John F. Schultze

OVERVIEW OF STRUCTURAL DYNAMICS MODEL VALIDATION ACTIVITIES AT LOS ALAMOS NATIONAL LABORATORY

This presentation will provide a summary of the research and applications of structural dynamics model validation at Los Alamos National Laboratory. In this context model validation refers to the assessment of confidence in the usefulness of computational structural dynamics predictions for a particular application. The presentation will cover the problem definition, objectives, and motivation for studying model validation. Current paradigms for the model validation problem will also be presented. Supporting technologies such as uncertainty quantification, global sensitivity analysis, metamodeling, parameter updating, and design of experiments will be discussed, along with their role in the model validation process. The usefulness of model validation results for the computational modeling of system-level structural dynamics will be demonstrated. Examples of model validation techniques applied to transient structural dynamics problems of interest will be shown.

Application of Non-Linear System Model Updating Using Feature Extraction and Parameter Effects Analysis

This research presents a new method to improve analytical model fidelity for non-linear systems. The approach investigates several mechanisms to assist the analyst in updating an analytical model based on experimental data and statistical analysis of parameter effects. The first is a new approach at data reduction called feature extraction. This is an expansion of the classic update metrics to include specific phenomena or character of the response that is critical to model application. This is an extension of the familiar linear updating paradigm of utilizing the eigen-parameters or FRFs to include such devices as peak acceleration, time of arrival or standard deviation of model error. The next expansion of the updating process is the inclusion of statistical based parameter analysis to quantify the effects of uncertain or significant effect parameters in the construction of a meta-model. This provides indicators of the statistical variation associated with parameters as well as confidence intervals on the coefficients of the resulting meta-model. Also included in this method is the investigation of linear parameter effect screening using a partial factorial variable array for simulation. This is intended to aid the analyst in eliminating from the investigation the parameters that do not have a significant variation effect on the feature metric. Finally an investigation of the model to replicate the measured response variation is examined.

VALIDATION OF THE TRANSIENT STRUCTURAL RESPONSE OF A THREADED ASSEMBLY

This paper will demonstrate the application of model validation techniques to a transient structural dynamics problem. The problem of interest is the propagation of an explosive shock through a complex threaded joint that is a surrogate model of a system assembly. The objective is to validate the computational modeling of the key mechanical phenomena in the assembly, so that the component can be represented with adequate fidelity in the system-level model. A set of experiments was conducted on the threaded assembly where the acceleration and strain responses to an explosive load were measured on mass-simulators representing payloads. A significantly detailed computational model of the threaded assembly was also created. Numerical features that represent the important characteristics of the response were defined and calculated for both the experimental and computational data. Each step of the model validation process will be described as applied to this problem. Fundamental issues regarding the nature of model validation and the role of model validation in the engineering analysis process will also be discussed.