Acoustic Emission Event Detection Research Articles

Micromechanical BEoL robustness evaluation methods enabling loading condition customization and acoustic emission damage monitoring

For micromechanical robustness evaluation methods, it is advantageous if the mechanical loading conditions applied can be controlled as precisely as possible. For microchips, this is required to determine the robustness under specific conditions, e.g. during assembly or characteristic application/usage scenarios. In this work, three different micromechanical BEoL (Back End of Line) robustness evaluation methods are presented which should enable a more precise and flexible mechanical load induction and damage identification. They have been subsequently developed. Three main aspects characterize the customization of the developed approaches:•The design and testing of customized micro-tools to precisely apply mechanical load to individual Cu-pillars.•The implementation of an AE (Acoustic Emission) monitoring approach to detect minor damages during mechanical loading. This strategy also enabled the development of sub-critical loading experiments for which AE signals served as a damage indicator and mechanical loading was aborted upon the detection of AE events.•The development of a new measurement setup and approach to enable the solder attach of individual Cu-pillars to a mechanical testing system.The applications of these approaches should enable the induction of customized mechanical loading conditions and the identification of failure modes and damage initiation locations.

Fiber optic acoustic emission distributed crack sensor for large structures

AbstractPreliminary experiments leading to the development of an optical fiber acoustic emission sensor is described. The objective was to develop a single sensor for simultaneous detection of acoustic emission events, from many locations within a large structure. The optical fiber sensor can be adhered to the surface of structural materials, i.e. steel or concrete. There are no individual sensor arrays or components built into the fiber. This characteristic provides simplicity and renders the system practical for applications in bridge structures. Alternatively, the optical fiber could be embedded in new concrete construction. Acoustic emissions from micro‐cracks or defects from various locations in the structure create stress wave perturbations in the optical fiber that are detected by a portable interferometer. Time‐domain measurements are instantaneous, in real‐time, and the entire structure is interrogated through a one‐time operation. The time domain signal acquired from the optical fiber discerns the number and locations of damage zones i.e., weld cracks, bolt‐hole cracks, corrosion activity, or brittle fracture of fibers in composite materials.

深部グリーンタフ層に対する水圧破砕について

JNOC and Teikoku Oil Co. have studied hydraulic fracturing for a naturally fractured deep volcanic reservoir in Niigata prefecture facing the Japan sea since 1988.First two year of the project was spent for pre-fracturing study. Data obtained from mini-frac, such as step rate test, pump in/flow back test, and pump in/shut in test, were used to design the main fracturing job. Well logging date were used to determine the stress distribution of the formation.In 1990, the main fracturing job was done, succeeded in the improvement of the well production rate about twice as much as that before fracturing, but couldn't be injected the scheduled amount of proppant, because of screen out. The high net pressure and two kinds of closure pressure, which were analyzed from mini-frac, indicate the possible presence of natural fractures.Laboratory experiments have been made to inspect the simulation model. Water is injected to acrylic resin or mortal block, which is put in the true triaxal confining pressure apparatus. Fracturing pressure and surface strain can be measured under various confining pressures. Acoustic emission event detection has also tried to investigate formed fracture geometry.

Acoustic emission monitoring results from the MFTF magnets

Abstract A technique for monitoring disturbances using acoustic emission (AE) in superconducting magnets was applied to the superconducting yin-yang magnet pair for the Mirror Fusion Test Facility (MFTF-B) at the Lawrence Livermore National Laboratory (LLNL). Signals from twelve AE sensors mounted on the magnet were recorded during magnet charging tests. A minicomputer-based signal processing technique was then developed for real-time AE event detection, location, and characterization. Acoustic emission events caused by movement of conductors in the energized magnet windings or by structural disturbances such as epoxy cracking and debonding could be identified. The data recorded from the MFTF tests were then analysed. The results showed a wide range of AE activity detected by the sensors. Activity from structure and conductor motion showed different behaviour with increasing magnet current. Sensors mounted in the small radius regions of the magnet exhibited the highest levels of activity, agreeing with analysis of maximum loads and independent magnet voltage monitoring results.

Detection of acoustic emission events in the presence of parasitic noise

The optimum threshold for the detection of acoustic emission bursts, which are masked by parasitic noise is calculated. The theoretical results are applied to the acoustic noise generated by boiling sodium.