research

In this contribution, an elasto-viscoplastic constitutive model based on the single mode EGP (Eindhoven Glassy Polymer) model is proposed to describe the deformation behaviour of solid polymers subjected to finite deformations under different stress states. The material properties of the original model are determined and calibrated from a uniaxial compression-loading test. Then, several numerical examples under different stress states are presented to illustrate the limitations.

The elastic Ericksen's problem consists of finding deformations in isotropic hyperelastic solids that can be maintained for arbitrary strain-energy density functions.  In the compressible case, Ericksen showed that only homogeneous deformations are possible. Here, we solve the anelastic version of the same problem, that is we determine both the deformations and the eigenstrains such that a solution to the anelastic problem exists for arbitrary strain-energy density functions. Anelasticity is described by finite eigenstrains.

Imitating origami principles in active or programmable materials opens the door for development
of origami-inspired self-folding structures for not only aesthetic but also functional purposes. A
variety of programmable materials enabled self-folding structures have been demonstrated across
various fields and scales. These folding structures have finite thickness and the mechanical
properties of the active materials dictate the folding process. Yet formalizing the use of origami
rules for use in computer modeling has been challenging, owing to the zero-thickness theory and

A multiphase field model is developed to study the effects of metastable ζ and γ hydrides on the nucleation and growth of the stable δ hydrides in α zirconium matrix.  Acta Materialia 123 (2017) 235-244 

RVE analysis is popular for computational homogenization. It can be used independently for virtual testing or as a module for multiscale modeling. Its popularity is mainly due to the maturity and acceptance of commercial finite element software. RVE analysis usually requires a 3D domain to obtain 3D properties and local fields. If a 2D RVE is used, only 2D properties and local fields are obtained. To obtain the complete set of properties, multiple analysis is needed. For example, to obtain the complete stiffness matrix, six 3D RVE analyses are needed.

Highly-stretchable 3D-architected Mechanical Metamaterials

Lightweight Mechanical Metamaterials with Tunable Negative Thermal Expansion

In an article published today in Science, we have demonstrated the creation of an extreme gradient-nano-grained (GNG) structure in single-crystal microcubes through high-velocity impact. We use the defect-free single-crystal silver microcubes, synthesized using a seed-growth process, as the model system, and fire them at supersonic velocities onto a rigid target to create the GNG structure.