Effect Of Water Environment Research Articles

Proposed New Fatigue Design Curves for Carbon and Low-Alloy Steels in High Temperature Water

Abstract High temperature (>300°F, 149°C) water has been found to greatly accelerate fatigue crack growth rates in carbon and low-alloy steels. Current ASME Code fatigue design curves are based entirely on data obtained in air. While a factor of 2 on life was applied to the air data to account for environmental effects, the actual effects have been found to be an order of magnitude greater in the low-cycle regime. A great deal of work has been carried out on these environmental effects by talented investigators worldwide. The ASME Code Subgroup on Fatigue Strength has been working for 20years on the development of new fatigue design methods and curves to account for high temperature water environmental effects. This paper presents an overview of the data and analyses used to formulate proposed new environmental fatigue design curves, which maintain the same safety margins as existing Code fatigue design curves for air environments, and a historical summary of ASME Code Work in this field.

Soil and water environmental effects of fertilizer-, manure-, and compost-based fertility practices in an organic vegetable cropping system

Degraded soil quality, which decreases agricultural productivity and increases nonpoint source pollution of surface water, may be ameliorated by employing soil organic matter enhancing management, such as practiced by compost use in organic farming. The value of compost applied at rates lower than those required to supply crop nutrient needs requires investigation because applying compost at agronomic nitrogen rates may not be economically feasible for organic vegetable producers. We conducted field research during 2000–2002 on a Luvisol to compare the nutrient and non-nutrient effects of various rates and timings of mixed poultry litter-yard waste compost with a traditional organic fertilizer (poultry litter) and inorganic fertilizer on environmental soil attributes and water quality in an organic vegetable crop rotation. Soil organic C, total N, and available P increased 60%, 68%, and 225%, respectively, above the control with the application of 144 Mg ha −1 compost (dry wt.) during the 3-year study, but the low rate of compost (31 Mg ha −1) did not affect soil C or N. Compost N mineralization was not synchronous with sweet corn N assimilation, resulting in excess root zone nitrate that would have posed a leaching risk without the use of a winter rye N-scavenging cover crop. The concentrations of nitrate N that leached below the tillage zone occasionally exceeded the 10 mg L −1 health standard but were not different among the agronomic rates of compost, poultry litter, fertilizer, and control treatments for nearly every sampling event. Despite increasing runoff water concentrations of N and P, the high compost rate reduced the amounts of N and P that were transported from the soil surface by five-fold and four-fold, respectively, compared to the inorganic fertilizer due to a four-fold reduction in runoff volume. Crop yields did not benefit from low compost rates during the 3-year duration of the study; however, improvements in some bulk density and porosity indicated that benefits of longer term, low compost rate additions may accrue over time.

Study of the high cycle thermal fatigue of austenitic stainless steels components in PWR water environment

The new approaches that have been recently introduced to account for the potential effects of the PWR water environment on the high cycle thermal fatigue of austenitic stainless steel components have been experimentally assessed under conditions matching the actual in service loadings.

Effects of water environment on tribological properties of DLC rubbed against stainless steel

The effects of water environment on tribological properties of DLC against stainless steel were studied for development of the hydraulic pumps, valves and cylinders based on metal. A ball-on-disk tribotester was developed for detailed examination of water environment, such as temperature (20–80 °C), dissolved oxygen (0.01–8 ppm), water pressure (0.1–20 MPa) and dissolved ions. DLC was deposited on the disk by the unbalanced magnetron spattering system. Pure water and quasi-tap water were used to study the effects of dissolved ions. The results showed that temperature and dissolved ions have a major impact on friction and wear of DLC. EPMA, XPS and AES indicated that tribofilm on the metal surface, which consists mainly of C, O and Fe, plays important role for the phenomena.

Effects of Humidity and Water Environment on Fatigue Crack Propagation in Magnesium Alloys

This paper presents the effects of environment on fatigue crack propagation (FCP) in two magnesium alloys, rolled AZ31 and extruded AZ61. FCP tests have been performed using electro-hydraulic fatigue testing machine operating at a frequency of 1Hz at a stress ratio, R, of 0.05 in distilled water and in dry air. The dew point of dry air was −60°C. The obtained results were compared with those already established in laboratory air, and the effects of humidity and water environment were discussed on the basis of fractographic analysis of fracture surfaces. The effect of cyclic frequency was also studied. Both alloys exhibited basically the same FCP behaviour regardless of environment. FCP rates were nearly the same in laboratory air and in distilled water, while approximately an order of magnitude slower in dry air than in those environments. After allowing for crack closure, the effect of environment still existed, where FCP rates were the fastest in laboratory air, then in distilled water, in dry air in decreasing order. Fractographic analysis revealed that fracture surfaces were extensively brittle in laboratory air, while entirely covered with corrosion products in distilled water. It was believed, therefore, that different FCP mechanisms operated in laboratory air and in distilled water, possibly hydrogen embrittlement and anodic dissolution, respectively. The frequency dependence of FCP rate was not recognized in dry air and less remarkable in laboratory air over a wide range of frequencies of 0.01Hz to 10Hz, while FCP rates became faster with decreasing frequency in distilled water.

2820 ステレオコンプレックス型ポリ乳酸繊維の機械的特性に及ぼす環境効果(J08-2 バイオメカニクス,J08 生体・環境適合材料の創製・強度評価技術開発)

Stereocomplex-type polylactic acid (SCPLA) is gaining attention in the various field due to its melting point of 220℃, which is higher than that of pure poly-L-lactic acid (PLLA) and poly-D-lactic acid (PDLA). However, exposure of polylactic acid (PLA) to environmental agents such as sunlight, water, heat, degrades its mechanical properties. This study reports the effect of water and high temperature environment on properties of PLA fiber. When SCPLA fiber was immersed in water at high temperature, tensile strength drastically decreased with the hydrolysis of SCPLA. Compared to the PLLA fiber, however, SCPLA fiber had a greater resistance to hydrolysis. When SCPLA fiber and PLLA fiber were immersed in water at high temperature, sem examination of these fibers revealed regular patterns of cracks running in the vertical direction to the fiber axis.

ICONE15-10293 Development of in-pile SCC test technique and crack initiation behavior using pre-irradiated austenitic stainless steel at JMTR

Irradiation assisted stress corrosion cracking (IASCC) is one of the critical concerns when stainless steel components have been in service in light water reactors (LWRs). In general, IASCC can be reproduced on the materials irradiated over a certain threshold fluence level of fast neutron by the post-irradiation examinations (PIEs). It is, however, considered that the reproduced IASCC by PIEs must be carefully distinguished from the actual IASCC in nuclear power plants, because the actual IASCC occurs in the core under simultaneous effects of radiation, stress and high temperature water environment. Hence, we have embarked on a development of the test technique for the in-pile IASCC testing. We adopted the uniaxial constant load (UCL) tensile test method with small tensile specimens for in-pile SCC initiation test, and tried to evaluate the crack initiation behavior as the detection of specimen rupture or detailed observation of surface of loaded specimens. In this paper, we described the techniques for in-pile crack initiation test and the results of evaluation for crack initiation behavior comparing results from in-pile and out-of-pile tests on type 304 stainless steel. As a result of this study, it was inferred that an acceleration effect of in-pile environment for SCC initiation behavior was not observed under the test condition of this study.

Hydro-ecological Processes, Water-Environmental Effects and Integrated Control of Ecological Security for Wetlands in Huang-Huai-Hai Region of China

This presentation is based on Hydro-ecological Processes,Water-Environmental Effects and Integrated Control of Ecological Security for Wetlands in Huang-Huai-Hai Region of China,a project of the National Basic key Research Program.It recommends the important meaning of hydro-ecological processes,water-environmental effects and integrated control of ecological security for wetlands studies to the China's social technological development,research status and evolution trend,key scientific issues that need to be solved,main research contents and general approaches.The general goals of the project are to:(1) enrich and develop wetland theory at a wetland-system level including rivers,lakes and estuaries;(2) deal with a series of fundamental scientific problems faced by the wetland researchers in China;(3) effectively coordinate the contradictions between regional socio-economic development and wetland protection and provide basis on theory and technology for integrated control modes of wetland systems and environment-friendly society.

Effect of Water Environment on Fatigue Behaviors of Magnesium Alloys

Fatigue characteristics of two kinds of magnesium alloys ; AZ92A casting plate and AZ31M rolled plate, in air and in purified water have been investigated. Plane bending fatigue tests were carried out and fatigue crack initiation behaviors were observed successively. In the air, S-N curve for AZ92A was continuous curve type, however, the one for AZ31M was bi-line type with fatigue limit, because it has a non-propagating microcrack at the fatigue limit. In the water environment, the fatigue strength decreased for both alloys. The tendency of degradation was remarkable under long life region and the fatigue limits decreased by about 50% of that in the air. Crack growth tests under push-pull loading were carried out with center notched specimens. For AZ92A, crack growth rates were found to increase with water environment. However, for long crack their growth rates were lower than that in the air because of crack closure by wedge effect of a corrosion product. Such a effect of water environment on crack growth was not much notable for AZ31M.

3011 PLA系グリーンコンポジットへの水環境の影響 : 母材樹脂について(S40-3 生分解ポリマー,木質材料の強度評価,S40 バイオマス由来材料の成形加工と特性評価)

Green composites are expected as alternative materials of multipurpose plastics. As the runup to green composites, it is necessary to explain various properties of matrix. This study reported the effect of water Environment on mechanical properties of matrix (PLA). As a result, PLA absorbed water in water environment and its mechanical properties decreased with increase of water absorption. On occasions When PLA was in water environment at high temperature and for a long time, its mechanical properties decreased with development of degradation. It is recognized, by observation of specimens and decreasing of its weight, that this decreasing of mechanical properties are caused by corrosion layer weaken by elution. And It is recognized by FT-IR analysis that Corrosive layer was caused by ester hydrolysis.

The predictions and applications of fatigue lifetime in alumina and zirconia ceramics

The lifetime prediction of ceramics has been discussed on the basis of the relation between the stress intensity factor K I and the crack velocity V. In this paper, the effects of both cyclic loading and water environment on the K I– V characteristics were studied by the crack growth tests using the double torsion method under static and cyclic loading in both environments of air and water for alumina and zirconia ceramics. The K I– V characteristics determined by the double torsion method were used to predict time-to-failure under cyclic fatigue of alumina and zirconia ceramics. The predictions agreed qualitatively with the experimental results.

Crack propagation behavior and lifetime prediction in alumina and zirconia

The lifetime prediction of ceramics is discussed on the basis of the relationship between stress intensity factor KI and crack velocity v. The effects of water environment, the cyclic loading and microstructure of material on KI-v characteristics are studied by carrying out the crack growth tests by the double torsion (DT) method under the static and cyclic loading in both environments of air and water for alumina and zirconia. KI-v characteristics determined by the double torsion method are used to predict time-to-failure under the cyclic loading of alumina and zirconia ceramics. The predictions agree qualitatively with the experimental results.

Place-Based Environmentalism and Global Warming: Conceptual Contradictions of American Environmentalism

Until recently, the history of environmentalism was primarily a history of attention to place. In the United States, environmentalists have gotten rather good at protecting and managing particular places such as mountains, forests, and watersheds and specific resources such as trees, soil, wildlife, air, and water. Environmentalism has become an enormously popular social movement, with, by some measures, more than 80 percent of Americans considering themselves environmentalists. Thousands of organizations, ranging from local volunteer groups to national nonprofits, address issues as diverse as open space, air and water pollution, biological diversity, environmental justice, and environmental effects on human health. The successes of this movement have been striking. Our National Parks, National Forests, and wilderness areas are touted as models for the world and are well complemented by state, municipal, and private protected areas. The Endangered Species Act successfully resolves many conflicts between rare creatures and development. Rivers have been cleaned up, and once-spurned urban waterfronts now draw real estate and tourism development. Americans drink cleaner water and breathe cleaner air than much of the rest of the world, and attempts to weaken regulatory frameworks are consistently met with public disapproval.

The effect of water environment on the hopping conductivity of an aperiodic nucleotide base stack

We have used the matrix block negative factor counting method to calculate the density of states of an aperiodic single stack of DNA (a part of a human oncogene), consisting of 100 nucleotide bases in the DNA B conformation. The nearest water molecules were taken into account in the calculation. The work refers to the valence bands region of the stacks. Consequently the inverse iteration method was used to determine the Anderson localization of the physically interesting wave functions. The hopping frequencies between the units were determined from these. They have been used as input in a random walk theory. According to the results obtained, the real part and the absolute value of the complex hopping conductivity gets saturated at the frequency of 10 12 s −1. Its value lies at ∼10 −4 Ω −1 cm −1, which is by two orders of magnitude larger than the one obtained previously in the absence of water (∼10 −6 Ω −1 cm −1). Different reasons for this rather large effect of water are discussed (e.g. basis set improvement by bases set superposition, the effect of the water dipoles).

アルミナおよびジルコニアの疲労き裂進展特性に及ぼす水環境および繰返し負荷の影響

The lifetime prediction of ceramics has been discussed on the basis of the relationship between the crack velocity, V, and the stress intensity factor KI. In the present study, crack growth tests by double torsion (DT) method were carried out under static and cyclic loadings in order to examine the effect of both water environment and stress cycling on the KI-V characteristics for alumina and zirconia. In both materials in static and cyclic loading crack velocity in water was higher than that in air, and that tendency was more remarkable in zirconia. In addition, the decrease in crack propagation parameter n and the increase in crack velocity due to cyclic stress were clearly observed in both materials in air and water environment. The KI-V characteristics determined by double torsion method were used to predict time-to-failure under static and cyclic loading of alumina and zirconia ceramics. The predictions agreed qualitatively with the experimental results.

Laser Flash Photolysis Investigation of the Triplet−Triplet Annihilation of Anthracene in Supercritical Water

The effects of the supercritical water environment on the triplet−triplet annihilation of anthracene, a simple, well-characterized reaction that is known to be diffusion controlled in normal liquids, was investigated at temperatures from 375 to 450 °C and pressures from 50 to 350 bar. The reaction was found to occur just slightly above the diffusion-control limit, which was estimated from the Stokes−Einstein based Debye equation, when spin statistical factors are taken into account. This is in qualitative agreement with previous studies of diffusion-controlled reactions in lower temperature supercritical fluids (SCFs). Thus, the supercritical water environment is similar to that of lower temperature SCFs for diffusion-controlled reactions of nonpolar hydrocarbon species. There is no evidence of solvent clustering and any influence of solute/solute interactions is small. Finally, the mechanism of the reaction appears to be the same as in nonpolar liquid solvents.

Effect of Water Environment on Mode II Delamination Fatigue in Interlayer-Toughened CFRP.

The effect of water environment on delamination fatigue crack propagation behavior was investigated using unidirectional CFRP laminates made from Toray prepregs T800H/3900-2. T800H/3900-2 has toughened interlayer which is composed of epoxy resin and thermoplastic polyamide particles. Tests were carried out under mode II loading using end notched flexure specimens which were moisture-conditioned up to the saturated level. In the static tests, the value of the fracture toughness for the moisture-saturated specimen was slightly smaller than that for the dry specimen in air. In the fatigue tests, the crack propagation rate, da/dN, was expressed as a power-low function of the maximum energy release rate, GII max in the region where da/dN>5×10-10m/cycle. Below this region, there exists the threshold value of GII max. The threshold value for the moisture-saturated specimen in water was smaller than that for the dry specimen in air. Glass transition temperatures were measured both in moisture-saturated state and in dry state using differential scanning calorimetry. The decrease in the glass transition temperature indicated the ductility increase of epoxy. Microscopic observation revealed that the ductility increase of the epoxy affected the morphology of the fracture surfaces under fatigue loading.

Effect of the Crystal Grain Size on the Cyclic Fatigue Behavior of Glass Ceramics. (Examination for Multiple Surface Cracks in Water Environment).

In order to examine the effect of crystal grain size on the fatigue behavior of glass ceramics, cyclic fatigue tests were carried out by four-point bending load under both environments in air and water. A single crack and three collinear cracks were introduced on the surface of plate specimens by Vickers micro hardness indentation. The crystal grain size of the glass ceramics in this work was about 1μm, and it was increased from about 0.05μm used in previous work. As a result, the time-to-failure to the cyclic fatigue of the glass ceramics with a large crystal grain size obviously did not decrease by the effects of water environment and the multiple surface cracks, comparing with that of the glass ceramics with a small crystal grain size. Therefore, the interaction between multiple surface cracks may not be effective sufficiently for glass ceramics with a large crystal grain size. In addition, the fatigue strength of the glass ceramics increased with increasing crystal grain size. These facts mean that a dominant crack propagates along crystal grain boundaries.

Effect of Water Environment on Mode II Delamination Fatigue in Interlayer-Toughened CFRP.

The effect of water environment on delamination fatigue crack propagation behavior was investigated using unidirectional CFRP laminates made from Toray prepregs T 800 H/3900-2. T 800 H/3900-2 has toughened interlayer which is composed of epoxy resin and thermoplastic polyamide particles. Tests were carried out under mode II loading using end notched flexure specimens which were moisture-conditioned up to the saturated level. In the static tests, the value of the fracture toughness for the moisture-saturated specimen was slightly smaller than that for the dry specimen in air. In the fatigue tests, the crack propagation rate, da/dN, was expressed as a power-law function of the maximum energy release rate, GIImax, in the region where da/dN>5×10-10m/cycle. Below this region, there exists the threshold value of GIImax. The threshold value for the moisture-saturated specimen in water was smaller than that for the dry specimen in air. Glass transition temperatures were measured both in moisture-saturated state and in dry state using differential scanning calorimetry. The decrease in the glass transition temperature indicated the ductility increase of epoxy. Microscopic observation revealed that the ductility increase of the epoxy affected the morphology of the fracture surfaces under fatigue loading.

Effect of Water Environment and Multiple Surface Cracks on Cyclic Fatigue Behavior of Glass Ceramics.

This paper examines the effects of interaction and coalescence of multiple surface cracks in water environment on fatigue behavior in brittle materials such as glass ceramics. For glass ceramic specimens with the three collinear cracks which introduced the different crack center distances by Vickers indentation, the cyclic fatigue tests in water environment were carried out with four point bending load. It was found that the time to failure for glass ceramics in water environment significantly decreased with the decrease in the crack center distance of multiple surface cracks, and was shorter than that in air. Moreover, from the crack growth parameter for a single crack, the predictions of the time to failure for multiple surface cracks were conducted by taking the interaction and coalescence into consideration. The predictions using the proposed crack growth model agree well with the experimental results.