圆柱滚子轴承外圈双挡边磨削方式的改进

对圆柱滚子轴承外圈双挡边的磨削方式进行了分析。采用砂轮端面磨削方式易使挡边表面产生烧伤、划伤 ,而采用砂轮外圆磨削方式则可解决上述问题且可提高磨削精度 ,需注意 :砂轮的磨削角度应在 70°～ 80°之间取值     

CFX245型圆 柱滚子分选机

国内外轴承圆柱滚子分选机已有多种,但仅限于分选直径＜２０mm和长度＜４０mm的普通滚子。对于直径＜３０mm、长度＞５０mm圆柱滚子的分选,由于存在一定的难度,尚没有相应的自动分选机。如铁路机车和客车轴承,要求有较高的可靠性和安全性,滚子素线设计成有一定的凸度,滚子的端面设计成球面,对每组滚子的直径和长度尺寸差要求较严格。另外需要解决大型滚子尺寸自动分选中上下料磕碰划伤的问题。为了解决以上问题,我们为洛阳轴承（集团）公司研制了一台准高速列车用圆柱滚子高精度自动分选机,经过两年多的使用,取得了比较满意的效果…     

中大型轴承滚道超精工序端面划伤原因分析

针对中大型轴承外圈滚道超精过程中,出现端面支承划伤轴承端面的现象,根据端面划伤的分类以及划伤时机床的工作状态,对产生划伤的原因进行了分析。     

高速动车组车轮内孔纵向划伤的试验研究

高速动车组车轮在注油退卸时会出现内孔纵向划伤现象,为研究纵向划伤对车轮压装和退卸的影响,文中对内孔划伤车轮进行试验研究.根据试验数据得出,划伤深度＜ 0.25mm时,内孔划伤对车轮压装和退卸均无明显影响;划伤深度≥0.2mm时,车轮无法满足注油退卸要求.     

难加工材料的磨削

第五篇难加工材料的磨削划伤磨削划伤,是个比较新颖的问题,在通常情况下,往往被表面粗糙度所代替,对在正常工作条件下的普通零件,其影响并不明显,故磨削划伤易被忽视。但是,在磨削难加工材料中出现的划伤问题,却经常成为影响零件抗疲劳强度和耐腐蚀能力的主要因素,有时还会造成重大技术故障。因此,对难加工材料的磨削划伤问题,进行深入探讨是完全必要的。一、磨削划伤的形貌在已加工表面上形成不同于正常磨削纹路,较深的、独立的磨削划痕,称为磨削划伤。其划伤的方向     

高速动车组车轮检修技术研究

高速动车组车轮在退卸后会出现内孔划伤现象，目前暂无车轮内孔划伤标准，为保证车轮检修质量，上述划伤车轮需封存处理。为节约检修成本，本文对划伤深度和宽度与压装力的影响进行了理论分析，得出划伤深度对压装的影响。为验证理论的正确性，本文对划伤车轮进行了工艺压装试验，试验结果证明了理论的正确性。     

高速列车制动盘制动过程的有限元模拟及表面划伤对应力场的影响研究

在高寒环境下高速列车制动盘由于外界硬质颗粒随着冰雪包裹进入制动盘和闸片而导致划伤是制动盘的主要失效形式,因此对制动盘的制动过程进行有限元模拟分析有助于辅助研究和解决制动盘失效问题,而针对数值模拟划伤的产生对制动盘制动性能的影响规律国内外鲜有研究。采用ABAQUS软件中的子模型技术研究了划伤位置、深度和缺口角度对铸钢制动盘紧急制动过程中的温度场及应力场分布的影响。研究结果表明:在相同的缺口圆角半径下(r=0.1 mm),对制动盘最大等效应力的影响程度为划伤深度划伤位置缺口角度。最大等效应力随着划伤深度的增大而增加,但在划伤深度一定的条件下,最大等效应力对缺口角度的敏感度较低。在划伤处于半径为247.5 mm,缺口角度为30°,当划伤深度为3 mm时,最大等效应力超过常温时制动盘材料的屈服强度。     

压缩机滑片表面黑带成因分析

本文对压缩机滑片热处理后表面黑带的成因进行了分析,认为生产厂家的模具长期使用使其表面受损(如出现沟槽),在轧制或拉拔带材时划伤其表面从而在划伤处产生应力集中。在热处理过程中由于热应力和组织应力的作用,导致划伤部位产生大量的显微裂纹。     

液压油缸划伤的胶粘修复

500t液压油缸在工作中,螺帽松动掉入油缸内,造成两处划伤.一处划伤长度520 mm,宽3 ～4 mm,深0.6～1.2 mm;另一处划伤长度240 mm,宽2～3 mm,深0.4～0.8 mm.再度工作时,高压油液从密封圈与缸壁划伤部位的空隙中泄漏,无法达到额定工作压力,为了尽快修复液压油缸,采用超金属修补剂进行修复.过程如下:     

中大型轴承滚道超精工序端面划伤的解决方案

针对中大型轴承套圈端面划伤的具体原因,采取了增加端面支承修磨机构、改进压轮机构等措施,有效解决了超精工序的端面划伤问题。     

表面划痕对滚子润滑性能的影响

对滚子表面划痕对润滑性能的影响进行研究。研究表明,划痕两侧将产生压力和温度升高及膜厚跌落,划痕中部将出现压力和温度跌落及膜厚增加,并且这一现象随划痕深度和宽度的增加趋于剧烈,将恶化滚子的应力状态;与划痕深度比,划痕宽度对划痕两侧最小膜厚的影响不显著。     

Characteristics of SBR,Neoprene and EPDM compounds in a single-pass pendulum scratch

In this study, the effect of carbon black on the scratch and deformation characteristics of styrene–butadiene rubber (SBR), polychloroprene (Neoprene) and ethylene propylene diene monomer rubber (EPDM) were evaluated using single-pass pendulum scratch technique. The introduction of carbon black as a reinforcing agent tends to impart better scratch resistance characteristics to all rubber compounds except EPDM. The scratch mode was observed to change from brittle to ductile. The energy lost, average frictional force, scratch resistance and scratch damage response were found to be greatly influenced by scratch load and release angle of the pendulum.     

Tribological Behavior of New Martensitic Stainless Steels Using Scratch and Dry Wear Test

This paper focuses on the tribological characterization of new martensitic stainless steels by two different tribological methods (scratch and dry wear tests) and their comparison to the austenitic standard stainless steel AISI 316L. The scratch test allows obtaining critical loads, scratch friction coefficients, scratch hardness and specific scratch wear rate, and the dry wear test to quantify wear volumes. The damage has been studied by ex situ scanning electron microscopy. Wear resistance was related to the hardness and the microstructure of the studied materials, where martensitic stainless steels exhibit higher scratch wear resistance than the austenitic one, but higher hardness of the martensitic alloys did not give better scratch resistance when comparing with themselves. It has been proved it is possible to evaluate the scratch wear resistance of bulk stainless steels using scratch test. The austenitic material presented lower wear volume than the martensitic ones after the dry wear test due to phase transformation and the hardening during sliding.     

Scratch and normal hardness characteristics of polyamide 6/nano-clay composite

This paper investigates the scratch and normal hardness characteristics of polyamide 6/nano-clay composite. It is found that the weight percentage (wt%) of nano-clay greatly affects the scratch properties of the composite because of the intercalated structure of the nano-clay in the composite for higher clay loading. The scratch hardness, computed using the scratch width data, decreases while the scratch force increases as the wt% of nano-clay particles added into the composite increases. On the other hand, normal hardness increases and so do the yield strength and the elastic modulus when the percentage of nano-clay is increased in the composite. The SEM images show that the width of the scratch groove increases as the weight percentage of nano-clay in composite increases. However, the depth of the scratch groove indicates the opposite trend. Such contrasting behavior between the scratch hardness and other mechanical properties is explained based on the microscopic image study and the change in the nature of this nano-composite with increasing wt% of the nano-clay. Finally, important sources of error in the measurement of scratch hardness of these nano-composites are also highlighted.     

The study of the adhesion of a TiN coating on steel and titanium alloy substrates using a multi-mode scratch tester

A titanium nitride (TiN) coating was deposited by magnetron sputter ion plating onto steel and titanium alloy polished substrates. The adhesion of the coating on each substrate material was investigated using a newly developed multimode scratch tester. Progressive loading scratch tests, constant load scratch tests, multiple scratch tests in the same track and indentation tests were all performed. It was shown that the modified scratch tester can be used to identify not only coating detachment during progressive load scratch tests, but also other failure events such as cracking and cohesive damage to the coatings. By using the additional modes of operation, it was possible to study the fracture mechanisms in more detail i.e. chipping in the scratch track was cohesive for the TiN coated steel and adhesive for the TiN coated Ti alloy.     

Effect of stick-slip on the scratch performance of polypropylene

For the scratch process of polypropylene (PP), the stick-slip phenomenon always exists and contributes to the observed periodic surface damage patterns. The stick-slip, one main cause for scratch visibility, alters the surface characteristics of substrate and eventually induces scratch visibility. Both ASTM/ISO and Erichsen scratch test methods are employed to study the stick-slip phenomenon and its effects on scratch behavior of PP. Image analysis shows that the stick-slip phenomenon was responsible for material removal and severe surface damage. Possible solutions to improve the scratch performance of polymeric materials are also discussed in this paper.     

氧化锌晶须填充尼龙的划痕实验

用划痕测试方法测定了ZnOw填充尼龙1010复合材料的划痕系数和划痕过程中的声发射信号。结果发现,当ZnOw含量小于20%(质量分数)时,划痕系数随ZnOw的含量线性增加。纯尼龙材料在划痕过程中没有发生声发射事件,而复合材料的声发射振铃计数随ZnOw的含量线性增加。根据ZnOw的特殊空间结构,建立了其在尼龙基体的细观几何模型,并根据模型得出了划痕系数与晶须含量的关系。模型计算结果与试验结果相一致。     

Atomic-scale anisotropy of nanoscratch behavior of single crystal iron

In this paper a parallel molecular dynamics (MD) model has been developed to investigate the nanoscratch process of single crystal iron. The simulations were performed for two cases with different crystallographic orientations and scratch directions. In Case I the scratch plane is (1 0 0) and the scratch direction is [0 0 1]. In Case II the scratch plane and the scratch direction are (1,−1,2) and [1 1 1], respectively. To validate the MD simulation the nanoscratch testing was conducted using the TriboIndenter. The simulation results reveal that the vertical force and the lateral force tend to increase with the scratch displacement for both cases. Case I has smaller forces than Case II. However, the coefficient of friction for both cases is similar, which is in good agreement with the experimental value. The crystallographic orientation also affects the scratch hardness. The scratch hardness of Case I is smaller than that of Case II.     

Effects of normal load on single-pass scratching of polymer surfaces

The effects of normal load and the resulting scratch depth on scratch force profile, scratch hardness and the mechanisms of deformation and material removal for a number of industrially important polymers are studied. Upon scratching by a 30° angled conical tip, the mean tangential or scratch force is found to be linearly related to the normal load at lower speed (0.2 mm s⁻¹); however, at higher scratching speed (2.0 mm s⁻¹), there is a decrease in the slope of the scratch force versus normal load curve for all polymers. The phenomenon of stick-slip is severe at higher normal loads and scratch depths for the polymers that show ductile nature. The scratch hardness for softer polymers tends to decrease with normal load, whereas for harder polymers, scratch hardness increases for intermediate loads and tends to decrease at very high loads. The deformation mechanism, to a large extent, is insensitive to the imposed normal load or the depth of scratching; however, material removal and debris formation process depends upon the scratch depth.     

An experimental study of the scratch properties of poly(methyl methacrylate) as a function of the concentration of added slip agent

A scratch test was performed on poly(methyl methacrylate) (PMMA) material that had been optimised for electronic products. In this study, the scratch properties of PMMA containing various concentrations of slip agent were investigated by performing scratch tests under two different load conditions, i.e., a static normal load and a variable normal load. The effects of the concentration of slip agent on the scratch properties of PMMA were characterised by some key tribological parameters, based on a new standard test methodology. Additionally, the damaged surfaces of the specimens were investigated to understand the variations in scratch mechanisms.