Biomekanisk optimering av stötdämpande beläggning som fallskadeprevention för fotgängare och cyklister SVE Sammanfattning


Biomekanisk optimering av stötdämpande beläggning som fallskadeprevention för fotgängare och cyklister

A fall is a serious health issue for the elderly. Among different fall types, the sideways fall is considered to be more severe concerning the injury outcome. When elderlies experience an unintentional sideways fall, they can either resist the impact forces with the soft tissue force attenuation capacity and femoral strength or need external protections to reduce the injury risk. In this project, these two aspects were investigated. Finite element whole-body models are valuable instruments for analyzing the fall biomechanics and investigating the possible preventive measures more conveniently. The whole-body models were developed to investigate the traffic accidents; however, a sideways fall has different kinematics than the other types of accidents. Consequently, it is necessary to enhance the whole-body models according to the major fall parameters, leading to severe injury cases, before assessing the external protection capabilities.
The current project attempted to advance these two critical aspects regarding the fall induced injuries. A finite element whole-body model was chosen to study three critical parameters in the fall biomechanics: body posture, soft tissue, femoral strength. The whole body model was positioned in different body configurations relevant for the sideways fall to evaluate the body posture that leads to the highest internal forces on the femoral head. Next, different soft tissue constitutive material models and soft tissue thicknesses were investigated to find a material model that could accurately reproduce the experimental results according to an objective rating method named CORA. Finally, the separate and combined effects of geometrical and mechanical properties changes due to aging on the femoral strength were assessed for the elderly males and females. In the second aspect of the project, the shock-absorbing rubberized asphalt pavements' preventive capacity was examined. First, different rubberized asphalt mixtures were implemented in bicycle and pedestrian accident reconstructions to evaluate the head injury risks. Later, the asphalt mixtures were studied in the sideways fall incidents to evaluate the hip fracture risk in elderly medium-size males and small-size females.
The first aspect of the project presented the results and methods to improve the sideways fall analysis, and the second aspect of the project focused on assessing the rubberized asphalt mixtures for injury prevention purposes. The sideways falls with the upright trunk, and a slightly forward-tilted pelvis could lead to the highest internal forces. A nonlinear Ogden material model scored better among different soft tissue material models in the side impacts to the hip segments. The geometrical and mechanical properties changes due to aging lead to a different behavior for males and females. Females experience a higher rate of strength loss due to aging. Moreover, it was indicated that a rubberized asphalt mixture could reduce the head injury risk for pedestrians and cyclists and the hip fracture risk for the elderly. The amount of rubber in the asphalt mixtures needs to exceed a specific limit to observe rubberized asphalts' preventive effects. Consequently, it is necessary to optimize the mixtures' rubber content to improve its prevention capacity.
In summary, the current project presented a method to improve the whole-body models according to the sideways fall requirements and assessed the protective capacity of the rubberized asphalt mixtures in head and hip injuries.

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Författare: Svein Kleiven, Pooya Sahandifar, Viveca Wallqvist
Utgivare: KTH/RISE
Utgivningsdatum: 2021-09-20
Diarienummer: TRV 2016/93101
Antal sidor: 10
Språk: Svenska
Kontaktperson: Helena Sjöberg, UHvr

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