Pub Date : 1997-01-15DOI: 10.1299/JSMEA1993.40.1_44
S. Yoneyama, Daisuke Ayame, J. Gotoh, M. Takashi
The authors discuss the first step in the approach to the fundamental mechanism of small-scale local fracture near the contact surface between a rigid traveling roller and a viscoelastic plate which has a deep groove on the upper edge of the plate, which simulates pitting or surface cracking around the contact surface. The photoviscoelastic method is applied to investigate the time-dependent stress and strain state under the condition of nonproportional loading, taking a typical case of the interaction of stress fields due to a traveling contact load and a surface groove into account. Complicated variations of the time-dependent photoviscoelastic fringe pattern are observed near the tip of the surface groove. The time variations of not only the principal stress difference and principal strain difference, but also principal directions of stress, strain and birefringence are evaluated using a convenient computer-aided photoviscoelastic technique under the temperature at which the material shows marked viscoelastic behavior. Time variations of stress intensity factors, K I and K II , are also evaluated using the least-squares method following the technique proposed by Sanford and Dally.
{"title":"Photoviscoelastic Stress and Strain Analysis around a Surface Groove under Rolling Contact Load","authors":"S. Yoneyama, Daisuke Ayame, J. Gotoh, M. Takashi","doi":"10.1299/JSMEA1993.40.1_44","DOIUrl":"https://doi.org/10.1299/JSMEA1993.40.1_44","url":null,"abstract":"The authors discuss the first step in the approach to the fundamental mechanism of small-scale local fracture near the contact surface between a rigid traveling roller and a viscoelastic plate which has a deep groove on the upper edge of the plate, which simulates pitting or surface cracking around the contact surface. The photoviscoelastic method is applied to investigate the time-dependent stress and strain state under the condition of nonproportional loading, taking a typical case of the interaction of stress fields due to a traveling contact load and a surface groove into account. Complicated variations of the time-dependent photoviscoelastic fringe pattern are observed near the tip of the surface groove. The time variations of not only the principal stress difference and principal strain difference, but also principal directions of stress, strain and birefringence are evaluated using a convenient computer-aided photoviscoelastic technique under the temperature at which the material shows marked viscoelastic behavior. Time variations of stress intensity factors, K I and K II , are also evaluated using the least-squares method following the technique proposed by Sanford and Dally.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134376268","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-01-15DOI: 10.1299/JSMEA1993.40.1_37
M. Ji, H. Ishikawa, M. Anahara, Y. Yasui
The degree of the enhancement of the fracture resistance of an orthogonal three-dimensional composite of cabon fiber reinforced epoxy is experimentally determined using a DCB testing method. By analyzing the load-displacement curve and the energy change caused by the breaking of the bridging fiber yarn, the mechanism of the enhancement of the bridging fiber for the fracture resistance is considered. It was found that the greater the number of bridging yarns in the crack, the greater is the amount of deformation energy per cracking area necessary for crack propagation. An estimation method for the mode I fracture toughness of the material is presented.
{"title":"The Estimation of Fracture Resistance of Orthogonal Three-Dimensional Fiber-Reinforced Composite by DCB Testing","authors":"M. Ji, H. Ishikawa, M. Anahara, Y. Yasui","doi":"10.1299/JSMEA1993.40.1_37","DOIUrl":"https://doi.org/10.1299/JSMEA1993.40.1_37","url":null,"abstract":"The degree of the enhancement of the fracture resistance of an orthogonal three-dimensional composite of cabon fiber reinforced epoxy is experimentally determined using a DCB testing method. By analyzing the load-displacement curve and the energy change caused by the breaking of the bridging fiber yarn, the mechanism of the enhancement of the bridging fiber for the fracture resistance is considered. It was found that the greater the number of bridging yarns in the crack, the greater is the amount of deformation energy per cracking area necessary for crack propagation. An estimation method for the mode I fracture toughness of the material is presented.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132644219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1997-01-15DOI: 10.1299/JSMEA1993.40.1_15
T. Iwasaki, N. Sasaki, A. Yasukawa, N. Chiba
Impurity effects on grain boundary grooving in crystalline aluminum are studied using computer molecular-dynamics simulation. We use a Morse potential that includes equilibrium spacing (v A1 ) and potential well depth (|(u A1 |) to characterize aluminum/aluminum interaction, and a two-body interatomic potential that includes equilibrium spacing (v m ) and potential well depth (|u min |) to characterize aluminum/ impurity interaction. Simulations show that when v m is smaller than v A1 and when |u min | is close to |u A1 | (within ±20% of it), grain boundary grooving is prevented. This is effect is explained by a decrease in the ratio of grain boundary diffusion to surface diffusion. Diffusion coefficients obtained in our simulations show that impurities at grain boundaries which satisfy the above conditions (e.g. copper) strengthen surface diffusion without strengthening grain boundary diffusion.
采用计算机分子动力学模拟方法研究了杂质对结晶铝晶界开槽的影响。我们使用包含平衡间距(v A1)和势阱深度(|(u A1 |))的莫尔斯势来表征铝/铝相互作用，使用包含平衡间距(v m)和势阱深度(|u min |)的两体原子相互作用势来表征铝/杂质相互作用。仿真结果表明，当v m小于v A1时，当u min |接近u A1 |时(在±20%范围内)，晶界开槽现象不会发生。这种效应可以用晶界扩散与表面扩散之比的减小来解释。模拟得到的扩散系数表明，满足上述条件的晶界杂质(如铜)加强了表面扩散，但不加强晶界扩散。
{"title":"Molecular Dynamics Study of Impurity Effects on Grain Boundary Grooving","authors":"T. Iwasaki, N. Sasaki, A. Yasukawa, N. Chiba","doi":"10.1299/JSMEA1993.40.1_15","DOIUrl":"https://doi.org/10.1299/JSMEA1993.40.1_15","url":null,"abstract":"Impurity effects on grain boundary grooving in crystalline aluminum are studied using computer molecular-dynamics simulation. We use a Morse potential that includes equilibrium spacing (v A1 ) and potential well depth (|(u A1 |) to characterize aluminum/aluminum interaction, and a two-body interatomic potential that includes equilibrium spacing (v m ) and potential well depth (|u min |) to characterize aluminum/ impurity interaction. Simulations show that when v m is smaller than v A1 and when |u min | is close to |u A1 | (within ±20% of it), grain boundary grooving is prevented. This is effect is explained by a decrease in the ratio of grain boundary diffusion to surface diffusion. Diffusion coefficients obtained in our simulations show that impurities at grain boundaries which satisfy the above conditions (e.g. copper) strengthen surface diffusion without strengthening grain boundary diffusion.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1997-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132848966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_479
K. Tohgo, M. Sakaguchi, H. Ishii
Elastic and elastic-plastic analyses of a crack in a particulate-dispersed functionally graded material (FGM) have been carried out using a newly developed finite element method based on Tohgo-Chou-Weng's(1994, 1996) constitutive relation for particulate-reinforced composites. By setting the mechanical properties of particles and a matrix and their content graded in the thickness direction, FGMs and non-FGM are designed. From comparison of the numerical results for the FGMs and non-FGM, the influence of the gradient of the mechanical properties on a stress intensity factor and the crack tip field is discussed. The following conclusions are derived: (1) The stress intensity factor of a crack under constant boundary conditions is considerably affected by the gradient of the mechanical properties. (2) The elastic and plastic stress singular fields around a crack tip in a FGM are basically described by the fracture mechanics parameters(K 1 and J 1 ) as well as in a non-FGM, using the mechanical properties of the material at the crack tip. (3) The size of the singular field decreases with an increase in the gradient of the mechanical properties. This means that the applicability of fracture mechanics, such as the small-scale-yielding condition and the validity of the J-integral, is affected by the gradient.
{"title":"Applicability of Fracture Mechanics in Strength Evaluation of Functionally Graded Materials","authors":"K. Tohgo, M. Sakaguchi, H. Ishii","doi":"10.1299/JSMEA1993.39.4_479","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_479","url":null,"abstract":"Elastic and elastic-plastic analyses of a crack in a particulate-dispersed functionally graded material (FGM) have been carried out using a newly developed finite element method based on Tohgo-Chou-Weng's(1994, 1996) constitutive relation for particulate-reinforced composites. By setting the mechanical properties of particles and a matrix and their content graded in the thickness direction, FGMs and non-FGM are designed. From comparison of the numerical results for the FGMs and non-FGM, the influence of the gradient of the mechanical properties on a stress intensity factor and the crack tip field is discussed. The following conclusions are derived: (1) The stress intensity factor of a crack under constant boundary conditions is considerably affected by the gradient of the mechanical properties. (2) The elastic and plastic stress singular fields around a crack tip in a FGM are basically described by the fracture mechanics parameters(K 1 and J 1 ) as well as in a non-FGM, using the mechanical properties of the material at the crack tip. (3) The size of the singular field decreases with an increase in the gradient of the mechanical properties. This means that the applicability of fracture mechanics, such as the small-scale-yielding condition and the validity of the J-integral, is affected by the gradient.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120914125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_598
Y. Hwang, T. Chen
A mathematical model for asymmetrical sheet rolling is proposed, using the stream function method and the upper bound theorem to investigate the plastic deformation behavior of the sheet at the roll gap. The curvature of the rolled product obtained under various rolling conditions of roll speed ratio, roll radius ratio, friction factor ratio, and inlet angle of the sheet at the entrance of the roll gap, are discussed systematically. The predicted curvature of the rolled product and rolling force are in good agreement with those of experimental measurements. Therefore, the proposed analytical approach is considered to be applicable for simulating asymmetrical sheet rolling.
{"title":"Analysis of Asymmetrical Sheet Rolling by Stream Function Method","authors":"Y. Hwang, T. Chen","doi":"10.1299/JSMEA1993.39.4_598","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_598","url":null,"abstract":"A mathematical model for asymmetrical sheet rolling is proposed, using the stream function method and the upper bound theorem to investigate the plastic deformation behavior of the sheet at the roll gap. The curvature of the rolled product obtained under various rolling conditions of roll speed ratio, roll radius ratio, friction factor ratio, and inlet angle of the sheet at the entrance of the roll gap, are discussed systematically. The predicted curvature of the rolled product and rolling force are in good agreement with those of experimental measurements. Therefore, the proposed analytical approach is considered to be applicable for simulating asymmetrical sheet rolling.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124190648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_548
Byung‐Nam Kim, Hidehumi Naitoh, S. Wakayama, M. Kawahara
Microfracture processes of microcracking and crack propagation are simulated along with fracture strengths for 2-dimensional alumina polycrystals which have thermal anisotropy within a grain. Microcracks are generated by thermally induced residual stresses at a grain boundary. The stress concentration near the microcrack is calculated numerically by the body force method, and superposed on the pre-existing residual stress. Stress intensity factors at the microcrack tip are also obtained by the method, and the location at which the next microfracture occurs is determined by the competition between microcracking and crack propagation in the new stress state. The microfracture stress increases with the progress of the fracture and decreases after maximum indicating a fracture strength. In many cases, the propagation of microcracks induces an unstable fracture. With decreasing grain size and increasing grain boundary toughness, the number of microfractures prior to the unstable state decreases, while the fracture strengths increase. For alumina of grain size 17.5 μm, when the fracture toughness of the grain boundary is 0.6 times that of the grain or greater, unstable fracture occurs prior to stable microcracking.
{"title":"Simulation of Microfracture Process and Fracture Strength in 2-Dimensional Polycrystalline Materials","authors":"Byung‐Nam Kim, Hidehumi Naitoh, S. Wakayama, M. Kawahara","doi":"10.1299/JSMEA1993.39.4_548","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_548","url":null,"abstract":"Microfracture processes of microcracking and crack propagation are simulated along with fracture strengths for 2-dimensional alumina polycrystals which have thermal anisotropy within a grain. Microcracks are generated by thermally induced residual stresses at a grain boundary. The stress concentration near the microcrack is calculated numerically by the body force method, and superposed on the pre-existing residual stress. Stress intensity factors at the microcrack tip are also obtained by the method, and the location at which the next microfracture occurs is determined by the competition between microcracking and crack propagation in the new stress state. The microfracture stress increases with the progress of the fracture and decreases after maximum indicating a fracture strength. In many cases, the propagation of microcracks induces an unstable fracture. With decreasing grain size and increasing grain boundary toughness, the number of microfractures prior to the unstable state decreases, while the fracture strengths increase. For alumina of grain size 17.5 μm, when the fracture toughness of the grain boundary is 0.6 times that of the grain or greater, unstable fracture occurs prior to stable microcracking.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128818319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_613
F. Tamai, K. Hirano
In general, structural integrity depends on material performance under cyclic loading. It is therefore very important to characterize the fatigue strength characteristics of ceramic/metal joints for wide use in structural applications of engineering ceramics. In this work, in order to clarify the strength characteristics of alumina joints, static strength and cyclic fatigue tests were carried out for joints of Al 2 O 3 /Al 2 O 3 and Al 2 O 3 /Mo/SUS 304/Mo/Al 2 O 3 formed with Ticusil and Cu 80 Ti 20 fillers in vacuum. Static tests were conducted at room temperature and elevated temperature. Fatigue tests were conducted at constant stress ratio R (=0.1) and constant frequency f(=50 Hz) at room temperature. The strength characteristics of the joints of Al 2 O 3 /Al 2 O 3 formed using Ticusil were similar to the strength characteristics of Al 2 O 3 . The strength characteristics of the joints of Al 2 O 3 /Mo/SUS 304/Mo/Al 2 O 3 were mainly determined by those of the joint of Mo/Al 2 O 3 .
{"title":"Characteristics of static and fatigue strength of alumina ceramic joints","authors":"F. Tamai, K. Hirano","doi":"10.1299/JSMEA1993.39.4_613","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_613","url":null,"abstract":"In general, structural integrity depends on material performance under cyclic loading. It is therefore very important to characterize the fatigue strength characteristics of ceramic/metal joints for wide use in structural applications of engineering ceramics. In this work, in order to clarify the strength characteristics of alumina joints, static strength and cyclic fatigue tests were carried out for joints of Al 2 O 3 /Al 2 O 3 and Al 2 O 3 /Mo/SUS 304/Mo/Al 2 O 3 formed with Ticusil and Cu 80 Ti 20 fillers in vacuum. Static tests were conducted at room temperature and elevated temperature. Fatigue tests were conducted at constant stress ratio R (=0.1) and constant frequency f(=50 Hz) at room temperature. The strength characteristics of the joints of Al 2 O 3 /Al 2 O 3 formed using Ticusil were similar to the strength characteristics of Al 2 O 3 . The strength characteristics of the joints of Al 2 O 3 /Mo/SUS 304/Mo/Al 2 O 3 were mainly determined by those of the joint of Mo/Al 2 O 3 .","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116557371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_496
F. Ma, K. Kishimoto
Based on the internal variable theory of thermodynamics, a continuum interface constitutive model relating interface traction with interface separation was developed. An interface damage variable was introduced, and an evaluation equation was derived to characterize the degradation of interfacial rigidity with interface debonding. The present constitutive model was applied to fiber pullout from the matrix, and bridging matrix cracking of composites. Relatively simple closed form formulas were obtained for shear stress distribution along the interface, pulling stress of fiber from the matrix, and stress intensity factor of the small matrix crack tip with fiber bridging. The effects of interface parameters involved in the evaluation equation on interface shear stress distribution, and pulling stress of fiber were also discussed.
{"title":"A Continuum Interface Debonding Model and Application to Matrix Cracking of Composites","authors":"F. Ma, K. Kishimoto","doi":"10.1299/JSMEA1993.39.4_496","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_496","url":null,"abstract":"Based on the internal variable theory of thermodynamics, a continuum interface constitutive model relating interface traction with interface separation was developed. An interface damage variable was introduced, and an evaluation equation was derived to characterize the degradation of interfacial rigidity with interface debonding. The present constitutive model was applied to fiber pullout from the matrix, and bridging matrix cracking of composites. Relatively simple closed form formulas were obtained for shear stress distribution along the interface, pulling stress of fiber from the matrix, and stress intensity factor of the small matrix crack tip with fiber bridging. The effects of interface parameters involved in the evaluation equation on interface shear stress distribution, and pulling stress of fiber were also discussed.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117197204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_633
Byung‐Nam Kim, Hidehumi Naitoh, S. Wakayama
AE (Acoustic Emission) generation behavior during microfracture process of 2-dimensional alumina polycrystals is simulated along with its characteristic parameters, by assuming that a microfracture corresponds to an AE event. The microfracture process is simulated by using the body force method. Various AE generation behaviors are predicted as a function of the grain boundary toughness (Kcb), the grain size and the distribution state of residual stresses due to crystalline anisotropy. The predicted AE events have a tendency to occur at higher stress with increasing K cb and with decreasing grain size. By the fracture-mechanical calculation of the crack opening volume, the relative variation of AE amplitude is also simulated. The actual AE measurements are carried out in vacuum for two kinds of alumina with different grain size, and compared with the simulated results. The cumulative AE event curve for 11.5 μm grain size shows good agreement with the simulation when the K cb is 0.35 times the grain toughness (K cg ), and that for 28.2μm shows good agreement with the simulation at K cb =0.45K cg . The results of AE location for both the simulation and the measurement show the similar characteristics of the scattered distribution over the stressed fields.
{"title":"Simulation of AE Generation Behavior in 2-Dimensional Polycrystals by Using the Body Force Method","authors":"Byung‐Nam Kim, Hidehumi Naitoh, S. Wakayama","doi":"10.1299/JSMEA1993.39.4_633","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_633","url":null,"abstract":"AE (Acoustic Emission) generation behavior during microfracture process of 2-dimensional alumina polycrystals is simulated along with its characteristic parameters, by assuming that a microfracture corresponds to an AE event. The microfracture process is simulated by using the body force method. Various AE generation behaviors are predicted as a function of the grain boundary toughness (Kcb), the grain size and the distribution state of residual stresses due to crystalline anisotropy. The predicted AE events have a tendency to occur at higher stress with increasing K cb and with decreasing grain size. By the fracture-mechanical calculation of the crack opening volume, the relative variation of AE amplitude is also simulated. The actual AE measurements are carried out in vacuum for two kinds of alumina with different grain size, and compared with the simulated results. The cumulative AE event curve for 11.5 μm grain size shows good agreement with the simulation when the K cb is 0.35 times the grain toughness (K cg ), and that for 28.2μm shows good agreement with the simulation at K cb =0.45K cg . The results of AE location for both the simulation and the measurement show the similar characteristics of the scattered distribution over the stressed fields.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133200309","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1996-10-15DOI: 10.1299/JSMEA1993.39.4_489
Kohji Ohgushi, M. Ichikawa
In our previous papers, we showed that the ring crack initiation strength (microfracture strength) of gas-pressure-sintered silicon nitride, evaluated by the sphere indentation method, is not related to the conventional flexural strength of the same material, using the concept of effective area based on the Weibull distribution function. In the present study, to clarify the reason for this, a model for initiation of a ring crack emanating from a surface microcrack was introduced. Using this model, the microfracture strength was discussed from the viewpoint of fracture mechanics. The dependence of the ring crack initiation load on the indenter radius was also examined. As a result, the essential difference between the microfracture and flexural strengths was well interpreted using this model.
{"title":"Fracture Mechanics Study of Ring Crack Initiation in Ceramics by Sphere Indentation","authors":"Kohji Ohgushi, M. Ichikawa","doi":"10.1299/JSMEA1993.39.4_489","DOIUrl":"https://doi.org/10.1299/JSMEA1993.39.4_489","url":null,"abstract":"In our previous papers, we showed that the ring crack initiation strength (microfracture strength) of gas-pressure-sintered silicon nitride, evaluated by the sphere indentation method, is not related to the conventional flexural strength of the same material, using the concept of effective area based on the Weibull distribution function. In the present study, to clarify the reason for this, a model for initiation of a ring crack emanating from a surface microcrack was introduced. Using this model, the microfracture strength was discussed from the viewpoint of fracture mechanics. The dependence of the ring crack initiation load on the indenter radius was also examined. As a result, the essential difference between the microfracture and flexural strengths was well interpreted using this model.","PeriodicalId":143127,"journal":{"name":"JSME international journal. Series A, mechanics and material engineering","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132158604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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