不锈钢热连轧机粗轧支持辊剥落影响因素的有限元分析

该文分析某2250不锈钢热连轧粗轧机频繁发生支持辊严重边部剥落难题的影响因素。通过理论及实际剥落断口形貌分析,指出世界上不锈钢产量最大的该生产线复杂轧制工艺条件和服役期内辊系力学行为引起的不均匀辊间接触压应力分布是该轧机轧制过程中轧辊剥落的主要原因。根据现场跟踪实测数据,采用大型通用有限元软件建立了四辊轧机辊系三维有限元模型,仿真分析了带钢宽度、轧制力、轧辊磨损对辊间接触压应力峰值和位置的影响。结果表明:随着带钢宽度和轧制力的增大,辊间接触压力峰值增幅明显,辊间接触压力分布不均匀度系数基本不变;在不同磨损阶段,当工作辊和支持辊都处于服役后期时,压力峰值、不均匀度系数显著增大,均在距轧辊辊身边部附近存在接触压应力尖峰,且此位置与实际剥落位置一致。研究结果为成功研制的新支持辊形技术投入长期稳定工业应用累计轧制600万t以上未再发生剥落提供了理论依据。     

六辊轧机扭振动态建模及与板带钢质量关系研究

考虑轧机扭振与辊系沿轴向动态特性和板带材质量的关系,基于连续体动力学建立了六辊轧机扭振动力学模型,包括轧机辊系等效模型和辊身与辊径过渡部分等效模型。根据轧制速度与轧辊角速度的关系,建立了板带钢前后张力、轧制力等参数与辊系扭振的关系模型。基于所建模型对某六辊轧机施加位移激励模拟扭振情况,仿真分析了轧机辊系和板带钢在扭振激励下的三维动态响应。仿真结果表明,轧辊角位移和角速度沿辊身长度方向波动较小;轧辊扭振使轧制压力、前张应力和后张应力横向分布发生不同程度的波动,扭振对前张应力分布影响较大,即对板带钢板形产生影响,且传动侧的波动幅值大于操作侧。     

考虑紧固螺栓的三排滚柱式转盘轴承载荷分布计算

螺栓是转盘轴承的关键紧固件。为考察紧固螺栓工作参数对转盘轴承载荷分布的影响,提出了一种针对三排滚柱式转盘轴承的有限元等效建模方法。首先,基于三排滚柱式转盘轴承的结构特点和受力情况,建立考虑紧固螺栓的转盘轴承有限元模型,并从减少计算量和保证计算效率等方面考虑,采用非线性弹簧单元模拟滚子,通过有限元仿真快速获取了该转盘轴承的载荷分布。然后,设计并开展三排滚柱式转盘轴承静态加载试验,通过有限元仿真结果和试验结果的对比验证了所构建有限元模型的准确性。最后,基于构建的有限元模型,分析了螺栓预紧力和螺栓结合面处摩擦系数对三排滚柱式转盘轴承载荷分布的影响。仿真结果表明：螺栓预紧力对三排滚柱式转盘轴承载荷分布的影响显著,而螺栓结合面处摩擦系数的影响微弱,其中上排滚子承受的最大载荷随螺栓预紧力的增大而增大,下排滚子承受的最大载荷随预紧力的增大而减小;在轴向力和倾覆力矩的联合作用下,三排滚柱式转盘轴承下排滚子承受的载荷总体上高于上排滚子,充足的螺栓预紧力可以提高转盘轴承的承载能力,而螺栓预紧力不足则会使下排滚子承受更大的载荷,导致转盘轴承提前失效。研究结果可为转盘轴承的安装和后期维护提供参考。     

轧制导入角对AZ31镁合金薄板头部翘曲的影响

目的研究轧制导入角对镁合金薄板轧制过程中头部翘曲的影响。方法设计实验导入角分别为-4.8°,-1.4°,3.1°,4.3°,7.2°的5组方案,并进行轧制实验。结果当入射角为-1.4°时轧制板材翘曲程度最小,入射角为7.2°时翘曲程度最大。随着导入角的增加,轧件非对称咬入,上下表层与轧辊的接触面积差、延伸变形量差增大,附加应力也随之增加,结果造成轧件翘曲程度逐渐增大。结论当导入角为-1°~2°时,轧件的上下表层接触面积、延伸变形量相当,产生的附加压力较小,轧制效果最佳。     

高速压力机转子-轴承系统的动力学研究

以有限元方法为基础,建立了曲柄压力机的转子-轴承系统的运动方程,通过计算压力机的曲柄连杆之间的作用力,获得主轴转子的径向载荷,并集成建立转子-轴承系统的振动模型;采用Newmark方法进行求解,进行模拟仿真,分析转子-轴承系统的振动响应;对主轴转子的振动特性进行实验研究,验证了转子-轴承系统的振动模型及其模拟仿真,进而为压力机转子-轴承系统的设计提供了数值分析及实验研究依据。     

轧机辊系垂直非线性参激振动特性分析

考虑了轧制界面间的非线性阻尼以及辊系间的非线性刚度,建立了四辊轧机辊系垂直非线性参激振动模型。采用多尺度法求解了系统在不同频率激励下的主共振、超谐波共振以及亚谐波共振的解析近似解,得到了系统的幅频特性方程。分析了该系统的稳定性,得到了阻尼与刚度对系统稳定性的影响关系。分析了非线性刚度、非线性阻尼等参数对系统振动的影响,得到非线性刚度的变化会引起激励幅值的跳跃,导致幅值的振荡。用数值仿真验证了分析结果的正确性。研究结果为抑制轧机辊系这类垂直颤振提供了一定理论指导。     

振动冲击对海水润滑塑料轴承时变热弹流润滑的影响

建立了冲击载荷作用下综合考虑热效应和时变效应的海水润滑塑料轴承弹流润滑数学模型;利用压力求解的多重网格法,弹性变形的多重网格积分法及温度求解的逐列扫描技术数值模拟了连续冲击载荷作用下海水润滑膜压力及膜厚的分布;对比分析了正弦周期脉冲及三角形周期脉冲作用下的润滑膜中心压力、中心膜厚及最小膜厚随时间变化的特性;讨论了载荷幅值及脉宽对润滑膜特性的影响。数值计算结果表明,压力的变化周期同载荷的一致,膜厚的变化滞后于冲击载荷及压力的变化;随载荷幅值的增大,压力和膜厚的振幅增大,中心压力的对称线下移,相应膜厚的对称线上移;随脉宽的增大,中心压力的最大值变大,最小膜厚的最小值变小。     

颗粒阻尼吸振器对轧机辊系减振特性的研究

轧机在高速轧制过程中经常会发生垂直振动现象，这种振动行为会影响轧制过程的稳定性以及复合板表面质量和结合强度，不利于轧制生产高效连续进行。为了抑制轧机辊系在轧制过程中产生的垂直振动，该研究设计了一种多自由度颗粒阻尼吸振器。建立了安装吸振器的轧机上工作辊垂直非线性参激振动模型。运用多尺度法求解了系统的幅频特性方程，仿真分析了振动系统的奇异特性、时域特性、频谱特性以及幅频特性。对静定轧机上工作辊进行了垂直振动控制试验，对比发现理论分析与试验结果基本吻合，证明所建立的四自由度振动模型的可靠性。结果表明，颗粒阻尼吸振器能够有效地抑制轧机辊系的垂直振动并满足设计要求。     

加速工况下滚动轴承动态载荷特性研究

滚动轴承运动部件的动态效应将对滚动轴承的载荷分布及其性能产生重要作用,特别是在变速工况下。以深沟球轴承为研究对象,考虑轴承游隙、滚动体离心力与重力、内圈和滚动体的动态效应等,建立了滚动轴承动力学分析模型,对加速工况下滚动轴承的运行过程进行了动力学仿真,分析了径向载荷作用下滚动体动态载荷分布特性及其机理,并揭示了游隙、内圈质量和角加速度对滚动体动态载荷的影响。研究结果表明:加速工况下滚动体的载荷分布曲线不再沿载荷作用线对称且出现不同程度的波动,尤其是在加速过程的后期;滚动体的最大接触载荷在加速过程初期基本保持不变,而在后期波动上升,加速过程中内圈的不稳定运动是导致滚动体接触载荷发生变化的主要原因;加速过程中动态载荷的变化程度随着径向游隙和内圈质量的增加而增大,而角加速度的增加使得加速过程后期的动态载荷变化愈加剧烈。本文结果可为滚动轴承载荷计算与设计提供理论依据。     

考虑轧制界面粗糙形貌的轧机辊系非线性振动特性研究

轧制界面的粗糙形貌可导致界面行为的根本变化,极大地影响着轧机辊系的动力学响应行为。考虑轧制界面粗糙形貌的影响,建立了轧机辊系系统的非线性垂直振动动力学模型,计算了具有不同粗糙形貌轧制界面的轧机辊系系统非线性刚度特性和固有频率特性,并与采用Duffing振子描述界面刚度的传统轧机模型进行了对比。采用多尺度法求解了考虑界面粗糙形貌影响的轧机系统主共振幅频特性方程,并推导了系统受迫振动响应的跳跃频率和跳跃幅值表达式,分析了轧制界面粗糙形貌、激励载荷、非线性刚度率和阻尼对轧机辊系系统动力学响应特性的影响,为抑制轧机振动提供有效的理论参考。     

Fatigue Life of Slewing Bearings under Combined Radial,Axial and Tilting Moment Loads

A calculation method of fatigue life for slewing bearings under combined radial,axial and tilting moment loads was proposed.Single row four-point contact ball slewing bearing being used as a case,the statics model of the slewing bearing was established and a set of equilibrium equations were obtained.By solving the equilibrium equations,the rolling element loads were obtained and the equivalent rolling element loads were calculated further.By using the geometrical parameters of the bearing,the rating rollin...     

高速滚动球轴承动态载荷计算改进方法的研究

在离心力和陀螺力矩的作用下,滚动球轴承高速旋转时的内部载荷分布与轴承静止情况下的载荷分布具有显著差异,其主要影响因素包括,滚动轴承的接触角、轴承预紧位移以及旋转速度等。基于JonesHarris(简称JH)力学模型的轴承载荷分布的分析方法已经得到了广泛的应用。然而其计算公式多、迭代繁琐、收敛速度慢。针对此现象,研究了轴承动态载荷分布规律及其算法,提出了改进的JH轴承数值计算模型,给出相应的简化计算步骤。计算与对比结果表明,改进的JH计算模型在其应用范围内,可以大幅减少计算时间。     

径-轴向辗环机轴向轧制机构结构分析

采用三维造型软件SolidWorks建立了某型号径-轴向辗环机轴向轧制机构的实体模型。以有限元软件ANSYS为分析平台,通过合理处理接触、约束和载荷等边界条件,建立了有限元分析模型,对轴向轧制机构进行了三维弹性接触分析,得到了轴向轧制机构及主要部件的等效应力、位移变形、等效应变。对变形角进行了定义,提出了求解变形角的方法。计算结果表明,变形角为0.041°时,各部件的最大等效应力均小于屈服极限,轴向轧制机构刚度符合设计要求,各部件满足强度要求。     

风电齿轮箱高速轴圆锥滚子轴承动态特性分析

齿轮箱是风电机组故障率最高的部件之一,其中高达50%的故障停机源于高速轴轴承的过早失效。外部变风载激励和齿轮箱内部激励下,高速轴轴承动载增大,将加速高速轴轴承破坏失效。论文以某750kW风电齿轮箱高速轴圆锥滚子轴承为分析对象,采用ADAMS软件建立圆锥滚子轴承的多体动力学仿真分析模型,研究轴向载荷和径向载荷变化对轴承动态响应特性的影响,基于美国Spectra Quest转子实验台开展了圆锥滚子轴承振动响应特性实验,掌握了圆锥滚子轴承的动态接触力与振动响应变化规律,将为风电齿轮箱高速轴圆锥滚子轴承选型与齿轮箱设计提供理论依据。     

Contact Fatigue Failure of a Tapered Roller Bearing Used in a Lorry Wheel

Tapered roller bearings, which are also known as angular-contact bearing, are suitable for supporting radial and axial loads. The more frequent types of defects in such bearings are caused by contact fatigue in these machine components, and this examination focuses on a contact fatigue failure in a tapered rolling bearing. The examination included visual inspection, microscopic analysis (optical and scanning electron microscope), and microhardness measurements. These measurements were conducted to help understand the failure mechanisms. Based on the results of visual examination and microstructure and fracture surface analysis, it was determined that the tapered roller bearing failed by contact fatigue that was caused by overloading of the bearing.     

Method to determine the local load cycles of a blade bearing using flexible multi-body simulation

Conventional methods for designing rolling bearings against fatigue assume that a bearing ring is fully rotating and that the load is ideally distributed over the rolling elements. Blade bearings in wind turbines, are operated under oscillating motions and dynamic loads. The load distribution is strongly dependent on the stiffness of the bearing rings and the surrounding structural components. This has been shown in numerous studies using FEM simulations for static load cases. In this paper a method is presented that reduces the calculation effort of the deformation of the bearing rings, so that a flexible integration into an aeroelastic mbs model of a wind turbine is possible. Thereby an average accuracy of 6.5% between FEM and mbs could be achieved. The model allows the determination of time series of the global load distribution of each raceway. By data processing of the simulation results, the number of load cycles and the maximum contact pressure for individual segments of the raceways could be determined and their fatigue probability could be estimated using the linear damage hypothesis according to Palmgren-Miner.

     

Computational model for determination of dynamic load capacity of large three-row roller slewing bearings

In the presented paper a calculation procedure for determination of dynamic load capacity of large three-row roller slewing bearings is presented. The calculation procedure consists of three main parts: (i) determination of internal contact force distribution in a large three-row roller slewing bearing with consideration of bearing clearances and ring support deformations, (ii) determination of stress field in the contact area between raceway and rollers as a consequence of contact forces and (iii) determination of the bearing’s fatigue life due to contact fatigue of the raceway. The internal contact force distribution is determined numerically by using a symmetry 3D FEM-model of a large three-row roller slewing bearing. Another numerical procedure is used to determine the stress field in the contact area between rollers and raceway. This problem is studied on different roller types: cylindrical roller (without profile correction), fully crowned roller (logarithmic-profile) and partially crowned roller (ZB-profile). Numerically determined contact stresses then serve as a basis for fatigue analyses, where the bearing’s service life of the bearing is determined by using the stress-life approach, considering typical material parameters of the bearing’s raceway.     

对转圆柱滚子轴承动态特性分析

针对内外圈对转圆柱滚子轴承内部复杂的运动特性及相互作用力,通过分析轴承径向游隙的影响因素以及考虑滚子与滚道的接触变形和热效应对油膜厚度的影响,利用拟静力学法建立了轴承的分析模型,并采用NewtonRaphson法进行求解;同时,利用该模型对滚子打滑率进行计算,以验证所采用分析方法的正确性和可靠性。然后,进一步探讨了不同工况下对转圆柱滚子轴承内部组件的转速变化规律与接触特性。结果表明：滚子的自转转速、滚子与滚道的接触载荷均随径向载荷的增大而增大;内、外圈转速变化会使受载区滚子与滚道的接触载荷以一定的规律重新分配,且转速对最小油膜厚度的影响较径向载荷更为明显。研究结果可为对转圆柱滚子轴承的结构优化和生热机理分析提供理论依据。     

An improved dynamic model for angular contact ball bearings under constant preload

High-speed spindles are typically installed with angular contact ball bearings. This research has established a dynamic model for angular contact ball bearings under constant preload. By analyzing the constant preload mechanism, and the gyroscopic and centripetal forces, a dynamic non-linear model for angular contact ball bearings was proposed using Hertz contact theory. The model was solved by numerical iteration to obtain the dynamic parameters of an angular contact ball bearing which included: the dynamic normal contact force and contact angle, the maximum compressive stress and axial displacement, the contact pattern, stiffnesses, etc. To validate the model, a test device was designed which was equipped with a constant preloaded bearing group. By measuring the relative displacement of the bearings’ inner and outer rings under different conditions, the accuracy of the model was proved. This modeling method provided a theoretical basis for calculating bearing thermal characteristics, fatigue life, and an optimized radius of curvature of the bearing ring channel.