The flow stress behavior of cast A356 aluminum alloy has been studied by a set of isothermal hot compression tests. The compression tests were carried out in the temperature range of 400–540 °C and strain rates of 0.001, 0.01 and 0.1 s −1 up to a true strain of 0.6. The effects of temperature and strain rate on deformation behavior were represented by Zener–Hollomon parameter in an exponent type equation. Employing an Arrhenius-type constitutive equation, the influence of strain has been incorporated by considering the related materials’ constants as functions of strain. The accuracy of the developed constitutive equations has been evaluated using standard statistical parameters such as correlation coefficient and average absolute relative error. The results indicate that the strain-dependent constitutive equation can lead to a good agreement between the calculated and measured flow stresses in the relevant temperature range.

The flow behavior modeling of cast A356 aluminum alloy at elevated temperatures considering the effect of strain

Artificial neural network modeling to predict the hot deformation behavior of an A356 aluminum alloy

Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy.

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Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

The influence of hot working parameters on the microstructural evolution of cast A356 aluminum alloy has been studied emphasizing the changes in eutectic phase morphology. Toward this end, a set of isothermal compression tests were conducted in the temperature range of 400–540 °C. The results indicate that the eutectic Si platelets are fragmented, spheroidized and also evenly distributed in the matrix as a result of applying proper thermomechanical cycles. The mechanical fragmentation and thermal disintegration play a prominent role in Si particles breaking up under the different deformation conditions, whereas the average particle size is decreased with decreasing the temperature and increasing the strain rate. The lowest shape factor and aspect ratio are also achieved for the specimens deformed at higher temperatures and lower strain rates. The current work also explores the high temperature flow behavior of cast A356 alloy to address the dominant restoration processes taken place at different thermomechanical conditions.

The effect of thermomechanical parameters on the eutectic silicon characteristics in a non-modified cast A356 aluminum alloy

Effect of various melt and heat treatment conditions on impact toughness of A356 aluminum alloy

Microstructure and mechanical properties of the forged A356 alloy have been investigated in this paper. Results reveals that at micro level forged structure was more refined than as in the as cast conditions. This is due to the work hardening effect, where the original structure is destroyed during the forging and recrystallization helped in creating large number of nucleating sites leading to fine grain structure. From the investigations on the mechanical properties, we deduce that the PS, UTS and hardness of forged materials are obviously higher than those of the ones treated with as cast condition without and with the addition of grain refiners and modifier.

Studies on the influence of grain refining and modification on microstructure and mechanical properties of forged A356 alloy

Nanosized metal particle filled polymer composites are finding numerous tribological applications in recent years. In the present work, the matrix properties were investigated by introducing nickel nanoparticles (60–100 nm, filler content of 0·5–10 wt-%) into epoxy resin. The influence of these particles on friction and dry sliding wear behaviour was measured using a pin on disc wear set-up. The experimental results indicated that the coefficient of friction and the specific wear rate of epoxy resin can be reduced with a rather low weight fraction of Ni particles. The lowest specific wear rate of 0·64×10−4 mm3 N−1 m−1 (compared to neat resin’s value of 2·2×10−4 mm3 N−1 m−1) was observed for composites with the filler content of 0·5 wt-%. The reinforcement of Ni particles leads to improved mechanical properties of the epoxy composites. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms.

Friction and dry sliding wear behaviour of Ni filled epoxy nanocomposite

/pdf/distributed-wormhole-attack-mitigation-technique-in-wsns-fjph4ww12m.pdf

Distributed Wormhole Attack Mitigation Technique in WSNs

Fondness for fish aquarium is a trendy affair. Thus, many of them welcome it in their home just as a hobby or an eye-pleasing tool. It looks beautiful and brings a charm to the house, but it’s not easy to maintain. It requires time-to-time care where its responsibility resides in freshwater, brackish, and marine. Between these three, freshwater holds a popular place of keeping fish because it is effortless to handle with freshwater fish and aquariums. Taking care of fish and aquariums is an intricate task like feeding fish on-time, maintaining temperature, and also managing the light, heater, and filter of the aquarium. Till now it has been a manual process, thus it demands a well turned-out technology. Thus in this paper, smart aquarium has been planned by keeping in mind, the problems of those who cannot take care of their aquarium on daily basis. The feeder is powered by servomotor which on trigger of a button feeds the fish, heater keeps the temperature of the aquarium under control, and we can also be in charge of the fluorescent lamp which helps in the growth of fish and plants. Proposed technology uses Raspberry pi Webcam server to capture live video stream of aquarium, feed fishes through servomotor using pulse-width modulation, relays are used to ON/OFF light, temperature control, filter control, and android app to allow the user to access various functionalities.

Smart Live Monitoring of Aquarium—An IoT Application

Sensor systems are acquiring more fame because of their wide range of applications like process automation, environment (habitat) monitoring, seismic monitoring, and battlefield surveillance. Though they are popular because of their applications, they do come with various challenges like random deployment of nodes, limited energy, computation and memory. Apart from these challenges, the most critical aspect to handle is security. Information is exchanged in Wireless Sensor Networks (WSNs) between the nodes through wireless links in “air” through electromagnetic waves. This feature attracts the invaders to steal data, disrupt the normal system action by disturbing the data flow and so on. WSNs are prone to attacks at various layers of networks like jamming, denial of service, sinkhole, black hole, wormhole to name a few. Each attack is characterized by its own consequences. Various countermeasures are proposed to defend against these various attacks. Out of these attacks, we pick up wormhole attack at network layer because of its unique nature. Wormhole attack can be launched in the network even if the network is secured with cryptographic techniques. In this paper we address wormhole attack by proposing a RTT centered Wormhole Outbreak discovery. Our proposed system is simple with no extra hardware requirement and no tight clock synchronization.

Sharada Kori

Papers

Studies on the influence of grain refining and modification on microstructure and mechanical properties of forged A356 alloy

Friction and dry sliding wear behaviour of Ni filled epoxy nanocomposite

Distributed Wormhole Attack Mitigation Technique in WSNs

Smart Live Monitoring of Aquarium—An IoT Application

RTT Centered Automatic and Dynamic Wormhole Attack Discovery in Sensor Network