Interior Fracture Research Articles

Effects of Shot Peening on Fatigue Strength of 18%Ni Maraging Steel.

Rotating bending fatigue tests were carried out for an 18%Ni maraging steel to investigate the effect of shot peening on the fatigue strength. The fatigue strength increased markedly by the shot peening. The increase in the fatigue strength due to the shot peening depended on the shot size and the stress level. Fracture mode changed from the surface fracture in the short life region to the interior fracture i. e. fish-eye fracture in the long life region. And in the middle life region, both cracks initiated from the surface and the inside of material in dividually coalesced and lead to the final fracture. These results were discussed from the effect of shot size on the surface roughness and the depth and magnitude of compressive residual stress and work hardening.

Effect of an oxide dispersion on the hydrogen embrittlement of a Ni3Al base alloy

The susceptibility of a hot isostatically pressed Ni3AI, Cr, Zr alloy to hydrogen embrittlement has been studied. The base alloy and a second alloy containing 5 vol. % Y2O3 particles were tested by cathodically charging with hydrogen prior to or simultaneously with tensile testing. Embrittlement of both alloys was noted under both charging conditions, but was much more severe for simultaneous charging. Intergranular fracture due to hydrogen was noted in the base alloy, while the dispersoid-containing alloy failed along prior particle boundaries. The results are explained by a dislocation transport mechanism in which hydrogen is delivered to interior fracture sites by mobile dislocations. Much greater penetration of hydrogen is achieved under simultaneous charging conditions.

ポリカーボネートの疲労き裂進展における加速および遅延現象と破面の様相

Fatigue crack propagation behavior under single and multiple overloading conditions in polycarbonate was studied fractographically. The results obtained are summarized as follows:(1) The fracture surface of the crack extension accelerated by a single peak overload consists of two different regions, one contains many fine tearing lines oriented parallel to the crack propagation direction, and the other contains many voids. The former is similar to that found in the striation, and the latter is similar to that found in the discontinuous growth band.(2) The amount of crack extension accelerated by the overload is almost constant inside the specimen, but decreases markedly near the boundary between the interior fracture surface and the shear lips formed at the specimen surface layers.(3) The acceleration factor of crack propagation due to the overload is dominantly dependent on the ratio of peak to baseline stress, and is not affected appreciably by the crack propagation history.(4) The degree of retardation of crack propagation after a single peak overload shows the dependence on baseline stress, which can be explained from the viewpoint of crack propagation mechanisms.(5) The width of characteristic retardation region which is produced after the multiple overloads is about equal to the size of plastic zone at the crack tip produced by the overloads.

THE NORTH WEST SHELF

The region of the North West Shelf dealt with in this paper is underlain by three of the four basins which make up the Westralian Superbasin. The Bonaparte Basin lies outside the scope of this paper; the other basins are the Browse Basin, the offshore Canning Basin, here named the Western Canning Basin, and the offshore Carnarvon Basin, here called the Northern Carnarvon Basin. Sediments belonging to ten depositional sequences (Pz5, Mzl to Mz5, and Czl to Cz4) are present in the basins, the oldest being of Late Carboniferous and Permian age (Pz5).Deposition commenced in rift (interior fracture) basins under fluvial/deltaic conditions in the Late Permian/Early Triassic (Mzl), when the North West Shelf was part of Gondwana. Continental breakup took place in the Middle Jurassic (breakup unconformity between Mz2 and Mz3), and marine conditions prevailed over the Westralian Superbasin thereafter, with deposition taking place in a marginal sag setting. Siliciclastic sediments gave place to carbonates in the Late Cretaceous (Mz5) as the Indian Ocean grew larger.Parts of the area have been under permit since 1946, and to date some 227 exploration wells have been drilled. The most intensive exploration has taken place in the Northern Carnarvon Basin (191 wells), followed by the Browse Basin (20 wells), and Western Canning Basin (16 wells). Thirty- four economic and potentially economic discoveries have been made. The main target reservoirs are Triassic, Jurassic and Cretaceous, and the regional seals are Triassic and Cretaceous. The fields are of two types: pre- breakup unconformity (mainly tilted horst blocks), and post- breakup unconformity (usually four- way dip closures). Of the five producing fields, the North Rankin Gas Field is a pre- breakup field, while the four oil fields (Barrow, Harriet, South Pepper and North Herald) are all post- breakup.

Tecto-sedimentary cycles and depositional sequences of the Mesozoic and Tertiary from the Pyrenees

Tectonic deformation in the Pyrenees is the result of an essentially continuous process which has a discontinuous effect in the style of deformation and consequently, in the sedimentary record. Tecto-sedimentary discontinuities can be correlated on a regional scale, allowing the differentiation of tecto-sedimentary cycles and depositional sequences. The relations between tectonics and sedimentation in the Pyrenees are expressed in the Mesozoic and Tertiary cyclicity. Ten tecto-sedimentary cycles have been distinguished. They are controlled by basin-forming and basin-modifying tectonics (rifting, wrenching, convergence) and are related to different successive basin-types. A first group of cycles corresponds to the episodic rifting: post-Hercynian interior fracture basin (cycle 1), spreading of the Ligurian Ocean (cycle 2), spreading of the central North Atlantic Ocean (cycle 3) and rifting of the Bay of Biscay in the context of the rotation of Iberia (cycle 4). A second group corresponds to the opening of the North Atlantic Ocean and to the change in the trajectory of Iberia along a W-E direction (cycle 5). The third group corresponds to prevailing wrench conditions grading from strike-slip plate displacement (cycle 6) to progressive oblique convergence (cycle 7). The fourth group of cycles (8, 9 and 10) corresponds to the generalization of convergence conditions; cycle 8 is the transition from wrench to foreland basin; cycle 9 corresponds to the development of migrating foreland basins in relation to thrust sheet emplacement; cycle 10 includes the unconformable clastic wedge ahead of the last thrust. These tecto-sedimentary cycles include one or several depositional sequences in which sedimentation is controlled by the interrelations between local tectonics, subsidence, eustacy and sediment supply. The analysis and definition of these sequences is given for the Cretaceous and Tertiary cycles. The depositional sequences from the Cretaceous wrench basin are essentially related to eustacy (sea level rise) together with subsidence during cycle 6, and wrench structuring during cycle 7. The depositional sequences from the foreland basins (cycles 8, 9 and 10) are related to changes in the type of basin.

Estudio sedimentológico del Saxoniense y del Buntsandstein entre Molina de Aragón y Albarracín (Cordillera Ibérica)

The sedimentological analysis of the Saxonian unit «Lutitas y Aremscas de Tormon» and the five Buntsandstein units of this area provides several examples of alluvial sedimentation. Ihe unit «Lutitas y Areniscas de Tormon» reflects a flood-dominated, alluvial fan, complex system, which gradually evolved into the unit «Conglomerados de la Hoz del Gallo» (Lowest fluntsandstein) that can be interpreted as stream dominated, alluvial fan deposits passing basinward into a grave! dominated alluvial plain. Paleocurrent trends of tbis two clastic units are transversal to the main NW-SE fracture directions in the aren (Fig. 6). The red sandstones that overly the conglomerates, can be divided into three lithostratigraphic units (Fig. 1). This sandstones are interpreted as sandy dominated braided streams flowing aecording to the main NW-SE fault unes (Fig. 15). Ihe «Limos y Areniscas de Rillo» unit comprises mixed grave! sand fluviatile deposits evolving up into a more sandy fluvial system with low sinuosity braided channels and, finally, into a more distal alluvial plain. The complete unit sbows a fining-upward trend. Ihe sedimentary evolution of this area, together with the palaeogeographical distribution is interpreted as a interior fracture basin type, according to KINGSTON a al. (1983), reflecting a tensional tectonie environment. There is a very outstanding struetural feature in this area consisting on a horst, named «Umbral del Tremedal» by previous authors, where many of the clastic and sorne of the carbonatic units wedges out and some of them have a great thickness decrease. Buntsanostein thickness is about 50 m on the horst avea, reaehing up to 800 m towards the northeast in the surrounding graben area.

Relationship between fatigue strength and hardness for high strength steels.

To make a quantitative analysis of the defect size for high strength steels, fatigue properties and fatigue fracture mechanism were examined for 3 different low alloy steels tempered at several temperatures. Fatigue strength was evaluated up to about 108 cycles under rotating bending at room temperature in dry air. Two types of S-N curves were found, the one has fatigue limit for medium strength steels fractured from the specimen surface, the other for higher strength steels has temporal fatigue limit because of the interior fracture in the long life region over about Nf=107. Fatigue strength would be predicted by the liner relation between the threshold stress intensity factor and the hardness of the materials. It is suggested that the defect size to originate the fatigue crack would have important role for high strength steels up to about HV600.

Worldwide Basin Classification and Oil-Play Prediction: ABSTRACT

A system is proposed that classifies sedimentary basins worldwide into specific as well as general categories. The system is based on the origin and evolution of basins in the context of their geologic history. The main elements used to classify basins are basin-forming tectonics, depositional cycles, and basin-modifying tectonics. Basin-forming tectonics are deduced by knowledge of the type of underlying crust, past plate tectonic history, basin location on the plate, and type of primary structural movement involved in the basin formation (such as sagging or faulting). The result is eight single tectonic-cycle or simple basin types: interior sag, margin sag, interior fracture, wrench, trench, trench associated, oceanic sag, and oceanic wrench. Basin-modifying tectonics include episode wrenches, basin-adjacent foldbelts, and completely folded basins. These have been identified and placed on a scale of increasing magnitude, from movements of slight to major structural effects. More complex basins, called polyhistory basins, may contain several different tectonic cycles plus basin-modifying tectonic events. The eight simple basin types, their depositional fills, and tectonic modifiers have been given letter and number symbols so the specific geologic history of each basin may be written as a formula. The formulas may then be compared between basins, and similarities or differences noted. After the basins have been classified, major hydrocarbon plays are located and the specific parameters responsible for these plays are noted. For example, certain types of basins commonly may be the site of rich source rock or clean reservoir sand deposition, or may contain block-fault or wrench-type structures. From producing basins, these oil-play parameters can be projected into frontier areas via the global basin classification system, and oil-play predictions can be made. End_of_Article - Last_Page 2045------------

Hydrocarbon Plays and Global Basin Classification

Hydrocarbon plays and the global basin classification system have important connections. After a basin has been classified, its similarities or differences with other basins may be compared. Prolific hydrocarbon basins are categorized, and the plays are compared to specific tectonic and depositional events. Some plays are controlled by basin-initiating tectonic events, such as interior fracture or interior sag, and the type of sedimentation inherent in each basin type. In more complex polyhistory basins, oil and gas plays are commonly associated with combinations of various cycles, or by basin-modifying tectonics such as episodic wrenching, subsidence, foldbelts, and basin tilt.

Precipitation of Laumontite with Quartz, Thenardite, and Gypsum at Sespe Hot Springs, Western Transverse Ranges, California

AbstractWell-crystallized laumontite has been found for the first time precipitating naturally at the earth's surface at temperatures of 89° to 43°C as a component of gray to white coatings and efflorescences on exterior surface and as precipitates on interior fractures of stones and blocks lining Hot Springs Creek immediately downstream from Sespe Hot Springs, Ventura County, California. X-ray powder diffraction, scanning electron microscope (SEM), and electron microprobe analyses show thenardite to be the dominant phase in the exterior coatings, in association with minor microcrystalline (<50 μm) laumontite and gypsum. Macrocrystalline (>1 mm) laumontite is the dominant phase in interior fracture coatings and is associated with quartz, potassium feldspar, and gypsum. Trace amounts of smectite(?), halite, a mercury sulfide, an iron sulfide, an iron-bearing mineral (possibly an oxide or carbonate), and a copper mineral are also present. Zeolites other than laumontite have not been seen, and carbonate minerals are either entirely or nearly absent. SEM textures indicate nonreactive intergrowths of laumontite, quartz, potassium feldspar, and gypsum. Unbroken laumontite crystals are generally euhedral or have skeletal growth characteristics and exhibit sharp, fresh, non-corroded faces, edges, and corners.The water issuing from the hottest and largest spring is 89°C, has a pH of 7.74, 1200 mg/liter total dissolved solids, and contains Na+, Cl−, SO42-, and H4SiO4 as the dominant dissolved species. Computations indicate that the water is supersaturated with respect to laumontite, quartz, chlorite, and prehnite and is slightly undersaturated with respect to calcite and noncrystalline silica. Water-dominated water-rock interaction is indicated by isotopic analyses. The δO18 composition expectable on the basis of the −81‰ δD composition is −11.38‰ instead of the −9.5‰ actually found (all referred to SMOW). The water chemistry suggests that the subsurface water source may have a temperature of 125°–135°C. This temperature range, together with the regionally low geothermal gradient, implies that the source is probably 3550 to 3900 m beneath the springs in fractured and permeable Mesozoic and older plutonites and gneisses.The discovery of laumontite crystallizing at atmospheric pressure and 43°C (or lower) provides important insight into the processes responsible for burial diagenetic laumontite and a valuable perspective on the zeolite metamorphic facies.

Magnetic lineations of early Cretaceous age in the western equatorial Pacific Ocean

Magnetic anomaly lineations just north of the Phoenix Islands in the western equatorial Pacific trend N 80° E for over 1400 km. They are off-set 180 km left-laterally along an interior fracture zone and truncated to the west by another zone. It is not clear how they are terminated to the east. A Deep Sea Drilling Project hole dates these lineations as about 120 mybp. They represent 20 my or less of history from one flank of an early Cretaceous spreading system.