Browsing by Author "Tsehayneh Negash"

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    Numerical Analysis on the Impact Resistance and Energy Absorption Behavior of Motorcycle Helmet for Different Impact Conditions
    (Addis Ababa University, 2023-10) Tsehayneh Negash; Araya Abera (PhD); Tadesse Nega (Mr.) Co-Advisor
    Head injuries are common during different activities of daily life – one is related to motorcycle vehicle traffic accident. The aim of this research was concerned on the analysis and evaluation of the effect of impact loads on the basis of impact velocities and angles in the case of accidents. The investigations were carried out using numerical analysis. The independent variables were impact velocities – ranged from 7.5 m/s to 17.5 m/s and impact angles – ranged from 00 to 900. Flat anvil and footpath scenarios were also conditions on which the effects of angles were determined. The peak linear acceleration (PLA) and head injury criteria (HIC) as well as energy absorption effect were the output parameters for the study. Solidworks 2022 SP1 30.1.0.82 and ANSYS – LS DYNA (HyperMesh 2019.1 – LsDyna (Keyword971_R10.1)) were employed for the modellings and numerical analysis. The Economics Commission for Europe (ECE 22.05) specification was selected to investigate the specified parameters related to the standards. Based on the obtained results when using stiff liner component, the PLA ranges from 199G to 622G (PLA per gravity) and HIC ranges from 1927 to 23900 when the impact velocity increases from 7.5 m/s to 17.5 m/s for frontal impact. Similar incremental trends were also recorded on the crown, rear and lateral impact positions. Using soft liner material, the effect of angles on the crown impact position at 16.5m/s were investigated and 153G of PLA and 1708 of HIC recorded at impact angle of 900. But when the value of the angle decreased, PLA and HIC values also continuously decreased. So, the severity of the accident increases with impact velocity and impact angels on flat anvil impacts. The extent of risk for the accidents which happened on footpath curve, minimized as the inclination of the resultant impact velocity was about 450 for the given specified impact velocity; this is because the impact load decomposed towards the two impact points. Using the model for the specified limit can provide the protection; but crossing the limit may result the risk too severe.