Modelling and measuring the thermal behaviour of the molten pool in closed-loop controlled laser-based additive manufacturing

2003 ◽  
Vol 217 (4) ◽  
pp. 441-452 ◽  
Author(s):  
D Hu ◽  
R Kovacevic
Keyword(s):  
Finite Element ◽  
Additive Manufacturing ◽  
Thermal Behaviour ◽  
Molten Pool ◽  
Closed Loop ◽  
Three Dimensional ◽  
Infrared Camera ◽  
Element Model ◽  
Experimental Investigations ◽  
Process Conditions

Laser-based additive manufacturing (LBAM) is a promising manufacturing technology that can be widely applied in solid freeform fabrication (SFF), component recovery and regeneration, and surface modification. The thermal behaviour of the molten pool is one of the critical factors that influences laser deposition indices such as geometrical accuracy, material properties and residual stresses. In this paper, a three-dimensional finite element model is developed using ANSYS to simulate the thermal behaviour of the molten pool in building a single-bead wall via a closed-loop controlled LBAM process in which the laser power is controlled to keep the width of the molten pool constant. The temperature distribution, the geometrical feature of the molten pool and the cooling rate under different process conditions are investigated. To verify the simulation results, the thermal behaviour of the molten pool is measured by a coaxially installed infrared camera in experimental investigations of a closed-loop controlled LBAM process. Results from finite element thermal analysis provide guidance for the process parameter selection in LBAM, and develop a base for further residual stress analysis.

Investigation of Vibration Characteristics of the Ligamentous Lumbar Spine Using the Finite Element Approach

1994 ◽  
Vol 116 (4) ◽  
pp. 377-383 ◽  
Author(s):  
Vijay K. Goel ◽  
Hosang Park ◽  
Weizeng Kong
Keyword(s):  
Finite Element ◽  
Resonant Frequency ◽  
Cyclic Load ◽  
Static Load ◽  
Three Dimensional ◽  
Element Model ◽  
Upper Body ◽  
Experimental Investigations ◽  
Flexion Extension

A nonlinear, three-dimensional finite element model of the ligamentous L4-SI segment was developed to analyze the dynamic response of the spine in the absence of damping. The effects of the upper body mass were simulated by including a mass of 40 kg on the L4 vertebral body. The modal analyses of the model indicated a resonant frequency of 17.5 Hz in axial mode and 3.8 Hz in flexion-extension mode. Accordingly, the predicted responses for the cyclic load of −400 ± 40 N applied at four different frequencies (5, 11, 16.5, and 25 Hz) were compared with the corresponding results for axial compressive static loads (−360, and −440 N). As compared to the static load cases, the predicted responses were higher for the cyclic loading. For example, the effect of cyclic load at 11 Hz was to produce significant changes (9.7 – 19.0 percent) in stresses, loads transmitted through the facets, intradiscal pressure (IDP), disk bulge, as compared to the static load predictions. The responses were found to be frequency dependent as well; supporting the in vivo observations of other investigators that the human spine has a resonant frequency. For example, the 11 Hz model (DYN11) compared to the DYN5 model showed an increase in majority of the predicted parameters. The parameters showed an increase with frequency until 17.5 Hz (resonant frequency of the model); thereafter a decrease at 25 Hz. A chronic change in these parameters, especially at the resonant frequency, beyond the “base” values may trigger the bone remodeling process leading to spinal degeneration/disorders associated with chronic vibration exposure. Future directions for extending the present model as a complement to the experimental investigations are also discussed.

Three-Dimensional Simulations of Blood Flow With Systemic Arterial Baroreflex

2009 ◽  
Author(s):  
H. J. Kim ◽  
C. A. Taylor
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Closed Loop ◽  
Three Dimensional ◽  
Element Model ◽  
Loop System ◽  
Loop Model ◽  
Arterial Baroreflex ◽  
Closed Loop System ◽  
Venous Compliance

The systemic arterial baroreflex controls the systemic arterial pressure to maintain homeostasis. The carotid sinus and aortic arch are the major systemic arterial baroreceptors, and they respond to distention of the carotid and aortic walls causing compensatory mechanisms, which regulate heart rate, cardiac contractility, peripheral arterial resistance, venous compliance, and venous unstressed volume [1]. In this study, we connect a feedback control loop, which represents the systemic arterial baroreflex, to the closed loop system we developed in a previous study [2]. The three-dimensional finite element model of the aorta and the closed loop system enable us to obtain not only the physiologic flow rate and pressure fields of the finite element model but also the global characteristics of the cardiovascular system from the closed loop model. We study the autoregulatory mechanisms occurring due to the systemic arterial baroreflex by considering the interactions between the heart and the systemic and pulmonary circulations.

Finite Element Modeling of Hybrid Friction Diffusion Welding of Tube–Tubesheet Joints

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
Fadi Al-Badour
Keyword(s):  
Finite Element ◽  
Numerical Study ◽  
Three Dimensional ◽  
Infrared Camera ◽  
Element Model ◽  
Optical Microscope ◽  
Steel Tube ◽  
Diffusion Welding ◽  
Temperature Dependent ◽  
Mechanical Nature

Abstract A three-dimensional thermo-mechanical finite element model (FEM) was developed and solved to study the feasibility of hybrid friction diffusion bonding (HFDB) technique for welding tube–tubesheet joints using Abaqus/explicit enviroment. Considering the process thermo-mechanical nature, temperature-dependent material properties and Johnson–Cook model were adopted. Two tube configurations were considered in the numerical study; zero projection (flush) and 3 mm projection (extended). For validation purposes, HFDB of tube–tubesheet was experimentally performed on a 19 mm (¾ in.) ASTM 179 cold-drawn carbon steel tube into ASTM A516-70 tubesheet, considering a flush tube configuration. The tool–workpiece temperature was measured using infrared camera, and produced joints were sectioned and examined under optical microscope. A good agreement was found between numericaly estimated temperatures and material deformation with experimentaly measured ones. According to the estimated results, spring back of tube was found to negatively affect the joint integrity. Also, contact stresses during processing phase were found less in the projected tube (extended) as compared to the flush one.

Torsional Analysis of a Steel Cord-Rubber Tire Belt Structure

1996 ◽  
Vol 24 (4) ◽  
pp. 339-348 ◽  
Author(s):  
R. M. V. Pidaparti
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Composite Structures ◽  
Three Dimensional ◽  
Element Model ◽  
Torsional Stiffness ◽  
Element Analysis ◽  
Rubber Belt ◽  
Steel Cord ◽  
Torsional Analysis

Abstract A three-dimensional (3D) beam finite element model was developed to investigate the torsional stiffness of a twisted steel-reinforced cord-rubber belt structure. The present 3D beam element takes into account the coupled extension, bending, and twisting deformations characteristic of the complex behavior of cord-rubber composite structures. The extension-twisting coupling due to the twisted nature of the cords was also considered in the finite element model. The results of torsional stiffness obtained from the finite element analysis for twisted cords and the two-ply steel cord-rubber belt structure are compared to the experimental data and other alternate solutions available in the literature. The effects of cord orientation, anisotropy, and rubber core surrounding the twisted cords on the torsional stiffness properties are presented and discussed.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

scholarly journals Comparison of Tooth- and Bone-Borne Appliances on the Stress Distributions and Displacement Patterns in the Facial Skeleton in Surgically Assisted Rapid Maxillary Expansion—A Finite Element Analysis (FEA) Study

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1152
Author(s):  
Rafał Nowak ◽  
Anna Olejnik ◽  
Hanna Gerber ◽  
Roman Frątczak ◽  
Ewa Zawiślak
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Rapid Maxillary Expansion ◽  
Stress Distributions ◽  
Maxillary Expansion ◽  
Facial Skeleton ◽  
Element Analysis ◽  
Maxillary Constriction

The aim of this study was to compare the reduced stresses according to Huber’s hypothesis and the displacement pattern in the region of the facial skeleton using a tooth- or bone-borne appliance in surgically assisted rapid maxillary expansion (SARME). In the current literature, the lack of updated reports about biomechanical effects in bone-borne appliances used in SARME is noticeable. Finite element analysis (FEA) was used for this study. Six facial skeleton models were created, five with various variants of osteotomy and one without osteotomy. Two different appliances for maxillary expansion were used for each model. The three-dimensional (3D) model of the facial skeleton was created on the basis of spiral computed tomography (CT) scans of a 32-year-old patient with maxillary constriction. The finite element model was built using ANSYS 15.0 software, in which the computations were carried out. Stress distributions and displacement values along the 3D axes were found for each osteotomy variant with the expansion of the tooth- and the bone-borne devices at a level of 0.5 mm. The investigation showed that in the case of a full osteotomy of the maxilla, as described by Bell and Epker in 1976, the method of fixing the appliance for maxillary expansion had no impact on the distribution of the reduced stresses according to Huber’s hypothesis in the facial skeleton. In the case of the bone-borne appliance, the load on the teeth, which may lead to periodontal and orthodontic complications, was eliminated. In the case of a full osteotomy of the maxilla, displacements in the buccolingual direction for all the variables of the bone-borne appliance were slightly bigger than for the tooth-borne appliance.

Reduction of Free-Edge Stress Concentration

1985 ◽  
Vol 52 (4) ◽  
pp. 801-805 ◽  
Author(s):  
P. R. Heyliger ◽  
J. N. Reddy
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Free Edge ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Interlaminar Shear ◽  
Three Dimensional Elasticity

A quasi-three dimensional elasticity formulation and associated finite element model for the stress analysis of symmetric laminates with free-edge cap reinforcement are described. Numerical results are presented to show the effect of the reinforcement on the reduction of free-edge stresses. It is observed that the interlaminar normal stresses are reduced considerably more than the interlaminar shear stresses due to the free-edge reinforcement.

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