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Pedestrian dynamic response and injury risk in high speed vehicle crashes

Nie Jin, Lv Xiaojiang, Li Kui, Li Guibing, Huang Xing

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 3

57--67

EN

The purpose of the current study is to understand pedestrian kinematics, biomechanical response and injury risk in high speed vehicle crashes. Methods: Vehicle-to-pedestrian crashes at the impact speeds of 40 km/h (reference set) and 70 km/h (analysis set) were simulated employing FE models of a sedan front and an SUV front together with a pedestrian FE model developed using hollow structures. The predictions from crash simulations of different vehicle types and impact speeds were compared and analyzed. Results: In crashes at 70 km/h, pedestrian head-vehicle contact velocity is by about 20–30% higher than the vehicle impact speed, the peak head angular velocity exceeds 100 rad/s and is close to the instant of head-vehicle contact, brain strain appears two peaks and the second peak (after head contact) is obviously higher than the first (before head contact), and AIS4+ head injury risk is above 50%, excessive thorax compression induces rib fractures and lung compression, both sedan and SUV cases show a high risk (>70%) of AIS3 + thorax injury, and the risk of AIS4 + thorax injury is lower than 40% in the sedan case and higher than 50% for the SUV case. Conclusions: Pedestrians in vehicle crashes at 70 km/h have a higher AIS3 + /AIS4 + head and thorax injury risk, high vehicle impact speed is more easily to induce a high head angular velocity at the instant of head-vehicle contact, brain strain is strongly associated with the combined effect of head rotational velocity and acceleration, and pedestrian thorax injury risk is more sensitive to vehicle impact speed than the head.

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Biomechanical analysis of thorax-abdomen response of vehicle occupant under seat belt load considering different frontal crash pulses

Qiu Jinlong, Li Kui, Xiang Hongyi, Xie Jingru, Fan Zhuangqin, Qin Mingxin

Acta of Bioengineering and Biomechanics

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2022

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Vol. 24, no. 4

31--38

EN

The purpose of this work was to understand the biomechanical response and injury risk of thorax and abdomen of vehicle front seat occupants caused by seat belt load under different frontal crash pulses. Methods: A vehicle-seat-occupant subsystem finite element (FE) model was developed using the a assembly of vehicle front seat and seat belt together with the THUMS (Total Human body Model for Safety) AM50 (50th% Adult Male) occupant model. Then the typical vehicle frontal crash pulses from different impact scenarios were applied to the vehicle-seat-occupant subsystem FE model, and the predictions from the occupant model were analyzed. Results: The modeling results indicate that the maximum sternal compression of the occupant caused by seat belt load is not sensitive to the peek of the crash pulse but sensitive to the energy contained by the crash pulse in the phrase before seat belt load reaching its limit. Injury risk analysis implies that seat belt load of the four crash scenarios considered in the current work could induce a high thorax AIS2+ injury risk (>80%) to the occupants older than 70 years, and a potential injury risk to the spleen. Conclusions: The findings suggest that control of the energy in the first 75 ms of the crash pulse is crucial for vehicle safety design, and thorax tolerance of the older population and spleen injury prevention are the key considerations in developing of seat belt system.

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A novel modeling approach for finite element human body models with high computational efficiency and stability: application in pedestrian safety analysis

Li Guibing, Meng Hengshuai, Liu Jinming, Zou Donghua, Li Kui

Acta of Bioengineering and Biomechanics

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2021

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Vol. 23, no. 2

33--40

EN

Purpose: The purpose of the current study was to develop and validate a finite element (FE) pedestrian model with high computational efficiency and stability using a novel modeling approach. Methods: Firstly, a novel modeling approach of using hollow structures (HS) to simulate the mechanical properties of soft tissues under impact loading was proposed and evaluated. Then, an FE pedestrian model was developed, employing this modeling approach based on the Total Human Model for Safety (THUMS) pedestrian model, named as THUMS-HS model. Finally, the biofidelity of the THUMS-HS model was validated against cadaver test data at both segment and full-body level. Results: The results show that the proposed hollow structures can simulate the mechanical properties of soft tissues and the predictions of the THUMS-HS model show good agreement with the cadaver test data under impact loading. Simulations also prove that the THUMS-HS model has high computational efficiency and stability. Conclusions: The proposed modeling approach of using hollow structures to simulate the mechanical properties of soft tissues is plausible and the THUMS-HS model could be used as a valid, efficient and robust numerical tool for analysis of pedestrian safety in vehicle collisions.