مجله مهندسی مکانیک
پیاپی 151 (مهر و آبان 1402)

In this paper, a numerical study on the collapse and energy absorption of carbon/epoxy composite absorbers with different geometrical cross sections, including circle, square and octagonal in the fiber orientations of zero, 30, 45, 60 and 90 degrees is conducted using Abaqus software. In order to validate and ensure the accuracy of the simulation, the results of these simulations are compared with the experimental results of previous researchers. The results reveal that the non-zero degree orientation of the fibers causes twisting, changes in the stress distribution and loss of geometric stability. Also, the results show that the circular section has the highest energy absorption capacity among the introduced sections. The results show that the fiber orientation is directly effective in the collapse of composite shells. The behavior of the absorber in the zero degree orientation of fibers is similar to the behavior of ductile materials (along with crushing and wrinkling). In the 90 degree orientation of fibers, the fibers are aligned with the axis of the composite shell and the collapse becomes more similar to the behavior of brittle materials (crushing and fracture).

Nowadays, due to the limitation of natural resources and the increase in energy demand, the use of modern cycles including the supercritical carbon dioxide cycle with high thermodynamic and economic efficiency is considered for energy production. In this research, the thermal design of the recuperator in two modes of recuperator cycle and split cycle has been done using relationships and hand calculations and compared with the results of HTRI and EDR softwares. In these designs, both large size tubes and microtubes are used. The results show that the number of the tubes of the heat exchanger in recuperator cycle with large size tubes is equal to 1840 with a diameter of 19.05 mm, while the same design with a microtube will be equal to 21815 with a diameter of 6.35 mm. In the split cycle, where the flow of cold fluid in the tube side is 35% of the recuperator cycle, the number of large size tubes is equal to 3267 and the design with microtubes is equal to 11679. Therefore, the design of new heat exchangers with microtubes is presented which is not a usual design procedure in the industry, but for the supercritical carbon dioxide fluid, it is under study and investigation by researchers.

In this research, computational fluid dynamics (CFD) was used to undertake a numerical simulation of the influence of several design factors on the hydrodynamic performance of a pump-mixer, including the baffle and impeller clearance. For single phase flow simulation, the k-ε turbulence model as well as the multiple reference frame (MRF) were used. Results showed that the tangential flow in pump-mixer without baffles was dominant and led to poor mixing. The flow pattern in pump-mixer with baffles changed to axial flow that reduced the hydraulic head and increased the power consumption. The effects of three different clearances on the pump-mixer macroscopic parameters were also studied. The results indicated that the axial flow pattern changed to radial flow by increasing the clearance, which led to an increase in power consumption and a decrease in head. Power consumption at the clearance 135 and 200 mm, compared to the initial clearance of 82.5 mm, increased by 157 and 214% and the head also decreased by 47 and 58%, respectively.

In this article, a T-shaped microchannel with mixing periods ranging from 1 to 25 units and variations in the geometry of each mixing period in a two-dimensional and steady state has been numerically evaluated using the COMSOL software. An MQ parameter has been used to determine the quality of mixing at the channel outlet as well as the pressure drop. Additionally, the influence of the number of mixing periods and obstacles present in the mixing unit on the mixing quality has been investigated. Initially, six geometric models were designed for one mixing period, and after obtaining the numerical results, the best geometry was selected for fur ther calculations and work. The numerical results obtained for geometry "c" indicate that using 1, 5, 10, 15, 20, and 25 mixing units in the channel results in mixing qualities of 30%, 46%, 73%, 85%, 92%, and 98% respectively for blood fluid, which can be considered suitable for use in chemical systems.

The topic of this research is cargo transportation and the challenge that has been addressed is how to do it in the production lines of automobile factories. Cargo transportation is the movement of a shipment from the parts warehouse to the production line and vice versa. These lines are continuously engaged in production and every time the line stops, it causes heavy losses. Therefore, intelligent cargo transportation is required. The purpose and nature of this research is applied and qualitative-descriptive. It used a survey method to collect data and, used the verbal-visual questionnaire and the Delphi group in the field research. By applying the so-called Design up, which is based on interaction and user-centered design, and the use of Analytical Hierarchy Process, the design method has been formed. The automated guided vehicle (AGV) scope, which includes the needs as well as subject view, has been realized in the form of library research. Field research has been followed by the method of users and product clinics, and in the design stage, the AGV and its brand logo have been designed via battlefield designs. This achievement is obtained under the name of DanRo. In comparison to similar products, it has advantages such as lower maintenance costs, faster training of users, the ability to work instead of the production line conveyor belt and its removal, the ability to rotate 360 degrees in place and move in perpendicular directions, and increases the flexibility and speed of production.

In this paper, a multi-objective differential evolution with fuzzified mutation factor using the combination of non-dominated sorting and crowding distance criterion (MODE-FM) is used for Pareto optimization (in bi- and 7-objectve spaces) of a 5-degree of freedom active and linear suspension vehicle model considering the seven conflicting functions simultaneously, under stationary random road profile. The significant conflicting objective functions that have been utilized here for assessing the applicability of the aforesaid suspension system reaching the compromise between ride comfort and road holding capability are, namely, vertical seat acceleration, vertical forward tire velocity, vertical rear tire velocity, relative displacement between sprung mass and forward tire, relative displacement between sprung mass and rear tire, forward control and rear control force. Further, the design variables include the coefficients of springs and dampers of suspension system and seat and coefficients of control force along with the seat position in relation to the center of mass of sprung mass in which the suggested design can be achieved. It should be noted that the road roughness used here is in class C based on the ISO 8608 standard. Comparison of the attained results of this work with those in the literature has proved the superiority of the results of this work.