CAD-based Simulation Research Articles

Mechanism design optimization through CAD-based Bayesian optimization and quantified constraints

This study addresses the challenge of mechanism design optimization, particularly focusing on the energy efficiency and design space of reciprocating mechanisms. The research question centers on how to effectively utilize Computer-Aided Design (CAD) simulations alongside Bayesian optimization (BO) and a constrained design space to streamline the design optimization process, overcoming the limitations of traditional kinematic and dynamic analysis methods. The objective is to investigate and develop a novel optimization framework that integrates CAD-based simulations with a BO approach. To achieve this, the study employs a methodological approach. At first, the feasibility of a chosen mechanism design is evaluated through a sequence of CAD-motion simulations to quantify the (in)feasibility of this design. When this design appears to be feasible, a CAD-based design evaluation method is started, in which the objective value is extracted by a sequence of CAD-motion simulations. In this paper, we advocate the use of non-parametric Gaussian processes to build a surrogate model of the objective function and the feasible design space constrained by static and dynamic constraints. The main research results demonstrate that the proposed CAD-based Bayesian optimization framework can effectively identify optimal design parameters that minimize the root mean square (RMS) torque while adhering to specified static and dynamic constraints. This optimization approach significantly reduces the complexity associated with analytic methods, making it scalable to more complex mechanisms and implementable by machine builders. In conclusion, the study successfully develops a novel optimization framework that leverages CAD-based simulations and Bayesian optimization to streamline the design process of mechanisms. The results of an emergency ventilator case study with three design parameters show a reduction of the RMS torque with 71% after 255 CAD-based design evaluations. Moreover, the results demonstrate the effectiveness of incorporating constraints into the design optimization process and the usage of Bayesian optimization (BO), providing insights into the obtained optimum. This approach offers probabilistic insights into the expected improvement of the optimum, highlighting that the full optimization potential is utilized in a computationally efficient manner.

CAD and constructive solid geometry modeling of the Molten Salt Reactor Experiment with OpenMC

In this study, we present a detailed comparison of two independently developed models of the Molten Salt Reactor Experiment (MSRE) for Monte Carlo particle transport simulations: the constructive solid geometry (CSG) model that was developed in support of the MSRE benchmark in the International Handbook of Evaluated Reactor Physics Benchmark Experiments, and a CAD model that was developed by Copenhagen Atomics. The original Serpent reference CSG model was first converted to OpenMC’s input format so that it could be systematically compared to the CAD model, which was already available as an OpenMC model, using the same Monte Carlo code. Results from simulations using the Serpent and OpenMC CSG models showed that keff agreed within 10 pcm while the flux distribution in space and energy generally agreed within 0.1%. Larger differences were observed between the OpenMC CAD and CSG models; notably, the keff computed for the CAD model was 1.00872, which is more than 1% lower than the value for the CSG model and much closer to experiment. Several areas of the reactor that were modeled differently in the CSG and CAD models were discussed and, in several cases, their impact on keff was quantified. Lastly, we compared the computational performance and memory usage between the CAD and CSG models. Simulation of the CSG model was found to be 1.4–2.3× faster than simulation of the CAD model based on the Embree ray tracer while using 4× less memory, highlighting the need for continued improvements in the CAD-based particle transport ecosystem. Finally, major performance degradation was observed for CAD-based simulations when using the MOAB ray tracer.

High-precision CAD-based simulation for turning considering tool microgeometry

High-precision CAD-based simulation for turning considering tool microgeometry

A finite-element based mesh morphing approach for surface meshes

We present a finite element (FE) approach that deforms a given meshed CAD-based simulation model to a shape represented by a triangulation. We use an FE solver to calculate a smooth deformation field that we apply to the simulation mesh. The FE load case derives displacement boundaries from computed distance estimates between source and target meshes. We reduce mesh distortions via an iterative approach until a specified required mesh quality threshold is achieved. Our specific application is concerned with meshes used for sheet metal simulations arising in automotive applications where one wants to construct digital twins of measured sheet metal parts or entire assemblies. The approach is validated for parts and assemblies, considering simulation as well as experimental data. Our computational experiments produce errors below ± 0.05 mm, which is on the order of measurement uncertainty of common optical measurement devices. We provide test results for fully and partially measured parts to document the robustness of our implementation. • Iterative FE simulation-based mesh morphing algorithm. • Handling complex geometries, measurement errors, and partially measured geometries. • Validations with simulation and experimental data, with errors below ±0.05 mm. • Easy to implement algorithmic scheme for commercial FE simulation software.

CAD-Based Simulation Model for the Calculation of Chip Geometry and Cutting Force Components in Gear Shaping

Abstract Involute gears are a vital component used in industry due to their ability to provide flexible and accurate rotary motion. Gear shaping is one of the most prominent gear cutting processes as it can be used to effectively manufacture spur and helical external as well as internal gears. Thus, the accurate prediction of the cutting forces developed during the cutting process is of great importance because it can greatly affect the wear and the cutting tool’s life. In this work, a simulation model was developed based on a commercial CAD software, able to simulate the kinematics involved in the process and provide accurate results regarding the undeformed chip geometry as well as the cutting forces. In order to verify the accuracy of the model, the produced gear flanks are compared with the theoretical ones and the calculated cutting forces are compared with the respective measured forces obtained from the literature.

A novel CAD-based simulation model for manufacturing of spiral bevel gears by face milling

Bevel gears are employed in the transmission of motion and torque via non-parallel shafts. When higher strength and lower noise is the objective, spiral bevel gears are used because of their higher tooth contact ratio. Face milling and face hobbing are among the most significant operations for the machining of hypoid and spiral bevel gears due to their high productivity. Although the optimization of these processes is crucial for the production of high-quality gears and the minimization of the total manufacturing cost, there are not many studies reported in this research area, owing to the high complexity of process kinematics. Furthermore, several kinematic variations of the two methods are applied in industry and their results depend highly on the cutting tool geometry. A novel simulation model integrated into a commercial CAD platform has been developed. The model achieves the 3D kinematic simulation of both face milling and face hobbing processes, generating the undeformed solid chip geometry as well as the simulated tooth solid geometry of a spiral bevel gear pinion and a spiral bevel gear wheel as an output. The simulation approach has two main purposes. First, is the optimization of the process through the investigation of the effect of cutting parameters on the quality of the obtained solid tooth flank geometry and second, is the calculation of cutting forces with the use of the obtained solid chip geometries. Aiming towards the validation of the model, the resulted tooth flank geometry is compared with the theoretical tooth exported from a well-established commercial gear calculation and design software and it is verified by means of a novel validation algorithm, also developed as part of this study. This paper focuses on the presentation of the kinematic simulation methodology and the simulation results for the face milling process. An insight into the validation model is provided and validation results are also presented. Finally, a sample investigation of the effect of generating feed rate on the produced gear geometry is conducted with the use of both algorithms.

A Real-Time-Link-Adaptive Operation Scheme for Maximum Energy Storage Efficiency in Resonant CM Wireless Power Receivers

The development, analysis, and experimental validation of an energy storage algorithmic scheme for performance optimization of resonant inductive power receivers are presented. Motivated by the crucial role of efficient energy storage in the next generation of brain-implantable devices, we introduce an energy management strategy in the design of wireless powering links, in which, the key performance measure is the energy stored during a limited time interval rather than the average energy delivered to the load. The presented strategy is proven analytically to yield the theoretically-maximum energy storage efficiency over a pre-determined period of time. Additionally, thanks to the algorithm's closed-form solution, the optimization can be done in real time, offering the potential for a solution that is adaptive to any variations in physical (e.g., coil separation, Rx rotation, etc.) and/or electrical (e.g., Q-factor, media conductivity, etc.) properties of the link, conditional to a low-power circuit implementation for its evaluation. The efficacy and precision of the solution obtained from the presented analytical model is confirmed with CAD-based simulation results, and later validated using experimental measurements. Our experimental results for two links with different characteristics (resonance frequency, coils size and separation, etc.) show a 52.5% and 67.5% improvement in overall energy storage efficiency compared to the standard CM receiver design in which resonance-to-charging switching is performed when the receiver's LC tank energy accumulation starts to saturate. This is while the presented method does not require any calibration and is designed to be employed by any generic current-mode receiver.

Calculation of non-deformed chip and gear geometry in power skiving using a CAD-based simulation

Power skiving is a new machining process that allows the manufacturing of external and internal gears while achieving high throughputs. Although the process was first described during the nineteenth century, it is not until lately that advances in machine tool technology allowed for the process to be implemented on an industrial scale. This paper presents a novel simulation model that enables the accurate prediction of the non-deformed chip geometry, the form and dimensions of the chips produced during the cutting process as well as the characteristics of the gear gap. The simulation model is embedded on a CAD environment in order to take advantage of their increased accuracy. Through the simulation code, the virtual simulation of the manufacturing process is realised. The simulation model was verified with the use of analytical equations regarding the form of the gear. Chip geometry and dimensions for internal and external gears machined with different conditions are also presented.

Surface topomorphy and roughness prediction in micro-ball-end milling using a CAD-based simulation

Ball-end milling is a widely used finishing process in metal cutting. The small size and the complex of metal machining components are the main reasons for implementing milling in microscale. The surface profile and the dimensional accuracy are key factors on the quality of surface of a product. The selection of optimal cutting conditions can be accomplished by utilising simulation models which can involve the kinematics and the strategies of milling processes. Therefore, the analytical prediction of the produced surface quality (topomorphy and roughness) can be reached. The present study indicates a 3D simulation model of ball-end micro-milling process developed in commercial CAD software and its optical and computing results. Micro-milling experiments of Al7075-T6 were carried out in different conditions by the use of a high speed spindle. A computer application was developed to calculate the roughness out of the controlled points of a plane that intersects with the 3D workpiece. The calculated roughness was compared with the measured surface roughness and the surface topomorphy was captured through a stereo microscope.

Surface topomorphy and roughness prediction in micro-ball-end milling using a CAD-based simulation

Ball-end milling is a widely used finishing process in metal cutting. The small size and the complex of metal machining components are the main reasons for implementing milling in microscale. The surface profile and the dimensional accuracy are key factors on the quality of surface of a product. The selection of optimal cutting conditions can be accomplished by utilising simulation models which can involve the kinematics and the strategies of milling processes. Therefore, the analytical prediction of the produced surface quality (topomorphy and roughness) can be reached. The present study indicates a 3D simulation model of ball-end micro-milling process developed in commercial CAD software and its optical and computing results. Micro-milling experiments of Al7075-T6 were carried out in different conditions by the use of a high speed spindle. A computer application was developed to calculate the roughness out of the controlled points of a plane that intersects with the 3D workpiece. The calculated roughness was compared with the measured surface roughness and the surface topomorphy was captured through a stereo microscope.

A workcell calibration method for enhancing accuracy in robot machining of aerospace parts

Industrial robotics provides high flexibility and reconfigurability supported by a user-friendly programming, but still lacks in accuracy. An effective workcell calibration reduces errors in robot manufacturing and enables robot machining applications. A novel workcell calibration method is embedded in an integrated design framework for an in-depth exploitation of CAD-based simulations and offline programming. The method is composed of two steps: first calibration of the workpiece-independent equipment in the workcell layout and final automated online calibration of workpiece-dependent equipment. The method is finally applied to a changeable robotic workcell for finishing aluminium cast housings for aerospace gear transmissions characterised by complex shapes and by close dimensional and geometrical specifications. Experimental results prove the method effectiveness in enhancing accuracy in robot machining.

Influence of machining data on developed cutting forces in gear hobbing

In every manufacturing process the prior knowledge of the developed cutting forces is crucial in order to increase the cutting performance and make the optimal selection of cutting conditions. In gear hobbing the complexity of the process as well as the diversity of the produced chips makes it difficult to create and use empirical charts that predict cutting forces according to the process parameters. The CAD-based simulation model Hob3D was developed in an effort to create an accurate model for gear hobbing that can produce reliable results for the cutting forces. The effect of the various parameters of the gear hobbing on the developed cutting forces with the aid of Hob3D is presented in this paper.

CAD simulation and generation machining of discrete ring-involute spherical segment gear pair

A spherical segment gear pair is useful in robotic wrist and similar such applications that require two degrees of freedom. From the first principle, tooth surface of spherical gear can be mathematically derived from a rack-cutter profile using the coordinate transformation and one-parameter family of envelope theory. Alternatively, the spherical gear tooth surface is obtained as an envelope of a series of cutter surfaces formed during the kinematic motion between work blank and cutter. Conventional gear cutting machines cannot be used to generate the spherical gears and hence the spherical gears have remained a conceptual mechanism. In order to establish the feasibility of generation machining, a CAD-based simulation is carried out first where work blank and cutter are taken as solid models and the simulation is performed using the Boolean operation to remove the interfered material in an incremental manner, maintaining the kinematic relationship. The actual machining of the spherical segment gear is then carried out on a five-axis CNC machining centre using a specially developed conical end-mill cutter having a semi-cone angle of 20°. The script file for the CAD simulation has also been used for creating the program for CNC machining.

CAD-based simulations and design of experiments for determining thrust force in drilling operations

Drilling thrust force calculations require a large amount of experimental work, which can be greatly reduced, since an extensively validated CAD-based approach, using the DRILL3D software application, has become available. DRILL3D calculates the thrust force of both the cutting areas of the tool (main edges and chisel edge) simultaneously, which means that every simulation can substitute two separate lab experiments. Nevertheless, as the number of parameters involved is increasing, the amount of the necessary simulations becomes substantial. This is the reason that led to the combined use of the DRILL3D and the design of experiments methodology, which reduces the amount of the necessary digital experiments to an impressive degree. The main factors affecting the current analysis are the tool diameter, the web to diameter ratio, the feed rate and the cutting speed used. Using an L16 Taguchi table, a function of the developed thrust force can be calculated using the response surface methodology. This statistical modeling tool employs the regression analysis to establish the relationship between various process parameters and response.

Efficient Force Analysis in CAD-Based Simulations

The paper presents a BEM-based approach for efficient force analysis of the steady-state field problems. As an extension to the minimal-order H-phi formulation we introduce here an improved approach for the treatment of the skin-effect problems. This approach enables the designers to perform the CAD-based simulations without any additional modeling requirement. The classical BEM modeling methodology is combined with the multipole-based integral technique (MBIT) to accelerate/compress the densely populate BEM matrix. The verification of the discussed approach is done by comparison with the known analytical solutions. The proposed method is illustrated on the problems dealing with the force calculation in the real-world bus-bars systems.

A 3D CAD-based simulation tool for prediction and evaluation of the thermal improvement effect of passive cooling walls in the developed urban locations

As a passive cooling strategy aimed at controlling increased surface temperatures and creating cooler urban environments, the authors have developed a passive cooling wall (PCW) constructed of moist void bricks that are capable of absorbing water and which allow wind penetration, thus reducing their surface temperatures by means of water evaporation. Passive cooling effects, such as solar shading, radiation cooling and ventilation cooling can be enhanced by incorporating PCWs into the design of outdoor or semi-enclosed spaces in parks, pedestrian areas and residential courtyards. The purpose of the present paper is to detail the development of a 3D CAD-based simulation tool that can be used to predict and evaluate the thermal improvement effect in urban locations where PCW installation is under consideration. Measurement results for the surface reduction effect of a PCW are introduced in the first part of the paper. In the second part, thermal modeling of a PCW is proposed based on analysis results of experimental data. Following that, a comparison study that integrates the proposed thermal modeling was conducted to validate the simulation method. In order to demonstrate the applicability of the developed simulation tool, a case study was then performed to predict and evaluate the thermal improvement effect at an actual urban location where PCWs were installed. Simulations were performed by modeling the construction location in two scenarios; one where the PCWs were composed of dry bricks, and another where the bricks were wet. The results show that, in terms of surface temperature and mean radiant temperature (MRT), this simulation tool can provide quantitative predictions and evaluations of thermal improvements resulting from the installation of PCWs.

蒸発冷却型孔空きレンガ壁体を利用した都市・建築空間におナる熱環境の予測・評価手法の開発に関する研究

This paper presents a numerical simulation method to predict and evaluate the thermal environment in the developed urban locations where void-brick walls with evaporative cooling effect were applied, using the 3D CAD-based simulator developed by the authors. The thermal modeling of a void-brick wall was proposed from the experimental data and calculation algorism of its surface temperature was integrated into the simulator. A case study was carried out to quantify the thermal improvement of the void-brick wall applied to a bus waiting arbor. The simulation results show that the developed simulation tool can be used as a design tool to evaluate the thermal effect of the void-brick wall on the urban built environment.

Measurement and simulation of the thermal environment in the built space under a membrane structure

This paper presents a study to clarify characteristics of the summer thermal environment in an actual membrane structure with a semi-closed space underneath by using field measurements and simulations. The first part of this paper describes the following findings from the field measurements conducted during a summer period: (1) the solar transmission through the membrane had a greatest impact on the thermal environment in the living space under the membrane structure during the daytime; (2) the mean radiant temperature (MRT) at the central part of the living space went higher than the air temperature due to heat storage in the ground and walls of surrounding buildings where radiation cooling to the sky was obstructed by the membrane. In the second part of the paper, a 3D CAD-based simulation tool (called the thermal environment simulator) developed by the authors' group was used to simulate the thermal environment in the test membrane structure. A comparison between the measured and simulated surface temperature of the membrane was carried out. As a result, it was found that the simulated results agreed well with the measurement data. In addition, the following subjects were discussed using the simulation tool: how the thermal environment under the membrane is influenced by changing the solar transmittance and absorptance of the membrane or changing the ground surface materials. Simulation results show that the simulation tool is able to provide a quantitative prediction and evaluation of the thermal environment in the living space under the membrane structure in terms of the surface temperature and mean radiant temperature distribution.

CAD-based simulation of the hobbing process for the manufacturing of spur and helical gears

Targeting an accurate and realistic simulation of the gear hobbing process, we present an effective and factual approximation based on three-dimensional computer-aided design. Hobbing kinematics is directly applied in one gear gap. Each generating position formulates a spatial surface path which bounds its penetrating volume into the workpiece. The three-dimensional surface paths generated from the combination of the relative rotations and displacements of hob and work gear are used to split the subjected volume, creating concurrently the chip and the remaining work gear solid geometries. The developed software program HOB3D simulates accurately the manufacturing of spur and helical gears, exploiting the modeling and graphics capabilities of a commercial CAD software package. The resulting three-dimensional solid geometrical data, chips and gears provide the whole geometrical information needed for further research, such as prediction of the cutting forces, tool stresses and wear development as well as the optimization of the gear hobbing process.

Mastering Conformal Meshing for Complex CAD-Based C-FDTD Simulations

A robust and automatic discretization algorithm for complex conformal finite-difference time-domain (C-FDTD) simulation is presented in this publication. The targeted application range is to enable C-FDTD simulations for real-word engineering problems. Based on computer-graphics methods, complex CAD models with thousands of distinct parts can be efficiently and robustly discretized. A versatile concept is introduced to avoid numerical inaccuracies while calculating intersections, and to lead to a symmetric discretization without the overhead of "virtual lines." In addition, a necessary three-dimensional consistency check/correction, as well as merging of conformal cells of different CAD parts, are explained. The conformal geometric information is incorporated into the conventional FDTD algorithm using the conventional updating coefficients, which are conformally enhanced. Due to the derived stability criterion, the conformal updating scheme is always stable. The robustness and performance of the discretization algorithm presented is demonstrated with CAD models of increasing complexity towards real-world benchmarks. A conformal FDTD simulation with 80 million computational cells and 229 distinguished parts, representing a complete mobile phone and a head with hand, demonstrates the capabilities of the versatile technique.