Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe

Erding, Germany

Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe

Erding, Germany
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Schulze Grachtrup D.,TU Braunschweig | Bleckmann M.,TU Braunschweig | Bleckmann M.,Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe | Willenberg B.,TU Braunschweig | And 6 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

The tetragonal compound UPt 2Si 2 has been characterized as a moderately mass-enhanced system with an antiferromagnetic (AFM) ground state below T N=32 K. Here, we present an extensive study of the behavior in high magnetic fields. We have performed pulsed field magnetization and static field resistivity measurements on single crystalline samples UPt 2Si 2. Along the crystallographic a axis, at low temperatures, we find a metamagnetic-like transition in fields of the order 40 T, possibly indicating a first-order transition. Along the crystallographic c axis, in magnetic fields of B ∼ 24 T, we find distinct anomalies in both properties. From our analysis of the data we can distinguish new high-field phases above the AFM ground state. We discuss the emergence of these new phases in the context of Fermi surface effects and the possible occurrence of a Lifshitz or electronic topological transition, this in contrast to previous modelings of UPt 2Si 2 based on crystal electric field effects. © 2012 American Physical Society.

Albers P.,Albers Engineering GmbH | Simon A.,Albers Engineering GmbH | Adolph H.,Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe
Tribologie und Schmierungstechnik | Year: 2010

A new automated state of the art test device was developed by Albers Engineering GmbH to carry out test method IP 186 to measure the low temperature torque of a grease-packed ball bearing. Topics of discussion included introduction; test method IP 186; the testing method to the present; the new test device (drive; torque measurement technique; test spindle; control); comparison of test data (round robin tests with conventional devices at five European laboratories and newly developed device); and summary and outlook. The test method is used mainly in specifications. The test devices were originally developed in the 1960's. They have been modified over time since then in line with technical progress. Probably there is no test device today that measures in the originally designed device in test method IP 186. Grease manufacturers and users demanded the modernization of the test device. The new automated test device keeps the subjective influence of the operator on the measurements to a minimum. The test method IP 186 describes the determination of the start and running torque of an axially loaded angular ball bearing. This procedure enables testing the usefulness of lubricating grease at temperatures down to -73°C. The test method is in numerous standards especially in specifications of civilian and military aviation. The test devices in the 1960's had disadvantages such as dependency of test results on the operator, awkward and costly handling, and ineffective cooling with methanol in an open Dewar flask. The new device offers precise controllable drive with disturbance-free direct power cooling; highly accurate electronic torque registration; rapid and simple assembly/disassembly of the test equipment; broad use of automation in the testing; electronic data indication of the data and framework conditions; integrated enclosed cooling; broad avoidance of errors in the use and testing, minimal operator interference. Model greases include LiPAO and LiPAOMIN with Li-12-hydroxystearate thickener and polyalphaolefin and mineral base oils. A new edition of the IP 186 test method is being undertaken and the introduction of a Part 2 is being considered that relates only to the newly developed test device.

The lubricity of Diesel fuels is measured with the High Frequency Reciprocating Rig (HFRR). In this test a hard steel ball is moved reversely over a soft flat specimen. Materials of Diesel injection pumps are mostly made from hardened steel. Tests with additized aviation fuel were carried out to investigate the influence of the flat specimen hardness on the lubricity of fuels established in the HFRR. Ball and flat wear were measured by using a 3D microscope. Wear numbers regarding material hardness and friction and wear mechanism indicate that specimen hardness has no significant influence on the lubricity of the examined fuel.

Sessler W.,Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe
Tribologie und Schmierungstechnik | Year: 2012

Two configurations were tested to evaluate the loosening behaviour of lubricated joints after thermal exposition. Two nuts were tightened on a screw thread against each other with controlled angle of rotation. In a second configuration to obtain a longer clamping length a sleeve was inserted between head and nut and the nut was tightened against the sleeve with controlled angle of rotation. The comparison tests with 4 screw pastes and 2 mating materials showed that the configurations are usefull to evaluate the anti-seize behaviour of the pastes. The configuration with the tightened sleeve leads to more uniform results.

Seipp S.,TU Chemnitz | Wagner M.F.-X.,TU Chemnitz | Hockauf K.,TU Chemnitz | Schneider I.,Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe | And 2 more authors.
International Journal of Plasticity | Year: 2012

In this study the hexagonal close packed magnesium alloy AZ31 is deformed plastically by equal-channel angular pressing (ECAP) at 523 K, bi-directional rolling (BR) at 573 K, and by combinations of these processes. The evolution of microstructures, crystallographic textures and of the mechanical properties is investigated systematically as a function of the processing method, the amount of accumulated strain or the ECAP processing route (strain path). Both BR and ECAP enforce a crystallographic reorientation, with an alignment of (0002) basal planes parallel to the direction of shear deformation. This results in significant changes of the strongly texture-dependent mechanical properties. In combined processing, ECAP is applied as a method to increase texture-induced softening and ductility, whereas BR followed by water quenching is used as a method to induce strengthening by work hardening. The aim of tailoring materials and microstructures that are strong, but still ductile, and that can consume a moderate amount of plastic work during deformation, is best met by a combination of ECAP and subsequent BR. The corresponding yield strength of 345 MPa and elongation to failure of 13.9% demonstrate the considerable potential of the novel processing routes presented here for the first time. © 2012 Elsevier Ltd. All rights reserved.

Albers P.,Albers Engineering GmbH | Simon A.,Albers Engineering GmbH | Adolph H.,Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe
17th International Colloquium Tribology 2010 - Solving Friction and Wear Problems | Year: 2010

Measuring the low temperature torque of a grease packed ball bearing, IP 186 determines the lower temperature operation limit of lubrication greases. The test method is mainly used for specification purposes. The test rigs were developed in the 60-s of the last century. They were altered by in-house modifications due to the technical progress. So, none of the test rigs in use today is fully in compliance with the standard. A basic revision / modernisation of the test rig has been strongly required by grease manufacturers and users. Following IP 186 a new test rig was developed. Due to technical improvements and a high grade of automation, the influence of the operator is minimized. Round robin test results show the comparison between the conventional and the newly developed test equipment. Differences are discussed.

Eibl S.,Wehrwissenschaftliches Institute For Werk Und Betriebsstoffe
Materialwissenschaft und Werkstofftechnik | Year: 2016

This work provides techniques to separately determine temperature (90-340 °C) and duration (1 minute to 240 days) of a thermal pre-load as well as residual strength of polymer matrix composites on basis of the degradation of the top-coat. Infrared spectroscopy and colorimetry characterizing binder degradation and colour changes of polyurethane top-coats were used to provide a non-destructive in-service method to quantify incipient heat damage. A multivariate (chemometric) analysis of infrared and colorimetric data was performed. The precision of the calculated values for duration and temperature of the thermal pre-load as well as residual strength for specimen with unknown thermal history is slightly better for the infraredspectroscopic analysis. Deviation of the calculated temperature is less than 10 °C. However, the sole analysis of colorimetric data allows a separate evaluation of these parameters. Limitations of the techniques are identified. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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