bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preventing Fracture By Inspection and Analysis
Authors: Selz A , Peterson DB 
Published: December 2008

A problem in operating pressure components under cyclic loading conditions is establishing an in-service inspection frequency to assure continued operability without threat of catastrophic failure. For some extremely high pressure components, this has been done on a rational basis by (1) establishing the regions of highest stress, usually thread roots or other local stress raisers in a high stress field, (2) establishing the minimum-size reliably observable crack-like defect, using proven inspection means, such as magnetic particle or eddy current testing, and (3) determining the number of design cycles this minimum observable crack needs to grow to critical size, using Paris law or analogous crack propagation relations, and then dividing the resulting number of cycles by a factor of at least three. This factor of three is based on retaining cyclic margin to failure, even if a given defect is below perceptible size at initial inspection and is missed during the next inspection. A factor of four would accommodate two consecutive failures to observe a defect. Methods have been also developed which permit modification of the inspection interval if the operating logs show the imposition of a distribution of operating cycles other than the design cycles upon the component.
The methods described were originally developed and applied to predicting safe life and establishing inspection intervals for a hypervelocity wind tunnel. They have since been applied to commercial pressure vessels and for recertification of pressure vessels for the National Aeronautics and Space Administration.
The OSHA Hazard Communication Standard
Authors: McDaniel DW 
Published: December 2008

On 25 Nov. 1983, The Occupational Safety and Health Administration (OSHA) issued a final rule on hazard communication. This final rule represents over ten years of rule-making activity. The purpose of the Hazard Communication Standard is to ensure that hazards of all chemicals produced or imported by chemical manufacturers are evaluated and that the information on these chemical hazards is transmitted to employers and employees within the manufacturing sector.
Employers in the manufacturing sector [Standard Industrial Classification (SIC) Codes 20–39] are to provide information to their employees about hazardous chemicals by means of a hazard communication program, labels and other forms of warning, Material Safety Data Sheets, and information and training. The purpose of the Hazard Communication Standard is threefold:
1. To ensure that the chemicals produced or imported or both by chemical manufacturers and importers are evaluated to determine their hazards.
2. To provide information about hazardous chemicals to all employers and employees in the manufacturing sector.
3. To establish uniform requirements nationwide by preempting state right-to-know laws applicable to the manufacturing sector. A state may assume responsibility in this area only through the provisions of Section 18 of the Occupational Safety and Health Act.
The standard applies to chemical manufacturers, importers, distributors, and employers in the manufacturing sector in SIC Codes 20 through 39. In addition, the standard applies to any chemical known to be present in the workplace in such a manner that employees may be exposed under normal conditions of use or in a foreseeable emergency. There is limited coverage for laboratories as well as exclusions for certain products.
There are six major elements of the Hazard Communication Standard:
1. Hazard assessment—the hazards of chemicals must be evaluated by chemical manufacturers and importers. The information must be passed on to employers in the manufacturing sector who purchase the hazardous chemicals.
2. Hazard communication program—employers covered by the regulation must develop a hazard communication program to transmit information on hazardous chemicals to their employees.
3. Labels and other forms of warning must be placed on containers of hazardous chemicals.
4. Materials Safety Data Sheets must be developed to transmit hazard information to the manufacturing employees and employers.
5. Employee information and training must be provided. This includes identifying work operations where hazardous chemicals are present as well as means that employees can take to protect themselves.
6. Trade secret provisions—there are provisions for the release and protection of trade secret information.
Labels and Material Safety Data Sheets in Hazard Communication
Authors: Freifeld M 
Published: December 2008

In the Hazard Communication Standard (HCS), the Occupational Safety and Health Administration (OSHA) chose labels, Material Safety Data Sheets (MSDSs), and training as the vehicles for conveying to workers information about hazards on the job. Labels have always been aimed at the worker. MSDSs, on the other hand, have been written largely for health professionals. Training should, therefore, include the meaning of technical terms in labels and MSDSs so that workers can understand them.
A label is intended to provide an immediate warning about hazardous materials in the workplace. It may be in written or graphic form and must be tied in with training and MSDSs. The label must include the identity of the hazardous chemicals and appropriate warnings about the hazards. The label format is optional, and existing systems may be used. Some alternatives to labeling are allowed, such as large posters describing contents and hazards of a series of similar reactors. Chemical manufacturers, importers, and distributors must also include the name and address of the manufacturer of materials being shipped out of a plant. Substances covered by other federal laws are exempt from HCS's shipped container labeling requirements.
MSDSs complement the label and are more complex. They include: (1) the identity used on the label (except trade secrets) and the specific chemical identity of the hazardous ingredients; (2) physical and chemical characteristics of hazardous materials; (3) fire, explosion, and reactivity hazards; (4) health hazards—both short- and long-term; (5) safe handling and use procedures; (6) emergency and first aid procedures; and (7) date and name of the responsible party preparing the MSDS.
The Hazard Communication standard requires chemical manufacturers to make MSDSs available to their employees. It also requires them to supply MSDSs to downstream manufacturing employers, who in turn must make them available to employees. Clearly then, the chemical manufacturers face the challenge of preparing complete MSDSs. Manufacturing employers must be sure that their workers do indeed get the message.
Hazard Communication in Other Jurisdictions: A Proposed Canadian System
Authors: Geoffrey C. Granville 
Published: December 2008

The Workplace Hazardous Materials Information System (WHMIS) was initiated as a tripartite project in 1982, and a final report was submitted to government during 1985. The report recommends an approach to the communication of hazardous properties of materials used in the Canadian workplace that is broadly similar to the OSHA Hazard Communication standard, although there are some notable differences.
At the time of publication, the report had not resulted in any new regulatory initiative.
Testing, Simulation, and Interpretation of Materials Impact Characteristics
Authors: Jemian WA , Jang BZ , Chou JS 
Published: December 2008

Research was initiated to measure the characteristics and properties of materials to support a valid simulation for general design purposes. Cushioning systems are used for personal protection in sports and transportation and for the safe transport of fragile materials. Design costs can be reduced by replacing prototype construction with simulation procedures.
Materials impact characteristics are in response to transient dynamic loading involving a sequence of structural processes during the period of contact. In most applications the engineering system responds in an overdamped configuration to eliminate oscillations. The cushioning component, however, is usually a viscoelastic, low-density substance with distinctive characteristics and properties. Cushioning is defined as the redirecting of motion under a controlled level of deceleration. The damping function is separate, being a dissipation of kinetic energy to terminate motion.
A variety of foamed plastics, including polypropylene, polystyrene, and polyurethane formulations were tested in the form of homogeneous blocks with dimensions of 3.8 by 3.8 by 2.5 cm (1.5 by 1.5 by 1.0 in.). Flat-surface impact was employed with drop heights ranging to 122 cm (48 in.). Voltage signals from an accelerometer in the impactor and a force cell below the specimen stage were recorded using a digital storage oscilloscope. These data were processed separately for analysis.
Specimen characterization also included measurement of density and stress relaxation and static testing at rates allowing effective specimen compliance. The objective of the experimental measurements was to determine the density, damping, and structural stiffness to provide the needed information for the deformation process in the governing differential equation Mü + C˙u + Ku = R where ü, , and u are the acceleration, velocity, and displacement in compression, respectively, and M, C, and K are the mass, damping, and structural stiffness properties of the materials in the test system.
Simulation was performed by finite element (FE) structural analysis developed in prior research. The FE program provided transient, dynamic analysis using nonlinear structural stiffness and damping. The FE model included the corresponding size, shape, and properties of the impactor, specimen, and stage in an appropriate manner. Simulation results were matched with measured responses to establish the validity of the simulation procedure.
Additional experimental drop tests showed pronounced differences between the characteristics of different materials. These observations and specific test procedures allowed conclusions to be drawn relative to the nature of the mechanical and structural responses at different stages of cushioning. These include separate effects of inertial stiffness, dynamic stiffness (due to damping), and structural stiffness occurring when motion is arrested.
Prediction of End-Use Impact Resistance of Composites
Authors: Peraro JS 
Published: December 2008

The ability to predict material behavior under impact loading is very important in the design and manufacture of products. To predict product performance adequately, it is important to simulate the conditions under which the material is used.
Traditional impact tests often fail to provide the data required to evaluate and predict behavior under impact stress. An instrumented multivariable high-rate impact tester is designed to provide this information. The instrument is capable of testing materials of almost any configuration at velocities from 0.0127 to 12.7 m/s (30 to 30 000 in./min) and in environments simulating service conditions. Electronic instrumentation and a sophisticated computerized microprocessor simplifies the gathering, processing, and calculation of the impact property data. The graphic and calculated values permit a detailed analysis of impact performance.
The high-rate impact tester used at Owens-Corning Fiberglas Corp. is described, with examples of test programs in which the instrument capabilities were utilized to simulate the impact forces on boat, pipe, and tire constructions. Modifications made to the ram, or mode of operation, better simulate end-use conditions.
The results adequately predict impact behavior experienced under service conditions within a laboratory environment. This provides the scientist with a means of observing the impact phenomenon under laboratory conditions. As new materials are developed, characterization can be accomplished rapidly and at minimum cost. Screening of candidate materials can be accomplished without the time-consuming and expensive process of producing a product and conducting in-service tests.
The information developed can be invaluable for improving existing products and developing new products. By observing the test and evaluating the traces obtained, one can identify potential weaknesses in a product, which can be corrected by redesign or substitution of alternative materials.
Assessment of Impact Characteristics for Incipient Crack Formation in Polymeric Materials
Authors: Lee WM , Rieke JK 
Published: December 2008

For many material applications, the evidence of a visible flaw (for example, a crack) can be regarded as the start of failure. It is important to determine the impact conditions for which incipient crack formation occurs. From the material design standpoint, it is essential to identify the key material properties governing this crack formation process. Therefore, its assessment and characterization become indispensable to polymeric material manufacturers as well as design engineers in material selection.
Typically, a Gardner impact tester has been employed to determine the first crack formed in a material. However, Gardner methods lack the capability of evaluating the crack initiation process as a function of impact speed. The Rheometrics impact tester can be used to determine the crack formation point by adjusting the ram travel distance into a test specimen short of complete penetration. Nevertheless, the large momentum of the impact ram at increasingly high speeds makes its stoppage at a preset travel distance extremely difficult. Hence, this mode of testing is limited to low impact speeds. In order to facilitate crack formation study at high speeds, the authors of this paper have developed a testing technique using a Dynatup impact tester. This technique involves the use of variable-thickness shims to raise the test specimen height from its lowest impact point, where contact between the tup and test specimen is just made. This allows us to control the distance the tup travels into the specimen.
The impact characteristics (that is, impact energy, impact force, and ram displacement) at crack formation are analyzed in connection with material selection. One of these three quantities is suggested for impact toughness evaluation, and its underlying rationale and significance are discussed. Also, the impact characteristics at crack initiation and at complete puncture are compared in relation to material design and selection.
Pressurization Testing, Infiltration Reduction, and Energy Savings
Authors: Jacobson DI , Dutt GS , Socolow RH 
Published: December 2008

House tightening has become an important component of residential energy conservation programs. The technique of pressurization as a means of improving the effectiveness and labor productivity of house tightening has been increasingly used. It would be desirable if the measurements taken as part of the house pressurization activity could be used to quantify the degree of tightening actually accomplished. Such measurements were taken both immediately before and immediately after a house tightening activity carried out, as part of the Modular Retrofit Experiment (MRE), in 98 single-family houses in seven sites in New Jersey and New York. We have reduced the pressurization data from 55 homes according to two prescriptions, one rooted in the airflows actually observed at a relatively high pressure (50 Pa) and one requiring the extrapolation to a low pressure (4 Pa) by means of a curve fit through and beyond the observations. The two prescriptions turn out to give very different answers to the question: By what percent has the average air infiltration rate been reduced? In a large fraction of cases, the process of house tightening leaves a signature in the pressurization data such that the percent reduction in airflow is greater at lower pressures; as a consequence, the prescription which involves extrapolating to 4 Pa gives much larger estimates of the percent reduction in air infiltration achieved by the tightening process. In the seven sites we examined, the estimated percentage savings for the 4-Pa extrapolation was over twice as large on the average. The differences in the interpretation of pressurization data also lead to wide discrepancies in the expected reduction in naturally induced air infiltration, which was not measured in the MRE. In a subsequent experiment, known as the Dual Infiltration Reduction Experiment (DIRE), tracer gas decay measurements before and after house tightening supplement pressurization data. This experiment helps to clarify the relationship between air leakage reduction as measured by the two techniques—an area that has not been explored in past research relating natural air infiltration and leakage reduction pressurization.
The natural air infiltration reduction can be interpreted directly in terms of energy savings. For the MRE houses, the air infiltration energy savings component is computed from estimates of natural air infiltration reduction. This component is compared woth total savings in space heating energy use where available utility billing data permit the latter to be calculated.
Building Site Measurements for Predicting Air Infiltration Rates
Authors: Bassett MR 
Published: December 2008

This paper examines the sensitivity of the predicted air infiltration rate to measured building airtightness data and the wind exposure index determined from site inspection. Results of airtightness tests in New Zealand houses are presented to indicate the range of leakage resistance for components (windows, doors, and chimneys, etc.), for solid materials (such as wall and ceiling lining materials), and for cracks separating major components such as the floor and walls. The distribution of leakage opening is discussed in relation to the driving forces of wind- and stack-induced airflows and also in relation to New Zealand styles of house building.
The building site exposure class must be determined in order that standard wind engineering formula can be used to calculate site wind speeds from meteorological weather data recorded some distance away. In the New Zealand situation, with high wind speeds and modest indoor-outdoor temperature differences, predicted natural air infiltration rates are particularly sensitive to site exposure details. Examples of measured and predicted air change rates are given for a number of houses together with comment on the sensitivity to experimental error.
Dynamic Delamination Crack Propagation in a Graphite/Epoxy Laminate
Authors: Grady JE , Sun CT 
Published: December 2008

Ballistic impact tests of [90/0]5s T-300/934 graphite/epoxy laminates of beam-like dimension with embedded delamination cracks were conducted. High speed photography (16 000 frames/second) was used to record the impact response and subsequent crack propagation. From the photographic data, impact characteristics such as the contact duration and the dynamic response of the impact specimen were measured. In addition, the time of initiation of delamination propagation and measurements of the subsequent delamination length versus time were obtained. By changing the location of the embedded delamination in the specimens relative to the impact point, additional results were obtained on the variation of the threshold impact velocity necessary to cause crack propagation in the different specimen configurations. These data, together with the photographic results, suggest that the mode of crack propagation is dependent on the specimen geometry as well as the loading condition. The time dependent nature of the crack velocity and its variation with impact conditions was investigated.
A finite element program was used to calculate the dynamic strain energy release rate before the onset of crack propagation. This strain energy release rate was used to gage the instability of the delamination crack during impact.
Probabilistic Fracture Kinetics of “Natural” Composites
Authors: Krausz AS , Krausz K , Necsulescu DS 
Published: December 2008

The behavior of crack propagation in “natural” composite materials (eutectics) was investigated. It was shown that the conditions of failure should be described by a probabilistic analysis that represents correctly the physical properties, rather than by the usual deterministic approach. It is considered that the method is applicable for the failure analysis of “artificial” composite materials as well.
The environment-enhanced subcritical crack velocity, v, is represented by the appropriate kinetics combination of the elementary rate constants, ƙ, as v = f(ƙ). The rate constants are described explicitly as ƙ=kThexp(−ΔGkT)withΔG=ΔG≠−W(K) where k is the Boltzmann constant, h is Planck's constant, T is the absolute temperature, ΔG≠ is the appropriate atomic bond energy of the low- and high-strength components encountered, respectively, as the crack tip moves into the corresponding zone, W is the mechanical work in the corresponding zone, and K is the stress intensity factor.
The physical process is controlled by thermal activation; the consequence of this is that crack growth in a probabilistic process is controlled by the instantaneous state of the load-material-crack system. It is recognized that on the atomic scale, bond breaking as well as healing occurs—the equivalent of the birth-death Markovian processes of probability mathematics. The analysis defines the crack size distribution as a function of time: The expectation value of the probability distribution is the experimentally measurable average; the spread of the probability density function defines the failure time probability of the composite material. It is concluded that the probabilistic physical process leads to a significantly different, and often more dangerous, failure occurrence than what is expected from the usual deterministic analysis.
Damage Mechanics Analysis of Matrix Effects in Notched Laminates
Authors: Aronsson C-G , Bäcklund J 
Published: December 2008

The main objective of this study was to investigate the matrix influence on the fracture behavior of carbon/epoxy three-point bend specimens. The matrices investigated were a brittle Fiberite 1034 and a more ductile Fiberdux 914C epoxy matrix. For the analysis of strength and load versus displacement behavior of the specimens, a damage zone model (DZM) was used. The damage is represented by a Dugdale/Barenblatt cohesive zone, where the cohesive stresses are assumed to decrease linearly with an increased crack opening.
Excellent agreement is obtained between predicted and measured fracture loads of the specimens. Also the nonlinear load versus displacement curves are accurately reproduced by the analysis. The present model is compared with previous models, such as the inherent flaw and the point stress criteria. The damage zone extension in the brittle and ductile matrix specimens was studied and compared with the DZM calculations, as an attempt to explain the difference in fracture behavior between the brittle and ductile matrix specimens.