超声滚压加工表面微织构的研究

为了研究超声滚压加工表面微织构工艺,选用45钢试样作为研究对象,分析了工艺参数包括滚压球直径、步距、静压力和进给速度对织构形貌及深度的影响,并对织构化后工件的表面性能进行了单因素实验.结果 表明,超声滚压工艺可以在表面制备稳定的织构,滚压球直径与步距对表面形貌影响较大,采用8 mm滚压球与0.2 m步距参数,能获得较为...     

不锈钢棒表面滚压加工工艺参数设计与研究

提出一种新的不锈钢棒表面滚压加工方式,使得滚压后钢棒的表面硬度和疲劳强度等机械性能得到提高,解决了传统加工方式中钢棒加工长度受机床床身限制这一难题.并对不锈钢棒表面滚压加工工艺参数进行了设计与研究,着重分析了各工艺参数对不锈钢表面质量及机械性能的影响.     

高强度耐磨铝青铜材料的滚压性能研究

在自行研制的气动滚压装置上,应用响应曲面法中的Box-Bahnken试验设计对高强度耐磨铝青铜材料的滚压性能进行了研究,分别建立了表面粗糙度、显微硬度与滚压参数(滚压力、滚压速度和滚压次数)的数学模型,分析了各参数对表面粗糙度和显微硬度的影响。试验结果表明该滚压装置能使铝青铜工件的表面质量由加工前的Ra2·02μm、HV201达到Ra≤0·12μm、HV330以上。最后根据试验结果对滚压参数进行了优化。     

ZK60镁合金表面滚压强化试验研究

试验研究了ZK60镁合金表面滚压加工中工艺参数对试件表面粗糙度、表面形貌、表面残余应力和表层显微硬度的影响,结果表明滚压力和重复滚压次数对试件的表面粗糙度、表面形貌以及表面残余应力和表层硬度影响程度较大,滚压速度影响较小。对精车ZK60镁合金试件进行滚压加工,试件表面粗糙度R a、R z最大减小了50.3%和48.1%;残余压应力最大可达-54.55 MPa;显微硬度从试件表层到内部基体材料逐渐降低,表层硬度值最大为92.83 HV 0.25,比基体材料硬度提高了15.32%。     

超声滚压载荷对25CrMo4车轴钢表面强化特征的影响规律

为了提高列车车轴的使用寿命,研究分析了不同强化处理后试样的表面形貌及其粗糙度、表层组织结构、表面硬度及其深度和表面残余应力,探索了滚压处理和不同载荷超声滚压处理对25CrMo4车轴钢表面强化特征的影响规律。结果表明：与磨削试样相比,滚压和超声滚压处理均改善了试样的表面粗糙度,其中低载荷超声滚压试样的表面粗糙度最低,达到了0.2μm;高载荷超声滚压试样的表层获得的塑性变形层最深;高载荷超声滚压试样的表面硬度值最大,达到了370 HV0.1,并形成了深度为150μm左右的硬化层;滚压试样和超声滚压试样表面均产生了较高的残余压应力。滚压和超声滚压处理使25CrMo4车轴钢表面硬度及硬化层深度的增加、产生较高的残余压应力和表面粗糙度的降低均会对其疲劳性能的提高产生有利的影响,特别是超声滚压处理的效果更佳。但过高的载荷会使车轴钢的表面粗糙度升高,从而对其疲劳性能的提高产生不利的影响。     

滚压强化对45钢螺纹根部表面完整性的影响研究

采用自制的基于普通车床CA6140的螺纹根部滚压强化装置对45钢螺纹试样进行滚压强化工艺处理。使用三维形貌测量仪、显微硬度计、X射线残余应力检测仪、超景深显微镜等检测设备,对滚压完成后的螺纹根部表面粗糙度、表层显微硬度、残余应力,表层显微组织等表面完整性参数进行检测。通过进行单因素试验,探究了螺纹根部滚压强化工艺参数对表面完整性的影响。45钢螺纹试样经过滚压强化工艺后,其螺纹根部的表面粗糙度S_a由1.71μm减小到0.874μm;螺纹根部形成了明显的晶粒细化层,深度达到了120μm;显微硬度由199.3 HV增加到379.5 HV,硬化程度N=90.4%;表层残余应力呈勺型分布,残余应力在距离表面105μm处达到峰值,为-542 MPa,残余压应力层深度可达700μm。研究结果表明：滚压强化技术可以显著提高螺纹根部的表面完整性,且滚压深度这一工艺参数对其的影响最为显著。     

表面超声滚压参数对轴承套圈表面性能的影响

为了研究超声滚压工艺参数对工业机器人轴承套圈表面性能的影响,选用目前工业机器人轴承常用材料为对象,选取主轴转速与静压力两个工艺参数进行试验,结果表明超声表面滚压加工对GCr15表面性能的提升具有很大的作用,其中表面粗糙度的提升随着主轴转速及静压力的增加而降低,但是静压力超过一定值时表面会产生裂缝,导致粗糙度增大;表面硬度提则随着静压力的增大而提高;表面残余应力在一定的静压力的情况下,会随着主轴转速的增加而降低。     

超声滚压工艺对6061铝合金表层特性的影响研究

为了系统地探究超声滚压工艺对6061铝合金表层特性的影响,设计了三因素三水平正交实验,分析在不同超声滚压加工参数(主轴转速、进给速度以及往复次数)下对工件表面粗糙度、晶粒尺寸以及表面硬度的影响.结果表明:工件的表面粗糙度随着不同加工参数的增加先降低后增大;工件的表面晶粒尺寸随着主轴转速和往复次数的增加先降低后变大,进给...     

球形滚压模型及参数相互作用分析

建立了球形滚压模型,考虑了工件的初始粗糙峰的力学性能、工件—工具接触面的几何形状、加工表面的实际状况以及初始加工表面粗糙峰尖端间距对滚压工具压力的影响。定义了滚压过程的特定参数对粗糙峰尖端滑移的影响,计算了在各种滚压条件下的粗糙峰尖端滑移和滚压力的最佳值,通过理论分析验证了分析结果。     

金属材料超声滚压表面强化的研究进展

超声滚压表面强化技术具有良好的光整特性,能够实现对被处理材料的表面改性,提高其综合性能,不同程度地克服了滚压、喷丸等传统工艺的缺陷,具有广阔的发展前景。本文介绍了超声滚压技术的加工原理,总结了目前国内外超声滚压技术的研究进展,指出其重点研究方向是将该技术应用于工程部件的表面强化与修复,并对超声滚压表面强化技术的研究趋势进行了展望。     

An Investigation of the Surface Topography of Ball Burnished Mild Steel and Aluminium

An experimental analysis was undertaken on ball burnished mild steel and aluminium using a purpose built burnishing tool. The analysis was designed to assess the effects of burnishing feed, force and speed and the number of tool passes on the surface roughness and surface hardness of a mild steel and an aluminium workpiece. In some cases, experiments showed that improvements of as much as 70% in surface quality were obtained when varying the mix of parameters.     

Effects of tool overhang on selection of machining parameters and surface finish during diamond turning

In precision machining leading to nano-metric surface finish, selection of the suitable machining parameters is a critical task. To ensure the desired surface quality, one needs to optimally select the machining parametric matrix. Towards this effort, this paper adds another critical parameter in terms of tool overhang. A well-defined set of machining exercises is carried out with different tool overhangs and machining parameters. In this investigation, an attempt has been made to locate the optimum range of tool overhang with minimum tool vibrations. The interaction between tool overhang with other parameters is also thoroughly investigated. Another important focus of this study is to find out the optimum machining parameters for the situations where it is not possible to select an optimum tool overhang. One such situation occurs when a steep concave parabolic surface needs to be fabricated. In this case a large tool overhang has to be selected. Power spectral density distribution analysis of surface roughness for different tool overhangs is performed to find out significant parameters and their degree of contribution to surface roughness. Analysis of variance is also applied to ascertain statistically significant factors contributing to surface roughness. To model the surface roughness, response surface methodology is being used. The model has been verified by conducting a series of experiments and a steep concave parabolic surface is developed by following the predictions of the developed model.     

A New Roughness Parameter Including Hardness and Contact Frequency Effects on Lubricated Rolling/Sliding Wear

Surface roughness, roughness arrangement, film thickness, material hardness, and run-in process have significant effects on the lubricated rolling/sliding wear of mechanical components such as gears and bearings. In conventional analysis, a film thickness parameter is calculated by a geometric approach to study the wear resistance of a contact system without considering the effects of material hardness and run-in process. Although the conventional parameter is simple, it does not correlate with some experimental observations. In this work, a new roughness parameter is developed for the prediction of lubricated rolling/sliding wear. Surface roughness will be adjusted by its hardness and contact frequency. The calculation results are consistent with four groups of experimental data. It is proved that the conventional models can be derived as a special case of the new model when two contact surfaces have the same properties. The new model can be used in the optimal design and manufacturing of mechanical interfaces to reduce lubricated rolling/sliding wear.     

OPTIMAL MACHINING CONDITIONS FOR TURNING OF PARTICULATE METAL MATRIX COMPOSITES USING TAGUCHI AND RESPONSE SURFACE METHODOLOGIES

The present investigation focuses on the influence of machining parameters on the surface finish obtained in turning of LM25 Al/SiC particulate composites. The experiments are conducted based on Taguchi's experimental design technique. In this work, the effect of machining parameters on the surface roughness is evaluated and optimum machining conditions for maximizing the metal removal rate and minimizing the surface roughness are determined using response surface methodology. A second-order response surface model for the surface roughness is developed to predict the surface roughness. The predicted values and measured values are fairly close to each other, which indicates that the developed model can be effectively used to predict the surface roughness on the machining of Al/SiC-MMC composites with 95% confidence intervals within the ranges of parameters studied.     

OPTIMAL MACHINING CONDITIONS FOR TURNING OF PARTICULATE METAL MATRIX COMPOSITES USING TAGUCHI AND RESPONSE SURFACE METHODOLOGIES

The present investigation focuses on the influence of machining parameters on the surface finish obtained in turning of LM25 Al/SiC particulate composites. The experiments are conducted based on Taguchi's experimental design technique. In this work, the effect of machining parameters on the surface roughness is evaluated and optimum machining conditions for maximizing the metal removal rate and minimizing the surface roughness are determined using response surface methodology. A second-order response surface model for the surface roughness is developed to predict the surface roughness. The predicted values and measured values are fairly close to each other, which indicates that the developed model can be effectively used to predict the surface roughness on the machining of Al/SiC-MMC composites with 95% confidence intervals within the ranges of parameters studied.     

线切割加工条件对模具零件表面粗糙度的影响

为改善快走丝电火花线切割加工的表面粗糙度,提高模具加工的质量和使用寿命,分析了快走丝电火花线切割加工条件中放电参数、工作液和电极丝对零件表面粗糙度的影响,并在此基础上提出了改善零件表面粗糙度的相应措施和方法。     

Investigation of the burnishing process with PCD tool on non-ferrous metals

It is well known that the no-chip machining process, burnishing, can easily improve surface roughness, waviness and hardness. To get the practical useful parameters, the effects of various burnishing parameters (spindle speed, depth, feed, burnishing radius and lathe) on surface roughness and waviness of the non-ferrous components were studied experimentally with a theoretical analysis. The experiments were conducted with a simply designed cylindrical surfaced polycrystalline diamond tool developed by us. It was found that smaller parameters do not mean lower surface roughness or waviness and different optimum burnishing parameters can be got under different burnishing conditions.     

不锈钢超细长轴表面滚压加工工艺参数研究

介绍了不锈钢超细长轴表面滚压加工工艺参数的选取,使得超细长轴的加工长度不在受到其缺点的限制,经过加工后可使表面硬度和疲劳强度等机械性能得到提高。并对加工出的超细长轴表面粗糙度进行详细的分析。     

Face Grinding Surface Quality of High Volume Fraction SiCp/Al Composite Materials

The existing research on SiCp/Al composite machining mainly focuses on the machining parameters or surface morphology.However,the surface quality of SiCp/Al composites with a high volume fraction has not been extensively studied.In this study,32 SiCp/Al specimens with a high volume fraction were prepared and their machining parame-ters measured.The surface quality of the specimens was then tested and the effect of the grinding parameters on the surface quality was analyzed.The grinding quality of the composite specimens was comprehensively analyzed taking the grinding force,friction coefficient,and roughness parameters as the evaluation standards.The best grinding parameters were obtained by analyzing the surface morphology.The results show that,a higher spindle speed should be chosen to obtain a better surface quality.The final surface quality is related to the friction coefficient,surface roughness,and fragmentation degree as well as the quantity and distribution of the defects.Lower feeding amount,lower grinding depth and appropriately higher spindle speed should be chosen to obtain better surface quality.Lower feeding amount,higher grinding depth and spindle speed should be chosen to balance grind efficiently and surface quality.This study proposes a systematic evaluation method,which can be used to guide the machining of SiCp/Al composites with a high volume fraction.     

Influence of milling strategy on the surface roughness in ball end milling of the aluminum alloy Al7075-T6

Surface roughness has an important role in the performance of finished components. End ball milling is used for achieving high surface quality, especially in complex geometries. Depending on the cutting conditions selected for ball end milling, different milling strategies can be applied. The produced surface quality is greatly affected from the selected milling strategy. The present paper examines the influence of the milling strategy selection on the surface roughness of an Al7075-T6 alloy. A number of cutting parameters are tested (axial and radial depth of cut, feed rate, inclination angles φ and ω) in order to perform 96 experiments and their results are processed using regression analysis and analysis of variance. All possible milling strategies are considered (vertical, push, pull, oblique, oblique push and oblique pull) and for each one of them, a mathematical model of the surface roughness is established, considering both the down and up milling. All models are statistically validated and experimentally verified, and can be used within the limits of the investigating cutting conditions. The polynomials produced are of the third order and the statistically most significant parameters are presented.