علی زین العابدین بیگی

The production of orthopedic screws of Ti6Al4V alloy presents challenges due to the need for a fast, cost-effective method of cutting difficult-to-cut alloys. This study addresses these issues by determining the kinematics of thread whirling for orthopedic screws made of Ti6Al4V alloy and investigating the effect of cutting parameters on the dimensional accuracy and texture of spinal screws. The proposed method enables rapid production while maintaining high precision. The main process parameters, such as tool rotational speed and workpiece feed rate, were varied at two levels for a total of four samples. The output parameters included surface roughness, thread root surface texture, sidewall profile, and thread angle. The results showed that a higher feed rate produced a rougher thread root surface and a lower ploughing effect. This increased roughness was considered ideal because it promotes cell growth on the screw surface and improves screw osteointegration in bone tissue. Furthermore, increasing the cutting speed, while creating a serrated texture on the thread wall, improved overall screw quality by reducing cutting force and eliminating crown thread defects. Within the specified manufacturing tolerance, the effect of cutting parameters on thread angle was negligible.

In the present research, a three-degree-of-freedom haptic device was used to simulate a virtual object located on a point on a two-dimensional wall. Two spatial coordinates of the operating point on the wall were arbitrary. Therefore, the robot would have two degrees of freedom redundancy for this task. These two degrees of robot redundancy were specified by the artificial bee colony optimization and crow optimization algorithm in such a way that while ensuring the stability of the robot, the damping coefficient of the simulated virtual object was also maximized. The optimization process was performed in two different ways. In the first case, the stiffness of the robot was assumed to be a constant value in the whole workspace, while in the second case, the stiffness was considered a function of the robot configuration. In each case and at each operating point, first an effective mass, an effective damping coefficient, and an effective stiffness for the robot were obtained, and then using some theoretical relations, a stable operation boundary was obtained. Finally, the optimization methods specify the location of the operating point in such a way that the simulated damping coefficient was maximized. The results show that in the case of constant robot stiffness, both of the mentioned methods were able to simulate the maximum value of 1.825 for the virtual damping coefficient. However, in the case of variable robot stiffness, the crow and bee algorithms reached the values of 2502 and 2498, respectively as the maximum damping coefficient that could be simulated. In addition, although the number of cost function calculations is the same in both methods, the crow optimization algorithm was faster and more repeatable.

The cold roll forming is one of the common processes to form metal profiles in the industry. Due to the nature of the bending deformation in cold roll forming process, spring-back is one of the most important defects. In order to compensate the spring-back, the amount of spring-back must be correctly predicted. In this article, the effect of the hole and its position on the spring-back has been investigated by experimental and numerical methods. three channel section profiles made of St12 and thickness of 1 mm, without hole, with circular holes on the bend area and with holes on the flange were used. Cold roll forming was done in three stations with a fixed bending radius pattern with 15 degree bending in each forming station and numerical solution using Abaqus finite element software. The results indicate that there is a relationship between the amount of spring-back and the position of the hole in such a way that the amount of spring-back in hole on the bend area profile is 9% more than the hole-less profile and in hole on the flange profile is 16% less than hole-less profile. Also, according to finite elements results, it was observed that the amount of equivalent strain in the bend area of the profile with holes on the bend area is 20% less and in the profile with holes near the bend area is 16% more than the profile without holes, which can justify the difference observed in the amount of spring-back.

Metallic bipolar plates can be mentioned as one of the main components of the fuel cell. Various methods such as hydroforming process, electromagnetism, stamping, and rubber forming are used to produce these plates. In this study, the effect of rubber layer on the production of the metallic bipolar plate by the rubber forming method was investigated. The forming die with a convex pattern and parallel helical grooves was used to fabricate bipolar plates made of SS316 with a thickness of 0.1 mm. First, the effect of forming force on channel depth in both transverse and longitudinal directions was studied. Experimental results indicated that there is a direct relationship between the depth of the channel and the applied force, and the maximum depth of the channel occurs in the transverse direction. In addition, the effect of hardness of rubber on the channel depth of bipolar plates was investigated. The results showed that the maximum depth of the channel decreases with increasing hardness of the rubber. On the other hand, with a large decrease in the hardness of the rubber layer, it would be difficult to provide the pressure for applying the plastic deformation on the sheet metal. Then, the depth of the middle and side channels in the longitudinal direction was measured in order to evaluate the dimensional accuracy of the channels. The experimental results showed that the depth of the channels is uniform in this direction, which indicates the acceptable dimensional accuracy for the fabricated samples.

Achieving the minimum thinning and required forming force is one of the main purposes in the manufacturing of sheet products using the hydroforming process. This paper investigates forming of the copper sheet using the hydrodynamic deep drawing assisted by radial pressure via the design of experiment method and finite element (FE) analysis. Firstly, the necessary experiments have been designed using the Taguchi design of experiment method. In this design, maximum fluid pressure, punch velocity, the friction coefficient between punch and sheet, the friction coefficient between die and sheet, the gap between blankholder and die, punch nose radius, die entrance radius, and prebulge pressure were considered as input variables and thinning ratio and punch force considered as response functions. Then, designed experiments were performed using an experimental verified FE model and the desired results were obtained. Finally, the optimum levels of input variables were obtained using the Taguchi optimization method and the confirmation experiments were performed using the FE simulation. Results show that the punch nose radius and die entrance radius are the essential parameters on the thinning ratio. Also, the maximum fluid pressure is the most effective parameter on the punch force.

Thickness distribution is one of the important parameters in the sheet metal forming processes. This paper investigates the forming of flat cylindrical cups made of steel using the hydrodynamic deep drawing process via experiment and simulation. At first, the process was simulated using the ABAQUS finite element software. Afterward, the results of the finite element simulation are compared with results of the experiments. Comparing the results showed that the thickness distribution and punch force have an acceptable agreement in the experiment and numerical methods. Then, using the validated finite element model, the effect of the process parameters including the friction coefficient between the punch and the sheet, the friction coefficient between the blank holder and the sheet, the corner radius of the punch and the die, as well as the gap between the blank holder and the die on the maximum thinning of the steel cups have been investigated. Finally, the obtained results revealed that the corner radius zone of the punch is the critical forming zone since the maximum thinning occurs in this region. Also, by increasing the friction coefficient between the sheet and the punch, the maximum thinning decreases by 10% at the corner radius zone of the punch. In addition, by increasing the friction coefficient between the sheet and the blank holder, the maximum thinning increases by 20%. Likewise, by increasing the corner radius of the punch and the die, the maximum thinning decreases by 25%, and also, by increasing the gap between the die and the blank holder, the maximum thinning decreases by 10%.

One of the most significant and applicable machining processes in surgeries and medical engineering is the bone drilling process. In this process, it is intended to minimize the axial force on the bone tissue during surgery. To reduce force, different methods have been considered; including the use of a variety of lubricants, ultrasonic oscillations, material replacement, tool geometry, and also the use of coated tools. The purpose of this paper is to investigate the effect of a specific type of nano coating on steel tool, and to investigate the effect of effective input parameters on force behavior in orthopedic drilling with medical requirements in mind. In this study, the polymeric material of poly-methyl-meta-carylate (PMMA), which has similar properties to the bone, was selected; and by creating titanium nitride nano coating on the tool, the effect of tool rotational speed, feed rate, and the tool diameter on the drilling process force have been extracted using the design of experiment by the response surface method, modeling and second-order linear regression equation governing the model. The optimum values of each input parameter are also presented in order to achieve the minimum and the best amount of force created during orthopedic drilling. The results show that the creation of titanium nitride nano coating reduces the force by 40 percent. Also, the axial force with the maximum cutting speed, the minimum feed rate, and in the tools with smaller diameters has been significantly reduced.

Tailor welded blanks (TWBs) are increasingly used in the automotive and aerospace industries with the aim of reducing weight. Studying the forming processes of these sheets, examining their formability, as well as controlling factors such as the displacement of the weld line during forming can help to develop their application. The rubber pad forming process is a flexible forming process in which the sheet is deformed due to the pressure of a rigid punch with the help of a rubber cushion. In this paper, the rubber pad forming of tailor welded blank consisting of two welded sections with the same material but different thicknesses were simulated based on the finite element method and using ABAQUS software. The effects of various factors such as friction, thicknesses of the sheets that compose the TWB and the force applied to each section on the maximum displacement of the weld line were investigated through the use of a design of an experimental method. The results illustrated that increasing the thicknesses of the sheets that compose TWB, increasing the blank holding forces applied to each section, and reducing the friction between the TWB and the punch reduce the maximum amount of weld line displacement. In addition, increasing the thickness ratio of tailor welded blank led to an increase in the maximum weld line displacement. The simultaneous increase in the thickness of each section and the blank holding force applied to that section or the opposite section reduced the maximum amount of weld line displacement.

In the present study, the effect of different parameters including of tool rotational speed, feed rate and tool diameter on the damage caused by drilling operations near the drilling hole in the E-glass/epoxy composite laminates with twelve layers of plain woven fabric manufactured using hand lay-up method was investigated and the experimental tests conducted on them. Then, using the Sobol statistical sensitivity analysis method, the effect of the above-mentioned parameters on the induced damage near the drilling hole was investigated. The statistical and experimental results show that for analyzing the damage variable, the simultaneous effect of rotational velocity in conjunction with feed rate of the drilling tool should be taken into account in order to minimize the damage variable, so that in the low velocities, the reduction of feed rate along with the reduction of the rotational speed causes the damaged variable to be minimized, while at the same time, in the high diameters, the simultaneous increase of the two mentioned parameters, minimizes delamination induced damage in laminated composites. The Sobel sensitivity analysis shows that the diameter of the tool, the velocity, and the rotational speed will have the greatest effect on damage variable in laminated composites, respectively.

In the present study, the effect of natural microfibers (cork particles) on the mode I fracture toughness of plain-woven laminated composites has been investigated. For this purpose, double cantilever beam (DCB) specimens manufactured using hand lay-up method with stacking sequence of [0]28. To investigate the effect of cork particles on fracture toughness, samples with two different weight percentages (1% by weight and 3% by weight) were manufactured and the experimental results were compared with one obtained from sample with pure epoxy resin. Experimental results show that as the amount of cork particles increases, the onset of crack growth requires more energy. The amount of improvement in initiation fracture toughness for the DCB sample with 1% and 3% cork weigh has been increased by 67.15% and 71.96%, respectively which is due to the role of the cork in the resin rich area near the crack tip that arrested the delamination growth. Unlike the initiation fracture toughness, the propagation value is reduced by adding cork particles to the resin.   During delamination growth, due to the agglomeration of micro fiber at delamination interface and role of stress concentration of these particles, hence, micro-cork fibers have not been able to increase the propagation fracture toughness and in some cases have slightly reduced the propagation fracture toughness of the delamination. Also, in order to investigate the mechanisms of damage, the fracture surfaces of the samples were scanned using scanning electron microscopy.

Incremental sheet forming is a flexible forming technology in which the sheet metal is gradually formed by the movement of tools in specified path. Due to the progressively localized deformation of the sheet and concentration of the forces on contact area of tool and sheet metal, the formability of the sheet increases compared with other common forming methods. In this study, numerical simulation of the incremental forming of AA3105-St12 two-layer sheet has been performed to calculate forming force and final thicknesses of the layers. The validity of the simulation results is evaluated by comparing them with those obtained from experiments. Numerical models for estimating the vertical force applied on the tool and the final thicknesses of the layers in terms of the process variables have been obtained using artificial neural network. Multi-objective optimization has been conducted to achieve the minimum force and the minimum thickness reduction of layers using obtained numerical models based on genetic algorithm method. Optimum thickness of the two-layer sheet and the thickness ratio the layers in different states of contact of the aluminum or the steel layers with the forming tool have been determined.

One of the types of machining processes on industrial materials that is of great economic importance is the machining of aluminum alloys, which is widely used in most industries such as automotive, aircraft, military, nuclear, etc. If you study carefully, methodically and use advanced analysis methods, you can understand the effect of input parameters on output parameters more accurately and achieve a piece with the desired parameters. In this study, for the first time, the effect of important machining parameters, ie feed velocity, rotational speed and depth of cut on the quality of the machined surface has been modeled using the response surface method, and using a second-order linear regression model, the effect of each One of the input factors is investigated. Also, by using the Sobel sensitivity analysis method, the quality sensitivity of the machined surface to the changes of each of the input factors has been determined and using the Dringer algorithm, the input parameters have been optimized. After reviewing the results, the best input factors include a feed velocity of 200 mm / min, a rotational speed of 1700 rpm and a depth of cut of 1.8 mm. Also, the highest sensitivity of machining surface quality to changes in input parameters is related to the feed velocity with 50% impact, followed by the rotational speed with 42.5% and the lowest is related to the depth of cut with an impact rate of 7.5%.

Delamination is one of the most common modes of damage in laminated composites that can reduce stiffness and load-bearing capacity of the composite structure, which highlights the importance of studying of this phenomenon. For this purpose, in this study, the effect of the interface fiber angles on the mode II fracture toughness of plain woven laminated composites has been investigated. The end notch flexure specimens (ENF) with 24 layers which have 0//0, 0//30 and 30//-30 interface angles manufactured using hand lay-up method and experimental tests conducted on them in accordance with ASTM standard under load II mode loading. Experimental results show that the interface fiber angle has a significant effect on initiation and propagation of delamination toughness the initial and propagation fracture toughness, so that the load bearing capacity of the specimens with the non-zero interface fiber angle was the highest value. Moreover, the initiation and propagation value of fracture toughness for specimens with 0//0 interface fiber angle was less than the corresponding values for other samples with non-zero interface angles. In addition, the fracture process zone (FPZ) length was approximately the same for all samples. Taken images of fracture surfaces using scanning electron microscopy (SEM) show that in addition to the separation of fibers from the resin at delamination, other damage mechanisms Including fiber breakage and highly deformed matrix play a key role in increasing of the fracture toughness of the sample with 0//30 and 30//-30 interface fiber angle.