Simulation of Cross-Sectional Geometry During Laser Powder Deposition of Tall Thin-Walled and Thick-Walled Features

2016 ◽  
Author(s):  
Keith A. Bourne ◽  
Parisa Farahmand ◽  
David Roberson
Keyword(s):  
Average Error ◽  
Calibration Data ◽  
Stainless Steel 316L ◽  
Cross Sectional ◽  
Laser Powder Deposition ◽  
Powder Deposition ◽  
Thin Walled ◽  
The Cross ◽  
Validation Tests ◽  
Catchment Model

A model of the laser powder deposition (LPD) process is presented, which predicts the cross-sectional geometry of parts that are made up of thin-walled and thick-walled features, deposited via multiple passes. The model builds up the part shape incrementally by predicting the cross-section of a bead of material deposited on the part, updating part shape to reflect the added material, and repeating for each additional deposition pass. The effects of laser power and deposition speed are accounted for empirically, and the effect of nozzle stand-off distance is accounted for via a powder catchment model suitable for coaxial deposition nozzles. The model was calibrated via deposition experiments using stainless steel 316L powder and via measurement of nozzle characteristics. Validation tests showed that the powder catchment model captured the effect of nozzle stand-off distance on deposited bead size. Validation tests also showed that the model predicted the overall shapes of both thin-walled and thick-walled features, including rounding present at the edges of some thick-walled features. Using calibration data from short thick-walled depositions, the average error in predicted feature height, after ten layers, was 9.3% and 9.5% for thin-walled and thick-walled features, respectively. The model was also shown to predict the effects of using a step-up distance per layer that is too small, resulting in inefficient deposition, or too large, resulting in deposition failure after a few layers.

Multi-Scale Overlapping Domain Decomposition to Consider Local Deformations in the Analysis of Thin-Walled Members

2014 ◽  
Vol 553 ◽  
pp. 667-672
Author(s):  
R. Emre Erkmen
Keyword(s):  
Numerical Technique ◽  
Global Analysis ◽  
Local Deformation ◽  
Local Analysis ◽  
Type Model ◽  
Cross Sectional ◽  
Multi Scale ◽  
Shell Type ◽  
Thin Walled ◽  
The Cross

Thin-walled members that have one dimension relatively large in comparison to the cross-sectional dimensions are usually modelled by using beam-column type finite element formulations. Beam-column elements however, are based on the assumption of rigid cross-section, thus they cannot consider the cross-sectional deformations such as local buckling and only allows considerations of the beam axis behaviour such as flexural or lateral-torsional buckling. Shell-type finite elements can be used to model the structure in order to consider these local deformation effects. Based on the Bridging multi-scale approach, this study proposes a numerical technique that is able to split the global analysis, which is performed by using simple beam-type elements, from the local analysis which is based on more sophisticated shell-type elements. As a result, the proposed multi-scale method allows the usage of shell elements in a local region to incorporate the local deformation effects on the overall behaviour of thin-walled members without necessitating a shell-type model for the whole member.

Collapse of Thin-Walled Elliptical Tubes for High Values of Major-to-Minor Axis Ratio

1993 ◽  
Vol 115 (4A) ◽  
pp. 432-440 ◽  
Author(s):  
C. Ribreau ◽  
S. Naili ◽  
M. Bonis ◽  
A. Langlet
Keyword(s):  
Contact Pressure ◽  
Cross Section ◽  
External Pressure ◽  
Straight Line Segment ◽  
Minor Axis ◽  
Cross Sectional ◽  
Axis Ratio ◽  
Straight Line ◽  
Thin Walled ◽  
The Cross

The topic of this study concerns principally representative models of some elliptical thin-walled anatomic vessels and polymeric tubes under uniform negative transmural pressure p (internal pressure minus external pressure). The ellipse’s ellipticity ko, defined as the major-to-minor axis ratio, varies from 1 up to 10. As p decreases from zero, at first the cross-section becomes somewhat oval, then the opposite sides touch in one point at the first-contact pressure pc. If p is lowered beneath pc, the curvature of the cross-section at the point of contact decreases until it becomes zero at the osculation pressure or the first line-contact pressure p1. For p<p1, the contact occurs along a straight-line segment, the length of which increases as p decreases. The pressures pc and p1 are determined numerically for various values of the wall thickness of the tubes. The nature of contact is especially described. The solution of the related nonlinear, two-boundary-values problem is compared with previous experimental results which give the luminal cross-sectional area (from two tubes), and the area of the mid-cross-section (from a third tube).

A super-convergent thin-walled 3D beam element for analysis of laminated composite structures with arbitrary cross-section

2021 ◽  
pp. 1-23
Author(s):  
M. Talele ◽  
M. van Tooren ◽  
A. Elham
Keyword(s):  
Cross Sections ◽  
Composite Structures ◽  
Three Dimensional ◽  
Laminated Composite ◽  
Beam Element ◽  
Arbitrary Cross Section ◽  
Beam Model ◽  
Cross Sectional ◽  
Thin Walled ◽  
The Cross

Abstract An efficient, fully coupled beam model is developed to analyse laminated composite thin-walled structures with arbitrary cross-sections. The Euler–Lagrangian equations are derived from the kinematic relationships for a One-Dimensional (1D) beam representing Three-Dimensional (3D) deformations that take into account the cross-sectional stiffness of the composite structure. The formulation of the cross-sectional stiffness includes all the deformation effects and related elastic couplings. To circumvent the problem of shear locking, exact solutions to the approximating Partial Differential Equations (PDEs) are obtained symbolically instead of by numerical integration. The developed locking-free composite beam element results in an exact stiffness matrix and has super-convergent characteristics. The beam model is tested for different types of layup, and the results are validated by comparison with experimental results from literature.

Experimental Study on Residual Cross-Sectional Flattening of Thin-Walled Pipes Under Pure Plastic Bending

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Ziqian Zhang
Keyword(s):  
Cross Section ◽  
Wall Thickness ◽  
Residual Deformation ◽  
Outer Diameter ◽  
Cross Sectional ◽  
Plastic Bending ◽  
Thin Walled Pipe ◽  
Bending Radius ◽  
Thin Walled ◽  
The Cross

Abstract Cross-sectional ovalization (ovalization) usually occurs when thin-walled pipe is subjected to large plastic bending. This paper is concerned with residual deformation of thin-walled pipe's cross section in a radial direction when external bending moment is removed. In order to clarify the fundamental ovalization characteristics, find out what factors influence the residual flattening (value of ovalization), the ovalization behavior is investigated experimentally. The experiments are carried out on 21 stainless steel specimens with different geometric parameters under different bending radii by means of a four-point pure bending device. The residual cross-sectional flattenings are monitored continuously by scanning the cross section periodically along the circumferential direction. From the experimental results, it is observed that the cross-sectional shape of the thin-walled pipe is not perfect standard ellipse, and the appearance of the maximum residual flattening is usually found in the direction normal to the neutral surface. It is also revealed the relationships between the residual flattening and the bending radius, the wall thickness, and the pipe outer diameter, i.e., the residual flattening increases as the bending radius and the wall thickness reduce, but it increases as the outer diameter increases. These results are expected to find their potential application in thin-walled pipe bending operation.

Feedforward Laser Power Specification for Uniform Cooling of Thin-Walled Parts

2004 ◽  
Author(s):  
Umesh A. Korde ◽  
Michael A. Langerman ◽  
Gregory A. Buck ◽  
Vojislav D. Kalanovic
Keyword(s):  
Laser Power ◽  
Thermal Model ◽  
Deposition Process ◽  
Ongoing Research ◽  
Laser Powder Deposition ◽  
Powder Deposition ◽  
The Matrix ◽  
Thin Walled ◽  
The Time Domain ◽  
Power Sequence

This paper presents results from ongoing research on thermal-model based feedforward specification of laser power in a laser powder deposition process. The goal of this algorithm is to compute, before deposition of a layer, the laser power sequence and distribution that would produce a desired temperature distribution over that layer. This in turn will enable uniform cooling of the layer and avoid build up of residual stresses. In this paper, results based on a simplified thermal model and second-order spatial discretization are presented. Two types of discretization in the time domain are examined. The matrix-exponential-based discretization is expected to be more accurate at lower laser speeds. The desired laser power sequence and the resulting temperature histories for a prescribed laser speed are discussed within the context of a thin-walled part.

Influence of Cross-Section Distortion on the Bending Vibration of Thin-Walled Beams of H Section

1964 ◽  
Vol 6 (3) ◽  
pp. 211-218 ◽  
Author(s):  
A. D. S. Barr ◽  
T. Duthie
Keyword(s):  
Differential Equations ◽  
Cross Section ◽  
Reasonable Agreement ◽  
Experimental Results ◽  
Hamilton’S Principle ◽  
Hamilton's Principle ◽  
Bending Vibration ◽  
Cross Sectional ◽  
Thin Walled ◽  
The Cross

Approximate differential equations describing the bending vibration of beams of thin-walled H section, in which the distortion of the cross-section in its own plane is taken into account, are derived from Hamilton's principle using an assumed form for the cross-section deformation. Only the simplest of the cross-sectional deformation configurations which will couple with ordinary bending is considered. The variation with wavelength of the two spectra of frequencies which result from this coupling of the bending and cross-sectional motions is shown for several section geometries. Theoretical curves show reasonable agreement with experimental results from free beams.

scholarly journals AXIAL COMPRESSION TESTING OF BAMBOO PLYWOOD-ENCASED THIN-WALLED STEEL TUBE/STONE DUST CONCRETE COLUMNS

Wood Research ◽  
2021 ◽  
Vol 66 (3) ◽  
pp. 489-504
Author(s):  
Weifeng Zhao ◽  
Zongjian Luo ◽  
Yajun Li ◽  
Jing Zhou
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Steel Tube ◽  
Ultimate Bearing Capacity ◽  
Cross Sectional ◽  
Content Ratio ◽  
Stone Dust ◽  
Spacing Ratio ◽  
Thin Walled ◽  
The Cross

A novel structural member, the bamboo plywood-encased thin-walled steel tube/stone dust concrete composite column (BSDCC), was investigated in this study. Axial compression tests were conducted on 10 BSDCC specimens; their failure characteristics and modes were examined, and the effects of the stone-dust concrete content ratio and strength, specimen slenderness ratio, cross-sectional composition and binding bar confinement pattern, and binding bar spacing ratio on the bearing capacity and deformation of the columns were investigated. Two main compressive failure modes were observed: (1) adhesive failure by cracking and debonding between the bamboo plywood boards and between the bamboo plywood and the steel tube and (2) compressive-flexural failure of the bamboo plywood between the binding bars in the middle of the specimen. For specimens with the same cross-sectional dimensions, the cross-sectional content ratio of the stone dust concrete impacted the deformation and failure mode but did not significantly affect the ultimate bearing capacity. The bearing capacity decreased with increasing specimen slenderness and binding bar spacing ratio and increased with increasing stone dust concrete strength and bamboo plywood constraint (in terms of the cross-sectional composition and binding bar restraint pattern). A model for the ultimate bearing capacity of BSDCCs was established through regression analysis.

scholarly journals On the role of large cross-sectional deformations in the nonlinear analysis of composite thin-walled structures

2020 ◽  
Author(s):  
E. Carrera ◽  
A. Pagani ◽  
R. Augello
Keyword(s):  
Composite Structures ◽  
Laminated Composite ◽  
Nonlinear Effects ◽  
Higher Order ◽  
Cross Sectional ◽  
Thin Walled Structures ◽  
Static Responses ◽  
Geometrical Nonlinear ◽  
Thin Walled ◽  
The Cross

AbstractThe geometrical nonlinear effects caused by large displacements and rotations over the cross section of composite thin-walled structures are investigated in this work. The geometrical nonlinear equations are solved within the finite element method framework, adopting the Newton–Raphson scheme and an arc-length method. Inherently, to investigate cross-sectional nonlinear kinematics, low- to higher-order theories are employed by using the Carrera unified formulation, which provides a tool to generate refined theories of structures in a systematic manner. In particular, beams and shell-like laminated composite structures are analyzed using a layerwise approach, according to which each layer has its own independent kinematics. Different stacking sequences are analyzed, to highlight the influence of the cross-ply angle on the static responses. The results show that the geometrical nonlinear effects play a crucial role, mainly when higher-order theories are utilized.

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