Bryce Gardner

Models of the acoustic radiation and transmission properties of complex trimmed structures

A number of advances have been made recently in the development of a hybrid method for rigorously coupling finite element and statistical energy analysis descriptions of the dynamics of a vibro‐acoustic system. The method provides an efficient way to analyze the acoustic radiation and transmission properties of a complex structure across a broad frequency range. In this paper, two case studies of engine components are used to validate the ‘‘hybrid area junction’’ formulation for coupling FE structures with trimmed SEA fluids, and to demonstrate the use of the method in a design process.

Experimental validation of finite element–boundary element model dynamic strain model under diffuse acoustic field loading.

Structural finite element (FE) models naturally output displacement or acceleration response data. However, they can also be used to compute stress, internal forces, and strain response. When coupled with a boundary element model (BEM) of the fluid surrounding the structure, a fully coupled analysis can be performed. Modeling a diffuse acoustic field in the BEM fluid provides an excitation like that found when the structure is placed in a reverberation chamber. Fully coupling the structural FE model to the acoustic BEM model provides a means to predict not only the acceleration response of the panel to diffuse field loading but also the ability to predict the dynamic stress and strain response. This type of model has been available with current predictive tools, but experimental validation of the prediction of dynamic stress or strain is difficult to find. An aluminum panel was instrumented with accelerometers and strain gauges and hung in a reverberation room and subjected to a diffuse acoustic field. Th...

Comparison of sea modeling approaches for vibration transmission through beam structures.

Transmission through beams can become a significant path in many structure‐borne problems, especially in aircraft or launch vehicles. Statistical energy analysis (SEA) is widely used for the vibro‐acoustic modeling of high‐frequency problems. However, in a system‐level SEA model, even at higher frequencies, some beams can exhibit low‐modal behavior and might not be a good SEA representation. Vibration transmission through beams involves both resonant and non‐resonant transmission paths. Typically the non‐resonant path is dominant at low frequencies and the resonant path at high frequencies. This paper describes various modeling approaches for describing the transmission through beams over a broad frequency range. SEA modeling techniques will be compared to the hybrid FE‐SEA method, energy flow method, and the finite element method for various beam configurations. Modeling beams under pre‐stressed conditions is also investigated.

Modeling vibration isolator performance with hybrid finite element/statistical energy (FE‐SEA) analysis

Vibration isolators are often modeled as simple single degree of freedom systems. Such an approach is often adequate for characterizing the low frequency performance of a vibration isolator (assuming that the effective spring stiffness and damping loss factor of the isolator can be obtained). However, at mid to high frequencies, two problems are often encountered. The first is that the impedance of the structures connected to the isolator become important (assumptions of rigid body behavior of the components of interest are generally not valid). The second is that the internal dynamic behavior of the isolator becomes important (internal resonances of the isolator degrade the isolation performance). This paper describes the development of a hybrid FE‐SEA model of an in situ vibration isolator that addresses these problems. The key factors affecting the mid and high frequency performance of an isolator are investigated.

Vibro-acoustic analysis of large space structures using the Hybrid FE-SEA method

A number of advances have been made recently in the development of a Hybrid method for rigorously coupling deterministic and statistical descriptions of the dynamics of a vibro-acoustic system. The method provides an efficient way to describe the response of a complex vibro-acoustic system across a broad frequency range. This paper provides an overview of various numerical and experimental validation studies that have been performed using the method.