Debonding of metal coating of a track-etched membrane

Behavior of metallic nano-coating of the track membrane based on polyethylene terephthalate film under tension was investigated. In the vicinity of cracks in the coating, conical-shaped debondings of the coatings were observed. Debondings have the form of sharp cones, elongated along the tension axis and perpendicular to the cracks. Nanopores initiate multiple cracking of the coating, and the cracks initiate local debondings. Short microcracks mutually suppress their growth. As a result, long cracks crossing the entire coating do not appear. As a result, the coating retains its continuity and conducts electric current.

Gradient Microstructure of FeCr30Co8 Hard Magnetic Alloy Subjected to Plastic Deformation by Complex Loading

Magnetically hard Fe-Cr-Co-based alloys are distinguished by their good ductility, excellent magnetic properties and low cost. Their superior magnetic properties are obtained by magnetic treatment and multistage tempering, which results in spinodal decomposition of the solid solution into the isomorphous α1 and α2 phases. However, the α1+α2 microstructure causes a reduction in the plasticity and strength of the material. It can often be advantageous for permanent magnets to maintain fine magnetic properties throughout their volume along while retaining good mechanical properties only in the subsurface layer. To improve the mechanical properties of the latter, FeCr30Co8 samples were deformed in tension combined with torsion. Loading was applied at 750°C, which ensured that the conditions for superplastic deformation were fulfilled. Here, we present the results of microstructure investigations of the samples treated in the aforementioned manner. Observations of the longitudinal section of the samples showed the formation of a gradient microstructure with the maximum grain refinement in the surface layer and the characteristic rotation of the elongated α phase grains from positions nearly perpendicular to the tension axis at the surface to positions tilted at approximately 45º to the tension axis inside the material. Deformation at superplastic conditions also activated precipitation of the σ intermetallic phase, particularly in the areas of highest deformation. The refinement of the microstructure and precipitation of the σ-phase resulted in a significant increase in hardness at the surface of the FeCr30Co8 samples.

The Meade County, Kentucky, Earthquakes of January and March 1990

The series of earthquakes that occurred in Meade County, Kentucky, in January and March of 1990, are the first events in an otherwise aseismic area. First motions recorded for the three largest events in January suggest a predominantly strike-slip mechanism with a pressure axis of trend = 275° and plunge = 14° , and a tension axis of trend = 178° and plunge = 31°. A comparison between the mechanisms for the Meade county events and those shown in Taylor et al. (1989) for the southeastern Illinois area, indicates a continuity in the regional deviatoric stress from southeastern Illinois into north-central Kentucky. This finding conflicts with that previously suggested by Ault et al. (1985) who proposed that the two areas were in regions of differing stress regimes.

Reanalysis of the 1963 Baffin Island Earthquake (MS 6.2) and its Seismotectonic Environment

The 1963 Baffin Island earthquake of MS 6.2 is reanalyzed to determine whether or not it involved normal faulting, as previously suggested. The revised fault-plane solution has nodal planes with strike 113°, dip 66°, rake 235° and strike 352°, dip 41°, rake 322°. The T-axis trends 227° and plunges 14°, and the P-axis trends 338° and plunges 55°. Thus though this solution confirms normal faulting, it suggests a larger strike-slip component than most previous studies. The tension axis is oriented SW, which is normal to the NW geographic trend of Baffin Island. We consider that the normal-fault regime could be a transient phenomena related to extensional stress in the glacial forebulge presently centered over northeast Baffin Island, and is associated with incomplete postglacial rebound. However, future geophysical measurements such as heat flow, in-situ stress and vertical uplift rate, as well as more fault-plane solutions are required to test this hypothesis.

A Tension Crack Impinging Upon Frictional Interfaces

A crack impinging normally upon a frictional interface is studied theoretically. We employ a solution technique which superposes the solution of a crack in a perfectly-bonded elastic medium with a continuous distribution of dislocations which represent slippage at the frictional interface. This procedure reduces the problem to a singular integral equation which is solved numerically. Specifically, we consider the problem of an infinite sheet subjected to uniaxial tension containing a finite crack which lies normal to the tension axis and has both crack tips impinging normally on frictional interfaces. The limiting problem of a semi-infinite crack impinging on a frictional interface is considered as well. Posed as model problems for cracking in weakly bonded fiber composites, these studies reveal the effective blunting that can result when a weak interface serves to deflect a propagating crack.

The Stiffness of a Two-Cell Anisotropic Tube

SummaryAn analysis is made of the general two-cell thin-walled cylindrical tube subjected to longitudinal tension, bending and torsion. The walls of the tube may be of fibre composite with an asymmetric lay-up resulting in a coupling between direct and shear stresses and strains. The two-cell tube differs from the single-cell tube in that the tension axis and the principal axes of bending are not necessarily aligned to the c.g. and the principal moments of inertia of the longitudinal stress bearing material.

The Vancouver Island earthquake of 5 July 1972

An earthquake occurred at 10 h 16 m 39 s GMT on 5 July 1972 in close proximity to the west coast of Vancouver Island, near 49.5 °N and 127.2 °W. Its magnitude (mb) was 5.7 and the hypocenter was near the middle of the crust. A well defined P nodal solution has a pressure axis with a north-south orientation and a tension axis with an east-west orientation. The preferred nodal plane suggests right lateral strike-slip faulting on a near vertical fault, striking in a north-northwest direction. The other nodal plane suggests that left lateral strike-slip faulting on a near vertical fault striking in an east-northeast direction is also a plausible solution. A field study with portable seismographs revealed that very few aftershocks were associated with this earthquake. The largest aftershock had a magnitude (ML) of 3.4. The distribution of intensity of the mainshock observed on Vancouver Island differs from that predicted by the intensity versus distance relation presently used for western Canada.

Microearthquakes in the Mono Lake-Northern Owens Valley, California, region from September 28 to October 18, 1970

A portable seismograph network was operated by the U.S. Geological Survey in the Mono Lake-northern Owens Valley, California, region in the autumn of 1970. From 20 days of recording, 74 microearthquakes were located. The geographic extent of the microearthquakes is similar to the historic seismicity from 1934 to 1970. Focal mechanisms are mostly right-lateral strike slip; one very good dip-slip solution was obtained. The relative tension axis was found to be very nearly east-west.

Distribution, focal mechanisms, and frequency of earthquakes in the Fairview Peak area, Nevada, near the time of the BENHAM explosion

Six portable seismographs were operated for 30 days in a network centered 25 km south of the epicenter of the 1954 Fairview Peak earthquake. The recording period lasted from 15 days before to 15 days after detonation of the one-megaton BENHAM underground nuclear explosion 250 km to the southeast of the Nevada Test Site on December 19, 1968. Approximately 950 earthquakes were detected within about 30 km of the network. No evidence was found that the explosion affected the rate of earthquake occurrence. Locations were computed for 152 earthquakes. The epicentral pattern shows north and northeast trends about 1 to 3 km wide. Focal depths range from 5 to 14 km. The main zones of activity seem to have a near-vertical orientation. Composite fault-plane solutions suggest that faulting within zones is not consistent with a single focal mechanism. Instead, a variety of mechanisms is indicated, consisting primarily of north-striking right-lateral oblique-slip, and northeast-striking dip-slip movements. In both cases, the pressure axis is near vertical and the tension axis is near horizontal, striking about S60°E.