Welcome to the Institute for Fluid Power Drives and Controls at RWTH Aachen University.
Our pages offer information on our present research activities, our equipment and our educational duties.
You will find contact partners or can order publications of our institute.

Univ.-Prof. Dr.-Ing. H. Murrenhoff

Institut für fluidtechnische Antriebe und Steuerungen der RWTH Aachen

Steinbachstraße 53
D-52074 Aachen
Telefon: +49/241/80 275 12
Telefax: +49/241/80 221 94

Fast access

11th IFK 2018 - CfP now open

All news [enlarge]                                    

Elastohydrodynamics for Soft Solids with Surface Roughness: Transient Effects

Julian Angerhausen, June 12th 2017

Link to publication

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.

J. Angerhausen, M.Sc.
Tel.: +49-241-80-27530
E-Mail: Julian.Angerhausen@ifas.rwth-aachen.de

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.

Dipl.-Ing. M. Petry (geb. Hirtz)
Tel.: +49-241-80-27530
E-Mail: Matthias.Petry@ifas.rwth-aachen.de

IFAS Pentecost Excursion 2017

Florian Schoemacker, May 9th 2017

This year IFAS offers an excursion to company of the fluid power industry. The excursion is dated within the pentecost week, from 06.06. to 09.06.

Please send your registration to: Florian.Schoemacker@ifas.rwth-aachen.de

Further information can be found on the information sheet.

F. Schoemacker, M.Sc.
Tel.: +49-241-80-27532
E-Mail: Florian.Schoemacker@ifas.rwth-aachen.de

11th IFK 2018 - CfP now open

March 10th 2017

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

R. Leifeld, M.Sc.
Tel.: +49-241-80-27528
E-Mail: Roland.Leifeld@ifas.rwth-aachen.de

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.

G. Matthiesen, M.Sc., M.Sc.
Tel.: +49-241-80-27523
E-Mail: Gunnar.Matthiesen@ifas.rwth-aachen.de

New project: Survey on the Industrial Internet in the sector of fluid power – shown by the example of an automated commissioning process

February 2nd 2017

FKM - Forschungsfonds Fluidtechnik (FKM-Nr. 704080)
02/2017 - 01/2018

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.

R. Alt, M.Sc.
Tel.: +49-241-80-27490
E-Mail: Raphael.Alt@ifas.rwth-aachen.de

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.

T. Pietrzyk, M.Sc.
Tel.: +49-241-80-27532
E-Mail: Tobias.Pietrzyk@ifas.rwth-aachen.de

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.

N. Otto, M.Sc.
Tel.: +49-241-80-27523
E-Mail: Nicolai.Otto@ifas.rwth-aachen.de

ISC 2016: Influence of additives on rod seals

November 23th 2016

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.

F. Fischer, M.Sc.
Tel.: +49-241-80-27533
E-Mail: Felix.Fischer@ifas.rwth-aachen.de

ISC 2016: Influence of anistoropic surfaces

October 20th 2016

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.

J. Angerhausen, M.Sc.
Tel.: +49-241-80-27530
E-Mail: Julian.Angerhausen@ifas.rwth-aachen.de

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.

Dipl.-Ing. M. Petry (geb. Hirtz)
Tel.: +49-241-80-27530
E-Mail: Matthias.Petry@ifas.rwth-aachen.de

Wolfgang Backé passed away († July 21st 2016)

July 27th 2016

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
Hubertus Murrenhoff

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.

Dear Friends, Sponsors and Partners of IFAS

May 2nd 2016

Please click here to get to the message from May 2nd 2016

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

February 7th 2016

Please click here to get to the message from Feb. 7th 2016