Monthly Archives: June 2014

Ductile Fracture of Metals by Necking – Cup and Cone Failure

Ductile Fracture of Metals by Necking – Cup and Cone Failure extensive plastic deformation and energy absorption (“toughness”) before fracture Fracture: separation of a body into pieces due to stress, at temperatures below the melting point. Steps in fracture: crack formation crack propagation Major Fracture Mechanisms Depending on the ability of material to undergo plastic… Read More »

Concrete Creep Definition, Creep deformation Stages & Design Strategies

Concrete Creep Definition, Creep deformation Stages & Design Strategies When load is applied on a concrete specimen, shows an instantaneous deformation followed by slow increase of deformation is called concrete creep. Creep is a time-dependent permanent (plastic) deformation under a certain applied load.  Generally, creep occurs at high temperature (thermal creep) but can also happen… Read More »

Buckling of Columns – Euler Theory for Elastic Buckling

Buckling of Columns – Euler Theory for Elastic Buckling BUCKLING – Loss of stability –Axial loads cause lateral deformations (bending-like deformations) Buckling of Columns is a form of deformation as a result of axial- compression forces. This leads to bending of the column, due to the instability of the column. This mode of failure is… Read More »

Freeze Thaw Damage of Concrete – Effects & Preventive Measures

Freeze Thaw Damage of Concrete – Effects & Preventive Measures “damage to concrete caused by extreme temperature variations as noted by random pattern cracking.” A severe exposure condition on portland cement concrete structures is exposure to cycles of freezing and thawing. Air entrainment is used to enhance the freeze-thaw resistance of portland cement concrete exposed… Read More »

Significance of Delayed Ettringite Formation and Damage Mechanisms

Significance of Delayed Ettringite Formation and Damage Mechanisms Ettringite is formed in hydrated Portland cement system as a result of the reaction of calcium aluminate with calcium sulfate, both present in Portland cement. In the cement system, the presence of ettringite depends on the ratio of calcium sulfate to tri-calcium aluminate (C3A); when this ratio… Read More »

Fracture in Steel – Brittle fracture in ductile material

Fracture in Steel – Brittle fracture in ductile material Brittle failure is the brisk propagation of cracks through a material. This typically occurs so quickly that no plastic deformation takes place before fracture occurs. In structure failures, brittle failure usually causes a failure in structural integrity. Because of the rapid nature of this failure, it often leads… Read More »