Date:
Wed, 28/06/201712:00-13:30
Location:
Danciger B building, Seminar room
Lecturer: Mr. Itamar Kolvin
Affiliation: Racah Institute of Physics,
The Hebrew University of Jerusalem
Abstract:
Broken surfaces exhibit a dazzling variety of surface structures. Take a piece of a shattered glass and you'll find recorded on its surface: the tortuous path the crack took, waves emanating from the point of impact, steps – at times extremely delicate and at others jagged, and even colorful thin film interference – where the crack has split and left a small frustrated branch. Despite the impressive progress in our understanding of how cracks initiate and propagate, the study of fracture surfaces, Fractography, remains a largely qualitative science. Cracks are fast and surface detail is minute, making the observation of cracks while they form surface structure quite challenging.
In this Seminar, I will describe how we alleviated these difficulties by breaking soft solids – gels – and directly visualizing the leading edge of the crack – the crack front. We explored two generic mechanisms for the formation of surface structure. At low crack velocities, the crack front spontaneously nucleates steps, which drift along the front and divide the surface into discrete facets. At higher velocities, facets give way to the formation of highly localized chains of microscopic cracks – micro-branches.
I will show how crack fronts form these structures, and how, in turn, they affect crack front shape and dynamics, pointing to a new understanding of the toughness of brittle materials.
Affiliation: Racah Institute of Physics,
The Hebrew University of Jerusalem
Abstract:
Broken surfaces exhibit a dazzling variety of surface structures. Take a piece of a shattered glass and you'll find recorded on its surface: the tortuous path the crack took, waves emanating from the point of impact, steps – at times extremely delicate and at others jagged, and even colorful thin film interference – where the crack has split and left a small frustrated branch. Despite the impressive progress in our understanding of how cracks initiate and propagate, the study of fracture surfaces, Fractography, remains a largely qualitative science. Cracks are fast and surface detail is minute, making the observation of cracks while they form surface structure quite challenging.
In this Seminar, I will describe how we alleviated these difficulties by breaking soft solids – gels – and directly visualizing the leading edge of the crack – the crack front. We explored two generic mechanisms for the formation of surface structure. At low crack velocities, the crack front spontaneously nucleates steps, which drift along the front and divide the surface into discrete facets. At higher velocities, facets give way to the formation of highly localized chains of microscopic cracks – micro-branches.
I will show how crack fronts form these structures, and how, in turn, they affect crack front shape and dynamics, pointing to a new understanding of the toughness of brittle materials.