Standard Test Method For Measurement Research Articles

Determination of the Water Diffusivity of Concrete Using Drying/Absorption Test Results

Abstract Experimental procedures such as ASTM C1585, “Standard Test Method for Measurement of Rate of Absorption of Water by Hydraulic-Cement Concretes,” and ISO12572 have been recently developed to determine the rate of moisture transmission through hydrated cement systems. However, these methods do not provide an actual transport parameter that can be used in chloride ingress models to predict the service-life of concrete structures. This study focused on the development a reliable method to measure the nonlinear moisture diffusivity of concrete. The approach is based on the analysis of drying and wetting experiments performed with concrete samples of different thicknesses. The transport parameter is obtained by using Richards’ water transport model to analyze the mass variations measured during the tests. The method was tested over a wide range of different concrete mixtures produced with different water/cement ratios. Results indicate that the nonlinear function used to reproduce the mass variation curves must exhibit a strong increase for high water content values. The water diffusivity equation derived from this analysis allows reproducing the behavior of concrete during both the drying and absorption experiments using the same water transport model.

Experimental Estimation of J-R Curves from Load-CMOD Record for SE(B) Specimens

Abstract Fracture resistance of ductile materials is often characterized by a J-R curve, and measured using the fracture toughness testing standard ASTM E1820 (Standard Test Method for Measurement of Fracture Toughness). The recommended elastic unloading compliance method or resistance curve test method requires simultaneous measurements of applied load (P), load-line displacement (LLD), and crack-mouth opening displacement (CMOD) from a single test for the single-edge notched bend [SE(B)] specimen. The P-CMOD record is used to determine crack extension, and the P-LLD record in conjunction with the crack extension is used to calculate the J-integral. However, it is well known that while highly accurate CMOD measurements can be made, the measurement of LLD is less accurate and more difficult because of transducer mounting difficulties, specimen load point indentions and load train deflections, or a combination thereof. Extensive finite element analyses showed that the LLD-based J equation may give inaccurate results for a shallow-cracked SE(B) specimen because its geometry factor η may depend on the strain hardening exponent. In contrast for the same geometry, the CMOD-based η factor is insensitive to the hardening exponent, and thus a CMOD-based J equation could be more accurate to be used in the determination of J-R curves. Based on the energy principle, this paper proposes a CMOD-based J equation for a growing crack using an incremental function similar to the present ASTM E1820-06 formulation that is applicable to the J calculations for a J-R curve testing. The proposed CMOD-based J formulation contains two geometry factors, i.e., CMOD-based η and γ, and can consider the crack growth correction. The solutions of four geometry factors are presented for the SE(B) specimens with a wide range of crack length. The proposed formulation is then applied to determine J-R curves for HY80 steel using the load-CMOD record for SE(B) specimens, and the results are compared with those using the traditional LLD-based formulation. The comparison shows close agreement between these two formulations. It is recommended that the proposed formulation be used in ASTM E1820 to determine more accurate J-R curves and reduce test costs as well.

Application of the Normalization Method to Dynamic Fracture Toughness Testing of Alloy 718

Abstract The fracture toughness and tensile properties of Alloy 718 were measured at quasi-static and dynamic loading rates for two different heat treatments and two product forms. Two different methods for conducting the dynamic tests were investigated; one involving interrupted tests and the other utilizing a single impact. The interrupted test method used multiple impacts with displacement limits to enable measurement of crack lengths at intermediate points. The normalization method was used to generate tearing resistance curves for the dynamic tests following the guidelines in ASTM Standard Test Method for measurement of Fracture Toughness (E 1820). The analysis pointed out the importance of obtaining a good measurement of load, displacement, and crack length at the point of maximum displacement (the anchor point). As the amount of ductile crack extension increased, the uncertainty in the plasticity function fit also increased. Methods to improve the fit were investigated, including the addition of anchor points from multiple tests, and use of a tangency point to estimate initiation. The resulting curves are compared to ascertain the variability obtained from nominally identical specimens, and to evaluate the effect of loading rate on the plasticity function. The normalization tearing resistance curves are compared with curves generated from the interrupted tests using compliance measurements during unloads to determine crack extension. Good agreement was obtained between the two methods of measuring tearing resistance, thereby validating the normalization analysis. The tests showed that multiple impacts drive down the tearing resistance, which may be significant in applications where a dynamic event causes load fluctuation.

Experimental Evaluation of the J or C* Parameter for a Range of Cracked Geometries

Abstract In the current ASTM Standard Test Method for Measurement of Creep Crack Growth Rates in Metals (E 1457) the experimental C* parameter is related to the load and creep load line displacement rate through the geometry related η factor. In this work η factors for a range of geometries are presented. The geometries examined are the compact tension specimen, C(T), single edge notch specimen in tension, SEN(T), and bending, SEN(B), double edge notch specimen in tension, DEN(T), middle crack specimen in tension, M(T) and the C-shaped specimen in tension CS(T). Calculations have been performed for a linear elastic-power law hardening material but the resulting η factors are applicable to either power law plastic or power law creeping materials. Values for ηLLD and ηCMOD, based on the load line displacement and crack mouth opening displacement, respectively, have been determined. A wide range of crack depths, 0.1⩽a/W⩽0.7, where a is crack length and W is specimen width, and hardening exponents, 3 ⩽N ⩽10, under plane stress and plane strain conditions have been examined using the finite element method. The influence of specimen length, crack length, material properties and out of plane stress state on the η factor has also been considered. It has been found that for shallow cracks the value of η depends quite strongly on the exponent, N in the material power law, regardless of whether η is defined based on the load line displacement or crack mouth opening displacement. The ηLLD factor has also been found to be strongly sensitive to plane stress/strain conditions imposed, a/W and specimen length, whereas ηCMOD depends more weakly on a/W and is almost independent of specimen length for the cases examined. There is, however, no clear trend in these variations over the range of specimen geometries and a/W examined. These results are found to be consistent with those in the literature. Recommendations are made regarding the most appropriate values for η, depending on the specimen type and geometry while taking into account the variability due to the material properties, out of plane stress state and variations between the numerical analyses.

Analysis of Creep Crack Initiation and Growth in Different Geometries for 316H and Carbon Manganese Steels

Abstract Results obtained from a European collaborative project aimed at producing a draft code of practice for creep crack growth testing are presented. The tests were performed on an Austenitic Type 316H Stainless Steel at 550°C and a carbon manganese steel at 400°C. A range of specimen test geometries has been examined. These are the single edge notched specimen in tension and bending, the double edge notched specimen in tension, the middle cracked specimen in tension, and the C-shaped specimen in tension. The results obtained are compared to those obtained using the standard compact tension specimen following the ASTM Standard Test Method for Measurement of Creep Crack Growth Rates in Metals (E 1457). Creep crack creep growth rates and initiation times have been correlated with the fracture mechanics parameter C*. The applicability of the stress intensity factor K to describe the creep cracking behavior is also assessed. Recommendations are made to support the use of different geometries in creep crack growth and/or creep crack initiation testing.

Effect of specimen geometries on the C∗ versus d a/d t master curve for type 316L stainless steel

This work deals with engineering components made of stainless steels working at high temperature and subjected to creep-fatigue loading history. The defect assessment procedures generally use the crack growth properties curve d a/d t versus C ∗ parameter for estimating the creep-crack growth. The ASTM E 1457-98 [ASTM E 1457-98. Standard test method for measurement of creep crack growth rates in metals, 1998] procedure proposes the rule to establish such a master curve. In particular, it is stipulated that this rule only applies for CT specimens. Previously [Laiarinandrasana L, Kabiri R, Drubay B. In: Gupta A, editor. Proceedings of the 16th international conference on structural mechanics in reactor technology, Washington, USA, 2001], some practical methodology to produce this crack growth curve on CT specimens has been described by introducing the way to determine the upper and lower limits of relevant experimental points and by adopting the ASTM E 1457-98 method to estimate the creep component of the load line displacement rate (d δ/d t behavior). This latter is the interesting part of the total displacement rate recorded during the test. This paper focuses on the application of the procedure proposed in [Laiarinandrasana L, Kabiri R, Drubay B. In: Gupta A, editor. Proceedings of the 16th international conference on structural mechanics in reactor technology, Washington, USA, 2001] on specimen geometries other than CT, such as circumferentially cracked round bar (CCRB) and double edged notched in tension (DENT) specimens. The d a/d t versus C ∗ curves issued from all of these specimens are compared. Discussion about the effect of geometry on these curves is carried out. Additionally, some finite element analyses have been performed in order to simulate the creep crack growth using the node release technique. These simulations allow to verify the validity of the proposed expressions of C ∗ and consequently the master curve of the 316L(N) stainless steel.

Construction of J-R Curves Using the Common and Concise Formats

Abstract A new method for constructing J-R curves is presented, which directly generates the J-Δa relation in a closed, analytical form. This new method makes use of the Concise Format and the Common Format, both developed by Donoso and Landes. These formats relate load, P, to ligament length, b, and displacement — in the elastic and in the plastic deformation ranges, respectively — and have proved useful in calculations in fracture mechanics. Key to the method is the postulate of a “crack growth law” —a power-law relation between crack extension, Δa, and plastic displacement — used to express Jpl in terms of material properties, size parameters, and crack extension, giving rise to a Jpl-Δa analytical expression, similar to the power law J = CI(Δa)C2 suggested in ASTM Standard Test Method for Measurement of Fracture Toughness (E 1820). A few examples are included to show the use of the method, and comparisons are made with suggested in ASTM Standard Test Method for Measurement of Fracture Toughness (E 1820). A few examples are included to show the use of the method, and comparisons are made with J-Δa curves calculated as per ASTM E 1820.

A Framework for a Standardization Effort for Fatigue Crack Growth Testing Under Variable Amplitude Spectrum Loading

Abstract Fatigue crack growth testing under variable amplitude loading conditions is currently not standardized. Without standardization, the methods and techniques applied by different laboratories vary, and as such, lab-based bias can occur readily. The goal of this paper is to discuss in detail the experience developed and lessons learned during years of spectrum crack growth testing. Issues concerned with specimen geometry, crack geometry, precracking methodology, crack length measurement, spectrum content, load magnitude control, and interpretation of results are addressed herein. Although the ASTM Standard Test Method for Measurement of Fatigue Crack Growth Rates, E 647, provides guidance that is useful to this test, the specialized nature of spectrum testing does provide its own unique set of issues different from da/dN versus ΔK testing.

Verification of stress-intensity factors for various middle-crack tension test specimens

Recently, the stress-intensity factor equation used in the ASTM Standard Test Method for Measurement of Fatigue Crack Growth Rates (E-647) for the middle-crack tension M(T) specimens (friction-gripped or pin-loaded) has been questioned due to the influence of the specimen “height” specified in the standard. A boundary-element code has been used to calculate the stress-intensity factors for a wide range of crack-length-to-width ratios and various height-to-width ratios for M(T) specimens under remote uniform stress, remote uniform displacement, or pin-loaded holes. Comparisons are made with some of the well-known stress-intensity factor solutions and equations in the literature. Recommended specimen heights and stress-intensity factor equations have been made.

Freeze-Thaw Effects and Gas Permeability of Utility Line Backfill

Abstract Backfill materials used in utility trenches must maintain physical and mechanical integrity when subjected to the seasonal effects of freezing and thawing. Materials used over gas utility lines must also have adequate permeability to allow any leaking gas to flow upward and out. To help determine how soils and flowable fills might perform as backfill over utility lines, we conducted laboratory tests to measure the permeability of backfill materials before freezing, during freezing, and after thawing. The two materials investigated in this study were a silty sand, and a flowable fill made with Type F fly ash. Our work also examined the susceptibility of these materials to frost heave and thaw weakening. An apparatus and standard test method for performing permeability during freezing and after subsequent thawing did not exist. We developed a method by adapting the ASTM Standard Test Method for Frost Heave and Thaw Weakening Susceptibility of Soils (D 5918) and the ASTM Standard Test Method for Measurement of Pneumatic Permeability of Partially Saturated Porous Materials by Flowing Air (D 6539). Although more data are needed to confirm specific conclusions determined from this study, the test method developed here appears to be useful for evaluating the effects of freeze-thaw on backfill materials for utility trenches. Additional work is needed to demonstrate whether these laboratory results correspond to actual field conditions.

Creep crack growth of high temperature weldments

The experimental programme of the EC supported project (SMT 2070) SOTA aimed at addressing a technical and industrial need to provide guidelines for creep crack growth (CCG) testing and data analysis of weldments. Mechanical and creep properties were determined on two pressure vessel steels of P22 (2.25Cr1Mo) and P91 (9Cr1MoVNb). The specimens were taken from pipe welds for weld metal (WM) tests, and simulated heat affected zone (HAZ) material for the HAZ tests. The CCG tests were carried out on cross-weld compact tension (CT) specimens machined out from weldment of pipes. The tests were done at 550 and 600°C on P22 and P91 materials, respectively. The CT specimens were notched using electrical discharge method, for a sharp starter crack. This method of initiating sharp starter crack was chosen to make sure that all partners will test specimens with starter crack location as specified in the work programme to study crack initiation and growth in WM and HAZ (both in the centre and type IV region). The CCG tests were carried out following the ASTM E1457-92 [ASTM E1457-92, Standard test method for measurement of creep crack growth rates in metals, ASTM, Philadelphia, PA 19103, USA]. The partners assessed their data and sent both assessed and their raw data to be further assessed centrally. All the data from partners were analysed and compared with those of partners' own assessed data. The present paper reports on the analyses of CCG data obtained in the programme including six laboratories from six European countries. The programme addresses the differences and difficulties in testing and the assessment of weldments, and provides guidelines for harmonisation of testing procedures for reliable data production for remanent life assessment of plants with welded components.

Effect of specimen thickness on fatigue crack growth rate

Fatigue tests were performed on the compact tension (CT) specimens of Type 304 stainless steel and Inconel 718. To investigate the effects of specimen thickness on crack tip deformation and fatigue crack growth rate (FCGR), specimens of different thickness were used. In the analysis, the elastic plastic fracture mechanics (EPFM) parameter known as the cyclic J-integral, Δ J was adopted to observe the local plasticity at the crack tip and compared with the linear elastic fracture mechanics (LEFM) parameter known as the stress intensity factor range, Δ K. The results show that FCGR is a function of specimen thickness, the effect of which is accelerated as specimen thickness increases. Therefore, it is thought that not only applied stress level but also specimen thickness should be taken into account in the measurement of FCGR, which is not considered in ASTM E 647 (ASTM E 647, 1995. Standard test method for measurement of fatigue crack growth rates.).

Investigation of the effects of shed-rate, initial Kmax, and geometric constraint on Δ Kth in Ti–6Al–4V at room temperature

A correct definition of threshold stress intensity is critical to understanding the growth of small cracks in advanced gas turbine engine applications. A study of the effect of specimen geometry, constraint, and load shedding rate on the measured threshold stress intensity of Ti–6Al–4V (AMS 4928) was conducted to compare conventional through cracks (compact tension specimen) to surface flaw defects ( K b specimen). At room temperature, stress ratios of 0.1 and 0.8 were examined. The effect of shed rate was assessed and it was found that shed rates as low as −20 in −1 (−0.8 mm −1) give accurate threshold measurements in both geometries at both stress ratios. These results indicate that the more gradual shed rate of −2 in −1 (−0.08 mm −1) recommended in ASTM E647 (Standard test method for measurement of fatigue crack growth rates, Annual Book of ASTM Standards, E647-95a, 1997:557–93) may be conservative for high strength titanium alloys. A study of the effect of starting stress intensity factor on the resultant threshold value was also completed. It was found that starting at high initial stress intensity factors gave false values for threshold.

Proposed Standard Test Method for Measurement of Pneumatic Permeability of Partially Saturated Porous Materials by Flowing Air

Abstract This proposed standard describes a laboratory test method for the measurement of the coefficient of permeability for airflow (pneumatic permeability) through porous media (e.g., soils) partially saturated with water. Control and measurement of the airflow is effected at the inlet of the specimen. The permeameter cell is fitted with dual transfer lines that isolate the specimen pressure drop from the effects of gas flow in the apparatus. Electronic instrumentation results in short test times that minimize changes in water content. This proposed standard addresses the need to develop a body of knowledge in support of soil vapor extraction (SVE) systems and allied environmental remediation activities.