Computer-aided Design Geometry Research Articles

Integrated CFD-FEM approach for external gear pump vibroacoustic field prediction

In this work, a three-dimensional fluid-structural and vibro-acoustics coupled model of a gear pump is presented. Gear pumps represent the majority of the positive displacement machines used for flow generation in fluid power systems. Typically, the dynamics of gear pumps are dependent on the characteristics of the fluid dynamics inside the pump, which translates into vibrations to the housing. These vibrations then propagate to the surrounding medium and emit sound. The purpose of this study is to propose a three-dimensional fully integrated computational model to simulate the complete gear pump behaviour from the fluid dynamics to the structural vibrations, up to the vibroacoustic response. In this hybrid configuration, a transient CFD (Computational Fluid Dynamics) model is first developed to simulate the 3D flow field with a deforming and re-meshing approach to take into account the variation of the volume between the gears. Second, the internal pressure field calculated at each time step is then used as a loading into a structural FEM (Finite Element Method) model of the gear pump to compute the actual stresses and deformations of the housing. Third, the results of the structural response are used as excitation in a vibroacoustic sub-model to simulate the radiated noise using a high-order FEM technique. The comparison between the numerical and experimental flow curves validates the CFD model. The sound power calculations from the vibroacoustic model show good comparison with the sound intensity measurements around the pump casing, confirming the validity of the proposed coupled model. The described CFD-FEM approach proves to be a powerful gear pump design tool: it provides a reliable estimate of gear pump working parameters such as fluid power and vibroacoustic characteristics, starting from the CAD (Computer-Aided Design) geometry of the components. Furthermore, being one of the first multi-domain simulation models of a gear pump, this work can be useful to researchers as a starting point to correlate the noise emitted with the internal flow in full 3D conditions.

Automated shape and thickness optimization for non-matching isogeometric shells using free-form deformation

AbstractIsogeometric analysis (IGA) has emerged as a promising approach in the field of structural optimization, benefiting from the seamless integration between the computer-aided design (CAD) geometry and the analysis model by employing non-uniform rational B-splines (NURBS) as basis functions. However, structural optimization for real-world CAD geometries consisting of multiple non-matching NURBS patches remains a challenging task. In this work, we propose a unified formulation for shape and thickness optimization of separately parametrized shell structures by adopting the free-form deformation (FFD) technique, so that continuity with respect to design variables is preserved at patch intersections during optimization. Shell patches are modeled with isogeometric Kirchhoff–Love theory and coupled using a penalty-based method in the analysis. We use Lagrange extraction to link the control points associated with the B-spline FFD block and shell patches, and we perform IGA using the same extraction matrices by taking advantage of existing finite element assembly procedures in the FEniCS partial differential equation (PDE) solution library. Moreover, we enable automated analytical derivative computation by leveraging advanced code generation in FEniCS, thereby facilitating efficient gradient-based optimization algorithms. The framework is validated using a collection of benchmark problems, demonstrating its applications to shape and thickness optimization of aircraft wings with complex shell layouts.

A Digital Twin of an Off Highway Vehicle based on a Low Cost Camera

The operation of heavy equipment in the construction industry requires high-skilled workers: they must safely operate the equipment in an efficient manner to avoid project delays or damages, both to equipment and material as to their colleagues and themselves. Operator productivity and safety are therefore critical in the construction industry. The advancements in technologies such as digitization and automation are more and more applied in the industry, leading to more data and knowledge on the construction equipment and environment. This can be leveraged by a digital twin to provide value for the operator.In this work, we present a digital twin architecture applied to an off highway vehicle, which provides real-time feedback to the operator while operating the vehicle. Monitoring the interactions between an off highway vehicle and workers will result in a safer and more productive environment. This work focuses on detection of the environment and monitoring the state of the vehicle. Images of a low cost camera are used to extract information of the vehicle implement as well as the environment. The motion and state of the machine can be realistically visualized in real-time in Unreal, using a 3D CAD (Computer-Aided Design) geometry model, enriched with additional relevant information and color schemes. A modular pub-sub architecture enables the communication between the sensors and camera, the data processing and the visualization of the digital twin.

Practical Guidance on the Additive Manufacturing of Acoustic Materials

This study draws on experiences and knowledge gained from the additive manufacturing of acoustic materials to provide a best practice guide to their design and manufacture. The emphasis is primarily on porous materials and metamaterials. 3D printing technologies enabled the creation of complex structures that otherwise could not be produced using traditional subtractive methods. Additively manufactured components are subject to various production defects which primarily originate from: layer-by-layer fabrication, the influence of post-processing and properties of the build material. These include surface roughness, poor geometric tolerances and micro-porosity of the built material. Thus, produced parts differ from the computer-aided design geometries on which they are based. These issues must be well understood and considered during the development of novel acoustic materials to provide a good match between numerical and experimental results and achieve the designed performance. Here three distinct 3D printing technologies are examined: extrusion-based FDM, resin-based MSLA and powder-based SLM. Our findings offer insights into the impact of additive manufacturing on the acoustic performance of novel materials and provide recommendations for acoustic material development.

An adaptive B-spline representation of topology optimization design for Additive Manufacturing

Topology optimization is a renowned structural optimization approach used to compute the optimal topology for the enhancement of structural performance. It has been in common practice in different engineering fields such as automobile and aerospace. However, there still exist gaps between topology optimization and its engineering operations, which considerably impedes topology optimization’s applications. One of these gaps is how to make (especially finite element-based) topology optimization results machine-readable, which means, how to transform these into computer-aided design (CAD) models, which are ready-to-use models for manufacturing. In the proposed work the authors adopted a unique methodology that plugs the gap between topology optimization and manufacturing. This methodology seamlessly integrates the structural analysis tool, boundary description tool and standard CAD geometry representation; equipped with the Hausdorff distance approach for 3D printing/additive manufacturing of optimal structures. Initially, we extract the skeleton of the optimal design (in the form of a points cloud) using the level set method, followed by an interpolation technique with shape preservation property, the extracted skeleton is made dense. Incorporating the shape and curvature information of the data set, an adaptive B-spline approximation is devised for fitting a smooth curve through the points cloud. This approach interprets topology optimization results as a parametric CAD model with minimum possible control points and minimum approximation error. The CAD-based optimal designs are then used for additive manufacturing. The numerical results exhibit in detail the validity and accuracy of the proposed method.

Performance analysis and optimisation of spatially-varying infill microstructure within CAD geometries

The article is aimed to provide an effective digital solution in support of the infill microstructural design within objectives generated from normal computer aided design (CAD) systems. The key here is to deploy the microstructure and to analyse the performance of the resulting multiscale objective in the parameter domain, from which a CAD objective is mapped, usually by means of Non-Uniform Rational B-Splines (NURBS) functions. In the regularly shaped domain defined in the parameter space, another set of mapping functions are defined for the description of spatially-varying microstructure (in the parameter space), and the actual multiscale CAD objective gets represented through composition of these mapping functions with the NURBS-based functions for CAD geometry generation. When the introduced mapping functions are also NURBS-based, the proposed representation strategy becomes more favoured by CAD systems, in the sense that the CAD geometry and its infill can be tuned simultaneously but independently with a same set of NURBS basis. Moreover, our computer-aided engineering (CAE) module is also installed over the parameter domain, based on a machine-learning-based homogenisation formulation for compliance and strength analysis. Thus the finite element meshes stay unchanged although the accommodating CAD geometry keeps varying. With the aforementioned treatments, a consecutive CAD-consistent scheme is proposed. Our numerical results show that each time as the control points are moved (by a CAD designer), one may choose to wait several seconds for two-dimensional cases and/or a few minutes for three-dimensional cases, to get a CAD geometry filled with microstructure bearing optimised compliance.

Contributions of deep learning to automated numerical modelling of the interaction of electric fields and cartilage tissue based on 3D images.

Electric fields find use in tissue engineering but also in sensor applications besides the broad classical application range. Accurate numerical models of electrical stimulation devices can pave the way for effective therapies in cartilage regeneration. To this end, the dielectric properties of the electrically stimulated tissue have to be known. However, knowledge of the dielectric properties is scarce. Electric field-based methods such as impedance spectroscopy enable determining the dielectric properties of tissue samples. To develop a detailed understanding of the interaction of the employed electric fields and the tissue, fine-grained numerical models based on tissue-specific 3D geometries are considered. A crucial ingredient in this approach is the automated generation of numerical models from biomedical images. In this work, we explore classical and artificial intelligence methods for volumetric image segmentation to generate model geometries. We find that deep learning, in particular the StarDist algorithm, permits fast and automatic model geometry and discretisation generation once a sufficient amount of training data is available. Our results suggest that already a small number of 3D images (23 images) is sufficient to achieve 80% accuracy on the test data. The proposed method enables the creation of high-quality meshes without the need for computer-aided design geometry post-processing. Particularly, the computational time for the geometrical model creation was reduced by half. Uncertainty quantification as well as a direct comparison between the deep learning and the classical approach reveal that the numerical results mainly depend on the cell volume. This result motivates further research into impedance sensors for tissue characterisation. The presented approach can significantly improve the accuracy and computational speed of image-based models of electrical stimulation for tissue engineering applications.

Exact forming for additive manufacturing using an irregular element-based compensating approach: Simulation, experiment, and detection

During the additive manufacturing, the shape of workpieces is influenced by printing parameters. To achieve the desired shape of the workpiece, an optimization algorithm is often used to determine an effective combination of printing parameters. Although multiparameter optimization can improve structure quality, they are very time-consuming. In this article, we propose a timesaving irregular element-based compensating approach, which allows a more precise fitting of the geometric boundaries without needing additional computing resources. Finally, we demonstrate that the proposed approach can accurately shape the workpiece to fulfill the expected computer-aided design geometry by experimental verification and error comparison analysis.

Shutdown Dose Rate with Cartesian Mesh for High-Energy Nuclear Systems

In accelerator-driven systems, charged particles and high-energy neutrons can contribute to the production of nuclides that can persist long after the system has been shut down. These nuclides release photons that contribute to the biological dose. It is essential to quantify the biological dose as a function of time after shutdown to ensure safe working conditions for laborers during maintenance procedures. The shutdown dose rate (SDR) can be calculated with the Rigorous Two-Step (R2S) method, which includes a neutron and photon transport coupled with an activation calculation. For accelerator-driven systems, calculating SDR presents challenges related to the neutron cross-sectional data available for high-energy neutrons. A tally was implemented to collect isotope production data directly in a Monte Carlo N-Particle (MCNP) calculation. The output of this RNUCS tally is then used directly in an activation calculation, bypassing the need to use cross-section data with the neutron flux to obtain the isotope production and destruction data. A mesh-based RNUCS-R2S workflow has been developed based on this tally to calculate SDR in accelerator-driven systems. This workflow operates directly on computer-aided design geometry and supports using a meshed photon source. This workflow has been verified against a cell-based RNUCS-R2S workflow. A test problem with the essential characteristics of an accelerator-driven system was created to use in this analysis. The SDR results are within 40% of the cell-based RNUCS-R2S results. The workflow was also validated with the spallation neutron source system. Most detectors’ SDR results are within 50%, with a few detectors having a significantly lower SDR result than the experimental value.

MRADSIM-Converter: A new software for STEP to GDML conversion

Radiation effects analysis of instruments operative in harsh radiation environment is crucial for performance and functionality of electronic devices and components. Engineering design of instruments is usually carried out in Computer Aided Design (CAD) engineering software. Geant4-based Monte Carlo codes are extensively used for particle transport simulation and analysis. However, Geant4 is not prepared to accept CAD Standard for The Exchange of Product data (STEP) format. MRADSIM-Converter is a new software for STEP to Geometry Description Markup Language (GDML) format conversion, readable by Geant4-based Monte Carlo codes. Its validation with two different converters confirms its higher speed for importing CAD geometries with arbitrary size and complexity having a user-friendly interface for modifying volumes properties. Program summaryProgram title: MRADSIM-ConverterCPC Library link to program files:https://doi.org/10.17632/8kzsyn79gh.1Licensing provisions: LGPLProgramming language: C++Supplementary material: CMake, Qt5, OpenCascadeNature of problem: Geant4 toolkit simulation code developed at CERN is widely used for high energy physics community as well as health physics and radioprotections communities. However, Geant4 is not prepared to receive the CAD formats file, and the geometry implementation in Geant4 is a time-consuming task as it requires the creation of each volume using specific classes.Solution method: MRADSIM-Converter is a software designed to perform a conversion between the files written in STEP format, prepared by CAD software, into the GDML format, accepted as input in Geant4. All existent volumes in the input STEP file are visualized in the Graphical User Interface (GUI), where it is possible to interactively assign the material to the components and modify each volume's properties, such as material, color, and name.Additional comments including restrictions and unusual features: MRADSIM-Converter is tested under Ubuntu, versions 18 and 20. All the libraries necessary to run the program are provided in the package hence no additional library or software is required to be installed. Under MacOS and Windows, MRADSIM-Converter is running through virtual machine (VM) with above-mentioned Ubuntu versions.

Smart Cloud Collocation: Geometry-Aware Adaptivity Directly From CAD

Computer Aided Design (CAD) is widely used in the creation and optimization of various industrial systems and processes. Transforming a CAD geometry into a computational discretization that be used to solve PDEs requires care and a deep knowledge of the selected computational method. In this article, we present a novel integrated collocation scheme based on smart clouds. It allows us to transform a CAD geometry into a complete point collocation model, aware of the base geometry, with minimum effort. For this process, only the geometry of the domain, in the form of a STEP file, and the boundary conditions are needed. We also introduce an adaptive refinement process for the resultant smart cloud using an a posteriori error indication. The scheme can be applied to any 2D or 3D geometry, to any PDE and can be applied to most point collocation approaches. We illustrate this with the meshfree Generalized Finite Difference (GFD) method applied to steady linear elasticity problems. We further show that each step of this process, from the initial discretization to the refinement strategy, is connected and is affected by the approach selected in the previous step, thus requiring an integrated scheme where the whole solution process should be considered at once. • CAD files are used to generate smart point clouds without any intermediate step. • Exact normal vectors and boundary conditions are based on the CAD geometry. • ZZ-type error indicators are the basis for model adaptivity and are quick to compute. • Model adaptivity speeds up the convergence rate of the solution. • Model adaptivity is based on the exact CAD geometry.

The gamma dose rate analysis method for the maintenance of China initiative accelerator driven subcritical system based on the voxelized algorithm

Gamma dose rate analysis is the important issue for the maintenance of China initiative accelerator driven subcritical system (CiADS), which has direct impact on the nuclear radiation protection and the safe working environment for operators. However, the gamma radiation assessment in CiADS facility is the complex and challenge task, since there are a lot of complicated geometries with large amount of high order curve surfaces that are difficult to describe in the simulation process. Additionally, the shielding design in maintenance scenario has the requirement of high efficient calculation with acceptable accuracy. In this context, the point kernel method and the model simplification procedure by means of the voxelized model description have been adopted in the dose rate analysis for the purpose of obtaining the required flexible and diverse features, where the complex three dimensional geometries constructed by computer aided design (CAD) tools can be automatically converted to the approximate voxelized structure, and the radiation sources with arbitrary shapes are sampled based on the basic units in the conversion model. Furthermore, the CAD geometry optimization method has been verified in considering the volume deviation between the original CAD structure and the voxelized model. The feasibility and applicability of the dose rate analysis method have been tested in comparison with the FLUKA code, where all the numerical simulation results demonstrate that the proposed assessment method has the potential in meeting the design requirements during the maintenance of CiADS facility.

User-Driven Computer-Assisted Reverse Engineering of Editable CAD Assembly Models

Abstract This paper introduces a novel reverse engineering (RE) technique for the reconstruction of editable computer-aided design (CAD) models of mechanical parts’ assemblies. The input is a point cloud of a mechanical parts’ assembly that has been acquired as a whole, i.e., without disassembling it prior to its digitization. The proposed framework allows for the reconstruction of the parametric CAD assembly model through a multi-step reconstruction and fitting approach. It is modular and it supports various exploitation scenarios depending on the available data and starting point. It also handles incomplete datasets. The reconstruction process starts from roughly sketched and parameterized CAD geometries (i.e., 2D sketches, 3D parts, or assemblies) that are then used as input of a simulated annealing-based fitting algorithm, which minimizes the deviation between the point cloud and the adapted geometries. The coherence of the CAD models is maintained by a CAD modeler that performs the geometries’ updates while guaranteeing the possibly imposed constraints and model coherence. The optimization process leverages a two-level filtering technique able to capture and manage the boundaries of the geometries inside the overall point cloud in order to allow local fitting and interfaces detection. It is a user-driven approach where the user decides what are the most suitable steps and sequence to operate. It has been tested and validated on both real scanned point clouds and as-scanned virtually generated point clouds incorporating several artifacts that would appear with real acquisition devices.

Irregular Symmetrical Object Designed By Using Lambda Miu B-Spline Degree Four

In Computer Aided Geometry Design (CAGD), B-splines curves are piecewise polynomial parametric curves that play an important role. CAGD involves the interpolation and approximation curves and surfaces. CAGD has been widely used which brings good impact of computers to industries in manufacturing. There are many improved methods in the B-spline curve such as extended cubic B-spline, trigonometric B-spline, quasi trigonometric B-spline, and λμ-B-spline. Each of the methods has its behaviour and advantage. In this paper, λμ-B-spline was used to be implemented in generating irregular symmetrical objects. λμ-B-spline has a shape parameter that can change the global shape by manipulating the value of the shape parameter. The bottle has been chosen as an irregular symmetrical object. The 2-dimensional symmetrical curves of Bottle design were formed by using λμ-B-spline degree 4. The curves designed are dependent on the shape parameter which can be adjusted. Then, the curves generated were revolved using the Sweep Surface method to form 3-dimensional objects. Every object has its volume and this research focused on the numerical method which was Simpson’s 3/8 to compute the volume. The volumes obtained were compared to the actual volume to determine the best shape parameter used. The results show that the λμ-B-spline curve with a shape parameter of 1 is the best shape parameter in designing symmetrical irregular objects with the desired volume.

A systematic review of Bezier-like Triangular in surface reconstruction

The application of spline triangular surface has recently been critically discussed in Computer Aided Geometry Design (CAGD). This type of surface has significantly contributed to many important areas especially in reconstructing medical images such as bone and organs. The reconstructed surface is used in further study for example behavioural analysis, safety analysis and surgical planning. Many successful methods have been developed for example Bezier, Ball and Timmer triangular surfaces. In this paper, a comprehensive review of the literature on the triangular surface is presented. The advantages and disadvantages of existing methods on triangular surface are discussed and highlighted in this paper. The methods will be compared in terms of basis function development and the results of produced surface are shown visually. The main objective of this paper is to assist researchers in deciding the best method to be used in surface reconstruction.

Upper bound limit analysis of circular tunnel in cohesive-frictional soils using isogeometric analysis based on Bézier extraction

This paper presents an isogeometric analysis (IGA) based on Bézier extraction to investigate the stability of a circular tunnel in cohesive-frictional soils subjected to uniform surcharge loading. The basic concept of IGA is to use non-uniform rational B-splines (NURBS) basis functions for both the parametrisation of the geometry in computer-aided design (CAD) and the finite approximation for analysis. In this study, IGA based on Bézier extraction is applied to model a circular tunnel's geometry discretisation. The soil is modelled to be a homogeneous material obeying the Mohr-Coulomb failure criterion. The ultimate surcharge loading and failure mechanisms of the circular tunnel are obtained via upper bound limit analysis. Based on the results of isogeometric analysis, design tables and charts are generated for various soil properties, internal friction angles and ratios of tunnel cover to tunnel diameter. The numerical results for plane strain circular tunnels are compared with those of other available solutions to prove the reliability and efficiency of the present method.

Simulating wave propagation in acoustic metamaterials with isogeometric analysis

Finite element analysis (FEA) is commonly used to simulate and design acoustic metamaterials (AMM). Numerical studies employing FEA often rely on Bloch-Floquet analysis of a single unit cell or direct numerical simulations that include many unit cells. Unfortunately, AMM unit cells with fine features necessitate dense computational meshes to resolve the geometry and accurately model wave motion, sometimes prohibiting the use of FEA. Isogeometric Analysis (IGA) is a potential alternative approach to FEA for wave propagation problems. IGA utilizes basis functions that are typically employed in Computer Aided Design (CAD) software, such as B-splines and Non-Uniform Rational B-Splines (NURBS), to represent both the geometry and the wave solution. The direct utilization of the CAD geometry eliminates the need for a separate computational mesh of the geometry and the smoothness of the NURBS basis functions provides increased accuracy per degree of freedom. The latter point is particularly useful for high frequency problems. This talk presents IGA as a means to model AMM behavior and compares results with FEA simulations in terms of total simulation time and accuracy. Finally, we comment on the current limitations of IGA and discuss avenues of future research. [Work supported by the ARL:UT postdoctoral fellowship program.]

TOWARDS CAD-BASED GEOMETRY MODELLING WITH THE RANDOM RAY METHOD

The Advanced Random Ray Code (ARRC) is a high performance computing application capable of high-fidelity simulations of full core nuclear reactor models. ARRC leverages a recently developed stochastic method for neutron transport, known as The Random Ray Method (TRRM), which offers a variety of computational and numerical advantages as compared to existing methods. In particular, TRRM has been shown to be capable of efficient simulation of explicit three dimensional geometry representations without assumptions about axial homogeneity. To date, ARRC has utilized Constructive Solid Geometry (CSG) combined with a nested lattice geometry which works well for typical pressurized water reactors, but is not performant for the general case featuring arbitrary geometries. To facilitate simulation of arbitrarily complex geometries in ARRC efficiently, we propose performing transport directly on Computer-Aided Design (CAD) models of the geometry. In this study, we utilize the Direct-Accelerated Geometry Monte Carlo (DAGMC) toolkit which tracks particles on tessellated CAD geometries using a bounding volume hierarchy to accelerate the process, as a replacement for ARRC’s current lattice-based accelerations. Additionally, we present a method for automatically subdividing the large CAD regions in the DAGMC model into smaller mesh cells required by random ray to achieve high accuracy. We test the new DAGMC geometry implementation in ARRC on several test problems, including a 3D pincells, 3D assemblies, and an axial section of the Advanced Test Reactor. We show that DAGMC allows for simulation of complex geometries in ARRC that would otherwise not be possible using the traditional approach while maintaining solution accuracy.

Desain dan Pembuatan Prototype Piston Honda MEGAPRO FI Menggunakan 3D Printing

3D printing technology has great potential in today's manufacturing world, one of its uses is in making miniatures or prototypes of a product such as a piston. One of the most famous and inexpensive 3D printing (additive manufacturing) technologies is Fused Deposition Modeling (FDM), the principle FDM works by thermoplastic extrusion through a hot nozzle at melting temperature then the product is made layer by layer. The two most commonly used materials are ABS and PLA so it is very important to know the accuracy of product dimensions. FDM 3D Printing Technology is able to make duplicate products accurately using PLA material. FDM machines work by printing parts that have been designed by computer-aided design (CAD) and then exported in the form of STL or .stl files and uploaded to the slicer program to govern the printing press according to the design. Using Anet A8 brand 3D printing tools that are available to the public, Slicing of general CAD geometry files such as autocad and solidwork is the basis for making this object. This software is very important to facilitate the design process to be printed. Some examples of software that can be downloaded and used free of charge such as Repetier-Host and Cura. by changing the parameters in the slicer software is very influential in the 3D printing manufacturing process.

Reconstruction of a CAD model from the deformed mesh using B-spline surfaces

ABSTRACTFor several years, researchers have focused on Reverse Engineering techniques, which generate the geometric model of an object from a point set, a mesh, a triangulation, etc. These data are provided by 3D scanners, three-dimensional Coordinate Measuring Machines, finite elements results, deformed meshes, etc. In this field, the reconstruction of the Computer Aided Design (CAD) model from a deformed mesh remains a challenge. This CAD model can be used in order to visualize 3D objects that were scanned and approximate their shapes by mathematical formulations. It can represent the geometric support for many other activities (analysis, manufacturing, assembly, etc.). In this paper, we propose a method to rebuild the CAD geometry model from a deformed mesh. This approach is based on the B-Spline formulation for rebuilding the CAD model entities (faces, edges and vertices) from those extracted from the deformed mesh (triangulations, arcs, nodes). The reconstruction is based on the Levenberg Marquardt algorithm as a method for the interpolation/approximation. An illustration of the developed method is proposed discussed at the end of this paper.