车削参数和滚挤压参数对滚轮滚挤压表面质量影响分析

滚挤压是一种金属表面微塑性连续变形精加工工艺,现在日益被用作切削加工后的表面强化终处理工艺以获得具有压缩残余应力的高性能低粗糙度的镜面零件表面。本文分析了车削前处理工艺对后续滚挤压加工效果的影响,采用考虑交互作用的L27(313)正交试验设计与分析方法研究了车削滚挤压复合工艺中车削三要素(即车削速度v、车削进给量f、车削深度ap)和滚挤压三要素(即滚挤压速度vb、滚挤压进给量fb、滚挤压深度ab)对滚轮滚挤压45号钢的滚挤压效果(即表面粗糙度Ra、小负荷维氏硬度Hv的影响规律),其中考虑了对滚挤压效果影响最显著的车削进给量f、滚挤压深度ab与滚挤压进给量fb两两之间的交互作用,分析得出了对滚挤压效果影响最显著的主要因素及其规律。从试验的角度发现车削进给量对滚挤压效果有显著影响,与理论分析和预测相吻合。     

Investigating the Tribological Characteristics of Burnished Polyoxymethylene—ANFIS and FE Modeling

ABSTRACT

Polymers are utilized in numerous tribological applications because of their excellent characteristics; for example, accommodating shock loading and shaft misalignment. A high surface finish is required to ensure consistently good performance and extended service life of manufactured polymeric components. Burnishing is the best choice as a finishing process for this study due to its ability to increase hardness, fatigue strength, and wear resistance and also introduce compressive residual stress on the burnished workpiece. Due to the complexity and uncertainty of the machining processes, soft computing techniques are preferred for anticipating the performance of the machining processes. In this study, ANFIS as an adaptive neuro-fuzzy inference system was applied to anticipate the workpiece hardness and surface roughness after the roller burnishing process. Five burnishing variables, including burnishing depth, feed rate, speed, roller width, and lubrication mode, were analyzed. A Gauss membership function was used for the training process in this study. The predicted surface roughness and hardness data were compared with experimental results and indicated that the Gauss membership function in ANFIS has satisfying accuracy as high as 97% for surface roughness and 96% for hardness. Furthermore, the generated compressive residual stress on the burnished surface was studied by a 2D finite element model (FEM). The simulated results of residual stress were validated with the experimental results obtained from X-ray diffraction (XRD) tests.     

Prediction of surface characteristics obtained by burnishing

To reduce the irregularities of machined surface, burnishing is used as a finishing process by plastic deformation. This process does not only improve surface finish but also generates compressive residual stresses throughout the surface. In this work, an analytical study and a finite element modelling were performed to provide a fundamental understanding of the burnishing on an AISI 1042 workpiece. The analytical results were concentrated on the surface roughness and on some burnishing parameter effects. The simulations were devoted to the study of the surface profile, the residual stresses and the influence of burnishing parameters (penetration depth, feed rates, diameter of the ball of burnishing tool and initial surface quality) on surface roughness and the residual stress distribution. It has been noted that burnishing improves surface quality and introduces compressive residual stresses. These results were successfully compared to experimental data obtained in previous works.     

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%。     

Increasing the wear-resistance of steel components by ball burnishing

The influence of several parameters of ball burnishing such as the diameter of the ball, feed, burnishing load and initial surface finish on the surface finish, surface hardness and wear-resistance were investigated. The experiments were conducted with a ball burnishing tool used on a lathe. The burnishing load is the major factor affecting wear-resistance of the surface layer of burnished components. There is an optimum burnishing load which gives the best results.     

Finite element analysis and design optimization of low plasticity burnishing process

In the present study, Low Plasticity Burnishing (LPB®) process on the half-space specimen has been simulated using a 3D explicit nonlinear finite element model. The developed finite element model is then used to investigate the effect of main parameters including ball diameter, burnishing force, burnishing feed, and number of passes on the resultant profile of residual stress and plastic deformation. Due to high computational cost associated with the nonlinear finite element model and in order to practically conduct design optimization of the LPB process, the design of experiment combined with the response surface methodology has been used to develop smooth response functions to efficiently and accurately approximate the residual stress profile and plastic deformation over the entire design space. Finally in order to improve the LPB process, a design optimization using the developed response functions has been formulated to obtain the optimum set of parameters such that a deep residual compressive stress with small plastic deformation is generated throughout the thickness of component.     

Effect of a combined machining/burnishing tool on the roughness and mechanical properties

Burnishing is a cold working surface treatment process in which plastic deformation of surface irregularities occurs by exerting pressure through a very hard and a very smooth roller or ball on a surface to generate a uniform and work‐hardened surface. This treatment occurs generally after the machining process. In this study, a new combined machining/burnishing tool is designed and is fabricated. This tool allows for generating simultaneously the machining (turning) and the burnishing of the cylindrical surface using a turning machine. First, turned surfaces at different conditions, sketches, finishing and half finishing were performed using only the cutting tool. The evolutions of a surface roughness parameter and the technological time relative to every test condition have been investigated. Second, using the combined machining/burnishing tool at coarse conditions, the evolutions of the surface roughness and the technological time have been also investigated. A comparison among the parameters obtained under different machining conditions and those obtained using the combined machining/burnishing tool has been carried out. Moreover, the analyses of the layers obtained on the combined machined/burnished surface have shown that the burnishing process induces compressive residual stresses on the subsurface treated specimens. Copyright © 2013 John Wiley & Sons, Ltd.     

Ductility improvement of aluminum 1050A rolled sheet by a newly designed ball burnishing tool device

Conventional ball burnishing processes using a roller or a ball pressed against round or small flat surfaces have long been used to improve hardness, fatigue strength, and wear resistance of mechanical parts by plastic deformation. However, the treatment of large flat surfaces using conventional techniques is rarely considered because of its time consumption. In the present work, the optimal burnishing parameters of rolled sheets of aluminum 1050A are determined by means of a newly developed burnishing tool device especially designed to treat large flat surfaces with orders of magnitude reduction in burnishing time. Experiments were designed and performed on a machining center based on response surface methodology with central composite design. The burnished specimens were then tested to find the burnishing condition under which ductility was improved. This study has resulted in significant new insights into the effect of burnishing on the surface quality and workpiece properties of aluminum 1050A plates. A second-order mathematical model, validated using data obtained from atomic force microscopy, was developed to predict the surface roughness as functions of speed, force, and feed rate. The results indicate that burnishing of aluminum 1050A plates improves its ductility, but not its micro-hardness. Following the various burnishing conditions, the micro-hardness measurements range from 40 to 43?HV (50?g), indicating that there is little or no hardening. Although a moderate effect with varied degrees is found on the surface roughness as functions of the investigated parameters, the burnishing force has a significant effect on ductility. The results also indicate that lower values of roughness do not guarantee better ductility for aluminum 1050A plates. Furthermore, the effect of the burnishing loads on the residual stresses was found to depend on the feed direction.     

Ball burnishing of tool steel

In place of the traditional methods of finishing a surface, the ball-burnishing process was investigated. Experimental work was conducted on a vertical machining center to establish the effects of various burnishing parameters on the surface finish of ASSAB XW-5 steel (high-carbon, high-chrome steel), including burnishing speed, ball material, lubricant, burnishing forces (depth of penetration), and feed. Within the parameter space explored, it was found that the burnishing speed affects the surface finish, with a burnishing speed of 1,200 mm/min giving the worst surface finish. WC (Tungsten carbide) ball gave the best and most consistent surface finish. Grease was a better lubricant than cutting oil. By varying the burnishing speed, the burnishing forces varied also, and these forces showed no obvious relationship to the surface finish of the burnished workpiece.     

Stress in the surface layer of objects burnished after milling

This paper presents the effects of modeling the stress in the burnished layer of a complex spatial surface that was previously milled. A spatial kinematic-geometric model of the surface structure after milling is used. This paper presents the results of a numerical experiment on the synergic influence of the technological milling and burnishing parameters responsible for the final state of the geometric structure of a surface on the post-machining stress in the surface layer. The stress in the surface layer plays an important role because it is frequently responsible for the development of cracks, corrosion, and cavitation (in the surface area of injection aluminum molds, press tools, and core cutters). A proper understanding of the mechanisms responsible for the origin and development of residual stress will be conducive to the improvement of functional properties and longer tool life.     

滚挤压加工对颗粒增强铁基复合材料表面硬度的影响

研究滚挤压加工工艺对颗粒增强铁基复合材料表面硬度的影响,结果表明,滚挤压加工工艺在一定程度上改善了颗粒增强铁基复合材料的表面硬度.随滚压力及滚挤压次数的增加,表面显微硬度随之上升,而随进给量的增加,表面显微硬度变化的幅度减小.通过试验得出加工这种复合材料合理的工艺参数范围.     

Analysis and experimental investigation of a simplified burnishing process

A slipline field model of a simplified burnishing process is used to derive equations for estimating the burnishing force, the depth of the burnished layer and the plastic strains in this layer. A detailed comparison is made between predicted and experimental results. An observation of considerable practical interest is the high quality surface finish (low surface roughness) which can be obtained by the burnishing process described.     

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.     

Theoretical Investigation of the Influence of Combined Machining Modes on the Value and Character of Residual Stresses in the Surface Layer of Cylindrical Friction Pairs

In this paper, analysis of influence of residual stresses in the surface layer of cylindrical friction pairs on the operational wear resistance index is carried out. Stresses of the first kind after application of combined machining are investigated. Combined machining is consecutive electromechanical machining and diamond burnishing. A formula for calculation of residual stresses originating in the surface layer after the combined machining is obtained. For computational convenience, a computer program calculating the residual stress parameter is written in Visual studio 2017 C#. The combined machining method creates a potential for improving performance indices due to creation of compressive residual stresses.     

Investigating the surface quality of the burnished brass C3605—fuzzy rule-based approach

In this work, prediction of burnished surface roughness (R _a) is achieved by using a fuzzy rule-based system. The process state variables used were burnishing speed, feed, and depth. The fuzzy rule-based system has achieved an accuracy of 95.4 % to predict the burnished surface roughness and proved to be convenient in terms of least computational complexity and dealing with nonlinear data such as that obtained in this work.     

Finite element analysis of ball burnishing process: comparisons between numerical results and experiments

Ball burnishing is a surface enhancement process where a residual compressive stress is created in the surface layers of the workpiece. Several studies have been conducted on this process, but they are more concerned with the experimental aspect. So, there is still a real need for reliable numerical models that enable us to understand the mechanical behaviour of the workpiece during the process. These models also serve to optimise the studied process. Two-dimensional and three-dimensional finite element (FE) ball burnishing modelling is presented in this paper, where an elastic–plastic material model is assumed in the framework of the FE analysis. The pertinence of these models to predict residual stresses created by the process is discussed by drawing comparisons between simulation results and experimental data. The obtained results show that the three-dimensional FE model predicts the residual stresses and provides useful information on the effect of the process parameters.     

预应力切削钛合金的有限元分析

为揭示预应力切削对钛合金Ti6Al4V加工表面残余应力的调整机理,探讨切削时锯齿形切屑的形成过程,基于预应力切削原理建立了钛合金的预应力切削有限元模型,模拟了0、280 MPa和560 MPa这3种预应力下的锯齿形切屑形成过程以及已加工表面的残余应力分布。结果表明:采用预应力切削方法可以调整钛合金已加工表面的残余应力状态;预应力对锯齿形切屑的形成过程和切屑特征无明显影响;在材料弹性极限内施加越大的预应力,表面层残余压应力效果越显著,次表层最大残余压应力值越高,残余压应力层分布也越深。     

Experimental study on grinding-induced residual stress in C-250 maraging steel

Residual stress plays a significant role in the performance of a part, while the residual stress in the ground maraging steel, which is often used in the manufacture of precision parts, is rarely mentioned. In order to understand the variations of residual stress in ground maraging steel and provide insight into the controlled-stress grinding process of the steel, the surface and subsurface residual stress distributions in ground C-250 maraging steel (3J33) were studied. The results show that the mechanical effects dominate the thermal effects in the dry grinding process, indicated by only compressive residual stress generated in the ground workpiece. Furthermore, more insights into the residual stress distribution were provided by proposing four residual stress distribution parameters including surface residual stress, peak compressive residual stress, the depth of peak compressive residual stress, and residual stress penetration depth. The variations of these parameters were comprehensively studied. Results show that the surface residual stress and peak compressive residual stress depend greatly on the grinding speed and higher grinding speed generates larger compressive residual stress, while the depth of peak compressive residual stress varies slightly with the grinding parameters. The residual stress penetration depth increases with the increase of the grinding speed and grinding depth, and decreases with the increase of the workpiece speed. The results in this study can be used to assist in controlled-stress grinding applications for high performance critical parts of maraging steel.     

An investigation of surface roughness of burnished AISI 1042 steel

The aim of this study is to analyse the evolution of surface roughness finished by burnishing. Burnishing is done on a surface that was initially turned or turned and then ground.It has been noted that burnishing an AISI 1042 steel offers the best surface quality when using a small feed value. This finishing process improves roughness and introduces compressive residual stresses in the machined surface. So, it can replace grinding in the machining range of the piece.Also, an analytical model has been defined to determine the R_t factor in relation to the feed. Good correlations have been found between the experimental and analytical results.     

Study on strengthened layer of workpiece in prestress dry grinding

The prestress dry grinding which combines with prestress grinding and surface strengthening is an innovative approach to substitute conventional grinding process. The residual stress and the thickness of strengthened layer have an important effect on surface performance of workpiece. In order to analyze the effect mechanisms of prestress on residual stress and thickness of strengthened layer, experiment and simulation are carried on for 45 steel. The result of prestress dry grinding experiment shows that the grains in the strengthened layer are refined with increase of prestress. The thickness of strengthened layer tends to decrease first and then increase with increase of prestress. The simulation model of temperature field is created. The effect of temperature field on the thickness of strengthened layer and different grinding parameters especially the prestress on temperature field are analyzed. Then, the relationship between prestress and residual stress on different directions are analyzed. The variation curve of residual stress shows that tensile residual stress can transform to compressive residual stress on the surface of workpiece by controlling the prestress. Besides, compressive residual stress increase first and then decrease with the increase of depth.