Lecture

Dynamic Fracture Instability: Monitoring Crack Velocity with Analog Electronics

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In course

ME-412: Experimental methods in engineering mechanics

This course gives an advanced treatment of experimental methods in the context of mechanics by way of example. Students will construct significant components of experimental apparatus, use their apparatus to collect data, interpret the resulting data, and ...

Description

This lecture explores the use of a simple analog electronic circuit to measure crack speed in dynamic fracture experiments, reaching speeds close to 1,000 m/sec. The instructor discusses the background theory of crack propagation, the experimental setup involving a Wheatstone bridge and high-speed op-amp, and the use of profilometry to analyze crack surface features. Discrepancies between theoretical predictions and experimental data on crack tip speeds are highlighted, showing unexpected spikes and accelerations. The critical transition to unstable crack propagation is examined through cross-correlation of velocity with surface profilometry, revealing a uniquely valued critical velocity. The lecture concludes by emphasizing the importance of monitoring crack velocity fluctuations for a deeper understanding of dynamic fracture behavior.

Instructor

John Martin Kolinski

Dr. Kolinski studied Applied Mathematics (Sc.M.) and Applied Physics (Ph.D.) at Harvard University, completing a PhD under the supervision of L. Mahadevan and Shmuel Rubinstein on the role of air in droplet impact. John did his post-doc at the Hebrew University of Jerusalem in Israel supported by the Fulbright post-doctoral fellowship. At HUJI, he worked on interfacial instabilities in soft matter in the labs of Eran Sharon and Jay Fineberg. John continues his research into interfacial mechanics at EPFL in EMSI, his newly founded laboratory for the study of Engineering Mechanics of Soft Interfaces.

Official source

Related concepts (5)

Interferometry

Interferometry is a technique which uses the interference of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber optics, engineering metrology, optical metrology, oceanography, seismology, spectroscopy (and its applications to chemistry), quantum mechanics, nuclear and particle physics, plasma physics, biomolecular interactions, surface profiling, microfluidics, mechanical stress/strain measurement, velocimetry, optometry, and making holograms.

Nondestructive testing

Nondestructive testing (NDT) is any of a wide group of analysis techniques used in science and technology industry to evaluate the properties of a material, component or system without causing damage. The terms nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also commonly used to describe this technology. Because NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research.

Analogue electronics

Analogue electronics (analog electronics) are electronic systems with a continuously variable signal, in contrast to digital electronics where signals usually take only two levels. The term "analogue" describes the proportional relationship between a signal and a voltage or current that represents the signal. The word analogue is derived from the word ανάλογος n(analogos) meaning "proportional". Analogue signal An analogue signal uses some attribute of the medium to convey the signal's information.

Electronics

Electronics is a scientific and engineering discipline that studies and applies the principles of physics to design, create, and operate devices that manipulate electrons and other charged particles. Electronics is a subfield of electrical engineering, but it differs from it in that it focuses on using active devices such as transistors, diodes, and integrated circuits to control and amplify the flow of electric current and to convert it from one form to another, such as from alternating current (AC) to direct current (DC) or from analog to digital.

Analog computer