A Spline-Based Stress Function Approach for the Principle of Minimum Complementary Energy

TL;DR

This paper introduces a spline-based stress function method for the principle of minimum complementary energy, enabling accurate stress predictions in complex geometries with fewer degrees of freedom than traditional FEMs.

Contribution

It develops a novel stress function formulation using splines that improves flexibility and reduces computational complexity in stress analysis of structures.

Findings

Achieves stress accuracy comparable to FEMs with fewer DOFs.

Successfully applied to complex geometries and boundary conditions.

Validated against analytical solutions and challenging test cases.

Abstract

In computational engineering, ensuring the integrity and safety of structures in fields such as aerospace and civil engineering relies on accurate stress prediction. However, analytical methods are limited to simple test cases, and displacement-based finite element methods (FEMs), while commonly used, require a large number of unknowns to achieve high accuracy; stress-based numerical methods have so far failed to provide a simple and effective alternative. This work aims to develop a novel numerical approach that overcomes these limitations by enabling accurate stress prediction with improved flexibility for complex geometries and boundary conditions and fewer degrees of freedom (DOFs). The proposed method is based on a spline-based stress function formulation for the principle of minimum complementary energy, which we apply to plane, linear elastostatics. The method is first validated against analytical solutions and then tested on two test cases challenging for current state-of-the-art numerical schemes, a bi-layer cantilever with anisotropic material behavior, and a cantilever with a non-prismatic, parabolic-shaped beam geometry. Results demonstrate that our approach, unlike analytical methods, can be easily applied to general geometries and boundary conditions, and achieves stress accuracy comparable to that reported in the literature for displacement-based FEMs, while requiring significantly fewer DOFs. This novel spline-based stress function approach thus provides an efficient and flexible tool for accurate stress prediction, with promising applications in structural analysis and numerical design.