Thick-walled Cylinder Theory Research Articles

A method for obtaining radial stress in the freezing direction in frozen soil samples

In this study, we design an innovative frost heave cell to investigate the characteristics of stress in the radial direction during the freezing of a soil sample. The frost heave cell is divided into several independent rings connected by silicone sheets, which aims to reduce the deformation influence of the frozen part on the unfrozen part. By installing mini-sized water pressure gauges, strain gauges, and thermal sensors in the frost heave cell, the circumferential strain measured by strain gauges on the surface of frost heave cell can be effectively evaluated. In order to transfer this circumferential strain into stress in the radial direction, we adopt the thick-walled cylinder theory. Then, we conducted one freezing test with Dotan to investigate the characteristics of radial stress during freezing. The results suggest that the radial stress caused by frost heave increases rapidly when the temperature drops from 0 °C to −2 °C. However, as the temperature decreases below −2 °C, the radial stress gradually increases. When the temperature approaches −10 °C, the radial stress plateaus and does not increase further. These findings indicate the unique characteristics of radial stress perpendicular to the freezing direction and suggest the need for further research on this topic. As more complicated applications of artificial freezing method in underground space of urban area are expected, the influence on the surrounding structures brought by three-dimensional freezing shows its significance. Our research is aiming to investigate the mechanism of freezing phenomenon of soil in three-dimensional space and then promote the application of artificial freezing method in a wide area.

Analytical model for the winding process-induced residual stresses of the multilayered filament wound cylindrical composite parts

The residual stresses due to winding tensions have significant influence on the product quality of the filament wound composite parts. In this paper, an analytical model is proposed to calculate the winding process-induced residual stresses for the multilayered filament wound composite parts with metal linear based on the three-dimensional thick-walled cylinder theory. In the modeling of winding process, the contribution of the current outmost winding tension to the residual stresses of the previously wound composite layers is first calculated and then the total residual stresses is obtained based on the elastic superposition principle. Moreover, the winding tensions are modified for equal residual stress in fibers based on the inverse iteration principle. Compared with the results in other work and obtained by finite element method, it shows that the proposed analytical model is of high accuracy and can be used to calculate the residual stresses due to winding tensions for the multilayered filament wound composite parts. The expected winding tensions for the equal residual fiber stresses can be quickly obtained after several iterations. Moreover, the effects of thickness of metal linear on the winding tensions distributions are further investigated based on the proposed model and the iterative algorithm.

Automatic press-fit assembly of small precision interference fitting parts: armature of electro-hydraulic servo valve

PurposeThe purpose of this paper is to design an automatic press-fit instrument to realize precision assembly and connection quality assessment of a small interference fitting parts, armature.Design/methodology/approachIn this paper, an automatic press-fit instrument was developed for the technical problems of reliable clamping and positioning of the armature, automatic measurement and adjustment of the attitude and evaluation of the connection quality. To compensate for the installation error of the equipment, corresponding calibration method was proposed for each module of the instrument. Assembly strategies of axial displacement and perpendicularity were also proposed to ensure the assembly accuracy. A theoretical model was built to calculate the resistant force generated by the non-contact regions and then combined with the thick-walled cylinder theory to predict the press-fit curve.FindingsThe calibration method and assembly strategy proposed in this paper enable the press-fit instrument to achieve good alignment and assembly accuracy. A reasonable range of press-fit curve obtained from theoretical model can achieve the connection quality assessment.Practical implicationsThis instrument has been used in an armature assembly project. The practical results show that this instrument can assemble the armature components with complex structures automatically, accurately, in high-efficiency and in high quality.Originality/valueThis paper provides a technical method to improve the assembly quality of small precision interference fitting parts and provides certain methodological guidelines for precision peg-in-hole assembly.

Contact stress analysis of disc cutter peg-hole with interference fit

To study the relation of the interference fit between cutter body and cutter ring, a theoretical design of interference fit of the cutter peg-hole is carried out according to the theory of thick-walled cylinders. The finite element method is used to analyzed the mapping relationship between the contact stress of cutter ring and cutter body. Thermal expansion assembly of the cutter ring is simulated, and the temperature of the thermal expansion assembly of the cutter ring is determined. The result shows that the contact length between the cutter body and the cutter ring has little influence on the contact stress of the cutter ring, but with increasing contact length the stress concentration of the retaining ring will increase. The contact stress of the cutter ring is basically the same at the same amount of interference and temperature, but the contact stress of the ring decreases with increasing contact length at high temperature. When the contact length is the same, the contact stress and the radial force of the mating surface increase with increasing amount of interference. The reasonable temperature for thermal expansion assembly of the cutter ring is 160 °C.

A Model for Bond Strength in Presence of Corrosion in Concrete

Corrosion of steel in concrete is the most detrimental source for reinforced concrete structures. Among the other effects, corrosion deteriorates the interface between steel and concrete. An axisyimmetric numerical model able to simulate the structural behaviour of bond between steel and concrete is here presented. The model is based on the thick-walled cylinder theory so that bond performance is a direct consequence of radial pressure acting on the rebar and coming from the surrounding elements and corrosion. Both elastic and inelastic contribution of concrete is also taken into account. The model is used to simulate pull-out tests present in literature. The results show the effectiveness of the model and is also compared with an empirical model already proposed in literature.

Mechanical Performances of Transverse Rib Bar During Pull-Out Test

To evaluate mechanical performances of the transverse rib bar and reveal anchoring mechanism between the grout and steel bar, a series of pull-out tests were carried out, the numerical simulations and theoretical analysis of grout failure modes were also analyzed. Results show that the grout in front of the transverse rib display wedge-shape damage and the simulation results verify this damage forms. The formula of the effective transverse rib angle, the grout strength and anchorage force were derived based on elastic thick-wall cylinder theory. During the pull-out tests, the radial stress of the grout lagged the tangential stress reaching the ultimate tensile strength with the inner pressure increasing. The anchoring force of the transverse rib bar increases with the increase of the grout strength, and with the increase of the effective transverse rib angle. These conclusions provide the theoretical basis and technical support for the engineering practice.

Theoretical and experimental investigation on interference fit in electromagnetic riveting

As an advanced interference-fit joining technology, electromagnetic riveting (EMR) has wide engineering application prospects in manufacturing and assembly fields. In this paper, a theoretical model on interference fit for EMR process is derived based on the stress wave theory and thick wall cylinder theory. EMR experiments are conducted to verify the analytical model. The compared results show that the analytical solutions agree well with experimental values. The interference-fit model synthetically considers many process parameters factors, not only the material properties and size of rivet, sheets and punch, but also the riveting force. The residual stress distribution, which is an important factor on fatigue life, can be predicted by this model. In addition, this can provide scientific guidance for the process parameter design and riveting setup optimization in engineering application.

A model to characterize the lateral expansion of a cylinder containing a polymer filler subjected to compression

This article presents a model to characterize the lateral expansion of metal cylinder expanded by polymer filler and analyzes the influencing factors to the expansion. Based on the elastoplastic theory of thick-walled cylinder and the Drucker–Prager yield criterion, the expansion model which considers the material properties and dimensions of the filler and the cylindrical shell is constructed. To verify the accuracy of the model, a series of experiments, compared with the model, are conducted under different conditions (different materials of the filler, different thickness, and materials of the cylindrical shell), which illustrates that the proposed model is able to capture the response observed in experimental tests. Meanwhile, it is demonstrated that the relationship between axial stress and radial strain of the expansive specimen is mainly determined by the properties of the cylindrical shell instead of those of the filler, and the expansion decreases with the growth of the hydrostatic pressure.

Prediction of stress distribution in press-fit process of interference fit with a new theoretical model

Interference fit is widely used in many industrial fields for its high ability to transmit an axial force or torque between a shaft and hub. But the performance of interference fits during their life in service is limited by stress concentrations and surface wear. Nowadays, theoretical methods based on thick-walled cylinder theory become increasingly abundant. However, the prediction results of stress distribution in press-fit process are not accurate for ignoring the stress concentrations. Since the stress distribution is significant for analysis of surface wear and assembly quality, especially for precision assembly of small parts, the purpose of this study is to build a new theoretical model to predict the stress distribution. The stress distribution equation was deduced based on a simplified model that a nonuniform linear load acts on a portion of semi-infinite plane. Finally, the stress distribution in the press-fit process was analyzed by the theoretical model, as well as the stress distribution of different material pairs (Ni36CrTiAl–50Ni-50Fe, AISI 1045–AISI 1045) under full contact condition. The comparison between theoretical and numerical results shows that the new theoretical model has high accuracy in predicting stress distribution and maximum stress, and the relative error is less than 17%. Therefore, the new theoretical model can give more reasonable results and provide a more reliable approach for design of interference fits. Furthermore, the model provides a method for the optimization of interference analysis under different structures and working conditions, and gives a theoretical basis for real-time estimation of assembly quality.

Investigation on the experimental determination of the apparent preconsolidation stress and effective-sealing condition for clay cap rock

Seal ability of clay cap rock is impacted by not only the current physical and mechanical characteristics but also the diagenetic experiences and stress state. Thereby, both the diagenetic actions and stress state when conversing from brittleness to ductility should be further investigated. Only by this way can the oil/gas generation and the transportation relationship be thoroughly revealed and then the seal ability of cap rocks be accurately evaluated. Aimed at the clay rocks subjected to different diagenetic states from E’xi-Yudong regions, a thick-wall steel sleeve was manufactured and utilized as the lateral restrictor to implement the uniaxial strain compression experiments. Based on the thick-wall cylinder theory, the procedure of calculating the apparent preconsolidation stress (APS) was established. To reveal the factors that influence the APS, the relationships between APS and uniaxial compression strength, ultrasonic velocity, and porosity as well as clay mineral content were investigated, respectively. The mechanisms of the lateral pressure coefficients’ variations were also discussed. The transition condition of “brittleness to ductility” is preliminary discussed, so is the calculation method for the effective-sealing burial depth. This study could provide a significant indication of evaluating the seal ability of diagenetic clay cap rocks.

Fracturing mechanism of coal-like rock specimens under the effect of non-explosive expansion

A non-explosive expansion method (NEM) is proposed to apply in the field of reservoir fracturing for the extraction of coalbed methane. Specimens with mechanical properties similar to primary coal were prepared, and their fracture behavior was investigated under different side stresses. Acoustic emission (AE) and infrared thermal imagery were utilized to record the parameters (energy and amplitude) of the AE events and the surface temperature distributions, respectively. The results showed that specimens were all destroyed using NEM with different crack morphologies under diverse side stresses, and the fracture evolutions were greatly dependent on the structure and side stresses, which caused complex crack numbers and crack distributions. Several periodic energy concentrations and the stair increasing pattern of cumulative energy all indicated that the fracturing process of NEM did not finish instantaneously but continued for a long time. A quantitative analysis of crack number and distribution by box counting showed that the larger the number of fractures, the greater the fractal dimension and the greater the complexity, and the difference in fracture density positively correlated to the fractal dimension was influenced by side stresses. Fractures might be determined by the coupled effect of swelling force and released heat according to the chemical reaction of agents. The relationship between swelling force and tension stress was deduced based on the thick-wall cylinder theory. A semi-submersion test was carried out to evaluate the effect of released heat on crack generation preliminarily in consideration of material volume and influence time. The greater material volume and longer influence time created a number of blocks and produce complex crack faces, largely related to the released heat inducing a complete temperature gradient.

EXPERIMENTAL STUDY AND STRESS ANALYSIS OF MECHANICAL PERFORMANCE OF GROUTED SLEEVE SPLICE

The paper presents the test results of twelve grouted sleeve splices under direct tensile load. Their performance was evaluated based on the failure process, failure mode, load and displacement curves. The cylinder wall stress impacted by anchorage length and bar diameter was analyzed. The transfer processes among the grouted sleeve splice were revealed by the thick-walled cylinder theory, and then the relationship between the cylinder wall stress and the axial force was established using a calculation model. The result shows that the failure process consists of four stages:elastic stage, yield stage, strengthening stage and neck stage. The behaviors of yield strength and ultimate strength measured in the specimens are similar to those of the steel bar. The cylinder wall stress decreases slightly as the anchorage length increases, and it increases obviously as the bar diameter increases. The analytical values agree well with the experimental values, which could provide references for relevant design and research.

Feasibility of measuring the pressure vs. volume relationship of compressible solids using a thick-walled cylinder

According to the theory of thick-walled cylinder (TWC), the internal radial stress of the cylinder can be determined by measuring the hoop strain at the outer wall of the cylinder. We here investigate the feasibility of measuring the radial stress of compressible solids, such as a powder compact positioned inside of a cylinder, using the theory of TWC. Based on finite element analysis, we have shown that provided the geometry of the TWC is appropriately designed, TWC theory can be utilized up to significant volume strains of the specimen positioned in the TWC. The design guidelines for the geometry (thickness and internal radius) of the TWC are provided from the viewpoints of (1) the maximum magnitude of the volume strain up to which TWC theory is applicable, (2) the maximum measurable radial stress before yielding of the cylinder occurs, and (3) the magnitude of the hoop strain when the internal radial stress of the cylinder is very low, especially at the initial stage of powder compaction.

A new analytical method for press-fit curve prediction of interference fitting parts

Press-fit assembly is one of the traditional methods for assembly of interference fitting parts. But the connection quality cannot be obtained directly from this method. At present, the press-fit curve is employed for quality estimation, and thick-walled cylinder theory (TCT) is used for standard press-fit curve prediction. However, the prediction results have a large relative error which may reach to larger than 18% for neglecting the influence of non-contact regions. This paper aims to build an accurate analytical method to predict the press-fit curve under the linear elastic hypothesis. The finite element method (FEM) was used to analyze the influence of non-contact regions, and the results show that the non-contact regions generate a constant resistant force in the press-fit process. To establish the analytical method, a simplified model was proposed. The calculation method of resistant force was deduced based on the simplified model, and the analytical method was established based on both of TCT and the resistant force calculation method. The analytical results were compared with numerical results and validated by experimental results. The results show that the new analytical method can predict the press-fit curve accurately, and it is more efficient than FEM in design of interference fitting parts.

A higher-order equation for modeling strand bond in pretensioned concrete beams

In pretensioned concrete members, the bond between prestressing strands and concrete in the transfer zone is necessary to ensure the two materials can work as a composite material. This study develops a computer program based on the Thick-Walled Cylinder theory to predict the bond behavior within the transfer zone. The bond was modeled as the shearing stress acting at the strand-concrete interface, and this generated a normal stress to the surrounding concrete. The stresses developed in the concrete often exceeded its tensile strength, which resulted in radial cracks at the strand-concrete interface. These cracks reduced the concrete stiffness and redistributed the bond strength along the transfer zone. The developed program was able to determine the bond stress distribution, degree of cracking, and transfer length of the prestressing strands. The program was validated using a data set of transfer lengths measured at the University of Arkansas and a data set collected from the literature.

Study of elastic deformation on dimensional accuracy in ironing process of spur gear

The cold ironing process of a warm forged spur gear was applied to investigate the elastic distortions arising by the behavior of die elastic expansion and gear elastic recovery in this article. An elasto-plastic finite element simulation was performed to analyze the elastic behavior characteristics of gear and die. The effects of interference between gear and die on the elastic distortions were investigated through finite element simulation and experiment, respectively. The change of geometrical profile and dimension of the gear tooth were measured; the estimated dimension of ironed gear by finite element simulation was fitted to the experimental results well within the range of 5% relative error. Furthermore, in order to improve the dimensional accuracy of final forged gear, this study proposed a die cavity compensation method to compensate cavity of the ironing die, which was obtained by shrink fitting a outer ring into the initial ironing die. The optimum radial interference between stress ring and initial shrink-fitted die was calculated based on the Lame formula and thick wall cylinder theory. Finally, an experiment according to the proposed die cavity compensation method was carried out to examine the validity of analytical results and demonstrated that predicted dimensions could be achieved and dimensional accuracy greatly improved. It was shown that the manufacture gear satisfies the IOS6 class by measuring the iron-forged gear.

Analysis of bond-slip between concrete and steel bar in fire

This paper presents a robust model for predicting the bond-slip between the concrete and steel reinforced bar at elevated temperatures. The model is established based on a partly cracked thick-wall cylinder theory and the smeared cracking approach is adopted to consider the softening behaviour of concrete in tension. The model is able to consider a number of parameters: such as different concrete properties and covers; different steel bar diameters and geometries. The proposed model has been incorporated into the Vulcan program for 3D analysis of reinforced concrete structures in fire. The model has been validated against previous test results.

Influence of the WHCP on cement sheath stress and integrity in HTHP gas well

The wellhead casing pressure (WHCP) resulted from gas production, downhole operations, casing and oil tubing or packing leakage poses great challenges to the mechanical integrity of cement sheath in HTHP gas wells. This paper proposed an analytical model of cement sheath on the basis of the multi-layer thick wall cylinder theory and Mohr–Coulomb failure criterion. The pressure and temperature loads were both considered in the model and the calculated stresses are all in good agreement with those obtained by FEA method. Meanwhile, the influences of the WHCP on cement sheath stress and integrity have been investigated with the proposed model, also a safety factor diagram of cement sheath at the weakest casing interface has been drawn by considering WHCP ranged from 10 to 70 MPa and wellbore temperature change ranged from −60 to 60 °C. Results show that the greater the WHCP, the lower the safety factor and the smaller the influence of wellbore temperature change on it. If the WHCP is less than 40 MPa, wellbore temperature effect cannot be ignored. For a specific gas well, the safety factor diagram can be used to determine the reasonable maximum allowable WHCP, which is of great guiding significance for protecting the cement sheath integrity and improving the WHCP management level in HTHP gas well.

Modelling the prestress transfer in pre-tensioned concrete elements

Three models were developed to simulate the transfer of prestress force from steel to concrete in pre-tensioned concrete elements. The first is an analytical model based on the thick-walled cylinder theory and considers linear material properties for both steel and concrete. The second is an axi-symmetric finite element (FE) model with linear material properties; it is used to verify the analytical model. The third model is a three dimensional nonlinear FE model. This model considers the post-cracking behaviour of concrete as well as concrete shrinkage and the time of prestress releasing. A new expression from the analytical model is developed to estimate the transmission length as well as the stress distribution along the tendon. The paper also presents a parametric study to illustrate the impact of diameter of prestressing steel, concrete cover, concrete strength, initial prestress, section size, surface roughness of prestressing steel, time of prestress release, and the member length on the transfer of stress in pre-tensioned concrete elements.

Fabrication of Faucet Using Hydroforming and Bending Processing

This research aims at the development of faucet using the techniques of hydroforming and bending. In this study, a tube made from stainless steel SUS 304 is used. Finite element model, including tube, dies and punches, are established using a commercial code LS-DYNA. Tensile test is used to obtain the material properties especially in true stress-strain curve. Piecewise linear plasticity model is used to simulate the plastic deformation of material during the forming process. The initial internal pressure is designed by using the theory of thick-walled cylinder subjecting to internal pressure only. Simulation is first used to find the optimal loading conditions for hydroforming and bending forming. Experiment is then performed to fabricate the prototype of faucets using the simulated loading parameters. The results show that good correlation of the distributed thickness and profile dimension between simulation and experiment are obtained.