Nowadays, polymeric foams have attracted special attention in scientific and industrial societies due to their unique properties such as high strength to weight ratio, excellent thermal-insulation, sound-insulation, and good mechanical properties. One of the main goals of the studies of polymeric foams is to increase the cell density and aligning with it, is to reduce the cell size of these materials. Researchers have shown that the extraordinary properties of polymeric foams such as superior thermal-insulation can be achieved by increasing the cell density/ decreasing the cell size. In this regard, firstly the most important processes for the production of polymeric foams (batch, extrusion, and injection molding processes) were studied in the present research. Then, cell nucleation stage as the most important process for achieving high cell density/ low cell size is studied in details. In the following, the most important researches in the field of polymeric foams were introduced in which, the highest cell densities/ lowest cell sizes were achieved. The investigations show that the most significant results (highest cell densities/ lowest cell sizes) are belonging to the batch process. Also, the use of nucleating agents, increasing the solubility of blowing agent into the polymer, and the use of nanoparticles are the most efficient solutions in order to achieve microcellular and nanocellular structures.

Nowadays, due to mechanical, physical, thermal, electrical, and vibration properties, metallic multilayer rods have specific applications in industry. Bimetallic rods made from layers with two different materials have been considered by manufacturers in recent years for simultaneous use of the properties of several materials in a single work piece, such as high strength, corrosion resistance, wear resistance, and improved stress distribution. In this research, the tensile test was performed on steel wire and stainless steel pipes to obtain the stress-strain curve of each sample. Wire drawing dies have been used to make bimetallic rods. Then, two samples of the bimetallic rod were made by swaging with the reduction ratio of 9.75% and 21%. Samples were cut by wire cut machine after production. For interlayer strength testing, dies were designed based on the punch method. The test results were used to calibrate the parameters of the adhesive element in the software. The simulation was performed, using Ansys 17.0 software. Then the results were compared with experimental results. The effects of reduction ratio, internal diameter, sample length, and clad thickness were investigated. The experimental results were in good agreement with the simulation results. By increasing the reduction ratio, the force required for the separation of the two layers has increased, resulting in increased bonding strength between layers.

In this study, the method of releasing strains for calculating residual stresses in hole drilling process has been considered. For this purpose, a thick piece of cylindrical aluminum of 5 mm thickness has been investigated. Stepwise and high-speed drilling was performed in several successive steps, and released strains were recorded by a rosette strain gauge. The distribution of released strains in 3 forms of functions in the depth of the hole has been studied to transform strains to stresses, a linear function, a second-order function, and a third-order function. For each case, the longitudinal, tangential, shear stresses, principle stresses, and principle angles in the thickness of the piece were calculated and the results of the convergence analysis by the Tikhonov regularization were evaluated. In the end, the results are evaluated and compared for 3 modes. The results of the comparison of stresses and the degree of curves have shown that the third-order curve is more suitable for evaluation of released strains and using to transform them to residual stresses, and the magnitude of the error in the second-order curve is greater than the two other modes.

Heat transfer of polymeric foams is consisting of three different mechanisms including heat transfer through a solid phase, gas phase, and thermal radiation. Thermal insulation properties of polymeric foams are affected by different structural properties. Also, these structural properties have a different influence on the different heat transfer’s mechanisms. Therefore, it is necessary to use theoretical models. Several theoretical models have been presented so far, meanwhile, providing theoretical models that can estimate the thermal conductivity using the easiest measurable properties along with sufficient accuracy and reliability can be very helpful. In this regard in the present study, a theoretical model based on cell size and foam density is developed in order to predict the thermal properties of polymeric foams. It was concluded that the error of the developed theoretical model is lower than 8% in comparison to the experimental results. In the following, the effect of most important structural parameters i.e. foam density and cell size on the thermal conductivity is investigated. Based on the results, determining the optimum density is necessary to achieve the lowest thermal conductivity. Also, the gas thermal conduction has the most contribution to the overall thermal conductivity and achieving the nanometer cell sizes can be useful in order to decrease it.