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Due to integrated stochastic wind and wave loads, the supporting platform of a Floating Offshore Wind Turbine (FOWT) has to bear six Degrees of Freedom (DOF) motion, which makes the random cyclic loads acting on the structural components, for instance the tower base, more complicated than those on bottom-fixed or land-based wind turbines. These cyclic loads may cause unexpected fatigue damages on a FOWT. This paper presents a study on short-term fatigue damage at the tower base of a 5 MW FOWT with a spar-type platform. Fully coupled time-domain simulations code FAST is used and realistic environment conditions are considered to obtain the loads and structural stresses at the tower base. Then the cumulative fatigue damage is calculated based on rainflow counting method and Miner's rule. Moreover, the effects of the simulation length, the wind-wave misalignment, the wind-only condition and the wave-only condition on the fatigue damage are investigated. It is found that the wind and wave induced loads affect the tower base's axial stress separately and in a decoupled way, and the wave-induced fatigue damage is greater than that induced by the wind loads. Under the environment conditions with rated wind speed, the tower base experiences the highest fatigue damage when the joint probability of the wind and wave is included in the calculation. Moreover, it is also found that 1 h simulation length is sufficient to give an appropriate fatigue damage estimated life for FOWT.

Summary: The accuracy of multiscale modeling approaches for the analysis of heterogeneous materials hinges on the representativeness of the micromodel. One of the issues that affects this representativeness is the application of appropriate boundary conditions. Periodic boundary conditions are the most common choice. However, when localization takes place, periodic boundary conditions tend to overconstrain the microscopic problem. Weakly periodic boundary conditions have been proposed to overcome this effect. In this study, the effectiveness of weakly periodic boundary conditions in restoring transverse isotropy of representative volume elements (RVE) for a fiber‐reinforced composite with elastoplastic matrix is investigated. The formulation of weakly periodic boundary conditions is extended to allow for force‐controlled simulations where a uniaxial stress can be applied. A series of simulations is performed where the orientation of applied stress is gradually varied and the influence of this orientation on the averaged response is examined. An original method is presented to test the correlation between the ultimate principal stress and average localization angle of shear bands within an RVE. It is concluded that weakly periodic boundary conditions alleviate anisotropy in the RVE response but do not remove it. [ABSTRACT FROM AUTHOR]

Buried gas pipelines are vital assets of natural gas transportation system for every country. Therefore, investigation of their potential failure's roots is prominent. There are different causes for their failure among which imposed loads are the majority. In this study, considering soil as an elastoplastic material and deriving its constitution equation, a steel gas pipeline was modeled in its critical cross section where it passes under a road. Studying the behavior of the axial stress as maximum stress component and pipeline displacement under live and dead loads, a safe depth of 2 m was found so as to decrease and increase failure probability and safety factors, respectively. This height not only negates live loads, it alleviates the effect of dead loads. [ABSTRACT FROM AUTHOR]

The axial stress of high strength bolts for bridges affects the service life directly, it is necessary to measure it regularly. Based on the theory of acoustic elasticity and combination of longitudinal and shear waves, a new theoretical analysis method is proposed. The stressed and non-stressed areas of bolt are separated, and the derived formula only use the flight time and difference of acoustoelastic coefficients to get axial stress. Further, the preload experiments with high strength bolts of grade 8.8S and 10.9S is designed, the experimental results show that the proposed method is applicable to the axial stress of the bridge bolts with any specifications, material and different screwing depth used in this paper, the effect of elastic deformation on the flight time is eliminated, and the measuring error is within 5%. [ABSTRACT FROM AUTHOR]

In order to reduce the effect of delayed fracture of high-strength bolts on train operation and structural safety, a non-destructive testing method for axial force of high-strength bolts in railway steel bridges is studied to identify and replace over-twisted bolts in time, so as to reduce the probability of delayed fracture caused by external factors. Based on the acoustic-elastic effect theory, considering the uneven internal stress distribution of bolts in service, in this paper, the bolt force area is differentiated into three regions: the nut, the screw and the thread; the author calculates the ultrasonic flight-time in different bolt stress areas and revises the impact of bolt elastic deformation and temperature by external force on sound speed and puts forward a more precise measurement method of axial force of bolt in service. According to the results of the test, the relative error between the ultrasonic measurement result and the displayed value of pressure sensor is less than 10%. [ABSTRACT FROM AUTHOR]

Superior structural, physical, and electronic properties make ferroelectric nanocrystals essential in enabling a range of next‐generation devices. Ferroelectric responses are determined by crystal structure and domain morphology. The ability to reversibly displace, create, and annihilate elastic domains is critical to device applications. Although electric‐field control has been demonstrated for ferroelectric 180° surface domain walls and vortices, similar control of ferroelastic domains and domain boundaries within individual nanocrystals remains challenging. Using controlled external compressive and tensile axial stress, deterministic and reversible control of highly mobile ferroelastic domains and axial polarization in three dimensions is demonstrated. While many studies exist on ferroelastic domains in thin films and bulk, little is known about ferroelastic interactions at the single nanoparticle level, especially involving domain boundaries. Through combining Bragg coherent X‐ray diffractive imaging and Landau theory, strain gradients in individual BaTiO3 nanocrystals are shown to stabilize needle‐like ferroelastic twin domains. These domains are highly labile under applied axial stress, producing a locally enhanced electric polarization mediated by a ferroelectric phase transition. The efficacy of Bragg coherent X‐ray diffractive imaging in studying in operando domains in three dimensions is demonstrated, while synergy with theory provides a paradigm for domain boundary engineering and potential for nanoscale functional devices. [ABSTRACT FROM AUTHOR]

Bolts are important fasteners indispensable in the manufacturing field for their advantages, which include convenient assembly and disassembly, easy maintenance, refastenability to prevent looseness, and the avoidance of a phase change in the connected material composition. The precise control of the tightening force in bolts is closely related to the safety and reliability of the connected equipment or structure. Although there are many methods for estimating the tightening force applied to a bolt during assembly, poor accuracy in controlling the preload during the tightening process and a lack of monitoring to determine the residual axial force in service remain issues in evaluating the safety of bolted assemblies. As a nondestructive testing technology, ultrasonic measurement can be applied to successfully address these issues. In order to help researchers understand the theoretical basis and technological development in this field and to equip them to conduct further in-depth research, in this review, the basic knowledge describing the state of stress and deformation of bolts, as well as conventional testing methods are summarized and analyzed. Then, through a review of recent research of the ultrasonic measurement of the axial stress in bolts, the influence of the effective stressed length and temperature are analyzed and proposed methods of calibration and compensation are reviewed. In order to avoid coupling errors caused by traditional piezoelectric transducers, two newly proposed ultrasonic coupling technologies, the electromagnetic acoustic transducer (EMAT) and the permanent mounted transducer system (PMTS), are reviewed. Finally, the new direction of research of the detection of residual axial stress in in-service bolts that have been assembled to yield is discussed. [ABSTRACT FROM AUTHOR]

Temperature and stretching are important factors in the high-temperature treatment of carbon fiber. The axial stress during carbon-fiber high-temperature treatment affects its ability to stretch. The high-temperature axial stress evolution mechanism of polyacrylonitrile-based carbon fiber was studied through in situ tension tests, Raman spectroscopy, X-ray diffractometry, elemental analysis, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, thermal expansion coefficient tests, and density methods. The high-temperature axial stress evolution of polyacrylonitrile-based carbon fiber involved three stages: rapid increase, rapid decrease, and relaxation. The highest stress and relaxation temperatures of the polyacrylonitrile-based carbon fiber were 1600°C and 1950°C, respectively. The main factors that affected the fiber axial stress included carbon-structure rearrangement and the effect of thermal expansion and cold shrinkage on fiber length. During the first stage (T < 1600°C), carbon-structure rearrangement after nitrogen atom removal increased the fiber axial stress. In the second stage (1600 ≤ T ≤ 1950°C), the difference in the thermal expansion of fibers that entered the graphite furnace and the cold shrinkage of fibers that exited the graphite furnace increased gradually, which resulted in a decrease in fiber axial stress by up to 1950°C, where the fiber relaxed and the third stage (T > 1950°C) began. The difference between expansion and shrinkage increased significantly, which increased fiber relaxation. Carbon fibers with fewer nitrogen atoms and more regular structures had a lower axial stress during high-temperature treatment, but the trend and characteristic temperature remained unchanged. The corresponding fiber high-temperature maximum stretching ratio and axial stress showed opposite trends below 1950°C. The ability to stretch the carbon fiber increased above 1950°C, which differed from the axial stress relaxation. [ABSTRACT FROM AUTHOR]

Copyright of Mechanics & Advanced Technologies is the property of National Technical University of Ukraine KPI and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Strain-softening analyses were performed around a circular bore in a Mohr–Coulomb rock mass subjected to a hydrostatic stress field in cross section and out-of-plane stress along the axis of the bore. Numerical procedures that simplify the strain-softening process in a step manner were employed, and on the basis of the theoretical solutions of the elastic–brittle–plastic (EBP) medium, the strain-softening results of the displacements, stresses and the plastic zones around the circular bore were obtained. The numerical solution was validated based on the fact that the strain-softening process became EBP when the softening slope was very steep and elastic-perfectly plastic (EP) when the softening slope was near zero. The results illustrated that the stresses and displacements in the rock mass surrounding the bore were affected by axial stress and that a proper consideration of out-of-plane stress was necessary. Moreover, the presented results can be used for the verification of numerical codes.

The paper discusses developed of theoretical model of deformation of the fibers, depending on the values of axial force and the twist angle of the yarn. To describe the development of plastic fibers deformation zone it is proposed to use the Prandtl scheme, according to which the connection between the fiber strain and axial stress is represented by two straight lines (bilinear diagram). The condition of axial strain is found when all fibers in the yarn are in a state of plastic deformation. In the absence of hardening the tension in the plastic zone for the twist angle between some values may decrease up to 1.5–3 times. Thus, with the presence in the yarn fibers deformable by elastically plastic according Prandtl law scheme, the yarn may form a core layer of fibers with irreversible deformations

Waste tyre rubber has become an environmental and health concern that needs to be sustainably managed to avoid fire hazards and save natural resources. This research work aims to study the structural behavior of glass fiber reinforced polymer (glass-FRP) reinforced rubberized concrete (GRC) compressive elements under monotonic axial compression loads. Nine GRC circular compressive elements with different axial and crosswise reinforcement ratios were fabricated. All the elements were 300 mm in diameter and 1200 mm in height. A 3D nonlinear finite element equation (FEM) was suggested for the GRC compressive elements using a commercial package ABAQUS. A parametric study has been done to examine the effect of various parameters of GRC elements. The test outcomes revealed that the ductility of GRC elements ameliorated with the lessening in the spaces of glass-FRP ties. The addition of rubberized concrete improved the ductility of GRC elements. The damage to GRC elements occurred due to the vertical cracking along the height of the elements. The estimates of FEM were in close agreement with the test outcomes. The suggested empirical equation depending on the 600 test elements, which considered the lateral confinement effect of FRP ties, presented higher accuracy than previous equations., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author(s).)

Correlating the microscopic structural characteristics with the macroscopic electrochemical performance in electrode materials is critical for developing excellent-performance lithium-ion batteries, which however remains largely unexplored. Here, we show that the Zn 2 SnO 4 (ZTO) nanowires (NWs) with smaller diameters ( d < 5 nm) exhibit slower capacity fade rate and better cycling stability, as compared with the NWs with larger diameters ranging from tens to hundreds of nanometers. By applying in situ transmission electron microscopy (TEM), we discover a strong correlation of cracking behavior with the NW diameter. Upon the first lithiation, there exists a critical diameter of ∼80 nm, below which the NWs neither crack nor fracture, and above which the cracks could easily nucleate and propagate along the specific planes, resulting in the deteriorated cycling stability in larger sized electrodes. Further theoretical calculations based on the finite element model and the climbing image nudged elastic band method faithfully predict the size-dependent cracking behaviors, which may result from the synergistic effect of axial stress evolution as well as preferential Li-ion migration directions during the first lithiation. This work provides a real-time tracking of the tempo-spatial structural evolution of a single ZTO NW, which facilitates a fundamental understanding of how the sample size affects the electrochemical behavior and thus offers a reference for future battery design and application strategy.

The present paper is concerned with the failure analysis of the wall loss defect in pipelines reinforced with a polymer-based composite repair system. The main goal is to propose a methodology that accounts for the pipe extremities (axial stress) in an analysis to predict an accurate failure pressure. The proposed methodology defines a simple expression for a real test specimen condition (closed-cap cylinder), which allows to estimate the failure pressure using the elastic properties of the materials and test specimen geometry. Hydrostatic tests performed in different laboratories are used to validate the proposed methodology. The results show a good agreement between the model prediction and the experimental failure pressure results in all cases. However, a careful selection of the remaining strength factor is needed, as it impacts on the accuracy and conservative level of the failure pressure. In addition to the axial stress, there is a possibility to refine the theoretical prediction of the failure pressure value by accounting for the plastic deformation far from the defect region as well as the radial stress in the failure analysis. [ABSTRACT FROM AUTHOR]

The present research deals with the study of transversely isotropic thermoelastic beam in the context of Green-Naghdi (GN) theory of thermoelasticity of Type-II and Type-III. The mathematical model is prepared for the thin beam in a closed form with the application of Euler Bernoulli beam theory. The Laplace Transform technique has been used to find the expressions for displacement component, lateral thermal moment, deflection and axial stress in transformed domain. The general algorithm of the inverse Laplace Transform is developed to compute the results numerically in physical domain. The effect of two theories of thermoelasticity Green- Naghdi-II and Green-Naghdi-III has been depicted on the various quantities. Some particular cases have also been deduced. [ABSTRACT FROM AUTHOR]

Abstract—In wire drawing, instability of the deformation parameters produces variable axial stress. The contact friction changes within an extremely short period and depends on many factors, such as the uniformity of the workpiece's physicomechanical properties over its length; lubricant quality; stability of the tensile force on entering the deformation zone; and the cooling rate for the drawplates, tension drums, disks, and guide rollers. To assess the influence of the frictional coefficient on the stability of the drawing force (stress), the first derivative of the drawing stress with respect to the frictional coefficient is considered. Specifically, its relative value is considered: in other words, the ratio of the derivative and the initial yield point of the wire is monitored. That permits comparison of the derivatives with different initial yield points of the wire. The derivative is calculated by means of an equation for the axial stress in which the following factors are taken into account: the countertension; the change in yield point along the length of the plastic-deformation zone; and the decrease in radial stress in the calibration band as a function of the increase in axial stress in the drawplate's working cone. The relative value of the first derivative is expressed in terms of the countertensile stress and the frictional coefficient, with different models of strengthening and different deformation parameters. The derivative declines with increase in countertensile stress. Consequently drawing with countertension is expedient in order to stabilize the drawing force and decrease the fatigue wear of the drawplate's working surface. The behavior of the derivative is plotted on the basis of the formula obtained. Drawing is considered in the case where the frictional coefficient is constant in the calibration band and variable in the drawplate's working cone. For that process, the relative value of the first derivative of the drawing stress with respect to the frictional coefficient is determined for the axial stress. The calibration band stabilizes the drawing stress (force) if the frictional coefficient is constant in that band. The instability of the drawing stress with deviation in the frictional coefficient depends on the other deformation parameters. For example, the derivative increases with decrease in the drawing angle. The steady influence of the deformation parameters on the stability of the drawing stress with variation in the frictional coefficient is consistent with Brovman's results and also with the results of calculating the axial stress with the constant and fluctuating frictional coefficient. Greater stability of the drawing stress improves the wire quality and the working life of the components in the drawing system—for example, on account of decrease in the fatigue wear of the working surfaces of drawplates, drums, guide rollers, and adjustment rollers. The stress state in the zone where the wire is deformed may be improved by drawing with countertension and using special drawplate designs. [ABSTRACT FROM AUTHOR]

The permeability characteristics of gas‐containing coal under different radial stress, different axial stress, and gas pressure were studied by orthogonal experiments, using a self‐developed three‐axis servo fluid infiltration system with a gas‐solid coupling of gas‐containing coal, on the basis of a single‐factor influence on the permeability of gas‐containing coal. By considering the effective stress, three kinds of relationships between permeability and radial stress, permeability and axial stress, as well as permeability and gas pressure were established. The results show that radial stress, axial stress, and gas pressure have a great influence on the permeability characteristics of gas‐containing coal: (a) The influence of radial stress on gas permeability is significant, whereas the influence of axial stress is negligible. The degree of influence of radial stress, gas pressure, and axial stress on the permeability decreases in turn; (b) The permeability decreases following a power function with the increase of the radial stress; (c) The permeability gradually increases with the increase of axial stress. With the increase of axial stress, the permeability increases following a power function; (d) The increase in gas pressure will reduce the effective stress on the coal, and the number of pores and cracks inside the coal body will decrease. This will increase the effective seepage flow and gas flow rate of the gas and eventually lead to the increase of coal permeability. There is a quadratic function relationship between the permeability and gas pressure. The influence of radial stress on gas permeability of gas‐containing coal is significant, whereas the influence of axial stress is negligible. The permeability of coal sample increases with the radial stress and it decreases following a power function. With the increase of axial stress, the permeability of coal samples increases following a power function. There is a quadratic function relationship between the permeability of gas‐containing coal and gas pressure. [ABSTRACT FROM AUTHOR]

This study reports the effect of the radial, axial, and hoop electromagnetic stresses caused by the large current density and the self-field (screening current-induced magnetic field) on REBCO superconducting coil stacks. A two-dimensional numerical model is used to study the stress distribution of a superconducting coil stack under current. The electromagnetically homogenized coil stack is assumed to be composed of four equally spaced coils with rectangular cross-section. Initially, the verification of the model is done by comparing the analytical calculations (which were in good agreement) of stress distributions of a superconducting slab exposed to a variable magnetic field and in a superconducting strip exposed to a variable current. Then, the two-dimensional model is used to obtain the components of stress that occurred in the coil stack under sinusoidal varying currents. The stress component distributions are calculated at different time intervals, currents, frequencies, and coil distances. Besides, one-dimensional stress distributions are plotted to show how the stress distributions change while the current increases. The upper and lower coils have much higher magnetic stress than the inner coils. Results obtained from the one-dimensional stress distribution calculations show that the stress occurring in the radial direction is lower than the stress in the z -direction in the coil stack. The stress distributions do not show a significant change as the frequency of the applied current changes. The stresses in both the radial and axial directions decrease as the distance between coils increases. All results are presented, and the possible reasons are explained. [ABSTRACT FROM AUTHOR]

The paper presents new and original results of investigation on magnetoelastic effect in Ni-Zn ferrite formed into ring core and subjected to the axial stress up to 20 MPa. The core was magnetized with relatively low magnetizing field, corresponding to the so-called Rayleigh region. The obtained results indicate, that there is a significant correlation between applied stress and magnetic properties of the material and the Ni-Zn ferrite can be utilized in development of magnetoelastic sensor of force and stress. [ABSTRACT FROM AUTHOR]

Abstract The reliable prediction of excavation responses for squeezing rock remains a challenging issue in rock engineering. This paper presents a numerical procedure for a strain-softening rock mass around highly deformed circular opening based on the finite strain theory, so the overall elasto-plastic analysis is a Lagrangian method which focuses on the motion of each material point and is well suited for the problems involving large deformation. The influence of axial in-situ stress is considered by introducing the initial axial stress into the elastic constitutive equations, and the axial plastic flow is realized by redefining the plastic internal variable and considering different stress distributions in the plastic zone. Thus, the numerical procedure enables prediction of the rock deformation and squeezing potential in a more rational and rigorous manner. The capability of the method for estimating the small strain and squeezing deformation is verified by being compared with the existing analytical results and the field measuring data. Negligence of the axial in-situ stress or the axial plastic flow underestimates the rock deformation, and the induced deviation essentially depends on the post-peak constitutive relation and the rock heterogeneity after rock yields. The higher level of the material homogeneity in the plastic zone, the lower effects of the axial in-situ stress on the rock responses. The stress distribution and strain-softening behavior of surrounding rock can be significantly affected by the axial in-situ stress and the critical plastic internal variable η *. Tunnel instability is independent of large deformation for the high η * but is closely associated with the squeezing problem when η * is small. As η * decreases, both of the plastic radius and wall convergence increase initially and remain constant afterwards. Lastly, the paper investigates the rock responses and ground-support interaction when the small strain theory is applied on the squeezing rock. [ABSTRACT FROM AUTHOR]

Taking the Yuheng mine in Northern Shaanxi as an example，aeolian-sand incipience experiment and water-sand inrush experiment were expansion by high-velocity seepage and entire visual equipment of water-sand two-phase flow. The experiment results indicated that， the loss of fine particles is the precondition of water-sand inrush and creates expansive space for the coarse particle migration. The process of water-sand inrush is a physical process， when the aeolian-sand size between 0.3~0.6mm， the energy transmits mainly in the form of particles collision.But it is different for the aeolian-sand size between 0.15~0.3mm， because the friction and squeeze are in the dominant role， that will lose less energy compared with collision. So the variation mass of aeolian-sand inrush is inversely proportional to the particle size. The critical velocity of aeolian-sand inrush is becoming higher with the increasing of axial stress. When the aeolian-sand begins to move， the seepage state is linear laminar flow and the critical velocity is 0.03~0.4cm/s for the aeolian-sand size d<0.6mm.The mass of sand inrush is proportional to the hydraulic gradient in unit time. It can be deduced from this result that water pressure of aquifer is the key factor， which greatly decisive the disaster degree of water-sand inrush. [ABSTRACT FROM AUTHOR]

In this paper, two 1:2 scaled substructure models for a typical 110 kV transmission tower were designed and fabricated. The scaled tower substructure models were tested subjected to the stretching movements of horizontal ground surface under different wind load conditions. The wind speeds were assumed to be 15 m/s and 30 m/s, respectively in this study. The deformations of the tested tower models and the stresses and strains within the different members of the tower were fully measured. A large amount of the comprehensive test data was generated. Also a FE model using ANSYS was developed and validated by the test data. The research indicated that wind load has a significant unfavourable influence on the resistance of the transmission tower subjected to the ground surface deformation. Also the research showed that it is possible to use the FE model for the analysis and design of power transmission towers under ground surface movements. [ABSTRACT FROM AUTHOR]

The interaction of surrounding rock with a support system in deep underground tunnels has attracted extensive interest from researchers. However, the effect of high axial stress on tunnel stability has not been fully considered. In this study, compression tests with and without confining pressure were conducted on solid specimens and hollow cylinder specimens filled with aluminium, lead, and polymethyl methacrylate (PMMA) to investigate the strength, deformation and failure characteristics of circular roadways subjected to high axial stress. The influence of the three-dimensional stress on the surrounding rock supported with different stiffness was studied. The results indicate that the strength and peak strain of hollow cylinders filled with PMMA are higher than those of hollow cylinders filled with aluminium or lead, indicating that flexible retaining is beneficial for roadway stability. The results obtained in this paper can contribute to better understanding the support failure of a buried roadway subjected to high axial stress and thus to analyzing and evaluating roadway stability. [ABSTRACT FROM AUTHOR]

The phenomenon of core disking is commonly seen in deep drilling of highly stressed regions in the Earth’s crust. Given its close relationship with the in situ stress state, the presence and features of core disking can be used to interpret the stresses when traditional in situ stress measuring techniques are not available. The core disking process was simulated in this paper using the three-dimensional discrete element method software PFC3D (particle flow code). In particular, PFC3D is used to examine the evolution of fracture initiation, propagation and coalescence associated with core disking under various stress states. In this paper, four unresolved problems concerning core disking are investigated with a series of numerical simulations. These simulations also provide some verification of existing results by other researchers: (1) Core disking occurs when the maximum principal stress is about 6.5 times the tensile strength. (2) For most stress situations, core disking occurs from the outer surface, except for the thrust faulting stress regime, where the fractures were found to initiate from the inner part. (3) The anisotropy of the two horizontal principal stresses has an effect on the core disking morphology. (4) The thickness of core disk has a positive relationship with radial stress and a negative relationship with axial stresses. [ABSTRACT FROM AUTHOR]

Copyright of China Petroleum Machinery is the property of China Petroleum Machinery Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hole containing cylindrical specimens confined by thick steel drum were compressed in the axial direction to investigate the development of toroidal fractures and its impact factors under high axial stress. Results showed that toroidal fractures develop from the intersection of shear-slip lines and propagate sub-parallelly away from tunnel boundary mainly in tension. For the close twin tunnel with overlapped concentrated stress in between， the toroidal fractures enclose the twin tunnel and take on an elliptical shape; for distant twin tunnel with little overlapped concentrated stress in between， the toroidal fractures enclose each single tunnel respectively. The shape of toroidal fractures and the distance between the fractures are affected by tunnel curvature and tunnel span as well as the heterogeneity of the rock mass. [ABSTRACT FROM AUTHOR]

An electromagnetic method for determining axial stress in ferromagnetic bars is proposed. In this method, the tested bar is under the static magnetization provided by permanent magnets. The tested bar do not have to be magnetized up to the technical saturation because reciprocal amplitude of initial differential susceptibility (RAIDS) is adopted as the feature parameter. RAIDS is calculated from the radial magnetic flux density Br Lo = 0.5 at the Lift-off Lo =  0.5 mm, radial magnetic flux density Br Lo = 1 at the Lift-off Lo =  1 mm and axial magnetic flux density Bz Lo = 1 at the Lift-off Lo =  1 mm from the surface of the tested bar. Firstly, the theoretical derivation of RAIDS is carried out according to Gauss’ law for magnetism, Ampere’s Law and the Rayleigh relation in Rayleigh region. Secondly, the experimental system is set up for a 2-meter length and 20 mm diameter steel bar. Thirdly, an experiment is carried out on the steel bar to analyze the relationship between the obtained RAIDS and the axial stress. Experimental results show that the obtained RAIDS decreases almost linearly with the increment of the axial stress inside the steel bar in the initial elastic region. The proposed method has the potential to determine tensile axial stress in the slender cylindrical ferromagnetic bar. [ABSTRACT FROM AUTHOR]

This paper made a research about the change rule of elastic wave velocity with stress applied on rock from theoretical and experimental aspect. Firstly, a mathematical model of P-wave velocity and confining pressure of rock was set up from the point of acoustoelastic character. Effect of axial stress on P-wave velocity in granite and sandstone during uniaxial compression process was studied experimentally by using GAW-2000 rock mechanical testing system and RSM-SY5 ultrasonic wave testing system, and the relation curves of axial stress with P-wave velocity were obtained. Based on test data, acoustoelastic theoretical formulas of granite and sandstone were established and the best empirical formulas were fitted by using regression method. Meanwhile, a comparative analysis of the empirical and theoretical calculated values was carried out. Finally, the reliability of applying acoustoelastic theoretical formula in hard rock range was further verified based on the experimental data of granitic gneiss. The results show that the P-wave velocity experiences a rapid increase, gentle increase and then a sharp fall during the uniaxial compression process. The B-value in acoustoelastic theoretical formula (proportion coefficient determined by elastic modulus and third-order elastic constant) decreases exponentially with axial stress. The acoustoelastic theoretical formula can effectively reflect the relationship between rock acoustic velocity and stress within the allowable error, which can be the theoretical foundation of acoustoelastic geo-stress measurement of subsurface rock mass. [ABSTRACT FROM AUTHOR]

Hardinge Bridge is the first railway bridge in Bangladesh which is made up of prefabricated trusses. As an old steel bridge, fatigue crack and rust can affect steadily on truss members. Steel truss bridges have the determinate system and which have not any redundancy, can progressively collapse over the entire span, if a single primary member or gusset plate connection of the main trusses is damage. Beside this, as it is a railway bridge, it is very important to know the dynamic behavior of this bridge. A train at high speed can cause large vibration of the bridge super-structure and this large vibration might be affect on truss members. This paper describes the redundancy analysis and the free vibration analysis of Hardinge bridge truss after fracture of its different primary members. In this paper redundancy is described with respect to change in axial stresses before and after fracture of different members. From free vibration analysis, vibrational behavior of the bridge structure before and after fracture of different members can be observed. From these analyses it is observed that increase of axial stress of the adjacent members and natural frequencies of corresponding mode shapes varied with different damage scenario. Fracture of diagonal member drastically increased the axial stress of one of its adjacent member and the lowest natural frequency was obtained. Therefore, the fractured diagonal condition is the most critical condition. [ABSTRACT FROM AUTHOR]