Zaini Ahmad

Application of foam-filled conical tubes in enhancing the crashworthiness performance of vehicle protective structures

This paper treats the feasibility of including a supplementary energy-absorbing device in the form of foam-filled conical tubes onto vehicular protective structures to enhance their energy absorbing capacity and hence to enhance safety for the occupants during accidental impacts. The effect of the supplementary energy absorber device was investigated for varying values of the wall thickness of the tube and the foam density of the filler. Research findings have shown the inclusion of this supplementary energy-absorbing device to be a cost-effective and beneficial solution, which promoted an enhanced level of occupant safety by enhancing the energy absorption, reducing the amount of plastic deformation sustained by the protective structure as well as reducing the severity of the peak decelerations transferred to the occupant compartment during such an event.

Computational Approach in Formulating Mechanical Characteristics of 3D Star Honeycomb Auxetic Structure

Auxetic materials exhibit a unique characteristic due to the altered microstructure. Different structures have been used to model these materials. This paper treats a development of finite element model and theoretical formulation of 3D star honeycomb structure of these materials. Various shape parameters of the structural cell were evaluated with respect to the basic mechanical properties of the cell. Finite element and analytical approach for various geometrical parameters were numerically used to formulate the characteristics of the material. The study aims at quantifying mechanical properties for any domain in which auxetic material is of interest for variations in geometrical parameters. It is evident that mechanical properties of the material could be controlled by changing the base wall angle of the configuration. The primary outcome of the study is a design guideline for the use of 3D star honeycomb auxetic cellular structure in structural applications.

Influence of auxetic foam in quasi-static axial crushing

Abstract This paper treats the influence of auxetic foam on the crush response and energy absorption response of square-section tubes when subjected to uniaxial quasi-static loading. The study aims at quantifying the energy absorption capability of auxetic foam-filled square tubes for variations in wall thickness, initial height, aspect ratio and slenderness ratio of the tube. The capability of simulating the crush response of auxetic foam-filled tubes using the validated numerical models is also presented. Based on the experimental results, the influence of the auxetic foam in the thin-walled square tubes was quantified in terms of energy absorption capacity, specific energy absorption and crush force efficiency. It is evident that a thicker tube filled with auxetic foam is preferable if the energy absorption level is the primary goal, yet this compromises the crush force efficiency. The outcome of this present study is the establishment of empirical models for estimating the quasi-static crushing response of auxetic foam-filled tubes with varying slenderness ratio and aspect ratio.

Experimental and Numerical Studies of Fiber Metal Laminate (FML) Thin-Walled Tubes Under Impact Loading

Fiber metal laminate (FML) in form of tubular structures is a modern light-weight structure fabricated by incorporating metallic and composite materials. This present study deals with the impact characteristics and energy absorption performances of fiber metal laminate (FML) thin-walled tubes subjected to impact loading. Dynamic computer simulation techniques validated by experimental testing are used to perform a series of parametric studies of such devices. The study aims at quantifying the crush response and energy absorption capacity of FML thin-walled tubes under axial impact loading conditions. A comparison has been done in terms of crush behaviour and energy absorption characteristics of FML tubes with that of pure aluminium and composite tubes. It is evident that FML tubes are preferable as impact energy absorbers due to their ability to withstand greater impact loads, thus absorbing higher energy. Furthermore, it is found that the loading capacity of such tubes is better maintained as the crush length increases. The primary outcome of this study is design information for the use of FML tubes as energy absorbers where impact loading is expected particularly in crashworthiness applications.

Experimental and Numerical Analysis of Foam-Filled Aluminum Conical Tubes Subjected to Oblique Impact Loading

Abstract This study aims to investigate the response of AA6061-T6 conical tubes under oblique impact loading, for variations in filler density and tube material by using experimentally validated model. Good correlations between the numerical and experimental results were observed. The initial peak force and dynamic force increase from AA6061-T6 to carbon steel tubes and further increase with increasing filler density, leading to increased energy absorption capacity. Conversely, the initial peak force and dynamic force of empty and foam-filled AA6061-T6 conical tubes decrease with the introduction of oblique loading as the load angle increases from 0° to 20°, leading to reduced energy absorption capacity. Carbon steel is relatively more advantageous compared with AA6061-T6 in terms of energy absorption, whereas AA6061-T6 is comparable with carbon steel because of its lower initial peak force.

Finite Element Modelling of Different 2D Re- Entrant Structures of Auxetic Materials

Auxetic materials exhibit a unique characteristics when subjected to uniaxial loading. Various structures have been used to model these materials. Among most important auxetic structures, re-entrant structures are of interest in this present study. These structures have different shapes in which are known as lozenge grids, sinusoidal ligaments, square grids, double arrowhead, and structurally hexagonal re-entrant honeycomb could be named. In this paper, finite element approach for the abovementioned structures was employed to obtain basic mechanical properties including Poissons ratio and elastic modulus. The study aims at investigating the effect of cross sectional geometry on mechanical properties. For each structure, three different cross sectional geometries were numerically examined. It is evident that mechanical properties of the material could be controlled by changing the geometry of the cross section. The primary outcome of the study is the design guideline on the effect of cross sectional geometry on mechanical properties of auxetic structures. In the present study, finite element technique has been employed in modelling these structures to represent the characteristic of the auxetic re-entrant structures. Five different shapes of 2D re-entrant structures have been considered to examine the influence of cross sectional geometry on the mechanical properties. It is evident that mechanical properties of auxetic material are controllable, thus facilitating the fabrication technique used in preparing samples in the laboratory.

Inclusion of Tapered Tubes in Enhancing the Crash Performance of Automotive Frontal Structures

This paper treats the design and analysis of an energy absorbing system. Experimental tests were conducted on a prototype, and these tests were used to validate a finite element model of the system. The model was then used to analyze the response of the system under dynamic impact loading. The response was compared with that of a similar system consisting of straight circular tubes, empty and foam-filled conical tubes. Three types of such supplementary devices were included in the energy absorbing system to examine the crush behavior and energy absorption capacity when subjected to axial and oblique impact loadings. The findings were used to develop design guidelines and recommendations for the implementation of tapered tubes in energy absorbing systems. To this end, the system was conceptual in form such that it could be adopted for a variety of applications. Nevertheless, for convenience, the approach in this study is to treat the system as a demonstrator car bumper system used to absorb impact energy during minor frontal collisions.

Coating Life Assessment: The Use of Adhesion Strength in Parametric Development in Coating Degradation Evaluation

Most of the steel structures used in industrial and non-industrial applications are exposed to outdoors weathering conditions. Organic coating typically protects them from corrosion. The maintenance actions can be done efficiently only if there is sufficient information of the condition. Therefore, the deterioration of the coating system and its lifetime has to be assessed accurately. This paper focuses on the development of parameters based on adhesion strength useful for that purpose. Three parameters are proposed, namely stress intensity factor, strain energy density, and J-integral.

Ductile Failure Prediction of Spot Welded Lap Joint

A finite element (FE) model incorporating a progressive material damage with Rice-Tracey damage initiation criterion is developed in this study. The relationship between local ductility reduction and stress triaxiality was established experimentally. The FE model was validated by comparisons of load-displacement response of the spot welded lap joint specimen at displacement rate of 5 mm/min and the observed ductile failure mechanism. Results show that Rice-Tracey damage initiation criterion used is sufficient to reproduce the observed ductile failure response of the specimen. Failure of the spot welded lap joint is initiated at the HAZ/fusion zone interface with localized necking.

Energy Absorption Capacity of Basalt Sandwich Composite Cylinder Subjected to Axial Compression Loadings

In this report presented the investigation of axial progressive compression on sandwich composite cylinder made from basalt fibre reinforced composite tube as skins and polyurethane (EPU) foam as core of the structure. The effect of braid orientation angle of the sandwich skins and foam core thickness were evaluated on the parameter performance namely peak force, average force, total energy absorption, crush force efficiency, and specific energy absorption. The primary failure mode observed was progressive failure fibre cracking and tube’s wall folding and crumping. Experiment result showed that the effect of outer wall braid angle of sandwich tube structure was the dominant factor contributed to high energy absorption capacity. Furthermore, the foam thickness has no significant influences on the SEA value; however, the total diameter size of sandwich tube skins was.