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A piezoelectric traveling-wave motor model has been developed with parameters entirely related to physical properties. The approach is well-rooted in the formulation suggested earlier by Hagood and McFarland, but several model improvements have been integrated in an effort to realize an accurate model suited for automated design optimization. Additional model considerations include a flexible rotor model and a hysteretic stick-slip friction contact model which replace the previous assumptions of a rigid rotor and pure slip. The most notable contribution has been the use of lossy (complex) material properties to account for inherent material losses, supplanting the use of non-physical damping coefficients. The model is partly formulated in the frequency domain, and by representing the modal states and forces as Fourier series expansions and retaining higher harmonic terms, it has been generalized to account for non-ideal traveling-wave excitation. Needing to simulate the hysteretic contact model in the time domain, a mixed-domain solution procedure has been implemented to maintain some of the computational efficiency of frequency domain analysis. A preliminary validation study has demonstrated excellent correlation between simulation results and experimental data for a commercial motor.

Modern developments in shaped charge technology have resulted in greater explosive loads being used on perforating guns, which has stretched the capacity of perforating guns into uncharted territory. Traditional gun design approaches and standards use collapse pressure calculation and swell measurement with overloaded charges as design verification methods. The extremely complicated interactions between explosives, fragmented casings, and the gun wall are evaluated on an empirical basis, and the nature of these interactions is not well understood. In this paper, a new design model is presented that augments traditional design approaches and provides gun designers with better data on gun system structural performance, including the effects of phasing, shot density, and charge type.The loads imposed on the gun body by the explosives are multidimensional because of the spiral arrangement of most shaped charges. The resulting dynamic response of the gun body is therefore quite complex and requires three-dimensional (3D) analysis. High-frequency bending, torsion, and tensile loads are expected. The casings are typically fragmented, and some of the larger fragments can impose high impact loads on the gun wall. A fully coupled computer model has been developed that incorporates the rapid explosion, casing fragmentation, and multidimensional structural responses.Multiple instrumented surface tests were performed to validate the dynamic 3D model. Proprietary testing techniques were used to extract gun internal pressure history and gun stress history at multiple locations immediately following detonation. Redundant strain gauges were used, and shots were repeated to ensure the integrity of the data. This paper presents the instrumented gun test setup and results, along with the newly developed 3D simulation model and shock hydro model results. This paper also presents validation of the newly developed 3D model through comparisons with test data.

Modern development of shaped charges has resulted in greater and greater explosive loads on the perforating guns and has stretched the capacity of perforating guns into uncharted territory. Traditional gun design approaches and standards use collapse pressure calculation and swell measurement with overloaded charges as design verification methods. The extremely complicated interactions between explosives, fragmented casings, and the gun wall are evaluated on an empirical basis, and the nature of these interactions is not well understood. In this paper, we present a new design model that augments traditional design approaches and provides gun designers with better data on gun system structural performance including the effects of phasing, shot density, and charge type. The loads imposed on the gun body by the explosives are multi-dimensional due to the spiral arrangement of most shaped charges. The resulting dynamic response of the gun body is therefore quite complex and requires three-dimensional analysis. High-frequency bending, torsion, and tensile loads are expected. The casings are typically fragmented, and some of the larger fragments can impose large impact loads on the gun wall. A fully-coupled computer model has been developed that incorporates the rapid explosion, casing fragmentation, and multi-dimensional structural responses. Multiple instrumented surface tests were carried out to validate the dynamic three-dimensional model. Proprietary testing techniques were used to extract gun internal pressure history and gun stress history at multiple locations immediately following detonation. Redundant strain gages were used and shots were repeated to ensure the integrity of the data. This paper first presents the newly developed three-dimensional simulation model in full details. The second section describes the instrumented gun test set up and results. The final section of this paper presents validation of the model through comparison with test data.

Measurements of the elastic modulus of fused silica, 606 l-T6 and 7075-T651 aluminum alloys, GaAs, Ge, and Si samples are reported. A pulsed laser is used to generate surface acoustic waves in a sample and the wave velocity is measured using a knife-edge detection method. From the velocity of the surface waves the elastic modulus can be calculated.[ 1 ] Extension of this work to thin films is discusssed.