Holes Of Different Diameters Research Articles

DC Potential Drop Calibration in Creep-Fatigue Loading Conditions

Abstract The direct current potential drop method (DCPD) is used to detect the initiation of cracks and monitor their growth under the conditions of high gross inelastic deformations (plastic and creep). Testing is conducted on flat SS-304 plates with central circular holes of different diameters under fatigue and creep-fatigue loading at 600°C. The potential drop is measured using two pairs of voltage probes across the hole. The variation of the voltage ratio with the number of cycles is considered in order to eliminate the dependency of the DCPD on the current and material resistivity. The visible crack length is measured by a video camera with image processing to assess the reliability of the DCPD technique. The effects of notch shape and notch plastic zone size prior to initiation are removed by using a special reference voltage ratio. Because of the high inelastic deformations at the crack tip and larger crack opening displacement under fatigue and creep-fatigue conditions at high temperature, the calibration curve developed at room temperature is modified using material property variation with temperature. Furthermore, the variation of notch opening displacement with voltage ratio is employed to correct measured crack length and to determine crack initiation under fatigue with hold time.

LAMB WAVE SCATTERING FROM A THROUGH HOLE

Ultrasonic guided waves, Lamb waves, are useful for evaluating the integrity of plate and shell structures common in many applications. Tomographic reconstruction with Lamb waves allows for the accurate reconstruction of the variation of quantities of interest throughout the investigated region, and it presents the data as a quantitative map. The location, shape, and extent of flaws can then be easily extracted from this tomographic image. The scattering of Lamb waves from severe flaws introduces artifacts in such reconstructions, however. In this paper higher order plate theory is used to derive analytical solutions for the scattering of the lowest order symmetric Lamb waves from a circular inclusion, focusing in particular on isolated through holes in plates. Plane wave and point source scattering behavior is explored for holes of different diameters, and a finite-beam solution is constructed by superposition of point source solutions. These results are then used to explain the scattering effects seen in Lamb wave contact scanning tomographic reconstructions.

An anthropomorphic phantom for receiver operating characteristic studies in CT imaging of liver lesions.

The purpose of the study was to develop a methodology that allowed quantitative assessment of image quality in CT and its relationship to dose. An anthropomorphic phantom was designed for use in receiver operating characteristic (ROC) studies of the detectability of liver lesions with CT. The lesions were simulated by different mixtures of glycerol and water that were filled into holes of different diameters in a liver tissue substitute. A pilot study was carried out on five different scanners that were operated at various exposure settings. A positive correlation was demonstrated for each of the scanners between the weighted CT dose index (CTDIW) and the area under the ROC curve. For the exposure settings used in the clinical routine in the five laboratories, the CTDIW ranged from 15 to 31 mGy. Three observers who read the corresponding set of five phantom images agreed, as judged from the areas under the ROC curves, that there was a marked difference in quality between the three best images and the other two. The two newest scanners in the study had the lowest CTDIW, and at the same time the best ROC results. The phantom and the ROC methodology may, with a set of suggested improvements, be used for comparison of the performance in different CT laboratories, and to establish the dose needed to ensure adequate image quality for a particular scanner.

SUMHOLE DRILLING: WELLBORE STABILITY CONSIDERATIONS BASED UPON FIELD AND LABORATORY DATA

Slimhole drilling is becoming an attractive option as it provides significant cost savings in the petroleum industry. Furthermore, many of the technical obstacles in adapting slimhole drilling for the petroleum industry have been addressed, such as rig modifications, small volume kick detection, drilling fluid design, etc. However, wellbore stability in slimholes is largely taken for granted, when it could potentially increase costs dramatically. In this paper, a review of the available information on the effects of hole size on hole stability is presented. Wellbore stability in holes of different diameters is discussed qualitatively based on published laboratory data and unpublished field data. The quantitative assessment of wellbore instability in slimholes is addressed using observations of instability in a well in which the far field stresses were measured.The field data presented here suggest that slimhole wells are not more stable than conventional wells. The slimhole drilled in NSW shows that even using the most conservative prediction model, wellbore instability would not be predicted—instability was however, observed.

The effect of accuracy constraints on three-dimensional movement kinematics

The kinematics of three-dimensional arm movements were recorded during a task in which subjects were required to place a peg in a hole. The accuracy constraint was varied by using holes of different diameters. If the diameter of the hole was large relative to the diameter of the peg, the tangential velocity profile of hand trajectories was relatively symmetric and bell-shaped, but it became increasingly asymmetric as the diameter of the hole was reduced. Peak tangential velocity decreased, overall movement duration increased and the proportion of the movement spent in deceleration increased systematically. The shape of the accelerative phase of the velocity profile showed little dependence on hole diameter, but the decelerative phase became increasingly irregular as the hole diameter was reduced. This irregularity was attributed to submovements corresponding to small changes in the direction of the hand path. On the other hand, deliberately slowing the movement in the absence of a strict accuracy constraint induced a change in the velocity profile which produced irregularity in both the accelerative and decelerative phases of the movement. The results of our experiments are consistent with the idea that movements requiring extreme accuracy and other slow movements are composed of a series of submovements. In the case of movements requiring accuracy these submovements may represent corrective actions that are taken throughout the course of the movement.

Disturbances to viscometric flow patterns: Birefringence observations

A visual preliminary investigation has been made of the flow pattern adjacent to piezometric holes of different diameters and also the flow pattern upstream and downstream of a jet exit using a birefringence technique. Perturbations to the main flow pattern are noted near to the piezometer hole entrances. At the jet exit initial curvature just upstream of the exit plane is noted at higher flow rates.

Instruments and Methods: The Measurement of Vertical Strain in Glacier Bore Holes

A method to measure the vertical strain in glacier bore holes is described that entails placement of passive markers at varying depths. The position of these markers with respect to a surface reference is measured by an electronic sensor lowered into the hole. These measurements can be combined with inclinometer measurements to yield the total velocity vector in the ice surrounding the hole. Although the method was designed for use in a 0.05 m diameter hole, it can easily be applied to holes of different diameters and to winter snow covers as well as glacier ice.

Instruments and Methods: The Measurement of Vertical Strain in Glacier Bore Holes

A method to measure the vertical strain in glacier bore holes is described that entails placement of passive markers at varying depths. The position of these markers with respect to a surface reference is measured by an electronic sensor lowered into the hole. These measurements can be combined with inclinometer measurements to yield the total velocity vector in the ice surrounding the hole. Although the method was designed for use in a 0.05 m diameter hole, it can easily be applied to holes of different diameters and to winter snow covers as well as glacier ice.

Stresses around One Hole or Two Holes Subjected to Internal Pressures in Semi-Infinite or Infinite Medium

The formulas for the numerical determination of stresses in an infinite elastic medium having two circular holes of different diameters subjected to different hydrostatic pressures on their walls, have been deduced from the well-known Airy's stress function represented by the bipolar coordinate system.Modifying the above formulas, we can also determine the stresses in a semi-infinite elastic medium having a circular hole closed to the straight boundary, under the cases of loading on both the walls of the hole and the straight boundary, and of loading on either of them.In the present study, we calculated the stresses in an infinite or a semi-infinite medium under the above mentioned conditions using the formulas, and discussed the results of the stress analysis. Some examples of the results obtained are as follows:(1) In the case of the infinite medium having one hole subjected to hydrostatic pressure and another hole with free surface, unless the interval of their holes is extremely small, the maximum tensile stress on the wall of the hole subjected to pressure does not occur at the intersection (A) of the wall and the line through the center of their holes, but occurs at the point having the value of θ=30°∼60° (Fig. 2, ∼4).(2) In the case of the infinite medium having two holes subjected to equal pressure, the maximum tensile stress occurs at the inner intersection of the wall of the smameter diameter hole and the line through the center of two holes (Fig. 8, 9).(3) In the case of the semi-infinite medium having a hole subjected to pressure, the maximum tensile stress on the wall of the hole occurs at the point having the value of θ=80°∼90° (Fig. 11).

Stresses in a pressurized cylindrical shell with two unequal diametrically opposite reinforced circular holes

This paper deals with an experimental determination of the stress distribution in a cylindrical shell with two diametrically opposite reinforced circular holes of different diameters. The shell is subjected to internal pressure. Both brittle coating and three-dimensional photoelasticity were used in the analysis. The results obtained are compared with those corresponding to a non-reinforced hole in a cylindrical shell with and without ribs.

Fatigue strength of marine shafting1

The results of torsional fatigue tests on forged mild-steel shafts, 3 in. in diameter and having transverse holes of different diameters, are presented and discussed. It is shown that the theoretical stress-concentration factors for shafts having the