bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alpine Skiing Injuries in Scandinavian Skiers
Authors: Ekeland A , Holtmoen Å , Lystad H 
Published: March 2009

The skiing injuries and skiing behavior of skiers from Norway, Sweden, and Denmark were studied in 4 Norwegian ski resorts during the winter of 1985/1986. A total of 328 injured skiers were recorded and compared with a randomly selected control population of 316 uninjured skiers.
The skiing injury ratio—injured skiers (%)/uninjured skiers (%)—was significantly higher for Danes (2.0) than for Norwegians (0.9) and Swedes (1.0) (P &lt; 0.01). This national difference was also observed after correction for skiing ability and skiing experience, which are the main determinants of injury risk in alpine skiing. In accordance with this, Danish beginners had an injury ratio about four times those for Norwegian and Swedish beginners. Present or previous skiing instruction reduced the injury ratio significantly only for the Norwegians; no significant differences were observed between the skiers from the three countries regarding binding testing.
The previously reported higher injury risk for Norwegian compared to Swedish alpine skiers no longer exists. This may be due to more information about skiing safety in Norway in the 1980s. The relatively higher injury ratio for the Danes may be due to shorter skiing seasons, but less public information about skiing safety may also have contributed.
Pain Threshold Along the Lower Leg in Alpine Ski Boots
Authors: Schaff PS , Ruckdeschl P , Hauser W , Rosemeyer B 
Published: March 2009

The pain threshold (PT) along the lower leg was analyzed in both female and male skiers to better understand current sex-related requirements for alpine ski boots. PT was found to be at an average of 32 N/cm2 for the male group and 23 N/cm2 for the female group. The difference between groups was significant (p = 0.05). We found no significant difference in PT distribution along the lower leg within the groups. Lowering the skin temperature more than 10°C resulted in a significantly higher PT. A 40% higher PT was found with twice as large an area used to apply the pressure (p = 0.05). The variation of PT to each subject is comparable to other psycho-physical methods, for example, vibration measurements. Because of a great variation among subjects, a definition of a maximum value to be tolerated in ski boots could not be given within a sufficient confidence interval.
Based on our findings, the following requirements are given: Ski boots must be classified according to sex, because women have a significantly lower PT that may lead to a restriction of motion in a stiff boot designed for male athletes. Temperature isolation for ski boots is very important, not only for comfort but also for safety reasons. Constant sensation feedback, necessary for accurate skiing, is only granted at constant temperature. To avoid pain at low pressure, the force along the lower leg should be distributed homogeneously over a large area. The area of most pressure should not be along the tibialis anterior tendon, because even pressure below the pain level over a long time may lead to a tendovaginitis in that area.
Behavioral Risk Factors for Ski Injury: Problem Analysis as a Basis for Effective Health Education
Authors: Bouter LM , Knipschild PG 
Published: March 2009

A problem analysis dealing with the importance of behavioral risk factors for ski injuries is based on the results of a case-control study conducted among Dutch skiers. In this study, cases (N = 572) were a sample of those who filed insurance claims for medical costs incurred as the result of a ski injury that prevented them from skiing for more than one day. Controls (N = 576) were a sample of uninjured skiers who filed insurance claims for nonmedical reasons.
Not taking ski lessons appeared to be a risk factor among beginners (odds ratio [OR] = 2.5; etiologic fraction [EF] = 12%). Failure of bindings to release is associated with a higher risk (OR = 3.2) for lower extremity injury, indicating that optimal binding adjustment can have a substantial preventive effect. Surprisingly, binding adjustment in the Netherlands more often involved the use of a test device compared to the ski resorts involved. In the latter case, the injury risk was higher (OR = 1.6; EF = 17%). From our data and the available literature, it can be concluded that alcohol consumption is probably not an important risk factor for ski injury. Several findings from our study seem to indicate that risk underestimation may be a risk factor for ski injury, but further study is necessary on this point. Taken together, the empirical basis for behavioral risk factors other than those mentioned above is still rather weak and thus a restrictive policy with respect to health education for downhill skiers would seem appropriate.
Wear Modeling : How Far Can We Get with First Principles ?
Authors: Godet M , Berthier Y , Lancaster J , Vincent L 
Published: March 2009

A brief description of what is meant by “wear modeling for design,” is given. The three contributors or triplet that must be considered in any wear modeling attempt are identified. These are : - mechanisms : i.e. all systems in which one or more contacts are established. Quasi-static liaisons such as gaskets, high speed bearings and gears are examples of mechanisms. - first-bodies : i.e. the rubbing elements of each mechanism; gear teeth, balls, races and cable strands, are examples of first-bodies. - third-bodies : i.e. any material, whether natural or artificial, which separates the rubbing first-bodies. Solid and liquid lubricants and debris beds are examples of third-bodies.
The diversity of conditions (loads, speeds, temperatures, environments) encountered in different mechanisms, the differences noted in stress and temperature fields found in first-bodies, the variations in composition and rheology observed in third-bodies are highlighted.
Materials Designation Systems: Their Problems and Possible Solutions
Authors: Reynard KW 
Published: March 2009

The VAMAS (Versailles Project on Advanced Materials and Standards) Technical Working Area 10, Materials Data Banks, has a project on materials designation systems in progress at the present time. The author is coordinator of this project that seeks to produce a world-wide inventory of materials designation systems. With it there will be a guide describing the method by which each system works, how new designations are assigned and by whom, and the conflicts and pitfalls of which users of multiple systems are often unaware.
As a growing reliance is placed upon information from computerized sources and more design and manufacturing processes are linked directly to numerical data banks, so the dangers from a lack of expertise and knowledge in the total system increase. Data exchange across the man-computer and the computer-computer interfaces rely increasingly on a lack of ambiguity and lack of uncertainty in the terminology and labels attached to the information.
In the western world, this situation may be aggravated by falling numbers of scientists and engineers in industry and the increasing numbers of computers. While a computerized system is more capable of producing repeatable results, it is also more likely to make connections that might either not be made other than by an expert, or might in some cases be rejected by an expert. Some of these connections could be advantageous, and some, disastrous if they go undetected.
A computer search for data on a material using the string 356 could produce numbers that relate to a brass, a steel, or an aluminum alloy. The response might be appreciated by some users but not necessarily by another computer program.
There needs to be greater understanding of the present situation with a view to constructing the appropriate interfaces and safeguards, and to reducing the complexity at the source.
The paper reviews items of interest from the project and the possible methods of dealing with the problems.
Water Vapor Behavior in Exterior Insulation and Finish Systems
Authors: Thomas RG 
Published: March 2009

Exterior Insulation and Finish Systems (EIFS's) are a type of cladding for exterior building walls. They are attached to the outside face of the wall structure. EIFS's were developed in Europe where exterior wall structures are predominantly unit masonry and concrete. In America, EIFS's are usually attached to lightweight wall structures of studs and gypsum sheathing.
In America, EIFS's are used in a wide range of climate conditions, including air conditioned buildings in hot, humid climates as well as arctic conditions. EIFS's are used in virtually every type of building including residential and high-rise commercial structures. Because of their light weight and relatively short track record, the longevity of EIFS's has been questioned. In particular, the effects of water from both liquid and water vapor sources is a concern. This concern has come from both field experience and theoretical analysis.
The American way of using EIFS's results in different water vapor behavior in the wall assembly. Condensation can occur in different locations in the wall under different conditions. The effects of water on the wall can be pronounced. The durability of the wall can be greatly affected if water vapor problems occur.
This paper reviews the American style of using EIFS's on light weight wall structures in terms of water vapor flow behavior. A computer program is used to demonstrate various conditions that affect the development of condensation in EIFS wall systems. The paper identifies common American wall designs that require attention and offers solutions for dealing with water vapor problems.
Computer Simulation of Wall Condensation Problems
Authors: Carlson AR 
Published: March 2009

Field reports from colder climates such as Alaska, Minnesota, Ohio, etc. indicate that wall moisture is a major problem, if there is no vapor retarder. A polyethylene vapor retarder is recommended in Alaska. Studies of retrofitted walls in older residences from warmer climates such as Oregon intimates that moisture in the wall may not be a problem even though there is no vapor retarder. However, the Oregon study still recommends a polyethylene vapor retarder for new construction.
There are two potential vapor retarders, which are designated in this paper as the primary and secondary vapor retarders. The primary vapor retarder for heated buildings, in cold climates such as Alaska, should consist of a polyethylene membrane placed at the inner skin directly under the gypsum wallboard (drywall). If the primary vapor retarder does not function as intended, then the outer skin consisting of a combination of plywood sheathing, siding, wind barrier, etc., may function as a secondary vapor retarder, which may trap moisture in the wall cavity.
Computer spreadsheet simulations of various wall sections indicate that wall moisture problems are dependent on inside and outside psychrometric conditions. The vapor pressure differential of the inside and outside air determines the driving force of the vapor. The vapor pressure and permeability of the primary and secondary vapor retarders determines how much water vapor may diffuse into the wall cavity. If the temperature gradients at the vapor retarder remains below dew point the moisture will condense in the cavity. If the temperature in the cavity remains below 32°F for prolonged periods the condensate will freeze and continue to build up as frost.
Effects of T-Tabs and Large Deflections in Double Cantilever Beam Specimen Tests
Authors: Naik RA , Crews JH , Shivakumar KN 
Published: March 2009

A simple strength of materials analysis was developed for a double cantilever beam (DCB) specimen to account for geometric nonlinearity effects due to large deflections and T-tabs. A new DCB data analysis procedure was developed to include the effects of these nonlinearities. The results of the analysis were evaluated by performing DCB tests on materials having a wide range of fracture toughnesses. The composite materials used in the present study were T300/5208, IM7/8551-7, and AS4/PEEK.
Based on the present analysis, for a typical load-point deflection/crack length ratio of 0.3 (for AS4/PEEK), T-tabs and large deflections lead to a 19 and 6% effect, respectively, in the computed Mode I strain energy release rate. Design guidelines for DCB specimen thickness and T-tab height were also developed in order to keep effects due to these nonlinearities within 2%.
Based on the test results, for both hinged and tabbed specimens, the effects of large deflection (compared to linear DCB results) on the Mode I fracture toughness (GIc) were almost negligible (less than 1%) in the case of T300/5208 and IM7/8551-7; however, for AS4/PEEK, the effect was from 2 to 3%. The effects of T-tabs (compared to a linear DCB with tabs) on GIc were more significant, with T300/5208, IM7/8551-7, and, AS4/PEEK showing a 5, 15, and 20% effect, in that order.
Combined Effect of Matrix Cracking and Free Edge on Delamination
Authors: Salpekar SA , O'Brien TK 
Published: March 2009

The effect of the stress-free edge on the growth of local delaminations initiating from a matrix crack in a composite laminate is investigated using a three-dimensional finite element analysis. Two glass epoxy layups, (02/904)s and (±45/904)s, were modeled with a matrix crack in the central group of eight 90° plies, and delaminations initiating from the matrix cracks in the 0/90 and -45/90 interfaces, respectively. The analysis indicated that high tensile interlaminar normal stresses were present at the intersection (corner) of the matrix crack with the stress-free edge, suggesting that an opening (Mode I) delamination may initiate at these intersections.
In order to analyze the strain energy release rates associated with delaminations that may form at the corners, three different configurations of the local delamination were assumed. One configuration was a uniform through-width strip growing normal to the matrix crack in the direction of the applied load. The other two configurations were triangular shaped delaminations, originating at the intersection of the matrix crack with the free edge, and growing away from the corner. The analysis of the uniform delamination indicated that the magnitude of both the total strain energy release rate, GT, and its components increased near the free edges. This edge effect was symmetric for the (02/904)s layup. However, for the (±45/904)s layup, the G distribution across the front was asymmetric, with the total G and its components having higher values near one free edge than the other. For both layups, the GI component was large at small delamination lengths, but vanished once the delamination had reached a length of one-ply thickness.
The second and third delamination configurations consisted of triangular-shaped delaminations with straight fronts inclined at angles of 10.6 and 45°, respectively, to the matrix crack. The total G along the delamination front decreased sharply near the matrix crack for both configurations and increased sharply near the free edge for the 10.6° configuration. However, the total G distribution was fairly uniform in the middle of the delamination front for the 10.6° configuration. These inclined models suggest that if the exact geometry of the delamination front could be modeled, a uniform G distribution may be obtained across the entire front. However, because the contour of the delamination front is unknown initially, it may only be practical to model the uniform through-width delamination and use the peak values of G calculated near the free edges to predict delamination onset. For the layups modeled in this study, the total G values near the free edge agreed fairly well with a previously derived closed-form solution. However, a convergence study may need to be conducted to have confidence that peak values of G calculated from three-dimensional finite element analyses near the free edges are quantitatively correct.
Analysis of Delamination Growth in Compressively Loaded Composite Laminates
Authors: Tratt MD 
Published: March 2009

An analytical and empirical study was conducted to investigate delamination behavior in composite structures.
The objective of the analysis was to predict the threshold stress for the initiation of delamination growth in compressively loaded composite laminates. MSC/NASTRAN geometrically nonlinear finite element analysis and a virtual crack opening technique were used to compute strain energy release rate distributions around circular delaminations. The distributions were computed for various compressive stress levels and the threshold stress for delamination growth was then determined by applying the strain energy release rates in a mixed-mode fracture criterion.
A number of static compression tests were conducted on specimens made from AS4/3501-5A graphite fabric-reinforced epoxy. The specimens contained circular delaminations of various sizes. The delaminations had been created by implanting Teflon inclusions in the prepreg layup.
Computed predictions of the delamination growth threshold stresses were significantly in error relative to the test data. The analysis did, however, concur with observed trends and provided qualitative insight into the process of quasi-static delamination growth.
A Study of an Implanted Delamination Within a Cylindrical Composite Panel
Authors: Palazotto A , Wilder B 
Published: March 2009

This research studied the effects of an inserted circular delamination on the strength of an eight-ply, quasi-isotropic composite laminate. Cylindrical panels were loaded compressively, and the global buckling load of the delaminated plies were examined. It was found that, for the level of delamination defect investigated, a linear bifurcation analysis gave fairly accurate predictions of the global panel strength. Load values, which caused local instabilities in the region of panel damage, were also recorded and compared to an approximate analysis.
During the experimental phase of this research, certain physical responses of the panels led to a set of simplifying assumptions. It was thought that there existed a value of strain that when applied to a circular delamination would cause the sublaminate to buckle. The value of strain in the sublaminate should be related to a value of strain in the curved panel. Some method of relating these two values of strain was suggested by the results of experimental tests.
A Comparison of Experimental Observations and Numerical Predictions for the Initiation of Fiber Microbuckling in Notched Composite Laminates
Authors: Guynn EG , Bradley WL , Ochoa OO , Whitcomb JD 
Published: March 2009

Previous experimental observations indicate that the compressive failure of open-hole multidirectional thermoplastic composites begins with in-plane fiber microbuckling at the hole. Growth of this damage requires little additional load, suggesting that compressive strength is controlled by initiation, rather than propagation, of in-plane microbuckling. The significant role of local constraint on the initiation of fiber microbuckling is indicated in this work.Stacking sequence and resin ductility (varied as a function of the test temperature) are the two primary variables in this investigation, both of which provide systematic variation of support to the load-bearing 0° plies. The material system selected for this investigation is a thermoplastic composite, APC-2: AS4/PEEK.The compression specimens used are 2.54 cm wide with a 2.54 cm long gage length. Each specimen contains a 0.3175-cm-diameter semicircular notch at each free edge, centered along the gage length. This polished notch facilitates the observation of the initiation of damage in the form of in-plane fiber microbuckling into the notch. High-temperature tests are conducted using a controlled forced-air heat gun rather than an environmental chamber to allow high-magnification observation of the failure processes at the higher temperatures.Geometric and material nonlinear two-dimensional finite element analysis is used to model the effects of the initial fiber waviness in combination with matrix nonlinearity on the fiber microbuckling initiation strain levels and the resulting shear strain developed in the matrix.
Compression Testing of Thick-Section Composite Materials
Authors: Camponeschi ET 
Published: March 2009

As composite materials become more attractive for use in large Navy structures, the need to understand the mechanical response of composites greater than 6.4 mm (0.25 in.) in thickness becomes a necessity.
In this program, a compression test fixture that allows the testing of composites up to 25.4 mm (1 in.) in thickness and greater was designed and refined. This fixture was used to evaluate the effects of constituents, fiber orientation, and thickness on the compressive response of composite materials. In addition, the fixture was used to determine if the failure mechanisms observed for thick composites are similar to those that have been observed and reported for composite materials less than 6.4 mm (0.25 in.) thick.
The in-plane moduli, in-plane and through-thickness Poisson's ratios, compression strength, and failure mechanisms of the thick composites were shown to be independent of material thickness. The predominant failure mechanisms for both materials were kink bands and delaminations, and were identical in geometry to those that have been reported for composite materials in the range of 2.54 mm (0.1 in.) thick.
Although unchanged with thickness, the through-thickness Poisson's ratio for the carbon- and glass-reinforced laminates were found to be significantly nonlinear, resulting in changes in this property of up to 58% from the initial region of the strain-strain curve to the final region of the strain-strain curve.
Influence of Low-Velocity Impact on Composite Structures
Authors: Madan RC 
Published: March 2009

Composite materials are sensitive to out-of-plane loads because they are weaker through the thickness than in the plane of lamination. Consequently, composite structure subjected to impact may suffer significant damage, which results in a loss in strength. The effect of impact energy on different thicknesses of laminate with respect to ultimate compressive strength was evaluated using the NASA ST-1 specimen test. Impact damage was measured using ultrasonic C-scans and quality was assessed by visual observations. A semiempirical model for impact damage was proposed to determine residual strength in terms of laminate properties, static influence coefficients, and impact energy.
To determine residual compression strength, single- and multiple-impact damage was inflicted on bonded stiffened structures. The results were verified by the residual strength method, which uses laminate properties and measured damage size to predict the residual strength of composites. The correlation between predicted and actual strength was very encouraging. Although the damage was inflicted with different impactor masses, velocities, and impact energy, the data indicated that residual strength is a function only of damage present and does not reflect the manner in which the damage is inflicted. Finally, a semiempirical relationship was developed for damaged areas in stitched laminates.