MATLAB in Engineering Education

One of the most important aspects of engineering education is problem solving. This paper intends to show how MATLAB can be utilized to solve various problems in science and engineering. A simple vibration problem is solved using MATLAB’s ODE solver to illustrate the excellent capability of MATLAB in numerical integration of matrix differential equations.

Response of Submerged Structures by the Finite Element-Cum-Boundary Element Method

A double asymptotic approximation based finite element-cum-boundary element approach for fluid-structure interaction problems is being proposed. In particular a staggered solution scheme has been applied to the analysis of various coupled fluid-structure systems. A stabilization scheme by reformulation, proposed by DeRuntz et al. was employed to circumvent the instability problem. In addition, the singularity in the excitation term was eliminated through a variable transformation as suggested by Everstine. Another feature of the present work is its incorporation of the hybrid strain based lower order triangular shell finite element developed by To and Liu. The eigenvalue solution exhibits high convergence rate for the particular shell finite element employed. The responses calculated exhibit the effectiveness of the proposed approach with application of the aforementioned shell finite element in dealing with three dimensional fluid-structure interaction problems. The reduction in problem size that this approach affords allows these complex interaction problems to be dealt with in a desktop engineering workstation environment, as opposed to the mainframe and supercomputer arenas where they have been implemented in the past.

Prediction of Thermal Displacements in Finite Element Tool Models

Precision and productivity are very important criteria for the evaluation of modular tool systems and require a thermally stable process with tolerances in the micrometer range. During the past decades there has been an increasing interest in compensating thermally induced errors. In this paper we investigate wheather a prediction of thermal displacement based on a nonlinear regression analysis is possible, namely using the alternating conditional expectation algorithm (ACE) introduced by Breiman and Friedman, 1985. The data we are analyzing were generated by two different finite element spindle models of modular tool systems. As the main result we find that the ACE-algorithm is a powerful tool to model the relation between temperatures and displacements. It could also be a promising approach to handle well-known hysteresis effects. Limitations of this study are the model restricted results, next our findings have to be validated on real data.

Automatic Unstructured Mesh Generation Around Two-Dimensional Domains Described by B-Spline Curves

A computer code for the generation of unstructured two-dimensional triangular meshes around arbitrary complex geometries has been developed. The code is based on Delaunay triangulation with an automatic point insertion scheme and a smoothing technique. The geometrical definition of the domain to be meshed is prescribed by means of B-spline curves obtained from two approaches of interest in Computer-Aided Geometric Design named inverse design and interpolation problems. The presented scheme is based on an interpolation procedure along a B-spline curve proposed by the author in a recent paper. This technique prevents that the resulting grid may overlap convex portions of the boundaries. The main goal is to study the possibility of extend the methodology of unstructured grid generation beginning with boundaries described by polylines to other in which they are prescribed by piecewise polynomials curves capable to drive more realistic problems. Several figures and examples from Computational Fluid Dynamics have been included to show the various steps of the algorithm. The results show that the code is able to solve the problem of automatic grid generation in a robust manner opening new perspectives for the development of a black-box grid generator.

Analysis of the Robotic Assembling Accuracy Based on Virtual Assembly Environment

Multi-degree freedom robots have many advantages including agility, heavy-loading capability and high flexibility. They play a very important role in mechanical assembly. Due to the complexity of their spatial pose, the robot assembling accuracy analysis should not be confined to the 2-D plane. This paper applies the accuracy analysis to the virtual environment by constructing accurate models of robot assembly unit such as 3-D geometrical modeling, physical modeling, and behavioral modeling. Using the interactive and 3-D graphical environment to observe and evaluate the effects of assembling process. By operating the virtual 3-D model of the robot assembly unit and simulating the assembling process in the virtual assembly environment, the influence of errors in assembly can be analyzed and the statistical value of errors can be obtained. This paper also presents the method of visualization in analyzing the robot assembling accuracy, and studies the influence of spatial pose of robot assembly on the axis-hole assembly success rate, especially the robot teaching accuracy. Through the integration of the various errors and on the basis of the assembling accuracy, the tolerance of error source can be reasonably distributed to meet the requirement for assembling accuracy, and the planning of robot assembly unit can be improved.

Fuzzy Logic Application in Data Acquisition

The aim of this paper is to introduce an expansion of the practice of using surveys when making subjective judgments or decisions. This method is particularly useful in situations in which precise data is limited or nonexistent. It can be especially valuable when working with new designs by reducing the error associated with estimates in the beginning of the product’s life cycle in which costs are greatest. Our approach modifies the traditional survey style by including fuzzy logic and expert judgment. Using fuzzy logic, we solicit the information in a way that gives the evaluator a continuous choice for the cost estimate and a method to indicate the level of confidence in a linguistic manner. By doing this, a range of the likely values for the real value can be defined, and a subjective judgment can be turned into objective information that can be more useful than the traditional approach.

Integrating Design Process Knowledge With CAD Models

Solid models are static entities, often defined by boundary representation models as sets of enclosing surfaces. Constructive Solid Geometry and feature-based computer-aided design environments create procedural descriptions of 3D objects in forms of history or CSG trees. These representations are temporally fixed, i.e., they describe the state of an object at a point in time. This paper describes a method to represent and capture temporal evolution of solid models — what we call model process history. We define process history to be all states of a model — the search space of design process. This paper presents a representational formalism we call model process graphs (MPGs). We use MPGs to integrate a model’s description with a model of temporal changes that occur during the design process. We believe that MPG representations can have valuable application for many design and manufacturing problems. The paper describes our preliminary results to use MPGs to (1) create a record of design process; (2) store process-based design rationale; (3) represent in-process shapes for machined artifacts. We anticipate that similar structures will find application in other design and manufacturing problems where important process knowledge is embodied by temporal changes occurring in model evolution.

Product Life-Cycle Management and the Virtual Enterprise

This paper presents an approach to provide a complete Product Life-Cycle Management architecture across a virtual enterprise. Today’s worldwide marketplace requires; Teaming arrangements, Collaboration across multiple continents and time zones, Protection of corporate assets and Configuration Management of the team’s product. Each of the key building blocks will be reviewed: • Infrastructure • Legacy data • Collaboration • Product Data Management • Configuration Management • Support Management • Data Storage

Development of the STEP-to-DB Converter for the Web-Based PDM

STEP data exchanged for collaborative engineering is usually used in CAD systems. However, it is not used so well in PDM systems due to differences in data scope and structure. In order to resolve this inefficiency, we developed the STEP file converter which can manipulate STEP data in web-based PDM systems. The translation scope is limited to AP203. The translator consists of two modules: 1) the viewer which displays STEP data in web environments and 2) mapping editor and translator between STEP schema and PDM database schema.

Relative Cooling: Part II — Design Considerations and Efficiency

Cooling systems with liquid for gas turbine engines that use the relative motion of the engine stator with respect to the rotor for actuating the coolant pump can be encapsulated within the engine rotor. In this manner, the difficult problem of sealing stator/rotor interfaces at high temperature, pressure and relative velocity is circumvented. A first generation of such cooling systems could be manufactured using existing technologies and would boost the thermal efficiency of gas turbine engines by more than 2% compared to recent designs that use advanced air-cooling methods. Later, relative cooling systems could increase the thermal efficiency of gas turbine engines by 8%–11% by boosting the temperatures at turbine inlet to stoichiometric levels and recovering most of the heat extracted from turbine during cooling. The appreciated high reliability of this cooling system will allow widespread use for aerospace propulsion.