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It has been shown by Shibata et al. that serrated deformation behavior of metals at cryogenic temperatures can be simulated generally very well by computer calculation. At the CEC-ICMC 2003, however, they reported that there are several differences between the deformation behavior of 304L steel obtained by the calculation and by actual tensile tests. For instance, the degree of load drops in the calculated serration of 304L steel is smaller than that of 316L steel in liquid helium, while the degree of load drops in the actual serration of 304L steel is larger than that of 316L steel. Shibata et al. suggested that this confliction was attributed to martensitic transformation, which is induced by much amount in practice during deformation of 304L steel but had not been considered in the calculation. In the present paper, heat, strain and strengthening generated by the transformation are considered in the calculation and their effects on the serration are examined. As a result, it was shown that the transformation strain decreases strain-hardening rate and transformation heat increases the degree of the load drops and temperature rises in the serration. Transformation strengthening increases strain hardening rate increases. If only martensite nucleated in Stage 3 is assumed to strengthen the steel, calculations reveal overall stress-strain curves approximately similar to ones actually observed. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Ogata et al. reported in 1996 results of international Round Robin tests on mechanical property measurement of several metals at cryogenic temperatures. Following the report, the standard deviation of Young’s modulus of 316L steel is much larger than those of yield and tensile strengths, that is, 4.6 % of the mean value for Young’s modulus, while 1.4 % and 1.6 % of the mean values for yield and for tensile strengths, respectively. Therefore, an international Round Robin test on Young’s modulus of two austenitic stainless steels at cryogenic temperatures under the participation often institutes from four nations has been initiated within these two years. As a result, the ratios of standard deviation to the mean values are 4.2 % for 304L and 3.6 % for 316L. Such a drop in the standard deviation is attributable to the decrease in the number of institute owing to the application of single extensometer or direct strain gage technique. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Tensile tests using round bar type specimens of 3, 5 and 7 mm in diameter were conducted at 20K in liquid hydrogen and also in gaseous helium at the same temperature for three major austenitic stainless steels, JIS SUS304L, 316L and 316LN, extensively used for cryogenic applications including liquid hydrogen transportation and storage vessels. Stress-strain curves were considerably different between circumstances and also specimen diameter, resulting in differences of strength and ductility. In liquid hydrogen, serrated deformation appeared after considerable work hardening and more active in specimens with larger diameter. Meanwhile serrated deformation was observed from the early stage of plastic deformation in gaseous helium at 20 K and serration was more frequent in specimens with smaller diameter. The serrated deformation behaviors were numerically simulated for 304L steel with taking thermal properties such as thermal conductivity, specific heat, heat transfer from specimens to cryogenic media into account, and some agreement with the experiments was obtained. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

In order to clarify the effect of test frequency on the fatigue crack growth rates (da/dN) of Ti-6Al-4V ELI alloy have been investigated at cryogenic temperature. The fatigue crack growth tests were conducted using the test frequencies of 5 and 20 Hz, respectively. At 4 K, the effects of the test frequencies on the fatigue crack growth rates of Ti-6Al-4V ELI alloy were not clear or significant. The fatigue crack growth rates in the low propagation rate region at 4 K were smaller than those at 293 K. On the other hand, those in the high propagation rate region at 4 K were bigger than those at 293 K. The former is considered that the crack closure level was higher as compared to that at 293 K and the latter is due to the difference values of the fracture toughness at 4 and 293 K, respectively. The fracture surfaces of compact tension (CT) specimens in the high propagation rate regions at each test temperature revealed the striations, and furthermore accompanied with the flute fracture surface at 4 K. On the other hand, those of CT specimens in the low propagation rate region at 4 K were found facet-like fracture surfaces corresponding with almost the α-grain size. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The notch effects on the high-cycle fatigue properties of Ti-6Al-4V ELI alloy have been investigated at cryogenic temperatures. Smooth and notched specimens with the Kt=1.5, Kt=2 and Kt=3 were prepared. High-cycle fatigue tests were carried out at 4, 77 and 293 K. One million cycles fatigue strength (FS) of smooth specimen was increased with a decrease of the test temperature. Although the FS of each notched specimen at 4 K were lower than those of 77 K. Fatigue crack initiation sites of the smooth, the Kt=1.5 and the Kt=2 notched specimens at 4 K were facets in the specimen interior (internal type fracture) and those of the Kt=3 notched specimens were at the notch root (surface type fracture). The size of individual facets comprising the internal fatigue crack initiation sites correspond to almost the α-grain size. Therefore, improvement of the fatigue strength of the notched specimens for Ti-6Al-4V ELI alloy which show internal type fracture at cryogenic temperatures requires attaining a smaller area size by grain refining. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

High-cycle fatigue properties at 4 K, 20 K, 77 K and 293 K were investigated in forged-INCONEL 718 nickel-based superalloy with a mean gamma (γ) grain size of 25 μm. In the present material, plate-like delta phase precipitated at γ grain boundaries and niobium (Nb)-enriched MC type carbides precipitated coarsely throughout the specimens. The 0.2% proof stress and the tensile strength of this alloy increased with decreasing temperature, without decreasing elongation or reduction of area. High-cycle fatigue strengths also increased with decreasing temperature although the fatigue limit at each temperature didn’t appear even around 107 cycles. Fatigue cracks initiated near the specimen surface and formed faceted structures around crack initiation sites. Fatigue cracks predominantly initiated from coarse Nb-enriched carbides and faceted structures mainly corresponded to these carbides. In lower stress amplitude tests, however, facets were formed through transgranular crack initiation and growth. These kinds of distinctive crack initiation behavior seem to lower the high-cycle fatigue strength below room temperature in the present material. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Wave propagation in an austenitic stainless steel specimen with a slit open to the lower surface is modeled using finite element method, with consideration of the effects of scattering at grain boundaries. The distribution of energy of a diffracted longitudinal wave shows that this wave has the strongest energy directly above the slit. As a consequence of this result, a new testing method is proposed. The new method is verified using austenitic stainless steel specimens. Experimental results show that the new method is applicable to austenitic stainless steel with high accuracy, to which the time of flight diffraction method (TOFD) is not applicable. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

MIRRORCLE-6X, the unique portable synchrotrons, generates brilliant hard X-rays. The purpose of this study is to investigate the biological effects of synchrotron radiation on cancer cells to identify its effectiveness. A549 human lung adenocarcinoma and DU145 human prostate adenocarcinoma cells were used. We examined biological effects on cancer cells by colony formation assay, micronucleus assay, WST-1 method, and apoptosis detection of flow cytometry. Results of these assay revealed that the biological effects of X-ray generated from MIRRORCLE-6X on cancer cells are similar to those of 4 MV X- ray from linear accelerator (linac). [ABSTRACT FROM AUTHOR]

In the development of Japan’s self-developed H-IIA launch vehicle, it is important to sufficiently comprehend the properties of materials under conditions in which the materials are used in the system for its design and the improvement of its reliability. Through the process of failure analysis of the LE-7 engine of H-II No. 8 in 1999, detailed materials data and photographs of the fracture surface were required as reference data to determine in terms of fracture morphology and to analyze the fracture stress. A series of mechanical properties tests, such as tensile tests, impact tests, fracture toughness tests, and fatigue tests, on Ti-5Al-2.5Sn ELI and Alloy 718 at room temperature to 4K were mainly conducted by NIMS and NASDA. The obtained tensile and fracture toughness properties were a little bit smaller than those reported by NASA and NRIM, however, the fatigue properties were relatively lower than the data reported so far. Data resulting from the tests were reviewed in detail and published in the form of data sheets. This paper will introduce the data sheet program on space use materials and discuss an effect of microstructure of Ti-5Al-2.5Sn ELI and Alloy 718 on their mechanical properties at cryogenic temperatures. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

To evaluate material risk caused by human-error, the notch effects on the fatigue properties of forged Ti-5Al-2.5Sn ELI alloy have been investigated at cryogenic temperatures. Smooth and notched specimens with the Kt=1.5, 2 and 3 were prepared. High-cycle fatigue tests were carried out at 4, 77 and 293 K. The S-N curves of each specimen shifted to higher stress level with a decrease of the test temperature. At 4 K, the fatigue strength of the Kt=3 specimens were substantially lower than those of the smooth specimens. Although the notch effects on the fatigue properties of the Kt=1.5 and the Kt=2 notched specimens are not clear or significant. Fatigue crack initiation sites of the smooth and the Kt=1.5 notched specimens were in the specimen interior (internal type fracture) and those of the Kt=2 and the Kt=3 notched specimens were at the notch root (surface type fracture). The location of the fatigue crack initiation sites showed transition from the internal type fracture for the Kt=1.5 notched specimens to the surface type fracture for the Kt=2 notched specimens. Therefore, the Kt values of the internal fatigue crack initiation sites correspond between 1.5 and 2. The sizes of the internal fatigue crack initiation sites were calculated by the √area. The √area sizes of the Kt=1.5 notched specimens and the smooth specimens were in a similar range and the fatigue strength of the two are not significant. [ABSTRACT FROM AUTHOR]

There has been a growing need in the electric utility industry to assess the remaining life of blades in gas turbines. It is quite important to nondestructively comprehend the depths of surface-breaking cracks in blades. Flexible eddy current array probes have been developed to overcome the major limitations of existing eddy current inspection systems. The use of an array of sensors allows cracks of all lengths to be detected and will ultimately allow real time data imaging to provide rapid inspection and easy interpretation. For this study using eddy current techniques, crack detection equipment has been developed and applied to gas turbine Stage 1 blades for field use. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Local fracture toughness of top, middle, bottom, and heat-affected zones of weld joints of SUS304L and SUS316L have been evaluated by a new testing procedure of J-evaluation on tensile test (JETT) with circumferentially notched round bar specimen. Delta (δ)-ferrite contents of those welds were changed between 0% and 10%. The tests were carried out at 293, 77, and 4 K. In the case of austenitic stainless steels, being too ductile at room temperature, this test method is effective at low temperatures. Fracture toughness at 4 K obtained by JETT was a little bit higher than that obtained by conventional CT specimens and was lower in weld metals than in base metals and decreased as the content of delta ferrite increased in both 304L and 316L. Scatter in the values of fracture toughness among the locations in weld metals were less than 50 % and were considered to be caused by effects of δ-ferrite grains. [ABSTRACT FROM AUTHOR]

Since 1986, a series of international interlaboratory comparisons on the evaluation of mechanical properties of cryogenic structural materials have been performed among the participants of VAMAS (the Versailles Project on Advanced Materials and Standards) TWA (Technical Working Area) 17 in order to establish unified test methods. Through these international collaborations and Round-Robin Tests (RRTs), we have accumulated knowledge about mechanical tests at 4 K, and have prepared a draft of an international standard for tensile testing in liquid helium. The draft was submitted to ISO TC164/SC1 as a new work item, and testing conditions, strain measurements, and other technical points have been discussed. The outline, development, and discussion of the document so far, with the results of RRTs, are presented. Objectives of other international standardization programs on mechanical testing in high magnetic field, J-Evaluation on Tensile Test, and for composite material are summarized also in this paper. [ABSTRACT FROM AUTHOR]

We studied the effects of δ-ferrite and welding structure on high-cycle fatigue properties for austenitic stainless steel weld metals at cryogenic temperatures. SUS304L and SUS316L weld metals contained 0% δ-ferrite (0% material) and 10% δ-ferrite (10% material) were prepared. High-cycle fatigue tests were carried out at 293, 77 and 4 K. The S-N curves of those weld metals shifted towards higher stress levels, i.e., the longer life side, with decreasing test temperature. The ratios of 10[sup 6]-cycles fatigue strength (FS) to tensile strength (TS) of 0% material decreased from 0.8 to 0.45 and those of 10% material decreased between 0.35 to 0.65 with decreasing test temperature. Fatigue crack initiation sites of SUS304L 10% material were almost at blowholes, and those of SUS316L 10% material were at weld pass interface boundaries. On the other hand, those of 0% materials were considered to be due to the interface of the solidification structure. Although δferrite reduces toughness at cryogenic temperatures in austenitic stainless steel weld metals, the effects of δ-ferrite on high-cycle fatigue properties are not significant. [ABSTRACT FROM AUTHOR]

A new J-evaluation method named JETT has been investigated through international round robin tests within the frame work of VAMAS activity. On the first stage, SUS316LN was tested as a common test material and it was found that JETT has potential to clarify the local fracture toughness. During last two years, 9% Ni steel was used and the effect of serrations on the toughness was investigated. As the results, the serration produces additional blunting at the notch tip resulting in delaying the crack initiation and giving higher fracture toughness. Nevertheless, it is recognized that JETT is a very conventional method to evaluate a relative toughness at the local area of the material. [ABSTRACT FROM AUTHOR]

From a practical viewpoint, it is convenient if Young's modulus can be determined without any special technique or device. There are standards to determine Young's modulus. However, the research about magnetic effects on the measurement of Young's modulus is not enough and the standard in a magnetic field has not been established especially at cryogenic temperatures. In the present research, four institutes measured Young's modulus of specimens machined from a unique commercial purity titanium plate with and without an application of magnetic fields up to 13 Tesla at liquid helium temperature, and the obtained values are compared. All participants used two or three extensometers and the slopes of the stress-strain curves obtained with them were averaged. The magnetic effect on the value of Young's modulus was not observed. But some deviation in the value was observed among participants. To use the averaging method and longer gage length is recommended. [ABSTRACT FROM AUTHOR]

This paper presents the results of a round-robin test program on cryogenic interlaminar shear strength of G-10CR glass-cloth/epoxy laminates. This program was organized under the auspices of the Technical Working Area 17 (TWA17) on Cryogenic Structural Materials of the Versailles Project on Advanced Materials and Standards (VAMAS), and performed to investigate the applicability of ASTM Standards D 3846-94 and D 2344-84 to woven fabric composite laminates at cryogenic temperatures. Specifically, two standard test specimen geometries (the double-notch shear specimen, and the short-beam shear specimen) were prepared. A total five laboratories in four different countries participated in this testing program. Each laboratory tested both specimens at cryogenic temperatures. A three-dimensional finite element analysis was also utilized to conduct a detailed study of the stress distributions within the specimens. [ABSTRACT FROM AUTHOR]