Walter J. Horn

Investigation of Multi-Material Bird Models for Predicting Impact Loads

This research work investigated the use of multi-material bird models for accurately predicting bird impact loads. Numerical simulations carried out using the SPH (Smoothed Particle Hydrodynamics) technique of LS-Dyna showed excellent correlation with the experimental results. The multi-material bird models of this work are more rigorous than in any previously published work, and include a realistic bird shape. Each material model was distinct, having its own density value (different from the other materials) and an associated equation of state. Results indicated that using a multi-material bird with various combinations of materials permits better correlation with experimental results.Copyright

GEOMETRIC MODIFICATION OF LAMINATED CYLINDRICAL SHELLS WITH EMBEDDED NTTINOL

A laminated composite circular cylindrical shell prototype of a leading edge deicing system with embedded Nitinol wire was designed, constructed and analyzed to determine the feasibility of such a system for the removal of ice from the leading edge of an aircraft wing. This simple system was analyzed to determine the level of strain that could be generated by the activation of the embedded Nitinol wires. These predicted values of strain were then compared with those strains measured during laboratory tests of the prototype system. The embedded Nitinol wire was incorporated into the laminate of the finite element model of the curved laminated as a lamina of the sytem with appropriate effective thickness and a pseudo-thermal reaction to generate the recovery forces associated with the shape memory alloy. A Rayleigh-Ritz analysis was also used to confirm the results of the finite element model.

Neural network approach of active ultrasonic signals for structural health monitoring analysis

Maintenance is an important issue for aerospace systems, since they are in service beyond their designed lifetime. This requires scheduled inspections and damage repair before failure. Research is in progress to develop a structural health monitoring system (SHMS) to improve this maintenance routine. Ultrasonic testing, utilizing a system of piezoelectric actuators and sensors, is a promising concept Measured wave signals are compared with signals for previously scanned states. Changes to the signal could be the result of damage to the component. This paper focuses on analyzing the differences of states, using artificial neural networks. Neural network analysis has the potential of creating a SHMS of greater ability and processing. Experiments were performed on a thin, flat aluminum panel. Ultrasonic actuators and sensors were installed and a baseline scan was performed on the undamaged panel. Simulated damage was introduced in specific areas, and scans were conducted for several damaged states. Neural networks were created to assess the changing conditions of the panel. The system was later tested on a lap joint specimen to confirm the abilities of the neural network. This form of analysis performed well at locating and quantifying areas of change within the structure. The neural network performance indicated that it has a role in the SHMS of aerospace structures.

Investigation of Material Density Variations for Predicting Bird Impact Loads

Typical bird models used in bird strike analysis are built with a homogeneous mixture of water and air, represented as a single material. In this research, simple heterogeneous bird models were built consisting of mixtures of water and air, discretely modeled as separate materials. SPH (Smoothed Particle Hydrodynamics) spatial discretization was used for modeling the bird. Two different types of bird models were chosen for this study – a heterogeneous bird model with randomly distributed mixtures of water and air particles throughout the bird volume, and another heterogeneous bird model that has lumps of high and low density materials within the traditional bird model. The high density material represents the bone structure and the low density material represents the lungs and other soft tissue. The effect of various material density variations within these heterogeneous bird models is investigated both on impact loads and target deflection.