Radial Wear Research Articles

Wear behavior of monolayer-brazed CBN wheels with small diameter during internal traverse grinding

Due to its ability to provide more inter-grit chip space and higher grit protrusion, monolayer-brazed CBN wheel has great potentials in internal traverse grinding (ITG) of small holes of high strength and toughness materials. Before engineering application, it is necessary to study the wear behavior and wear mechanism of the brazed CBN wheels. A series of internal traverse grinding tests was conducted with a small self-manufactured monolayer-brazed CBN wheel. The radial wear, grinding ratio, and ground surface roughness was measured to evaluate the wear behavior of the brazed CBN wheel. Besides, the topographic features of the wheel surface were also observed to explore the wear mechanism. It can be concluded that the wear behavior of the brazed CBN wheel in ITG can be divided into three stages according to the grinding ratio, namely rapid wear stage, transitional wear stage, and stable wear stage. Macro-fracture, attritious wear, and large wear flat were respectively the main wear characteristics during the three wear stages. From the point of grinding ratio and ground surface roughness, the stable wear stages were the most suitable for production, followed by the transitional wear stage.

Tool Wear Research And Milling Parameter Optimization During High-Speed Milling 3Cr2Mo

This paper focuses on the copy measurement to measure radial wear of ball end mill. Then, the model of tool wear was established through tool wear test. The results of experiment show that the model is of higher precision and is useful to predict the amount of wear. Finally, a milling process optimization model was proposed by maximizing efficiency and minimizing cost targets. In addition, we aimed to get the reasonable high speed milling parameters by choosing nondominated sorting genetic algorithm II (NSGA- II) to solve the model.

Investigation on size effect of grain wear behavior during grinding nickel-based superalloy Inconel 718

In order to explore the effect of undeformed chip thickness (UCT) on the grain wear behavior, the single grain grinding experiment was carried out on the typical difficult-to-cut material, such as nickel-based superalloy Inconel 718. The grinding forces of single grain were measured, and the grain wear morphology was also characterized under different UCT values. The variations of grain wear behavior, grinding forces, and radial wear of single grain were investigated under the conditions of UCT range from 0.2 to 1 μm. The results show that size effect could change the grain wear behavior in grinding. In the beginning of wear, the crescent depression is observed on the rake face at each value of UCT. As the grain wears more seriously, the crescent depression would change into a new rake face or new cutting edge. Besides, with the increase of specific material removal volume (SMRV), the grinding forces tend to increase firstly and then remain stable under different UCT values. Furthermore, the size effect of grain wear behavior also takes effects on the grinding force ratios. The quantitative analysis of radial wear further proves that size effect leads to the change of grain wear amount in grinding.

Investigation of wear, groove shape and load capacity of PPS-PTFE hybrid radial ball bearings

In order to improve the radial load capacity and wear loss of the PPS-PTFE hybrid bearings, the groove shape of the PPS inner ring in the PPS-PTFE hybrid bearing was designed based on ceramic bearing’s ball radius (r). The rolling contact fatigue tests were performed by using the PPS-PTFE hybrid bearings with the original (r*1.0) and modified (r*1.1) inner rings. The radial load capacity of the bearing using the rl.1 inner ring was improved 150% over the capacity of the bearing using the r1.0 inner ring. While the operation temperature of the bearing with the r1.1 inner ring was stable at 40 °C, that of the bearing with the r1.0 inner ring incresed rapidly over 100 °C and thermal failure occurred. Moreover, the wear loss of the bearings with the r1.1 inner ring was lower than that of the r1.0. Thus the groove shape influenced the tribology performance of the PPS-PTFE hybrid bearings.

Modeling and experiment of surface error for large-aperture aspheric SiC mirror based on residual height and wheel wear

In the grinding process of large-aperture aspheric silicon carbide mirror, the wear of grinding wheel affects the surface accuracy seriously due to high hardness of silicon carbide and large diameter of aspheric mirror. Therefore, establishing surface error model of large-aperture aspheric silicon carbide mirror taking the wear of grinding wheel into account is of great significance to improve the processing quality and the imaging quality of aspheric mirror. The spiral grinding method is chosen to grind large-aperture aspheric SiC mirror in this work. The surface error of large-aperture aspheric silicon carbide mirror is established based on residual height and radial wear of grinding wheel using the grinding ratio as a bridge. The influence of grinding parameters on surface error is analyzed based on theoretical model. The results show that surface error increases with the increase of the rotation radius of workpiece and feed velocity of wheel, while it decreases with the increase of rotation velocity of workpiece and arc radius of wheel. The influence of the rotation velocity of workpiece and feed velocity of wheel is greater than that of the rotation radius of workpiece and arc radius of wheel. The regression equation of grinding ratio is established through grinding experiment, and the correlation coefficient is 0.9774 which verifies the reliability of the regression equation. Furthermore, the complete formula of surface error is acquired based on regression equation of grinding ratio. Finally, the grinding experiment of large-aperture aspheric silicon carbide mirror is carried out on the five-axis NC milling and grinding machine tool of HZ-091 type, and the error between measured value of grinding experiment and prediction value of theoretical model is less than 20%, which indicates that the theoretical model is reliable.

Tool Wear Characteristics and Effect on Microstructure in Ti-6Al-4V Friction Stir Welded Joints

In the present paper, tool wear and the rate of wear during friction stir welding (FSW) of Ti-6Al-4V alloy are investigated. A conical tungsten carbide tool was used to produce butt-type friction stir welded joints in two-millimeter thick Ti-6Al-4V sheets. An original design of a movable pin allowed for the examination of the tool damage for each process condition. The influence of tool degradation on the quality of the welded joints and the damage brought to the microstructure are examined and discussed. For this purpose, optical and scanning electron microscopies as well as EDX analyses were used to examine the tool wear and the resulting macrostructures and microstructures. The type and nature of the defects are also analyzed as a function of FSW processing parameters. Important geometry and weight variations were observed on the pin and shoulder for all welding conditions, in particular when low tool rotation and travel speeds were used. Experimental results also show that the radial wear of the pin is not uniform, indicating the presence of important frictional temperature gradients through the thickness of the joint. The maximum wear was measured at a location of about one millimeter from the pin root center. Finally, tool rotation was determined as the most significant process parameter influencing both tool wear and microstructure of the joints.

Ocena zużycia promieniowego nowych narzędzi do szlifowania zawierających mikroagregaty ścierne z wykorzystaniem metody skanowania przestrzennego

Ocena zużycia promieniowego nowych narzędzi do szlifowania zawierających mikroagregaty ścierne z wykorzystaniem metody skanowania przestrzennego

Experimental study on grinding wheel radial wear in surface grinding of steel CrV12 using a zonal centrifugal coolant provision system

The tribology of the grinding process can be considered in the context of a tribosystem, in which the main structural elements (grinding wheel, workpiece, grinding fluid, and environment) are interrelated and interdependent. One of the most important factors influencing the contact conditions of these listed elements of the grinding process tribosystem are the proper selection of grinding fluids and anti-adhesive substances, as well as careful consideration of how they are applied. This article describes a new zonal centrifugal coolant provision system as well as the results of experimental studies conducted into its use. The aim of these experiments was to determine the impact of the system of grinding fluids provision on grinding wheel radial wear in the surface grinding process of steel CrV12. Reference methods within the described studies consisted of dry grinding and grinding using the flood method, among others. The obtained results of the experiment revealed that the use of a zonal centrifugal coolant provision system enabled the acquisition of a similar radial wear rate of the grinding wheel at 90% reduction of grinding fluids flow rate, compared with flooding method. It was also demonstrated that in the most favorable conditions, it is even possible to significantly reduce the intensity of the radial wheel wear, compared with the conventional method.

Grinding Tungsten Carbide Used for Manufacturing Gun Drills

This paper presents a study of grinding cemented carbide DK460UF (91 % WC and 9 % Co), a material used to produce cutting tools with solid cutting edges. The aim is to establish the manufacturing conditions that lead to high surface quality. A model of the main factors that influence the grinding process is presented first. Following that, grinding wheel wear and surface roughness are analysed. Grinding wheel wear is studied in experimental conditions under which small diameter gun drills were sharpened with two diamond grinding wheels of different grain sizes. Finally, the wear curve can be made. The “G ratio” is used to characterise the performance of the grinding process. Next, the experimental research examines how independent parameters, depth of cut, feed, grit, and speed influence roughness. The influence of the grinding wheel wear on roughness is also studied. The aspect of ground surfaces is examined by using a scanning electron microscope (SEM). The experimental study allowed the determination of the required grinding wheel grit (46 μm) and the optimum processing parameters (depth of cut ap = 0.01 mm, feed = 0.005 mm/rev, cutting speed v = 55 m/s) to obtain the imposed surface roughness for cutting tool surfaces (Rz = 0.3 μm). The maximum allowed radial wear (Δr) of the grinding wheel is 30 μm.

AN INVESTIGATION OF RECONDITIONING AND DEVELOPMENT OF WEAR AND FRICTION TESTING MACHINE

The paper objective is to overcome the various problems and shortcomings associated with the present wear and friction testing machine. A new compact track radius attachment is developed, that simplifies the task of adjusting the track radius on to the disc. The various concepts has been generated to develop the track radius mechanism from those it is found that manual operated lead screw concept was most reliable. The product concept was successfully tested and validated by making a physical prototype that yields positive results. The new track radius mechanism setup by itself can be mounted on the guide ways in horizontal position without much physical efforts, demonstrating the flexibility to adjust different track radius feature of the product. The track radius mechanism is offered with flexibility to mount two different specimens in different track radius at a time and tested. The new track radius mechanism has been developed with the additional feature of digital display. The wear and friction testing machine had been reconditioned with all units after rectify the problems of this machine and experiments were conducted to get results on the electronic display. This machine can be used extensively for research applications and precision results can be obtained for industrial applications. The graph is plotted for Aluminum specimen on weight loss with different radial wear track and observed that weight loss increases with an increase in wear track radius.

Wear analysis of disc cutters of full face rock tunnel boring machine

Wear is a major factor of disc cutters’ failure. No current theory offers a standard for the prediction of disc cutter wear yet. In the field the wear prediction method commonly used is based on the excavation length of tunnel boring machine(TBM) to predict the disc cutter wear and its wear law, considering the location number of each disc cutter on the cutterhead(radius for installation); in theory, there is a prediction method of using arc wear coefficient. However, the preceding two methods have their own errors, with their accuracy being 40% or so and largely relying on the technicians’ experience. Therefore, radial wear coefficient, axial wear coefficient and trajectory wear coefficient are defined on the basis of the operating characteristics of TBM. With reference to the installation and characteristics of disc cutters, those coefficients are modified according to penetration, which gives rise to the presentation of comprehensive axial wear coefficient, comprehensive radial wear coefficient and comprehensive trajectory wear coefficient. Calculation and determination of wear coefficients are made with consideration of data from a segment of TBM project(excavation length 173 m). The resulting wear coefficient values, after modification, are adopted to predict the disc cutter wear in the follow-up segment of the TBM project(excavation length of 5621 m). The prediction results show that the disc cutter wear predicted with comprehensive radial wear coefficient and comprehensive trajectory wear coefficient are not only accurate(accuracy 16.12%) but also highly congruous, whereas there is a larger deviation in the prediction with comprehensive axial wear coefficient(accuracy 41%, which is in agreement with the prediction of disc cutters’ life in the field). This paper puts forth a new method concerning prediction of life span and wear of TBM disc cutters as well as timing for replacing disc cutters.

An Experimental Study on Grinding Fir-Tree Root Forms Using Vitrified CBN Wheels

An experimental study was undertaken to explore the conditions and performance on rough and finish grinding fir-tree root forms of turbine blades made of a nickel-based alloy using vitrified CBN wheels and water-based grinding fluid. This work was motivated by switching the grinding of fir-tree root forms from grinding with conventional abrasive wheels to vitrified CBN wheels for reducing overall production cost and enhancing productivity. Grinding experiments were conducted to measure grinding forces, power, surface roughness, and stress near the blade roots under various dressing and grinding conditions. Wheel re-dressing life in terms of the total number of good parts ground between dressing was tested with the condition producing the maximum material removal rate while satisfying preset part quality and process requirements. It was found that the maximum material removal rate achievable in rough grinding was restricted by the stress limit and the wheel re-dressing life was dominated by the radial wheel wear limit. The targeting part quality and process requirements were achieved. It was proved that vitrified CBN grinding process is feasible and very promising to machine fir-tree root forms.

Wear of non-segmented and segmented diamond wheels in high-speed deep grinding of carbon fibre-reinforced ceramics

Carbon fibre-reinforced ceramics (CFRCs) are relatively new and promising materials for various high-tech. industrial applications due to their superior properties. However, the employment of these materials has been impeded by their high machining costs. A specially designed metal-bonded segmented diamond wheel has been developed in order to reduce the cutting forces and temperatures and enhance the MRR. Studying the wear behaviour and wear mechanisms of the segmented wheel, compared to a non-segmented wheel with the same specification, was necessary for economic assessment of the process. The investigation was conducted for a surface grinding process. The selected cutting conditions assure an acceptable range of the surface roughness and a high material removal rate. The radial wear, the G-ratio and the wear behaviour of the wheels were examined at the specified specific material removals up to 4,704 mm3/mm. Compared to the non-segmented wheel, the segmented wheel has experienced higher radial wear. However, the G-ratio can be increased considerably by the intermittent grinding process. The main wear mechanisms of the segmented wheel are the inter-crystalline grain fracture and grain pull-out, while in the case of non-segmented wheel, the grain flattening is the main wear mechanism. Furthermore, grinding forces and temperatures, which influence the wear behaviour of a wheel considerably, are significantly reduced by the intermittent grinding process. The residual stress analysis showed that the utilized grinding processes have induced just a negligible residual stress into the CFRC workpieces.

Trapezial Topography in Thumb Carpometacarpal Arthritis

Objective Contradictory reported arthritic patterns of the metacarpal surface of the trapezium include preferential volar wear, radial wear, and dorsal-ulnar sparing. We investigated whether a predominant wear pattern exists in surgical trapeziectomy for advanced thumb carpometacarpal (CMC) arthritis. Methods We examined 36 intact trapezia from 34 thumb CMC arthroplasty patients over an 18-month period. The first metacarpal articular surface revealed three consistent morphology patterns: (1) saddle, (2) dish, and (3) cirque. The saddle represented cartilage loss with preservation of the normal trapezial morphology. The dish shape represented concave curvature, with loss of the normal saddle configuration. The cirque shape represented preferential volar concave wear, disrupting the convex volardorsal arc. Two surgeons classified the randomized specimens twice, blinded to patient identity and each other's categorization. Radiographic Eaton staging was correlated retrospectively for 35 of 36 of the trapezial specimens. Eight specimens were further quantified with micro-computed tomography (micro-CT). Results Thirty-six trapezia were classified as follows: 17 (47%) saddle, 12 (33%) dish, and 7 (19%) cirque. Intra-rater reliability was 0.97 and 0.95; inter-rater reliability in the second round was 0.95. The 36 trapezia represented 27 female (75%) and 9 male (25%) patients; 18 (50%) represented the dominant hand. Age at surgery averaged 64 (33-76). Complete cartilage loss of the entire metacarpal surface was seen in 15 (42%) of all specimens. Osteophyte presence was typically minimal in the saddle group; the dish group had characteristic extensive rimming osteophytes in a 91% female population (11/12), and the cirque group had volar osteophytes. Radiographic severity ranged from Eaton stage II to IV; less severe radiographic staging (Eaton II) predominated in the saddle configuration; advanced Eaton III-IV disease predominated in both cirque and dish shapes. Micro-CT verified the three discrete shapes with volardorsal and radioulnar orientation measurements. Conclusion The metacarpal surface of the trapezium demonstrates three distinct patterns of wear in arthritic surgical specimens. Sex, dominance, age distribution, and Eaton stage varied across the different shapes. Level of Evidence Level 3 Study Type Observational.

Wear patterns of taper connections in retrieved large diameter metal‐on‐metal bearings

Wear of the modular taper between head and shaft has been related to clinical failure resulting from adverse reactions to metallic debris. The problem has become pronounced in large metal-on-metal bearings, but the mechanism has not yet been fully understood. We analyzed retrieved components from five patients revised with various diagnoses. Two distinct wear patterns were observed for the head tapers. Three samples demonstrated "asymmetric" wear towards the inner end of the head taper. The other two showed "axisymmetric" radial wear (up to 65 µm) presenting the largest wear volumes (up to 20 mm(3)). Stem tapers demonstrated relatively little wear, and the fine thread on the stem taper surface was observed to be imprinted on the taper inside of the head. Our findings demonstrate that the cobalt-chrome head wears preferentially to the titanium stem taper. "asymmetric" wear suggests toggling due to the offset of the joint force vector from the taper. In contrast, samples with "axisymmetric" radial wear and a threaded imprint suggested that corrosion led to head subsidence onto the stem taper with gradual rotation.

Tool optimization for high speed grinding

Vitrified bonded cBN grinding wheels catches on for batch production especially in the automotive industry for components of power trains. In pursuit of higher productivity with steady quality the optimization of manufacturing processes and tools are getting more relevant. In this contribution potentials and challenges of structured grinding tools for the optimization of grinding processes are discussed. Technological investigations with structured and non-structured vitrified bonded cBN grinding wheels were carried out and the results of varying setting parameters were analyzed. The main aspects of interest for these studies were the detection of possible coolant savings and phenomena of vibrations, the reduction of the thermal damage of the workpieces as well as the influence on the workpiece roughness and the grinding wheel radial wear. The experiments show the potentials of structured cBN grinding wheels for roughing and finishing in cylindrical plunge grinding processes. But there are some basic requirements for the geometry of the structures especially due to the vibrations of the grinding process. For the roughing tests the adequate structured abrasive layers show less grinding forces and thermal damage of the workpiece. For finishing processes the results show comparable values of roughness and waviness referring to non-structured grinding wheels. In addition, a limit for suitable grinding wheel structures in conjunction with the setting parameters could be identified that offers valuable clues for the dimensioning of structured abrasive layers even for non-circular grinding processes.

Evolution of Surface Roughness in Grinding and its Relationship with the Dressing Parameters and the Radial Wear

Grinding is a machining process specially indicated for finishing operations in hard materials, in order to obtain low surface roughness (Ra 0.1μm to 2μm) and tight tolerances. The cutting tool is the grinding wheel which is formed by abrasive particles attached in a bond. The wear of these abrasive particles modifies significantly the roughness obtained in the workpiece. In this work, the evolution of part roughness has been continuously monitored as the grinding process progresses and the wheel gets worn. The roughness evolution is then related to different process variables such as the dressing parameters, the grinding conditions, the grinding forces and the radial wear of the wheel.

Tool Wear Monitoring Based on Milling Acoustic Spectrum LPCC

Cutting sound signal are acquisited in the vertical machining center using electret microphone, and would be applied to monitor tool wear. Linear Predictive Cepstrum Coefficient (LPCC) of milling sound signal within audibility threshold would be extracted as acoustic spectrum characteristic parameters, and the relativity between LPCC each order component and tools radial wear was analyzed. The experiments and analysis results conclude that there are characteristic components associated with tool wear in characteristic parameters LPCC of milling sound signal; the characteristic components associated with tool wear are mainly concentrated in the 6th, 7th and 8th order components LPCC; the method by characteristic parameters LPCC monitoring tool wear is feasible.

High Efficiency Precision Surface Grinding of Fused Silica

High efficiency and high surface integrity grinding of fused silica lens used in the ultraviolet (UV) laser transmission equipments is highly demanded. It is necessary to decrease the undeformed chip thickness for producing better surface integrity. We conducted creep feed grinding (CFG) and conventional shallow cut grinding (SCG) experiments of fused silica with a resin bond diamond wheel. Experiment results shows that owing to thinner undeformed chip thickness, the normal grinding force, radial wheel wear and P-V value of surface roughness of CFG are smaller than those of SCG at the same MRR. At the same table speed, surface roughness decreased with the increase of MRR in both CFG and SCG as a result of decreased undeformed chip thickness which is attributed to the elasticity of resin bond.

Software Development and Data Processing of Tool Wear Based on Mapping Measurement

In NC milling process, tool wear has great influence on the machining quality of product. In this paper, a mapping measurement method is used to obtain tool wear and a data processing method is proposed to deal with the data getting from the measurement. First, tool wear along radius of tool’s cross-section, which is called radial wear, can be obtained by mapping measurement method. Then tool flank wear can be easily calculated based on the established relationship between radial wear and flank wear. In order to get radial wear, we process those measured data that are obtained from mapping measurement. In this process, least square method is adopted to fit these data to get the radius of section circle at a certain position. So the radial wear can be obtained by comparing the radius of the fitting circle and the original radius of tool at a certain section. Finally, the data processing software is realized by using Visual C++ development tool according to the designed data processing method of tool wear.