ملخص البحث :

Free vibration analysis of the isotropic skew plate with three supporting conditions (CCCC, CFCFand FCFC) were studied. ANSYS APDL version 17.2. with two-dimensional model (SHELL281 element) andthree-dimensional model (SOLID186 element) were adopted. The effects of width-thickness ratio (a/t), aspectratio (a/b), mode number, skew angle and supporting conditions on the first five natural frequencies wereinvestigated. The results showed that the non-dimensional fundamental frequency coefficients (Kf) increaseswhen the skew angle at any aspect ratio (a/b) , mode number and supporting type. Also, the effect of skew angleappears sharply when the skew edges are clamped (i.e. CCCC and CFCF) while in when the skew edge is free ,the effect of skew angle is not appear . Finally, the comparison between the two elements (SHELL281 andSOLID186) shows that there is a good agreement between them when the skew angle is smaller than 60o and themode number is smaller than fourth mode.

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This study is presented of two models were built to simulate the skew composite plates and these models are SHELL281 and SOLID186 element. Three types of laminates arrangement were used to study the effect of skew angle, fiber orientation and length-to-width ratio on the first five natural frequencies of the clamped composite plates. The skew angle was changed from (0°) to (75°) with (15°) steps while the fiber orientation was changed from (0°) to (90°) with (15°) steps and the length-to-width ratio was (0.5, 1, 1.25, 1.5 and 2). The results showed that the first five frequency parameters increase for three layouts when the skew angle increases at constant fiber orientation and constant length-to-width ratio. Also, the fiber orientation has a slight effect on the first five frequency parameters in (0/β/0) layout. The effect of length-to-width ratio on the first five frequency parameters depends on the skew angle (smaller or larger than (60o)), fiber orientation and the laminates layout. Finally, the values of the first five frequency parameters of (β/0/β) and (β/β/β) layouts are close to each other.

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Abstract. A numerical simulation is performed to study the effect of two types vortex generators (VGs) on heat transfer coefficient and pressure drop in duct. There are two types of V.G., one is concave V.G. and the other is rectangular. The aim of the study is observe effects of the shape and arrangement this V.Gs in channel to the increase of heat transfer with Reynolds number range from (300 to 1500). Both types of V.Gs were placed in 45o angle of attack, in an in line and staggered position. The results shows that the staggered position gives the high heat transfer coefficient enhancement and concave is better than rectangular V.Gs by 7-10%

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Helical springs play a pivotal role in various engineering applications, ensuring controlled motion and stability in mechanical systems. This study presents a comprehensive analysis of solid and hollow compression helical springs using advanced numerical simulations conducted in ANSYS Software. The investigation encompasses geometric modeling, material characterization, finite element analysis (FEA) setup, parameter monitoring, and result analysis. Detailed 3D models of both solid and hollow springs are developed to accurately represent their geometric complexities. Material properties, including Young's Modulus and Poisson's Ratio, are precisely characterized. ANSYS Software is employed for FEA due to its capability to handle intricate geometry and loading conditions. Boundary conditions are defined to replicate real-world scenarios, with systematic variation of loads applied to cover a range of practical forces. Critical parameters, including buckling load, deflection behavior, and stress distribution, are closely monitored and analysed. The comparative study between solid and hollow springs reveals significant insights into their mechanical behavior. This research integrates prior literature to provide a holistic understanding of spring performance. By conducting numerical analysis, the findings provide a distinct perspective on the anticipation of failure and understanding the characteristics of materials employed in springs when subjected to static and dynamic loads. The results of this study provide engineers and designers with valuable insights for selecting the most suitable compression helical spring for specific applications. Practical recommendations based on the findings offer guidance for optimizing mechanical systems. This research contributes to the advancement of engineering knowledge and underscores the importance of ANSYS-based simulations in spring design and analysis.