Journal of Computational and Applied Research in Mechanical Engineering
Volume:7 Issue: 1, Autumn 2017

This article explores the heat and mass transfer behaviour of magnetohydrodynamic free convective flow past a permeable vertical rotating cone and a plate filled with gyrotactic microorganisms in the presence of nonlinear thermal radiation, thermo diffusion and diffusion thermo effects. We presented dual solutions for the flow over a rotating cone and a rotating flat plate cases. Similarity variables are employed to convert the nonlinear partial differential equations into ordinary differential equations. Comparisons with previously published work are performed and results are found to be in excellent agreement. The resultant non-dimensional governing equations along with associated boundary conditions are solved numerically using Runge–Kutta and Newton’s methods. The impact of pertinent parameters on velocity, temperature, concentration and density of the motile microorganisms along with the friction factor, local Nusselt, Sherwood numbers and the local density of the motile microorganisms was determined and analyzed with the help of graphs and tables. Results proved that there is a significant variation of heat and mass transfer in the flow over a rotating cone and a plate. It is also found that the heat and mass transfer performance of the flow over a rotating cone is significantly high when compared with the flow over a rotating plate.

Functional electrical stimulation (FES) is the most commonly used system for restoring function after spinal cord injury (SCI). In this study, we used a model consists of a joint, two links with one degree of freedom, and two muscles as flexor and extensor of the joint, which simulated in MATLAB using SimMechanics and Simulink Toolboxes. The muscle model is based on Zajac musculotendon actuator and composed of a nonlinear recruitment curve, a nonlinear activation-frequency relationship, calcium dynamics, fatigue/recovery model, an additional constant time delay, force-length and force-velocity factors. In this study, we used a classic controller for regulating the elbow joint angle; a Proportional- Integral- Derivative controller. First, we tuned the PID coefficients with trial and error, and then a particle swarm optimization algorithm was used to optimize them. The important features of this algorithm include flexibility, simplicity, short solution time, and the ability to avoid local optimums. This PSO -PID controller uses particle swarm optimization algorithm to get the required pulse width for stimulating the biceps to reach the elbow joint to the desired angle. The fitness function was defined as sum square of error. The results for PSO -PID controller show faster response for reaching the range of the set point than the PID controller tuned by trial and error. However the PSO -PID is much better in terms of the rise time and the settling time, the PID tuned by trial and error has no overshoot. The time to reach the zero steady state error is half in PSO -PID in comparison to PID tuned by trial and error.

Effect of nonlinear thermal radiation on the unsteady magnetohydrodynamic slip flow of Casson fluid between parallel disks in the presence of thermophoresis and Brownian motion effects are investigated numerically. A similarity transformation is employed to reduce the governing partial differential equations into ordinary differential equations. Further, Runge-Kutta and Newton’s methods are adopted to solve the reduced ordinary differential equations. The effect of non-dimensional governing parameters, namely magnetic field parameter, Casson parameter, thermophoresis parameter, Brownian motion parameter, thermal radiation parameter, unsteadiness parameter, velocity slip parameter and temperature slip parameter on velocity, temperature and concentration fields are discussed and presented through graphs. Reduced Nusselt and Sherwood numbers are computed and presented through a table. It is found that rising values of nonlinear thermal radiation parameter depreciate the reduced Nusselt and Sherwood numbers. Thermophoresis and Brownian motion parameters have tendency to regulate the thermal and concentration boundary layers. Rising values of Casson parameter enhances the heat and mass transfer rate.

In this study, hot metal gas forming process of AA6063aluminumtubeis studied with a focus on heat transfer of both fluid and solid phases numerically. An experimental study is simultaneously conducted to validate the numerical method. Some of the most important outputs of the present study, are velocity distribution of fluid inside the tube as well as the fluid in the gap between tube and matrices. As a result of non-homogenous distribution of temperature on tube surface, circulating flows are generated inside the tube which may have considerable effects on heat transfer phenomenon. It is seen that in 600 s after start, number of the circulating flows doubles. Analysis of temperature distribution reveals thatmiddle part of the tube reaches 500 ̊C after 600 s from process start and other parts have higher temperature. By applying an efficient control method for heater elements, temperature distribution of the tube reaches a homogenous form.

In this paper the ratcheting behavior of carbon steel(ASTM A106B) and stainless steel(304L) elbows is studied under steady internal pressure and in-plane external moments at frequencies typical of seismic excitations. The finite element analysis with the nonlinear isotropic/kinematic (combined) hardening model has been used to evaluate ratcheting behavior of the elbows. Material parameters have been obtained from several stabilized cycles of specimens that are subjected to symmetric strain cycles. The rate of ratcheting depends significantly on the magnitudes of the internal pressure, dynamic bending moment and material constants for combined hardening model. The results show that the maximum ratcheting is occurred in the hoop direction at crown. Also, the results show that initially, the calculated rate of ratcheting is large and then decreases with the increasing of cycles. Also, the results obtained by using the Combined hardening model gives acceptable adaptation in comparison with the other hardening models(AF and Chaboche hardening models); however this model gives over estimated values comparing with the experimental data.

Single point incremental sheet metal forming is a sheet metal forming process that forms products without the complex dies and tools with low cost. In this study, the incremental sheet metal forming process has been experimentally investigated on the explosively-welded Al/Cu bimetal sheets. Also, the effects of process parameters, such as arrangement of layer`s bimetal, tool diameter and tool path were investigated on the forming force, thickness distribution, formability and roughness. At first, the bimetals were produced by explosive welding process. Then, two tool diameters, step and spiral tool paths and layer arrangement were chosen as input parameters. The results showed that the forming force increases with increasing the tool diameter and using aluminum as a top layer (contact with tool). Also, using spiral tool path increases the average forming force and decreases the maximum thickness changing. The formability increases with increasing the tool diameter and using the copper as top layer with spiral tool path.

The purpose of this paper is control of simply supported flexible core sandwich beam's linear vibration equipped with piezoelectric patches under different loads. The effects of external forces imposed on sandwich beam can be reached to a minimum value by designing an appropriate controller and control the beam's vibration. Three-layer sandwich beam theory is used for analytical modeling of sandwich beam vibration. Euler-Bernoulli beam theory and linear displacement field are used for the face-sheets and the soft core, respectively. The piezoelectric stress resultants are expressed in terms of Heaviside discontinuity functions. Governing equations of motion are obtained using Hamilton’s principle. The state space equations of system are derived from governing equations of motion, by defining suitable state variables and using Galerkin’s method. The controller is designed using linear quadratic Gaussian (LQG) technique and Kalman filter is used to estimate the state of the system. The numerical results are compared with those available in the literature. The obtained results show that the controller can play a big role toward damping out the vibration of the sandwich beam. It also shows the difference between the vibration of top face sheets and bottom face sheets because of the flexibility of the core and the situations of sensor and actuator on the top or bottom face sheets have an important role on the dynamic response of sandwich beam.

In the present study, multiscale nanosilica/E-glass/epoxy anisogrid composite panels were investigated for flexural properties as a function of nanosilica loading in the matrix (0, 1, 3 and 5 wt.%). The surface of the silica nanoparticles was firstly modified with 3-glycidoxypropyltrimethoxysilane (3-GPTS). The fourier transform infrared (FTIR) spectroscopy revealed that the organic functional groups of the silane were successfully grafted on the surface of the nanoparticles. It was illustrated that flexural properties of the composite panel loaded from the skin side can be significantly enhanced by incorporating silica nanoparticles. The use of 3 wt.% nanosilica was the most effective in increasing the load bearing capacity and energy absorption value, while the specimen containing 5 wt.% nanosilica demonstrated the highest flexural stiffness. From the results obtained for the anisogrid panels loaded from the skin side, it was found that these structures displayed excellent damage resistance which is represented by their energy absorption capability. Moreover, a significant portion of energy absorbed after the primary failure at the peak load. Finally, the results correlated well with the observation of field emission scanning electron microscopy (FESEM) micrographs where the nanocomposite panels exhibited higher degree of fiber-matrix interfacial strength and also enhanced matrix characteristics, imparted by the incorporation of surface modified silica nanoparticles.

Using differential quadrature method (DQM), this study investigated pull-in instability of beam-type nano-switches under the effects of small-scale and intermolecular forces including the van der Waals (vdW) and the Casimir forces. In these nano-switches, electrostatic forces served as the driving force, and von-Karman type nonlinear strain was used to examine nonlinear geometric effects. To derive nonlinear governing equations as well as the related boundary conditions for the nano-beam, variation method was used. Besides, to study the influence of size effect, the nonlocal elasticity theory was employed and the resulting governing equations were solved using DQM. Finally, the pull-in parameters were studied using the nonlocal theory and the results were compared with the numerical results of the classical continuum theory as well as experimental results contained in the references. Results demonstrated that taking into consideration the von-Karman type nonlinear strain increases the beam stiffness and hence, the pull-in voltage. Besides, use of the small scale, compared with the classical theory of elasticity, yields results much closer to experimental results.

An efficient and accurate analytical solution is provided using the homotopy-Pade technique for the nonlinear vibration of parametrically excited cantilever beams. The model is based on the Euler-Bernoulli assumption and includes third order nonlinear terms arisen from the inertial and curvature nonlinearities. The Galerkin’s method is used to convert the equation of motion to a nonlinear ordinary differential equation, which is then solved by the homotopy analysis method (HAM). An explicit expression is obtained for the nonlinear frequency amplitude relation. It is found that the proper value of the so-called auxiliary parameter for the HAM solution is dependent on the vibration amplitude, making it difficult to rapidly obtain accurate frequency-amplitude curves using a single value of the auxiliary parameter. The homotopy-Pade technique remedied this issue by leading to the approximation that is almost independent of the auxiliary parameter and is also more accurate than the conventional HAM. Highly accurate results are found with only third order approximation for a wide range of vibration amplitudes.