scholarly journals Laser Doppler Vibrometer Based Examination of the Efficiency of Introducing Artificial Delaminations into Composite Shells

2015 ◽  
Vol 22 (3) ◽  
pp. 75-81
Author(s):  
Kamila Kustroń
Keyword(s):  
Foreign Bodies ◽  
Load Capacity ◽  
Laser Doppler Vibrometer ◽  
Laminate Shell ◽  
Diagnostic Systems ◽  
Adhesive Layers ◽  
Hull Structure ◽  
Advisory Systems ◽  
Non Destructive ◽  
Thin Polyethylene

Abstract During its operation, the laminate shell of the watercraft hull can be exposed to local stability losses caused by the appearance and development of delaminations. The sources of these delaminations are discontinuities, created both in the production process and as a result of bumps of foreign bodies into the hull in operation. In the environment of fatigue loads acting on the hull, the delaminations propagate and lead to the loss of load capacity of the hull structure. There is a need to improve diagnostic systems used in Structural Health Monitoring (SHM) of laminate hull elements to detect and monitor the development of the delaminations. Effective diagnostic systems used for delamination assessment base on expert systems. Along with other tools, the expert diagnostic advisory systems make use of the non-destructive examination method which consists in generating elastic waves in the hull shell structure and observing their changes by comparing the recorded signal with damage patterns collected in the expert system database. This system requires introducing certain patterns to its knowledge base, based on the results of experimental examinations performed on specimens with implemented artificial delaminations. The article presents the results of the examination oriented on assessing the delaminations artificially generated in the structure of glass- and carbon-epoxy laminates by introducing local non-adhesive layers with the aid of thin polyethylene film, teflon insert, or thin layer of polyvinyl alcohol. The efficiency of each method was assessed using laser vibrometry. The effect of the depth of delamination position in the laminate on the efficiency of the applied method is documented as well.

scholarly journals Detection of Internal Holes in Additive Manufactured Ti-6Al-4V Part Using Laser Ultrasonic Testing

2020 ◽  
Vol 10 (1) ◽  
pp. 365 ◽  
Author(s):  
Jie Yu ◽  
Dongqi Zhang ◽  
Hui Li ◽  
Changhui Song ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Ultrasonic Testing ◽  
Laser Doppler Vibrometer ◽  
Laser Ultrasonic ◽  
Ultrasound Waves ◽  
Hole Defect ◽  
X Ray Computed ◽  
Hole Defects ◽  
Pulse Echo ◽  
The Relationship ◽  
Non Destructive

For a non-contact, non-destructive quality evaluation, laser ultrasonic testing (LUT) has received increasing attention in complex manufacturing processes, such as additive manufacturing (AM). This work assessed the LUT method for the inspection of internal hole defects in additive manufactured Ti-6Al-4V part. A Q-switched pulsed laser was utilized to generate ultrasound waves on the top surface of a Ti-6Al-4V alloy part, and a laser Doppler vibrometer (LDV) was utilized to detect the ultrasound waves. Sub-millimeter (0.8 mm diameter) internal hole defect was successfully detected by using the established LUT system in pulse-echo mode. The method achieved a relatively high resolution, suggesting significant application prospects in the non-destructive evaluation of AM part. The relationship between the diameter of the hole defects and the amplitude of the laser-generated Rayleigh waves was studied. X-ray computed tomography (XCT) was conducted to validate the results obtained from the LUT system.

APPLICABILITY OF WIDE-RANGE ULTRASONIC TESTING TO NON-DESTRUCTIVE INSPECTION OF GROUT CONDITION IN PRESTRESSED CONCRETE BRIDGES

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Kuniharu Fukushima ◽  
Kimihiko Amaya ◽  
Takanori Kinoshita ◽  
Isamu Yoshitake
Keyword(s):  
Prestressed Concrete ◽  
Ultrasonic Testing ◽  
Load Capacity ◽  
Comparative Investigation ◽  
Concrete Cover ◽  
Concrete Bridges ◽  
Inspection Method ◽  
Wide Range ◽  
Inspection Techniques ◽  
Non Destructive

Complete grouting of tendon ducts is important for durability of post-tensioned prestressed concrete (PC) bridges. Voids in the ducts may induce failure of PC tendons, possibly causing a reduction in load capacity and collapse of the bridge. The wide-range ultrasonic testing (WUT) is one of the non-destructive inspection techniques. The focus of this study is to examine the applicability of the WUT to grout inspection. This paper summarizes the characteristics of the non-destructive methods available for the PC grout inspection and outlines the sensing and analyzing techniques of the WUT method performed in practice in PC bridge construction. The inspection accuracy of the WUT method was examined by comparison to a sensor-based inspection method. This paper also reports comparative investigation and discusses the advantages of the WUT method including inspection accuracy, cost performance, time efficiency and safety. It was confirmed in on-site application that the WUT method was capable of determining grout condition at a concrete cover depth of 250 mm.

Repair and Health Monitoring for Historical Structures

2010 ◽  
Vol 133-134 ◽  
pp. 205-209
Author(s):  
Mohamad Hossein Maleki Tabrizi
Keyword(s):  
Dynamic Characteristics ◽  
Health Monitoring ◽  
Structural Integrity ◽  
Laser Doppler Vibrometer ◽  
High Accuracy ◽  
Historical Buildings ◽  
Height Ratio ◽  
Historical Structures ◽  
Destructive Analysis ◽  
Non Destructive

Historical structures, like to masonry towers and another structures are among the structures subjected to the higher risk, due to their age, elevation and low base area on height ratio. In this paper introduce a technique of monitoring the structural integrity of historical buildings by a noncontact and non-destructive analysis is presented and discussed. The damage and destroy of a structure and building, in terms of cracks and overall structural degradation, is detected throughout the measurement of its dynamic characteristics by various ways, for example by a laser Doppler vibrometer(LDV). These techniques can show the frequency spectrum of the structure with high accuracy and reliability and reaction of structure against this technique. Also we will introduce that timber components have no influence on the system behaviour, which is mainly determined by the properties of connections and reactions.

Quality Assessment of Friction Stir Welded Joints – Using the Fundamental Anti-Symmetric Lamb Wave Mode

2018 ◽  
Vol 941 ◽  
pp. 2429-2434
Author(s):  
Ramsey F. Hamade ◽  
Mohammad Ali Fakih ◽  
Mohammad Harb ◽  
Samir Mustapha
Keyword(s):  
Guided Waves ◽  
Laser Doppler Vibrometer ◽  
Wave Mode ◽  
Guided Wave ◽  
Material Interface ◽  
Friction Stir ◽  
Different Types ◽  
Filtering Technique ◽  
Non Destructive

Having a robust non-destructive evaluation (NDE) technique for friction stir welded (FSWed) joints is of interest to the processing community. Such a technique has to be sensitive to the different types and shapes of internal weld defects and has to be applicable for both similar and dissimilar material FSW joints. Investigated was the ability of ultrasonic guided waves to detect and assess the quality of FSW joints. The fundamental anti-symmetric (A0) mode was selected to detect the flaws in FSW joints. Guided waves were excited (using PZT wafers) and received (using a laser Doppler vibrometer, LDV). Implemented was the frequency-wavenumber filtering technique to separate forward propagating wave from any back propagating reflected wave due to the welded joint. Identified was the reflection of the A0mode caused by the presence of the interface and/or defects within the joint. The findings indicate little sensitivity to the presence of material interface suggesting this technique to have a promising potential among guided-wave-based techniques in the qualitative and quantitative assessment of FSW joints.

Modelling of Magnetic Fields with the Finite Element Method in Machine Diagnostic Systems

2009 ◽  
Vol 147-149 ◽  
pp. 155-160 ◽  
Author(s):  
Jakub Łagodziński
Keyword(s):  
Load Capacity ◽  
Active Vibration Control ◽  
Magnetic Bearing ◽  
Active Magnetic Bearing ◽  
The Finite Element Method ◽  
Diagnostic Systems ◽  
Bearing Load ◽  
Switch System ◽  
Active Vibration ◽  
The Magnetic Field

Two issues are discussed in the paper. The first one concerns the FEM modelling of the magnetic field enclosing the permanent magnet – reed switch system. The system works as the motion detection device of the hydraulic servoactuator distributor to improve the helicopter steering reliability and flight safety. The second one describes optimization of the active magnetic bearing (AMB) design with the FEM. The optimization has two goals: weight reduction and bearing load capacity. The bearing is applied to active vibration control of helicopter flexible tail rotor shaft.

scholarly journals Non-destructive Detection of Insect Foreign Bodies in Finishing Tea Product Based on Terahertz Spectrum and Image

2021 ◽  
Vol 8 ◽  
Author(s):  
Xudong Sun ◽  
Jiajun Li ◽  
Yun Shen ◽  
Wenping Li
Keyword(s):  
Least Squares ◽  
Time Domain ◽  
Foreign Bodies ◽  
Nearest Neighbor ◽  
K Nearest Neighbor ◽  
Terahertz Time Domain Spectroscopy ◽  
Destructive Testing ◽  
Safety Control ◽  
Main Challenge ◽  
Non Destructive

Non-destructive testing of low-density and organic foreign bodies is the main challenge for food safety control. Terahertz time-domain spectroscopy (THz-TDS) and imaging technologies were applied to explore the feasibility of detection for insect foreign bodies in the finishing tea products. THz-TDS of tea leaves and foreign bodies of insects demonstrated significant differences in terms of time domain and frequency signals in the range of 0.3–1.0 THz. These signals were corrected by the use of adaptive iteratively reweighted penalized least squares (AirPLS), asymmetric least squares (AsLS), and baseline estimation and de-noising using sparsity (BEADS) for reducing baseline drift and enhancing effective spectral information. The K-nearest neighbor (KNN) and partial least squares discrimination analysis (PLS-DA) models showed the best performance after AirPLS correction with the prediction accuracy of 98 and 100%, respectively. In addition, the locations and outlines of insect bodies could be clearly presented via the THz-TDS image. These results suggested that THz-TDS spectroscopy and imaging provide an alternative tool for the detection of insect foreign bodies in finishing tea products.

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