Estimation of die service life for a die cooling method in a hot forging process

Dies may have to be replaced for a number of reasons, such as changes in dimensions due to wear or plastic deformation, deterioration of the surface finish, breakdown of lubrication, and cracking or breakage. In this paper, die cooling methods are suggested to improve die service life with regards to wear and plastic deformation in a hot forging process. The yield strength of die decreases at higher temperatures and is dependent on hardness. Also, to evaluate die life due to wear, a modified Archard’s wear model has been proposed by considering the thermal softening of die expressed in terms of the main tempering curve. This paper describes the effects of die cooling methods such as cooling hole and direct spray cooling on the life of finisher die during the hot forging of an automobile part. It is shown that the cooling hole method during hot forging is necessary for an effective die service life to be obtained.     

提高热锻模具使用寿命的有效途径

正火预处理可以细化原始组织和碳化物 ,可使 5Cr Mn Mo钢在临界温度加热淬火 ,提高其强韧性 ,减少脆裂现象发生。经生产验证 ,正火预处理是提高 5Cr Mn Mo钢热锻模具使用寿命的有效途径之一     

基于Deform的刮板锻造工艺及模具设计研究

刮板由于其较复杂的结构,在模锻过程中常存在折叠、局部填充不足、欠压及裂纹等缺陷.实践表明,锻造过程中坯料与模具温度的控制不当、坯料与毛边槽设计不够不合理,导致金属流动困难是造成缺陷的主要原因.借助有限元仿真软件Deform,通过对刮板模锻成型的模拟分析,可以提供金属材料流动、模具填充、毛坯与模具温度变换等工艺分析数据.研究表明,Deform软件的应用,可有效地避免锻造缺陷的发生、提高材料利用率、减少试锻次数,对此类锻件的生产有很强的参考价值.     

A study on the forging of gear-like components

This paper describes kinematically admissible velocity fields for forging of gear-like components such as involute spur gear, trapezoidal spline, square spline, serration and trochoidal gear. Half pitch of each gear-like component was divided into several deformation zones with respect to their tooth profile. A neutral surface has been used to represent the inward flow of material during a forging operation by using a hollow billet with a flat punch. By using the suggested kinematically admissible velocity fields, the power requirements were successfully calculated and they were compared with experimental inspections. As a result, the suggested velocity fields are shown to be useful to predict the forging load. The contour of neutral surface varied with the number of teeth.     

应用修正的P-S-N曲线计算齿轮疲劳寿命

疲劳破坏是机械结构的主要破坏形式之一,准确预测机械结构工作疲劳寿命至关重要.一般的线性损伤累积理论忽略了高频率低疲劳应力所引起的构件疲劳损伤,致使预测结果与实际寿命相差很大.为准确确定双圆弧齿轮的疲劳寿命,提出以修正的材料P-S-N曲线为基础,采用传统的名义应力法和Miner法则估算双圆弧齿轮的疲劳寿命,计算结果表明该方法可行,为预估螺杆泵的井下工作寿命提供了参考依据.     

汽轮机叶片精锻模具预补偿方法研究

针对汽轮机叶片加工精度要求高、精锻模具误差补偿难度大以及加工效率低等问题,以某型号汽轮机叶片为例,利用DEFORM-3D数值模拟软件分别对叶片精锻模具Z=5 mm叶根截面、Z=35 mm叶身截面以及Z=75 mm叶尖截面在不同锻压步数下的弹性变形进行了模拟分析,得出精锻模具型腔曲面变形规律。基于数值模拟结果,提出利用反向迭代补偿与黄金分割相结合的方法来修正精锻模具型腔。以该汽轮机叶片最大允许误差80μm为迭代目标,采用黄金分割法调整迭代区间,对各迭代点进行仿真,确定最优修正系数为0.94,最后得到满足终锻叶片精度要求的合理模具型腔,大大提高了模具设计质量与效率。     

300MN模锻水压机提升管道液压冲击仿真分析

针对300MN模锻水压机加压.提升过程中提升管道液压冲击较大的问题,建立水压机水路系统的AMESim仿真模型,设定加压-提升过程主分配器轴角度由170°～5°的变化时间t为1、0.5、0.3、0.1s,仿真分析提升管道中液压冲击值为27.8、89.6、100.5、146.8bar,并得出加压一提升过程主分配器轴角度由170°～5°的变化时间、提升管道压力、以及工作缸压力之间的关系.分析结果表明:加压-提升过程主分配器轴角度由170°～5°的变化时间缩短将使工作缸卸压不充分,引起提升管道较大的液压冲击.     

Fatigue life estimation of MD36 and MD523 bogies based on damage accumulation and random fatigue theory

Bogies are one of the multifunctional parts of trains which are extremely subjected to random loads. This type of oscillating and random excitation arises from irregularities of the track including rail surface vertical roughness, rail joints, variance in super-elevation, and also wheel imperfections like wheel flats and unbalancy. Since most of the prementioned sources have random nature, a random based theory should be applied for fatigue life estimation of the bogie frame. Two methods of fatigue life estimation are investigated in this paper. The first approach which is being implemented in time domain is based on the damage accumulation (DA) approach. Using Monte-Carlo simulation algorithm, the rail surface roughness is generated. Finite element (FE) model of the bogie is subjected to the generated random excitation in the first approach and the stress time histories are obtained, and consequently the fatigue life is estimated by using the rain-flow algorithm. In the second approach, the fatigue life is estimated in frequency domain. Power spectral density (PSD) of the stress is obtained by using the FE model of the bogie frame and the fatigue life is estimated using Rayleigh technique in random fatigue theory. A comprehensive parametric study is carried out and effects of different parameters like the train speeds and level of the rail surface vertical roughness on the estimated fatigue life are investigated. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Davood Younesian received his MSc and PhD in Mechanical Engineering, both from Sharif University of Technology, Iran. He joined the Iran University of Science and Technology in 2005 as an Assistant Professor in the School of Railway Engineering. Dr Younesian’s research area is mainly focused on non-linear and random vibrations, optimal control of vibrations, dynamics and vibration of structures and railway vehicle systems. He has published more than 75 papers in international journals and conference proceedings in the areas of his research. Ali Solhmirzaei received his BSc in Railway Engineering (Rolling Stock) from Iran University of Science and Technology and his MSc in Mechanical Engineering from K.N.T University of Technology, Iran. His research is mainly focused on finite elements, railway vehicle dynamics and fatigue analysis of railway structures. Alireza Gachloo received his BSc in Railway Engineering (Rolling Stock) from Iran University of Science and Technology, Iran. His research is mainly focused on random vibration, railway vehicle dynamics and random fatigue.     

工程结构钢疲劳寿命分散性评价方法

随着可靠性应用研究工作的深入,材料试验结果不可避免存在的分散性处理日益受到人们的重视,特别是工程结构钢的疲劳寿命数据的可靠性评价已经引起人们的关注。本文针对常见的工程结构材料的疲劳寿命数据,采用威布尔三参数法进行处理并对数据处理中的问题进行探讨,得到了一种快速计算材料疲劳寿命可靠性评价方法,该方法有助于小样本试样结果的精度提高,从而可以节省试验时间和费用。     

Prediction of the film thickness for the normal approach of a rigid sphere towards a thin soft layer

A semi-analytical solution to the problem of the squeeze film between a rigid sphere and a thin soft layer attached firmly to rigid foundation is presented. It is assumed that the shapes of the solids are the same as the elastically deformed shapes under the unlubricated conditions (the Grubin’s approximation). Formulae for the variation of the film thickness with time are presented in the full range of Poisson’s ratio using two different pressure boundary conditions. It was found that only the magnitude of the film thickness predicted for an incompressible layer (ν=0.5), is influenced by the type of the pressure condition considered in the analysis.     

Inverse determination of the loading source of the infinite beam on elastic foundation

The primary aim of the paper is to identify the loading source of infinite beams on an elastic foundation from given information of vertical deflection of infinite beams. An integral equation is obtained for the relationship between loading distribution and vertical deflection. It is shown that the inverse identification of a loading source is one-to-one but ill-posed. Because of ill-posedness, the usual numerical schemes produce arbitrarily large errors. A method for the solution is proposed by using Tikhonov’s regularization. L-curve criterion is introduced for the determination of optimal regularization parameter. Numerical experiments show that the present methodology is accurate and robust in the inverse determination of loading source. This paper was recommended for publication in revised form by Associate Editor Joo Ho Choi T. S. Jang, the corresponding author of the paper, is by birth a Korean, with Naval Architecture and Ocean Engineering Ph.D degrees from Seoul National University, who worked at the department of Naval Architecture and Ocean Engineering in Pusan National University from 2003 until now. His main field of research has been the optimization theory, water wave motion and inverse problem with special focus on ocean-related fields     

Suitability of CAE neural networks and FEM for prediction of wear on die radii in hot forging

Prediction of tool wear in hot die forging along the entire arbor radius by wear models known so far is a very difficult task. On these parts of tools significant changes of contact pressure and sliding lengths occur along the die curvature during the plastic flow of material formed. A new approach presented in the paper combines the use of a conditional average estimator neural network (CAE NN) with the exploitation of results obtained by the finite element method (FEM) and also data from other sources. Consequently new parameters as well as the results of experimental work can be taken into account. In this paper a brief overview of models for prediction of tool (die) wear are discussed. The theoretical background of CAE NN, as well as its application to the modeling of the tool wear phenomenon, is presented. Some results of FEM analysis of the hot forging process that serve as input parameters in the CAE NN model are also briefly discussed. Two relevant practical applications are shown. In the first example, tool wear was modeled at a higher number of strokes (blows), by knowing wear at a lower number of strokes. In the second example, the number of strokes was the output parameter—the number of strokes causing predetermined wear at any point of the tool engraving curvature (arbor radius) was predicted. A comparison between the measured and predicted values of wear demonstrated good agreement that was assessed by a corresponding coefficient of determination.     

基于Matlab的现役港口起重机剩余寿命估算

考虑到Matlab在数值计算、图形数据转换等方面的优点,这里以它为计算平台,并采用名义应力法估算出一现役港口起重机的剩余疲劳寿命,为其日后服役期间的定期安全检查、维修决策提供参考依据.     

基于MSC.Fatigue的捡膜弹齿疲劳寿命分析与优化

应用MSC. Fatigue疲劳分析软件,对捡膜弹齿进行强度和疲劳寿命分析,得到捡膜弹齿的应力云图和疲劳寿命云图,通过仿真分析,找出捡膜弹齿折断的原因,并进行优化,为捡膜弹齿的设计提供理论依据.     

A study of spur gear pitting formation and life prediction

In this study, a numerical prediction on pitting formation is carried out in spur gear made from austempered ductile iron. General two-dimensional rolling sliding contact situations are considered for the development of the analytical model. The problem is assumed under linear elastic fracture mechanics and the finite element method is used for numerical solutions. Mixed mode stress intensity factors K_I and K_II for cyclic loading are evaluated and related to crack extension by a Paris-type equation. The maximum tangential stress criterion is used to determine the crack-turn-angle during crack propagation under cyclic loading.A series of experimental study is also carried out to determine the pitting formation life. Test specimens were first austenitized in salt bath at 900 °C for 90 min after which they were quenched in salt bath at 325 and 425 °C, for 60 min. A comparison is carried out between numerical and experimental results.     

可重构卫星锂离子电池剩余寿命预测系统研究

针对卫星锂离子电池剩余寿命预测问题,提出一种基于FPGA的可重构卫星锂离子电池剩余寿命预测系统设计方法.首先利用具备不确定性表达能力的相关向量机实现锂离子电池的RUL预测,进而采用FPGA动态重构技术,实现了基于相关向量机的预测算法的嵌入式计算,解决了核函数矩阵和矩阵求逆的计算方法和结构设计等关键问题,为解决硬件计算资源有限条件下的机器学习算法计算问题提供了一种新颖的思路.实验结果表明,在与PC平台保持相近计算精度的条件下,利用FPGA实现的剩余寿命预测计算效率提升了4倍,同时证明了机器学习的可重构计算方法在嵌入式计算体系中的应用具有良好的前景.     

A study on the forging of spur gears

In this paper, the forging of spur gears have been analysed by using the upper-bound method. The tooth profile of the gear consists of an involute curve and a circular arc shaped fillet. A kinematically admissible velocity field is newly proposed. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, addendum modification coefficient and friction factor on the forging of spur gears. Some forging experiments were carried out with Al-2024 to show the validity of the analysis. Good agreement was found between the predicted values of the forging load and those obtained from the experimental results.     

Comparative study on tool life and wear resistance of titanium nitride (TiN) and aluminium chromium nitride (AlCrN) coated carbide inserts

Abstract

The objective of this study is to investigate the enhancement of tool life and wear resistance with a physical vapour deposition (PVD) process applied using aluminium chromium nitride (AlCrN) and titanium nitride (TiN) coating on carbide inserts. Flank wear experiments are carried out on a computer numerically controlled (CNC) machine under wet conditions with both the coated inserts. Effectiveness of the coating on the tool life and its resistance to flank wear are observed at various cutting parameters such as cutting speed and feed rate by following the principle of design of experiments (DOE). It is inferred that AlCrN coated carbide tools perform nearly 70% better than the TiN coated carbide tools under high cutting speed and feed rate. AlCrN coating also enhances the durability of tool for metal cutting and thereby improves tool life even under harsh cutting conditions. A response surface methodology (RSM) is utilised to arrive at the optimum value for the various parameters which are responsible for improving the wear resistance and tool life.     

基于可靠性评价的超高压压缩机二段出口螺栓疲劳寿命预测

超高压压缩机螺栓在交变载荷作用下,会产生疲劳失效破坏.对两种工况下超高压压缩机二段出口螺栓进行了受力分析、断裂分析、疲劳分析与剩余寿命评估;利用裂纹扩展速率与螺栓的临界裂纹尺寸对含缺陷的超高压压缩机二段出口螺栓两种工况下疲劳寿命进行了预测,为设备的诊断维护提供了合理的依据.     

基于Hypermesh的汽车驱动桥壳有限元分析与疲劳寿命预测

驱动桥壳是汽车中的重要部件,应具有足够的强度、刚度以及疲劳寿命。基于CAD/CAE一体化技术,首先利用CATIA软件建立了某轻型汽车驱动桥壳的三维实体模型,虚拟装配后,导入Hy-permesh中建立以3D实体单元为基本单元的有限元模型,并以MSC.Nastran为求解器,通过模拟相关行业标准规定的台架试验及典型工况,得出驱动桥壳强度与刚度满足要求;最后,通过建立驱动桥壳S-N曲线,将有限元结果导入MSC.Fatigue进行模拟台架疲劳试验,得到桥壳整体的疲劳寿命分布,结果表明驱动桥壳疲劳寿命满足要求,验证了设计的合理性。