Browsing by Author "Foote, Peter"

Now showing 1 - 8 of 8
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    Automated shot counter system for through-life support of target rifles
    (Elsevier, 2015-10-27) Gagar, Daniel; Hockley, Chris; Foote, Peter
    Competitive target shooting requires rifles with high levels of performance and small margins of error. Optimal performance of rifles in terms shot velocity can be expected over a period of use until an indeterminate but critical number of rounds has been fired when it will start to deteriorate. The rifle barrel must then be renewed. Accurate and reliable record-keeping of number of shots fired is therefore critical to minimise the through-life cost of owning a target rifle and also maintaining maximum performance. This can be most effectively done using an automated means for monitoring the number of rounds fired. In this paper the acoustic emission technique is used to monitor and identify shot rounds fired based solely on the features of Acoustic Emission (AE) signals for the first time. The results obtained from experiments showed unambiguous identification of shots fired and the capability to monitor degradation of the barrel as a function of number of shots fired.
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    Comparison of alternatives to amplitude thresholding for onset detection of acoustic emission signals
    (Elsevier, 2016-10-10) Bai, F.; Gagar, Daniel; Foote, Peter; Zhao, Yifan
    Acoustic Emission (AE) monitoring can be used to detect the presence of damage as well as determine its location in Structural Health Monitoring (SHM) applications. Information on the time difference of the signal generated by the damage event arriving at different sensors in an array is essential in performing localisation. Currently, this is determined using a fixed threshold which is particularly prone to errors when not set to optimal values. This paper presents three new methods for determining the onset of AE signals without the need for a predetermined threshold. The performance of the techniques is evaluated using AE signals generated during fatigue crack growth and compared to the established Akaike Information Criterion (AIC) and fixed threshold methods. It was found that the 1D location accuracy of the new methods was within the range of <1–7.1%<1–7.1% of the monitored region compared to 2.7% for the AIC method and a range of 1.8–9.4% for the conventional Fixed Threshold method at different threshold levels.
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    Development of probability of detection data for structural health monitoring damage detection techniques based on acoustic emission
    (Stanford University, 2013-12-12) Gagar, Daniel; Irving, Phil E.; Jennions, Ian K.; Foote, Peter; Read, Ian; McFeat, Jim
    Structural Health Monitoring (SHM) techniques have been developed as a cost effective alternative to currently adopted Non-Destructive Testing (NDT) methods which have well understood levels of performance. Quantitative performance assessment, as used in NDT, needs to be applied to SHM techniques to establish their performance levels as a basis for technique comparison and also as a requirement for practical aerospace application according to set regulations. One such measurand is Probability of Detection (POD). This paper reports experiments conducted to investigate the location accuracy of the Acoustic Emission (AE) system in monitoring events from HsuNielson and fatigue crack AE sources as a route to establish the POD of AE in SHM. It was found that fatigue crack tips could be located at 90% POD within 10 mm accuracy.
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    New methods for onset detection of acoustic emission signals
    (NDT.net, 2016-07-08) Gagar, Daniel; Bai, Fangliang; Zhao, Yifan; Foote, Peter
    Acoustic Emission (AE) monitoring can be used to detect the presence of damage as well as determine its location in Structural Health Monitoring (SHM) applications. The onset time of AE signals detected at different sensors in an array is used to determine their relative time difference of arrival which is essential in performing localisation of the signals’ originating source.Typically, this is done using a fixed threshold which is particularly prone to errors when not set to optimal values. This paper presents three new methods for determining the onset of AE signals without the need for a predetermined threshold. The performance of the techniques in terms of location accuracy is evaluated using AE signals generated during fatigue crack growth and compared to the established fixed threshold method. It was found that the mean absolute error in performing 1D location using the new methods was between 11.6 to 14.3 mm compared to a range of 19.3 to 37.2 mm for the conventional Fixed Threshold method at different threshold levels.
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    Review of Non-destructive Testing (NDT) Techniques and their applicability to thick walled composites
    (Elsevier, 2015-10-27) Jolly, Mark R.; Prabhakar, Arun; Sturzu, Bogdan; Hollstein, K.; Singh, R.; Thomas, S.; Foote, Peter; Shaw, Andy
    A tier 1 automotive supplier has developed a novel and unique kinetic energy recovery storage system for both retro-fitting and OEM application for public transport systems where periodic stop start behaviour is paramount. A major component of the system is a composite flywheel spinning at up to 36,000 rpm (600 Hz). Material soundness is an essential requirement of the flywheel to ensure failure does not occur. The component is particularly thick for a composite being up to 30 mm cross section in some places. The geometry, scale and material make-up pose some challenges for conventional NDT systems. Damage can arise in composite materials during material processing, fabrication of the component or in-service activities among which delamination, cracks and porosity are the most common defects. A number of non-destructive testing (NDT) techniques are effective in testing components for defects without damaging the component. NDT techniques like Ultrasonic Testing, X-Ray, Radiography, Thermography, Eddy current and Acoustic Emission are current techniques for various testing applications. Each of these techniques uses different principles to look into the material for defects. However, the geometry, physical and material properties of the component being tested are important factors in the applicability of a technique. This paper reviews these NDT techniques and compares them in terms of characteristics and applicability to composite parts.
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    Size differentiation of a continuous stream of particles using acoustic emissions
    (Institute of Physics, 2016-12-01) Nsugbe, Ejay; Starr, Andrew; Foote, Peter; Ruiz Carcel, Cristobal; Jennions, Ian K.
    Procter and Gamble (P&G) require an online system that can monitor the particle size distribution of their washing powder mixing process. This would enable the process to take a closed loop form which would enable process optimisation to take place in real time. Acoustic Emission (AE) was selected as the sensing method due to its non-invasive nature and primary sensitivity to frequencies which particle events emanate. This work details the results of the first experiment carried out in this research project. This experiment involved the use of AE to distinguish between the sizes of sieved polyethylene particle (53-250microns) and glass beads (150-600microns) which were dispensed on a target plate using a funnel. By conducting a threshold analysis of the impact peaks in the signal, the sizes of the particles could be distinguished and a signal feature was found which could be directly linked to the sizes of the particles.
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    Size differentiation of a continuous stream of particles using acoustic emissions
    (Acoustical Society of America, 2016-04-30) Nsugbe, Ejay; Starr, Andrew G.; Foote, Peter; Ruiz Carcel, Cristobal; Jennions, Ian K.
    Procter and Gamble (P&G) requires an online system that can monitor the particle size distribution of their washing powder mixing process. This would enable the process to take a closed loop form which would enable process optimization to take place in real time. Acoustic emission (AE) was selected as the sensing method due to its non-invasive nature and primary sensitivity to frequencies which particle events emanate. This work details the results of the first experiment carried out in this research project. The first experiment involved the use of AE to distinguish sieved particle which ranged from 53 to 250 microns and were dispensed on a target plate using a funnel. By conducting a threshold analysis of the peaks in the signal, the sizes of the particles could be distinguished and a signal feature was found which could be directly linked to the sizes of the particles.
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    Transforming composite design by use of structural health monitoring
    (Cranfield University, 2016-12) Liddel, Paul Daniel; Foote, Peter
    Commercial composite aerospace structure is required to be designed and managed under the damage tolerant principle. Airworthiness is maintained through a process of regulated inspections and if required maintenance. Currently inspections use visual and assisted visual (non-destructive inspection - NDI) techniques. Damage tolerant operation is therefore reliant on inspectability. Unlike metal structure composite and adhesively bonded structure may show few if any recognisable indicators prior to rapid failure, either visually or using NDI. Although stringent manufacturing processes are demanded to best ensure components are fit for service strategies such as reducing stresses by oversizing components or in the case of bonded features additional mechanical fasteners may be included to allow operation with this potential structural uncertainty. Structural Heath Monitoring (SHM) uses data from in-situ sensors to assess the condition of the structure. If via SHM any uncertainty associated with difficult to inspect components could be eliminated less reliance would be required of additional structure or features allowing lighter and more efficient structure to be viable with no impact on current airworthiness demands. Despite much previous research no SHM system is in use with in-service composite or bonded aerospace components. When operating a structure under Damage-tolerance operational requirements damage must be positively identified to allow repairs to be made whist ensuring appropriate airworthiness demands are maintained. Such demands must also be met by structure inspected using SHM. Unlike previous studies this research combines the process of structural design and in-situ monitoring to address the issues identified. Termed SHM enabled design this approach allows the implementation of monitoring technology and the potential for benefits including the reduced reliance on inefficient additional structure to be viably included in actual structure ... [cont.].