bluuebunny/crossref_metadata_2025 huggingface dataset:
An Integrated Joint Dynamics System for Elastically Jointed Structures
Authors: Rong Y. , Tzou H. S.
Published: April 2021

The dynamic behavior of elastic joints strongly affect the dynamic performance of a jointed mechanical system. The dynamic contacts introduced by joint clearances create a system with nonlinear characteristics. Special effort needs to be made to study jointed mechanical systems. This paper presents an integrated joint dynamics system, which can be used to predict the dynamic characteristics of a newly designed structure, or to analyze an existing jointed structure. This joint dynamics system can also be applied as a real time monitoring and diagnosis system when it is connected with a vibration measuring device. The joint dynamics system includes: 1) a theoretical model of jointed structures, in which the joint clearance and joint friction effects are considered; 2) a stochastic simulator which is used to generate vibration data and evaluate system dynamic characteristics; 3) a diagnostic monitoring algorithm for vibration state detection; and 4) a forecasting vibration control scheme. The joint dynamics system is applied to the dynamic analysis of a truss-cell unit structure. The results presented in this paper show that the joint dynamics system is effective.
Measuring Nonlinear Dynamic Behavior Using Microcomputers
Authors: Caccese V. , Martin D.
Published: April 2021

This paper details a relatively inexpensive data acquisition/analysis system that was developed at the University of Maine to facilitate the measurement of nonlinear dynamic motion into the chaotic regime. The characteristics of the hardware and specially developed software will be discussed.

The testing system includes a software package, written in TURBO Pascal, that is used to reduce and graphically present the time-history of up to six channels of data simultaneously. The program contains algorithms for digital filtering, smoothing, and Fast Fourier Transforms. The data retrieval software was designed to maximize in-core storage of data and overcomes the current 64 kilobyte memory segment boundary of MS-DOS. Phase Plane projections and Poincaré sections can also retrieved. Analog differentiation and a pulse trigger used to control Poincaré section retrieval are described. A surface of section at any desired phase angle can be taken with this trigger device. A program called POINCARE acquires the signal and its derivative and automatically plots them on the CRT as the test is in progress. A case study of a cantilever beam attracted by two magnets is also presented.
A CAD Program for Optimum Nonlinear Characteristics of a Vehicle Shock Absorber
Authors: Hossamel-deen Yehia H. , Metwalli Sayed M. , Hassan Abdel-hamed S.
Published: April 2021

A Computer Aided Design (CAD) program has been developed in which both simulation and optimization techniques are utilized. A nonlinear representation of the shock absorber damping characteristics has been considered. The output of this CAD program is the optimum shape of this nonlinear characteristics. This is obtained by minimization of a performance index consisting of a weighted sum of the root mean square (rms) of both tire terrain normal force (as a measure of controllability) and the sprung masses acceleration (as a measure of ride comfort). The time response can also be obtained graphically as an output option.

Two different mathematical models are considered: A simple one with two degrees of freedom (Bounce of the sprung and unsprung mass) and a more sophisticated one with four degrees of freedom (Bounce and pitch of the sprung mass and vertical motion of the unsprung rear and front masses). The two models are checked and validated by comparing their results with other published works.

The program results obtained for a typical vehicle show a good improvement of the performance of the optimum nonlinear system compared to the optimum linear one.
PLAN: A Software Package for the Optimization of Planar Four-Bar Linkages
Authors: Tandirci Murat , Angeles Jorge , Liu Zheng
Published: April 2021

This paper introduces a software package called PLAN containing Fortran and C routines to optimize, and visualize planar four-bar linkages for rigid body guidance and path generation. The problem formulation and the design methodology, fully discussed elsewhere, are briefly recalled for quick reference. Examples are included to highlight, the usage of the package, and illustrate the design and analysis stages involved.
SPHERE: A Software Package for the Optimization of Spherical Four-Bar Linkages
Authors: Liu Zheng , Angeles Jorge , Tandirci Murat
Published: April 2021

Introduced in this paper is a software package called SPHERE, meant for the optimization of spherical four-bar linkages for problems of path generation and rigid-body guidance. The optimization methodology is based on an equality-constrained least-squares scheme, as described elsewhere. Considering the similarities of the two problems, we established a more general formulation to cover both synthesis cases. SPHERE is developed based on this formulation. An outline of the methodology and the package is presented in this paper. Two examples are included to illustrate the usage of the package.
SIXPAQ: A Comprehensive Software Package for Analysis and Synthesis of Six-Bar Dwell Linkages
Authors: González-Palacios Max Antonio , Angeles Jorge
Published: April 2021

SIXPAQ is a software package that was created for the interactive analysis and synthesis of six-bar dwell linkages. The package is structured so that any six-bar dwell planar linkage can be designed by simply choosing a reduced number of parameters. Robust algorithms are introduced that allow an accurate and reliable construction of the two loci on which the linkage synthesis procedure is based. Input-output plots and animation are available within the package as visualization aids. The package allows the user to interact with the program to satisfy the dwell and geometry conditions. Animation is achieved using a powerful graphics workstation.
Concurrent Design and Analysis of Mechanisms
Authors: Hollars Michael G. , Rosenthal Dan E.
Published: April 2021

Concurrent design and analysis of mechanisms offer significant improvements in product quality while greatly reducing design cycle time. Recent advances in CAE software now give very powerful analysis and design capability directly to the design engineer. The key advances are intuitive graphical interfaces, adapation of analysis software to the design process, and seamless integration with existing CAD/CAM/CAE products. Several examples of concurrent mechanism design and analysis are given along with an overview of CAE mechanism design and analysis software, including Applied Motion® from Rasna Corporation.
IGES Success on a Shoestring: A Management Case Study of CAD/CAM Data Exchange
Authors: Stokes Harlan
Published: April 2021

In the Autumn of 1988, the Materials Operations at Control Data Corporation’s Computer Products Group began a program to electronically exchange mechanical CAD models with its suppliers. The “Supplier CAD-Link” program provided many immediate benefits and offers a unique learning experience about electronic data interchange. Existing technologies are used, so the program operates on a shoestring budget with no major dollar investments required of CDC or the suppliers. The program uses the IGES standard file format, so suppliers can apply the lessons learned to CAD/CAM data exchanges with other companies. Now, with the continuing success of the CAD-Link program. Computer Products is re-evaluating many of the old paper based methods of doing business. This paper explores some of the issues for managing a CAD/GAM data exchange program.
A Framework for Feature Based Part Modeling
Authors: Chen Yuh-Min , Miller R. Allen , Vemuri K. Rao
Published: April 2021

To increase the capabilities and intelligence of CAD/CAM systems, a feature based modeling environment, integrated with a knowledge based environment, is under development utilizing a commercial CAD system. This environment allows designers to model parts with features, and provides high-level part models to support geometric reasoning in manufacturing assessment and related functions. Two fundamental issues have been considered: (1) What kind of information is required to specify a part and to support reasoning about the part in a wide variety of applications?, and (2) How can the results serve the geometric reasoning needs of the various engineering applications which need geometric information about the part? This paper will discuss the information required for defining net shaped parts (parts to be manufactured by net shape processes), a framework for a feature based modeling environment, the procedures for feature based design, and the construction of high-level (semantic) pan models suitable for geometric reasoning in a knowledge based environment.
A Computer Modeling of the Czochralski Growth of Bismuth Silicon Oxide With Free Surface
Authors: Liaw G. S. , Zheng Y. M. , Mo J. D. , Chou L. C.
Published: April 2021

A comprehensive numerical modeling of the Czochralski crystal growth system has been conducted for the growth of Bismuth Silicon Oxide (BSO). Both the thermal buoyancy and the surface tension effects are taken into account in the convective flow field. A pressure-based numerical algorithm in conjunction with an algebraic adaptive grid procedure is employed for the simultaneous solution of the melt flow field and the global melt/solid temperature distribution. The free surface effect is treated by coupling the Young-Laplace equation with the flow field along the interface. The results of the quasi-steady-state model at three different stages are presented, they agree with the experimental observations qualitatively.
A Methodology to Handle Inequality Constraints in an Interactve Design Process
Authors: Sridhar Natarajan , Agrawal Rajiv , Kinzel Gary L.
Published: April 2021

The treatment of mechanical design as a constraint management problem has long been related to equality constraints. Work involving inequality constraints has been generally restricted to optimization and symbolic computation. This paper presents a methodology for handling inequality constraints in an interactive mechanical design process. The presented method is similar to the basis interchange algorithm used in the Generalized Reduced Gradient (GRG) method for constrained nonlinear optimization. The main difference is that our method relies on user guidance to select which specification has to be changed in order to satisfy the violated inequality constraint. Also, the specification is only adjusted; unlike the procedure in the GRG method where the basis is changed. An inequality constraint violation is detected whenever the corresponding slack variable becomes negative. An occurrence-matrix formulation is used to represent both the equality and inequality constraints that govern the design. The work is illustrated for the classical weldment design problem.
New Approach to the Design of Multitechnology Systems
Authors: Viitanen Pasi , Yli-Paunu Pekka , Yli-Pietilä Timo , Suoranta Risto
Published: April 2021

We introduce a design environment for complex multitechnology systems. The design environment supports hierarchical, multi-level and mixed-mode simulation. The design environment is based on commercially available CAE-tools including graphical interfaces for both mechanical and analog simulators. The system is built around the high-level hardware description language and interactive postprocessor tools for simulators. Linear and non-linear systems can be modelled in time and frequency domains. There is a simulation example of multitechnology system including, electronical, hydraulical and mechanical components.
On Implementing an Integrated Design-Manufacturability Assessment Environment
Authors: Chen Yuh-Min , Miller R. Allen , Vemuri K. Rao
Published: April 2021

Due to the incomplete representation schemes and the lack of high-level reasoning capability of current CAD/CAM systems, manufacturability assessment is performed by experienced designers and manufacturing engineers. The problems associated with automating manufacturing assessment include (1) the integration of a knowledge based environment within a design environment to provide reasoning capability, and (2) the development of flexible, modularized and responsive part models with levels of abstraction to support high-level reasoning which is required. Since modification of part geometries are frequently made during manufacturability assessment, the capability for part geometry modification is required at the level of interacting procedures. Consistency problems therefore occur between the geometric database in design environment and the part model in knowledge based environment. This paper presents a framework for an integrated design and manufacturability assessment environment which address these concerns.
Computer Aided Design of Support Structures for Stereolithographic Components
Authors: Kirschman C. F. , Jara-Almonte C. C. , Bagchi A. , Dooley R. L. , Ogale A. A.
Published: April 2021

Stereolithography is a process used to rapidly produce polymer components directly from a computer representation of the part. Support structures, required for all parts built this way, are used to support a component during the build but are removed once building is complete. They anchor the component to the platform and prevent distortion, and are designed simultaneously with the component.

A software package to aid the designer is under development at Clemson University. The Clemson Intelligent Design Environment for Stereolithography (CIDES) serves as an interface between the CAD systems and the SLA, cornbining utilities and research efforts. One aspect of this is the automatic support generation algorithm, which designs support structures using knowledge gained from experimentation and experts.

The algorithm uses a stereolithographic format representation of a part and gives the user several design options. It then produces both base and projection supports. Output is in slice-ready form.
Optimal Design of Structural Components Fabricated With Composite Materials
Authors: She Kun , Sadler J. P. , Tauchert T. R.
Published: April 2021

The static and dynamic optimal design of structural components fabricated with advanced composite materials are studied by combining the finite element method and optimization techniques. Different element types, loads, component structures and objective functions are investigated. Beams and torsion members are analyzed using the ANSYS finite element program and are optimized via an interface to an optimization software package. The particular element types used to model the composite components include beam elements with equivalent overall material properties and layered shell elements. The optimization variables include member cross sectional dimensions and composite lamina thicknesses and fiber orientations. The optimal results show significant improvement in deflection amplitude levels and dynamic settling times relative to conventional metals and nonoptimized composite materials.
DAMP: A General Purpose Optimization Program for Modeling, Analysis, and Synthesis of Mechanisms
Authors: Krishnamurty Sundar , Turcic David A.
Published: April 2021

This paper presents the description of an integrated software package titled DAMP (Design and Analysis of Mechanisms Program) that has been developed for the purposes of modeling, analysis, and synthesis of planar linkage mechanisms. DAMP is a comprehensive computer-aided design tool with the ability to design complex planar mechanisms including higher order mechanisms with multiple loops and multiple degrees of freedom. It is also capable of addressing a wide range of design objectives such as the position, velocity, acceleration, and force requirements. DAMP employs matrix methods for the modeling and analysis of mechanisms, and the method of nonlinear goal programming in the determination of the optimal mechanism solutions. Two mechanism design examples are presented to illustrate the various capabilities of this software package.
Geometric Modeling and Visualization of Manipulator Workplace
Authors: Chen X. , Gupta K. C.
Published: April 2021

This paper introduces a new and powerful technique to determine the workspace shape of a general n-joint manipulator by utilizing geometric modeling. A complete three-dimensional geometric model of the workspace shape can be generated which is compatible with the computer graphics. The resulting workspace image can be visualized in three-dimensions realistically, manipulated interactively and analyzed for topological and volumetric features. The first part of the paper presents a general discussion of the workspace geometry and boundary representation concept. The remainder of the paper focuses on two workspace boundary extraction methods in a CAD environment: Radial-Slice-Layering method (RSL) and Apparent-Contour method (AC). Several specific examples are presented to illustrate the basic technique.
Commercial Software for Tolerance Analysis
Authors: Turner Joshua U. , Gangoiti Alex Beascoechea
Published: April 2021

This paper provides a review of the capabilities for tolerance analysis in currently available commercial software packages. Only those packages which make some use of geometric models to assist in solving the analysis problem are considered. Three basic strategies are identified.
A Constrained Optimization Approach to Finite Element Mesh Smoothing
Authors: Parthasarathy V. N. , Kodiyalam Srinivas
Published: April 2021

The quality of a finite element solution has been shown to be affected by the quality of the underlying mesh. A poor mesh may lead to unstable and lor inaccurate finite element approximations. Mesh quality is often characterized by the “smoothness” or “shape” of the elements (triangles in 2-D or tetrahedra in 3-D). Most automatic mesh generators produce an initial mesh where the aspect ratio of the elements are unacceptably high. In this paper, a new approach to produce acceptable quality meshes from an initial mesh is presented. Given an initial mesh (nodal coordinates and element connectivity), a “smooth” final mesh is obtained by solving a constrained optimization problem. The variables for the iterative optimization procedure are the nodal coordinates (excluding, the boundary nodes) of the finite element mesh, and appropriate bounds are imposed on these to prevent an unacceptable finite element mesh. Examples are given of the application of the above method for 2/3-D triangular meshes generated using a QUADTREE | OCTREE automatic mesh generators. Results indicate that the new method not only yields better quality elements when compared with the traditional Laplacian smoothing, but also guarantees a valid mesh unlike the Laplacian method.
A General Purpose Automatic Mesh Generation Using Shape Recognition Technique
Authors: Takahashi H. , Shimizu H.
Published: April 2021

This paper proposes a new automatic mesh generation algorithm, in which an artificial intelligence technique is introduced to imitate the process of human thinking for generating meshes. In this paper, the word “mesh” is used in lieu of element used in Finite Element Method. This system satisfies the user requirement that a geometric model should be divided into only quadrilateral meshes such that distortions are relatively small. The shape of a geometric model is recognized to provide the system with the ability to generate meshes for an arbitrary shape, and the ambiguity contained in the shape recognition is expressed by the membership function used in Fuzzy Logic.

The algorithm for two dimensional automatic mesh generation is described and the application of this algorithm to a surface model is presented in this paper.
The Development of a Two-Dimensional Automatic Free-Form Mesh Generator
Authors: Sezer Levent , Zeid Ibrahim
Published: April 2021

A fully-automatic free-form mesh generation method is described in this paper. The related mesh generator is capable of meshing planar regions. In addition to being fully-automatic, the method produces quadrilateral or triangular elements with aspect ratios near one. The input to the method includes the region’s boundary curves, the element size, and the mesh grading information. The method begins by decomposing the planar region to be meshed into convex subregions. Each subregion is meshed by first generating nodes on its boundaries using the input element size. The boundary nodes are then offset to mesh the subregion. The resulting meshes are merged together to form the final mesh. The free-form mesh generator and its related method has been tested and applied to a wide number of regions. Sample examples are presented.
Simulation of Submicron Particle Deposition in Laminar and Turbulent Stagnation Point Flows
Authors: Abuzeid Salem , Busnaina Ahmed A.
Published: April 2021

The two dimensional laminar and turbulence stagnation-point flow over a wafer surface within a cleanroom environment are numerically simulated. This study shows the relationship between particle capture area on the wafer and the particle size and flow conditions. The mean flow field is simulated using a two equation k-ϵ turbulence model. Trajectories of aerosol particles are evaluated by solving the corresponding Lagrangian equation of motion that includes effects of drag, gravity, lift force, Brownian motion and turbulence fluctuations. The Brownian motion is modeled as a white noise process and turbulence fluctuation is assumed to behave as Gaussian random process. Simulations are carried out for aerosol particles (of various sizes) released at different locations over the surface. Depositions of particles on the wall are evaluated and a capture area which varies with particle sizes is produced. The results show that Brownian motion becomes very significant when turbulence fluctuations start to disappear near the wall for particles smaller than 1 μm in diameter. The results also show that, deposition of particles in turbulent flows are usually higher than that in laminar flows for all particle sizes considered. The effect of fluid on particle deposition rate is predicted for fluid of air and water. The results show that, particles deposition rate in air is higher than that in water.
A Boundary Integral Method for Examining Underwater Explosion Bubble Dynamics
Authors: Wilkerson Stephen
Published: April 2021

A boundary integral formulation for the numerical calculation of an underwater explosion bubble’s expansion and collapse is presented. The formulation makes use of first-order three-dimensional panels and adapts the methodology specifically for the simulation of an underwater explosion bubble. These simulations include a free field bubble as well as a bubble’s interaction with a nearby fixed surface. A number of explosion bubble codes have been written using the boundary integral formulation and are discussed throughout the three-dimensional formulation. Specifically, a spherically symmetric code, an axisymmetric code for simple geometries, and a first-order three-dimensional code was developed. The validity of the three-dimensional code presented is established through direct comparisons with the previously validated axisymmetric code (Wilkerson, 1989).
Investigations of Liquid Motion in Rigid Containers Under Microgravity Conditions
Authors: Vatistas G. H. , Kozel V. , Yan W. , Sankar T. S.
Published: April 2021

The dynamic behavior of the free surface of a liquid placed in rectangular or cylindrical containers, during a step transition from terrestrial conditions to weightlessness and liquid drainage from rectangular containers in zero gravity are investigated numerically. The required time for the surface oscillations to decay to 1% of the original amplitude was found to depend on Reynolds number and the contact angle. The numerically obtained results are shown to approach the exact zero-gravity equilibrium state asymptotically. During liquid drainage through a central hole, the degree of surface depression was found to depend strongly on the exit velocity. The amount of residual liquid could be reduced by strategically placing the exit ports at the lower corners of the tank.
Computational Evolution of Optimal Iceform Shapes Over a Flat Plate
Authors: LaFleur Ronald S.
Published: April 2021

This paper presents the computational evolution of minimum energy dissipation iceform contours. The ice/water interface is shaped according to fluid dynamic and heat transfer characteristics of the flow field near the interface. A Couette iceform design model is used to approximate flow and thermal field behavior near the interface. The theory used to calculate the interface shape is based on a wedge model of the ice contour over a cold flat plate.

The steady state ice profile is calculated when Reynolds number and the thermal parameter are selected. The generation function, designation function and energy dissipation are related to the nonlinear geometric development. An optimal preprocess criterion is prescribed as zero evolution length. The result is optimal geometries that are adapted to the flow and thermal constraints.
Electrostatic Effects on Submicron Particles Deposition
Authors: Abuzeid Salem , Busnaina Ahmed A.
Published: April 2021

Laminar air flow in a two-dimensional stagnation point flow is numerically simulated. This geometry resemble the flow of air in clean room over a clean bench. The Lagrangian equation of motion of aerosol particle that includes effects of drag, gravity, lift force, Brownian motion and electrostatic force is solved numerically. The Brownian force is simulated as a Gaussian white noise random process. Trajectories of aerosol particles in the flow are evaluated and a deposition capture area which varies with particle sizes is produced. The effects of particle diameter and surface voltage on particle capture area (deposition area) are shown. Different surface voltages of 0.0, 1.0, and 4.0 kv/cm are considered. The results show that, deposition of particles increases as the surface voltage increases for all particle sizes considered. Also, the particles which have a minimum capture area are in the range of 0.50–1.0 μm. This implies that the particles which have a minimum deposition rate are in that range.
Optimizing the Operation of Gas Transmission Networks
Authors: Luongo C. A. , Yeung W. C. , Gilmour B. J.
Published: April 2021

This paper presents a generalized procedure for optimizing steady-state operation of natural gas networks based on different objectives: minimum fuel consumption, minimum fuel cost, maximum throughput, and maximum operating margin (profit). The generalized procedure is a hierarchical approach that combines linear and non-linear optimizers in order to achieve good performance without compromising accuracy in modeling physical network components (compressors, pipes, etc.). The non-linear optimizer is used to optimize the physical flows in the transmission networks. The non-linear optimizer calls the linear optimizer to find the optimum allocation of flows among the contracts for the best objective function. The solution technique used by the linear optimizer can handle thousands of contracts with and without two-tier priced structure. Separating the physical flow optimization and economic optimization makes the global optimization feasible for large problems usually encountered in the gas transmission industry. In that sense, the present optimization method bridges the gap between engineering modeling and economic dispatch optimization of natural gas networks.
Piston Geometry Design Effects on Combustion and Emission Characteristics
Authors: Gupta Ashwani K. , Jiang Lu , Keating Eugene L.
Published: April 2021

Numerical simulation of flow, combustion phenomena and pollutants emission characteristics have been obtained on an internal combustion engine having conventional flat piston and advanced piston geometries. The code employed the time marching procedure that solves the governing partial differential equations of multi-component chemically reactive fluid flow by finite difference method. The transient solution is marched out in a sequence of time steps. The results show that both the piston geometry and inlet flow conditions affects the local flame properties which subsequently alters the pollutants emission levels. The numerical results provide a cost effective means of developing advanced internal combustion engine chamber geometry design that provides high efficiency and low pollution levels. It is expected that increased computational tools will be used in the future for enhancing our understanding of the detailed combustion process in internal combustion engines and all other energy conversion systems. Such detailed information is critical for energy conservation and environmental pollution control.
Modeling of Free Vertical Turbulent Diffusion Flames
Authors: Gadalla M. A. , Sharif M. A. R.
Published: April 2021

A mathematical/empirical model compatible with the jet mixing theory for predicting the flow field properties, flame envelope, temperature distribution, and flame heights around a free vertical axi-symmetric turbulent diffusion flame has been developed. The model considers the effects of buoyancy force and the relative angle between the reactant jets. The flames are issued from a burner which consists of a central air jet and an annular fuel (commercial butane) jet. The annular jet is issued either vertically or at an angle to the flame axis. Experiments were performed earlier to measure the temperature distribution and concentration of carbon dioxide and oxygen in such flames. Three angular positions of the annular fuel jet and nine burner geometries were investigated. The model predictions in similar configurations are found to be in fair agreement with the experimental data.
Computer Simulation of Dynamic Impact Processes: A Visual and Audio Presentation
Authors: Cheng Wing L. , Craig Alan , Dilber Ilhan
Published: April 2021

Complicated dynamic phenomena as occurred in high velocity impact processes were studied using a numerical approach. A transient nonlinear finite element program was used to model and simulate the impact events. The use of supercomputers was required in these simulations due to the size of the problem and the duration of the events. Techniques designed to visualize 3D geometry as well as scientific data were developed to help researchers make sense out of the tremendous amount of data generated by the supercomputers. Resulting animation sequences provided a means to the researchers to study these dynamic processes. A newly developed technique called data sonification was also exploited to provide an additional medium to display scientific data. This is accomplished by mapping various parameters of the dataset to various parameters of sound. Two complex 3D numerical examples were used to demonstrate both visual and sonic techniques.
Finite Element Stress Analysis of Engine Piston
Authors: Mistry Anil , Sodhi Raj
Published: April 2021

In this analysis, Ford Motor Company’s, modular engine series piston was selected for the analysis purposes. The engine has a capacity of 4.6 liter, V-8 cylinder and with 2 valves. The piston is made of aluminum alloy material Z-16-T6. A three-dimensional finite element model was created to analyze the piston. The model, which contains only the quarter section of the piston due to loading symmetry and geometry, was used to calculate operating temperatures and the corresponding thermal expansion. Operating stresses due to thermal and mechanical loads were also calculated. The accuracy of the model was verified by material data published in the literature, as well as from the data provided by Ford Motor Company. The obtained results are very useful in the designing and developing the existing piston to increase wear resistance capacity. These results are also useful for design and development that will absorb more heat load, and reduce noise by proper barrel planning of the skirt from the deformation data of the piston. Additionally, it helps in reducing the piston weight and inertia forces through optimization.
Guidelines for Using Finite Element to Model Cortical Defects
Authors: Gessel G. R. , Bartlett J. P. , An K.-A. , Morrey B. F.
Published: April 2021

Guidelines for using finite element to model cortical defects were established by determining the consequences for solution accuracy of various modeling strategies. Solution accuracy was established by comparing finite element results to an existing experimental benchmark for the torsion of circular tubes that contained transverse through circular holes. A new automated modeling approach was developed that could be used to support clinical modeling of cortical defects.
Evaluating Optical Surfaces Using the Finite Element Method
Authors: Hatheway Alson E. , Bella David , Ghazarian Vigen
Published: April 2021

In the late 1960’s Malvick and Pearson (1968) used dynamic relaxation techniques to solve for the deflections of a four meter mirror in a variety of mounting configurations. The material has been widely used to design the mounting of large primary mirrors for a generation of optical instruments. In view of the advances in computational techniques and hardware in the intervening twenty years there has been interest in validating the analysis in a contemporary finite element code.

The writers have undertaken the task to update the analysis originally performed by Malvick and Pearson. The same problems are being solved using MSC/NASTRAN, Version 66. This paper is a discussion of the initial results with comments directed to analysts attempting to evaluate mounts for large mirrors.
An Attempt at the Detection of a Flaw Using the Inverse Problem Solution of Impedance Imaging
Authors: Hussain M. A. , McKee M. , Frankel J.
Published: April 2021

In this paper we present some preliminary numerical simulations which allow us to predict a single flaw in a simply connected body. The purpose of this investigation was to detect flaws and cracks of engineering components using the method of electrical current computed tomography (ECCT), which is used in non-destructive testing technology. As in the previous paper, we have utilized the network analogy to detect a single flaw anywhere in the object. For detection of multiple flaws, the analysis has to be refined to give consistent results.
Dynamic Response Formulation for Pneumatically Driven Liquid in a Pressure Vessel
Authors: Loucks Richard B.
Published: April 2021

The Thermal Radiation Simulator (TRS) at the U.S. Army Ballistic Research Laboratory uses aluminum powder reacting with liquid oxygen to create a large jet like flame. The flame acts as a large thermally radiant wall, exposing targets to a nuclear weapon equivalent. The aluminum powder is driven pneumatically to the combustion chamber from a pressurized containment vessel. Unfortunately the thermal output of the flame oscillates with large amplitude relative to the mean yield. The fluctuating mass flow rate of aluminum powder from the aluminum powder containment vessel seemed the cause of the unstable output.

A computer model of the aluminum vessel was constructed to determine the pressure dynamics in the pressure vessel. The aluminum powder was assumed to behave as a Newtonian liquid. The pneumatic fluid was assumed to be an ideal gas. The model concentrated inside the vessel and at the exit. The result was to determine the mass flow rate of aluminum from the exit given the inlet gas pressures.

The model did reveal the source of mass flow fluctuations not to be caused directly by the existing pneumatic set-up. The variation was shown to be perturbated by forces outside the pressure vessel. Once the outside influence was eliminated, the model showed a clean mean flow rate of aluminum powder. The results were applied to the TRS and the thermal output was stabilized.
Dynamic Overturning Response of an Army Vehicle Subjected to a Side-On Blast Overpressure
Authors: Gupta Aaron Das , Wisniewski Henry L.
Published: April 2021

The dynamic overturning response of combat vehicles and vehicles with electronic equipment shelters is of interest to the defense community since critical internal equipments can be damaged contributing to system malfunction and reduction of vehicle effectiveness which can jeopardize the mission. To overcome sensitivity of vehicles and associated equipments to overturning, the Army is actively engaged in a hardening program which will result in overturning mitigation. The current investigation is devoted to determination of overturning response and sliding motion of a specific Army vehicle i.e., HMMWV jeep and the S-250 shelter assembly subjected to side-on diffraction and drag loads from a 10 psi blast overpressure. Assemblage of aerodynamic box models has been configured to represent the two vehicles and the generated models have been run upto 1.6 s using MINITRUCK which is an implicit two-dimensional version of a flexible multibody dynamics code available at the Ballistic Research Laboratory. The study indicates large sliding and overturning response of these vehicles in the absence of restraints and demonstrates the need for stabilization and overturning mitigation using outrigger pairs, cables, guywires and other active devices attached to the vehicle body.
Structural Finite Elements With High-Order Basis Functions
Authors: Balch Chad D.
Published: April 2021

In the p-version of the finite element method, convergence is achieved by increasing the polynomial order of the elements. This paper discusses high-order three-dimensional carved beam and shell elements which have been implemented in a general purpose p-version linear finite element code. The displacement and rotation fields are represented by polynomials up to ninth order. Beam axes are three-dimensional space curves, and shell midsurfaces are general doubly-curved surfaces. Results for linear static and modal analyses are presented. In particular, it is demonstrated that a relatively small number of elements provide highly accurate results for typical benchmark problems. The elements perform robustly, with no locking or spurious deformation modes.
Analysis of Stiffened Plates Using the Boundary Element and Finite Element Hybrid Method
Authors: Shih Hui-Ru , Duffield Roger C.
Published: April 2021

The boundary element and finite element hybrid method, based on a combination of unstiffened plate boundary element method and stiffener finite elements, is employed for static analysis of concentrically stiffened plates subjected to transverse loading. The integral equation formulation and its boundary element solution procedures for bending of a unstiffened plate are briefly reviewed. The algorithm which permits coupling of the unstiffened plate boundary elements with the beam (stiffener) finite elements is presented. The numerical implementations of the equilibrium and compatibility conditions along the interface between the plate and its stiffener are given in detail. Numerical examples illustrate the accuracy as well as the capability of the proposed method to determine the solution of stiffened plate bending problems.
Distribution of Flow Across the Radius of an Axisymmetric Shock Tube With Variable Cross-Sectional Area
Authors: Schraml Stephen J. , Pearson Richard J.
Published: April 2021

Experiments were conducted to study the characteristics of unsteady flow in a small, axisymmetric shock tube. These experiments have been supplemented by calculational results obtained from the SHARC hydrodynamic computer code. Early calculational results indicated that a substantial gradient in flow velocity and dynamic pressure may exist along the cross-section of the shock tube. To further investigate this phenomenon, a series of experiments was performed in which dynamic pressure measurements were made at various radii in the expansion section of the shock tube. Additional calculations with the SHARC code were also performed in which turbulence modelling, artificial viscosity and second order advection were employed.

The second set of calculations agree very well with the experimental results. These results indicate that the dynamic pressure is nearly constant across the radius of the shock tube. This contradicts the early computational results which were performed with first order advection and without turbulence modelling. As a result of these findings, it was concluded that turbulence modelling was necessary to obtain accurate shock tube flow simulations.
Analysis of EDM Process: A Finite Element Approach
Authors: Madhu P. , Jain V. K. , Sundararajan T. , Rajurkar K. P.
Published: April 2021

A model has been proposed for predicting the material removal rate and depth of damaged layer during Electro Discharge Machining (EDM). The transient heat conduction equation for the workpiece which accounts for the heat absorption due to melting, has been solved by the finite element method (FEM). Gaussian heat distribution of power within a spark has been considered and unlike in earlier theoretical works, the periodical updating of the shape of the workpiece surface has been performed. Computations have been performed for a single spark in the form of a pulse and a multi-sparks situation with a continuous power input and zero off time. The estimated results match fairly well with the experimental results.
Elastic-Plastic FEM Analysis of Deformations of a Cylinder Subjected to Severe Uniaxial and Bilateral Compression by Flat Plates
Authors: Gotoh M. , Shibata Y.
Published: April 2021

Uni-lateral and bi-lateral elastic-plastic compressions of a circular cylinder with three different wall thicknesses by flat plates are numerically analysed by the Finite Element Method (FEM). J2-flow theory (J2F), and J2-Gotoh’s corner theory (J2G) which was previously proposed by one of the authors are used as the constitutive equations. In the case of uni-lateral compression, the cylinder is compressed up to a completely flattened shape, which is considered a kind of plastic forming processes. The deformed shapes and the compressive force are predicted better by J2G than by J2F. The spring-back behaviours are also analysed by imposing unloading process during deformation. The deformation process in the compression of a ring (plane stress state) and a spherical shell (axi-symmetric state) is also analysed. In the case of bi-lateral compression, the process is considered a kind of square-tube forming. In its final stage, the cylinder deforms into a completely unexpected shape which could be thought of as a square tube reinforced with ribs. The J2G allows the process to proceed at a lower compressive force than that for J2F. The effect of n-value (the strain-hardedning exponent) on the deformation pattern is also discussed.
Finite Element Technique for the Curved Beam Analysis: In-Plate Vibration of Curved Beam With Varying Cross Section
Authors: Tanaka Michihiko , Kobayashi Motoki
Published: April 2021

The purpose of this paper is to present details of an algorithm for performing the numerical analysis of in-plane free vibration problem of curved beam by using the finite element technique. Although the finite element techniques for the straight or flat structures such as rods, beams and plates are well established, the finite element formulation for curved beam has not yet been completely discussed because of analytical complexity of the beam. The analysis of curved beam is reduced to the coupled problems of the axial and the transverse components of forces, bending moments, displacements and slopes in the beam. Sabir and Ashwell have discussed the vibrations of a ring by using the shape functions (interpolation functions) based on simple strain functions[1]. The discrete element displacement method was applied to the vibrations of shallow curved beam by Dawe[2]. Suzuki et al have presented the power series expansions method for solving free vibration of curved beams[3]. Irie et al have used spline functions to analyse the in-plane vibration of the varying cross section beams supported at one end[4].
Editing of Finite Element Models
Authors: Lundgren Gert M.
Published: April 2021

Meshing of complex shapes is often performed automatically with many of todays preprocessors. However in the case where the mesh has to be modified locally, the analyst needs tools that can conveniently be applied to individual elements. One reason for this may be the need to apply an external load at a specific location. Another reason may be that a local cutout has to be reflected, or a transition from a coarse to a finer mesh is needed. This paper discusses the design and usage of such tools, in the following referred to as ‘Micro-Editing’ tools.
Automatic Mesh Generation of Complex Hollow Structures via Substructuring Into Box-Like Components
Authors: Abhary Kazem
Published: April 2021

A method has been developed for finite element modelling of complex hollow structures. The structure is first simulated as a number of simple box-like substructures, then the finite element mesh is generated in each substructure, and finally the finite element model of the whole structure is built up through coupling the components together. An example has been illustrated by applying the method to the structure of a milling machine, which as a hollow structure is sufficiently complex.
Description of an Interface Between MSC/NASTRAN and MATRIXx With Example Applications
Authors: Morrison Scot , Caffrey John
Published: April 2021

This paper describes an existing interface which allows extraction of linear models from an MSC/NASTRAN output file and conversion into MATRIXX readable format for control design and simulation. The interface is demonstrated using an MSC/NASTRAN model of a satellite microwave antenna.

In addition to the existing interface, a proposed expanded interface allowing additional information to be transfered between MSC/NASTRAN and MATRIXX is presented. Candidate information includes component mass and stiffness matrices, and outputs from MSC/NASTRAN’s Design Sensitivity Analysis (DSA) package. This sensitivity data would allow open or closed loop robustness analysis, and simultaneous structural and controller design. Additionally, the ability to transfer linear controllers designed in MATRIXX to MSC/NASTRAN would allow evaluation of such controllers on the full order model.
Upgrades for Engineering Software
Authors: Hadjistylianou Marinos , Hoffman Daniel
Published: April 2021

Improvements in hardware and software technology offer exciting opportunities for software development in the 1990’s. Nonetheless, because wholesale replacement of large systems is rarely feasible, most computing in the 90’s will be done by way of improving software written in the 70’s and 80’s. Consequently, methods for incremental improvement are critically needed. We propose software upgrades, in which improvements in internal system structure are scheduled with each user request for new features or error removal.
Reduction of Vehicle Interior Noise Using Our New Structural-Acoustic Sensitivity Analysis Methods
Authors: Hagiwara Ichiro , Kozukue Wakae , Ma Zheng-Dong
Published: April 2021

Since interior noise has a strong effect on vehicle salability, it is particularly important to be able to estimate noise levels accurately by means of simulation at the design stage. The use of sensitivity analysis makes it easy to determine how the analytical model should be modified or the structure optimized for the purpose of reducting vibration and noise of the structural-acoustic systems.

The present work focused on a structural-acoustic coupling problem. As the coefficient matrices of a coupled structural-acoustic system are not symmetrical, the conventional orthogonality conditions obtained in structural dynamics generally do not hold true for the coupled system. To overcome this problem, the orthogonality and normalization conditions of a coupled system were derived by us. In this paper, our sensitivity analysis methods are applied to an interior noise problem of a cabin model. It will be shown how a sensitivity analysis process is performed, and how vibration and noise can be reduced.