Abstract

"Bolts and Rivets often used in large numbers in assemblies to join components together. The chal-lenge is to evaluate these many connections as efficiently and reliably as possible. For this reason, the Fast+More was developed. Fast+More is an ANSYS extension that is easily installed via the ACT console. It is fully integrated into the ANSYS interface and can therefore be learned quickly. The workflow is perfectly tailored to large models, which are one of the application's particular strengths. Here the application example of a all-wheel expedition vehicle with over 340 bolts is shown. For the strength assessment of the vehicle frame of the expedition vehicle it was necessary, among other things, to validate the bolted connections. As is often the case, the aim here was to get a first impression of the design as quickly as possible and to identify the critical bolts and the critical load case. Using Fast+More, over 340 bolts with different dimensions were generated fully automatically in just a few minutes. In other projects, models with well more than 1,000 bolts were also generated. Model class 1 was initially selected. In this case, ""joints"" with fixed degrees of freedom (fixed DOF) are generated in the interface of the holes to connect the components. This has several ad-vantages: the user is spared the often tedious contact definition between the components and thus obtains a solvable model very quickly. Since the model is linear and the evaluation of the bolts against the limit values takes place virtually, bolt parameters such as type, diameter, strength class and many more can also be varied later without the model having to be solved again in ANSYS. ""What If"" studies can thus be carried out very quickly: For example, the question of whether a higher bolt strength grade with its higher preload force provides more safety against slipping can be investigated. Once the critical bolts were identified and modified, we switched to model class 2. This more de-tailed method uses beam elements with full FE prestressing to model the bolts. This allows effects such as bolt (micro-) can be taken into account and evaluated, which leads to load redistributions in the bolt field. Without this effect, the outer screws are usually overloaded according to purely ana-lytical considerations, although they function well in reality. In addition, the bolt load and the resid-ual clamping force are considered more realistically and uncertainties of an analytical evaluation with stress diagrams such as load introduction factor, pressure cone and so on are left out. The results are available for each analysis, for each load case and for each bolt in graphical and tabu-lar form. As shown in Figure 3, a detailed report with the large number of input parameters and calculated results can also be displayed for each bolt. The bolt data can then be transferred to KISSsoft via the software-interface, where a further, de-tailed verification can be performed in accordance with VDI 2230.  "