Local Interaction Simulation Approach (LISA): A simulation framework for guided wave generation and propagation

Student : Kalyan Nadella

Sponsor : National Rotorcraft Technology Center (NTRC) Vertical Lift/Rotorcraft Center of Excellence (VLRCOE)


A complete 3-D elasticity based models to characterize GW propagation in complex structures become intricate because of the boundary effects and interface conditions. Traditional numerical tools such as finite elements (FE) are computationally inefficient because of the small wavelength discretizations required to attain converging results. It has been shown that local interaction simulation approach (LISA), a numerical method based on finite difference (FD) transformations is capable of efficiently and accurately modeling GW propagation.

Overview of LISA’s theoretical formulation.


  • To extend and assess the LISA’s capabilities to model 3D multilayered orthotropic structures with non-uniform cell aspect ratio. The iterative equations for the simulations are extended for orthotropic materials in a non-principal axis frame which will bene fit in modeling generic laminated composite structures.
  • To model the actuator effects by completely modeling the piezoelectric material characteristics into LISA. The iterative equations are extended for piezoelectric materials taking into account the electromechanical coupling of the governing equilibrium equations.
  • The iterative equations are validated by comparing the numerical results with experimental ones for isotropic, uni-directional, cross-ply and quasi-isotropic laminates.
Out-of-plane displacement pattern for uni-ply laminate when the input waves are incident along (a)-(d) 0 deg, (e)-(h) 45 deg and (i)-(l) 90 deg directions. Snapshots of the propagating waveform are shown at (a)-(b) 57 μs, (c)-(d) 67 μs, (e)-(f) 67 μs, (g)-(h) 77 μs, (i)-(j) 87 μs and (k)-(l) 97 μs.