Lumbar Spine Biomechanical Responses and Chest Injury Risks for Reclined Occupants under MPDB Impact

doi:10.3969/j.issn.1004-132X.2026.07.016

Abstract

Abstract:

To investigate the lumbar spine biomechanical responses and chest injury risk of reclined occupants in a 50% overlap MPDB crash， three sets of simulations are conducted using the THUMS finite element human body model in accordance with the 2024 version of the C-NCAP protocol. The results indicate that foot-interior footrest contact significantly influences the probability of submarining. When a “belt-on-neck” phenomenon occurs for the reclined occupant during the crash， maximum chest compression alone may not adequately reflect the chest injury risk. The axial compressive force on the lumbar vertebrae increases progressively with increasing seatback recline angle. Under different postures， a correspondence exists between the lumbar bending center of rotation and the vertebra sustaining the maximum bending moment. The overall lumbar spine of the reclined occupant exhibits a pronounced S-shaped lateral bending motion and is subjected to combined compression， bending， and lateral bending loads.

Key words: lumbar spine loading, chest injury, reclined occupant, mobile progressive deformable barrier （MPDB）, submarining

摘要：

为研究后倾乘员在50%重叠移动渐进变形壁障碰撞中的腰椎生物力学响应及胸部损伤风险，采用THUMS人体有限元模型并按照2024版C-NCAP法规进行了三组仿真。仿真发现，后倾乘员脚部与内饰踏板的接触会显著影响乘员下潜的发生概率；若后倾乘员在碰撞过程中出现“勒脖子”现象，则胸部最大压缩量可能无法有效评估胸部损伤风险；随着靠背倾角的增大，腰椎椎体所受轴向压缩力增大；不同姿态下的腰椎弯曲旋转中心与最大弯曲力矩椎体存在对应关系；后倾乘员的腰椎整体表现出大幅度的S形侧倾运动，腰椎承受压缩、弯曲、侧倾三种载荷。

关键词: 腰椎载荷, 胸部损伤, 后倾乘员, 50%重叠移动渐进变形壁障碰撞, 下潜

CLC Number:

U461.4

XIAO Zonghan, PAN Di, HUANG Zhishan, LIU Hui, LYU Xiaojiang, HAN Yong. Lumbar Spine Biomechanical Responses and Chest Injury Risks for Reclined Occupants under MPDB Impact[J]. China Mechanical Engineering, 2026, 37(7): 1664-1672.

肖宗瀚, 潘迪, 黄志山, 刘慧, 吕晓江, 韩勇. 后倾乘员在MPDB碰撞中的腰椎生物力学响应与胸部损伤风险[J]. 中国机械工程, 2026, 37(7): 1664-1672.

Figures/Tables 20

Fig.1 The finite element model of Accord vehicle-MPDB -THUMS occupant

Fig.2 Three representative occupant postures

Fig.3 Three loading directions of lumbar vertebral

Fig.4 Occupant kinematic response

Fig.5 Trajectory of key parts of the occupant

Fig.6 Relative position between the occupant's pelvis and the seatbelt in the resting posture

Fig.7 Peak axial compressive force of vertebrae

Fig.8 Kinematic response of vertebrae flexion-extension in the standard posture occupant

Fig.9 Kinematic response of vertebrae flexion-extension in the relaxed posture occupant

Fig.10 Kinematic response of vertebrae flexion-extension in the resting posture occupant

Fig.11 Peak flexion-extension moment My of vertebrae

Fig.12 Kinematic response of vertebrae Left tilt-Right tilt in the standard posture occupant

Fig.13 Kinematic response of vertebrae Left tilt-Right tilt in the relaxed posture occupant

Fig.14 Kinematic response of vertebrae Left tilt-Right tilt in the resting posture occupant

Fig.15 Peak Left tilt - Right tilt moment Mx of vertebrae

Fig.16 Chest resultant acceleration curve

Tab.1 Chest 3ms resultant acceleration and maximum compression

	乘员姿态
	标准	放松	休息
靠背倾角/（°）	25	45	56
胸部3 ms合成加速度/g	24.71	32.31	36.88
胸部最大压缩量/mm	19.56	16.19	15.41

Tab.2 Cloud diagram of heart-lung pressure and maximum principal strain of ribs

乘员姿态	心脏压力	肺部压力	肋骨最大主应变
标准
标准	891.70 kPa@85 ms	704.18 kPa@95 ms	5.26％@107 ms
放松
放松	765.84 kPa@143 ms	723.38 kPa@130 ms	5.63％@107 ms
休息
休息	999.35 kPa@130 ms	1013.37 kPa@91 ms	3.86％@118 ms
阈值	170 kPa	16 kPa	2.4%

Tab.3 Mechanical response parameters of lumbar vertebral bodies

椎体	轴向压缩力/kN			弯曲力矩/（N·m）			伸展力矩/（N·m）			左倾力矩/（N·m）			右倾力矩/（N·m）
椎体	标准	放松	休息	标准	放松	休息	标准	放松	休息	标准	放松	休息	标准	放松	休息
T12	2.32	3.03	3.30	-23.81	-67.83	-90.28	/	/	/	/	/	/	-15.52	-45.59	-53.01
L1	2.54	3.36	3.56	-48.95	-87.04	-96.92	/	/	/	/	/	/	-19.45	-44.15	-47.94
L2	2.54	3.06	3.26	-66.43	-92.77	-77.69	/	/	/	/	/	/	-7.63	-13.45	-12.57
L3	2.80	3.15	3.39	-78.49	-77.65	-57.52	/	/	/	14.50	23.39	31.29	/	/	/
L4	2.69	3.09	3.58	-57.32	-57.07	-37.82	/	/	17.66	33.38	54.39	50.92	/	/	/
L5	2.73	2.98	3.30	-61.45	-58.29	-29.44	/	6.99	39.13	38.49	55.07	42.35	/	/	/

Tab.4 Chest injury assessment indices

损伤参数	乘员姿态
损伤参数	标准	放松	休息
胸部3 ms合成加速度/g	24.71	32.31	36.88
胸部最大压缩量/mm	19.56	16.19	15.41
心脏压力/kPa	891.70	765.84	999.35
肺部压力/kPa	704.18	723.38	1013.37
肋骨最大主应变/%	5.26	5.63	3.86

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