Transverse Distributions of Front and Back Tension Stresses in Cold Strip Rolling

In this paper,such a new lateral displacement function is proposed that the lateral flow velocity is con- tinuous at the entry and the exit of deformation zone.A new kind of finite strip method—the third power B-spline finite strip method—is put forward to simulate strip rolling process.Front and back tension stresses are formulated.The computed results of the transverse distributions of the front and back tension stresses are close to the experimental results.The paper lays a foundation for further analysing the three-dimensional stresses and deformations of strip rolling.

Prestressed tensioning method and its application to testing anchor stress of anchor cables for side-slope stabilization

The anchor stress extent of a prestress anchor cable project has a direct relation with the project safety and performance. Prestressed tensioning method is a kind of nondestructive testing method, by which a reverse stretching load is applied on the external exposure section of anchor cable under construction or in service, and then the elongation variation of stress bars is measured to determine the anchor stress. We elaborated the theory and testing mechanism of prestressed tensioning method, and systematically studied key issues during the prestressed tensioning process of anchor cable by using physical model test, including the composition of tension stress-elongation curve, the variation of anchor stress, the compensation of locked anchor stress, and the judgment of anchor stress, and verified the theory feasibility of prestressed tensioning method. A case study on slope anchor cable of one highway project was conducted to further discuss on the test method, operation procedures and judgment of prestressed tensioning method on obtaining anchor stress, and then the test data of three situations were analyzed. The result provides a theoretical basis and technical base for the application of prestressed tensioning method to the evaluation of construction quality and operation conditions of anchor cable project.

Role of gelatinous layer in growth stress generation in tension wood

To elucidate what controls the magnitude of longitudinal growth stress in tension wood, anatomical measurements of gelatinous fibres were carried out on poplar tension wood (Populus I4551). Sections were cut from embedded blocks to avoid a border artefact described earlier. Results showed that: 1) no gelatinous fibres were observed under a growth strain level from 0.06% to 0.08%; 2) almost all of the non-conductive tissues contained gelatinous fibres above a growth strain level from 0.15% to 0.19%; 3) the amount of fibres, the amount of fibres with gelatinous layer, per unit of tissue area, and the thickness of the gelatinous layers controlled most of the magnitude of growth stress; 4) the contribution of the S2 layer in both fibre types could also play a role in the growth stress generation.

Charactersitics of Stress-strain Curve of High Strength Steel Fiber Reinforced Concrete under Uniaxial Tension

A whole of 110 specimens divided into 22 groups were tested with varying the volume fraction of steel fibers and the matrix strength of these specimens. The stress-strain behaviors of four types of steel fiber reinforced concrete （SFRC） under uniaxial tension were studied experimentally. When the matrix strength and the fiber content increase, the tensile stress and tensile strain vary differently according to the fiber type. The mechanisms of reinforcing effect for different types of fiber were analyzed and the stress-strain curves of the specimens were plotted. Some experimental factors for stress or strain of SFRC were given. A tensile toughness modulus Re0.5 was introduced to evaluate the toughness characters of SFRC under uniaxial tension. Moreover, the formula of the tensile stress-strain curve of SFRC was regressed. The theoretical curve and the experimental ones fit well, which can be used for references in construction.

ANALYTICAL SOLUTIONS TO STRESS CONCENTRATION PROBLEM IN PLATES CONTAINING RECTANGULAR HOLE UNDER BIAXIAL TENSIONS

The stress concentration problem in structures with a circular or elliptic hole can be investigated by analytical methods. For the problem with a rectangular hole, only approximate results are derived. This paper deduces the analytical solutions to the stress concentration problem in plates with a rectangular hole under biaxial tensions. By using the U-transformation technique and the finite element method, the analytical displacement solutions of the finite element equations are derived in the series form. Therefore, the stress concentration can then be discussed easily and conveniently. For plate problem the bilinear rectangular element with four nodes is taken as an example to demonstrate the applicability of the proposed method. The stress concentration factors for various ratios of height to width of the hole are obtained.

Design and Analysis of Tapered Stress Joint for Top Tensioned Riser System

Stress Joint （SJ） plays a key role in the Top Tensioned Riser （TTR） system for deep water engineering. A preliminary design method of tapered SJ is proposed in the paper, which could help designers obtain accurate design data. After a further sensitive analysis is carried out, the related parameters choice and control methods are recommended in the engineering practice. By taking the extreme environment conditions into consideration, the effects of bending stress reduction and curve control are analyzed, and the 3-D FE models are established by ABQOUS for numerical evaluation to verify the correctness of design results. At last, dynamic analysis and fatigue analysis, based on actual project, are carried out with designed stress joint. The analysis results prove the feasibility and guidance of this method in the practical engineering applications.

The relationship between microstructure and stress-strain behavior in tension in high strength pipeline steel

In this paper the relationship between microstructure and stress-strain behavior in tensile test of high strength pipeline steel was investigated.The steel with polygonal ferrite-bainite(PF + B) microstructure has a "round-house" type tensile stress-strain curve with low Y/T ratio,highly uniform elongation and high n-value,which means PF + B microstructure has the best deformability(i.e.Ideal stress-strain behavior) among the four microstructures.The steel with acicular ferrite-martensite&austenite(AF + MA) microstructure has a "continuous-yielding" type tensile stress-strain curve,whose deformability is worse than that of PF + B microstructure.Both the steels of polygonal ferrite-acicular ferrite(PF + AF) and polygonal ferrite-pearlite (PF+P) microstructure have "luders elongation" type tensile stress-strain curve with high Y/T ratio,low uniform elongation and low n-value,which means PF + AF and PF + P microstructures have the worst deformability among the four microstructures.

The Load-Displacement Curves of Deep Fascia in Response to Tension Stress Principle during Limb Lengthening: a Preliminary Study

Objective:To investigate the load displacement curves of deep fascia of leg in response to the Tension Stress principle during limb lengthening. Methods:Limb lengthening animal model was established in New Zealand white rabbits using a unilateral external fixator applied with four pins to the medial surface of tibia and monofocal proximal diaphysis with closed multiple drill holes and osteoclasis between the second and the third pins.Seven days after operation,distraction was initiated at distraction rates of 1mm/day and 2mm/day in two steps,and proceeded until increases of 10% and 20% in the initial length of tibia had been achieved.The fascia samples of 30mm×10mm were clamped with the Instron 1122 tensile test device at room temperature with the constant tensile rate of 5mm/min.After 5 load download tensile tests had been performed,the samples were elongated until rupture.And the load displacement curves were automatically generated. Results:The normal fascias showed typical load displacement rule of collagenous tissues.And each experimental group of fascias kept the characteristics.The curves of fascias at a rate of 1mm/day were closer to the curves of normal fascias.For the normal fascias,the ultimate tension strength was avarage 2.69N,and the strain at rupture was avarage 14.11%.And the ultimate tension strength of the fascias after limb lengthening increased. Conclusion:These results prove that the Tension Stress during limb lengthening has great effect upon the load displacement curves of fascia.The curves of fascia at a distraction rate of 1mm/day were closer to the curves of normal fascia.

Stress concentration factor expression for tension strip with eccentric elliptical hole

Two explicit expressions of the stress concentration factor for a tension finite-width strip with a central elliptical hole and an eccentric elliptical hole, respectively, are formulated by using a semi-analytical and semi-empiricai method. Accuracy of the results obtained from these expressions is better, and application scope is wider, than the results of Durelli＇s photo-elastic experiment and Isida＇s formula. When eccentricity of the elliptical hole is within a certain range, the error is less than 8%. Based on the relation between the stress concentration factor and the stress intensity factor, a stress intensity factor expression for tension strips with a center or an eccentric crack is derived with the obtained stress concentration factor expressions. Compared with the existing formulae and the finite element analysis, this stress intensity factor expression also has sufficient accuracy.

基于3D-DIC技术的金属棒材单轴拉伸大应变硬化曲线测量研究

为精确测量金属棒材单轴拉伸颈缩后大应变范围硬化曲线,采用三维数字图像相关技术(3D-DIC)测量试样颈缩区域几何构型,基于Bridgman模型对颈缩后流动应力进行修正,评估Ludwik、Swift、Hockett-Sherby(H-S)和Voce模型对硬化曲线的拟合效果,开展单轴拉伸有限元模拟以验证大应变硬化曲线的可靠性。结果表明:以6061铝合金棒材为例,3D-DIC技术可以精确地获取试样颈缩最小横截面半径a和外轮廓曲率半径R的演化规律,结合Bidgman模型可以有效地获取颈缩后大应变硬化曲线,其应变范围(0~0.41)是常规单轴实验所获取硬化曲线应变范围(0~0.058)的7倍,Hockett-Sherby硬化模型具有最佳的硬化曲线拟合优度,基于该模型的单轴拉伸模拟输出载荷-位移曲线和应变云图与实验测量结果基本一致,证实3D-DIC技术结合Bridgman模型能够精确地测量金属棒材单轴拉伸颈缩后大应变范围的硬化曲线。

Influence of local tensile loading on the distribution of welding residual stress fields in cylinder shells

The feasibility of reducing the welding residual stress through local tensile loading is verified using the finite element method （FEM）. The mechanism and effect of reducing stress during and after welding are compared. The results show that the effect of the former is better than that of the latter. Applying an external tension load of 200 MPa after welding, the maximum residual stress drops down from 235 MPa to about 90 MPa, moreover, it decreases to 30MPa when an external tension load of 200 MPa is applied during welding.

Strain Monitoring and Stress Analysis of a Post-Prestressed Tunnel Liner

The strain monitoring and stress analysis of a new type of post-prestressed tunnel liner were carried out. The instrumentation block of the tunnel liner, with the dimensions of 12.06 m in length, 6 500 mm in diameter, and 650 mm in thickness, was post-prestressed with the unbonded tendons, each of which consists of 8 pieces of double-looped strands and the axial spacing of the tendons is 500 mm. Concrete strain meters, rebar meters, load cell and zero-stress meters were installed for the strain monitoring. The tensioning loads were applied incrementally in three cycles (50%, 77% and 100%) at the concrete age of 28 d and the tensioning work lasted for 187.1 h. Strain readings were taken before and after each cycle during tensioning period and at the specified time interval after tensioning period. It is found that concrete creep developed over tensioning period is 30% of total strain and 41.5% of elastic strain respectively. Prestress force in the unbonded tendon and concrete stress in the liner were evaluated according to the observed strain variations. Both of them are time-dependent, and about 5.3%, 8.3% and 9.0% of the prestress losses are observed at the age of 1 d, 30 d and 60 d respectively after stressing. The distribution of prestress in the liner is relatively uniform and meets the design requirement.

Effect of pre-deformation on the stress corrosion cracking susceptibility of aluminum alloy 2519

The effects of pre-deformation and strain rate on the stress corrosion cracking （SCC） behavior of aluminum alloy 2519 in air and in 3.5% NaCI water solution were investigated by means of slow strain rate tension （SSRT）, scanning electron microscopy （SEM）, and transmission electron microscopy （TEM）. The results indicate that the alloy is susceptible to SCC in 3.5% NaCI water solution and not in air. At the same pre-deformation, the alloy is more susceptible to SCC at 1.33 × 10^-5 s^-1 than at 6.66 × 10^-5 s^-1. Moreover, it is more susceptible to SCC at free pre-deformation than at 10% pre-deformation at the same strain rate. The number of 0 precipitated along the grain boundaries is reduced and distributed discontinuously, at the same time, the precipitate-free zones （PFZ） become narrow and the susceptibility to stress corrosion cracking is reduced after 10% pre-deformation.

Thermal stresses analysis of casing string used in enhanced geothermal systems wells

In the enhanced geothermal systems wells, casing temperature variation produces casing thermal stresses, resulting in casing uplift or bucking. When the induced thermal stresses exceed casing material's yield strength, the casing deforms and collapses. The traditional casing design standard only considers the influence of temperature variation on casing material's yield strength. Actually, for commonly used grades of steel pipe, casing's material properties-such as yield strength, coefficient of thermal expansion, and modulus of elasticity change with temperature variation. In this paper, the modified thermal stress equation is given. Examples show that the allowable temperature of the material grade N80's casing is only 164 ℃, which is much lower than that of the traditional design standard. The effective method to improve the casing pipe's allowable temperature is pre-stressed cementing technology. Pre-stressed cementing includes pre-tension stress cementing and pre-pressure stress cementing. This paper focuses on the design method of full casing pre-tension stress cementing and the ground anchor full casing string pre-tension cementing construction process.

Tensile stress regulated microstructures and ferroelectric properties of Hf_(0.5)Zr_(0.5)O_(2) films

The discovery of ferroelectricity in HfO_(2) based materials reactivated the research on ferroelectric memory.However,the complete mechanism underlying its ferroelectricity remains to be fully elucidated.In this study,we conducted a systematic study on the microstructures and ferroelectric properties of Hf_(0.5)Zr_(0.5)O_(2)(HZO)thin films with various annealing rates in the rapid thermal annealing.It was observed that the HZO thin films with higher annealing rates demonstrate smaller grain size,reduced surface roughness and a higher portion of orthorhombic phase.Moreover,these films exhibited enhanced polarization values and better fatigue cycles compared to those treated with lower annealing rates.The grazing incidence x-ray diffraction measurements revealed the existence of tension stress in the HZO thin films,which was weakened with decreasing annealing rate.Our findings revealed that this internal stress,along with the stress originating from the top/bottom electrode,plays a crucial role in modulating the microstructure and ferroelectric properties of the HZO thin films.By carefully controlling the annealing rate,we could effectively regulate the tension stress within HZO thin films,thus achieving precise control over their ferroelectric properties.This work established a valuable pathway for tailoring the performance of HZO thin films for various applications.

套筒灌浆搭接及对接接头高应力反复拉压试验

为比较套筒灌浆搭接及对接接头间力学性能差异,进行了41个搭接接头和20个对接接头的单拉及高应力反复拉压试验。结果表明:单拉及高应力反复拉压时,两种接头均能实现最大力下总伸长率大于6%、延性系数大于4,强度基本满足规范要求;高应力反复拉压后单拉时,两种接头承载力均有所提高,但接头初始刚度和延性下降;防偏转措施可减少搭接接头残余变形,但其约束刚度有限,搭接接头残余变形略大于对接接头,防偏转搭接接头及对接接头残余变形基本满足规范要求;高应力反复拉压后单拉时,搭接接头套筒中部截面在加载前期纵向受拉、环向受压,加载后期纵向受压、环向受拉,对接接头套筒加载过程中均为纵向受拉、环向受压;高应力反复拉压结束后单拉时,防偏转、不防偏转搭接接头套筒中部截面近钢筋侧最大纵向拉应变分别为对接接头的0.10~0.39倍、0.13~0.18倍,最大环向压应变分别为对接接头的0.09~0.49倍、0.02~0.32倍,搭接接头对套筒材性要求较低;钢筋直径相同时搭接接头材料成本较对接接头降低约35%。

新型拉压复合型锚杆锚固性能研究Ⅳ:数值模拟

新型拉压复合型锚杆具有良好的锚固性能,在抗浮工程中优势明显并逐渐推广应用,但其荷载传递规律尚不明晰。基于此,针对已完成的现场试验,对拉压复合型锚杆的荷载传递机理开展了数值模拟研究。结果表明,拉压复合型锚杆筋体轴向拉力在承压锚固段保持不变,拉力传递至受拉锚固段后大幅降低,破坏时受拉承载系数略低于受拉长度系数。承压锚固段灌浆体受压,压应力向端头递减;受拉锚固段灌浆体受拉,拉应力先增大后减小,且最大拉应力显著低于全黏结型锚杆;优化拉压长度比,可以进一步减小受拉锚固段灌浆体受到的轴向拉应力。拉压复合型锚杆浆土界面剪应力在承载体处最大,向两侧减小;与全黏结型和压力型锚杆相比,相同拉力下,拉压复合型锚杆浆土界面剪应力显著减小,应力集中现象明显削弱,且分布更加均匀。

Numerical Simulation of Continuous Tension Leveling Process of Thin Strip Steel and Its Application

Cold-rolled thin strip steel of high flatness quality undergoes multistage deformation during tension leveling. Thus, the parameters of set-up and manipulating are more difficult. With the aid of FE code MSC. MARC, the tension leveling process of thin strip steel was numerically simulated. Concentrating on the influence of the roll intermeshes in 2# anti-cambering on the distribution and magnitude of residual stresses in leveled strip steel, several experiments were clone with the tension leveler based on the results from the simulation. It was found from the simulation that the magnitude of longitudinal residual stresses in the cross-section of the leveled strip steel regularly presents obvious interdependence with the roll intermeshes in 2# anti-cambering. In addition, there is a steady zone as the longitudinal residual stresses of the surface layers in leveled strip steel vary with the roll intermeshes of 2# anticambering, which is of importance in the manipulation of tension levelers. It was also found that the distribution of strains and stresses across the width of strip steel is uneven during leveling or after removing the tension loaded upon the strip, from which it was found that 3D simulation could not be replaced by 2D analysis because 2D analysis in this case cannot represent the physical behavior of strip steel deformation during tension leveling.

神经科护士工作投入的现状及影响因素分析

目的分析神经科护士工作投入现状及其影响因素。方法采用便利抽样的方法,于2022年4月—5月对北京某三级甲等综合医院神经科护士进行横断面调查。采用自行设计的一般资料调查问卷、工作投入量表、中文版知觉压力量表,对神经科护士进行调查问卷。结果本研究共发放问卷660份,回收630份,回收率95.45%;有效问卷630份,有效率100.00%。630名神经科护士工作投入得分为(35.15±5.34)分,各个维度的平均分对比,差异有统计学意义(P<0.05)。单因素分析结果显示,神经科护士的工作投入评分在年龄、聘用关系、技术职称、工作年限和子女情况上的差异有统计学意义(P<0.05)。神经科护士的知觉压力总分为(36.76±8.10)分,工作投入总分与失控感评分、知觉压力总分呈正相关(P<0.05),与紧张感评分呈负相关(P<0.05)。多因素分析结果显示,失控感、聘用关系、工作1~10年、紧张感是工作投入的独立影响因素(P<0.05)。结论神经科护士工作投入的影响因素众多。作为临床护理管理者可以通过有效的科学管理办法,采取有效措施缓解护士心理压力,降低反刍思维水平,正向引导建立正向的应急心理,从而提高护士工作投入程度,最终达到提高护理质量和患者满意度的目的。

Application of Stationary Phase Method to Wind Stress and Breaking Impacts on Ocean Relatively High Waves

Wind stress impacts on ocean relatively high waves can be perfectly illustrated by a recurrent phenomenon in the Sahara desert. Indeed, on this area where the surface wind can blow without encountering major obstacle out of the sand dunes, these main targets are gradually eroded and displaced by the wind on dozens of meters. This experience highlights the action of wind on granular targets (clusters of sand or water slides) and motivates studies similar to ours, where we want to simulate impact of wind stress and breaking on the spatio-temporal evolution of the envelope of ocean relatively high waves: Impact which can inappropriately deflect the waves on ships, oil platforms or coastal infrastructures. Euler and Navier-Stokes equations allow a mathematical formulation of the gravity wave motion (ocean waves are considered in our work as a system of water particles which are held together by low surface tension) and wind acts on targets through friction forces or stress. Michel Talon stationary phase method is used to numerically solve the equations that model the impact of wind on a stationary Gaussian.