High Pressure Falling Cylinder Viscometer - Error Analysis and Improvement Proposal
Marcel Rückert, April 24th 2018
A paper on “High Pressure Falling Cylinder Viscometer - Error Analysis and Improvement Proposal” was published at the 11th International Fluid Power Conference IFK in Aachen.
With pressure levels rising for applications such as compression-ignition engines and numerical design approaches are used to optimise fluid power components, rheological properties of the fluid in the according operation points gain interest. The measurement of viscosity under high-pressure has been subject to research for many years. However, to this day, it still bears uncertainty. This paper presents typical errors for high-pressure measurements and strategies to minimise uncertainty. With a focus on material combinations, geometric parameters and the measurement principle, the errors are explained, and an improvement proposal is given based on the findings.
Surface tension of fuels – Analysis of measurement methods and applicability on rail-pressure environments
Marcel Rückert, April 17th 2018
A paper on “Surface tension of fuels – Analysis of measurement methods and applicability on rail-pressure environments” was published at the 11th International Fluid Power Conference IFK in Aachen.
Spray characteristics during the injection process of a combustion system, bubble formation in chemical reactors or hydraulic fluids all share surface tension as a key variable regarding aforementioned behaviours. Depending on the system liquid-liquid or liquid-gas interphases play a defining role. In this work, the most relevant measurement methods are discussed. Based on the Du Noüy method, the surface tension of common fuels and mixtures is measured and presented. The measurements do illustrate the influence of mixture components on surface tension as the behaviour can be strongly non-linear. Additionally, the applicability of the aforementioned measurement methods on high-pressure environments is investigated and a possible solution for measurements up to multiple 100 MPa is introduced.
Thermo-Elastohydrodynamics of the Piston-cylinder Contact in High-pressure Pumps
Felix Fischer, March 30th 2018
In the issue 03/2018 of the engine technical newspaper (MTZ) an article for the investigation of an abstracted piston-bushing contact appeared using thermo-elastohydrodynamic simulations (TEHD).
The paper was prepared by the Chair of Machine Elements and Tribology of the University of Kassel (iaf) in cooperation with the IFAS.
An increase of the rail pressure in common-rail systems from currently 2500 bar
to 3000 bar is to be expected due to stronger emission laws. Within the FVV
research project Diesel 3000 bar, at the University of Kassel and the RWTH Aachen
University the basics for the design of the piston-cylinder contact of common-rail
pumps at high pressures were developed. For this purpose, measurements of
pressure and temperature were performed in a flat gap and compared with the
results of a thermo-elastohydrodynamic simulation model.
Influence of transient effects on the behaviour of translational hydraulic seals
March 27th 2018
A paper on “Influence of transient effects on the behaviour of translational hydraulic seals” was published at the 11th International Fluid Power Conference IFK in Aachen.
In common practice a hydraulic cylinder undergoes permanent acceleration and deceleration. In general this transient behaviour is neglected in the simulation of hydraulic seals, especially regarding the fluid film where stationary conditions are assumed. In order to gain a detailed understanding of the dynamic sealing process, a finite element based, elastohydrodynamic simulation model for hydraulic seals has been developed, including transient effects. In this paper the influence of these transient effects on the behaviour of a hydraulic seal is investigated. The influence is studied under different system conditions in order to examine to which extend the consideration of transient effects in a simulation of hydraulic seals is inevitable.
Entrainment of free water into hydraulic systems through the rod sealing
Tobias Mielke, March 26th 2018
A paper on “Entrainment of free water into hydraulic systems through the rod sealing” was published at the 11th International Fluid Power Conference IFK in Aachen.
Water in oil-based hydraulic systems is a source for many machinery failures. It accounts for up to 20% of the life expectancy failures and even before that, it impacts the expected performance negatively.
Water can enter a hydraulic system in various ways. In this article, the entry through the dynamic seal of the rod is investigated.
After a brief description of the damage mechanisms of water in a hydraulic system, the theory of the entrainmentis explained. The test bench is then described to study the effect. Finally, entrainment results for two test fluids
(oil and water) are presented and compared to the theory.
Validation of a thermo- and a hydromechanical model of a brake system for high-speed rail applications
Matthias Petry, March 26th 2018
A paper "Validation of a thermo- and a hydromechanical model of a brake system for high-speed rail applications" was published in the Journal of Rail and Rapid Transit.
The contribution was issued in corporation with the Institute of General Mechanics (IAM) at RWTH Aachen University.
This research deals with a numerical and experimental investigation of the vibratory frequency and the thermal response
of a railway brake disc and pad under varying conditions. Railway brake systems play a vital role in passenger safety and
comfort. The performance of disc brakes with regard to the dynamic effects like brake torque oscillations and brake
judder depends on the contact properties and wear surfaces. Brake fading occurs due to accumulated frictional heat
thereby reducing the stopping power. For an improved understanding of the complex processes of a brake system during
long-term braking, a comprehensive numerical investigation is performed initially using the finite element software
Abaqus for a thermomechanical and modal analysis. While the thermomechanical analysis based on the calculations
of frictional heat is used to investigate the increase of temperature during braking, the contact pressure is a crucial
parameter that influences the distribution of temperature both on the brake disc and on the pads. The modal analysis is
used to investigate the frequency behaviour of the vibrations. Then, a simulation model of a self-energised electrohydraulic
brake provides the results of brake force oscillations with regard to the observed topologies of the brake disc’s
wear surface, which is measured at a full-scale test rig by an enlarged experimental set-up. In addition to the dynamic
brake force, the set-up contains the online measurement of the side face run-out and the temperature of one side of a
ventilated brake disc. By comparing the results of our experimental and numerical investigations, the simulation models
are validated. Future research should focus on a thermomechanical analysis that considers heating, cooling, and the wear
effects. A detailed implementation of the contact pressure distribution between the brake pads and disc can lead to a
more precise prediction of brake torque oscillations. The achieved results can be used to improve riding comfort and
resolve safety critical problems in high-speed trains.
A paper on “Piston Slippers for Robust Water Hydraulic Pumps” was published at the 11th International Fluid Power Conference IFK in Aachen.
Water hydraulics are used for applications which require an environmental safety standard for the fluid. In comparison to oil, lubrication with water is a challenging aspect because of the fluid’s lower viscosity. Wear and leakage in water lubricated contacts require lower pressure loads. In order to estimate the possible load carrying capacity in water hydraulics, the tribological contact between the piston slipper and swash plate in axial piston machine and respectively eccentric shaft in radial piston machines is investigated. For this purpose simulations based on the Reynolds-Equation are carried out and analysed.
The results show that the gap height distribution due to manufacturing tolerances between the slipper of a radial piston pump and the eccentric shaft has major impact on the resulting load carrying capacity and the occurring leakage. Furthermore the deformation due to the pressure distribution of slippers made of plastic materials is of the same magnitude as the gap height itself. Therefore the deformation needs to be considered while designing a tribological contact for a water hydraulic pump.
Im kommenden Sommersemester findet wieder die Vorlesung „Simulation fluidtechnischer Systeme“ mit Hr. Prof. Christian Stammen statt. Die Veranstaltung richtet sich an Studierende, die sich für Systemsimulation interessieren. Im Rahmen der Veranstaltung werden die Grundlagen für die Berechnung hydraulischer Systeme gezeigt und in den Übungen bieten wir die Möglichkeit die Anwendung der Software DSHplus kennen zu lernen.
Die Veranstaltung wird dieses Jahr als Blockseminar im Monat September angeboten. Am 13.04. um 14 Uhr findet eine Infoveranstaltung im Seminarraum des KEmikro statt.
Aus organisatorischen Gründen sind die Teilnehmerplätze begrenzt. Eine Anmeldung zur Vorlesung in CampusOffice ist bis zum 20. April erforderlich (wird noch freigeschaltet).
Weitere Informationen findet sich im Flyer (siehe Bilder).
Machine elements and mechanical components have often surfaces with anisotropic roughness, which may result from the machining processes, e.g. grinding, or from wear. Hence, it is important to understand how surface roughness anisotropy affects the contact mechanics properties, such as friction and the interface separation, which is important for lubricated contacts. Here we extend a multiscale mean-field model to the lubricated contact between a soft (e.g. rubber) elastic solid and a rigid countersurface. We consider surfaces with anisotropic surface roughness, and discuss how the fluid flow factors and friction factors depend on the roughness power spectral density, as well as on the location of roughness on the interacting solids. Finally, we present an experimental study of the lubricated sliding contact between a nitrile butadiene rubber O-ring and steel surfaces with different kinds of isotropic and anisotropic surface roughness. The good quantitative comparison between the experimental results and the theory predictions suggests that the multiscale lubrication mechanisms are accurately captured by the theory.
The work on the recommissioning of the laboratory I is making progress. After several call for bids, e.g., for the electrical infrastructure, have been published, the work on the concrete structure and the preparation for the power rail installation has begun. The rail should be installed and connected in the beginning of 2018.
Meanwhile, the replacement area in the Karl-Friedrich-Street (KFS) is used to full capacity, so that the experimental research capabilities are reinstated on a broader scope. Only the fields of acoustic and climatic measurements are currently still limited due to the unavailable / missing infrastructure, as well as the operation of test rigs with high power demands. In the KFS laboratory several test rigs with a power scope of 50 kW are operated. Additionally some laboratory space is obtained from the Aachen Center for Integrative Lightweight Production (AZL), which we would like thank cordially!
All in all the Bau- und Liegenschaftsbetrieb NRW (BLB) estimates to hand over the fully reinstated laboratory in the 4th quarter of 2018. Unfortunately, an exact schedule is not at our disposal at the moment. This date includes the termination of all work as well as the new acoustic chamber and the new climate chamber. Prior to this a stepwise recommissioning of certain test rigs will begin in February, so that the laboratory I, if only partially, will be accessible for visitors and guests during the upcoming IFK.
Influence of a new hollow piston design on volumetric losses of a common-rail pump
December 7th 2017
A paper on “Influence of a new hollow piston design on volumetric losses of a common-rail pump” was published at the ASME/Bath Symposium on Fluid Power and Motion Control 2017 in Sarasota.
Within the cluster of excellence "Tailor-Made Fuels from Biomass" alternative fuel candidates are being investigated. One of the most promising candidates is Di-n-Butylether (DnBE). Because of its lower viscosity compared to diesel, the injection pump expiriences high volumetric losses. A new hollow piston concept was developed to reduce aforementioned losses. Test rig measurements show good results and a great potential for hollow pistons.
Holistic Investigation of a 50/50 DnBE - 1-Octanol blend regarding the complete injection system
December 7th 2017
A paper on “Holistic Investigation of a 50/50 DnBE - 1-Octanol blend regarding the complete injection system” was published at the seventh international Tailor-Made Fuels conference in Aachen.
In this publication the focus is put on the biofuel candidates Di-n-Butylether (DnBE) and 1-Octanol (1-OCT). With the good spray-characteristics of DnBE and the good tribological and rheological properties of 1-OCT, blending these two fuels could increase the overall efficiency of the engine and injection system. A blend containing 50 vol. % DnBE and 50 vol. % 1-OCT is investigated. The work focuses on key elements of the engine and injection system. Starting with pump measurements and lubricity evaluation using the High-Frequency-Reciprocating-Rig (HFRR). In terms of ignit-ability, the derived cetane number (DCN) of the blend is determined using the Advanced Fuel Ignition Delay Analyzer (AFIDA). Furthermore, experiments using a single cylinder engine are conducted. The results and possible blending strategies are discussed by comparison the blend with the pure fluids.
Hollow Pistons in Hydraulics – Possibilities of Increasing Volumetric Efficiencies
December 7th 2017
A paper on "Hollow Pistons in Hydraulics – Possibilities of Increasing Volumetric Efficiencies" was published at the 23rd international fluid power conference Hervex in Romania.
Within the cluster of excellence "Tailor-Made Fuels from Biomass" a new hollow piston concept for injection pumps was developed and succesfully tested. In hydraulics, high leakage within pumps appear due to low viscosities for example. A low viscosity application is water hydraulics. Therefore, the hollow piston concept was adapted to water hydralics and first simulative studies were conducted. The simulations indicate a potential of the same magnitude as in injection pumps.
Analytical, Experimental and Numerical Methods to Quantify the Pressurization in the Piston Chamber of Axial Piston Machines
November 16th 2017
A paper on “Analytical, Experimental and Numerical Methods to Quantify the Pressurization in the Piston Chamber of Axial Piston Machines” was published at the 10th JFPS International Symposium on Fluid Power in Fukuoka.
The behavior of the tribological system piston - bushing in axial piston machines is investigated experimentally on a single piston test rig at the IFAS laboratory. Due to extensive test bench peripherals, various operating states can be reliably reproduced and component design variants examined. By means of a synchronously driven rotary valve, a realistic commutation between high and low pressure level takes place.
In addition to the hydraulic-mechanical losses, due to the axial and tangential friction force, as well as the loss due to leakage at the sealing gap and the dissipated compression work is mentioned. Depending on the design of the commutation, this loss leads to a reduction in the volumetric or hydraulic-mechanical efficiency. Main influencing factors are the high and low pressure levels, as well as the dead volume of the displacement unit and the bulk modulus of the hydraulic fluid, which is lowered by entrained gas. Avoiding the dissipated compression work is not possible even when the dead volume is reduced to zero.
Control Concept for a Novel Integrated Pressure Booster
November 15th 2017
A paper on the "Control Concept for a Novel Integrated Pressure Booster” was published at the 23rd Hervex Conference in Baile Govora, Romania.
The paper proposes a novel concept for pressure boosters based on rotational equipment. Instead
of double piston boosters as they are common in industrial applications today, the proposed concept is
based on a pneumatic radial piston motor. During one cycle, all cylinder chambers act as actuator and
compressor as well. The paper shows a mathematical model of the cycle and its simulative implementation.
A control concept using fast switching valves is proposed. To evaluate the efficiency, a parameter variation is
undertaken. This includes the number and size of the pistons as well as pressure levels for input and output
respectively. The thermodynamic concept of exergy is used to compare the different system configurations.
Mathematical Modeling of a Pneumatic Vane Motor in Matlab/Simulink
Stephan Merkelbach, November 14th 2017
A paper on “Mathematical Modeling of a Pneumatic Vane Motor in Matlab/Simulink” was published at the 10th JFPS International Symposium on Fluid Power in Fukuoka.
Air driven motors are used in a variety of applications, for example as drives for tools in manufacturing. Pneumatic vane motors in particular feature high speed and eminent power density. The paper presents the development and experimental validation of a one dimensional simulation model for pneumatic vane motors in Matlab/Simulink. The model developed in the study can be used as a basis for future work on the optimization and control of pneumatic vane motors. The validation is carried out by an experimental setup which consists of the vane motor mounted on a common shaft with a hydraulic gear pump building up the load.
VALIDATION OF AN ENHANCED MODEL OF STEADY-STATE FLOW FORCES FOR SPOOL VALVES
November 13th 2017
A paper on “Validation of an Enhanced Model of Steady-State Flow Forces for Spool Valves” was published at the 10th JFPS International Symposium on Fluid Power in Fukuoka.
One of the valve types often used in hydraulics is the spool-type valve. A typical example of a spool valve is a directional valve. In order to move the spool, an actuator is needed to overcome forces acting on the spool. Beside spring and friction forces, flow forces are the most relevant. They influence the static and dynamic performance of valves.
In this paper, the validation of an enhanced model for the calculation of steady-state flow forces in spool valves is described. Both the momentum influx and the efflux are considered in the model. In addition, it was found that the accuracy of the calculation of steady-state flow forces can be improved by using variable quantities, such as the inlet and outlet flow angles and the discharge coefficient, instead of constants.
Analysis of Flow Angles and Flow Velocities in Spool Valves for the Calculation of Steady-State Flow Forces
November 13th 2017
A paper on “Analysis of Flow Angles and Flow Velocities in Spool Valves for the Calculation of Steady-State Flow Forces” was published at the 15th Scandinavian International Conference on Fluid Power in Linköping.
A detailed analysis of the flow inside valves has become necessary for the optimization of their static and dynamic performance. In addition, the flow velocities and flow angles on defined areas inside valves are needed for the estimation of physical quantities such as flow rates, flow forces, etc.
Within this paper, measurements and CFD-simulations of a 2/2-way spool type test valve are analyzed regarding flow angles and flow velocities including their distribution on the inlet and outlet areas. Different spool edge geometries are investigated in both flow directions. Furthermore, the impact of a chamfer and a fillet on a spool edge, on the flow angles and the flow velocities are analyzed.
The analysis results show that the shape of a spool edge influences the flow angles and the flow velocities. Both flow variables are significantly affected by the direction of the fluid flow through the valve. Moreover, considering the same inlet area, an increasing chamfer width, respectively an increasing fillet radius, result both in lower inlet and outlet flow angles.
Interaction between Swash Plate Movement and Commutation in Axial Piston Machines
Florian Schoemacker, November 13th 2017
A paper on “Interaction between Swash Plate Movement and Commutation in Axial Piston Machines” was published at the 10th JFPS International Symposium on Fluid Power in Fukuoka.
In an axial piston pump the alternating pressure force of the pistons produce a periodically changing torque load on the swash plate. The torque load results in a movement of the swash plate, especially if the damping of the swash plate is quite low. The swash plate movement changes the piston stroke and therefore interacts with the commutation which leads to altered piston pressure forces.
The impact of different valve plate designs, using silencing grooves and bores, on the swash plate torque load and the resulting oscillation has been investigated via simulation. The results show that the design of the valve plate has a major impact on the periodic behavior of the torque load. Therefore this aspect needs to be considered while designing pumps for closed-loop control.
Disc Brake with Hydromechanically Controlled Brake Torque for Railway Applications
Matthias Petry, November 10th 2017
A paper on “Disc Brake with Hydromechanically Controlled Brake Torque for Railway Applications” was published at the 10th JFPS International Symposium on Fluid Power in Fukuoka.
Hydraulic disc brake systems are widely spread in commuter train applications. Due to their operation with an open loop control system, they are not able to deal with the influences of varying conditions surrounding the frictional contact zone between the brake pads and the disc. This results in a variable friction coefficient and affects the system performance. To detect the variation a closed loop control system with a feedback signal needs to be implemented in existing brake solutions to maintain high reliability and operating permit. This paper examines the design features of an existing system and finds a suitable mechanical feedback signal, whose eligibility is experimentally verified. Subsequently the geometrical calculations of the system are made and the control system is simulated. Based on the simulation results a preliminary design of the system is presented.
The Influence of Temperature and Surface Structure on the Friction of Dynamic Hydraulic Seals
November 10th 2017
A paper on “The Influence of Temperature and Surface Structure on the Friction of Dynamic Hydraulic Seals” was published at the 10th JFPS International Symposium on Fluid Power in Fukuoka.
A test rig and a transient, finite element (FE) based elastohydrodynamic (EHD) simulation for translational hydraulic seals have been set up to investigate a soft, lubricated line contact in detail. In this paper the influences of temperature and surface structure on the friction force is investigated numerically and experimentally. The focus is upon the mixed friction regime as - especially during a change in the cylinder stroke’s direction - solid body friction and fluid friction occur in the tribological contact between seal and cylinder surface.
Dr. Katharina Schmitz, currently technical director at Hunger Maschinen GmbH, was appointed the university professorate for Fluid Power Drives and Systems by the RWTH Aachen University starting from March 1st, 2018.
She will take over the management of the institute from Prof. Murrenhoff commencing with the 11. International Fluid Power Conference IFK (19.-21.03.2018 in Aachen).
The new appointment ensures long-term research and teaching in the field of fluid power at RWTH Aachen University. Therefore the institute will be renamed in to Institute for Fluid Power Drives and Systems.
Elastohydrodynamics for Soft Solids with Surface Roughness: Transient Effects
A huge number of technological and biological systems involve the lubricated contact between rough surfaces of soft solids in relative accelerated motion. Examples include dynamical rubber seals and the human joints. In this study, we consider an elastic cylinder with random surface roughness in accelerated sliding motion on a rigid, perfectly flat (no roughness) substrate in a fluid. We calculate the surface deformations, interface separation and the contributions to the friction force and the normal force from the area of real contact and from the fluid. The driving velocity profile as a function of time is assumed to be either a sine function, or a linear multi-ramp function. We show how the squeeze-in and squeeze-out processes, occurring in accelerated sliding, quantitatively affect the Stribeck curve with respect to the steady sliding. Finally, the theory results are compared to experimental data.
New project: Rail vehicle brake with hydraulic-mechanically controlled braking torque
Christian Schleihs, May 30th 2017
DFG-knowledge transfer project (MU 1225/40-1)
07/2017 - 06/2019
The objective of the knowledge transfer project is the investigation of a practical and simplified system for the implementation of the direct frictional force control based on the self-energizing hydraulic brake (SEHB) developed at IFAS. The main focus is on the development of a prototype based on components of today's braking systems with the aim of a simple integration into an established rail vehicle in the local traffic area as well as its testing and validation in the application. As industrial partner, Hanning & Kahl GmbH & Co. KG, Oerlinghausen, accompanies and supports the project funded by the DFG.
The 11th edition of the International Fluid Power Kolloquium in Aachen will be held from March 19 through 21, 2018.
The "Call for Papers" is now open.
For further information and downloads of CfP and an abstract template, please visit www.ifk2018.com.
IFAS receives VIP/VIP+ validation award for STEAM project
Roland Leifeld, February 13th 2017
For the research results in the project STEAM the Institute for Fluid Power Drives and Controls (RWTH Aachen) was awarded second place in the VIP/VIP+ validation prize by the German Federal Ministry for Education and Research (BMBF).
It was presented by Parliamentary State Secretary Stefan Müller on February 1st, 2017, within the Innovation Convention “Validation of the Social and Technological Potential of Scientific Research" (VIP/VIP+).
For further information about the STEAM project, see: www.ifas.rwth-aachen.de/?steam
New project: Development of a standardized, simplified process control and test evaluation beyond the current stability limit of gas-based deep drawing tests to determine warm extrusion material data
February 2nd 2017
AiF/FOSTA (IGF-Nr. 19229 N/2)
12/2016 - 11/2018
In collaboration with the IBF (Institut für Bildsame Formgebung) a new deep-drawing test for the determination of material data is currently being developed. In this process, a glowing sheet metal sample is subject to a one-sided pressure load and hereby reshaped. The aim of this project is to improve the stability of the forming process, for which proportional high-pressure pneumatics as well as new control methods are to be tested.
The case study examines different aspects of the Industrial Internet by investigating the special case of an automated commissioning process of a machine. The goal is to propose a need of action for the sector of fluid power and all related parties in order to take part at its benefits and stay involved in a highly advanced future, achieved by the 4th Industrial Revolution.
New project: Decentralized compact hydraulic power supply
January 31st 2017
AiF/FVB (IGF-Nr. 19224 N/2)
01/2017 - 03/2019
During the project the IFAS and the Institute for Machine Elements and Machine Design (IME) will develop a functional model for an electro-hydraulic axis. For this purpose a high-speed pump and an associated transmission will developed, which is driven by a high-speed electric motor. The aim is to increase the power density of the power unit by increasing the rotational speed level which make it attractive for mobile applications.
New project: Development of a bio-polymer based hydraulic fluid with plant-based corrosion protection additives (BioHydra)
January 31st 2017
BMEL - Fachagentur Nachwachsende Rohstoffe e. V. (FKZ: 22013716)
12/2016 - 05/2019
At the moment a completely new hydraulic fluid with a water content of more than 90 % will be developed at IFAS. Further fluid components will be primary based on renewable resources. To achieve the needed viscosity and lubricity bio-polymers based on carbohydrates will be used. Due to the high water content corrosion protection is paramount during the entire project. Thus, for the first time secondary plant metabolites will be used as anticorrosive additives.
A paper on “Influence of additives on the frictional behavior of hydraulic rod seals” was published at the International Sealing Conference (ISC 2016) in Stuttgart. The Authors are Felix Fischer, M.Sc., Prof. H. Murrenhoff and Dr. O. Reinertz.
Due to the high power density, high efficiency and the robust design, hydraulic cylinders are widely used in technical applications. Energy losses within the hydraulic cylinder as well as dynamic losses arise primarily in the hard-soft contacts of the seals. Specifically dynamic effects, such as the stick-slip phenomenon, difficult positioning tasks with high accuracy requirements and are strongly correlated to the frictional behavior of the tribological system (TS). Methods to reduce, or even to eliminate these phenomena require further investigations to obtain a better understanding of the TS “seal-rod”.
Initial experimental studies of the authors have shown that the additive package of the oil has a major impact on the friction characteristics of the rod seal, whereas the influence of the viscosity is of secondary importance. When using automatic transmission fluid as working fluid, the dynamic behavior of the system should be considered more docile than in the case of conventional hydraulic oil. Here, the friction modifiers (FM) play a special role as components of the automatic trans-mission fluid´s additive package. using a friction test rig it was revealed, that the addition of a model FM helps to influence the frictional behavior of the TS positively.
In this paper, the effect of a variation of the FM molecule on the frictional behavior of the TS is investigated experimentally. In order to achieve this goal, FM are add-ed to a conventional hydraulic fluid and the impact on the TS “seal-rod” is deter-mined and discussed. For this purpose, the system is excited with an actuator and the trajectory of the frictional force is analyzed. Furthermore, quasi-stationary Stribeck curves are recorded and compared to the results from the excitation experiments, where a causal relationship can be pointed out.
At the International Sealing Conference (ISC 2016) in Stuttgart the paper “Influence of anisotropic surfaces on the friction behaviour in hard/soft line contacts” was published. Authors are Julian Angerhausen, M.Sc. and Prof. H. Murrenhoff
When modelling leakage rate, friction force or fluid and contact pressure distribution of hydraulic seals often a perfectly smooth or randomly rough isotropic surface is assumed. But due to different surface finishing methods, like coating, grinding or polishing, rough and anisotropic surface topographies are generated. In this paper an experimental investigation of the influence of such anisotropic surfaces on the friction behaviour of a hard-soft contact is reported.
A test rig has been designed and set up to investigate a soft, lubricated line contact in detail. An O-ring cord is brought into contact with the lateral surface of an uniform rotating hard cylinder. In order to simulate a cylinder-on-flat test configuration, the diameter of the hard cylinder is significantly larger than the O-ring’s diameter. Three cylinders with different surfaces are used: One sandblasted, isotropic surface and two anisotropic surfaces, grooved orthogonal or longitudinal to the direction of motion. The contact pressure is adjustable by varying the test weights. The test chamber is temperature-controlled to consider different viscosities of the fluid and the temperature-dependent material behaviour of the elastomer.
Friction force and rotational speed are measured to carry out Stribeck curves and compare the influence of anisotropic surfaces for different relative velocities, temperatures and contact pressures. Very slow velocities (2.5 mm/s - 25 mm/s) are studied in particular. Additionally the effect of idle time on the breakaway force is investigated. A distinct influence of anisotropic surfaces can be detected. The friction force decreases when the surface is grooved longitudinal to the direction of motion.
Update regarding the fire damage - New reopening date of laboratory 1 and substitute lab
October 7th 2016
The reopening date of laboratory hall 1, which was first expected to be the end of 2016, has proven impossible to maintain. Due to the time intensive modernization of the electrical infrastructure, the ventilation and the fire prevention system in laboratory 1, the reopening is presumably planed for the 3rd to 4th quarter of 2017! An exact plan of the necessary renovations by the Bau- und Liegenschaftsbetrieb (BLB) NRW, which illustrates this schedule, is not yet available.
In the meantime we resort to the utilization of the laboratory space in hall 2. The research activities in hall 2 are successfully continuing, since its reopening at the beginning of May.
Additionally, a substitute space available on short notice is being acquired in cooperation with the University’s central administration in order to expand the current capacities and relieve laboratory 2, so that the research capabilities can also be expanded. With this step, the research abilities of the institute will be reinstated on a broad range. Only the fields of acoustic and climatic measurements are currently still limited due to the currently unavailable missing infrastructure, as well as the operation of test rigs with high power demands.
O+P: Compensation of Brake Force Oscillations
Matthias Petry, August 22nd 2016
The paper "Compensation of brake force oscillations with a self-energizing hydraulic brake (SEHB)" was published in the O+P Fluidtechnik Journal, edition 07/08 2016. Authors are Dipl.-Ing. Matthias Petry, Dr.-Ing. Olivier Reinertz and Prof. Dr.-Ing. H. Murrenhoff.
Friction force and brake torque oscillations of disc brake systems represent a relevant topic regarding brake comfort and safety aspects. The self-energizing hydraulic brake (SEHB) makes it possible to compensate these oscillations actively. Compensation rates up to 86% are possible for both constant speed and speed ramps.
Shortly before entering his 88th year of life he died caused by a severe illness.
On the 21st of July 2016 fluid power lost an outstanding researcher and advocate of hydraulics and pneumatics with the death of em. Univ. Prof. Dr.-Ing. Dr. h. c. mult. Wolfgang Backé.
Wholeheartedly his life belonged to the development of fluid power. The decision was made early on by him studying mechanical engineering at RWTH Aachen University choosing the study direction
of production engineering. He deepened the subject in fluid power research and got promoted to Dr.-Ing. in 1959 at the machine tool laboratory WZL under the direction of Prof. Opitz. Building upon
this he further qualified by a habilitation towards the subject of flow forces in valves in the year 1962.
After a time as Chief Engineer at WZL, a following industrial career as head of the development department of the company Rheinstahl Wagner and teaching obligations by his Venia Legendi for the subject
“Ölhydraulische Steuerungen und Antriebe“ in Aachen, Wolfgang Backé , born on July 25th in 1929, accepted the offer to take over the newly created chair “Lehrstuhl für
hydraulische und pneumatische Antriebe und Steuerungen“ (IHP) and the directorship for the Institute carrying the same name, todays IFAS. He was head of the Institute till his official retirement in 1994
and led it to the biggest and most renowned institution in the field of fluid power with national and international recognition and an outstanding worldwide reputation.
Wolfgang Backé was scientist and researcher with full believe and thereby devoted to fluid power like nobody else. With his creative power he transformed fluid power in Germany, Europe and overseas.
In academia as well as in the industrial sector he helped this process by manifold consulting and his directorships in company boards leading to the success story we know. Early on he forged unique networks,
which are still used by the following generations of researchers in our field. For me it is important to emphasize that these networks also stretched into the social environment and actively included the partners.
This way many conference, business and cultural travels were backed by the families. They were part of it, involved in the preparation and unofficially the group was called the “Fluid Power Gang“.
He passed on his knowledge by teaching students and conducting as well as supervising research and development projects with the upcoming engineering generations. Even after being retired he still actively
participated in the scientific live and kept publishing papers and books.
He supervised 124 doctoral candidates and guided them to graduation, thereby starting their subsequent industrial careers. Many former students and scientific researcher are employed in notable positions in the
fluid power industry. Some returned to Universities and Universities of Applied Sciences to pass on the knowledge to young academics they themselves learned through him. Some examples are Prof. Young-Xiang
Lu, who was President of the Zhejiang University in Hangzhou and Prof. Chung-O. Lee, who for a long time was Minister of Research and Technology in South Korea.
Manifold contacts and partnerships with other institutes in the field of fluid power in America, Asia, Australia and Europe give evidence of his worldwide recognition in the industry. Within RWTH Aachen University
his interdisciplinary research was backed by collaborative research centers where he participated and took over leadership functions. This work was complemented by common research projects initiated and guided
by the Engineering Federation Fluid Power within VDMA in Frankfurt. These projects covered fluid power in industrial and mobile hydraulic applications, handling and automation technology, as well as biomedicine.
In addition to these commitments in his subject, he also participated in the academic self-administration of the University. In that regard he was Dean of the Faculty of Mechanical Engineering in 1974 and 1975.
Without exaggeration it can be stated that based on his research and teaching focal points, as well as his involvement in the in appointments for Institute leaderships , his research, development and teaching activities,
todays fluid power in Germany has achieved a highly recognized technical stand.
Together with high ranked industrial representatives he founded the society for the advancement of fluid power (Fördervereinigung Fluidtechnik, e.V., Aachen) to promote, e.g., infrastructural projects, conduct
national and international conferences and support teaching. This way he was able to found the biannually organized international fluid power conference. It started in 1974 as 1. AFK and continues today with
the IFK, alternating between the cities of Aachen and Dresden.
Next to a lot of academic honors, he was awarded three honorary doctor degrees and two honorary professorships. He obtained the highly ranked German Federal Cross of Meritin 1988 (“Verdienstkreuz am
Bande des Verdienstordens der Bundesrepublik Deutschland“) and in 1997 (“Bundesverdienstkreuz 1. Klasse der Bundesrepublik Deutschland“).
With his death the Institute - and with it the “Fördervereinigung Fluidtechnik“ - loses his highly regarded scientist, researcher and teacher, as well as its founding member.
Our deep sympathy is with his wife, Ms. Rosi Seiz-Backé, and his Family. We will always keep our mentor in highest regard and in honorable memory.
Aachen, July 2016
Update regarding the fire damage - Reopening of lab hall 2
May 9th 2016
At the beginning of this week the IFAS and its employees celebrated the reopening of the smaller lab hall 2 much sooner than expected. Hence, research activities are possible in hall 2. This also includes the opening of our library and the conference room.
Update regarding the fire damage - Removal of ventilation system underway / Infrastructure partly operational
April 6th 2016
One part of the ventilation system, emerging over the destroyed area of our neighboring institute WZL, has been removed. The remaining part, situated above the IFAS laboratory roof, is expected to be removed by mid-April. The necessary preliminary work is already underway.
The majority of the debris in the area surrounding the completely destroyed WZL laboratory has also been removed. Parts of the IFAS laboratory infrastructure are once again operational. Plans to restore the electrical supply and distribution are being discussed. These steps will however take some time. The recommissioning of the pneumatic pressure supply network, the water supply and radiators is nearly finished. The central cooling water supply for test rigs and hydraulic units will follow shortly.
The cleaning of the laboratory and the measuring equipment is mostly finalized. The re-installment of the measuring equipment, which was cleaned in a separate location, is underway. The largest part of the laboratory is therefore awaiting final inspection of the cleaning work. This will take place after the outstanding greater clean-up operations in the vicinity of the laboratory are completed.
Update regarding the fire damage - Cleaning efforts are in progress
March 10th 2016
Due to the fast cleaning process of the building and the inventory, IFAS hall 1 is completely decontaminated. In combination with isolation interventions in compliance with the chemist, the area is categorized as hazard class 0. The current cleaning process is focused on switchboards, test boxes and the test rigs situated within as well as rooms located within the lab. First steps regarding the restart of the infrastructure are also in progress. Since beginning of the week heavy machinery is used for the cleanup efforts of the destroyed neighbouring institute hall of the WZL.
Update regarding the fire damage - Status of the decontamination process
February 25th 2016
Parallel to the ongoing decontamination of the inventory, the "Bau- und Liegenschaftsbetrieb NRW" also assigned the decontamination of the building itself. This process has begun and is being carried out by the company BELFOR. The machine decontamination process in our main lab is almost completed. An on-site inspection by a planning office for the infrastructure's recommissioning promises a quick return to normal operation in our lab - first on a limited level, reaching full operation step by step.
Update regarding the fire damage - Approval of the structural engineers was issued
February 18th 2016
Meanwhile all effected laboratory rooms of IFAS were examined and approved for entering by the structural engineers. Exempted for now is the anechoic room which is partly located in the fire damaged area of WZL machine tool laboratory. Here we need to wait for the clearance of fire damaged parts and materials before the access becomes possible. Thanks to the approval of the structural engineers the damage to the central infrastructure can be analyzed and the necessary steps for its recovery will be taken accordingly.
Update regarding the fire damage - pictures
February 15th 2016
Cleaning work is in progress.
Update regarding the fire damage
February 11th 2016
The structural clearance of our laboratory was partly issued, so that the building can be entered. Thus, the cleaning and the chemical neutralization of the lab was started by the company BELFOR DeHaDe GmbH, which was appointed by the insurer and the RWTH University. A preliminary categorization of the main lab has been set to hazard class 1 until completion of the chemical analysis.
The attached test chambers, the labs and offices on the first floor have partially been categorized as hazard class 2 and are not yet cleared in structural regard. For the second lab building, which is less affected, the chemical analysis is still pending as well. Luckily, the basement could be kept dry during firefighting operations. The structural clearance of all other labs is pending and the stepwise reactivation of the infrastructure needs to be carried out.
Message to our friends, supporters, customers, sponsors and associations regarding the fire in the neighbouring building on February 4th, 2016