نشریه مهندسی مکانیک و ارتعاشات
سال هفتم شماره 2 (پیاپی 23، تابستان 1395)

One of the biggest problems of artisans , is notching the high speed steel roller is due to the inability to do this work, become high speed steel roller bearings are disposable. When the roller is placed on the production line, because of the retained austenite make it very hard. High speed roller used in this study is barely above 70 Shc. To notch this rollers, diamond tools, ceramic and CBN were tested. Our goal is to obtain the optimum machining parameters that it requires a high number of tests that are practically impossible. So in order to achieve optimal machining parameters with the lowest test, RSM method in Minitab software was used. After investigation we can say that diamond tools have not the ability to influence the level of high speed roller. Ceramic tools are able to machining HSS rollers, but in terms of time and cost, it is not good. CBN tools performed well in all tests and succeeded with the best cutting speed 25 m/min, 0.05 mm feed and 0.05 mm depth of cut at the time of 1080 seconds, in notching one caliber.

In this study, numerical investigation of energy absorption of cylindrical grooved tubes under dynamic axial load by LS DYNA was considered. In order to achieve axisymmetric collapse mode inner and outer grooves were created around the surface of cylindrical tubes. The purpose of this study was consideration of the effects of number of grooves on energy absorption and crush force efficiency. The results indicate that with the increase in number of grooves the collapse modes would not change. In addition to this, with the increase in number of grooves maximum crush load and collapse modes decrease but the force-displacement curves would be smoother. The results of this study can be used in automobile, railway and aerospace industries.

Due to the limited fresh water sources and reduce the increasing these resource In recent years a lot of attention to the use of solar desalination for water desalination is available In this paper, a desalination using collector, heat pipe, solar panels and natural ventilation design and built. To increase the efficiency of desalination has used various means Such as pre-heat the water in the collector by heat pipes and water circulation pump and the use of natural ventilation to reduce the pressure of the fluid level To lower the temperature of the water evaporates As well as the use of natural ventilation for cooling water in the steam distillation available on this route After designing and constructing this system, all data were recorded on weather conditions of Semnan And at the end performance of the device in different scenarios were compared.

Use of energy is increasing due to creating a comfortable environment in the buildings. So investigating all approaches related to using energy or saving should be considered before implementing each plan. One of the methods for measuring the rate of energy is use of modeling plans for using of energy. In this research we could review energy plus in different buildings. In these buildings , we have used of the result as monthly or annually due to saving cost. Also we could combine these approaches as energy reduction methods or advanced air conditioning systems and renewable energy. These results show energy performance based on software plans which should be considered in accordance with ASHRAE standard.

One of the common methods of structural damage detections in structures is investigation of changes in modal parameters before and after damage. These methods which are mostly based on optimization techniques use an objective function based on natural frequencies and mode shapes. Success in detection of location and severity of the damage in these methods is severely a function of sensitivity of the objective function to the damage. As the objective function itself is function of natural frequencies or mode shapes or both of them, it is necessary that the sensitivity of modal parameters to damage location and severity is investigated. To this end, a cantilever beam is simulated numerically in this paper. Changing the location and severity of the damage, the effect of them on natural frequencies and mode shapes is studied. The results show that by increasing damage severity, natural frequencies decrease. On the other hand, moving the crack from the fix end to the free end of the cantilever beam, changes in the natural frequencies does not obey a specific pattern and for a crack of constant severity, decrement of natural frequencies from intact beam depends on the location of crack on the beam. Also it is observed that as the cracks approaches to the fix end, decrement of natural frequencies increased. The results show that the sensitivity of mode shapes to crack is low in beam. Therefore it is recommended to use natural frequencies or both natural frequencies and mode shapes together in objective functions.

In recent years, due to population growth and the reduction of water resources, the human has forced to sweeten brackish water. While this work takes energy and high costs. Thus, the scientists studied a lot about solar desalination and the factors influencing them. In this study, we tried to have a review on the literature of numerical simulation of solar desalination systems with Assumptions: laminar natural convection, heat and mass transfer using finite volume method which presented by researchers who have been working in this field. This research is prepared for researchers who interested in this subject or those who intend to get acquainted of solar desalination systems, to have an appropriate reference for specialized study.

In this article, using a central composite design response surface methodology is that design of the optimal propeller geometry for khazar dredger will be discussed. B_Wageningen standard series is designed propeller-type licenses. To verify the performance and Check non-occurrence of cavitation ,the propeller designed using Computational Fluid Dynamics, numerical modeling and compare with B_Wageningen series. The results show the ability of response surface methodology in finding the optimal geometry propeller. Numerical solution of fluid flow, to prove non-occurrence of cavitation in the propeller designed for kazar dredger.