Jan Hol’s research while affiliated with Delft University of Technology and other places

This paper discusses the results of a one-year experiment of a course on aircraft stress analysis and design in the second year of the BSc phase at the Faculty of Aerospace Engineering, Delft University of Technology. The experiment entails an electronic version of a classical reader in wiki format. The reason for this experiment is based on a practical need, namely the nature of the course having a large content and a wide diversity. This makes it difficult to present all the material in a classical reader in a comprehensive way and to clearly indicate the links between the different parts of the course content. Therefore a wiki provides an ideal environment to easily link different subjects to each other. Furthermore since students are allowed to edit the wiki, which is an innate property of the software, the course contents should become more comprehensive for the students. It was shown that students are not really enthusiastic about a wiki format reader, and prefer a written version. The main reason for not editing a wiki reader is that students find themselves too inexperienced, or simply do not have the time to edit the content.

Although digital learning applications have been available to lecturers for several years, they are still hesitant to intensively use these tools due to restrictions in time and budget. To help lecturers overcome this hurdle TU Delft offers its lecturers small grants to implement digital learning in their courses through the GRASSROOTS project[1]. One such project is the development of a dedicated Wikipedia encyclopaedia[2] using course material generated jointly by teachers and students participating in the 2nd year BSc course Aircraft Stress Analysis and Structural Design [3]. Teaching staff at TU Delft generally have a double appointment combining research with lecturing in their area of research. Including their research work as state of the art topical content in courses requires course material to be generated on-the-fly. Publishing of course materials such as lecture notes and books usually lags behind presentation thereof. Also developing course material while aiming for sufficient study results is in the current social environment a cooperative teacher-student activity requiring efficient generation of course material, immediate incorporation of feedback and optimal delivery of course material. Thirdly activating students to assist in developing course material is a strong motivator for participation. Considering the social aspects and continuous on-line availability a Wikipedia encyclopaedia is the social software tool of choice. This paper describes the experiences and lessons learned whilst developing a Wikipedia encyclopaedia of course material[4]. Conclusions from project development and deployment together with recommendations for future improvement are presented. Also the opinions and responses of the students participating in the project are reported.

As a consequence of the introduction of a new 5-year Bachelor-Master degree programme by the Faculty of Aerospace Engineering of the Delft University of Technology the study results for the mandatory Finite Element Analysis course were found to be unsatisfactory and cause a bottleneck in the curriculum. Identifying the underlying problems lead to rejuvenation of the course content and delivery by implementing state-of-the-art software and hardware facilities supported by the Blackboard environment. Study results where spectacularly improved and the bottleneck in the curriculum has successfully been removed. Student response to the improved course are excellent and course content is actively used in later BSc and MSc curriculum components. This paper reports in detail in the changes implemented and new components introduced to attain this result.

An initiative has been under way in restructuring the Aircraft Stress Analysis and Structural Design course at The Faculty of Aerospace Engineering at Delft University of Technology to meet the needs of changing undergraduate educational environment. These changes are the result of: 1. Changes in the students’ study and learning habits, 2. Expectation of the higher level course instructors and the industry employers from the undergraduate students 3. The availability of powerful numerical tools that enable graduating engineers to perform a variety of daily engineering tasks In the new course emphasis will be on the fundamentals of structural design and treatment of design of structural systems with multidisciplinary features, while integrating mathematical and engineering mechanics skills into the design process. More than the changes to the content of the course, however, addition of new curriculum elements that will prepare today’s engineers for tomorrow’s challenges are under way. These additions/changes are along the way of making the course material available to the students via web based content, carrying out the lectures via computer based tutorials and presentations, and conducting electronic exams ad quizzes via the “BlackBoard” tool. As a main tool for the in-class tutorials as well as the homework assignments use will be made of Mathematica. This paper will report on the new course, the use of Mathematica in in-class tutorials, and the response from students and lessons learned with the view of providing others with ideas on how to reform their traditional structural design courses.

Multi-level high-fidelity analysis is recognized as a viable strategy for obtaining improved safe knockdown factors based on the so-called "manufacturing signature" of a fabrication process. This approach is implemented in the hierarchical interactive computer code DISDECO, the Delft Interactive Shell Design Code, which enables interactive investigation of the various aspects of the nonlinear response of thin-walled shells. The goal of the research reported in this paper is the development of accurate inheritance of computed results from low-level parametric analysis modules through intermediate approximate analysis levels to high-level large general purpose computer codes. Accurate fitting, interpolation and extrapolation of computed results as well as reformulating to accommodate alternate computational methods are major requirements. The inheritance methods are demonstrated by the hierarchical analysis of the collapse behavior of a stringer stiffened cylindrical shell.

The development of “DISDECO”, the Delft Interactive Shell DEsign COde is described. The purpose of this project is to make the accumulated theoretical, numerical and practical knowledge of the last 25 years or so readily accessible to users interested in the analysis of buckling sensitive structures. With this open ended, hierarchical, interactive computer code the user can access from his workstation successively programs of increasing complexity. The computational modules currently operational in DISDECO provide the prospective user with facilities to calculate the critical buckling loads of stiffened anisotropic shells under combined loading, to investigate the effects the various types of boundary conditions will have on the critical load, and to get a complete picture of the degrading effects the different shapes of possible initial imperfections might cause, all in one interactive session. Once a design is finalized, its collapse load can be verified by running a large refined model remotely from behind the workstation with one of the current generation 2-dimensional codes, with advanced capabilities to handle both geometric and material nonlinearities.

The present paper presents the procedure used to write a user material subroutine UMAT for shell elements to include property degradation of the composite plies of a Fibre Metal Laminate (FML). The Hashim's three-dimensional piecewise stress-based criteria for in-plane failure has been implemented in the subroutine. The type of failure and its extension in the pre-preg layers can be visualised in ABAQUS-CAE. Case study has been the blunt notch strength of a GLARE plate. The numerical results were in good agreement with the experimental ones.