Design And Fabrication Of A Tropical Motorcycle Helmet

The present work is devoted to the design and evaluation of a new crashworthy motorcycle helmet taking into consideration the tropical climate of Malaysia. A multidiscipline literature review on the design problems of motorcycle helmet was carried out and current problems were formulated. Based on the literature review findings, a new shell and liner designs were then proposed to overcome or eliminate these problems. The shell design improvements consisted of developing hybrid natural fiber composite (NFC) shells which were fabricated and evaluated by the standard dynamic penetration test. The results of the new design were found to be satisfactory according to the related helmet standards. Three additional methods have been developed to assess the new shells performance in a more quantified manner. These tests are the helmet quasi-static penetration, the helmet rigidity, and the helmet crushing. All these tests were performed and the results confirmed the superior performance of the new natural fiber shell helmets as compared to the market dominant ABS shell helmets. Other factors also supported this design improvement such as cost, and the utilization of environmental friendly material. In the liner design improvement, the shell was kept to the current ABS shell and the EPP foam as a liner. A 3D finite element algorithm has been developed using LSDYNA- 3D software. Based on the simulation results, the helmet with EPP foam liner was found to be satisfactory according to the related helmet standards. A parametric study of the helmet design was performed using the Response Surface Methodology in the Design of Experiment (DOE) statistical method. From this parametric study, the foam thickness and the foam density were found to have more significant effect on the helmet energy absorption than the she]] effects. Design optimizations were also conducted and optimum design was obtained. Finally, thermal analysis for commercially available helmet without ventilation system and the new helmet design with ventilation system were made. from which it was found that helmet ventilation is essential to avoid possible health problems. A design chart for helmet with ventilation system to obtain the minimum cross sectional area required for ventilation nozzles has been developed. This chart is suitable for a wide span of amounts of heat generated from the motorcyclist head. The effect of adding the ventilation system to the helmet has been structurally investigated by the finite element simulation and found to positively improve the energy absorption performance of the helmet

Effect of process parameters and optimization of CO2 laser cutting of ultra high performance polyethylene

The aim of this work is to relate the cutting edge quality parameters (responses) namely: upper kerf, lower kerf, ratio of the upper kerf to lower kerf and cut edge roughness to the process parameters considered in this research and to find out the optimal cutting conditions. The process factors implemented in this research are: laser power, cutting speed and focal point position. Design of experiment (DoE) was used by implementing Box-Behnken design to achieve better cut qualities within existing resources. Mathematical models were developed to establish the relationship between the process parameters and the edge quality parameters. Also, the effects of process parameters on each response were determine. Then, a numerical optimization was performed to find out the optimal process setting at which the quality features are at their desired values. The effect of each factor on the responses was established and the optimal cutting conditions were found

Thermo-Mechanical Modeling of High-Strength Concrete Column Subjected to Moderate Case Heating Scenario in a Fire

This paper presents a numerically developed computer model to simulatethe thermal behavior and evaluate the mechanical performance of a fixedend loaded loaded High Strength Concrete Column (HSCC), subjectedto Moderate Case Heating Scenario (MCHS), in a hydrocarbon fire. Thetemperature distribution within the mid-height cross-sectional area of thecolumn was obtained to determine the thermal and mechanical responsesas a function of temperature. The governing two-dimensional transient heattransfer partial differential equation (PDE), was converted into a set of ordinary algebraic equations, subsequently, integrated numerically by usingthe explicit finite difference method, (FDM). A computer program, VisualBasic for Applications (VBA), was then developed to solve the set of ordinary algebraic equations by implementing the boundary as well as initialconditions. The predictions of the model were validated against experimental data from previous studies. The general behavior of the model as wellas the effect of the key model parameters were investigated at length in thereview. Finally, the reduction in the column’s compression strength and themodulus of elasticity was estimated using correlations from existing literature. And the HSCC failure load under fire conditions was predicted usingthe Rankine formula. The results showed that the model predictions of thetemperature distribution within the concrete column are in good agreementwith the experimental data. Furthermore, the increase in temperature ofthe reinforced concrete column, (RCC), due to fire resulted in a significantreduction in the column compression strength and considerably acceleratesthe column fire failure load

Material property determination of the lining layers of a versatile helmet

This paper deals with material property identification of a helmet lining consisting of an outer layer of an expanded polystyrene (EPS) and inner layer of an open-closed cell foam (OCCF). A combined numerical simulation and experimental testing was used for the material property identification. Compression and drop tests were performed. The ABAQUS finite element commercial code was used for numerical simulations in which the OOCF was modelled as a rate dependent viscoelastic material, while the EPS as a crushable foam. The reaction force time histories coming from the numerical simulation and the experiment have been used as a criterion for material parameter determination. After the identification of the material properties, numerical drop-tests were used to study the behaviour of a plate and a conical composite OOCF and EPS liners to decide which of them suits more for the helmet

Drop Weight Testing Rig Analysis and Design

Crashworthiness studies are becoming increasingly important in mechanical design, particularly with the new advancement of the computer simulation codes. These studies generally require material and prototype testing for both modelling and validation. Large percentages of these studies lie on the limits of medium strain rate, which could be achieved by a drop weight test rig. Therefore, the drop weight test rig becomes an essential tool for such research activities besides the universal quasi-static testing machines. This paper is devoted to the analysis and design of the drop weight impact-testing rig. First, the different aspects of the mechanical design such as the propulsion, guidance, and frame layout, foundation and energy aspects are presented and discussed. Then, the basic types of data retrieval and analysis systems applicable for drop weight impact testing machines are presented and discussed. Data retrieval components considered in this study include the sensors for load, acceleration, and velocity measurements, image acquisition including high-speed cameras and PC-based image acquisition system, and data acquisition including oscilloscope or PC-based data acquisition system which utilizes an AID card and application software for visualizing and analyzing of the results. At the end of this article the designed and constructed test machine is presented as a case study

Motorcycle Helmet Part II. Materials and Design Issues.

The main objective of this paper is to formulate a methodology, which could be used for material selection and basic design of motorcycle helmets. The importance of simplified solutions to motorcycle helmet material selection and design are first highlighted. Two methods are presented. The first approach is based on energy absorption theory for packaging design and also was used for bicycle helmets design with some adjustments. This method is reviewed and modified to cope with the motorcycle helmet design requirements. The second approach is also base on energy absorption principle. This method was developed for packaging design but the same principle could be employed to the motorcycle helmet problem. It was found that the two approaches have the same energy absorption principles but differ in the way of formulation and utilization. These differences could have significance effect on the results particularly the energy per unit volume calculation. However, both procedures could be used as useful tool for the helmet foam material selection and helmet preliminary analysis and design. Using these energy approaches together with advanced computational techniques could reduce the lead-time of helmet design and manufacture