International Journal of Advanced Design and Manufacturing Technology
Volume:10 Issue: 1, Mar 2017

In this paper, vibrational response of a variable-length cable in longitudinal, lateral and torsional directions is analysed in a cable robot using FE method. The flexibility of cables has remarkable effect on positioning of the end-effector in cable robots. Also considering the fact that the length of the cables are time dependent in a dynamic cable structure like robocrane, the numerical approaches are preferable compared to analytic solutions. To do so, the cable is divided into finite elements in which the virtual work equation and Galerkin method can be implemented for the equations. Considering the stiffness matrix, the characteristic equations and Eigen values of each element can be defined. A simulation study is done in the ANSIS on a planar robocrane with 2-DOF and also for a spatial case with 6-DOF that is controlled by the aid of six variable-length flexible cables in the space for two different types of solid and flexible end-effectors. Whole the cable robot flexibility is analyzed simultaneously instead of separation calculation of each cable. Not only all of the 3-D vibrating behaviour of the whole structure is studied in this paper but also the lengths of the cables are considered as variable. The vibrating response of mode shapes, amplitude and frequencies are extracted and analysed, and the results are compared for two case of solid and flexible end-effector which shows the effect of the flexibility in the position of the end-effector and the tension of the cables in different situations.

Equal channel angular extrusion (ECAE) is one of the most powerful processes for manufacturing microstructure and nanostructure ýmaterials. This process is a kind of severe plastic deformation technique, which requires large extrusion force. In this study, the numerical and experimental investigation of extrusion ýforce in ultrasonic assisted equal channel angular extrusion process (UAECAE) is carried out. ABAQUS Software is used for 2D ýfinite element analysis of the process considering superimposed ultrasonic vibrations to the round billet work material. Experimentally, the conventional and ultrasonic assisted ECAE are performed with copper material to validate simulation results. The reduction in extrusion force is observed due to ultrasonic vibrations. In order to achieve more ýaverage force reduction, it is recommended that the ýextrusion speed decreases and (or) vibrations amplitude ýincreases. Stress and strain distributions are numerically investigated in various vibrational conditions and die angles. The best die angle to obtain optimum force ýreduction is 120º. In other die angles, vibrations ýamplitudes of 15ý μmý and higher ýis necessary. Ultrasonic vibrations lead to oscillatory stresses with reduced ýaverage value, but do not influence the amount of plastic strain ýdistribution. Achieving the beneficial products in ýECAE requires heavy special equipment, whereas using UAECAE will lead to more accessible equipment. ýFinally, some optimal process parameters such as die angle, vibrations amplitude, for the proper application of these vibrations are ýproposed.

A combined metal forming process consisted of backward extrusion (BE) and constrained ironing (CI) is used to produce thin walled ultrafine grained (UFG) magnesium cups. In this new method, the initial thick-walled cup is formed from the bulk material using the BE process and then the CI process is used to produce a UFG thin-walled cups. The advantage of the CI process is applying compressive stresses that are suitable to form hard to deform materials like magnesium alloys without fracture while achieving higher thickness reduction ratio (TRR). The results showed that after this new combined method, the tensile strength raised to 233 MPa, from the initial values of 123 MPa. Simultaneous improvement in strength and ductility attributes to very high hydrostatic compressive stresses and also breakage of Mg17Al12 precipitates in to smaller parts that facilitate the movement of dislocation. Also, the hardness increased to about 233 MPa from the initial values of 58 HV. Significant grain refinement was also taken place and the grain size in the BE sample reduced to ~1 μm from the initial value of ~150 μm due to imposing high value of strain. This combined method is very promising for processing of UFG thin-walled cup-shaped samples from hard to deform materials. SEM images illustrated the brittle fracture at unprocessed and BE samples with existence of wide crack and shallow-elongated dimples but BE sample revealed brittle fracture with fewer cracks due to hydrostatic pressure.

In this paper, the effects of various parameters on the process of T-shaped copper tube bulge forming have been investigated. This evaluation is based on the properties of the copper tubes, properties of polyurethane rod and practical conditions of a bulge forming process such as the friction coefficient between die and tube, between tube and rod, boundary conditions and their constraints. The effect of each condition on a T-shaped copper tube has been explicitly simulated using the Abaqus software. The experimental results have been validated by conducting a series of experiments. After simulating the process, the effect of other parameters such as die corner radius, friction coefficient, thickness of the tube and counterpoise can be evaluated and used in practical experiments. Then, the simulation results have been compared with the obtained results from the experiments. Once the accuracy of the simulation results has been endorsed, the optimal values of different parameters have been determined using simulations. The optimal values for die corner radius, friction coefficient and counterpoise are 5 mm, 0.05 and 200 N, respectively. The findings shows the positive effect of utilization of optimal value for die corner radius, optimal value for counterpoise and lubricate on optimize forming process properties.

In this paper, a free vibration of nano-plates is investigated considering the small scale parameter. The used rectangular nano plate is thin and under different boundary conditions. In order to obtain the natural frequencies of the nano-plates, classical plate theory on the basis of non-local theory is used. The governing equation is solved using a semi-analytical method DTM[1]. The results for free vibration of those plates are compared with the theoretical data published in the literature. Results show that DTM is a powerful, simple, accurate and fast method for solving equations in comparison with other methods. Non-local parameter is very effective in vibration of nano-plates and its influence is different in various boundary conditions. Influence of this parameter in simply supported-clamp boundary condition is higher than other boundary conditions.

The aim of this manuscript is to study the implication of aluminium-oxide nanofluid for an amphibious vehicle engine (viable on land and under water) cooling system both analytically and experimentally. To achieve this, a one-dimensional model of the engine cooling system (radiator) is considered through a computational fluid code in which the mass flow rate for a range of the coolant temperature is assumed to be constant. By knowing the volumetric flow rate of the air passing over the radiator, the heat transfer rates for different aluminium-oxide nanofluid volume concentrations at different amphibious engine gears are determined. The analytical results indicate that a 7% aluminium-oxide nanofluid increases the engine radiator heat transfer performance by 24.9%, while the experimental results show that the coolant outlet temperature is about 3˚C lower than the case without the nanofluid in the coolant.

FGM dental implants are a very good alternative with respect to homogenous implants. In this study by focusing on mechanical property as one of the most important factors in implant design, the static behaviour of Ti/Nanostructure HA (hydroxyapatite) FGM dental implant has been fabricated and investigated experimentally and numerically. At the first step, the nanostructure hydroxyapatite powders were synthesized by natural origin. At the second step, the initial powders were cold compacted in order to fabricate Ti/HA FGM samples for 4 different volume fraction exponents (N=1/3, 2/3, 1, 2). Then the compacted powders have been sintered using a vacuum furnace, in which compressive strength of each particular sample was finally assessed. A three-dimensional geometrical model of FGM dental implant system and surrounding bone was created by using the macro programming language in ANSYS software and then finite element analysis under static forces was performed. Finally the experimental results strength tests were compared with numerical solutions. According to the results, the FGM dental implants made of Ti/HA under static forces were sufficiently safe. As a result, FGM sample with volume fraction exponent of N=2/3 was chosen as the best sample.

In this study, in order to investigate the effect of increasing the manganese content on microstructure and mechanical properties of high manganese austenitic steels, three alloys with successive increases in weight percentages of manganese (7.55, 13.1, and 16.5) and carbon (0.8 and 1.2) were cast in the presence of a constant amount of chromium (1.5 wt.%) and silica (0.6 wt.%). The samples experienced solution annealing heat treatment comprised of austenitizing at 1100°C for 2 h followed by rapid quenching in stirred water. Hardness, tensile, and wear tests were conducted by dry sand/rubber-wheel abrasion method. Microstructural observations were performed by using optical (OM) and scanning electron microscopies (SEM) and energy dispersive spectroscopy (EDS). The obtained results revealed that after heat treatment a uniform austenite structure has developed in all three samples. With increase of weight percent of the elements from sample 1 to sample 3, the hardness value reaches from 191 to 218 Vickers. Also, with increase of manganese weight percent from 7.55 to 16.5, the ultimate tensile strength and wear resistance showed 11% and 29% increase, respectively, to the effect that the most enhanced mechanical properties and maximum wear resistance were observed in sample 3 with 16.5wt.% of manganese. This improvement in mechanical properties and wear resistance is related to the formation of the solid solution in the matrix, the increase of hardenability, and the increase of work hardening capacity resulted from the increase of manganese percentage. Examination of the abraded surfaces demonstrated that the involved wear mechanism was scratch wear mechanism.

In this paper a new method for Nondestructive testing or Nondestructive evaluation is proposed for Glass-Epoxy composite. For this purpose, impact-echo is used to evaluate the properties of composite materials, detecting internal defects and thickness measurement. In the impact-echo method a steel ball impacts on a composite plate and generates stress waves or P-waves which will be transferred into the plate. The results show that impact response of the composite plate for dominant thickness frequency for measuring thickness and locating the defect is in agreement with the normal measurement. Results represent that this method could be used for thickness measurement and flaw detection of Epoxy-Glass composites with a reasonable accuracy.

In manufacturing industry, it has been acknowledged that tool wear prediction has an important role in higher quality of products and acceptable efficiency. Being an emerging area of research in recent years, drilling tool wear is an important factor which directly affects quality parameters of machined hole such as hole centring, roundness, burr formation and finished surface. In this paper, the genetic equation for prediction of drilling tool flank wear was developed using the experimentally measured wear values and genetic programming for two different materials, AISI1020 and AISI8620 steels. These equations could be used to compare the behaviour of wear in both mentioned materials and analyse the effect of materials characteristics on wear rate and wear pattern. The suggested equations have been shown to correspond well with experimental data obtained for flank wear when machining in various cutting conditions.The results of experiments and equations showed that properties of work material can affect drill bit flank wear drastically. It was concluded that greater toughness and strength of AISI8620, compared to AISI1020, lead to higher cutting stresses and temperatures, resulting more flank wear.

The Micro wire electrical discharge machining (Micro wire-EDM) process is a modern machining process with various applications in manufacturing micro-parts. The recast layer remaining on the machined surfaces is an inevitable complication of this process. This layer can subsequently affect the machined parts performance. To optimize the recast layer in the micro wire-EDM of the molybdenum microparts, effect of the process parameters on the distribution amplitude of the recast layer was investigated using the Taguchi method. The obtained results showed that the optimal levels of the micro wire-EDM process parameters for achieving the optimal distribution amplitude of the recast layer are as follows: spark pulse-on time of 0.2 μs, cutting speed of 7 mm/min, process voltage of 17 V, and wire tension of 0.45 kg. Also the importance order of the effect of the process parameters on the distribution amplitude of recast layer is as follows: spark pulse-on time, process voltage, cutting speed, and wire tension.