Clear Pit Research Articles

Study on Fracture Failure Behavior of Super 13Cr Tubing Caused by Deposited Corrosion

Fracture failure of super 13Cr can occur in complex and harsh environments such as high temperature, high pressure, and corrosive gas wells, which damages the economic benefit of oil and gas development and also poses a great threat to wellbore integrity. Therefore, it is urgent to study the corrosion mechanism of super 13Cr tubing in oil and gas wells, and this study performed an on-site experimental analysis on failed super 13Cr tubing, employing the microarea electrochemical scanning Kelvin probe (SKP) method to investigate the causes of corrosion of super 13Cr material. In addition, the thermodynamics of the mechanism by which pits turn into cracks was examined in light of the experimental findings on the nucleation and development of pitting corrosion. The findings reveal scale and clear pits on the surface of the failed super 13Cr tubing and that CaCO3 as well as FeCO3 are the scale’s primary constituents. According to the SKP scan results, the super 13Cr tubing has a risk of pitting under wells, and the galvanic cell with microcorrosion is the primary cause of pitting corrosion, which also shows that the potential difference between the anode area and the cathode area of the super 13Cr material gradually increases with the increase in immersion time. Under the autocatalytic effect of the occlusive corrosion cell and the applied load, the corrosion pits and cracks of super 13Cr tubing propagate, eventually leading to tubing breaks and failure.

Fracture of elastic-brittle and elastic-plastic material in cantilever cyclic bending

The paper analyses the fatigue tests of a specimen made of 16Mo3 steel and 6082-T6 aluminium alloy performed under bending and tensile conditions. It has been shown that in the case of bending of the 16Mo3 steel specimen, in low cycle fatigue (LCF) range, the fatigue life is increased with respect to the results obtained under tension-compression conditions. On the other hand, in the case of the aluminium specimen, the load condition practically does not affect the fatigue life. Microstructural analysis revealed almost homogeneous fatigue cracks in the 16Mo3 steel samples which are practically elastic-plastic. The analysed 6082-T6 aluminium alloy belongs to the group of materials characterized by elastic and brittle properties. In the case of pendulum bending in the obtained images, it is possible to notice the clear pits at an angle of about 45 degrees relative to the surface of the breakthrough. They penetrate the broken specimen to about 33%. In the middle of the material, the bending plane is clearly visible, where the stress is constant and equals 0 MPa.

Near-Field Recording with a 266 nm Laser for Disc Mastering Process

A near-field mastering process was realized with a 266 nm laser and a solid immersion lens (SIL) of 1.35 numerical aperture (NA). The air gap was detected with a 532 nm laser and it was servo-controlled at about 100 nm by driving the SIL with an air-suspended pad and a piezoelectric transducer (PZT) actuator. A residual fluctuation of the air gap was constrained within 10 nmPP. For a rear converging lens, one of the molded lenses with a wave front error (WFE) of below 70 mλrms was selected. It was assembled with a supersphere SIL of about 10 mλrms WFE. As a result of read-only memory (ROM) recording in a density corresponding to 40 gigabytes (GB) in compact disc (CD) size, a clear pit pattern was fabricated. As for 25 GB ROM recording, acceptable signal quality was obtained.

An auto-focusing method in a microscopic testbed for optical discs

An auto-focusing method in a digital image system is demonstrated that uses a standard deviation of pixel gray levels as a feedback signal. In this system, an optical microscope and a charge coupled device (CCD) camera are used to create clear pit images of optical discs. A dynamic focusing scheme is designed in the system-control software, which is able to eliminate environmental disturbances and other noises so that a fast and stable focus can be achieved. The method shows an excellent focusing accuracy. The performance and possible applications of this method are discussed. The test results for optical discs are given in this paper.

Simulation of degradation of dielectric breakdown field of thermal SiO/sub 2/ films due to voids in Si wafers

Degradation of the dielectric breakdown field of thermal SiO/sub 2/ film caused by voids that are formed during growth of silicon single crystal has been a serious problem with reliability of MOS devices. To understand the degradation of breakdown field, local thinning of oxide film grown on pits (i.e., voids exposed at the wafer surface) is simulated using a simple model, and the degradation of breakdown field expected from the thinning is compared with experimental reports. In the model, oxide film grown on the inner surface of a sphere is calculated by assuming that deformation of oxide film is visco-elastic and that oxidation reaction rate is reduced by compressional normal stress acting on the Si/SiO/sub 2/ interface. The calculated results show appreciable thinning of oxide film, which explains the low breakdown field observed experimentally. It also helps to understand the unique degradation characteristics reported for pits and voids: lower breakdown field for thicker oxide film and recovery of breakdown field by chemical etching. No clear pit size dependence observed in the experiments suggests that the oxide thinning is localized at corners of voids.

Rapid freezing replica studies of membrane specializations in the proximal tubules of mouse kidney.

The membrane specializations of the fresh unfixed kidney cortex of adult and neonatal ICR mice were examined by using rapid freezing replica methods. In proximal tubular cells, numerous apical intracellular tubules exhibited helical patterns on the E face with a pitch of about 12 nm. This regular pattern was often continuous with similar striped indentations on the edge of the vacuoles connecting with the tubules. On the luminal surface (ES) of these vacuoles, membrane surface particles were arranged regularly in striped patterns with a center-to-center spacing of about 12 nm. We could not identify differentiations on the PF or PS of the same membrane systems. Another membrane specialization was a plaque or patch of clear pits in tilted lattice alignments on the P face of the large vacuoles with a center-to-center spacing of about 20 nm. This type of specialization was often observed in the neonatal mice proximal tubular cells. These membrane specializations may indicate the active membrane functions in the proximal tubules and suggest the functional continuity and structural relationship of these apical endocytic membrane systems.

On the morphology of developing eggs of the camel tick Hyalomma dromedarii Koch, 1844

External egg morphology of the camel tick Hyalomma dromedarii was studied. Injection of egg-laying females with 1% trypan blue resulted in incorporation of vital stain in the oviposited eggs. Daily measurements of fresh eggs revealed changes in egg length and width during embryonic development. Scanning electron microscopy showed the outermost layer of the egg to be spongy and porous containing clear pits of different sizes. An elevated longitudinal hatching ridge encircled the egg chorion. The development of cephalothorax, appendages, Malpighian tubules, and rectal sacs were monitered.

On the Occurrence of Thanet Beds and of Crag at Sudbury, Suffolk

I. Thanet Beds. The newer Tertiary deposits of the Eastern Counties have had such a power of fascination over geologists that the older beds have been left almost unnoticed: indeed since the description of a few sections in Mr. Prestwich's essays on the Lower London Tertiaries, which have now been published 20 years and more, I know of but one paper (and this probably known to very few geologists)* that gives us any information about that series in the district in question, whereas the number of papers that treat of Crag and Drift is legion. It has therefore been an agreeable surprise to me to find, in the course of my Geological Survey work, that there are fine sections of the older Tertiary beds in Suffolk and the neighbouring part of Essex; and it was with some astonishment that I saw one of the finest sets of sections in the London Basin round the town of Sudbury, on the border of those two counties. These sections convinced me that the lowest member of the Lower London Tertiaries, the Thanet Beds, crops out along part of the northern edge of the Tertiary district, an occurrence of which I had a very slight suspicion from other sections near Ipswich. Mr. Prestwich has, indeed, doubtfully referred some of the sands of the northern outcrop to this division, though without describing any section; but he does not notice the particular part where it is now to be seen in many large and clear pits,