مجله مهندسی ساخت و تولید ایران
سال هشتم شماره 2 (اردیبهشت 1400)

The addition of nanoparticles to the multilayer sheets improves the properties and performance of these laminates. In this research, the deformation process in metal-nanocomposite laminates including polypropylene matrix reinforced with nanoclay and glass fibers as core layer and annealed aluminum 1050A as the skin layer has been investigated using experimental method. In this regard, the effect of different weight percentages of nanoclay relative to the base phase, including 1, 3, 5 and 7 wt% on the values of drawing depth and maximum drawing force in the stamping process has been measured. In order to determine the effects of adding nanoclay particles, the results of deformation of metal/nanocomposite laminates are compared with metal/composite laminate including pure polypropylene reinforced with glass fibers. The results show the ability to perform stamping process of metal/nanocomposite laminates. It was observed that in general, with the addition of different percentages of nanoclay particles, drawing parameters including the maximum drawing force and the drawing depth have changed. Also, the failure mechanisms in all samples are crack growth in layers and delamination of layers. Addition of nanoclay particles has no effect on the principle of failure mechanism in the stamping process of metal/composite laminates and only affects the values of the process parameters.

Uneven expansion and contraction and the resulting plastic deformation are the main source of residual distortion and stress in welded structures. The distribution of residual stresses in a welded joint depends on factors such as inlet heat, arc welding speed, material properties, preheating, part thickness, groove geometry and welding execution schedule. In this research, a head to head joint is investigated by penetration welding with experimental methods and finite element simulation. Residual stresses are measured by the central hole drilling method and by converting the obtained data into residual stresses, the obtained results are used to verify the developed finite element model. In the finite element model, the non-coupled thermal-mechanical mode is used and the method of birth and death of the elements is used in the simulation of filler materials. In the simulation, the phase transformation process is considered and with the help of LTT filler introduced, the residual stresses in the single-pass welding show a 15% reduction and in the two-pass welding show a 17% reduction in the tensile residual stresses. By examining the effect of the arrangement and composition of the passes and the type of welding fillers, it was found that the combination of LTT electrode with 6010 electrode provides more favorable results for residual stresses. Regarding the effect of thickness change in the cross section of the samples, the output of the results of both numerical analysis software does not show significant changes.

Manipulation and movement of micro / nanoparticles has become very important today in the manufacture and production of microscale equipment. The nanomanipulation process is performed in two phases using an atomic force microscope. The first phase involves the target particle before it begins to move, and its purpose is to extract the force and critical time for the micro / nanoparticles to start moving. In the second phase, the motion of the particles from the origin to the destination is examined. Modeling, simulation and investigation of parameters affecting this phase are of great importance. In this paper, the effects of eight parameters including particle radius, probe radius, probe height, cantilever length, cantilever width, particle length, Poisson's ratio and modulus of elasticity on force in the second phase of manipulation are investigated. For this purpose, in this paper, e-Fast statistical sensitivity analysis method has been used. The results show that the probe height with 48%, cantilever width with 19%, modulus of elasticity with 14% and cantilever length with 8%, will have the greatest effect on force changes in the second phase of manipulation. The resulting effects of changes in particle radius, probe radius, probe Poisson's ratio, and the length of the target micro / nanoparticle cylinders can be ignored.

Design and optimization of heterogeneous multifunctional microstructures is of great interest to researchers in the field of material design. In this research, a new method for designing the microstructure of materials in order to achieve the desired properties using the surface approximation method based on multisided patch is presented. In multisided patch, based on boundary curves, the surface connected to these curves is approximated. For this purpose, first the boundary curves used to create the patch are determined and then the surface connecting these curves using the relation of multisided patch is presented. The resulting patch is then used to build a two-phase cell, which will alternately create the structure. Due to the flexibility of boundary curves, it is possible to construct various structures with different volume fractions. These structures are compared and evaluated based on the effective thermal conductivity. The results show that the proposed method is well able to provide structures with the desired ratio for thermal and electrical conductivity as well as diffusion coefficient for two-phase structures.

Thermex is a thermo-mechanical process which is used as an in-line operation after rolling process. By using this process, the yield strength of the rebar reaches to at least 500 MPa. Due to the importance of using high-strength rebars, in the present study, the influences of the process parameters on the rebar’s mechanical properties are investigated using experimental techniques. Considering four effective factors including water flow rate, Thermex pressure, rolling speed and different furnace temperatures, standard tensile tests were performed. The required experiments according to Taguchi method were designed and then the effect of mentioned parameters on the mechanical properties (yield strength, ultimate strength and ductility) of the rebar was studied. Statistical investigation includinf signal to noise (S/N) ratio and analysis of variance (ANOVA) showed that all the mentioned parameters have s significant influence on the mechanical properties. Based on the results, the optimal values of the parameters were determined to achieve optimal conditions of strength and ductility.

AISI630 is a stainless steel that is strengthened by precipitation-hardening mechanism. This steel has high hardness and low thermal conductivity, has made it one of the difficult-to-cut materials. These two factors have its machining is associated with high tool wear and poor workpiece surface quality. In this study, the conventional and hot turning of AISI630 hardened stainless steel have been investigated. To determine the effect of machining parameters on tool wear, a hot turning process up to a preheating temperature of 400°C was performed. Turning was conducted at three feed rates and three levels of cutting speed using PVD-(Ti,Al)N/(Al,Cr)2O3 coated carbide tools. Tool flank wear and wear mechanisms have been studied in different cutting conditions as well as different preheating temperatures using SEM microscope. Experimental results showed that the lowest wear on the free surface of the tool was obtained by hot turning at 300 °C. Hot turning at this temperature reduced the flank wear by 33%. Observation of the worn surface of the tools showed that the tool wear mechanism in hot turning and conventional turning is of the type of abrasive wear and adhesive wear.Moreover, at each cutting speed and feed, with increasing the workpiece initial temperature up to 400°C, the surface roughness decreases. The optimal values of temperature, cutting speed and feed rate were obtained using Minitab software with the aim of reducing tool wear and surface roughness.