ASTM STP Research Articles

Automated semantic segmentation of NiCrBSi-WC optical microscopy images using convolutional neural networks

Convolutional neural networks (CNNs) were used for the semantic segmentation of angular monocrystalline WC from NiCrBSi-WC optical microscopy images. This deep learning approach was able to emulate the laborious task of manual segmentation effectively, with a mean intersection over union (IOU) and a mean dice coefficient (DC) of 0.911 and 0.953, respectively, across the entire test dataset. From the model output, the carbide percent can be determined by dividing the area of positively labeled pixels by the total area of the image. Additionally, the mean free path can be quantified using the method described in ASTM STP 839, and by physically counting the black pixels (CPB) between the particles in the image. Comparing the models predictions to the ground truth, the carbide percent had an average difference of 1.2 area %, while the mean free path differed by 15.7μm for the ASTM method, and 24.8μm for the CPB method. The robustness of the model was tested on images containing both spherical eutectic WC and angular monocrystalline WC to determine whether the model was capable of accurately predicting the location of objects that were not part of the training dataset. The U-Net CNN was able to segment the spherical and angular WC with considerable accuracy. These results show that the application of computer vision models for microstructural characterization is not limited to complex imaging modalities, and can be applied to readily available methods such as optical microscopy.

The mechanical testing of a novel interlocking forearm nail

BACKGROUND: Mechanical testing of newly designed implants provides valuable insight into their mechanical properties. This provides surgeons with information about implant choice for the treatment of fractures and the effect of the implant's mechanical properties on fracture healing METHODS: A novel interlocking forearm nail was subjected to standardised mechanical testing according to the Standard Specification and Test Methods for Intramedullary Fixation Devices (ATSM 126416), using static and dynamic four-point bending and static torsion (ASTM STP 588). Three nails were used for the static bending and torsion and nine for the dynamic bending tests. All nails were catalogued, numbered and photographed before testing RESULTS: The mechanical testing results showed a mean force yield (Fy) of 566 ± 20 N, a moment of yield (My) 10.75 ± 0.37 Nm, a stiffness of 67.10 ± 2 N/mm and structural stiffness of 1.53 ± 0.50 m2. The torsional stiffness of the nail was 0.088 ± 0.002 Nm/°. The four-point dynamic bending test showed a fatigue strength of 5.23 Nm. This value was determined using the semi-log moment/ number of cycles (M-N) diagram and showed a 50% failure at a million cycles. If the moment were reduced to 4.4 Nm, mathematically, the survival rate would improve to 90% CONCLUSION: The results from this mechanical testing show that this novel intramedullary forearm nail can resist mechanical forces experienced during fracture healing and could potentially be used in future clinical studies Level of evidence: Level 4

Development of Short Time Impedance Measurement Method for PEM Electrolysis Cell

Electrochemical impedance spectroscopy (EIS) is expected as a method to evaluate a polymer electrolyte membrane (PEM) water electrolysis cell. The internal state of electrolysis cell can be investigated by EIS without destruction. However, it may be difficult to measure stable impedance during electrolysis at high voltage since the large amount of oxygen is generated on the anode. Therefore, a short time impedance measurement is required. The purpose of this study is to develop short time impedance measurement method1,2) that can estimate the electrolyte membrane resistance R M and the charge transfer resistance R ct in a short time.A Japan Automobile Research Institute (JARI) standard cell with an electrode area of 25 cm2 was used as the test cell. The impedance measurement was performed in a frequency range from 100 mHz to 1 kHz and started from high frequency toward low frequency in the logarithmic scan.The Nyquist plot of impedance spectrum shows inductive behavior caused by wiring in the high frequency region and capacitive semicircle related to the anode in the middle frequency region. Under the condition of high current density, it was found that impedance spectrum was scattered in the low frequency range. The scattering originated from oxygen evolution at the anode when the measurement time is long. The measurement time was about 80 s to obtain an impedance spectrum, thus it is necessary to measure in a shorter time. Therefore, we obtained R ct in a short time by the two-point frequency method proposed by Haruyama et al.1,2) The equation (1) is used to calculate R ct. R ct = Re [Z] - R M + Im [Z]2/( Re [Z] - R M) (1)In the equation (1), R M is the electrolyte membrane resistance, which is the real component of the impedance at the high frequency. The real and imaginary parts of the impedance at the low frequency are represented by Re [Z] and Im [Z]. The measurement was performed by fixing the frequency at 1 kHz as a high frequency value and changing the low frequency value from 100 Hz to 10 mHz. R ct obtained from the measurement results by the two-point frequency method was compared with R ct obtained from the curve fitting of the impedance spectrum with the equivalent circuit. As a result, the relative error of the R ct calculated from the measurements at two frequencies 1 kHz and 10 Hz was -2.15% from the fitted result, and the measurement time was 5.33 s. From these results, it was found that the two-point frequency method was able to reduce the measurement time significantly compared to the normal EIS and to estimate R ct accurately. References 1) S. Haruyama, T. Tsuru, ASTM STP 727, ASTM Philadelphia, p.167 (1981).2) T. Tsuru, S. Haruyama, Boshoku Gijutsu, 33, p.579-582 (1984).

An innovative laboratory characterization: hydrogen interaction with X60 pipeline steel

Corrosion is evaluated to be one of the most important cause for pipeline failures. Given the serious consequences of these events in terms of human safety, environmental preservation and cost saving, it is evident that on-field corrosion control could have a fundamental role. The aim of the present work was to meet this need with preliminary feasibility study to develop a test procedure, characterized at the same time by non-invasive approach and scientific rigor, to evaluate the possibility of on-line monitoring and assess the integrity of a pipeline during its operation. The experimental campaign was performed on a HSLA Steel X60, characterized by a ferritic microstructure with fine grains and ultimate tensile strength equal to 520MPa. The hydrogen interaction with steel was investigated by means of an advanced equipment based on an innovative high sensitivity hydrogen gas sensor. The following types of investigations were carried out [1]: - Various permeation tests were performed with reference to EN ISO 17081:2014 increasing test temperature from 10°C to 60°C. - Afterwards a series of Hydrogen Induced Cracking nucleation tests was performed with reference to ASTM STP 692:0. - Finally, permeation concept was applied in an innovative way to Hydrogen Induced Cracking nucleation phenomena.

Microelectrochemical Investigation of Atmospheric Aging Effect on Pitting Corrosion Resistance at Manganese Sulfide Inclusion in Type 304 Stainless Steel

Stainless steels are widely used in architectural applications, such as roofing and walls. In atmospheric environments, pitting causes discoloration (rust staining) on the steel surfaces, which compromises the esthetic appearance of architecture considerably. The pitting behavior of stainless steels in outdoor environments has been extensively investigated through long-term exposure tests 1. It is generally accepted that most stainless steels experience severe corrosion within the first two years in marine environments, and there is a correlation between rust staining resistance and pitting resistance 2. Even in atmospheric environments, sulfide inclusions, such as MnS, act as initiation sites for pitting. Considering these points, it is reasonable to consider the possibility that atmospheric aging improves pitting corrosion resistance at MnS inclusions in stainless steels. In our previous works 3-5, we studied the pit initiation behavior at the MnS inclusions in Type 304 stainless steels. The pit initiation mechanism was found to be as follows: 1) the dissolution of the MnS inclusions leads to the deposition of elemental sulfur on and around the inclusions; 2) the synergistic effect of the elemental sulfur and chloride ions causes the dissolution of the stainless steel side at the MnS/steel boundaries, resulting in the formation of trenches; 3) the hydrolysis reaction of Cr3+ released from the steel matrix dissolution decreases the pH in the trenches, and at the same time, the electrode potential at the bottom of the trenches decreases due to the IR-drop. Finally, the pit initiation is defined as the local transition from the passive to active state at the bottom of the trenches. Atmospheric aging is an important subject for the corrosion engineering of stainless steels, and a thorough understanding how the aging affects the described pit initiation process at the MnS inclusions is expected to help in the endeavor to create corrosion resistant surfaces for stainless steels. Micro-scale electrode areas with dimensions of approximately 300 μm×150 μm which contained a stripe-like MnS inclusion were prepared to analyze the effect of atmospheric aging on the dissolution of MnS inclusions and the pitting initiation process at the inclusions. A commercial re-sulfurized Type 304 stainless steel bar with a diameter of 70 mm containing large MnS inclusions was used in this study. This stainless steel was heat-treated at 1353 K for 0.5 h and quenched in water. The specimen surfaces parallel to the rolling direction were mirror polished, and then exposed to air at 298 K and 50% relative humidity (RH) for 1, 30, and 90 days. A SEM/EDS (scanning electron microscope/energy-dispersive X-ray spectroscopy) analysis indicated that the MnS inclusions did not dissolve during the 90-day exposure, and the atomic ratios of Mn and S of the inclusions remained almost 1:1. An AES (auger electron spectroscopy) analysis indicated no outstanding changes in the thickness of passive film on the steel matrixes after the 30 days of exposure, whereas the thickness of the oxide layer on the MnS inclusions had doubled after the 30-day exposure period. In order to investigate the correlation between the oxide layer formed on the MnS inclusions and the pit initiation at the inclusions, the anodic polarization curves of a micro-scale electrode area were measured in 3 M NaCl. It is interesting to note that the exposure for in excess of 30 days improved the resistance of the investigated stainless steel to pitting at the MnS inclusions with no stable pitting found on the specimens exposed. The extent of the dissolution of the MnS inclusions on the specimens exposed for more than 30 days measured in 0.1 M Na2SO4and 0.1 M NaCl was suppressed to less than half that of the specimens exposed for one day. In addition, the exposure for 90 days inhibited the trench formation at the MnS/steel boundaries in 3 M NaCl. The over 30 days of exposure (atmospheric aging) resulted in the suppression of the MnS dissolution by the growth of the oxide layer on the inclusions, and then inhibited the formation of the trenches at the MnS/steel boundaries as a trigger for the pit initiation at the MnS inclusions. This explains the lower activity of MnS inclusions in atmospheric environments. 1. M.J.Johnson and P.J.Pavlik, in: W.H.Ailor (Ed.), Atmospheric Corrosion, John Wiley, New York, 1982, p. 462. 2. I.Muto, E.Sato, and S.Ito, ASTM STP 1194, American Society for Testing and Materials, Philadelphia, 1994. 3. A.Chiba, I.Muto, Y.Sugawara, and N.Hara, J. Electrochem. Soc., 159, C341 (2012). 4. A.Chiba, I.Muto, Y.Sugawara, and N.Hara, J. Electrochem. Soc., 160, C511 (2013). 5. A.Chiba, I.Muto, Y.Sugawara, and N.Hara, Mater. Trans., 55, 857 (2014).

Prediction of permanent deformation model parameters of unbound base course aggregates under repeated loading

Prediction of rutting is a key element in the newly developed mechanistic-empirical pavement design guide (M-EPDG). The model developed by Tseng and Lytton (1989. Prediction of permanent deformation in flexible pavement materials. ASTM STP 1016, pp. 154–172: American Society for Testing and Materials) is used in the M-EPDG to estimate the permanent deformation of unbound materials, but does not predict parameters of the model satisfactorily. This research was conducted to study the effect of water content on permanent deformation model parameters of unbound aggregate base layers. Different aggregates were compacted at different water contents and were subjected to repeated loading tests. For the material tested, the permanent deformation increases rapidly when the water content exceeds that of the optimum. Under optimum water content, wopt, limestone is more resistant to permanent deformation than basalt and quartzite. However, above wopt, the permanent deformations of limestone grow rapidly and become higher than those of Basalt. This indicates a high sensitivity of limestone to water content, which increases the plastic deformation. An exponential relationship is more appropriate to describe the evolution of permanent deformation as a function of water content and gives a higher coefficient of determination. Assuming that the rutting parameters decrease exponentially with increasing water content, empirical relationships are proposed for predicting these parameters. These results should be used for further development of the M-EPDG rutting model.

Atmospheric Corrosion of Zinc Coated Steel- Results from a Worldwide Outdoor Exposure Program

In the last decades, numerous national or international exposure programs have been launched to collect data on atmospheric corrosion rates and to establish prediction tools for atmospheric corrosion of metallic structures [1]. Most commonly, carbon steel, zinc, copper and aluminum samples are exposed in selected locations for a year or more. Based on weight loss measurements, dose-response functions and corrosivity maps have been compiled [2,3]. A major limitation of most previous studies is that data have been acquired mainly for bulk metals while studies on metallic coatings are rare. Similarly, the evolution of corrosion products with exposure time has been studied for bulk zinc [4] but few studies on zinc coated steel is reported. This work is a part of a larger research program were steel with different zinc coatings are exposed on a worldwide basis on well characterized exposure sites in Europe, Asia and North America, see table 1. Corrosion rates of HDG were determined after exposure under different climatic conditions. Corrosion rates for HDG after two years exposure have been measred. Uniformity of the coating corrosion and performance at cut edges was evaluated. The effect of sample orientation and sheltering was investigated. Correlation of data on mass loss with environmental data collected at the exposures sites enabled the derivation of dose-response function HDG. The formation and development of corrosion products was followed by detailed analysis of samples exposed 0.5, 1 and 2 years using XRD, FTIR-spectroscopy and SEM-EDS. The main corrosion products formed on HDG on the different sites are Zn5(OH)6(CO3)2, NaZn4(SO4)(OH)6Cl·6H2O, (Zn(OH)2)3 ZnSO4·5H2O and Zn5(OH)8Cl2·H2O. The type and relative amounts of different corrosion products were related to the location and type of exposure site but no systematic changes were observed with the time of exposure. Table 1. Test sites in the exposure program Code Name Country Distance to Sea(m) A Brest France <5 B Bohus-Malmön (I) Sweden <5 C Bohus-Malmön (II) Sweden 300 D Ijmuiden Netherlands 2600 E Cadiz Spain 750 F Jiangjin China ̴900 km G Ostrawa Czech Republic ̴500 km H Dubai UAE 2000 I Daytona Beach USA 100 J Quindao China 10 K Wanning China 100 L Bangkok Thailand 35 km M Sattahip Thailand 10 N Singapore SIngapore 10 References 1- D. Knotkova, V. Kucera, P. Boschek: ASTM STP 1421 Outdoor Atmospheric Corrosion, pp.107, 2002 2- A. Mikhailov, J. Tidblad and V. Kucera: Protection of Metals, 40(6),pp 541-550, 2004 3- M. Morcillo, E. Almeida, B. Chico, D. De la Fuente Analysis of ISO Standard 9223 (Classification of Corrosivity of Atmospheres) in the Light of Information Obtained in the Ibero-American Micat, ASTM STP 1421 Outdoor Atmospheric Corrosion, 2002, pp. 59. 4. I. Odnevall, C. Leygraf, Atmospheric Corrosion, ASTM STP 1239, ASTM, Philadelphia, 1995, pp. 215–229

Rolling Contact Fatigue of Superelastic Intermetallic Materials (SIM) for Use as Resilient Corrosion Resistant Bearings

Superelastic intermetallic materials (SIM), such as 60NiTi, are emerging as candidates for corrosion and shock-resistant rolling element bearings. Compared with metals, the intermetallic materials are more brittle and may be prone to rolling contact fatigue degradation. In this paper, a series of three ball-on-rod rolling contact fatigue tests were conducted using polished steel balls and NiTi rods prepared by vacuum casting and powder metallurgy techniques. The test protocol matched that used in ASTM STP 771 except that the steel balls were not intentionally roughened. In general, the NiTi rods exhibit fatigue damage at much lower stress levels than commercial bearing steels. At the lowest stress level tested (1.7 GPa), 60NiTi rods that were largely free from processing defects gave acceptably long lives, and testing was terminated without failure after 800 h. At elevated stress (2.5 GPa), failure occurred for some specimens, while others reached the preset test length goal of 800 h. Improperly prepared 60NiTi rods that had unconsolidated particles or significant ceramic inclusions occasionally experienced surface fatigue prior to completion of the test period even at the lowest stress level. Alloyed NiTi rods containing small amounts of Hf as a microstructural processing aid generally endured higher stress levels than the baseline 60NiTi composition. Two predominant fatigue failure mechanisms were observed: intergranular (grain boundary) fracture and intragranular (through the grains) crack propagation. The results suggest that further fatigue capability improvements could be obtained through process improvements, microstructural refinements and alloying. SIM currently available are recommended for mechanically benign applications involving modest stress levels and rates of stress cycle accumulation. Applications that include high continuous loads (stress) and high speeds for long durations should be avoided.

Physically appropriate characterization of fatigue crack propagation rate in elastic–plastic materials using the $$J$$ J -integral concept

The current paper discusses the physically correct evaluation of the driving force for fatigue crack propagation in elastic–plastic materials using the $$J$$ -integral concept. This is important for low-cycle fatigue and for short fatigue cracks, where the conventional stress intensity range ( $$\Delta K$$ ) concept cannot be applied. Using the configurational force concept, Simha et al. (J Mech Phys Solids 56:2876–2895, 2008) , have derived the $$J$$ -integral for elastic–plastic materials with incremental theory of plasticity, $$J^{\mathrm{ep}}$$ , which is applicable for cyclic loading and/or for growing cracks, in contrast to the conventional $$J$$ -integral. The variation of this incremental plasticity $$J$$ -integral $$J^{\mathrm{ep}}$$ is studied in numerical investigations conducted on two-dimensional C(T)-specimens with long cracks under cyclic Mode I loading. The crack propagates by an increment after each load cycle. The maximum load is varied so that small- and large-scale yielding conditions prevail. Three different load ratios are considered, from pure tension to tension-compression loading. By theoretical considerations and comparisons with the variation of the crack tip opening displacement $$\delta _{\mathrm{t}}$$ , it is demonstrated that the cyclic, incremental plasticity $$J$$ -integral $$\Delta J_{\mathrm{actPZ}}^{\mathrm{ep}}$$ , which is computed for a contour around the active plastic zone of the growing crack, is physically appropriate to characterize the growth rate of fatigue cracks. The validity of the experimental cyclic $$J$$ -integral, $$\Delta J^{\mathrm{exp}}$$ , proposed by Dowling and Begley (ASTM STP 590:82–103, 1976), is also investigated. The results show that $$\Delta J^{\mathrm{exp}}$$ is correct for the first load cycle, however, not fully appropriate for a growing fatigue crack.

A new basis for the application of the $$J$$ J -integral for cyclically loaded cracks in elastic–plastic materials

Fatigue crack propagation is by far the most important failure mechanism. Often cracks under low-cycle fatigue conditions and, especially, short fatigue cracks cannot be treated with the conventional stress intensity range \(\Delta K\)-concept, since linear elastic fracture mechanics is not valid. For such cases, Dowling and Begley (ASTM STP 590:82–103, 1976) proposed to use the experimental cyclic \(J\)-integral \(\Delta J^{\exp }\) for the assessment of the fatigue crack growth rate. However, severe doubts exist concerning the application of \(\Delta J^{\exp }\). The reason is that, like the conventional \(J\)-integral, \(\Delta J^{\exp }\) presumes deformation theory of plasticity and, therefore, problems appear due to the strongly non-proportional loading conditions during cyclic loading. The theory of configurational forces enables the derivation of the \(J\)-integral independent of the constitutive relations of the material. The \(J\)-integral for incremental theory of plasticity, \(J^{\mathrm{ep}}\), has the physical meaning of a true driving force term and is potentially applicable for the description of cyclically loaded cracks, however, it is path dependent. The current paper aims to investigate the application of \(J^{\mathrm{ep}}\) for the assessment of the crack driving force in cyclically loaded elastic–plastic materials. The properties of \(J^{\mathrm{ep}}\) are worked out for a stationary crack in a compact tension specimen under cyclic Mode I loading and large-scale yielding conditions. Different load ratios, between pure tension- and tension–compression loading, are considered. The results provide a new basis for the application of the \(J\)-integral concept for cyclic loading conditions in cases where linear elastic fracture mechanics is not applicable. It is shown that the application of the experimental cyclic \(J\)-integral \(\Delta J^{\exp }\) is physically appropriate, if certain conditions are observed.

SRH Recombination Strength of Interstitial Iron in Solar Grade Silicon

Shockley-Read-Hall (SRH) recombination is the main determinant for the effective minority carrier lifetime in silicon. This research has focused on the study to find the recombination strength of interstitial iron on low injection Shockley-Read-Hall recombination in compensated solar grade silicon by means of analytical modelling. This study found that strength of iron in SRH recombination is depends on the doping concentration and symmetry of minority carrier capture cross-section. This study shows that iron become more recombination active at higher doping and at lower symmetry of capture cross-section. Full Text: PDF References A.A. Istratov, T. Buonassisi, R.J. McDonald, A.R. Smith, R.Schindler, J.A. Rand, J.P. Kalejs, and E.R. Weber, "Metal content of multicrystalline silicon for solar cells and its impact on minority carrier diffusion length", J. Appl. Phys. 94, 6552 (2003). CrossRef T. Buonassisi, M.A. Marcus, A.A. Istratov, M. Heuer, T.F. Ciszek, B. Lai, C. Zhonghou, and E.R. Weber, "Analysis of copper-rich precipitates in silicon: Chemical state, gettering, and impact on multicrystalline silicon solar cell material", J. Appl. Phys. 97, 63503 (2005). CrossRef T. Buonassisi, A.A. Istratov, M. Heuer, M.A. Marcus, R. Jonczyk, J. Isenberg, B. Lai, C. Zhonghou, S. Heald, W. Warta, R. Schindler, G. Willeke, and E.R. Weber, "Synchrotron-based investigations of the nature and impact of iron contamination in multicrystalline silicon solar cells", J. Appl. Phys. 97, 74901 (2005). CrossRef T. Buonassisi et al., "Chemical natures and distributions of metal impurities in multicrystalline silicon materials", Prog. Photovolt: Res. Appl. 14, 513?531 (2006). CrossRef T. Buonassisi, A.A. Istratov, M.D. Pickett, J.P. Rakotoniaina, O. Breitenstein,M.A. Marcus, S.M. Heald, and E.R. Weber, "Transition metals in photovoltaic-grade ingot-cast multicrystalline silicon: Assessing the role of impurities in silicon nitride crucible lining material", Journal of Crystal Growth 287, 402?407 (2006). CrossRef A.A. Istratov, H. Hieslmair, and E. R. Weber, "Iron and its complexes in silicon", Appl. Phys A: Material Science and Processing 69, 13 ? 44 (1999). CrossRef D. Macdonald, PhD thesis, Australian National University (2001). K. Graff, "Metal impurities in silicon-device fabrication", Springer-Verlag, Berlin (1995). CrossRef R . Hall, "Electron-Hole Recombination in Germanium", Physics Review 87, 387 (1952). CrossRef W. Shockley and W. Read, "Statistics of the Recombinations of Holes and Electrons", Physical Rev.87, 835-842 (1952). CrossRef Y. Yoon, B. Paudyal, J. Kim, Y. Ok, and P. Kulshreshtha, "Effect of nickel contamination on high carrier lifetime n-type crystalline silicon", Journal of Applied Physics 111, 033702 (2012). CrossRef Libal J. et al, "Effect of compensation and of metallic impurities on the electrical properties of Cz-grown solar grade silicon", Journal of Applied Physics 104, 10450 (2008). CrossRef M. Ziaur Rahman and M. Jahangir Alam, "Enhancement of Minority Carrier Lifetime of Fe Contaminated Boron-Phosphorus Compensated p-Type SoG Silicon", Photonics Letters of Poland 5(2), 75 ? 77 (2013) DirectLink D. K. Schroder, American Society for Testing and Materials, ASTM STP 1340, 1998. J. Schmidt, C. Berge, A.G. ABerle, "Injection level dependence of the defect-related carrier lifetime in light-degraded boron-doped Czochralski silicon", Appl. Phys. Lett. 73 (15), 2167-9 (1998). CrossRef M. Ichimura et al., "Temperature Dependence of Carrier Recombination Lifetime in Si Wafers", J. Electrochem. Soc. 145 (9), 3265 ? 71 (1998). CrossRef

Improved Incremental J-Integral Equations for Determining Crack Growth Resistance Curves

The J-integral resistance curve is the most important material properties in fracture mechanics that is often used for structural integrity assessment. ASTM E1820 is a commonly accepted fracture toughness test standard for measuring the critical value of J-integral at the onset of ductile fracture and J-R curve during ductile crack tearing. The recommended test procedure is the elastic unloading compliance method. For a stationary crack, the J-integral is simply calculated from the area under the load-displacement record using the η-factor equation. For a growing crack, the J-integral is calculated using the incremental equation proposed by Ernst et al. (1981, “Estimations on J-integral and Tearing Modulus T From a Single Specimen Test Record,” Fracture Mechanics: Thirteenth Conference, ASTM STP 743, pp. 476–502) to consider the crack growth correction. For the purpose of obtaining accurate J-integral values, ASTM E1820 requires small and uniform crack growth increments in a J-R curve test. In order to allow larger crack growth increments in an unloading compliance test, an improved J-integral estimation is needed. Based on the numerical integration techniques of forward rectangular, backward rectangular, and trapezoidal rules, three incremental J-integral equations are developed. It demonstrates that the current ASTM E1820 procedure is similar to the forward rectangular result, and the existing Garwood equation is similar to the backward rectangular result. The trapezoidal result has a higher accuracy than the other two, and thus it is proposed as a new formula to increase the accuracy of a J-R curve when a larger crack growth increment is used in testing. An analytic approach is then developed and used to evaluate the accuracy of the proposed incremental equations using single-edge bending and compact tension specimens for different hardening materials. It is followed by an experimental evaluation using actual fracture test data for HY80 steel. The results show that the proposed incremental J-integral equations can obtain much improved results of J-R curves for larger crack growth increments and are more accurate than the present ASTM E1820 equation.

A Numerical Strip-Yield Model for the Creep Crack Incubation in Steels

Abstract A numerical strip-yield model was developed to simulate creep crack incubation in heat-resistant steels. The model is based on a formulation proposed by Newman (Newman, J. C., Jr., “A Crack-Closure Model for Predicting Fatigue Crack Growth under Aircraft Spectrum Loading,” Methods and Models for Predicting Fatigue Crack Growth under Random Loading, ASTM STP 748, J. B. Chang and C. M. Hudson, Eds., ASTM International, West Conshohocken, PA, 1981, pp. 53–84) for fatigue crack growth under variable amplitude loading. The time evolution of the plastic deformation ahead of a crack loaded in tension is modeled using the Norton law for secondary creep stage, and the primary and tertiary creep stages are neglected. The model assumes a pre-existing crack in a specimen and models the behavior of the material prior to the beginning of crack propagation due to creep loading. The evolution with time of the crack-tip plastic zone, crack-tip opening displacement, and yield strength in the plastic zone are computed at constant temperature for center crack panels. Comparison with two previous strip-yield models and experimental data is performed, and good correlation is obtained for several Cr-Mo-V steels. This approach to modeling creep crack incubation has the potential to be applied to other types of cracked specimens under constant or variable amplitude loading.

Principles of Design and Installation of Below-Grade and Building Deck Waterproofing in 2010

Abstract The introduction of new materials, the innovative use of various construction methods, and the popularity of vegetative (green) roofs make it timely to update and expand the 1990 article, “Principles of Design and Installation of Building Deck Waterproofing” [Ruggiero, S. S. and Rutila, D. A., “Principles of Design and Installation of Building Deck Waterproofing,” Building Deck Waterproofing, ASTM STP 1084, L.E. Gish, Ed., ASTM International, West Conshohocken, PA, 1990, p. 5. We review the state of the art for materials and practices, and apply the lessons learned over the past 20 years of below-ground and building deck waterproofing. Of particular importance are the following: Performance and durability advancements in fluid-applied systems have resulted in increased use. New chemical formulations as well as recognition of settled technologies that work allow some fluid-applied membranes to demonstrate proven durability equal to sheet membrane systems. Sodium bentonite-polymer composite systems resolve many past performance questions and often provide advantages over other options. Blind-side and other foundation waterproofing systems are increasingly driven by foundation forming and concrete placement, and support of excavation designs. Vegetative (green) roofing has created challenges not completely addressed by “plaza waterproofing” designs, but key principles of deck waterproofing must still be applied to vegetative roofing.

Comparative Analysis of Macrotexture Measurement Tests for Pavement Preservation Treatments

Field pavement preservation research concerning two accepted methods for measuring pavement macrotexture was done on a state highway in Oklahoma. The 2.5-year project used the outflow meter ASTM STP 583 and the Transit New Zealand TNZ T/3 sand circle to measure macrotexture on 23 asphalt and concrete pavement preservation treatments. Through a protocol of monthly macrotexture measurements in the field, the researchers observed functional limitations, caused by the physical mechanics of the methods, on the accuracy of macrotexture measurements on both standard tests. It was found that the sand circle should be used on pavements with macrotexture greater than 0.79 mm (0.03 in.); the outflow meter should be used on pavements with textures of less than 1.26 mm (0.05 in.). Both tests were accurate in the range of 0.79 to 1.26 mm. These results applied to both asphalt and concrete pavements.

More Accurate Approximation of J-Integral Equation for Evaluating Fracture Resistance Curves

Abstract Accurate estimate of the J integral is required in a valid experimental evaluation of J-based fracture resistance curves for ductile materials. The fracture toughness test standard ASTM E1820 allows a basic method and a resistance curve method to be used experimentally to evaluate the J values via standard specimens. The basic method obtains J estimates using the η factor method that was developed for a stationary crack. The resistance curve method obtains crack growth corrected J estimates using an incremental equation that was proposed by Ernst et al. (“Estimation on J-Integral and Tearing Modulus T from a Single Specimen Test Record,” Fracture Mechanics: Thirteenth Conference, ASTM STP 743, 1981, pp. 476–502) for a growing crack and has been accepted as the most accurate equation available for about three decades. Recently, Neimitz (“The Jump-Like Crack Growth Model, the Estimation of Fracture Energy and JR Curve,” Eng. Fract. Mech., Vol. 75, 2008, pp. 236–252), and Kroon et al. (“A Probabilistic Model for Cleavage Fracture with a Length Scale-Parameter Estimation and Predictions of Growing Crack Experiments,” Eng. Fract. Mech., Vol. 75, 2008, pp. 2398–2417) presented two different approximate equations for the J-integral, which they proposed as more accurate than the Ernst equation. Therefore, further investigation is needed to determine a truly accurate approximation for the J-integral equation. With this objective, the present paper proposes different mathematical and physical models to approximate the J-integral equation. The physical models are developed in terms of the deformation theory and the jump-like crack growth assumption. Relations between the proposed models and the existing equations are identified. Systematic evaluations of the proposed models are then made using a theoretical procedure of J-R curves for both low and high strain hardening materials, and using experimental data from an actual single edge-notched bend specimen made of HY80 steel. Accuracy of the proposed models is determined, and a more accurate approximation of J-integral equation is thus suggested for J-R curve testing.

Revised Incremental J-Integral Equations for ASTM E1820 Using the Crack Mouth Opening Displacement

Abstract The incremental J-integral equations used in ASTM E1820 were developed utilizing the work input to the test specimen, and utilize the load versus load-point/line displacement (LLD) data obtained from the fracture test. The analysis of Ernst et al. [Fracture Machanics: Thirteenth Conference, ASTM STP 743] was then used to obtain crack growth corrected estimates of the J-integral as needed for an accurate J-R curve evaluation. For the compact type specimens, the crack mouth opening displacement (CMOD) gage was moved to the load line so that an adequate estimate of LLD could be obtained from the clip gage and utilized for compliance-based crack extension and incremental J-integral estimates. For the single edge-notched bend [SE(B)] specimens, however, it has been necessary to measure both CMOD for compliance-based crack length estimates and LLD for the crack growth corrected J-integral calculations. Additional experimental complexity and expense are thus added. ASTM E1820 includes a “basic” procedure which allows evaluating the J-integral using CMOD without crack growth corrections if the result is used only for evaluation of initiation toughness. Recently, Annex A16 based on work of Wallin and Laukkanen [Engineering Fracture Mechanics, Vol. 71, 2004, pp. 1601–1614] has been added to ASTM E1820 that presents a multiple-step procedure to obtain a crack growth corrected J-R curve from the basic method data. A more direct approach was proposed recently by Zhu et al. [Journal of ASTM International, Vol. 5, No. 5, 2008, paper ID: JAI 101532] using an incremental procedure to obtain the desired, crack growth corrected J-R curve from the CMOD data of SE(B) specimens with two geometry factors ηCMOD and γCMOD similar to the parameters presently used in the existing LLD-based J-integral analysis. Using fracture toughness test data for SE(B) specimens, detailed comparisons and discussions are made between the proposed method and the ASTM E1820 CMOD methods in determination of J-R curves for HY80 steels. As the basis of comparison, the “accurate” solutions obtained from the standard LLD-based incremental J-integral method are provided for all specimens considered. The difference between the CMOD and LLD methods are then quantified. The results show that the proposed CMOD incremental J-integral equations are simple and effective, and thus are recommended here for use in ASTM E1820 for testing J-R curves and for reducing test costs and complexity.

Bearing strength of pin‐connected polymer composites subjected to dynamic loading

AbstractIn this study, static load bearing strength of pin‐connected carbon fiber‐reinforced polyphenylenesulphide (PPS) composites that have [(0°/90°)]3s stacking sequence was investigated. Firstly, the samples were loaded dynamically, and then the same samples were loaded statically. The results obtained from this sequential experiment were compared with the results obtained from samples that were loaded only statically. In addition, the fatigue life and failure mechanisms were investigated with respect to the selection of the geometrical parameters. Dynamic and static loading experiments were performed according to the ASTM STP 749 and ASTM D953 standards, respectively. To obtain optimum load bearing values, the ratio of distance between the edge and hole center to hole diameter (E/D) and ratio of sample width to hole diameter (W/D) has been systematically changed. According to the experimental results, maximum load bearing values have been obtained when E/D ratio was equal to 2. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Fatigue life prediction for toe ground welded joints

The paper presents the results of an investigation of the effect of weld toe burr grinding on the fatigue performance of non-load-carrying transverse fillet welded joints. Crack initiation and propagation were monitored by a modified replica method. It was found that, although the average life increase due to toe grinding was in agreement with published data, the majority of the fatigue cracks in specimens that gave fatigue lives <∼10 6 cycles initiated at flaws just beneath the ground surface. Both the experiments and calculations based on fracture mechanics suggested that the fatigue lives of the toe ground joints in this life regime were dominated by the crack propagation process. However, in the long life regime (>10 6 cycles), crack initiation became significant. Reasonable estimates of the crack initiation period were made using the local stress approach proposed by Lawrence et al. [Lawrence FV, Mattos RJ, Higashida Y, Burk JD. Estimating the fatigue crack initiation life of welds. In: Hoeppner DW, editor, Fatigue Testing of Weldments, ASTM STP 648, American Society for Testing and Materials; 1978, p. 134–58]. The investigation suggested that more benefit from weld toe grinding could be claimed in the long ( N > 10 6 cycles) than the short life regime.

An anisotropic mechanical fatigue damage evolution model for Pb-free solder materials

Evaluating state of damage in a ductile material as it experiences mechanical fatigue and cyclic loading poses much complexity, and has been the subject of many researches. This study revisits the anisotropic damage model developed by Lemaitre [Lemaitre, J. 1992. A course on damage mechanics. Springer-Verlag Publishing, Berlin] and proposes to use his model combined with two damage models, a micro-mechanics and mechanism-based damage evolution model (Energy Partitioning Damage Evolution (EPDE) [Ladani, L.J., Dasgupta, A., 2008b. A meso-scale damage evolution model for cyclic fatigue of viscoplastic materials. Int. J. Fatigue 2. doi:10.1016/j.ijfatigue.2008.03.013]), and a Unified Creep Plasticity-based (UCP-based) model [ McDowell, D.L., Miller, M.P., Brooks, D.C., 1994. A unified creep plasticity theory for solder alloys. In: Schroeder, S.A., Mitchell, M.R. (Eds.), Fatigue of Electronic Materials, ASTM STP 1153. American Society of Testing and Materials, Philadelphia, pp. 42–59] to predict the state of damage. These two models are then examined for pure shear and are applied to Pb-free solder materials. New anisotropic damage model exponents are generated using experimental data for Pb-free solder for both EPDE and UPC-based models. The exponents generated using these anisotropic models are compared with exponents generated previously under the assumption of isotropic and homogenous damage evolution. These two models were verified using a 3-D Finite Element simulation of the test specimen. Load drops produced by EPDE and UCP-based models were compared with the experiments. The same test set up was used formerly (by Zhang [Zhang, Q. 2004. Isothermal Mechanical and Thermo-Mechanical Durability Characterization of Selected Pb-free solders. Ph.D. Dissertation Defense, Department of Mechanical Engineering, University of Maryland, College Park]) to generate the creep and plastic material properties, and E-P damage model constants for Pb-free solders. Therefore, EPDE exponents that were generated in this study show a much closer correlation with the experimental results.