Calibration of High-Frequency Mechanical Impact Simulation Based on Drop Tests

A series of drop tests was implemented in the present study in order to allow the reproduction of a single impact identical to the high frequency mechanical impact (HFMI) under monitored conditions in the laboratory. Therewith, characterization of the investigated material’s mechanical behavior by explicitly considering possible irregularities concerning the present deformation modes would be enabled. Main goal was the determination of the investigated material’s dynamic yield stress for various strain rates inside the spectrum of interest, so that the Cowper–Symonds viscous material model would be calibrated for the subsequent HFMI simulation. The values of the dynamic yield stress extracted by the present drop tests show good agreement with other experimental methods regarding the investigated material S355. The introduction of the calibrated material behavior on the present drop tests in the finite element (FE) analysis of HFMI led to reduced preciseness though, in comparison with the FE analysis, which considered high strain rate tensile tests found in literature. A series of conclusions was drawn from both the experimental and numerical investigations, confirming most of the initial expectations. Further work is proposed, in order to clarify an incompatibility met during the numerical investigations

A pseudothermal approach for simulating the residual stress field caused by shot blasting

Industrial practice often prescribes cleaning of steel surfaces prior to welding with shot blasting. Shot blasted components have been considered free of residual stresses. Hence, recent studies show that these residual stresses from mechanical surface treatments are not negligible. A simulation of the surface treatments and their mechanical effect in full scale though, is not possible under modern computational capabilities. Instead, a straightforward, pseudothermal approach is proposed and tested in the present study, in order to introduce an initial residual stress field from shot blasting by application of thermal strains. This engineering concept is applied for validation reasons on a small-scale specimen, where a measured profile of residual stresses from shot blasting is simulated with preciseness. Subsequently a component with dimensions of real weldments is modelled, so that simplifications reducing the computational time to acceptable levels can be derived

Silos with stepped wall thickness on local supports

p. 2577-2589Some years ago the authors presented an engineering model for the design of cylindrical shells with uniform wall thickness on local supports [4], based on a concept of effective width. In the meantime this model has been improved for the application of silo design. In this paper numerical studies are presented. The stress field is described which originates from the local support at the bottom of a silo and widens towards the top of the silo. This information helps the engineer to design silos with stepped wall thickness under local loads. Special consideration is given to the hopper junction where additional circumferential stiffness is provided which improves the spreading of the local load.Knoedel, P.; Ummernhofer, T. (2009). Silos with stepped wall thickness on local supports. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/659