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Pipelines are extensively used in offshore equipment. Accurate and non-destructive measurement of hoop stress conditions within pipes is critical for ensuring the integrity of offshore structures. However, the existing technology to measure the hoop stress of the pipeline needs to planarize the surface of the pipeline, which greatly limits the detection efficiency. This study proposes a method for pipeline hoop stress measurement using a planar longitudinal critically refracted (LCR) probe, based on correcting LCR wave-propagation paths, which solves the problem of pipeline planarization in pipeline hoop stress measurement. First, a linear relationship between stress variations and ultrasonic time-of-flight changes in the material was established based on the acoustoelastic effect. Finite element analysis was then used to construct an acoustic simulation model for the hoop direction of the pipeline. Simulation results showed that LCR waves propagated within a wedge as quasi-plane waves and, upon oblique incidence into the pipeline, traveled along the chordal direction. Furthermore, using ray tracing methods, a mapping relationship between the pipeline geometry and the ultrasonic propagation path was established. Based on this, the LCR pipeline hoop stress measurement (LCR-HS) method was proposed. Finally, a C-shaped ring was employed to verify the measurement accuracy of the LCR-HS method. Experimental results indicated that the measurement error decreased with increasing pipe diameter and fell below 8% when the diameter exceeded 400 mm. This method enables precise measurement of hoop stress on curved surfaces by revealing the hoop propagation behavior of LCR waves in pipelines. The findings provide a technical reference for evaluating pipeline stress states, which is of significant importance for assessment of pipeline integrity.

The decrease of collapse and burst strength of wear casing increases the risk of wellbore failure, and limits the selection of testing and completion operation parameter. For determining the residual strength of wear casing. 95/8“x 11.99mm-P110 casing is processed into the crescent and eccentric wear casing specimens with wear depth as 4 mm and 6 mm respectively. The experiments of wear casing loaded with radial centralized forces are carried out, and the finite element method is used to verify the experimental results. The circular stresses of outer surface at worn and unworn position of casing increase with the load exerted by the compression tester, and reach the yield strength of material of casing finally. The circular stress of the external surface of the worn position of casing is greater than the ones of unworn casing. The differences between the results which come from the analysis of the finite element method and the experimental data are less than 10%. So the results which are obtained by the experiment of the crescent-shaped and eccentric wear casing loaded with radial centralized forces are reliable. The circular stress of the external surface of the worn position of crescent-shaped wear casing is greater than the one of eccentric wear casing. The differences between them are less than 10%.

Three-dimensional finite element analyses were performed on closed-ended thick-walled cylinders with a radial cross bore under internal pressure. The aim of this study was to determine the behaviour of the hoop stress as well as to establish the optimal Stress Concentration Factors (SCF). Cylinders of thickness ratios of 3.0 down to 1.4 with cross bore size ratios (cross bore to main bore ratio) ranging from 0.1 to 1.0 were studied. The maximum hoop stress was found to increase with the increase in the cross bore size. Amongst the five different circular radial cross bore size ratios studied, the smallest cross bore size ratio of 0.1, gave the lowest hoop stress while the highest stress occurred with a cross bore size of 1.0. Moreover, the lowest SCF occurred in the smallest cross bore size ratio of 0.1 at a thickness ratio of 2.25 with a SCF magnitude of 2.836. This SCF magnitude indicated a reduction of pressure-carrying capacity of 64.7% in comparison to a similar plain cylinder without a cross bore.

To explore the effect of considering thermoplasticity of gun steel on the thermomechanical coupling of the barrel during artillery firing, the thermoplastic coupling behavior of the barrel under transient thermal and mechanical loads is investigated. A thermomechanical coupling finite element model of the barrel was established. The transient temperature field and stress field of the barrel during the gun firing process were analyzed. By comparing the results of the thermoelastic model with that of thermoplasticity model, the effect of considering thermoplastic of gun steel on thermomechanical coupling response of barrel was investigated. The results show that the peak of Mises stress evolution considering thermoplasticity of material in the bore of the barrel is significantly reduced during the gun firing process, and the hoop stress evolution appears double-peak phenomenon. In addition, at the peak moment of bore pressure, the peak values that the hoop and Mises stress distributions along the radial direction at the midpoint of the land are reduced by 14.5 % and 20.9 %, respectively. This paper can provide a reference for the design of a large-caliber barrel.

Drilling the wells using water based mud through shale formations, causes their exposure to serious time-dependent wellbore instability due to shale swelling. Operating companies, before drilling operations through demanding shale formations, usually conduct drilling fluid optimization studies in order to define the proper mud type, mud density, salt type and concentration for inhibition. Through the analysis of offset wells, they are interpreting data about mud filtrate breakouts into the rock formations and chemical potential mechanisms to understand their influence on the time-dependent wellbore instability. The main objective of this paper is to give an insight in time-dependent and mechanical wellbore instability problems faced while drilling the wells through different shale formations in the gas condensate field D in the Persian Gulf. The importance of drilling fluid design optimization and solutions applied to overcome hole instability problems were analysed and highlighted. Besides the development of a model for mud density calculations, a concept of effective hoop stress and its influence on time dependent failure mechanisms is discussed. As a contribution to the method improvement, mud density calculation is verified by taking into the consideration the relationship between pore pressure and effective hoop stress and it is based on measured data from Well A in gas condensate field D from the Persian Gulf.

Originally, Kelvin–Helmholtz instability (KHI) describes the growth of perturbations at the interface separating counterpropagating streams of Newtonian fluids of different densities with heavier fluid at the bottom. Generalized KHI is also used to describe instability of free shear layers with continuous variations of velocity and density. KHI is one of the most studied shear flow instabilities. It is widespread in nature in laminar as well as turbulent flows and acts on different spatial scales from galactic down to Saturn’s bands, oceanographic and meteorological flows, and down to laboratory and industrial scales. Here, we report the observation of elastically driven KH-like instability in straight viscoelastic channel flow, observed in elastic turbulence (ET). The present findings contradict the established opinion that interface perturbations are stable at negligible inertia. The flow reveals weakly unstable coherent structures (CSs) of velocity fluctuations, namely, streaks self-organized into a self-sustained cycling process of CSs, which is synchronized by accompanied elastic waves. During each cycle in ET, counter propagating streaks are destroyed by the elastic KH-like instability. Its dynamics remarkably recall Newtonian KHI, but despite the similarity, the instability mechanism is distinctly different. Velocity difference across the perturbed streak interface destabilizes the flow, and curvature at interface perturbation generates stabilizing hoop stress. The latter is the main stabilizing factor overcoming the destabilization by velocity difference. The suggested destabilizing mechanism is the interaction of elastic waves with wall-normal vorticity leading to interface perturbation amplification. Elastic wave energy is drawn from the main flow and pumped into wall-normal vorticity growth, which destroys the streaks.

The presented research focuses on masonry shells with dry (cohesionless) contacts. In the mechanical analysis of such structures, the material is often assumed to have zero resistance to tension. This simplification can be questioned in light of the fact that due to the frictional resistance between masonry layers compressed to each other, significant tension can be carried perpendicularly to the direction of the compression. The effect can be so considerable that the typical orange-slice cracking of masonry domes can be prevented purely by choosing a suitable brick shape and bond pattern. Based on preliminary 3DEC discrete element simulations with realistic and experimentally validated material parameters in order to understand the failure modes, the phenomenon is quantified in the present paper for the two main types of bond patterns applied in masonry shells: (i) different versions of the running bond pattern, and (ii) two versions of the herringbone pattern. The theoretically predicted failure tensile stresses are checked and validated with 3DEC discrete element simulations.

This paper examines the effect of changing temperature on the curved natural composite material pipe (Walnut husks powder with polyester) and curvature angle θ= 34° practically. This work involves the design and fabricates of curved pipe samples with an angle of curvature θ=34° at 50 % weight fraction. Also, tensile and thermo-mechanical test were performing to find the mechanical properties of the specimens. Experimental work included design and manufacturing test rig to simulate thermal stress. The experimental results revealed that a maximum hoop strain and longitudinal strain increased with increasing the temperature. The hoop stresses at crown and intrados positions were more than the hoop stress at extrados position by 150.762% and 138.363% respectively, and the von mises stresses at crown and intrados positions were more than the von mises stress at extrados position by 218.259% and 178.193% respectively. In the curved pipe, the hoop strains at intrados and crown positions were more than the hoop strain at extrados position by 114.583% and 60.416% respectively.

Finite element analysis was carried out for the welding and heat treatment process of TC4 titanium alloy pressure vessel, aiming at revealing the distribution characteristics of welding residual stress and its changing law in the heat treatment process. By establishing a two-dimensional axisymmetric welding model, and considering the material properties, boundary conditions, heat source model and analysis methods, the temperature and stress fields in the welding process are successfully simulated.Based on the results of the post-welding stress field, the time-hardened creep model is quoted for the finite element calculations of the post-welding heat treatment process, and the effect of creep effect on the residual stresses of welded annulus is investigated, the results show that: the stress characteristics of the girth weld of the TC4 titanium alloy pressure vessel are obvious. The axial residual stress shows a tensile - compressive - tensile distribution along the thickness direction, while the hoop residual stress is a high tensile stress in the near-weld and heat affected zone, and the stress peak even exceeds the yield strength of the material; By comparing the heat treatment schemes considering and not considering the creep mechanism, it is found that the heat treatment introducing the creep mechanism significantly reduces the residual stress in the weld area. Among them, the hoop stress decreases by 80% and the axial stress decreases by 50%, and the stress distribution is more uniform, effectively alleviating the stress concentration phenomenon of the weld. In addition, the rebound amount of the residual stress in the cooling stage of the heat treatment scheme considering the creep mechanism is small. This study indicates that the creep mechanism plays a dominant role in eliminating residual stresses during heat treatment.

In this study, the influences of eggshell powder application on random fiberglass/polyester composite pipes thermal stresses were investigated experimentally and numerically. The experimental part involved industrializing tube samples which are Egg Shell Powder with Polyester at 50% volume fraction.(E50), Random Fiberglass with plyester at 50% volume fraction (F50) and Egg Shell Powder with Random Fiberglass with Polyester at 50% volume fraction (E25F25). Resin molding procedure and experimental rig design to study how tube samples are faced with thermal loads. Pipes are made with (95 mm) inner diameter, (400 mm) circumference, and (5 mm) wall thicknesses. Computational Fluid Dynamic, ANSYS software package version 11, is simulated with product form SHELL63. Results show that, composite samples (F50) had an average longitudinal strain, while composite samples (E50) had a low longitudinal strain. The composite (F50) had average longitudinal and hoop stress (62.2 MPa, and 61.1 MPa) respectively, while the composite (E50) had low longitudinal hoop stress (28.5 MPa, ad 30.8 MPa) respectively.