Plasticity Von-Misces vs Linear Elastic Isothropic

Hi, Im running a simulation for a college work. We need to obtain a force/displacement curve from a heavy vehicle security arch. Problem is: Im running both nonlinear simulations to compare the behavior of the beams. Everything is exactly the same in both simulations except the model type material (1 - Linear Elastic Isothropic and 2 - Plasticity Von-Misces). But the results don´t make much sense tbh. I have large displacement and strain on. The Stress Strain curve seems ok (Solidworks library). Now what i expected was both simulations should be similar up to the yield point, and then diverge from there. However the Plasticity one doesn´t even reach yield stress. If someone could help out I'd greatly appreciate it.

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