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1、Structural-Acoustic Analysis with ABAQUS,Coupled Structural-Acoustic Analysis,Lecture 4,深圳ABAQUS培训 http:/ 深圳ANSYS培训 http:/ 深圳ANSYS http:/ 深圳ABAQUS http:/ 深圳有限元培训 http:/ ABAQUS培训 http:/ ANSYS培训 http:/,Structural-Acoustic Analysis with ABAQUS,Overview,Introduction Near-Field and Far-Field Effects Full
2、y Coupled Analysis Sequentially Coupled Analysis Acoustic-to-Structural Submodeling Coupled Acoustic-Structural Substructures Boundary Impedances Creating ASI elements on geometry Creating ASI elements on orphan meshes,Structural-Acoustic Analysis with ABAQUS,Introduction,Structural-Acoustic Analysi
3、s with ABAQUS,Introduction,Structural-acoustic coupling If the acoustic medium adjoins a structure, structural-acoustic coupling occurs at the interface. The pressure field in the acoustic medium creates a normal surface traction on the structure. The acceleration field in the structure creates the
4、natural forcing term at the fluid boundary. Recall that volumetric acceleration is the conjugate of acoustic pressure in an acoustic analysis. Volumetric acceleration is what you apply as a concentrated load in an acoustic analysis. Generically, the acoustic and structural fields must be solved for
5、simultaneously.,Structural-Acoustic Analysis with ABAQUS,Introduction,Simplifications In air the forces on structures caused by the air are usually weak. In such a case, rather than performing a coupled analysis, you might model the effect of the structure on the acoustic fluid using boundary condit
6、ions or loads on the acoustic model. The value of acoustic pressure can be specified directly (*BOUNDARY in an input file or use the ABAQUS/CAE Load module). This includes the case of complicated boundary pressure fields computed in a previous structural analysis see Sequentially Coupled Analysis be
7、low. A concentrated volumetric acceleration can be specified (*CLOAD in an input file or use the ABAQUS/CAE Load module). A distributed volumetric acceleration can be specified using the *INCIDENT WAVE options. Requires the use of the Keywords Editor in ABAQUS/CAE.,Structural-Acoustic Analysis with
8、ABAQUS,Introduction,Interface impedances The structural-acoustic interface can have an impedance, Z, of its own. This means that the relationship between the structural motion and the acoustic pressure need not be continuous: Used to include easily the effects of thin interface layers, such as carpe
9、t on the floor of a car, or the absorptive acoustic coating of a submarine.,Structural-Acoustic Analysis with ABAQUS,Near-Field and Far-Field Effects,Structural-Acoustic Analysis with ABAQUS,Near-Field and Far-Field Effects,Near and far fields,Structural-Acoustic Analysis with ABAQUS,Near-Field and
10、Far-Field Effects,Near field The region within one wavelength of the interface is generally considered the near field. Near-field region shrinks with increasing frequency. The near-field solution tends to be complicated. Includes “evanescent” effects (effects that fade quickly). In the near field th
11、e mesh has a strong effect on accuracy. The element size on both sides of the interface is governed by the medium that requires the finer mesh.,Structural-Acoustic Analysis with ABAQUS,Near-Field and Far-Field Effects,Far field Beyond one wavelength the complexities of the near field diminish. The n
12、ear-field mesh has limited effect on far-field results. Whether or not the near-field mesh is refined often does not strongly affect the results away from the interface. The mesh in the far field needs to be appropriate only for the material and the simulation requirements, as discussed in Lecture 3
13、. Unlike in static problems, in acoustic simulations the far field is oscillatory, not constant. The far-field mesh still needs to be fine enough to capture these waves.,Structural-Acoustic Analysis with ABAQUS,Near-Field and Far-Field Effects,Speaker with finely meshed air (left) and coarsely meshe
14、d air (right),Structural-Acoustic Analysis with ABAQUS,Fully Coupled Analysis,Structural-Acoustic Analysis with ABAQUS,Fully Coupled Analysis,When is fully coupled analysis appropriate? Fully coupled analysis is the most general approach to structural-acoustic problems. All problems can be solved ap
15、propriately using the fully coupled approach. Makes no assumptions about which direction has the strongest coupling effects. Structural deformation Acoustic pressure A drawback of coupled analysis is that it can be unnecessarily expensive for large problems where the acoustic pressure has little eff
16、ect on the structure. In these cases sequentially coupled analysis can be more efficient (discussed in the next section).,Structural-Acoustic Analysis with ABAQUS,Fully Coupled Analysis,Coupling with ASI (acoustic-structural interface) elements If the structural mesh and the acoustic mesh share nodes at their interface, lining the interface with ASI elements enforces the required coupling
