Ultrascalable Implicit Finite Element Analyses in Solid Mechanics with over a Half a Billion Degrees of Freedom

2005 ◽  
Author(s):  
M.F. Adams ◽  
H.H. Bayraktar ◽  
T.M. Keaveny ◽  
P. Papadopoulos
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Solid Mechanics ◽  
Finite Element Analyses

A New Stress-Intensity Factor Solution for an External Surface Crack in Spheres

2021 ◽  
Author(s):  
James C. Sobotka ◽  
Yi-Der Lee ◽  
Joseph W. Cardinal ◽  
R. Craig McClung
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Crack Front ◽  
Surface Crack ◽  
Degrees Of Freedom ◽  
External Surface ◽  
Crack Plane ◽  
Finite Element Analyses ◽  
Stress Variations ◽  
Geometric Formulation

Abstract This paper describes a new stress-intensity factor (SIF) solution for an external surface crack in a sphere that expands capabilities previously available for this common pressure vessel geometry. The SIF solution employs the weight function (WF) methodology that enables rapid calculations of SIF values. The WF methodology determines SIF values from the nonlinear stress variations computed for the uncracked geometry, e.g., from service stresses and/or residual stresses. The current approach supports two degrees of freedom that denote the two crack tips located normal to the surface and the surface of the sphere. The geometric formulation of this solution enforces an elliptical crack front, maintains normality of the crack front with the free surface, and supports two degrees of freedom for fatigue crack growth from an internal crack tip and a surface crack tip. The new SIF solution accommodates spherical geometries with an exterior diameter greater than or equal to four times the thickness. This WF SIF solution has been combined with stress variations common for spherical pressure vessels: uniform internal pressure on the interior surface, uniform tension on the crack plane, and uniform bending on the crack plane. This paper provides a complete overview of this solution. We present for the first time the geometric formulation of the crack front that enables the new functionality and set the geometric limits of the solution, e.g., the maximum size and shape of the crack front. The paper discusses the bivariant WF formulation used to define the SIF solution and details the finite element analyses employed to calibrate terms in the WF formulation. A summary of preliminary verification efforts demonstrates the credibility of this solution against independent results from finite element analyses. We also compare results of this new solution against independent SIFs computed by finite element analyses, legacy SIF solutions, API 579, and FITNET. These comparisons indicate that the new WF solution compares favorably with results from finite element analyses. This paper summarizes ongoing efforts to improve and extend this solution, including formal verification and development of an internal surface crack model. Finally, we discuss the capabilities of this solution’s implementation in NASGRO® v10.0.

Large Scale Finite Element Analysis Via Assembly-Free Deflated Conjugate Gradient

2014 ◽  
Vol 14 (4) ◽  
Author(s):  
Praveen Yadav ◽  
Krishnan Suresh
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Conjugate Gradient ◽  
Degrees Of Freedom ◽  
Large Scale ◽  
Solid Mechanics ◽  
Processing Unit ◽  
Element Analysis ◽  
Central Processing ◽  
Computational Bottleneck

Large-scale finite element analysis (FEA) with millions of degrees of freedom (DOF) is becoming commonplace in solid mechanics. The primary computational bottleneck in such problems is the solution of large linear systems of equations. In this paper, we propose an assembly-free version of the deflated conjugate gradient (DCG) for solving such equations, where neither the stiffness matrix nor the deflation matrix is assembled. While assembly-free FEA is a well-known concept, the novelty pursued in this paper is the use of assembly-free deflation. The resulting implementation is particularly well suited for large-scale problems and can be easily ported to multicore central processing unit (CPU) and graphics-programmable unit (GPU) architectures. For demonstration, we show that one can solve a 50 × 106 degree of freedom system on a single GPU card, equipped with 3 GB of memory. The second contribution is an extension of the “rigid-body agglomeration” concept used in DCG to a “curvature-sensitive agglomeration.” The latter exploits classic plate and beam theories for efficient deflation of highly ill-conditioned problems arising from thin structures.

Enhancements to AMB Force Measurement Procedures for Application to a Rocket Thrust Measurement System

2000 ◽  
Author(s):  
Joe Imlach ◽  
Mary E. F. Kasarda ◽  
P. A. Balaji
Keyword(s):  
Finite Element ◽  
Measurement System ◽  
Degrees Of Freedom ◽  
Force Measurement ◽  
Calibration Procedure ◽  
Magnetic Bearings ◽  
Finite Element Analyses ◽  
Thrust Measurement ◽  
On Line ◽  
Rocket Thrust

Active Magnetic Bearings (AMBs) can be used concurrently as support bearings and as load cells for the measurement of support forces. This paper discusses the preliminary design for a test rig to simulate a full-scale rocket thrust measurement system utilizing AMBs and procedures that have been developed to enhance the use of AMBs in this application. These enhancements include the development of a model of the effect of fringing on force measurements and an on-line calibration procedure. The fringing effect model is based on actuator geometry and has been verified through finite element analyses. On-line calibration procedures for a magnetic thrust bearing arrangement have also been developed and verified through finite element analyses. Since the rocket thrust measurement system is not rotating, planar magnetic bearings will also be used for vertical support and will utilize the same calibration procedure, resulting in force and torque measurements in all six degrees of freedom.

scholarly journals Vibration Induced by Moving Cranes in High-Tech Buildings due to Rail Pad Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
S. H. Ju ◽  
H. H. Kuo ◽  
S. H. Ni
Keyword(s):  
Finite Element ◽  
Displacement Field ◽  
Degrees Of Freedom ◽  
Laboratory Experiments ◽  
Low Cost ◽  
High Tech ◽  
Full Model ◽  
Finite Element Analyses ◽  
Two Degrees Of Freedom ◽  
Low Stiffness

In this work, an appropriate rail pad is proposed to reduce the vibration induced by moving cranes near the source location in high-tech buildings. Using a simple two-degrees-of-freedom model and laboratory experiments, we found that a low-cost rubber pad is effective to reduce crane-induced vibration. A number of finite element analyses with the full model are then performed for a high-tech factory and a moving crane. The results show that a decrease in the stiffness of the rail pad can decrease crane-induced vibration, and it is obvious that the proposed low-stiffness rubber rail pad with significant damping is an appropriate material to reduce crane-induced vibration by as much as five dB. In addition, the displacement field using the rubber pad is still much smaller than 2 mm, which is the working requirement for moving cranes.

Accuracy Enhancement of Flexible Fourbar Mechanisms via the Curvature-Based Finite Element Method

2008 ◽  
Author(s):  
Y. L. Kuo ◽  
W. L. Cleghorn
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Great Reduction ◽  
Degrees Of Freedom ◽  
Solid Mechanics ◽  
Accuracy Enhancement ◽  
Displacement Based ◽  
Curvature Distribution ◽  
High Degree ◽  
Element Method

The paper investigates accuracy enhancement of flexible four-bar mechanisms via the curvature-based finite element method. Conventionally, the displacement-based method is usually applied to solid mechanics, and it needs more elements or high-degree polynomials to obtain highly accurate solutions. The curvature-based method assumes a polynomial to approximate a curvature distribution, and the expressions are investigated to obtain the displacement and rotation distributions. During the process, the boundary conditions associated with displacement, rotation, and curvature are imposed, which leads the great reduction of the number of degrees of freedom which are required. The numerical results demonstrate that the errors obtained by applying the curvature-based method are much smaller than those by applying the displacement-based method, based on the comparison of the same number of degrees of freedom.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

2020 ◽  
Vol 1 (1) ◽  
pp. 93-102
Author(s):  
Carsten Strzalka ◽  
◽  
Manfred Zehn ◽  
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
A Priori ◽  
High Stress ◽  
Von Mises Stress ◽  
Detailed Knowledge ◽  
Variable Loading ◽  
Numerical Effort ◽  
Von Mises

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

scholarly journals A Finite Element Approach to the Analysis of Rotating Bladed-Disk Assemblies Coupled With Flexible Shaft

1994 ◽  
Author(s):  
Wen Zhang ◽  
Wenliang Wang ◽  
Hao Wang ◽  
Jiong Tang
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Coupled System ◽  
Equation Of Motion ◽  
Coupled Systems ◽  
The Finite Element Method ◽  
Bladed Disk ◽  
Modal Synthesis ◽  
Element Approach ◽  
Final Equation

A method for dynamic analysis of flexible bladed-disk/shaft coupled systems is presented in this paper. Being independant substructures first, the rigid-disk/shaft and each of the bladed-disk assemblies are analyzed separately in a centrifugal force field by means of the finite element method. Then through a modal synthesis approach the equation of motion for the integral system is derived. In the vibration analysis of the rotating bladed-disk substructure, the geometrically nonlinear deformation is taken into account and the rotationally periodic symmetry is utilized to condense the degrees of freedom into one sector. The final equation of motion for the coupled system involves the degrees of freedom of the shaft and those of only one sector of each of the bladed-disks, thereby reducing the computer storage. Some computational and experimental results are given.

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