Search results for "Destructive testing"
showing 10 items of 88 documents
Crack detection using electrostatic measurements
2001
In this paper we extend recent work on the detection of inclusions using electrostatic measurements to the problem of crack detection in a two-dimensional object. As in the inclusion case our method is based on a factorization of the difference between two Neumann-Dirichlet operators. The factorization possible in the case of cracks is much simpler than that for inclusions and the analysis is greatly simplified. However, the directional information carried by the crack makes the practical implementation of our algorithm more computationally demanding.
Ultrasonic Guided Wave Inspection of Bonded Lap Joints: Noncontact Method and Photoelastic Visualization
2001
The main topic of this paper is the nondestructive inspection of adhesively bonded lap joints by using ultrasonic guided (plate) waves. A noncontact, couplant-free method that employs capacitive air-coupled transducers is demonstrated for the inspection of thin aluminum joints with dimensions typical of aircraft fuselage and wing panels. Two types of bond defects, disbonded regions and regions of poorly cured (low-cohesive-strength) adhesive, are successfully detected by measuring the amplitude decrease of selected plate waves leaking from one adherend to the other one through the bondline. It is shown that proper choice of the vibrating mode structure, in terms of cross-sectional displacem…
Sensitivity on earth core and mantle densities using atmospheric neutrinos
2009
11 pages, 11 figures.-- ISI article identifier:000267776100008 .-- ArXiv pre-print avaible at: http://arxiv.org/abs/0904.0796
RGB Photoelasticity: Review and Improvements
2010
: This paper considers the main developments of RGB photoelasticity with reference to the maximum measurable retardation. In this paper, a new procedure based on the standard error function evaluated on a subset of the calibration array is also proposed and experimentally tested. The experiments show that the filament lamp makes it possible to find retardations until approximately 4 fringe orders while the fluorescent lamp makes it possible to determine higher fringe orders (12 fringe orders in this paper) owing to the discrete spectrum of the source. The paper shows that, by using the incandescent lamp, the primary limiting factor is the lack of modulation of the R, G and B signals wherea…
Elastic Metasurfaces for Deep and Robust Subwavelength Focusing and Imaging
2021
International audience; Metasurfaces are planar metamaterials with a flat surface and a subwavelength thickness that are able to shape arbitrary wave fronts such as focusing or imaging. There is a broad interest in the literature about subwavelength focusing and imaging based on bulk metamaterials while the utilization of metasurfaces for elastic waves has rarely been reported. Here, we present a type of elastic metasurface consisting of a line of gradient resonant pillars for robust deep subwavelength focusing and imaging of elastic waves in a plate. Numerical approaches supported by analytic Huygens-Fresnel demonstrations show that the subwavelength full width at half maximum (FWHM) behav…
Defect detection in laser powder deposition components by laser thermography and laser ultrasonic inspections
2013
Laser Powder Deposition (LDP) techniques are being adopted within aerospace and automotive manufacturing to produce innovative precision components. Non-destructive techniques (NDT) for detecting and quantifying flaws within these components enables performance and acceptance criteria to be verified, improving product safety and reducing ongoing maintenance and product repair costs. In this work, software enabled techniques are presented for in-process analysis of NDT laser ultrasonic signals and pulsed laser thermography images of sequential metallic LPD layers. LPD tracks can be as thin as 200μm while deposited at a rate of 500 mm/min, requiring ultrafast inspection and processing times. …
Optimization of depth increment distribution in the ring-core method
1996
The integral equation method is the most suitable calculation procedure for the determination of non-uniform residual stresses by semi-destructive mechanical methods such as hole and ring-core drilling. However, the high sensitivity to strain measurement errors due to the ill-conditioning of the equation sets has prevented its practical use. Examination of the influence of the strain measurement error on the calculated stresses and its propagation has shown that, for given maximum groove depth and total steps number, the error sensitivity depends on the particular depth increment distribution used. By means of an alternative matrix formulation of the equation sets the depth increment distr…
Introducing a new method for efficient visualization of complex shape 3D ultrasonic phased-array C-scans
2017
Automated robotic inspection systems allow the collection of large data volumes, compared to existing inspection systems. To maximize the throughput associated with the non-destructive evaluation phase, it is crucial that the reconstructed inspection data sets are generated and examined rapidly without a loss of detail. Data analysis often becomes the bottleneck of automated inspections. Therefore, new data visualization tools, suitable to screen the NDT information obtained through robotic systems, are urgently required. This paper presents a new approach, for the generation of three-dimensional ultrasonic C-scans of large and complex parts, suitable for application to high data throughput…
Assessment of bonding defects in FRP reinforced structures via ultrasonic technique
2016
Fiber reinforced polymer (FRP) composite systems are widely used for the rehabilitation of concrete structures such as building that need to resist to seismic loads, bridges that have to carry heavier traffic loads. The technique consists in bonding the composite plate to the concrete surface element in order to increase the flexural capacity. A proper attachment of the FRP plate to the concrete surface is necessary for the efficiency of the load transfer between the reinforcement and the substrate. In this work, the quality of composite bonding is characterized through ultrasonic testing. The proposed technique is relative to a time domain analysis of the ultrasonic signals and couples the…
FRP-Substrate bonding quality investigation making use of ultrasonic waves
2016
Fiber reinforced polymer (FRP) composite systems are widely used to repair structurally deficient constructions thanks to their good immunity to corrosion, low weight and excellent mechanical properties. The quality of the FRP-substrate interface bond is a crucial parameter affecting the performance of retrofitted structures. In this framework, ultrasonic testing could be used to assess the quality of the bonding [1-2]. In the case of FRP laminates adhesively bonded to roughly inhomogeneous materials, such as concrete, high scattering attenuation occurs due to the presence of heterogeneities. The concrete behaves almost like a perfect absorber generating a considerable number of short-space…