119 research outputs found
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The application of durable press treatment to bleached softwood kraft handsheets
There are several chemical treatments for paper to
Improve its strength properties. Durable press treatment is
usually used as a textile chemical finishing; however, there
is little information available on the application of durable
press treatment for paper. The durable press treatment was
applied to bleached softwood kraft handsheets using maleic
acid, citric acid and 1,2,3,4-butanetetracarboxylic acid
(BTCA) as crosslinking agents in this study. One catalyst
(NaHâPOâ) was particularly effective toward promoting the
esterification reaction between handsheets and the
crosslinking agents. This reaction was confirmed by the
weight gain of the handsheets, by FT-IR spectroscopy, and by
the change in the paper properties. The wet strengths of
handsheets were improved significantly (as high as 63% of the
dry strength) when the BTCA WAS used as a crosslinking agent.
No tensile strength losses were found from BTCA and citric acid treatments, and the brightness of the handsheets
increased with durable press treatment. However, the fold
strength was severely affected by this treatment
A finite element approach for a coupled numerical simulation of fluid-structure-electric interaction in MEMS
In this analyze, a novel finite element coupled algorithm using numerical meth-
ods to analyze the interaction between fluid-structure-electric fileds has been presented for
piezoelectric actuators. Piezoelectricity is fundamentally an interaction between structure and
electric fields. In this paper, at first we analyze the piezoelectric interaction using 3D solid
elements and MITC4 shell elements. Solid elements are used for electric analysis and MITC4 shell
elements are used for geometric nonlinear structural analysis. The induced electric forces and
moment of forces are translated from 3D solid elements to MITC4 shell elements using a novel
translation method, and displacements from MITC4 shell elements are translated to 3D solid elements
using shell element displacement interpolation func- tions. A projection method is employed in
order to solve the interaction between MITC4
shell structure and fluid field
Pseudoelastic meshâmoving using a general scenario of the selective mesh stiffening
The selective mesh stiffening in this study changes the stiffness of the element based on both the element area and shape. It includes the stiffening in the previous studies as a specific case, and leads to a general scenario in the pseudoelastic meshâmoving. This scenario gives better mesh quality in the mesh-moving of a rectangular domain with a structure consisting of a square and a fin undergoes large rotations. This is because the shear deformation of the element is adaptively considered
Microscale electrical contact resistance analysis for resistance spot welding
Electrical contact resistance is an important parameter for resistance spot
welding. In this study, a microscale electrical contact resistance analysis method is pro-
posed for resistance spot welding. The microscale electrical contact resistance analysis method
is combination of an elastoâplastic large deformation contact analysis and an electric
current analysis. The electric current analysis is performed for deformed shape of asperity. The
tendency of the electrical contact resistance on contact pressure and tem- perature for the
electrical contact resistance analysis agrees with that for Babuâs electrical contact resistance
model.
A multiscale coupled analysis method is also proposed for resistance spot welding. The multiscale
analysis consists of macroscale elastoâplastic large deformation contact, electric current and
thermal conduction triply coupled analysis and microscale electrical contact resistance analysis.
It is conïŹrmed that the resistance spot welding analysis without measurement of
electrical contact resistance can be performed by using the microscale
electrical contact resistance analysis
Hierarchical Modeling and Finite Element Analysis of Piezoelectric Energy Harvester From Structure-Piezoelectric-Circuit Interaction
The piezoelectric energy harvesting devices for the conversion of mechanical vibration into electric energy via a flexible piezoelectric energy harvesting (FPED) structure have gained greater attention. Here, the large deformation of the FPED structure causes a strong interaction with the electric field (direct-piezoelectric effect) and structural field (inverse-piezoelectric effect), and vice-versa. Also an electrical circuit is attached to the electrodes covering the piezoelectric layers. This becomes a three-way coupling of the structure, the electromechanical effect of the piezoelectric material, and the electrical circuit. A mathematical and numerical model of the complex physical system of the involved multiphysics coupling characteristics in order to predict the operational properties and to increase the performance is very important. The presentation will discuss a partitioned coupling algorithm based hierarchical decomposition using finite element method for piezoelectric energy harvesting from structurepiezoelectric-circuit interaction. Results obtained with the finite element analysis are compared with the experimental results of PEHDs with base excitation reported in the literature
Hierarchal decomposition for the structure-fluid-electrostatic interaction in a microelectromechanical system
In this study, a hierarchal decomposition is proposed to solve the structure-fluid-electrostatic interaction in a microelectromechanical system (MEMS). In the proposed decomposition, the structure-fluid-electrostatic interaction is partitioned into the structure-fluid interaction and the electrostatic field using the iteratively staggered method, and the structure-fluid interaction is split into the structure-fluid velocity field and the fluid pressure field using the projection method. The proposed decomposition is applied to a micro cantilever beam actuated by the electrostatic force in air. It follows from the comparisons among the numerical and experimental results that the proposed method can predict the MEMS vibration characteristics accurately
A novel coupling algorithm for the electric fieldâstructure interaction using a transformation method between solid and shell elements in a thin piezoelectric bimorph plate analysis
Thin piezoelectric bimorph cantilever is increasingly employed throughout the field of actuator and sensor applications in the microelectromechanical system (MEMS). Generally for finite element analysis of piezoelectric bimorph cantilever, threeâdimensional (3D) solid element can accurately takes into account a linear or quadratic distribution of electric potential over the thickness for various electric configurations of the actuator and sensor applications. As the MEMS structures usually are quite thin and undergo large deformations, shell elements are very well suited for the structural discretization. This paper is focused on the development of a novel coupled algorithm to analyze the electromechanical coupling in a piezoelectric bimorph actuator and sensor using the shell and solid elements to simulate the structural and electric fields, respectively. The electric force induced by the inverse piezoelectric effect is transformed from the solid elements to the shell elements as an equivalent external force and moment, and the resultant displacements are transformed from the shell elements to the solid elements to evaluate the direct piezoelectric effect. Two different approaches were developed to analyze the electric fieldâstructure interaction. In the first approach, for each block GaussâSeidel (BGS) iteration, multiple full NewtonâRaphson (NâR) iterations are executed until the tolerance criteria are satisfied. In the second approach, the BGS and NâR loops are unified into a single loop. A piezoelectric bimorph actuator and sensor were analyzed for various electrical configurations to demonstrate the accuracy of the proposed method
Performance Evaluation of Numerical Finite Element Coupled Algorithms for StructureâElectric Interaction Analysis of MEMS Piezoelectric Actuator
This work presents multiphysics numerical analysis of piezoelectric actuators realized using the finite element method (FEM) and their performances to analyze the structure-electric interaction in three-dimensional (3D) piezoelectric continua. Here, we choose the piezoelectric bimorph actuator without the metal shim and with the metal shim as low-frequency problems and a surface acoustic wave device as a high-frequency problem. More attention is given to low-frequency problems because in our application micro air vehicleâs wings are actuated by piezoelectric bimorph actuators at low frequency. We employed the Newmarkâs time integration and the central difference time integration to study the dynamic response of piezoelectric actuators. Monolithic coupling, noniterative partitioned coupling and partitioned iterative coupling schemes are presented. In partitioned iterative coupling schemes, the block Jacobi and the block GaussâSeidel methods are employed. Resonance characteristics are very important in micro-electro-mechanical system (MEMS) applications. Therefore, using our proposed coupled algorithms, the resonance characteristics of bimorph actuator is analyzed. Comparison of the accuracy and computational efficiency of the proposed numerical finite element coupled algorithms have been carried out for 3D structureâelectric interaction problems of a piezoelectric actuator. The numerical results obtained by the proposed algorithms are in good agreement with the theoretical solutions
Hierarchically decomposed finite element method for a triply coupled piezoelectric, structure, and fluid fields of a thin piezoelectric bimorph in fluid
This paper proposes a numerical method for analyzing a thin piezoelectric bimorph in fluid. A hierarchically decomposed finite element method (FEM) is proposed for modeling the triply coupled piezoelectric-structureâfluid interaction. The electromechanical coupling (piezoelectric-structure interaction) behavior in a thin piezoelectric bimorph is described by the classical constitutive equation, the incompressible fluid flows by the NavierâStokes equation and the structure by the Cauchy equation of motion. The piezoelectric-structureâfluid interaction system is decomposed into subsystems of fluidâstructure interaction (FSI) and piezoelectric field, then the piezoelectric field and the FSI are coupled using the block GaussâSeidel method, the fluidâstructure interaction is split into the fluidâstructure velocity field and the pressure field using an algebraic splitting and the fluidâstructure velocity field is partitioned into fluid velocity field and structure velocity field. Using the proposed method, the resonance characteristics of a piezoelectric bimorph cantilever made of PVDF and PZT-5H material in fluid are investigated for actuation and sensor configurations
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