Thick-walled Cylinder Research Articles

Bond-slip behavior of deformed rebar in grouted duct connection: Experiment, theoretical analysis and cohesive-zone element model

In precast bridge piers, the grouted corrugated duct (GCD) connection can offer advantages of accommodating large construction tolerances and being cost-effective. However, this connection is relatively new, and its bond strength and effective bond length are a concern in structural design. To fill the research gap of the bond behaviors of the GCD connection, experimental tests of 36 pull-out specimens with/without GCD were conducted in this paper. The influencing factors of bond strength were investigated, including duct, rebar diameter and anchorage length. The results revealed that the GCD connection required a shorter anchorage length and exhibited a plumper bond-slip curve and higher bond strength compared to the specimen without GCD connection. Then, an analytical model based on thick-walled cylinder theory was proposed to construct the bond-slip curve of GCD connection, and to identify the criteria for mortar strength. To simulate the bond-slip relationship in finite element model, a cohesive-zone element model realized by the zero-thickness user defined element was developed at the interface between rebar and dummy rebar. Finally, a comparison was made among the solution of proposed bond-slip model, finite element analysis, and the tested data, demonstrating good consistency between the three.

Analytic solution of pull-out failure on bond-slip relationship between deformed rebar and ultra-high-performance concrete

Numerous studies have explored the bond performance between deformed rebar and ultra-high-performance concrete (UHPC), yet an analytical solution to the bond-slip relationship remains elusive. This study presents an analytical solution of pull-out failure for the staged bond-slip constitutive relationship between rebar and UHPC, taking into account the meso-scale bond properties of fibers. The critical point coordinates for different stages are determined by the analytical solution. Utilizing the elastic mechanic solution of thick-walled cylinder under uniform internal pressure, the fictitious crack model, and the fiber-matrix discrete model, analytical solutions and simplified formulas for bond stress and slip at the critical points are provided respectively. The simplified formulas for predicting bond characteristics are proposed. The bond-slip test data are composed of 107 groups from 15 literatures, and the predictions of different formulas are compared. The average ratios of the theoretical ultimate bond stress and peak slip to the test results are 0.995 and 1.033, with a standard deviation of 0.179 and 0.231, and the error is generally within 20%. Compared with the bond-slip relationship, it is more reasonable that the ascending and descending sections are exponential. Moreover, the parameters in the bond-slip relationship can be calculated by the theoretical predictions of bond characteristics at each critical point.

Analytical Formulation to Predict Residual Stresses in Thick-Walled Cylinders Subjected to Hoop Winding, Shrink-Fit, and Conventional and Reverse Autofrettages

Abstract Shrink-fit, wire-winding, and autofrettage processes and their combinations can be effectively used to increase the strength and fatigue life of metallic thick-walled cylinders for a given volume. While several numerical solutions have been developed for determining the residual stress profile through the thickness of thick-walled cylinders for different combinations of the shrink-fit and autofrettage processes, there are no analytical solutions available to predict the residual stress profile induced by the combination of the shrink-fit and inner and outer autofrettage processes with the hoop winding. In this study, the analytical formulations to predict the residual stress distribution for various combinations of the three processes (hoop-winding, shrink-fit, and autofrettage) have been formulated considering the same manufacturing sequences. The results demonstrate that combinations that include the wire-winding process significantly improve the residual stress profile through the wall thickness of single- or two-layer thick-walled cylinders. Specifically, when the wire-winding process is included, the residual stress at the inner surface increases by 25% in single-layer configurations and by 12% in two-layer thick-walled cylinders, respectively, compared to configurations without the wire-winding process.

Early-age bond behavior of embedded CFRP bars in UHPFRC: Test study and theoretical analysis

The combination of carbon fiber-reinforced polymer (CFRP) bars and ultra-high-performance fiber-reinforced concrete (UHPFRC) has great potential for use in producing structures with exceptional mechanical properties. Nevertheless, a research gap exists regarding the early-age bond behavior of embedded CFRP bars in UHPFRC, which is key to evaluating structural crack resistance. To address this gap, in this study, a series of tests was conducted on 90 pull-out specimens consisting of UHPFRC and CFRP bars. The influences of the concrete age (t), bond length (lb), and cover thickness-to-bar diameter ratio (C/D) on bond behavior were investigated. Each pull-out test generated the acquisition of a complete bond stress–slip curve. The bond interface was analyzed mechanically using the thick-walled cylinder theory and elasticity theory. A bond strength theoretical model that accounted for the surface wear of CFRP bars was proposed. The results of the pull-out test and theoretical analysis indicated that the bond strength tended to grow as t and C/D increased and was negatively correlated with lb. The model predictions agreed well with the test results while exhibiting excellent predictive accuracy compared to existing models. Furthermore, a three-branch bond stress–slip model was established to depict the bond behavior, demonstrating acceptable consistency with test curves.

Research on the zoning of blasting for ultra-deep hole cylindrical charges based on thick-walled cylinder theory

To address the challenges faced by coal miners when encountering collapsed pillars in local hard rock formations, we researched ultra-deep hole loosening blasting technology. To overcome issues related to the inapplicability of existing blasting zoning theories and the lack of a solid foundation for borehole design in ultra-deep hole loosening blasting sites, we introduced a blasting zoning model and theoretical calculation formula based on thick-walled cylinder theory. Building on this foundation, we proposed coupled and uncoupled charge calculation methods that take into account strain rate variations and confining pressure effects. Furthermore, numerical simulations using the ANSYS/LS-DYNA software demonstrated that the results obtained from this theory were consistent with the simulation results. Ultimately, based on the blast zone results derived from both theory and simulation, we determined the blasting range of individual blast holes to design effective construction plans for ultra-deep hole blasting sites, achieving satisfactory results.

STUDY ON SEALING PERFORMANCE OF AIRTIGHT BUCKLE UNDER COMPLEX LOADS

The existing studies on sealing performance of airtight buckle of production strings in oil and gas extraction mainly focus on complex loads without bending moment. In this paper, a numerical model of an airtight buckle under the complicated load with bending moment is constructed. The precision of the model is verified by comparing with theoretical value for thick-walled cylinders. The impact of simple and complex loads on the contact stress of the sealing surfaces is discussed. It should be noted that the contact stress exhibits a combined effect of multiple factors, and the internal pressure plays a dominant role. However, the influence of bending moments on the contact stress of the sealing surface can “reverse” under specific load combinations. The reason for this phenomenon is that the sensitivity of the tension side and compression side to internal pressure is different under bending moment. The obtained results can guide the design and usage for airtight buckle of the production string.

Implementing a simple 2D constitutive model for rocks into finite element method

Our research group has developed a 2D constitutive model for rocks that incorporates a strain-dependent elastic modulus. This model efficiently represents nonlinear stress–strain curves using just three equations and four parameters. In this study, we have implemented the simple 2D model into finite element codes to tackle engineering problems. We have calculated and compared stresses and displacements around a pressurized thick-walled hollow cylinder, a lined non-circular tunnel, and a rock slope using the elastic, simple 2D, and elasto-plastic models. The results confirmed that the simple 2D model closely matches the stress distribution obtained from the elastic solution at low-stress levels. Additionally, the simple 2D model produces a plastic zone with a larger inward displacement than the elasto-plastic model at higher stress levels. Only the simple 2D model captured sidewall convergence, roof sag, and floor heave in non-circular tunnels, and the toppling failure for 90° slope and toe translational slide for 60° slope in rock slopes with smooth critical slip surface. We did not encounter any convergence difficulties while solving the simple 2D model.

Enhancing Fatigue Life of Thick-Walled Cylinders through a Hybrid Rotational-Swage Autofrettage-Induced Residual Stresses

Enhancing Fatigue Life of Thick-Walled Cylinders through a Hybrid Rotational-Swage Autofrettage-Induced Residual Stresses

The stress distribution around a thick-walled cylinder by a proposed constitutive model for rocks.

To simulate the nonlinear stress-strain curve of rocks under static loads and contribute to the design and construction of rock engineering structures, a constitutive model has been proposed based on the elastic modulus E decreasing with the increase in longitudinal cracks. This constitutive equation offers numerous advantages, with the most noteworthy being that the simulation of stress-strain curves for rocks necessitates only three equations (Eqs 1-3) and four parameters (A, k0, C and εs). Following this, we employ the constitutive equation to analyze the stress distribution around a thick-walled cylinder and explore the impact of its four parameters on the stress distribution surrounding the thick-walled cylinder. Parameter A primarily affects the range of the plastic zone and the magnitude of the maximum tangential stress; parameter C mainly influences the magnitude of the maximum tangential stress; parameter εs mainly affects the range of the plastic zone and the magnitude of the maximum tangential stress; parameter k0 primarily influences the magnitude of the maximum tangential stress. We got the similar results with Bray model, but distribution of stress around the tunnel are different present that the shape of stress-strain curves are different.

Analiza elastično-plastičnog naprezanja skupljajućih debelih FGM cilindara

This paper addresses the stress analysis of shrink-fitted thick-walled cylinders made of functionally graded material (FGM). Analytical solutions are provided for the elastic-plastic behavior of shrink-fitted axisymmetric thick-walled FGM cylinders based on the linear plane elasticity theory and plasticity laws. Due to the material's functional gradation, mechanical characteristics like Young's modulus, yield stress, and plastic parameters are controlled by a power function along the wall thickness. Considering a plane strain case, elastic-perfectly plastic model and Von Mises yield criterion; theoretical solutions are obtained for both elastic and plastic phases. The radial, hoop, axial, and equivalent Von Mises stresses are obtained for up to 25%, 50%, and 75% of cylinder plasticization for the elastic and plastic zones. Stresses are given in terms of interference and geometrical and mechanical parameters of the assembly. In addition, the interferences to start plastic deformation and the full plastic collapse of the cylinder are discussed. Moreover, the effect of the gradient index on the contact pressure and both the start of yield and plastic collapse pressures are conducted. The analytical results found in the current research are compared with the numerical solutions carried out by Ansys Workbench. Both results show a good agreement.

Coupled modeling circulating multi-layer wellbore temperature and stress field during deepwater high-temperature and high-pressure gas well testing

During the testing of offshore high-temperature and high-pressure (HTHP) gas wells, the heat transferred by the high temperature gas flowing through the tubing frequently leads to the rupture of the wellhead cement sheath, which can directly result in the failure of the wellhead seal and pose a significant safety hazard. In this study, an advanced multi-layer temperature and stress coupling model is introduced, which combines wellbore heat transfer and the multi-layer thick-walled cylinder theory. Subsequently, commercial software and measured data are utilized to verify the validity of the coupling model. The simulation results show that the average error between the model and the commercial software is 0.84%, and the average error between the model and the measured data is 1.65%. There is the optimal gas production in testing process by calculating the temperature and stress distribution during the test of the South China Sea HTHP gas well, and the stress distribution sensitivity of the multi-layer model is analyzed. The sensitive parameters are ranked in descending order of importance as follows: the number of cement sheath layers, gas-oil ratio (GOR), performance parameters of the cement sheath, performance parameters of the formation, and casing wall thickness. Furthermore, in the three-layer model, the circumferential stress at the first interface of the cement sheath is lower compared to the two-layer model. The findings provide a theoretical reference for comprehending the distribution of wellbore temperature and stress during testing, which is crucial for accurately assessing wellbore safety and ensuring optimal operational conditions.

Integrated Design of Hydraulic Coupling Bolts for Large Shaft Systems

Hydraulic coupling bolts are used in a wide range of industrial sectors, where ensuring the structural integrity and reliability of shaft systems is of paramount importance. However, research on systematic design methods for these specialized bolts is still lacking. In this study, an integrated design was used on hydraulic coupling bolts with M72 specification, considering both the tightening and untightening processes. First, the second tightening load was determined based on material strength, stress concentration and safety factors. Subsequently, the upper and lower limits of the first tightening loads were calculated using the thick-walled cylinder theory. An appropriate first tightening load maintaining the tightening force in both the axial and radial directions was obtained using finite element analysis. Design variables for the adapter configuration and oil passage shape were selected, and their impact on structural integrity was assessed using finite element analysis. The optimal combination of these design variables was derived. Finally, operational experiments for hydraulic coupling bolts were conducted according to the design results. The test results demonstrated a successful tightening and untightening process, confirming the effectiveness of the proposed design method.

Mechanical properties and bonding strength of twisted wire strands at elevated temperatures

This paper experimentally investigates the mechanical properties of 1860 MPa twisted wire strands and the load capacity of hot casting sockets at elevated temperatures. The stress-strain curves of the strands at the temperature in 20 °C to 600 °C range are reported, and the elastic modulus, yield strength, ultimate strength, ultimate strain and rupture strain are obtained and compared to EC2 and other existing studies. The failure mode, load capacity, failure displacement and critical temperature of the sockets at the temperature in 20 °C to 440 °C range are acquired. The test results show that 1860 MPa twisted wire strands have significantly improved ductility in necking stage after 200 °C, which is underestimated in EC2. The strands with hot casting sockets rupture before 180 °C, and are pulled out from the sockets after 230.5 °C. The load capacity drops after 150 °C, and the failure displacement dropped after 300 °C, indicating significant influence of the sockets on the fire resistance. Based on thick-walled cylinder model, calculation methods are proposed to determine the bonding strength and load capacity of the strand with hot casting sockets. The prediction of the failure modes and load capacity agrees well with test results. The parametrical analysis by the calculation methods shows that the load capacity of the strands with sockets increases as the embedded length or internal diameter of socket increases, or the diameter of the strands decreases in a limited range. For fire protection, it is recommended to keep the socket temperature under the critical temperature in accordance with load ratio.

Calculation of Stresses Initiated by an Electrical Explosion of Conductors in a Composite Thick-Walled Cylinder

Calculation of Stresses Initiated by an Electrical Explosion of Conductors in a Composite Thick-Walled Cylinder

Automatic Measurement of Contact Stress and Connection Force of Interference Components by Ultrasound

Tiny interference components play an important role in the aerospace and instrumentation fields. Contact stress and connection force are important factors in evaluating the reliability and service life of components. In this study, the ultrasonic method is used to measure the stress distribution and the connection force on the mating interface. Based on statistical microcontact theory, the virtual thin-layer model, and the asperity interaction model, the contact acoustic model is optimized. On this basis, the mapping relationship between contact stress and contact stiffness can be further obtained. This relationship was obtained by calibration experiments. Then, the stress distribution on the interface with two different structures, namely the uniform cylinder and the step cylinder, was measured and compared with the theoretical results of the thick-walled cylinder theory. The results show that the two have good consistency. Finally, based on the stress distribution, the connection force was calculated and compared with the experimental results. The results show that the ultrasonic measurement method can accurately measure the connection force, and the relative error is within 16%. Therefore, this study can provide a good method for the quality assessment of interference components.

Mathematical Model of Anal Canal for Anal Fistula Surgery

Abstract: Purpose: Surgery is necessary for the treatment of an anal fistula. However, excision of some sphincter muscle would compromise sphincter integrity or function, which is the cause of a reduced success rate in the long term. In order to develop an appropriate surgical plan, a mathematical model that describes the relationship between the internal pressure of the anal canal and the structure of anal sphincters is required.
 Methods: The anatomical structure of the anal canal and the corresponding sphincter pressure can be measured by endoanal ultrasound (EAUS) imaging and manometry, respectively. Length-tension relationships for skeletal and smooth muscles, two major components of the external and internal anal sphincter, respectively, were reviewed first. 
 Results: Based on the information about the internal and external sphincters, two mathematical models, the thick-wall cylinder model and the two-layer model, have been created, from which the influence of complete or partial excision of the sphincter muscle can be estimated.
 Conclusions: The proposed thick-wall cylinder and two-layer models could describe the relationship between the internal anal canal pressure and the structure of anal sphincters, from which the influence of complete or partial excision of the sphincter muscle may be estimated.

Numerical manifold method for thermo-mechanical coupling simulation of fractured rock mass

As a calculation method based on the Galerkin variation, the numerical manifold method (NMM) adopts a double covering system, which can easily deal with discontinuous deformation problems and has a high calculation accuracy. Aiming at the thermo-mechanical (TM) coupling problem of fractured rock masses, this study uses the NMM to simulate the processes of crack initiation and propagation in a rock mass under the influence of temperature field, deduces related system equations, and proposes a penalty function method to deal with boundary conditions. Numerical examples are employed to confirm the effectiveness and high accuracy of this method. By the thermal stress analysis of a thick-walled cylinder (TWC), the simulation of cracking in the TWC under heating and cooling conditions, and the simulation of thermal cracking of the Swedish Äspö Pillar Stability Experiment (APSE) rock column, the thermal stress, and TM coupling are obtained. The numerical simulation results are in good agreement with the test data and other numerical results, thus verifying the effectiveness of the NMM in dealing with thermal stress and crack propagation problems of fractured rock masses.

An Explicit Modeling for the Pseudoelastic Response of Porous SMA Thick-Walled Cylinders under Internal and External Pressure

Shape-memory alloy (SMA) structures, either dense or porous, are widely used because of their functional characteristics arising from shape-memory effect and pseudoelasticity. Hence, the precise modeling of these materials is essential due to design issues. In this study, the solution algorithm based on an explicit phenomenological constitutive model is investigated to analyze pressurized cylinders. The proposed method is extracted following return mapping scheme to find the evolution of phase transformation in these structures. The formulation is validated by comparing uniaxial tension–compression curves during loading, unloading and thermal actuation against published literature. By the aid of this model, assuming elastic and phase transformation strains, a comprehensive study is presented to inspect stress, strain and displacement fields along the thickness of internally and externally pressurized thick-walled cylinders. To this end, the governing nonlinear equation in elastic–inelastic zones is discretized by the efficient method of generalized differential quadrature (GDQ) and the resultant relations are solved numerically. The influences of internal and external pressure on stress distribution along the cylinder wall during loading–unloading for different temperatures including phase transformation and saturation states are discussed. Also, the closed-form solution for critical pressure at the onset of the phase transformation is studied.

Cracking time and prediction model of low-alloy steel reinforced seawater sea-sand concrete based on DIC technology

The cracking of seawater sea-sand concrete (SSC) cover due to the corrosion of low-alloy steel (LS) is a critical factor affecting its serviceability and durability. To analyze the cracking behavior of the SSC cover, a thick-walled cylinder model was developed in this study. The cylinder was divided into multiple coaxial rings of equal thickness, and damage variables were introduced to determine the extent of damage for each cracked ring based on the position of the rust expansion crack front. A predictive model for the cracking time of SSC cover was established by using the displacement compatibility equation at the interface of reinforcing steel and cover concrete, in combination with Faraday's law. To verify the accuracy of the model, the Digital Image Correlation (DIC) technique was utilized to determine the timings of two pivotal stages: the initial cracking and complete cracking of the cover. The comparison between the predictive outcomes and experimental results showed an error range of 4 %–10 %, indicating that the predictive model is relatively accurate.

Creep Analysis of Rotating Thick Cylinders Subjected to External and Internal Pressure: Analytical and Numerical Approach

Creep analysis is crucial when dealing with thick rotating cylinders exposed to a steady load or stress at a higher temperature. These cylinders present a fundamental constituent in a variety of dynamic engineering applications, such as pressure vessels, hydraulic cylinders, gun barrels, boilers, fuel tanks, aerospace technologies, nuclear reactors, and military equipment. Thus, severe mechanical and thermal loads cause significant creep and reduce service life. Hence, the prediction of creep in such axisymmetric components, including pressure vessels, subjected to steady load at elevated temperatures is extremely important and quite a complex task. Thus, in this study, the creep behavior in a rotating thick-walled cylinder made of Al-SiCp composite subjected to constant load as well as internal and external pressures is investigated, both analytically and numerically, using FEM. A wide range of rotational speeds effect on the process is also included. The creep behavior is assumed to follow the Norton constitutive model, and for stress failure analysis, von Mises yield criteria are adopted. The effect of internal and external pressures, as well as the rotational speed on the stresses, strains, and strain rates in the cylinder, is studied and presented. Both finite element analysis (FEA) and Lame’s theory were used to determine the radial, tangential, and longitudinal displacements and corresponding stresses, as well as the equivalent Von Mises stresses and strain rate distributions in the cylinder revolving about its own axis. It is observed that with the increase of the internal pressure in the cylinder, the strain rate increases. Meanwhile, when subjecting the cylinder to both external and internal pressures, the strain rates tend to decrease. For instance, it was also found that stress and strain rates were higher for the 1000 rad/sec rotational speed of thick cylinder in comparison with lower rotational speeds of 300 and 500 rad/sec. Also, it is noticed that the variation in these values at the inner radius was more than those found at the outer radius. All results of the stresses, strains, and strain rate distributions obtained are found to be in full agreement with the published data. Furthermore, all plotted results of the stresses, strains, and strain rate distributions obtained through the analytical approach were found to be in exceptional compliance with those solutions obtained using finite element analysis (FEA).