulation model， resulting in the effectiveness of the simulation model verified. Next， a simulation on all factors affecting the seat’s whiplash performance is conducted by using full-factor method， and based on simulation results and using deep learning method， a long- and short-term memory （LSTM） neural network model is established to rapidly predict the whiplash injury response of dummy. The results show that the dummy response curve obtained from prediction by LSTM neural network model agrees well with simulated curve， so can be used in subsequent seat’s whiplash performance optimization.
Auto headlights may cause great damage to pedestrians’ legs in a vehicle-pedestrian crash. This paper aims to enhance the simulation accuracy of headlight fracture failure by studying the failure behavior of headlights in a vehicle-pedestrian crash condition， so as to accurately predict the pedestrian protection performance of vehicle in design stage. With the material of headlight housing PP-GF30 as the object， its elastic-plastic property and fracture failure behaviors are characterized based on static， dynamic and fracture failure material mechanical tests. The fracture failure model is verified through the simulation on PP-GF30 material fracture failure model established based on MAT_SAMP-1 constitutive， the headlight impact subsystem test and the vehicle-pedestrian leg impactor collision test，. The results show that the PP-GF30 fracture failure model built has a high simulation accuracy and can accurately predict the fracture failure behavior of auto headlights in vehicle-pedestrian collision. The research can also provide a reference for the establishment of failure simulation models of other related plastic materials.
The refined heart aorta model established earlier are filled with blood based on the fluid-cavity function of software Abaqus， a blood-heart aorta liquid-solid coupling model is constructed， and the fluid exchange with different flow rates are set on aortic valve according to the pressure difference between left ventricle and aorta. Simulations on the frontal crash of driver against steering wheel are carried out under different working conditions to analyze the effects of the cardiac blood output and the inclined angle of steering wheel on the blunt aortic injuries of driver. The results show that ：（1） The blood flow from left ventricle to aorta reduces the peak blood pressure of left ventricle and alleviated the blood pressure fluctuations in the aorta， but the effect on the maximum stress of aorta is not significant； （2） When the tilted angle of steering wheel is 30°， the maximum stress in the aorta reaches 2417 kPa， which is caused by the pressing of anterior chest wall on ascending aorta； （3） When the tilted angle of steering wheel is 60°， the maximum stress in the aorta lowers to 1375 kPa， which is caused by the relative tensile displacement between aortic root and descending aorta.
Enlightened by horsetail plant， a bionic self-similar hierarchical honeycomb structure is proposed in this paper. Based on the finite element model verified by test， the crashworthiness performance of the novel and traditional honeycomb structures under multi-angle oblique collision conditions are comparatively analyzed， including deformation modes， stress-strain curves and energy absorption characteristics. The results show that the self-similar hierarchical honeycomb structure has stable deformation mode under both ideal frontal and oblique impact conditions， and stable and excellent energy absorption performance when the impact angle changes.
In this paper， the finite element models for the front-end structure of four typical vehicles， i.e. family car （FCR）， multi-purpose vehicle （MPV）， roadster （RDS） and sport utility vehicle （SUV） specified in Pedestrian Human Model Certification （TB024） of the Euro NCAP protocol and a finite element model for six-year-old child pedestrian with detailed anatomical and structural features are used to simulate the child pedestrian-car crash accident with the effects of the structural parameters of vehicle front-end on the lower extremity injuries of children pedestrians analyzed under typical conditions. The results show that the RDS causes the fractures in the greater trochanter of impact-side femur of children pedestrians due to the smaller ground clearance of the front edge of engine hood， and the high ground clearance of the spoiler in MPV and SUV leads to the more severe injuries in tibia， fibula and knee ligament of lower limbs. Finally a parameter of sectional bending moment of long bones is proposed for assessing the lower extremity injury of six-year-old child pedestrian based on the simulation results， providing references for the development and digital assessment of child's leg impactor.
In this paper， life cycle assessment method is adopted to analyze the equivalent carbon emission and energy consumption of a fuel vehicle with four different materials i.e. common steel， advanced high strength steel （AHSS）， aluminum alloy and carbon fiber reinforced polymer （CFRP） as the material of its body-in-white in different stages of production， use （driving operation） and recovery after discard， with the influences of driving mileage on the emission reduction effects of different materials discussed. The results show that under current technical conditions， using AHSS and aluminum alloy to replace common steel as the material of body-in-white can reduce carbon emission and energy consumption， while using CFRP to replace common steel may increase the carbon emission and energy consumption. The life cycle carbon emission of aluminum alloy mainly depends on that in its production stage， while the selection of material is related to the carbon emission and energy consumption level in the region： in the region with general carbon emission and energy consumption level， aluminum alloy is superior than AHSS， while in the region with high carbon emission and energy consumption level， AHSS is superior than aluminum alloy. With the increase of driving mileage， the emission reduction effects of aluminum alloy become more remarkable. In a condition that the driving mileage of the fuel vehicle reaches 150 thousand km， it will get the comprehensively optimum carbon emission and energy consumption level when the materials of its body-in-white have a proportion of 77.9% AHSS versus 22.1% aluminum alloy.
The finite element model for a 12 m monocoque hybrid power city bus is created and the effects of body structure optimization on the energy-saving and emission reduction of the bus are analyzed through strength， stiffness and modal analyses as well as structural lightweighting and life cycle assessment. The results show that compared with original body skeleton， the mass of structurally optimized body skeleton reduces by 52.5 kg and both the strength and stiffness meet the requirements under bending and ultimate torsion conditions with a good natural vibration characteristic. As for the full life cycle， after lightweghting the mining resource consumption reduces by 0.4E04kg Sb-eq.， fossil energy resources consumption reduces by 0.7E04MJ and the overall environment influence factor reduces by 0.42E11， equivalent to a reduction rate of 3.81%， 4.46% and 4.56% respectively.
In this paper， a lightweight design procedure including the parallel optimization of material and structure is proposed for the inner panel of tail door made of injection-molded short-fiber-reinforced polymer composite in a car. A layered material model is built with consideration of the layered distribution feature of short fiber， on the basis of which a parameterized constitutive model for material is put forward to rapidly predict its mechanical performance when its parameters are changed. An extraction and mapping method for material parameters is proposed according to the distribution features of fiber orientation， so effectively enhancing the accuracy of structural analysis. Considering the design variables of material and structure， combined with Kriging surrogate model and boundary-searching based improved particle swarm optimization algorithm， a lightweight design procedure for composite tail door inner panel is proposed. As a final result， the parallel optimization of material and structure is fulfilled while assuring the design requirements for various working conditions with a lightweighting result of 10.5% mass reduction achieved.
For investigating the kinematic response and injury differences of riders in different emergent avoidance postures， human finite element model THUMS is used to develop four driving postures， i.e. one normal posture and three emergent avoidance postures： struck side foot landing （SFL）， non-struck side foot landing （NSFL） and landing on both feet （LBF）. A simulation model for a car impacting electric two-wheeler and its rider is built with eight groups of simulations （combination of 20 and 40 km/h two speeds and 4 driving postures） conducted to comparatively analyze the head injury parameters （peak angular acceleration， peak linear acceleration， HIC15， intracranial pressure， CSDM0.15 and MPS） and the Von-Mises stress distribution in lower limbs， and to evaluate the ground impact injury risk of two-wheeler rider. The results show that with a vehicle speed of 20 km/h， the head injury of normal posture rider in ground impact exceeds AIS 4+， while the lower limbs injury of riders with all types of postures do not exceed the fracture threshold. With a vehicle speed of 40 km/h， the head-ground impact injury of riders with all types of postures exceeded AIS 4+， the rider with an emergent avoidance posture of LBF has the highest risk of head injury， the rider with a normal posture has the lowest risk of lower limbs injury， while the rider with an emergent avoidance posture of SFL has a risk of lower limbs fracture. This study clarifies the effects of different emergent avoidance postures on riders' injuries in ground impact and provides an important reference basis for automotive safety technology research.
Most existing studies on driver’s mental load evaluation give the driver’s mental load classification label with the presence or absence of sub-tasks in driving scenes， but drivers may sometime fall into self-thinking， leading to the increase in their mental load in normal driving scenes. In addition， even the same driving sub-tasks may not have the same effects on the mental load of different drivers due to the discrepancy of individuals. As a result， there may exist some noisy labels in the data set collected by traditional methods， hence affecting the training results of the mental load evaluation models of drivers. In view of these problems， the method of confidence learning is adopted to process （detect and filter） the mental load classification labels of drivers in this paper. By using the processed labels， with electroencephalogram， electrocardiogram and skin electricity signal features as model inputs， the driver’s mental load models based on algorithms of support vector machine， random forest， K-near neighbor， decision tree， logic regression， and multi-layer perceptron are constructed to comparatively analyze the effects of noisy label processing on the enhancement of the performance of different models. The results show that after the noise label processing by using confidence learning， the performances of various driver’s mental load models constructed remarkably improve， among which support vector machine model achieves the best results in performance enhancement.
This paper aims to investigate the effects of active force of neck muscle on pedestrian head injury under different impact speeds and pedestrian gaits. Firstly， the head-neck part of LSTC pedestrian model is replaced by HHNM III head-neck model developed by Hunan University to form a hybrid pedestrian dummy model， whose effectiveness is then verified by cadaver test data. Then a simulation is conducted to analyze the effects of pedestrian gaits， i.e. struck leg backward （SLB） and struck leg forward （SLF） on pedestrian head injury under different impact speeds. The results show that in low-speed collisions， the neck muscles will reduce the amplitude of head movement， but increase the risk of head injury， the pedestrian head injury with a gait of SLB is severer than that with SLF， and the neck muscles have smaller effects on head injury in high-speed collisions.
Through the statistics and summing-up of real frontal crash test data in NHTA and IIHS and analytical solving， an evaluation method for the impact waveform and intrusion in 100% overlap frontal rigid barrier （FRB） crash and 50% overlap moveable progressive deformable barrier （MPDB） offset crash evaluated by C-NCAP， and frontal small overlap barrier （SOB） offset crash evaluated by C-IASI （China insurance automobile safety index） is established， which can lay down a good foundation for the matching of occupant restraint system and provide assurance for vehicles to obtain excellent star grade.
By means of literature research and simulation analysis， the condition input of seat rear impact dynamic test is determined， and the corresponding requirements of seat strength and dummy injury are proposed in this paper. The test methods and requirements proposed can be applied to the revision of the national standard for school bus seats and the static anti-backward-pitching test is upgraded to a dynamic one， so solving the problem that the static test cannot reflect the seat performance in actual traffic accidents and meeting the requirements of technological development.
According to the requirements of C-NCAP （2021 version）， the validated biomechanical model of Chinese three-year-old child occupant with detailed anatomical structure is used to establish a model for frontal 100% overlap rigid barrier crash test with a simulation conducted so as to compare the kinematic and biomechanical responses of three-year-old child occupant’s head and chest in different restraint systems in this paper. The results show that the use of safety seat belts can reduce the injury risks of child occupants in vehicle crash with high probability， the five-point seat belt has better child protection performance than three-point seat belt， and the application of biomechanical model for three-year-old child occupant with good bio-fidelity can use biomechanical evaluation parameters to analyze in-depth the injury mechanism of child occupant and hence to conduct all-around and multi-layer assessment on child protection devices and tested vehicle model.
In this paper， taking the pedestrian protection test system launcher as the research object and based on the high speed hydraulic ejection control technology ， the structure of the launch device， as well as structure design of the high speed hydraulic cylinder and the control principle of high speed hydraulic launching and electrical control system is introduced respectively. Finally， verification tests are carried out for various impact models. The test results show that the launch velocity is stable， accurate and reliable， which meets the test requirements. The proposed device can alleviate the situation that the domestic pedestrian protection test equipment is mainly dependent on import， which forms a proprietary technology of using high-speed hydraulic cylinder for pedestrian protection test equipment.
