טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentZhang Longhui
SubjectControlling Adiabatic Shear Failure by Tailoring
Microstructural Toughening Factors
DepartmentDepartment of Mechanical Engineering
Supervisors Professor Daniel Rittel
Dr. Shmuel Osovski
Full Thesis textFull thesis text - English Version


Abstract

The prediction of the onset of adiabatic shear band (ASB) formation and subsequent failure is a major issue due to the unstable character of this failure mechanism. During the last decade, our group has proposed a new approach to the phenomenon, based on the dynamically stored energy of cold work and dynamic recrystallization (DRX), which are identified as key factors for the onset of shear localization. A physical explanation to dynamic shear localization was the development of DRX as a microstructure-related instability. The deeper identification of the toughening-softening mechanisms will pave the road for a control of the propensity to adiabatic shear localization.

Ti6Al4V is chosen as a model material to study the influence of impact-induced dynamic recrystallization (DRX) on the subsequent quasi-static flow properties through a systematic combination of dynamic tests up to a pre-defined level of strain, followed by static testing to fracture.

A systematic characterization of the Taylor-Quinney Coefficient (TQC) for seven different metals loaded in dynamic tension, compression and dominant shear is presented and a unified database of Taylor-Quinney coefficient for those materials is provided, as well as its dependence on strain and loading mode (for some of the characterized materials).

A joint thermal-mechanical characterization of near α Ti3Al2.5V and near β Ti-55511 titanium alloys at high strain rates is carried out to study the thermomechanical response and dynamic failure of these two titanium alloys.