I. Senjanović, I. Čatipović, N. Alujevic, D. Čakmak, N. Vladimir
In this paper rigorous formulae for natural frequencies of in-plane and out-of-plane free vibrations of a rotating ring are derived. An in-plane vibration mode of the ring is characterised by coupled flexural and extensional deformations, whereas an out-of-plane mode is distinguished by coupled flexural and torsional deformations. The expressions for natural frequencies are derived from a generalised toroidal shell theory. For the in-plane vibrations, the ring is considered to be a short top segment of a toroidal shell. For the out-of-plane vibrations, the ring is considered to be a side segment of the shell. Natural vibrations are analysed by the energy approach. The expressions for the ring strain and kinetic energies are deduced from the corresponding expressions for the torus. It is shown that the ring rotation causes bifurcation of natural frequencies of the in-plane vibrations only. Bifurcation of natural frequencies of the out-of-plane vibrations does not occur. Otherwise, for non-rotating rings, the derived formulae for the natural frequencies of the in-plane and the out-of-plane flexural vibrations are very similar. The derived analytical results are validated by a comparison with FEM and FSM (Finite Strip Method) results, as well as with experimental results available in the literature.
{"title":"Free in-plane and out-of-plane vibrations of rotating thin ring based on the toroidal shell theory","authors":"I. Senjanović, I. Čatipović, N. Alujevic, D. Čakmak, N. Vladimir","doi":"10.24423/aom.3013","DOIUrl":"https://doi.org/10.24423/aom.3013","url":null,"abstract":"In this paper rigorous formulae for natural frequencies of in-plane and out-of-plane free vibrations of a rotating ring are derived. An in-plane vibration mode of the ring is characterised by coupled flexural and extensional deformations, whereas an out-of-plane mode is distinguished by coupled flexural and torsional deformations. The expressions for natural frequencies are derived from a generalised toroidal shell theory. For the in-plane vibrations, the ring is considered to be a short top segment of a toroidal shell. For the out-of-plane vibrations, the ring is considered to be a side segment of the shell. Natural vibrations are analysed by the energy approach. The expressions for the ring strain and kinetic energies are deduced from the corresponding expressions for the torus. It is shown that the ring rotation causes bifurcation of natural frequencies of the in-plane vibrations only. Bifurcation of natural frequencies of the out-of-plane vibrations does not occur. Otherwise, for non-rotating rings, the derived formulae for the natural frequencies of the in-plane and the out-of-plane flexural vibrations are very similar. The derived analytical results are validated by a comparison with FEM and FSM (Finite Strip Method) results, as well as with experimental results available in the literature.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"429-455"},"PeriodicalIF":0.8,"publicationDate":"2018-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42287626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, three different soft pneumatic actuators (SPA) are designed and directly fabricated through additive manufacturing using thermoplastic polyurethane (TPU) filaments. The equal total inner volume size is used in the three varied designs to compare their effect on the bending response. A material model is selected and implemented according to the uniaxial tensile test parameters. The experimental results obtained from three different soft pneumatic actuators are compared with numerical model results. Especially, the experimentally measured bending forces are compared with the numerical model counterparts. The highest continuous bending deformation is determined among the three different soft pneumatic actuators. Additionally, a new integrated design and manufacturing approach is presented aiming to maximize the potential bending capability of the actuator through additive manufacturing.
{"title":"Experimental and numerical analysis on the bending response of the geometrically gradient soft robotics actuator","authors":"S. Dilibal, H. Sahin, Y. Çelık","doi":"10.24423/AOM.2903","DOIUrl":"https://doi.org/10.24423/AOM.2903","url":null,"abstract":"In this study, three different soft pneumatic actuators (SPA) are designed and directly fabricated through additive manufacturing using thermoplastic polyurethane (TPU) filaments. The equal total inner volume size is used in the three varied designs to compare their effect on the bending response. A material model is selected and implemented according to the uniaxial tensile test parameters. The experimental results obtained from three different soft pneumatic actuators are compared with numerical model results. Especially, the experimentally measured bending forces are compared with the numerical model counterparts. The highest continuous bending deformation is determined among the three different soft pneumatic actuators. Additionally, a new integrated design and manufacturing approach is presented aiming to maximize the potential bending capability of the actuator through additive manufacturing.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"391-404"},"PeriodicalIF":0.8,"publicationDate":"2018-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41572322","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Sohankar, M. Abbasi, M. Nili-Ahmadabadi, M. Alam, F. Zafar
An experimental investigation is conducted on the air flow past two wallmounted finite length side-by-side square cylinders, each of the aspect ratio AR = 7. The cylinder center-to-center spacing ratio T/d is varied from 2 to 6, where d is the side-width of the cylinder. The cylinders are placed at three incidence angles with respect to the freestream velocity, i.e. both cylinders at zero incidence angle (case I), both cylinders at 45° incidence angle (case II), and one cylinder at zero incidence angle with the other at 45° incidence angle (case III). The pressure distributions on the surfaces of the cylinders are measured at Reynolds numbers of 5.9 × 10 4 –8.1 × 10 4 . In addition, the flow structures are visualized in a smoke wind tunnel at the Reynolds number of 2 × 10 3 . Depending on the flow characteristics, four flow structures are identified at the mid-height of the cylinders, namely the asymmetric flow, antiphase shedding flow, leading-edge separated flow and wedge flow. The sectional drag near the bottom is more sensitive to T/d than that near the top. The sectional drag coefficient measured at 0.5 d below the mid-span can represent the surface-averaged drag coefficient on the entire cylinder.
{"title":"Experimental study of the flow around two finite square cylinders","authors":"A. Sohankar, M. Abbasi, M. Nili-Ahmadabadi, M. Alam, F. Zafar","doi":"10.24423/aom.2965","DOIUrl":"https://doi.org/10.24423/aom.2965","url":null,"abstract":"An experimental investigation is conducted on the air flow past two wallmounted finite length side-by-side square cylinders, each of the aspect ratio AR = 7. The cylinder center-to-center spacing ratio T/d is varied from 2 to 6, where d is the side-width of the cylinder. The cylinders are placed at three incidence angles with respect to the freestream velocity, i.e. both cylinders at zero incidence angle (case I), both cylinders at 45° incidence angle (case II), and one cylinder at zero incidence angle with the other at 45° incidence angle (case III). The pressure distributions on the surfaces of the cylinders are measured at Reynolds numbers of 5.9 × 10 4 –8.1 × 10 4 . In addition, the flow structures are visualized in a smoke wind tunnel at the Reynolds number of 2 × 10 3 . Depending on the flow characteristics, four flow structures are identified at the mid-height of the cylinders, namely the asymmetric flow, antiphase shedding flow, leading-edge separated flow and wedge flow. The sectional drag near the bottom is more sensitive to T/d than that near the top. The sectional drag coefficient measured at 0.5 d below the mid-span can represent the surface-averaged drag coefficient on the entire cylinder.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"457-480"},"PeriodicalIF":0.8,"publicationDate":"2018-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47609495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, we consider the design of neutral coated holes in two particular cases when the thick coating itself is altered by the presence of some form of material imperfection. In the first case we consider anti-plane deformations of a linearly elastic solid when the thick coating applied to the hole includes a screw dislocation dipole. In the second case, we investigate the design of neutral coated holes in plane elasticity when the thick coating contains a circular thermal inclusion and the surrounding linearly elastic solid is subjected to uniform remote hydrostatic stresses. The design is achieved by constructing particular forms of the conformal mapping function for the coating itself. Several examples are presented to demonstrate the resulting solutions. Our numerical results show that the existence of the screw dislocation dipole or the circular thermal inclusion in the coating exerts a significant influence on the shape of the neutral coated hole.
{"title":"Neutrality of coated holes in the presence of screw dislocation dipoles or circular thermal inclusions","authors":"X. Wang, P. Schiavone","doi":"10.24423/AOM.2972","DOIUrl":"https://doi.org/10.24423/AOM.2972","url":null,"abstract":"In this paper, we consider the design of neutral coated holes in two particular cases when the thick coating itself is altered by the presence of some form of material imperfection. In the first case we consider anti-plane deformations of a linearly elastic solid when the thick coating applied to the hole includes a screw dislocation dipole. In the second case, we investigate the design of neutral coated holes in plane elasticity when the thick coating contains a circular thermal inclusion and the surrounding linearly elastic solid is subjected to uniform remote hydrostatic stresses. The design is achieved by constructing particular forms of the conformal mapping function for the coating itself. Several examples are presented to demonstrate the resulting solutions. Our numerical results show that the existence of the screw dislocation dipole or the circular thermal inclusion in the coating exerts a significant influence on the shape of the neutral coated hole.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"405-427"},"PeriodicalIF":0.8,"publicationDate":"2018-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43098950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, the nurbs-based isogeometric analysis is developed to optimize natural frequencies of bidirectional functionally graded (BFG) beams by tailoring their material distribution. One-dimensional Non-Uniform Rational B-Spline (NURBS) basis functions are utilized to construct the geometry of beam as well as approximate solutions, whereas the gradation of material property is represented by two-dimensional basis functions. To optimize the material composition, the spatial distribution of volume fractions of material constituents is defined using the higher order interpolation of volume fraction values that are specified at a finite number of control points. As an optimization algorithm, the differential evolution (DE) algorithm is employed to optimize the volume fraction distribution that maximizes each of the first three natural frequencies of BFG beams. A numerical analysis is performed on the examples of BFG beams with various boundary conditions and slenderness ratios. The obtained results are compared with the previously published results in order to show the accuracy and effectiveness of the present approach. The effects of number of elements, boundary conditions and slenderness ratios on the optimized natural frequencies of BFG beams are investigated.
{"title":"NURBS-based optimization of natural frequencies for bidirectional functionally graded beams","authors":"N. Kim, T. Huynh, Qui X. Lieu, Jaehong Lee","doi":"10.24423/AOM.2897","DOIUrl":"https://doi.org/10.24423/AOM.2897","url":null,"abstract":"In this study, the nurbs-based isogeometric analysis is developed to optimize natural frequencies of bidirectional functionally graded (BFG) beams by tailoring their material distribution. One-dimensional Non-Uniform Rational B-Spline (NURBS) basis functions are utilized to construct the geometry of beam as well as approximate solutions, whereas the gradation of material property is represented by two-dimensional basis functions. To optimize the material composition, the spatial distribution of volume fractions of material constituents is defined using the higher order interpolation of volume fraction values that are specified at a finite number of control points. As an optimization algorithm, the differential evolution (DE) algorithm is employed to optimize the volume fraction distribution that maximizes each of the first three natural frequencies of BFG beams. A numerical analysis is performed on the examples of BFG beams with various boundary conditions and slenderness ratios. The obtained results are compared with the previously published results in order to show the accuracy and effectiveness of the present approach. The effects of number of elements, boundary conditions and slenderness ratios on the optimized natural frequencies of BFG beams are investigated.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"337-364"},"PeriodicalIF":0.8,"publicationDate":"2018-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47036763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Asymptotic solutions for the clamped-pinned elastica when the displacement of the pinned end is small (immediately after buckling) and when it approaches its limiting displacement (when the force in the rod tends to infinity) are presented. Simple leading order relationships describing the force as a function of the pinned end’s displacement are derived. Those approximate the force-displacement behaviour of the clamped-pinned elastica for small and limiting end displacements. All our results are valid for the clamped-pinned elastica in any mode.
{"title":"Asymptotic analysis of the clamped-pinned elastica","authors":"P. Singh, V. Goss","doi":"10.24423/aom.2893","DOIUrl":"https://doi.org/10.24423/aom.2893","url":null,"abstract":"Asymptotic solutions for the clamped-pinned elastica when the displacement of the pinned end is small (immediately after buckling) and when it approaches its limiting displacement (when the force in the rod tends to infinity) are presented. Simple leading order relationships describing the force as a function of the pinned end’s displacement are derived. Those approximate the force-displacement behaviour of the clamped-pinned elastica for small and limiting end displacements. All our results are valid for the clamped-pinned elastica in any mode.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"317-336"},"PeriodicalIF":0.8,"publicationDate":"2018-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41513147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the following study we rigorously analyze the problem of a circular inclusion with inhomogeneous imperfect sliding interface in finite deformation of harmonic materials. The work begins by defining the inhomogeneous sliding boundary conditions characterized by two interface parameters corresponding to the normal and tangential coordinate directions (with respect to the interface boundary curve), respectively. Then, through the process of analytic continuation the problem is eventually reduced to the determination of a single analytic function given by an ordinary differential equation with variable coefficients. A specific example is selected to illustrate the method. The effects of the circumferential variation of the interface parameter on the mean stress at the interface and the average mean stress in the inclusion are discussed.
{"title":"A circular inclusion with inhomogeneous sliding imperfect interface in harmonic materials","authors":"D. McArthur, L. Sudak","doi":"10.24423/AOM.2917","DOIUrl":"https://doi.org/10.24423/AOM.2917","url":null,"abstract":"In the following study we rigorously analyze the problem of a circular inclusion with inhomogeneous imperfect sliding interface in finite deformation of harmonic materials. The work begins by defining the inhomogeneous sliding boundary conditions characterized by two interface parameters corresponding to the normal and tangential coordinate directions (with respect to the interface boundary curve), respectively. Then, through the process of analytic continuation the problem is eventually reduced to the determination of a single analytic function given by an ordinary differential equation with variable coefficients. A specific example is selected to illustrate the method. The effects of the circumferential variation of the interface parameter on the mean stress at the interface and the average mean stress in the inclusion are discussed.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"365-386"},"PeriodicalIF":0.8,"publicationDate":"2018-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42553792","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this paper, based on the original argumentation of Reynolds and Maxwell, with consideration of previous experiences of the authors in the nano- and micro-flows area, a general form of boundary forces, that consist of contributions from the friction and the mobility components: f ∂V = f r + f m , has been extended to common effects of the bulk and surface motion. Hence, adopting Reynolds’ reasoning to a porous media as a whole, we reexamine the Poiseuille–Knudsen–Reynolds equation in terms of the sum of three contributions: the bulk pressure-driven flow, and two mobility surface forces, namely the Knudsen surface slip-driven flow and the Reynolds surface thermally-driven flow. The main motivation of our work is to find the dimensionless contribution of the Navier slip number and the Reynolds thermal transpiration number in materials with high volumetric surface density.
{"title":"On Navier slip and Reynolds transpiration numbers","authors":"P. Ziółkowski, J. Badur","doi":"10.24423/AOM.2807","DOIUrl":"https://doi.org/10.24423/AOM.2807","url":null,"abstract":"In this paper, based on the original argumentation of Reynolds and Maxwell, with consideration of previous experiences of the authors in the nano- and micro-flows area, a general form of boundary forces, that consist of contributions from the friction and the mobility components: f ∂V = f r + f m , has been extended to common effects of the bulk and surface motion. Hence, adopting Reynolds’ reasoning to a porous media as a whole, we reexamine the Poiseuille–Knudsen–Reynolds equation in terms of the sum of three contributions: the bulk pressure-driven flow, and two mobility surface forces, namely the Knudsen surface slip-driven flow and the Reynolds surface thermally-driven flow. The main motivation of our work is to find the dimensionless contribution of the Navier slip number and the Reynolds thermal transpiration number in materials with high volumetric surface density.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"269-300"},"PeriodicalIF":0.8,"publicationDate":"2018-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49257989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The temperature evolution and the mechanical characteristics of pseudoelasticity TiNi alloys have been studied experimentally at different strain rates. During SHPB testing, the temperature changes were in situ measured by an infrared system recording infrared radiation emitted from the surface of the specimen. It was found that the temperature evolution and the mechanical behavior has a remarkable strain rate effect. With the strain rate increasing, both phase transition subsequent stress and modulus of loading the phase transition stage were higher, exhibiting significant strain and the strain rate hardening characteristic. They were accompanied by the temperature increasing, which suggest that the stress increments result from the temperature change, independently of the strain rate. Calculation analysis results show that latent heat and the dissipated energy in the form of the hysteresis loops, are mainly the sources of the temperature change.
{"title":"Experimental study temperature evolution of pseudoelastic TiNi alloys during shock-induced phase transformation","authors":"L. Shen, Y. Liu, J. Shan","doi":"10.24423/AOM.2760","DOIUrl":"https://doi.org/10.24423/AOM.2760","url":null,"abstract":"The temperature evolution and the mechanical characteristics of pseudoelasticity TiNi alloys have been studied experimentally at different strain rates. During SHPB testing, the temperature changes were in situ measured by an infrared system recording infrared radiation emitted from the surface of the specimen. It was found that the temperature evolution and the mechanical behavior has a remarkable strain rate effect. With the strain rate increasing, both phase transition subsequent stress and modulus of loading the phase transition stage were higher, exhibiting significant strain and the strain rate hardening characteristic. They were accompanied by the temperature increasing, which suggest that the stress increments result from the temperature change, independently of the strain rate. Calculation analysis results show that latent heat and the dissipated energy in the form of the hysteresis loops, are mainly the sources of the temperature change.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"191-205"},"PeriodicalIF":0.8,"publicationDate":"2018-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41810818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present paper focuses on the derivation of the constitutive relations and field equations for anisotropic thermoelastic medium with mass diffusion and double porosity. The variational principle, uniqueness and reciprocity theorems are also derived.
{"title":"Generalized theory of thermoelastic diffusion with double porosity","authors":"T. Kansal","doi":"10.24423/AOM.2856","DOIUrl":"https://doi.org/10.24423/AOM.2856","url":null,"abstract":"The present paper focuses on the derivation of the constitutive relations and field equations for anisotropic thermoelastic medium with mass diffusion and double porosity. The variational principle, uniqueness and reciprocity theorems are also derived.","PeriodicalId":8280,"journal":{"name":"Archives of Mechanics","volume":"70 1","pages":"241-268"},"PeriodicalIF":0.8,"publicationDate":"2018-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49595936","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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