The relationships between a resistance curve (R-curve), the corresponding fracture process zone length, the shape of the traction/displacement softening law, and the propagation of fracture are examined in the context of the through-the-thickness fracture of composite laminates. A procedure that accounts for R-curve toughening mechanisms by superposing bilinear cohesive elements is proposed. Si...

Hydraulic fracturing with constant fluid injection r a t e was numer ica l ly model led for a p a i r of rectangular longitudinal fractures intersecting a wellbore i n a n i m p e r m e a b l e rock m a s s , a n d numerical calculations have been performed to investigate the relations among the form of pressuretime curves, fracture opening/propagation behavior a n d permeabi l i ty of t h e me...

Many injection/production wells have been hydraulically fractured to enhance injectivity/productivity. Various engineering models for fracture geometry have been developed, which define the propagation of a fracture with time and wellbore treatment pressure. These models combine with elasticity, fluid flow, material balance, and propagation criterion/in-situ stresses. When this combination desc...

The shearing of natural fractures is important in the permeability enhancement of shale gas reservoirs during hydraulic fracturing treatment. In this work, the shearing mechanisms of natural fractures are analyzed using a newly proposed numerical model based on the displacement discontinuities method. The fluid-rock coupling system of the model is carefully designed to calculate the shearing of...

We investigate the initiation and early-stage propagation of an axi-symmetric hydraulic fracture from a wellbore drilled in the direction of the minimum principal stress in an elastic and impermeable formation. Such a configuration is akin to the case of a horizontal well and a hydraulic fracture transverse to the well axis in an open hole completion. In addition to the effect of the wellbore o...

Interfacial fracture toughness and cyclic fatigue-crack growth properties of joints made from 99.5% pure alumina partially transient liquid-phase bonded using copper/niobium/copper interlayers have been investigated at both room and elevated temperatures, and assessed in terms of interfacial chemistry and microstructure. The mean interfacial fracture toughness, Gc, was found to decrease from 39...

INTRODUCTION FRAX®, an assessment algorithm for estimating fracture probability, has been widely used for the evaluation of osteoporosis since 2008. Its clinical use requires that osteoporotic fracture probability is established at which treatment can be recommended. OBJECTIVES The aim of the present study was to explore possible treatment thresholds for Poland. PATIENTS AND METHODS The FRA...

An analysis is presented for transient response of a mode-III interfacial crack propagating between two dissimilar piezoelectric half spaces. The dynamic fracture toughness of a piezoelectric interface is examined, which is a central issue related to the interface strength of multi-layered sensors and ferroelectric thin film devices. For the mode-III crack propagation in piezoelectric materials...

Fracture surface of Zircaloy-2 specimens tested under constant crosshead speed in CH3OH/0.4 Vol. %HCI solution with and without selenium (25 ppm) addition was studied. Using a combined process of deformation and annealing, coarse grained material was also obtained and examined. Two modes of stress corrosion crack propagation were observed: an intergranular zone caused by stress assisted anodic ...