M. Nalla Mohamed

Energy Enhancement of Long Cylindrical Tubes with Grooves Subjected to Axial Impact

Long cylindrical tubes exhibit poor energy absorption due to Euler’s buckling mode when they are used to absorb impact energy. Circumferential grooves are introduced in the tube to force the plastic deformation which helps to control the buckling mode. Quasi-static and impact tests are performed and the load-displacement curves are studied. The results are also compared with the ones for the geometrically identical tubes. Non-linear finite element analyses are also carried out to simulate quasi-static and impact test conditions. The numerical predicted crushing force and fold formation are found to be in good agreement with the experimental results. The results revealed that grooves can stabilize the deformation behaviour and thus the proposed method could be a good candidate as a controllable energy absorption element.

A comparative analysis on tensile strength of dry and moisture absorbed hybrid kenaf/glass polymer composites:

Economic and environmental concerns lead the researchers toward development of sustainable and renewable materials of which reinforced composites are part of. The abundantly available natural fiber...Economic and environmental concerns lead the researchers toward development of sustainable and renewable materials of which reinforced composites are part of. The abundantly available natural fibers have attracted the researchers to study their performance as reinforcements and feasibility for making automobile components. The performance of composite materials is mainly assessed through their mechanical properties. However, natural fibers to date were mainly used as reinforcements to create bulk composite components with reduced cost rather than improved mechanical performances. Among the methods available for improving mechanical properties of the natural fiber composites, combined mercerization treatment, hybridization, and incorporation of fly ash fillers in the matrix are the best solutions. Therefore, the objective of this research is to evaluate the tensile properties of hybrid kenaf/glass composites with and without fly ash particulate filler as per ASTM standards. Moisture absorption behavior and its effect on the tensile properties of hybrid composites are also investigated. The results revealed that the addition of 10wt % fly ash particles with natural fiber composites increased the tensile strength of composites while hybridization with glass fibers reduced the water absorption properties.

Investigation on the Process Parameters of Double-Sided Friction Stir Welded AA6082-T6 Joints with Different Tool Pins Using Response Surface Methodology

Aluminium alloys are of much use in several vital areas including aerospace, marine, defence and railways, which becomes obligatory to have a welded joint of high strength. The input considerations of the friction stir welding process of double-sided type play an imperative part in identifying the performance and characteristics of the joints. This research is a novel approach to investigate the influence of weld input parameters on the output responses of aluminium 6082-T6 alloy using tapered square and tapered pentagonal tool pin profiles. The double-sided friction stir welding (FSW) was chosen for the research work, as it gives better strength joint than single-sided ones. Response surface methodology (RSM) was used to establish the interactions through mathematical relationships, considering the FSW process parameters and output responses. The influence of tapered square (TSP) and tapered pentagonal pin (TPP) profiles on the welding characteristics was analysed. Also, an extended investigation was carried out in achieving the welding parameters in optimum level, so as to maximize the output responses.

Experimental investigation and optimization of abrasive water jet cutting parameters for the improvement of cut quality in carbon fiber reinforced plastic laminates

The utilization of composite materials has nowadays increased in aerospace applications due to their less weight and superior mechanical properties. Nevertheless, machining of composite materials without damage is quite challenging through conventional system due to their inherent heterogeneity, anisotropy, and thermal sensitivity. To overcome this problem, abrasive water jet machining process can be employed. It is a non-conventional machining processes with high accuracy, high flexibility and with no heat generation. However, there are more challenges in cutting fiber reinforced plastics with this technique. Hence, this work deals with the assessment of the optimum process parameters in abrasive water jet cutting of carbon fiber reinforced plastic composite. Cutting experiments were conducted by varying input parameters such as the traverse rate, standoff distance on three laminates of different thickness. Analysis of variance through response surface methodology technique was used to study the effect of each input parameters on the output responses such as kerf taper and surface roughness. Optimum parameters that provide the best machining quality were found using numerical and graphical optimization techniques. The results showed that increasing the traverse rate results in increased surface roughness and taper angle of the cut kerf. Hence lower traverse rate is preferable when machining quality is of high importance.

Effect and Contribution of Weld Parameters on Peak Temperature during Friction Stir Welding

This paper discusses the effect of weld parameters on peak temperature during the friction stir welding process. The weld parameters such as rotational speed and welding speed are considered for this analysis. Friction stir welding trails were conducted on 6 mm AA6061-T6 plates for different combination of process parameters using Taguchi orthogonal array. Thermocouples were inserted into the plates at different distances from weld center line and temperatures were measured during friction stir welding at regular intervals. Using the Taguchi method, Peak temperature is calculated for untried combinations of process parameters. Graphs depicting the effect of different weld parameters on the peak temperature were presented and analyzed.

Numerical Modeling of Energy Absorption Behaviour of Aluminium Foam Cored Sandwich Panels with Different Fibre Reinforced Polymer (FRP) Composite Facesheet Skins

Sandwich structures based on Fibre Reinforced Polymer (FRP) facesheet skins bonded with low density aluminium foam core are increasing in use in aerospace and marine industries. These structures are very sensitive to high velocity impact during the service. Therefore, it is necessary to study the energy absorption of the structures to ensure the reliability and safety in use. Experimental investigation of these transient events is expensive and time-consuming, and nowadays the use of numerical approaches is on the increase. Hence, the purpose of this paper is to develop a numerical model of sandwich panels with aluminium foam as a core and Glass, Carbon and Kevlar Fibre Reinforced polymer composite as faceplate, subjected to high velocity impact using ABAQUS/Explicit. The influence of individual elements of the sandwich panel on the energy absorption of the structures subjected to high velocity impact loading was analysed. Selection of suitable constitutive models and erosion criterion for the damage were discussed. The numerical models were validated with experimental data obtained from the scientific literature. Good agreement was obtained between the simulations and the experimental results. The contribution of the face sheet, foam core on the impact behaviour was evaluated by the analysis of the residual velocity, ballistic limit, and damaged area.

Development of Novel Natural Composites with Fly Ash Reinforcements and Investigation of their Tensile Properties

Increasing demand for special materials leads to new inventions. One of the most promising inventions is the concept of composites. Natural fibers have the potential as a reinforcing material as an alternative to the use of glass, carbon and other synthetic fibers in automotive industries. Among various natural fibers, Kenaf is a widely used fiber due to its easy availability, low density, low production cost and satisfactory mechanical properties. To enhance the mechanical properties of natural fibre composites, strengthening of the matrix and fibre is very much essential. A prospective reinforcement in this regard is fly ash, which is abundantly available as a waste product from thermal power plants. In this paper, a new novel natural composite with epoxy as a resin and reinforcing both bio waste (Kenaf) and industrial waste (Fly ash) has been developed. All the laminates were prepared with a total of 4 plies. Laminates without fly ash filler were also fabricated for comparison purpose. A hand lay-up method was used for the fabrication of composites and was tested as per ASTM standards for evaluation of tensile properties. The effect of fly ash weight percentage (5, 10, 15% wt.) on tensile properties was studied experimentally. Due to the incorporation of fly ash fillers into the kenaf fiber composites, there is considerable improvement in the mechanical properties. Overall results supported the effective utilization of natural composites for automotive applications.

Estimation of Aerosol Emission in Die Sinking EDM Process through Numerical Modelling

Emission of metallic particulate (aerosol) is an important hazard associated with the EDM process. These emissions can cause adverse health effects to the operators and has a direct impact on the environment. Therefore, concurrent investigations of the aerosol emission and machining aspects of the EDM process are essential for achieving hygienic and efficient machining. The aerosol emission from the process is directly related to the temperature at the process location. Hence, this paper first addresses a numerical model that quantifies the temperature distribution on the surface of a work piece and tool using ANSYS® 14.5. The model first calculates the temperature distribution in the workpiece material and then Material Removal Rate above the boiling temperature of workpiece and tool were estimated from the temperature profiles. Then, a model that quantifies the aerosol generated from EDM process is developed using energy balance and heat transfer equations. Validation of model has been done by comparing the results against the published experimental results obtained under the same process parameters. A good agreement was found between the experimental and numerical results. The model used in this paper can predict the level of emissions at different process locations in order to suggest suitable process conditions for green manufacturing.

Experimental Prediction and Numerical Modeling of Ductile Damage and Failure Modeling of Aluminium Sheet Metal Specimen

Aluminium sheet metal is nowadays used to fabricate lighter, crashworthy, fuel efficient and environment friendly vehicles. Ductile damage of sheet metals affects significantly the crashworthiness, as it naturally exhibits anisotropic behavior due to the grain orientation. Johnson-Cook (J-C) damage model is widely used in numerical simulation for assessing the failure modeling of crash component in particular at high strain rate. The Johnson-Cook material model available in literature is meant for isotropic material behavior which cannot be used directly for anisotropic behavior of materials. To characterize the plastic anisotropy of the rolled sheet, the modified Johnson-Cook material model should be developed. In this research the combination of experimental work and numerical analysis with clear and simpler calibration strategy for damage model is demonstrated. It aims to reduce laboratory tests using advanced numerical analysis to predict failure in order to save overall cost and development time.