共查询到20条相似文献,搜索用时 31 毫秒
1.
Hockin H. K. Xu Said Jahanmir Lewis K. Ives Lenox S. Job Kevin T. Ritchie 《Journal of the American Ceramic Society》1996,79(12):3055-3064
Hardness and toughness are often used to analyze the abrasive machining behavior of ceramic materials. However, toughness values of silicon nitride ceramics with microstructures containing elongated grains increase with crack extension. The present study investigates the effect of toughness on the process of abrasive machining to determine which value of toughness should be used in the analysis. The toughness curves (i.e., toughness as a function of crack length) of ten different silicon nitride materials are characterized by an indentation-strength technique and an indentation technique. The forces in surface grinding are measured as a function of the depth of cut. Examination of ground surfaces by scanning electron microscopy indicates that the material-removal processes in grinding follows the formation of short cracks (i.e., microcracks) and grain-scale material dislodgement. An indentation fracture model for material removal in abrasive machining is used to correlate the grinding forces with toughness and hardness of the materials. An agreement is obtained between the experimental results and the indentation model only when the toughness associated with short cracks is used. This study shows the importance of using appropriate toughness values corresponding to the microfracture processes in analyzing abrasive machining results for materials possessing rising toughness curves. 相似文献
2.
Kimberly Yates Donaldson D. P. H. Hasselman 《Journal of the American Ceramic Society》1986,69(12):296-C
A comparative study was conducted of the single-point diamond scratching response of a cordierite glass and glass-ceramic. For the glass, deformation and material removal occurred by viscous flow at the lowest values of load, viscous flow combined with crack formation adjacent to the contact area over the intermediate load range, and extensive spoiling at the highest values of load. The density of the spalls and spall size were found to be proportional and inversely proportional to perpendicular scratching load, respectively. The glass-ceramic exhibited plastic flow and abrasive wear at loads as low as could be reliably measured, the particle size of the debris being of the order of the grain size. At the highest ranges of load, the glass-ceramic exhibited material removal by spall formation with a spall size proportional to load. At the lower ranges of load, the widths of the scratch for the glass and glass-ceramic were comparable. However, at the highest values of load tne size of the spall of the glass-ceramic was significantly less than the size of the spall in the glass. 相似文献
3.
Yao Liu Beizhi Li Chongjun Wu Lingfei Kong Yihao Zheng 《Ceramics International》2018,44(11):12194-12203
Crack induced surface/subsurface damage in SiC ceramic grinding limits the industrial application. A single-grain scratching simulation based on the smoothed particle hydrodynamics (SPH) has been used to analyze the SiC grinding mechanism, including the material removal process, scratching speed effect on crack propagation, ground surface roughness, and scratching force. The simulation results showed that the material removal process went through the pure ductile mode, brittle assisted ductile mode, and brittle mode with the increase of the depth of cut. The critical depth of cut for ductile-brittle transition was about 0.35?µm based on the change of ground surface crack condition, surface roughness, and maximum scratching force. Increasing the scratching speed promoted the transformation of deep and narrow longitudinal crack in the subsurface into the shallow and wide transverse crack on the surface, which improved the surface quality. The SPH simulation results were indirectly validated by the cylindrical grinding experiments in terms of the critical single grain depth of cut for ductile-brittle transition, and the trend of ground surface roughness and grinding forces. 相似文献
4.
A study was conducted of the effect of crystallization on the fracture toughness, strength, and resistance to surface damage of glass-ceramic materials with a range of microstructures obtained by different heat treatments. The hardness indentation method was used as a quantitative tool to simulate mechanical surface damage. In the uncrystallized glass and in the glass-ceramic heat-treated to result in a uniform fine-grained structure, crack size increased monotonically with indentation load. In contrast, in the glass-ceramics heat-treated to result in a microstructure consisting of larger crystallites (a few micrometers) contained within a fine-grained matrix, a discontinuity in the crack size vs load curve presented evidence for crack-pinning at crack sizes which were a small multiple of the intercrystallite spacing. At the position of crack-pinning, the fracture toughness showed a discontinuous increase with increasing crack size that was attributed to crack deflection. The strength of the glass and fine-grained glass-ceramic measured in biaxial flexure decreased monotonically with indentation load. The strength at low values of indenter load of the glass-ceramic heat-treated to yield the coarser crystallites within the fine-grained matrix was independent of indentation load, indicating stable crack propagation prior to fast fracture. At the higher values of indenter load, the coarse-grained glass-ceramics exhibited a monotonic decrease in strength with increasing indentation load. The results of this study indicate that the strengthening observed on crystallization of a glass can be attributed to a combination of a decrease in flaw size achieved at a given mechanical surface treatment, an increase in fracture toughness, and a modification in the mode of crack propagation. 相似文献
5.
Machinable Ceramics Containing Rare-Earth Phosphates 总被引:34,自引:0,他引:34
Janet B. Davis David B. Marshall Robert M. Housley Peter E. D. Morgan 《Journal of the American Ceramic Society》1998,81(8):2169-2175
Two-phase composites consisting of LaPO4 or CePO4 and alumina, mullite, or zirconia were found to be machinable; i.e., they can be cut and drilled using conventional tungsten carbide metal-working tools. Single-phase LaPO4 was also machinable. Measurements of drilling rates, grinding rates, and normal forces are used to compare the ease of machining in these materials and in a conventional machinable glass-ceramic material, and to provide preliminary information on the relation between microstructure and machining properties. In Hertzian contact experiments these materials showed extensive nonlinear behavior associated with a damage zone beneath the contact site, similar to other machinable ceramics. Mechanisms of material removal are discussed. 相似文献
6.
《Ceramics International》2017,43(15):11596-11609
A critical function for crack propagation for the single grit scratching of fused silica is developed based on the fracture mechanics. The effects of original crack density on the surface, strain rate and grinding coolant are considered in the function. A theoretical model for controlled material removal mode and depth of micro cracks precision grinding is presented based on the critical function for crack propagation. It can be predicted by the model that the material removal mode in the grinding of fused silica with original cracks damage will change from a ductile mode to a semi-brittle mode, a full-brittle mode and a semi-brittle mode in sequence with the increasing single grit scratching depth. It was found that the micro crack damage depth of fused silica does not increase with the single grit scratching depth after a full brittle mode grinding and it is always smaller than that after a semi brittle mode grinding even with a smaller single grit scratching depth. These interesting results are explained by the fracture mechanics. The ductile mode grinding is a recognized desirable process of fabricating fused silica while the full-brittle grinding is also a feasible process for its shallow subsurface damage, high efficiency, low grinding force and energy consumption. Therefore, the depth of micro cracks after grinding can be controlled by choosing suitable grinding parameters. Grinding experiments are conducted on fused silica. The undeformed chip thickness of randomly distributed effective grits is simulated based on 3D reconstruction of wheel topography to reveal the relationship between the grinding parameters and the single grit scratching depth. Ground surface roughness, sub-surface damage (SSD) depth and grinding force are measured and discussed. It is shown that the model predictions correlate well with the experimental trend of grinding modes. 相似文献
7.
Payel Bandyopadhyay Arjun Dey Anoop K. Mukhopadhyay 《International Journal of Applied Glass Science》2012,3(2):163-179
Many advanced applications of glass demand fabrication of engineering parts of utmost dimensional precision which require very accurate grinding and polishing that involves controlled removal of glass. Despite the wealth of literature, however; the mechanism of material removal in glass grinding and polishing is still far from well understood. For instance, it is not known at all to what extent the mechanical properties are compromised inside a scratch groove so as to optimize the machining parameters. Therefore, to develop better understanding about the mechanism of material removal, a series of combined nanoindentation and single pass scratch experiments were conducted on a commercially available soda-lime-silica glass as a function of various normal loads (2–20 N) and scratch speeds (0.1–1 mm/s). It was found that the nanohardness and Young's modulus at the local microstructural length scale inside the scratch groove could decrease quite dramatically (~30% to 70%) depending on the combination of load and scratching speed. Further, the tribological properties, the severity and the spatial density of damage evolution were sensitive to the normal loads, scratching speeds, and tensile stresses. Extensive scanning electron microscopy leads to interesting observations on material removal mechanisms. These observations were explained by the theoretical predictions of a model for a brittle, microcracked solid. 相似文献
8.
Study on the subsurface damage mechanism of optical quartz glass during single grain scratching 总被引:2,自引:0,他引:2
Ming Li Xiaoguang Guo Ruifeng Zhai Xichun Luo Renke Kang Zhuji Jin Dongming Guo 《Ceramics International》2021,47(6):7683-7691
The single grain scratching SPH simulation model was established to study the subsurface damage of optical quartz glass. Based on the analysis of the stress, strain and scratching force during scratching, the generation and propagation of subsurface cracks were studied by combining with the scratch elastic stress field model. The simulation results show that the cracks generate firstly at the elastic-plastic deformation boundary in front of the grain (φ = 28°) due to the influence of the maximum principal tensile stress. During the scratching process, the median crack closes to form the subsurface damage by extending downward, the lateral crack promotes the brittle removal of the material by extending upward to the free surface, and microcracks remain in the elastic-plastic boundary at the bottom of the scratch after scratching. The depth of subsurface crack and plastic deformation increases with rising scratching depth. The increase of scratching speed leads to the greater dynamic fracture toughness, accompanied by a significant decrease of the maximum depth of subsurface crack and the number of subsurface cracks. The subsurface residual stress is concentrated at the bottom of the scratch, and the residual stress on both sides of the scratch surface would generate and propogate the Hertz crack. When the scratching depth is less than 1.5 μm or the scratching speed is greater than 75 m/s, the residual stress value and the depth of residual stress are relatively small. Finally, the scratching experiment was carried out. The simulation analysis is verified to be correct, as the generation and propagation of the cracks in the scratching experiment are consistent with the simulation analysis and the experimental scratching force indicates the same variation tendency with the simulation scratching force. The research results in this paper could help to restrain the subsurface damage in grinding process. 相似文献
9.
Hockin H. K. Xu † Said Jahanmir Yushu Wang‡ 《Journal of the American Ceramic Society》1995,78(4):881-891
Dramatic effects of scratch interactions on material removal are observed in alumina. A series of parallel scratches are made in aluminas with different grain sizes to investigate the influence of scratch interactions on the material removal process in abrasive machining. The separation distance between the two scratches and the normal load are varied and subsurface microfracture and damage modes are examined to assess the mechanisms of material removal. A very small amount of material is removed when the separation distance between the two parallel scratches is large or when the two scratches completely overlap. However, at intermediate distances the volume of material removed increases dramatically as a result of the interactions between the two scratches. The maximum amount of material removed and the corresponding distance between the two scratches are found to depend strongly on the grain size and the load. Observations of surface and subsurface damage reveal that grain dislodgement is the predominant mechanism of material removal, irrespective of the grain size. The relation between grain size, scratch interactions, and the material removal process in grinding and abrasive machining of ceramics is discussed in terms of the short-crack toughness of ceramics. 相似文献
10.
In this study, the scratch resistance of several monolithic structural ceramics and soda lime glass was investigated using repeated scratching. Rockwell indentation was used to perform unidirectional multi-pass scratches at progressive loads. It is shown that there is a build up of sample damage as the number of scratches increases, the severity of which being assessed by measuring the depth of the scratches and by performing optical observations of the worn tracks. For each applied load, there is a critical number of passes above which the material removal rate increases dramatically through chipping. By plotting the critical number of passes against the applied load, strength/number of cycles (S/N) like diagrams can be obtained. Although soda lime glass exhibits a lower resistance than most of ceramics for single scratch tests, the glass removal rate becomes similar to that of ceramics when repeated scratch tests are considered. It is suggested that the material resistance to multiple scratch tests rely on the presence of a thin layer of re-compacted and plastically deformed material under the action of the indenter. The absence of such a layer in silicon carbide may explain the surprisingly poor resistance of this material for high applied forces and important number of cycles. It is suggested that this layer improves the material resistance against scratching by decreasing the friction coefficient, thereby diminishing the level of stresses generated within the specimen. 相似文献
11.
Infrared Transparent Germanate Glass-Ceramics 总被引:1,自引:0,他引:1
Shyam S. Bayya Jasbinder S. Sanghera Ishwar D. Aggarwal Joshua A. Wojcik 《Journal of the American Ceramic Society》2002,85(12):3114-3116
A new germanate glass-ceramic material in the BaO-Ga2 O3 -GeO2 system is developed for infrared (IR) dome and window applications. This glass-ceramic material has a grain size of ∼0.2–0.5 μm and is transparent in the 3–5 μm IR region. Glass ceramization results in 40% improvement in hardness, 65% increase in elastic modulus, 116% increase in strength, and 134% increase in fracture toughness over the base glass. 相似文献
12.
Masaomi Oguma Kenneth Chyung Kimberly Yates Donaldson D. P. H. Hasselman 《Journal of the American Ceramic Society》1987,70(1):2-C-3
The resistance of a canasite glass-ceramic to the initiation of thermal stress fracture due to a water quench was found to be higher than for the original glass, due to higher values of strength and thermal conductivity which offset increases in thermal expansion and Young's modulus. Relative strength retention behavior of the glass-ceramic was also higher than for the glass, attributed to its crack-size-dependent fracture toughness. 相似文献
13.
《Journal of the European Ceramic Society》2023,43(10):4322-4335
Due to their exceptional and distinctive qualities, 3D C/C-SiC composites are widely utilized in producing high-end equipment and the aerospace national defense industries. However, the hard and pseudo plastic nature of the material and its anisotropies make it challenging to process. To improve the processing quality of 3D C/C-SiC composites, laser-assisted precision grinding technology is introduced in this paper, which innovatively controls the depth of the thermally induced damage layer by adjusting the laser process parameters to reduce the hard brittleness of the material, and then the surface is created by precision grinding with a grinding wheel on this basis. Experiments on laser-induced damage, laser-assisted grinding, and diamond scratching were carried out to investigate the effect of laser parameters on material damage and the effect of laser-assisted grinding processes, with an emphasis on revealing the mechanism of material removal. The results show that laser irradiation causes complex reactions such as sublimation, decomposition, and oxidation of 3D C/C-SiC composites, resulting in SiO2 and Si and recondensed SiC, causing surface/subsurface damage. A maximum reduction in normal grinding force, tangential grinding force, specific grinding energy, and surface roughness of 35.6%, 43.6%, 43.58%, and 24.22%, respectively, compared to conventional grinding processes with laser-assisted grinding. After laser irradiation, the degree of brittle fracture in the precision grinding of workpieces is significantly reduced due to the degradation of matrix and fiber damage caused by laser irradiation, which reduces the hard and pseudo plastic properties of the material. The removal mechanism shows a trend of ductile domain removal in the grinding of thermally damaged layers, which reduces the grinding force and improves the surface quality. 相似文献
14.
Different types of SiC whiskers were incorporated into lithium aluminosilicate (LAS) and calcium aluminosilicate (CAS) glass-ceramic matrices. Interfaces in these composites were characterized using Auger spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and the observations were correlated with measurements of fracture toughness and strength. The chemistry and morphology of the resulting interfaces affected the composite strength and toughness and controlled the mode of crack propagation. Certain types of SiC whiskers were characterized by a carbon-rich near-surface chemistry that became more carbon rich after composite fabrication. In these materials, the flexural strength at 20°C increased by up to 400% and the fracture toughness increased by up to 500%. Crack propagation modes were characterized by crack deflection, whisker–matrix debonding, and crack bridging. In contrast, SiC whiskers with stoichiometric near-surface chemistry generally did not form carbon-rich interfaces during composite fabrication, resulting in composites with low strength and fracture toughness. 相似文献
15.
Crack Suppression in Strongly Bonded Homogeneous/Heterogeneous Laminates: A Study on Glass/Glass-Ceramic Bilayers 总被引:1,自引:0,他引:1
Sataporn Wuttiphan Brian R. Lawn Nitin P. Padture 《Journal of the American Ceramic Society》1996,79(3):634-640
A study is made of a glass/glass-ceramic bilayer as a model homogeneous/heterogeneous laminate. The underlying objective is microstructural design of ceramic layer systems with optimum mechanical properties, alternating hard layers, for wear resistance, with tough layers, for fracture resistance. Mica flakes in the glass-ceramic layer inhibit the propagation of well-developed intrusive cracks, by bridging; these same flakes render the structure susceptible to distributed damage, by providing discrete weakness at the microstructural level. A major distinguishing feature of the bilayer design is the incorporation of a strong interface, so that cracks are inhibited by the underlayer rather than deflected between the layers. Vickers and Hertzian indentation tests on specimen cross sections demonstrate the capacity of the glass-ceramic layer to arrest radial and cone cracks penetrating from the adjacent glass layer. Additional Hertzian tests on the outer surfaces of glass layers in a coating/substrate configuration show diffuse damage accumulation in the glass-ceramic substrate layers. This diffuse damage absorbs energy and shields cone cracks in the glass from the applied loading. Implications concerening the design of damage-tolerant laminate structures are discussed. 相似文献
16.
Thomas J. Hill John J. Mecholsky Kenneth J. Anusavice 《Journal of the American Ceramic Society》2000,83(3):545-552
The objective of this paper was to analyze the crystal aspect ratio (AR), the fracture toughness, and the fractal dimension of 3BaO. 5SiO2 glass-ceramics and to relate the topography of fracture surfaces to fractal behavior. These analyses demonstrate that crystal morphology strongly affects the fracture path, the fracture toughness, and the fractal dimension. Fracture toughness increased from 0.7 ± 0.1 MPa. m1/2 for the glass to 2.2 ± 0.6 MPa. m1/2 for the glass-ceramic with an AR of 8.1 while the fractal dimensional increment ( D *) for the glass and the glass-ceramic increased from 0.10 ± 0.01 to 0.25 ± 0.02, respectively. The materials with lower aspect ratios (AR = 1.4 and 3.6) exhibited the predicted relationship between toughness and D * while the glass-ceramic with an aspect ratio of 8.1 did not satisfy the expected relationship because of multiple toughening mechanisms. 相似文献
17.
Fracture Toughness Measurement of Glass and Ceramic Materials Using Chevron-Notched Specimens 总被引:1,自引:0,他引:1
K. Pattabhi Rami Reddy Eugene H. Fontana Jchn D. Helfinstine 《Journal of the American Ceramic Society》1988,71(6):310-C
Fracture toughness of several different materials was measured using chevronnotched short bar and four-point bend specimens For glass-ceramic and ceramic samples both specimens gave valid results. Fracture toughness values measured with bend specimens are 5% to 10% higher compared to those of the short bar. Consistent results for glass could be obtained only with short bar specimens. The notch width of the bend specimen affected the stability of crack growth in glass samples. Fracture toughness values measured in the present study are in good agreement with those of the previous studies. 相似文献
18.
19.
Fracture Behavior of SiC-Whisker-Reinforced Barium Aluminosilicate Glass-Ceramic Matrix Composites 总被引:1,自引:0,他引:1
Feng Ye Jue Ming Yang Li Tong Zhang Wan Cheng Zhou Yu Zhou Ting Chuan Lei 《Journal of the American Ceramic Society》2001,84(4):881-883
Barium aluminosilicate (BAS) glass-ceramic composites reinforced with various volume percents (0, 10, 20, 30, 40 vol%) of SiC whiskers were fabricated by hot pressing. The microstructure, the whisker/matrix interface structure, the phase constitution, and the mechanical properties of the composites were systematically studied by means of SEM, TEM, and XRD techniques as well as by indentation crack microfracture and single-edge-notched-beam bend testing. It was demonstrated that the incorporation of SiC whiskers could significantly increase the flexural strength and fracture toughness of BAS glass-ceramic matrices. The addition of active Al2 O3 to the BAS matrix reduced the amount of SiO2 in the matrix, forming needlelike mullite, which further improved the mechanical properties. 相似文献