Z-sim

Material Simulation

Z-sim is a constitutive equation driver that enables users to simulate the behavior of a representative volume element (RVE) without relying on a full finite element model. By bypassing the FE framework, it provides fast and efficient evaluations of material responses at the element level.

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Constitutive Simulation Driver

Z-sim is designed to compute the response of any constitutive model from Z-mat, under either stress-controlled or strain-controlled loading, instead of force or displacement control. Compared to running an equivalent single-element FE simulation, Z-sim delivers substantial reductions in CPU time.

Key features include:

• Straightforward input definition, requiring only the loading history (stress, strain, or external parameters such as temperature), the material file, integration scheme settings, and output controls.
• Flexible loading definitions: hybrid stress/strain loading, unlimited loading blocks, simple cyclic load setup, and the ability to switch between stress and strain control during the simulation.
• Loading histories can be provided directly in the input file or imported from an external ASCII file.
• For finite strain simulations, loading can be expressed directly in terms of the deformation gradient.
• Support for both explicit and implicit integration methods, or a combination of the two.
• Advanced data output management.

Because Z-sim and Z-mat share the same model library, all standard and user-defined material models (implemented via ZebFront) are available. Additional tools allow users to plot yield surfaces, damage surfaces, or any potential function in stress space at different stages of the loading history.

Material Parameter Identification

Together with Z-opt, Z-sim forms the backbone of the Z-simopt GUI for material parameter calibration. The software minimizes the least-square distance between simulation results and experimental data, an optimization process that typically requires a very large number of simulations. By replacing element-based FE calculations, Z-sim greatly reduces simulation time, making the identification process faster and more efficient.

Beyond Material Simulation

Z-sim is not limited to constitutive models. It can also integrate any system of ordinary differential equations (ODEs).
Users simply define the variables to integrate with respect to time (or another kinematic variable), provide a list of parameters, and specify the governing equations in the dedicated environment. This flexibility allows Z-sim to address problems ranging from simplified reduced-order models (e.g., Neuber’s rule, three-bar systems) to complex finite difference schemes.