拉刀刃口半径对拉削表面质量的影响

前言通常,在研究刀具磨损对被加工件表面质量的影响时,大都将后刀面磨损值VB的变化与表面质量的状况联系起来。然而,在拉削过程中,尤其在拉削速度较低时,VB值的变化极其缓慢,甚至不易觉察。而拉刀刃口半径ρ值却有相当明显的增长。据观察,拉刀在工作相当长的一段时间后(50mm长的工件,拉削600余次),才形成比较均匀的后刀面磨损带。     

巧改拉削冷却方式

在拉削零件的键糟时,采用原有喷嘴将冷却液喷淋在拉刀上,靠刀齿间存液自行冷却润滑,往往由于渗入量不足,影响冷却润滑性能,拉刀易磨损,工件表面质量及精度不能保证。     

Inconel718合金拉削加工硬化研究

分析了Inconel718合金拉削时,速度、齿升量、拉刀前角对拉削表面加工硬化的影响。试验结果表明,拉削表面加工硬化程度较大,是拉刀磨损的主要原因。     

新型发动机用高温合金拉削加工硬化研究

研究新型高温合金GH761拉削时产生加工硬化的现象和变化规律,这对研究GH761合金的实际应用和探讨拉刀磨损原因是非常必要的.主要分析了拉削速度、齿升量、拉刀前角、后角对拉削表面加工硬化的影响情况.试验结果表明:拉削表层加工硬化程度和深度都较大;是高速钢拉刀磨损的主要原因.     

拉孔表面质量分析

用拉刀拉孔可以获得较高的表面质量,但也常会出现一些问题,而尤以圆孔拉削最甚。由于拉孔时拉刀是通过工件内壁的紧紧包围而进行切削的,故表面质量上存在的一些问题,往往因不能直接观察切削情况而难以辨明其原因。通过实践证明,拉刀本身的制造质量是影响拉孔表面质量的主要因素。为便于控制拉刀制造和修磨质量,合理使用拉刀,以利提高拉     

圆孔拉刀设计方案综合分析

结合拉刀的制造与使用,从拉刀的刃磨角度入手,对拉刀关键参数进行了优化设计,达到提高拉削表面质量、延长拉刀使用寿命的目的。     

拉削GH761高温合金的刀具磨损试验研究

研究了拉削GH761高温合金时M42刀具的磨损情况,分析了拉削速度、齿升量、拉刀前角和后角对刀具磨损的影响;同时利用扫描电镜分析了刀具磨损机理,证实主要为机械磨损并略带有冷焊磨损。     

圆孔拉刀设计方案综合分析

结合拉刀的制造与使用，从拉刀的刃磨角度入手，对拉刀关键参数进行了优化设计，达到提高拉削表面质量、延长拉刀使用寿命的目的。     

新型圆孔拉刀

<正> 目前,圆孔拉削存在着质量不稳定、被加工表面粗糙度较差,常出现一些纵向带状区域,且拉刀寿命较短等问题。为此,我们设计了新型圆孔拉刀,并已用于生产,收到了明显的效益。新型圆孔拉刀的主要特点是:拉刀切削齿的首部为三角花键齿,后部为圆拉齿,不开分屑槽,或者仅在个别(1～3个)精切齿开窄分屑槽。我们知道,在拉削过程中,为了断屑,传统的拉刀齿上开出许多分屑槽,这些沟槽在拉刀的切削部分形成了后角很小的副切削刃。因而在主副切削刃的过渡区形成许多易损段(即转角),这些区段的磨损远远大于线型刃段的磨损,使加工表面质量变坏,并降低拉刀     

改进工艺,提高拉削表面质量

<正> 拉削表面质量的好坏,很大程度上取决于拉刀分屑槽的形状和角度;对于圆孔拉刀,这个问题的解决尤其重要。一般常见的拉削表面,其缺陷是鳞刺和犁沟,而鳞刺、犁沟形成的部分原因是由于拉刀刀齿,尤其是精切齿分屑槽尖角处后刀面磨损严重,使它的后角等于零度所致;目前采用磨分屑槽的工艺方法,使     

钢轨滚动磨损性能试验研究

在JD-1型轮轨摩擦试验机上研究了轴重与曲线半径对钢轨滚动磨损性能的影响。结果表明：轴重与曲线半径是影响钢轨磨损的主要因素。试样磨损量随着载荷的增加而增加,也随着曲线半径的减小而增加;试样表面磨损形貌随着载荷与曲线半径的改变而表现出不同的变化,其中大载荷和小曲线半径试验使钢轨试样磨损程度严重,表面容易产生较明显的塑性形变以及龟裂现象;制动力条件下滚动试样磨损更为严重。     

Assessment of flank wear and nose radius wear from workpiece roughness profile in turning operation using machine vision

Although literature on the measurement of flank wear and crater wear in single-point turning tools using machine vision is well documented, the study on the effect of nose radius wear on the roughness profile and dimensional changes of workpiece is less explored. The measurement of flank wear using the 2-D profile of the tool nose region or the roughness profile of the workpiece has also not been attempted in the past. In this work, the nose radius wear of cutting tools and roughness profile of turned parts in a lathe operation were measured using the machine vision method. The flank wear width VB_C in the nose area was determined from the nose radius wear using the tool setup and machining geometry. The nose radius wear was also determined from the roughness profile of the workpiece and used in calculating the flank wear width. Comparison between the maximum flank wear width VB_Cmax determined from the roughness profile and that obtained using a toolmaker’s microscope showed a mean deviation of 5.5%. This result indicates that flank wear can be determined fairly accurately from the workpiece roughness profile if the tool and machining geometry are known.     

Simulation of friction and wear in the contact between the valve bridge and rocker arm pad in a cam mechanism

In this paper the surface velocities obtained from a rigid body model are used to simulate friction and wear in the contact between the rocker arm pad and valve bridge in the cam mechanism of a diesel engine. The friction is simulated with two different friction models, a 3D brush model capable of handling transient conditions such as an varying normal load and varying surface velocities and a Coulombian friction model. The wear simulations are based on a generalised form of Archard's wear model.The results presented here show that both the maximum wear depths and the wear distributions are influenced significantly by the combination of wear pad radius and the position of the wear pad radius centre relative to the rocker arm bearing centre. A combination with wear pad radius of 20 mm and centre position of 5 mm is found to give the least wear depths on both the wear pad and the valve bridge. It is also seen that the contact between the wear pad and the valve bridge is mainly a sliding contact and that the transitions from sliding in one direction to the opposite are very rapid. The change of the surface shapes due to wear has a negative effect on the contact situation causing very high contact pressures.     

Analysis of mixed lubrication mechanism in metal-on-metal hip joint replacements

A simple mixed lubrication model has been developed to predict the asperity contact and wear for the metal-on-metal bearing couple for total hip joint replacements. It has been shown that the femoral head radius has a large effect on the predicted asperity contact and wear depending on the lubrication regime. An increase in the femoral head radius can lead to an increase in wear under a predominantly boundary lubrication regime, but this trend can be reversed under a mixed lubrication regime towards fluid film lubrication. These observations are consistent with the recent experimental findings from hip simulator studies by Smith and co-workers.     

飞轮轴承许用磨损寿命估算算法

在轴承拟静力学法和轴承磨损理论基础上建立了飞轮轴承磨损寿命估算模型,分析了轴承预紧力、转速和结构参数对轴承磨损特性的影响并进行了试验验证。结果表明:轴承磨损寿命随着预紧力和沟道半径的增大而增加,当增加到一定值后,随其增大而减小;随着转速增大,磨损寿命降低,当转速较低时,转速对轴承磨损寿命影响较大,转速较高时对磨损寿命影响变小。     

钛合金高速铣削刀具磨损机理和预测方法研究

钛合金的加工非常困难,刀具磨损严重。为了尽可能减小刀具磨损,在高速铣削状态下能预测刀具的耐用度,本文研究了在高速铣削钛合金时刀具磨损的机理,并提出了一种基于切削试验的刀具磨损预测方法,建立了粗、精加工两种状态下刀具磨损预测数学模型,研究了顺逆铣方式、刀尖圆弧半径对刀具磨损的影响。     

平面拉刀磨损有限元分析

拉削加工过程中,刀齿在切削力、热耦合作用下较易产生磨损。由于高速拉削技术的发展,拉刀刀齿前刀面的磨损逐渐引起了更多的关注。随着拉削的进行,刀齿的磨损量不断增加。通过有限元分析,确定了拉削速度、齿升量、刀尖圆弧半径对前刀面磨损带深度和宽度的影响。     

高速铁路小半径曲线钢轨磨耗影响因素分析

随着高速铁路运营里程的增大和运量的激增,钢轨磨耗成为不容小觑的问题,尤其在小半径曲线段钢轨磨耗更为复杂和严重。针对高速铁路小半径曲线段钢轨磨耗问题,利用SIMPACK多体动力学软件建立高速动车组车辆动力学模型,利用Archard磨耗模型计算钢轨磨耗深度,并分析不同运营工况、车轮磨耗状态及车辆一系悬挂参数和轨道参数对动车组车辆通过小半径曲线时钢轨磨耗的影响。仿真结果表明：动车组车辆以匀速、制动、牵引3种工况下通过曲线段时,制动工况下钢轨磨耗量最大,牵引工况下磨耗最小;车轮踏面磨耗加剧也会导致钢轨的磨耗量增大,而定期镟修车轮踏面可以减轻钢轨磨耗情况;车辆一系悬挂参数的变化对小半径曲线段钢轨磨耗的影响相对较小;为减小钢轨磨耗,宜采用较小的轨底坡和适当增加轨距,且曲线段超高设置不宜过大。     

Effect of Flank Wear on the Topography of Machined Surfaces

The effect of flank wear on the topography of machined surfaces is investigated by studying its effect on the shape of the tool nose. For this purpose, turning experiments were performed to produce surfaces corresponding to different levels of flank wear. The distribution of flank wear at the tool nose during these experiments caused the nose radius to decrease, which when replicated on the machined surface resulted in narrower and deeper feedmarks. This change in the geometry of feedmarks was represented by the increase in the arithmetic average roughness of the surface profile heights.     

[轮轨磨耗及预测]弹性车轮作用下低地板有轨电车轮轨磨耗研究

为研究使用弹性车轮的车辆踏面以及运行弹性车轮的钢轨磨耗情况,基于Archard磨耗模型建立了轮轨磨耗预测模型,对不同轨道不平顺条件、不同曲线半径条件下的车轮踏面以及钢轨磨耗情况进行了分析。对比分析弹性车轮和刚性车轮,结果表明：在线路较差的情况下,弹性车轮具有更好的降磨效果;弹性车轮在曲线半径较小的线路上对磨耗的降低效果较小,随着曲线半径的增大,弹性车轮的降磨效果明显;运行弹性车轮时比运行刚性车轮时钢轨的最大累积磨耗量减小了33%;弹性车轮对曲线钢轨磨耗有一定的降低作用。