A bolted joint is one of the most common fastening techniques. While the behavior of bolted joints under static or quasi-static conditions is well documented, their behavior under shock/impact loading is not well-understood. In many applications, where a bolted joint connects a sensitive component to the rest of a structure, it is important to interpret shock propagation through the bolted joints. This problem is further complicated owing to the fact that a bolted joint exhibits multiple types of nonlinearities, due to the interaction between the bolts and clamped parts, thread friction between the shank and nut, pre-tension, damping characteristics, and interference with the hole. This study was focused on developing computational techniques for understanding shock propagation through a bolted joint. As a case study, the behavior of a bolted joint within a two-component cylindrical structure subjected to impact loading was considered. A finite element (FE) model of the fixture was developed. Two different approaches were considered. The first one modeled the bolt assembly as one part. The second model had the bolt and nut as separate parts. In this model, the tie contact between the bolt shank and the nut was defined using a shear failure criterion. Both models included bolt pre-tension. The two models were compared based on energy balance, acceleration signal, and displacement at the base of the fixture. The results indicated that the model with the separate bolt and nut resulted in a more realistic performance.
{"title":"Effect of Bolted Joints on Shock Propagation Across Structures Under Medium Impact Loading","authors":"P. Shojaei, M. Trabia, B. O’Toole","doi":"10.1115/imece2019-11799","DOIUrl":"https://doi.org/10.1115/imece2019-11799","url":null,"abstract":"\u0000 A bolted joint is one of the most common fastening techniques. While the behavior of bolted joints under static or quasi-static conditions is well documented, their behavior under shock/impact loading is not well-understood. In many applications, where a bolted joint connects a sensitive component to the rest of a structure, it is important to interpret shock propagation through the bolted joints. This problem is further complicated owing to the fact that a bolted joint exhibits multiple types of nonlinearities, due to the interaction between the bolts and clamped parts, thread friction between the shank and nut, pre-tension, damping characteristics, and interference with the hole.\u0000 This study was focused on developing computational techniques for understanding shock propagation through a bolted joint. As a case study, the behavior of a bolted joint within a two-component cylindrical structure subjected to impact loading was considered. A finite element (FE) model of the fixture was developed. Two different approaches were considered. The first one modeled the bolt assembly as one part. The second model had the bolt and nut as separate parts. In this model, the tie contact between the bolt shank and the nut was defined using a shear failure criterion. Both models included bolt pre-tension. The two models were compared based on energy balance, acceleration signal, and displacement at the base of the fixture. The results indicated that the model with the separate bolt and nut resulted in a more realistic performance.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125527888","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}
Immersed boundary methods have gained increasing attention in modeling fluid-solid body interaction using non-body conforming computational fluid dynamics, due to their robustness and simplicity. They usually do this by adding a body force term in the momentum equation. The magnitude and direction of this body force ensure that the boundary condition on the solid-fluid interface is satisfied without invoking complicated body-conforming numerical methods to impose the boundary condition. The body force is usually calculated and imposed using some interpolation or extrapolation around the solid-fluid interface. It can also be calculated based on the solid volume fraction in the cells around the solid-fluid interface. Therefore, it is critical to have a robust method to represent or track arbitrary solid bodies immersed in a fluid field and facilitate the needed interpolation, extrapolation, or calculation of solid volume fraction. To that end, the level set method has been used as a robust method to represent and track arbitrary solid bodies in a fluid field. In the presented paper, the level set based approaches used to handle arbitrary solid bodies in a fluid field are reviewed, and a new higher order method is presented to resolve the solid-fluid interface using the given level sets at each grid point.
{"title":"A Level Set Based Geometry Handling Approach Used in the Immersed Boundary Methods for Fluid-Structure Interaction","authors":"G. Yao","doi":"10.1115/imece2019-10237","DOIUrl":"https://doi.org/10.1115/imece2019-10237","url":null,"abstract":"\u0000 Immersed boundary methods have gained increasing attention in modeling fluid-solid body interaction using non-body conforming computational fluid dynamics, due to their robustness and simplicity. They usually do this by adding a body force term in the momentum equation. The magnitude and direction of this body force ensure that the boundary condition on the solid-fluid interface is satisfied without invoking complicated body-conforming numerical methods to impose the boundary condition. The body force is usually calculated and imposed using some interpolation or extrapolation around the solid-fluid interface. It can also be calculated based on the solid volume fraction in the cells around the solid-fluid interface. Therefore, it is critical to have a robust method to represent or track arbitrary solid bodies immersed in a fluid field and facilitate the needed interpolation, extrapolation, or calculation of solid volume fraction. To that end, the level set method has been used as a robust method to represent and track arbitrary solid bodies in a fluid field. In the presented paper, the level set based approaches used to handle arbitrary solid bodies in a fluid field are reviewed, and a new higher order method is presented to resolve the solid-fluid interface using the given level sets at each grid point.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131691588","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}
Displacement and stress fields in a functionally graded (FG) fiber-reinforced rotating annular disk with a non-uniform thickness profile, subjected to angular deceleration and a temperature profile were investigated. Unidirectional fibers were considered to be circumferentially distributed within the disk with fiber volume fraction changing radially. The governing equations for displacement, stress, and temperature fields were solved using finite difference method. The results indicated that thermal induced stresses were more dominate than the rotational induced stresses. Disks which were fiber rich at the inner radius, the fibers made negligible difference on the displacement and stress fields when compared to a homogenous disk made from the matrix material. In addition, it was found that the deceleration magnitude had no effect on the radial and hoop stresses, nor the temperature on the developed shear stress. The shear stress was only affected by the disk deceleration. Tsai-Wu failure criterion was applied for decelerating disks to ascertain their failure behavior. The results show that Tsai-Wu failure index is dominated by the thermal stresses.
{"title":"Thermoelastic Response of Functionally Graded Fiber-Reinforced Rotating Disk With Non-Uniform Thickness Profile Under Variable Angular Velocity","authors":"H. Nayeb-Hashemi, Yue Zheng, A. Vaziri, M. Olia","doi":"10.1115/imece2019-10213","DOIUrl":"https://doi.org/10.1115/imece2019-10213","url":null,"abstract":"\u0000 Displacement and stress fields in a functionally graded (FG) fiber-reinforced rotating annular disk with a non-uniform thickness profile, subjected to angular deceleration and a temperature profile were investigated. Unidirectional fibers were considered to be circumferentially distributed within the disk with fiber volume fraction changing radially. The governing equations for displacement, stress, and temperature fields were solved using finite difference method. The results indicated that thermal induced stresses were more dominate than the rotational induced stresses. Disks which were fiber rich at the inner radius, the fibers made negligible difference on the displacement and stress fields when compared to a homogenous disk made from the matrix material. In addition, it was found that the deceleration magnitude had no effect on the radial and hoop stresses, nor the temperature on the developed shear stress. The shear stress was only affected by the disk deceleration. Tsai-Wu failure criterion was applied for decelerating disks to ascertain their failure behavior. The results show that Tsai-Wu failure index is dominated by the thermal stresses.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116549141","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}
Packed stuffing boxes are sealing devices used in valves, compressors and pumps. The compression packing is the most critical element of this assembly. Packing rings are compressed axially to produce lateral contact pressures large enough to confine the processed fluid within the pressurized valve and avoids leakage to the outer boundary. Although popular, this old method of sealing has seen very limited analytical and numerical development. There is no standard design procedure for engineers to follow, and the existing standard test procedures are limited to qualification and quality control tests such as API622, 624, ISO-15848 1 and 2. As a result, structural integrity and leak tightness are rarely verified, and consequently 60 % of pressurized equipment requiring fugitive emissions compliance are valves that use this type of sealing device. The mechanical properties of compression packing materials are the main factors affecting fluid tightness at room and high temperatures and yet there is little or no data available either in manufacturer’s catalogues or in the literature. Packed stuffing box research is scant and focuses mostly on the distribution of the contact pressure between the stem and packing at room temperature without considering packing mechanical properties such as rigidity, thermal expansion, creep and aging. It is proposed, in this project, to measure the mechanical properties such as pressure transmission ratio, short-term creep deformation and thermal expansion coefficient of two packing materials at high temperature. This initiative will serve as a basis to launch a North American testing program to develop ASTM-like testing procedures for compression packing at high temperature.
{"title":"Mechanical Characterization of Valve Compression Packing at High Temperature","authors":"Xavier Legault, A. Bouzid, Ali Salah Omar Aweimer","doi":"10.1115/imece2019-10103","DOIUrl":"https://doi.org/10.1115/imece2019-10103","url":null,"abstract":"\u0000 Packed stuffing boxes are sealing devices used in valves, compressors and pumps. The compression packing is the most critical element of this assembly. Packing rings are compressed axially to produce lateral contact pressures large enough to confine the processed fluid within the pressurized valve and avoids leakage to the outer boundary. Although popular, this old method of sealing has seen very limited analytical and numerical development. There is no standard design procedure for engineers to follow, and the existing standard test procedures are limited to qualification and quality control tests such as API622, 624, ISO-15848 1 and 2. As a result, structural integrity and leak tightness are rarely verified, and consequently 60 % of pressurized equipment requiring fugitive emissions compliance are valves that use this type of sealing device.\u0000 The mechanical properties of compression packing materials are the main factors affecting fluid tightness at room and high temperatures and yet there is little or no data available either in manufacturer’s catalogues or in the literature. Packed stuffing box research is scant and focuses mostly on the distribution of the contact pressure between the stem and packing at room temperature without considering packing mechanical properties such as rigidity, thermal expansion, creep and aging. It is proposed, in this project, to measure the mechanical properties such as pressure transmission ratio, short-term creep deformation and thermal expansion coefficient of two packing materials at high temperature. This initiative will serve as a basis to launch a North American testing program to develop ASTM-like testing procedures for compression packing at high temperature.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116069321","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}
J. Mersch, Jeffrey A. Smith, G. Orient, Peter W. Grimmer, J. Gearhart
Multiple fastener reduced-order models and fitting strategies are used on a multiaxial dataset and these models are further evaluated using a high-fidelity analysis model to demonstrate how well these strategies predict load-displacement behavior and failure. Two common reduced-order modeling approaches, the plug and spot weld, are calibrated, assessed, and compared to a more intensive approach — a “two-block” plug calibrated to multiple datasets. An optimization analysis workflow leveraging a genetic algorithm was exercised on a set of quasistatic test data where fasteners were pulled at angles from 0° to 90° in 15° increments to obtain material parameters for a fastener model that best capture the load-displacement behavior of the chosen datasets. The one-block plug is calibrated just to the tension data, the spot weld is calibrated to the tension (0°) and shear (90°), and the two-block plug is calibrated to all data available (0°–90°). These calibrations are further assessed by incorporating these models and modeling approaches into a high-fidelity analysis model of the test setup and comparing the load-displacement predictions to the raw test data.
{"title":"Calibration Strategies and Modeling Approaches for Predicting Load-Displacement Behavior and Failure for Multiaxial Loadings in Threaded Fasteners","authors":"J. Mersch, Jeffrey A. Smith, G. Orient, Peter W. Grimmer, J. Gearhart","doi":"10.1115/imece2019-10521","DOIUrl":"https://doi.org/10.1115/imece2019-10521","url":null,"abstract":"\u0000 Multiple fastener reduced-order models and fitting strategies are used on a multiaxial dataset and these models are further evaluated using a high-fidelity analysis model to demonstrate how well these strategies predict load-displacement behavior and failure. Two common reduced-order modeling approaches, the plug and spot weld, are calibrated, assessed, and compared to a more intensive approach — a “two-block” plug calibrated to multiple datasets. An optimization analysis workflow leveraging a genetic algorithm was exercised on a set of quasistatic test data where fasteners were pulled at angles from 0° to 90° in 15° increments to obtain material parameters for a fastener model that best capture the load-displacement behavior of the chosen datasets. The one-block plug is calibrated just to the tension data, the spot weld is calibrated to the tension (0°) and shear (90°), and the two-block plug is calibrated to all data available (0°–90°). These calibrations are further assessed by incorporating these models and modeling approaches into a high-fidelity analysis model of the test setup and comparing the load-displacement predictions to the raw test data.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"428 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126078308","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}
M. Ramzanpour, Mohammad Hosseini-Farid, M. Ziejewski, G. Karami
Hyperelastic constitutive models such as Ogden and Mooney-Rivlin are commonly used for nonlinear characterization of soft materials and especially biomaterials such as brain tissue. The parameters of these models are usually found by curve-fitting to the experimental or in some cases, the numerical data. Most of the times, common non-linear least square curve fitting method known as Levenberg-Marquardt (LM) is employed for this purpose. In this paper, we show that the result of this method is highly dependent to the initial guesses. In some cases, the approximated curve-fitting solution can be very close to the experimental data, however, the hyperelastic parameters can be very different to the actual ones despite the fact that a very good curve-fitting solution (high coefficient of correlation) may be achieved. To overcome this problem, we demonstrate the application of a derivative free (black box) optimization method called particle swarm optimization (PSO) for hyperelastic characterization of nonlinear materials using least square method. Using multiple search agents in PSO makes this method highly inclined to end up with global optimum points in the search space. In this study, the hyperelastic parameters for Ogden and Mooney-Rivlin hyperelastic models are found for bovine brain tissue by using the experimental uniaxial compression test data. The PSO method yields high coefficient of correlation for curve fitting and its results is comparable to the LM method in terms of accuracy of parameters. It is concluded that PSO can be successfully used for nonlinear hyperelastic characterization of soft materials such as brain tissue.
{"title":"Particle Swarm Optimization Method for Hyperelastic Characterization of Soft Tissues","authors":"M. Ramzanpour, Mohammad Hosseini-Farid, M. Ziejewski, G. Karami","doi":"10.1115/imece2019-11829","DOIUrl":"https://doi.org/10.1115/imece2019-11829","url":null,"abstract":"\u0000 Hyperelastic constitutive models such as Ogden and Mooney-Rivlin are commonly used for nonlinear characterization of soft materials and especially biomaterials such as brain tissue. The parameters of these models are usually found by curve-fitting to the experimental or in some cases, the numerical data. Most of the times, common non-linear least square curve fitting method known as Levenberg-Marquardt (LM) is employed for this purpose. In this paper, we show that the result of this method is highly dependent to the initial guesses. In some cases, the approximated curve-fitting solution can be very close to the experimental data, however, the hyperelastic parameters can be very different to the actual ones despite the fact that a very good curve-fitting solution (high coefficient of correlation) may be achieved. To overcome this problem, we demonstrate the application of a derivative free (black box) optimization method called particle swarm optimization (PSO) for hyperelastic characterization of nonlinear materials using least square method. Using multiple search agents in PSO makes this method highly inclined to end up with global optimum points in the search space. In this study, the hyperelastic parameters for Ogden and Mooney-Rivlin hyperelastic models are found for bovine brain tissue by using the experimental uniaxial compression test data. The PSO method yields high coefficient of correlation for curve fitting and its results is comparable to the LM method in terms of accuracy of parameters. It is concluded that PSO can be successfully used for nonlinear hyperelastic characterization of soft materials such as brain tissue.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122234550","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}
In this paper, the Method of Multiple Scales (MMS) is used to investigate the influences of the nonlinear intertube van der Waals coefficient, dimensionless damping, and voltage on the amplitude-frequency response of an electrostatically actuated double-walled carbon nanotube (DWCNT). The forces responsible for the nonlinearities in the vibrational behavior are intertube van der Waals and electrostatic forces. For perturbation, a small viscous damping and soft AC actuation are assumed for numerical simulation. For the first time in literature, forced vibration of the noncoaxial (out-of-phase) case is investigated. In this mode of vibration, the outer and inner carbon nanotubes move at ultra-high frequency in opposite direction, i.e., negative amplitude ratio. The DWCNT structure is modelled as a cantilever beam with Euler-Bernoulli beam assumptions since the DWCNT is assumed to have a high length-diameter ratio. The results shown assume steady-state solutions in the second-order MMS solution. The importance of the results in this paper are the effect of the strong nonlinearity of the van der Waals coefficient, damping, and voltage on the the DWCNT vibration.
{"title":"Noncoaxial Vibration of Electrostatically Actuated DWCNT: Frequency Response of Primary Resonance","authors":"D. Caruntu, E. Juarez","doi":"10.1115/imece2019-11187","DOIUrl":"https://doi.org/10.1115/imece2019-11187","url":null,"abstract":"\u0000 In this paper, the Method of Multiple Scales (MMS) is used to investigate the influences of the nonlinear intertube van der Waals coefficient, dimensionless damping, and voltage on the amplitude-frequency response of an electrostatically actuated double-walled carbon nanotube (DWCNT). The forces responsible for the nonlinearities in the vibrational behavior are intertube van der Waals and electrostatic forces. For perturbation, a small viscous damping and soft AC actuation are assumed for numerical simulation. For the first time in literature, forced vibration of the noncoaxial (out-of-phase) case is investigated. In this mode of vibration, the outer and inner carbon nanotubes move at ultra-high frequency in opposite direction, i.e., negative amplitude ratio. The DWCNT structure is modelled as a cantilever beam with Euler-Bernoulli beam assumptions since the DWCNT is assumed to have a high length-diameter ratio. The results shown assume steady-state solutions in the second-order MMS solution. The importance of the results in this paper are the effect of the strong nonlinearity of the van der Waals coefficient, damping, and voltage on the the DWCNT vibration.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127758753","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}
The widespread use of sodium aluminosilicate glass in many critical applications due to its hardness, weight, density and optical properties (transparency, dielectric etc.), instead of metals or plastics has become common in recent years. However, glass which is known to be a brittle material has its own vulnerability to fracture. Processes such as heat treatment (heat tempering) or chemical strengthening, through ion-exchange have been deployed to create residual stress profile on the glass, in a bid to improve its strength for applications such as in the automobile windshield design, consumer electronics mobile communication devices e.g. smartphones and tablet etc. However, failure still occurs which is mostly catastrophic and expensive to repair. Therefore, understanding, predicting and eventually improving the resistance to damage or fracture of chemically strengthened glass is significant to designing new glasses that would be tougher, while retaining their transparency. The relationship between the glass residual stress parameters, compressive stress (CS), depth of layer (DOL), center tension (CT) and fracture strength was investigated in this study using a grit particle blast plus ring on ring test method, based on IEC standard for retained biaxial flexural strength measurements. This technique can be used to measure both the surface and edge fracture strength of the glass. Preliminary results showed that for a reasonable level of CS, and CT, high DOL are beneficial to resisting fracture due to severe surface damage, while a high CS and low CT are beneficial to resisting fractures due to shallower flaws. The correlation of critical stress intensity factor versus DOL and CT for various level of CS were also determined and discussed. These results provide a valuable piece of information in the design of a more robust glass in engineering applications.
{"title":"Effect of Ion-Exchange Chemistry on the Fracture of Chemically Strengthened Sodium Aluminosilicate Glass","authors":"Benedict Egboiyi, T. Sain","doi":"10.1115/imece2019-11700","DOIUrl":"https://doi.org/10.1115/imece2019-11700","url":null,"abstract":"\u0000 The widespread use of sodium aluminosilicate glass in many critical applications due to its hardness, weight, density and optical properties (transparency, dielectric etc.), instead of metals or plastics has become common in recent years.\u0000 However, glass which is known to be a brittle material has its own vulnerability to fracture. Processes such as heat treatment (heat tempering) or chemical strengthening, through ion-exchange have been deployed to create residual stress profile on the glass, in a bid to improve its strength for applications such as in the automobile windshield design, consumer electronics mobile communication devices e.g. smartphones and tablet etc. However, failure still occurs which is mostly catastrophic and expensive to repair. Therefore, understanding, predicting and eventually improving the resistance to damage or fracture of chemically strengthened glass is significant to designing new glasses that would be tougher, while retaining their transparency. The relationship between the glass residual stress parameters, compressive stress (CS), depth of layer (DOL), center tension (CT) and fracture strength was investigated in this study using a grit particle blast plus ring on ring test method, based on IEC standard for retained biaxial flexural strength measurements. This technique can be used to measure both the surface and edge fracture strength of the glass. Preliminary results showed that for a reasonable level of CS, and CT, high DOL are beneficial to resisting fracture due to severe surface damage, while a high CS and low CT are beneficial to resisting fractures due to shallower flaws. The correlation of critical stress intensity factor versus DOL and CT for various level of CS were also determined and discussed. These results provide a valuable piece of information in the design of a more robust glass in engineering applications.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127624167","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}
Isabella Bozzo, M. Amabili, Prabakaran Balasubramanian, I. Breslavsky, Giovanni Ferrari
Heart disease is the second leading cause of death in Canada resulting in $20.9 billion annual healthcare expenditures [1,2]. Understanding the mechanics of the human descending thoracic aorta is fundamental for comprehending the development of pathologies and improving surgical prostheses. This study presents hyperelastic and viscoelastic material characterizations of the human descending thoracic aorta from twelve different donors, with a mean age of 49.4 years. The specimens were dissected into the three constituent layers: intima, media and adventitia. Evaluating the layer-specific opening angles led to the computation of the circumferential residual stresses. Uniaxial tensile tests of each layer, in both the circumferential and axial direction, were used to model the hyperelastic behavior according to the Gasser-Ogden-Holzapfel model (GOH). The storage modulus and loss tangent for the layers were obtained from uniaxial harmonic excitations at varied frequencies, to model the viscoelastic behavior with the generalized Maxwell model. The results showed a positive correlation between age and stiffness for all layers, both axially and circumferentially. Similar loss tangent values were found across the three layers. A large increase in the storage modulus from static to dynamic experiments further corroborates the importance of a viscoelastic model of the aorta, rather than solely hyperelastic.
{"title":"Experimental Determination of Layer-Specific Hyperelastic Parameters of Human Descending Thoracic Aortas","authors":"Isabella Bozzo, M. Amabili, Prabakaran Balasubramanian, I. Breslavsky, Giovanni Ferrari","doi":"10.1115/imece2019-10667","DOIUrl":"https://doi.org/10.1115/imece2019-10667","url":null,"abstract":"\u0000 Heart disease is the second leading cause of death in Canada resulting in $20.9 billion annual healthcare expenditures [1,2]. Understanding the mechanics of the human descending thoracic aorta is fundamental for comprehending the development of pathologies and improving surgical prostheses. This study presents hyperelastic and viscoelastic material characterizations of the human descending thoracic aorta from twelve different donors, with a mean age of 49.4 years. The specimens were dissected into the three constituent layers: intima, media and adventitia. Evaluating the layer-specific opening angles led to the computation of the circumferential residual stresses. Uniaxial tensile tests of each layer, in both the circumferential and axial direction, were used to model the hyperelastic behavior according to the Gasser-Ogden-Holzapfel model (GOH). The storage modulus and loss tangent for the layers were obtained from uniaxial harmonic excitations at varied frequencies, to model the viscoelastic behavior with the generalized Maxwell model. The results showed a positive correlation between age and stiffness for all layers, both axially and circumferentially. Similar loss tangent values were found across the three layers. A large increase in the storage modulus from static to dynamic experiments further corroborates the importance of a viscoelastic model of the aorta, rather than solely hyperelastic.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120880484","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}
Previously, we experimentally studied high-temperature behavior of three types of castable particle-reinforced ceramic composites that we designed for application in aerospace industry. These composites contain Zirconia particles (ZrO2) and bubbles, and silicon-carbide (SiC) particles as reinforcements, dispersed in an alumina (Al2O3) matrix. The present work aims to implement a Finite Element (FE) damage mechanics modeling approach based on the experimental results to investigate micro-scale mechanisms of failure in these materials and ascertain the effect of particle size and volume fraction (VF). Different mechanisms of failure are detected for different types of inclusions, and the percentage of yielded elements seem to strongly correlate with the theoretical thermal shock indices. Additionally, within the limits of this study, VF showed to have a positive correlation with the percentage of yielded elements, whereas inclusion size depicted an inverse correlation to that parameter. These novel findings shed new light on the micro-scale mechanisms of thermal failure in ceramic composites with complex microstructures.
{"title":"Finite Element Microstructural Analysis of Thermal Damage in High Volume Fraction RVE of Particle-Reinforced Refractory Composites","authors":"Kamran Makarian, S. Santhanam","doi":"10.1115/imece2019-12040","DOIUrl":"https://doi.org/10.1115/imece2019-12040","url":null,"abstract":"\u0000 Previously, we experimentally studied high-temperature behavior of three types of castable particle-reinforced ceramic composites that we designed for application in aerospace industry. These composites contain Zirconia particles (ZrO2) and bubbles, and silicon-carbide (SiC) particles as reinforcements, dispersed in an alumina (Al2O3) matrix. The present work aims to implement a Finite Element (FE) damage mechanics modeling approach based on the experimental results to investigate micro-scale mechanisms of failure in these materials and ascertain the effect of particle size and volume fraction (VF). Different mechanisms of failure are detected for different types of inclusions, and the percentage of yielded elements seem to strongly correlate with the theoretical thermal shock indices. Additionally, within the limits of this study, VF showed to have a positive correlation with the percentage of yielded elements, whereas inclusion size depicted an inverse correlation to that parameter. These novel findings shed new light on the micro-scale mechanisms of thermal failure in ceramic composites with complex microstructures.","PeriodicalId":375383,"journal":{"name":"Volume 9: Mechanics of Solids, Structures, and Fluids","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125304261","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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