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.

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.

Investigation on experimental load spectrum for high and low cycle combined fatigue test

As the outfield load spectrum is so complicated that it cannot be used directly for test study in laboratory.This paper presents a method to determine load spectrum for high and low cycle combined fatigue of turbine mortise at elevated temperature through experimental and numerical method.First of all,the low cycle load spectrum with duration time is determined through cumulative damage rule.The rain flow counting method is applied to obtain main cycles and sub cycles,and then the stress cycle is converted into pulsation cycle(stress ratio=0)based on the S-N curve and the Goodman curve;Secondly,three groups of different amplitudes tests are established to determine the high cycle amplitude.Finally,another three groups of the high-low combined cycle fatigue(HLCCF)tests for turbine mortise of a certain type engine are carried out.The results show that the macro and micro failure modes are identical with outfield's,which verifies the accuracy of the conversion method.

Effects of planting distance and depth on PTO load spectrum of a small riding-type transplanter

The aim of this study was to analyze the effects of the planting distance and depth on the power take-off(PTO)load spectrum of a small riding-type transplanter for the optimal design of the transplanter.To measure load data during actual planting operation,a load measurement system was developed using a torque sensor,a data acquisition system,and an inverter.Field experiments were conducted at four planting distances(26 cm,35 cm,43 cm,and 80 cm)and three planting depths(85 mm,105 mm,and 136 mm)in a field with similar soil conditions.The measured load data were inverted into a load spectrum using rain-flow counting and Smith-Watson-Topper(SWT)methods.The safety factor of a transplanter according to the planting conditions was analyzed using the converted load spectrum and commercial software.The load spectrum for all planting conditions showed torque ratios similar within a high cycle region of 108 to 109.The torque ratio increased when the planting depth increased and planting distance decreased in the low cycle region under less than 108 cycles.The safety factors of the PTO driving gear and the driven gear increased as the planting distance increased at all planting depths.When the planting depth decreased at the same planting distance,the safety factor of the PTO gears increased.The results of this study might provide useful information for a transplanter PTO design considering the working load according to the various planting conditions.

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.

基于旋转采样谱的海上风机叶片翼尖摆振特性评估

为了评估叶片旋转受风场作用的时频振动特性,本研究开展了基于旋转采样谱的海上风机叶片振动特性评估方法研究。以NREL-5 MW海上单桩风机叶片为研究对象,基于脉动风谱与旋转采样理论,对比分析了旋转风谱的能量扰动机制。然后,结合Prandtl叶尖损失修正和Grauert修正来评估叶片空气动力载荷,详细分析风机叶片翼尖在静止与运行状态下的摆振动力响应规律。结果表明,基于旋转采样谱的频域叶片翼尖摆振响应可准确表征风机叶片在运行状态下的1~3P(1~3倍风轮转动频率,0.2~0.6 Hz),同比湍流风作用的时域静态叶片摆振位移上限幅值增加42.21%,即考虑旋转效应对于叶片疲劳寿命评估具有重要工程价值。

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.

基于实测载荷谱的横向稳定杆连杆疲劳分析与优化

为解决某皮卡车横向稳定杆连杆疲劳断裂问题,以实测载荷谱为数据支撑,基于多体动力学载荷分解法进行连杆疲劳分析与结构改进。开展稳定杆连杆载荷谱采集试验,进行传感器信号之间的关联分析,验证了采集信号的有效性。通过悬架运动学与柔顺性(Kinematics Compliance,KC)试验,校验了悬架系统动力学模型传力的准确性,采用虚拟迭代法,以实测载荷谱信号为激励,验证了整车动态模型的精度。对比运用多体动力学载荷分解法、压杆失稳理论法、台架试验法3种方法分别获取连杆的临界载荷,对连杆强度进行校核,并与连杆实测载荷值进行对比,对3种方法准确性进行评价。结果表明,多体动力学载荷分解法能精准地预测连杆的临界载荷,而台架试验法结果存在一定误差,压杆失稳理论不能直接用于连杆的强度校核。结合名义应力法与多体动力学分解的载荷谱对连杆开展疲劳仿真与优化,仿真预测连杆疲劳里程数为12143 km,与真实寿命相对误差值为14%,证明了仿真方法的有效性,对连杆杆身端口危险部位进行结构改进,消除了连杆应力集中现象,使连杆设计寿命满足使用要求。

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.

基于道路载荷的副车架台架试验载荷谱编制研究

某轻型商用车在整车道路耐久测试中出现副车架开裂失效问题,针对该问题,采集控制臂球销处的道路载荷谱,按虚拟S-N曲线计算球销载荷谱的伪损伤,根据Miner线性疲劳损伤累积原则,计算得到球销处的全寿命损伤。选取合适的多级载荷幅值,并根据损伤等效原则,得到各级载荷幅值的循环次数。按照损伤等效计算得到的多级载荷谱对副车架和控制臂进行台架试验,台架试验结果复现了副车架的路试开裂问题,且失效台架失效模式、寿命与整车路试结果有很好的关联性。后续优化后的副车架用该多级载荷谱进行台架验证通过后同样通过了路试耐久考核。

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。

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。