Description: Two interfaces are now available in ABAQUS for applying incident wave loading; a redesigned interface (referred to as the “preferred interface” and supported in ABAQUS/CAE) and the interface that has been available in previous versions (referred to as the “alternative interface” and not supported in ABAQUS/CAE). The preferred interface is conceptually the same as the alternative interface and uses essentially the same data but stores it in different locations internally. The preferred interface options include the term “interaction” to distinguish them from the incident wave and incident wave property options of the alternative interface. The alternative interface is supported in this release; however, it will be removed in a subsequent release of ABAQUS.

The acoustic impedance interface now allows either admittance values or impedance values to define an impedance. Nonreflecting boundary conditions are specified in the impedance instead of the impedance property. Nonreflecting boundary impedance effects are included in natural frequency extraction in ABAQUS/Standard.

Natural frequency extraction now also includes the effects of acoustic infinite elements. Together with the nonreflecting impedances, the acoustic infinite elements allow you to analyze the effects of immersion in fluid on the resonant behavior of structures.

Two new triangular element types are available for acoustic interface elements: ASI3D3 and ASI3D6. The acoustic interface elements types previously available for planar, three-dimensional, and axisymmetric models have been renamed to use more standard naming conventions; for example, ASI2A has been renamed to ASIAX2. The obsolete element types are supported in Version 6.6 but will be removed in a subsequent release of ABAQUS.

In ABAQUS/CAE you can define acoustic infinite and acoustic interface sections. You apply incident wave loading to the model by defining incident wave interaction properties and incident wave interactions. You can define acoustic impedance properties and acoustic impedance interactions, as shown in Figure 6–8 and Figure 6–9.

Property module:
   SectionCreate: Solid, Homogeneous; Other, Acoustic infinite or Acoustic interface: Material: 
   select acoustic medium
Interaction module:
   InteractionPropertyCreate: Acoustic impedance or Incident wave
   InteractionCreate: Acoustic impedance or Incident wave