Volume 54, Issue 1

Kurzfassung Der Sonderforschungsbereich (SFB) 696 Forderungsgerechte Auslegung von intralogistischen Systemen – Logistics on Demand wurde im Juli 2006 an der Technischen Universität Dortmund eingerichtet, um analytische Methoden und Technologien zur anforderungsgerechten Gestaltung und Organisation intralogistischer Systeme zu entwickeln. In zwölf Teilprojekten ging es darum, die heutigen und zukünftigen Anforderungen der Anwender, darunter auch den produktbegleitenden Service, stärker in den Mittelpunkt der Produktentwicklung intralogistischer Systeme zu rücken. Vision ist es, die methodische und technische Basis für flexible, auf Veränderungen automatisch reagierende, sich selbst kontrollierende und reparierende zuverlässige Intralogistiksysteme zu schaffen.

The influence of welding parameters, namely welding current and gas flow rate, on the mechanical properties of Gas Tungsten Arc Welding (GTAW) and Shielded Metal Arc Welding (SMAW) welded 6063 Aluminum alloy (AA 6063) has been investigated. In order to study the effect of the welding current and gas flow rate, microstructural examination, hardness measurements and room temperature tensile tests have been carried out. The experimental results show that the mechanical properties of GTAW welded joints have better mechanical properties than those of SMAW welded joints. Increasing the welding current appeared to have a beneficial effect on the mechanical properties. However, either increasing or decreasing the gas flow rate resulted in a decrease of hardness and tensile strength. It was also found that, the highest strength was obtained in GTAW welded samples at 220 A and 15 l/min gas flow rate.

Performance of automotive composite bumper beam subjected to frontal impact is presented and discussed in this paper. The aim of this study is to analyze the effect of steel and composite materials on internal energy of the automotive front bumper beam and with respect to pedestrian head injury at the hood. The front bumper beams and hood made of aluminum AA5182, e-glass/epoxy composite and carbon epoxy composite were studied and characterized by impact modeling using LS-DYNA V971, according to United States New Car Assessment Program (US-NCAP) defining the frontal impact velocity and based on European Enhanced Vehicle-Safety Committee. The most important variables of this structure were mass, material, internal energy, and the so-called Head Injury Criterion (HIC). The results are compared with a bumper beam and a hood made of mild steel. The in-plane failure behaviors of the composites were evaluated by using the Tsai Wu failure criterion. LS-DYNA Finite Element Analysis software was used. The results showed that a carbon fiber/epoxy composite bumper can reduce the bumper mass and has the highest value of internal energy followed by the glass fiber/epoxy composite. The FE model of a production hood was introduced and validated. In order to evaluate the protective performance of the baseline hood, the FE models for a 50 percentile of an adult pedestrian dummy were used to impact the hood. It was found that the aluminum AA5182 hood can obviously reduce the Head Injury Criterion (HIC) values compared to the baseline hood. The HIC values of the dummy model were further reduced to much lower than 1000.

The effect of applied pressure on microstructures and properties of an in-situ formed Mg 2 Si/Al-Si-Cu reinforced metal matrix composite fabricated by squeeze casting are investigated. Due to the wide solidification range and the high viscosity, this type of composites is prone ro shrinkage and gas porosity. In order to improve cast ability and to obtain better properties, the squeeze casting technique has been used. The results showed that primary Mg 2 Si crystals are formed by adding pure Mg into the hypereutectic Al-Si-Cu alloy (A380). It was found that, with the application of 30 MPa and 40 MPa pressure during solidification, the average size of primary Mg 2 Si particulates decreases from about 87 µm to about 21 and 18 µm and that the average porosity values of the cast samples is significantly decreased from 8.75 % to 0.50 and 0.35 %, respectively.

Surface modification of a Ti6Al4V titanium alloy was made by the plasma nitriding process. Plasma nitriding was performed in a constant gas mixture of 20% H 2 –80% N 2 at temperatures between 700 and 1000° C and process times between 2 and 15 h. Samples nitrided at different treatment times and temperatures were subjected to the dry sliding wear test using the pin-on-disc set up under 80N normal load with rotational speed of counter face disc of 0.8 m/s at room conditions. An artificial neural network (ANN) model of was developed for prediction of wear performance of the plasma nitrided Ti6Al4V alloy. The inputs of the ANN model were processing times and temperatures, diffusion layer thickness, Ti 2 N thickness, TiN thickness and hardness. The output of the ANN model was wear loss. The model is based on the multilayer backpropagation neural technique. The ANN was trained with a comprehensive dataset collected from experimental conditions and results of authors. The model can be used for the prediction of wear properties of Ti6Al4V alloys nitrided at different parameters. The ANN model demonstrated the best statistical performance with the experimental results.

In this study, the effect of aging heat treatment on the hardness of AA 2024 and AA 6063 aluminum alloys was investigated by experimental and an Artificial Neural Network (ANN). AA 2024 and AA 6063 aluminum alloys were solution treated at two different temperatures of 490° C and 520° C. Then both samples were cooled to room temperature. After this process, the samples were aged at three different temperatures (140° C, 180° C, 220° C) for ten different periods of time (2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 h.). The experimental results were trained in an ANNs program, and the results were compared with experimental values. It is observed that the experimental results coincided with the ANNs results.

In this study, mechanical properties of cylindrical composite specimens were measured experimentally. Composite cylinders oriented at 0° C and 90° were manufactured by using the hand lay -up technique. The cylinders were loaded axially for measuring the axial tensile strength and compressive strengths. Some specimens were attached to a torsion machine for measuring shear strength and shear modulus. Thus, a close and true measuring was performed in the cylindrical specimens. A finite element solution was performed in closed ended composite cylinders under internal pressure and thermal loading. Thermal stresses occur at low and high temperatures with respect to the room temperature. For a true or close solution in composite cylinders, mechanical properties should be determined in cylindrical composite specimens.

The brake friction materials in automotive brake systems play an important role in the overall braking performance of a vehicle. Wear test results have previously been presented for a 1040 steel disc interacting with a PM copper-based brake lining material without and with MoS 2 additive at constant applied load and sliding velocity. In this paper, a non-linear model has been developed and compared with a previously developed linear model and experimental results. Nonlinear ARX model structure with sigmoid network having one hidden layer was used to find the best possible results. Linear and non-linear approaches have been applied to simulate the wear behaviour of the brake lining material. Comparative results showed that the nonlinear model provides results closer to the experimental study. Therefore, non-linear process modelling can be used as an effective tool for the prediction of brake lining material properties instead of time-consuming experimental processes.

Remaining service life of a petrochemical plant reformer tube, which has been exposed to water vapour at 540° C for 22 years under an internal pressure of 88 bar, was analysed via the Larson-Miller approach. Samples machined from the exposed and the original tubes were subjected to stress rupture tests at various stress levels and temperatures to determine the variation of the Larson-Miller parameter with the applied stress. At a service temperature of 540° C, the remaining service life decreased with increasing applied stress. For the stress of 42 MPa, which corresponded to the hoop stress generated on the tube during service, it was estimated that the tube has completed about 50 % of its actual service life.

The paper highlights new aspects in the evaluation of cavitation erosion resistance based on the chromium content variation and implicit on the Cr/Ni equivalent which constitutes the microstructure development using the information given by the Schaeffler diagram. The presented and analysed results show that it is possible to establish an optimum relation between the chromium and nickel content, in order to obtain a substantial increase of the cavitation erosion resistance. For this purpose, four stainless steels used in manufacturing of machinery parts, heavily subject to cavitation such as hydraulic turbine runners and pump impellers, were analyzed from the point of view of cavitation erosion. The cavitation erosion behaviour was evaluated by the microstructure behaviour investigated through optic and electronic microscopy and by comparisons with the characteristic curves for reference steels.