Material Modelling of Adipose Tissue for Traffic Injury Prevention
Doktorsavhandling, 2020

Traffic injury is one of the main reasons for traumatic injuries. Obese occupants are among the vulnerable populations with a higher risk of death and severe injuries. Notably, obesity is associated with a thick layer of subcutaneous adipose (fat) tissue. In case of a crash, this may influence how the lap belt engages with the pelvis resulting in submarining, i.e., the lap belt slipping over the iliac crest of the pelvis, causing severe injuries. A popular numerical method to study occupant injuries in motor-vehicle collisions involves using Finite Element Human Body Models (FEHBMs). However, current FEHBMs, such as the THUMS or GHBMC models, do not represent the obese population in body shape or material properties, and are unable to represent the submarining phenomenon. In particular, there is no appropriate constitutive model for adipose tissue in the FEHBMs, while the mechanical property of adipose tissue is important in the simulation of interaction between the human body and restraint systems or the impact with interior objects.

The first aim of this research was to establish a biofidelic constitutive model for adipose tissue mechanical response, at high strain rates and large deformations. For this purpose, a nonlinear viscoelastic constitutive model was formulated. Global sensitivity analysis was used as a tool to learn what mechanical properties of adipose tissue are identifiable from different test setups. Thus, a frequency-sweep test and a ramp loading-unloading shear test were applied to account for the adipose tissue behaviour at high strain rates and large deformations, respectively. The second aim was to identify which parameters influence submarining the most. It was found that the incompressibility (Poisson's ratio) of adipose tissue is the most important material parameter.
With regard to safety design, important parameters include lap belt angle and pelvis rotation. Due to a thicker layer of adipose tissue, the effect of these parameters becomes more important for obese occupants, resulting in a higher risk of submarining. These findings support the development of biofidelic FEHBMs, as well as suitable restraint system designs in order to reduce the risk of submarining.

Global sensitivity analysis

Finite element human body models

Submarining

Constitutive modelling

Adipose tissue

Obesity

Stödet Room Radion SB3 - 3086B, 8 pl.
Opponent: Prof. Duane Cronin, Mechanical and Mechatronics Engineering, University of Waterloo, Canada.

Författare

Hosein Naseri

Chalmers, Mekanik och maritima vetenskaper, Dynamik

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A Nonlinear Viscoelastic Model for Adipose Tissue Representing Tissue Response at a Wide Range of Strain Rates and High Strain Levels

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The effect of adipose tissue material properties on the lap belt-pelvis interaction: A global sensitivity analysis

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Naseri, H., Iraeus, J., Johansson, H., 2020. “A Numerical Study on the Risk of Lap Belt Submarining Considering Occupant and Vehicle Design Parameters”.

Safety belts were first introduced in 1959 and still represent the main protection for preventing injuries in vehicular crashes. In a collision, seatbelts restrain the moving body by distributing the load over the chest, shoulders, and pelvis, slowing down the body to avoid impact with the vehicle interior. Still, does wearing a seat belt suffice to remain confident of its functionality? Indeed, improper seat belt fit can in itself be responsible for causing injury in vehicle collisions.

Submarining, a severe situation in car crashes defined as the lap belt slipping over the hip bone instead of gripping it, may ensue as a result of wearing the lap belt incorrectly. Consequently, the victim is propelled under the lap belt leading to serious injuries. Several factors may influence submarining, such as reclining the seatback, lap belt positioned high on the stomach or having lap belt in a flat angle. Obesity is also one reason increasing the risk of submarining.

In this thesis, a material model that can capture the soft and load rate-dependent bahviour of adipose tissue is suggested. It has been found that for obese occupants, the thick layer of adipose (fat) tissue prevents the lap belt securely gripping the pelvis bone resulting in higher risk of submarining. Moreover, adipose tissue compressibility plays an important role in submarining. Other important factors are lap belt angle and pelvis angle.

Future Occupant Safety for Crashes in Cars (OSCCAR)

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Utveckling av ramverk för modellprediktioner med felkontroll med tillämpning på mänsklig fettvävnad

Vetenskapsrådet (VR), 2014-01-01 -- 2017-12-31.

Styrkeområden

Transport

Ämneskategorier

Teknisk mekanik

Annan medicinteknik

Farkostteknik

ISBN

978-91-7905-254-6

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4721

Utgivare

Chalmers tekniska högskola

Stödet Room Radion SB3 - 3086B, 8 pl.

Online

Opponent: Prof. Duane Cronin, Mechanical and Mechatronics Engineering, University of Waterloo, Canada.

Mer information

Senast uppdaterat

2020-05-05