QUEST Projects

QUEST Projects

Wavefield Imaging for Far Surface Defect Characterization

Sponsor: Universal Technology Corporation / Air Force Research Laboratory

The objective of this project is to characterize macro damage on the inaccessible surface of airframe components by first interrogating areas of interest with bulk waves and then measuring and analyzing the transmitted, reflected and scattered wave motion recorded on the accessible surface.

Ultrasonic Guided Wave Methods for Combined SHM and NDE of Composite Airframe Structures

Sponsor: NASA Langley

The objective of this project is the development of a wave-based approach to health state assessment and management of airframes that combines the rapid detection capabilities of in situ transducer arrays with the resolution provided by the detection and analysis of acoustic wavefields. In the proposed hybrid SHM/NDE system, Sparse Guided Wave Arrays (SGWAs) are considered as the embedded SHM technique that is augmented by, and integrated with ground-based Acoustic Wavefield Imaging (AWI). Tight integration is ensured by employing embedded sparse array transducers as sources for wavefield imaging, which enables good sensitivity with minimum disassembly. The proven ability of SGWAs to detect typical defects sizes resulting from impacts on composite airframes is key to success of the approach. Performance limitations of SGWAs, such as their tendency of producing imaging artifacts and their limited ability to characterize (e.g., accurately size) damage, are mitigated through adaptive imaging and sparse reconstruction algorithms, and the augmented resolution and characterization capabilities of AWI. In turn, SGWA results will dramatically limit the area that has to be scanned using the wavefield imaging method. In summary, integration of SGWA and AWI will enable reduction in inspection time while providing accurate flaw sizing.

Principal Investigator: Prof. Massimo Ruzzene, Aerospace Engineering

Load-Enhanced Methods for Lamb Wave in situ NDE of Complex Components

Sponsor: American Society for Nondestructive Testing (Fellowship to Mr. Xin Chen)

This fellowship award is in support of research leading towards the development and demonstration of a methodology that leverages applied loads to enable improved detection, localization and characterization of damage in complex metallic structures.

Multi-Path Guided Wave Imaging for Inspection and Monitoring of Large, Complex Structures (Completed)

Sponsor: Hidden Solutions, LLC (NASA SBIR)

There is a well-recognized need within the structural health monitoring community to interrogate large, complex structures in a rapid, reliable, and cost-effective fashion. Distributed arrays of permanently attached, inexpensive piezoelectric transducers are perhaps the most effective means for performing guided wave structural health monitoring; however, guided wave signals recorded from these arrays are very complex and can be difficult to interpret. Current imaging algorithms used to interpret recorded guided waves address the complexity by considering only the direct-path propagation between each sensor and points of interest on the structure. Built-up structures that contain multiple features, such as stiffeners, ribs, cut-outs and fasteners, compound the difficulty of interpretation by substantially increasing the number of multi-path echoes and even precluding direct-path propagation between many portions of the structure. This project addressed the inherent challenges of working with complex structures by leveraging, rather than ignoring, the multi-path echoes present in ultrasonic guided wave signals through the use of experimentally estimated Green’s functions.

Understanding and Exploiting the Effects of Loading on Ultrasonic Sensing Systems for Structural Health Monitoring (Completed)

Sponsor: Air Force Research Laboratory

Guided elastic waves are being considered for large area monitoring of plate and shell-like components using spatially distributed arrays of sensors. Besides temperature, flight-induced loads are the environmental effect that is most likely to have a significant adverse effect on guided wave signals. In an undamaged structure, loads cause anisotropic dimensional and wave speed changes, and can also cause boundary conditions of built-up structures to change. In a damaged structure, load changes can cause cracks to open and close, and poor bonds to make and break contacts. This project has developed the theory to understand the effect of loads on guided wave signals in undamaged structures, then considered the effect of loads on damaged structures, and lastly has exploited the effects of loads for improved and baseline-free structural health monitoring.

A University Testbed for Development, Verification and Validation of Multi-Scale Structural Health Monitoring Techniques (Completed)

Sponsor: Air Force Office of Scientific Research

Implementation of structural health monitoring (SHM) methods in aircraft has the potential to reduce maintenance costs, prevent catastrophic failures, and eliminate unnecessary overdesigns. However, few if any such methods have been transitioned to practice, primarily because of uncertainty in how such methods will perform in an actual operating environment and for unanticipated damage modes. A good deal of this uncertainty is related to lack of appropriate facilities to support not only development of SHM methods, but also their verification and validation for realistic damage and under reasonable operating conditions. This testbed was developed to enable university researchers to transition SHM methods from artificial defects under laboratory conditions to a variable load testing environment with real fatigue-induced damage. It consists of a large test frame suitable for mounting test panels and aircraft components, applying static loads, and inducing damage via realistic spectrum loading as well as associated sensors and instrumentation.

Principal Investigator: Prof. Massimo Ruzzene, Aerospace Engineering

A Multi-Scale Structural Health Monitoring Approach for Damage Detection, Diagnosis and Prognosis in Aerospace Structures (Completed)

Sponsor: Air Force Office of Scientific Research

A multi-scale approach to structural health monitoring was considered to analyze the progression of damage starting from the characterization of its precursors, moving ahead to quantifying its location, type and extent, and finally investigating its effects at the component and structural levels. Fatigue and damage generation and progression are processes consisting of a series of interrelated events that span large scales of space and time. If dynamics-based monitoring with elastic waves and mechanical vibrations is considered, the spatial and temporal scales can be related to the frequency and time span of interrogation. The obvious relationship is that the sensitivity of detection decreases as the inspection frequency decreases. A unified approach to structural health monitoring is therefore envisioned where the spatial resolution and types of damage that can be detected span a continuum from the local and microscopic to the global and macroscopic. This project thus incorporated multiple monitoring methods that were properly selected and integrated to detect damage precursors and actual defects across the length scales, quantitatively characterize the state of the component or structure, and ultimately provide a better diagnosis and prognosis than would be possible with a single interrogation method alone.

Co-Principal Investigators: Profs. Massimo Ruzzene and Laurence Jacobs

Nonlinear Inverse Methods for Ultrasonic Inspection and Monitoring of Complex Structures (Completed)

Sponsor: NASA / GSRP

This project, which was a NASA Graduate Student Researcher’s Program grant to Mr. James Hall, consisted of the development of several inverse modeling algorithms for the purpose of using ultrasonic guided waves in nondestructive evaluation and structural health monitoring applications. These models leveraged the natural complexity of realistic multimode propagation and modern multi-channel signal processing techniques to provide improved resolution to detect, localize, and characterize structural flaws using a sparse array of permanently attached transducers.

Ultrasonic Sensor Systems for Prognostic Health Monitoring (Completed)

Sponsor: Northrop Grumman / DARPA

The primary focus of this program was to consider novel uses of ultrasonic wave propagation in order to design a system suitable for prognosis of critical metallic components. Ultrasonic methods are one of the most promising technologies for diagnosis and prognosis of structural components due to their ability to interrogate a significant volume of material with a small number of sensors. In this project, we combined laboratory and in situ ultrasonic measurements with extensive mechanical fatigue testing to develop methods for both diagnosing the current state of damage and predicting the remaining life. In Phase I of this program, a novel in situ ultrasonic method was developed to monitor initiation and growth of small fatigue cracks originating from fastener holes. During Phase II additional local and global ultrasonic methods were considered including guided wave imaging whereby larger areas were monitored.

Analysis and Modeling of Diffuse Ultrasonic Signals for Structural Health Monitoring (Completed)

Sponsor: National Science Foundation

The use of permanently mounted sensors to monitor the health of critical structures such as airplanes, bridges and buildings is rapidly becoming a reality in order to detect damage so that appropriate action can be taken prior to catastrophic failure. Sensors for measuring such physical quantities as temperature, moisture and strain are becoming smaller and more robust, but these devices are limited to point, or local, measurements. This research project considered sparse arrays of permanently mounted ultrasonic sensors, acting as both transmitters and receivers, which send ultrasonic energy throughout the entire structural volume and thus have the potential to globally detect local changes. The primary testing mode considered was that of diffuse-like ultrasonic waves whereby a point-like impulsive excitation is used to generate multi-modal elastic waves that “fill” the structure with sound. Development of signal processing and classification methods in conjunction with modeling and experiments have provided a foundation essential for successful deployment of ultrasonic sensors for monitoring of structural integrity.

High Temperature Sensing System for Ultrasonic Monitoring of Critical Energy Infrastructure (Completed)

Sponsor: Mechanical Integrity, Inc. / NSF STTR

Petroleum refineries critical to the nation’s energy infrastructure include high temperature piping systems and vessels carrying liquid and gaseous petrochemical products. Failure of these components has serious safety and financial consequences in addition to the impact on our nation’s energy supply. Continuous on-stream moni­toring of structural integrity at high temperatures is a critical capability for minimizing plant downtime and simultaneously improving plant reliability while requiring fewer highly trained inspection personnel. Failures are frequently due to wall thinning caused by corrosion and erosion, and such failures could be avoided by taking appropriate corrective action if thinning is detected early enough. This project considered ultrasonic sensing methods operating at high temperatures to monitor the thickness at designated “spot” locations while simultaneously monitoring large areas for distributed thickness reductions.

Advanced Ultrasonics for Material Microstructure Characterization (Completed)

Sponsor: Corning, Inc.

Performed advanced ultrasonic measurements on specialized materials to characterize microstructure.

Last revised on November 15, 2012.