ANSYS Help Viewer(压电仿真).doc

ANSYS压电分析帮助文件位置ANSYS Documentation Mechanical APDL Coupled-Filed Analysis Guide Direct Coupled-Filed Analysis 2.3.Piezoelectric Analysis2.3.Piezoelectric AnalysisPiezoelectrics is the coupling of structural and electric fields, which is a natural property of materials such as quartz and ceramics. Applying a voltage to a piezoelectric material creates a displacement, and vibrating a piezoelectric material generates a voltage. A typical application of piezoelectric analysis is a pressure transducer. Possible piezoelectric analysis types (available in the ANSYS Multiphysics or ANSYS Mechanical products only) are static, modal, harmonic, and transient.To do a piezoelectric analysis, you need to use one of these element types:PLANE13, KEYOPT(1) = 7 coupled-field quadrilateral solidSOLID5, KEYOPT(1) = 0 or 3 coupled-field brickSOLID98, KEYOPT(1) = 0 or 3 coupled-field tetrahedronPLANE223, KEYOPT(1) = 1001, coupled-field 8-node quadrilateralSOLID226, KEYOPT(1) = 1001, coupled-field 20-node brickSOLID227, KEYOPT(1) = 1001, coupled-field 10-node tetrahedronThe KEYOPT settings activate the piezoelectric degrees of freedom, displacements and VOLT. For SOLID5 and SOLID98, setting KEYOPT(1) = 3 activates the piezoelectric only option.Large deflections, stress stiffening effects, and prestress effects are available via the NLGEOM and PSTRES commands. (See the Command Reference for more information on these commands. See the Structural Analysis Guide and Structures with Geometric Nonlinearities of the Mechanical APDL Theory Reference for more information on these capabilities.) Current-technology elements PLANE223, SOLID226 and SOLID227 also support a linear perturbation piezoelectric analysis. (See Linear Perturbation Analysis in the Structural Analysis Guide for information about the procedure.)For PLANE13, large deflection and stress stiffening capabilities are available for KEYOPT(1) = 7. For SOLID5 and SOLID98, large deflection and stress stiffening capabilities are available for KEYOPT(1) = 3. In addition, small deflection stress stiffening capabilities are available for KEYOPT(1) = 0.For a large-deflection piezoelectric analysis, you must use nonlinear solution commands to specify your settings. For general information on these commands, refer to Set Solution Controls in the Structural Analysis Guide.For sample analyses, see Example: Piezoelectric Analysis and Example: Piezoelectric Analysis with Coriolis Effect.2.3.1. Hints and Recommendations for Piezoelectric AnalysisThe analysis may be static, modal, harmonic, transient, or prestressed modal, harmonic, or transient. Some important points to remember are: For modal analysis, Block Lanczos is the recommended solver. The Supernode and Subspace solvers are also allowed. PCG Lanczos is not supported unless using Lev_Diff = 5 on the PCGOPT command. For static, full harmonic, or full transient analysis, select the sparse matrix (SPARSE) solver or the Jacobi Conjugate Gradient (JCG) solver. The sparse solver is the default for static and full transient analyses. Depending on the chosen system of units or material property values, the assembled matrix may become ill-conditioned. When solving ill-conditioned matrices, the JCG iterative solver may converge to the wrong solution. The assembled matrix typically becomes ill-conditioned when the magnitudes of the structural DOF and electrical DOF start to vary significantly (more than 1e15). For transient analyses, specify ALPHA = 0.25, DELTA = 0.5, and THETA = 0.5 on the TINTP command (Main Menu Preprocessor Loads Time/FrequencTime Integration). A linear perturbation piezoelectric analysis is available only with PLANE223, SOLID226, and SOLID227 elements. For PLANE13, SOLID5, and SOLID98, the force label for the VOLT DOF is AMPS. For PLANE223, SOLID226, and SOLID227, the force label for the VOLT degree of freedom is CHRG. Use these labels in F, CNVTOL, RFORCE, etc. To do a piezoelectric-circuit analysis, use CIRCU94. The capability to model dielectric losses using the dielectric loss tangent property (input on MP,LSST) is available only for PLANE223, SOLID226, and SOLID227. The Coriolis effect capability is available only for PLANE223, SOLID226, and SOLID227. For information on how to include this effect, see Rotating Structure Analysis in the Advanced Analysis Guide. For a sample analyses, see Example: Piezoelectric Analysis with Coriolis Effect. If a model has at least one piezoelectric element, then all the coupled-field elements with structural and VOLT degrees of freedom must be of piezoelectric type. If the piezoelectric effect is not desired in these elements, simply define very small piezoelectric coefficients on TB. Mode-superposition transient and harmonic analyses are available. For volt excitation, use the enforced motion procedure (for an example, see Example: Mode-Superposition Piezoelectric Analysis). Because mode-superposition analysis assumes proportional damping, electrical sensitivity (MP,RSVX, RSVY and RSVZ) and electric loss tangent (MP,LSST) are not supported. If you are interested in results such as electric fields (Item = EF on PRNSOL, PLNSOL, PRESOL, or PLESOL) or charges (Item = CHRG on PRESOL or PLESOL), request an expansion which is not based on modal elements results by specifying MSUPkey = NO on the MXPAND command.2.3.2. Material Properties for Piezoelectric AnalysisA piezoelectric model requires permittivity (or dielectric constants), the piezoelectric matrix, and the elastic coefficient matrix to be specified as material properties. These are explained next.The following related topics are available: Permittivity Matrix (Dielectric Constants) Piezoelectric Matrix Elastic Coefficient Matrix2.3.2.1. Permittivity Matrix (Dielectric Constants)For SOLID5, PLANE13, or SOLID98 you specify relative permittivity values as PERX, PERY, and PERZ on the MP command (Main Menu Preprocessor Material Props Material Models Electromagnetics Relative Permittivity Orthotropic). (Refer to the EMUNIT command for information on free-space permittivity.) The permittivity values represent the diagonal components 11, 22, and 33 respectively of the permittivity matrix S. (The superscript S indicates that the constants are evaluated at constant strain.) That is, the permittivity input on the MP command will always be interpreted as permittivity at constant strain S.Note: If you enter permittivity values less than 1 for SOLID5, PLANE13, or SOLID98, the program interprets the values as absolute permittivity.For PLANE223, SOLID226, and SOLID227, you can specify permittivity either as PERX, PERY, PERZ on the MP command or by specifying the terms of the anisotropic permittivity matrix using the TB,DPER and TBDATA commands. If you select to use the MP command to specify permittivity, the permittivity input will be interpreted as permittivity at constant strain. If you select to use the TB,DPER command (Main Menu Preprocessor Material Props Material Models Electromagnetics Relative Permittivity Anisotropic), you can specify the permittivity matrix at constant strain S (TBOPT = 0) or at constant stress T (TBOPT = 1). The latter input will be internally converted to permittivity at constant strain S using the piezoelectric strain and stress matrices. The values input on either MP,PERX or TB,DPER will always be interpreted as relative permittivity.2.3.2.2. Piezoelectric MatrixYou can define the piezoelectric matrix in e form (piezoelectric stress matrix) or in d form (piezoelectric strain matrix). The e matrix is typically associated with the input of the anisotropic elasticity in the form of the stiffness matrix c, while the d matrix is associated with the compliance matrix s.Note: The program converts a piezoelectric strain matrix d matrix to a piezoelectric stress matrix e using the elastic matrix at the first defined temperature. To specify the elastic matrix required for this conversion, use the TB,ANEL command (not the MP command).This 6 x 3 matrix (4 x 2 for 2-D models) relates the electric field to stress (e matrix) or to strain (d matrix). Both the e and the d matrices use the data table input described below:The TB,PIEZ and TBDATA commands are used to define the piezoelectric matrix; see your Command Reference for the order of input of these constants.To define the piezoelectric matrix via the GUI, use the following:Main Menu Preprocessor Material Props Material Models Piezoelectrics Piezoelectric matrixFor most published piezoelectric materials, the order used for the piezoelectric matrix is x, y, z, yz, xz, xy, based on IEEE standards (see ANSI/IEEE Standard 1761987), while the input order is x, y, z, xy, yz, xz as shown above. This means that you need to transform the matrix to the input order by switching row data for the shear terms as shown below: IEEE constants e61, e62, e63 would be input as the xy row IEEE constants e41, e42, e43 would be input as the yz row IEEE constants e51, e52, e53 would be input as the xz row2.3.2.3. Elastic Coefficient MatrixThis 6 x 6 symmetric matrix (4 x 4 for 2-D models) specifies the stiffness (c matrix) or compliance (s matrix) coefficients.Note: This section follows the IEEE standard notation for the elastic coefficient matrix c. The matrix is also referred to as D.The elastic coefficient matrix uses the following data table input:Use the TB,ANEL (Main Menu Preprocessor Material Props Material Models Structural Linear Elastic Anisotropic) and TBDATA commands to define the coefficient matrix c (or s, depending on the TBOPT settings); see the Command Reference for the order