We have decided to discontinue the publication of preprints on our preprint server end of 2024. The publication culture within mathematics has changed so much due to the rise of repositories such as ArXiV (www.arxiv.org) that we are encouraging all institute members to make their preprints available there. An institute's repository in its previous form is, therefore, unnecessary. The preprints published to date will remain available here, but we will not add any new preprints here.
We review recent theories of non-classical, structured deformations and integral representations for their Helmholtz free energy. Energy minimizers for a body undergoing shearing at two different length scales and for a bar experiencing both smooth extension and macroscopic fractures then are determined, and applications to the shearing of single crystals and to the cohesive fracture of solids are discussed. Yield, hysteresis, and the associated dissipation in two-level shears are shown to arise from instabilities at the microlevel, and the dichotomy between brittle and ductile fracture is related precisely to a critical length of a bar.