Accession Number:

ADA196873

Title:

Structural Optimization Including Centrifugal and Coriolis Effects

Descriptive Note:

Doctoral thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

1988-01-01

Pagination or Media Count:

133.0

Abstract:

This theses investigates the effects of centrifugal and Coriolis forces on the mode shapes and frequencies of a rotating system. The rotational effects have a profound influence on the eigenfrequencies this is important in optimal structural redesign where the frequencies must be adjusted. The structural matrices for the rotating system were obtained by examining the expression for the total system energy. This provides a differential stiffness matrix that models centrifugal force and a provides velocity-dependent Coriolis matrix. By using a high-level programming language Direct Matrix Abstraction Programming a modal analysis solution sequence was modified to account for rotational effects in free vibration. Finite element models were then created for a typical compressor blade in a modern jet engine and for a cantilever beam rotating about the vertical axis. The optimal redesign was done by deriving complex nonlinear inverse perturbation equations for the problem involving both magnitude and phase components. The perturbation problem is solved by using nonlinear mathematical programming. Optimal redesign uses an underdetermined system, i.e., the feasible design must not be unique. This allows the application of an objective function, such as minimum structural weight or minimum change from the baseline design. Constraints, such as those on frequency, are applied. Optimal structural changes are obtained that meet the frequency goals to within three percent. Examples were carried out using the general purpose software package MSCNASTRAN and ADS Automated Design Synthesis.

Subject Categories:

  • Aerodynamics
  • Computer Programming and Software

Distribution Statement:

APPROVED FOR PUBLIC RELEASE