Decubitus ulcers, more commonly known as bed sores, have become a serious and life threatening infection risk for extended stay hospital patients. Their causes and formation are still not completely understood, as they involve multiple, complex and interdependent biological processes and external factors. The surface on which the patient lies is clearly a paramount factor. This document presents the initial stages of a methodology development project focused on numerically simulating and virtually predicting how hospital bed surfaces interact with soft tissues and in turn effect ulcer formation as well as general patient comfort. A co-simulation analysis approach is presented which couples LifeMOD, an MSC.Adams plug-in from LifeModeler, Inc., with MSC.Marc, an implicit finite element code for solving problems with high degrees of non-linearity. It was necessary to create and customize this approach in order to accurately capture the simultaneous, interdependent physics which exist between a full human body model and a highly flexible, multi layered foam and bladder surface.

The calibration of non-linear material models remains a complex issue for many analysts. This relatively new problem has come to the fore with the widespread use of plastics, rubber and foams in products today. Failure to correctly capture the behavior of these materials in the simulation results in loss in accuracy and poor design confidence. In this presentation, we seek to provide clear guidelines for the different kinds of behavior seen in complex materials and relate these to the most appropriate MSC material models. Non-linear modeling of plastics in MARC and rate dependent characterization for crash applications in DYTRAN will be discussed. Foam behavior modeling, including the capture of volumetric behavior and it's influence on the simulation will be conaidered. A discussion on hyperelastic behavior will include thoughts about biaxial testing, effects of precycling and the consequences of combining hyperelastic and visco-elastic material models.

The behavior of biological muscle is a dynamic and sophistically interconnected physiological phenomenon. As more intricacy is demanded from implantable medical devices and precision required from the surgical procedures which place them, it has become imperative that methods exist for predictively estimating how these bodies generate loads, effect device lifetime performance, and influence patient comfort and recovery. This document presents a generalized approach for modeling muscle behavior via the finite element method. It includes details of a constitutive model designed and built specifically for analyzing passive and active muscle tissues. It also provides a demonstration of custom tools developed for creating, activating, and visualizing muscle fiber activity. Applications of these tools are exhibited via a finite element model of the human tongue, the most complex muscle system in the human body, in order to understand how surgical sleep apnea procedures may affect critical functions such as speech and swallowing.

Due to manufacturing tolerance and residual stresses in the stock material, it is not uncommon for a machined pipe to be out-of-round, eccentric and non-uniform in thickness. These geometric imperfections can considerably deteriorate the pipe's collapse pressure rating. Collapse pressure can be substantially overestimated if the geometric imperfections are not considered. As an example, the collapse pressure of a pipe with 15.458-in OD and 14.842-in ID under 40,000 lb tensile load can drop from 4,600 psi (317 bar) for a completely round pipe to 2,300 psi (158.6 bar) for an oval pipe with 0.005-in ovality. Finite Element Analysis (FEA) can include the geometry imperfections in the model easily and is an ideal tool for calculating the collapse pressure. In this presentation, the collapse pressure of the above-mentioned pipe with various tensile loads and different degrees of eccentricity, ovality and material non-uniformity are investigated with MSC.Marc. Test results of a machined mandrel also are compared with guidelines for calculating collapse pressure with FEA are given.

As early as 1970's the simple billet and ring upsetting simulation was attempted by the early finite element analysts using the rigid-plastic material models. As the computer becomes faster, the finite element technology grows more and more mature. After 30 years, the area of metal forming simulation has expanded dramatically from a simply metal compression to a complex crankshaft forging, from isothermal forming to hot forging taking into account of plastic deformation and friction heat generation, from single stage forming to a multiple stage forming with upsetting, forging, trimming and heat treatment all simulated in one software. The benefit of metal forming simulation is getting clearer and well recognized by the metal forming industry. The software is no longer the tool for the finite element analysts. It has become a simple tool that designers and engineers can understand and easy to use. More and more engineers and tool designers are using the metal forming simulation software in their tool and forming process design. Instead of trial and error on the shop floor, it is now done on their desktop or laptop computers. The cost and time saving is well-justified for the cost of the software. The author wishes cover most of the advances in the recent development of the metal forming simulation software, its applications and the benefit of using the software. Simufact.Forming based on MSC.Marc technology will be demonstrated in the presentation.

For better understanding of the vibration and noise in the airplane passenger cabin, a typical fuselage section equipped with nearly full interior was tested and analytically studied using NASTRAN. The test results validated the FEM model predictions to 100 Hz, which is more than twice the N1 engine speed for wide body aircraft. The results of this study validates that accurate vibro-acoustic predictions can be made using existing NASTRAN FEM capabilities. The structure FEM used in this study is based on typical low frequency technology with emphasis on proper stiffness, mass and damping model representation. Therefore, a highly detailed FEM is not required as long as the primary and secondary load paths are accurately represented with flexible element types. Such strong test-analysis agreement builds confidence in modeling of complete airplanes that are used to simulate the flight tests for structure-borne noise studies, and will remove some uncertainties in the structure-acoustic predictions.

The finite element modeling of fastener joints is described in detail in previous papers of the authors. However, these papers addressed only the fasteners joining metallic parts. The continued trend is to use more composite materials in aircraft structures. The finite element analysis of such structures requires modeling of fastener joints connecting composite parts, metallic parts, or combination of the two. The work presented in this paper extends the fastener FEM formulation previously developed for metallic parts to enable its use with composite parts. The main difference between modeling of fasteners in metallic and composite parts is in the interface between the fastener and the part. In composite parts the bearing stiffness depends on the direction of the fastener reaction. Because of this, the problem becomes non-linear and requires a number of iteration to solve it. At every iteration, the bearing stiffness in the fastener - composite part interface should be updated. The presented procedure describes this iterative process which can be used with any number of fasterners and joined composite and metallic parts. This modeling techniques is described in terms of MSC.Nastran but can be extended to other FE codes.

A growing need in Boeing arose to consolidate comparable software tools and to provide a common standard tool set that could be used across various engineering communities and programs within Boeing. During the search for a common environment to host these tools, it was agreed upon to adapt MSC Patran with its open architecture for easily facilitating additional capabilities into patran (using PCL). At that time, this viable candidate was becoming a widely accepted pre- and post- processing FE tool throughout the company not just within the defense business sector of Boeing but on the commercial side as well.

In cooperation with MSC.Software, we have leveraged features from Patran's MSC.Random and developed an in-house tool called Sonic Response Analysis (SRA) in Boeing Research & Technology. The SRA tool contains features for automatically setting up a nastran analysis job for typical acoustic or vibration type problems and features for performing random analysis of the results which integrates the core MSC.Random engine. The capabilities within the SRA tool were adapted from an existing Boeing tool called N-FEARA (based on NIKE-3D). The implementations of features into SRA were cross-validated with this complimentary tool. The SRA tool has a broad application base such as satellite systems, electronic boards and propulsion structures The SRA tool has been used in many sites across Boeing.

A military aircraft carries external stores like missiles, drop tanks etc. During hard landing, it has to be ensured that there is no inadvertent release of the store due to the loss of structural integrity of the store to pylon and the pylon to wing attachments. It is also necessary that the resulting vibration and shock stresses do not lead to mechanical failure of various electronic equipments mounted inside the pylon. This paper presents the details of the shock response analysis carried out in MSC/NASTRAN, for the pylon - store assembly of an aircraft wing and the Pylon Interface Box (PIB) installed inside the pylon. The pylon - store assembly as well as the PIB are modeled separately. The shock loading for the assembly, specified by the appropriate MIL standard for store components, is a half-sine pulse, reaching a peak value of 25g in 15 milliseconds. The analysis is carried out in two steps. In the first step, the shock acceleration pulse is input at the wing to pylon attachments. The integrity of the pylon is checked by monitoring the dynamic reactions at the wing-pylon and store-pylon attachments. Next, the shock response spectrum (SRS) of the transient response, at the mounting points of the PIB, is generated. In the second step this SRS is applied to the PIB model in the X, Y and Z directions, separately, and the maximum dynamic response is estimated at critical locations.

Several issues typically encountered in the analysis of composite materials including element formulation, criteria for both macro- and micro-mechanical failure analysis, damage and crack growth and propagation in the material are discussed in this paper. We also discuss modeling the crack growth and propagation in an efficient manner using the automatic and adaptive remeshing algorithms. Other technologies that are central to nonlinear analysis of composite materials - namely, efficient elements to model bending and transverse shear stresses, robust solution algorithms with adaptive time stepping and frictional contact able to handle large deformation analysis - are also discussed.

Airframe survivability and hydrodynamic ram effect of aircraft are investigated. Penetration and internal detonation of a simple tank and fighter wings included ICW (Intermediate Complexity Wing) are simulated by nonlinear explicit calculation. Structural rupture and fluid burst are analytically realized using general coupling of FSI (Fluid-Structure Interaction) and adaptive master-slave contact. Besides, multi-material Eulerian solver and porosity algorithm are employed to model explosive inside fuel and tank bays which are defined in multi-coupling surfaces. Structure and fluid results are animated on the same viewport for enhanced visualization.

Automotive Powertrain models have evolved from the simple concentrated mass and distribution element to fully meshed detailed finite element models. This evolution of powertrain models has enabled complex analysis methodologies by linking multiple vendor software packages to perform end to end simulations. However the linking and multiple vendor codes entails inefficiencies that lead to excessive times not only for the compute cycles but in the physical times in the development cycles. This paper will outline the exposure of new features, advanced matrix solvers and automation advancements used to reduce the storage, cpu cycles and physical time requirements and allow multiple simulations for a powertrain response analysis.

Ford Motor Company required a new rear cover manual transmission to be part of an existing vehicle program and a new vehicle program. The transmission had to be exchangeable between both programs, had to have good structural behavior and exceed target vibration values (first significant frequency) when placed in the power train; all this despite the fact that the development time was too short. CAD tools were used to do packaging studies of the transmission and CEA tools (Patran/Nastran) were used to complete the structural behavior studies and to determine the way to reduce weight. Once the structural behavior target was achieved the transmission was included in the power train and the first significant frequency checked; the results exceeded the defined target. CAD was then frozen on time for tooling and completing the DVP&R of the vehicle. Ford and TREMEC worked closely together to achieve this objective.

Modern computer architectures utilizing multi-core CPUs and increased memory have facilitated more sophisticated structural and manufacturing simulation. The first part of this presentation will discuss new parallel processing procedures implemented in Marc that utilize these architectures and computational performance results will be provided.

Compaction and sintering of a powder is an attractive alternative for manufacturing of precision parts from high strength alloys which otherwise would be difficult to machine. Behavior of these powders is similar to soil and other granular materials. The Sandia Geomod material model has been implemented to represent these materials where the yield surface is a function of hydrostatic stress. Both the classical and the new model will be discussed. In these types of manufacturing simulations, it is necessary to automatically remesh the region, which previously led to difficulty in interpreting the results. A new Particle Tracking capability that may be used in the post processing stage will be discussed.

Wind and earthquake forces acting on tall buildings are resisted by either: (a) bending action in the structural frames, (b) by the truss action of the braced frames, (c) by shear action of shear walls; or (d) by a combined action of preceding three elements. In this project our focus was to study behavior of steel plate shear walls in combination with a boundary moment frame when subjected to lateral loads due to wind or earthquakes. Due to large forces involved in the system, actual physical testing of these large systems is very difficult and almost impossible. We used MSC.Nastran and MSC.Patran to create "Virtual" multi-story steel plate shear wall test specimens with nonlinear material and geometric properties and subjected the realistic virtual test specimens to push-over lateral forces until specimens failed. Our most important findings were: (1) Shear strength and shear stiffness of steel shear wall systems could be reliably investigated by MSC.NASTRAN and nonlinear finite element analysis, (2)The MSC.NASTRAN could efficiently predict the buckling and yielding performance of the steel shear wall systems including predicting behavior of actual physical specimens tested in the laboratory with good accuracy, (3)The application of the "strip model" which is the basis of provisions for seismic design of steel shear walls in the current seismic design codes of the Unites States and Canada to steel shear walls with width-to-thickness ratio less than 300 is questionable and needs further investigation for necessary revisions.

The most important structure among all parts of cable-stayed bridge is generally the pylon structure system. If pylons do not resist against any type of loadings, the whole bridge system does not survive under that loading. Then the pylon system must be safe under any extreme condition. Two common types of pylon structure in cable-stayed bridges are the steel box and concrete box pylon. This paper focused on the steel box pylon system and its response to blast loads due to a car bomb explosion close to the pylon. The studies were performed by subjecting the inelastic, non-linear finite element models of typical steel box pylon structures used in major cable-stayed bridges to simulated blast effects using the MD Nastran SOL700 finite element analysis software. The main suggestion in the study was how to reduce the response under blast loading. From the results of these analyses, the failure modes of the steel box pylon structures were identified and strengthening measures to enhance blast-resistance were developed. The most important finding of this study was that the concrete filled pylon structures perform extremely well when subjected to blast loads.

The demand for automation in MCAE software tools is soaring as design and manufacturers transition from conventional "trial-and-error" physical testing to more efficient "simulation-driven design" in product development. This presentation will provide an overview of a technology known as BubbleMesh^TM which is a leap forward in commercial, off-the-shelf mesh automation for highly sought after functions like hex-dominant and mid-surface meshing. The paradigm shift toward greater automation in simulation is occurring because global competition, global supply networks and consumer demands dictate dramatically shorter product development schedules, increased quality, and lower costs. In the past, automation in engineering simulation has been largely developed by expert users that have exceptional "tribal" knowledge of their products and development process, in addition to doctorate level skill-sets in finite element analysis and mathematics. These human resources are extremely valuable and typically in very limited supply. Therefore, problems arise when processes change and the automation needs to be modified to maintain the targeted productivity level. MSC Software has developed technology in SimXpert to help users to capture and modify automated simulation processes and this capability offers proven business value. Ciespace offers another level of automation that is focused on the function of meshing, as opposed to a unique development process. The theory of this new meshing technology and examples of surface and volume meshing results will be presented along with their potential business value.