Search results for "Drill"
showing 10 items of 130 documents
The Shielding Effect of Drilling Fluids on Measurement While Drilling Tool Downhole Compasses—The Effect of Drilling Fluid Composition, Contaminants,…
2016
Materials such as added clays, weight materials, drill solids, and metallic wear products in the drilling fluid are known to distort the geomagnetic field at the location of the measurement while drilling (MWD) tool magnetometers that are used to measure the direction of well path. This distortion contributes to substantial errors in determination of azimuth while drilling deviated wells. These errors may result in missing the target of a long deviated 12 ¼ in. section in the range of 1–200 m, representing a significant cost to be mitigated. The error becomes even more pronounced if drilling occurs in arctic regions close to the magnetic north pole (or south pole). The effect on the magneto…
Effects of the indentation process on fatigue life of drilled specimens: optimization of the distance between adjacent holes
2016
The generation of permanent compressive stresses around the holes is recognized as a valuable mean to delay the onset and propagation of the defects and to extend the fatigue life of the mechanical components. In the work, a bilateral indentation process, performed on each side of the component, is widely used in order to create a residual circumferential stress field around the area to be drilled and that persists after the drilling operation. In order to evaluate the process parameters and to identify optimal geometric solutions, several static and fatigue tests are conducted on AW 6082-T6 aluminum alloy specimen where two holes are created. In particular, experimental tests on only drill…
Enamel evaluation by scanning electron microscopy after debonding brackets and removal of adhesive remnants
2017
Made available in DSpace on 2022-04-29T08:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Background: The bonding of accessories in the dental crown during the orthodontic treatment creates microporosities, thus promoting micromechanical retention of the adhesive to the enamel structure. After debonding brackets, at the end of the active orthodontic treatment, a certain amount of adhesive remnants must be mechanically removed from the enamel. The objective of this study was to compare, by means of scanning electron microscopy, three different methods to remove the adhesive remnants after orthodontic bracket removal. Material and Methods: An experimental analytical study w…
Orthogonal and Oblique Cutting Mechanics
2008
This chapter provides the engineering knowledge and modelling techniques applied in description of the material behaviour in the cutting zone resulting in chip formation and its separation from the bulk material. Geometrical and kinematical characteristics of orthogonal and oblique cutting models are classified and specified. Forces acting on the cutting tools and their measurement methods for several machining operations, such as turning, milling, drilling, boring and grooving, are presented. Moreover, forces acting in the cutting zone and their resolution on the shear plane and the rake and flank faces, along with stress distributions, are presented. The chapter highlights how components …
Ultrasonic phased array inspection of wire plus arc additive manufacture samples using conventional and total focusing method imaging approaches
2019
In this study, three aluminium samples produced by wire + arc additive manufacture (WAAM) are inspected using ultrasonic phased array technology. Artificial defects are machined using a centre drill, ø 3 mm, and electrical discharge machining (EDM), ø 0.5-1 mm, in a cylindrical through-hole topology. The samples are first inspected using a single-element wheel probe mounted on a KUKA robot in order to investigate the feasibility of using a conventional ultrasonic transducer approach. Unfortunately, the wheel probe is found to be unsuitable for scanning the WAAM specimens and ultrasonic phased arrays are employed next. The set-up includes 5 MHz and 10 MHz arrays (128 elements) in direct cont…
Holocene climate variability of the Western Mediterranean: Surface water dynamics inferred from calcareous plankton assemblages
2020
A high-resolution study (centennial scale) has been performed on the calcareous plankton assemblage of the Holocene portion of the Ocean Drilling Program Site 976 (Alboran Sea) with the aim to identify the main changes in the surface water dynamic. The dataset also provided a seasonal foraminiferal sea surface water temperatures (SSTs), estimated using the modern analog technique SIMMAX 28, and it was compared with available geochemical and pollen data at the site. Three main climate shifts were identified as (1) the increase in abundance of Syracosphaera spp. and Turborotalita quinqueloba marks the early Holocene humid phase, during maximum summer insolation and enhanced river runoff. It i…
Drilling predation on Gryphus vitreus (Brachiopoda) off the French Mediterranean coasts
2004
Abstract A total of 145 valves of Gryphus vitreus with naticid drillholes have been recorded from samples during 21 cruises in the Northwestern Mediterranean, out of about 30,000 empty valves. Drilling was lower than 1% in all stations, except in one station where it reached up to 25.5%. Selectivity of drillhole site by the naticid Euspirella pulchella seems to apply in G. vitreus as drillholes are mainly concentrated in the relatively meaty distal half of the shell, which is also the thickest part of the valve (about 0.6–2 mm). Attacks occur generally on the ventral valve (86.2%) according to the life position of Gryphus. The predation pressure on G. vitreus by drilling appears exceptional…
Intraosseous monitoring of drilling in lumbar vertebrae by ultrasound: An experimental feasibility study.
2016
The rationale for this project is to evaluate the efficiency of a novel sonographic method for measurements of interosseous distances. The method utilizes a propagating ultrasonic beam through aqueous milieu which is directed as a jet into a drilled tract. We used a plastic model of human L5 vertebra and ex vivo specimen of L5 porcine vertebra and generated 2 mm in diameter tracts in vertebral pedicles. The tracts were created in the "desired" central direction and in the "wrong" medial and lateral directions. The drilled tracts and the residual, up to opposite cortex, distances were measured sonographically and mechanically and compared statistically. We show that "true" mechanical measure…
Investigating the effect of residual stress on hydrogen cracking in multi-pass robotic welding through process compatible non-destructive testing
2021
Abstract In this paper, the effect of Welding Residual Stress (WRS) on the size and morphology of hydrogen-induced cracks (HIC) is studied. Four samples were manufactured using a 6-axis welding robot and in two separate batches. The difference between the two batches was the clamping system used, which resulted in different amounts of welding deformation and WRS. The hydrogen cracks were intentionally manufactured in the samples using a localised water-quenching method, where water was sprayed over a specific weld pass in a predetermined position. The Phased-Array Ultrasonic Testing (PAUT) system was implemented during the welding process (high-temperature in-process method), to detect the …