Fundamentals of Artificial Neural Networks (Z. Waszczyszyn).- Genetic Algorithms and Neural Networks (W. M. Jenkins).- Applications of Neural Networks in Modeling and Design of Structural Systems (P. Hajela).- The Neural Network Approach in Plasticity and Fracture Mechanics (P. D. Panagiotopoulos, Z. Waszczyszyn).- Neural Networks in Advanced Computational Problems (B. H. V. Topping et al.).- Neural Networks and Fuzzy Logic in Active Control of Mechanical Systems (P. Venini).

Neural networks in the analysis and design of structures

The evolution of computational methods for crashworthiness and related fields is described and linked with the decreasing cost of computational resources and with improvements in computation methodologies. The latter includes more effective time integration procedures and more efficient elements. Some recent developments in methodologies and future trends are also summarized. These include multi-time step integration (or subcycling), further improvements in elements, adaptive meshes, and the exploitation of parallel computers.

On Computational Methods for Crashworthiness

Presented in this paper are the results of three nonlinear computer programs, KRASH, ACTION and DYCAST used to analyze the dynamic response of a twin-engine, low-wing airplane section subjected to a 8.38 m/s (27.5 ft/s) vertical impact velocity crash condition. This impact condition simulates the vertical sink rate in a shallow aircraft landing or takeoff accident. The three distinct analysis techniques for nonlinear dynamic response of aircraft structures are briefly examined and compared versus each other and the experimental data. The report contains brief descriptions of the three computer programs, the respective aircraft section mathematical models, pertinent data from the experimental test performed at NASA Langley, and a comparison of the analyses versus test results. Cost and accuracy comparisons between the three analyses are made to illustrate the possible uses of the different nonlinear programs and their future potential.

Nonlinear structural crash dynamics analyses

Automotive Crashworthiness Performance on a Supercomputer

An analytical investigation has been made of the dynamic collapse of an elastic periodically supported column having an attached mass at one end and impacting a rigid surface at the other end with prescribed velocity and angle of incidence. The investigation has been carried out using a first-order approximate nonlinear solution and a nonlinear finite element solution. The first-order approximate solution has led to the determination of four basic nondimensional parameters which govern the response. These parameters include mass, impact velocity, initial imperfection, and impact angle parameters. Three regions of these parameters have been identified in which the character of the column's response is markedly different. These regions have been designated as the linear, transition, and dynamic collapse regions. Threshold values of the parameters which separate these regions have been defined. Results obtained reveal that responses in the linear region are dominated by axial motion, those in the transition region exhibit some axial-flexural coupling, and those in the collapse region are dominated by flexure. The rebound velocity in the transition and dynamic collapse regions is shown to be less than that predicted by the linear dynamic solution. The dynamic peak axial compressive load in the transition region is shown to be the same as that predicted by the linear dynamic solution. In the collapse region, the peak load decreases to a value less than the linear dynamic value, but greater than the static Euler buckling load. Moreover, it is shown that whereas the peak axial compressive load predicted by the linear solution grows unbounded with increasing values of the mass parameter, an ultimate dynamic load value is approached in the collapse region.

The dynamic collapse of a column impacting a rigid surface

: The results of a four-phase study to develop helicopter structural crashworthiness analytical and design techniques are presented. The study consisted of the development of a computer program (KRASH) and the verification of a mathematical model to predict the dynamic response during a survivable accident in which combined vertical and lateral impact velocities are present. Included in the study were a literature survey and evaluation, a detailed analysis of 32 accident cases, a drop test of a UH-1H helicopter with ground impact conditions of 23 fps vertical velocity and 18.6 fps lateral velocity, and parameter studies. It is concluded that program KRASH is capable of accurately predicting the dynamic responses during a multi-directional accident and that the program is a valuable tool with which to perform design tradeoff studies.

Experimental Program for the Development of Improved Helicopter Structural Crashworthiness Analytical and Design Techniques. Volume 1. Computerized Unsymmetrical Mathematical Simulation and Experimental Verification for Helicopter Crashworthiness in which Multidirectional Impact Forces are Present

: Volume 2 contains supporting data for the details presented in Volume I. The report contains abstracts for the 32 technical reports reviewed during the program. Included in the literature survey section is a matrix categorization of the reports by subject and applicable areas of interest. A brief description is presented on STAGS, the LMSC computer program used to perform the analysis of the P2V-4 fuselage bumper. A comprehensive description of program KRASH is presented, including the theory, initial conditions, the User's Guide, and a sample problem. Twenty-six channels of recorded test data and film data are presented in another section. Additional analytical data are presented in the last section.

Experimental Program for the Development of Improved Helicopter Structural Crashworthiness Analytical and Design Techniques. Volume 2. Test Data and Description of an Unsymmetrical Crash Analysis Computer Program, Including a User's Guide and Sample Case

Gilbert Wittlin

Papers

Experimental Program for the Development of Improved Helicopter Structural Crashworthiness Analytical and Design Techniques. Volume 1. Computerized Unsymmetrical Mathematical Simulation and Experimental Verification for Helicopter Crashworthiness in which Multidirectional Impact Forces are Present

Experimental Program for the Development of Improved Helicopter Structural Crashworthiness Analytical and Design Techniques. Volume 2. Test Data and Description of an Unsymmetrical Crash Analysis Computer Program, Including a User's Guide and Sample Case