bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison and Evaluation of Tests for Coarse Aggregate Particle Shape, Angularity, and Surface Texture
Authors: Hossain MS , Parker F , Kandhal PS
Published: February 2009

Particle shape, angularity, and surface texture are critical properties in assessing aggregate usage for asphalt concrete. Fractured and flat and/or elongated particles are used in most specifications to assure quality. The particle index and uncompacted void tests indirectly measure particle shape, angularity, and surface texture and offer alternative options. Several methods were used to test crushed gravels and crushed stones. Test results were compared and evaluated. Fractured and flat and/or elongated particle tests are somewhat subjective for evaluating aggregate structural quality. The basis for determining percentages (mass or particle count) for fractured faces did not make any difference. However, the basis (mass or particle count) for computing percentages of particles with particular dimensional ratios (flat and/or elongated) should be clearly stated in specifications since the results are distinctly different. Procedures in ASTM D 4791 contain two methods for assessing particle shape, i.e., flat or elongated particles and flat and elongated particles. Percentages of flat and elongated are larger than flat or elongated.

Particle index (ASTM D 3398) and uncompacted void (proposed) tests provide comparable measures of aggregate particle shape, angularity, and surface texture. They are somewhat more analytical and precise than the “fractured particle” and “flat and/or elongated” tests. Flat and/or elongated particles have a contrary influence on the assessment of aggregate quality with particle index and uncompacted voids. Flat and/or elongated particles are generally thought undesirable, but increase both particle index and uncompacted voids, which is generally thought desirable.
The Effect of Load and Crack Misalignment on Stress Intensity Factors for Bend-Type Fracture Toughness Specimens
Authors: Baratta FI , Fett T
Published: February 2009

Mode I and Mode II stress intensity factors (SIF) are presented for three-point bend specimens with misaligned locations of loadings and cracks. Such stress intensity factors were obtained through the application of the weight function technique and the particular stress distribution applicable to a three-point eccentrically loaded beam. Mode I and Mode II stress intensity factors for an eccentrically loaded four-point beam having a misaligned crack were obtained by superposing the data applicable to the load and crack on a misaligned three-point loaded beam. The results of these analyses were then employed to evaluate the effect of load and crack misalignment on Mode I and Mode II stress intensities of specimen configurations included in ASTM E 399 for Plane-Strain Fracture Toughness of Metallic Materials and in ASTM C 1421-99 for the Determination of Fracture Toughness of Advanced Ceramics at Ambient Temperature. The SIF ratios for Mode II-to-Mode I were also determined for both the eccentrically loaded three-point beam and the four-point beam having misaligned cracks. Differences in the Mode I stress intensities were determined for the cases where the load and crack misalignments are taken into account and those idealized cases where they are not. Finally, recommendations are presented to reduce, where necessary, these differences to an acceptable degree.
Extension and Evaluation of Fatigue Model for Product Shock Fragility Used in Package Design
Authors: Burgess G
Published: February 2009

Earlier work that incorporated fatigue into the description of the shock fragility of products is expanded to include more sophisticated models of failure. The robust nature of the original model, which treats fragile interior components as single-degree-of-freedom spring/mass systems deforming in an elastic/perfectly plastic manner under dynamic loading, is demonstrated in three ways. The first compares the model predictions with experimental results, which include the generic findings referenced in an ASTM standard. The second and third are based on comparisons with an exact analysis of elastic/linear plastic springs and an approximate analysis of the most general model possible.
Dynamic Shear Modulus and Damping in Iron-Copper and Steel-Based Metal Matrix Composites
Authors: Wolfenden A , Hodge JQ
Published: February 2009

Measurements were made of the density, dynamic shear modulus, damping, strain amplitude, and resistivity in iron-copper and steel-based metal matrix composites. The density was determined using the Archimedes method and was found to be in the range of 7463 to 8257 kg/m3. The shear modulus, damping, and strain amplitude were determined using the piezoelectric ultrasonic composite oscillator technique (PUCOT). The shear modulus was in the range of 73 to 81 GPa. Electrical resistivity measurements were performed to assess the change in the conductivity of the composites by adding copper. Metallographic studies and microhardness testing were performed to assess the distribution and hardness of the fibers in the composites. The variation of shear modulus and electrical conductivity with respect to the percentage of copper in some of the composites followed the rule of mixtures. The damping in the specimens was near 3 × 10-3 and independent of strain amplitude.
Characterization of Mechanical Properties in Surface-Treated Materials
Authors: Batista AC , Dias AM
Published: February 2009

An experimental methodology was developed for identification of mechanical behavior laws, in which the evolution of the stresses and strains in the surface of the samples is determined by X-ray diffraction and electric resistance strain gages, respectively, as a function of the loading in four-point bending tests. The determined stress-strain curve is then characteristic of the near-surface layers of the samples. The method was validated for different steels by comparing the results of samples with homogeneous properties on the cross section with the results of tension tests. The developed methodology was applied to the study of steel samples submitted to surface treatments, presenting gradients of chemical composition, microstructure, and mechanical properties from the surface to the bulk material.
A Novel Instrument for Automated Principal Strain Separation in Reflection Photoelasticity
Authors: Pacey MN , Haake SJ , Patterson EA
Published: February 2009

A novel instrument is presented capable of measuring the principal strains at a point on a photoelastic coating. The oblique incidence method of principal strain separation is employed, using three fringe order measurements, which are made by the automated method known as spectral contents analysis. The oblique incidence measurements are made after rotation of the polariscope about any two orthogonal axes. Three polariscopes are built into the instrument, as is a CCD camera, to facilitate accurate positioning of the instrument. The instrument was used to analyze the principal strain distributions in a disk under diametrical compression, a plate with a central hole under tension, and a stepped plate in tension. The strains in the disk and the plate with a hole were compared with theoretical results, and the strains in the stepped plate were compared with a finite element analysis of the problem. The correlation between the experimental and theoretical or numerical strains was better than 0.95 in most cases.
Low-Cycle Fatigue Characteristics of Precipitation-Hardened Superalloys at Cryogenic Temperatures
Authors: Suzuki N
Published: February 2009

In order to examine the axial-strain-controlled low-cycle fatigue characteristics of precipitation-hardened superalloys at cryogenic temperatures, Ni-base alloy Inconel 718 and iron-base alloy A286 were selected as superalloys for cryogenic use. Low-cycle fatigue characteristics of these alloys including the weld were investigated at 300, 77, and 4 K, in order to clarify the relation between mechanical properties and fatigue strength, especially in the high-cycle fatigue life regime. As for Inconel 718, the modified alloy improving the weldability and manufacturing of large-sized ingots was used. The tests clarified that fatigue strength of both alloys increases with decreasing temperature on the basis of a relation between total strain range and fatigue life (Nƒ). However, even though apparent stress amplitudes are normalized by 0.2% yield strength at the same temperatures, the fatigue strength of these alloys was found to decrease with the increase of temperature in the high Nƒ regime. Taking 105 cycles as a typical fatigue life in the high Nƒ regime and adjusting the data for the relation between normalized apparent stress amplitude at 105 cycles and 0.2% yield strength, including the reference data of 300-series stainless steels, it was made clear that the higher the static strength of the alloy with stable austenite, the relatively lower the fatigue strength in the high Nƒ regime tends to be, when it is normalized by 0.2% yield strength at the same temperatures. Further, focusing on the alloys with stable austenite at 4 K, the relation between normalized apparent stress amplitude at 105 cycles and 0.2% yield strength was generally characterized, and an upper bound of 0.2% yield strength for providing apparent stress amplitude value at a fatigue life of 105 cycles, which is larger than 0.2% yield strength, was established.
Development of a Machine for Closely Controlled Rolling Contact Fatigue and Wear Testing
Authors: Fletcher DI , Beynon JH
Published: February 2009

In order to gain detailed insight into the processes taking place during rolling contact fatigue (RCF) and rolling contact wear, the test machine used must be closely controllable and offer comprehensive data collection facilities. This paper describes a machine that has been developed to offer these facilities over a wide range of test conditions, and that has the facility for the early detection of cracks by an eddy current method.

An existing twin-disk contact simulation machine has been comprehensively updated to enhance the range of tests possible and, most importantly, to offer close control over very short numbers of machine cycles, allowing the very early stages of the development of fatigue cracks and wear damage to be examined. Results of tests to examine the capabilities of the rebuilt machine and a study of the repeatability of results under two particular test conditions are presented.
Experimental Study of Residual Stress Distributions in Quenched Parts by the Incremental Large Hole Drilling Method and by the Neutron Diffraction Method
Authors: Yazdi SR , Retraint D , Lu J
Published: February 2009

The incremental hole-drilling method has been used to measure the residual stress field in a quenched part. In quenched parts, there is great compressive residual stress at the surface and tensile residual stress in the middle of the part, so in this case we used an unusually large hole diameter. The classical rosette system cannot be used. The rosette we studied is made up of six strain gages that are placed in a circle with a diameter two times the hole diameter. This system can be adapted to any chosen hole diameter. An error estimation about the positions of the gages has been developed. This procedure is based on a statistical study of measured strains by the six gages. To learn the validity of the incremental large hole drilling and to obtain the complete residual stress field through the thickness of the part, the neutron diffraction method has been used as well. This second method, however, is time consuming and expensive.

The aim of this study is to integrate the residual stress field due to quenching into a fatigue life calculation. As is known, only the compressive residual stress field influences the fatigue life, so in the case of quenched parts only the part depth with compressive residual stress need be studied.

The quenching of the studied part has been modeled by the finite element method. All the experimental results have been compared to numerical results.
Exterior Insulation and Finish Systems (EIFS) Use in Wood-Framed Residential Construction: Design Concepts to Avoid Common Moisture Instrusion Problems
Authors: Bronski MB , Ruggiero SS
Published: February 2009

During our field observations and water tests of wood-framed houses in North Carolina that are clad with EIFS, we noted common features in their exterior wall construction that caused significant deterioration to the sheathing and stud wall framing. For several reasons, these problems would be less severe or absent if the houses were clad with traditional residential wall systems (i.e., wood shingles or clapboards, brick veneer, or traditional stucco).

To define the design “problem” we review issues relevant to the performance of surface-sealed barrier EIFS including common sources of moisture intrusion, the potential for moisture entrapment within the wall system, i.e., the lack of drying capacity of the wall, and the moisture sensitivity of various substrates. We focus on presenting suggestions for resolving the problems and designing a functional EIF system for use on moisture-sensitive substrates such as wood-framed construction, with particular attention to structures in climates with heavy rainfall and high humidity.
Diagnostic Scores for Interlaboratory Study Data
Authors: Proctor CH
Published: February 2009

The primary goal of an interlaboratory study (ILS), or of a collaborative study as it is also called, is to verify that a measurement method will work over many testing or analytic laboratories. The data produced and the calculations of the precision statement are well established in statistical standards. We suggest some calculations beyond the precision statement to deal with detecting laboratory and data point outliers. These calculations, as suggested by Mandel, were designed to mesh with those of the precision statement but to be applied when the data first arrive back to the study director. We apply these calculations to 11 sets of ILS data from a variety of test methods and show how to read the results for indications of problems with the test method and for locating deviant laboratories.
Cyclic Loading and Creep of Intracranial Aneurysm Clips
Authors: Woods TO
Published: February 2009

Intracranial aneurysm clips are used to clamp closed a portion of a blood vessel in order to prevent the rupture of cerebrovascular aneurysms. After implantation, the clips are subjected to stress, produced by the clamped tissue, in a corrosive environment. Aneurysm clips can fail by fracture or by loosening and slippage, and a failure can result in death if the aneurysm ruptures. Previous research has shown that the force required to open an aneurysm clip may decrease with repeated openings. The influence of repeated loadings on the ultimate survivability of the clip is not known. Factors such as creep and stress relaxation, which may cause a clip to loosen or slip after implantation, have not been studied. Standard test methods do not address these performance characteristics. The objective of this research is to develop test methods to investigate the cyclic load-displacement and creep behavior of intracranial aneurysm clips in both air and a simulated physiologic environment. Results of testing aneurysm clips with three spring geometries are given.
Estimation of Particle Size Distribution in Materials in the Case of Spheroidal Particles Using Quantitative Microscopy
Authors: Hashimoto A , Miyazaki T , Kang H , Noguchi H , Ogi K
Published: February 2009

In this paper, an estimation method is proposed for the size distribution of particles in materials. The configuration of particles is assumed to be spheroidal and all observed information is gathered from cutting planes. The apparent size distribution measured from 2D is corrected to the 3D true size distribution, then the expected size distribution can be estimated from a small size up to an extreme size. This estimation method is most versatile, and involves Saltycov's method and extreme statistics at the same time. The procedure is applied to an artificial material with a given particle size distribution in computer simulation in order to examine its validity. The estimated results are compared with the given distribution, and the validity of the method is confirmed.
Finite Element Analysis and Small Punch Testing for Determining the Cryogenic Fracture Toughness of Austenitic Stainless Steel Welds
Authors: Shindo Y , Horiguchi K , Sugo T , Mano Y
Published: February 2009

The small punch (SP) test has been used successfully to characterize the elastic-plastic fracture toughness (JIC) of structural alloys and weldments for superconducting magnets in fusion energy systems with thin plate specimens of 10 by 10 by 0.5 mm. This study was performed to demonstrate the feasibility of performing SP tests on austenitic stainless steels and their welds at liq uid helium temperature (4 K). Correlations between SP energy, equivalent fracture strain, and JIC were assessed. All JIC data were obtained using 25 mm thick compact specimens that followed the standard test method for JIC. A finite element analysis was also performed to convert the experimentally measured load-displacement data into useful engineering information. The maximum strain en ergy density was calculated and correlated with JIC.
Experimental Evaluation of the Dynamic Shear Strength of Adhesive-Bonded Lap Joints
Authors: Srivastava V , Shukla A , Parameswaran V
Published: February 2009

An experimental method utilizing a novel specimen geometry was developed to determine dynamic shear strength of adhesive-bonded lap joints using the classical Split Hopkinson Pressure Bar (SHPB) technique in compression. The specimens were loaded dynamically at four different loading rates, and the transmitted load through the joint was obtained from the time-resolved strain history assuming one-dimensional stress wave propagation. The shear strength of the joint was determined from the maximum transmitted load, assuming the load was transferred predominantly as shear load through the adhesive-bonded joint. The shear strength of a lap joint bonded using a general purpose epoxy adhesive was obtained at loading rates varying from quasi-static to 2300 N/µs. The results indicate that as the loading rates are increased to 1000 N/µs the shear strength of the particular adhesivebonded lap joint increases to three times its static value, after which it stabilizes.
Effects of Fixturing Mass on Dynamic Strain Errors in Structural Fatigue Testing
Authors: Hewitt RL
Published: February 2009

Improvements in control systems have allowed significant increases in testing frequencies for full-scale aircraft structural fatigue tests. This means that it is possible to be testing at frequencies that result in significant dynamic strains, with consequent over-testing.

This paper presents an analysis of a simple cantilever beam as a representation of a test on an aircraft wing. Using a state space formulation and the MatLab mathematical programming system, comparisons between static and dynamic strains for various locations on the beam are made for a variety of loading arrangements.

It is shown that significant dynamic strain errors will occur at testing frequencies above about 10% of the first natural frequency of the specimen itself. The errors can increase significantly due to the mass of the fixturing, and are further exacerbated by static counterbalancing.
A Comparison of Two Methods for Measuring Light Scattered from Aerospace Transparencies
Authors: Marasco PL
Published: February 2009

ASTM D 1003 is often used to characterize light scattered (haze) from aerospace transparencies. However, due to the strong angular dependence of light scattered from these materials, information gathered using ASTM D 1003 is limited in determining the effect of scatter on visual performance. Another technique, one capable of measuring scattered light as a function of observation angle and illumination angle similar to ASTM E 167, is more time consuming to perform but yields information that may be better suited to visual modeling. Even though the techniques are considerably different, it is possible to compare measurements made on several samples using these two methods. This paper compares the results of measurements made using both test procedures on a number of transparent parts.
Optimum Lime Content for Fly Ashes and the Role of the Curing Period
Authors: Sivapullaiah PV , Prashanth JP , Sridharan A
Published: February 2009

The determination of the optimum lime content of fly ash is very important to enhance its use. Recently, methods have been established to obtain the optimum lime content of fly ashes. Strength obtained at different ages becomes important for different applications. The effect of the curing period on the optimum lime content of fly ashes is not established, nor are methods available for obtaining the same. Based on detailed strength tests on different fly ashes with various lime contents after curing for different periods, it has been established that the effect of the curing period becomes important for optimum lime content of certain fly ashes depending upon their chemical composition. The optimum lime content corresponds to the production of a maximum amount of calcium silicate hydrate compounds of Type I. In addition to the strength test, the sediment volume test has also been used to study the effect of the curing period on the optimum lime content of the fly ashes. Both methods compared well and hence the simpler free swell sediment volume test may be adopted.
Consolidation Behavior of Bentonite in Electrolyte Solutions
Authors: Sivapullaiah PV , Savitha S
Published: February 2009

Volume change behavior of clays in different pore fluids is very important in their use as compacted clay liners for landfills. The present study brings out the variations in the consolidation behavior of bentonite compacted at Proctor's optimum conditions in different electrolyte solutions. Qualitatively the behavior can be explained using diffuse double layer theory. Existing methods to calculate theoretically e-log p curves based on this theory have been referred to the theoretical curves that agree closely with experimental curves. Clay properties, which are critical in the theoretical prediction of the curves, have been identified. However, the effect of potassium ions, which link bentonite clay particles, cannot be assessed by diffuse double layer theory.
Automatic Field Permeameter for Drainage Properties of Porous Asphalt Mixes
Authors: Tan SA , Fwa TF , Chuai CT
Published: February 2009

A new automatic field permeameter was designed to measure the in situ permeability of porous asphalt roads under field testing conditions. This apparatus works on the falling head principle; the falling head with time is measured through a porous road slab with a precise pressure transducer at the base of the apparatus at very close intervals of 100 (Hz) data points/s. With the falling head data, the specific discharge (υ) can be computed and plotted against the hydraulic gradient (ip1); the 3D flow permeability of the material is obtained at ip1>=1. The falling head data are shown to agree with constant head test data and are independent of the initial head at the start of the test. This demonstrates the repeatability of test measurements and the reliability of the test method, as it agrees very well with the wellaccepted constant head measurements. However, direct 1D permeability measurements of vertical and horizontal cored specimens from tested slabs showed the influence of permeability anisotropy on test results. Therefore, to make the 3D measurements useful for practical applications, a correction factor accounting for the effects of anisotropy, thickness, and size of slab on the test interpretation of the k value is obtained from a comprehensive finite element study, which allows for conversion from the 3D permeability to the effective 1D isotropic permeability. This is validated from the results of 14 porous test slabs (3 asphalt mixes and 1 portland cement concrete mix) where independent measurements of the 3D as well as the 1D horizontal and vertical permeabilities have been made, and excellent agreement is obtained when compared to finite element results.
On the Determination of JIC Using the Stretch Zone Width Method
Authors: Suresh RKV , Ramakrishnan N , Srinivas M , Ramarao P
Published: February 2009

The stretch zone width (SZW=1∕2CTOD, the crack tip opening displacement) method for determining JIC involves fewer specimens and lesser size restrictions compared to the con ventional J-R curve method. However, the accuracy of the SZW-based procedure depends on each term of the J-CTOD relationship, i.e., JIC=m∙σ∙CTODC. This paper presents a numerical investigation of the J-CTOD relationship, which has been carried out using a large-deformation finite element method (FEM). The slope of the blunting line (m) is computed for various combinations of yield strength-to-elastic modulus ratio (σo∕E), power law strain-hardening exponent (n), and different measures of stress (σ in the J-CTOD relationship). This work brings out the importance of the correct choice of the stress measure, and the one suggested here is the integral average of the flow stress [σ*=∫0ε*σdε/∫0ε*dε]. Also, an effective CTOD approach is numerically validated where a sharp fatigue precrack of fracture specimens can be substituted by one with a finite notch root radius without loss of accuracy in JIC.
Interlaboratory “Pilot Run” Study of Small Heat-Flow-Meter Apparatus for ASTM C 518
Authors: Zarr RR , Lagergren ES
Published: February 2009

Thermal conductivity measurements of a high-density glass-fiber thermal insulation material near 24°C are presented for the determination of the precision and bias of ASTM Test Method C 518. The measurements have been conducted by 13 laboratories using small (305 by 305-mm) heat-flow-meter apparatus on three specimens of high-density glass-fiber thermal insulation material that were circulated among the laboratories. Test results are analyzed using ASTM Practice E 691 and subsequently compared to measurements of the same specimens conducted in a guardedhot-plate apparatus using ASTM Test Method C 177. The 95% repeatability and reproducibility indexes for precision have been determined to be no worse than 1.1 and 4.0%, respectively. A method for estimating bias is presented.
Effects of Silica Fume and Steel Fibers on Some Mechanical Properties of High-Strength Fiber-Reinforced Concrete
Authors: Eren Ö , Marar K , Çelik T
Published: February 2009

There are many test methods to measure the impact resistance of fiber-reinforced concrete that are complicated, time consuming, and expensive. A practical test method has been developed to measure the impact resistance of high-strength fiber-reinforced concrete (HSFRC). The equipment developed can also be used for testing aggregate impact values by simply changing the base plate of the machine. A machine was developed to measure the surface abrasion resistance of HSFRC. Testing fiber-reinforced concrete for surface abrasion resistance was found to be extremely difficult if realistic and practical results were desired. In this study the influence of silica fume on the properties of HSFRC was investigated by using silica fume at two different percentages and with three different hooked-end fibers, namely, 30/0.50, 60/0.80, and 50/0.60 length/diameter (mm/mm). Fibers were added to concrete in three different percentages of 0.5, 1.0, and 2.0% by volume of concrete. The results show that including fibers in high-strength concrete improves impact resistance, surface abrasion, and splitting tensile strength.
General Constitutive Relations of Anorthotropic 6061-T6 Aluminum and Its Fatigue Life under Proportional and Non-Proportional Loadings
Authors: Nayeb-Hashemi H , Lin H
Published: February 2009

Anisotropic constitutive relations with respect to the principal axes of an orthotropic solid are formulated using the macroscopic continuum plasticity theory of Shih and Lee. The general anisotropic constitutive relations are derived for predicting the plastic deformation behavior of a new material orientation. Straincontrolled cyclic tests were conducted along the 45° direction in the plane of the plate to verify the general anisotropic constitutive relations. The predictions agree very well with the experimental yield and plastic flow behavior. The axial-torsional coupling terms in the general constitutive relations are also determined and explained.

The constitutive equations were used to predict the low-cycle fatigue life of this material under both proportional and non-proportional loadings. An anisotropic shear cracking model, developed earlier, provided a good prediction of the fatigue life of this material under both proportional and non-proportional loadings.
Reference Verification Fluids for Flash Point Determination
Authors: Montemayor RG , Rogerson JE , Colbert JC , Schiller SB
Published: February 2009

The flash point of a liquid material is used to classify whether the material is flammable or combustible. 1,4-dimethylbenzene (p-xylene) has been used historically to verify the proper operation of different flash point test equipment. Because of the toxicity and low flash point value of 1,4-dimethylbenzene, an interlaboratory study was conducted to determine alternate flash point reference standards. This study reports the flash points of n-decane, n-undecane, n-tetradecane, and n-hexadecane using various flash point test methods. The flash points of these materials were found to be testmethod dependent because of the inherent differences in the various flash point test methods. The reported reference flash point values of these materials are now used to verify the proper operation of flash point test equipment in place of 1,4-dimethylbenzene.
Explaining the Hveem Stabilometer Test: RelatingR-value,S-value, and the Elastic Modulus
Authors: Chua KM , Tenison J
Published: February 2009

The Hveem stabilometer is used by several states to obtain materials characteristics for designing pavements. This paper presents equations that relate the Hveem stabilometer R-value and S-value with the elastic modulus. It is shown that the elastic modulus is dependent on the following: the R- or S-value, the exudation pressure, the overconsolidation ratio, the Poisson's ratio, and the angle of internal friction of the material. It is also shown how the compaction pressure might affect the calculation if the material is time-dependent or viscoelastic. An example problem is provided to show how to calculate the elastic modulus using these pertinent factors. Typical laboratory test data are also presented to demonstrate the relationship between the R-value and the elastic modulus for three different highway soil materials. It is shown that the exudation pressure is indicative of the moisture content of the test samples. The R-value and elastic modulus are shown to be quite sensitive to the moisture content.
The Determination of JIc Using the Time-Frequency Analysis Method
Authors: Ahn S-H , Nam K-W
Published: February 2009

Elastic-plastic fracture toughness, JIc, can be used as an effective design criterion. Among the JIc test methods approved by ASTM, the unloading compliance method has been used in this paper. In order to examine the relationship between the fracture behavior of the JIc test and acoustic emission (AE) signals, the post processing of AE signals was carried out by a joint time-frequency analysis method, i.e., the fast Fourier transform. The objective of this study is to evaluate the application of the characterization of AE signals for the unloading compliance method of the JIc test. Using a time-frequency analysis, AE signals can be extracted from the raw signal and be analyzed at the same time. The AE signal generated in the elastic-plastic fracture of material shows different aspects in the elastic and the plastic range or at the first portion of the crack growth by fracture. For example, energy obtained from the AE count method increases rapidly at the beginning of the plastic fracture. The elastic-plastic fracture of the material can be analyzed using real time AE characteristics.
Fracture Toughness of Thin Polymer Films Using Miniature Specimens
Authors: Bose WW , Landes JD
Published: February 2009

Thin polymer films were tested to determine fracture toughness. This was done to provide a measure of the resistance of the materials to crack-related damage and as a method for material evaluation and selection. The films tested were of a transparent polymeric material and were in the range of 0.03–0.10 mm thick. The testing procedures required to determine the fracture toughness for these materials were new, so several aspects of the testing had to be developed. These included the design and machining of appropriate specimens, the test setup and fixtures needed, and the method of data evaluation. This paper describes the procedures used to do this. The development work was done on a model material, 3M transparency overhead film for copiers. Most of the results presented here are for that material.
Evaluation of the Mean Plastic Strain Ratio rm of Metallic Sheets Prestrained Along Different Biaxial Strain Paths
Authors: Vankudre HV , Date PP
Published: February 2009

ASTM standards are widely used to determine the plastic strain ratio r to characterize the normal anisotropy and the planar anisotropy of sheet metal. The values determined by mechanical testing are quoted at a strain of 15%. These are used for comparing two techniques of measuring the plastic strain ratio or the anisotropy of two materials.

The present work reports the variation in the plastic strain ratio of prestrained material. The r values of biaxially prestrained steel sheet have been investigated using the ASTM as well as the magnetostrictive methods of measurement. An error analysis on the mechanical measurements has been performed to examine the agreement between the different definitions of the plastic strain ratio (rr, rint, rt, and rmx1) and the accuracy (based on coefficient of variation), in view of the need to measure the plastic strain ratio at low strain levels. Various means to ensure accuracy in measurement are described.

Plastic strain ratio of sheet deformed to different biaxial prestrains has also been characterized using the magnetostrictive method (Modul r test). It is found that the difference between the r values determined using the ASTM and the Modul r methods changes with strain and strain path. The nominal difference between the two methods was found to be comparatively consistent over strain paths ranging from plane strain to equibiaxial tension. The Modul r values for prestrains along these strain paths investigated were found to be relatively consistent and hence usable. For prestrain along the strain path β = −0.45 (negative minor strain regime), the nominal difference was considerable.

In view of the above, it is not appropriate to measure rapidly the r value of the material in the negative minor strain regime, in particular using magnetostrictive means, and to correct it using the “systematic error” between the two techniques. This restricts the usability of the Modul r test in measuring the plastic strain ratio of deformed sheet metal, particularly after a prestrain in the negative minor strain region.
Fatigue Crack Closure Evaluation Under Constant Amplitude and Spectrum Loading
Authors: Parida BK , Manjunatha CM , Girish HM
Published: February 2009

Fatigue crack growth behavior of through-the-thickness cracks emanating from the notch root in an aluminum alloy was investigated with particular emphasis on the evaluation of crack closure and its effects on fatigue crack growth rate. The tests were performed on SE(T) specimens both under constant amplitude (CA) and spectrum (modified FALSTAFF) loads. The near-tip strain measurement method was used for crack closure estimation in the short and long crack ranges. An attempt was also made to determine the crack closure value corresponding to the crack-tip shielding through fractographic analysis.

In CA fatigue loading, short cracks grew faster than long cracks under the same nominal applied SIF range, ΔK, and also grew below the threshold SIF range, ΔKth, for long cracks. The crack closure level gradually increased in the short crack range and was observed to stabilize at a crack length of about 0.5 mm. The discrepancy in the observed crack growth rates between long and short cracks was attributed partly to the difference in crack closure levels. The fatigue crack growth rates of short cracks under modified FALSTAFF loading were observed to be rather scattered, and the crack closure level was found to gradually increase and stabilize within a larger scatter band. These observations are explained on the basis of likely effects of several high-peak overloads present in the applied spectrum load. In the long crack range, the crack closure value obtained by the near-tip strain measurement method appears to provide an upper-bound value, whereas that obtained through fractographic analysis provides a slightly lower estimate, which may be considered as a lower-bound fatigue crack closure value.
Effect of Heat Treatment on Mechanical Properties and Surface Roughness of Aluminum Alloy 601
Authors: Frost FF , Karri V
Published: February 2009

Aluminum alloy 601 has an extensive range of industrial applications due to its consistent mechanical properties and structural integrity. The other intrinsic features of this alloy include excellent corrosion resistance and lack of brittleness or susceptibility to stress-corrosion cracking. Continued attempts are being made to decrease the processing time of this alloy without affecting the associated mechanical properties. This paper shows a systematic experimental investigation carried out in a modern aluminum wheel manufacturing plant to study the effects of heat treatment of this alloy. It is shown in this work that a reduction in processing time at the heat treatment stage of manufacturing is achievable without significant effect on the mechanical properties of the alloy wheel produced. A comprehensive set of experimental investigations has shown that the mechanical properties of the alloy, processed using two separate heat treatment methods, are not significantly different. The findings reported in this paper have real implications to aluminum-processing industries in which heat treatment is a fundamental part of the manufacturing process.
A Method to Determine the Transition Point of Fatigue Crack Growth Rate from Near-ΔKth to Paris Regions
Authors: Zheng J , Powell BE
Published: February 2009

The transition point of fatigue crack growth (FCG) between the near-ΔKth and the Paris regions is an important value to study fatigue behavior. This study introduces a curve-fitting technique to identify this point for nickel-based superalloy U720 with stress ratio of R = 0.1 at room temperature. The value of ΔKth under these conditions is also determined.
Comparison of Finite Element Results and Experimental Measurements of CTOD δ5 in CT Specimens
Authors: Nikishkov GP , Heerens J , Hellmann D
Published: February 2009

Elastic-plastic finite element modeling of the CTOD δ5 measuring procedure is performed for CT specimens made from 22NiMoCr37 containing fatigue precracks with curved crack fronts. It is shown that a discrete model with curved crack front and actual position of the clip gage provides reasonable accuracy of results. An approximate model with straight crack front of average crack depth and actual location of the clip gage can also be used. It is proposed to adjust experimental δ5 values for the deviation of actual crack front curvature a from a specific value. The use of the adjustment procedure decreases the scatter of experimental values of CTOD δ5 considerably.
Prediction of Fatigue Performance of Asphalt Concrete Mixes
Authors: Ramsamooj DV
Published: February 2009

The suitability of dense-graded hot-mix asphalt concrete mixtures for fatigue-resistant flexible pavements is investigated. The fatigue lives of several mixes including those with additives of latex, rubber, and sulfur are predicted by a theory derived from fracture mechanics. There is good agreement between the model predictions for the fatigue lives and the experimental results for the laboratory tests. The material properties are then used to predict the fatigue performance of two of these mixes in a simulated full-depth flexible pavement and a three-layer flexible pavement. There is poor agreement between the model predictions for the performance of the simulated pavements and the laboratory tests. Several reasons are postulated for the differences in the fatigue lives for the laboratory beam tests and the simulated pavements.
Instability of Stacked Pallet Loads Due to Misalignment
Authors: Singh SP
Published: February 2009

Double-stacked empty corrugated fiber-board boxes were conditioned in normal and tropical climates and then compression tested in aligned, laterally offset, and diagonally offset configurations to determine the effect on compression strength. The results showed that offsets caused a greater reduction in strength than humidity effects. In a separate experiment, three-high pallet loads of infant formula in two-piece plastic cans were stacked in various staggered positions to evaluate the effect of pallet offset on stack stability. It was found that factors other than the amount of offset, such as pallet strength, uneven floors, and stretch wrapping were most influential.
Displacement and Strain Fields at a Stone/Mortar Interface by Digital Image Processing
Authors: Raffard D , Ienny P , Henry J-P
Published: February 2009

This work is part of a study of historical masonry behavior. It deals with the homogenization of periodic and heterogeneous structures like masonry, which is composed of stones linked by joints of mortar. Combined compressive-shearing tests were performed in order to study the mortar interface behavior. Deformation properties were measured, locally, by an optical extensometer. Like the speckle method, this principle uses digital image correlation processing. Compared to the volume of the joint, the size of aggregates induces heterogeneities. An experimental protocol is proposed to determine homogenous deformation according to joint width and localized deformation according to joint height. This approach accurately characterizes the interface at a microscale level and enhances high compaction strain at the interface.
Test Method Using Energy to Evaluate the Cut Resistance of Protective Clothing Against Chain Saws
Authors: Turcot D , Daigle R
Published: February 2009

Work with chain saws involves the risk of injury; workers wear protective equipment to protect themselves against these injuries. The question arises: How can the resistance of the protective equipment be evaluated? It can be evaluated either by using one of the test methods described in current standards or by using a new test method that has advantages over existing methods. The new test method is chosen because it measures the energy needed by a chainsaw to cut the protective equipment to be evaluated. The energy then becomes the performance criterion to classify the equipment and is an overall physical measurement parameter for evaluating the cut resistance of the material to a chainsaw.

In the test method developed, a motor drives a fly wheel that acts as an energy reservoir, which in turn drives the chain. Once the test velocity has been reached, the motor is disengaged and the flywheel becomes the only source of energy driving the chain. The chain then comes in contact with the protective equipment to be evaluated.

The total cut-through energy, selected as performance criterion, is determined by evaluating the difference between the initial and final kinetic energies of the rotating system. Also, a sensor installed between the flywheel and the chain records the torque transmitted by the flywheel to the chain. This method determines the energy dissipated when the equipment evaluated is being cut.

The test phase was used to validate the operation of the test bench and to verify the feasibility of the measurement principle. The energy dissipated during cutting was evaluated for different materials and under different test conditions.

The results obtained show that the energy necessary to cut through a sample is a repetitive measurement independent of the initial test velocity.

In contrast to existing test methods, the method developed is independent of the drive system used, and consequently the motor driving the flywheel can be replaced or undergo maintenance without affecting the results. This ensures that the test method will retain its precision over time.
The Determination of the In-Plane Shear Characteristics of Aluminum Alloys
Authors: Gilmour KR , Leacock AG , Ashbridge MTJ
Published: February 2009

The test method detailed in ASTM Standard Test Method for Shear Testing of Thin Aluminum Sheet Alloy Products (B 831) approximates the conditions of pure shear. The newly proposed test regime removes the rigid body rotation associated with pure shear and hence creates a simple shear deformation. The test also makes available an additional volume of empirical data by facilitating the measurement of both shear stress and strain throughout the test. The proposed test procedure was used to analyze the directionality of simple shear deformation in an aerospace 2024-T3 aluminum alloy. The shear yield strength determined using the newly proposed method was found to be approximately half of the uniaxial yield strength. The orthotropic response in shear was seen to differ from that exhibited during uniaxial testing. The stress-strain response in simple shear also illustrated the effect of the deformation restrictions through the appearance of serrated yielding.
A Performance Evaluation of Lightweight Non-Contact Pavement Profilers
Authors: Hand AJ , Mondal AK , Ward DR
Published: February 2009

Pavement smoothness was recently identified as the most significant factor the motoring public uses to judge the quality of U.S. roadways. A new generation of lightweight profilers has been developed that have the potential of providing nearly instantaneous smoothness measurements, giving contractors a tool to identify and address process control issues promptly and cost effectively. This new technology was cooperatively evaluated by a team of Purdue University and Indiana Department of Transportation (INDOT) researchers to assess the performance of the devices, as well as the potential for their use in Indiana.

A successful field test was conducted using four lightweight profilers that performed five replicate measurements at each of six sites: three, hot mix asphalt (HMA) and three, portland cement concrete (PCC). Smoothness data were reported in terms of International Roughness Index (IRI) and Profile Index with 0.0 and 0.2 in. (PI-0.0 and PI-0.2) blanking bands. The field test data showed good repeatability and poor reproducibility in terms of the smoothness indices considered, the profiles generated, and the identification of must-grind locations. Estimates of precision for the devices were determined in accordance with ASTM standards. The observed precision statements as well as statistical tests of between-vendor performance suggest that the performance of the devices, especially the reproducibility, should be improved prior to implementation of their use in construction specifications.