Using structural intensity approach to characterize vibro-acoustic behavior of the cylindrical shell structure

Wang, Yuran,Huang, Rong,Liu, Zishun Techno-Press 2018 Coupled systems mechanics Vol.7 No.3

In this paper, the vibro-acoustic behaviors of vibrational cylindrical shells are investigated by using structural intensity approach. The reducing interior noise method for vibrating cylindrical shells is proposed by altering and redistributing the structural intensity through changing the damping property of the structure. The concept of proposed novel method is based on the properties of structural intensity distribution on cylindrical shells under different load and damping conditions, which can reflects power flow in the structures. In the study, the modal formulas of structural intensity are developed for the steady state vibration of cylindrical shell structures. The detailed formulas of structural intensity are derived by substituting modal quantities, in which the effect of main parameters such as weight coefficients and distribution functions on structure intensity are analyzed and discussed. Numerical simulations are first carried out based on the structural intensity analytical solutions of modal formulas. Through simulating the coupling vibration and acoustical radiation problems of cylindrical shell, the relationship between vibro-acoustic and structural intensity distribution is derived. We find that for cylindrical shell, by properly arranging damping conditions, the structural intensity can be efficiently changed and further the noise property can be improved. The proposed methodology has important implications and potential applications in the vibration and noise control of fuselage structure.

Mimicking the pattern formation of fruits and leaves using gel materials

Li Chen,Yang Zhang,Somsak Swaddiwudhipong,Zishun Liu 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.5

Gel materials have recently gained more attention due to its unique capability of large andreversible volumetric changes. This study explores the possibility of mimicking the pattern formation ofcertain natural fruits during their growing process and leaves during drying processes through the swellingand de-swelling of gel materials. This will hopefully provide certain technical explanations on themorphology of fruits and plants. We adopt the inhomogeneous field gel theory to predict the deformationconfigurations of gel structures to describe the morphology of natural fruits and plants. The growingprocesses of apple and capsicum are simulated by imposing appropriate boundary conditions and fieldloading via varying the chemical potential from their immature to mature stages. The drying processes ofthree types of leaves with different vein structures are also investigated. The simulations lead to promisingresults and demonstrate that pattern formation of fruits and plants may be described from mechanicalperspective by the behavior of gel materials based on the inhomogeneous field theory.

Numerical study on concrete penetration/perforation under high velocity impact by ogive-nose steel projectile

Md. Jahidul Islam,Somsak Swaddiwudhipong,Zishun Liu 사단법인 한국계산역학회 2011 Computers and Concrete, An International Journal Vol.8 No.1

Severe element distortion problem is observed in finite element mesh while performing numerical simulations of high velocity steel projectiles penetration/perforation of concrete targets using finite element method (FEM). This problem of element distortion in Lagrangian formulation of FEM can be resolved by using element erosion methodology. Element erosion approach is applied in the finite element program by defining failure parameters as a condition for element elimination. In this study strain parameters for both compression and tension at failure are used as failure criteria. Since no direct method exists to determine these values, a calibration approach is used to establish suitable failure strain values while performing numerical simulations of ogive-nose steel projectile penetration/perforation into concrete target. A range of erosion parameters is suggested and adopted in concrete penetration/perforation tests to validate the suggested values. Good agreement between the numerical and field data is observed.

Mechanical behavior of composite gel periodic structures with the pattern transformation

Hu, Jianying,He, Yuhao,Lei, Jincheng,Liu, Zishun,Swaddiwudhipong, Somsak Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.5

When the periodic cellular structure is loaded or swelling beyond the critical value, the structure may undergo a pattern transformation owing to the local elastic instabilities, thus leading to structural collapse and the structure changing to a new configuration. Based on this deformation-triggered pattern, we have proposed the novel composite gel materials. This designed material is a type of architectural material possessing special mechanical properties. In this study, the mechanical behavior of the composite gel periodic structure with various gel inclusions is studied further through numerical simulations. When pattern transformation occurs, it results in a different elastic relationship compared with the material at untransformed state. Based on the obtained nominal stress versus nominal strain behavior, the Poisson's ratio and corresponding deformed structure patterns, we investigate the performance of designed composite materials and the effects of the uniformly distributed gel inclusions on composite materials. A better understanding of the characteristics of these composite gel materials is a key to develop its potential applications on new soft machines.

Mechanical behavior of composite gel periodic structures with the pattern transformation

Jianying Hu,Yuhao He,Jincheng Lei,Zishun Liu,Somsak Swaddiwudhipong 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.5

When the periodic cellular structure is loaded or swelling beyond the critical value, the structure may undergo a pattern transformation owing to the local elastic instabilities, thus leading to structural collapse and the structure changing to a new configuration. Based on this deformation-triggered pattern, we have proposed the novel composite gel materials. This designed material is a type of architectural material possessing special mechanical properties. In this study, the mechanical behavior of the composite gel periodic structure with various gel inclusions is studied further through numerical simulations. When pattern transformation occurs, it results in a different elastic relationship compared with the material at untransformed state. Based on the obtained nominal stress versus nominal strain behavior, the Poisson‟s ratio and corresponding deformed structure patterns, we investigate the performance of designed composite materials and the effects of the uniformly distributed gel inclusions on composite materials. A better understanding of the characteristics of these composite gel materials is a key to develop its potential applications on new soft machines.

Light intensity controlled wrinkling patterns in photo-thermal sensitive hydrogels

Toh, William,Ding, Zhiwei,Ng, Teng Yong,Liu, Zishun Techno-Press 2016 Coupled systems mechanics Vol.5 No.4

Undergoing large volumetric changes upon incremental environmental stimulation, hydrogels are interesting materials which hold immense potentials for utilization in a wide array of applications in diverse industries. Owing to the large magnitudes of deformation it undergoes, swelling induced instability is a commonly observed sight in all types of gels. In this work, we investigate the instability of photo-thermal sensitive hydrogels, produced by impregnating light absorbing nano-particles into the polymer network of a temperature sensitive hydrogel, such as PNIPAM. Earlier works have shown that by using lights of different intensities, these hydrogels follow different swelling trends. We investigate the possibility of utilizing this fact for remote switching applications. The analysis is built on a thermodynamic framework of inhomogeneous large deformation of hydrogels and implemented via commercial finite element software, ABAQUS. Various examples of swelling induced instabilities, and its corresponding dependence on light intensity, will be investigated. We show that the instabilities that arise have their morphologies dependent on the light intensity.

Mimicking the pattern formation of fruits and leaves using gel materials

Chen, Li,Zhang, Yang,Swaddiwudhipong, Somsak,Liu, Zishun Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.50 No.5

Gel materials have recently gained more attention due to its unique capability of large and reversible volumetric changes. This study explores the possibility of mimicking the pattern formation of certain natural fruits during their growing process and leaves during drying processes through the swelling and de-swelling of gel materials. This will hopefully provide certain technical explanations on the morphology of fruits and plants. We adopt the inhomogeneous field gel theory to predict the deformation configurations of gel structures to describe the morphology of natural fruits and plants. The growing processes of apple and capsicum are simulated by imposing appropriate boundary conditions and field loading via varying the chemical potential from their immature to mature stages. The drying processes of three types of leaves with different vein structures are also investigated. The simulations lead to promising results and demonstrate that pattern formation of fruits and plants may be described from mechanical perspective by the behavior of gel materials based on the inhomogeneous field theory.

Light intensity controlled wrinkling patterns in photo-thermal sensitive hydrogels

Toh, William,Ding, Zhiwei,Ng, Teng Yong,Liu, Zishun 테크노프레스 2016 Multiscale and multiphysics mechanics Vol.1 No.1

Undergoing large volumetric changes upon incremental environmental stimulation, hydrogels are interesting materials which hold immense potentials for utilization in a wide array of applications in diverse industries. Owing to the large magnitudes of deformation it undergoes, swelling induced instability is a commonly observed sight in all types of gels. In this work, we investigate the instability of photo-thermal sensitive hydrogels, produced by impregnating light absorbing nano-particles into the polymer network of a temperature sensitive hydrogel, such as PNIPAM. Earlier works have shown that by using lights of different intensities, these hydrogels follow different swelling trends. We investigate the possibility of utilizing this fact for remote switching applications. The analysis is built on a thermodynamic framework of inhomogeneous large deformation of hydrogels and implemented via commercial finite element software, ABAQUS. Various examples of swelling induced instabilities, and its corresponding dependence on light intensity, will be investigated. We show that the instabilities that arise have their morphologies dependent on the light intensity.