bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tribological Models for Solid/Solid Contact: Missing Links
Authors: Rice SL , Moslehy FA 
Published: March 2009

This paper presents a brief overview of the tribological information which mechanical designers need, such as equations to predict frictional forces and wear rates. This is contrasted with the forms of result that typify wear testing in research, for example, comparative rates which are meaningful only for the apparatus used. And while the “systems nature” of tribology is well known by researchers, there is a natural tendency to overlook at least some complexities as attempts are made to isolate particular contact phenomena. Thus, both designers and researchers seek simplicity in problems which are inherently complex.
This complexity is manageable, provided one is willing to deal with complete specification of the system. This paper addresses that issue, and suggests a representation for a tribosystem which incorporates features that require attention from both mechanical modelers and materials scientists. Specifically, there is a need for characterization of the dynamic behavior of tribosystems — including both specimen and counterface “sides,” of the apparatus — together with solution of the tribological problem set. That is, once time varying dynamic loads and motions are known, then the study of actual contact areas and force transmission to and through asperities can begin. Additionally, when the associated heat transfer problem is solved, it becomes possible to study the material response of specimen and counterface in terms of fundamental processes such as diffusion, adhesion, bond formation and rupture, and plastic strain accumulation in the substrate.
A general tribosystem representation is suggested to underscore a sequence of mechanical problems which must be addressed in parallel with fundamental materials-related problems. Only when both sets are treated can the resulting systems' behavior be modeled from first principles. Thus, the new representation serves to highlight what is missing in tribological models for solid/solid contact.
Development and Coordination of Materials Data Banks in France
Authors: Marx B 
Published: March 2009

A survey was done in 1988 by CODATA FRANCE and the Ministry of Education on Materials Data Banks Production in France. Forty data banks were analyzed in relation to producers, subject coverage, type of data, mode of access, and method of use.
Given the major effort required to build a data bank, a large number of these data banks are the result of national or international cooperation. An analysis of the fields covered shows the importance of metals, polymers, and building materials. The properties covered are mechanical properties and a description of the materials. This information is expressed in terms of textual-numerical data and inventories.
Calculation software provides an important plus for the use of numerical data. Two thirds of data banks are accessible from a distance, and access by videotex is common. The various types of materials data banks belong to two main categories: 1. Scientific data produced by higher education covering fundamental properties expressed in the form of numerical data, associated with calculation programs, and accessible locally or at a distance in ASCII mode. 2. Technological data produced by other public sector bodies, nonprofit making organizations, and industrial companies. These data describe the characteristics of the materials and their mechanical properties in the form of textual-numerical data and inventories. They are often accessed at a distance and by minitel.
The results of this study are being analyzed by different ministries involved in Materials Data Banks production, for example, Education nationale, Recherche et Technologie, Industrie. Proposals are being discussed for an easier access and search method adapted to end users in different activity sectors.
Cooperation—A Good Chance for Industry in Setting Up Materials Data Banks
Authors: Brandstätter A 
Published: March 2009

The situation in the field of materials data banks in the Federal Republic of Germany is described in this paper.
An analysis of early data banks resulted in the following conclusions: (1) it is not helpful to build an overall materials data bank with a lot of data gaps, (2) there was no information on the quality and reliability of the data, (3) the results of searching the data were often less effective than thumbing through the pages of a book, (4) there was no user friendliness within the retrieval systems, and (5) the data banks were very different from each other and the users had to learn several systems.
On the basis of these results, new concepts of materials data banks were developed that included two groups of activities: 1. building a framework with (a) setting up an overall conceptual scheme, (b) user friendly access, (c) programs for data calculation and interpretation, and (d) building up expert systems; and 2. collecting, validating, and evaluating data on the basis of the framework and special agreed rules for (a) collecting and validating data in an agreed structured format, (b) collecting data with high quality and complete information, (c) measuring of missing data, (d) working out algorithms for calculating and extrapolating data, and (e) building data banks out of data produced by several institutions.
Carrying out all of these activities is a tremendous job that can be done only with the cooperation of all the data producers.
Increasing Data System Responsiveness to End-User Expectations
Authors: Kaufman JG 
Published: March 2009

Responsiveness to user expectations on ease of use, content, and style of presentation are paramount in gaining engineers' and materials scientists' acceptance and utilization of computerized numeric/factual databases and information networks. In this paper, the factors that influence both users' comfort and efficiency with such electronic data sources, whether single databases, clusters of databases, or networks of data from a variety of sources will be discussed.
Among the key subjects that will be covered are: 1. User-oriented interface. 2. Interactive thesaurus. 3. Options in search strategies. 4. Logical displays of data.
In addition, for online networks in particular, there are additional requirements that will be also discussed: 1. Compatibility with personal computer, compact disk, and other mainframe applications. 2. Diversity of database management systems. 3. Graphics; interactions with numeric databases.
In addressing these issues, the experience gained in building both the Pilot National Materials Property Data (MPD) Network, operating online from Stanford University, and in developing the production version of the MPD Network on STN International is called upon in this paper. Through the iterative process of gaining user feedback from trials of the developmental system, much has been learned and, to the degree practical, used in establishing the MPD Network system.
As the capability and ease of use of commercially available computerized materials data sources increase, we can expect to see a substantial increase in the utilization of such sources by the end users of the information for which searches are being carried out.
HIGHTEMP—A Database for Mechanical Properties at Elevated Temperatures
Authors: Sandström R , Ivarsson B , Lindblom J 
Published: March 2009

A database for elevated-temperature tensile and creep properties for steels called HIGHTEMP has been developed. Materials that are included in the database are unalloyed, low alloyed, 12% chromium, and austenitic stainless steels, mainly of pressure vessel type. The data have been collected previously from Swedish industry and laboratories. Full metallurgical background information can be found in the system. This includes metallurgical casting and working processes, as well as product form, specimen geometry, heat treatment, room temperature tensile properties, microstructure, and testing methods.
To illustrate the use of the database, the correlation between room-temperature tensile properties and creep properties have been studied for a few stainless steels. For 15Cr-15Ni-1Mo and 17Cr-12Ni-2Mo-0.15N, the creep rupture strength increases significantly with increasing room-temperature strength at testing temperatures below 750°C. In the same way, the creep ductility was reduced when the room-temperature strength was high. For 15Cr-15Ni-lMo, the variation in the room temperature tensile strength was related to a variation in the grain size.
Establishing Appropriate Field Test Pressures for Investigation of Leakage Through the Building Envelope
Authors: Cole GG , Schwartz TA 
Published: March 2009

Most performance standards for building envelope components, such as those for certified windows, have been developed for evaluating new products or for helping assure the quality of mass produced products. There are, however, few standard procedures for evaluating performance problems with installed wall systems. Many investigators have attempted to apply performance standards for new assemblies to problematic buildings; and this often leads to the wrong conclusion regarding the cause of building leakage.
This research explores the appropriate use of water test procedures for field investigation of leakage through building walls. We explore both the type of testing and appropriate criteria for judging the contribution to leakage from various components of the exterior envelope. We also discuss a methodology for developing test parameters based on actual weather records and surrounding topography. These exposure conditions can be used to formulate test pressures that can be applied to elements of the building envelope during water testing to more closely simulate the past exposure conditions that these wall components experienced during leakage events.
Tracing Roof and Wall Leaks Using Alternating Electric Fields and Vapor Detection
Authors: May JC , Vassiliades JM 
Published: March 2009

Exterior water can penetrate a building and move in either continuous or discontinuous flow. In the case of continuous flow, from point of entry to point of observation, surfaces of construction materials are wetted and may provide a path of adequate conductivity to produce a detectable alternating electric field when a voltage is applied. Where this is the case, a suitable a-c ource and detector can be used to determine the source of water entry.
For cases where water flow is discontinuous, detection of vapor from water mixed with organic solvent can assist in tracing water movement and source of origin. Commercial equipment is available to measure, non-destructively, moisture behind and within non-conducting substrates such as wood and exterior foam panels. Using these methods one can often unambiguously locate the source of a water leak.
Effects of Moisture Absorption on Edge Delamination, Part II: An Experimental Study of Jet Fuel Absorption on Graphite-Epoxy
Authors: Hooper SJ , Subramanian R , Toubia RF 
Published: March 2009

An experimental study was conducted to investigate the environmental effects of jet fuel absorption on the mixed-mode fracture toughness Gc of AS4/3501-6 graphite-epoxy. Edge delamination tension tests of saturated and partially saturated (30/-302/30/90n)s (n = 1, n = 2), (35/-35/0/90)s and (35/0/-35/90)s layups were conducted. Three types of jet fuels were considered including JP-4 military jet fuel, Jet-A commercial jet fuel, and Type VII rubber swelling test fluid. Additional tests were conducted at the room temperature dry (RTD) and water soaked conditions. The water soaked specimens were also tested in the saturated and partially saturated conditions.
The total and the mixed-mode strain energy release rates were evaluated using a modified quasi-three-dimensional finite element (Q3DG) analysis. Edge delamination data of partially saturated and saturated specimens was used to quantify the relative influence of typical aircraft fluids on interlaminar fracture for composite materials. The effects of hygroscopic strain gradients on the interlaminar fracture toughness was investigated for the fluids considered.
Effect of Porosity on Flange-Web Corner Strength
Authors: Kan H-P , Bhatia NM , Mahler MA 
Published: March 2009

A strength of materials based model was developed to determine the interlaminar tensile stress at the corner radii of curved composite structures. The model assumes that the stress state in the local area near the corner is under pure bending. The force in each layer (ply) of the laminate is determined by classical lamination theory and the curved beam analysis method. The interlaminar tensile stress is then obtained by enforcing the force and moment equilibrium in each layer.
To verify the accuracy of this analytical model, a series of corner specimens were fabricated and tested. These specimens were fabricated under controlled conditions and no porosity was detected in the specimens. The corner specimens were tested by pulling apart the sides of the corner to introduce bending moment at the corner. The maximum interlaminar tensile stress computed using the analysis model was compared to the flatwise tensile strength of the material in order to predict the failure moment of the test specimen. Excellent correlations between the measured and predicted failure moment were achieved.
A series of tests were conducted on flange-web corner elements obtained from graphite composite frames that had porosity in their corners. The objectives of these tests were to determine: (1) level of porosity in the corners by using ultrasonic inspections and photomicrographic examinations, and (2) the effect of porosity in the corner on the bending strength and the interlaminar tensile strength. Ultrasonic inspections revealed the locations along the corners where porosity was present. Photomicrographic examinations showed that the porosity occurred in clusters between plies and appeared similar to delaminations. Qualitative levels of porosity, based on photomicrographic observations, were established; these were (1) no porosity, (2) low porosity, and (3) high porosity. Attempts to use acid digestion methods to establish quantitative measures of porosity were not successful because the porosity was localized between only a few plies.
A relationship was established between ultrasonic signal attenuation loss due to porosity and interlaminar tensile strength of porous structures. Strength testing was conducted on the flange-web corner specimens. Post-failure examination of the test specimens showed that interlaminar tension dominated the failure with little evidence of shearing effects. The failure strength data were used with the analytical model to calculate the interlaminar tensile failure stress for each specimen.
Fatigue Delamination Onset Prediction in Unidirectional Tapered Laminates
Authors: Murri GB , Salpekar SA , O'Brien TK 
Published: March 2009

Tapered [0°] laminates of S2/CE9000 and S2/SP250 glass/epoxies, and two different specimen types of IM6/1827I, a graphite/epoxy with a toughened interleaf, were tested. Specimens were subjected to cyclic tension in a hydraulic load frame. The specimens usually showed some initial stable delaminations in the tapered region, but these did not affect the stiffness of the specimens, and loading was continued until the specimens either delaminated unstably, or reached 106 to 2 × 107 cycles with no unstable delamination. The final unstable delamination originated at the junction of the thin and tapered regions, and extended into both the tapered and thin regions.
A finite element (FE) model was developed for the tapered laminate, both for the laminate with no initial delamination, and for the tapered laminate with the initial stable delaminations observed in the tests. The analysis showed that for both cases the most likely place for an opening (Mode I) delamination to originate is at the junction of the tapered and thin regions. For each material type, the models were used to calculate the strain energy release rate, G, associated with delaminations originating at that junction and growing either into the thin region between the belt and core plies, or into the tapered region, between the belt and dropped plies. For delamination growth in either direction, calculated values of G reached a peak at a delamination length equal to few ply thicknesses, and then decreased. The highest values of G were calculated for the laminate with an initial stable delamination in the tapered region and an opening mode delamination growing from the junction into the tapered region.
For the materials tested, cyclic GImax values from double cantilever beam (DCB) tests were used with the maximum G values calculated from the FE analysis for delamination growth in the tapered and thin regions, to predict the onset of unstable delamination at the junction as a function of fatigue cycles. The predictions were compared to experimental values of maximum cyclic load as a function of cycles to unstable delamination from fatigue tests in tapered laminates. The predictions, assuming delamination initiated in the tapered region, agreed reasonably well with the test data, although the correlation was slightly conservative for all except the S2/SP250 material. The measured and calculated results, assuming delamination initiated in the thin region, showed good agreement, although the predictions were slightly unconservative for the S2/SP250 laminates
Effects of Stacking Sequence on Impact Damage Resistance and Residual Strength for Quasi-Isotropic Laminates
Authors: Dost EF , Ilcewicz LB , Avery WB , Coxon BR 
Published: March 2009

Residual strength of an impacted composite laminate is dependent on details of the damage state. Stacking sequence was varied to judge its effect on damage caused by low-velocity impact. This was done for quasi-isotropic layups of a toughened composite material. Experimental observations on changes in the impact damage state and post-impact compressive performance were presented for seven different laminate stacking sequences. The applicability and limitations of analysis compared to experimental results were also discussed.
Post-impact compressive behavior was found to be a strong function of the laminate stacking sequence. This relationship was found to depend on thickness, stacking sequence, size, and location of sublaminates that comprise the impact damage state. The post-impact strength for specimens with a relatively symmetric distribution of damage through the laminate thickness was accurately predicted by models that accounted for sublaminate stability and in-plane stress redistribution. An asymmetric distribution of damage in some laminate stacking sequences tended to alter specimen stability. Geometrically nonlinear finite element analysis was used to predict this behavior.
Fatigue Damage Mechanics of Notched Graphite-Epoxy Laminates
Authors: Spearing M , Beaumont PWR , Ashby MF 
Published: March 2009

A modeling approach is presented that recognizes that the residual properties of composite laminates after any form of loading depend on the damage state. Therefore, in the case of cyclic loading, it is necessary to first derive a damage growth law and then relate the residual properties to the accumulated damage.
The propagation of fatigue damage in notched laminates is investigated. A power law relationship between damage growth and the strain energy release rate is developed. The material constants used in the model have been determined in independent experiments and are invariant for all the layups investigated. The strain energy release rates are calculated using a simple finite element representation of the damaged specimen. The model is used to predict the effect of tension-tension cyclic loading on laminates of the T300/914C carbon-fiber epoxy system. The extent of damage propagation is successfully predicted in a number of cross-ply laminates of the form (90i/0j)ns and the quasi-isotropic laminate (90/+45/-45/0)s. The dependence of damage on load amplitude and specimen size is also well described.
Residual strength is calculated as a function of damage dimensions for (90/0)s specimens using a stress-based failure criterion in conjunction with a Weibull dependence of the 0° ply strength on the volume under stress.
Effect of Interlaminar Normal Stresses on the Uniaxial Zero-to-Tension Fatigue Behavior of Graphite/Epoxy Tubes
Authors: Krempl E , An D 
Published: March 2009

During the past several years, the Mechanics of Materials Laboratory of Rensselaer Polytechnic Institute (RPI) has developed a method of obtaining biaxial fatigue data under axial/torsion loading. A thin-walled tubular specimen can be made from prepregs by a layup procedure and tested in an MTS servohydraulic axial/torsion testing machine with computer control. We have provided completely reversed load-controlled fatigue data on graphite/epoxy materials under uniaxial and combined loadings using [± 45]s and [0, ± 45]s layups. The edgeless specimen eliminates suspected end effects and can be used for tests involving significant compressive loading.
Interlaminar normal stresses were thought to influence fatigue performance by enhancing delamination. To check on this hypothesis, zero-to-tension fatigue tests were run on graphite/epoxy [± 45]s tubes with and without internal pressurization. The pressure levels were chosen so as to compensate the suspected interlaminar tensile stresses. Fatigue test results in the range from 104 to 106 cycles with and without pressurization were within the same reasonable scatter band. In the course of testing, it was discovered that performance could be considerably improved by providing a restraint in the hoop direction by either inserting a mandrel or by including a 90° layer on the inside and outside. Fatigue tests with [90,±45]s specimens under zero-to-tension loading showed a significantly improved fatigue performance.