  Ductile fracture of metallic materials typically involves the elastoplastic
deformation and associated damaging process. The nonlocal lattice particle
method (LPM) can be extended to model this complex behavior. Recently, a
distortional energy-based model is formulated into LPM to simulate J2
plasticity. However, this model is based on the incremental updating algorithm
which needs very small loading steps to get reasonable results. This is
time-consuming and unstable for large systems. Therefore, in this paper, a
tensor-based return-mapping algorithm is proposed to deal with these
deficiencies. The material deterioration process is modelled as a nonlocal
damage evolution process. The particle-size/lattice dependency of macroscopic
mechanical responses are handled properly by using the proposed model.
Numerical examples of predicting the elastoplastic behavior of engineering
structures with/without damage and fracture are also provided. A multi-threaded
implementation of LPM using C is available on the website:
https://github.com/ymlasu/LPM-C.
