Towards a Safer Design of Helmets: Finite Element and Experimental Assessment

2016 ◽  
Author(s):  
Sari Kassar ◽  
Sarah Siblini ◽  
Bilal Wehbi ◽  
Omar Abro ◽  
Mutasem Shehadeh
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Experimental Testing ◽  
Linear Acceleration ◽  
Road Accidents ◽  
Micro Structure ◽  
Experimental Assessment ◽  
Liner Material ◽  
Ratchet Mechanism ◽  
Motorcycle Helmets

Motorcycle helmets are vital to protect from recurrent road accidents as they prove crucial in reducing brain trauma. This research piece presents a new and plausible bio-inspired design affined to the foam liner material and structure in helmets. The proposed liner design is inspired from animal horn micro-structure and tubule arrangement. An innovative drop-testing apparatus is presented with a spring-ratchet mechanism for experimental testing. The aim is to validate the new design by meeting the ECE 22.05 standard for motorbike helmets using peak linear acceleration and HIC criteria. Experimental results are partly verified against FEA simulations for two proposed samples. Further samples call for more complex simulations at a later stage to best describe material properties and structures.

Design of Dual Layer Liner with Deformable Semi-Spherical Convex for Bicycle Helmet

2013 ◽  
Vol 284-287 ◽  
pp. 681-686
Author(s):  
Tso Liang Teng ◽  
Cho Chung Liang ◽  
Van Hai Nguyen
Keyword(s):  
Finite Element ◽  
Heat Dissipation ◽  
Linear Acceleration ◽  
Liner Material ◽  
Bicycle Helmets ◽  
Risk Of Injury ◽  
Standard Finite Element Method ◽  
Energy Absorbing ◽  
The Impact ◽  
Impact Absorption

Bicycle helmets aim to reduce the risk of injury due to impacts on the head. Generally, a bike helmet consists of the outer shell, liner, vents and straps. The liner helps absorb the effects of the impact to keep that force away from your head. To satisfy the functions of helmet liner, several criteria should be considered. The ideal liner would be stiffer in hard impacts, softer in lighter impacts, light, cheap, reliable to manufacture and easy to ventilate. Currently, there are many different design trends and concepts in the design of helmet liner. Researchers have tended to focus on the liner material. The Expended Polystyrene (EPS) foam is the most popular choice for liner material of helmet. The EPS foam is commonly used in helmets as an energy absorbing liner. However, EPS has some disadvantages, such as the difficulty to optimize energy absorbing in different areas of head and inferior effect of heat dissipation. Moreover, EPS is generally too brittle. In order to overcome its drawback, to search a better alternative is necessary. In this study, a dual layer liner is proposed to yield enhanced impact absorption, that is to say, the liner is constructed by two layers of polycarbonate with deformable semi-spherical convex. The energy absorbed by deformation of convexes which is described by a combination of folding and collapsing. The main advantages of this liner design not only show the energy absorbing capabilities like EPS foam but also gain a better optimization of energy absorbing for different sites. This study focuses on assessment of a helmet with dual layer liner based on the shock absorbing test of CPSC’s standard. Finite element method (FEM) is available contribution greatly to helmet test modeling. This study performs finite element analyses of helmet impact tests using LS-DYNA software. The simulation of helmeted headform drop test is implemented for the four kinds of liner thickness. To confirm the energy absorbing capabilities of dual layer liner, the resultant CG linear acceleration of the headform is measured from the helmet test simulation. According to the CPSC’s standard specification, the acceleration of headform should be less than 300 g's during the impact.

scholarly journals Numerical prediction of mechanical properties of zirconium alloy with hydrides using finite element method

Energetika ◽  
2018 ◽  
Vol 64 (1) ◽  
Author(s):  
Remigijus Janulionis ◽  
Gintautas Dundulis ◽  
Rita Kriūkienė ◽  
Albertas Grybėnas
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Zirconium Alloy ◽  
Experimental Testing ◽  
Zirconium Alloys ◽  
Numerical Prediction ◽  
Alternative Methods ◽  
Zirconium Hydride ◽  
Fe Method

During nuclear power plant (NPP) operation, degradation effects like ageing, corrosion, fatigue, and others may significantly impact component integrity. One of the degradation mechanisms is hydrogen absorption. High levels of hydrogen in zirconium alloys can lead to the formation of zirconium hydrides and that can influence material properties. Therefore, determination of material properties under different levels of hydrogen concentration in zirconium alloys is important. It is not always possible to conduct an experimental testing. Therefore, there is a need for alternative methods for determination of material properties. This article presents the numerical prediction of material properties of zirconium 2.5% niobium alloy with hydrides. According to the objective of the work, numerical prediction was performed using the finite element (FE) method. This was done by creating a finite element model of zirconium hydride embedded in zirconium alloy. The geometry and size of hydride were measured from a real specimen. The size of zirconium alloy surrounding the hydride was selected in such a way that hydride volume part in the model would match experimental measurements. The prognosis results were compared with the experimental data.

scholarly journals Finite element analysis of mechanical response of a bed side rail

2006 ◽  
Vol 54 (2) ◽  
pp. 59-66
Author(s):  
Petr Koňas ◽  
Milan Šimek
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Efficient Solution ◽  
Mechanical Response ◽  
Experimental Testing ◽  
Furniture Design ◽  
Element Analysis ◽  
Test Room ◽  
Side Rail

According to non-existence of mechanical material properties for selected combination of materials it is appropriate to give a notice, that suggested solution should be examined in test-room of furniture by related norms. The suggested verification was finally realized on furniture test-room by Departure of Furniture, Design and habitation and approved availability of suggested numerical solution for defined tasks. If we take into account large amount of variants, which were modelled by this method (and which are not mentioned in this project) without requirements of experimental testing for each suggestion it is appropriate to remind the significant financial saving, due to realized numerical simulations which allowed to find efficient solution and which may not be attainable by experimental way (mainly with regard to financial severity).

Determination of Charge Coefficient of Piezoelectric Films Using a Combined Finite Element Model and Dynamic Loading Technique

2020 ◽  
Vol 835 ◽  
pp. 229-242
Author(s):  
Oboso P. Bernard ◽  
Nagih M. Shaalan ◽  
Mohab Hossam ◽  
Mohsen A. Hassan
Keyword(s):  
Finite Element ◽  
Dynamic Loading ◽  
Material Properties ◽  
Accurate Determination ◽  
Substrate Material ◽  
Experimental Results ◽  
Piezoelectric Composite ◽  
Piezoelectric Film ◽  
Piezoelectric Charge

Accurate determination of piezoelectric properties such as piezoelectric charge coefficients (d33) is an essential step in the design process of sensors and actuators using piezoelectric effect. In this study, a cost-effective and accurate method based on dynamic loading technique was proposed to determine the piezoelectric charge coefficient d33. Finite element analysis (FEA) model was developed in order to estimate d33 and validate the obtained values with experimental results. The experiment was conducted on a piezoelectric disc with a known d33 value. The effect of measuring boundary conditions, substrate material properties and specimen geometry on measured d33 value were conducted. The experimental results reveal that the determined d33 coefficient by this technique is accurate as it falls within the manufactures tolerance specifications of PZT-5A piezoelectric film d33. Further, obtained simulation results on fibre reinforced and particle reinforced piezoelectric composite were found to be similar to those that have been obtained using more advanced techniques. FE-results showed that the measured d33 coefficients depend on measuring boundary condition, piezoelectric film thickness, and substrate material properties. This method was proved to be suitable for determination of d33 coefficient effectively for piezoelectric samples of any arbitrary geometry without compromising on the accuracy of measured d33.

A semianalytical and finite-element solution to the unbonded contact between a frictionless layer and an FGM-coated half-plane

2017 ◽  
Vol 24 (2) ◽  
pp. 448-464 ◽  
Author(s):  
Jie Yan ◽  
Changwen Mi ◽  
Zhixin Liu
Keyword(s):  
Integral Equation ◽  
Finite Element ◽  
Singular Integral Equation ◽  
Contact Problem ◽  
Singular Integral ◽  
Material Properties ◽  
Elastic Layer ◽  
Coated Substrate ◽  
Receding Contact ◽  
Contact Size

In this work, we examine the receding contact between a homogeneous elastic layer and a half-plane substrate reinforced by a functionally graded coating. The material properties of the coating are allowed to vary exponentially along its thickness. A distributed traction load applied over a finite segment of the layer surface presses the layer and the coated substrate against each other. It is further assumed that the receding contact between the layer and the coated substrate is frictionless. In the absence of body forces, Fourier integral transforms are used to convert the governing equations and boundary conditions of the plane receding contact problem into a singular integral equation with the contact pressure and contact size as unknowns. Gauss–Chebyshev quadrature is subsequently employed to discretize both the singular integral equation and the force equilibrium condition at the contact interface. An iterative algorithm based on the method of steepest descent has been proposed to numerically solve the system of algebraic equations, which is linear for the contact pressure but nonlinear for the contact size. Extensive case studies are performed with respect to the coating inhomogeneity parameter, geometric parameters, material properties, and the extent of the indentation load. As a result of the indentation, the elastic layer remains in contact with the coated substrate over only a finite interval. Exterior to this region, the layer and the coated substrate lose contact. Nonetheless, the receding contact size is always larger than that of the indentation traction. To validate the theoretical solution, we have also developed a finite-element model to solve the same receding contact problem. Numerical results of finite-element modeling and theoretical development are compared in detail for a number of parametric studies and are found to agree very well with each other.

Sign in / Sign up

Export Citation Format

Share Document