A computationally efficient universal platform for thermal numerical modeling of laser-based additive manufacturing

2017 ◽  
Vol 232 (13) ◽  
pp. 2317-2333 ◽  
Author(s):  
Emmanuel Stathatos ◽  
George-Christopher Vosniakos
Keyword(s):  
Additive Manufacturing ◽  
Numerical Models ◽  
Computationally Efficient ◽  
Modeling Framework ◽  
Element Analysis ◽  
Shell Elements ◽  
Reduction Techniques ◽  
Key Characteristics ◽  
Wide Range ◽  
Multiscale Modeling Framework

A macroscopic thermal finite element analysis modeling platform for laser-based additive manufacturing is presented and validated. Its key characteristics include highly automated creation of simulation scenarios and increased computational efficiency. An investigation is carried out proving thermal shells a viable alternative to traditional solid elements, for building smaller and faster models. Full parameterization allows for rapid creation of specific modeling instances/scenarios. The use of shell elements, combined with model reduction techniques and advanced solver technology, result in very significantly reduced simulation times, compared to conventional modeling methods. Validation of the presented platform is carried out by comparison to results from other numerical models as well as experiments identified in the literature. Very good agreement for a wide range of materials and process parameters attest to its accuracy and universal application. This platform is the necessary basis for an Integrated Multiscale Modeling framework for systematically studying thermal patterns thereby ultimately increasing the scope of simulation to complete layers and whole parts.

scholarly journals Rapid Evaluation for Position-Dependent Dynamics of a 3-DOF PKM Module

2014 ◽  
Vol 6 ◽  
pp. 238928 ◽  
Author(s):  
Hai-wei Luo ◽  
Hui Wang ◽  
Jun Zhang ◽  
Qi Li
Keyword(s):  
Natural Frequencies ◽  
Mode Shapes ◽  
Parallel Kinematic Machine ◽  
Computationally Efficient ◽  
Element Analysis ◽  
Reduction Techniques ◽  
Modal Reduction ◽  
Governing Differential Equation ◽  
Parallel Kinematic ◽  
Analytical System

Based on the substructure synthesis and modal reduction technique, a computationally efficient elastodynamic model for a fully flexible 3-RPS parallel kinematic machine (PKM) tool is proposed, in which the frequency response function (FRF) at the end of the tool can be obtained at any given position throughout its workspace. In the proposed elastodynamic model, the whole system is divided into a moving platform subsystem and three identical RPS limb subsystems, in which all joint compliances are included. The spherical joint and the revolute joint are treated as lumped virtual springs with equal stiffness; the platform is treated as a rigid body and the RPS limbs are modelled with modal reduction techniques. With the compatibility conditions at interfaces between the limbs and the platform, an analytical system governing differential equation is derived. Based on the derived model, the position-dependent dynamic characteristics such as natural frequencies, mode shapes, and FRFs of the 3-RPS PKM are simulated. The simulation results indicate that the distributions of natural frequencies throughout the workspace are strongly dependant on mechanism's configurations and demonstrate an axial-symmetric tendency. The following finite element analysis and modal tests both validate the analytical results of natural frequencies, mode shapes, and the FRFs.

scholarly journals Evaluation of Anterior Cruciate Ligament Surgical Reconstruction Through Finite Element Analysis

2021 ◽  
Author(s):  
Konstantinos Risvas ◽  
Dimitar Stanev ◽  
Lefteris Benos ◽  
Konstantinos Filip ◽  
Dimitrios Tsaopoulos ◽  
...  
Keyword(s):  
Finite Element ◽  
Anterior Cruciate Ligament ◽  
Reference Model ◽  
Numerical Models ◽  
Cruciate Ligament ◽  
Surgical Techniques ◽  
Surgical Reconstruction ◽  
Modeling Framework ◽  
Element Analysis ◽  
Anterior Cruciate

Abstract Anterior Cruciate Ligament (ACL) tear is one of the most common knee injuries. The ACL reconstruction surgery aims to restore healthy knee function by replacing the injured ligament with a graft. Proper selection of the optimal surgery parameters is a complex task. To this end, we developed an automated modeling framework that accepts subject-specific geometries and produces finite element knee models incorporating different surgical techniques. Initially, we developed a reference model of the intact knee, validated with data provided by the OpenKnee project. This helped us evaluate the effectiveness of estimating ligament stiffness directly from MRI. Next, we performed a plethora of “what-if” simulations, comparing responses with the reference model. We found that a) increasing graft pretension and radius reduces relative knee displacement, b) the correlation of graft radius and tension should not be neglected, c) graft fixation angle of 20 degrees can reduce knee laxity, and d) single-versus double-bundle techniques demonstrate comparable performance in restraining knee translation. In most cases, these findings confirm reported values from comparative clinical studies. The numerical models are made publicly available, allowing for experimental reuse and lowering the barriers for meta-studies. The modeling approach proposed here can complement orthopedic surgeons in their decision-making.

Stress Classification Using the R-Node Method

2006 ◽  
Author(s):  
Ihab F. Z. Fanous ◽  
R. Seshadri
Keyword(s):  
Experimental Data ◽  
Complex Geometries ◽  
Element Analysis ◽  
Shell Elements ◽  
Linear Elastic ◽  
Stress Classification ◽  
Wide Range ◽  
Asme Code ◽  
Section Viii ◽  
Division 2

The ASME Code Section III and Section VIII (Division 2) provide stress classification guidelines to interpret the results of a linear elastic finite element analysis. These guidelines enable the splitting of the generated stresses into primary, secondary and peak. The code gives some examples to explain the suggested procedures. Although these examples may reflect a wide range of applications in the field of pressure vessel and piping, the guidelines are difficult to use with complex geometries. In this paper, the r-node method is used to investigate the primary stresses and their locations in both simple and complex geometries. The method is verified using the plane beam and axisymmetric torispherical head. Also, the method is applied to analyze 3D straight and oblique nozzle modeled using both solid and shell elements. The results of the analysis of the oblique nozzle are compared with recently published experimental data.

Feedback Control Applied to Finite Element Models of Morphing Structures

2014 ◽  
Author(s):  
Christopher Bertagne ◽  
Peyman Moghadas ◽  
Richard Malak ◽  
Darren Hartl
Keyword(s):  
Finite Element ◽  
Feedback Control ◽  
Finite Element Model ◽  
Numerical Models ◽  
Element Model ◽  
High Fidelity ◽  
Element Analysis ◽  
Wide Range ◽  
Flexible Framework ◽  
The Finite Element Model

This paper demonstrates a framework for integrating full feedback control with a high-fidelity finite element model in order to simulate control of morphing structures. Most of the previous finite element simulations involving control of morphing structures consider the effects of the controller, but do not incorporate true feedback control. Additionally, when feedback control is considered, numerical models other than finite element analysis are used. Thus, a trade-off must be made between a high-fidelity model and consideration of feedback control. In this work, these aspects are unified to create a tool that can simulate real-time feedback control of a finite element model. The framework itself consists of two components: the finite element model and the controller. The finite element model must be capable of varying external loads as the solution evolves in time. In this paper, the finite element model is implemented in ABAQUS. The controller component is written in Python. In order to ensure the framework is suitable for a wide range of applications, no assumptions are made regarding the natures of the finite element model or the control architecture. Additionally, the components are designed to be modular. For example, simulating different controller architectures does not require alteration of the finite element model. The result is a highly flexible framework that is particularly well-suited for validating and demonstrating controllers on high-fidelity models.

scholarly journals Torque Ripple Minimization of the Permanent Magnet Synchronous Machine by Modulation of the Phase Currents

Sensors ◽  
2020 ◽  
Vol 20 (8) ◽  
pp. 2406 ◽  
Author(s):  
Cezary Jędryczka ◽  
Dawid Danielczyk ◽  
Wojciech Szeląg
Keyword(s):  
Permanent Magnet ◽  
Permanent Magnets ◽  
Numerical Models ◽  
Permanent Magnet Synchronous Motor ◽  
Torque Ripple ◽  
Minimization Method ◽  
Element Analysis ◽  
Current Harmonics ◽  
Wide Range ◽  
Zero Sequence

This paper deals with the torque ripple minimization method based on the modulation of the phase currents of the permanent-magnet synchronous motor (PMSM) drive. The shape of the supply current waveforms reducing the torque ripple of the machine considered was determined on the basis of finite element analysis (FEA). In the proposed approach, the machine is supplied by a six-leg inverter in order to allow for the injection of zero sequence current harmonics. Two test PMSMs with fractional-slot concentrated windings (FSCW) and surface-mounted permanent magnets (SPMs) have been examined as a case study problem. Wide-range fractional analyses were performed using developed numerical models of the electromagnetic field distribution in the considered machines. The results obtained show that the level of torque ripple in FSCW PMSMs can be effectively reduced by the modulation of the phase currents under the six-leg inverter supply.

scholarly journals Torsional and Transversal Stiffness of Orthotropic Sandwich Panels

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5016 ◽  
Author(s):  
Tomasz Garbowski ◽  
Tomasz Gajewski ◽  
Jakub Krzysztof Grabski
Keyword(s):  
Transverse Shear ◽  
Numerical Models ◽  
Analytical Formula ◽  
Shear Stiffness ◽  
Torsion Test ◽  
Torsional Stiffness ◽  
Identical Result ◽  
Shell Elements ◽  
Aspect Ratios ◽  
Wide Range

In the present work, an analytical equation describing the plate torsion test taking into account the transverse shear stiffness in sandwich plates is derived and numerically validated. Transverse shear becomes an important component if the analyzed plate or shell is thick with respect to the in-plane dimensions and/or its core has significantly lower stiffness than the outer faces. The popular example of such a sandwich plate is a corrugated cardboard, widely used in the packaging industry. The flat layers of a corrugated board are usually made of thicker (stronger) material than that used for the corrugated layer, the role of which is rather to keep the outer layers at a certain distance, to ensure high bending stiffness of the plate. However, the soft core of such a plate usually has a low transverse shear stiffness, which is often not considered in the plate analysis. Such simplification may lead to significant calculation errors. The paper presents the generalization of the Reissner’s analytical formula, which describes the torsional stiffness of the plate sample including two transverse shear stiffnesses. The paper also presents the implementation of the numerical model of the plate torsion test including the transverse shear stiffnesses. Both approaches are compared with each other on a wide range of material parameters and different aspect ratios of the specimen. It has been proved that both analytical and numerical formulations lead to an identical result. Finally, the performance of presented formulations is compared with other numerical models using commercial implementation of various Reissner–Mindlin shell elements and other analytical formulas from the literature. The comparison shows good agreement of presented theory and numerical implementation with other existing approaches.

Stress Classification Using the r-Node Method

2006 ◽  
Vol 129 (4) ◽  
pp. 676-682 ◽  
Author(s):  
Ihab F. Z. Fanous ◽  
R. Seshadri
Keyword(s):  
Experimental Data ◽  
Finite Element Analysis ◽  
Complex Geometries ◽  
Element Analysis ◽  
Shell Elements ◽  
Linear Elastic ◽  
Stress Classification ◽  
Wide Range ◽  
Asme Code ◽  
Division 2

The ASME Code Secs. III and VIII (Division 2) provide stress-classification guidelines to interpret the results of a linear elastic finite element analysis. These guidelines enable the splitting of the generated stresses into primary, secondary, and peak. The code gives some examples to explain the suggested procedures. Although these examples may reflect a wide range of applications in the field of pressure vessel and piping, the guidelines are difficult to use with complex geometries. In this paper, the r-node method is used to investigate the primary stresses and their locations in both simple and complex geometries. The method is verified using the plane beam and axisymmetric torispherical head. Also, the method is applied to analyze 3D straight and oblique nozzles modeled using both solid and shell elements. The results of the analysis of the oblique nozzle are compared with recently published experimental data.

Comparison on Stress Concentration Factors of Y/T Tubular Joints Between Numerical and Parametric Formulation Results

2005 ◽  
Author(s):  
Stefano Baratella ◽  
Dario Boote ◽  
Fabio Petrillo ◽  
Fabrizio Stefani
Keyword(s):  
Stress Concentration ◽  
Numerical Models ◽  
High Stress ◽  
Bending Moment ◽  
Steel Structures ◽  
Element Analysis ◽  
High Stress Concentration ◽  
Wide Range ◽  
Long Time ◽  
Stress Concentration Factors

The action of environmental loads such as wind and waves on offshore steel structures is locally emphasized by complex tubular connections, giving place to high stress concentration in correspondence of welds between pipe elements. This phenomenon, which heavily influences the fatigue life of the joint and, as a consequence, the operability of the whole platform, can be quantified by the Stress Concentration Factor. SCF can be determined either by experimental approach, numerical analysis and parametrical formulas developed mainly in the seventies-eighties by specialized authors like Kuang, Wordsworth, Smedley and Efthymiou. Even though these formulas, quoted as reference in the main world recognized rules, represented for a long time a useful tool for the designers of most projects, some discrepancies have been found to exist among them. A research has then been jointly promoted by University of Genoa and RINA Industry in order to compare the results of the parametric formulas with those coming from a finite element analysis performed on very refined numerical models made of brick elements. In this investigation attention has been focused on Y/T type joints; a wide range of configurations has been analysed by varying the most important parameters defining the geometry of the joint. Each configuration has been loaded by axial force and in/out of plane bending moment.

scholarly journals Two-Dimensional Numerical Modeling of Flow in Physical Models of Rock Vane and Bendway Weir Configurations

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 458
Author(s):  
Drew C. Baird ◽  
Benjamin Abban ◽  
S. Michael Scurlock ◽  
Steven B. Abt ◽  
Christopher I. Thornton
Keyword(s):  
Numerical Modeling ◽  
Physical Model ◽  
Numerical Models ◽  
Hydraulic Performance ◽  
Physical Models ◽  
Protection Measures ◽  
Design Engineers ◽  
Model Study ◽  
Study Results ◽  
Wide Range

While there are a wide range of design recommendations for using rock vanes and bendway weirs as streambank protection measures, no comprehensive, standard approach is currently available for design engineers to evaluate their hydraulic performance before construction. This study investigates using 2D numerical modeling as an option for predicting the hydraulic performance of rock vane and bendway weir structure designs for streambank protection. We used the Sedimentation and River Hydraulics (SRH)-2D depth-averaged numerical model to simulate flows around rock vane and bendway weir installations that were previously examined as part of a physical model study and that had water surface elevation and velocity observations. Overall, SRH-2D predicted the same general flow patterns as the physical model, but over- and underpredicted the flow velocity in some areas. These over- and underpredictions could be primarily attributed to the assumption of negligible vertical velocities. Nonetheless, the point differences between the predicted and observed velocities generally ranged from 15 to 25%, with some exceptions. The results showed that 2D numerical models could provide adequate insight into the hydraulic performance of rock vanes and bendway weirs. Accordingly, design guidance and implications of the study results are presented for design engineers.

scholarly journals EXPRESS: Overcoming the Cold Start Problem of CRM using a Probabilistic Machine Learning Approach

2021 ◽  
pp. 002224372110329
Author(s):  
Nicolas Padilla ◽  
Eva Ascarza
Keyword(s):  
Machine Learning ◽  
Cold Start ◽  
Customer Relationship ◽  
Exponential Families ◽  
Modeling Framework ◽  
Wide Range ◽  
The Moment ◽  
Probabilistic Machine Learning ◽  
Marketing Actions ◽  
Cold Start Problem

The success of Customer Relationship Management (CRM) programs ultimately depends on the firm's ability to identify and leverage differences across customers — a very diffcult task when firms attempt to manage new customers, for whom only the first purchase has been observed. For those customers, the lack of repeated observations poses a structural challenge to inferring unobserved differences across them. This is what we call the “cold start” problem of CRM, whereby companies have difficulties leveraging existing data when they attempt to make inferences about customers at the beginning of their relationship. We propose a solution to the cold start problem by developing a probabilistic machine learning modeling framework that leverages the information collected at the moment of acquisition. The main aspect of the model is that it exibly captures latent dimensions that govern the behaviors observed at acquisition as well as future propensities to buy and to respond to marketing actions using deep exponential families. The model can be integrated with a variety of demand specifications and is exible enough to capture a wide range of heterogeneity structures. We validate our approach in a retail context and empirically demonstrate the model's ability at identifying high-value customers as well as those most sensitive to marketing actions, right after their first purchase.

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