Pub Date : 2020-09-27DOI: 10.15625/0866-7136/15494
I. Elishakoff
In this Note the generalization of the celebrated formula by Young, applicable to homogeneous columns, is provided for inhomogeneous columns.
在本注中，对非齐次列给出了适用于齐次列的杨氏著名公式的推广。
{"title":"Note on extension of the Young’s formula to inhomogeneous columns","authors":"I. Elishakoff","doi":"10.15625/0866-7136/15494","DOIUrl":"https://doi.org/10.15625/0866-7136/15494","url":null,"abstract":"In this Note the generalization of the celebrated formula by Young, applicable to homogeneous columns, is provided for inhomogeneous columns.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"16 12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116203357","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 : 2020-09-27DOI: 10.15625/0866-7136/15476
J. Reddy, A. Srinivasa
The purpose of this article is to bring some examples of misattributes (i.e., theories and models that bear some one’s name while the idea belongs to someone else) and misnomers (i.e., words or phrases that are either incorrect or inaccurate) to the attention of the colleagues in the field, and correct them so that these incorrect phrases and attributions and misnomers are not repeated in the future writings. In the process, we also discuss the purpose of a literature reviews and the need for precision of thought in naming ideas or concepts. It is hoped that people will be careful and precise in using the words, names, and phrases correctly (since after all, these represent ideas that need to be communicated) and not propagate inaccurate information in the literature. The discussion presented is restricted to mostly structural and computational mechanics.
{"title":"Misattributions and misnomers in mechanics: Why they matter in the search for insight and precision of thought","authors":"J. Reddy, A. Srinivasa","doi":"10.15625/0866-7136/15476","DOIUrl":"https://doi.org/10.15625/0866-7136/15476","url":null,"abstract":"The purpose of this article is to bring some examples of misattributes (i.e., theories and models that bear some one’s name while the idea belongs to someone else) and misnomers (i.e., words or phrases that are either incorrect or inaccurate) to the attention of the colleagues in the field, and correct them so that these incorrect phrases and attributions and misnomers are not repeated in the future writings. In the process, we also discuss the purpose of a literature reviews and the need for precision of thought in naming ideas or concepts. It is hoped that people will be careful and precise in using the words, names, and phrases correctly (since after all, these represent ideas that need to be communicated) and not propagate inaccurate information in the literature. The discussion presented is restricted to mostly structural and computational mechanics. ","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114409572","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 : 2020-09-27DOI: 10.15625/0866-7136/15336
W. L. Nicomedes, K. Bathe, F. Moreira, R. Mesquita
When the method of finite spheres is used for the solution of time-harmonic acoustic wave propagation problems in nonhomogeneous media, a mixed (or saddle-point) formulation is obtained in which the unknowns are the pressure fields and the Lagrange multiplier fields defined at the interfaces between the regions with distinct material properties. Then certain inf-sup conditions must be satisfied by the discretized spaces in order for the finite-dimensional problems to be well-posed. We discuss in this paper the analysis and use of these conditions. Since the conditions involve norms of functionals in fractional Sobolev spaces, we derive ‘stronger’ conditions that are simpler in form. These new conditions pave the way for the inf-sup testing, a tool for assessing the stability of the discretized problems.
{"title":"The method of finite spheres in acoustic wave propagation through nonhomogeneous media: Inf-sup stability conditions","authors":"W. L. Nicomedes, K. Bathe, F. Moreira, R. Mesquita","doi":"10.15625/0866-7136/15336","DOIUrl":"https://doi.org/10.15625/0866-7136/15336","url":null,"abstract":"When the method of finite spheres is used for the solution of time-harmonic acoustic wave propagation problems in nonhomogeneous media, a mixed (or saddle-point) formulation is obtained in which the unknowns are the pressure fields and the Lagrange multiplier fields defined at the interfaces between the regions with distinct material properties. Then certain inf-sup conditions must be satisfied by the discretized spaces in order for the finite-dimensional problems to be well-posed. We discuss in this paper the analysis and use of these conditions. Since the conditions involve norms of functionals in fractional Sobolev spaces, we derive ‘stronger’ conditions that are simpler in form. These new conditions pave the way for the inf-sup testing, a tool for assessing the stability of the discretized problems.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131650426","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 : 2020-09-27DOI: 10.15625/0866-7136/15337
D. Steigmann
We develop an asymptotic model for the finite-deformation, small-strain response of thin laminated shells composed of two perfectly bonded laminae that exhibit reflection symmetry of the material properties with respect to an interfacial surface. No a priori hypotheses are made concerning the kinematics of deformation. The asymptotic procedure culminates in a generalization of Koiter’s well-known shell theory to accommodate the laminated structure, and incorporates a rigorous limit model for pure bending.
{"title":"Asymptotic theory for thin two-ply shells","authors":"D. Steigmann","doi":"10.15625/0866-7136/15337","DOIUrl":"https://doi.org/10.15625/0866-7136/15337","url":null,"abstract":"We develop an asymptotic model for the finite-deformation, small-strain response of thin laminated shells composed of two perfectly bonded laminae that exhibit reflection symmetry of the material properties with respect to an interfacial surface. No a priori hypotheses are made concerning the kinematics of deformation. The asymptotic procedure culminates in a generalization of Koiter’s well-known shell theory to accommodate the laminated structure, and incorporates a rigorous limit model for pure bending.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114608265","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 : 2020-08-22DOI: 10.15625/0866-7136/14823
Phạm Hồng Phúc
This paper describes design and calculation of an electrothermal V-shaped actuator (EVA) and an amplification mechanism integrated into a force measuring microsystem (FMMS), aims to apply for characterization of a micro beam. Displacement and driving force are generated by thermal expansion of the V-shaped silicon beams while applying a voltage to the electrodes of the EVA. ANSYS simulation helps to find out the relations between thermal force and displacement corresponding to driving voltage and determine the temperature of V-shaped beam at various applying voltages. In our simulation, with applying voltage Um = 38 volt for six pairs of V-shaped beam, the maximal temperature of the beam reaches approximately to 1100°C and causes a melting phenomenon of the silicon beam. The additional amplification mechanism allows actuator’s displacement to be 6 times larger than before the improvement, thus the bending deformation of the micro beam can be seen perfectly, i.e. the force loading on the beam can be computed more exactly via a measured displacement of the beam tip. In addition, this FMMS has smaller size and supplies a larger beam’s deformation at the same voltage in comparison with previous design.
{"title":"A force measuring microsystem bases on electrothermal V-shaped actuator","authors":"Phạm Hồng Phúc","doi":"10.15625/0866-7136/14823","DOIUrl":"https://doi.org/10.15625/0866-7136/14823","url":null,"abstract":"This paper describes design and calculation of an electrothermal V-shaped actuator (EVA) and an amplification mechanism integrated into a force measuring microsystem (FMMS), aims to apply for characterization of a micro beam. Displacement and driving force are generated by thermal expansion of the V-shaped silicon beams while applying a voltage to the electrodes of the EVA. ANSYS simulation helps to find out the relations between thermal force and displacement corresponding to driving voltage and determine the temperature of V-shaped beam at various applying voltages. In our simulation, with applying voltage Um = 38 volt for six pairs of V-shaped beam, the maximal temperature of the beam reaches approximately to 1100°C and causes a melting phenomenon of the silicon beam. The additional amplification mechanism allows actuator’s displacement to be 6 times larger than before the improvement, thus the bending deformation of the micro beam can be seen perfectly, i.e. the force loading on the beam can be computed more exactly via a measured displacement of the beam tip. In addition, this FMMS has smaller size and supplies a larger beam’s deformation at the same voltage in comparison with previous design.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128668138","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 : 2020-08-17DOI: 10.15625/0866-7136/14874
Nhat Linh Ho, Minh Phung Dang, Thanh-Phong Dao
This study evaluates the displacement sensitivity of a new compliant microgripper. The microgripper is designed based on a four-bar mechanism and the concept of a compliant mechanism. The effects of the width of the right circular hinge, the thickness of microgripper, and the material properties on the dis-placement sensitivity are considered via using the finite element method. In the beginning, the stress and deformation of the compliant microgripper are evaluated. Subsequently, the displacement of the microgripper is then analyzed. The results showed that the design parameter and the displacement sensitivity have a close relationship. To increase the grasping reliability and measure the displacement or force, a micro-displacement sensor is integrated with the proposed microgripper. Finally, the modeling and analysis of the proposed sensor are conducted.
{"title":"Design and analysis of a displacement sensor-integrated compliant microgripper based on parallel structure","authors":"Nhat Linh Ho, Minh Phung Dang, Thanh-Phong Dao","doi":"10.15625/0866-7136/14874","DOIUrl":"https://doi.org/10.15625/0866-7136/14874","url":null,"abstract":"This study evaluates the displacement sensitivity of a new compliant microgripper. The microgripper is designed based on a four-bar mechanism and the concept of a compliant mechanism. The effects of the width of the right circular hinge, the thickness of microgripper, and the material properties on the dis-placement sensitivity are considered via using the finite element method. In the beginning, the stress and deformation of the compliant microgripper are evaluated. Subsequently, the displacement of the microgripper is then analyzed. The results showed that the design parameter and the displacement sensitivity have a close relationship. To increase the grasping reliability and measure the displacement or force, a micro-displacement sensor is integrated with the proposed microgripper. Finally, the modeling and analysis of the proposed sensor are conducted.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134024043","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 : 2020-07-16DOI: 10.15625/0866-7136/14897
Vu Duc Phuc, Tong Van Canh, Phạm Văn Liệu
Dynamic vibration absorber (DVA) is a simple and effective device for vibration absorption used in many practical applications. Determination of suitable parameters for DVA is of significant importance to achieve high vibration reduction effectiveness. This paper presents a method to find the optimal parameters of a DVA attached to a linear damped rotary system excited by harmonic torque. To this end, a closed-form formula for the optimum tuning parameter is derived using the fixed-point theory based on an assumption that the damped rotary systems are lightly or moderately damped. The optimal damping ratio of DVA is found by solving a set of non-linear equations established by the Chebyshev’s min-max criterion. The performance of the proposed optimal DVA is compared with that obtained by existing optimal solution in literature. It is shown that the proposed optimal parameters allow to obtain superior vibration suppression compared to existing optimal formula. Extended simulations are carried out to examine the performance of the optimally designed DVA and the sensitivity of the optimum parameters. The simulation results show that the improvement of the vibration performance on damped rotary system can be as much as 90% by using DVA.
{"title":"Optimal parameters of dynamic vibration absorber for linear damped rotary systems subjected to harmonic excitation","authors":"Vu Duc Phuc, Tong Van Canh, Phạm Văn Liệu","doi":"10.15625/0866-7136/14897","DOIUrl":"https://doi.org/10.15625/0866-7136/14897","url":null,"abstract":"Dynamic vibration absorber (DVA) is a simple and effective device for vibration absorption used in many practical applications. Determination of suitable parameters for DVA is of significant importance to achieve high vibration reduction effectiveness. This paper presents a method to find the optimal parameters of a DVA attached to a linear damped rotary system excited by harmonic torque. To this end, a closed-form formula for the optimum tuning parameter is derived using the fixed-point theory based on an assumption that the damped rotary systems are lightly or moderately damped. The optimal damping ratio of DVA is found by solving a set of non-linear equations established by the Chebyshev’s min-max criterion. The performance of the proposed optimal DVA is compared with that obtained by existing optimal solution in literature. It is shown that the proposed optimal parameters allow to obtain superior vibration suppression compared to existing optimal formula. Extended simulations are carried out to examine the performance of the optimally designed DVA and the sensitivity of the optimum parameters. The simulation results show that the improvement of the vibration performance on damped rotary system can be as much as 90% by using DVA.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121762967","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 : 2020-06-29DOI: 10.15625/0866-7136/14749
L. Q. Vĩnh, N. Cuong
This research presents a continuous element model for solving vibration problems of FG stepped truncated conical shells having various material properties and surrounded by Pasternak foundations. Based on the First Order Shear Deformation Theory (FSDT) and the equations of the FGM conical shells, the dynamic stiffness matrix is obtained for each segment of the shell having constant thickness. The interesting assembly procedure of continuous element method (CEM) is employed for joining those segments in order to analyze the dynamic behavior of the FG stepped truncated conical shells an assembly procedure of continuous element method (CEM) is employed for joining those segments. Free vibrations of different configurations of FG stepped truncated conical shells on elastic foundations are examined. Effects of structural parameters, stepped thickness and elastic foundations on the free vibration of FG stepped truncated conical shells are also presented.
{"title":"Dynamic analysis of FG stepped truncated conical shells surrounded by Pasternak elastic foundations","authors":"L. Q. Vĩnh, N. Cuong","doi":"10.15625/0866-7136/14749","DOIUrl":"https://doi.org/10.15625/0866-7136/14749","url":null,"abstract":"This research presents a continuous element model for solving vibration problems of FG stepped truncated conical shells having various material properties and surrounded by Pasternak foundations. Based on the First Order Shear Deformation Theory (FSDT) and the equations of the FGM conical shells, the dynamic stiffness matrix is obtained for each segment of the shell having constant thickness. The interesting assembly procedure of continuous element method (CEM) is employed for joining those segments in order to analyze the dynamic behavior of the FG stepped truncated conical shells an assembly procedure of continuous element method (CEM) is employed for joining those segments. Free vibrations of different configurations of FG stepped truncated conical shells on elastic foundations are examined. Effects of structural parameters, stepped thickness and elastic foundations on the free vibration of FG stepped truncated conical shells are also presented.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116787857","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 : 2020-06-11DOI: 10.15625/0866-7136/13753
Nguyen Nhat Phi Long, S. Nguyen, N. Quân
When performing a laser processing, one of the parameters to consider is the laser heat flux. This is a very important parameter of the processing. It is difficult to directly and correctly measure this parameter during the processing. Therefore, to estimate this parameter, a solution has been implemented. In this study, the Newton–Raphson method has been calibrated as an operational algorithm to evaluate the laser heat flux value accurately in the 3-D conduction model. To confirm the effectiveness of the presented method, the paper has given two specific applications. It is obtained that the sequential method is a reasonable, correct, and powerful method to determine the inversely laser heat flux in the three-dimensional conduction model.
{"title":"Determining of the laser heat flux for three-dimensional conduction model by the sequential method","authors":"Nguyen Nhat Phi Long, S. Nguyen, N. Quân","doi":"10.15625/0866-7136/13753","DOIUrl":"https://doi.org/10.15625/0866-7136/13753","url":null,"abstract":"When performing a laser processing, one of the parameters to consider is the laser heat flux. This is a very important parameter of the processing. It is difficult to directly and correctly measure this parameter during the processing. Therefore, to estimate this parameter, a solution has been implemented. In this study, the Newton–Raphson method has been calibrated as an operational algorithm to evaluate the laser heat flux value accurately in the 3-D conduction model. To confirm the effectiveness of the presented method, the paper has given two specific applications. It is obtained that the sequential method is a reasonable, correct, and powerful method to determine the inversely laser heat flux in the three-dimensional conduction model.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128110934","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 : 2020-06-05DOI: 10.15625/0866-7136/14875
N. Kien
Based on the circle assemblage model, the effective properties of the inclusion with imperfect interface are derived. The equivalent inclusion is incorporated in the Fourier Transform algorithm to determine the effective conductivity of the composite with lowly conducting or highly conducting interface. The size effect is considered for both cases. Numerical results are provided to illustrate the dependence of the effective conductivity on the size of inhomogeneities.
{"title":"Size dependent of the effective conductivity of composite with imperfect interfaces","authors":"N. Kien","doi":"10.15625/0866-7136/14875","DOIUrl":"https://doi.org/10.15625/0866-7136/14875","url":null,"abstract":"Based on the circle assemblage model, the effective properties of the inclusion with imperfect interface are derived. The equivalent inclusion is incorporated in the Fourier Transform algorithm to determine the effective conductivity of the composite with lowly conducting or highly conducting interface. The size effect is considered for both cases. Numerical results are provided to illustrate the dependence of the effective conductivity on the size of inhomogeneities.","PeriodicalId":239329,"journal":{"name":"Vietnam Journal of Mechanics","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129772078","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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