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Open Access Article
1 - Effect of Temperature on Diffusion-Bonded Joint of AZ31 Magnesium and 7075 Aluminum Alloy
Hossein Alimardan Sahebali Jamal SeidiIn this study, the effect of temperature on the diffusion welding of AZ31 magnesium alloy and 7075 aluminum was discussed. Diffusion welding temperature was the most important parameter since all mechanisms are sensitive to temperature in Diffusion welding method. Intru MoreIn this study, the effect of temperature on the diffusion welding of AZ31 magnesium alloy and 7075 aluminum was discussed. Diffusion welding temperature was the most important parameter since all mechanisms are sensitive to temperature in Diffusion welding method. Intrusive contacts between the two alloys at temperatures of 430, and 440 °C 450 and took 60 min. In all tests constant pressure and vacuum, respectively 29 MPa and 1×10-3 torr were considered. Interface connections using Scanning Electron Microscope (SEM) equipped with EDS analysis was conducted to evaluate the mechanical properties of joints as well as a survey of microhardness and shear strength tests were analyzed. As a result of the presence of intermetallic compounds and Al3Mg2 Al12Mg17 binding was observed in the weight of these compounds increased with increasing temperature. Manuscript profile -
Open Access Article
2 - Machinability evaluation of Titanium alloy in Laser Assisted Turning
Kamran Puladsaz Razavi Shojae Rezavi Mehdi TajaddaraThe use of titanium and its alloys has increased in various industries recently, because of their superior properties of these alloys. Titanium alloys are generally classified as difficult to machine materials because of their thermo-mechanical properties such as high s MoreThe use of titanium and its alloys has increased in various industries recently, because of their superior properties of these alloys. Titanium alloys are generally classified as difficult to machine materials because of their thermo-mechanical properties such as high strength-to-weight ratio and low thermal conductivity. Laser Assisted Machining (LAM) improves the machinability of high strength materials in various aspects. LAM is a high temperature cutting process using a laser beam as the heat source. The laser is used as an intense heat source to increase workpiece temperature locally and decrease the strength of the machined material in front of the cutting tool. Decreasing of workpiece material strengh in material removal region resulted to improvement of material removal conditions. In this study the effectiveness of the LAM on machinability of Ti6Al4V is invetigated by compared to conventional machining in varying process parameters such as cutting speed, feed rate, laser power and material removal temperature. The machinability of the titanium alloy under varying conditions is evaluated by examining specific cutting energy, surface roughness and chip morphology. This investigation has shown that LAM reduces specific cutting energy about 30% and improvement of surface roughness as compared to conventional machining. Manuscript profile -
Open Access Article
3 - Evaluating Organizational Performance Based on Safety Management Using Data Envelopment Analysis; Case Study: Isfahan Car Industry
Hadi Shirooyezad Negin Berjis Farimah Mokhatab RafieiOccupational accidents severely deteriorate human capital, and hence negatively affect the productivity and competitiveness. But despite these negative points, there are still deficiencies in safety management performance and indicators. Therefore the safety issue needs MoreOccupational accidents severely deteriorate human capital, and hence negatively affect the productivity and competitiveness. But despite these negative points, there are still deficiencies in safety management performance and indicators. Therefore the safety issue needs an active management. For this reason, the writer has proposed an approach to evaluate organizations based on safety management. Data envelopment analysis is used to assess organization’s performance. After efficient and inefficient DMUs were found, the next step would be sensitivity analysis of DEA Model’s inputs. The proposed approach has been solved in Isfahan car industry. The results show that, there are 5 efficient DMU’s between 12 ones. Then DMU’s have been ranked by two ranking methods of super efficiency and Ideal and Anti Ideal Ranking Method. The sensitivity Analysis of model’s inputs results signify that among indicators, safety risks management has the most influence, on DMU’s efficienc. Manuscript profile -
Open Access Article
4 - Machinability Improvement of 17-4PH Stainless Steel by Cryogenic Cooling
Salman Khani Mohammad Razfar Masoud Farahnakyan17-4PH stainless steel is a martensitic precipitation hardening stainless steel that provides an outstanding combination of high strength, good corrosion resistance, good mechanical properties, good toughness in both base metal and welds, and short time, low-temperature More17-4PH stainless steel is a martensitic precipitation hardening stainless steel that provides an outstanding combination of high strength, good corrosion resistance, good mechanical properties, good toughness in both base metal and welds, and short time, low-temperature heat treatments that minimize warpage and scaling. This valuable alloy is widely used in the aerospace, nuclear, chemical, petrochemical, food processing, power generation, and naval industries; however, 17-4PH stainless steel is categorized as hard to machine materials due to low thermal conductivity and high toughness. Tool wear in traditional machining of 17-4PH stainless steel is high; hence, low tool life causes high tooling cost. In this paper, indirect cryogenic machining was used, in order to improve machinability of 17-4PH stainless steel in turning operation with TiN coated carbide insert tool. Pressurized-liquid-nitrogen (LN) was used as a cryogenic coolant. Nitrogen gas applied on the liquid nitrogen to pressurize it. A specific tool holder was designed and manufactured for cryogenic turning. Cryogenic machining decreases temperature-dependent tool wear and increases tool life by keeping tool temperature low. Cutting force, tool flank wear and maximum tool temperature have been studied as machinability parameters. Cutting force was measured by the Kistler 9121 piezoelectric dynamometer. The Dino-Lite digital microscope with 20-200X magnification was used to measure tool flank wear. The experimental results showed that cryogenically enhanced machining decreases cutting force and tool flank wear by 22 and 23 percent, respectively, compared with dry turning. Predicting of tool life using linear extrapolation showed that tool life in cryogenic turning improved by 39% over dry turning. In addition, cutting force in cryogenic machining became more stable than the force in dry condition. Thermal analysis of the carbide tool performed in the ANSYS Software using experimental data. Thermal analysis showed that the maximum temperature of cutting tool in cryogenic machining is 75 percent lower than dry condition. Manuscript profile -
Open Access Article
5 - Investigation on Wear Behavior of W-Cu Nanocomposite Fabricated Through Thermochemical Synthesis
Mehdi Jahangiri Mazdak Hashempour Hekmat Razavizadeh Hamid Reza RezaieIn this work, homogeneous thermochemical co-precipitation method was used to fabricate W-25wt%Cu nanocomposite. Synthesized nanocomposite powder was calcined and reduced. A hydrogen atmosphere sintering at 1200oC for 105 consolidated the product up to a density close to MoreIn this work, homogeneous thermochemical co-precipitation method was used to fabricate W-25wt%Cu nanocomposite. Synthesized nanocomposite powder was calcined and reduced. A hydrogen atmosphere sintering at 1200oC for 105 consolidated the product up to a density close to 98% theoretical density. Wear experiment were carried out using a pin-ondisc set up at three normal loads of 5, 10 and 15 N and the dissipated energy was calculated in each case as a funsction of wear distance. Evalustion of the slope of the “dissipated enargy-wear distance” plot demonstrated the constancy of this slope at each certain normal load. However, the steepness of this slope, was in direct relation with the magnitude of the normal load (a J/m for 5N, b J/m for 10N and c J/m for 15N), demonstrating the higher potency of larger normal loads for injecting energy and thus, wear damage to the material. According to this constant slope of this plot at each normal load, constancy of the wear mode under each loading condition can be ruled out. Simultaneous consideration of mechanical and microstructural parameters of wear revealed that the dominant wear mode in all loading conditions was fatigue wear and the corresponding active wear process was delamination. Formation of sub-surface cracks and gradual degradation of the worn surface by flaking off, were of importance in the evolution of this type of wear damage. Manuscript profile -
Open Access Article
6 - Simulation of a Microgripper with Electrothermal Actuator Using COMSOL Software Based on the Finite Element Method
Amin Rouhani Esfahani Mojtaba Kolahdouzan Mehran MoradiMicro-electro-mechanical systems (MEMs) are Combination of electrical and mechanical components in Micron dimensions. In recent years, holding, actuating methods and handling of MEMs components such as microgripper, microsensors and etc. have been deeply studied. Microg MoreMicro-electro-mechanical systems (MEMs) are Combination of electrical and mechanical components in Micron dimensions. In recent years, holding, actuating methods and handling of MEMs components such as microgripper, microsensors and etc. have been deeply studied. Microgrippers for handling, positioning and assembling of micro components are very useful so that for clamping need actuation created using electrostatic, electrothermal, and electromagnetic actuators. In this paper, a new design of an electrothermal microgripper with U-shape actuators for holding and carrying a wide range of parts at the same time, For voltages corresponding between 1 to 10 volts, have been fabricated. The microgripper is made of silicone with thickness of 25 microns, and pieces between 460 to 480 microns that can hold it. The behavior of the microgripper in Multi physics powerful finite element software (COMSOL) was evaluated and the displacements of arms hold and heat generations have been simulated. Manuscript profile
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