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.

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.

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.

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.

Simulating Study of Dynamic Load Spectra Identification Method of Machinery in Cepstrum Domain

Based on the platform of Matlab and the theory of digital signal processing, we propose a method in the cepstrum domain for dynamic load spectra identification of machinery. We demonstrate that the dynamic load spectra can be identified from the response signal of the system, based on cepstra. An ARMA model is built based on the harmonic retrieval by high-order spectra. The coefficients of a Green function are determined and the window width can be estimated. Finally the effectiveness of the method is validated by simulation results.

Numerical Simulation on Dynamic Load of Main Bearing of Tunnel Boring Machine Based on Combination Stratum

The load spectrum of the main bearing of tunnel boring machine( TBM) is difficult to establish because of the complex factors affecting the driving load of tunneling. In this paper, a simulation model of dynamic load of cutterhead is established,with a view to structural features and special conditions, based on a complex combination stratum, the cutter layout model and cutterhead control parameters,and it is a dynamic load boundary of the main drive bearing. Combined with the load distribution calculation of the main bearing and Hertz contact theory, the prediction model of dynamic load spectrum of the main drive bearing is completed during tunneling,and in accordance with the predicted results,the static and dynamics characteristics of load spectrum for the main drive bearing on the thrust and tilting moment are analyzed. The results of cutterhead load show that,in the certain complex stratum, the fluctuations of load for thrust rollers can reflect formation interface information of complex stratum in current tunneling. The main drive bearing bear the thrust and overturning moment of cutterhead under the composite,the external load has a greater influence on the load-spectrum of reverse thrust roller than that of main thrust roller,and the maximum contact stress of the two row roller is almost the same. The load spectrum,obtained by this method,can provide a meaningful reference for the design and checking of the main drive bearing,and also can be the basis of its fatigue reliability.

Probabilistic Tolerance Method for Omitting Small Fatigue Loads

The simplification of fatigue load spectrum,which can effectively reduce experimental cost,is of great importance for structural fatigue tests.By introducing random variables,the probabilistic tolerance method of removing small amplitude cycles proposed in this paper takes into account the randomness of both load and fatigue limit.The probability of the damage occurrence caused by the removed small loads is calculated to ensure that it cannot exceed the given probabilistic tolerance.Accordingly,the omission level is obtained and the truncated spectrum is formed.The unnotched aluminum sheet specimens are used to perform the fatigue test on the original fatigue spectrum and truncated fatigue spectrum of a transporter.The test results show that there is no statistical difference between the test life of the truncated spectrum and that of the original spectrum,which demonstrates the validity of the small-load-omitting method that considers randomness.

Study of Load Modeling Technology on Hardware-in-the-Loop Simulator of Gun Servo System

A hardware-in-the-loop (HWIL) simulator for gun servo system is described in this paper, and its load modeling technologies,such as road spectrum model,sea wave model are studied. The simulation results show that the models can be used in HWIL and satisfy the requirements of hardware-in-the-loop simulator of gun servo system.

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。

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。

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。

基于虚拟迭代法的跨座式单轨车辆车体疲劳分析

跨座式单轨车辆的车体作为列车的主要承载部件,其疲劳强度对列车的安全运行起着至关重要的作用。为提高单轨车体疲劳分析精度,模拟出单轨车辆运营实践中车体的疲劳损伤,对单轨车辆车体进行柔性化处理,建立包含柔性车体的跨座式车辆刚柔耦合动力学模型,采用虚拟迭代法,在车辆特征部位施加白噪声作为初始输入激励,以跨座式单轨车辆线路实测加速度为目标信号,对车辆模型仿真响应谱与试验实测响应谱进行系统识别与反复迭代,获取车体与车辆其他部件连接位置处激励谱。基于虚拟迭代激励谱获取高精度载荷谱,根据线性疲劳损伤理论对跨座式单轨车辆车体开展疲劳损伤与寿命分析,提出车体结构改进方案。分析结果显示:疲劳仿真结果与车体实际损伤位置具有良好的一致性,验证了采用虚拟迭代法获取的车体载荷谱开展的疲劳分析结果具有高精度;结构改进方案使车体结构改进位置处寿命提高了191%。

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。

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。

基于移动荷载谱的高速铁路简支梁桥基频限值分析

控制桥梁振动响应是保证高速列车安全稳定运行的关键,遵循梁体不发生共振或较大位移响应的原则,提出了简支梁桥基频限值频域分析法。首先基于移动荷载列模型,通过傅里叶变换得到了桥梁振动响应谱和移动荷载谱,并从时域角度验证了谱的正确性;然后通过引入间跨比γ和无量纲速度κ,探究了在不同移动荷载列作用下桥梁自由振动发生最大位移响应时,无量纲速度κ和间跨比γ之间的关系;其次根据γ-κ关系曲线分析了24 m、32 m、40 m简支梁桥最大位移响应下的无量纲速度κ;最后为了避免列车激励下桥梁发生共振或较大位移响应,参考国际铁路联盟基频限值规范,基于移动荷载谱给出了移动荷载列在不同设计时速下24 m、32 m、40 m简支梁桥基频限值建议值。研究表明:移动荷载幅值谱与时域计算的桥梁自由振动位移幅值响应规律一致;单节车长25 m左右的移动荷载列以共振速度激励桥梁时,24 m、32 m简支梁桥自由振动都能达到最大位移响应,而40 m简支梁桥仅产生较大位移响应,且在列车运营速度范围内达不到产生最大位移的条件;桥梁基频限值随着列车时速的增加而增大,当最大设计时速400 km/h时24 m、32 m、40 m简支梁桥基频建议下限值分别为6.00 Hz、4.94 Hz、5.66 Hz。

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。