Viscoelastic Fiber Bundle: Creep & Relaxation Spectrum (2D)

Real viscoelastic solids — polymers, biological tissue, asphalt — almost never relax with a single clean exponential the way an idealized three-parameter spring-dashpot model predicts; they relax with a spectrum of relaxation times because different microstructural elements yield at different rates. This 2D simulator models that directly with a generalized Maxwell (Wiechert) bundle: a set of independent spring-dashpot fibers in parallel, each with its own modulus and viscosity drawn from a spread you control, every one of them numerically integrated frame by frame with a real 4th-order Runge–Kutta ODE solver rather than evaluated from a closed-form formula. Drive the bundle with a constant-stress creep step or a constant-strain relaxation step, watch each fiber's internal node settle at its own rate, and see how widening the relaxation-time spread pulls the aggregate response away from the single-exponential curve it collapses to when the spread is zero.