Department Engineering Mechanics   Engineering Mechanics

Professor: prof.dr.ir. L.J. Ernst

The field of Engineering Mechanics comprises the mechanics of solids, in particular those dealing with technical applications and developments. On the one hand attention is paid to the development and implementation of new theories and new methods and on the other hand to the utilisation thereof in actual engineering practice. This involves a wide range of applications, such as the analysis and/or optimization of pressure vessels, machines, machine parts, packing materials, design processes, manipulators, offshore constructions, means of transport, means of oil exploration, foil transport systems, prostheses etc., for the greater part aimed at the improvement of its functional behaviour, its reliability and/or its life span. Due to this wide range of applications, young engineers with an "engineering mechanics background" consequently acquire positions in a wide variety of industries.

With the aforementioned applications use is often made of simulation software based on the developed theories and methods. A frequently used method is the "Finite Element Method". All Mechanical Engineering students get acquainted with this method during their first years of study. In addition to the well-known "standard packages" the section also has self-developed FEM-software at its disposal with which, for instance, the calculation and optimization of complicated plate and shell constructions can be carried out in a (more) efficient way (the CHARLES package) and special FEM software for the simulation of the nonlinear mechanical behaviour of (transformable and non-transformable) mechanisms (the SPACAR95 package). For development and simulation purposes the section has very powerful computer systems at its disposal. These systems are also available for our undergraduates.

Computer simulation models are not being used for all development and/or application-oriented activities. The section also boasts a well-equipped laboratory where "experimental mechanical research" is executed. Available are, e.g. a number of modern testing machines with various measuring facilities, special image processing systems with CCD-cameras for contactless measuring (and automatic monitoring of the measuring area) and a modern system for measuring dynamic phenomena and the processing thereof (such as e.g. experimental modal analysis). If so desired, undergraduates can further qualify themselves at a second aspect of engineering mechanics: "experimental mechanics".

Within the main subject research is being carried out both in the field of "dynamics" and in the field of "mechanics of materials". We shall continue with a brief description of he research themes concerned:

Within this theme we concentrate on the development of methods for the calculation and optimization of the dynamic behaviour of ,especially, nonlinear mechanical systems and the application of the acquired methods in actual practice. The mechanical behaviour of nonlinear dynamic systems is much more complicated than that of linear systems.

Therefore, one of the objectives is to characterize the dynamic behaviour by means of modern numerical methods depending on various model parameters. Thus, it can be indicated when periodic solutions are possible and when "chaotic behaviour" may be expected. Another objective is the development of models for the simulation of flexible "multibody systems" and the implementation within special software, through which these can be used for optimization within a wide range of application areas. A method developed within this section and based on the finite element method, has been laid down in the computer programme system SPACAR95. Applications can be found in the simulation of, e.g., the dynamic behaviour of manipulators (robots), railway vehicles, cranes, offshore constructions and biomechanics.

The analytical modelling of "mechanics of materials" problems is only possible for a very restricted number of constructions/systems or parts. However, because of the increasing availability of ever more powerful computer facilities a (fastly) increasing number of mechanical problems can be modelled and analysed numerically. Analyses based on numerical techniques are complicated, however, because nonlinearities may occur as a result of, for instance, the material behaviour, geometric effects, and contact/friction problems. As a result of this, the analysis of many problems arising from engineering practice still demands a huge effort (of both the analyst and the computer hardware). For various practical problems this still constitutes an insurmountable handicap. For this reason a further development of more efficient numerical modelling techniques is one of the objectives within this theme.

If numerical simulation techniques are used in a design process, in which several intermediate designs have to be evaluated, the efficiency of the numerical simulation is even more important. This applies even more pronounced if automatic design optimization techniques are used. Therefore, the improvement of such techniques cannot be detached from the new developments in "computational mechanics". A second activity within this theme concentrates thus on these improvements. If necessary, the manufacturing process is taken into account in the optimization cycle.

Another obstacle arises when numerically simulating the behaviour of constructions of modern materials (such as composites) or of bio-materials and when simulating transformation processes. A missing link is often constituted by the absence of an appropriate description of the material behaviour or of , e.g., the absence of knowledge about the contact mechanism between various components. A third activity within this theme concentrates, therefore, on the improvement of the knowledge of this subject. Within this scope experimental research is indispensable.

Final projects within both themes may be aimed at a further development of methods and tools, or may be entirely aimed at practical application (whether or not in collaboration with industry) or may consist of experimental research. All of this depending on the preference of the undergraduate concerned.

The course programme of the Engineering Mechanics main subject has been extensively described in "Richtlijnen voor de studie in het hoofdvak Technische Mechanica". This booklet can be obtained from the secretary's office (Ms M.C. Stolker, tel 6513). For further information on the main subject you can contact Prof. Ernst.