International Journal of Advanced Design and Manufacturing Technology
Volume:8 Issue: 4, Dec 2015

In this paper, a thermoelasticity solution for steady state response of thick cylinders which are subjected to pressure and external heat flux in inner surface is presented. Displacement field obeys the kinematics of the first order shear deformation theory (FSDT). It is assumed that the temperature varies both along the length and the thickness. The variation of the temperature occurs linearly through the thickness. Using energy method, the equilibrium equations and general boundary conditions are derived for the cylinder. Based on the developed analytical solution, adequate numerical results are depicted to provide an insight into the influence of the thermal and mechanical loads and boundary conditions on thermo-mechanical behavior of cylinder. Results show that shear stresses are noticeable at boundaries; moreover, temperature, displacement fields and stresses are strongly depended on length. Furthermore, the capability of the proposed method to solve any axisymmetrically cylindrical shells with general boundary conditions and thermo-mechanical loading is proven.

In this paper, nonlocal Euler–Bernoulli beam theory is employed for transverse vibration analysis of an initially pre-stressed size-dependent rotating nanotube. The nonlocal Eringen theory takes into account the effect of small size, which enables the present model to become effective in the analysis and design of nanosensors and nanoactuators. Governing equations are derived through Hamilton’s principle and they are solved applying semi analytical differential transform method (DTM). It is demonstrated that the DTM has high precision and computational efficiency in the vibration analysis of nanotubes. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as preload stress, hub radius, angular velocity and small scale parameter on vibration behaviour rotating nanotubes in detail. It is explicitly shown that the vibration of a spinning nanotube is significantly influenced by these effects.

This paper presents dynamic modelling and control of a linear prismatic series of elastic actuator. The capability of generating large torques is why this actuator is increasingly used in human-assistive robotic systems. Due to having human in the loop, the actuator requires precise control. A fractional PID controller known for its improved performance is used for the control, due to having additional degrees of freedom than the classical PID. The actuator has one servo driver and five controller gains to be tuned. The gains are optimized using both Particle Swarm Optimization (PSO) and Imperialist Competitive Algorithms (ICA). Comparison of the results from the two optimization methods illustrates that the PSO tuned FOPID controller has a slightly better performance, faster convergence and better settling time. Next, the PSO tuned controller is compared with a Genetic Algorithm (GA) tuned PID controller. It is shown that the PSO tuned FOPID controller continues to offer better performance, especially in terms of its rise time and settling time.

In this paper, the hydrogen embrittlement of the high strength Cr-Si spring steel with after Zn-12%Ni electroplating, have been evaluated. Slow strain rate test with 3.34 × 10-6 sec-1 strain rate was performed, and the hydrogen embrittlement index of the different samples was calculated. The effect of shot peening before plating and the baking after plating and also the effect of applying a nickel interlayer by electroless method, is examined by using the weibull statistical model. The results showed that alloying Zn with nickel considerably reduce the diffusion of hydrogen on the substrate steel structure. So that it increases the average failure time of samples from 4.9 hours for pure Zn to 8.7 hours for Zn- Ni. By applying nickel interlayer, the failure time increased to 11.15 hour. Also by shot peening process before electroplating, the average failure time increased to 12.7 hours which showed the least amount of hydrogen embrittlement among the studied samples. Baking after the electroplating of Zn-Ni samples without interlayer, leaded to an increase in the failure time to 10.15 hours. While baking in samples containing nickel interlayer, showed the opposite effect, reducing the failure time to 8.15 hours.

In this study, the three parameters of the abrasive particle size, distance of tool to the work piece, and the rotational speed of cylindrical surface finishing of steel AISI 321 by abrasive particles in the MAF magnetic field was studied. The advantages of this process that can be noted are the lack of residual stress after the process and modification of the coaxial shaft. Surface roughness was considered as a function of rotational speed (RPM), the distance between tool and work piece (GAP) and the size of the abrasive particles.Special tools for finishing the cylindrical surface (shaft) are designed from mentioned material and the rotational motion of the shaft is provided by the lathe. Experiments were performed according to full factorial method, using abrasive powders consisting of a mixture of silicon carbide SiC with carbonyl iron Fe in different particle size and SAE40 oil. After the surface roughness measurement of samples, the influence of various parameters on the final surface quality was evaluated, the results have shown that in the mentioned stainless steel shaft finishing, variables of 1. Distance between tool and work piece 2.Abrasive particle size 3. Rotation speed, respectively, have the highest influence on obtained surface roughness. Finally, by using the neural network analysis, a better condition in terms of three parameters was obtained to achieve better surface finish.

In this paper, optimization of Boeing 747 wing has been accomplished for cruise condition (Mach Number=0.85, Flight Altitude=35000 ft), where an optimal wing shape is proposed. Objective functions are minimization of wing weight and drag force that as well as confining design parameters, two functional constrains are applied. The first functional constrain is fuel tank volume in the aircraft wing which supplys the required fuel. The second functional constrain is the lift coefficient that should be equal to the initial lift coefficient. Design parameters are root chord, wing span and wing sweep angle. Non-dominating genetic algorithm has been used in optimization process for one optimal solution, until a set of solutions (pareto front) were obtained for two objective functions. Finally a criterion for selecting a best solution for the aircraft on the pareto frontier is addressed.

This paper considers the problem of scheduling N jobs on M unrelated parallel machines with sequence-dependent setup times. To better comply with industrial situations, jobs have varying due dates and ready times and there are some precedence relations between them. Furthermore sequence-dependent setup times and anticipatory setups are included in the proposed model. The objective is to determine a schedule that minimizes makespan and number of tardy jobs. The problem is NP-hard, so for obtaining an optimal solution in reasonable computational time, two multi objective genetic algorithms (MOGA) are proposed. To evaluate the proposed algorithms, random test problems are produced in medium and large sizes with tight due dates. After setting the parameters, the performances of these algorithms are evaluated using the concept of data envelopment analysis (DEA), distance method, and a number of non-dominated solutions.

The main aim of the vibration energy harvesters is to locally power autonomous devices such as wireless sensors. Generally, power levels are low and the environmental benefit of the technology is to replace batteries rather than saving energy per se. Piezoelectric vibrational energy harvesters are usually inertial mass based devices, where a cantilever beam with a piezoelectric outer layer is excited into resonance by a mechanical vibration source at the root of the cantilever beam. However, the geometry of a piezoelectric cantilever beam will greatly affect its vibration energy harvesting ability. This paper deduces a remarkably precise analytical formula for calculating the fundamental resonant frequency of unimorph V-shaped cantilevers using Rayleigh-Ritz method. This analytical formula, which is convenient for mechanical energy harvester design based on piezoelectric effect, is then validated by ABAQUS simulation. This formula raises a new perspective that, among all the unimorph V-shaped cantilever beams and in comparison with rectangular one (the simplest tapered cantilever), can lead to the highest resonant frequency and maximum sensitivity.

The present study deals with the buckling analysis of the laminated composite truncated conical sandwich shells with flexible core subjected to combined axial compressive load and external pressure. Higher order governing equations of the motion are presented for conical composite sandwich shells, where they are derived from the Hamilton principle. Then, by the use of Improved Higher-order Sandwich Shell Theory, the base solutions of the governing equations are obtained in the form of power series via general recursive relations. The first order shear deformation theory is used for the face sheets and a 3D-elasticity solution of weak core is employed for the flexible core. By application of various boundary conditions such as clamped and simply-supported edges, the natural frequencies of the conical composite sandwich shell are obtained. The obtained results are compared with the numerical results from FEM analysis and good agreements are achieved. An extensive parametric study is also conducted to investigate the effect of total thickness to radius ratio on the buckling load.

In this paper, the results of experimental and numerical simulation of low velocity impact process have been carried out to investigate energy absorption of composite sandwich panels with 3D woven fabrics of glass fibers and epoxy resin. For this purpose, diagrams of force-displacement of the quasi-static and quasi-dynamic impact tests were studied. For the finite element simulation, Sandwich panel is considered as a composite material with anisotropic elastic properties. In this simulation, Hashin’s damage criteria have been used to model the fracture mechanics. The energy absorption in quasi-dynamic test is greater than the quasi-static test. Comparison of the numerical and experimental simulation shows good agreement between the results.