Effect of Tin Addition on the Mechanical Properties and Microstructure of Aluminium Bronze Alloyed with 4% Nickel

The current study investigates the impact of adding tin to aluminium bronze alloyed with 4% nickel on its microstructure and mechanical properties. Sand casting was chosen as the most cost-effective and efficient method of preparing the aluminium bronze alloy. Following their melting points, six distinct samples of aluminium bronze alloyed with 0% to 10% tin were added into the crucible furnace. Nickel with the highest melting point of 1453°C was added into the crucible furnace first, while tin with the lowest melting of 231.9°C was added last into the crucible furnace. The alloying components were mixed well by manually mixing the liquid for around five minutes. After sand casting, the specimens were machined, sectioned, and grounded then tests were carried out to measure their hardness, tensile strength, and impact resistance. The results of the tests indicate that the tensile strength first increases and subsequently declines as the tin addition increases. The hardness of the aluminium bronze alloy increases as the proportion of tin addition increases. The results of the investigations also demonstrate that as the hardness of the specimens increases, their impact resistance decreases and the tensile stress of each specimen increases with strain.&nbsp

Transition to Turbulence of a Laminar Flow Accelerated to a Statistically Steady Turbulent Flow

This current study investigates the turbulence response in a flow accelerated from laminar to a statistically steady turbulent flow utilising Particle Image Velocimetry (PIV) and Constant Temperature Anemometry (CTA). The dimensions of the rectangular flow facility are 8 m in length, 0.35 m in width, and 0.05 m in height. The flow is increased via the pneumatic control valve from a laminar to a statistically steady turbulent flow, and the laminar-turbulent transition is examined. As the flow accelerates to turbulent from laminar, the friction coefficient increases quickly and approaches its maximum value within a short period. As a result, a boundary layer forms extremely near to the wall, increasing the velocity gradient and viscous force. The friction coefficient and viscous force decrease with increasing boundary layer thickness, and transition occurs as a result of instability of the boundary layer. The friction coefficient is used to specify the beginning and end of the transition. The transition starts when the friction coefficient reaches its minimal value. It increases again, and its maximum value marks the end of the transition to turbulence. The study shows that three stages lead to turbulence near the wall when the flow is accelerated from laminar to turbulent. These phases are similar to the transient turbulent flow reported. The reaction of mean velocity as laminar flow is accelerated to turbulent flow is investigated. The mean velocity behaves like a "plug flow" when the flow accelerates from laminar to turbulent, meaning that everywhere in the flow zone, except for the position extremely near the wall, the flow behaves like a solid body. The changes in the channel flow that accelerates from a laminar to a turbulent condition are presented, together with the turbulence statistics, wall shear stress, bulk velocity, and friction coefficient. Like the boundary layer bypass transition and transient turbulent flows, the transition to turbulence follows a similar process

Experimental Study of Turbulence in Transient Channel Flows

Experimental studies have been carried out to improve our understanding of the behaviour of turbulence under transient conditions by expanding the new perspective recently established numerically by He and Seddighi (J. Fluid Mech., 715: 60-102, 2013), Seddighi et al. (Flow Turbulence Combustion., 92: 473-502, 2014) and He and Seddighi (J. Fluid Mech., 764: 395-427, 2015). The present work significantly extends the flow conditions investigated in a previous study by Mathur et.al. (J. Fluid Mech., 835: 471-490, 2018) using the same experimental facility. Particle Image Velocimetry (PIV) has been used to measure instantaneous velocities during the transient conditions and Constant Temperature Anemometry (CTA) with hot-film sensors is used to measure the wall shear stress. The length, width, and height of the test rig measured 8000 mm, 350 mm and 50 mm, respectively, and water is used as the working fluid. Flow is accelerated from an initial statistically steady turbulent flow to final statistically steady turbulent flow. This is achieved using a pneumatic control valve. The ramp rate, start and end Reynolds numbers and the period of acceleration are varied to study their effects. The response of all the accelerating flows investigated is shown to be characterised by laminar-turbulent transition, which follows a three-stage development that is similar to the three-stage response reported by He and Seddighi (J. Fluid Mech., 715: 60-102, 2013) resembling the three stages of boundary layer bypass transition induced by free-stream turbulence. These are buffeted laminar boundary layer, intermittent turbulence spot formation, and a fully developed turbulent boundary layer. The first stage consists of an enhancement and elongation of the pre-existing streaky structures in the flow. In the second stage, the secondary instabilities of the streaky structures increase, and the formation of isolated turbulence spots can be seen. The turbulence spots grow with time and merge with each other. These turbulence spots fill the entire wall-bounded surface when the flow has become fully developed turbulent flow in the third stage. In accordance with this three-stage response, the skin friction coefficient (C_f) increases sharply initially and reaches its maximum value due to the creation of a thin boundary layer near the wall that results in an increase of velocity gradient, strain rate and viscous force. As the boundary layer thickness increases by diffusion, the viscous force and skin friction coefficient decrease. The minimum point of the skin friction coefficient marks the beginning of transition. It increases again during the transitional period due to the generation of ‘‘new’’ turbulence near the wall. The first peak that the C_f attains after its recovery marks the completion of transition. It has been shown that as the initial Reynolds number increases while the final Reynolds number remains fixed, the time of onset of transition reduces. The process of transition to turbulence becomes very subtle and the transition features are not clearly seen from the visualisation and C_f responses when the initial Reynolds number is high. The characteristic of transition is however unambiguously seen in the response of turbulence especially in the wall normal fluctuating velocity, which remains unchanged during the pre-transition period. On the other hand, the process of transition to turbulence is strong when the initial Reynolds number is small and the transition features are visible in the responses of C_f as well as turbulence. The effect of varying the acceleration period is investigated while the initial Reynolds number and final Reynolds numbers remain fixed. The time at which transition to turbulence occurs increases as the acceleration period increases and vice versa. The response of the wall shear stress follows rather closely the quasi-steady variations when the acceleration is very slow. However, again, the response of turbulence clearly demonstrates the distinct nature of transition even in such slow accelerations. It has previously been shown that the time-developing boundary layer in a step increase of flow rate forms rapidly near the wall and grows into the flow. In the present study, it has been demonstrated that a temporally developing boundary layer is also resulted in the gradually accelerating flows which is formed as a result of a continuous change in velocity gradient near the wall and then expands into the flow. The pre-transitional stage of the temporally developing boundary layer of the present gradual acceleration coincides with the temporally developing boundary layer illustrated by an extended solution to Stokes’ first problem based on the integration of many small step increases in flow rate. Modifications have been made to the equivalent Reynolds number (〖Re〗_t) and the initial turbulence intensity (〖Tu〗_0) proposed by He and Seddighi (J. Fluid Mech., 764: 395-427, 2015) in order to account for the slow accelerating flows and the continuous change of the bulk velocities of the cases investigated. It has been shown that the critical equivalent Reynolds number (〖Re〗_(t,cr)) based on these modifications and the initial turbulence intensity (〖Tu〗_0) are well correlated for all cases studied and a power-law relation is established

Design and Fabrication of a Mass Balancing Machine

<p><strong>Abstract:</strong> This work is aimed at producing a mass balancing laboratory apparatus that will serve for the demonstration of the principle of balancing of rotating masses which is a fundamental part of the study of Theory of Machines in engineering. The machine was constructed with the locally available materials and fabrication methods, and consists of a shaft, a pair of bearings, metal sheets, springs, dampers, a 0.25KW one phase motor, set of detachable balance mass blocks and a transparent safety dome to cover the moving components. The dome prevents them from harming users especially if failure occurs. ANSYS simulation tests results showed that they were within acceptable stress limits. The study established that locally sourced materials could be used to produce excellent Mass Balancing Machine at a low production cost.</p><p><strong>Keywords:</strong> Static Balance, Dynamic Balance, Imbalance, Laboratory Apparatus. </p><p><strong>Title:</strong> Design and Fabrication of a Mass Balancing Machine</p><p><strong>Author:</strong> Okolie Paul Chukwulozie, Enyi Chukwudi Louis, Oluwadare Benjamin Segun, Chikelue Edward Ochiagha</p><p><strong>International Journal of Novel Research in Electrical and Mechanical Engineering</strong></p><p><strong>ISSN 2394-9678</strong></p><p><strong>Vol. 11, Issue 1, September 2023 - August 2024</strong></p><p><strong>Page No: 35-46</strong></p><p><strong>Novelty Journals</strong></p><p><strong>Website: www.noveltyjournals.com</strong></p><p><strong>Published Date: 13-November-2023</strong></p><p><strong>DOI: </strong><a href="https://doi.org/10.5281/zenodo.10118401"><strong>https://doi.org/10.5281/zenodo.10118401</strong></a></p><p><strong>Paper Download Link (Source)</strong></p><p><a href="https://www.noveltyjournals.com/upload/paper/Design%20and%20Fabrication%20of%20a%20Mass%20Balancing%20Machine-13112023-6.pdf"><strong>https://www.noveltyjournals.com/upload/paper/Design%20and%20Fabrication%20of%20a%20Mass%20Balancing%20Machine-13112023-6.pdf</strong></a></p&gt