complex geometry
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2022 ◽  
Vol 3 (1) ◽  
pp. 46-54
Paweł Turek ◽  

Designing an anatomical structure for a surgical procedure is not a simple task. It is especially true of the craniofacial area, which consists of bone tissues with very complex geometry. CAD modelers need appropriate knowledge and skills in medicine and technical sciences to fully use the currently available tools in related processes with the reconstruction of the craniofacial areas. The presented preliminary studies are based on four patients treated at the Department of Maxillofacial Surgery. The segmentation process of the mandible model was performed in the ITK SNAP software. The process of generating surface body models was performed in the Auto Surfacing module in Geomagic software using two different methods: organic and mechanical. Then compare both methods for the accuracy of generating a CAD model of the mandible based on a triangle mesh structure in the Focus Inspection and the GOM Inspect software.

2022 ◽  
pp. 1-13
James J A Hammond ◽  
Francesco Montomoli ◽  
Marco Pietropaoli ◽  
Richard Sandberg ◽  
Vittorio Michelassi

Abstract This work shows the application of Gene Expression Programming to augment RANS turbulence closure modelling, for flows through complex geometry designed for additive manufacturing. Specifically, for the design of optimised internal cooling channels in turbine blades. One of the challenges in internal cooling design is the heat transfer accuracy of the RANS formulation in comparison to higher fidelity methods, which are still not used in design on account of their computational cost. However, high fidelity data can be extremely valuable for improving current lower fidelity models and this work shows the application of data driven approaches to develop turbulence closures for an internally ribbed duct. Different approaches are compared and the results of the improved model are illustrated; first on the same geometry, and then for an unseen predictive case. The work shows the potential of using data driven models for accurate heat transfer predictions even in non-conventional configurations and indicates the ability of closures learnt from complex flow cases to adapt successfully to unseen test cases.

2022 ◽  
Vol 12 (2) ◽  
pp. 779
Carlos Aurelio Andreucci ◽  
Abdullah Alshaya ◽  
Elza M. M. Fonseca ◽  
Renato N. Jorge

A new biomechanism, Bioactive Kinetic Screw (BKS) for screws and bone implants created by the first author, is presented using a bone dental implant screw, in which the bone particles, blood, cells, and protein molecules removed during bone drilling are used as a homogeneous autogenous transplant in the same implant site, aiming to obtain primary and secondary bone stability, simplifying the surgical procedure, and improving the healing process. The new BKS is based on complex geometry. In this work, we describe the growth factor (GF) delivery properties and the in situ optimization of the use of the GF in the fixation of bone screws through a dental implant. To describe the drilling process, an explicit dynamic numerical model was created, where the results show a significant impact of the drilling process on the bone material. The simulation demonstrates that the space occupied by the screw causes stress and deformation in the bone during the perforation and removal of the particulate bone, resulting in the accumulation of material removed within the implant screw, filling the limit hole of the drill grooves present on the new BKS.

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 313
Sergey Shevtsov ◽  
Igor Zhilyaev ◽  
Shun-Hsyung Chang ◽  
Jiing-Kae Wu ◽  
Natalia Snezhina

The increasingly widespread use of vacuum assisted technologies in the manufacture of polymer-composite structures does not always provide the required product quality and repeatability. Deterioration of quality most often appears itself in the form of incomplete filling of the preform with resin as a result of the inner and outer dry spot formation, as well as due to premature gelation of the resin and blockage of the vacuum port. As experience shows, these undesirable phenomena are significantly dependent on the location of the resin and vacuum ports. This article presents a method for making a decision on the rational design of a process layout. It is based on early forecasting of its objectives in terms of quality and reliability when simulating its finite element model, on the correlation analysis of the preliminary and final quality assessments, as well as on the study of the cross-correlation of a group of early calculated sub-criteria. The effectiveness of the proposed method is demonstrated by the example of vacuum infusion of a 3D thin-walled structure of complex geometry.

Ahmed Haddar ◽  
Alain Daidie ◽  
Emmanuel Rodriguez ◽  
Louis Augustins

This work presented in this paper concerns the modeling of the tensile and bending behavior of bolts in an airplane wheel. The design of a very rigid airplane tire means that the airplane wheel must be separated into two parts. In order not to have a separation between the two parts, several bolts with high preload are used. The main objective of this work is to predict the mechanical behavior of this assembly in a preliminary design phase with geometrical and global mechanical data. To achieve this objective, a simplified semi-numerical 1D model is developed. The complex geometry of the wheels is modeled by axisymmetric elements, while beam elements define the geometries and mechanical behavior of the bolts. The model is improved in non-axisymmetric cases to include the ring effect due to the wheel ovalization. Different cases are simulated (inflation and rolling). For each load case, the most stressed fastener is examined. Then, a comparison between its static and fatigue stress results and those of the 3D finite element reference model considered is analyzed for the validation of the developed tool. The semi-numerical model is used in the preliminary design phase and permits the geometric and mechanical properties of the aircraft wheel and fasteners to be defined so as to find the best assembly configuration that prevents separation.

2022 ◽  
pp. 107754632110421
Beena Limkar ◽  
Gautam Chandekar

Dynamic analysis of Sitar, an Indian string instrument, is important for better understanding of the instrument behavior during performance. Sitar has complex geometry, and most of its components have anisotropic material properties, which generate a lot of challenges in performing numerical modal analysis. Considering this, an experimental approach of operational modal analysis (OMA) is performed on Sitar to extract its natural frequencies using the Stochastic Subspace Identification method. Hammer or shaker excitation required for conventional experimental modal analysis (EMA) has huge limitations of using harder hammer tips and high magnitude force as the instrument is delicate. However, to validate OMA results, EMA is performed with extreme care using an instrumented hammer with soft tip and with a very low excitation force. PolyMAX algorithm is used in EMA. It is observed that most of the correlated OMA and EMA modes lie in the audible frequency range. The maximum absolute percent error observed for these frequencies is 2.14%. All the modes obtained in OMA are significant as the string excitation simulate close to the real-life performing situation. Most of these modes map to musical note frequencies. Considering the detrimental effect of excitation required for EMA, OMA is a recommended method for extracting modal characteristics of Sitar.

2022 ◽  
Alessandro Tomasiello

String theory is a leading candidate for the unification of universal forces and matter, and one of its most striking predictions is the existence of small additional dimensions that have escaped detection so far. This book focuses on the geometry of these dimensions, beginning with the basics of the theory, the mathematical properties of spinors, and differential geometry. It further explores advanced techniques at the core of current research, such as G-structures and generalized complex geometry. Many significant classes of solutions to the theory's equations are studied in detail, from special holonomy and Sasaki–Einstein manifolds to their more recent generalizations involving fluxes for form fields. Various explicit examples are discussed, of interest to graduates and researchers.

2022 ◽  
pp. 329-339
Raja Das ◽  
Mohan Kumar Pradhan

This chapter describes with the comparison of the most used back propagations training algorithms neural networks, mainly Levenberg-Marquardt, conjugate gradient and Resilient back propagation are discussed. In the present study, using radial overcut prediction as illustrations, comparisons are made based on the effectiveness and efficiency of three training algorithms on the networks. Electrical Discharge Machining (EDM), the most traditional non-traditional manufacturing procedures, is growing attraction, due to its not requiring cutting tools and permits machining of hard, brittle, thin and complex geometry. Hence it is very popular in the field of modern manufacturing industries such as aerospace, surgical components, nuclear industries. But, these industries surface finish has the almost importance. Based on the study and test results, although the Levenberg-Marquardt has been found to be faster and having improved performance than other algorithms in training, the Resilient back propagation algorithm has the best accuracy in testing period.

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Alexander Idesman ◽  
Bikash Dey

Purpose The purpose of this paper is as follows: to significantly reduce the computation time (by a factor of 1,000 and more) compared to known numerical techniques for real-world problems with complex interfaces; and to simplify the solution by using trivial unfitted Cartesian meshes (no need in complicated mesh generators for complex geometry). Design/methodology/approach This study extends the recently developed optimal local truncation error method (OLTEM) for the Poisson equation with constant coefficients to a much more general case of discontinuous coefficients that can be applied to domains with different material properties (e.g. different inclusions, multi-material structural components, etc.). This study develops OLTEM using compact 9-point and 25-point stencils that are similar to those for linear and quadratic finite elements. In contrast to finite elements and other known numerical techniques for interface problems with conformed and unfitted meshes, OLTEM with 9-point and 25-point stencils and unfitted Cartesian meshes provides the 3-rd and 11-th order of accuracy for irregular interfaces, respectively; i.e. a huge increase in accuracy by eight orders for the new 'quadratic' elements compared to known techniques at similar computational costs. There are no unknowns on interfaces between different materials; the structure of the global discrete system is the same for homogeneous and heterogeneous materials (the difference in the values of the stencil coefficients). The calculation of the unknown stencil coefficients is based on the minimization of the local truncation error of the stencil equations and yields the optimal order of accuracy of OLTEM at a given stencil width. The numerical results with irregular interfaces show that at the same number of degrees of freedom, OLTEM with the 9-points stencils is even more accurate than the 4-th order finite elements; OLTEM with the 25-points stencils is much more accurate than the 7-th order finite elements with much wider stencils and conformed meshes. Findings The significant increase in accuracy for OLTEM by one order for 'linear' elements and by 8 orders for 'quadratic' elements compared to that for known techniques. This will lead to a huge reduction in the computation time for the problems with complex irregular interfaces. The use of trivial unfitted Cartesian meshes significantly simplifies the solution and reduces the time for the data preparation (no need in complicated mesh generators for complex geometry). Originality/value It has been never seen in the literature such a huge increase in accuracy for the proposed technique compared to existing methods. Due to a high accuracy, the proposed technique will allow the direct solution of multiscale problems without the scale separation.

2021 ◽  
Vol 20 ◽  
pp. 77-88
Rafał Gawałkiewicz

For many years in Poland, anthropogenic objects constructed underground have been very popular with tourists. In the past they fulfilled various functions (historic mines, underground merchant warehouses, military objects, special objects, caverns and grottoes). Many of them were secured and rebuilt in such a way that a new form was created. They make interesting tourist offers and still more objects can be made available to tourists. An example of strongly modified underground anthropogenic objects of very complex geometry and extremely interesting architectural form is the Underground Tourist Route (Polish: Podziemna Trasa Turystyczna – PTT) in Sandomierz. Owing to much effort and financial means, in 1960s many interesting cellars and merchant warehouses were saved from destruction – and – with the application of mining techniques, they were joint into attractive spatial forms. So far, few publications give the full characteristic and parametric data of this object. Today’s possibilities of available measurement and information technologies allow comprehensive inventory of complicated engineering constructions, as well as the 3D visualization, regarding even tiniest elements of small architecture (doors, lattice, lamps, etc.). The article presents the results of the visualization and parameterization based on the data from integrated surveying (levelling, transects, total stations, laser scanning and other direct measurements). ELEKTRONICZNA WIZUALIZACJA PODZIEMNYCH TRAS TURYSTYCZNYCH NA PRZYKŁADZIE TRASY W SANDOMIERZU W Polsce dużą popularnością turystyczną od lat cieszą się obiekty antropogeniczne wzniesione pod powierzchnią ziemi, pełniące różnorodne funkcje użytkowe w przeszłości (zabytkowe kopalnie, podziemne składy kupieckie, obiekty militarne, obiekty specjalne, jaskinie i groty). Wiele z nich zostało w stopniu istotnym zabezpieczone i przebudowane w taki sposób, by nadać im nową formę. Udostępnione, dziś stanowią ciekawe oferty turystyczne, a ich liczba stanowi dziś zbiór otwarty. Przykładem mocno przetworzonego podziemnego obiektu antropogenicznego o bardzo zróżnicowanej geometrii i niezwykle ciekawej formie architektonicznej jest Podziemna Trasa Turystyczna w Sandomierzu. Dzięki zaangażowaniu wielu środków udało się w latach 60. XX w. ocalić od zniszczenia wiele interesujących piwnic i składów kupieckich i połączyć je z zastosowaniem technik górniczych w atrakcyjne formy przestrzenne. Dotychczas powstało niewiele opracowań, które ukazałyby w pełni ich charakterystykę oraz sparametryzowały obiekt. Możliwości dostępnych dzisiaj technik pomiarowych oraz informatycznych pozwalają na kompleksową inwentaryzację skomplikowanych budowli inżynierskich, a także wizualizację przestrzenną z uwzględnieniem nawet najdrobniejszych elementów małej architektury (drzwi, kraty, lampy itp.). W artykule zaprezentowano wyniki wizualizacji i parametryzacji na podstawie danych zintegrowanych pomiarów geodezyjnych (niwelacji, poligonizacji, tachimetrii elektronicznej, skaningu laserowego i innych pomiarów bezpośrednich).

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