变螺距螺杆真空泵转子温度场和热变形的有限元分析

以变螺距螺杆真空泵转子为研究对象,建立主动转子的三维有限元分析模型,对转子在热载荷作用下的温度场和热变形进行有限元分析。计算得到每一级的当量温度和对流换热系数,确定变螺距转子热边界条件,对螺杆转子的温度场分布进行模拟分析,得出转子的温度分布规律,并进一步对转子的热变形进行研究。研究结果表明:变螺距转子温度场和热变形分布均匀,最高温度为146.97℃,最低温度为68.30℃,轴向形变量最大值为0.41168 mm,径向形变量最大值为0.17245mm,为变螺距螺杆真空泵的设计提供了理论依据。     

风电装备行星轮系过盈接触特性分析

风力发电对于保障我国能源安全具有重大意义,但我国风电装备发展中还存在巨大技术瓶颈,如何进一步提高装备可靠性及寿命是亟需解决问题。以行星轮系过盈配合面接触特性与微动磨损关系为切入点,针对NGW型行星轮受力分析,计算获取过盈配合接触分析的载荷边界条件;通过对比不同过盈量在无外载工况下的配合面压力值,理论计算与仿真分析结果的平均误差约为5.74%,验证了仿真的可信度;通过对比不同过盈量在无外载下的变形量,行星轮内孔面与轴承外圈变形占比分别为89.5%和10.5%,定量描述了行星轮相较于轴承的变形程度,更易损伤;稳态载荷工况下,通过对比不同配合公差P6和R6下的最大微动滑移量可知,P6公差带下最大微动量随载荷变化幅度较大,因此风电行星轮配合公差应选R6更合适;非稳态载荷工况下,通过数值积分计算获取不同过盈量下的配合面打滑极限载荷,该极限值作为评定实际服役工况下出现剧烈"打滑现象"的准则,因此设计时应考虑该极限工况。     

油垫可倾式静动压混合支承摩擦副变形

液体静压支承在高速重载工况下运行时,由于强挤压和高速剪切联合作用,微间隙油膜温度和油腔压力分布不均匀,导致静压支承摩擦副发生热固耦合变形,影响液体静压支承的承载能力和高精度稳定运行。为了解决该难题,提出一种新型油垫可倾式静压支承结构,其运行过程中可实现任意方向微摆,产生附加动压,形成静动压混合支承,达到高速重载工况条件下静压支承高精度稳定运行的目的。依据流热固耦合理论,采用ANSYS Workbench对支承摩擦副变形进行流热固耦合分析,探讨承载0 t~32 t极端工况条件下旋转工作台、可倾油垫和底座的流热固耦合变形规律。提取变形数据,并经MATLAB编程处理后得到摩擦副变形关系,发现油腔外侧封油边边角处变形最大,此处间隙油膜最薄,最易发生摩擦学失效,成果为进一步控制摩擦副变形和摩擦学失效机理研究提供新方法。     

复杂载荷下油井管接头数值仿真平台的研发与应用

日益复杂的油气井钻采条件使得油井管柱面临越来越苛刻的载荷工况,油井管接头作为整个管柱的薄弱环节,其失效问题非常突出。实物实验费用昂贵、实验周期长,且复杂载荷工况难以施加,无法满足实际要求。该文基于油井管接头三维全尺寸弹塑性有限元分析,构建了复杂载荷下油井管接头数值仿真平台,是实物实验的一个有力补充。该仿真平台所得极限工作扭矩与API标准提供数据基本吻合(零轴向力条件下),同时具有分析复杂工况条件下油井管接头三维力学特性的能力。通过该仿真平台,能很好地描述复杂载荷作用下油井管接头的受力特征,快速、全面地评估复杂载荷作用下油井管接头的连接强度和密封性能,明确油井管接头的极限载荷工况。     

HIAF强流重离子加速器真空室烘烤功率计算及热-结构耦合分析

针对薄壁真空室的使用特点,首先利用ANSYS有限元软件进行结构优化设计。其次通过理论计算和数值模拟相结合的方法计算出真空室烘烤功率,并给出在达到热平衡后真空室的温度分布规律。此外采用间接耦合法得到薄壁真空室在热-结构耦合状态下的变形及应力分布规律,结果表明升温阶段损失功率随时间而逐渐增加,真空室达到热平衡后损失功率保持恒定;仅大气压作用下真空室被压缩,高度方向的变形占主导地位,在烘烤过程中热载荷带来的影响较大,真空室长度方向的变形占主导地位;由于气体载荷和热载荷在某一点处所引起的应力方向不一致,所以真空室在热-结构耦合作用下的最大应力不是各个载荷应力值的线性叠加。     

基于流固耦合的钢桶跌落仿真及结构优化

目的 为了实现钢桶轻量化设计,对考虑流固耦合的钢桶进行跌落仿真分析,在保证其抗跌落性能的条件下,对钢桶关键结构进行优化设计。方法 以210 L钢桶为例,利用Ansys Workbench建立有限元模型,进行垂直跌落、棱跌落和角跌落等3种工况下的仿真分析;建立优化设计模型,进行多目标优化设计。结果 得到钢桶在3种工况下的总变形量和等效应力情况,并发现钢桶跌落时的薄弱位置位于底部和环筋处,且在角跌落工况下受到的总变形量和等效应力最大;通过改变钢桶的壁厚和环筋距离进行多目标优化设计,得出优化设计点,当壁厚设置为1.1 mm,环筋位置对称且均为233.17 mm时,能够减小钢桶的重量并保证其抗跌落性能。结论 通过对钢桶进行跌落强度流固耦合仿真分析和多目标优化设计,获得满足结构强度、减少材料用量的优化结构,降低了包装成本,为包装产品轻量化设计提供理论支持和设计参考。     

气动效应地面模拟装置光学窗口设计与评价

气动热效应地面模拟装置是航空载荷成像性能地面检测设备的核心部分。本文设计了一种光学窗口用于气动热效应地面模拟装置,使用理论计算与模型仿真相结合的方式,严谨地阐述气动环境下光学窗口的设计理论。首先使用计算流体动力学理论(Computational Fluid Dynamics,CFD)进行仿真,计算给定条件下的气动压力和温度值,给出最严苛的条件值;然后根据经典强度理论和断裂力学理论,提出光学材料加工工艺要求,并设计窗口满足安全使用要求的厚度;最后依据流固热耦合仿真分析,验证设计的合理性,并依据导致载荷光学成像质量下降程度的变形量优化窗口的厚度。     

MT300/KH420碳纤维/聚酰亚胺树脂复合材料层合圆柱壳高温承载性能

基于Donnell-Mushtali近似理论及热弹性理论,考虑结构热变形和材料高温性能衰减等温度影响因素,对MT300/KH420碳纤维/聚酰亚胺树脂复合材料圆柱壳在常温、420℃及周向210~420℃不均匀温度场等热载工况下的承载性能进行了理论分析。并引入一阶屈曲模态缺陷作为几何初始扰动,利用ABAQUS,采用非线性显式动力学方法完成对MT300/KH420复合材料圆柱壳在以上热载工况下的轴压稳定性有限元仿真计算,计算结果与理论分析较为一致。设计并开展MT300/KH420复合材料圆柱壳力-热载荷联合轴压试验,获得圆柱壳在以上热载工况下的破坏载荷和破坏模式。研究表明:高温工况下,力学性能衰减和温场不均匀引起的结构热变形是影响MT300/KH420复合材料圆柱壳轴向失稳载荷的主要因素。      

低温风洞电动推杆热防护结构设计及传热分析

为解决低温风洞中电动推杆的热防护问题,设计了使其能够在低温风洞高温工况(323 K)和低温工况(110 K)下正常工作的热防护结构。采用数值模拟方法校核了热防护结构强度及刚度,分析了电机发热功率,冷却气体流量和加热片加热功率等因素对推杆元件温度的影响。结果表明:低温风洞内压力达到极值0.35 MPa时,由厚度5 mm,材料S30408不锈钢制成的圆筒形热防护结构最大变形量为0.397 mm,最大应力为160.62 MPa;冷却气体流量大于等于0.005 kg/s时,高温和低温工况下电机最高温度均不大于418 K的允许工作温度;当加热功率达到500 W时,缸杆端部各考察截面温度均高于263 K;在高温工况和加热功率为500 W的低温工况下,冷却气体流量为0.005 5kg/s时,缸体、缸杆均能维持在263—313 K的工作温度,且高温工况最大温升与温差分别为3.62、2.81 K,低温工况最大温降与温差分别为4.94、6.82 K,满足温度稳定性与均匀性要求。     

双螺杆挤压机操作参数对加工质量影响的研究

通过实验研究了双螺杆食品挤压机的机筒温度、供料速度、螺杆转速对产品质量(以比容衡量)的影响规律,建立了相应的统计模型,并对操作参数进行了优化.研究表明,随着机筒温度的升高,比容呈增大趋势,螺杆转速与供料速度对比容的影响较复杂,与比容之间的关系呈非线性.当机筒温度在160～166℃之间,螺杆转速在143～147(r·min-1)之间,供料速度在20.6～21.4(r·min-1)之间时,加工质量较高,比容大于2.4(mL·g-1).     

啮合异向双螺杆挤出机仿真研究

采用 Solidworks 三维建模软件建立了啮合异向双螺杆螺纹元件与啮 合同向双螺杆螺纹元件的物理模型。运用 Polyflow 软件对聚乳酸流体进行三 维流体仿真,从聚乳酸流体的剪切速率、黏度、压力和速度等 4 个方面,对 比研究啮合异向双螺杆挤出机螺纹元件与啮合同向双螺杆挤出机螺纹元件对 聚乳酸流体的加工效果。研究结果表明,聚乳酸流体在啮合同向双螺杆挤出 机螺纹元件中,受到的剪切速率大、轴向运动速度慢而获得了较好的混合效 果;聚乳酸流体在啮合异向双螺杆挤出机螺纹元件中,轴向流动速度较快, 挤出效果好。     

Fracture toughness analysis of O-POSS/PLA composites assessed by essential work of fracture method

Essential work of fracture (EWF) method was employed to investigate the effect of the octavinylisobutyl based polyhedral oligomeric silsesquioxane (O-POSS) addition in poly(lactic acid) (PLA) matrix on the fracture behavior of O-POSS/PLA composites. The 2 mm thick rectangular shaped PLA-matrix composites containing various weight ratios of O-POSS were injection molded after processing in a twin-screw extruder. Constant deformation rate tensile tests at room temperature were performed on double edge notched tensile (DENT) specimens with various ligament lengths. It was found that the addition of O-POSS to PLA improved the toughness. It was observed that a greater energy consumed after the maximum load reached on load–displacement curves for the composites. Optimum additive value was obtained at 7 wt% O-POSS.     

A mixed semi analytical solution for functionally graded (FG) finite length cylinders of orthotropic materials subjected to thermal load

A simplified and accurate analytical cum numerical model is presented here to investigate the behavior of functionally graded (FG) cylinders of finite length subjected to thermal load. A diaphragm supported FG cylinder under symmetric thermal load which is considered as a two dimensional (2D) plane strain problem of thermoelasticity in (r, z) direction. The boundary conditions are satisfied exactly in axial direction (z) by taking an analytical expression in terms of Fourier series expansion. Fundamental (basic) dependent variables are chosen in the radial coordinate of the cylinder. First order simultaneous ordinary differential equations are obtained as mathematical model which are integrated through an effective numerical integration technique by first transforming the boundary value problem into a set of initial value problems. For FG cylinders, the material properties have power law dependence in the radial coordinate. Effect of non homogeneity parameters and orthotropy of the materials on the stresses and displacements of FG cylinder are studied. The numerical results obtained are also first validated with existing literature for their accuracy. Stresses and displacements in axial and radial directions in cylinders having various l/r _i and r _o/r _i ratios parameter are presented for future reference.     

基于正交试验的新型印刷滚筒结构优化

目的为了优化变刚度印刷滚筒结构,有效提升其抗轴向挠曲变形能力,改善印刷压力分布不均匀的状况。方法根据轴承径向载荷分布理论,建立变刚度印刷滚筒的等效支撑模型,利用有限元分析变刚度印刷滚筒轴向挠曲的变形情况,选出对其挠曲变形影响较大的因素,通过正交试验法建立变刚度印刷滚筒结构分布及结构尺寸的试验组,采用极差分析法,以变刚度印刷滚筒最大挠曲变形量为评判指标,分析各因素对轴向挠曲变形的影响主次程度及影响规律,得出较优的结构分布和结构尺寸。结果筒体壁厚、加强筋数量对变刚度印刷滚筒最大挠曲变形的影响程度较大,加强筋厚和芯轴直径的影响程度次之;优化后,变刚度印刷滚筒中部挠曲变形得到了改善,轴向最大挠曲变形量降低10.2%。结论合理改进变刚度印刷滚筒结构可减小其轴向挠曲变形,有效地提升了印品质量。     

A mesh-free method for analysis of the thermal and mechanical buckling of functionally graded cylindrical shell panels

The buckling response of functionally graded ceramic-metal cylindrical shell panels under axial compression and thermal load is presented here. The formulation is based on the first-order shear deformation shell theory and element-free kp-Ritz method. The material properties of shell panels are assumed to vary through their thickness direction according to a power-law distribution of the volume fraction of constituents. Approximations of the displacement field are expressed in terms of a set of mesh-free kernel particle functions. A stabilized conforming nodal integration approach is employed to estimate the bending stiffness, and the shear and membrane terms are evaluated using a direct nodal integration technique to eliminate membrane and shear locking for very thin shells. The mechanical and thermal buckling responses of functionally graded shell panels are investigated, and the influences of the volume fraction exponent, boundary conditions, and temperature distribution on their buckling strengths are also examined.     

双螺杆强制润滑挤出UHMWPE板材的研究

通过引入强制润滑成型原理．研制了UHMWPE强制润滑挤出成型装置，采用同向旋转双螺杆挤出机实施了对UHMWPE板材的连续挤出成型实验研究，对螺杆组合方式进行了优化对比，确定了合理的螺杆组合构型，并对挤出实验中出现的异常现象进行了剖析。研究工作表明，采用对机头流道的强制润滑、合理的螺杆组合、正确的工艺条件和机头流动压力的调整，可以成功实现对UHMWPE体系的连续高效挤出成型。     

发动机振动对排气歧管低周疲劳寿命影响研究

发动机排气歧管在动态热负荷与整机振动载荷耦合作用的恶劣环境中工作,在热负荷单独作用时其部分区域就已经发生塑性变形,而整机振动载荷的耦合作用将使其疲劳失效问题更为严峻。为量化整机振动载荷对排气歧管低周疲劳损伤的影响,以某三缸增压发动机为研究对象,首先,基于流固耦合方法获得了排气歧管在标定工况和怠速工况下内外流场的换热边界,并联合增压器、催化器等部件温度和换热边界对两工况下排气系统的温度场进行计算。然后,根据温度场计算结果,耦合螺栓预紧力的作用,对怠速工况下的弹性应力场以及标定工况下的弹性和弹塑性应力场进行了计算,并基于标定工况下的弹塑性应力场,应用模态瞬态动力学对标定工况下的整机振动载荷作用下的动应力进行分析。最后,依据标定和怠速工况下的弹性应力场、标定工况下的动应力场结果,参照发动机低周疲劳试验标准分别建立了排气歧管常规高温低周疲劳与整机振动-热耦合低周疲劳分析模型,引入Neuber准则对两者的载荷谱进行应力-应变修正后采用主应变法进行疲劳寿命评估。结果表明：排气歧管疲劳破坏风险点主要位于高温拉应力区域,叠加振动载荷会使整体疲劳寿命下降接近25.2%,部分区域下降幅度甚至高达57%。研究结果为排气歧管整机瞬态振动-热耦合低周疲劳寿命预测提供了一定的理论依据和参考。     

Transient thermoelastic analysis for a multilayered hollow cylinder with piecewise power law nonhomogeneity due to asymmetric surface heating

This paper is concerned with the theoretical treatment of transient thermoelastic problems involving a multilayered hollow cylinder with piecewise power law nonhomogeneity due to the asymmetrical heating of its surfaces. The thermal and thermoelastic constants of each layer are expressed as power functions of the radial coordinate, and their values continue on the interfaces. The exact solution for the two-dimensional temperature change in a transient state is obtained using the Laplace transformation and separation-of-variables method. The exact solution for the thermoelastic response of a multilayered hollow cylinder under the state of generalized plane strain, where the strain is not bound, is obtained herein. Some numerical results for the temperature change and the stress distributions are presented in figures. The influence of the functional grading on the thermal stresses is investigated. Furthermore, the influence on the axial stress of the restraint condition in the axial direction is investigated.     

Reduction of residual stresses in thick-walled composite cylinders by smart cure cycle with cooling and reheating

The nozzle parts of solid rocket motors must endure both the internal pressure generated by high temperature exhaust gas and the mechanical load generated by steering operation. Therefore, the nozzle parts of solid rocket motors are fabricated with thick carbon fiber phenolic resin composites. When the thick-walled phenolic composite cylinder is cooled down from the curing temperature of about 155 °C to the room temperature, thermal residual stresses are created due to the anisotropic thermal deformation of the composite structure.

In this paper, a smart cure method with cooling and reheating was developed to reduce residual stresses in thick-wound composite cylinders made of carbon phenolic woven composite. The optimal cure cycle was obtained to reduce the residual stresses without increasing processing time and applied to fabrication of the thick-walled composite cylinder. From the residual stresses measured by the radial-cut-cylinder-bending method, it was found that the residual stresses were reduced 30% by using the smart cure method.