大型滚筒式好氧发酵反应器筒体及支撑件结构分析

针对设计的一种处理量为50t/d的大型滚筒式城市生活垃圾好氧发酵反应器,运用三弯矩方程理论计算支撑处和筒体的受力,并在此基础上对筒体弯曲强度和滚圈与托轮间的接触强度进行分析。建立大型滚筒式城市垃圾好氧发酵反应器的有限元整体模型,修正以往分析过程中有限元模型物料载荷加载的不妥之处,建立一种更适合于经破碎后的城市生活垃圾的物料载荷力学模型,应用ANSYS对筒体弯曲应力和支撑装置接触应力进行模拟分析,得到更加接近实际工况的应力分布规律。对模拟分析结果与理论计算结果进行比较,两者具有很好的一致性结果。同时分析结果表明,该滚筒式反应器支撑位置布局设计很合理,并且筒体结构和支撑装置满足强度要求。这为应用于城市垃圾好氧堆肥的滚筒式反应器设计与研究提供了有意义的参考。     

筒体大开孔结构的应力分析设计法

筒体大开孔结构的应力分析设计法哈尔滨市化工学校徐毅一、筒体大开孔结构的应力分析设计法内容本文提出的筒体大开孔结构的应力分析设计法，其基本指导思想是：根据ＡＳＭＥ应力分类准则，利用三维有限元的应力计算结果，寻找最大应力点并确定应力处理线，用最小二乘法拟...     

大型回转窑筒体结构的力学行为分析

运用理论分析和有限元技术,研究复杂重载、多支承、变刚度和超静定的大型回转窑筒体结构力学行为。基于超静定连续梁模型和赫兹理论,计算筒体支撑与摩擦载荷以及轮带与托轮的接触压力和面积,为筒体有限元建模提供边界条件。综合考虑多个附件对筒体载荷与刚度的复杂影响。通过定义当量密度等效处理重力载荷。由于耐火砖层的松散堆砌特点,在含耐火砖筒体模型中,若将耐火砖作为整体赋以砖块刚度与实际不符,故将弹性模量赋以小值,以减弱其刚度影响。首次解析推导出耐火砖对筒体的压力分布公式,建立效率更高、不含耐火砖的函数加载筒体模型。两种模型相互验证地分析筒体的变形和应力状态,并与文献中同类回转窑的应力结果接近。结果表明,回转转矩和摩擦阻力对筒体变形及应力的影响很小;筒体应力最高和横截面圆度最差的薄弱部位均在中间档支承处,解释了掉碎砖现象和潜在安全问题的发生机理,且与该窑体的维护记录相符。文中分析方法和结果对回转窑筒体的安全评估、补强设计和窑线调整均有参考价值。     

活节螺栓法兰垫片连接系统有限元分析与结构改进

应用ABAQUS软件,在考虑预紧力和内压作用的工况下,对某厂所设计的压力容器非标活节螺栓法兰垫片连接系统进行三维有限元应力分析。根据应力分析结果进行线性化处理,按照JB4732-1995《钢制压力容器-分析设计标准》对其进行应力强度评定。结果表明,由于结构的复杂性,原设计结构的耳板、上法兰和筒体的应力强度不满足要求,需加厚上法兰并在筒体上安装加强板以减小其应力强度值。对具有不同厚度上法兰和不同长度加强板的该结构进行应力分析,得到既满足强度要求和密封要求,又节省材料的设计参数,同时总结了上法兰厚度和加强板长度对连接系统上法兰和筒体应力的影响规律。这对类似结构的设计具有一定的指导意义。     

基于有限元法的多层包扎筒体应力分析建模研究

本文运用有限元等数值模拟技术,对多层包扎筒体按接触和整体厚度两类情况对其应力分布状况进行模拟,先以两层为例进行分析,并将其与单筒应力分布情况进行比较,从而获得多层包扎筒体在无预应力情况下应力分析的建模方法,为结构的设计、制造和优化等提供有力的理论支撑.     

多层包扎高压容器承载能力分析

在多层包扎式高压容器制造过程中,理想情况下层板的包扎会使筒体产生预应力,但如果制造精度不够,容器层板间可能出现间隙,就无法保证预应力的充分施加。理论推导得到了有无预应力两种情况下受压力作用时多层包扎高压容器筒体中应力的计算表达式以及极限载荷计算式,并进行了数值模拟验证。研究发现,理论和数值模拟结果较为吻合,预应力的施加显著降低内筒体的工作应力水平,并且能有效改善弹性状态下筒体的应力状态,提高筒体弹性承载能力。然而,在全屈服状态,预应力没有提高容器的极限承载能力,容器极限承载能力仅取决于内筒体和层板的厚度与材料性能。另外,理论分析和数值模拟还表明层间间隙的存在也不会影响容器筒体的极限承载能力。     

压力容器封头处磁记忆信号特征分析

采用金属磁记忆检测方法对CNG储气瓶和乙炔气瓶的封头及筒体处进行检测,发现对应应力集中状态的磁信号有异常变化。用有限元分析软件Ansys对两种不同形式的封头及其与筒体的连接部位进行应力仿真分析。考察了磁信号的变化特征与有限元分析应力间的关系,为磁记忆的定量研究提出一个有效的方法。     

基于预载荷下球磨机筒体有限元分析

以Ф1.5m×3.5m的球磨机筒体为研究对象,在筒体正常工作的静态下,计算出此时筒体所受到的载荷函数,并加载到筒体上,利用ANSYS软件分析筒体受载状态下的应力分布和危险部位。     

小型远红外与热风联合加热式水稻干燥机的研制

设计研制了一种小型的远红外与热风联合加热式水稻干燥机.该机采用滚筒式结构,远红外和热风联合加热的干燥方法以及间歇性的干燥方式,具有结构简单、使用方便、干燥成本低等优点.     

PTA干燥机厚壁筒节裂纹模拟分析与预防

PTA(精对苯二甲酸)干燥机是生产PTA产品后期处理的核心设备,其性能的优劣直接关系到PTA产品的优劣。针对PTA(精对苯二甲酸)干燥机在现场运行过程中滚圈处厚壁筒节表面萌生轴向和周向裂纹的现象,对其建立模型,进行数值模拟计算,并分析产生此类现象的原因和探讨预防措施及结构改进。计算结果表明托轮之间厚壁筒节表面应力幅较大,且频率较大,是裂纹萌生的原因之一。此结论的得出,为PTA干燥机滚圈及垫板的设计具有很重要的指导意义,减少了干燥机在运行过程中的事故率及维修成本。     

超声滚压装置设计及试验研究

设计了一种新的超声滚压装置,并利用该装置研究了超声滚压加工对18CrNiMo7-6齿轮钢表面性能的影响。首先对滚压装置进行了结构设计,应用ANSYS Workbench对装置进行了模态分析和谐响应分析,通过调整滚压装置结构,使该装置能够正常高效地工作;然后综合利用NPFLEX型三维表面形貌测量系统、Proto高速大功率X射线残余应力分析仪、HV-1000型显微硬度计及VHX-2000E型超景深三维显微系统观察分析了超声滚压加工前后试样的表面粗糙度、表面二维形貌、表层显微硬度及残余应力。经超声滚压加工后试样的表面粗糙度从3.003μm降低至0.419μm,最大残余压应力出现在距离表面80μm处,大小约为-672.04MPa,高硬度层达到了200μm。结果表明,利用该装置能够有效的改善材料的表面性能。     

FEM Comparison of Ball and Roller Bullgears

A structural finite element model has been developed for calculating the forces transmitted through the rolling elements (load distribution) in a bullgear assembly. The elastic structural model consists of 3-D beam elements used to approximate the global race deflection and non-linear springs that approximate the combined rolling element/raceway contact deflections. For rollers, an upperbound on the contact stress (assuming linear variation of force along the length of the roller) is estimated by modeling the rollers as pairs of nonlinear springs. The finite element approach iteratively solves the contact forces at each, rolling element. Contact stresses are then calculated from the contact, forces using Hertz contact theory. This approach is applied to analyze two proposed designs of ball and crossed roller bearing, bullgear assemblies used for rotating the radar antenna on top of a ship's mast. The loads analyzed include those arising from wind loading and from out-of-flatness of the inner race of the bearings due to deflection of the mast. The distribution of the load and the maximum contact stresses for the proposed bullgear assemblies are estimated and compared. It is found that the maximum contact stress in the crossed roller bearing is less than that in the ball bearing for both types of loads. Furthermore, the analysis shows that the out-of-flatness loading produces significantly higher stresses than wind loading.     

Numerical Investigation on the Effects of Machining-Induced White Layer during Rolling Contact

It is well known that a thin phase-transformed white layer can be formed on component surfaces produced by hard machining. However, it is not clear as to how the white layer affects component performance, for example, in rolling contact fatigue. This study aims to determine the effects of white layer and associated residual stress on rolling contact stresses and strains. It is nearly impossible for an experimental study to identify the effects of white layer alone on rolling contact. Furthermore, small-scale contact stresses and strains (less than 30 μm) of the phase-transformed region are difficult to measure using the current experimental techniques. Therefore, a finite element analysis simulation model of rolling contact incorporating machining-induced surface integrity has been developed in this study. Three cases were investigated to decouple the effects of surface integrity factors: surface with white layer only, surface with residual stress only, and surface with white layer and residual stress. The simulation results show that distinct material properties of the white layer significantly influence the magnitudes and distributions of near-surface stresses and strains instead of those in the subsurface. Furthermore, it can be inferred that the white layer would affect near-surface fatigue damage instead of subsurface fatigue damage. The simulated near-surface fatigue damage mechanisms have been substantiated by the fatigue test data.     

Effect of Slide-to-Roll Ratio on Interior Stresses Around a Dent in EHL Contacts

The present, study extends the transient EHL point contact model and subsurface stress field calculation model to examine the influence of a surface dent on interior stresses in an EHL point contact under various slide-to-roll conditions. Results revealed that under the pure rolling condition the effect of a surface dent on the stresses is quite negligible. The presence of a shallow surface dent is unlikely to reduce the contact fatigue, life so long as pure rolling motion and good lubrication conditions are maintained. Unfortunately, the same cannot be said of the contact if it is operating in the boundary lubrication regime.

When sliding was introduced, the surface indentation generated significantly high pressure spikes with a strong directional preference. These high-pressure spikes cause severe stress concentrations either below the trailing edge of the dent, if it moves faster than the opposing surface, or below the leading edge of the dent, if it moves slower than the opposing surface. The maximum von Mises stress moved close to the surface and significantly increased in value as compared to the smooth surface solution. For the case of simple sliding, the maximum von Mises stress is even greater than the value calculated for the boundary lubrication case.

In regard to maximum tensile principle stresses, the presence of a dent increased the stresses only marginally over the smooth surface solutions. It is unlikely that surface indentation would significantly reduce the contact fatigue life due to Mode 1-type crack initiation.     

An Engineering Model for Three-Dimensional Elastic-Plastic Rolling Contact Analyses

Fatigue life of heavily loaded rolling bearings is strongly dependent on elastic-plastic material properties. For bearing steels these elastic-plastic properties can be accurately obtained by performing monotonic or half-compressive tests. A three-dimensional strain deformation analysis based on the incremental theory of plasticity and the use of Prandtl-Reuss relations in conjunction with the von Mises yield criterion was developed in order to evaluate the permanent deformation in dry contacts loaded above the elastic limit in case of normal loading. The Ramberg-Osgood stress-strain relation for two martensitically hardened variants of SAE 52100 bearing steel considered the nonlinear kinematic and/or isotropic material behavior. Parameters describing the influence of retained austenite are modeled by using a nonlinear isotropic law. Pressure distribution and contact surface displacements during incremental loading are evaluated by using a conjugate gradient method and the internal stress field is derived by using the superposition principle. Further, a fast analysis of smooth surfaces in elastic-plastic static and rolling contact is developed based on analytical relations for the internal stress field. Cyclic evaluation of plastic strains and residual stresses is carried out until shakedown. In order to verify the theoretical model, rolling contact tests under high normal load were performed. Residual stresses and residual profiles measurements show excellent agreement between numerical and measured cyclic values.     

A Critique of Rolling Contact Fatigue Criteria for Bearing Rings with Hoop Stresses

Tensile residual and interference fit stresses not treated in classical bearing formulations are known to reduce bearing rolling contact fatigue (RCF) life. Recent modifications of such theory to account for these stresses have simply included them in the computation of a single yield stress type criterion—either maximum shear or equivalent stress. An alternative modification is proposed and demonstrated for fatigue crack initiation that recognizes the primary influence of the maximum range of shear stress but includes the effect of normal stress on the critical planes, as in other successful bulk fatigue criteria for multiaxial nonproportional stress cycle fatigue.     

钢制和陶瓷圆柱滚子轴承高速性能的有限元分析

在高速圆柱滚子轴承理论研究的基础上,对普通钢制轴承和陶瓷轴承进行有限元分析,研究了转速对接触应力和等效应力的影响.结果表明,高速轴承的疲劳寿命主要取决于滚动体作用于外圈的离心力,减小滚动体离心力是提高此类轴承寿命的最有效途径;在中、低速时,钢轴承的寿命和可靠性均好于陶瓷轴承.但当转速达到高速时,陶瓷轴承在寿命方面显示出更大的优势.为陶瓷轴承的设计与应用提供参考.     

振动水平圆干燥机的动态分析

针对DZ-22型振动水平圆干燥机在实际使用中干燥机底板受到周期性变化的激振力作用易产生疲劳破坏的问题,利用有限元分析软件AN SY S对干燥机的整体进行了动态的应力、应变分析,得出应力和应变分布的变化图形和动载下的位移变化图形,并找出了易出现裂纹的位置,分析容易造成裂纹的原因。这为干燥机的设计提供了理论依据。     

十字环槽式双万向联轴器有限元分析

应用Pro／E、ANSYS等软件,对十字环槽式双万向联轴器的强度、刚度进行了有限元分析,获得了输入输出轴叉、中间球体、中间轴在载荷作用下的最大应力、最大变形位置及分布状况。计算分析结果为十字环槽式双万向联轴器的设计制造和应用提供了必要的依据。     

Determination of Static Load Distributions from Elastic Contacts in Rolling Element Bearings

A method has been developed for recording the elastic roll body contacts in the load zone for both radial and thrust rolling element bearings subjected to various static loading conditions. Employed in this investigation were a ball bearing and four types of roller bearings which included cylindrical, needle, tapered and spherical. Inspection of the contact areas, or footprints, yields a qualitative measure of the extent of loading arc, load sharing among rolling elements, contact characteristics such as end loading and effects of misalignment. Quantitative data on individual contacts permits the determination of load and stress distributions. Summation of the vertical components of individual roll body loads agrees with the total load applied to the whole bearing, thereby demonstrating the practicability and accuracy of this technique. Correlation of roll body loads with theoretical values varied, depending on angular position from the radial load plane. Finally, this paper indicates how static stress levels on the most heavily loaded element may be obtained and used as a basis for bearing life prediction.