Wire Stress Research Articles

A finite element analysis of sawing stress in fixed-abrasive wire saw slicing KDP crystal

Potassium dihydrogen phosphate (KDP) crystal is the preferred nonlinear optical crystal used in pockels cell and frequency multiplier. Slicing machining is the first process for KDP crystal, which has an important effect on the yield rate. However, KDP crystal is easy to crack when sliced due to the maximum tensile stress. This paper presents the finite element analysis of sawing stress in fixed-abrasive wire saw slicing KDP crystal. The finite element model of wire sawing KDP crystal is found, and the sawing forces are analyzed and loaded to the cutting kerf that are simplified as the normal sawing pressure p contrary to the workpiece feed direction and the tangential sawing pressure q along the wire moving direction, based on the analysis of fixed-abrasive wire saw cutting mechanism. The dynamic distribution and variation rule of the sawing stress and the coupling of sawing stress with crystal initial internal stress have been analyzed when slicing the (001) crystal plane optical device, and the critical initial internal stress of the KDP crystal to avoid cracking in wire saw cutting is discussed. Numerical simulation results show that the sawing stress for cutting KDP crystal without initial internal stress is a low-stress machining way, but a larger tensile stress produces due to the initial stress gathering in the kerf coupled with the low sawing stress. A greater crystal initial internal stress can lead to the more intense concentration of sawing stress; it suggests that the initial internal stress inside the sawed KDP crystal should be less than 2.294 MPa. The research results help to further understand the sawing stress field distribution and change in the process of slicing KDP crystal.

Dynamic torsional characteristics of mine hoisting rope and its internal spiral components

Dynamic torsional characteristics of mine hoisting rope and its internal spiral components were investigated in the present study. Theoretical models of tensions of rope segments at distinct locations were presented to obtain dynamic rope tensions. Theoretical models of torque, unit torsion angle, torsion angle, twisting parameters, and torsional stress were introduced to investigate dynamic torsional characteristics of hoisting rope and its internal spiral components under tension. Rope tests were conducted in order to validate dynamic torsional properties of the rope under fluctuation tensions. The results show three-stage fluctuating trends of rope tension and torque. An increase of hoisting time induces a decreased torsion angle of the rope, fluctuating upward trends of unit torsion angles of the rope, spiral strands and steel wires, respectively, fluctuating increases in lay angles of the spiral strand and steel wires, respectively, and the fluctuating decreased lay length of the spiral strand. An increase of the distance between rope segment and friction pulley tangent causes a decrease at first and then an increase in the unit torsion angle in cases of the rope, spiral strands and steel wires, an increase at first and then a decrease in the rope torsion angle, increased lay angle and decreased lay length of the spiral strand, a decrease at first and then an increase in the torsional stress of steel wire in every layer of the spiral strand.

Weakest link concept for springs fatigue

ABSTRACTIn the present manuscript, a new approach is developed to account the stress gradient effect on fatigue life of springs. The new formula of crack growths per cycle is introduced. The expressions for spring length over the number of cycles are derived in terms of higher transcendental function. The closed-form solutions are used for the estimation of the fatigue life of heterogeneously stressed structural members. The probability distribution of the fatigue limit for heterogeneously stressed structural elements is evaluated. The proposed approach for the stress gradient sensitivity of fatigue life is based on the weakest link concept. The weakest link approach is applied to calculate the number of cycles to crack initiation of structural elements under different probability levels. The effect of stress ratio on elongation of crack is discussed. The developed theory is applied to helical springs under cyclic load. The fatigue sensitivity to stress concentration is addressed in application to springs. Effect of fluctuating stresses on fatigue life of springs is combined with the influence of heterogeneous stress distribution (stress gradient) over the cross-section of wire and time-varying stresses. These two factors lead to complicated evaluation for fatigue life of helical springs. The stress field is inhomogeneous over the cross-section of the wire of spring. The stress distribution is uniquely defined by ratio of the diameter of wire to the diameter of spring body. The calculated lifetimes are compared with the lifetimes obtained from experiments performed on helical springs subjected to cyclic load of constant amplitude.

Residual stress characteristics in a non-circular drawing sequence of pearlitic steel wire

In this paper, characteristics of residual stress in pearlitic steel wire drawn by a non-circular drawing (NCD) sequence with two processing routes, NCDA and NCDB, were experimentally and numerically investigated up to the 12th pass in comparison with conventional wire drawing (WD). For experimental investigation of the axial residual stress at the surface of the drawn wire, destructive (deflection) and non-destructive methods were employed. According to the experimental results, axial surface residual stress of the drawn wire by the NCD sequence was lower and more homogeneous compared to the conventional WD. Based on the elasto-plastic numerical simulation results from the surface to the center of the drawn wire using a commercial DEFORM-3D, an empirical relationship between residual stress and reduction of area was determined to predict the residual stress evolution in the multi-pass WD, NCDA, and NCDB, in that order. From the results of this investigation, it can be construed that the NCD sequence, especially the NCDB, might be helpful in improving the residual stress characteristics of pearlitic steel wire to improve its mechanical behavior and service life.

Metastable effects on martensitic transformation in SMAs

The transformation and retransformation paths realized at constant stress in wires of NiTi SMAs show a horizontal or “flat” behavior in the hysteretic cycle. After sinusoidal cycling at 0.01 Hz (i.e., training) with a maximal strain of 8 %, the thicker wires of NiTi SMAs, with a diameter of 2.46 mm, have the stress–strain cycles with one S-shaped behavior. A “similar” change appears by varying the grain sizes in the samples, i.e., from 80 to 20 nm. Furthermore, the local measurements of temperature suggest that cycling induces changes in the transformation mechanisms associated with the evolution from horizontal to S shape. For instance, the associated energy evolves from localized transformation to homogeneous heat production in S-shaped cycles. Thermodynamic analysis establishes a link between heat capacity and the slopes of the coexistence curve in f–x or in σ–e via the (∂e/∂σ)coex. The flat cycles were coherent with the classical latent heat, i.e., dissipation at constant stress. In the S-shaped cycles, the heat during the phase change seems redistributed as heat capacity against progressive stress. Preliminary direct measurements are coherent with the evolution of the (∂e/∂σ)coex against strain.

A Steel Wire Stress Measuring Sensor Based on the Static Magnetization by Permanent Magnets.

A new stress measuring sensor is proposed to evaluate the axial stress in steel wires. Without using excitation and induction coils, the sensor mainly consists of a static magnetization unit made of permanent magnets and a magnetic field measurement unit containing Hall element arrays. Firstly, the principle is illustrated in detail. Under the excitation of the magnetization unit, a spatially varying magnetized region in the steel wire is utilized as the measurement region. Radial and axial magnetic flux densities at different lift-offs in this region are measured by the measurement unit to calculate the differential permeability curve and magnetization curve. Feature parameters extracted from the curves are used to evaluate the axial stress. Secondly, the special stress sensor for Φ5 and Φ7 steel wires is developed accordingly. At last, the performance of the sensor is tested experimentally. Experimental results show that the sensor can measure the magnetization curve accurately with the error in the range of ±6%. Furthermore, the obtained differential permeability at working points 1200 A/m and 10000 A/m change almost linearly with the stress in steel wires, the goodness of linear fits are all higher than 0.987. Thus, the proposed steel wire stress measuring sensor is feasible.

Layerwise numerical and experimental impact analysis of temperature-dependent transversely flexible composite plates with embedded SMA wires in thermal environments

In the present research, impact analysis of rectangular composite plates with embedded SMA wires is accomplished through including the following items for the first time: (1) the layerwise impact-induced temperature-rise (2) effects of the ambient/impact-induced temperature-rises on the material properties and the direct and converse phase transformations, (3) transverse flexibility of the layers, (4) a refined layerwise description of the displacement field, employing virtual sub-layers, (5) a modified constitutive law for the SMA wires, (6) effects of stiffness of the lower layers on the stiffness of the contact region, (7) considering the shape memory effect in addition to the pseudo-elastic nature of the SMA wire, and (8) partially verifying the results based on experimental results extracted by the authors. The coupled thermoelasticity and impact governing equations of the indenter-plate system are determined by means of a combined Galerkin-Energy finite element approach and solved by means of an updating-based Newton–Raphson procedure. Present results show a good concordance with the experimental results. Results reveal that the impact-induced temperature-rise and temperature-dependency of the material properties increase the start and finish stresses of the direct and converse phase transformation mechanisms and lead to larger hysteresis loops, strains, and stresses in the SMA wire.

Angular change and secondary stress in main cables of suspension bridges

Three basic cable equations are proposed for evaluating the deflected shape of the main cables of suspension bridges subject to angular changes near the saddles of the main towers as well as the cable bands. The secondary stress on the tensioned parallel wires can be estimated via the combined use of the three basic cable equations that take into account the free and/or friction slip between wires as a function of the lateral restraints by cable bands and wrapping wires. A series of laboratory loading tests were carried out for a parallel wire strand to validate the proposed procedure. The proposed method was also applied to the Yi Sun-sin Bridge to demonstrate the level of secondary stress in parallel wires and to identify the factors that have an impact on the secondary stress in the completed stage as well as during the construction phase. The residual tension of the wrapping wire, which impacts the frictional resistance between wires of the main cable, was measured from field tests. The evaluated secondary stress was found to exceed 10% of the tensile strength of the wires. The findings reported herein also confirm that the distance between the tower saddle and the first cable band is a critical factor for secondary stress. Based on the experimental validation and application to an actual bridge, the proposed approach, despite being based on simplified formulations, is demonstrated to be useful in predicting the secondary stress that develops in parallel wire cables.

Finite-Element Analysis of Transverse Compressive and Thermal Loads on Nb3Sn Wires With Voids

High-field superconducting magnets play a very important role in many large-scale physics experiments, particularly particle colliders and fusion confinement devices such as Large Hadron Collider (LHC) and International Thermonuclear Experimental Reactor (ITER). The two most common superconductors used in these applications are NbTi and Nb3Sn. Nb3Sn wires are favored because of their significantly higher $J_{c}$ (critical current density) for higher field applications. The main disadvantage of Nb3Sn is that the superconducting performance of the wire is highly strain sensitive and it is very brittle. This strain sensitivity is strongly influenced by two factors: plasticity and cracked filaments. Cracks are induced by large stress concentrators that can be traced to the presence of voids in the wire. We develop detailed 2-D and 3-D finite-element models containing wire filaments and different possible distributions of voids in a bronze-route Nb3Sn wire. We apply compressive transverse loads for various cases of void distributions to simulate the stress and strain response of a Nb3Sn wire under the Lorentz force. This paper improves our understanding of the effect voids have on the Nb3Sn wire's mechanical properties, and in so, the connection between the distribution of voids and performance degradation such as the correlation between irreversible strain limit and the void-induced local stress concentrations.

Mechanical Properties and Strain-Induced Filament Degradation of Ex Situ and In Situ MgB2Wires

We have compared the mechanical properties and the degradation of the critical current after uniaxial tensile loading at room temperature (RT) and at 77 K of ex situ and in situ MgB2 wires. The strain that the wires can withstand without degradation is at 77 K substantially higher than at RT. In order to explain the mechanical behavior of the wires, the lattice distortions of the different wire constituents and their texture have been measured simultaneously with the composite wire stress and strain in a high-energy synchrotron beamline. The different MgB2 microstructure in both wire types is revealed in filament cross sections prepared by the focused-ion-beam technique and in fracture surfaces.

Torsion Failure Analysis of 0Cr17Ni7Al Precipitation Hardening Stainless Steel Wire

0Cr17Ni7Al is a precipitation hardening stainless steel, which combines the advantages of austenitic stainless steel and martensitic stainless steel. 0Cr17Ni7Al shows good corrosion resistance, excellent processability and high strength. This paper is mainly focused on the fracture morphology of 0Cr17Ni7Al wire during torsional deformation. Cracking mechanism and torsion failure reason is analyzed in detail. The results show that AlN inclusions are observed both in raw steel wire and fracture, the micro-cracks appear along the axial direction of the steel wire. The torsion strength is normally 2958MPa. but, the local stress of steel wire reaches up to5295MPa when a 0.4mm deep micro-crack locates on the surface of steel wire, and the local stress is obtained to 2953MPa around a 10μm AlN inclusion. Stress concentrating is caused by inclusions and micro-cracks, and the crack propagation lead to the torsion failure of steel wire when the local stress is beyond the torsion limit.

Development of an extended Kalman filter for the self-sensing application of a spring-biased shape memory alloy wire actuator

This report presents the development of an extended Kalman filter (EKF) to harness the self-sensing capability of a shape memory alloy (SMA) wire, actuating a linear spring. The stress and temperature of the SMA wire, constituting the state of the system, are estimated using the EKF, from the measured change in electrical resistance (ER) of the SMA. The estimated stress is used to compute the change in length of the spring, eliminating the need for a displacement sensor. The system model used in the EKF comprises the heat balance equation and the constitutive relation of the SMA wire coupled with the force–displacement behavior of a spring. Both explicit and implicit approaches are adopted to evaluate the system model at each time-update step of the EKF. Next, in the measurement-update step, estimated states are updated based on the measured electrical resistance. It has been observed that for the same time step, the implicit approach consumes less computational time than the explicit method. To verify the implementation, EKF estimated states of the system are compared with those of an established model for different inputs to the SMA wire. An experimental setup is developed to measure the actual spring displacement and ER of the SMA, for any time-varying voltage applied to it. The process noise covariance is decided using a heuristic approach, whereas the measurement noise covariance is obtained experimentally. Finally, the EKF is used to estimate the spring displacement for a given input and the corresponding experimentally obtained ER of the SMA. The qualitative agreement between the EKF estimated displacement with that obtained experimentally reveals the true potential of this approach to harness the self-sensing capability of the SMA.

ПРЕИМУЩЕСТВА АРМАТУРНОГО СТАЛЬНОГО КАНАТА С ТОЧЕЧНЫМ КАСАНИЕМ ПРОВОЛОК

An analytical study of complex stress-strain state of the steel twisted rope with point contact of wires is introduced. The rope under investigation is used as a prestressed reinforcement of concrete structures. Currently, the set of rules and regulations SP 52-102-2004 contains only two types of steel strands: K1400 and K1500, which are the ropes with line contact of wires. The length of the wires of outer layer in such ropes depends on the length of the wires of inner layer. And at the same time the wires of each new independent layer are longer than the wires of inner layer and, thus, the wires of outer layer are more deformable. Consequently, they are less loaded, since minimum stress occurs in the longest wires, and maximum stress occurs in the shortest wires because of the difference of deformation characteristics. The stress in the wires is always distributed unevenly. The length of the wires of outer layer does not depend on the length of the wires of inner layer in the ropes with point contact. That is, it is possible to choose the length of outer wires so that the difference of lengths (deformation characteristics) of wires of various layers will be minimal. In this regard, the difference of stress in wires of various layers will be minimal as well. Hence, the coefficient of the use of wires strength, which is the determining criterion for the optimization of prestressed steel strand structures, will increase

Application of Adaptive Minimum-variance Control Technique for Cyclic Production Machine

In this paper, we consider the control problem of cyclic production machine. There are many mechanical parts produced by cyclic production machine. For example, springs are usually made of long stock wire which is fed into cyclic forming machine. A spring forming machine can force wire into a coiled shape during the cyclic motion, but the length of the produced spring in each cycle is varying according to the internal stress of wire, mechanical uncertainty of the forming machine etc. To improve the accuracy of free length of spring produced by forming machine, we propose an adaptive minimum-variance control strategy for cyclic production system and successfully applied to commercial spring forming machine.

The Thermal Hysteresis of a Standard Platinum Resistance Thermometer

The ETS-25-type standard thermometers manufactured by a single company are investigated. It is shown that instability of the thermometers during calibration may be due to the occurrence of stresses in the platinum wire of the sensitive element, and not due to oxidation of the platinum.

Strain induced irreversible critical current degradation in highly dense Bi-2212 round wire

The strain induced critical current degradation of overpressure processed straight Bi-2212/Ag wires has been studied at 77 K in self-field. For the first time superconducting properties, lattice distortions, composite wire stress and strain have been measured simultaneously in a high energy synchrotron beamline. A permanent Ic degradation of 5% occurs when the wire strain exceeds 0.60%. At a wire strain of about 0.65% a drastic n-value and Ic reduction occur, and the composite stress and the Bi-2212 lattice parameter reach a plateau, indicating Bi-2212 filament fracturing. The x-ray diffraction measurements show that Bi-2212 exhibits linear elastic behaviour up to the irreversible strain limit.

Estimation of the Level of Residual Stress in Wires with a Magnetic Method

AbstractResidual stress present in wires after drawing process affects their magnetic properties. The paper presents a concept to estimate the level of residual stress on the basis of measurements of hysteresis loops. In order to describe the effect qualitatively the Jiles-Atherton-Sablik description is adapted. On the basis of variations in hysteresis loop shapes the average values of residual stress in wires for different single draft values are determined. It was found that the estimated average values by magnetic stresses are comparable with the results of numerical modeling and experimental studies.

Effect of surface roughness on elastic limit of silicon nanowires

Effect of surface roughness on deformation mechanism and yielding strength of silicon nanowires under tension are investigated by using molecular dynamics simulation. By varying opening angle and depth of surface notches, different periodic V-type notches models are created on {100} or {110} side surfaces to simulate different types of surface roughness. The results show that the presence of rough surface can significantly reduce the initial elastic limit of silicon nanowires. The yield stress of rough wires with a certain cross-sectional size depends on the surface notch depth and is independent of the opening angle. We also investigated the size effect on this notch depth dependence, and observed that the yield stress becomes less sensitive when the wire height increases. In addition, the influence of surface orientation on the surface roughness effect was discussed.

Non-Linear Thermal Stability Analysis of SMA Wire-Embedded Hybrid Laminated Composite Timoshenko Beams on Non-Linear Hardening Elastic Foundation

In the present study, non-linear thermal post-buckling analysis of hybrid laminated composite Timoshenko beams embedded with the shape memory alloy (SMA) wires resting on a non-linear hardening elastic foundation were studied. Mechanical properties of composite media are considered temperature-dependent. The theory of Timoshenko beams and von Kármán's strain-displacement relations are applied simultaneously in virtual work principles to derive the system of non-linear equilibrium equations. Various types of boundary conditions such as clamped, simply supported, and rolled edges were studied for edge supports. Generalized Differential Quadrature Method (GDQM) was utilized to discrete the equilibrium equations in space domain. Different types of lay-ups, such as symmetric and asymmetric, were considered. Post-buckling paths are depicted for different values of non-linear elastic foundation parameters, volume fractions, pre-strains of the SMA fibers, and boundary conditions. The one-dimensional thermo-mechanical constitutive law suggested by Brinson [1] is applied to model the SMA wires. Numerical results make it possible to recognize that increases in the volume fraction and pre-strain of SMA lead to a dramatic enhancement in thermal buckling and post-buckling capacity of the beam. Pre-buckling, buckling, and post-buckling behavior of the beam are totally different and this is due to variations among critical buckling, austenite start and finish temperatures. Due to the recovery stress of SMA wires, particular consequences are shown.

Validity and limitation of analytical models for the bending stress of a helical wire in unbonded flexible pipes

Unbonded flexible pipe is one of the important pieces of equipment in floating production systems for transport of oil and gas between floaters and subsea wells located in deep water. To assure safety over a long-term service period, analysis of fatigue behavior under alternative bending is a key requirement. An analytical model for prediction of bending behavior is essential for understanding the mechanism of the local stress distribution in the helical wires of the tension armor layers under alternative curvatures and rapid estimation of the service life of flexible pipes for designers in engineering practice. In this paper, seven analytical models available in the literature are selected and summarized. Although the experimental results reported in the literature are limited, a three-dimensional finite element model is developed for investigation of the seven models, and the validity and limitations of these models for different structural parameters of helical wire are discussed, i.e., the width-thickness ratio of the wire section and helical angle. The analytical model based on spring theory resulted in a satisfactory estimation of bending stress for most cases and is recommended as a tool for the basic design of the helical armor wire structures in flexible pipes.