INTERNATIONAL JOURNAL OF ADVANCED DESIGN AND MANUFACTURING TECHNOLOGY
Year:2016 | Volume:9 | Issue:4|Papers Count:12

The vibratory finishing is one of the important mass finishing processes. This can be applied for finishing many metallic and non-metallic components using abrasive materials such as steel, ceramic, natural materials and etc. The vibratory finishing process is used for some purposes such as surfaces polishing, deburring, oxide layer removing and rounding the edges. Evaluation of surface roughness changes with time that is one of the important parameters during the vibratory finishing process. In this study, the effects of the working time and abrasive materials are investigated on the surface roughness changes of CK45 steel samples. The ceramic, glass and mixed abrasive particles are used as the abrasive media. The experiments are performed at different time from 10 to 120 minutes in the dry environment. Finally, the surface roughness values of samples were measured and then fitted by a regression equation for description of the surface roughness changes with time. According to the results, the maximum surface finish was obtained after 120 minutes by using mixed abrasive materials. The surface roughness improved approximately 60%.

This study is focused on investigating the parameters of laser percussion drilling process of nickel-base super alloy Inconel 718 with thickness of 1 mm. Fiber laser with the power of 500 watts was used as the laser source. Laser pulse frequency, duty cycle, laser power, focal point position, were assumed as the laser drilling process variables. The hole geometry features, i.e. entrance hole diameter, circularity of entrance hole, and hole taper were measured. The results indicated that pulse frequency of laser has a direct influence on the entrance hole diameter. Increasing the duty cycle leads to increases in hole taper. By increasing the laser power, entrance diameter and hole taper increases.

In this study, warm accumulative roll bonding (Warm- ARB) process has been used to produce Metal Matrix Composite (MMC: AA5083/-5% Al2O3). Starting materials were roll bonded as alternate layers up to 5 rolling cycles with 300°C preheating for five minutes before each cycle. The microstructure and mechanical properties of composites have been studied after different Warm- ARB cycles by tensile test, Vickers micro hardness test and scanning electron microscopy (SEM). The results revealed that during higher Warm- ARB cycles, breaking the layers of alumina particles led to the generation of elongated dense clusters with smaller sizes. This microstructural evolution led to improvement in the hardness, strength and elongation during the Warm- ARB process. The results demonstrated that the dispersed alumina clusters improved both the strength and tensile toughness of the composites. Finally, Warm- ARB process allowed producing metal particle reinforced with high uniformity, good mechanical properties and high bonding strength.

In this research, the coupling between non-gray radiation and separation convection flow in aductis investigated numerically. Distributions of absorption coefficients across the spectrum (50cm-1<h<20000cm-1) are obtained from the HITRAN2008 database. The full-spectrum k-distribution method is used to deal with the non-gray part of the problem, while the gray radiation calculations are performed using the Planck mean absorption coefficient. To find the divergence of radiative heat flux distribution, the radiative transfer equation (RTE) is solved by the discrete ordinates method (DOM). The effects of radiation-conduction parameter, scattering coefficient and wall emissivity on thermal behaviors are investigated for both gray and non-gray mediums. In addition, the results of gray medium are compared with non-gray results as a real case. There sults show that in many cases, use of gray simulations is not acceptable and leads to significant errors, especially in non-scattering medium with high values of radiation-conduction parameter and wall emissivity.

This paper addresses the concept of CO2 Laser beam machining (LBM) and development of intelligent knowledge base system (IKBS) for CO2 LBM. Feature based design is used for acquiring design specification. For optimization of laser beam machining computer based concurrent engineering environment is used. The IKBS is linked to feature base cad system. The IKBS is also linked to material database which holds attributes of more than 50 types of materials. It is also linked to Laser database which holds attributes of 3 types of laser machine. IKBS is also linked to Laser machine variables and parameters. For each design feature, IKBS provides information such as machining cycle time and cost and machining rate. By changing machine parameters, we can optimize machining cycle time and cost and cutting rate. The IKBS can be used as an advisory system for designers and manufacturing engineers. It can also be used as a teaching program for new CO2 laser operators in computer based concurrent engineering environment.

A decisive constraint for the long-term stability of the artificial joint is to minimize the release of debris particles. The wear/debris induced osteolysis and aseptic loosening are the result of failure of metal-on-metal joint implants. SPD processes have been used to adapt the surface integrity properties by generating ultrafine or even nano-sized grains and grain size gradients in the surface region of work materials. These fine grained materials often show enhanced surface integrity properties and improved functional performance (wear resistance, corrosion resistance, fatigue life, etc.) compared with their predictable coarse grained counterparts. To identify the implant material’s post machined behaviour in biological environment, the experiments were planned by precision CNC turning process and accordingly post machined surfaces were analyzed by contact type and electrochemical measurement processes. The work includes effect of machining parameters on machined surface roughness and corrosion rate by an electrochemistry of Co-Cr-Mo bio-implant alloy. The minimum machined surface roughness value 0.450 μm shows minimum corrosion rate as 0.00002 mm/year. It is also shown that feed rate is having predominating effect on machined surface roughness and rake angle is on corrosion rate of Co-Cr-Mo bio-implant alloy.

It would be difficult to deny the importance of optimization in the areas of science and technology. This is in fact, one of the most critical steps in any design process. Even small changes in optimization can improve dramatically upon any processor element within a process. However, determining whether an optimization approach will improve on an original design is usually a question that its response in this study has led to an optimal design out of an existing car model. First of all, the optimization of a passive car-quarter model has been accomplished by means of a genetic algorithm. This initial optimization gives a figure of points named “Pareto optimum points”. Secondly, through selecting a point amongst them, the design of active model has been completed and optimized based on genetic algorithm. Continuing with this thought, a similar process has been also accomplished with a car-half vehicle model with five degrees of freedom. Though the last optimized active model may prove a more reliable efficient design due to the more comprehensive feature related to the degrees of freedom, the results of each optimization should be considered and may supply equally attractive and diverse choices as well. Anyway, let's focus on the final purpose which is to reduce the vibrations as much as possible. This is what is observed through all the optimization jobs in this study. Comparison of these results with those reported in the literature affirms the excellence of the proposed optimal designs.

With the development of micro and nanotechnology, machining methods at micro and nanoscale have now become interesting research topics. One of the recently-proposed methods for sub-micron machining, especially nanomachining, is dynamic plowing lithography (DPL) method. In this method an oscillating tip is used for machining soft materials such as polymers. The geometry of the oscillating beam and its vibrational properties are the most important parameters in this nanomachining process. In this study, effects of the AFM beam geometry on its stiffness coefficient, resonant frequency, beam stability, and the maximum stress created in the beam structure were investigated for 12 different general shapes using the finite element method. The obtained results indicate that circular and square membranes are the most favourable AFM cantilever geometries because these structures provide higher machining force and speed; while for noisy conditions and environments, straight and V-shaped beams are recommended (because of their higher stability factor) for the DPL nanomachining process.

Changes of hydrodynamic parameters in microchannel branches affect the suspended biological samples in blood. To prevent denaturation and hemolysis, we have numerically investigated the effect of divergence angle on shear rate and velocity at branch entrance (discharge rate), under electroosmotic flow. In such flow, hydrodynamic properties are also affected by zeta potential at the microchannel walls. We have also studied the effect of change of zeta potential (x) proportion at main channel wall (x1) to that of branch channel (x2), on the discharge rate to find its maximum for different divergence angles. In the divergence angle of 60o and while zeta potential at the branch wall is equal to its value at main channel wall, the tendency of particles to pass through the branch is the highest among all examined degrees. At the zeta potential proportion of (x1/x2=0.5), the change of divergence angle has almost no effect on the maximum velocity in the branch. In addition, with increase of divergence angle from 60o to 150o, the shear rate at the branch will become 2.1 times higher.

Nowadays CMM machines are widely used in surface measurement and inspection. As inspection results from CMM machine are obtained by the means of measuring surfaces with direct contact, they are more precise than non-contact method (like optical measurement). Although, CMM machines give more reliable and accurate results rather than non-contact methods, these results come with error when outer surface contains porosity spaces. This paper proposes a new method for measuring outer surface of porous objects. In this method the probe will be located above the porous area and does not enter inside. The proposed strategy could be utilized whether CAD model of object is available or not. If CAD drawing of object exists, the probing stylus will not enter into the hole. On the other hand, if the CAD drawing does not exist, a perpendicular plane to the surface will be virtually modeled and by this normal plane the outer surface of the object will be estimated. In addition in this research an effort has been made to reduce dependence on CAD drawing.

In this paper, the direct extrusion process of bimetallic rods in conical dies is analyzed by an improved upper bound method. The deformation zone is subdivided into six smaller zones and by considering a non-spherical entrance boundary to the deformation zone, a velocity field is presented which is different from velocity fields employed in previous studies. The total power consumption of the process including internal, shear and frictional powers is obtained using this velocity field, and then the forming force is calculated by employing the upper bound theory. The superior accuracy of the proposed analysis is demonstrated by comparing the computed force with available experimental data and results of an upper bound analysis in the literature. Finally, the developed model is employed to study the effect of some process parameters on the forming load. It is observed that there is an optimal die angle that minimizes the extrusion force. The value of this optimum angle increases with friction coefficient.

Suspension system is one of the most important factors in provision of ride comfort and dynamic stability in any vehicle. However, the suspension system for the tracked vehicle has more particular specifications in compare with the other vehicles. Due to its continuous track, these specifications can help the tracked vehicles possess an improved dynamic stability in off-road maneuvers compared to the vehicles with discrete tiers. In this paper, off-road performance of the tracked vehicle has been thoroughly investigated. In this regard, firstly the mathematical model of a tracked vehicle suspension system with governing dynamic equations are derived and the state-space representation are represented. After on, the off-road inputs such as hill inputs, passing over Belgian block and irregular terrain are applied to the dynamic model and the system outputs, especially body hull vertical acceleration as one of the most important criteria of stability, are reviewed. The results show that the responses are in range of acceptable overshoot and there suggest the related critical speed of the vehicle. Furthermore, for model validation the results are compared with ACMP reference model in response to the standard off-road inputs and the results are satisfactory.