Nonlinear Mechanics for Structural Engineering Simulation

Modeling products realistically and accurately often requires use of nonlinear capabilities. In fact, many structural engineers use nonlinear features in their simulation on a daily basis but may not be aware of it. Every engineer dealing with assemblies uses contact. Every engineer dealing with plastics or rubber parts needs nonlinear material models. Every product submitted to large deformations requires a nonlinear simulation to predict stress stiffening effects and potential collapse. In severe cases, an explicit dynamics simulation may be warranted.

Making the assumption a rubber is a linear material might be true for very limited deformations, but it proves to be totally inaccurate when parts are subject to large deformations. To reach accuracy requires minimizing the number of assumptions on the model: Material models need to closely follow real behavior; contacts and interactions between parts require detailed modeling.

Nonlinear buckling of a stiffened vessel

Fortunately, dealing with nonlinear responses has become easier, thanks to ongoing improvements in engineering simulation software. Today, nonlinear analysis is so accessible that any engineer capable of running a linear analysis already has the skills required to perform a good nonlinear simulation.

Too often, nonlinear modeling is perceived as requiring painful processes, specific meshing techniques, long computation times and model debugging to achieve convergence. ANSYS offers all the tools necessary to accurately compute models with nonlinear behavior — while providing unparalleled ease of use. ANSYS Structural Mechanics solutions provide high-end solver capabilities, an intuitive user interface, and all the necessary tools to understand the simulation process and results. The software incorporate all materials, elements and algorithms required for nonlinear simulations.

Experimental data and analytical model for rubber materials: Rigid plastics exhibit an elastoplastic response in which their stress–strain relationship is linear up to their elastic limit and nonlinear beyond that point. When subjected to continuous loading over an extended time period, plastics also creep, a visco-elastic behavior that results in nonlinear deformations and changes in load-carrying capabilities. Yet another nonlinear aspect of plastics comes from their strain-rate dependency.

The ANSYS Mechanical interface offers an unique user experience and reduces the overall time required for any simulation. It lets structural engineers focus on defining the physics of the model rather than dwelling on the mathematics. The overall setup time for any nonlinear problem, even with a large number of bodies, is minimal. The interface features superior bidirectional interfaces to all major CAD systems, automated meshing capabilities, advanced pre- and post-processing technologies and generalized parametric capabilities to easily compute design variations and perform design optimization.

For nonlinear analyses, automated contact detection reduces the setup time by orders of magnitude. All nonlinear analysis settings are exposed in an easily understandable way.

Automatic contact detection with advanced default settings: With today’s automated software, the once-laborious manual process can be completed with a few mouse clicks. The default setup parameters and element options built into much of today’s simulation software further this trend in automation. In fact, most users will not have to make any changes to run a successful nonlinear analysis. 

ANSYS Structural Mechanics solutions offer default settings for elements and algorithms to ensure proper convergence of a vast majority of nonlinear models — while leaving the user free to access advanced settings when required. A comprehensive set of post-processing tools is available to investigate global and local results.

Static structural analysis of engine gasket

Analysis of a rubber boot

Many tracking tools are available for use while the solution is being computed or after the solution has been obtained, including graphical convergence trackers and real-time contact information (pressures and gaps, for example). Users can simply monitor in real time how the solution progresses and take corrective actions when required.

Graphical tracking tool: Dealing with nonlinear responses has become easy thanks to ongoing improvements in engineering simulation software. Today, nonlinear analysis is so accessible that any engineer capable of running a linear analysis already has the skills required to perform a good nonlinear simulation.