THE APPLICATION OF BOUNDARY ELEMENT METHOD IN STRESS ANALYSIS OF AUTOFRETTED TUBE WITH NOTCH

In this paper, the boundary element method is applied to investigate the internal state of stress of autofretted tube with notch and the calculated results are important in the practical design.

THE APPLICATION OF COMPATIBLE STRESS ITERATIVE METHOD IN DYNAMIC FINITE ELEMENT ANALYSIS OF HIGH VELOCITY IMPACT

There is a common difficulty in elastic-plastic impact codes such as EPIC[2,3] NONSAP[4], etc.. Most of these codes use the simple linear functions usually taken from static problem to represent the displacement components. In such finite element formulation, the stress components are constant in each element and they are discontinuous in any two neighboring elements. Therefore, the bases of using the virtual work principle in such elements are unreliable. In this paper, we introduce a new method, namely, the compatible stress iterative method, to eliminate the above-said difficulty. The calculated examples show that the calculation using the new method in dynamic finite element analysis of high velocity impact is valid and stable, and the element stiffness can be somewhat reduced.

STRAIN-GRADIENT STRESS ANALYSIS IN SAINT-VENANT BENDING

Light beam deflections caused by stress or strain gradients are inves- tigated analytically and experimentally in homogeneous beam specimens which are subjected to a particular case of flexure with shear. This study is a generalization of the prior an alytical-experimental examination of strain-gradient light deflections produced in stressed plates, which had concentrated on the simplest case where in- formation of interest is collected along a line of symmetry of the stress field. Main purpose of the present investigation is to document the efficacy of the strain-gradient method in analysis of the general case of stress state. The most interesting stress state is that in a beam subjected to the Saint-Venant bending, where the transversal and the longitudinal axes of the beam are in pure shear. The obtained results are compared with the predictions of the developed analytical models and with the pre- dictions of Filon's stress function. The procedures of evaluating the photoelastic and material coefficients using strain-gradient techniques were tested positively.

Design of an Experimental Set‑up Concerning Interfacial Stress to Promote Measurement Accuracy of Adhesive Shear Strength Between Ice and Substrate

Accumulation of ice on airfoils and engines seriously endangers the safety of the fight.The accurate measurement of adhesion strength at the ice-substrate interface plays a vital role in the design of anti/de-icing systems.In this pursuit,the present study envisages the evaluation of the stress at the icesubstrate interface to guide the design of experimental set-ups and improve the measurement accuracy of shear strength using the finite element analysis(FEA)method.By considering such factors as the peeling stress,maximum von-mises stress and uniformity of stress,the height and radius of ice and the loading height are investigated.Based on the simulation results,appropriate parameters are selected for the experimental validation.Simulation results show that the peeling stress is decreased by reducing the loading height and increasing the height of ice.Higher ice,increasing loading height and smaller ice radius are found to be beneficial for the uniformity of stress.To avoid cracks or ice-breaking,it is imperative that the ice should be of a small radius and greater height.Parameters including the ice height of 25 mm,radius of 20 mm,and loading height of 9 mm are adopted in the experiment.The results of FEA and the experimental validation can significantly enhance the measurement accuracy of shear strength.

Micro sliding friction model considering periodic variation stress distribution of contact surface and experimental verification

Micro sliding phenomenon widely exists in the operation process of mechanical systems,and the micro sliding friction mechanism is always a research hotspot.In this work,based on the total reflection method,a measuring device for interface contact behavior under two-dimensional(2D)vibration is built.The stress distribution is characterized by the light intensity distribution of the contact image,and the interface contact behavior in the 2D vibration process is studied.It is found that the vibration angle of the normal direction of the contact surface and its fluctuation affect the interface friction coefficient,the tangential stiffness,and the fluctuation amplitude of the stress distribution.Then they will affect the change of friction state and energy dissipation in the process of micro sliding.Further,an improved micro sliding friction model is proposed based on the experimental analysis,with the nonlinear change of contact parameters caused by the normal contact stress distribution fluctuation taken into account.This model considers the interface tangential stiffness fluctuation,friction coefficient hysteresis,and stress distribution fluctuation,whose simulation results are consistent well with the experimental results.It is found that considering the nonlinear effect of a certain contact parameter alone may bring a greater error to the prediction of friction behavior.Only by integrating multiple contact parameters can the accuracy of friction prediction is improved.

Stress Analysis of a Circularly-Perforated Finite Orthotropic Composite Plate

Stresses, particularly those at geometric discontinuities, can influence structural integrity of engineering components. Motivated by the prevalence of cutouts in components, the objective of this paper is to demonstrate ability to stress analyze finite, circularly-perforated orthotropic composites whose external loading may be unknown. Recognizing difficulties in obtaining purely theoretical or numerical solutions, the paper presents a hybrid means of stress analyzing such structures. Individual stresses, including those on the edge of the hole, are obtained in a loaded finite graphite/epoxy composite tensile plate containing a round hole by processing measured values of a single displacement field with an Airy stress function in complex variables. Displacements are recorded by digital image correlation. Traction-free conditions are satisfied analytically at the edge of the hole using conformal mapping and analytic continuation. Stresses satisfy equilibrium and strains satisfy compatibility. Significant features of the technique include its wide applicability, it smooths the measured information, does not require knowing the applied loading, and the rigorous mechanics foundation by which strains are determined from measured displacements.

Study on the application of spectral fatigue analysis

Fatigue failure has long been an important issue for ships and offshore structures. Among the numerous methods for predicting fatigue life, the spectral method is accepted as the most reliable. Although the theory behind spectral analysis is straight-forward, the analysis itself is complicated and time-consuming because it is closely related to critical technical details such as the application of fatigue loading (wave pressures and the inertial forces due to cargoes), the extraction of the stress, and the calculation of stress RAO. Here, four key technical details-loading application, displacement boundary condition, the calculation of stress RAO, and the extraction of the fatigue stress-are discussed thoroughly. For each aspect, a resolution is presented based on the finite element pre-and post-processing software MSC/PATRAN or FE solver MSC/NASTRAN. The resolutions are effective and efficient, which can help engineers perform spectral fatigue analysis accurately and faster.

Examination of effective stress in clay rock

This paper examines the effective stress in indurated clay rock theoretically and experimentally.A stress concept is derived from the analysis of the microstructure and of the pore water in the highly-indurated Callovo-Oxfordian and Opalinus clay rocks,and subsequently validated by various experiments performed on these claystones.The concept suggests that the interparticle or effective stress in a dense clay ewater system is transferred through both the adsorbed interparticle pore water in narrow pores and the solidesolid contact between non-clay mineral grains.The experiments show that the adsorbed pore water in the claystones is capable of bearing deviatoric effective stresses up to the failure strength.The applied stresses are for the most part or even totally transferred by the bound pore water,i.e.the swelling pressure in the interparticle bound pore water is almost equivalent to the effective stress.This stress concept provides a reasonable view to the nature of the effective stress in argillaceous rock and forms the fundamental basis for studies of the hydro-mechanical properties and processes in clay formations.

PLANE-STRESS CRACK-TIP STRESS FIELDS FOR ORTHOTROPIC PERFECTLY-PLASTIC MATERIALS

Under the hypothesis that the stress components of crack-tip fields are only the functions of θ, the differential equations of plane-stress crack-tip stress fields for orthotropic perfectly-plastic materials are obtained by using Hill's yield condition and equilibrium equations. By combining the general analytical expression with the numerical method the crack-tip stress fields for orthotropic perfectly-plastic materials for plane stress are presented.

Effect of cutting speed on residual stress of special coating during remanufacturing

To study the residual stress of the special coating at different cutting speeds, the cutting of FeA1CrBSiNb coating is analyzed with the finite element method （FEM） and experiment according to the coating characteristics. The CNC machine tool is used to cut the coating and the X-ray stress equipment is used to measure the residual stress of coating. The experimental and FEM results agree with each other. Also, the residual-stress coating depth is deeper and the residual stress of the coating surface is larger with increasing cutting speed. In addition, the residual stress of the coating surface is in the suppression state affected by axial residual stress and circumferential residual stress, and the residual stress of the deeper coating is in the tensile state based on the original state of arc spraying and cutting process.

A simplified testing method for stress-induced of tunnel surrounding rock

A simple testing method for secondary or induced stress of surrounding rockwas presented by laboratory experiment, numerical simulation and in situ testing based onthe basic principle of the historical stress restoring method.First, stress equivalent coefficient,which key coefficient of stress restored testing, was obtained by laboratory experiment.Second, experimental results were examined using 3D finite element numericalanalysis and the influence factors were analyzed by 2D finite element numerical analysis.The correctness of induced stress measuring results in situ for highway tunnel wereproved by elastic mechanics theory solution and single-hole stress rescission method.Thenew simple method of induced stress measuring has important practical value for undergroundengineering induced stress field analysis.

Modification of B3 Model for Sealed Concrete with Additives Based on Experimental Observations

Thirteen specimens were tested out of which nine were for creep of sealed concrete and four for shrinkage test,for a period of 700 d under controlled temperature condition.The experimental results for creep and shrinkage were compared with creep and shrinkage computation model B3 and distinct discrepancies between observed and calculated creep and shrinkage strains were observed.Based on regression analysis,modification on B3 model has been formulated which will be applicable at least for concrete of characteristics strength of C40 and C50 with additives.Besides,on the basis of observation on identical specimens with varied stress strength ratio,a function is generated which accounts effect of stress strength ratio on creep.Finally,Civil Engineering community is suggested not to follow the creep prediction models without correction at least for modern concrete,as they do not account the effect of additives on its compliance function.

基于人工智能压力性损伤图片分析系统的精细干预在神经内科重症患者中的应用

目的探讨基于人工智能压力性损伤图片分析系统的精细干预在神经内科重症患者中的应用。方法选取2021年1月至2022年12月神经内科收治的重症患者120例,随机数字表法分为研究组(n=60)采用基于人工智能压力性损伤图片分析系统的精细干预,对照组(n=60)采用常规护理,比较2组患者护理效果。结果研究组压力性损伤发生率为6.67%(4/60)低于对照组12.67%(13/60)(P<0.05),研究组HAMA量表评分和HAMD量表评分均低于对照组(P<0.05);研究组压力性损伤相关知识掌握评分高于对照组(P<0.05)。结论基于人工智能压力性损伤图片分析系统的精细干预在神经内科重症患者中的应用效果显著,可显著减少患者压力性损伤发生率,改善患者负性情绪,提升护理人员压力性损伤相关知识掌握情况。

基于负压的浅海养殖海参捕捞系统设计与性能研究

现有的海参捕捞装置捕捞效率低、操作复杂,并不适用于浅海养殖海参捕捞。针对以上问题,设计一种真空负压式海参捕捞装置。以西门子PLC为核心控制器,通过水环式真空泵获取负压,依次控制各个阀件进行启停操作,依靠负压生成罐中的负压将海参虹吸到储存罐中,再将海水泥沙等杂物排出储存罐并收集海参;并自制内嵌加速度传感器的海参仿真模型(质量为130~160 g),对该设备进行性能测试。结果表明:吸管(钢管0.8 m和PVC钢丝管2 m)长为2.8 m,负压储存罐压力值为-0.04 MPa时,海参在管中最大(X轴)初始加速度为0.97g,矢量加速度为1.09g,可认为悬浮式吸取海参。

大吉区块深部(层)煤层气储层地应力测井预测研究

深部(层)煤层气勘探开发过程中,精准预测地应力对于安全高效钻完井具有重要意义。曾被认为是勘探开发禁区的深部(层)煤层气,近几年相继获得高产而备受关注,但与之相适应的地应力预测模型尚未进行过有益探讨。据此,本文翔实梳理和系统分析了常规油气储层和煤层气等非常规天然气储层中常用的6种地应力预测模型,基于常用的预测模型开展了地应力计算,通过闭合压力对比分析,得知组合弹簧模型和Newberry模型精度相对较高。为提升地应力预测模型的精度,采用煤岩的有效应力系数对两种模型进行优化。优化后的地应力模型预测精度较优化前误差降低了4%,其精度基本能满足大吉区块深部(层)煤层气勘探开发对地应力预测精度的要求。

行星传动系统均载与动载系数试验测量改进设计

试验测量行星传动系统均载与动载系数的精准度是评价系统动态性能的基础。针对现有行星传动系统均载与动载系数测量方法存在灵敏度与精度欠佳、系数测试算法缺失、测试应力点存误等问题,本文提出了一种方便、实用且具有高精度的行星传动系统均载与动载系数测试方法,定义了系统系数的测试算法与概念,明确了精确应力测试位置点及不同位置间差异性,采用应变片电桥传感器串并联设计,实现了拉压应力叠加、温度补偿以及繁琐标定免除等优点,为精准测取行星传动系统均载与动载性能提供了重要的理论基础和技术手段。

基于有限元的顶驱下套管装置密封胶筒设计

密封胶筒是顶驱下套管装置实现套管密封、泥浆循环等作业功能的关键部件。为探究密封胶筒工作原理并为其研发提供理论依据,通过有限元分析软件建立了数值仿真模型,采用自适应网格技术模拟了密封胶筒插入套管及密封高压泥浆的动态过程。分析了密封胶筒的密封原理,研究了动态过程中密封胶筒几何形态及应力状态的变化特性。并对密封胶筒进行了力学分析和强度校核,结果表明:当密封最大泥浆压力时,胶杯最大应力为15.77 MPa,骨架最大应力为370.3 MPa,表明密封胶筒强度满足设计要求。最后通过应用试验检验密封胶筒的密封效果,验证了仿真计算各项数据的准确性,表明此密封胶筒性能满足现场使用要求。

软岩巷道围岩破碎机理及控制技术

基于临汾宏大雪坪煤矿三采区轨道巷掘进期间受集中应力影响,巷道在450~520 m段巷帮及顶板出现应力显现现象,集中表现在顶板下沉、破碎,两帮收敛及底板鼓起等,严重制约着巷道安全快速掘进,分析了巷道围岩破碎机理,并对破碎区顶板提出了“JW型锚索吊棚+桁架锚索+密集工字钢棚”等联合支护技术,取得了显著应用成效。

老年髋关节置换术后应激性高血糖风险预测模型的建立及验证

目的建立老年髋关节置换术后应激性高血糖的风险预测模型,并验证其应用价值。方法便利抽样法选取2018年3月至2023年3月郑州市骨科医院收治的340例行髋关节置换术的老年患者作为研究对象,并将其分为建模组(230例)与验证组(110例),收集患者年龄、糖尿病家族史、术后应激性高血糖发生情况等资料,采用多因素Logistic回归分析老年髋关节置换术后并发应激性高血糖的独立危险因素,根据分析结果建立老年髋关节置换术后应激性高血糖风险预测模型,并验证模型有效性及预测价值。结果多因素Logistic回归分析结果显示,年龄>75岁、有焦虑、有抑郁、C反应蛋白>8 mg/L、糖化血红蛋白>6%、有营养风险、营养支持方式为肠外营养、手术持续时间>15 h是老年髋关节置换术后并发应激性高血糖的独立危险因素(95%CI为1200~13322、1156~3792、1205~4375、1849~9444、4507~22929、1135~3496、1058~3084、2282~21737,P=0024、P=0014、P=0011、P=0001、P<0001、P=0016、P=0030、P=0001);得出预测模型公式为P=1/[1+exp[-(-3857+危险因素总分×0591)]];受试者操作特征(ROC)曲线分析结果显示,曲线下面积为0801,敏感度为812%,特异度为749%,P<001;Hosmer-Lemeshow卡方检验结果显示,χ^(2)=5235,P=0601。结论预测模型能够预测老年髋关节置换术后应激性高血糖的发生风险,且具有较高的拟合校正性能以及良好的预测识别能力。

框架剪力墙结构建筑施工技术在建筑工程中的应用

建筑行业作为国家的重要支柱产业对促进城市建设以及拉动经济发展具有重要意义。随着人们物质水平的不断提升,对建筑项目施工质量以及居住环境质量也提出了更为严格的要求。框架剪力墙结构是建筑工程项目中最为主要的结构形式,对项目整体稳定性具有重要影响。因此,文章深入研究了框架剪力墙结构的施工技术,总结了框架剪力墙结构的受力情况以及施工中存在的技术问题,并提出了有效的应用方式,旨在保障建筑工程的施工质量。