bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen Pick Up and Diffusion in TIG Welding of Supermartensitic 13% Cr Stainless Steel With Superduplex Wire
Authors: Olden V. , Aune R. , Ro̸rvik G. , Akselsen O. M.
Published: November 2008

Supermartensitic 13% Cr stainless steels have been in use in offshore satellite flowlines for several years. Since they contain microstructure that is susceptible to hydrogen cracking, the pick up of hydrogen in welding with subsequent transport to critical areas may be very important, also with respect to hydrogen embrittlement when hydrogen is coming from other sources than welding (e.g., cathodic protection). In the present investigation the pick up of hydrogen has been assessed using mechanized TIG welding with superduplex 25% Cr wire. The WM and HAZ hydrogen levels were analyzed. With addition of hydrogen in the shielding gas in multipass welding, the mean WM hydrogen contents were found to be approximately 10 and 6 ppm in the cap layer and root pass, respectively. The corresponding mean HAZ concentration was 3.1 ppm (scatter between 1.3 and 4.8) immediately after welding. Post weld hydrogen diffusion heat treatment showed that hydrogen diffusion was retarded at room temperature, even for 1 month storage. Limited diffusion took place at 90°C, particularly for the cap region. The results indicate that superduplex weld metal with high hydrogen content (6–10ppm) will act as a hydrogen reservoir supplying H to the 13% Cr HAZ as long as 2–3 years after welding. Fitting the data by using the uniaxial diffusion model gave diffusion coefficients in the range of ∼3–5×10−13m2/s at room temperature for the superduplex WM. At 90°C a diffusivity of 5.5×10−12 m2/s for the cap area and 2.5×10−11 m2/s for the root area were found. For a holding temperature of 150°C, diffusion from the WM was much more significant. The hydrogen WM cap content was reduced from an initial level of 10 ppm down to 2 ppm within 3 months giving a diffusion coefficient of 1.0×10−11 m2/s. The supermartensitic HAZ samples contained up to 5 ppm hydrogen a short time after welding. This is an important observation, since it may provide sufficient amount of hydrogen in the HAZ to cause cold cracking in the as welded condition. The uniaxial model indicated diffusivities of D = 8.0×10−11 m2/s at 20°C and D = 2.0×10−10 m2/s at 90°C in the HAZ.
Experimental Study and Simulation on Heat Exposed Liquid Filled Process Equipment
Authors: Berge Geir , Olstad Harald
Published: November 2008

Heat exposure of process equipment is a complex problem area that has gained interest over the last years. The reason is that existing standards vague on the subject and operate with too low heat load compared to what has been found in experiments. It has also been shown that the subject is more complex than expected when the existing standards were formed. It has been clear lately that simple formulas will not cover all the aspects and variation of the phenomenon. It seems that multi physic simulations are needed to be able to predict the behaviour satisfactorily. VessFire is such a simulation system that can handle this problem and has been widely used the last years by several companies and projects. One of the major parameters that need to be modelled is the heat transfer phenomenon inside the equipment shell. This is a difficult task and it is not easy to find data for verification. This paper describes a number of experiments performed for verification purposes. The project was supported by The Petroleum Safety Authority Norway and is a result of the authorities’ need for better means in safety management as new technology is introduced. The simulation results show good agreement to the experiments and indicate that the simulation system gives a reasonably good representation of the phenomena.
Interactions Between Vertical Structures in Waves
Authors: Wang J. , Calisal S. M. , Qiu W.
Published: November 2008

This paper presents experimental and theoretical results obtained during the hydrodynamic study of a multi-cylinder system. The main focus of the study was to quantify hydrodynamic interactions between heaving vertical cylinders of a conceptual wave energy conversion system. Several identical circular cylinders representing platforms in an energy conversion system and a parabolic shaped wave reflector were tested in a wave flume tank. Wave heaving forces, radiation and diffraction effects were studied experimentally and numerically. The theoretical calculations were carried out for hydrodynamic coefficients, the radiation and diffraction effect analysis. Experimental results for multi-cylinders were compared with the numerical solutions by a panel-free method in the frequency domain. One main objective of the experimental tests was to calibrate the experimental set up, obtain validation data for numerical calculations. The diffraction studies showed that the hydrodynamic interactions could be constructive or destructive for heave wave forces. The positive magnification of the wave exciting force can be significant if a parabolic shaped reflector is used. It was observed that the wave force magnification and the wave energy absorption depend on incoming wavelength, and the cylinder to wavelength ratio. It has been found in the radiation tests that heave added mass and damping coefficients compare well with the calculations based on potential flow calculations.
Probabilistic Integrity Assessment of Pipelines and Pressure Vessels With Localized Corrosion
Authors: Tronskar Jens P. , Li Zhang , Edwards John D.
Published: November 2008

The acceptability of localized corrosion for pipelines in service is discussed and the methodology for probabilistic assessment of corrosion damage using the 2004 revision of Det Norske Veritas document DNV-RP-F101 is presented with regard to predicting the remaining life of onshore, offshore pipelines and also pressure vessels for the oil and gas industry. Capacity assessment of corrosion defects in pipelines and pressure vessels is a challenge for the industry, and has resulted in several methods and codes in the recent years. The methods include ASME B31G for pipelines and other standards and recommended practices that can be applied for pipelines as well as pressure vessels such as BS7910 Annex G and API 579. In 1999 DNV issued a recommended practice for the assessment of corroded pipelines, DNV-RP-F101, which was developed in co-operation with the pipeline industry. A revision of this document was issued in October 2004. The latest revision provides guidelines for probabilistic assessment of the pipeline reliability and remaining life. Pipeline corrosion is often of localized nature and depends on many factors such as fluid composition and partial pressures, temperature, pH, flow rate and efficiency of corrosion inhibition. These factors may not be easy to quantify with great certainty and a probabilistic approach is particularly justified. An approach is presented in this paper where the actual measured corrosion damage is fitted to an extreme value distribution. The future corrosion rate distribution for internal CO2 corrosion is predicted using the latest de Waard and Milliams model and an inhibitor distribution, to predict the corrosion of each pipeline segment. An Gumbel type extreme value approach is applied to estimate the present condition and the local corrosion flaw distribution that may cause a leak of the pipeline in the future. The future corrosion is estimated using the anticipated future operating conditions of the pipeline to predict the corrosion rate distribution expressed in terms of a Weibull distribution. The paper highlights three cases as examples where the approach has been applied for assessing the probability of failure and reliability during service of two offshore pipelines carrying oil and gas with wet CO2, and one stainless steel pressure vessel in a process plant occasionally exposed to trace amounts seawater originating from leaking heat exchangers.
3-Dimensional Bifurcations of Pipe-in-Pipe Structures
Authors: Konuk Ibrahim , Fredj Abdelfettah , Yu Shenkai
Published: November 2008

Explicit and implicit three dimensional Finite Element (FE) models of a pipe-in-pipe (PIP) system are developed. The models represent the casing pipe and the carrier pipe using shell elements. Frictional contact ensures kinematic compliance between the pipes while allowing unlimited axial relative movement. Steel for both pipes is modeled using a kinematic hardening material model capturing plastic deformations. The model allows large deformations and rotations. The developed models are used to study structural response of a PIP system under typical loadings experienced by pipelines. It is shown that a PIP system can be designed to avoid upheaval buckling without any external support. It is also shown that a PIP system has significantly superior structural response when measured in terms of strains experienced by the carrier pipe against the same size single pipe under some extreme axial and lateral loadings. Currently most PIP applications are motivated by the insulation properties of PIP systems or for ease of construction. The results presented here open opportunities for the application of PIP systems. Examples include offshore pipelines designed to protect against ice scour and onshore pipelines against unstable slopes. It is shown that explicit FE can be used to determine closely spaced chaotic solutions for the carrier pipe. It is known that the elastica problem has many closely spaced solutions. The results obtained compared to known chaotic solutions of elastica. Behavior of a PIP system presents interesting real life examples for bifurcations of elastica.
Plastic Design of Flexible Breasting Dolphins
Authors: Bruijn E. , Terpstra J. D. , Gresnigt A. M. , Molenaar W. F.
Published: November 2008

In the development of design methods for single-pile flexible dolphins used for the berthing of bulk carriers, the design stress has been gradually increased to the yield stress to employ the elastic energy absorption capacity of the pile more optimally. In recent guidelines, e.g. EAU 1996 [3] and PIANC 2002 [5], also the plastic yielding capacity is implicitly or explicitly included in the ultimate load-bearing capacity. This movement towards plastic design is not accompanied by the development of calculation models and design criteria to assess the plastic load-bearing capacity and relevant failure modes such as local buckling and ovalisation of the cross-section. To investigate the nonlinear load-deflection behaviour of a dolphin, a numerical model was developed based on the Beam on Nonlinear Winkler Foundation (BNWF) method [7] and extended for the plastic range of the steel pile using plasticity theory, which has been verified and confirmed by FEM analysis. The resulting Bruijn model enables the assessment of the elastic and plastic load-bearing capacity in terms of energy absorption including all significant failure modes, resulting in an improved assessment of the safety against failure and allowing more optimal designs. Case study calculations with the Bruijn model show that buckling, and to a lesser degree ovalisation, are significant failure modes for a diameter-wall thickness (D/t) ratio of 62 and 83, and should therefore be included in the design guidelines. The use of the plastic yielding capacity is limited to a low diameter-wall thickness ratio (about 40), where an increase in the elastic energy absorption capacity of up to 1,37 times the original elastic energy absorption capacity can be obtained after some plastic yielding. At a larger D/t ratio the buckling sensitivity reduces the advantages of plastic design.
Hydroelastic Response of VLFS on Uneven Sea Bottom
Authors: Song Hao , Tao Longbin , Cui Weicheng , Liu Yingzhong
Published: November 2008

Hydroelastic response of VLFS under inhomogeneous sea environment is an important issue in offshore engineering applications. The most typical inhomogeneous ocean environment in offshore engineering is the inhomogeneity caused by the uneven sea bottom. In this paper, the hydroelastic response of VLFS due to the variation of water depth is studied experimentally and numerically. Experiments were performed in the state key laboratory of ocean engineering at Shanghai Jiao Tong University (SJTU). Different shoals were set on the bottom of the wave basin to simulate the uneven sea bottom. The cases tested in the Lab were studied by extending the traditional hydroelastic method in constant water depth to the varied water depth. Comparisons between the experimental measurements and the numerical results show good agreement. It is found that the inhomogeneous ocean environment has some effect on the hydroelastic response of VLFS.
Effects of Drained Pre-Loading on the Performance of Shallow Foundations on Overconsolidated Clay
Authors: Lehane B. M. , Gaudin C.
Published: November 2008

This paper presents results from a programme of centrifuge experiments which examined the effects of drained preloading on the stiffness and load carrying capacity of shallow square footings founded on an overconsolidated clay. The increases in stiffness and bearing capacity induced by various levels of preloading are quantified and compared with standard design guidelines and previously published numerical predictions.
The Use of Charpy/Fracture Toughness Correlations in the FITNET Procedure
Authors: Lucon E. , Wallin K. , Langenberg P. , Pisarski H.
Published: November 2008

In an ideal situation, fracture toughness data to be used in structural integrity assessments are generated through the use of appropriate fracture mechanics-based toughness tests. In reality, such data are often not available or cannot be easily obtained due to lack of material or the impracticability of removing material from the actual structure. In such circumstances, and in the absence of appropriate historical data, the use of correlations between Charpy impact energy and fracture toughness can provide the fracture toughness value to be used in the assessment. The FITNET (Fitness-for-Service) procedure, presently being developed in the frame of a European Thematic Network, includes a section which deals with the use of empirical correlations between Charpy and fracture toughness data. This paper will outline the contents of this chapter, along with some examples of application of selected correlations to actual test data.
Formal Safety Assessment and Goal Based Regulations at IMO: Lessons Learned (Invited Lecture)
Authors: Skjong Rolf
Published: November 2008

In the maritime industry the International Maritime Organization (IMO) is the UN organization responsible for developing international safety and environmental protection regulations. IMO has now developed the second version of ‘Guidelines for Formal Safety Assessment (FSA) for use in the IMO rule making process’. The Guidelines are available as circulars both from the Marine Safety Committee (MSC) and the Marine Environmental Protection Committee (MEPC). This standard is, as far as the author knows, the first risk assessment standard adopted in an UN organization. The work with developing this standard was initiated in 1995 at IMO based on an UK initiative. As there have been some attempts to develop internationally accepted risk assessment and risk management standards also in other industries, this paper tries to describe some of the experience and lessons learned from developing and implementing FSA at IMO. Paralleling the development of the guidelines there has been a number of applications of the guidelines, recently focusing on bulk carrier safety. Relevant studies have been carried out by UK, by Japan, by Norway and International Confederation of Free Trade Unions (ICFTU), and by the International Association of Classification Societies (IACS). These studies will be briefly reviewed with respect to methods used, assumptions made and conclusions drawn. The entire process from the initial terms of reference formulated by IMO to the final decisions is considered. The main conclusion is that the maritime industry has made a lot of progress, quite fast, in the use of risk assessment as part of the decision making process. This being the case, despite the many communication problems that arises in discussing risk issues in international forums. Furthermore, the FSA has helped balancing the often conflicting interest of the flag states and non-governmental organizations present in IMO. In 2004, a new initiative was taken on developing Goal Based Standards at IMO. This initiative was taken by Greece and Bahamas, and has now been debated at three meetings of MSC. The paper will also discuss the relationship between GBS and FSA based on the experience gained.
Combined Steady State and Transient Analysis of a Patrol Vessel as Affected by Varying Amounts of Damping and Periodic and Random Wave Excitation
Authors: Falzarano Jeffrey M. , Vishnubhotla Srinivas , Juckett Sarah E.
Published: November 2008

Traditional naval architecture analysis of ship survival-ability involves analyzing the vessel righting arm curve in isolation or as compared to a steady wind heeling moment. It is well known that ships do not capsize in calm water and infinite time but do so in rough seas and do so dynamically in short time. Understanding the shortcomings of the traditional approach especially for advanced vessels numerous researchers in the ship dynamics field have proposed an alternative view of ship stability analysis, which involves dynamical analysis. Unfortunately, most ship motions analysis is linear and uses ideal flow theory both of which are inadequate descriptions of large amplitude ship rolling motion. Moreover, much of engineering nonlinear vibrations analysis involves perturbation methods where the nonlinearity is assumed small. Numerical simulation and physical model testing to find this critical behavior is time consuming and expensive. An alternative approach involves directly calculating critical behavior. This approach was originally developed for periodic forcing at a single frequency possibly the linear natural frequency. However, nonlinear resonance is much more complicated than linear resonance and more than a single frequency, multi-valued behavior can occur over a range of frequencies. Moreover, the phenomena which are possible for a nonlinear system are much more varied and diverse. In this paper we will analyze a traditional displacement hull form’s critical response in harmonic waves at the system’s linear natural frequency and compare this to the system’s critical response in random waves. We will compare these responses for different values of damping using these different analysis techniques.
Simulation of Sloshing Loads on Moving Tanks
Authors: Peric´ Milovan , Zorn Tobias
Published: November 2008

The aim of the presentation is to demonstrate the possibilities of predicting loads on partially submerged, moving structures, in particular on tanks in ships and on offshore platforms. Since tanks can in reality move arbitrarily, we are using the moving grid approach and a Finite Volume solution method designed to cater for arbitrary motions of polyhedral control volumes. The motion of liquid is computed using an interface-capturing scheme which allows overturning and breaking of waves. By performing a coupled simulation of the flow and vessel motion, it is possible to obtain a realistic response of the liquid in a tank to external excitation, e.g. by sea waves. Results are first presented for tanks whose motion is prescribed in accordance with experimental setups, with which the solutions are compared. A very good agreement between pressures computed in simulations and experimental data at representative locations is obtained. It was possible by means of simulation to clearly distinguish between off-resonance and resonance cases, in which peak pressures reached the highest values, in accordance with experimental observations. Following validation by experimental data in laboratory setups, we demonstrate the plausibility of simulation of both vessel motion and the flow inside and outside vessel. The forces and moments exerted by the sea cause the vessel to move, which excites the sloshing of liquid in tanks. For the computation of vessel motion, both sea-induced forces and forces due to sloshing in tanks are taken into account. While there are no experimental data to compare with, the results look plausible and encourage further validation and application studies.
Effect of TiC Content on Friction and Wear Behavior of Al-TiC Composites
Authors: Tyagi Rajnesh
Published: November 2008

The Al-TiC composites containing three different volume fractions 0.07, 0.12 and 0.18 of TiC have been fabricated and wear characteristics of Al-TiC composites have been investigated under dry sliding. Dry sliding wear tests have been carried out using a pin-on-disk wear tester at normal loads of 9.8, 14.7, 19.6 and 24.5 N and at a constant sliding velocity of 1.0 m/s. The wear rate has been found to vary linearly following Archard’s law. The wear rate is significantly lower in composites as compared to that in base material. The wear mechanism appears to be primarily oxidative under the test conditions taken in the present investigation. Average coefficient of friction also decreases linearly with increasing normal load and volume fraction of TiC.
Novel Superabsorbent Polymer-Based Lubricant Technology
Authors: Levy Richard , Nichols Michael A. , Opp William R.
Published: November 2008

Superabsorbent polymers and one or more solid and/or liquid lubricants, with and without lubricant additives, were formulated into a variety of solid and variable-viscosity lubricant compositions. A series of laboratory trials showed that superabsorbent polymer-based solid (e.g., agglomerated) lubricant compositions and variable-viscosity greases were more effective in reducing friction between moving surfaces than non-superabsorbent polymer-based lubricants.
Study of the Stress Contact Spur Gear, Using the Numerical Asymptotic Method and the Classical Contact Law
Authors: Chaouachi Frej , Zghal Ali
Published: November 2008

This work is a contribution to optimize the size of gears, by studying the variations of spur gear contact stress. The formulation is based on the virtual work principal and the classical contact law. Such contact problem is non-linear and is generally treated through the Newton-Raphson’s method, which is a robust method but nevertheless requires high computational resources. In this work and as an alternative the used methodology jointly applies the asymptotic numerical method and the finite element method that is a good compromise between efficiency and computational resources. It consists in rewriting the different dependent variables as an asymptotic development which transforms a non-linear problem into a succession of linear ones. The contact is formulated by Hertz theory which assimilate teeth contact to a contact between two cylinders; by applying the classical contact law we take into account the real geometry profile of the teeth.
Wear Rate of Cast Alloys of the System Cu-Al-Ni Having Martensite Transformation for Work Under Sliding Friction
Authors: Shcheretsky Alexander A. , Novytskyy Viktor G. , Lakhnenko Vladimir L.
Published: November 2008

In this paper the influence of initial structure of alloys of system Cu-Al-Ni on wear rate under dry friction is shown. It is established that the wear rate of alloys of system Cu-Al-Ni with martensite structure (β1′-phase) is in 2–38 times less than one of standard bronze.
Analogy of the Full Curves of Fatigue Under Cyclic Loading and Friction
Authors: Sosnovskiy Leonid A. , Marchenko Alexander V. , Makhutov Nikolai A.
Published: November 2008

The analogy of the full fatigue curves under cyclic loading and friction was determined. It is shown that the equations for any of the regions (I, II, III, IV) of the curves of sliding and mechanical fatigue are similar, with the only difference in the numerical values of the parameters.
The Method of Strength Calculation in Volume Fracture and Surface Damage
Authors: Sosnovskiy Leonid A.
Published: November 2008

In this paper the development of the methods of strength calculation are described: an engineering procedure is developed to perform calculations using the criteria of surface strength, i.e. wear resistance.
Design, Analysis and Testing of an Inside-Out Tilting-Pad Journal Bearing With Real-Time Controllable Preload and Stiffness
Authors: Adams Maurice L. , Laurich Michael A.
Published: November 2008

It has recently been shown that high-speed grinding can be applied to the finishing of ceramics with considerable improvements in throughput and quality. This will require new high-speed high-power centerless grinding spindles (7,000 RPM, 50 HP), with high-stiffness of three hundred and fifty million Newtons/meter (2 million lb/in). To meet these requirements a novel inside-out, three-pad, pivoting-pad oil-fed hydrodynamic journal bearing has been devised, built and tested. One of the three pad’s pivot point is supported by a hydraulically-actuated radial-motion loading piston. This provides real-time controllable preload to all three bearing pads, thereby controlling bearing stiffness, providing less-stiff spindle bearings for initial rough grinding and very high stiffness spindle bearings for precision finish grinding. Extensive bearing test data compare favorably with theoretically predicted bearing performance.
Water Lubricated Hybrid Propeller Shaft Bearings With Polymer Bearing Bush
Authors: Litwin Wojciech
Published: November 2008

The article deals with water lubricated hybrid marine propeller shaft bearing which was designed and built at the Faculty of Ocean Engineering and Ship Technology of the Gdansk (Poland) University of Technology. The article contains the following parts: • Description of the test stand, the simulated working conditions, and tested bearings’ specifications. • Results of the conducted measurements. The results of the experimental work include: graphs of friction coefficient, pressures in the water hydrodynamic film and shaft trajectory. • Comparison of hybrid bearing with two others bearings. Typical main shaft bearing with grooved bearing bush working in a semi fluid friction conditions and hydrodynamic bearing with cull bearing bush (without any grooves). The work’s essential conclusion is that fluid film lubrication is possible also in hybrid bearings with grooves. As it was proven under simulated working conditions hydrodynamic lubrication does not take place in typical bearing with grooved bearing bush.
Direct Observations of Emulsion Flow in EHL Contacts
Authors: Yang Haixia , Schmid Steven R. , Reich Ronald A. , Kasum Thomas J.
Published: November 2008

Oil-in-water emulsions are widely used as lubricants in metal forming, machining and some machinery elements where non-flammable lubricants are required. Their lubricating mechanisms have been extensively investigated based on the measurements of film thickness and/or traction in the past few decades and a number of physical explanations for their performance have been forwarded. However, direct observation of the emulsion flow, as a direct method of evaluating suggested theoretical explanations, has been greatly restricted by the available instruments. In this paper, a newly devised digital video camera and microscope were used to directly observe the emulsion flow in EHL contacts at industrially relevant speeds for both line and point contacts. Previous low-speed results for line contact were confirmed and extended into high-speed cases. That is, some droplets were rejected from the inlet, others penetrated to the contact zone, and others remained fixed in position a certain distance from the edge of contact. For point contact, side flow behavior was also observed, and the number of droplets that remained stationary were limited to a single streamline. To clarify the oil droplet behavior and investigate the effect of particle size on entrainment, three tight emulsions with different mean droplet sizes were examined on an EHD rig at speeds from 12 mm/s up to 1.5 m/s.
Three-Dimensional Thermal Field in Slider Bearings
Authors: Zengeya Miles , Gadala Mohamed , Segal Guus
Published: November 2008

A three dimensional thermohydrodynamic lubrication model which couples the Reynolds and energy equations is developed. The model uses the streamline upwind Petrov-Galerkin (SUPG) method to solve the non-symmetric stiffness matrix that results from the convective-dominated flow. Model results indicate that the peak temperature is not on the mid-plane surface, a fact that cannot be predicted with two dimensional models. This position shifts towards the mid-plane as the width to length ratio is reduced from ten to one (square slider) as well as when pressure boundary conditions are altered in such a way that the inlet/outlet pressure is higher than the side pressure. The square slider has a peak temperature 4°K less than the wider slider. This is due to the higher side flow in the square slider.
New Solutions in Choice of Material and Design of Brake Shoes Required by Railroad Applications
Authors: Vukolov L. A. , Voronchikhin A. I.
Published: November 2008

The results of interaction of cast iron and composite brake shoes against wheel treads on dynamometer during carry out certificate tests of brake shoes are examined. It has been established that cast iron brake shoes are more aggressive against the wheel running surface. They have inclination to emerge of transverse cracks in tread. On the contrary the composite brake shoes and sintered materials too did not cause the formation of the thermal cracks in the wheel tread owing to more low temperatures rise in friction contact layers. Like this use of composite and sintered material brake shoes in field service on Railway Rolling Stock is more preferable.
Integrated Multi-Sensor Tribo-SPM Nano+Micro Tribo-Metrology
Authors: Gitis Norm , Daugela Antanas , Xiao Jun , Vinogradov Michael
Published: November 2008

A novel quantitative nano+micro tribometer with integrated AFM and optical microscope has been utilized to characterize tribological and mechanical properties of liquid and solid thin films and coatings, with in-situ monitoring their changes during micro and nano indentation, scratching, reciprocating, rotating and other tribology tests.
Solid Lubricant Coatings for Automotive Engine Pistons
Authors: Schuetz Michael , McIntyre Gary
Published: November 2008

The demand for more powerful internal combustion engines with lower weight, reduced fuel consumption, and favorable environmental properties has led to engine piston designs having lower weight, reduced thermal expansion, and good thermal conductivity. These improvements were needed without sacrificing high thermal strength, reduced operating friction, and increased wear resistance. The need for reduced frictional properties resulted in pistons with shorter skirt lengths, which led to a reduction in effective hydrodynamic surface area perpendicular to the pin bore. At the same time, complex cold start cycles and fuel injection systems were developed that brought enriched fuel mixtures into the engine, causing a dramatic reduction in the viscosity of the lubricant film and thereby its capabilities to protect the sliding surfaces from wear. These higher mechanical stresses on the piston combined with the reduced lubricating ability of the oil film led to increased friction and wear rates, which often resulted in decreased customer satisfaction due to high noise (i.e., piston “slap”) or complete engine failure. To counteract these tribological problems, a variety of piston coatings were developed, but the composition of these coatings often brought a new set of environmental concerns, e.g., the use of heavy metals. The current solution for this problem is to utilize Anti-friction Coatings (AFC’s) on specific areas of the piston. These coatings are based on solid lubricant technology combined with that of high performance resins. The coatings are resistant to fuels and engine oils over the normal operating temperature range of the engine. They also provide a long-term lubricant coating with exceptional capability to handle intermittent excursions outside an engine’s normal duty cycle.
Investigation of Liquid Nitrogen Lubrication Effect in Cryogenic Machining
Authors: Hong Shane Y.
Published: November 2008

In cryogenic machining, liquid nitrogen (LN2) is well recognized as an effective coolant due to its low temperature, however, its lubrication effect remains unknown. Our previous studies of the change in cutting forces, tool wear, chip microstructure, and friction coefficient indicate a possible lubrication effect by LN2. To verify proposed LN2 mechanisms and distinguish them, idealized disk-flat contact tests were performed. From the test results, the LN2 lubrication effect by altering material properties at low temperature was dependent on the material pairs. An uncoated carbide insert with a low carbon steel or titanium alloy disk test showed reduction of friction under LN2 cooling, but a coated insert increased the friction force. LN2 injection to form a physical barrier or hydrodynamic effect between two bodies is always effective to reduce friction force.
Tribo-Electric Behaviors of Copper Under Dry Sliding Against Cu-Cr Alloys
Authors: Zhang Yongzhen , Qiu Ming , Sun Lemin , Chen Yue , Shangguan Bao
Published: November 2008

The tribological and electrical conduction behaviors of copper under dry sliding against copper-chromium alloys were investigated on the basis of simulation tests. The experimental results show that electrical current and tribological parameters have combined effects on both electrical conduction ability and tribological properties. High sliding velocity and electrical current density deteriorate both the tribological and electrical conduction properties in tribo-electrical sliding system. In the end, the worn surface analysis suggests that friction, resistance heat and electrical arc spoiling are the main factors to influence the tribological and electrical conduction properties.
High-Pressure Viscometry and Dilatometry for Lubricant Oils in a Diamond Anvil Cell Up to 6 GPa
Authors: Nakamura Yuichi , Sanda Kazuyuki , Matsubo Hideki
Published: November 2008

To measure the properties of lubricant under high pressure, a diamond-anvil pressure cell was employed. With a falling sphere viscometry, viscosities were measured up to 2 GPa at up to 200 °C for traction oils. The results showed linearity between logarithmic viscosity and pressure at any temperatures. At 200 °C, lubricant viscosity-pressure coefficient fell to between 1/4 and 1/3rd of the value at 40°C. A simple expression for the dependence of high pressure viscosity on temperature has been suggested. Pressure temperature phase diagram of liquid-solid transition was plotted from the obtained viscosity. The change in volume due to solidification was estimated up to 6 GPa.
Influence of Test Conditions on Tribological Behavior
Authors: Woydt M. , Ebrecht J.
Published: November 2008

A series of cooperative interlaboratory tests (RR, round robins) was conducted annuallly from 1997 to 2005 by the DIN 51834 Working Group on Tribological Tests using a Translatory Oscillation Apparatus (SRV™®) in cooperation with ASTM D02. The statistical analysis of these test results shows the influence of cleaning solvent and seizure criteria on the tribological properties regarding O.K.-load of the lubricants tested. Coefficients of friction and wear results are ranked according to the effects of ten different cleaning solvents, where isopropanol gave the lowest values and isoparaffin solvents the highest. The wear volume is more descriptive than the wear scar diameter. The effect of machine model on coefficients of friction varied from about 0.2% to 0.9% of mean. Wear results were not affected. The load step interval of 1, 3 or 6 minutes influences the pass load of solid bonded films.
Corrected FFT-Based Method for the Calculation of Deformations in Line Contacts
Authors: Bakolas Vasilios , Borchers Wolfgang , Liebel Alexander F.
Published: November 2008

During the last years the Fast Fourier Transforms (FFT) technique was applied by many researchers for the calculation of the deformations in contact problems. The use of conventional convolution algorithms however led to the inclusion of a periodicity error that proved hard to correct. The correction procedures that had been suggested so far, involved the extension of the calculation grid and thus negated any time gains that the FFT would provide. In order to overcome the lack of accuracy of the current FFT methods, a new method for the calculation of deformations for line contacts was developed. In the framework of this method the so-called periodicity error has been identified as a discretization error in the Fourier space. The new method imposes a correction on the Fourier transformed kernel function in order to compensate the discretization error and achieve better accuracy. Tests have proven that the new method provides the desired accuracy while having a cost of arithmetic operations of O(N log(N)). Numerical examples are presented showing the improved accuracy of the proposed method.
Acoustic Emission Analysis for Monitoring of Tribological Systems
Authors: Burger W. , Albers A. , Scovino R. , Dickerhof M.
Published: November 2008

Today, for the monitoring of hydrodynamic bearings, a multitude of measurement systems is available, of which however none has yet prevailed in practice. A practicable and effective principle to detect first rubbing processes in nonstationary charged sliding contacts is still missing. E. g., a failing bearing in a ship’s engine may lead to the threat of machine, ship and environment as far as to human lives, and certainly to high repairing costs and downtime. Failure-free running machinery demands efficient and reliable monitoring systems which make possible to evaluate the current condition of the bearing arrangement in operation.
Elastic-Plastic Analysis of the Cylindrical Contact Between Layered Bodies
Authors: Bachelet L. , Sainsot P.
Published: November 2008

Metallic gaskets are frequently used in applications operating under extreme conditions (very high or low temperatures). The elastic-plastic contact conditions between a layered toroidal seal and its seat are presented in this paper using a bi-dimensional finite element method. This problem is similar to the contact between an elastic cylinder and an elastic substrate coated by a soft elastic-plastic layer. Three different types of behavior could be defined according to the thickness of the layer: (A) very thin, (B) very thick and (C) intermediate layer. First we propose a new equivalent elastic modulus, taking into account the properties of the layer and substrate. This new formula is a function of the ratio of the thickness of the layer to the contact width. Then, by using a dimensional approach, two criteria related to the layer thickness (very thin or very thick) are defined. Finally, for intermediate layers, the specific shape of the pressure field is explained.
Micro Testing of As Found Grease Taken From Double Shielded Bearings After 10 Years Service
Authors: Johnson Bryan , Hofmann Stephen
Published: November 2008

An important industry question concerning the performance of shielded/sealed bearings is how long do they really last? This type of bearing is marketed to the end user as a sealed for life bearing which to many implies very long time of service. The limiting performance characteristic however for many of these bearings is how long the grease will last. Grease can have a relatively short service life compared to the bearing steel and is critical to bearing operation. Well performing bearings will fail rapidly when the lubrication fails.
Amorphous Carbon Thin Films for Interfaces in MEMS
Authors: Malyska K. , Erdemir Ali , Chizhik Sergey A. , Rymuza Zygmunt , Ratajczyk Lukasz
Published: November 2008

Friction and nanoscratch tests were performed on amorphous carbon thin films deposited on silicon. The effect of process and conditions on CVD deposited films was studied. Coefficient of friction between the films was estimated by using a special oscillating microtribometer. The lateral force and maximum depth of scratching were measured during nanoscratch tests. The comparison of tribological behavior of the tested films is presented and discussed.
The Validity of the Reynolds Equation in Modeling Hydrostatic Effects in Gas Lubricated Textured Parallel Surfaces
Authors: Feldman Yuri , Kligerman Yuri , Etsion Izhak , Haber Shimon
Published: November 2008

The pressure distribution and load carrying capacity for a single 3D dimple, representing laser surface texturing (LST) of gas-lubricated tribological components with parallel surfaces, were obtained via two different methods of analysis: 1) a numerical solution of the exact full Navier-Stokes equations; 2) an approximate solution of the much simpler Reynolds equation. Comparison between the two solutions illustrated that the differences in load carrying capacity were negligible for clearances that are 3% or less of the dimple diameter. At larger realistic clearances the error in the load carrying capacity may reach a maximum of 10%.
An Investigation on Machining Behaviour of Metal Matrix Composites by Using PCD Inserts
Authors: Muthu Krishnan N. , Vikram D. , Kaushik S. , Rao K. Prahalada
Published: November 2008

The present work has been undertaken to study the tool wear behavior of poly crystalline diamond (PCD) inserts during the machining of Al-SiC – MMC; Al-Si alloy containing 15%wt of SiC was used for machining and PCD inserts of three different grades were used as cutting tools. The main aim of this paper is to explore the feasibility of machining conditions by setting the spindle speed, depth of cut and thereby determining the cutting force, surface roughness, power consumed, material removal rate and tool wear. The worn surface of the insert was examined by Scanning electron microscope (SEM). The influence of cut was examined for the PCD inserts.
Surface Topography and Friction Dynamics in Brake Systems Described by a Cellular Automaton
Authors: Mueller M. , Ostermeyer G. P.
Published: November 2008

For the description of a friction event it is necessary to understand the friction coefficient μ as a process-parameter dependent not only on the surface-structure but also for instance on the relative velocity, normal load, temperature and the event itself. In brake systems, for example, growing and destroying processes of hard thin patches determine the friction power and the transfer of kinetic energy into heat and plastic deformations, such as wear. So the interaction of friction and wear is given by an equilibrium of flow of different processes resulting in growing effects or lowering effects on the friction coefficient itself [2]–[4]. The aim of this paper is to show the detailed interaction of this topographical dynamics and the friction behavior with the Method of Cellular Automata.
Simulation of EHD Lubrication of Common-Pin Conrod Big End Bearings in High Speed IC Engines
Authors: Ma Ming-Tang , Loibnegger Bernhard
Published: November 2008

This paper describes a methodology for the analysis of elastohydrodynamics (EHD) of connecting-rod (conrod) big end bearings in high-speed internal combustion (IC) engines. In addition to the elasticity of the conrod structure and crankpin, the dynamic and inertial effect of conrod motion on the bearing tribological behaviour is considered realistically based on a multi-body system (MBS) approach. Results show that it is necessary to simulate two big end bearings of common-pin simultaneously with the inclusion of a complete crankthrow in the MBS model.
Wear Behaviour of Binary Oil Mixtures Under Extreme-Pressure Conditions
Authors: Fernandez Rico J. E. , Hernandez Battez A. , Chou Rodriguez R.
Published: November 2008

This work presents and discusses the extreme-pressure properties of binary oil mixtures made with a low viscosity polyalphaolefin (PAO 6) and two esters (TMP-05 and sunflower oil, SO). Tests were made in a four-ball machine tester using the ASTM D 2783-88. The ball test material was AISI 52100 steel, 12.7 mm. in diameter, with a hardness of about 65 HRC. The wear scar diameter (WSD) was measured with an optical microscope. The results showed that: although PAO 6, TMP-05 and SO have different physical properties, they perform similar behavior under high loads; TMP-05 and SO have better results in wear tests than PAO 6, but their extreme-pressure properties are similar; and TMP-05 and SO act as wear reducers when they are added to PAO 6, but they do not improve its behavior under high loads.
Issues in Vapor Phase Lubrication of Magnetic Data Storage Media
Authors: Gellman Andrew J. , Yun Yang
Published: November 2008

Vapor phase lubrication (VPL) integrates media lubrication with the vacuum processing steps used throughout most of the hard disk media fabrication process. This avoids exposure of the unlubricated a-CHx overcoat surface to the ambient air and airborne contamination. In vapor lubrication the a-CHx surface can be oxidized under controlled conditions immediately prior to lubricant adsorption. The kinetics of a-CHx oxidation have been studied using x-ray photoemission spectroscopy in an apparatus that allows oxidation of freshly deposited a-CHx films. The dissociative sticking coefficient of oxygen is ∼10−6 and the initial oxidation kinetics can be described by a Langmuir-Hinshelwood mechanism.
Preparation and Tribological Behavior of PAH/PAA Molecular Deposition Films
Authors: Wang Deguo , Yu Xuexin , Zhang Siwei , Feng Dapeng
Published: November 2008

PAH/PAA polymer multilayer ultrathin film was prepared by molecular deposition technology. The morphology and nano-tribological behaviors of the film were investigated by using atomic force microscope (AFM). It has been found that the friction force of the PAH/PAA polymer molecular deposition film is obviously less then that of the glass substrate, and the friction force increased with increasing load. However, the friction force decreased in the beginning and increased in the sequel with increase in the number of layers, which might be attributed to the change of surface topography with different layers. Moreover, it was found that the profile of both topography and lateral force has good coherence by analyzing the AFM images.
Investigation of the Hydrodynamic Behavior of New Construction Hydrodynamic Tilting-Pad Journal Bearing
Authors: Vekteris Vladas , Mokshin Vadim
Published: November 2008

The paper describes features of new construction pad-type (segmental) hydrodynamic bearing with mobile ring and results of investigations of this bearing. The researchers obtained complex method of interaction between the mobile ring and pads. Except the diagram of distribution of lubricant pressure on the surface of pad there are presented photos of the flowing lubricant in the bearing and graphs of trajectories of the rotor journal’s axis for various number of revolutions of the rotor. Presented results of investigations show high stability of new construction hydrodynamic bearings in case of big number of revolutions of the rotor. Researchers hope that new construction bearings can be successfully used in tribological systems at the mentioned condition.
Experimental Study of Real Roughness Features Within EHD Point Contacts
Authors: Krˇupka I. , Hartl M. , Lisˇka M.
Published: November 2008

A combination of thin film colorimetric interferometry and phase shifting interferometry has been used to study the effect of slide-to-roll ratio on the micro-elastohydrodynamic action and asperity-contact mechanism on the real asperity scale. The phase shifting interferometry was used to measure in-situ initial undeformed rough surface profiles and thin film colorimetric interferometry provided accurate information about micro-EHD film thickness behaviour over a wide range of operating conditions. Lubricant film thickness distribution within mixed EHD contact has been found to change significantly as a function of a slide-roll ratio. A high resolution color camera has enabled a closer look at film thickness changes in the vicinity of surface irregularities that helped to describe these processes in detail. Obtained results indicate the presence of either a boundary film less than 1 nm thick or some solid-like contact in front of roughness features for positive slide to roll ratios. No such a local film thickness reduction has been found for negative slide-to-roll ratio conditions.