Friction and wear behaviour of AISI 5140 steel under rectangular wave loading conditions

Abstract

The tribological characteristics and wear mechanisms of AISI 5140 steel at ambient temperature were investigated using a home built ball on disc tribometer under constant normal loading and rectangular wave loading respectively. The worn surface and wear debris collected from the disc were studied using scanning electron microscope. Results show that the friction coefficients under the constant normal force correspond to the traditional theory. The coefficients all exhibited increased normal loads, whereas under the rectangular wave condition, the highest coefficient appeared when the peak value of the periodically alternative load was 90?N. The different underlying wear mechanism under different loading conditions was explored. It was found that abrasive wear was the main mechanism in the constant loading, whereas severe plastic deformation and adhesive wear were the main wear mechanism in the rectangular wave loading cases. This phenomenon can be attributed to the role of debris in the ‘lubrication’ process under the rectangular wave loading conditions.     

40Cr调质钢外圆磨削淬硬试验研究

采用外圆磨削方式对40Cr调质钢进行磨削淬硬试验,通过测量试样的金相组织和显微硬度对外圆磨削淬硬的可行性、磨削参数对淬硬效果的影响规律等进行研究。结果表明:40Cr钢外圆磨削淬硬是可行的;试样的表层组织由完全淬硬层、过渡层和基体组成;表面硬度均在690 HV左右,淬硬层深度最高可达1.10 mm;磨削深度对表面硬度无显著影响,但对淬硬层深度具有显著影响,工件速度和砂轮型号对表面硬度及淬硬层深度均无显著影响。     

Influence of temperature on the fretting response between AISI 301 stainless steel and AISI 52100 steel

Fretting of AISI 301 stainless steel sheet in contact with AISI 52100 steel from 20 °C to 550 °C in air and argon has been studied. Transitions in the mechanical properties of 301SS and oxidative behavior of this pair have been identified as a function of temperature. Strength and ductility of 301SS is reduced from 20 °C to 250 °C, increasing susceptibility to fretting damage. Steady state friction decreases as temperature increases, reducing cyclic stresses. Wear resistance increases in this temperature range, increasing fatigue damage due to the increase in fatigue life associated with increased wear. This study aims to identify the causes of the transitions in behavior and determine the net outcome of the competing effects with regard to fatigue damage.     

Erosion of AISI 4140 steel

The erosion behavior of AISI 4140 steel under various heat treatment conditions was investigated. A variety of microstructures, such as the primary and tempered martensites, varying proportions of martensite and bainite, cementite spheroids embedded in a ferrite matrix and ferrite and pearlite were obtained. The erosion tests were performed in a sand-blast-type test rig. Except in the region where temper embrittlement occurred, the erosion decreased with increasing tempering temperatures. Erosion decreased with the increasing percentage of bainite in the austempered condition and also with increasing tempering time during spheroidization. From the point of view of the mechanical properties, erosion decreased with increasing ductility and decreasing hardness or ultimate strength. The abraded surfaces were also studied using scanning electron microscopy.     

基于双目立体视觉的工业机器人在线温度补偿

工业机器人在工业现场进行连续高速作业过程中,电机发热和关节摩擦生热将导致机械臂本体温度升高,引起机器人末端定位漂移,严重影响机器人的重复定位精度和作业精度。针对制造现场的工业机器人,提出了一种基于双目立体视觉的温度误差在线补偿方法,并基于微分运动学和双目视觉原理构建了温度误差补偿模型。在机器人末端安装基准球,同时在基座附近固定视觉测量传感器,机器人完成作业循环之后,以不同的姿态带动基准球至传感器视场内进行补偿测量。此外,通过分析各关节参数随时间变化的规律,筛选出符合温度漂移规律的显著性参数进行补偿,有效降低了补偿测量次数和耗时。实验结果显示,补偿后机器人的重复定位精度可维持在±0.1mm的水平,能够显著改善制造现场工业机器人的作业精度,且整个补偿测量过程耗时10s左右。     

L-M神经网络的磨削淬硬参数预测

针对基于传统BP算法的神经网络训练中收敛速度较慢的缺点,提出一种基于L-M(Lev-enberg-Marquardt)算法的磨削淬硬层厚度预测,并开发了基于L-M算法的磨削淬硬神经网络预测系统.仿真结果表明:该系统模型显著缩短了训练时间,具有较高的准确性.通过网络训练和网络检验,得出该神经网络系统的预测值与实测值十分接近的结论,可充分证明L-M法BP神经网络对于磨削淬硬参教预测具有很好的效果.     

Dynamic error compensation for industrial robot based on thermal effect model

This paper analyses the kinematic parameters and the positioning accuracy of robot end effectors influenced by temperature factors. Temperature factors include robot self-heating and environmental temperature changes. This paper also builds the thermal distribution model and deformation model using finite element theory. A thermal compensation strategy is presented to validate the significant correlation between the robot kinematics parameters and previous thermal models mentioned above. It is convenient and suitable for industrial field. Thermal compensation is experimentally proved to adjust the position error of the end effectors by less than 0.1 mm.     

Experimental research on micro mill-grinding AISI 1045 steel with a cold spraying compound micro cutting tool

Journal of Mechanical Science and Technology - Micro mill-grinding is a novel compound machining process. This article presented a novel micro mill-grinding tool fabricated by cold spray...     

基于热喷涂的再制造技术研究综述

从热喷涂再制造工程中的发展及其种类、材料、加工工艺、被加工对象、应用方向等方面做简要介绍.     

基于负膨胀材料的光纤Bragg光栅温度补偿研究

伴随着光纤通信技术的发展,光纤Bragg光栅已成为光纤通信的基本元件.由于光纤Bragg光栅的中心反射波长λB随着环境温度的起伏而发生漂移,为光纤Bragg光栅的应用带来很大困难.本文用负热膨胀系数陶瓷粉末ZrW2O8对光纤Bragg光栅进行了温度补偿,取得了一定的补偿效果,为深入研究奠定了一定的基础.     

基于HEIDENHAIN数控系统主轴轴向热变形补偿技术

分析HEIDENHAIN数控系统实现机床热变形误差补偿的原理,介绍将其应用于数控机床主轴轴向热变形误差补偿的方法和步骤,以及一种自行设计PLC控制程序,识别温度变化过程,自动计算补偿值的原理和方法。经过在某大型加工中心上应用验证,证实基于数控系统的主轴轴向热变形补偿具有显著效果,并且通过识别温度变化过程控制补偿值计算方法具有更加稳定的效果。     

Abrasive wear behavior of boronized AISI 8620 steel

In this study, AISI 8620 steel was boronized using the solid state boronizing technique. Processes were carried out at the temperatures of 850, 900 and 950 °C for 2, 4 and 6 h of treatment. Abrasive wear behavior of the samples boronized at different temperatures and treatment durations have been examined. Using boronized and unboronized samples, abrasive tests were conducted using pin on disc test apparatus. 80 and 120 mesh aluminum oxide (Al₂O₃) abrasive papers were used in the abrasion experiments and the samples were subjected to abrasion under 10, 20 and 30 N loads. Boronized steels exhibited an improvement in abrasive wear resistance reaching up to 500%. Microstructures and wear surfaces of the samples were inspected using SEM microscopy. SEM examinations revealed that the thickness of the boride layer on the steel surfaces changes with changing process durations and temperatures. The presence of boride formed in the borided layer at the surface of the steels were determined by XRD analysis and microhardness values of the iron borides (FeB, Fe₂B) formed on the steel surface were found to be over 1600 HV.     

Sand-water slurry erosion of carburized AISI 8620 steel

The erosion behavior of carburized AISI 8620 steel for sand slurry service was investigated. The jet impingement type of test was used where sand slurry is directed at flat specimens to determine the erosion rates and mechanism of erosion. The effects of steel heat treatments, slurry velocities and particle concentrations on erosion rates were investigated.     

Magnetic abrasive finishing of hardened AISI 52100 steel

Surface finish has a vital influence on functional properties such as wear resistance and power loss due to friction on most of the engineering components. Magnetic abrasive finishing (MAF) is one of the advanced finishing process in which a surface is finished by removing the material in the form of microchips by abrasive particles in the presence of magnetic field in the finishing zone. In this study an electromagnet with four poles has been used which was found to give better performance in terms of achieving surface quality in lesser processing time. Voltage, mesh number, revolutions per minute (rpm) of electromagnet, and percentage weight of abrasives have been identified as important process parameters affecting surface roughness. The experiments were planned using response surface methodology and percentage change in surface roughness (??Ra) was considered as response. Analysis of experimental data showed that percentage change in surface roughness (??Ra) was highly influenced by mesh number followed by percentage weight of abrasives, rpm of electromagnet, and voltage. In this study, the least surface roughness value obtained was as low as 51?nm in 120?s processing time on a hardened AISI 52100 steel workpiece of 61 HRC hardness. In order to study the surface texture produced and to identify finishing mechanism, scanning electron microscopy and atomic force microscopy were also conducted. Shearing and brittle fracture of small portion of peaks of grounded workpiece have been found to be finishing mechanisms during MAF of AISI 52100 steel.     

基于模糊神经网络的数控机床热误差补偿技术研究

热变形误差(即热误差)是影响数控机床定位精度的重要因素之一.针对机床热误差具有非线性等特点,将模糊控制技术与神经网络技术相结合,提出一种基于模糊神经网络的数控机床热误差补偿技术.以MAKINO立式加工中心为对象,经过MATLAB仿真,结果表明模糊神经网络作为热误差的预报模型是理想的,具有较高的预报精度.     

Effect of MQL flow rate on machinability of AISI 4140 steel

Abstract

Many studies were performed about the influence of minimum quantity lubrication (MQL) technique on cutting performance in the literature, but there is no paper examining the effect of different MQL flow rates and cutting parameters on machinability of AISI 4140 material as a whole. In this study, the effects of different MQL flow rates and cutting parameters on surface roughness, main cutting force and cutting tool flank wear (VB), with great importance among the machinability criteria, and forming as a result of the machining of AISI 4140, were revealed. At the end of the experiments, it was determined that rise of flow rate affected main cutting forces positively to a certain extent; yet, it exhibited no significant effect on surface roughness, but reduced VB. Also, it was observed that both main cutting force and surface roughness increased with the increase of feed, while generally decreased with the increase of cutting speed. It was seen that flank wear was positively affected by the increase in flow rate; and this decreased with the increase in flow rate. R² values obtained as 99.8% and 99.9% for main cutting forces and surface roughness values modeled statistically with the help of quadratic equations, respectively.     

Precision radial turning of AISI D2 steel

This paper compares finite element model (FEM) simulations with experimental and analytical findings concerning precision radial turning of AISI D2 steel. FEM machining simulation employs a Lagrangian finite element-based machining model applied to predict cutting and thrust forces, cutting temperature and plastic strain distribution. The results show that the difference between the experimental and simulated cutting force is near 20%, irrespectively of the friction coefficient used in the simulation work (approximately 19.8% for a friction of 0.25% and 18.4% for the Coulomb approach). Concerning the thrust force, differences of about 22.4% when using a friction coefficient of μ?=?0.25 and about 56.9% when using the Coulomb friction coefficient (μ?=?0.378) were found. The maximum cutting temperature obtained using the analytical model is 494.07°C and the difference between experimentation and simulation methods is 15.2% when using a friction coefficient of 0.25 and when using the Coulomb friction only 3.1%. Regarding the plastic strain, the differences between analytical calculations and FEM simulations (for the presented friction values) suggest that the finite element method is capable of predictions with reasonable precision.     

Wear of AISI 4340 steel under boundary lubrication

Wear tests were conducted using AISI 4340 steel sliding on AISI 01 tool steel under boundary lubrication conditions. The AISI 4340 steel was heat treated to obtain different microstructures and hardness levels. The results indicated that the wear behavior depends on the heat treatment procedure. It was found that hardness alone cannot be used as a measure of wear and that the microstructure and other mechanical properties should also be used. Chemical reaction products containing phosphorus, sulfur and zinc were found on the wear surfaces lubricated with a fully formulated light oil containing zinc dithiophosphates. The chemically reacted film was nonuniform and consisted of patches 1–1500 μm in size. The larger patches were formed on the surface of steel with a pearlite-ferrite microstructure and resulted in a high wear rate. In contrast, the small patches and the thin blue and brown films were formed on the wear surface of tempered martensite steel and produced low wear rates.     

Finite element modeling of burnishing of AISI 1042 steel

The aim of this study is to analyze the evolution of surface roughness finished by burnishing. Burnishing is done on a surface that was initially turned or turned and then ground. In a previous work, we have defined an analytical model to determine the R_t factor of burnished surfaces in relation to the feed f, the material displacement δ and the roughness R_ti of the initial surface. δ has been calculated using the Hertz contact theory which supposes that the behavior of the workpiece material is elastic. Hence, in this paper, we have defined a finite element model in which the elasto-plastic behavior of the piece is taken into account to determine the material displacement δ. This model has also permitted the calculation of the residual stresses related to the macroscopic contact geometry. Good correlations have been found between experimental and finite element results when burnishing an AISI 1042 steel.     

基于MATLAB／Simulink的DVR同相位补偿策略的仿真研究

将电压定向控制应用于动态电压恢复器(DVR)控制中,结合负荷电压外环、滤波电容电流内环的双闭环控制策略对DvR的同相位补偿进行了研究.应用MATLAB进行系统仿真,结果表明该方法具有良好的动态性能与补偿效果.验证了控制策略的正确性、优越性与有效性.