Mehdi Safari

Investigation into the effects of process parameters on bending angle in the laser bending of tailor machined blanks based on a statistical analysis

In this paper, the effects of process parameters on bending angle in laser bending of tailor machined blanks are investigated experimentally. The Taguchi experimental design method is employed to study various parameters, which significantly affect the bending angle in the laser bending of tailor machined blanks. The start point of scan path, irradiating method, laser output power, beam diameter, and number of radiation passes are considered in the evaluations. A L18(21×34) Taguchi standard orthogonal array is chosen for the design of experiments. The level of importance of the process parameters on the bending angle is determined by using analysis of variance. The optimum process parameters combination is obtained by using the analysis of signal-to-noise (S/N) ratios. The variation of bending angle with process parameters is mathematically modeled by using the regression analysis method and a closed form equation is derived. The results show irradiating method, laser output power, beam diameter, number o...

Nd:YAG laser micro-welding of ultra-thin FeCo–V magnetic alloy: optimization of weld strength

Abstract The main aim of this research is to optimize the tensile strength of laser welded FeCo–V alloy. A mathematical relationship was developed to predict tensile strength of the laser beam welded FeCo–V foils by incorporating process parameters such as lamping current, welding speed, pulse duration and focused position. The procedure was established to improve the weld strength and increase the productivity. The results indicate that the pulse duration and welding speed have the greatest influence on tensile strength. The obtained results showed that the tensile strength of the weld joints increase as a function of increasing pulse duration reaching to a maximum at a pulse duration value of 2.25 ms. Moreover, the tensile strength of joints increases with decrease in welding speed reaching to a maximum at a welding speed of 125 mm/min. It has been shown that increase in pulse duration and decrease in welding speed result in increased effective peak power density and hence formation of more resistant welds. At higher pulse durations and lower welding speeds, the tensile strength of weld joints decreases because of formation of solidification microcracks in the fusion zone.

EBSD Study on Grain Boundary and Microtexture Evolutions During Friction Stir Processing of A413 Cast Aluminum Alloy

The as-cast Al alloys contain heterogeneous distributions of non-deforming particles due to non-equilibrium solidification effects. Therefore, these alloys have poor tribological and mechanical behaviors. It is well known that using friction stir processing (FSP), very fine microstructure is created in the as-cast Al alloys, while their wear resistance can be improved. In this research work, FSP is used to locally refine a surface layer of the coarse as-cast microstructure of cast A413 Al alloy. The main objective of this study is to investigate the effect of FSP on microstructure and microtexture evolutions in A413 cast Al alloy. The grain boundary character distribution, grain structure, and microtexture evolutions in as-cast and friction stir processed A413 Al alloy are analyzed by electron back scatter diffraction technique. It is found that with the FSP, the fraction of low ∑boundary such as ∑3, 7, and 9 are increased. The obtained results show that there are no deformation texture components in the structure of friction stir processed samples. However, some of the main recrystallization texture components such as BR and cubeND are formed during FSP which indicate the occurrence of dynamic recrystallization phenomenon due to the severe plastic deformation induced by the rotation of tool.

Formability Prediction of Two-Layer Sheets Based on Ductile Fracture Criteria

Two-layer sheets which consist of dissimilar metallic components are widely used in various industries. In this paper, formability of Al3105–St14 two-layer sheet is evaluated numerically and experimentally. Freudenthal, Cockroft & Latham, Oh and Brozzo ductile fracture criteria are implemented to predict forming limits in the numerical approach. Numerical FLDs and FLSDs are compared with experimental observations for Al3105–St14 two-layer sheet, and a good agreement is seen. The results show that the prediction of forming limits based on Oh and Brozzo ductile fracture criteria are more accurate than the predictions based on Freudenthal and Cockroft criteria.

A Study on Flame Forming of Bowl Shaped Surface with Various Spiral Irradiating Schemes

In this paper, various strategies of spiral irradiating scheme for the flame forming of a bowl shaped surface are investigated experimentally and numerically. Experimental work is performed using a flame torch integrated with a 2-axis CNC workstation. The ABAQUS implicit solver is used in the numerical simulation. Three different strategies of the spiral irradiating scheme are investigated for the flame forming of a bowl shaped surface. The first strategy is the Simple spiral irradiating scheme, the second is the Rotational spiral irradiating scheme, and the third is the Symmetrical-Rotational spiral irradiating scheme. The results show that using the Symmetrical-Rotational spiral irradiating scheme, a bowl shaped surface with the maximum deformation can be produced, followed by using the Rotational scheme, and the Simple spiral scheme. It is also concluded from the results that the spiral irradiating scheme with Symmetrical-Rotational, Rotational and Simple spiral schemes lead to the maximum symmetries in the produced bowl shaped surface, respectively. All the numerical results are in good agreement with the experimental observations.

A comparison on Properties of Gudgeon Pin Parts Manufactured by Cold Extrusion and Machining Process

Gudgeon pin or wrist pin is a segment of rotary engines that exists in automobile industries all around the world. This pin experiences a complicated and semi-random fatigue loading with tribological contact. Mechanical properties and geometrical dimensions and tolerances of gudgeon pin can be affected by manufacturing process. In this article, two manufacturing processes (cold extrusion process and machining process) are utilized for the fabrication of gudgeon pins from 16MnCr5 steel bars. Tensile test, surface roughness, surface hardness and geometrical tolerances are measured and compared. The results show that gudgeon pins manufactured by cold extrusion process have notably higher tensile properties and surface hardness, better surface roughness and tighter geometrical tolerances than machining process. Microstructure study shows grain refinement due to cold extrusion process.

Microstructual and mechanical studies of the dissimilar tabular joints of Incoloy alloy 825 and AISI 316 stainless steel

ABSTRACT In this work, dissimilar welding of Incoloy alloy 825 and AISI 316 stainless steel tubes is experimentally investigated using gas metal arc welding process. For this purpose, different filler metals such as stainless steel 308, stainless steel 309, stainless steel 316 and Inconel 82 are employed for joining of Incoloy alloy 825 and AISI 316 stainless steel tubes. The results show that during tensile tests, fracture occurred in all weldments in the heat-affected zone (HAZ) of stainless steel 316. Also, it is concluded that dissimilar welds produced by stainless steel 309 filler metal have the maximum tensile strength while the lowest strength is obtained with Inconel 82 filler metal. The results of average hardness prove that the dissimilar joint with filler metal say stainless steel 309 and filler metal say Inconel 82 have maximum and minimum values of average hardness in the weld metal, respectively. The results show a considerable unmixed zone (UMZ) in the form of laminar layers between filler 82 weld metal and the Incoloy 825 base metal along the welding line. In addition, considerable UMZ is seen in the interface of the weld metal/AISI 316 base metal, but more grain growth occurred in the AISI 316 HAZ due to the temperature increase during various welding passes. It is indicated that there is a very narrow UMZ between the 309 weld metal and Incoloy 825 base metal; however, no considerable UMZs can be observed in the AISI 316 base metal.

Airfoil Shape Design via Elastic Surface Inverse Design Method

In this research, a novel inverse design algorithm called, Elastic Surface Algorithm (ESA), is developed for viscose and inviscid external flow regimes. ESA is a physically based iterative inverse design method that uses flow analysis code to estimate the pressure distribution on the solid structure, i.e. airfoil, and a 2D solid beam finite element code to calculate the deflections due to the difference between the calculated and target pressure distribution. The proposed method is validated through the inverse design of three different airfoils. In addition, two design examples are presented to prove the robustness of the method in various flow regimes. Also, the convergence rate of this method is compared with flexible membrane method (MGM) and Ball-Spine Algorithm (BSA) methods in inviscid flow regime. The results of this study showed that not only the ESA method is an effective method for inverse design of airfoils, but also it can considerably increase the convergence rate in transonic flow regimes.© 2014 ASME

An analysis of curved tubes finishing by magnetic abrasive finishing

Applications of finished pieces have been increased by developing of industry. But finishing of some pieces such as the tubes with special shapes is impossible by common methods like grinding. In magnetic abrasive finishing (MAF), the chipping force is controlled by the magnetic field. Using this method, we can get high quality finishing close to nanometre on plane surfaces and internal or external surface of the tubes. MAF can finish the magnetic and non-magnetic materials such as aluminium and corrosion-resistant steel. This paper offers a new and an efficient method for internal finishing of curved tubes. We have discussed the influences of piece material, abrasive material, poling and weight of abrasive material on finishing quality using the design of experiments. The results show that copper has the best surface quality and the most chipping rate.