On processing development for fabrication of fiber reinforced composite, part 2

Fiber-reinforced composite laminates are used in many aerospace and automobile applications. The magnitudes and durations of the cure temperature and the cure pressure applied during the curing process have significant consequences for the performance of the finished product. The objective of this study is to exploit the potential of applying the optimization technique to the cure cycle design. Using the compression molding of a filled polyester sheet molding compound (SMC) as an example, a unified Computer Aided Design (CAD) methodology, consisting of three uncoupled modules, (i.e., optimization, analysis and sensitivity calculations), is developed to systematically generate optimal cure cycle designs. Various optimization formulations for the cure cycle design are investigated. The uniformities in the distributions of the temperature and the degree with those resulting from conventional isothermal processing conditions with pre-warmed platens. Recommendations with regards to further research in the computerization of the cure cycle design are also addressed

Methodology for sensitivity analysis, approximate analysis, and design optimization in CFD for multidisciplinary applications

In this study involving advanced fluid flow codes, an incremental iterative formulation (also known as the delta or correction form) together with the well-known spatially-split approximate factorization algorithm, is presented for solving the very large sparse systems of linear equations which are associated with aerodynamic sensitivity analysis. For smaller 2D problems, a direct method can be applied to solve these linear equations in either the standard or the incremental form, in which case the two are equivalent. Iterative methods are needed for larger 2D and future 3D applications, however, because direct methods require much more computer memory than is currently available. Iterative methods for solving these equations in the standard form are generally unsatisfactory due to an ill-conditioning of the coefficient matrix; this problem can be overcome when these equations are cast in the incremental form. These and other benefits are discussed. The methodology is successfully implemented and tested in 2D using an upwind, cell-centered, finite volume formulation applied to the thin-layer Navier-Stokes equations. Results are presented for two sample airfoil problems: (1) subsonic low Reynolds number laminar flow; and (2) transonic high Reynolds number turbulent flow

Methodology for sensitivity analysis, approximate analysis, and design optimization in CFD for multidisciplinary applications

Fundamental equations of aerodynamic sensitivity analysis and approximate analysis for the two dimensional thin layer Navier-Stokes equations are reviewed, and special boundary condition considerations necessary to apply these equations to isolated lifting airfoils on 'C' and 'O' meshes are discussed in detail. An efficient strategy which is based on the finite element method and an elastic membrane representation of the computational domain is successfully tested, which circumvents the costly 'brute force' method of obtaining grid sensitivity derivatives, and is also useful in mesh regeneration. The issue of turbulence modeling is addressed in a preliminary study. Aerodynamic shape sensitivity derivatives are efficiently calculated, and their accuracy is validated on two viscous test problems, including: (1) internal flow through a double throat nozzle, and (2) external flow over a NACA 4-digit airfoil. An automated aerodynamic design optimization strategy is outlined which includes the use of a design optimization program, an aerodynamic flow analysis code, an aerodynamic sensitivity and approximate analysis code, and a mesh regeneration and grid sensitivity analysis code. Application of the optimization methodology to the two test problems in each case resulted in a new design having a significantly improved performance in the aerodynamic response of interest

First- and Second-Order Sensitivity Analysis of a P-Version Finite Element Equation Via Automatic Differentiation

Sensitivity analysis is a technique for determining derivatives of system responses with respect to design parameters. Among many methods available for sensitivity analysis, automatic differentiation has been proven through many applications in fluid dynamics and structural mechanics to be an accurate and easy method for obtaining derivatives. Nevertheless, the method can be computational expensive and can require a high memory space. This project will apply an automatic differentiation tool, ADIFOR, to a p-version finite element code to obtain first- and second- order then-nal derivatives, respectively. The focus of the study is on the implementation process and the performance of the ADIFOR-enhanced codes for sensitivity analysis in terms of memory requirement, computational efficiency, and accuracy

An Integrated Curriculum for Technical Writing in Higher Education in China

This study aims to develop an effective curriculum plan to improve technical writing in higher education in China. The paper first investigated the deficiency in the curriculum design in China for English technical writing by comparing the required courses offered in Southwest Jiaotong University (SWJTU) in China with those in Old Dominion University (ODU) in US. Questionnaires and interviews were then conducted among studying abroad Chinese students, visiting scholars, English as Second Language (ESL) instructors as well as engineering professors. The collected data revealed that the oversea Chinese students were struggled more with higher order concerns in writing than lower order ones. This comparison and survey led to the development of a curriculum plan that includes both Chinese and English writing classes for all majors in an engineering college in China

Initial Investigation of Analytic Hierarchy Process to Teach Creativity in Design and Engineering

This paper investigates the use of Analytic Hierarchy Process to teach design creativity and innovation in undergraduate engineering students. Examples are included to assess its effectiveness in the classroom. The purpose of this research is to investigate the suitability of the Analytic Hierarchy Process (AHP) to teach design innovation and creativity in undergraduate engineering classrooms. AHP is a very structured, multi-criteria, decision-making process and traditionally has been used to solve complex problem sets. This investigation takes a fresh look at how AHP provides the framework to engage and encourage students to think creatively and innovatively in design and engineering. This paper presents several separate case studies that incorporate the AHP technique in the classroom to teach design innovation and creativity to undergraduate engineering students, including introduction at the freshmen engineering level. These case studies include: the design of a robotic water vehicle; the design of a coffee maker; and the design of a website. These diverse case studies explore the suitability of this decision-making technique across abroad range of design problems to assess how AHP can be utilized to give students a better understanding of the design process, to foster a personal motivation towards creative and innovative thinking and to equip students with a strategy for creative problem solving theycan use through their engineering careers. Students who participated in the case studies completed questionnaires to assess the application of AHP and its effectiveness to understand the problem and to reach a creative and innovative solution. Based on the results of these student questionnaires, there is positive evidence that AHP can be utilized to remove barriers that inhibit creativity and to foster an environment for students to achieve more design creativity and innovation in engineering classrooms. This study has implications to change the pedagogical approach used to teach engineering design and provides a methodology for design creativity that students will carry with them throughout their career

Sensitivity Analysis Method to Address User Disparities in the Analytic Hierarchy Process

Decision makers often face complex problems, which can seldom be addressed well without the use of structured analytical models. Mathematical models have been developed to streamline and facilitate decision making activities, and among these, the Analytic Hierarchy Process (AHP) constitutes one of the most utilized multi-criteria decision analysis methods. While AHP has been thoroughly researched and applied, the method still shows limitations in terms of addressing user profile disparities. A novel sensitivity analysis method based on local partial derivatives is presented here to address these limitations. This new methodology informs AHP users of which pairwise comparisons most impact the derived weights and the ranking of alternatives. The method can also be applied to decision processes that require the aggregation of results obtained by several users, as it highlights which individuals most critically impact the aggregated group results while also enabling to focus on inputs that drive the final ordering of alternatives. An aerospace design and engineering example that requires group decision making is presented to demonstrate and validate the proposed methodology

Static, Vibration Analysis and Sensitivity Analysis of Stepped Beams Using Singularity Functions

A systematic approach is presented in this paper to derive the analytical deflection function of a stepped beam using singularity functions. The discontinuities considered in this development are associated with the jumps in the flexural rigidity and the applied loads. This approach is applied to static and vibration analyses of stepped beams. The same approach is later extended to perform sensitivity analysis of stepped beams. This is done by directly differentiating the analytical deflection function with respect to any beam-related design variable. The particular design variable considered here is the location of discontinuity in flexural rigidity. Example problems are presented in this paper to demonstrate and verify the derivation process

Numerical Methods for Fluid-Structure Interaction - A Review

The interactions between incompressible fluid flows and immersed structures are nonlinear multi-physics phenomena that have applications to a wide range of scientific and engineering disciplines. In this article, we review representative numerical-methods based on conforming and non-conforming meshes that are currently available for computing fluid-structure interaction problems, with an emphasis on some of the recent developments in the field. A goal is to categorize the selected methods and assess their accuracy and efficiency. We discuss challenges faced by researchers in this field, and we emphasize the importance of interdisciplinary effort for advancing the study in fluid-structure interaction

Communicating Wave Energy: An Active Learning Experience For Students

We have conducted an education project to communicate the wave energy concept to high school students. A virtual reality system that combines both hardware and software is developed in this project to simulate the buoy-wave interaction. This first-of-its-kind wave energy unit is portable and physics-based, allowing students to conduct a number of hands-on activities. This system is the core component of an educational experience that integrates demonstration and hands-on learning, with an aim of introducing the wave energy conversion process to students in an interactive environment. Presentations have been made at two different high schools with diverse student populations, and students involved in this project rated very positively about their learning experience. As revealed by their feedback, the virtual environment and its combination with the hardware are the most important factors that help students to appreciate the knowledge in the wave energy conversion process