مجله مهندسی ساخت و تولید ایران
سال ششم شماره 8 (بهمن 1398)

The use of bimetal tubes due to the improvement of its mechanical and physical properties compared to single layer tubes has been considered by various industries. These tubes are produced in a variety of processes, but because of the compressive stress in the extrusion process, this process is more suitable for making rods and tubes which increases the possibility of forming metallurgical bands between the two metals. In this study, the effect of the tube surface shape on the production of bimetal tubes in both copper shell and aluminum core and vice versa has been investigated through extrusion process. In order to achieve the proper mechanical connection and optimum connection quality, the tubes were prepared in three different surface shapes. In this way, grooves between the bimetal tubes were created to form the layers and were filled by the process of extrusion of the empty space of the layers. Finally, extrusion process of bimetal tubes was carried out in two extrusion ratio of 40 and 60 percent. In order to investigate the mechanical properties, the crushing test was performed on the produced bimetal tubes. Microscopic images in both copper shell and aluminum core and vice versa showed that the formation of the groove in each two-layers, causes the proper mixing between the two tube layers. Also, the results of the crushing test showed that the tubes with both grooves had better resistance than the other ones.

The Incremental Sheet metal forming is one of the dieless forming processes. In this process, the ball nose tool runs the predetermined path to form the sheet by applying the local pressure on the sheet. One of the disadvantages of the incremental forming process is the springback phenomenon. In this paper, the effect of parameters on the springback in the two layear sheet Cu / Austenite St produced by the Single Point Incremental Sheet Forming has been investigated. The input parameters of this process include the tool diameter, vertical step, sheet thickness, depth of form, forward velocity, and arrangement of layers of the double layer sheet. Using the finite element simulation via Abaqus software and the Taguchi design of experiments method via Minitab software, the effect of input parameters on springback and forming force has been investigated. Also, the results of the simulation were validated by the empirical test and it was determined that the finite element has an appropriate overlap in extraction of the final results. At the end, the effect of each of the parameters mentioned on the springback and forming force was analyzed. It was determined that the thickness of the sheet had the greatest effect on both springback and forming force.

17-4 ph stainless steel is one of the high strength stainless steel that is widely used in military, oil and gas industries, which has many problems due to its high strength, such as other new and high strength materials face to a lot of problems. Due to the great improvement in material properties especially their strength and hardness in recent years, this has become more evident. The use of controlled heat source along with machining (hot machining) (heat-assisted machining) has been introduced as an efficient way for machining hard-cutting materials. This also significantly improves the process output parameters. Minimum quantity lubrication (MQL) has been used to eliminate other dangers, such as tool wear and high-temperature infiltration. The surface roughness as an important parameter in machining due to its high strength and hardness is one of the challenges of machining this steel. Using this method, surface integrity has improved significantly. In this study, the effect of cutting velocity, feed rate and applied temperature on the surface have been investigated on the surface integrity. The surface roughness has been improved by using a hybrid machining up to 70 to 100%, as well as a uniform surface roughness profile. The hybrid machining has shown that all surface imperfections, such as tricks and microcracks, sticking particles Eliminates at the surface, which can indicate a dramatic improvement in fatigue strength.

3D printers have become widely used in the industry in the last decade so that this technology is sometimes referred to as the fourth industrial revolution. Stereolithography is one of the oldest and, at the same time, the most accurate method used in this industry. Despite numerous studies in various fields involved in this technology, there is a lack of quantitative studies on strengthening the mechanical properties of resins used in this method for application as the final piece and without post-processing, especially in button-up printers (mainly used in desktop printers). In this paper, the physical and mechanical properties of an industrial grade resin were improved via addition of calcium carbonate micro and nanoparticles, with and without surface modification with a mechanical stirrer, at the same time the limitations and effects of adding this filler on other properties such as printability have been studied. It was found that optimal viscosity for use in these printers is ranged between 180 to 300 centipoise. It was also observed that the addition of calcium carbonate particles reduced the curing induced shrinkage and improved the mechanical properties up to 70% with the increase of micro and nanoparticles. In addition, it was observed that the post-curing process is critical to achieving the optimal properties.

Tooth restoration is the most frequent operation in dentistry. During this process, the dentist removes chip from carious or damaged restoration part of tooth by a high speed rotating tool. The forces generated due to tool and tooth layers contact are called cutting forces. In medical works, knowing the magnitude of cutting forces is very important, as many efforts has been done in this area to measure those experimentally. However, a lot of time, money, and energy would be require for experimental tests. The cutting force varies at different tooth layers and the dentist has no feedback on which layer is under milling operation (objective layer). In other words, a dentist detects objective layer based on experiments and physical sense during the operations. Consequently, online detection of objective layer is a challenging issue. The main object of current research is the simulation of force and vibration of dental bur. Vibration signals are a powerful source of information that can be used to detect dental layers. To the best author's knowledge, the specific cutting force coefficients for the two main dental layers are obtained for the first time in current study. In addition, vibration and force in the two main layers of the tooth are compared and analyzed using the Timoshenko beam theory, the milling force equations and the dynamic chip thickness. The results of this effort can be used to improve the quality and efficiency of dental restoration and to give an initial view on producing an intelligent hand-piece.

In this paper, a parametric study on the effect of thickness and stacking sequence of composite layers in a hybrid energy absorber with an aluminum tube wrapped with glass/epoxy composite layers has been experimentally and numerically investigated. The samples were fabricated by vacuum assisted resin transfer molding (VARTM) and tested under a quasi-static crushing load. Specific absorbed energy was used as a criterion for evaluating. In addition, the type and mode of failure mechanisms during the crushing have been thoroughly investigated. The energy absorbers used by the multi-layered shell element is modeled in Ls-Dyna software and the effect of the trigger is considered with continuous reduction of the length of the shell layers relative to each other. The interlayer cracks are modeled according to the force-separation formulation and are used to eliminate the mesh size effects from the adhesion length criterion. Most of the mechanical properties required for modeling were also measured using standard tests. The results show an acceptable correlation between experimental data and numerical modeling. As the thickness increased, the maximum force, mean force, and absorbed energy (EA) increased. Aluminum Crash mode in aluminum tube compared to hybrid tube, it has been transformed from accordion to diamond. In addition, fiber collapse has been associated with the formation of outward bending layers.