UNIVERSITY/ RESEARCH - Technical Abstracts




Dr. Xi Wu
Associate Professor, California Polytechnic State University
Presenting: Practical considerations for transient and FFT analyses of planetary gears using ADAMS

Planetary gears are more compact and efficient as power transmissions than fixed-axis gear trains but exhibit complicated dynamic behaviors due to the nonlinearity of the combination of backlash and teeth defects. This paper will share the teaching experience of applying ADAMS in planetary gear design and dynamic analysis with graduate students. Since the dynamic behavior of the system is highly dependent on point-to-point contact forces between the gear pairs, students are required to precisely design the involute profile of gears using CAD software. Comprehensive vibration responses of two types of planetary gears with different backlash and teeth damage are investigated in the class. Backlash between the sun gear and planet gears are precisely specified to avoid teeth interference and undercut. Constraints, bearing resistant torques, and some key parameters in ADAMS are applied as close as possible to real operating conditions. The students compare their simulation results from ADAMS with theoretical hand calculations to judge if their results are reasonable. Steady-state frequency analysis demonstrates the appearance of side band modulations as well as harmonics of the gear mesh frequency. A joint time-frequency analysis during start-up illustrates a unique oscillating spectrum for the differential planetary gear in which contact forces increase during acceleration. JTFA is a speed-dependent powerful analytical tool which tracks vibrations in the rotating components of planetary gears. As a result of using ADAMS in the classroom, students are able to identify specific vibration signatures in both the frequency domain and time domain for different type of teeth damage.





Dr. Sami Kilic
Assistant Professor, Bogazici University
Presenting: Modeling sloshing effects in cylindrical tanks subjected to base excitation

Sloshing phenomenon of liquid fuel stored in metal cylindrical tanks at petrochemical industrial complexes caused heavy damages during the past earthquakes. Examples can be found from the damage investigation studies of the 1994 Northridge California and 1999 Marmara Turkish earthquakes. In order to assess the sloshing risk of such containment structures, this study presents the efforts in modeling the fluid-structure interaction effects for tanks of cylindrical geometry. The SOL 700 approach available in MD.Nastran offers the possibility of modeling sloshing effects by using the Eulerian approach of the MSC.Dytran CFD solver for the liquid material, and couples the system with the Langrangian shell containment structure modeled with the material library of the finite element code LS-Dyna. The time marching scheme is explicit and uses small time steps. Therefore, computations are carried on an eight-core computing platform. The ground motion records of the 1999 Marmara Turkish earthquake are utilized in the numerical studies. The finite element model of the tank under investigation comes from an actual design using the API 650 Standard. Results are illustrated for the maximum wave height of the sloshing liquid and the pressures exerted on the side walls of the tank.




Dr. Basem Alzahabi
Professor, Kettering University
Presenting: The Role of Simulation in Engineering Education

As a result of the increasing worldwide competition, today’s industries require engineers to design better products, with improved performance, in less time, and with less cost. Therefore, it’s more critical than ever before for practicing engineers to not only use simulation tools, but to understand how to use these simulation tools properly and effectively for design synthesis within a digital or virtual environment.

Industry, educational institutions, engineering providers, and government agencies all have important roles in developing simulation based engineering to improve the product development process. For example, Industry is required to acquire and develop the right tools and expertise to maintain their competitiveness. This will often involve sponsoring improvement programs where internal and external resources are brought together to collaborate.

Educational institutions have the role of providing the core professional preparation for the technical professionals who carry out the engineering development process. Engineering education must prepare future engineers for the multi-disciplinary nature of the engineering problems they face.

In response to industry needs and in collaboration with MSC.Software, the Mechanical Engineering department at Kettering University has systemically incorporated MSC Software in its Computer Aided Engineering simulation curricula.

This presentation will discuss the very important role of simulation in engineering education for the preparation and development of engineering, and the integration of MSC Software into the engineering mechanics curriculua.


 



Bernard Antkowiak
Staff Engineer, Draper Laboratory
Presenting: Creating Reduced Order Thermal State-Space Models  From MSC Nastran Finite Element models

To develop comprehensive thermal control strategies, reduced order thermal plant models from Finite Element models provide for real time domain simulations. It has been found that these reduced order models contain additional thermal considerations over traditional 1’st order thermal systems and provide additional insight for the Proportional-Integral controller in the design phase.  Furthermore, using existing FE models that generally already exist in the design phase to construct these reduced order models does not require a significant modeling effort. 

Reduced order plant control models for mechanical structures are routinely created using modal reduction from FE structural eigenvalue analyses.  Based on this same general technique, reduced order thermal models can also be constructed from Finite Element models using the standard state-space form: 

The modal reduction is found to be generally a bit more complicated than with the Structural counterparts.  However, various reduction techniques are found to be quite effective.   This paper reviews the mathematical theory for creating reduced order state-space models, the application of the technique using MSC.Nastran, including sample DMAPS, and  an implicit balancing technique in Matlab for modal reduction.






Dr. Lin Liao
Aeronautical Engineer, AEROS
Presenting: Application of MSC NASTRAN in Modeling and Analysis of 3D Truss Structures

Trusses have attracted tremendous interests due to their extensive applications in the construction of infrastructures and space structures. MSC NASTRAN serves as an efficient tool for modeling and analysis of trusses. In this paper, the structural members of 3D trusses are modeled as beam elements, which can support both axial loads and bending loads. First, static load analysis of 3D truss beams is carried out. Hence, linear buckling analysis and normal mode analysis of truss beams are performed. Design optimization of trusses based on parametric study of truss buckling capability and natural frequency is presented as a separate topic.

Cable_truss structures containing multiple truss beams and cables is studied. Cables can only withstand tension and are utilized to maintain stability and strength of truss structural systems. Cables are modeled as tension-only elements and cable pretension can be prescribed by thermal loads. MSC NASTRAN is utilized to study the effect of cable pretension, the interaction between cables and truss beams, and the influence of cable and truss property on structural performance. The enhancement of cable stiffness and the increase of cross-sectional area result in the decrease of truss deformation. Cable tension of deformed trusses changes significantly in contrast with pretension, and cables could completely lose tension in deformed configurations. Tensioned cables offer structural flexibility and accommodate diverse loading by the variation of tension. At last, linear dynamic analysis of cable_truss structures is addressed.



Gilad Shainer
Chairman, HPC Advisory Council
Presenting: The Effect of HPC Clusters Architecture on MSC Nastran Performance

From concept to engineering, and from design to test and manufacturing, engineering relies on powerful virtual development solutions. Finite Element Analysis is performed in an effort to secure quality and speed up the development process. MSC Nastran is the world's most widely used (FEA) solver, built on work done by NASA scientists and researchers.

The recent trends in cluster environments, such as multi-core CPUs, GPUs and new interconnect speeds and offloading capabilities are changing the dynamics of clustered-based simulations. Software applications are being reshaped for higher parallelism and multi-threads, and hardware configuration for solving the new emerging bottlenecks, in order to maintain high scalability and efficiency.

The paper and presentation will review the recent developments of high-performance clustering architectures, CPUs and interconnect solutions and how they influence MSC Nastran simulations, scalability and performance. A deep analysis and profiling of MSC Nastran will be described and guidelines for optimized productivity will be explored.




Scott Wood
PhD Candidate, Clemson Bioengineering Dept
Presenting: Structural modeling of vascular smooth muscle cell mechanics using Marc

In this study, the nonlinear mechanical behavior of biological cells under static and dynamic loading are simulated using the FEM capabilities of MSC Marc. Vascular smooth muscle cells (VSMCs) are chosen for this study due to the strong correlation of the geometric arrangement of their structural components on their mechanical behavior and the implications of that behavior on diseases such as atherosclerosis (Buerke M. BBA. 2007;1774:5-15.).

VSMCs are modeled here using a generalized Maxwell viscoelastic material model together with rebar elements in Marc which simulate the cytoskeletal fiber network that provides the cells with much of their internal structural support. Geometric characterization of single VSMCs of two physiologically relevant phenotypes in 2D cell culture is achieved using confocal microscopy in conjunction with novel image processing techniques. These techniques allow for the creation of representative 3D model structures consisting of the cell nucleus, cytoplasm, and actin stress fiber network of each cell, which are then imported into Patran for structural analysis with Marc. Mechanical characterization is achieved using atomic force microscopy (AFM) indentation and stress relaxation techniques. Material properties for each VSMC model are input based on values individually obtained through experimentation, and the results of each model are compared against those experimental values. This study is believed to be the first of its kind, in which not only are the geometries of cells in a FEM based on confocal microscopy images of actual cells, but the results of the model are then compared against experimental data for those same cells.