Hardness, tensile and impact behaviour of hot forged aluminium metal matrix composites

Tensile and impact testing and hardness measurements were carried out on hot forged aluminium metal matrix composites to understand the influence of alloying element and forming process on their mechanical properties. Pure aluminium preforms together with its composites such as Al4TiC, Al4Fe3C, Al4Mo2C and Al4WC were prepared using a suit-able die-set assembly on a 1 MN capacity hydraulic press. Sintering operation was carried out in an electric muffle furnace at the temperature of 1200◦C for a holding period of 1 h.Immediately after the sintering process the cylindrical preforms were hot deformed in to a square cross-section bar of size 24 mm × 24 mm × 60 mm for preparing of tensile test and impact test specimens as per the respective ASTM standards. Standard tensile and impact test specimens were machined from the forged square rods. Standard ASTM procedure was followed to conduct the aforementioned mechanical testing. Further, micro-structural studies on the hot forged square cross-section bar and hardness measurements were obtained and analysed

Strain hardening behaviour in sintered Fe–0.8%C–1.0%Si–0.8%Cu powder metallurgy preform during cold upsetting

Cold upsetting experiments were performed on sintered Fe–0.8%C–1.0%Si–0.8%Cu steel preforms in order to evaluate the strain hardening characteristics. Powder preforms of 86 per cent theoretical density and an initial aspect ratio of 0.4 were prepared using a suitable die and a 1MN capacity hydraulic press. Sintering was carried out in an electric muffle furnace for a period of 90 min at 1150 �C. Each sintered compact was subjected to an incremental compressive loading of 0.04MN until fractures appeared on the free surface. Experiments were performed with no lubricant and using graphite as a lubricant. The behaviour of the applied stress as a function of both strain and densification level exhibits a continuous enhancement over three different response modes. The first and third stage responses offer a high resistance to deformation, whereas the second stage shows virtually steady-state behaviour. The instantaneous strain hardening exponent ni and strength coefficient Ki of the steel preforms were calculated and found to continuously increase with an increase in the deformation and densification levels

Workability studies of sintered aluminum composites during hot deformation

Experimental investigation has been carried out to evaluate the effect of titanium carbide (TiC), molybdenum carbide (Mo2C), iron carbide (Fe3C) and tungsten carbide (WC) addition on the composite aluminium preforms. The hot upsetting of the composite aluminium preforms with various carbide contents, namely, Al-4% TiC, Al-4% WC, Al-4% Fe3C and Al-4% Mo2C, and different aspect ratios, namely, 0.4 and 0.6, was carried out and the workability behaviour of the same was determined. The influence of carbide addition in the aluminium composite and initial preform geometry on the relative density (R), stress ratio parameters, su=seff, sm=seff and sz=seff, and formability stress index was studied

Effect of titanium carbide addition on the workability behavior of powder metallurgy aluminum preforms during hot deformation

Experimental investigation has been carried out to evaluate the effect of titanium carbide (TiC) addition on the composite aluminium preforms. The hot upsetting of the composite aluminium preforms with varying TiC contents, namely, 1%, 2%, 3% and 4%, and different aspect ratios, namely, 0.2, 0.4 and 0.6, was carried out and the workability behavior of the same was determined. The influence of TiC addition, in the aluminium composite, on the relative density (R), stress ratio parameters

Enhancing Learners’ Engagement with Educational Apps

Technology-enabled learning environment provides increased opportunities for enhancing learners’ engagement, interaction and collaboration. With the advent of technology, educational applications (apps) have become popular in learning, teaching, and research at all levels of education. Learning through the use of apps is therefore gaining momentum as it affords flexible learning opportunities, coupled with 21st century learning paradigm. The nature of educational apps is varied, be it an app downloadable on a mobile device or customized apps, designed to provide bite sized information or a learning activity based on learning design. The core function of these apps remain the same, which is to provide learners an engaging and meaningful interaction with content and interface such that it enhances not only the learning experience but also success in learning. In short, apps are designed to enhance learning efficiency and effectiveness. The use of apps, from early childhood education through to higher education, provides continuous opportunities to enhance learners’ engagement with learning materials (Diliberto-Macaluso, & Hughes, 2016; Hirsh-Pasek, Zosh, Golinkoff, Gray, Robb, & Kaufman, 2015; Pechenkina, Laurence, Oates, Eldridge, & Hunter, 2017), however there is a need for more research in this area (Hirsh-Pasek et al, 2015; Pechenkina et al, 2017). Hamari, Koivisto, and Sarsa (2014) reported that integration of gamified elements into apps has the potential to engage students and motivate them in a way that it can in turn affect other factors, which influence the learning process

Design of a horizontal axis wind turbine for Fiji

The demand and cost of electricity has increased for Pacific Island Countries (PICs). The electricity from main grid does not reach rural areas and outer islands of Fiji. They burn fuel for electricity and daily lighting. Therefore, there is a need to look for alternative energy sources. Wind turbine technology has developed over the past years and is suitable for generating electricity by tapping wind energy. However, turbines designed to operate at higher wind speed do not perform well in Fiji, because Fiji’s average wind velocity is around 5-6 m/s. A 10 m, 3-bladed horizontal axis wind turbine is designed to operate at low wind speed, cut in speed of 3 m/s, cut off speed of 10 m/s and rated wind speed of 6 m/s. The blade sections were designed for different locations along the blade. The airfoil at the tip (AF0914) a has maximum thickness of 14% and maximum camber of 9%; the thickness varies linearly to the root, at the root the airfoil (AF0920) has a maximum thickness of 20% and maximum camber of 9%. The aerodynamic characteristics of airfoil AF0914 were obtained using Xfoil and were validated by experimentation, at turbulence intensities (Tu) of 1% and 3%, and a Reynolds number (Re) of 200,000. The aerodynamic characteristics of other airfoils were also obtained at operating Re at the turbulence intensities of 1% and 3%. These airfoils have good characteristics at low wind speed, and were used to design the 10 m diameter 3-bladed HAWT for Fiji. The turbine has a linear chord distribution for easy manufacturing purpose. Twist distribution was optimized using Blade Element Momentum (BEM) theory, and theoretical power and turbine performance were obtained using BEM theory. At the rated wind speed of 6 m/s and a TSR of 6.5, the theoretical efficiency of the rotor is around 46% and maximum power is 4.4 kW. The turbine has good performance at lower wind speeds and is suitable for Fiji’s conditions

Design of a gorlov turbine for marine current energy extraction

As fossil fuels near depletion and their detrimental side effects become prominent on ecosystems, the world searches renewable sources of energy. Marine current energy is an emerging and promising renewable energy resource. Marine current energy can be alternative energy source for electricity production. Many marine current converters are designed to tap marine current energy; however, Gorlov turbine proves to have minimum manufacturing and maintenance cost, hence giving desired power output. A 0.3m diameter and 0.6m long 3 bladed Gorlov turbine was designed, fabricated and test to analyse its performance. The turbine produces average power 15 W and proves to be quite efficient for marine current energy extraction

Design and Performance Analysis of Micro Wind Turbine for Fiji

Today’s major research area is based on finding alternatives to fossil fuels. Wind energy can contribute significantly towards renewable energy production. A functional wind turbine built locally proposes a huge impact for Fiji and the Pacific Islands renewable energy industry. The design has to take into consideration the wind speed of the pacific which is quite different from other countries. A low Reynolds number airfoil was selected and modified for horizontal axis wind turbine (HAWT) and its aerodynamic characteristic was studied. The analysis were done using XFoil software, the numerical results were validated with experimental results before analysis were done. The Q-blade Software is used to design the blade for the wind turbine. The cut in velocity of wind turbine is 3 ms-1 , which is a big achievement when it comes for the power generation. The rated power is 50 watts at rated velocity of 6.5 ms-1 and the cut of velocity is at 20 ms-1 . The numerical results were validated with experimental results. The peak power after measurement was 23.73 watts at wind speed of 8 ms-1

Structural dynamic modification of cylindrical shells with variable thickness

In this paper, the effects of some geometrical parameters on dynamic behavior of cylindrical shells with constant and variable thickness are studied. The equation of motion for the shell with constant thickness is extracted based on classical shell theory using Hamilton’s principle. These equations which are a system of coupled partial differential equations are solved analytically and the natural frequency is determined for cylindrical shells with constant thickness. The natural frequency for cylindrical shells with variable thickness is determined using finite element method by employing ANSYS. The results are compared and the effect of different geometric parameters such as length, thickness, and radius on natural frequency is discussed. The specific ranges for geometric parameters have been determined in which there is no significant difference between shells with constant or variable thickness. Cylindrical shells with variable thickness have better stress and strain distribution and optimum weight, in compare with the shells with constant thickness and it is important to know in which ranges of dimensions and geometrical parameters, there are some significant differences between their mechanical properties such as natural frequency. The results are compared with some other references

Workability behaviour of Fe-C-Mo steel preforms during cold forging

A systematic method to construct the workability diagram for powder metallurgy (P/M) materials has been proposed. Preforms of Fe-0.8%C, Fe-0.8%C-1%Mo and Fe-0.8%C-2%Mo were prepared to the relative density of 0.86 with two different geometries through primary operations of P/M processes. Each sintered preform was cold upset forged with incremental compressive loading of 0.04MN under three different lubricant conditions till a visible crack appeared at the free surface. Oyane's fracture criterion was used to develop a theory to study P/M products. The least square method was used to determine the constants in fracture criteria and these equations were eventually used to construct workability diagram. It is found that the proposed method was well in agreement with the experimental results