Caltech
Ares J. Rosakis Ares J. Rosakis
Chair, Division of Engineering and Applied Science
Otis Booth Leadership Chair, Division of Engineering and Applied Science; Theodore von Kármán Professor of Aeronautics and Mechanical Engineering
Research Interests

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Current Projects

Laboratory Earthquakes 1: Rupture Speeds, Modes, Inhomogeneous Faults, Directionality
Collaborators:
H. Kanamori and N. Lapusta, Caltech; J. R. Rice, Harvard; M. Bouchon, Grenoble, France; S. Das, Oxford, UK. Students/Post Docs: Michael Mello and Harsha S. Bhat, Caltech



Laboratory Earthquakes 2: Ground Shaking Signatures of Supershear Earthquakes



Laboratory Earthquakes 3: The Feasibility of dynamic full-field earthquake measurements from space



Mechanics of Thin Films and Wafer Level Metrology



Hypervelocity Impact Phenomena
Collaborators:
Students: L. Lamberson, Caltech; J. Mihaly, Caltech
V&VUQ Meeting - Facility Poster (pdf)


Overview

Ares J. Rosakis works in the fields of Aerospace, of solid mechanics, mechanics of material's failure and the mechanics of earthquake seismology. He pioneered the development of experiments aimed at the discovery and elucidation of the physical processes involved in dynamic fracture and catastrophic failure of materials such as metals, polymers, metallic glasses composites, layered solids and frictional interfaces. He has invented a number of full field optical diagnostic techniques (both in the visible and infra-red wavelength range). These include the Coherent Gradient Sensor (CGS) which he applied to elucidate the multi-scale mechanics of dynamic interfacial fracture of bonded solids with applications to composite materials, sandwich structures and thin films.

In dynamic fracture mechanics, he has made multiple contributions, including the scientific discovery of shear dominated transonic de-bonding in various layered systems. He also discovered that earthquake ruptures may propagate with super-shear rupture speeds and may also do so as either shear cracks or pulses.

One of the most notable applications of CGS is the application of this method to the study of thin film problems. By combining analytical models with the CGS measurements, Rosakis made seminal advances to the study of the mechanical reliability of microelectronic devices. He has also applied CGS and high speed photography to the study of impact and fragmentation of ceramics and brittle polymers as well as the investigation of hypervelocity impact phenomena applied to the study of micrometeorite impact on space structures and the protection of space assets from space and orbiting debris.

Rosakis also invented the fastest existing high-speed, full-field, microprobe infrared thermal camera (1 million frames/second), which provided the first full-field recording of the transient temperature field developed during dynamic localized shear deformation. It also revealed the existence of dynamically evolving vortical structures at the core of adiabatically growing shear bands in both crystalline and amorphous metals. His invention of this high speed IR camera, which he applied to the study of both growing cracks and shear bands, has resulted in the elucidation of the basic physics which govern the complex, coupled, thermo-mechanical phenomena such as those involved in high speed machining and penetration mechanics.

Ares Rosakisí development of CGS interferometry has resulted in both the fundamental understanding of fracture of solids and in the development of metrology tools for real time and in-situ inspection of 300 mm production wafers in the microelectronics industry. The 13 patents related to CGS authored by him enabled a Caltech spin-off company and the resulting instrument has been used as a tool for yield management by microelectronics industry including Intel, Semetech and Applied Materials.

In the early nineties, Ares Rosakis and his co-workers introduced the concept of "laboratory earthquakes" which has enabled the experimental discovery of new phenomena (e.g.super-shear, pulse like ruptures, directionality etc.) of relevance to full scale earthquake processes. This was a natural evolution of Rosakisí earlier work on the dynamic intersonic fracture of heterogeneous and layered solids which had already attracted considerable attention from both the physics, and the geophysics communities. Of particular interest to these communities was a section of his work related to the dynamic rupture of frictionally held interfaces separating similar and dissimilar materials. In this body of work, Rosakis collaborates with seismologist, and seismo-mechanicians to design novel surrogate experiments which accurately mimic earthquake rupture in various controlled laboratory settings. Through these experiments, he was able to discover that earthquake ruptures may propagate with super-shear speeds and may also do so as either shear cracks or pulses. These discoveries proved to be of particular interest to the geophysical community and resulted in symposia at professional meetings in both engineering and geophysical societies such as ASME, the American Geophysical Union (AGU), the Seismological Society of America (SSA), the American Physical Society (APS) and in special volumes of journals. These were devoted to discussing and interpreting the experimental discoveries in relation to field observations of such supershear earthquake events and sequences hosted by the San Andreas, Denali, Alaska, North Anatolian and the Tibetan faults.

Rosakis has graduated 25 PhD students and mentored 16 postdoctoral fellows. Fourteen of his former students (11 of them tenured) and 10 of his former postdocs (6 of them tenured) now hold faculty positions in universities around the world. He has authored over 200 referred publications.

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