Search Results

Utilizing the Finite Element Method (FEM), two evolving CAE methods have recently reached a high level of efficiency and accuracy to optimize the properties of components in respect of stiffness, stress level or fatigue resistance. The first type of CAE-methods is a family of optimization methods known as (parameter-free) shape and topology optimization. Very remarkable and useful results can be generated with these methods to reach considerable stiffness increases or stress and weight reductions. The second CAE-method is fatigue life prediction which gives reasonable accurate outputs for component life if input data like stress history and material properties are well known. State of the art algorithms and software can handle a combination of complex load histories, detailed material description and large FEM-data to give reliable results in short time.

For lightweight automotive structures, the stiffness and the fatigue behaviour is greatly influenced by the properties of its joints. The used joining technology, the number and locations of the spot joints are of high importance for both engineers and cost accountants. An overview of common computational procedures including European and national standards is given for the assessment of the stiffness and fatigue behaviour of thin sheet structures with spot joints and arc welds. The influence of the quality and the size of finite shell elements on the fatigue result is investigated and it is shown, how this influence can be minimized.

Fatigue simulation is an essential part of the development of components and systems in the automotive and machinery industry. Weak points can be identified fast and reliable. A pure virtual optimization of the design can be performed without the need of prototypes. Only for the production release a final test is necessary. A lot of parameters influence the fatigue life as the local stress, material, surface roughness, temperature etc. Notches have the strongest impact on fatigue life since they cause an increase of the local stress. Also, the local fatigue strength is increased in notches because of a support effect from the neighboring areas. To account for this effect, several methods exist, each with their specific advantages and disadvantages. In this contribution an overview is given with brief descriptions for some common methods. The methods are compared both from a theoretical and practical point of view.