Effects of wave loads on the strength of semisubmersible drilling platform

In order to reduce the failure risk of the structures of semisubmersible drilling platform during its service life, this research studies the effects of ocean wave loads on the strength of the platform’s structures. The response spectra of the platform obtained from model test in wave tank were used to verify the accuracy of the numerical model employed in this research. Eight wave load cases, which may affect the strength of the platform but not involved in the classification societies such as ABS and DNV, were newly considered in this research. The results of the research indicate that a) four of the eight newly added wave load cases are found to be greatly affecting the strength of the platform and need to be considered in designing the structures; b) torsional moment and shearing force caused by the ocean wave would cause the stress of the structures of platform at a high level and need to be carefully evaluated.

Evaluation of the vertical strenght of a 3000 tdw barge using the equivalent beam approach

For the preliminary design stage, the evaluation of vertical strength is mandatory for the preliminary scantling of the structure. This paper presents the evaluation of the vertical sectional efforts by equivalent beam approach, using the 3D-CAD lines plan of a 3000 tdw barge and mass diagram. For numerical analysis the own program P_QSW is used, for sagging and hogging wave condition, ship headings 0 and 45o, wave height max. 1.2 m. The vertical sectional efforts are compared with the maximum bending moment and shearing force prescribed by the classification societies for the 3000 tdw preliminary vertical strength assessment.

Effect of interfacial friction on wear behavior and microstructure during extrusion of Pure Nickel N6

This paper combines field extrusion and finite element simulation to study the influence of the friction state on the extrusion deformation of pure nickel. The use of lubricant reduces the shearing force of the billet-die interface, resulting in lower heat generation at the interface, greater forming stress and strain, and reduced uneven deformation of the billet. As a result, the surface quality of the workpiece is relatively good, but uneven lubrication is the main cause of tearing damage on the surface of the billet. The grain morphology, grain boundary distribution, and geometrically necessary dislocations distribution on the surface of the lubricating extruded bar are uniform, the microtexture strength is weak, and the Schmidt factor is large.

Use of different cold water spray protocols on bovine carcasses during cooling and its effects on meat quality

This study was designed to evaluate the cold-water spraying (2 °C) on bovine carcasses during cooling, and its effects on meat quality. In protocols I, II, and III, 60-second spraying cycles were performed 10 min apart, with every cycle lasting 13 h, 15 h, and 17 h, respectively. In protocol IV, a software-controlled refrigeration unit was used, determining the interval and duration of the spray cycles. Data evaluated by counting colony forming units before the cooling period and after 24 h of carcass cooling were carcass features, such as body weight at slaughter, warm and cold carcass weight, weight losses on cooling, pH, temperature, and microbiological quality. Meat samples were collected to evaluate the Musculus longissimus thoracis for color, fat thickness, losses on cooking, loss of exudation, and shearing force, shortly after boning, and after 14 days of maturation. The protocols were effective in controlling the weight loss during cooling. The 17-hour protocol presented weight loss similar to that of the software-controlled. No significant difference was observed for the shearing force (kgF) evaluated in the same maturation period. The protocols tested did not create a favorable environment for the growth of psychrotrophic and enterobacteria in the evaluated carcasses. The use of the spray contributes to the reduction of mesophiles after 24 h of cooling. Differences between the results of the protocols for losses on exudation, losses on cooking, and color were observed, and the software-controlled protocol presented the highest loss values due to exudation, cooking, and luminosity.

Analysis of reliability of the drill pipe in the clamping mechanism

In oilfield equipment, a significant place is occupied by clamping mechanisms used to grip pipes during tripping operations. They are mainly divided into 2 groups. The first includes mechanisms with a forced clamping of the part. The second group includes self-clamping devices with a wedge mechanism. Here, the clamping force increases in proportion to the axial shear force. In these clamping devices, clamping jaws serve as a common element. In addition to smooth jaws, there may be jaws with notches on the inner cylindrical surface. Such notches contribute to an increase in the coefficient of adhesion when clamping cylindrical parts, in particular pipes. During the operation of clamping devices with corrugated jaws, the teeth of the notch are introduced into the pipe walls under the action of the clamping force. The shearing force can then displace the pipe relative to the jaws. The adhesion coefficient µ is the ratio of the shear force P to the clamping force Q, i.e. P/Q. Exceeding the shear force P of the limit value causes the pipe to be clamped to move. The correct choice of the place of load application is also of great importance. Optimum clamping performance can be achieved by clamping workpieces without slipping from shear forces. At the same time, it is necessary to ensure reliability, efficiency, productivity. Therefore, all factors that determine the holding capacity of clamping mechanisms should be considered. These factors include the coefficient of adhesion, the design of the working surfaces of the clamping elements, the type of notch of the corrugated jaws and the place of application of the clamping force

Prevent Barite Static Sag of Oil-Based Completion Fluid in Ultra-Deep Wells

Oil-based mud (OBM) is the first choice for complex deep wells due to its advantages of high-temperature resistance, good lubrication and borehole stability. But barite sagging under ultra-high temperature during the long-time stationary completion operation may lead to serious problems in ultra-deep wells, for instance, pipe sticking, density variation and well control problems. In this paper, the influence of high-temperature and high-pressure (HTHP) on the performance of oil-based completion fluid was studied, and a model of rheological parameters was established with HTHP static sag law. The barite sagging stability was evaluated by a high temperature (220°C) and high pressure (100MPa) sag instrument. The results indicated that RM6 value and static shearing force were the main factors of affecting the settlement stability. The viscosity of the completion fluid significantly decreased with the increase of temperature, but increased with the increase of pressure. In addition, the relationship was also studied between HTHP rheology and atmospheric pressure rheology at 50°C. The results showed that when RM6 value was kept above 10, the sag stability factor (SF) of oil-based completion fluid was less than 0.52 at 190°C for 10 days, which proved a good high-temperature sag stability. Furthermore, the anti-high temperature property of oil-based completion fluid was improved through enhancing the temperature-resistance of the additives. And the high-temperature-resistant organic soil was introduced to raise the RM6 value and the static shearing force. Based on these solutions, the barite sag under high temperature of the oil-based completion fluid was prevented during drilling and completion operation in ultra-high temperature wells. The oil-based completion fluid was successfully used in Well Keshen 17 (175°C,7475 m) in Kuche piedmont structure and TT 1 well (210°C,6500 m) in Sichuan basin. The casing run smoothly, the oil-test operation was completed smoothly for 15 days, and no barite sag happened. It testified that the oil-based completion fluid had excellent of high-temperature sag stability. Therefore, this oil-based completion fluid is expected to be used widely in ultra-deep wells.

STUDY OF THE BEHAVIOURS OF SINGLE-PHASE TURBULENT FLOW AT LOW TO MODERATE REYNOLDS NUMBERS THROUGH A VERTICAL PIPE. PART I: 2D COUNTERS ANALYSIS

This study presents a model to investigate the behavior of the single-phase turbulent flow at low to moderate Reynolds number of water through the vertical pipe through (2D) contour analysis. The model constructed based on governing equations of an incompressible Reynolds Average Navier-Stokes (RANS) model with (k-ε) method to observe the parametric determinations such as velocity profile, static pressure profile, turbulent kinetic energy consumption, and turbulence shear wall flows. The water is used with three velocities values obtained of (0.087, 0.105, and 0.123 m/s) to represent turbulent flow under low to moderate Reynolds number of the pipe geometry of (1 m) length with a (50.8 mm) inner diameter. The water motion behavior inside the pipe shows by using [COMSOL Multiphysics 5.4 and FLUENT 16.1] Software. It is concluded that the single-phase laminar flow of a low velocity, but obtained a higher shearing force; while the turbulent flow of higher fluid velocity but obtained the rate of dissipation of shearing force is lower than that for laminar flow. The entrance mixing length is affected directly with pattern of fluid flow. At any increasing in fluid velocity, the entrance mixing length is increase too, due to of fluid kinetic viscosity changes. The results presented the trends of parametric determinations variation through the (2D) counters analysis of the numerical model. When fluid velocity increased, the shearing force affected directly on the layer near-wall pipe. This leads to static pressure decreases with an increase in fluid velocities. While the momentum changed could be played interaction rules between the fluid layers near the wall pipe with inner pipe wall. Finally, the agreement between present results with the previous study of [1] is satisfied with the trend

Two Cases of Morel-Lavallée Lesion Which Resulted in a Wide Skin Necrosis from a Small Laceration

Morel-Lavallée lesion (MLL) is a degloving injury in soft tissues caused by shear force accompanying trauma. Even if it is a small lacrimal wound at the initial visit, there is a range of skin necrosis which is not suitable for it. As a cause of the injury, a shearing force was applied over a wide range, and penetrating blood vessel damage to the skin occurred, resulting in skin necrosis. Attention is required.

Seismic Reduction Effectiveness of Friction Pendulum Bearings in Underground Station Structures

Setting friction pendulum bearings (FPB) at the top of central columns may be a good strategy to reduce the stations’ seismic responses. In this paper, the FPB is simulated in a detailed manner. The seismic reduction effectiveness of the FPB is studied with the three-dimensional dynamic time history analysis method. It is found that FPB can effectively reduce the maximum shearing force of the central columns and slightly reduce the maximum bending moment. It is stated that FPBs are also effective in the underground station structures.