Conference Paper Abstracts

This section contains abstracts, summaries or contents of conference and symposium papers that discuss NEi Nastran finite element FEA stress analysis.

PDF NEW! Virtual Testing of Postbuckling Composite Structures With Micromechanics Based Damage Degradation - To take full advantage of the postbuckling strength reserves of aerostructures composite panels, understanding and "designing in" the First Ply Failure (FPF) to Last Ply Failure (LPF) evolution will further enable aircraft weight reduction while designing to ultimate loads. As the predictive failure model for Progressive Ply Failure Analysis, a feature in Finite Element Analysis Software, MultiContinuum Theory (MCT) is used to explore nonlinear postbuckling behavior such as mode jumping and to predict collapse or catastrophic failure. With the MCT method, failure in the composite lamina is calculated by evaluating the stress state in either the fiber or matrix, rather than the homogenized composite lamina, allowing one to capture interactions between the two.

PDF Simulating Fiber Metal Laminates - By combining thin metal layers and fiber reinforced layers, Fiber Metal Laminates are quickly becoming the next generation of composite materials for aircraft structures. As the predictive failure model for Progressive Ply Failure Analysis, a feature in Finite Element Analysis software, MultiContinuum Theory (MCT) is used to explore the benefits of GLARE (Glass Fiber Reinforced Aluminum) laminates over traditional CFRP (Carbon Fiber Reinforced Plastic) composite laminates. With the MCT method, failure in the composite lamina is calculated by evaluating the stress state in either the fiber or matrix, rather than the homogenized composite lamina, allowing one to capture interactions between the two.

PDF Simulating Impact Damage To Composite Structures - A widespread industry issue, in designing with composite structures to exploit high strength-to-weight ratio, has been impact damage. Progressive Ply Failure Analysis, a feature in Finite Element Analysis (FEA) software, is utilized to allow designers to examine the propagation of nonlinear impact damage through a composite structure after First Ply Failure (FPF). The important ABD matrix terms are output as part of the analyses and the influence of the different terms is explored in an interactive manner.

PDF Progressive Ply Failure Analysis for Composite Structures - When investigating composite structures, engineers typically use a linear solution and a failure index calculation based on the current state of stress in the model. Because of the linear elastic assumption, an analysis like this can only provide accurate results up to first ply failure. This case study will show how a progressive ply failure analysis overcomes this obstacle and allows designers to examine the propagation of damage through a structure after first ply failure.

PDF Introduction to Finite Element Analysis for Virtual Testing of Composite Structures - Composite analysis features in Finite Element Analysis (FEA) software that have been successfully used in industry over the past several years are reviewed to familiarize designers with capabilities that can help pinpoint problem areas and optimize designs. The presentation starts with the technique of building “virtual” coupons to explore and test structural responses. Then Failure Indices are used to predict composite strength and, with stacking sequence, to demonstrate the benefits of balanced and symmetric lay-ups for reducing membrane-shear and membrane-bending coupling, respectively. The important A,B,D matrix terms are output as part of the analyses and the influence of the different terms is explored in an interactive manner. Finally, 3D composite solid and 2D composite shell models are compared. In particular, the ability of 3D composites to identify delamination is noted because it takes into account the influence of through thickness stresses, including interlaminar shear stress.

PDF Finite Element Analysis Global - Local Modeling in Composites - Methods used to represent composite structures in Finite Element Analysis (FEA) at both global and local levels and attempts to give guidelines on applicability.

PDF Finite Element Analysis Global - Local Modeling in Composites Presentation - Global Local Modeling in Composites - Finite element analysis can be carried out on composites structures at both a global scale, and a local scale.

PDF Guide to Design and Analysis using Composite Materials - Material definitions for isotropic, anisotropic, orthotropic, 2d orthotropic, classical laminate theory, simplification, ply behavior, ply layups, design rules, 3D elements, plane strain elements, FEA Process for Composite Structure Analysis.

PDF A Review Of Finite Element Analysis For Maritime Applications - The Benefits For All - DDAM, tension, tension-only cables, large model support, Stiffness Requirements, Strength Requirements, Vibration Environment, Dynamic Response Behavior, Fatigue Behavior, Using Composites, whole vessel stress analysis, internal tank design, ship lifting and handling, normal modes to find natural frequencies, frequency response of superstructure, impact analysis, naval shock spectra.

PDF Idealization Options For Modeling Composites in Finite Element Analysis - Composite structures in Finite Element Analysis (FEA) at both global and local levels and guidelines on applicability. Includes 2D vs. 3D elements, thin shells, plane stress - classical laminate theory, fibre stress, plane strain.

PDF The Effective Dynamic Analysis of a Whole Boat Model for Naval Vibration and Shock Analysis - Naval vessels operate in a fundamentally dynamic maritime environment, some with shock and vibration loadings from man made devices. Dynamic Design Analysis Method (DDAM) utilizes a shock spectra technique modified for specific equipment locations and vessel types using a target Modal Effective Mass. Complex analysis techniques for full modal survey on whole vessel and specific equipment with DDAM. A typical naval vessel model is used as a case study.

PDF Seismic Analysis of Power Plant Turbine - Seismic analysis of high power, high rotating speed turbine at Nuclear Power Plant (NPP). Minimum intensity of seismic excitation of 0.1 g used in the design of NPPs buildings, structures and components. Turbine systems consists of many internal elements connecting to each other. Huge mass on pedestal base with influence on the whole building behavior during earthquake. Complete system “Building – Vibroisolation Pedestal – Turbine” (BVT) analysis, including detailed spatial model of the turbine hall building, seismic analysis with soil and seismic variations on base slab; detailed pressure models for main turbine parts; dynamic analysis with time history relative displacements and loads of turbine parts; rotor gap problem solved.

PDF Numerical Validation and Application of the Neuber-Formula in FEA-Analysis - Simulation of durability and life estimation of cyclic loaded parts, simulation models which consider material plasticity and damage effects such as the local strain concepts. Light weight structures typically dimensioned limiting local yielding. Reduce nonlinear simulation results using techniques based on the Neuber formula which estimate the plastic stress-strain state from linear analysis runs are utilized in commercial fatigue simulation software such as "NEi Fatigue/Winlife", FE-Fatigue or "MSC Fatigue" etc. Validate Neuber approach by comparing notched test specimen equipped with strain gages to the results of a finite element analysis with an elastic-plastic material model and different Neuber-based approximations.

PDF Nonlinear Static and Multi-Axial Fatigue Analysis of Automotive Lower Control Arm Using NEi Nastran - Lower Control arm is vital component in suspension system, a steel bracket that pivots on rubber bushings mounted to chassis. Significant loads transmitted through the control arm while during contact between wheel and road to control vehicle. The finite element analysis of the control arm using NEi Nastran with inertia relief analysis for measured road loads in self equilibrium. The zone of maximum stress is near the left strut bush, around lower ball joint bush. Stresses exceed material yield strength, so nonlinear static analysis of control arm with NEi Nastran, then compared with MSC.NASTRAN and ABAQUS analyses. Multi-axial Fatigue analysis using NEi Nastran and WINLIFE.

PDF Lessons From Premature Failure of Cross Arms in Transmission Line Towers During Prototype Testing - Testing of transmission line towers shows failures of cross arms. Part of tower body is modeled using beam and plate elements. Failures in four different towers, including effect of inner triangulation formed by redundant patterns on the cross arm performance. The staggering of secondary bracings in elevation and plan of the cross arm and detailing of cross arm tips (loading points), with nonlinear finite element analysis results compared with test results.

PDF Finite Element Implementation of Advanced Failure Criteria for Composites - High performance-to-weight ratio structures using composite materials analyzed using NASA developed LaRC02, set of first-ply-failure criteria in design for accuracy, material characterization requirements, computational effort and ease of results interpretation. Insights on LaRC02 criterion features and implementation into NEi Nastran finite element software. Accuracy and usefulness demonstrated by examples of simple validation cases to a real-world structure.

PDF A New Tool For Multidisciplinary CAE Simulations - Multi Disciplinary Optimization (MDO) of mechanical system using structural assessment (FEA), fluid dynamics analysis (CFD), coupled simulations allow seamless integration between different CAE tools through an interactive GUI and a robust interpolation engine. Method described and validated on Fluid Structure Interaction problems, a typical MDO application and interpolation.

PDF Contact Modeling in Medical Implant Design Using NEi Nastran - Structural analysis involving precise description of multiple bodies being in contact. Overview of the basic NASTRAN contact elements for arbitrary shaped surfaces with friction and large sliding, as well as general surface-to-surface contact element. Analysis of medical implants involving contact, including meshing, model setup, contact element parameters, common errors, trouble shooting, accuracy, convergence, model size and solution time considerations.

PDF Robust Design of Load Bearing Structures - Stochastic analysis tools in optimizing load-bearing structures complimented by structural testing and finite element simulation. Wiremold Company overhead ladder tray systems in large buildings carry power and data cables along ceilings. Reliability of trays, warping, manufacturing tolerances, and shipment damage. NE/Nastran for Windows was used to analyze the ladder trays for static and buckling capability. Within 2% of the mean of failure data. load carrying capability with ultimate strength the limiting criteria and were also able to identify.FEA models were able to identify the load carrying capability and ultimate strength. Once these margins were established, a robust design was obtained.By reducing margins of safety, reduces costs, increases confidence, and allows the engineer to build statistical data bases that can be applied to similar systems with a consistent coefficient of variation.

PDF A Performance Assessment of PCG Based Eigensolvers in NEi Nastran - Preconditioned Conjugate Gradient (PCG) Based solvers in NEi Nastran, with embedded direct and iterative solvers, subspace eigensolver,new Lanczos eigensolver performance comparisons.

PDF Experimental and Analytical Comparison of Machinery Vibration - Coal mill resonance at various coal feeder speeds, shaft failures. Dynamic displacements of three grinding rollers measured by Engineering Consultants Group Inc. (ECG). F finite element model of mill and grinding rollers with two major components tied together through the coal bed stiffness. Displacement caused by first and second vibration modes of the coal mill, revealing that bearing vibration was probable caused excitation of the resonance.

PDF An Historical Survey, Contemporary Assessment and Recommended Directions for FEA Pre- and Post-Processing - FE product evolution over thirty years to the modern day pre and post- processor. Range of modern tools for traditional dedicated analysts and the designer/analyst. Current functionality, as well as future attributes. Mesh types with associated loads and boundary.

PDF A Performance Assessment of NEi Nastran's New Sparse Direct and Iterative Solvers - Performance of Vector Sparse Solver (VSS) and Vector Iterative Solver (VIS) in NEi Nastran. One solver uses a direct approach while the other uses an iterative Pre Conjugate Gradient (PCG). Both are fully sparse and both store and operate only on non-zero matrix elements.

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