International Journal of Abrasive Technology (8 papers in press)
High-speed high-efficient grinding of CMCs with structured grinding wheels
by Bahman Azarhoushang, Mohammadali Kadivar, Robert Bösinger, Sergey Shamray, Ali Zahedi, Amir Daneshi
Abstract: Ceramic Matrix Composites (CMCs) are counted as new materials which are widely applied in various engineering and technological fields owing to their superior properties. In spite of their remarkable properties, their implantation is limited due to their high machining costs as a result of high grinding forces and tool wear. To overcome mentioned problems, modified grinding wheels, one macro-structured by segmenting and another micro-structured (half lasered structured and half non-structured) were used in this study. The grinding tests were carried out at different material removal rates and cutting speeds. The grinding forces, generated surface roughness, and induced residual stress by means of grinding with the structured and non-structured wheels were compared. Reduction in the static cutting edges via wheel structuring resulted in a better performance of the grinding wheel through the reduction of rubbing and ploughing regimes. The grinding forces were respectively 30% and 20% lower in the case of segmented wheel and laser-structured wheel in comparison with the conventional grinding. In addition, the tensile residual stress can be reduced as a negative output of the grinding process via structuring. Moreover, a high-speed high-efficient grinding of CMCs without presence of surface damage was achieved by optimizing the process parameters. The material removal rate can be elevated without changing the grinding forces with application of the structured wheel.
Keywords: High speed high efficiency grinding; CMCs; Segmented wheel; laser-structure.
An experimental investigation on precision machining mechanism of carbon fiber reinforced polymer
by Xiaojiang Cai, Ruhao Zhou, Lifeng Shen, Hongliang Tang, Qinglong An
Abstract: With the rapid development of carbon fiber reinforced polymers (CFRP) as main aerospace structural materials, it is necessary to manufacture CFRP structural components for high dimensional accuracy by means of precision machining. In this paper, orthogonal cutting was used to investigate machining process and surface quality of CFRP materials for precision machining An intensive discussion was given about fiber orientation and cutting parameter range when machining CFRP for high accuracy application and optimized cutting method, including cutting speed, cutting depth, edge radius, fiber orientation, was obtained to reduce cutting force and surface roughness and get smooth surface topography. The cutting speed over 200m/min and small cutting depth slightly large than edge radius were advisable, the fiber direction 0~45
Keywords: carbon fiber reinforced polymers (CFRP); precision machining; cutting force; cutting speed; cutting depth; surface roughness; surface topography.
Research on surface integrity in graphene nanofluid MQL milling of TC21 alloy
by Ming Li, Tianbiao Yu, Hongyu Li, Lin Yang, Jiashun Shi, Wanshan Wang
Abstract: As a new type of damage-tolerance titanium alloy, TC21 alloy is widely used in aerospace. However, TC21 is a difficult-to-machine material owing to its low thermal conductivity, high chemical activity and low elasticity modulus. In this work, Minimum Quantity Lubrication (MQL) with graphene nanofluid was adopted in TC21 milling. In order to evaluate the effects of graphene nanoparticle on the surface integrity, a series of milling experiments were performed under the dry, gas, pure MQL and graphene nanofluid MQL condition respectively. Results showed that the graphene additive was effective for improving the surface integrity. Overall, the results could be explained that graphene additive could enhance the cooling and lubrication performances of the oil film formed in cutting zone. The findings of this work are expected to give a feasibility and some experimental basis for the application of the graphene additive in MQL milling.
Keywords: graphene nanofluid; MQL milling; surface integrity; TC21.
Development of Nanofiber Abrasive Buffing Pad Produced with Modified Melt Blowing Method
by Wei WU, Eiichi Aoyama, Toshiki Hirogaki, Kenichi Urabe, Hiroyoshi Sota
Abstract: Nanofibers can be used in fields/applications such as medical care, environment protection, apparel, and agriculture. It can also be believed that these fields will experience rapid growth in the next few years. This study focuses on one of the applications: abrasive buffing. We proposed the oil adsorption physical model of abrasive buffing and compared it with experimental results to develop a nanofiber buffing pad. It can also be used to calculate the mass ratio of oil to abrasive grain and the abrasive size in abrasive machining when the fiber mass and bulk density are constant. Further, for realizing the free-form nano surface, such as molding die surface, we conducted a base experiment with different diameter fibers and different size grains and investigated its base polishing characteristics compared with commercial felt buff. From the experimental results, we considered the buffing mechanism of fiber and grain contact the workpiece surface to polish. As a result, the effect of combination of mesh size and grain size on polished surface roughness of the workpiece was demonstrated, and controlling the polished surface roughness using this low-cost new abrasive material in abrasive machining was realized. It can also be considered that the nanofiber abrasive pad can sufficiently be used in abrasive machining with oil slurry as a next generation abrasive material.
Keywords: Melt-blowing method; Nanofiber; Oil adsorption; Nonwoven polypropylene nanofiber; Buffing; Buffing pad.
Electroplated CBN Superabrasive Wheel for Grinding Intermetallic Titanium Aluminide
by Nithin Tom Mathew, Vijayaraghavan L
Abstract: An experimental investigation is reported on the surface grinding of intermetallic gamma titianium aluminide using electroplated cubic boron nitride grinding wheel. In order to implement the wide acceptability of this material in various fields, the machinability investigation finds crucial especially during grinding. In the present work, the machinability of gamma titanium aluminide of two different composition was investigated by analysing the normal and tangential force, surface integrity, chip morphology and the condition of grinding wheel after the experiments. The minor variation in the composition of titanium aluminide has influence on the generated cutting forces, the knowledge of which is essential for satisfactory use of these material in various applications. The observations from the machined surface has shown the presence of various surface defects and the analysis of chip morphology revealed the occurrence of high temperature during the grinding. The topography of the grinding wheel is also investigated after the experiments.
Keywords: Grinding; Electroplated; cubic boron nitride; intermetallic; Titanium aluminide; Normal force; Tangential force; Surface integrity; Surface roughness; Chip morphology.
Decision Support System for Principal Factors of Grinding Wheel Using Data-Mining Methodology
by Hiroyuki Kodama, Itaru Uotani, Kazuhito Ohashi
Abstract: The recommended grinding conditions are described in five factors (abrasive grain, grain size, grade, structure, and bonding material) of the three main elements (abrasive grain, bonding material, and pore) in the grinding wheel catalog data-set. As systematic arrangement is not made, grinding conditions (cutting speed, table feed, depth of cut) have to be decided on the basis of an experienced engineers information or experience. Moreover, although the setting of the five factors of the three elements of a grinding wheel is important parameter that affects the surface quality and grinding efficiency, it is difficult to determine the optimal combination of workpiece materials and grinding conditions. In this research, a support system for effectively deciding the desired grinding wheel was built by using a decision tree technique, which is one of the data-mining techniques. This system extracts a significant tendency of grinding wheel conditions from catalog data. As a result, a visualization process was proposed in correspondence to the action of the grinding wheel elements and their factors to the material characteristics of the workpiece material. In this report, we produced patterns to support selection of grinding wheels by visualizing the surface grinding wheel selection decision tendency from more amount of data, based on data mixed with JIS standard and maker's catalog data.
Keywords: Data-mining; Decision tree; Grinding wheel; surface grinding.
In-process grinding wheel wear evaluation using digital image processing
by Bahman Azarhoushang, Sebastian Ludwig
Abstract: The microtopography of the grinding tool surface is essential for the result of the grinding process. Micro wear (the flattening of the abrasive grits) and loading (the adhesion of chips between or on the grits), lead to an increase in process forces and temperatures. Subsequently, poor surface qualities, dimensional and profile errors and thermal damage to the workpiece, such as grinding burn, could be induced by the grinding process. Hence, cleaning (dressing) of the grinding wheel is necessary to restore the grinding ability of the tool. Industrial processes usually have short dressing intervals to avoid scrap parts. However, short dressing intervals cause a high loss of the valuable abrasive layer of both grinding and dressing tools. A novel process-oriented measuring method is developed in this study to evaluate quickly and efficiently the surface topography of grinding tools. Images of the tool surface, after being recorded via a camera system, are evaluated by an innovative image processing software for characterizing grit flattening and loading. This article describes the developed technique and the results of the application during grinding processes. The results show a direct proportionality between the output values of the proposed method and the measured grinding forces. Hence, the developed measurement method can be used for the evaluation of the grinding ability and for an assessment of the tool life.
Keywords: grinding; dressing; wheel wear; tool loading; tool life; image processing.
Study on the Material Removal Mechanism of Glass in Single Diamond Grain Grinding with Ultrasonic Vibration Assisted
by Jianyun Shen, Bin Dai, Xian Wu, Yuan Li, Zhongwei Hu
Abstract: The ultrasonic vibration assisted grinding is widely used in machining of hard and brittle material. This paper presents a study on the material removal mechanism in ultrasonic vibration assisted grinding of glass. The single diamond grain grinding experiments were performed with and without ultrasonic vibration assisted. The grinding force and acoustic emission signal were measured and analyzed, and the ground groove morphology was observed and analyzed in detail. The following conclusions can be obtained: (1) the material removal mechanism is changed from continuous crack propagation in conventional grinding to micro crack breakage in ultrasonic vibration assisted grinding. (2) The addition of ultrasonic vibration in grinding of brittle material can reduce the crack propagation distance. (3) Compared with the conventional grinding, the energy distribution of acoustic emission signal in ultrasonic vibration assisted grinding is more concentrated.
Keywords: Single diamond grain grinding; Ultrasonic vibration assisted; Material removal mechanism; Acoustic emission signal.