Research on Adaptive TSSA-HKRVM Model for Regression Prediction of Crane Load Spectrum

For the randomness of crane working load leading to the decrease of load spectrum prediction accuracy with time,an adaptive TSSA-HKRVM model for crane load spectrum regression prediction is proposed.The heterogeneous kernel relevance vector machine model(HKRVM)with comprehensive expression ability is established using the complementary advantages of various kernel functions.The combination strategy consisting of refraction reverse learning,golden sine,and Cauchy mutation+logistic chaotic perturbation is introduced to form a multi-strategy improved sparrow algorithm(TSSA),thus optimizing the relevant parameters of HKRVM.The adaptive updatingmechanismof the heterogeneous kernel RVMmodel under themulti-strategy improved sparrow algorithm(TSSA-HKMRVM)is defined by the sliding window design theory.Based on the sample data of the measured load spectrum,the trained adaptive TSSA-HKRVMmodel is employed to complete the prediction of the crane equivalent load spectrum.Applying this method toQD20/10 t×43m×12mgeneral bridge crane,the results show that:compared with other prediction models,although the complexity of the adaptive TSSA-HKRVMmodel is relatively high,the prediction accuracy of the load spectrum under long periods has been effectively improved,and the completeness of the load information during thewhole life cycle is relatively higher,with better applicability.

Load spectrum analysis for combined frame of closed high-speed press

Based on the basic theory of mechanics,kinematic and dynamic analysis for a slider-crank mechanism with a balance mechanism is performed.The theoretical formula of the load spectrum for the interaction between the crank shaft and the bearing seat of the upper beam is achieved by approximately simplifying the mechanical model of the crank shaft.The simulation for the load spectrum data of combined frame under the operating conditions of blanking or piling is performed using Matlab and the law of the load spectrum curves under these two conditions is analyzed.The simulation results show that under a no-load condition,the load spectrum curves of the interaction between the crank shaft and the bearing seat of the upper beam present a form of periodic sine wave and under the piling condition,the load spectrum curves of the interaction between the crank shaft and the bearing seat of the upper beam present a form of periodic pulse wave.The simulation results can provide a theoretical foundation for the load determination during the process of analyzing the dynamic characteristics on the combined frame of a closed high-speed press through the finite element method.

Rain-Flow and Reverse Rain-Flow Counting Method for the Compilation of Fatigue Load Spectrum

The rain-flow counting method is widely used to compile the fatigue load spectrum, The second stage counting of the rain-flow method is a troublesome process. In order to overcome this drawback, the rain-flow and reverse rain-flow counting method is proposed in this paper. In this counting method, the rule for counting of the rain-flow method is modified, so that the sequence of load-time need not be adjusted. This is a valid and useful method to count cycles and compile the load spectrum and it can be widely used in ocean engineering.

Filtering Method of Aero⁃engine Load Spectrum Based on Rain Flow Counting

A filtering method of aero-engine load spectrum based on the rain flow counting is proposed in this paper.Firstly,the original load spectrum is counted through the rain flow method to get the peak and valley values.Then,some data points in the original load spectrum are added between the peak and valley values.Finally,the filtering spectrum is obtained.The proposed method can reflect the path information of the original load spectrum.In addition,it can also eliminate the noise in the signal and improve the efficiency of signal processing,which is of practical significance for the research of aero-engine.

Improved Data Processing of Loading Spectrum for Applications of Rainflow Counting Method

The rainflow counting method is a reasonable cyclecounting procedure for fatigue life calculation and simulation testing of structures.It defines cycles as closed stress /strain hysteresis loops.Application of the rainflow counting method requires a data processing of the loading spectrum,which consists of the elimination of non-peak value data points,load time histories adjustment and loop extraction.In the data processing of the loading spectrum,if a stress point is neither the peak nor the valley,it will be identified and eliminated from the loading spectrum.Generally,the loading process is idealized as a single peak-valley straight line.But in actually,there are polylines or nearly straight lines between peaks and valleys which can't be ignored.Therefore,in the process of eliminating such data points,it will produce error in method itself.To reduce the error produced by the traditional method itself,a new method which can well simplify the polylines in data processing of loading spectrum is proposed in this paper.Comparing with the original approximation method,the proposed method has higher precision.

Coupling Singular Spectrum Analysis with Artificial Neural Network to Improve Accuracy of Sediment Load Prediction

Sediment load estimation is generally required for study and development of water resources system. In this regard, artificial neural network (ANN) is the most widely used modeling tool especially in data-constraint regions. This research attempts to combine SSA (singular spectrum analysis) with ANN, hereafter called SSA-ANN model, with expectation to improve the accuracy of sediment load predicted by the existing ANN approach. Two different catchments located in the Lower Mekong Basin (LMB) were selected for the study and the model performance was measured by several statistical indices. In comparing with ANN, the proposed SSA-ANN model shows its better performance repeatedly in both catchments. In validation stage, SSA-ANN is superior for larger Nash-Sutcliffe Efficiency about 24% in Ban Nong Kiang catchment and 7% in Nam Mae Pun Luang catchment. Other statistical measures of SSA-ANN are better than those of ANN as well. This improvement reveals the importance of SSA which filters noise containing in the raw time series and transforms the original input data to be near normal distribution which is favorable to model simulation. This coupled model is also recommended for the prediction of other water resources variables because extra input data are not required. Only additional computation, time series decomposition, is needed. The proposed technique could be potentially used to minimize the costly operation of sediment measurement in the LMB which is relatively rich in hydrometeorological records.

TREATMENT OF COMPLEX LOAD HISTORY AND CONSTRUCTION OF FATIGUE LOAD SPECTRUM

A new, more actual approach for omitting small loads in a loading history was pres-ented according to crack closure, and load interactive effects which are large on damage of com-ponents were studied. Intrinsic periodic spectrum block representing a damage element of a loadhistory, a new concept, was put out. It has been proven by theoretic analysis and tests that themodes of constructing fatigue loading spectrum have little effect on damage of components,which will change the incomplete knowledges on constructing fatigue spectrum ago.

基于S变换双阈值法的汽车零部件载荷谱加速编辑

针对S变换编辑法加速编辑效果不佳的问题,提出了一种基于S变换双阈值编辑方法。该方法先对载荷谱进行S变换以获取最大幅值谱,在以双阈值识别并保留的幅值谱片段为依据保留对应的载荷谱片段后,再将其拼接成加速后的载荷谱,最后对比分析S变换双阈值编辑法与S变换编辑法编辑的加速谱的统计参数、功率谱密度、穿级计数和疲劳仿真结果。研究结果表明,S变换双阈值编辑法可明显压缩原始载荷时间,且其压缩效率高于S变换编辑法,转向节的疲劳损伤和寿命分析误差更小,适用于汽车零部件载荷谱加速编辑研究。

主减速器台架疲劳试验等效方法研究

为了提高主减速器台架疲劳试验的准确性和效率,提出了基于实际行驶载荷谱的台架疲劳试验等效方法。在采集用户和试验场实际行驶载荷谱基础上,基于雨流计数和精英策略非支配排序遗传算法关联用户路面,等效重构试验场道路工况和道路载荷谱。为验证等效方法的有效性,建立主减速器有限元模型并进行静强度分析,验证了网格无关性和模型有效性。结合瞬态动力学模型研究了不同转矩、转速与齿轮应力之间的关系,得到程序载荷谱幅值所对应的频次等效关系;结合转速与齿轮应力之间的关系和各转矩区间的转速概率密度分析,确定了各个等级载荷谱对应的转速,编制了旋转弯曲疲劳试验程序载荷谱;结合有限元模型,验证了编制载荷谱与原始载荷谱的等效关系。结果表明,齿轮在等效载荷谱的作用下与原始载荷谱的损伤部位一致,损伤值最大误差为0.15%,并且加速了4.7倍。

大型空泡水洞试验设施结构有限元分析

大型空泡水洞试验设施是目前中国规模最大的水洞系统,为评估其整体结构强度和抗震设计安全性,对空泡水洞结构进行三维有限元数值分析,考虑正常工作工况和地震载荷作用极限工况下的结构刚强度,基于振型分解反应谱法计算了地震惯性加速度载荷,并对结构地震位移响应进行校核。结果表明:空泡水洞的结构变形在正常工作工况主要表现为水洞内壁的膨胀变形,在极限工况下主要表现为由地震载荷引起的水洞顶部水平位移;空泡水洞高应力区域主要位于结构角隅处的筒壁和加强筋。这对中国自主研发大型空泡水洞具有重要的借鉴意义。

基于不同标准的煤炭漏斗车车体焊缝疲劳寿命研究

利用接触非线性分析技术,基于AAR标准的名义应力法和ASME标准的结构应力法研究煤炭漏斗车车体焊缝的疲劳问题。首先,建立漏斗车重载车体强度分析模型,利用修正D-P本构模型的实体单元模拟散粒煤、接触单元模拟散粒煤与车体结构的作用,并通过主要载荷作用下车体静强度试验结果验证车体仿真分析结果,应力最大误差小于15%。其次,运用名义应力法,在标准和实测载荷谱下分析车体焊缝疲劳寿命,结果表明:端墙与端漏斗板焊缝寿命最短,为2.72×10^(6)km;基于标准纵向载荷谱的焊缝寿命小于基于实测的计算结果,表明标准的纵向载荷谱相对恶劣。最后,在标准中100t漏斗车重车心盘载荷谱和实测纵向载荷谱下运用结构应力法对车体焊缝进行应力与寿命分析。结果表明:基于结构应力法的焊缝疲劳寿命不及基于名义应力法的疲劳寿命,主要原因是结构应力法的疲劳性能参数适用于各类接头形式,且分析承载复杂焊缝时考虑了面内剪切结构应力的影响。因此,对接头几何形状和应力状态复杂的车体从板座及底架区域的焊缝建议采用结构应力法对其进行疲劳寿命分析。

飞机牵引滑行工况下前起落架疲劳寿命仿真分析

为使机场运行更加高效经济,提出一种由牵引车将飞机高速牵引滑行至跑道起飞端的新模式。在牵引滑行工况下,前起落架要承受长时间长距离的高速重载荷牵引,同时受牵引车的加速和制动特性的影响,可能导致前起落架疲劳寿命降低。于是,针对飞机前起落架在该工况下的载荷分析以及疲劳寿命验证十分重要。通过Adams软件建立多体动力学模型,模拟真实工况,对不同牵引滑行速度下的牵引车-飞机系统仿真,获取到前起落架的载荷谱信息。结合前起落架有限元模型静力学分析和载荷谱,通过频域寿命分析法,在nCode软件中计算得到前起落架的疲劳寿命。结果表明,高速牵引滑行工况产生的大载荷加剧前起落架疲劳损伤,疲劳损伤从减震支柱凸耳向下阻力臂延展,疲劳寿命缩短3个数量级,需要对前起落架下阻力臂进行结构优化。本文中的研究可以为新牵引滑行模式下前起落架的疲劳寿命结构优化提供参考。

全机疲劳试验几个问题的探讨

全机疲劳试验是规范要求的保障飞机结构完整性以及满足适航要求的大型、复杂以及持续时间长的地面验证试验。全机疲劳试验的几个重要问题,例如试验目的、载荷谱、持续时间和分散系数等,是飞机设计师/工程师非常关注和充分讨论的问题,其中的分散系数也是研究者研究较多的问题之一。针对近年来完成的多个飞机型号的全机疲劳试验,本文介绍了对上述几个问题的研究和认识,对比了国内外5种型号战斗机的疲劳设计与全机疲劳试验情况,提出了关于全机疲劳试验的工程实用的一些建议。本文的研究可以为其他飞机全机疲劳试验提供有益的参考。

基于损伤力学的矿用定向钻机金属结构寿命评估

针对ZYL-15000D型煤矿用履带式全液压定向钻机底座寿命评估,首先通过Q345B钢的脉动循环加载拉伸疲劳试验数据,拟合得到应力幅值和寿命的关系式,经由应力修正和安全系数的选取,转换得到对称循环下的应力幅值和寿命的关系式。结合基于损伤力学推导出的损伤退化模型,根据Q345B钢试验数据拟合确定损伤退化模型中的待定参数,将Q345B钢对称循环下应力幅值和寿命的关系式代入,得到Q345B钢的疲劳损伤退化模型。然后借助ABAQUS对钻机整机进行结构分析,得到钻机底座的危险点位置(即应力最大处),在该型号样机试验台上通过应变片测得钻机底座危险点处的应力—时间历程。最后采用雨流计数和应力修正,对测得的随机载荷谱进行处理得到雨流计数直方图(应力均值-幅值-循环次数),再转换为对称循环载荷的形式,代入确定的疲劳损伤退化模型中,评估钻机底座的疲劳寿命。

FGH96高温变幅疲劳载荷试验及损伤累积模型研究

针对涡轮盘用镍基高温合金FGH96,开展两级疲劳载荷试验以及谱载荷试验。试验载荷设计参考了涡轮盘关键点载荷及实测飞行任务谱特征。采用常见损伤累积模型对试验结果进行分析。结果显示,FGH96在低-高载荷次序下循环分数和大于1,在高-低载荷次序下循环分数和小于1,符合常见非线性疲劳损伤累积模型的预期;对于谱载荷的疲劳寿命,由Chaboche非线性疲劳损伤模型与时间分数模型组成的损伤累积模型的预测则偏保守,且具有较高的预测精度,预测结果均在2倍偏差带内。

强化坏路工况下冷却模块的加速耐久试验研究

提出一种加速疲劳试验功率谱编辑法。以某款商用车道路试验载荷谱为基础,通过分析各路况下的频域特征,结合冷却模块的计算模态结果,确认导致冷却模块失效的风险路况。基于采集的载荷信号计算得到各路况疲劳损伤谱分量,应用Miner线性叠理论获得总疲劳损伤,最终编辑生成台架加速试验用功率谱。通过对加速谱时域、幅值域和频域角度的对比,验证加速谱台架响应统计特征与原始谱的一致性。冷却模块的台架耐久试验表明,将振动量级提高1.85倍,通过57 h的台架试验模拟完成三种风险路段数百小时的道路试验。并复现道路试验的失效故障,验证其有效性。

基于差分进化算法的减速器齿轮参数优化设计

根据上海道路循环工况,利用载荷的随机连续性和20CrMnMo材料的低载强化特性进行减速器齿轮有限寿命的轻量化设计。基于线性损伤理论,分别计算编制载荷谱和连续载荷谱在低载强化效应下的疲劳损伤,将疲劳损伤约束在一定范围内为选取条件,以齿轮体积最小为优化目标,建立了齿轮有限寿命的轻量化优化模型,通过差分进化算法求解得到优化后的齿轮参数。实验结果表明,设计的模型可快速准确优化齿轮参数,在采用连续载荷谱和考虑低载强化效应时,优化的齿轮参数最小。优化的模型可移植性好,可直接迁移到其他变速系统零件的轻量化设计。

空间挠性作动器的可靠性验证试验方法

为了对空间挠性作动器在轨运行的可靠性进行评估,针对作动器在轨工况复杂、小子样、长寿命的特点,给出了作动器可靠性验证试验方法。首先,在分析作动器结构组成及工作原理的基础上,确定了作动器可靠性特征量。然后,以寿命型可靠性试验为基本思路,针对挠性元件在轨疲劳断裂失效这一主要故障模式,根据在轨典型工况载荷数据进行疲劳试验载荷谱设计,采用试验载荷谱开展挠性元件加速疲劳寿命试验,基于试验结果给出作动器的可靠性评估结果。最后,以某型号空间挠性作动器为例,基于挠性元件加速疲劳试验进行可靠性试验验证,得到作动器可靠性评估结果。研究结果表明,该作动器可靠度满足指标要求,评估结果符合工程实际。运用所提出的可靠性验证试验方法,可为空间挠性作动器在轨运行可靠性的定量评估提供有效的技术途径,可为航天器运动机构的可靠性验证提供参考。

商用车驾驶室虚拟迭代目标谱优化与分解

商用车驾驶室总成载荷谱是影响虚拟疲劳预测精度与计算效率的关键。本文探究了道路载荷谱采集与编辑、高保真动力学建模以及虚拟迭代等重点环节,以期从工程应用角度获取准确、高效的外联点时域载荷。首先,在试验场实车采集了驾驶室总成全路径道路载荷谱,考虑随机误差对原始数据进行归一化拆分并重组,得到统计性较强的试验场总损伤目标;然后,利用等效损伤原则优选出9段工况及其循环数,不仅将误差控制在10%以内,同时时效提高了75%;随后,结合实测减振元件的性能参数,建立了高保真驾驶室刚柔耦合动力学模型,并通过驾驶室7通道道路模拟台架验证了模型精度;最后,通过虚拟迭代完成了优选工况的载荷分解,迭代误差小于10%。基于上述优选并分解得到的外联点载荷,高效完成了驾驶室本体虚拟疲劳计算,并准确预测了驾驶室焊点失效情况,与道路模拟台架耐久试验结果有较高的吻合度,为商用车驾驶室的设计和优化提供了有力的技术支撑。