Study of Ligament Length Effect on Mode Mix of a Modified In-Plane Shear Test Specimen

Abstract

Shear fracture toughness is an important material behavior that needs to be determined and considered in many industrial fields. At the same time, shear testing is one of the complex material testing areas where available methods are few, often need special arrangements and most of the methods do not strictly satisfy the definition of pure shear. In this study, a modified shear test specimen was proposed to measure the shear fracture toughness by uniaxial loading in a tensile testing machine. High Density Polyethylene (HDPE) was used as test material for the experiments. The specimen was created in order to suit the most common used tensile test machine. The specimen was then optimized by using Finite Element Analysis (FEA) to find the geometry and the size of the pre-notch to avoid the mixed mode loading and minimize effects of normal stresses. For the specimen in discussion, an upper and lower limit of usable ligament length can be found. Finally, a method for determining the fracture toughness was discussed according to the essential work of fracture.

Characterization of Specific Essential Work of Fracture for various Fracture Modes on Thermoplastic Materials

“…In their observations made at the same rate of deformation, they found that we depend on the thickness of the groove and its value is twice that of mode I fracture. The use of finite element analysis in high-density polyethylene shows that EWF mode II corresponds to the ligament length of 2t < ℓo < W/2 [43]. This condition is also suitable for fractures from mode II which shift to mixed mode I-II.…”

Simplified Characterization of Anisotropic Yield Criteria for an Injection-Molded Polymer Material

“…However, in the context of finite element simulation, LDPE is often assumed to be isotropic in its material behavior [14,19,20], although this assumption yields inaccurate finite element model prediction. Widely used isotropic yield functions are Tresca and von Mises.…”