Friedrich Franek

AC2T Research GmbH | AC2T

Objective: During osteoarthritis progression, cartilage degrades in a manner that influences its biomechanical and biotribological properties, while chondrocytes reduce the synthesis of extracellular matrix components and become apoptotic. This study investigates the effects of inflammation on cartilage under biomechanical stress using biotribolog...

Osteochondral defects in middle-aged patients might be treated with focal metallic implants. First developed for defects in the knee joint, implants are now available for the shoulder, hip, ankle and the first metatarsalphalangeal joint. While providing pain reduction and clinical improvement, progressive degenerative changes of the opposing cartil...

Metal matrix composites are very inhomogeneous materials, and their properties depend on various parameters (production process, constituents, their interfaces, etc.). The influence of SiC microparticles (40 μm) reinforcement and graphite macroparticles (200–800 μm) addition on the mechanical properties of Al–Si A356 alloy, produced by compocasting...

Objective Cobalt and chromium (CoCr) ions from metal implants are released into the joint due to biotribocorrosion, inducing apoptosis and altering gene expression in various cell types. Here, we asked whether CoCr ions concentration-dependently changed viability, transcriptional activity, and inflammatory response in human articular chondrocytes....

Purpose The paper aims to focus on the individual contribution of water to the lubrication regimes in articular joints because understanding of these regimes is crucial not only for the treatment of diseases like osteoarthritis but also for the development of new implants to have a longer service cycle. Design/methodology/approach Cartilage specim...

The aim of this in‐vitro study was to investigate the response of articular cartilage to frictional load when sliding against a metal implant, and identify potential mechanisms of damage to articular cartilage in a metal‐on‐cartilage pairing. Bovine osteochondral cylinders were reciprocally slid against metal cylinders (cobalt‐chromium‐molybdenum a...

Partial knee replacement and hemiarthroplasty are some of the orthopedic procedures resulting in a metal on cartilage interface. As metal implant material, CoCrMo based alloys are commonly used. The aim of the present study is to assess the role of biotribocorrosion on the CoCrMo-cartilage interface with an emphasis on metal release during sliding...

Autologous osteochondral transplantation (AOT) utilizing autografts is a widely used technique for the treatment of small‐to‐medium cartilage defects occurring in knee and ankle joints. The application of viable cartilage and bone ensures proper integration, early weight bearing, as well as restoration of biomechanical and biotribological propertie...

The microstructural evolution of ferritic–pearlitic steel is studied during unidirectional sliding under boundary lubrication using a ball-on-flat configuration. Dislocation activity as a function of distance to surface is determined using orientation gradients by electron backscatter diffraction in logarithmic intervals up to one million of slidin...

A method on the macroscopic length scale is developed to determine frictional energy losses between a homogeneous solid bullet and a twisted barrel. This accounts for the entire interaction between the bullet and the barrel surface, the drag due to the engraving forces, and possible friction-optimized bullet coatings. The method applied is based on...

Experiments carried out during the last 50 years have elucidated the basic mechanism of the Biefeld-Brown effect. Recent research has focused on establishing design rules in order to maximize the lifting force resulting from this effect. For this purpose, a numerical estimation that takes the effect of altitude into account is needed. In the presen...

Microstructure evolution in polycrystalline metals, which undergo sliding contact, takes place by dislocation activity, followed by dislocation pile-up, formation of low-angle grain boundaries and consolidation of those low-angle grain boundaries as nanocrystaline grains, thus resulting in grain refinement. In dry contacts or boundary lubrication,...

Automotive parts made of ultra-high strength steels are produced by press hardening in order to obtain high-strength components. During this process, formed parts are pressed against tools at high temperature, which ultimately yields to tool damage. Tool damage is especially detrimental since it not only affects the quality of the parts but also ca...

This study deals with a comparison between new experiments on the frictional behavior of porous journal bearings and its prediction by previous numerical simulations. The tests were carried out on bearings lubricated with polyalphaolefin-based oils of distinct viscosities. The theoretical model underlying the simulations includes the effects of cav...

The aim of this investigation was to examine several types of commercially available polymers for potential application in machine elements that are exposed to abrasion. Selected materials were evaluated on a rubber and steel wheel abrasion test rig according to the standard ASTM G65, using as abrasive quartz sand (SiO 2 ) as abrasive, with a parti...

Using a thin film lubrication regime we investigated the PFPE-Z confined lubricant behaviour. The results of our simulations take into consideration the effect both of pressure and relative velocity of the confining walls. The occurring stick-slip phenomena are explored in detail. It was found that the lubricant properties change near the walls. Al...

In the paper production, doctor (scraping) blades are placed in contact with press rolls during wet pressing so as to purge the surface of the rolls from processing water, contamination and stickies. The contact is achieved by mounting the blade on a holder, which is tilted around a rotation axis until the blade tip contacts with the roll. The cont...

Metal injection moulding (MIM) offers advantages for mass production of components which may be subjected to tribological load. Obviously, MIM processing influences material and thus tribological properties. Contrariwise, it is possible to gain specific favourable tribological properties by MIM. MIM manufactured CuNi9Sn6 and CuSn8 based on commerci...

The continuously growing demands on standard components of machine elements with respect to power density, efficiency and durability while operating can reach the borders of load bearing capacity and lead to premature failure. Especially in engineering applications with insufficiently predictable operating conditions, bearings can usually meet thes...

The continuously growing demands to standard components of machine elements with respect to power density, efficiency and durability while operating may too quickly reach the borders of loadbearing capacity and lead to premature failure. Especially in engineering applications with insufficiently predictable operating conditions bearings can usually...

Doctor blades are commonly used in paper machines to keep the surface of rollers clean. Due to higher demanding conditions, the requirements for doctor blades have steadily increased. The wear rates must remain low, while simultaneously their cleaning function has to be ensured. For this reason, the paper industry has developed a high degree of emp...

A molecular dynamics simulation study has been conducted in order to point out the effect of steady shear and loading pressure on lubricant thin films. The model used in these simulations is composed of two solid walls and PFPE-Z lubricant. We apply steady shear by moving the walls in opposite directions while at the same time the upper wall exerts...

In order to numerically simulate the contact pressure distribution and area during sliding when wear occurs, the combined finite element method and boundary element method (FEM–BEM) developed by the authors is extended based on a linear wear law merged with the space- and time-resolved cumulative dissipated frictional energy. In each computed time...

Wide tribology concept through the knowledge interaction from physics, chemistry and various engineering disciplines, has put tribology in a group with interdisciplinary sciences. This work gives information about the international standardization in the field of tribology, International Tribology Council, whose members consist of 36 national tribo...

Tribology is the science of friction and wear. These are physical processes that can appear anywhere in everyday life — from the contact of shoe soles with the floor and the interaction of tires with the road to the use of the brakes in a vehicle. Researchers explore how wear and friction can be reduced or even eliminated, but also how to create fr...

In this study, an advanced wear volume measuring technique making use of the radioisotope concentration method is applied to a ball-on-disc experiment, which allows highly precise online wear volume measurements and distinguishes among different wear regimes. Furthermore, the adhesive transfer of material from the activated specimen to the countera...

Forming of internal threads is a common used process in several industries. Due to its process stability and economic efficiency, thread forming is more and more in use. The advantage compared to thread drilling and milling is the non-cutting production and induced strain hardening which improves the strength of the thread. However due to the incre...

An extremely small roughness of constant height magnitude is considered on the femoral head of an artificial hip joint in order to determine the consequences of various regular shapes and clearances on the mechanical performance of this hip prosthesis via a properly coupled finite and boundary element method. In addition, different material combina...

The mechanical and frictional properties of hydrogen- and oxygen-terminated nanocrystalline diamond films (NCD) grown by hot-filament chemical vapor deposition (HFCVD) have been investigated in the present work. The structure and morphology of the NCD films have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) a...

Transition metal dichalcogenides with a layered structure are well known for their self-lubricating properties, particularly in a vacuum or dry atmosphere. The macrotribological properties of these films have been studied extensively. However, the tribological behaviour of these films in the nanonewton load range has hardly been reported. Study of...

This paper presents the investigation of effects of phosphorus-containing coatings on the friction behaviour. Three types of technologically fabricated coatings are investigated: zinc phosphate, iron phosphate, and a third the composition of which is still confidential as it is being patented. For the description of the composition and the properti...

Fe-based hardfacing alloys are widely used to protect machinery equipment exposed to different loading situations where abrasives play a dominant role in restricting lifetime of tools. Wear at elevated temperatures is superposed by the effect of oxidation of the wearing surface. In view of the above, two hardfacing alloys based on Fe-Cr-C incorpora...

Hypereutectic aluminium-silicon (AlSi) alloys have been increasingly used in the fabrication of internal combustion engines in recent years. They combine low weight with good mechanical properties and high wear resistance at the cylinder surface. Owing to the inhomogeneous structure of these alloys, the tribological processes taking place at the su...

In this paper, it is shown that specific ionic liquids have great potential to be used as additives for tribological applications. The results promise a high load carrying capacity; especially for the cation 3-Octhylthiazolium and long term stability up to temperatures of 120°C is given. However, only extreme pressures/anti-wear properties are exam...

A selection of additives and their performance and compatibility with a variety of copper alloys have been evaluated in an SRV test set-up. The tests show a remarkable variation of tribological behaviour with a clear relation to both the type of lubricant / additive and the type of alloy. One ester-based additive showed outstanding friction and wea...

Diamond films are well known for their outstanding properties such as high hardness, possible low coefficient of friction, high thermal conductivity, excellent biocompatibility and electrical insulation. Diamond films with nanocrystalline grains (grain sizes between 3 and 15 nm) offer further advantages of low compressive stress, low surface roughn...

To understand the wearing behaviour of piston rings with respect to loading conditions or lubricant performance, measurements are necessary in model as well as in engine environments. Model or component tests allow for investigating the impact of a single parameter, contrary to engine tests, where the answer of the whole system is observed and part...

In order to stimulate pre-competitive research work a number of programmes were initiated in Austria. One specific programme was the frame of Kplus-initiatives, which enabled to establish the Austrian Center of Competence for Tribology (AC2T). The thematic structure of the Center offered interdisciplinary research work in the main fields of tribol-...

Diamond and diamond-like carbon films are well known for their outstanding properties such as high hardness, low coefficient of friction, good thermal conductivity, excellent biocompatibility and electrical insulation. Diamond films with nanocrystalline grains offer added advantages of higher hardness, improved surface finish (less roughness), very...

Many engineering components are subjected to erosive wear at elevated temperature. As erosive wear at elevated temperature is governed by the synergistic effect of erosive wear and oxidation, it is possible to modify surfaces of the components in order to achieve improved performances. In view of the above, two different types of hardfacing alloys...

In the present work, the tribological properties of different prototypical automotive lubricant additives are studied and compared. The simulated model tribosystems are made up of two amorphous iron substrates. The boundary lubricant between these sliders consists of one self-assembled monolayer (SAM) of fatty acid or fatty acid methyl ester (FAME)...

Porous sliding elements (especially porous bearings) as well as polymer sliding elements are used in large quantities and in many different applications. For special applications metallic sliding elements with hybrid lubrication (graphite-oil-compound, multiphase composites, MMC) are used. The valuation of the friction and wear behaviour of those "...

In many fields of industry, erosion is the dominant wear mechanism that reduces the lifetime of costly machine parts such as crushers, hammer bars, or cutting edges. Particles of specific mechanical and geometrical properties hit the surface with a certain energy and, under different angles of impact, cause abrasion and surface fatigue, or, in the...

A novel formulation of elastic multi-asperity contacts based on the boundary element method (BEM) is presented for the first time, in which the influence coefficients are numerically calculated using a finite element method (FEM). The main advantage of computing the influence coefficients in this manner is that it makes it also possible to consider...

In modern car engines the tribosystem piston ring and cylinder liner is mostly affected due to the latest trends towards high ignition pressure for low fuel consumption, low particle and low CO2 production, and due to bio-admixtures in fuels. To test the wear behaviour of such a system a model tribometer with realistic loading conditions and a very...

A newly developed measuring device is presented, that allows the evaluation of the frictional behaviour of different materials. The device does not need specific laboratory environment and due to its compact design-similarly the palpation by the fingertip-enables the measurement and differentiation, respectively, of the frictional coefficients unde...

The aim of this work was to find correlations between selected microstructural parameters such as hardness, content of hard phases and coarseness of microstructure and the wear resistance at high temperatures. Two materials with different microstructures, showing promising high-temperature wear performance, were investigated under combined impact a...

In many fields of industry, abrasion and erosion processes are dominant wear mechanisms that reduce lifetime of costly machine parts. Wear resistance against abrasion and/or impact or the ability to withstand other complex mechanical actions are often required. In order to quantify the specific properties of material that are applied in such fields...

Stick-Slip phenomena in wet friction disc systems used in drive trains of modern vehicles can canse comfort decreasing vibration or noise. For the investigation and characterization of these phenomena, a disc-on-disc tribometer is used at the Austrian Center of Competence for Tribology (AC 2T research GmbH). This study presents a method which allow...

Iron-based hardfacing alloys are widely used to protect machinery equipment. A strong correlation is given between microstructure and chemical composition of welding deposit with the resulting wear behaviour. Concerning precipitation of metallurgical hard phases and synthetic added hard particles, the bonding strength of the hard phases in the meta...

Iron-based hardfacing alloys are widely used to protect machinery equipment exposed either to pure abrasion or to a combination of abrasion and impact. The specific wear behaviour of a welding alloy under these conditions depends on its chemical composition, the microstructure obtained after welding and finally the welding technology used to apply...

The investigation of electrical low power switching contacts, including dry-circuit, is characterized as a highly interdisciplinary research field. The knowledge of plasma physics, the influence of kinetics on contact phenomena, material science and metallurgy, as well as thermal aspects and tribology, is demanded. The methods usually used at the A...

Sliding wear at elevated temperature is an important material removal mechanism in large number of engineering applications such as metal forming operation, gas turbine engines, etc. The material loss during sliding at elevated temperature is governed by the antagonistic effect of wear process and oxidation. The objective of the present work is to...

Sliding contacts of copper alloys and steels can commonly be found in numerous machine elements. The interactions of copper alloys and additives under mixed and boundary lubri¬cation conditions are far less understood than those of mating steel bodies. Furthermore, copper alloys can be sensitive to the formation of soft and heavily wearing surface...

Der vorliegende Beitrag beschreibt die organisatorische Struktur und die Forschungsaktivitäten im österreichischen Kplus-Kompetenzzentrum für Tribologie. Anhand von ausgewählten Beispielen wird die interdisziplinäre Herangehensweise an die Lösung wissenschaftlicher Fragestellungen im Bereich Reibung, Verschleiß und Schmierstoffanwendung dargestellt...

For the investigation of piston ring and cylinder liner systems, screening tests are usually run with pure engine oil as the only lubricant. Due to the fact that the combustion chamber of a cylinder is filled with a high-pressure gas-fuel-mixture, we assume that the piston ring and cylinder liner contact is lubricated by a mixture of oil and fuel r...

Stick-Slip phenomena in wet friction disc systems used in drive trains of modern vehicles can cause vibration or noise which considerably decrease comfort of drives and passengers. For the investigation and characterization of these phenomena, a disc-on-disc tribometer is used at the Austrian Center of Competence for Tribology. A method is presente...

Up till now it is not really common to solve tribological tasks using patterns from bionics. Such biomimetic approaches, of course, have to consider the specific conditions in which the engineering solutions have to prove their ability. If these beneficial conditions (which may be called 'tribological biotope') are not provided, the systems tend to...

Modelling and simulation are more and more upcoming tools in various fields in engineering. Most tasks request specialization in terms of the technical background as well as of the mathematical methods used. In this paper an overview is given about some commonly available software tools for simulation with respect to the specific conditions in the...

The objectives of this work are to deposit nanocrystalline Cr3C2-25(Ni20Cr) powder by thermal spraying and to compare the performance of this coating with that obtained using conventional powder. Towards that purpose, Cr3C2-25(Ni20Cr) powders with nanocrystalline grain size and with conventional grain size were deposited using OSU-SJS high-velocity...

Technological devices such as pressure sensors, gyroscopes and accelerometers get smaller and smaller. This increases the necessity for the fundamental understanding of tribological phenomena at the micro- and nanometer scale. Biological systems excel also at this scale. The thesaurus that nature has developed during the last millions of years of e...

Due to their improved hardness and toughness properties, nano-crystalline materials have become attractive for a wide variety of applications. However, as the processing of nano-crystalline materials is quite expensive, efforts have been made to develop coatings using nano-crystalline grains. The present study investigates the ambient temperature f...

The search for improved wear resistant materials for hip endoprostheses has lead to an international standard for wear testing of total hip joint prosthesis ISO 14242. The displacement and load curves in this standard are derived from clinical gait analysis. However the standard leaves the interpreta- tion of its displacement curves open since no c...

Until now, ionic liquids seldom have been the object of studies to evaluate their potential as lubricants or additives. In this paper, a critical study of the lubricating properties in steel/steel contacts is presented of some ionic liquids and reference samples. Emphasis was placed on the physico-chemical properties such as viscosity, density, mis...

Up to now, the suitability of uniform tractor transmission oils (UTTO) for truck and building machine drive, brake and hydraulic systems were often investigated in expensive on-vehicle or specific laboratory rig tests. Present work describes the layout and adoption of a test rig for application-oriented testing of wet brake system elements. The res...

In this work we intend to investigate the surface properties of laser sintered and coated parts. by measurement of friction coefficient and wear rate. The main aim of this research is to justify laser sintered prototype tools for injection molding of fibre-reinforced polymers. For increase of wear resistance we used hard Co-based and Fe-based coati...