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Showing 2 results for Optimum Thickness
Iman Azarbayejani, Nima Jamshidi, Ehsan Hajisadeghian,
Volume 17, Issue 5 (7-2017)
Abstract
One of the very important issues in designing hand prosthesis is to consider their cover or cortex. The purpose of this research is to design a cover to have a similar behavior, as much as possible, to the human natural skin, in power transmission and deformation pattern. A layer made of Lorica®, which has similar properties to natural skin, has been added to the conventional cover which composed of three layers. Using finite element analysis Software, ANSYS V.15, the new four-layered cover has been investigated on three dimensional model of the hand prosthetics with different thickness for the outer layer, and the pattern of deformation and internal stresses in the prosthesis are measured. Optimal thickness of the outermost layer is evaluated due to stress and strain distribution and their transformation to prosthesis metallic core. The relationship between the thickness of this layer and the distribution of stress and deformation of the cover is not linear and direct and the thickness of 1.5mm shows better results among the measured values in this section. In this study, the fourth layer was added to improve the frictional and elastic properties of formerly used prosthetic covers, and its effects on stress and strain distribution in the prosthesis was investigated. It is determined that due to lack of linear correlation between the thickness and stress distribution, the optimal thickness of each layer must be selected based on design limitation like the ability of embedding tactile sensors in future for the minimum thickness.
M. Akbari Paydar, B. Mohammad Kari, M. Maerefat, M. Abravesh,
Volume 19, Issue 6 (6-2019)
Abstract
The optimal insulation thickness is a function of the insulation initial cost and the cost of energy carriers for the internal space heating and cooling due to heat transfer from the wall. In Iran, by allocating subsidies to the energy sector, tariffs for energy carriers are sensibly lower than global prices. In order to determine the insulation optimal thickness, energy carrier tariffs were considered variable according to consumption. Electricity and gas costs were divided into 4 ascending tariffs for low, moderate, high, and very high consumption cases. In addition, the case of energy carriers without subsidies was also examined the 5 . The outer wall consists of a typical hollow with 20cm thickness, insulated with an expanded polystyrene layer, placed the outside. Heat load due to heat transfer from the external wall was calculated by using EnergyPlus simulation software in different geographical directions and different thermal insulation thicknesses in Tehran climate. The optimum insulation thickness was determined based on the total cost over the lifetime of 30 years. According to the results, in the first tariff, which refers to low-cost subscribers, the use of thermal insulation in some geographic directions does not allow the payback period over a lifetime. In other directions, economic savings are low and . For higher tariffs, the optimum insulation thickness increases. In the 2 5 , the thermal insulation thickness from 6 to 18 cm. Also, the calculated payback periods of these configurations are between 6 and 28 years.
