Dynamic characteristic of partially debonded sandwich of ferry ro-ro’s car deck: a numerical modeling

The dynamic behavior of a partially debonded Ferry Ro-Ro’s sandwich car deck is investigated by using commercial finite element software ABAQUS. Debonding in the car deck model is estimated by comparing the dynamic responses of the fully intact and damaged model of the bonding condition. The influence of the debonding ratio is investigated by free vibration analysis using Lanczos iteration method. The dynamic response of the car deck model is loaded with harmonic excitation and is examined in detail. The transverse displacements, velocities, accelerations, longitudinal strains, and phase portraits are investigated in the central point of the damaged area. To evaluate the effect of inserting the spring contact element during the dynamic analysis, both debonded models with and without spring contact elements are examined. From the report, it can be concluded that the dynamic analysis which relies on the modal analysis can be used to diagnose the possibility of debonding problem in the car deck structure. The natural frequencies of the debonded model decrease due to the presence of discontinuity in the debonded region. Further, the discontinuity also creates locally concentrated deformation and significantly affects the short-term time response.

An Out-of-Core Eigen-Solver with OpenMP Parallel Scheme for Large Spare Damped System

An out-of-core block Lanczos method with the OpenMP parallel scheme was developed to solve large spare damped eigenproblems. The symmetric generalized eigenproblem is first solved using the block Lanczos method with the preconditioned conjugate gradient (PCG) method, and the condensed damped eigenproblem is then solved to obtain the complex eigenvalues. Since the PCG solvers and out-of-core schemes are used, a large-scale eigenproblem can be solved using minimal computer memory. The out-of-core arrays only need to be read once in each Lanczos iteration, so the proposed method requires little extra CPU time. In addition, the second-level OpenMP parallel computation in the PCG solver is suggested to avoid using a large block size that often increases the number of iterations needed to achieve convergence.

Variational calculations on the vibrational level structure of S0 HDCO

We perform converged high precision variational calculations to determine the frequencies of the vibrational levels in S0 HDCO, extending up to 5000 cm−1 of vibrational excitation energy. For these calculations we use our specific vibrational method (recently employed for studies on H2CO and D2CO), consisting of a combination of a search/selection algorithm and a Lanczos iteration procedure and based on the Martin, Lee, Taylor potential energy surface for formaldehyde. The calculated level structure is compared to the recently measured frequencies by Ellsworth et al. in order to improve their assignments and further clarify the vibrational mixing pattern and vibrational resonances in HDCO that are very different from the other more symmetric formaldehyde species H2CO and D2CO studied recently.

Vibrational calculations in formaldehyde: the CH stretch system

An alternative procedure for the calculation of highly excited vibrational levels in S0 formaldehyde was developed to apply to larger molecules. It is based on a new set of symmetrized vibrational valence coordinates. The fully symmetrized vibrational kinetic energy operator is derived in these coordinates using the Handy expression [Molec. Phys. 61, 207 (1987)]. The potential energy surface is expressed as a fully symmetrized quartic expansion in the coordinates. We have performed ab initio electronic computations using GAMESS to obtain all force constants of the S0 formaldehyde quartic force field. Our large scale vibrational calculations are based on a fully symmetrized vibrational basis set, in product form. The vibrational levels are calculated one by one using an artificial intelligence search/selection procedure and subsequent Lanczos iteration, providing access to extremely high vibrational energies. In this work special attention has been given to the CH stretch system by calculating the energies up to the fifth CH stretch overtone at ∼16000 cm−1, but the method has also been tested on two highly excited combination levels including other lower frequency modes.