Journal of Aerospace Engineering

A process for evaluating lunar‐base construction equipment and methods concepts is presented. The process is driven by the need for more quantitative, systematic, and logical methods for assessing further research and development requirements in an area where uncertainties are high, dependence upon terrestrial heuristics is questionable, and quantitative methods are seldom applied. Decision theory concepts are used in determining the value of accurate information and the process is structured as a construction‐equipment‐and‐methods selection methodology. Total construction‐related, earth‐launch mass is the measure of merit chosen for mathematical modeling purposes. The work is based upon the scope of the lunar base as described in the National Aeronautics and Space Administration's Office of Exploration's “Exploration Studies Technical Report, FY 1989 Status.” Nine sets of conceptually designed construction equipment are selected as alternative concepts. It is concluded that the evaluation process is well suited for assisting in the establishment of research agendas in an approach that is first broad, with a low level of detail, followed by more‐detailed investigations into areas that are identified as critical due to high degrees of uncertainty and sensitivity.

This paper presents a statistical sensitivity analysis for shape distortions of space structures. The approach is based on a statistical shape‐distortion analysis on the structural errors and an adjoint method of sensitivity analysis. The statistical shape‐distortion analysis allows the stochastic errors to be represented by member‐length tolerances. The sensitivity analysis is performed to predict the effects of member‐length errors for lattice space antennas on the surface accuracy. The formulas presented in this paper give an effective approach to predict the effects of member‐length errors on the shape distortions, to obtain effective structural elements to correct the shape distortions, and to design tolerance errors of the structural elements. Numerical examples for statically determinate and indeterminate two‐dimensional truss beams have been demonstrated to identify the members contributing most to the errors. These results show that the errors of the longitudinal elements of the structure are important for designing accurate truss structures. Moreover, the validity and effectiveness of the present approach have been investigated.

Recent advances in computer hardware and software have made multiprocessing a viable and attractive technology. This paper reviews high‐performance computing methods in structural mechanics and engineering through the use of a new generation of multiprocessor computers. The paper presents an overview of vector pipelining, performance metrics for parallel and vector computers, programming languages, and general programming considerations. Recent developments in the application of concurrent processing techniques to the solution of structural mechanics and engineering problems are reviewed, with special emphasis on linear structural analysis, nonlinear structural analysis, transient structural analysis, dynamics of multibody flexible systems, and structural optimization.

This paper reviews and examines different numerical approaches for modeling and analyzing the behavior of structures having constrained‐layer damping. Specific topics that are addressed included: modeling of the material behavior, implementation of structural damping and constrained‐layer damping into two‐ and three‐dimensional finite elements, and assessment of the different analysis methods for calculating the damped response and estimation of the damping level in the structure. Two numerical studies are presented that reveal the accuracy limits of the different finite‐element modeling approaches for additive and integrally damped plate‐type structures. It was observed that an assembly of plate and solid elements will accurately predict both the natural frequencies and loss factors, whereas equivalent solid elements and equivalent plate‐element approaches poorly predict the natural frequency and incorrectly predict the loss factor. The assembled plate/solid elements are accurate up to an aspect ratio of 125 for the solid elements. Above this aspect ratio valve, the frequency predictions are acceptable, but the damping (loss factor) predictions are usually poor.

The effect of delamination on the flutter boundary of two‐dimensional laminated plates are investigated theoretically. Linear‐plate theory and qusai‐steady aerodynamic theory are employed. A simple beam‐plate‐theory model is developed to predict the flutter boundaries of delaminated homogeneous plates with simply supported ends. The effects of delamination position, size, and thickness on the flutter boundary are studied in detail. The results reveal that the presence of a delamination degraded the stiffness and the natural frequencies of the plate and thereby decreases the flutter boundary of the plate. However, for certain geometries the flutter boundaries were raised due to the flutter coalescence modes of the plate altered by the presence of a delamination in the plate.

The influence of structural flexibility on the magnitude and orientation of reflected pressures produced by blast shocks is examined. Present formulations for blast pressures based upon rigid‐surface assumptions are found to be inaccurate for applications to flexible aerospace structures. The effects of elastic behavior of panel‐type structures on reflected shock pressures are studied. A parametric study is completed in which the effects of structural flexibility including panel deflection, rotation, and velocity on the magnitude of the reflected pressures are investigated. The dynamic deflections and initial panel velocity of a flexible moving panel are found to be important parameters that influence the values of reflected pressures, particularly for aircraft panels in the near vicinity of a weapon‐blast or a rocket‐plume overpressure.