A review of past and recent developments in multiaxial excitation of linear and nonlinear structures is presented. The objective is to review some of the basic approaches used in the analytical and experimental methods for kinematic and dynamic analysis of flexible mechanical systems, and to identify future directions in this research area. In addition, comparison between uniaxial and multiaxial excitations and their impact on a structure’s life-cycles is provided. The importance of understanding failure mechanisms in complex structures has led to the development of a vast range of theoretical, numerical, and experimental techniques to address complex dynamical effects. Therefore, it is imperative to identify the failure mechanisms of structures through experimental and virtual failure assessment based on correctly identified dynamic loads. For that reason, techniques for mapping the dynamic loads to fatigue were provided. Future research areas in structural dynamics due to multiaxial excitation are identified as (i) effect of dynamic couplings, (ii) modal interaction, (iii) modal identification and experimental methods for flexible structures, and (iv) computational models for large deformation in response to multiaxial excitation.

Test courses are monitored at the U.S. Army Aberdeen Test Center (ATC) on a monthly basis and are altered as required to maintain a "constant" roughness. The monitoring process consists of a jury ride and analysis of data acquired using an instrumented, light wheeled vehicle. The surface profiles of test courses at ATC are also measured on a monthly basis using a profilometer. A series of displacement and angular measurements are made. These are used to compute surface roughness as a function of distance traveled over the test course. This article proposes two techniques for determining vehicle sensitivity to changes in test-course roughness (vehicle-dependent ride quality and vehicle-independent fatigue damage spectrum) and, thus, the requirement to maintain the course. Both of these techniques require a data transformation in the spatial domain analogous to the power spectral density function in the temporal domain. An example using data measured before and after grading of an actual test course is presented.

Vehicle manufacturers currently use dynamic modeling, finite element modeling, and durability analysis to incorporate reliability into their designs. Although these models are often used separately, there has been little effort toward integrating these analyses and performing an analysis from the "ground up" (i.e., using terrain data to determine dynamic stress and strain). This paper outlines the approach of an ongoing analysis of a US Army trailer, using an integrated process of dynamic modeling, finite element modeling, and durability analysis. This project outlines an approach to mechanical reliability analysis that can be used early in design.

Vibration and strain data were measured on a modified munitions trailer to ensure that the design strength criteria had not been exceeded. These data were used in conjunction with a computer model to determine if the stress levels were sufficiently low to allow adequate fatigue life without further modification to the trailer. By combining standard data verification techniques with a stress prediction technique, data from a number of channels were reviewed at the test site to determine the severity of measured levels. This information was used to control the test process.