VISCOELASTIC BENDING AND TORSION UNDER PIEZOELECTRIC CONTROL-ANALYTICAL AND MASSIVELY PARALLEL COMPUTATIONAL SIMULATIONS AND PERFORMANCE EVALUATIONS

Piezoelectric effects are of increasing importance in the control and sensing of structural element deflections. Elastic piezoelectric theory has been extensively developed (Leibowitz & Vinson 1993). Hilton et al. (1997) have presented an extended bibliography and discussed past contributions as well as formulated an analytical nonlinear theory of anisotropic piezoelectric-thermo-viscoelasticity. Only a limited number of analytical and experimental publications on linear piezo-viscoelastic materials may be found in the litera-ture (Holloway &Vinogradov 1997, Vinogradov & Holloway 1997). Yi et al. (1996) have formulated finite element solutions to demonstrate viscoelastic material damping. Hilton et al. (1997, 1998, 1999) and Beldica et al. (1998a, b, 1999) have applied this theory to a number of linear viscoelastic bending and aero-viscoelastic problems, such as creep flutter and torsional divergence and the response of piezo-viscoelastic structures to aerodynamic noise. Yi et al (1997) have formulated and carried out finite element solutions for a number of piezoelectric viscoelastic problems. In the present paper, the effects of combined bending, torsion and axial loads are ana-lyzed. The formulation of nonuniform rods leads to solutions which can only realized through massively parallel computations. Viscoelastic piezoelectric devices are attached to the outer surfaces of the rods. The numerical simulations lead to determinations of states of stress and deformation as functions of position and time. When these results are applied to composite rods, delamination failures are possible in time. Additionally, experimental failure data by Hiel et al 1991) for epoxy/fiber composite delaminations indicate Weibull distributions. Invariant deterministic and probabilistic stress failure theories have been developed by Hilton & Ariaratnam (1994). These analytical and experimental results are applied through the use of invariant failure theories of Hilton & Ariaratnam (1994) to the present problem and produce delamination onset probabilities. The effects of controlling deformations by extracting electrical energy through resistors or by the application of voltages to the piezoelectric devices are investigated. Analytical and numerical solutions are presented for viscoelastic beams with piezoe-lectric devices and probabilities of failure are calculated. Version 5.6-7 of ABAQUS with modifications was used on UIUC NCSA's HP-Exemplar computer to simulate relatively deep beams with thin piezo devices as well as their dissimilar viscoelastic properties. The finite element mesh consisted of 201,000 DOF. The ability of current ABAQUS program was examined and found accurate in handling viscoelastic meshes of different sizes and/or different viscoelastic materials. Computational performance evaluation studies are undertaken for distinct number of processors.