A Learning-Based Optimal Uncertainty Quantification Method and Its Application to Ballistic Impact Problems

TL;DR

This paper introduces a machine learning framework using neural networks and stochastic optimization to efficiently compute optimal uncertainty bounds in systems with partially known input distributions, demonstrated on ballistic impact problems.

Contribution

It presents a novel learning-based approach combining neural networks and stochastic gradient descent to solve high-dimensional optimal uncertainty quantification problems.

Findings

Successfully applied to magnesium alloy impact analysis

Achieved efficient approximation of extremal probability measures

Enabled construction of safety performance maps

Abstract

This paper concerns the study of optimal (supremum and infimum) uncertainty bounds for systems where the input (or prior) probability measure is only partially/imperfectly known (e.g., with only statistical moments and/or on a coarse topology) rather than fully specified. Such partial knowledge provides constraints on the input probability measures. The theory of Optimal Uncertainty Quantification allows us to convert the task into a constraint optimization problem where one seeks to compute the least upper/greatest lower bound of the system's output uncertainties by finding the extremal probability measure of the input. Such optimization requires repeated evaluation of the system's performance indicator (input to performance map) and is high-dimensional and non-convex by nature. Therefore, it is difficult to find the optimal uncertainty bounds in practice. In this paper, we examine the use of machine learning, especially deep neural networks, to address the challenge. We achieve this by introducing a neural network classifier to approximate the performance indicator combined with the stochastic gradient descent method to solve the optimization problem. We demonstrate the learning based framework on the uncertainty quantification of the impact of magnesium alloys, which are promising light-weight structural and protective materials. Finally, we show that the approach can be used to construct maps for the performance certificate and safety design in engineering practice.