Narrow Results

The complete evaluation of the side vehicle structure and the occupant protection is only possible by means of the full scale side impact crash test. But, auto part manufacturers such as door trim makers can not conduct the test especially when the vehicle is under the developing process. The main objective of this study is to obtain the design guidelines by a simple component level impact test. The relationship between the target absorption energy and impactor speed were examined using the energy absorbed by the door trim. Since each different vehicle type required different energy levels on the door trim. A simple impact test method was developed to estimate abdominal injury by measuring reaction force of the impactor. The reaction force will be converted to a certain level of the energy by the proposed formula. The target of absorption energy for door trim only and the impact speed of simple impactor are derived theoretically based on the conservation of energy. With calculated speed of dummy and the effective mass of abdomen, the energy allocated in the abdomen area of door trim was calculated. The impactor speed can be calculated based on the equivalent energy of door trim absorbed during the full crash test. With the proposed design procedure for the door trim by a simple impact test method was demonstrated to evaluate the abdominal injury. This paper describes a study that was conducted to determine sensitivity of several design factors for reducing abdominal injury values using the matrix of orthogonal array method.

In conclusion, with theoretical considerations and empirical test data, the main objective, standardization of door trim design using the simple impact test method was established.

The occupant's pelvis is most susceptible to injuries in side collision accidents. To further investigate the pelvis biomechanical responses and injury mechanisms in side impacts, a biofidelic pelvis finite element (FE) model was created. In contrast to previous studies, the model was based directly on the CT data of a volunteer representing the 50th percentile Chinese male. Both cortical and cancellous bone were modeled with hexahedral elements. Through model validations against Post Mortem Human Subjects (PMHS) tests, the pelvis responses and injuries under side impacts were analyzed. Meanwhile, additional simulations were carried out utilizing the validated model to study the effects of the femoral head, impactor pad and impactor velocity on pelvic injuries. The results indicated that the most frequent injury type of the pelvis is pubic rami fracture, followed by fractures of the femoral head, greater trochanter and acetabulum. In validation against the test of Guillemot et al., the critical load of pelvic fracture was 3.8 kN. In validation against the tests of Beason et al., the peak impact force under unpadded load and padded load was 4.3 kN and 3.1 kN, respectively, while the (VC)_max was 0.25 m/s and 0.16 m/s, respectively. Peak impact force appears to be a reasonable criterion to assess pelvic injury. Moreover, the femoral head and impactor pad play an important role in absorbing impact energy, distributing impact load, and alleviating pelvic injury.

In vehicle side collisions, traumatic brain injury caused by the impact between occupant’s head and the interior parts of A or B pillar is a major reason of death and disability. In order to analyze the biomechanical response and injury mechanism of occupant’s brain in side collisions, a refined finite element head model representing the 50th percentile Chinese male was developed. Its improvements of biofidelity comparing to the original head model were illustrated through model simulation against the same post mortem human subjects test. Based on the refined head model, the brain biomechanical responses and injuries in the side impact with interior parts of A pillar and B pillar were analyzed according to FMVSS 201U, and the influences of different impact locations and directions were investigated. The results showed that the brain tissues on impact side sustained positive pressure and those on the opposite side experienced negative pressure. The transmission of pressure wave was easy to cause brain concussion and other diffuse brain injuries. The intracranial pressure distribution exhibited a typical pattern of contrecoup injury. The extreme stress concentration in the junction area of the cerebrum, cerebellum and brain stem could lead to focal injury such as brain contusion and laceration. Moreover, the impact injury of A pillar was more serious than that of B pillar, which was consistent with the traffic injury statistics that the head injury in oblique side collisions was more serious than that of vertical side collisions. Therefore, the interior parts of A pillar should be designed to absorb more energy than those of B pillar under the same conditions. In addition, the severity of brain injury is more sensitive to the variation of the horizontal angle than that of the vertical angle. Both the peak values of the occipital fossa pressure in effect simulations of the horizontal and vertical angles were three to four times of the peak values of the forehead pressure. When the impact horizontal angle was up to 255${}^{\circ }$, or the vertical angle was up to 45${}^{\circ }$, the head HIC(d) values would be up to 1320.45 and 1101.06, respectively, which indicated a AIS 3$+$ injury risk of the head.

Finite element modeling has played a significant role in the study of human body biomechanical responses and injury mechanisms during vehicle impacts. However, there are very few reports on similar studies conducted in China for the Chinese population. In this study, a high-precision human body finite element model of the Chinese 50th percentile male was developed. The anatomical structures and mechanical characteristics of real human body were replicated as precise as possible. In order to analyze the model’s biofidelity in side-impact injury prediction, a global technical standard, ISO/TR 9790, was used that specifically assesses the lateral impact biofidelity of anthropomorphic test devices (ATDs) and computational models. A series of model simulations, focusing on different body parts, were carried out against the tests outlined in ISO/TR 9790. Then, the biofidelity ratings of the full human body model and different body parts were evaluated using the ISO/TR 9790 rating method. In a 0–10 rating scale, the resulting rating for the full human body model developed is 8.57, which means a good biofidelity. As to different body parts, the biofidelity ratings of the head and shoulder are excellent, while those of the neck, thorax, abdomen and pelvis are good. The resulting ratings indicate that the human body model developed in this study is capable of investigating the side-impact responses of and injuries to occupants’ different body parts. In addition, the rating of the model was compared with those of the other human body finite element models and several side-impact dummy models. This allows us to assess the robustness of our model and to identify necessary improvements.

Thoracic injury is one of the vital issues in vehicle side crashes. Experiments have been done widely to study thoracic injuries using biological subjects but less virtual tests were made by using Finite Element (FE) models. This study aimed at determining the correlation of the computationally calculated thoracic injury (Number of Rib Fractures NRF) with existing thoracic injury criteria under pure side and oblique impacts. For this purpose, a previously developed thorax FE model was validated by using Post Mortem Human Subject (PMHS) tests in pure side and oblique impacts in this study. The rib fractures were reconstructed and compared with the fractures observed in the PMHS tests. The model was then used to simulate rib fractures in human thorax impactor tests at Principal Direction of Force (PDOF) angles of 90${}^{\circ }$ to 35${}^{\circ }$ (total of 12 impacts). Furthermore, the normalized NRF were calculated and analyzed for comparing with normalized simulated injury parameters based on various human thoracic injury criteria, including contact force criterion, thorax deflection criterion, compression criterion, upper spine acceleration criterion and Thoracic Trauma Index (TTI). It is suggested that the TTI criterion has better correlation with the NRF than the other injury criteria.

Giving consideration to both strength and energy absorption in side impact, it is of great significance to investigate the variable strength design and forming of B-pillar reinforcement panel. In this work, the finite element (FE) model of side impact was established for a certain car under the environment of Hypermesh and LS-DYNA. Based on the orthogonal experiment and adaptive response surface method, the optimization design of the variable strength of B-pillar reinforcement panel was carried out to make the distribution of the strength reasonable. After that, the B-pillar reinforcement panel with variable strength was further hot stamped in FE methods. The results show that the car body with the optimized B-pillar reinforcement panel can better meet the requirements of the side impact performance and, meanwhile, realize the aim of reducing weight by 12.1%.

According to the regulations of C-NCAP 2012, A complete vehicle side-impact model is established with dynamic explicit simulation software LS-DYNA, Base on this side impact model ,The original B pillar were replaced by tailored property Partial Hardening and TWB hot stamping B pillar in vehicle, and the side impact performance were calculation. The velocity and Intrusion of key points in the B pillar and front door were obtained. The weight of the new solutions can be reduced 2.06Kg with the application of tailor property Partial Hardening. Compare to the common hot stamping B pillar, tailored property Partial Hardening B pillar can effective protect the head and chest of occupant. Using tailored property Partial Hardening B pillar and TWB hot stamping B pillar can achieve equivalent performance as the original solutions.

Element Nb has been proved with advantages of grain size refinement and mechanical property improvement. This paper focused on the effect of element Nb on the crashworthiness of hot stamping B-pillars from 22MnB5 steels. Both Nb-bearing and Nb-free 22MnB5 were studied. It was found that the impact toughness of Nb-bearing 22MnB5 was increased by 31.07 % compared with Nb-free 22MnB5. This difference was reflected by the equivalent plastic strain to failure in the FEM simulation of this study. Simulations of side impact of 22MnB5 B-pillars with hot stamping outer were carried out and it was found that the Nb-bearing 22MnB5 could delay the fracture during impact. Energy absorption of impact regions was increased by 19.26 % and the maximum impact velocity was decreased by 8.43 %. The crashworthiness of B-pillar can be effectively improved by applying Nb-bearing 22MnB5.