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Dragos Axinte - One of the best experts on this subject based on the ideXlab platform.
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temperature effect on the Material Removal Mechanism of soft brittle crystals at nano micron scale
International Journal of Machine Tools & Manufacture, 2020Co-Authors: Qi Liu, Zhirong Liao, Dragos AxinteAbstract:Abstract Soft-brittle crystals, e.g. KH2PO4 (KDP), are difficult-to-cut due to their high brittleness which can easily generate crack during the machining process. The conventional method to machine this kind of Material is by inducing ductile cutting Mechanism at room temperature with ultra-precision machining, which can only remove Materials at nanoscale level and hence yields very low Material Removal rate. While some thermal-assisted processes have been recently attempted to improve the machinability of some difficult-to-cut Materials, e.g. ceramics, there is no systematic understanding of the temperature effect on Material Removal Mechanism of soft-brittle KDP crystals yet. In this work, the temperature effect on the Material Removal Mechanism has been investigated for the first time using nano-scratch technique. While a decreased hardness and elastic modulus have been observed with the increase of temperature, an increase of fracture toughness has been revealed with a contradictory tendency, indicating a higher capacity of plastic deformation at elevated temperature. In contrast to the almost totally brittle scratch at room temperature (RT) caused by crack propagation and edge chipping, the scratch at 170 °C can achieve more ductile-regime surfaces with a larger critical undeformed cutting depth (3.61 μm), e.g. a significant increase of 8.60 times compared with that at RT (0.42 μm). Moreover, the TEM analysis on the subsurface microstructures shows that a great number of nano grits was generated in the subsurface at RT as the result of crack propagation and interaction, while at elevated temperature some crystallographic lattice misaligned structures (LMS) and nano crystals have been brought about due to the nucleation and evolution of thermal-activated dislocations, which explains the higher plasticity of KDP at elevated temperature. The results present in this paper are of great significance for understanding the specific temperature effect on the brittle-to-ductile transition of the cutting Mechanism for future designing thermal-involved processes to machine soft-brittle Materials.
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Temperature effect on the Material Removal Mechanism of soft-brittle crystals at nano/micron scale
International Journal of Machine Tools and Manufacture, 2020Co-Authors: Qi Liu, Zhirong Liao, Dragos AxinteAbstract:Abstract Soft-brittle crystals, e.g. KH2PO4 (KDP), are difficult-to-cut due to their high brittleness which can easily generate crack during the machining process. The conventional method to machine this kind of Material is by inducing ductile cutting Mechanism at room temperature with ultra-precision machining, which can only remove Materials at nanoscale level and hence yields very low Material Removal rate. While some thermal-assisted processes have been recently attempted to improve the machinability of some difficult-to-cut Materials, e.g. ceramics, there is no systematic understanding of the temperature effect on Material Removal Mechanism of soft-brittle KDP crystals yet. In this work, the temperature effect on the Material Removal Mechanism has been investigated for the first time using nano-scratch technique. While a decreased hardness and elastic modulus have been observed with the increase of temperature, an increase of fracture toughness has been revealed with a contradictory tendency, indicating a higher capacity of plastic deformation at elevated temperature. In contrast to the almost totally brittle scratch at room temperature (RT) caused by crack propagation and edge chipping, the scratch at 170 °C can achieve more ductile-regime surfaces with a larger critical undeformed cutting depth (3.61 μm), e.g. a significant increase of 8.60 times compared with that at RT (0.42 μm). Moreover, the TEM analysis on the subsurface microstructures shows that a great number of nano grits was generated in the subsurface at RT as the result of crack propagation and interaction, while at elevated temperature some crystallographic lattice misaligned structures (LMS) and nano crystals have been brought about due to the nucleation and evolution of thermal-activated dislocations, which explains the higher plasticity of KDP at elevated temperature. The results present in this paper are of great significance for understanding the specific temperature effect on the brittle-to-ductile transition of the cutting Mechanism for future designing thermal-involved processes to machine soft-brittle Materials.
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theoretical and experimental investigation of Material Removal Mechanism in compliant shape adaptive grinding process
International Journal of Machine Tools & Manufacture, 2019Co-Authors: Wule Zhu, Dragos Axinte, Yue Yang, Anthony BeaucampAbstract:Abstract Modeling of grinding process, especially the grinding forces, has been studied extensively. Most previous work concerns the conventional grinding process using a rigid wheel, where the forces are generally based on the preset depth of grinding. However, for compliant grinding such as Shape Adaptive Grinding (SAG) that adopts an elastic tool covered with abrasive pellets, the penetration depth of individual abrasive grains is not simply equal to the preset value. As elastic contact occurs between the tool and workpiece, previous models are not able to estimate the Material Removal Mechanism. Besides, the progressive transitions in grain-workpiece interaction for compliant cutting tools have not been reported yet. To fill these gaps and to offer a fundamental understanding of the compliant grinding process, we propose in this study a new multi-scale model spanning from macroscopic tool-workpiece contact to microscopic grain-workpiece interaction in the unique conditions of using a compliant grinding tool, i.e. SAG tool. Based on the spring-grain model and considering the stochastic nature of grain size and wear flat area, the static penetration and dynamic Removal of individual grain can be predicted. Particularly, the Removal Mechanism is clarified with a new consideration of the transition between rubbing, plowing and cutting stages for each individual grain of the compliant tool. Experiments including scratch tests and Removal footprints were carried out, and the high consistency with theoretical predictions validates the proposed model. Finally, considering the progressive abrasive wear in grinding, in-process wear compensation was conducted to enable consistent Material Removal on aspheric steel molds. The proposed method is not only meaningful to reveal the Mechanism of SAG process, but also offers a new foundation for studying other compliant grinding processes in future.
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aspects of Material Removal Mechanism in plain waterjet milling on gamma titanium aluminide
Journal of Materials Processing Technology, 2010Co-Authors: M C Kong, Dragos Axinte, Wayne Eric VoiceAbstract:Abstract Due to providing reduced mechanical and thermal damages to workpiece surfaces, waterjet machining that is one of the most promising non-conventional processing methods found its niche application in cutting/shaping of Materials with low machinability indexes. It can be even a more attracting technology if plain waterjet (PWJ) milling is employed due to reduced running costs (absence of abrasives) and the elimination of surface contaminations (grit embedment). The paper reports for the first time PWJ milling of a notoriously difficult-to-cut Material, gamma titanium aluminide (γ-TiAl). Trials of different jet paths with varied milling parameters (e.g. water-hammer pressures, stepovers, number of passes) were conducted for understanding the Removal Mechanism of γ-TiAl in plain waterjet milling. The findings showed that the threshold water-hammer pressure for eroding the target Material and for achieving uniform erosion were in the vicinity of 800 MPa and greater than 1 GPa, respectively. In addition, different fracture modes were observed on γ-TiAl when PWJ milling: (i) plastic deformation and crack initiation; (ii) stress wave propagation; (iii) micropits due to joint of crack lines; (iv) intergranular cracking/fracture, triple split and interlamellar/translamellar fracture. The stages (i)–(iii) occurred at lower water-hammer pressures and number of passes while the subsequent stage (iv) was only observed at higher water-hammer pressures or number of passes. The knowledge accumulated when studying the Material Removal Mechanism and surface morphology enabled successful generation of 3D PWJ milled features (e.g. shallow pocket). To evaluate the capability of PWJ milling process, the geometrical accuracy and surface quality of the pocket has been examined. Finally, the advantages and drawbacks of the PWJ milling process are discussed to allow the definition where the technology is economically viable.
Wenfeng Ding - One of the best experts on this subject based on the ideXlab platform.
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the influence of grain geometry and wear conditions on the Material Removal Mechanism in silicon carbide grinding with single grain
Ceramics International, 2017Co-Authors: Wenbo Zhou, Jianbo Dai, Wenfeng Ding, Yihao ZhengAbstract:Abstract High efficiency and precision grinding of brittle Materials is challenging due to Material physical and chemical properties. To understand the effect of grain geometry and wear conditions on the Material Removal Mechanism in brittle Material precision grinding, a single diamond grain grinding experiment was conducted on Silicon Carbide (SiC). The cutting edge radius and deflection angle were measured by confocal scanning. Under six different cutting edge radius and three maximum undeformed chip thickness, grinding force and ground surface were measured. Diamond grain wear was investigated by observing the grain morphology, wear rate, grinding force, and ground surface change over accumulative Material Removal volume. The result showed the existence of a critical cutting edge radius for improving SiC ground surface quality.. Normal grinding force increased with the cutting edge radius increase. Tangential grinding force increased with the cutting edge radius increase and reached the peak value at the critical cutting edge radius. Flank wear was the major wear mode in precision SiC grinding. The grain wear was associated with the grinding force and ground surface.
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the influence of speed on Material Removal Mechanism in high speed grinding with single grit
International Journal of Machine Tools & Manufacture, 2015Co-Authors: Lin Tian, Yucan Fu, Jiuhua Xu, Haiyan Li, Wenfeng DingAbstract:Abstract In this paper, the effect of speed on Material Removal was investigated by single grit grinding of the GH4169 super alloy which is difficult to machine, with a new test method. During the tests the whole Material Removal process, was observed and then the critical thickness of chip formation was quantitatively analyzed. In order to provide insight into the speed effect, the grinding forces, chip formation and pile-up ratio were investigated. It was found that the stages of Material Removal process changed with the grinding speed, and the graphical relationships between grinding speed and the critical thickness of chip formation, grinding forces and the pile-up ratio were found to have a common characteristic, namely a common turnover point which was about 100 m/s. This trend in the results is attributed to alternating predominance between the strain hardening and thermal softening effects. The results of this study demonstrated that the grinding speed has a significant impact on Material Removal Mechanism, and also provide a basis for sound understanding of the high speed grinding process of difficult to cut Materials.
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Effects of grinding speed on the Material Removal Mechanism in single grain grinding of SiCf/SiC ceramic matrix composite
Ceramics International, 1Co-Authors: Jingfei Yin, Wenfeng DingAbstract:Abstract Silicon carbide (SiC) fibers reinforced SiC ceramic matrix composite (SiCf/SiC) is an advanced Material for aeroengines because of its high-temperature resistance and high specific strength. However, it is rather difficult to machine. Though there have been many methods available for machining SiCf/SiC, the Material Removal Mechanism is not fully understood and the machining efficiency is still low. This paper studies the effects of grinding speed on the Material Removal Mechanism of SiCf/SiC by single grain grinding. Results indicate that increasing speed grinding could embrittle the Material and enhance the breakage of fibers. When grinding along the fiber longitude direction, fibers present brittle fracture and matrix is torn off in high speed grinding rather than the ploughing in fibers or the smearing in matrix in low speed grinding. When grinding transverse to the fiber longitude direction, fibers are removed completely without any residual cut-off fiber end which is common in low speed grinding. Both the groove surface quality and machining efficiency are improved by increasing speed grinding.
Xun Chen - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of Material Removal Mechanism in single grit grinding
International Journal of Machine Tools & Manufacture, 2012Co-Authors: Tahsin Tecelli Öpöz, Xun ChenAbstract:This paper presents an important investigation of Material Removal behaviour during single grit grinding, which provides critical insight of grinding mechanics for improving grinding efficiency and quality. During the investigation, CBN grits were used to perform scratch tests on En24T steel. Piles up ratio, chip Removal strength, effective grit engage radius are introduced to measure Material Removal performance. It has been discovered that grit cutting edge shape has significant influence on ploughing and cutting actions. By comparing scratch tests using grits with single edge or multiple edges, it has demonstrated that cutting is more efficient with single edge grit. More ploughing actions appear in multiple edges scratches. Furthermore, Material Removal Mechanism along a single scratch is investigated and found that Material Removal is more prominent at the grit entrance side of the scratch compared to the grit exit side of the scratch. The research findings provide critical information for grinding optimization.
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Process monitoring and metrology for single grit grinding test performance
The 17th International Conference on Automation and Computing, 2011Co-Authors: Tahsin Tecelli Öpöz, Xun ChenAbstract:Single grit scratch test may provide better understanding of complex Material Removal Mechanism of grinding process on the micro scale. In this paper, evaluation of single grit scratches was performed by utilizing monitoring and metrology devices. Particularly, AE and force sensors were used to monitor the process. AE sensitivity on Material deformation was found comparable to force sensor sensitivity. High contact area interaction result in increase of AE raw signal amplitude. Grit cutting edge wear phenomena was also investigated under the digital microscope. Multiple scratches formation was observed in one rotation, due to grit cutting edge wear. AE sensitivity on scratch tests and grit wear are investigated in this paper to provide more insight into grinding process monitoring and Material Removal Mechanism by single grit approach.
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Simulation of Grinding Surface Creation – A Single Grit Approach
Advanced Materials Research, 2010Co-Authors: Xun Chen, Tahsin Tecelli ÖpözAbstract:The paper presents an investigation of grinding Material Removal Mechanism using finite element method. Understanding of grinding Removal Mechanism relies on the investigation of Material Removal by each individual grain. Although some analytical formulations have been developed to predict and to quantify the machining events in grinding, they do not illustrate every stage of abrasive actions. Finite element analysis provides good facility to present details of physical behaviour in grinding. In this research, Material Removal Mechanism of grinding, namely rubbing, ploughing and cutting, is discussed with the variation friction coefficient. The major emphasis here is on the ploughing. Total force variation exerted during indention and sliding of a grain is also presented along its path.
Tahsin Tecelli Öpöz - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of Material Removal Mechanism in single grit grinding
International Journal of Machine Tools & Manufacture, 2012Co-Authors: Tahsin Tecelli Öpöz, Xun ChenAbstract:This paper presents an important investigation of Material Removal behaviour during single grit grinding, which provides critical insight of grinding mechanics for improving grinding efficiency and quality. During the investigation, CBN grits were used to perform scratch tests on En24T steel. Piles up ratio, chip Removal strength, effective grit engage radius are introduced to measure Material Removal performance. It has been discovered that grit cutting edge shape has significant influence on ploughing and cutting actions. By comparing scratch tests using grits with single edge or multiple edges, it has demonstrated that cutting is more efficient with single edge grit. More ploughing actions appear in multiple edges scratches. Furthermore, Material Removal Mechanism along a single scratch is investigated and found that Material Removal is more prominent at the grit entrance side of the scratch compared to the grit exit side of the scratch. The research findings provide critical information for grinding optimization.
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Investigation of Material Removal Mechanism in grinding : a single grit approach
2012Co-Authors: Tahsin Tecelli ÖpözAbstract:This thesis has investigated Material Removal Mechanisms in grinding by considering single grit workpiece interaction. The investigation was performed both experimentally and using finite element simulation. Rubbing, ploughing and cutting Mechanisms occurring during the grinding process were studied at the micro scale. Due to its nature the rubbing phase occurs in a very narrow region of grit-workpiece engagement and is difficult to examine under a microscope and so was investigated using FEM simulation. The ploughing Mechanism was thoroughly investigated using both experimental tests and FEM simulations, and a similar trend was observed for the pile up ratio along the scratch path from the experimental tests and the FEM simulations. Ploughing and cutting Mechanisms in grinding were found to be highly influenced by grit cutting edge shape, sharpness and bluntness. Cutting is the prominent Mechanism when the grit cutting edge is sharp, but ploughing is more prominent when the grit cutting edge becomes flattened. In the case of multiple edges scratch formation, ploughing is dramatically increased compared to single edge scratches. Feasibility of ground surface simulation using FEM is demonstrated using multiple pass scratch formation in a cross direction. Although chip formation Mechanism is developed at a relatively higher depth of cut (greater than 10 μm), at small scales down to 1 μm, FEM simulation was not a suitable method to use. To reduce the drawbacks of FEM simulation in micro scale cutting, a meshless simulation technique such as smooth particle hydrodynamics is recommended for future studies.
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Process monitoring and metrology for single grit grinding test performance
The 17th International Conference on Automation and Computing, 2011Co-Authors: Tahsin Tecelli Öpöz, Xun ChenAbstract:Single grit scratch test may provide better understanding of complex Material Removal Mechanism of grinding process on the micro scale. In this paper, evaluation of single grit scratches was performed by utilizing monitoring and metrology devices. Particularly, AE and force sensors were used to monitor the process. AE sensitivity on Material deformation was found comparable to force sensor sensitivity. High contact area interaction result in increase of AE raw signal amplitude. Grit cutting edge wear phenomena was also investigated under the digital microscope. Multiple scratches formation was observed in one rotation, due to grit cutting edge wear. AE sensitivity on scratch tests and grit wear are investigated in this paper to provide more insight into grinding process monitoring and Material Removal Mechanism by single grit approach.
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Simulation of Grinding Surface Creation – A Single Grit Approach
Advanced Materials Research, 2010Co-Authors: Xun Chen, Tahsin Tecelli ÖpözAbstract:The paper presents an investigation of grinding Material Removal Mechanism using finite element method. Understanding of grinding Removal Mechanism relies on the investigation of Material Removal by each individual grain. Although some analytical formulations have been developed to predict and to quantify the machining events in grinding, they do not illustrate every stage of abrasive actions. Finite element analysis provides good facility to present details of physical behaviour in grinding. In this research, Material Removal Mechanism of grinding, namely rubbing, ploughing and cutting, is discussed with the variation friction coefficient. The major emphasis here is on the ploughing. Total force variation exerted during indention and sliding of a grain is also presented along its path.
Qi Liu - One of the best experts on this subject based on the ideXlab platform.
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temperature effect on the Material Removal Mechanism of soft brittle crystals at nano micron scale
International Journal of Machine Tools & Manufacture, 2020Co-Authors: Qi Liu, Zhirong Liao, Dragos AxinteAbstract:Abstract Soft-brittle crystals, e.g. KH2PO4 (KDP), are difficult-to-cut due to their high brittleness which can easily generate crack during the machining process. The conventional method to machine this kind of Material is by inducing ductile cutting Mechanism at room temperature with ultra-precision machining, which can only remove Materials at nanoscale level and hence yields very low Material Removal rate. While some thermal-assisted processes have been recently attempted to improve the machinability of some difficult-to-cut Materials, e.g. ceramics, there is no systematic understanding of the temperature effect on Material Removal Mechanism of soft-brittle KDP crystals yet. In this work, the temperature effect on the Material Removal Mechanism has been investigated for the first time using nano-scratch technique. While a decreased hardness and elastic modulus have been observed with the increase of temperature, an increase of fracture toughness has been revealed with a contradictory tendency, indicating a higher capacity of plastic deformation at elevated temperature. In contrast to the almost totally brittle scratch at room temperature (RT) caused by crack propagation and edge chipping, the scratch at 170 °C can achieve more ductile-regime surfaces with a larger critical undeformed cutting depth (3.61 μm), e.g. a significant increase of 8.60 times compared with that at RT (0.42 μm). Moreover, the TEM analysis on the subsurface microstructures shows that a great number of nano grits was generated in the subsurface at RT as the result of crack propagation and interaction, while at elevated temperature some crystallographic lattice misaligned structures (LMS) and nano crystals have been brought about due to the nucleation and evolution of thermal-activated dislocations, which explains the higher plasticity of KDP at elevated temperature. The results present in this paper are of great significance for understanding the specific temperature effect on the brittle-to-ductile transition of the cutting Mechanism for future designing thermal-involved processes to machine soft-brittle Materials.
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Temperature effect on the Material Removal Mechanism of soft-brittle crystals at nano/micron scale
International Journal of Machine Tools and Manufacture, 2020Co-Authors: Qi Liu, Zhirong Liao, Dragos AxinteAbstract:Abstract Soft-brittle crystals, e.g. KH2PO4 (KDP), are difficult-to-cut due to their high brittleness which can easily generate crack during the machining process. The conventional method to machine this kind of Material is by inducing ductile cutting Mechanism at room temperature with ultra-precision machining, which can only remove Materials at nanoscale level and hence yields very low Material Removal rate. While some thermal-assisted processes have been recently attempted to improve the machinability of some difficult-to-cut Materials, e.g. ceramics, there is no systematic understanding of the temperature effect on Material Removal Mechanism of soft-brittle KDP crystals yet. In this work, the temperature effect on the Material Removal Mechanism has been investigated for the first time using nano-scratch technique. While a decreased hardness and elastic modulus have been observed with the increase of temperature, an increase of fracture toughness has been revealed with a contradictory tendency, indicating a higher capacity of plastic deformation at elevated temperature. In contrast to the almost totally brittle scratch at room temperature (RT) caused by crack propagation and edge chipping, the scratch at 170 °C can achieve more ductile-regime surfaces with a larger critical undeformed cutting depth (3.61 μm), e.g. a significant increase of 8.60 times compared with that at RT (0.42 μm). Moreover, the TEM analysis on the subsurface microstructures shows that a great number of nano grits was generated in the subsurface at RT as the result of crack propagation and interaction, while at elevated temperature some crystallographic lattice misaligned structures (LMS) and nano crystals have been brought about due to the nucleation and evolution of thermal-activated dislocations, which explains the higher plasticity of KDP at elevated temperature. The results present in this paper are of great significance for understanding the specific temperature effect on the brittle-to-ductile transition of the cutting Mechanism for future designing thermal-involved processes to machine soft-brittle Materials.