bluuebunny/crossref_metadata_2025 huggingface dataset:
Tensile, Flexural, and Shear Properties of Neutron Irradiated SiC/SiC Composites with Different Fiber-Matrix Interfaces
Authors: Nozawa T , Ozawa K , Kondo S , Hinoki T , Katoh Y , Snead LL , Kohyama A
Published: April 2008

Unidirectional SiC/SiC composites fabricated with highly-crystalline and stoichiometric fibers and matrix, but with three different interfacial types (single-layer pyrolytic carbon (PyC), multi-layered SiC/PyC, and pseudo porous SiC interfaces) were irradiated up to 1.0 × 1025 n/m2 (E > 0.1 MeV) at 1073 and 1273 K. Tensile, inter-laminar shear, and flexural properties were evaluated to compare the role of different interfaces on neutron irradiation behavior. There was nearly no significant degradation in tensile and flexural strength after high-temperature neutron irradiation, except for porous SiC interphase composite. Moreover, no meaningful reduction of tensile modulus was identified regardless of interphase types, although 20–40 % degradation in flexural moduli occurred due to a reduction in inter-laminar shear modulus. In contrast, matrix cracking stress was significantly dependent on interfacial properties. Multilayer interphase composites exhibited the best irradiation stability Irradiation instability of thick PyC and porous SiC interphase resulted in 20 % and 40 % degradations of matrix cracking stress, respectively.
The History of Instrumented Impact Testing
Authors: Manahan MP , Siewert TA
Published: April 2008

Pendulum impact testing is widely known to have a history that extends back to the turn of the20th century. To many researchers today, instrumentation of the impact test to acquire a load-time history,and thereby to provide important data in addition to absorbed energy, is usually considered to be a relatively recent development. However, our literature review has shown that starting from the earliest test machine development work, researchers have been interested in designing equipment capable of measuring both the energy expended in fracturing the specimen, and the force-deflection and energy-deflection curves. This paper recounts the early history of instrumented impact testing, and shows that it also extends back over 100 years. In fact, the earliest known paper on instrumented impact testing predates the firstpendulum test machine publication by one year.
The Development of Procedures for Charpy Impact Testing
Authors: Siewert TA , McCowan CN
Published: April 2008

This paper provides a broad overview of the progress in procedural improvements for Charpy impact testing. It includes a short summary of early developments, a discussion of topics that have been the subject of recent research, and a description of the importance of direct and indirect verification procedures. The need for standard procedures was recognized soon after the test was developed, and the early discoveries help to build the framework for our current procedures. Nevertheless, even after all these years of procedure development, researchers still find the need to learn more about certain aspects of the test procedures. Recent research seems to be concentrated in several broad categories: properties of the specimen (e.g., surface finish, tolerances, and miniature sizes for special applications), the anvils and striker (e.g., radii and surface finish), and general test procedures (e.g., time to reach test temperature and suitability for cryogenic testing).
Effects of Removing and Replacing an 8-MM Charpy Striker on Absorbed Energy
Authors: Vigliotti DP , Vigliotti JL
Published: April 2008

It has been thought that removing and replacing an in-tolerance 8-mm striker may affect the results of a Charpy test. This thought brought about a requirement in Standard Test Method E23 [1] that states that if a striker is removed and replaced on a Charpy machine, the indirect verification is void and a new verification test must be performed. Groups of NIST SRM 2092 and SRM 2096 specimens were tested on machines with three different striker-mounting designs. The specimens were tested with the striker removed and replaced between groups. The results of these tests support a change in the standard that can make removing and replacing the striker acceptable without performing a new indirect verification test.
International Comparison of Impact Reference Materials (2004)
Authors: McCowan C. , Roebben G. , Yamaguchi Y. , Lefrançois S. , Splett J. , Takagi S. , Lamberty A.
Published: April 2008

A three-year horizontal comparison has been completed between national laboratories that certify specimens for the indirect verification of Charpy impact test machines. The participants in this study were the Institute for Reference Materials and Measurements of the European Commission, the National Metrology Institute of Japan (NMIJ), the National Institute of Standards and Technology in the United States, and the Laboratoire National d'Essais in France. The comparison was conducted to evaluate the impact of reference specimens over a three-year period. Sets of certified reference specimens, at low (15 J), medium (30 J), and high energy (100 J) levels were produced and distributed at the start of the study. Specimens were tested approximately every six months on each of the machines in the study. The results of the testing are presented and the stability of the various impact machines and specimens are discussed.
Certification of Charpy V-Notch Reference Test Pieces at IRMM
Authors: Roebben G , Lamberty A , Pauwels J
Published: April 2008

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC) of the European Commission (EC) is one of the reference materials producers which certifies reference test pieces for the indirect verification of Charpy pendulum impact machines. The certification approach taken at IRMM consists of two main steps. In a first step, a Master Batch of reference test pieces is certified for each of a number of chosen nominal energy levels (currently 30 J, 60 J, 80 J, 120 J, and 160 J). The certified absorbed energy value of these Master Batches is determined in an international round-robin. In the second step of the certification process, the Master Batch test pieces are used to determine the certified value of Secondary Batches of reference test pieces of the same nominal energy. This is achieved by comparing samples of Master and Secondary Batch under repeatability conditions. In this paper, this Master Batch — Secondary Batch approach is critically assessed in terms of traceability and uncertainty of the certified absorbed energy. It is shown that the produced reference test pieces are fit-for-purpose: they meet the requirements of their intended use (indirect verification).
Utilization of an Asphalt Pavement Analyzer for Hot Mix Asphalt Laboratory Mix Design
Authors: Williams RC , Hill DW , Rottermond MP
Published: April 2008

The Superpave volumetric mix design system, developed by SHRP in the 1990s, has continued to gain widespread acceptance across the United States. Although it is widely believed to be an improvement over past mix design systems, it does have an inherent flaw. It does not include a performance test to assess HMA's resistance to rutting, fatigue, or low temperature cracking. With the development and implementation of newer performance test specifications, it is an appropriate time to work on integrating a performance based test for construction specifications. Rather than being based on material properties or construction practices, the payment for an HMA pavement could then be based primarily on the performance based specification. The results of this study indicate that although the APA works well as the pass/fail criterion used by state agencies, the variability of APA cycles to failure make it impractical to base a rut prediction model on data obtained from it.
Laboratory Investigation of HMA Performance Using Hamburg Wheel Tracking and DSR Torsional Creep Tests
Authors: Reinke G , Glidden S , Herlitzka D , Jorgenson J
Published: April 2008

Lack of existing fundamental mechanistic tests to evaluate performance potential of HMA mixtures has given rise to a number of empirical and mechanical-empirical test procedures. In an effort to understand how one of these tests, the Hamburg rutting test, was impacted by differences in HMA mixture variables, the following experimental work was conducted. Three aggregate types consisting of a crushed granite, a crushed siliceous gravel, and a crushed limestone were evaluated at four design ESAL levels. These four ESAL levels were 300 000, 1 million, 3 million, and 10 million. For each of these aggregate types and ESAL levels, 5 PG graded binders were investigated. The binders were PG 58-28, PG 64-28C (chemically modified), PG 64-28P, PG 64-34, and PG 70-28; the latter 3 binders were polymer modified. For all mixtures, Hamburg Wheel Tracking tests were performed under water at 50°C. In addition, a DSR Creep Test developed at MTE was performed on each mixture at 58°C and 34 kPa stress to determine the dry strength characteristics. The Hamburg test showed consistently better results as the ESAL level of the mix increased and as the high temperature PG grade of the binder increased for a given base asphalt. In the Hamburg test, mixes produced with PG 64-34 did not perform as well as PG 70-28 or PG 64-28P, while in the DSR Creep Test, mixes produced with PG 64-34 performed significantly better than PG 64-28P. This leads to speculation that the modulus of the base asphalt plays a more significant role in stress applied moisture resistance tests and that dry high temperature permanent deformation tests are influenced by the modified binder properties.
Use of HMA Stiffness Results as a Referee Test in Indiana
Authors: McDaniel RS , Gallivan VL , Huber GA , Andrewski DH , Miller M
Published: April 2008

The Indiana Department of Transportation (INDOT) began implementing volumetric acceptance of hot mix asphalt (HMA) mixtures in 2001. In some cases the air void contents of the plant-produced mixtures have been less than 2.0 %. Rather than require removal and replacement of low air void mixes in all cases, INDOT implemented an optional referee testing procedure. This procedure allows contractors to leave low air void material in place, at reduced pay, if the stiffness of the placed material is equal to or greater than a specified minimum. If the stiffness is less, that sublot must be removed and replaced. The rationale is that if the stiffness is high enough, even if the air voids are low, the material would be expected to perform adequately. If the low air voids are accompanied by low stiffness, rutting performance would likely be compromised. This paper describes the rationale, development, and implementation of this program.
Mechanistic Quality Management of Hot Mix Asphalt Layers with Seismic Methods
Authors: Nazarian S , Tandon V , Yuan D
Published: April 2008

Realistic field-test protocols and equipment, which in a rational manner, combine the results from laboratory and field tests with those used for quality control during construction, have been developed. Seismic nondestructive testing technology has been used for this purpose. Simple laboratory tests that are compatible with the field tests have been recommended. All these tests have several features in common. They can be performed rapidly (less than 3 min.), and their data reduction processes are simple and almost instantaneous.
Fracture Resistance Characterization of Superpave Mixtures Using the Semi-Circular Bending Test
Authors: Wu Z , Mohammad LN , Wang LB , Mull MA
Published: April 2008

The fracture resistance of asphalt mixture is an important property directly related to pavement distresses, such as cracking. This paper reports the investigation of a newly-developed semicircular bending (SCB) test as a candidate test for the fracture resistance characterization of asphalt mixtures. Thirteen Superpave mixtures, designed with four different binder types (AC-30, PAC-40, PG70-22M, and PG76-22M) and four different compaction levels (Ndesign = 75, 97, 109, and 125), were considered in this study. The SCB tests were conducted at 25°C using a three-point bending fixture in a MTS testing system. The fracture resistance was analyzed based on an elasto-plastic fracture mechanics concept of critical strain energy release rate, also called the critical value of J-integral (Jc). Preliminary results indicate that the JC values were fairly sensitive to changes in binder type and nominal maximum aggregate size (NMAS) used in Superpave mixtures. This study suggests that the SCB test could be a valuable correlative tool in the evaluation of fracture resistance of asphalt mixtures.
Characterization of Asphalt Concrete by Multi-Stage True Triaxial Testing
Authors: Wang L , Hoyos LR , Mohammad L , Abadie C
Published: April 2008

The feasibility of an existing servo-controlled true triaxial (cubical) apparatus for evaluating the mechanical response of nominal 4-in. cubical specimens of asphalt concrete (AC) under multi-axial stress states has been investigated. The apparatus allows the testing of specimens along a wide range of stress paths and stress levels that are not achievable in a conventional uniaxial or cylindrical apparatus. A multi-stage testing scheme can be followed by simultaneous control of the major, intermediate, and minor principal stresses directly applied to the specimens. Two cubical AC specimens cut from two WesTrack block samples were subjected to a series of multi-stage stress paths that included triaxial compression (TC), triaxial extension (TE), simple shear (SS), conventional triaxial compression (CTC), conventional triaxial extension (CTE), and cyclic conventional triaxial extension (CCTE). Experimental data were analyzed to assess volumetric creeping properties, resilient response, plastic deformation response, Poisson's ratio, loss angle, and dilatancy of asphalt concrete under general stress states. Test results highlight the potential of the cubical cell for mechanical characterization of asphalt concrete in a broad range of applications involving true triaxial stress states. Analysis of test results indicates all of the following: (a) Modulus of AC shows significant anisotropy in different orientations; (b) Volumetric creeping of AC is considerably significant at relatively high pressures; (c) AC shows significant dilatancy; and (d) Cubical Device can distinguish mixes of different performance.
Water Resistance and Durability of Weather-Resistive Barriers
Authors: Weston TA , Pascual X , Boone K
Published: April 2008

Weather resistive barriers function as the second line of defense against water that has intruded past a building's cladding. Despite its importance, however, the evaluation of weather-resistive barrier water resistance performance is not conducted in a consistent manner across product types. Several different test methods that include vastly different water exposure techniques are used. Because of the variance in test methods and rating systems, the selection of optimal weather resistive barrier for a specific project can be difficult. Complicating matters further, the water resistance of weather resistive barriers is almost always reported on as-received materials, with little if any information provided on how the water resistance will change during the construction period or in service. This paper presents data comparing the water resistance of weather resistive barriers measured by both standard methods and by a small-scale water spray test. Additionally, the change in water resistance performance due to direct environmental exposure is discussed.
Durability Testing of Polyurethane Foam Sealant in the Window-Wall Interface
Authors: Braun RG , Garcia J
Published: April 2008

In late 1990, the National Research Council of Canada (NRC-CNRC) and the Canadian Construction Materials Centre of Canada (CCMC) set about developing a durability protocol for aerosol foam sealants. Major input for this effort was supplied by Dr. Mark Bomberg then on the NRC-CNRC staff. At that time a major manufacturer of aerosol foam sealant wished to address some developing concerns whether foam sealant used around the perimeter of windows and doors during their installation was really durable. The manufacturer completed the durability testing according to the established NRC protocol. Now the protocol is also part of a new Standard CAN/ULC-S710.1 and CAN/ULC-S711.1. This paper will describe that testing as it was completed at the third party laboratory, Air-Ins Inc., of Montreal, Canada using criteria from the 1995 National Building Code of Canada [1]. The data obtained also formed the basis for CCMC Evaluation report 13074-R [2].
Performance Testing of Flashing Installation Methods for Brick Mold and Nonflanged Windows
Authors: Crowder-Moore BJ , Weston TA , Katsaros JD
Published: April 2008

One of the major sources of water intrusion in buildings is through openings in walls caused by windows and other fenestrations, in particular the interface between the window and wall. Numerous flashing products, including self-adhered products, have recently been developed to protect this window-wall interface from moisture intrusion. However, the proper installation of these flashing products is not well understood and installation methods are often misused. Various installation methods have been developed and tested to evaluate performance and ease of installation. While most of the flashing installation development has been focused on residential flanged-style windows, effective installation methods for wood framed “brick mold” windows as well as other “nonflanged” windows have not previously been developed and tested. A series of laboratory wall tests were used to compare the air leakage resistance (ASTM E 283), water leakage resistance (ASTM E 331), and durability (ASTM E 330) of various flashing materials and installation methods. The performance and durability of flashing as installed with round top windows, brick mold windows, and nonflanged windows were tested and evaluated.
A Review of Climate Loads Relevant to Assessing the Watertightness Performance of Walls, Windows, and Wall-Window Interfaces
Authors: Cornick SM , Lacasse MA
Published: April 2008

When assessing a wall assembly's ability to manage rainwater and control rain penetration, the two key climatic elements to consider are wind speed and rainfall intensity. However, of significance to rain penetration is the effect of wind-driven rain on the building cladding — that is wind coincident with rainfall. When water is present at openings in the cladding, water is driven into the layers of the assembly by the action of wind. Paths providing a direct line from openings in the cladding to inside the assembly offer particularly vulnerable points for water entry. Performance testing helps determine the location of vulnerable locations in a wall assembly and the test loads at which penetration occurs, and it possibly relates the amount of entry to specific details and simulated climate effects. Undertaking watertightness performance tests requires knowledge of extremes in wind-driven rain or specifically the occurrence and level of extreme rainfall events for locations of interest. A review of climate information on wind-driven rain is provided, and its relevance to assessing the watertightness performance of walls, windows, and wall-window interfaces is discussed. Values of rainfall intensity, duration, and frequency or occurrence are given, emphasizing the level of significance of these variables to different North American climates.
Tribological Design: A Real World Approach
Authors: Ludema KC
Published: April 2008

The general lack of basic principles for designing reliable components for hydraulic pumps and motors requires a strategy of applying experience and full scale testing. Hydraulic pump and motor components are very sparsely lubricated though they are immersed in fluid. They therefore slide in “boundary lubrication,” a regime for which there are no methods for predicting, or even estimating product life or frictional performance. The testing of sub-components in bench tests or in accelerated tests produces new uncertainties since the role of the many variables that control wear and scuffing are not well known. The best design procedure involves full scale testing of components with all of the recirculating contaminants, vibrations, and misalignments included. These practical conditions are impossible to simulate adequately. Finally, the tests must be done by people (or groups) who have full knowledge of hydrodynamic lubrication, contact mechanics, wear mechanisms, and product applications.
Mechanisms of Abrasive Wear in Lubricated Contacts
Authors: Williams JA , Hyncica AM
Published: April 2008

Despite the fact that many machine components are designed to operate with a comparatively thick film of lubricant between the loaded surfaces these often still deteriorate with time as hard particulate contaminants are swept through the bearing gap. Such particles may arise from the external environment or represent wear debris from other pairs of surfaces lubricated by, or in contact with, the same fluid. In order to investigate this phenomenon experimentally it is necessary to develop a predictable hydrodynamic film between the test surfaces which can be contaminated by small volumes of carefully graded abrasive particles. A foil bearing has been used to generate such films between 10 and 50 microns thick and to which contaminants such as powdered quartz or finely divided diamond can be added. As the ratio of the characteristic particle size to film thickness is varied not only do the wear rates of the solid surfaces change but examination of the wear tracks suggests that very different mechanisms of material loss come into operation. When the size ratio is low the worn surface consists of a large number of small pits and indentations; these display virtually no alignment in the direction of relative sliding and it appears that the particles tumble and roll freely through the gap. Above some critical value of the particler:film size ratio the appearance of the surface changes dramatically to a grooved or micro-machined surface with all the grooves aligned in the sliding direction. A relatively simple theoretical model is developed, based on what happens to a typical particle, which goes some way to explaining these observations. As well as being consistent with the observed transition from “tumbling” to “grooving”, the model can also explain why increasing the hardness differential between the hard and the soft surfaces does not always lead to a reduction in damage to the harder member of the pair.
Development of a New Application-Related Test Procedure for Mechanical Testing of Hydraulic Fluids
Authors: Feldmann DG , Kessler M
Published: April 2008

Traditionally, various testing methods are used to determine the lubrication properties of hydraulic fluids. The standard for mechanical testing of hydraulic fluids is based on the Vickers V-104 vane pump (DIN 51 389, DIN 51 524). Numerous other procedures for mechanical testing of lubricants are used with the FZG-Test (DIN 51 354) being the most important one, in which the tested fluid is exposed to a particular load by shearing it in a gear set. Moreover, industry uses several non-standard “in-house” testing methods.

This situation cannot be satisfying in many respects since only part of the interaction between fluid and component is tested with the existing test procedures and the validity of test results is limited, especially in the case of the vane pump test. When run under the same conditions, some tests are lead widely varying with the problem of reproducibility. Due to the number of necessary test procedures, cost and time expended is too high. Finally, there is no proof that commonly used procedures will be suitable for more modern fluids such as biodegradable fluids.

This paper describes the development of a new application-related test procedure for Mechanical Testing of Hydraulic Fluids, performed by the authors to overcome the problems discussed above.
Hydraulic Gear Pump Failure Analysis and Tribology Simulation
Authors: Wedeven LD , Bourdoulous R
Published: April 2008

Surface analysis of hydraulic gear pumps used in gas turbine failure power generation reveals service life limitations due to gear wear and scuffing. A flexible tribology testing capability (WAM) provides an ability to simulate lubrication and failure mechanisms. A load capacity test protocol developed for gas turbine MIL-PRF-23699 oils is found to invoke the same lubrication and failure mechanisms experienced in hydraulic gear pumps. Scuffing, micro-scuffing and traction (friction) data from load capacity tests show variable lubricating qualities among turbine engine oils used in service. A test protocol that monitors the traction coefficient over a range of load stages reflects both wear and scuffing attributes of oils used in service. The test method shows performance differences among oil types within the same specification and a reduction in wear performance with used oils. The test approach provides an opportunity for more efficient development of gear materials, lubricants and engineered surfaces.
Corrosive Wear in Hydraulic Systems: An Overview
Authors: Liang H , Totten GE
Published: April 2008

Hydraulic equipment continues to greatly improve, resulting in more powerful, faster, and versatile machines through advancements in hydraulic drives and controls. One basic step in improving hydraulic systems is to understand their failure mechanisms. In this work, basic corrosion mechanisms are summered and presented along with description of corresponding hydraulic system failure modes as well as a collection of common corrosive failure modes. Mechanisms and potential remedies are illustrated and discussed. Additionally, a wide collection of examples from contributors is provided.
Problems and Possibilities with Bottle Sampling for Assessment of Particle Concentration
Authors: Svedberg GC , Sundvall K
Published: April 2008

Reliable assessment of particle concentration is important for the condition monitoring of fluid power systems. Good filter efficiency and low contamination levels usually imply well working systems. But what should be regarded as low or acceptable levels? Historically bottle sampling has been the reference method for assessment of particle concentration. Recently more and more commercial equipment for on-line connection is available. Many times there is a difference between the two methods, so the question rises: Can we rely on these new on-line methods or is it the bottle sampling that is not good enough for modern, well filtrated fluid power systems?

Sending bottles to different laboratories very often gives different results. This is of course not satisfying. In Scandinavia there are several laboratories that perform particle counting of bottle samples from hydraulic and lubricating systems. Eight of these laboratories formed a group with the aim to produce results with better reproducibility. Good results were achieved on a round robin with MIL-H-5606 hydraulic fluid and standard Air Cleaner Fine Test Dust (ACFTD). Unfortunately similar round robin results from some systems in service with other fluids were completely different. The concentration was far higher compared with on-line measurements and the spread was very large.

The conclusion is that bottle sampling can be very accurate and reliable if the contaminants are standard test dust at high concentrations, with suitable fluids. Good applications can then be filter testing or automatic particle counter calibration. In ordinary fluid power systems, with good filtration, it seems to be very difficult to achieve relevant results.
Wear and Wear Debris in a Changing World
Authors: Roylance BJ
Published: April 2008

Hydraulic machinery and devices—key components in modern plant operations—are subject to wear and failure of one kind or another. The principal wear processes are described in conjunction with the creation of associated debris. The opportunities available for exploiting debris analysis techniques in pursuit of wear research is discussed against the background of some recent experimental test results. Their utilization as part of current and future condition-based maintenance programs is considered in the light of the ongoing changes occurring in relation to maintenance practice.
Advancements in Fluid Analysis Technologies and Strategies for Hydraulic System Condition-Based Maintenance
Authors: Fitch JC
Published: April 2008

World-class condition monitoring of hydraulic systems involves the successful integration of a number of strategic elements. While in the past, walk-around inspections and gage data were the primary means of monitoring system health, today's modern oil analysis programs apply a host of sophisticated new tools and instruments. Reliability teams at the plant site frequently commission small laboratories. In many cases the instrumentation suite includes portable and unattended sensors. The situational context is changing too as today's hydraulic systems are increasingly designed for higher pressures, speeds, and temperatures. This paper presents a review of strategic elements that, when well conceived and implemented, can deliver vital aiding information for achieving even the toughest condition-based maintenance goals. These include the selection of test slate, deployment of incipient failure advisories, setting of targets and limits that define non-conforming conditions, exception testing, and proactive maintenance.
Analysis of Common Failure Modes of Axial Piston Pumps
Authors: Fey CG , Totten GE , Sun YH
Published: April 2008

Hydraulic piston pump failures may be related to either hardware or fluid problems. In some cases, apparent hardware failures have been traced to various fluid problems. In this paper, selected examples of pump failures will be provided to illustrate some common modes of axial piston pump failures. In most cases, these will represent actual failures including: misalignment, insufficient fluid lubrication, particle contamination, brinelling, corrosion, and cavitation. Various examples of these and other pump failure modes are provided.
TRIZ-Based Root Cause Failure Analysis for Hydraulic Systems
Authors: Mann DL , Hughes EJ
Published: April 2008

Analysis of root cause failure mechanisms in hydraulic systems suggests that poor overall system specification, leakage and contamination issues are the dominant failure contributors. The paper examines how the Russian Theory of Inventive Problem Solving, TRIZ, is beginning to be applied in the specification and design of hydraulic systems and components. Several of the key TRIZ tools, methods and strategies Contradiction Elimination, Ideal Final Result, Trends of Evolution, and Function Analysis have been deployed on a number of case study examples. These examples include leak-free coupling and self-cleaning filter component design studies, and an examination of whole system energy management issues.
The Surface Behavior of Metallic Materials During the Incubation Period of Cavitation Erosion
Authors: Yabuki A , Noishiki K , Komori K , Matsumura M
Published: April 2008

Cavitation damage in hydraulic machines is still unavoidable as the downsizing and the increase in their power continue. One of the characteristic features of cavitation erosion is that the removal of metallic material occurs after an incubation period, during which no mass loss, but plastic and elastic deformation of the surface, occurs. The current methods for predicting the amount of erosion damage inflicted upon metallic materials in a cavitating environment are based on the mass loss of material. As a consequence, the erosion-resistance of a material can not be determined until a certain amount of mass loss has occurred. In this study, in order to quickly evaluate the erosion-resistance of metallic materials, the plastic deformation behavior of metallic materials during the incubation period was analyzed. The increment of the surface area was determined from the material surface profile data, measured through a surface roughness meter, to establish a good index for evaluating cavitation erosion development on the surface, as well as the intensity of the cavitation attack. According to the index, the incubation period of cavitation erosion is to be divided into two periods. In the first period, the rate of surface area increment is related to the hardness of the metallic material, and in the second period to the strain hardening exponent. These results can then be applied to the rapid determination of the level of erosion-resistance, in turn leading to a rapid prediction of the service life of the material.
Failure Mechanism of a Hydraulic Log Piston and Slipper Assembly
Authors: Sikes JT
Published: April 2008

A failure investigation was conducted on hydraulic log piston and slipper socket interfaces from aircraft Integrated Drive Generators (IDGs) to determine the reason for the occurrence of several in-service failures. Typically, one piston out of nine broke through the slipper socket. Once this occurred, secondary damage led to the removal of the unit from the aircraft. The effort to determine root cause proved difficult because despite the widespread usage of the components in numerous aircraft applications, only a few operators were experiencing failures. The scope of the effort was expanded from analysis of failed units to those exhibiting poor wear performance in order to define in detail the wear mechanism leading to failure. Expansion of the effort revealed that a complex wear process consisting of several stages and classic wear mechanisms was occurring, due primarily to the rapid deterioration of the lubrication film.
Development of Pseudoelastic TiNi Tribo Materials
Authors: Li DY
Published: April 2008

It has recently been demonstrated that TiNi shape memory alloy exhibits high resistance to wear and could be a superior tribo material. Excellent wear performance of this alloy benefits by its pseudoelasticity, resulting from a reversible martensitic transformation. Extensive research was conducted to investigate wear behavior of TiNi alloy during various wear processes, including sliding wear, erosion and corrosive wear. Friction of this alloy was also investigated with the emphasis on pseudoelastic effects on friction. The research manifests that this novel wear-resistant alloy is multi-functional and can be an excellent candidate for various tribological applications. Attempts have also been made to develop tribo composites using TiNi alloy as the matrix, reinforced by TiC, TiN and nano-TiN particles, respectively. The TiNi-matrix composites possess considerably improved wear resistance. This paper presents a brief review of our studies on the development of novel TiNi-based tribo materials.
PVD-Coatings — Applications in Fluid Power Technology
Authors: van Bebber D , Murrenhoff H
Published: April 2008

Hydraulic systems are used in many technical applications, for example, in agricultural and forestry machines as well as in aeroplanes and ships. Hydrostatic pumps and engines are essential components of hydraulic mechanisms. They transform mechanical energy into hydraulic energy and vice versa. Hydrostatic machines and their standard fluids based on mineral oils have developed to a high technical standard. In order to withstand the operating loads, engineers have made considerable effort to find the best combination of additives. The fluids in this case are not biologically harmless and often toxic. Fluids that are environmentally friendly cannot include additives that are toxic. Therefore, many environmentally friendly fluids have worse tribological qualities than standard fluids. If these liquids were used, important tribological qualities of the fluid must be found in the materials instead. This can be achieved by redesigned coatings. Considerations of displacement units show the most stressed tribological systems. These systems are: cylinder/valve plate, guide shoe/swash plate, plunger/cylinder bore and ball joint/guide shoe. In order to gain basic information about the quality of the coatings, experiments have to be performed using a tribometer. An experimental setup according to Siebel/Kehl is used for this. As a result of the experiments, coatings such as TiAlN/Al2O3 or CrAlN, which can be used for milling and drilling applications, have worse results than conventional materials such as bronze/steel. Improvements are achieved by adding carbon; however, the results are highly dependent upon the application method. Coatings that are graduated like HfCg show a low friction coefficient and wear rate. In addition to the tribological qualities of the coatings, the durability as well as the scratch resistance are important for the application. These considerations are especially important in the case of thin PVD coating which are used in applications with insufficient hydrodynamic lubrication.
Improving Tribological Performance of Mechanical Components by Laser Surface Texturing
Authors: Etsion I , Halperin G , Ryk G
Published: April 2008

Significant improvement in load capacity, wear resistance, friction coefficient etc. of mechanical components can be obtained by forming regular micro-surface structure in the form of micro-pores on their surfaces. A feasibility study was performed experimentally using Laser Surface Texturing (LST) technique to produce the micro-pores that can serve either as micro-bearings in cases of full lubrication or as micro-reservoirs for lubricant in cases of starved lubrication conditions. In all cases friction is reduced, wear resistance is increased and life is prolonged.
Influence of Lubrication on Wear and Friction on O-Rings in Contact with Yellow Metal
Authors: Vötter M , Schultz O
Published: April 2008

O-ring seals are usually used in static sealing applications. Under some circumstances they are applied in dynamic sealing. The project introduced here is about O-ring seals in oscillating rotation combined with an axial load. The insufficent durability of some seals at the blade bearing in controllable propellers is the reason this project was initiated.

The seal is placed between two plates. The seals are exposed to a constant axial force, so they are able to creep. During the experiment the torque, the angle of rotation, the distance between the plates, the temperature near the sealing zone, and the temperature in the laboratory are measured. Variations concerning load, sealing material and lubrication (oil, grease, water, no lubricant, and their combinations), and relative velocity are verified. The test range is up to 400 000 oscillations.

The paper presents the results and some hypotheses for modeling system of friction and wear, especially the influence of lubrication, time and material of the seal.
Extending Rolling Element Bearing Life in Hydraulic Systems with Water-based Fluids — The Grease Lubrication Option
Authors: Poll GW
Published: April 2008

This paper deals with the influence of rolling bearing lubrication on bearing operation and service life. Hydraulic fluids, especially when they contain water, do not always provide optimum conditions. Coatings or bearing steels specifically developed for such applications cannot completely compensate for the negative effects. It is therefore interesting to consider a separate lubrication system for the bearings, e.g. one based on grease. Then, however, grease service life can be more critical than bearing fatigue or wear. Accordingly, recent experimental and theoretical investigations into the tribological performance characteristics of bearing lubricating greases, especially the effect of their composition on service life, are presented.
Corrosive Wear Behavior of 304 Stainless Steel and Its Variation with Alloyed Oxygen-Active Element Yttrium
Authors: Zhang T , Li DY
Published: April 2008

Research was conducted to investigate the sliding wear of Y-free and Y-containing 304 stainless steel in 0.1 mol/1 H2SO4 solution. By the sliding wear test and worn surface analysis (SEM), the authors demonstrated that yttrium considerably improved the resistance of the stainless steel. In order to clarify the mechanism responsible for the improved corrosive wear resistance, yttrium effects on microhardness and polarization behavior of 304 steel were investigated. In particular, the damage and self-healing of passive film was determined using a scratch tester in combination with an electrochemical measurement system. Micro-scratch and micro-indentation tests were also performed with monitoring changes in the electrical contact resistance to evaluate the failure resistance of passive films respectively on Y-free and Y-containing 304 steel specimens. It was demonstrated that yttrium did not significantly influence the mechanical properties of the steel. However, a remarkable improvement in the polarization behavior of 304 steel with the formation of a stronger passive film was observed when a small amount of yttrium was alloyed into the steel. The mechanism responsible for the beneficial effect of yttrium on corrosive wear resistance of the stainless steel is discussed.
A Study of the Mechanism for Beneficial Effects of Yttrium Additive in Lubricant on Corrosive Wear and Friction of Metals
Authors: Liu R , Li DY
Published: April 2008

Previous work has demonstrated that the wear losses of stainless steel 304 and Al alloy 6061 under sliding in lubricant (oil and grease) mixed with dilute H2SO4 solution can be greatly reduced when a small amount of oxygen-active element (yttrium or cerium) powder is added to the lubricant. In order to explore the mechanism responsible for the beneficial effect of yttrium on corrosive wear resistance, corrosive-wear tests were carried out at different sliding speeds in lubricants with and without yttrium added respectively. Effects of yttrium on friction behavior of the materials were also studied. Worn surfaces were examined using SEM for better understanding of the role that yttrium played in corrosive wear. Possible mechanisms responsible for the beneficial effect of the oxygen-active element on corrosive wear are discussed.
The Effect of Oil Type on Wear in Fluid Power Components
Authors: Koivula T , Karjalainen R , Ellman A , Vilenius M
Published: April 2008

Different types of hydraulic oils are used in fluid power systems in various countries and conditions. Especially in mobile hydraulics, the range of used oils is very wide. Properties of oils (viscosity, density, foaming and additives) differ significantly from one oil type to another. Performance of a fluid power component is significantly dependent on the properties of oil, as the component consists of several orifices, clearances and tribological pairs.

Performance of a fluid power component can be greatly affected by wear. Properties of a hydraulic oil have an affect on the tribological behavior of a fluid power component as well as on the occurrence of cavitation. Material loss in a fluid power component is affected by oil type due to their different behavior in tribological pairs and cavitating flows.

The most commonly used hydraulic oils as well as motor oils have been studied in the IHA at two different test systems. In a cavitating-jet apparatus, the material loss due to cavitation erosion is studied and in a Vickers 20VQ test, the material loss due to tribological action in vane pump is studied.

Importance of oil type on wear in fluid power components is discussed. Material losses in Vickers 20VQ test and cavitating-jet apparatus are presented and compared.
Composite Flywheel Rotor Technology—A Review
Authors: Ratner JKH , Chang JB , Christopher DA
Published: April 2008

Flywheels with composite rotors are being developed as energy storage devices to replace conventional chemical batteries in satellites and other space systems, and are currently being used in terrestrial systems. The main advantages of composite flywheel systems are their ability to provide high instantaneous power and a capacity for large energy storage over many charge/discharge cycles. Currently, an industry working group is in the process of developing a standard that can be used to certify a composite rotor for safe and reliable operation in space. To assist in the development of such a standard, a review of state-of-the-art composite rotor technologies has been conducted. The goal of the review was to provide a clear picture of composite flywheel rotor technologies, and identify areas that require further development. Technical areas covered in the review were: rotor design approaches; composite analysis methods; composite materials' static strength, fatigue, creep, and stress rupture data; spin test and other test methods; nondestructive evaluation (NDE) methods; in-service health monitoring techniques; and fracture control requirements. This paper summarizes the review and provides recommended research and development topics that are needed to fill the technology gap.
Hydroburst Test Methodology for Evaluation of Composite Structures
Authors: Thompson RC , Pak TT , Rech BM
Published: April 2008

The University of Texas at Austin Center for Electromechanics (UT-CEM) is under contract to develop high-speed composite flywheel systems for a number of energy and power averaging applications in the transportation and space industries. Safe and reliable design of composite flywheels requires well-characterized material properties. Efforts have been focused on design optimization of a hydroburst test technique that demonstrates a useful method for characterizing the hoop (circumferential) properties of filament wound composite rings, and those results are then available to predict the performance of full-scale flywheels.

To demonstrate the usefulness of this method, this paper discusses typical hydroburst techniques to determine material properties for filament-wound composite rings. Test results are also presented. Seal design is a key element of this fixture, and a design has evolved that provides nearly uniform radial loading on the inside surface of the composite ring, while minimizing axial bending. Correlations of tow strand data with hydroburst lamina data are presented. Also discussed are hydroburst test applications for flaw assessment and fatigue property evaluation.
Time-Temperature Dependent Response of Filament Wound Composites for Flywheel Rotors
Authors: Thesken JC , Bowman CL , Arnold SM , Thompson RC
Published: April 2008

Flywheel energy storage offers an attractive alternative to the electrochemical battery systems currently used for space applications such as the International Space Station. Rotor designs utilizing the load carrying capacity of carbon fibers wound in the hoop direction are capable of high operational speeds and specific energies. However, the long-term durability of such rotors may be limited by the time-temperature dependent behavior of the epoxy matrix, which controls the uniaxial properties transverse to the fiber and the shear properties. This proposition was investigated for the prototypical rotor material, IM7/8552. Flat filament wound panels were made using the same process as for composite rotors. Coupon specimens, sectioned normal and parallel to the winding axis, were tested in compression and tension, at room temperature (RT), 95 °C and 135 °C for strain rates from 5 × 10-6/s to 5× 10-3/s. Creep and stress relaxation testing ran 72 hrs followed by a 72 hr recovery. Time, temperature and load sign dependent effects were significant transverse to the fiber. Under a fixed deformation of -0.5% strain for 72 hrs, compressive stresses relaxed 16.4% at 135 °C and 13% at 95 °C. Tensile stresses relaxed only 7% in 72 hrs at 135 °C for 0.5% strain. The postulate of a linear hereditary material response and the application of Boltzmann's principle of superposition to describe the behavior observed here are problematic if not intractable. Undoubtedly microstuctural analysis including the influence of residual stresses due to processing will be needed to resolve the observed paradoxes. Within the scope of these experiments, uniaxial compressive stress relaxation data may be used to bound the amount of relaxation with time of radial pre-load stresses in flywheel rotors. A more detailed appraisal of the design implications of these results is made in the analysis by Saleeb and co-workers [1].