Amir Radzi Ab. Ghani

Novel Design of Impact Attenuator for an 'Eco Challenge' Car

Thin-walled metallic tubular structures are generally used as impact energy absorber in automotive structures due to their ease of fabrication and installation, high energy absorption capacity and long stroke. However, unlike a normal passenger car where the impact energy can be distributed throughout the whole structure, the impact energy absorbing system of an Eco-Challenge car is confined within a limited space on the front bulkhead. The challenge is to develop an impact attenuator system that can effectively absorb the impact energy within the given space and fulfil the specified rate of deceleration. This new design utilized the standard Aluminium 6063 circular tubes, cut and welded into specific configurations i.e. stacked toroidal tubes with central axial tube sandwiched between two flat plates. Two configurations were investigated; circular and square toroids. Explicit non-linear FEA software was used to determine the impact response i.e. energy absorption, impact force and rate of deceleration. Both configurations showed promising results but the configuration that can be readily fabricated was chosen as the final design.

Impact Response of Circular Tube with Concentric Plunger

Thin-walled tubes are generally used as impact energy absorber in various application due to their ease of fabrication and installation, high energy absorption capacity and long stroke. However, the main drawback of plain tube is the high initial peak force. A concentric plunger in the form of tapered block is proposed to overcome this shortcoming while at the same time, improving the impact performance. Static and dynamic axial crushing were performed to determine the initial peak force (IPF), crush force efficiency (CFE) and specific energy absorption (SEA) for the concentric plunger with various taper angles. It was found that the concentric plunger affected the tube impact response. Comparison with plain circular tube was carried out and it was found that the concentric plunger improved the impact response of the tube especially in term of initial peak force.

Modelling and Simulation of a Single Deck Bus Subjected to Rollover Crash Loading

Buses are the most popular and common passenger vehicle for long distance travel in Malaysia. Increased bus usage as a public transport prompts researchers to study safety aspects of the vehicles subjected to various crash incidents. The most damaging bus accident is rollover crash. The bus structures must have sufficient crashworthiness and strength in order to reduce and prevent injuries and fatalities during the rollover accident. Initially, this paper overviews the current status of rollover accidents and requirement of UN-ECE Regulation 66 which is aimed to improve the bus structure in withstanding the rollover crash. The current bus framework structure comprises galvanized square hollow sections (SHS) which are welded and bolted together. Abaqus was used to simulate responses of bus structure subjected to loadings as specified in UN-ECE Regulation 66. The results showed that the gap allowances of the residual space are complied with the UN-ECE R66 requirements. Further work to optimize the bus structure in terms of weight, structural strength and crashworthiness is proposed.

Active tendon vibration control of cantilevered beam using shape memory alloy (SMA) actuators

This paper demonstrates, theoretically and experimentally, the feasibility of utilizing Shape Memory Alloy (SMA) as an actuator in controlling the flexural vibrations of a flexible cantilevered beam. The shape memory alloy used in this study is merely a straight wire which is made of nickel titanium alloy called Nitinol. Acting as tendons, these SMAs undergo phase transformation, to the austenitic phase, producing significant forces and displacement capabilities as well as low power consumption. This actuator unit is composed of a SMA wire attached to a spring in series. After being set-up with a load cell the transfer functions of the actuator are measured. Considering the uncertainty of the actuator unit performance the H-infinity optimal controllers are designed and installed into the control system. By integrating the thermal and dynamic characteristics of the SMA into beam dynamical model the composite beam-actuators system can now be developed. The robust stability performance of the designed controller is evaluated through vibrational test on the cantilever and the result is shown to be adequately attenuated.