Prediction of mechanical fatigue caused by multiple random excitations

A simulation method is presented for the fatigue analysis of automotive and other products that are subjected to multiple random excitations. The method is denoted as frequency domain stress-life fatigue analysis and was implemented in the automotive industry at DAF Trucks N.V. in Eindhoven, The Netherlands. As an example case, a chassis part is analysed. The results of the analysis are consistent with fatigue cracks encountered during testing, which illustrates the effectiveness of the adopted method in the automotive industry

Computational optimisation of robust sheet forming processes

Mathematical optimisation consists of the modelling and solving of optimisation problems. Although both the modelling and the solving are essential for successfully optimising metal forming problems, much of the research published until now has focussed on the solving part, i.e. the development of a specific optimisation algorithm and its application to a specific optimisation problem for a specific metal forming process. We propose a generally applicable optimisation strategy which makes use of FEM simulations of metal forming processes. It consists of a methodology for modelling optimisation problems related to metal forming. Subsequently, screening is applied to reduce the size of the optimisation problem by selecting only the most important design variables. Finally, the reduced optimisation problem is solved by an efficient optimisation algorithm. However, the above strategy is deterministic, which implies that the robustness of the optimum solution is not taken into account. Robustness is a major item in the metal forming industry, hence the deterministic strategy is extended in order to include noise variables (e.g. material variation) in optimisation. This yields a robust optimisation strategy that enables to optimise to a robust solution of the problem, which contributes significantly to the industrial demand to design robust metal forming processes. Just as the deterministic optimisation strategy, it consists of a modelling, screening and solving stage. The deterministic and robust optimisation strategies are compared to each other by application to an analytical test function

The robust optimisation of metal forming processes

Robustness, reliability, optimisation and Finite Element simulations are of major importance\ud to improve product quality and reduce costs in the metal forming industry. In this paper,\ud we review several possibilities for combining these techniques and propose a robust optimisation\ud strategy for metal forming processes. The importance of including robustness during optimisation\ud is demonstrated by applying the robust optimisation strategy to an analytical test function: for constrained\ud cases, deterministic optimisation will yield a scrap rate of about 50% whereas the robust\ud counterpart reduced this to the required 3 c reliability level

A Robust Optimisation Strategy for Metal Forming Processes

Robustness, reliability, optimisation and Finite Element simulations are of major importance to improve product\ud quality and reduce costs in the metal forming industry. In this paper, we propose a robust optimisation strategy for metal\ud forming processes. The importance of including robustness during optimisation is demonstrated by applying the robust\ud optimisation strategy to an analytical test function and an industrial hydroforming process, and comparing it to deterministic\ud optimisation methods. Applying the robust optimisation strategy significantly reduces the scrap rate for both the analytical\ud test function and the hydroforming proces

Noncompetitive Effects of Morning Glory on Growth of Soybeans

Competitive effects of weed infestations in soybean fields can severely reduce yields. Noncompetitive factors (allelopathy) may also be involved. Soybeans (Glycine max (L.) Merrill, Asgrow A 3127 mid group 3) show a marked reduction in growth due to root exudation, leaf leachate and total plant extracts from white-flowered morning glory (Ipomoea lacunosa L.)

Noncompetitive Effects of Morning Glory on Growth of Soybeans

Competitive effects of weed infestations in soybean fields can severely reduce yields. Noncompetitive factors (allelopathy) may also be involved. Soybeans (Glycine max (L.) Merrill, Asgrow A 3127 mid group 3) show a marked reduction in growth due to root exudation, leaf leachate and total plant extracts from white-flowered morning glory (Ipomoea lacunosa L.)

Search for the Tunguska event in the Antarctic snow

The Tunguska explosion in 1908 is supposed to have been produced by the impact of a small celestial body. The absence of any identifiable crater together with the huge energy released by the event suggest that the impactor exploded in midair and that its material was widely spread over the Earth. The short term contribution of such exceptional events to the total accretion rate of extraterrestrial material by the Earth could be significant. Samples were chosen in a core electromechanically drilled in 1984 near South Pole Station. There, the low temperatures, preventing melting all year long, and the nearly regular snow fall rate provide good conditions for a reliable continuous record of any infalling material. In many samples Ir was below the detection limit of the instrumentation. The iridium infall averaged over 45 samples is given. In a few samples the iridium content is significantly higher than the average: the frequency and amplitude of such fluctuations can be explained by the presence on some filters of finite size cosmic particles. No significant systematic increase above the average level is observed in the part of the core corresponding to the Tunguska event. The two major results of this study are: (1) The presence of Tunguska explosion debris in the Antarctic snow is not confirmed; and (2) The estimate of the average iridium infall, is an order of magnitude lower than the Ganapathy's background but is close to the values measured in Antarctic snow and atmospheric samples by Takahashi et al. The results are also consistent with the flux of micrometeoroids deduced from optical and radar observations or derived from the study of Greenland cosmic dust collection but are lower than the flux at mid-latitude measured in paleocene-oligocene sediments from the central part of the Pacific Ocean

Evaluation of the performance and feasability of the fluorescein diacetate (FTA) vital staining method for follow up of Tuberculosis (TB) treatment

IUATLD Conference, Paris, 200