Showing papers in "Journal of Testing and Evaluation in 1991"

An Introduction to the Design and Behavior of Bolted Joints

Abstract: Although the title of this book includes the word “introduction”, the treatment of the subject is extensive and complete. The material goes well beyond the coverage of bolted joint design received in a typical undergraduate machine design course. The easy-to-read text begins with the fundamentals of bolt strength, deformation, and material selection and proceeds to cover the topics of preload, torque, and stretch control. The emphasis is on practical considerations for the efficient design of joints, including cost, ease of assembly, inspection, and disassembly. This second, revised edition has expanded the coverage of corrosion, fatigue, gaskets, and ultrasonic measurement of bolt strain. Also included are discussions of the failure modes and mechanisms of bolted joints. Case histories from industry are presented throughout the text to illustrate key points. Many up-to-date references are presented at the end of each chapter to allow the reader to pursue individual topics further, if desired. The text contains several appendices with useful tables and formulas for quick reference. The author has broad experience in the subject area from many years as a consultant to the power generation and nuclear industry, active participation on society working groups such as ASME and PVRC, as well as the presentation of numerous seminars on the topic. This book would serve as a valuable desk reference for engineers concerned with the design and performance of bolted joints.

Specimen Size Requirements for Fracture Toughness Testing in the Transition Region

Abstract: The article utilizes plane strain elastic-plastic finite element analysis and a local criterion for cleavage fracture to establish specimen size requirements for the ductile-brittle transition region. Critical J and CTOD values, relative to the small-scale yielding value, were predicted as a function of specimen size, strain hardening exponent, and a/W. These analyses predict an increase in the apparent toughness with decreasing specimen size due to a loss in crack tip constraint; this effect is particularly pronounced in shallow notched specimens and low hardening materials. For deeply notched bend and compact specimens, the following size requirement must be met for critical J values for cleavage to be size independent: b , B , a > 200 J c σ Y where b is ligament length, B is thickness, a is crack length, and σγ is flow stress. This criterion is eight times more severe than the size requirements in ASTM E 813-87, but it is less stringent than the requirements of ASTM E 399-83. In order for a CTOD value to be nearly size independent, it must be less than 1/300 times the relevant specimen dimensions. The constraint loss in shallow notched specimens is usually far too rapid to obtain J-controlled cleavage fracture, but the analyses presented in this article provide a means for correcting fracture toughness data for constraint loss. Predictions of the effect of a/W on toughness in the transition region agree favorably with experimental data. Future work will consider the effects of specimen thickness and ductile tearing on transition region toughness.

Normalization Method for Developing J-R Curves with the LMN Function

Abstract: The normalization method has been used to develop J-R curves directly from load versus load-line displacement data without the need for on-line crack length measurement. This method, based on the original key curve-method, used the principal of load separation and an assumed functional form for the deformation function to determine a calibration equation for each specimen being evaluated. Originally the functional form was a power law with two unknown constants. A new functional form (the LMN function) containing three unknown constants is proposed for use in the method of normalization. This function requires three calibration points, one more than was needed by the power law function. The LMN function is described in this paper, and the method for determining the three needed calibration points is given in detail. The procedure for using this new normalization method is describedin a step-by-step manner. Some results are included which show that this approach to normalization gives a J-R curve which agrees well with those developed from the elastic compliance method used in the ASTM test standards.

Experimentation and Uncertainty Analysis for Engineers

Abstract: The stated objective of this book is to present “a logical approach to experimentation through the application of uncertainty analysis.” The book is intended for upper level undergraduate and graduate courses and as a reference. Its examples and discussions are geared towards mechanical engineering problems and experiments. In addition, the book may be used as a reference for quantifying sources of error within an experimental process.

Prediction of the Strength of Ceramic Tubular Components: Part I—Analysis

Abstract: The objective of this paper is to develop the analytical background for test methodologies that will enable accurate prediction of the strength distribution of ceramic tubular components from the strength distributions of simple specimens. Four simple specimen configurations and two tubular configurations were selected for this purpose. The simple specimen configurations were (1) four-point bend, (2) C-ring tested in compression, (3) C-ring tested in tension, and (4) O-ring tested in diametral compression. In addition, a short tube tested by axially compressing rubber inside the tube and a long tube subjected to internal pressure were analyzed. These specimen configurations were for the most part selected in a tubular shape in order to simulate the shape of tubular structural components. The prediction of the strength distribution of one specimen from that of another was based on Weibull statistical theory. Effective volume and area expressions, necessary for failure prediction, were derived for these specimen configurations.

Energy stored in a specimen under fatigue limit loading conditions

Abstract: This paper presents results of measuring the energy stored in a specimen made from Ck 35 carbon steel loaded with an alternating one-directional stress whose value is equal to the fatigue limit. The energy stored in the specimen was determined in an indirect way as the difference between the mechanical energy expended in the specimen and the energy released into the surroundings as heat. The proposed technique is a modified version of the dynamic hysteresis loop method. The energy released as heat was measured with an electric modelling method. It was found that the energy stored during one cycle in a specimen loaded with a stress equal to the fatigue limit was larger than zero (i.e., with Nf→ ∝, the stored energy value theoretically also tends to infinity). To make the theory of the experiment compatible with the fundamental assumption stating that the amount of energy needed to cause fracture is constant irrespective of loading conditions, it is necessary to introduce a rheological function accounting for all reversible processes occurring in a material under cyclic loading.

Science and Engineering Indicators—1989

Abstract: Every two years the National Science Board, part of the National Science Foundation, publishes a comprehensive report containing data on the state of American science and engineering with respect to its global counterpart. This report, “Science and Engineering Indicators—1989,” is the latest edition of a widely used resource in government, industry, and academia citing trends in worldwide interest in science and engineering and the relative ranking of the United States in R&D. The report also states the strengths and weaknesses of American science and technology and gives recommendations for action.

Prediction of fatigue life of plain concrete beams from fracture tests

Abstract: A substantial amount of experimental data is presented to verify a theoretical solution for predicting the fatigue life of asphalt concrete beams from fracture tests. The theory utilizes the principles of fracture mechanics and covers the full range of loading from low to high. The raw test data extracted from a report by Majidzadeh et al. [1] include dynamic modulus, ultimate tensile strength, critical stress-intensity factor, and fatigue life of asphalt concrete beams fabricated from over 46 different mixtures, consisting of three types of asphalts, five asphalt contents, three filler asphalt ratios, and several gradations. The fracture and fatigue tests were also conducted on one asphalt concrete mix at temperatures ranging from 16 to 35°C (35 to 95°F). The agreement between theory and experiment is excellent.

Evaluation of Variability in Resilient Modulus Test Results (ASTM D 4123)

Abstract: Samples of asphalt mixture were evaluated in the laboratory under various conditions to evaluate the repeatability of the resilient modulus test and the effect of stress on the measured resilient modulus. Some samples were prepared in the laboratory, others were obtained from in-place pavements that had been subjected to traffic. The independent variables included stress, test temperature, and maximum aggregate size. Tests were repeated a number of times, and the data were analyzed by Statistical Analysis System (SAS) to investigate their repeatability. This study quantified the repeatability of the ASTM D 4123 resilient modulus test as a function of stiffness. The repeatability of ASTM D 4123 is low. A significant increase in the number of samples or number of measurements is required to improve the repeatability. Tests conducted at different stresses showed the resilient modulus to be stress sensitive. This indicated that stress should be specified in the test procedure. A correction factor was established for stresses differing from the recommended stress (15% of tensile strength) for test temperatures of 25 and 40°C.

Prediction of the Strength of Ceramic Tubular Components: Part II—Experimental Verification

Abstract: The strength distribution of reaction-bonded silicon carbide tubes that failed by internal pressurization was predicted from strength distributions obtained from simple laboratory test specimens at room temperature. The strength distributions of flexure bars, C-rings tested in tension, C-rings tested in compression, diametrally compressed O-rings, and internally pressurized short tubes were compared with the strength distribution of internally pressurized long tubes. The methodology involved application of Weibull statistics using elasticity theory to define the stress distributions in the simple specimens. The flexural specimens did not yield acceptable results, since they were ground before testing, thereby altering their flaw population in comparison with the processing-induced flaw populations of the tubular specimens. However, the short tube internal pressure test, the C-ring tested in tension, and the diametrally compressed O-ring test configurations yielded accurate strength predictions of full-scale tubular components, since these specimens more accurately represent the strength-limiting flaw population in the long tubes.

Detection, Diagnosis, and Prognosis of Rotating Machinery to Improve Reliability, Maintainability, and Readiness Through the Application of New and Innovative Techniques

Abstract: The extraordinarily long title, Detection, Diagnosis, and Prognosis of Rotating Machinery to Improve Reliability, Maintainability, and Readiness Through the Application of New and Innovative Techniques, indicates the degree of topic specialization inherent in this book. It is forty-first in a series of proceedings from the Mechanical Failures Prevention Group, an organization dating back to 1967 and primarily devoted to strategies for addressing hardware reliability problems in military, especially naval, equipment. The book consists of thirty-seven articles divided into seven sections: Detection, Diagnosis and Prognosis; Wear; Structural Damage Assessment; Signature Analysis; Monitoring Systems; Failure Mechanisms; and Artificial Intelligence and Expert Systems. This grouping of papers is one of several possible arrangements, because there were elements of some of the papers which could have made them suitable for inclusion in other categories than the ones in which they were placed. However, this kind of organizational problem is common when papers contain interdisciplinary material.

Charpy impact tests near absolute zero

Abstract: We review Charpy impact testing at extreme cryogenic temperatures, especially at liquid helium temperature (4 K), considering methods of testing and calibration, thermal behavior during the various stages of testing, and correlations between Charpy absorbed energy and quantitative toughness parameters. Because of the very low specific heats of metals near absolute zero, any surface condensation of gases, convective or conductive heat transfer, or plastic deformation during a test will cause the specimen temperature to rise rapidly. Consequently, valid impact tests of alloys at 4 K can not be performed according to the procedure outlined in ASTM Methods E 23-88. During Charpy tests, the temperature of austenitic steel specimens, initially at or near 4 K, may in fact rise outside the cryogenic regime. Fracture does not occur at the intended temperature, but at an uncontrolled temperature, since materials with different work hardening rates heat differently. In view of the temperature rise variability and scatter in measurements and property correlations, we conclude that it is not possible to accurately estimate the 4 K fracture toughness of ductile steels, or rank them properly, using Charpy tests.

Fatigue predictions for components under biaxial reversed loading

Abstract: Fatigue failure under out-of-phase loading is a fairly common type of damage mode. For the reliable design of mechanical components under such loading, there is a strong need for the development of a compatible fatigue life prediction criterion. Many multiaxial fatigue theories have been developed since the early 1900s, and most of them are limited to proportional loading cases. Although some can be extended for out-of-phase loading, additional work must be done for general applicability. In this paper, data are correlated using an empirically modified approach which attempts to be more general. Modified from Findley's formula, this approach incorporates three mathematical expressions for the effects of out-of-phase loading, mean bending stress, and mean torsional stress on fatigue behavior. The reliability of this approach is evaluated by comparing analytically predicted results with experimental data from various publications.

High temperature, tube burst test apparatus

Abstract: A testing apparatus is described that enables both single and double-ended tubular members to be tested under pressure and at elevated temperatures. For double-ended tubular members, the apparatus comprises first and second pressure seals at either end of the tubular member under test, both seals including annular compliant members that bear upon the internal surface of the tubular member. A heater is positioned within the tubular member and one of the pressure seals has an orifice through which the heater is connected to a power source. Pressurization occurs through an orifice in the other pressure seal and cooling apparatus surrounds the first and second ends of the tubular member to cool the pressure seals, thereby enabling the annular compliant members to retain their compliancy when the tubular member is heated to test temperature. For single-ended tubular members, a single pressure seal is used having pathways for both electrical and pressurization connections to the interior of the tubular member.

Powder Testing Guide: Methods of Measuring the Physical Properties of Bulk Powders

Abstract: The scope of this guide is confined to dry solids with a top size of 3 mm and with limited amounts of moisture. Electrical and thermal properties that affect fire and explosion hazards are not addressed. The author reviews many tools and techniques to measure physical properties that affect flow characteristics of bulk solids and that may cause problems during storage, transport and transfer. The author discusses in detail the wide range of test methods used to measure the flow and handling properties of bulk solids.

A Thick Adherend, Instrumented Double-Cantilever-Beam Specimen for Measuring Debonding of Adhesive Joints

Abstract: An inexpensive test method for evaluating the debond resistance of adhesive joints is described. A double-cantilever-beam specimen is used, and a strain gage is mounted on the unbonded portion of one adherend. When a fixed displacement is applied to the end of the specimen, the strain gage output along with the specimen compliance and the amount of fixed displacement at the end of the specimen are used to calculate the crack length, a, and the sustainable crack driving force, G, at the time the gage is read.

Accuracy of a Volume Fraction Measurement Using Areal Image Analysis

Abstract: The method of interval estimation is used to determine the accuracy of a volume fraction measurement obtained from an areal image analysis of a series of images. The accuracy is found to depend upon the average number of objects found in each section and the number of sections that are analyzed. The method can be applied to completed measurements on a set of two-dimensional sections to estimate the error in the result. Or, the method can be used before making any measurements to select the number of sections and the size of each section for a desired accuracy.

Analysis of Gas-Fired Ceramic Radiant Tubes During Transient Heating: Part I—Thermal Transient Modeling

Abstract: Low profile thermocouples were used to measure the external transient temperature distributions on open-ended silicon carbide radiant tubes during cold-start heating. The measured tube and furnace temperatures were used with radiant exchange relationships for gray-diffuse surfaces and natural convection formulations to calculate quasi-static effective heat transfer coefficients along the length of the tubes. Finite-element analysis was then used with the effective heat transfer coefficients to calculate the transient temperature distribution throughout the tube. Results indicate relatively mild radial temperature distributions during the heating conditions studied and the applicability of the analysis to different tube geometries and burner systems.

Time-Saver Standards for Building Types: 3rd Edition

Abstract: The 1st Edition of Time-Saver Standards for Building Types has been an important part of my professional library since its publication in 1973. As stated in its preface: “It is intended to give basic design criteria for each major type of building. It will give those unfamiliar with a specific building type a talking or working knowledge of its functions, organization, and major components.” Over the years, I have referred to Time-Saver frequently for planning and design guidelines for building types such as gymnasiums, airport terminals, and police stations. But as the 1st Edition is now 17 years old and much of it is based on other even older versions of Time-Saver Standards, I have begunto find the book inadequate for contemporary design practice.The past two decades have been a period of profound change for building planning and design. Many building requirements have changed and entire new categories of buildings have evolved. It was with enthusiasm that I looked forward to the 3rd Edition; which the publisher promised would be “revised, expanded, and completely brought up to date.” I am greatly disappointed with the result. While the 3rd Edition has been expanded to approximately 1400 pages, nearly a third more than the 1st Edition, little of the original material has been revised and the updating has been insufficient.

Effect of Thickness on Elasto-Plastic Deformation and Hysteretic Energy Dissipated at Crack Tip

Abstract: A study was carried out to verify the influence of thickness on elasto-plastic deformation and the hysteretic energy dissipated at the crack tip. The analysis is based on global energy and local strain measurements that are made on 4,12, and 30 mm thick compact tension specimens. A discussion of fatigue crack growth in the plane stress and plane strain states is presented. The tests were conducted under constant ΔK at R = 0.1 and 0.5 on 2024-T351 aluminum alloy. Experimental results were compared with those obtained from linear elastic fracture mechanics and finite element methods.

Improved Wide Range Expressions for Displacements and Inverse Displacements for Standard Fracture Toughness Specimens

Abstract: Wide range expressions (interpolating polynomials) for displacements for standard ASTM fracture testing specimens have been developed. The strategy was to fit displacements as a function of crack length for all the specimens using a similar form of nondimensional displacement. Different forms appear in different ASTM standards for the same or similar specimens. The criterion used to establish the degree of polynomial fit and number of significant figures for the coefficients of the polynomial was for the polynomial to agree with the best available numerical displacement solutions to within 1% or better. Once the polynomials for displacement as a function of crack length were developed, inverted forms of the specific interpolating polynomials were obtained to determine relative crack length (a/W) as a function of displacement. Since the inverted polynomial will be used in tandem with the interpolating polynomial, the inverted polynomial was fit to the interpolating polynomial and not the numerical solution for displacement. Three forms of nondimensional displacements were used to invert the interpolating polynomials. The criterion used to establish the degree of polynomial and the number of significant figures of the coefficients of the polynomial was for the predicted relative crack length to agree with the actual relative crack depth to within 0.0005W. A sensitivity analysis was performed to suggest which form of interpolating polynomial should be used for standards.

A novel specimen geometry for double shear creep experiments

Abstract: A new specimen geometry has been developed to reduce the stress concentrations at the ends of the gage section in double shear creep specimens. The purpose of the geometry is to reduce the tendency for crack formation at the gage section ends when testing creep brittle materials. A comparison of creep data indicates that the sharp corners at the ends of the gage sections of the conventional geometry has a negligible effect on the steady-state creep behavior. The results also suggest that, when a nonuniform gage section is used, the stresses redistribute during primary creep such that steady-state flow is driven by the mean shear stress over the entire gage section.

Nondestructive density measurements of cylindrical specimens by gamma-ray attenuation

Abstract: Nondestructive density measurement of cylindrical specimens in the laboratory has several important applications. Many specimens in civil engineering laboratory testing are usually in the form of cylinders; undisturbed soil samples and field cores of concrete and asphaltic materials are primary examples. This paper describes a nondestructive laboratory technique for density measurement that can achieve a 95% confidence limit on the order of ± 0.01 g/cm3 for a useful range of density from 0.8 to 2.7 g/cm3, relevant to the above materials. The technique uses a 5 milliCurie (mCi) Cesium 137 source with a scintillation detector and counter assembly to record the radiation transmitted through the specimen. This is converted to a density value by calibration to an empirical radiation attenuation law. The principles of the method are described with consideration to the variables of the measuring system and the specimen geometry. It is shown that for solid cylindrical specimens of the materials tested, the radiation attenuation law is satisfied to a very high degree. From the law, a diameter ratio to count ratio relationship is established. Thus detailed calibration is only necessary for specimens of one diameter to determine the density of specimens of other diameters.

Predicting the durability of paving bricks

Abstract: The pore size distributions of approximately 110 bricks removed from existing pavements were measured using mercury intrusion. These distributions were used to calculate a Durability Factor using the method of Maage. This Durability Factor was then correlated with the observed durability performance of the pavements. It was found that all bricks with a Durability Factor greater than 90 exhibited no freeze/thaw durability problems. Further, with very few exceptions, all bricks with a Durability Factor less than 90 were suffering freeze/thaw failures. This procedure is both more accurate and faster for selecting potentially durable bricks than the current use of absorption measurements.

Analysis of the size effect in low-load hardness testing of metals

Abstract: Recent accounts of Vickers hardness tests in which the variation of hardness values with indentation size was suppressed by lubrication are re-examined to elucidate the nature of the size effect. It is shown that a simple constant error in either the measured indentation size or the force actually exerted would not explain the effect. A good description of the effect is obtained by reference to an indentation-size-dependent load error which is sensitive to both friction conditions and the plastic properties of the test material.

Design and Analysis of Jaw Crusher Gouging Abrasion Tests

Abstract: ASTM Standard Practice G 81-83 describes a laboratory procedure for determining the relative gouging abrasion resistance of materials in a jaw crusher. The authors have found a number of problems associated with the test procedure, particularly in respect of its inefficiency, the fact that it yields biased estimates of the wear parameter, and its lack of facility for assessing the significance of differences between test results. An alternative methodology for conducting the tests and for analyzing the data is proposed, and it is shown, by example, how substantially more information can be obtained from tests results than has hitherto been demonstrated.

A Cantilever-Type Bend Test Technique for Formability Analysis of Strip/Plate Metals

Abstract: The minimum bend radius-to-thickness ratio (R/t), determined by the conventional 90° bend test for strip materials, has been found insensitive to changes in formability of Cu-Be-Co alloys with thermo-mechanical treatment. In an attempt to improve the 90° bend tests, an alternating-current potential drop (ACPD) measurement technique was incorporated. The ACPD modification was successful in monitoring the onset of crack formation under laboratory conditions, but it is considered unsuitable for more widespread use such as in quality control. A new cantilever-type bend test apparatus has been designed and used to measure the maximum bend angle, θM, at which the sample cracks during bending in angular rotation up to 135°. The reproducibility of the apparatus was good and the sensitivity such that changes in θM as small as 3 to 4° could be detected. The θM value was found to be dependent on sample thickness. However, a thickness correction procedure, which was developed from an analytical model, allowed a corrected maximum bending angle, θCM, to be easily calculated. The θCM data have been successfully used to investigate the effect on bendability of thermo-mechanical treatment of Cu-Be-Co alloys and of both testing orientation and thermo-mechanical treatment on Al-Mg-Mn alloys. Results from Al-Mg-Mn alloys have shown that the apparatus is capable of testing samples with thicknesses up to 5 mm.

Application of the European Yield Model to Nailed Joints in Southern Hardwoods

Abstract: A study was conducted which utilized data obtained from 1056 tests of nailed joints in 18 commonly used species of southern hardwoods. The data was developed in 1950 by Scholten. This data included information regarding joint geometry, material specific gravity, discrete load-slip curves, and the ultimate load for each joint. The test specimens were laterally loaded and contained one 8d common wire nail in each joint. Joints were tested in compression at a rate of 0.07 in./min (1.78 mm/min) to ultimate load. With a British model to predict wood embedding strength from specific gravity and nail diameter, and an estimate of nail yield strength,the European Yield Model was employed to predict the failure mode and yield load of the joints. Failure modes which create one or two theoretical plastic hinges in the nail were predicted for all joints. The data suggested that behavior modes of the joints were consistent with model predictions. Further, theoretical nail yield load showed a high correlation (r2 = 0.90) with the experimentally obtained load at 0.015 in. (0.381 mm) slip, 5% offset load, and ultimate load (joint capacity).

Test Apparatus for Simulating Interactive Loads on Metal Plate Wood Connections

Abstract: A method was needed to test metal plate connector joints in combined tension and bending. This required the development of special test grips as well as test and analytical procedures. This paper discusses the design and evaluation of an apparatus for testing metal plate connector joints in nominal 2 by 4 in. (standard 38 by 89 mm) lumber. This apparatus can be easily fabricated and adapted to several testing machines.

Static and Impact Flexural Properties of Common Wire Nails

Abstract: To implement yield theory into design specifications for engineered nailed connections, some practical estimates of nail yield strength and other properties are needed. This short-term study sampled 1170 nails in five sizes from four locations in the United States. Twelve different manufacturers were represented in the sample. All nails were tested in centerpoint bending and their mechanical properties were determined. MIBANT angle, commonly used for quality control in the pallet nail industry, was also measured. The results showed that: (a) The pennyweight system of classification is inadequate for identifying nail properties for engineering purposes. (b) Nail yield stress decreases as diameter increases, but elastic modulus is reasonably constant. (c) Variation in yield stress between manufacturers is less than 13% coefficient of variation (COV) for any one size nail, which is generally much greater than the variation found for samples from an individual manufacturer. (d) A normalized MIBANT angle may provide a way to insure a minimal level of nail quality for engineering purposes, but additional research is needed.