Pub Date : 2020-11-19DOI: 10.2495/cmem-v8-n4-326-340
F. Evangelista, S. Hernández, S. Mambretti, D. Parola
Most of the water pipe infrastructure is outdated; therefore, frequent maintenance and repair works are required. To speed up the rehabilitation work and to have a more sustainable and efficient approach, trenchless methodologies have been developed in the last decades. One of the most cost-effective trenchless methods is the so-called Cured in Place Pipeline (CIPP) method, in which a resin-impregnated liner is pulled or inverted inside the host pipe and, when cured, it restores the old pipe structural and mechanical integrity. The aim of this study is to analyse the effects of the presence of a CIPP liner in a deteriorated pipe during unsteady flow for compressible fluids. In particular, the paper deals with a new formulation to compute the celerity of the wave which produces the overpressures, when the pipe wall is composed of both the host (old) pipe and the new liner, whose thickness depends on the required mechanical characteristics. The problem is strictly dependent on the mechanical properties of the liner. In order to obtain the new formula for celerity, the linear elastic problem for multi-layered pipes has been solved. The theoretical results have been validated by performing numerical simulation analysis using a Boundary Element model, with the software BEASYTM. The resulting circumferential strain is integrated in the continuity equation, deriving the new formula to compute the wave celerity. The values of the celerity are dependent on the thickness and on the elastic properties of the liner. The behaviour of several combinations of thickness of the liner and Young’s modulus values has been studied and the results have been critically shown in the paper.
{"title":"Wave celerity in hydraulic transients computation for CIPP-rehabilitated pipes","authors":"F. Evangelista, S. Hernández, S. Mambretti, D. Parola","doi":"10.2495/cmem-v8-n4-326-340","DOIUrl":"https://doi.org/10.2495/cmem-v8-n4-326-340","url":null,"abstract":"Most of the water pipe infrastructure is outdated; therefore, frequent maintenance and repair works are required. To speed up the rehabilitation work and to have a more sustainable and efficient approach, trenchless methodologies have been developed in the last decades. One of the most cost-effective trenchless methods is the so-called Cured in Place Pipeline (CIPP) method, in which a resin-impregnated liner is pulled or inverted inside the host pipe and, when cured, it restores the old pipe structural and mechanical integrity. The aim of this study is to analyse the effects of the presence of a CIPP liner in a deteriorated pipe during unsteady flow for compressible fluids. In particular, the paper deals with a new formulation to compute the celerity of the wave which produces the overpressures, when the pipe wall is composed of both the host (old) pipe and the new liner, whose thickness depends on the required mechanical characteristics. The problem is strictly dependent on the mechanical properties of the liner. In order to obtain the new formula for celerity, the linear elastic problem for multi-layered pipes has been solved. The theoretical results have been validated by performing numerical simulation analysis using a Boundary Element model, with the software BEASYTM. The resulting circumferential strain is integrated in the continuity equation, deriving the new formula to compute the wave celerity. The values of the celerity are dependent on the thickness and on the elastic properties of the liner. The behaviour of several combinations of thickness of the liner and Young’s modulus values has been studied and the results have been critically shown in the paper.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"164 1","pages":"326-340"},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73075480","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 : 2020-11-19DOI: 10.2495/cmem-v8-n4-387-404
J. Quintela, J. A. Jurado, C. Rapela, A. J. Álvarez, M. Roca, S. Hernández, M. C. Montoya, J. M. López, A. Ruiz, I. Moreno, S. Jiménez
The current development of renewable energies has originated a number of new structural typologies that are the physical support of the energy production systems. Photovoltaic energy is a very mature source and it is obtained using rows of panels implemented in a longitudinal grillage. Many studies have been carried out in the past with an aim to improve the capacity to obtain electrical power, but another important issue is the need to guarantee the performance of these industrial facilities under the phenomena induced by the turbulent wind flow, taking into account the fact that they are usually built in wide open spaces. This paper describes an extensive research carried out on two configurations of solar trackers by experimental and computational methods. The former was composed of a number of tests of reduced models of segments of the solar trackers, which were carried out in an aerodynamic wind tunnel. The latter consisted of a series of structural analyses worked out through a finite element model of the full panel subjected to aerodynamic and aeroelastic loads. Several angles of attack of the wind flow and a wide range of wind speeds were included in the study. This approach allowed to clearly evaluate the structural and dynamic performance of both the configurations of solar trackers under the most important wind-induced phenomena such as vortex shedding, torsional divergence, and flutter. The paper relates the phases of the study and informs about the more relevant numerical results obtained in the experiments and the computer analysis.
{"title":"Experimental and computational studies on the performance of solar trackers under vortex shedding, torsional divergence, and flutter","authors":"J. Quintela, J. A. Jurado, C. Rapela, A. J. Álvarez, M. Roca, S. Hernández, M. C. Montoya, J. M. López, A. Ruiz, I. Moreno, S. Jiménez","doi":"10.2495/cmem-v8-n4-387-404","DOIUrl":"https://doi.org/10.2495/cmem-v8-n4-387-404","url":null,"abstract":"The current development of renewable energies has originated a number of new structural typologies that are the physical support of the energy production systems. Photovoltaic energy is a very mature source and it is obtained using rows of panels implemented in a longitudinal grillage. Many studies have been carried out in the past with an aim to improve the capacity to obtain electrical power, but another important issue is the need to guarantee the performance of these industrial facilities under the phenomena induced by the turbulent wind flow, taking into account the fact that they are usually built in wide open spaces. This paper describes an extensive research carried out on two configurations of solar trackers by experimental and computational methods. The former was composed of a number of tests of reduced models of segments of the solar trackers, which were carried out in an aerodynamic wind tunnel. The latter consisted of a series of structural analyses worked out through a finite element model of the full panel subjected to aerodynamic and aeroelastic loads. Several angles of attack of the wind flow and a wide range of wind speeds were included in the study. This approach allowed to clearly evaluate the structural and dynamic performance of both the configurations of solar trackers under the most important wind-induced phenomena such as vortex shedding, torsional divergence, and flutter. The paper relates the phases of the study and informs about the more relevant numerical results obtained in the experiments and the computer analysis.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"3 1","pages":"387-404"},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89959568","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 : 2020-11-19DOI: 10.2495/cmem-v8-n4-289-315
B. Wilkins, T. Hromadka, Jackson McInvale
In this paper, we introduce a new node positioning algorithm (NPA) for determining suitable locations of the computational nodes that are a typical feature of mesh reduction numerical methods for partial differential equations – specifically, the Complex Variable Boundary Element Method (CVBEM). The novelty of the introduced NPA is a ‘position refinement’ procedure, which facilitates the relocation of nodes that are already being used in the current CVBEM model when such relocation reduces the maximum error of the associated CVBEM model. The results of the new NPA (referred to as NPA2) are compared to the results obtained using the recent NPA described in [1] (referred to as NPA1). We compare NPA1 and NPA2 by modeling two example Dirichlet boundary value problems that have been selected due to having regions of extreme curvature in the analytic flow regime that are difficult to model computationally. Consequently, these problems serve as good benchmark problems for testing the efficacy of the current and future NPAs. Our empirical findings suggest that the use of NPA2 can reduce the maximum error of the associated CVBEM model by several orders of magnitude compared to the corresponding result obtained using NPA1.
{"title":"Comparison of two algorithms for locating computational nodes in the complex variable boundary element method (CVBEM)","authors":"B. Wilkins, T. Hromadka, Jackson McInvale","doi":"10.2495/cmem-v8-n4-289-315","DOIUrl":"https://doi.org/10.2495/cmem-v8-n4-289-315","url":null,"abstract":"In this paper, we introduce a new node positioning algorithm (NPA) for determining suitable locations of the computational nodes that are a typical feature of mesh reduction numerical methods for partial differential equations – specifically, the Complex Variable Boundary Element Method (CVBEM). The novelty of the introduced NPA is a ‘position refinement’ procedure, which facilitates the relocation of nodes that are already being used in the current CVBEM model when such relocation reduces the maximum error of the associated CVBEM model. The results of the new NPA (referred to as NPA2) are compared to the results obtained using the recent NPA described in [1] (referred to as NPA1). We compare NPA1 and NPA2 by modeling two example Dirichlet boundary value problems that have been selected due to having regions of extreme curvature in the analytic flow regime that are difficult to model computationally. Consequently, these problems serve as good benchmark problems for testing the efficacy of the current and future NPAs. Our empirical findings suggest that the use of NPA2 can reduce the maximum error of the associated CVBEM model by several orders of magnitude compared to the corresponding result obtained using NPA1.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"17 1","pages":"289-315"},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85393327","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 : 2020-11-19DOI: 10.2495/cmem-v8-n4-316-325
Valeria Scapini, Eduardo Zuñiga
Motivated by the fact that Chile is one of the most seismically active countries in the world (located over the ‘Pacific Ring of Fire’), we define a methodology for estimating the cost of housing reconstruction by modelling the occurrence of natural disasters as a Markov chain. Specifically, the states of the chain correspond to the different possible conditions of the housing infrastructure and the transition probabilities represent the possibility of change from one condition to another once the disaster has occurred. We prove that for the case of the 2010 Chilean earthquake, the matrix representing the process admits a stationary state vector. Using this vector, which we interpreted as the portion of time that the chain spends in each state in the long term, we define a cost function associated with total reconstruction. If this cost function is continuous, then this methodology allows policymakers to make decisions when facing the trade-off between current partial reconstruction and future total reconstruction.
{"title":"A markov chain approach to model reconstruction","authors":"Valeria Scapini, Eduardo Zuñiga","doi":"10.2495/cmem-v8-n4-316-325","DOIUrl":"https://doi.org/10.2495/cmem-v8-n4-316-325","url":null,"abstract":"Motivated by the fact that Chile is one of the most seismically active countries in the world (located over the ‘Pacific Ring of Fire’), we define a methodology for estimating the cost of housing reconstruction by modelling the occurrence of natural disasters as a Markov chain. Specifically, the states of the chain correspond to the different possible conditions of the housing infrastructure and the transition probabilities represent the possibility of change from one condition to another once the disaster has occurred. We prove that for the case of the 2010 Chilean earthquake, the matrix representing the process admits a stationary state vector. Using this vector, which we interpreted as the portion of time that the chain spends in each state in the long term, we define a cost function associated with total reconstruction. If this cost function is continuous, then this methodology allows policymakers to make decisions when facing the trade-off between current partial reconstruction and future total reconstruction.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"24 1","pages":"316-325"},"PeriodicalIF":0.0,"publicationDate":"2020-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79621933","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 : 2020-08-25DOI: 10.2495/cmem-v8-n3-252-269
Arka Das, E. Divo, F. Moslehy, A. Kassab
This article introduces an innovative technique that integrates a genetic algorithm (GA)-based digital image correlation with laser speckle photography for the estimation of surface displacements in structures. The images (before and after deformation) are digitized using a digital camera, and the grayscale intensity matrices are read and processed by an image processing algorithm. The two matrices of the images are then inputted into GA-based optimizer that utilizes an advanced cross-correlation fitness function to approximate the surface displacements. Furthermore, the surface strains are computed from the displacements using radial basis function differentiation and interpolation. The computed displacements are compared with simulated results obtained by the boundary element method. Close agreement between the two results proves the validity of the developed noncontact technique for accurately estimating surface displacements and strains. These experimentally estimated displacements can further be used in an inverse technique to detect and characterize subsurface cavities in structures.
{"title":"GA-based laser speckle pattern digital image correlation method for surface strain measurements","authors":"Arka Das, E. Divo, F. Moslehy, A. Kassab","doi":"10.2495/cmem-v8-n3-252-269","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-252-269","url":null,"abstract":"This article introduces an innovative technique that integrates a genetic algorithm (GA)-based digital image correlation with laser speckle photography for the estimation of surface displacements in structures. The images (before and after deformation) are digitized using a digital camera, and the grayscale intensity matrices are read and processed by an image processing algorithm. The two matrices of the images are then inputted into GA-based optimizer that utilizes an advanced cross-correlation fitness function to approximate the surface displacements. Furthermore, the surface strains are computed from the displacements using radial basis function differentiation and interpolation. The computed displacements are compared with simulated results obtained by the boundary element method. Close agreement between the two results proves the validity of the developed noncontact technique for accurately estimating surface displacements and strains. These experimentally estimated displacements can further be used in an inverse technique to detect and characterize subsurface cavities in structures.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"1 1","pages":"252-269"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90747443","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 : 2020-08-25DOI: 10.2495/cmem-v8-n3-243-251
F. Concli, L. Maccioni
Cor-Ten is a weathering steel exploited in the last decade for several applications such as bridges, artworks, building facades, etc. Besides a good strength, it naturally oxides creating a protective layer. This oxide, unlike rust, has the same specific volume of the pure metal. This characteristic allows overcoming the need of protecting treatments like galvanization, etc. While its properties promote its exploitation in civil applications, there are also some examples of application where safety is a fundamental requirement. In the northern part of Italy, Cor-Ten is used for safety barriers (guard rails) along the highways. It is, therefore, fundamental to know the ductile behavior of this material, for which few data are available in literature. Quasi-static experimental tensile tests have been performed on eight samples having different shapes. Numerical simulations carried out with an open-source code (Code_Aster) reproduced the experimental setup. In this way, it was possible to calculate the stress state and the plastic strain at failure needed for the calibration of the ductile damage model. The material model is based on classical incremental plastic response with isotropic hardening and phenomenological concept of damage.
{"title":"Fracture locus of a Cor-ten weathering steel: Experimental–numerical calibration","authors":"F. Concli, L. Maccioni","doi":"10.2495/cmem-v8-n3-243-251","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-243-251","url":null,"abstract":"Cor-Ten is a weathering steel exploited in the last decade for several applications such as bridges, artworks, building facades, etc. Besides a good strength, it naturally oxides creating a protective layer. This oxide, unlike rust, has the same specific volume of the pure metal. This characteristic allows overcoming the need of protecting treatments like galvanization, etc. While its properties promote its exploitation in civil applications, there are also some examples of application where safety is a fundamental requirement. In the northern part of Italy, Cor-Ten is used for safety barriers (guard rails) along the highways. It is, therefore, fundamental to know the ductile behavior of this material, for which few data are available in literature. Quasi-static experimental tensile tests have been performed on eight samples having different shapes. Numerical simulations carried out with an open-source code (Code_Aster) reproduced the experimental setup. In this way, it was possible to calculate the stress state and the plastic strain at failure needed for the calibration of the ductile damage model. The material model is based on classical incremental plastic response with isotropic hardening and phenomenological concept of damage.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"14 1","pages":"243-251"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85931494","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 : 2020-08-25DOI: 10.2495/cmem-v8-n3-195-207
A. Zemanová, Jaroslav Schmidt, M. Šejnoha
The present study is focused on the application of phase-field modelling techniques to fracture simulation in laminated glass samples under bending. A damage model using a phase-field formulation of fracture is introduced and applied to three-layer laminated glass samples. The identification of material parameters of polymer foils and glass is also provided, based on a combined experimental and numerical analysis. Specifically, the results of small scale testing and the calibration of the constitutive models of polymer interlayers are discussed in connection to ethylen-vinyl acetate and polyvinyl butyral foils. The statistical data obtained by the evaluation of tensile strength of glass samples are used for the formulation of the tensile stress criterion. Therefore, a generalisation of the energetic formulation of phase-field models towards the stress-based criterion is employed here to simulate the fracture behaviour of laminated glass. The experimentally measured data are compared with the numerically derived response using the extreme values of tensile strength obtained. Then, the fracture response is analysed for one sample to support the proposed computational model and material parameters.
{"title":"On pre- and post-fracture behaviour of laminated glass under bending","authors":"A. Zemanová, Jaroslav Schmidt, M. Šejnoha","doi":"10.2495/cmem-v8-n3-195-207","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-195-207","url":null,"abstract":"The present study is focused on the application of phase-field modelling techniques to fracture simulation in laminated glass samples under bending. A damage model using a phase-field formulation of fracture is introduced and applied to three-layer laminated glass samples. The identification of material parameters of polymer foils and glass is also provided, based on a combined experimental and numerical analysis. Specifically, the results of small scale testing and the calibration of the constitutive models of polymer interlayers are discussed in connection to ethylen-vinyl acetate and polyvinyl butyral foils. The statistical data obtained by the evaluation of tensile strength of glass samples are used for the formulation of the tensile stress criterion. Therefore, a generalisation of the energetic formulation of phase-field models towards the stress-based criterion is employed here to simulate the fracture behaviour of laminated glass. The experimentally measured data are compared with the numerically derived response using the extreme values of tensile strength obtained. Then, the fracture response is analysed for one sample to support the proposed computational model and material parameters.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"23 1","pages":"195-207"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77171594","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 : 2020-08-25DOI: 10.2495/cmem-v8-n3-233-242
J. Quek, L. Chunlin, J. V. Musngi, P. B. Malalasekara
Fibre-reinforced polymer (FRP) as a protective hardening system has now become more commonly used in enhancing the capacity of reinforced concrete (RC) elements against blast loadings. Wrapping RC columns with FRP, depending on the wrapping configuration, will result in additional axial, moment and shear capacity. The FRP also prevents debris from being blown off and serves as a catcher system which minimises the possible cause of injuries/casualties in the event of blast. While analytical models built into popular finite element modelling (FEM) software are widely used to simulate and analyse the effects of a blast load to a structural element, little work has been carried out to validate the results of such analysis through experimental means. This paper examines the effect of blast loadings onto RC columns wrapped with FRP. The behaviour of the FRP-wrapped RC columns subjected to blast loading is simulated using finite element analysis. Results from the finite element simulation are compared to the corresponding wrapping configuration from actual experimental results. The comparison validates the reliability of using finite element analysis in predicting the response of FRP-wrapped RC columns subjected to blast loading.
{"title":"A comparison of finite element simulation and experimental results from reinforced concrete columns wrapped with fibre-reinforced polymer subjected to blast loading","authors":"J. Quek, L. Chunlin, J. V. Musngi, P. B. Malalasekara","doi":"10.2495/cmem-v8-n3-233-242","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-233-242","url":null,"abstract":"Fibre-reinforced polymer (FRP) as a protective hardening system has now become more commonly used in enhancing the capacity of reinforced concrete (RC) elements against blast loadings. Wrapping RC columns with FRP, depending on the wrapping configuration, will result in additional axial, moment and shear capacity. The FRP also prevents debris from being blown off and serves as a catcher system which minimises the possible cause of injuries/casualties in the event of blast. While analytical models built into popular finite element modelling (FEM) software are widely used to simulate and analyse the effects of a blast load to a structural element, little work has been carried out to validate the results of such analysis through experimental means. This paper examines the effect of blast loadings onto RC columns wrapped with FRP. The behaviour of the FRP-wrapped RC columns subjected to blast loading is simulated using finite element analysis. Results from the finite element simulation are compared to the corresponding wrapping configuration from actual experimental results. The comparison validates the reliability of using finite element analysis in predicting the response of FRP-wrapped RC columns subjected to blast loading.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"10 1","pages":"233-242"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78444974","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 : 2020-08-25DOI: 10.2495/cmem-v8-n3-220-232
F. Concli, L. Maccioni, C. Gorla
In the last decades, the growing mechatronic sector has promoted the development of more and more compact and efficient gearboxes. The margins of improvement are still big even if, sometimes, finding the optimal solutions is a trial and error procedure. For this reason, the development of dedicated tools for the optimization of the geometry and configuration of gearboxes can significantly increase the development effectiveness and help in reducing design costs. Moreover, having a more efficient solution could also reduce thermal problems during operation and increase the system reliability. The so-called ‘thermal limit’, i.e. the maximum transmittable power without an overheating of the systems, is particularly critical for high power density and compact solutions. Those relies mainly on planetary, harmonic and cycloidal architectures. While many empirical or analytical prediction models can be found in literature for the prediction of the power losses associated with the gear meshing and the bearing, few reliable models are nowadays available for the losses associated with the interaction with the lubricant, i.e. hydraulic losses. Experimental and computational fluid dynamics studies on parallel axis as well as planetary gear sets have been presented in the past. The goal of this research is the extension of the applicability range of those numerical approached to cycloidal kinematics for which no studies at all are available with respect to the hydraulic losses. The main challenge in numerically simulate the lubricant splashing in a cycloidal reduced is related to the topological modification of the computational domain during operation. For this purpose, a specific mesh handling technique, based on a 2.5D mesh, capable to handle the variations of the geometry of the domain was developed in the OpenFOAM® environment. The capability to analytically control the mesh generation at each time step ensures a very high numerical stability and a very high computational efficiency of the solution. Eventually, the approach was systematically applied to a real geometry and the results compared with those obtained for other gear architectures with comparable performances in terms of dimensions and reduction ratios.
{"title":"Development of a computational fluid dynamics simulation tool for lubrication studies on cycloidal gear sets","authors":"F. Concli, L. Maccioni, C. Gorla","doi":"10.2495/cmem-v8-n3-220-232","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-220-232","url":null,"abstract":"In the last decades, the growing mechatronic sector has promoted the development of more and more compact and efficient gearboxes. The margins of improvement are still big even if, sometimes, finding the optimal solutions is a trial and error procedure. For this reason, the development of dedicated tools for the optimization of the geometry and configuration of gearboxes can significantly increase the development effectiveness and help in reducing design costs. Moreover, having a more efficient solution could also reduce thermal problems during operation and increase the system reliability. The so-called ‘thermal limit’, i.e. the maximum transmittable power without an overheating of the systems, is particularly critical for high power density and compact solutions. Those relies mainly on planetary, harmonic and cycloidal architectures. While many empirical or analytical prediction models can be found in literature for the prediction of the power losses associated with the gear meshing and the bearing, few reliable models are nowadays available for the losses associated with the interaction with the lubricant, i.e. hydraulic losses. Experimental and computational fluid dynamics studies on parallel axis as well as planetary gear sets have been presented in the past. The goal of this research is the extension of the applicability range of those numerical approached to cycloidal kinematics for which no studies at all are available with respect to the hydraulic losses. The main challenge in numerically simulate the lubricant splashing in a cycloidal reduced is related to the topological modification of the computational domain during operation. For this purpose, a specific mesh handling technique, based on a 2.5D mesh, capable to handle the variations of the geometry of the domain was developed in the OpenFOAM® environment. The capability to analytically control the mesh generation at each time step ensures a very high numerical stability and a very high computational efficiency of the solution. Eventually, the approach was systematically applied to a real geometry and the results compared with those obtained for other gear architectures with comparable performances in terms of dimensions and reduction ratios.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"98 1","pages":"220-232"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76034377","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 : 2020-08-25DOI: 10.2495/cmem-v8-n3-270-280
S. Bahamon-Blanco, S. Rapp, Yi Zhang, Jing Liu, U. Martin
As part of an optimized maintenance strategy, track monitoring should provide information to predict track faults at an early stage. This is possible by continuously measuring the axle box accelerations and using artificial intelligence, which can detect short wave defects on the railway track with high accuracy. Such short wave defects include rail breaks, cracks, and local irregularities (mud spots). These types of faults can reduce the track quality in a short period of time. Different track irregularities were simulated in a track-vehicle scale model to generate acceleration data for typical track defects. The main focus of the current research is on recognition of local irregularities in the track-vehicle scale model. To implement the artificial intelligence, a Recurrent Neural Network is used to show the procedure and the results of recognition of track defects. The architecture and components of the neural network used are described in detail in this article. At the end of the article, a table summarizing the results of the different models trained for detecting the local irregularities in the track-vehicle scale model is presented.
{"title":"Recognition of track defects through measured acceleration using a recurrent neural network","authors":"S. Bahamon-Blanco, S. Rapp, Yi Zhang, Jing Liu, U. Martin","doi":"10.2495/cmem-v8-n3-270-280","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-270-280","url":null,"abstract":"As part of an optimized maintenance strategy, track monitoring should provide information to predict track faults at an early stage. This is possible by continuously measuring the axle box accelerations and using artificial intelligence, which can detect short wave defects on the railway track with high accuracy. Such short wave defects include rail breaks, cracks, and local irregularities (mud spots). These types of faults can reduce the track quality in a short period of time. Different track irregularities were simulated in a track-vehicle scale model to generate acceleration data for typical track defects. The main focus of the current research is on recognition of local irregularities in the track-vehicle scale model. To implement the artificial intelligence, a Recurrent Neural Network is used to show the procedure and the results of recognition of track defects. The architecture and components of the neural network used are described in detail in this article. At the end of the article, a table summarizing the results of the different models trained for detecting the local irregularities in the track-vehicle scale model is presented.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"52 1","pages":"270-280"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85612270","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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