基于nCode的挖掘机动臂疲劳寿命分析

疲劳失效是挖掘机工作装置的主要失效形式,现基于某种特定型号的挖掘机为基础,针对挖掘机动臂的疲劳寿命,本文运用有限元分析和疲劳软件n Code Design_Life相结合的分析方法得出挖掘机动臂的疲劳寿命分析结果。在分析过程中,首先通过ANSYS的APDL语言建立挖掘机动臂的参数化三维模型并得出有限元静态分析结果,然后确定载荷谱和动臂的材料参数,最后基于S-N疲劳分析方法,在疲劳分析软件n Code Design_Life中得出动臂的疲劳损伤云图和寿命云图,确定挖掘机动臂容易疲劳失效的部位,为挖掘机工作装置的设计提供依据。     

载荷特性对挖掘机动臂的性能影响分析

为了分析载荷特性对液压挖掘机动臂疲劳寿命的影响,利用有限元软件ANSYS建立某型号液压挖掘机的实体模型,在建模过程中工作装置的回转平台、动臂、斗杆和铲斗在销轴连接处建立非线性接触模型,较为真实的模拟力的传递作用,考虑载荷特性的不同(偏载和侧载作用),进行有限元计算,得出动臂的应力分布情况,分析动臂结构疲劳失效的原因,为挖掘机工作装置的结构改进提供参考。     

轮式装载机动臂疲劳寿命评估分析

以装载机动臂为研究对象,通过装载机动臂关键危险部位的动态实际作业测试,并利用雨流计数法获取危险点的应力谱和载荷谱,根据Mine疲劳损伤线性叠加原理,得到动臂载荷谱的等效载荷并评估动臂的疲劳寿命。这为制定装载机关键构件的在线监测、疲劳寿命台架加速试验及再制造等方面的研究提供了理论支持和一些合理的建议。     

基于ANSYS的液压挖掘机动臂失效分析与改进

针对液压挖掘机动臂前支座开裂故障，运用ANSYS疲劳分析模块对失效件进行有限元分析与结构优化。通过强度校核分析结果发现，挖掘机动臂油缸支承端头处存在应力集中，属于疲劳断裂危险区域。通过制定优化方案，结合焊接工艺验证、有限元静强度综合分析，选取最优方案，对动臂失效部分实施优化改进。     

装载机动臂薄弱点的应力分析

装载机动臂是工作装置的主要受力构件,其结构强度设计经校核计算都能得到保证,但有时局部的细节设计不当也会引起大的故障。借助于PATRAN／NASTRAN有限元分析软件,以装载机动臂为研究对象,对动臂上3个容易出现故障的细节位置进行线性静强度应力分析后发现,故障处均存在应力集中的现象。对应力集中处的结构进行改进与分析,对改进前后的有限元分析结果进行对比,结果表明装载机动臂的工作寿命与可靠性得到提高,说明细节结构设计在强度设计中具有重要作用。     

基于等效结构应力法的叉臂疲劳寿命研究

根据剪叉式高空作业平台有限元计算结果,提出在叉臂铰点处加贴板的优化方案,并基于等效结构应力法预测优化后叉臂的焊缝疲劳寿命,同时开展台架疲劳试验研究.研究结果表明:在叉臂铰点处加贴板的优化方案能明显降低结构应力,优化后叉臂的疲劳寿命满足要求;等效结构应力法能较为准确地预测焊缝疲劳寿命.     

基于NCODE-designlife的挖掘机关键部件寿命分析

本文利用ansys有限元和N-code疲劳分析软件分析了液压挖掘机斗杆处的应力分布与疲劳状况。首先对挖掘机斗杆进行建模,然后选择合适的材料参数和实验所得载荷谱,最后选用了S-N疲劳分析引擎和有限元静态分析,评估了斗杆的寿命状况并得出了以下结论 :斗杆疲劳寿命最薄弱的地方在斗杆与动臂的铰接处,这与实际情况是相符的。     

CHUY320型强夯机动力学计算

CHUY320型强夯机在实际运用过程中，臂架起臂工况和重锤突然释放工况的载荷条件比较复杂，给强度校核与疲劳评估带来困难；为了确定其载荷条件、弹簧选择是否满足要求、各部件之间的相互作用力等，特建立动力学模型，通过数值仿真计算获得动态载荷及各部件之间相互作用力，弹簧的压缩量及受力等，为弹簧的选型，整机的疲劳寿命分析提供载荷谱及结构优化提供理论依据。     

基于参数优化方法的挖掘机动臂轻量化设计

摘要：以某液压挖掘机动臂为研究对象,运用有限元分析软件ANSYSWorkbench建立动臂参数化模型,并对其结构进行静力学分析。选取动臂参数化模型中主要设计参数作为结构轻量化设计的优化变量,利用优化软件OptiSLang对结构进行优化设计。以动臂总质量最小为优化目标,在保证结构具有足够刚度和强度的条件下,寻求最优设计方案,使动臂结构具有最佳承载形式,并通过对优化后的动臂结构进行刚度及强度校核,验证该优化方案的可行性。     

液压挖掘机动臂结构优化分析

作为液压挖掘机关键承载结构件,动臂结构在使用过程中承受频繁交变载荷作用,若局部结构设计不合理则容易出现疲劳失效问题,严重影响整机使用寿命。本文基于某型号液压挖掘机动臂结构疲劳开裂现象,采用有限元法作为主要分析手段,以抗疲劳失效作为评判准则,对动臂结构受力特点进行研究,指出该结构疲劳失效问题产生的根源在于应力集中现象突出,并据此提出针对性改进方案。通过对比应力云图可知,改进方案可降低制造成本,并能有效消除应力集中,其理论疲劳寿命符合设计要求。     

混凝土泵车臂架疲劳载荷谱研究

混凝土泵车臂架工况繁多,获取泵车臂架疲劳载荷谱对臂架疲劳分析具有重要意义。进行混凝土泵车臂架多工况载荷谱采集试验以获取载荷谱,并进行雨流分析,统计处理,通过假设检验获取载荷谱分布规律。根据载荷谱对臂架造成的损伤进行整合编制,同时考虑载荷谱作用顺序效应和相互作用效应,提出一种全寿命载荷谱编制的方法。利用该方法编制载荷谱进行疲劳分析计算,并与实际故障信息作对比,所得计算结果与实际故障吻合。     

Fatigue life prediction of heavy mining equipment. Part 2: Behaviour of corner crack in steel welded box section and remaining fatigue life determination

Frequent fatigue failure of mining equipment has created a need for fatigue life prediction of several components that suffer from frequent recurrence of fatigue cracking. The focus of this paper is the frequent occurrence of fatigue cracks in the boom of cable shovels, which consists of a twin box girder joining together near both extremities. After the determination of load spectrum and the material fatigue properties by field monitoring and material testing, the fatigue behaviour of a cracked shovel boom was investigated. Two-tip corner cracks were of particular interest since they are commonly observed in the field. These cracks typically initiate in the flange at the toe of web to flange or flange to diaphragm welds and propagate into the web. Detailed finite element models with corner cracks were developed for the boom and stress intensity factors for various crack configurations were evaluated from the finite element analysis results. The growth behaviour of corner cracks was studied and a simplified method is presented for the fatigue life prediction. Fracture toughness tests were conducted on single edge notch bend specimens at room temperature and low temperature (−50 ^°C). The remaining life of a cracked boom is then determined based on brittle fracture or unstable crack growth.     

塔式起重机水平吊臂双吊点位置优化

塔式起重机水平吊臂双吊点位置对吊臂在工作工况的应力分布、位移均产生较大的影响，本文采用ＳＵＭＴ优化方法，吊臂简化为杵架结构，结构计算采用了ＡＤＩＮＡ分析软件，用拟合二次抛物线构造目标函数，求得以吊点的最优位置。     

重型采矿设备的疲劳寿命预测第一部分：疲劳荷载评估和裂纹发展速度试验

重型采矿设备的疲劳寿命预测十分重要。首先,对早已存在有慢性疲劳裂纹的铲矿机起动臂进行现场监测,从监测数据中归纳了吊杆的载荷范围。针对试验数据,建立吊杆的有限元模型来预测其压应力和应变。进行了8个裂纹发展速度试验,获得使用材料的疲劳特性。     

具有伸缩液压缸的起重机伸缩臂之整体稳定性

起重机伸缩臂通常由多级不同截面尺寸的筒式臂节套接而成,由内置液压缸驱动并承受轴向力,伸缩臂本身并不直接承受轴向力,因而不应以阶梯柱模型计算其整体稳定性.建立涉及伸缩液压缸支撑作用的多节伸缩臂稳定性分析模型,给出相应的欧拉临界力解析表达式,并将之与阶梯柱模型的解进行比较.比较结果表明:在液压缸不首先失稳的条件下,涉及伸缩液压缸作用的伸缩臂之欧拉临界力大于阶梯柱模型的欧拉临界力.     

Fatigue life prediction of heavy mining equipment. Part 1: Fatigue load assessment and crack growth rate tests

Frequent fatigue failure of heavy mining equipment has created the need for fatigue life prediction of its cracked components. As the first step, field monitoring of a cable shovel boom that had a history of chronic fatigue cracking was conducted. A set of load spectra for the boom was constructed from the collected field data. A finite element model of the boom was prepared and calibrated against the test data to predict the stress and strain histories. Eight crack growth rate coupon tests were carried out to obtain the fatigue properties of the material used. Constant amplitude equivalent stress ranges were calculated based on Palmgren-Miner’s cumulative damage rule and crack growth rate tests results.     

Investigation of fatigue resistance of fillet-welded tube connection details for sign support structures

Stiffened and unstiffened fillet-welded tube-to-transverse plate connection details are widely used for mast-arm and base-plate connections for highway sign structures. However, due to repetitive wind loads, cyclic fatigue stresses are induced and they are the primary source of failure in welded connections at these locations. The resistance of fatigue critical details has been an on-going research topic because of limited experimental results and the variability in existing fatigue testing results. The main objective of this study is to evaluate fatigue resistance of fillet-welded tube connection details by utilizing the advanced fatigue tool in ANSYS Workbench platform. Finite Element (FE) models development and model validation using existing test data was presented. The resulting fatigue resistance from FE analysis was expressed in terms of fatigue life, fatigue damage, and fatigue safety factor to determine the fatigue performance of fillet-welded connections. Existing fatigue test data was grouped to perform a synthetic analysis and then analysis results were provided to determine input data and fatigue limit for the fatigue module. The local stress level at fatigue critical locations was evaluated using a static FE model for different number of stiffeners and boundary conditions. The results of this investigation provides fatigue resistance of fillet-welded connection details in the form of fatigue life, fatigue damage and safety factor for various connection parameters and structural conditions.     

Fatigue analysis of long-span suspension bridges under multiple loading: Case study

Long-span suspension bridges are often subject to multiple types of dynamic loads, especially those located in wind-prone regions and carrying both trains and road vehicles. Fatigue assessment shall be performed to ensure the safety and functionality of the bridges. This paper proposes a framework for fatigue analysis of a long-span suspension bridge under multiple loading by integrating computer simulation with structural health monitoring system. By taking the Tsing Ma Bridge in Hong Kong as an example, a computationally efficient engineering approach is first proposed for dynamic stress analysis of the bridge under railway, highway and wind loading. The fatigue-critical locations are then determined for key bridge components, and databases of the dynamic stress responses at the critical locations are established. The time histories of dynamic stresses induced by individual loading during the design life of the bridge are generated based on the databases. The corresponding stress time histories due to the combined action of multiple loading are also compiled. Finally, fatigue analysis is performed to compute the cumulative fatigue damage over the design life of 120 years. The results indicate that it is necessary to consider the combined effect of multiple loading in the fatigue analysis of long-span suspension bridges.     

扒杆施工技术在高速公路桥梁架设中的应用

对扒杆施工技术作了简单介绍,从施工、受力分析及计算等方面探讨了扒杆施工技术在桥梁架设中的应用,并总结了扒杆使用过程中的安全注意事项,解决了高速公路桥梁架设难题。