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This paper presents free vibration analysis of partially perforated circular plates with a triangular hole pattern and clamped boundary condition. To reflect the effect of circular holes on natural frequencies of the perforated plate, the effective material properties based on the finite element analysis are introduced. The circular plates are divi...
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... partially perforated circular plate with a clamped edge has a radius R and equivalent radius of perforation region a, hole diameter d, pitch p, and thickness h as illustrated in Fig. 1. The plate is divided into two regions; central perforated region and annular solid region. The transverse displacement of a perforated circular plate can be written using a combination of spatial modal functions (W) and a harmonic time function exp (i ) t . ...
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Citations
... The idea of incorporating perforations into structural components is not a new concept. The impact of perforations on the natural frequencies of plates, with different shapes and distributions, has been discussed by Cunningham et al. (2020), Abdelrahman et al. (2019), Ghonasgi et al. (2016), Jeong and Jhung (2017). ...
There is a burgeoning demand for minimizing the mass of satellites because of its direct impact on reducing launch-to-orbit cost. This must be done without compromising the structure's efficiency. The present paper introduces a relatively low-cost and easily implementable approach for optimizing structural mass to a maximum natural frequency. The natural frequencies of the satellite are of utmost pertinence to the application requirements, as the sensitive electronic instrumentation and onboard computers should not be affected by the vibrations of the satellite structure. This methodology is applied to a realistic model of Al-Azhar University micro-satellite in partnership with the Egyptian Space Agency. The procedure used in structural design can be summarized in two steps. The first step is to select the most favorable primary structural configuration among several different candidate variants. The nominated variant is selected as the one scoring maximum relative dynamic stiffness. The second step is to use perforation patterns reduce the overall mass of structural elements in the selected variant without changing the weight. The results of the presented procedure demonstrate that the mass reduction percentage was found to be 39% when compared to the unperforated configuration that had the same plate thickness. The findings of this study challenge the commonly accepted notion that isogrid perforations are the most effective means of achieving the goal of reducing mass while maintaining stiffness. Rather, the study highlights the potential benefits of exploring a wider range of perforation unit cells during the design process. The study revealed that rectangular perforation patterns had the lowest efficiency in terms of modal stiffness, while triangular patterns resulted in the highest efficiency. These results suggest that there may be significant gains to be made by considering a broader range of perforation shapes and configurations in the design of lightweight structures.
... The idea of incorporating perforations into structural components is not a new concept. The impact of perforations on the natural frequencies of plates, with different shapes and distributions, has been discussed by Cunningham et al. (2020), Abdelrahman et al. (2019), Ghonasgi et al. (2016), Jeong and Jhung (2017). ...
... Отже, на етапі розробки необхідно дослідити динамічні процеси та властивості тонкостінних зварних конструкції, у першу чергу, -ВЧК та ВФК [33,34]. Задля цього залучаються різні моделі ті методи [35][36][37][38][39][40][41][42][43][44][45][46]. ...
At the stage of design research of armored bodies of lightly armored vehicles it is extremely important to determine the range of their natural frequencies and natural forms of oscillation. For this purpose, the finite element method is usually used. It is necessary to substantiate the parameters of the finite element model, which provide an acceptable level of accuracy of numerical modeling of dynamic properties of this type of structures. For this purpose, data from parallel numerical and experimental studies of the mock-up of the armored hull of the armored personnel carrier are used. The mock-up of the upper projection of the armored hull is made in the appropriate scale. The material is sheet steel. This mock-up is subjected to dynamic excitation on a vibrating table. Resonant excitation frequencies are recorded, as well as the natural vibration forms. Shock-pulse excitation of the armored hull’s mock-up was also performed. The response to this excitation is recorded using accelerometers. Then, the spectrum of natural vibration frequencies is determined from these oscillograms. In parallel, numerical modeling of natural frequencies and natural vibration forms of the armored hull’s mock-up is carried out. After that, the results of numerical and experimental studies are compared. By varying the parameters of the finite element model, a satisfactory correspondence between the results of numerical calculations and experimental measurements is achieved. In particular, the following are determined: the acceptable type of used finite elements; the number of finite elements required to satisfy the accuracy of numerical modeling of the dynamic properties of similar structures; zones of the recommended thickening-rarefaction of a grid of finite elements, etc. According to the research results, the parameters of finite-element models have been established, which can be used to study the dynamic processes and properties of full-scale armored hulls of lightly armored vehicles. Keywords: lightly armored vehicle, mock-up, natural frequency, spectrum of natural vibration frequencies
... The concept of implementing perforations on metallic structural components has been utilized before in engineering applications. Works by Cunningham et al. [15], Abdelrahman et al. [16], Ghonasgi et al. [17], Jeong and Jhung [18], and others describe the effect of the presence of perforations on the natural frequencies of plates. In the civil engineering field, Formisano et al. [19] implemented perforations in shear panels, and found that choosing suitable patterns allowed structures to experience relatively large shear deflections without reducing their stiffness and ductility to large degrees. ...
Satellite systems undergo several operational phases during their service life, including the assembly phase, ground transportation phase, the launch phase, and the in-orbit operation phase. Among these phases, the one that imposes the highest level of loadings on the satellite is the launch phase. This phase involves a number of highly dynamic loads, all being imposed upon the satellite simultaneously. Investigation of the responses of the structural subsystem of a satellite to these loadings, namely its maximum deformations and maximum von Mises stresses, is critical if a reasonably high level of confidence is to be achieved. This confidence is in terms of ensuring that no material yielding develops in the structure as a result of the imposed launch loadings. In an earlier work, the structural subsystem of a conceptual microsatellite was designed, employing aluminum 6061 alloy as its material. It was then modified through introducing sets of parametrically defined geometric patterns as perforation patterns to remove material, towards reducing the structure’s total mass, as an alternative to employing composite materials. That effort led to a mass reduction percentage of 23.15%. The current work’s research effort focused on computing the responses of the perforated structure to three of the dynamic launch loads that are imposed upon satellites while being launched, namely quasi-static, random, and shock loads. These responses were then compared to those of the baseline, unperforated, version of the same structure. The values of these loads were taken from the relevant sources, with the values being nominal, and represented the loads that any satellite must qualify for before it can be accepted by the provider for inclusion in a launcher. After imposing these load values upon the structural design it was found that the structural responses indicated that the structure would successfully survive these loads without developing stresses that would lead to material yielding failure. This was deduced from computing the yield margins of safety for each loading case, and all margin values were positive, indicating that the structure, at its current development stage, did have sufficient capacity to withstand these loads without material yielding. This reinforced the conclusion of the earlier work, namely that the perforation concept did have sufficient merit to be further developed towards being implemented in future satellite designs.
... The concept of introducing perforations into structural components is not entirely new. The effect of perforations, in various perforation shapes and distributions, on the natural frequencies of plates has been described in works by Cunningham et al. [22], Abdelrahman et al. [23], Ghonasgi et al. [24], Jeong and Jhung [25], and others, where it was found in all these works that the presence of perforations reduced the overall stiffness of the plates and which hence reduced their natural frequencies. Almitani et al. [26] studied the effect of the presence of perforations in multilayered beams on their natural frequencies and found a similar effect, namely that the number of perforations had an inversely proportional effect on the natural frequencies due to the reduction of stiffness. ...
Mass reduction is a primary design goal pursued in satellite structural design, since the launch cost is proportional to their total mass. The most common mass reduction method currently employed is to introduce honeycomb structures, with space qualified composite materials as facing materials, into the structural design, especially for satellites with larger masses. However, efficient implementation of these materials requires significant expertise in their design, analysis, and fabrication processes; moreover, the material procurement costs are high, therefore increasing the overall program costs. Thus, the current work proposes a low-cost alternative approach through the design and implementation of geometrically-shaped, parametrically-defined metal perforation patterns, fabricated by standard processes. These patterns included four geometric shapes (diamonds, hexagons, squares, and triangles) implemented onto several components of a structural design for a conceptual satellite, with a parametric design space defined by two scale factors and also two aspect ratio variations. The change in the structure’s fundamental natural frequency, as a result of implementing each pattern shape and parameter variation, was the selection criterion, due to its importance during the launcher selection process. The best pattern from among the four alternatives was then selected, after having validated the computational methodology through implementing experimental modal analysis on a scaled down physical model of a primary load-bearing component of the structural design. From the findings, a significant mass reduction percentage of 23.15%, utilizing the proposed perforation concept, was achieved in the final parametric design iteration relative to the baseline unperforated case while maintaining the same fundamental frequency. Dynamic loading analysis was also conducted, utilizing both the baseline unperforated and the finalized perforated designs, to check its capability to withstand realistic launch loads through applying quasi-static loads. The findings show that the final perforated design outperformed the baseline unperforated design with respect to the maximum displacements, maximum Von Mises stresses, and also the computed margin of safety. With these encouraging outcomes, the perforated design concept proved that it could provide an opportunity to develop low-cost satellite structural designs with reduced mass.
... Penulis juga telah melanjutkan penelitian ini dengan cara mengkombinasikan lubang makro dan mikro dalam satu panel yang sama, dimana hasil pergeseran nilai frekuensi natural yang lebih efektif telah didapatkan [6]. Selain dari penelitian di atas, jika dilihat dari segi penggunaan praktikal, panel berlubang juga didapati mampu berfungsi baik sebagai salah satu struktur di bidang teknologi nuklir [7]. ...
... Fenomena ini dapat dilihat dari penurunan nilai frekensi yang lebih besar jika dibandingkan dengan penurunan pada pembahasan pengaruh diameter lubang. Penelitian sebelumnya[6,7] juga memberikan hasil yang sama dan sepadan. Walaupun begitu, nilai rasio perforasi perlu divariasikan lebih lanjut untuk mendapatkan titik kritis nilai frekuensi natural.Hasil yang berbeda didapatkan untuk pengaruh sambungan antar panel. ...
Penelitian ini memberikan penjelasan tentang pengaruh diameter lubang, rasio perforasi dan sambungan antar panel terhadap frekuensi natural dari sebuah panel berlubang ganda. Penelitian ini merupakan penelitian lanjutan dari penelitian sebelumnya tentang frekuensi natural dari sebuah panel tunggal pejal dan berlubang dimana di dalam penelitian ini digunakan panel ganda. Sebuah panel alumunium berukuran 15 x 15 cm dengan tebal 2 mm digunakan sebagai model dasar panel ganda. Diameter lubang di panel divariasikan mulai 1 sampai 3 mm, rasio perforasi divariasikan mulai 0, 5 sampai 2%. Sebagai tambahan, pengaruh sambungan diantara panel ganda juga didiskusikan secara ringkas. Nilai frekuensi natural didapatkan dari simulasi di dalam perangkat lunak Autodesk Inventor mulai frekuensi pertama sampai ke lima. Hasil yang didapat dari penelitian ini adalah bahwa frekuensi natural panel berlubang ganda sangat dipengaruhi oleh diameter lubang dan rasio perforasi, sementara sambungan antar kedua panel hanya memberikan sedikit pengaruh kepada nilai frekuensi natural.
... This was a good information whereas many vibration phenomena in machinery happen at low frequency region. For instance, the natural frequency and modal analysis method has been used to examine the perforated plates performance in a nuclear engineering parts [15]. This was a significant proof that perforated plate still performs well in applied engineering. ...
... By referring to the previous works [13][14][15], a model of simply supported 15 x 15 cm square aluminum perforated plate was made in Autodesk Inventor environment as seen in Figure 1(a). The thickness of the plate was set to be constant at 2 mm. ...
... For instance, at the 1st natural frequency, the PP has the frequency of 786,33 Hz while the other plates are in the range around 783 Hz, giving roughly 3 dB of differences. This is similar to previous research [13][14][15] that the micro holes, somehow, affect the mass of the plate so that the natural frequency value decreases. ...
In this paper, an extensive work on the natural frequency of perforated plate has been made by introducing micro-holes on the plate. The micro-holes, which is known to have a remarkable performance in several applications, were arranged diagonally among the perforated holes in order to make a new combination of micro-macro perforated plate. A 3D geometrical model of the plate was made in the Autodesk Inventor and the Finite Element (FE) simulation was employed to calculate the natural frequency and visualize the mode shape. Four models were made with various micro-holes diameter starting from 0,25, 0,5, 0,75 and 0,9 mm, respectively. The macro holes diameter, however, was kept constant to be 1,5 mm purposely to know the effect of micro holes in particular. The results from the models were then compared to a single perforated plate (PP) for clarification. It is found that the micro holes gives considerable effect to the perforated plate natural frequency. Similar to the author previous findings, the diameter of the micro holes is proportional to the natural frequency reduction.
