The conference proceedings for the 1996 World Users' Conference are now available on-line in Adobe Acrobat PDF format. In addition, the papers that won the prize for best example of the conference theme from both 1995 and 1996 are available in HTML format. The papers have been categorized by topic.
Categories
ACRAT's software system design emphasis has been focused on standardized methods of electronic data modeling and exchange; a UNIX-less process management environment which insures geometric configuration management and material release control; integration of COTS and/or public domain software wherever possible to reduce the cost of development while maximizing system functionality and reducing future costs of ownership (upgrading/porting supportability); and a single user friendly graphical user interface (GUI) capable of supporting a wide range of perspective users (field technician or expert CAE/composites engineer).
Four (4) customized database schemas (M&P, Aircraft Design, Composite Repair, Component Test) were designed and sufficiently populated to evaluate each data model's ability to meet specific ACRAT system requirements. These prototype databases, coupled with the ACRAT Executive Control System (ECS) database, represent the foundation upon which the fully self contained ACRAT software system has been built.
The EMB-145 Nose Landing Gear Door is attached to the aircraft fuselage through three hinges which are driven by a hydraulic actuator attached to the central hinge. The EMB-145 N.L.G.D. structure, is made of two solid prepreg carbon/epoxy laminated skins, cold bonded and fastened. Carbon/epoxy tape is used in order to avoid panel buckling and to increase the required stiffness of the Aerodynamic Smoothness Requirements for EMB-145. The hinges are machined from aluminum alloy, attached to the structure by titanium alloy bolts.
The EMB-145 Nose Landing Gear Door is designed to resist the critical aerodynamical loading in normal condition and in case one of the hinges fails.
The EMB-145 Nose Landing Gear Door structural analysis including finite element data, boundary conditions and acting loading are presented in this report. The present output results in MSC.Nastran allow one to obtain the most critical condition among all subcases very quickly, when post-processed.
The immediate response analysis is determined with MSC/DYTRAN and the post explosion analysis is made by MSC.Nastran. A complete vulnerability map requires many failure scenarios and a large number of MSC/DYTRAN and MSC.Nastran analyses. Six points in the cargo hold were critically examined to demonstrate the concept.
This technique is applied to an automobile suspension component. Results show excellent correlation of back calculated load with the actual load. Also a conventionally instrumented (with designed load cell) component is used for comparison. The proposed method consistently showed considerable improvement over the conventional method.
In an effort to allocate more science to the problem of roll cage design it was proposed that nonlinear finite element analysis using MSC.Nastran would give a good indication of the true load carrying capacity and deflection under load of the roll cage/frame. The analysis carried out was verified by the test programmme on a full scale chassis. This analysis gave results within an accepatable 10% of the test results despite the simplifying assumptions.
This application of MSC.Nastran is new as most small automotive manufacturers rely on past experience for their development. This works well for evolutionary design but not for major structural modifications as were carried out. This report highlights the value of MSC.Nastran in this application.
MSC/ABAQUS has been used to analyze and design airbag crash sensors. The analysis was geometrically nonlinear due to the large deflections of the springs and the contact between the ball and springs. Bezier 3-D rigid surface elements along with rigid surface interface (IRS) elements were used to model ball-to-spring contact. Slideline elements were used with parallel slideline interface (ISL) elements for spring-to-spring contact. Finite element analysis results for the force-displacement response of the sensor were in excellent agreement with experimental results.
This paper presents the uses of MSC.Nastran and advantages of using this software for non-linear analyses of RC members. Brief discussion on modeling procedures and discussion of results of three RC shallow beams are also presented to illustrate the degree of accuracy in results which could be achieved from non-linear post-yielding analyses of R.C. members by using MSC.Nastran.
Initially, a simple model based on the results presented in ref. [ 1 ] was made, analyzed and compared with MSC.Nastran, ref. [ 2 ]. This model considered a two-dimensional geometrically nonlinear finite element. The results obtained by MSC.Nastran in finite element model with 153 nodes and 128 four-node isoparametric elements were in very good accordance when compared to classical theory, presented in ref. [ 1 ]. The model contained four sub-structures with a total of 813 nodes and 740 four-node isoparametric elements.
The next step was to analyse through-width delaminations in specimen made of graphite/epoxy tape with graphite/epoxy cloth. This specimen not only contains two types of graphite/epoxy, tape and cloth, but also presents a non-symmetrical laminated. The results obtained by MSC.Nastran were compared with the classical theory and were found to be in very good accordance. This report shows how these results were obtained.
A DMAP alter is presented which allows the user to include modal damping which is a function of the displacement (or velocity) measured at selected points.
The purpose of this paper is to show through an actual example how component mode synthesis can be performed in MSC.Nastran without the use of elaborate DMAPs. The analyst can do such tasks as plotting, data recovery, apply loads, transfer data forward and backward, without the use of a single structured solution based DMAP. The net result is an efficient process that reduces the time and cost of the analysis.
Several analysis types will be utilized for different steps of the design phase as follows:
The elastic stress concentration problem in a thin plane specimen under tension and thin-walled curved circular cylindrical shell subjected to torsion are considered carefully through the use of the Version 68.1. The accuracy of numerical results in both cases is established by comparing them with the corresponding experimental data obtained by means of holographic interferometric measurements. The calculation of maximum stress values is carried out by using QUAD4 Corner Output. An excellent agreement between numerical and experimental results have been revealed.
An evolution of local elasto-plastic strains in a thin plane strip with a circular open hole under static tension is studied. The data of holographic interferometric measurements are used again in order to estimate the accuracy of numerical solution for different levels of applied external load. An influence of the circumferential strain gradient on results of a maximum elasto-plastic strain calculation is dicussed in detail.
There are several options available in MSC.Nastran when one desires to create a finite element model of a vehicle structure. The question that remains unanswered is, what is the best way to model a vehicle in a real world environment economically, and believe in the results without creating the actual part for testing. In order to gain some insight and answer this question, one often looks into the well-known classical mechanics problems in literature where there is either a closed form solution or a repeatable lab experiment conducted in a controlled envionment, to compare with modeling techniques.
In this paper, several classical problems are sought from literature, which are modeled using MSC.Nastran, and the results are compared to one another. The problems range from linear static analysis of slender beams to free vibration and nonlinear static analysis. The conclusions are drawn from the comparison of several modeling methods to the closed form solutions available to the authors. It is found that one must take great caution when modeling a vehicle structure on choice of element types, their size and range validity. Discussions on the accuracy of results in deflection analysis vs. stress or vibration analysis are made by using different modeling methods and rationalizing the comparison of the results to the analytical solutions.
The proper choice of the occlusion pattern, hereafter considered the way prosthetic and dental cusps fit together, is fundamental for the homogeneous distribution of mastication loading around implants that totally support the prosthesis.
Through the Finite Element Method, the stress distribution around the prosthesis supporting implants has been studied. Two kinds of occlusion patterns have been considered: canine guide and balanced occlusion. The three-dimensional finite element model of the lower jaw with a prosthesis supported by six osseointegrated implants was developed and analyzed regarding both loading (occlusion) conditions. MSC/XL was used for pre and post-processing and MSC.Nastran for the analysis. Considering just the biomechanical aspects, it was observed that:
Vehicle body-in-white structures are a good illustration of this global-local phenomenon. Although the stiffnesses of the vehicle's joints strongly influence the global modes, the optimizer may have difficulty making design decisions owing to the detail inherent in the joints' description. Design variable linking is the obvious solution to the problem but it, in a sense, forces a constraint on the type of redesign the optimizer can perform.
In this paper, MSC.Nastran's design optimization capabilities, coupled with image superelements for the vehicle's joints are used to tune the global modes of a complex vehicle structure, while providing joint stiffness targets for subsequent local redesign.
ADP is a customized integration of analysis codes, CAE software and material information databases. The primary CAE integration tool for the ADP is MSC.Patran, a commercial-off-the- shelf (COTS) software tool. The open architecture of MSC.Patran allows customized installations with different application modules for specific site requirements. Integration of material databases allows the engineer to select a material and those material properties are automatically input into the relevant analysis code. The ADP materials database supports two independent schemas: (1) CAE Design Properties and (2) Processing and Test Data.
The design of the ADP places major emphasis on the seamless integration of CAE and analysis modules with a single intuitive graphical interface. This tool has been designed to serve and be used by an entire project team, i.e., analysts, designers, materials experts and managers. The final version of the software was delivered to the Air Force in June 1995. The Analytical Design Package (ADP) is intended to facilitate technology transfer to industry. The analysis system is capable of a wide range of design and manufacturing applications.
This paper explains how the Durability and NVH CAE attributes employed MSC.Nastran to produce high confidence results as part of an integrated process which allowed the vehicle to be verified for the Global and local performance at approximately 3 years to job 1.