Neural networks can be used in various subjects, such as the discovery of relationships, identification, system modelling, optimization and nonlinear pattern recognition. One of the interesting applications of this algorithm is heat transfer estimation between contacting surfaces. In the current investigation, a comparison study is done for temperature transfer function estimation between contacting surfaces using Group Method of Data Handling (GMDH) neural networks and ANFIS (Adaptive Neuro Fuzzy Inference System) algorithm. Different algorithms are trained and tested by means of input–output data set taken from the experimental study and the inverse solution using the Conjugate Gradient Method (CGM) with the adjoint problem. Eventually, the optimal model has been chosen based on the common error criteria of root mean square error. According to the obtained results among different models, ANFIS with gaussmf membership function has the best algorithm for identification of TCC between two contacting surfaces with 0.1283 error. Also, the inverse method has the lowest error for thermal contact conductance estimation between fixed contacting surfaces with root mean square error of 0.211. تفاصيل المقالة

In this research, the effect of CaCO3 nanoparticles was experimentally investigated on vibrational damping behavior and static mechanical properties of polypropylene (PP). Hammer tests along with modal analysis were carried out to evaluate the forced vibration behavior of composite plates under one edge clamped support conditions while tensile tests were performed to assess the static mechanical properties. A comparison of the results showed an increment in the static mechanical properties of nanocomposites by increasing the nanoparticles content in the PP matrix. Composite with 10 wt.% nanoparticles showed the highest rise in Young’s modulus (39.71 %) compared to pure PP. An increment in Young’s modulus and stiffness led to an increasing trend in the damped natural frequencies of the nanocomposites so that the composite with 10 wt. % nanoparticles showed the highest damped natural frequency augmentation (23.6 %, 36.78 %, and 252.62 %) compared to pure PP in the first three modes. In addition, an enhancement in the nanoparticles content of the PP matrix led to an increasing trend in damping ratios of the nanocomposites such that the composite with 10 wt. % nanoparticles in the first mode (28.99 %) and composite with 7.5 wt. % nanoparticles in the second and third modes (418.66 % and 9.93 %) showed the highest rise in damping ratio compared to pure PP. Increasing damping ratios can be due to the proper dispersion of nanoparticles in the matrix and consequently energy dissipation of the stick-slip mechanism between the matrix and nanoparticles. Moreover, high nanoparticle contents had destructive effects on both the static and dynamic behavior of the composites. تفاصيل المقالة

In this study, the size-dependent free vibration analysis of a geometrically imperfect single-layer graphene sheet (SLGS) is studied by an isogeometric approach along with the quasi-3D shear and normal deformation theory. Initial geometric imperfections alter the natural frequencies of the graphene sheets that may exist inherently or purposely created by researchers. The initial curvature is modelled by an analytical function in the governing Equations of the plate. A 4-variable quasi-3D theory with a seventh-order distribution function is used to include both shear deformation and thickness stretching influences. A weak form of a nonlocal plate for free vibration analysis is derived that requires the first-order continuity of the displacement fields. Inherent high-order continuity of non-uniform rational B-spline (NURBS) basis functions in isogeometric analysis can meet this condition. A comparison between the present study and other published works reveals the efficiency and accuracy of the proposed method in imperfect SLGS. The results of the present study show a significant effect of initial geometric imperfection on the natural frequency of single-layer graphene sheets. تفاصيل المقالة

Present study considered deformation of a solid plate as result of external pressure wave. So, a detailed investigation of underwater explosions (UNDEX) and their effects on solid structures is the main objective of this paper. To accomplish this, numerical methods have been used to analyze the UNDEX structure qualitatively and quantitatively. Afterward, perpendicular blades are used to reinforce a marine structure. Governing equations in solid and fluid media were discretized using finite element and finite volume schemes, respectively. As for fluid-structure interaction (FSI), two-way coupling methods were used to map the results of fluid and solid media. The numerical method's validity can be confirmed by comparing numerical results with the analytical solution. Pressure-time diagrams follow the analytical solution reasonably well, indicating that the numerical method is valid. Additionally, results indicate that a pressure wave with amplitude of 20 MPa is generated by the detonation of explosive charge under water. Furthermore, reinforcement blades appear to reduce deformation in structures by increasing their resistance to explosive charges. These blades increase the strength of the plate where it could tolerate the Von-Mises stress up to 750 MPa. تفاصيل المقالة

این مقاله به شناسایی مودال ساختار ماشینهای دوار با استفاده از روش تخمین طی دو آزمایش می‌پردازد. آزمایش1) شناسایی یک سیستم کامل بدون نیاز به اندازه گیری یک ردیف از ماتریس FRF درحالیکه یک ستون ماتریس مشخص باشد، با استفاده از یک مدل شبیه سازی روتور با چهار درجه آزادی. آزمایش2) شناسایی پارامترهای موجود در یک سیستم صنعتی که در آزمایش1 نمایان نشده است. سیستم آزمایشی یک سیستم ارتعاشی پیوسته بوده بنابراین شناسایی آن نیازمند استفاده از روشی است که آنرا به مانند یک سیستم گسسته توصیف کند و اغتشاش در اندازه گیریها نشان داده شده تا بتوان سیستم پیوسته را با یک مدل کوتاه در محدوده ی فرکانسی معین بیان کرد، آنگاه امکان تخمین پارامترهای مودال آن وجود دارد. همچنین نشان داده شد که دقتی که با آن بردارهای ویژه چپ تعیین می شوند می‌تواند تحت تاثیر دقتی باشد که با آن ثابت های مودال مربوط به همان مودها، از داده های اندازه گیری شده، تعیین می‌گردند. بنابراین می‌توان این نتیجه را گرفت که بردارهای ویژه چپ خود تحت تاثیر حضور اغتشاش موجود در اندازه گیری قرار خواهند گرفت. اثرات وجود اغتشاش برای درجات آزادی با دامنه های پاسخ کوچک برای نواحی فرکانسی در مجاورت مودهای نزدیک به هم، برجسته تر خواهد بود. همچنین علیرغم وجود ارتعاش، بردارهای ویژه چپ پیش بینی شده برای مشخص کردن یک ردیف از ماتریسFRF با استفاده از اندازه گیری یکی از ستون های آن مناسب است. تفاصيل المقالة

This is an adoptive design of ant colony system and has been generalised to AGV transport system, predetermined targets replacement results has been evaluated simulating four AGV in Mat lab by Particle Algorithm and fuzzification and simulating the operative environment with regard to constant velocity and different results has been compared to each other by changing robots’ location and replacement of obstacles in the environment and using laser guidance system. Optimising considered sensor’s arrays led to more efficient and faster feedback. Regarding improvements mentioned, AGVs passing the obstacles with ease, choosing the shortest distance to the target and are flexible enough in case of one of the AGVs failure. 1- The AGV that has worked less than the others (from distance perspective), 2- the AGV which has been the closest to the failed AGV and 3- the AGV that has replaced fewer load. in fact, the system was able to operate more efficiently than when using an AGV. تفاصيل المقالة

Industrial robots need instrument or parts transport to do which requires coordinate to show the robot’s instrument, parts and body. When investigating the robot location, we are usually interested in measuring its location relative to a reference coordinate system. In this system it is attempted to make the assemble direction smaller by designing the sensor board and making use of an instrument for self-adaptation of the gripper to the gripper working environment pallet. In addition, in order to eliminate the robot errors and parts transport system errors to the robot, there are different models employed using different sensors. In this research, the LASER sensors are used based on their applicability and cost. In present article, the V-REP software is used in order to simulate the mechanism. Considering the simulation results it can be stated that the RCC is an optimal model. Based on explained models in different sections of the article, this model can eliminate many of the errors in assemble by an optimal structure and reliable restriction and considering the geometrical uncertainty; for example, nail and hole, unreliability of friction coefficient etc. in addition, this model helps the fragile plastic parts assemble. تفاصيل المقالة

The researcher measured the least number of frequency response functions required for the identification of modal parameters, in order to simplify the identification of modal properties of such systems. In this work, the orbital machines are supposed to be a combination of orbital and non-orbital components. Structural Approach specified the identification of dynamic properties only to those phrases that contain responses to a driving force. It has been revealed that the identification of dynamic properties distinguishes the orbital and non-orbital components of the structures and as a result, non-symmetric sections of the space coordinate matrixes become obvious. The application of the above approach was examined on two different structures. The first examination was on a computer-simulated rotor model with four degrees of freedom. In this case, the theoretical properties of this approach were evaluated, while the noise factor was disregarded. The second examination was done on a true machine, whereby the probable problems of the implementation of the suggested approach were clarified. The complete modal identification of an orbital system takes place without the need to measure a complete row of FRF matrixes. The number of the elements to be measured in an FRF matrix depends on the number of degrees of freedom of the system and on the non-symmetric sections of the stuffiness and damping matrixes. The number of elements of the left specific axis that should be measured directly from the evaluated data depends on the matrix sub-ranks, which is composed of non-symmetric sections of space-featured matrixes. تفاصيل المقالة