A study on the effects of vibrations on the surface finish using a surface topography simulation model for turning

In this paper, a surface topography simulation model is established to simulate the surface finish profile generated after a turning operation. The surface topography simulation model incorporates the effects of the relative motion between the cutting tool and the workpiece with the effects of tool geometry to simulate the resultant surface geometry. It is experimentally shown that the surface topography simulation model can properly simulate the surface profile generated by turning operations. The surface topography simulation model is used to study the effects of vibrations on the surface finish profile. It is found that the vibration frequency ratio is a more important vibration parameter than the vibration frequency on the characterization of the surface finish profile. The vibration frequency ratio is the ratio between the vibration frequency and the spindle rotational speed.     

Statistical analysis of surface roughness and cutting forces using response surface methodology in hard turning of AISI 52100 bearing steel with CBN tool

The present work concerns an experimental study of hard turning with CBN tool of AISI 52100 bearing steel, hardened at 64 HRC. The main objectives are firstly focused on delimiting the hard turning domain and investigating tool wear and forces behaviour evolution versus variations of workpiece hardness and cutting speed. Secondly, the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and machining output variables (surface roughness, cutting forces) through the response surface methodology (RSM) are analysed and modeled. The combined effects of the cutting parameters on machining output variables are investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters with respect to objectives (surface roughness and cutting force values). Results show how much surface roughness is mainly influenced by feed rate and cutting speed. Also, it is underlined that the thrust force is the highest of cutting force components, and it is highly sensitive to workpiece hardness, negative rake angle and tool wear evolution. Finally, the depth of cut exhibits maximum influence on cutting forces as compared to the feed rate and cutting speed.     

An improved cutting force and surface topography prediction model in end milling

During the milling operation, the cutting forces will induce vibration on the cutting tool, the workpiece, and the fixtures, which will affect the surface integrity of the final part and consequently the product's quality. In this paper, a generic and improved model is introduced to simultaneously predict the conventional cutting forces along with 3D surface topography during side milling operation. The model incorporates the effects of tool runout, tool deflection, system dynamics, flank face wear, and the tool tilting on the surface roughness. An improved technique to calculate the instantaneous chip thickness is also presented. The model predictions on cutting forces and surface roughness and topography agreed well with experimental results.     

Experimental investigation of effects of cutting parameters on surface roughness in the WEDM process

The experimental study presented in this paper aims to select the most suitable cutting and offset parameter combination for the wire electrical discharge machining process in order to get the desired surface roughness value for the machined workpieces. A series of experiments have been performed on 1040 steel material of thicknesses 30, 60 and 80 mm, and on 2379 and 2738 steel materials of thicknesses 30 and 60 mm. The test specimens have been cut by using different cutting and offset parameter combinations of the “Sodick Mark XI A500 EDW” wire electrical discharge machine in the Middle East Technical University CAD/CAM/Robotics Center. The surface roughness of the testpieces has been measured by using a surface roughness measuring device. The related tables and charts have been prepared for 1040, 2379, 2738 steel materials. The tables and charts can be practically used for WEDM parameter selection for the desired workpiece surface roughness.     

Tool wear and machining performance of cBN–TiN coated carbide inserts and PCBN compact inserts in turning AISI 4340 hardened steel

PCBN is the dominant tool material for hard turning applications due to its high hardness, high wear resistance, and high thermal stability. However, the inflexibility of fabricating PCBN inserts with complex tool geometries and the prohibitive cost of PCBN inserts are some of the concerns in furthering the implementation of CBN based materials for hard turning. In this paper, we present the results of a thorough investigation of cBN plus TiN (cBN–TiN) composite-coated, commercial grade, carbide inserts (CNMA 432, WC–Co (6% Co)) for hard turning applications in an effort to address these concerns. The effect of cutting speed and feed rate on tool wear (tool life), surface roughness, and cutting forces of the cBN–TiN coated carbide inserts was experimented and analyzed using analysis of variance (ANOVA) technique, and the cutting conditions for their maximum tool life were evaluated. The tool wear, surface roughness, and cutting forces of the cBN–TiN coated and commercially available PCBN tipped inserts were compared under similar cutting conditions. Both flank wear and crater wear were observed. The flank wear is mainly due to abrasive actions of the martensite present in the hardened AISI 4340 alloy. The crater wear of the cBN–TiN coated inserts is less than that of the PCBN inserts because of the lubricity of TiN capping layer on the cBN–TiN coating. The coated CNMA 432 inserts produce a good surface finish (<1.6 μm) and yield a tool life of about 18 min per cutting edge. In addition, cost analysis based on total machining cost per part was performed for the comparison of the economic viability between the cBN–TiN coated and PCBN inserts.     

Influence of the direction and flow rate of the cutting fluid on tool life in turning process of AISI 1045 steel

High-pressure coolant (HPC) delivery is an emerging technology that delivers a high-pressure fluid to the tool and machined material. The high fluid pressure allows a better penetration of the fluid into the tool–workpiece and tool–chip contact regions, thus providing a better cooling effect and decreasing tool wear through lubrication of the contact areas.The main objective of this work is to understand how the tool wear mechanisms are influenced by fluid pressure, flow rate and direction of application in finish turning of AISI 1045 steel using coated carbide tools.The main finding was that when cutting fluid was applied to the tool rake face, the adhesion between chip and tool was very strong, causing the removal of tool particles and large crater wear when the adhered chip material was removed from the tool by the chip flow. When cutting fluid was not applied to the rake face, adhesion of chip material to the face did occur, but was not strong enough to remove tool particles as it moved across the face, and therefore crater wear did not increase.     

Effect of simultaneous surface modification process on wear resistance of martensitic stainless steel

In order to improve the wear resistance of martensitic stainless steel, a surface treatment system was developed that combines high-frequency induction heating (IH) with fine particle peening (FPP). In this system, a compressed air spray from the FPP nozzle rapidly cools the specimen surface, which is heated by the IH system. The specimen surface can be simultaneously modified by work hardening and quenching. Vickers hardness and retained austenite measurements were conducted to characterize the surface-modified layer generated by the developed process. Surface microstructures were also observed by scanning electron microscopy (SEM) and optical microscopy. The process created a surface with a high hardness and an extremely fine-grained microstructure. The fine-grained microstructure was generated by dynamic recrystallization. The process reduced the amount of retained austenite in the surface layer because it increased the precipitated chromium carbide content. Reciprocating sliding wear tests were conducted to evaluate the wear resistance of the surface. The specimen modified by the developed process exhibited higher wear resistance than specimens that had only been quenched. This implies that the developed simultaneous process can significantly improve the wear resistance of steel surfaces.     

Improving surface integrity in orthogonal machining of hardened AISI 52100 steel by modeling white and dark layers formation

In machining of hard parts, surface integrity is one of the most specified customer requirements. Often, the major indications of surface integrity are surface roughness and residual stresses. However, the material microstructure also changes in machined-hardened steels, and it must be taken into account for improving product performance. In this paper, a hardness-based flow stress and an empirical model for describing the white and dark layers formation were developed and implemented in a FE code. The proposed model was validated by comparing the predicted results with the experimental evidences.     

淬火钢的车削加工研究

淬火钢硬度较高,使用常规刀具加工时难以达到理想效果。现根据工件不同的硬度要求,提出了采用不同牌号的刀具材料,选择合理的切削用量,可获得较好的加工质量和经济效益。     

晶体材料车削表面粗糙度的实验研究

本文探讨了晶体材料的切削加工性,重点分析了切削条件对表面粗糙度的影响。     

High-pressure jet-assisted cooling: a new possibility for near net shape turning of decarburized steel

Ultra-high-pressure cooling (UHPC) in turning operations is an effective method for achieving higher productivity. Previous research has demonstrated that the introduction of a high-pressure fluid jet into the gap between the tool and chip interface can control chip form and breakage. The present work shows the effect of UHPC in the turning of near net shape (NNS) decarburized parts. The workpiece material properties are strongly influenced by the loss of carbon atoms to a depth of up to 1 mm, due to the aggressive atmosphere during forming (decarburization). The extremely soft material makes chips difficult to control. Consequently, productivity decreases since the machine must be frequently stopped in order to manually remove the chips from the working area. The results show the influence of UHPC on chip form, surface topography and tool life when turning decarburized parts close to NNS. An interesting observation was that the combination of small cutting depth (near net shape) and soft material (decarburization) allowed for the presence of built-up edge formation, even at a high cutting speed.     

冷却工艺对超低碳贝氏体钢组织和性能的影响

采用热模拟试验和实验室轧钢试验,研究了超低碳贝氏体钢在冷却过程中冷却速率和终冷温度对微观组织和力学性能的影响.结果表明,在相同的冷却速率条件下,随着终冷温度的降低,试验钢的微观组织中板条贝氏体数量逐渐增加,但马奥岛体积分数减少,并且形状由长条状全部转变为球状.相同的终冷温度条件下,试验钢微观组织随着冷却速率的增加,粒状贝氏体组织略为变细,马奥岛尺寸减小、数量减少.轧钢试验中,随着冷却速率的提高和终冷温度的降低,试验钢的屈服强度、抗拉强度和屈强比都增加,但冲击韧性随着冷速的增加而明显改善,400～500 ℃范围内终冷对韧性影响不明显.     

Experimental evaluation on the effect of minimal quantities of lubricant in milling

Implementation of stricter Environmental Protection Agency (EPA) regulations associated with the use of ample amount of flood coolant has led to this study on minimal quantities of lubrication (MQL) technique on milling of ASSAB 718 HH steel at 35 HRc with uncoated carbide inserts while the MQL amount and flood coolant flow rate were 8.5 ml h⁻¹ and 42,000 ml min⁻¹, respectively. Unlike fracture in flood cooling or flaking in dry cutting the MQL used aided inserts were still in serviceable condition despite the presence of higher width of flank wear. Analyses of the cutting force, surface roughness, chip shape and EDX findings reveal that MQL may be considered as an economical and environmentally compatible lubrication technique for low speed, feed rate and depth of cut.     

Research on the fractal of surface topography of grinding

Fractal theory is widely used in analysing the topography of machined surfaces. In this paper, the formula that describes the relation between the fractal dimension D and R_a or R_q or S_m of surface roughness of different ground surfaces is obtained by measuring ground surfaces and researching the fractal features of them. Using a computer, a theoretical basis is built for the fractal simulation of the ground surface.     

Effect of heat-treatment conditions on the microstructure and ductility characteristics of steel 45

Steel 45 is widely used in machine building for fasteners and other components operating at both room and elevated temperatures. This steel has been rather widely studied, however, the investigation of its ductility characteristics, and tendency to brittle failure at elevated temperatures, as well as the establishment of a relationship between these parameters and microstructure, is of interest. The results of these investigations are presented in this paper.Scientific-Production Union Kompozit. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 2, pp. 9–11, February, 1994.     

常化冷却工艺对低温取向硅钢组织及析出相的影响（英文）

利用OM、TEM与EDS技术,对Fe-3.2%Si低温取向硅钢热轧板进行不同常化冷却工艺处理后的显微组织、析出相及最终产品的磁性能进行分析,并与热轧板的组织和析出相进行对比。结果表明,常化板较热轧板的表层组织均匀,基体中再结晶比例增加,带状组织变窄;常化板中析出物的数量明显比热轧板的多,析出物主要有AlN、MnS及复合析出的(Cu,Mn)S等。在常化温度1120℃、保温3 min的条件下,采用二段式冷却较空冷、淬沸水、淬常温水的冷却工艺,常化板表层显微组织更均匀,沿板厚方向的显微组织的不均匀性显著,取向硅钢的磁性能最高;常化后采用二段式冷却工艺析出的细小析出物数量最多,且弥散分布在基体中,抑制剂的抑制效果最好,对成品获得高磁性最有利。     

In-process monitoring and detection of chip formation and chatter for CNC turning

In order to realize the intelligent machine tool, an in-process monitoring and detection of cutting states is developed for CNC turning machine to check and improve the stability of the processes. The method developed utilizes the power spectrum density, or PSD of dynamic cutting force measured during cutting. Experimental results suggested that there are basically three types of patterns of PSD when the cutting states are the continuous chip formation, the broken chip formation, and the chatter. The broken chip formation is desired to realize safe and reliable machining.     

Process mechanics and surface integrity by high-speed dry milling of biodegradable magnesium-calcium implant alloys

Compared to conventional metallic implant materials, biodegradable Mg-Ca alloys are attractive orthopedic biomaterials that avoid negative stress shielding and revision surgeries. However, the process mechanics and surface integrity by high-speed dry milling Mg-Ca0.8 are poorly understood. Key findings of the synergistic experimental and numerical study are: (a) Mg-Ca0.8 alloy is sensitive to strain rate and adiabatic softening; (b) high-speed dry milling can be safely performed using PCD tools with process characteristics of lamella structured chips and slight flank build-up; and (c) machined surface integrity is characterized by low roughness, highly compressive residual stress, increased microhardness, and microstructure without phase changes.     

Effect of surface mechanical attrition treatment (SMAT) on zinc phosphating of steel

The effects of surface mechanical attrition treatment (SMAT) of EN8 steel on the growth of phosphate coatings, morphological features and corrosion resistance of the resultant coatings have been studied. SMAT enabled the formation of a uniform surface profile although the average surface roughness is increased after treatment. SMAT increased the extent of metal dissolution and the rate of growth of phosphate coating. In spite of the similarity in phase composition, the phosphate crystallite size is relatively high for samples treated by SMAT. Compared to the untreated one, a cathodic shift in E_corr with a corresponding decrease in i_corr is observed for SMAT treated EN8 steel after phosphating. For all tested samples, zinc phosphate coatings deposited on EN8 steel after SMAT using 8 mm Ø balls for 30 min offers the highest corrosion resistance. The increase in surface roughness by SMAT is partly compensated by the expected improvement in corrosion resistance.     

Process related assessment and supervision of surface textures

The surface texture of a finished geometrically defined body is the fingerprint of all process stages of the manufacturing process. With machining processes like forming, cutting and abrasive processes including etching and laser texturing macro- and micromechanical deviations from the nominal geometry at the individual geometrical features are caused by machine, process, tool and workpiece dependent influences.The effect of these causes on the deviations from the nominal geometry with different processes will be demonstrated.For functional reasons more and more the nominal geometry includes defined deviations from simple form features like straight line, circle, flat and cylinder but also defined microgeometrical form features having dimensions in the micro- and submicrometer range and which are part of so called engineered surfaces.Par examples it will be shown by which metrological means and by which 2-D and 3-D parameters the individual process stage for producing different defined surface textures can be assessed and supervised.Concerning engineered surfaces with defined microgeometrical surface geometry it must be decided which geometrical parameters like size (diameter, length, curvature, depth), distance, position and orientation of the texture element e.g. of the pits of a compact disc or of craters of a laser beam etched part should be used for assessing the results of the process and how the roughness of the texture element and the surrounding area should be evaluated.The discussion of the measuring procedures includes the effect of the properties of the probing systems (e.g. the tip radius), of the electrical filtering and the statistical character of the surface roughness.