Nonlinear ultrasonic waves for structural monitoring: Thermal stress measurement and guided wave management

2015 ◽  
Vol 138 (3) ◽  
pp. 1835-1835 ◽  
Author(s):  
Francesco Lanza di Scalea ◽  
Claudio Nucera ◽  
Simone Sternini
Keyword(s):  
Thermal Stress ◽  
Stress Measurement ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Structural Monitoring ◽  
Nonlinear Ultrasonic

scholarly journals The Verification of Rail Thermal Stress Measurement System

2019 ◽  
Vol 48 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Duan Xiangyu ◽  
Zhu Liqiang ◽  
Yu Zujun ◽  
Xu Xining
Keyword(s):  
Thermal Stress ◽  
Measurement System ◽  
Large Scale ◽  
Stress Measurement ◽  
Field Tests ◽  
Guided Wave ◽  
Measuring System ◽  
Cold Weather ◽  
Expansion Joints ◽  
Hot Weather

Continuous Welded Rail (CWR) is widely used in modern railways. With the absence of the expansion joints, CWR cannot expansion freely when the temperature changes, which could cause buckling in hot weather or breakage in cold weather. Therefore, rail thermal stress measuring system plays an important role in the safe operation of railways. This paper designed a thermal stress measurement system based on the acoustoelastic effect of the ultrasonic guided wave. A large-scale rail testbed was built to simulate the thermal stress in the rail track, and to establish the relationship of time-delay of guided wave and thermal stress. After laboratory testing, the system was installed in several railway lines in China for field tests. The results showed that the system was stable and accurate in stress measurement. The performance and potentials of the system were discussed.

Stress measurement for steel slender waveguides based on the nonlinear relation between guided wave group velocity and stress

Measurement ◽  
2021 ◽  
pp. 109465
Author(s):  
Zuohua Li ◽  
Yingzhu Wang ◽  
Junchao Zheng ◽  
Nanxi Liu ◽  
Ming Li ◽  
...  
Keyword(s):  
Group Velocity ◽  
Stress Measurement ◽  
Guided Wave ◽  
Wave Group ◽  
Nonlinear Relation

scholarly journals Numerical Simulation on Micro-damage Detection In CFRP Composites Based on Nonlinear Ultrasonic Guided Waves

2021 ◽  
Keyword(s):  
Damage Detection ◽  
Composite Structures ◽  
Guided Waves ◽  
Second Harmonic ◽  
Wave Mode ◽  
Guided Wave ◽  
Reinforced Plastics ◽  
Matrix Cracks ◽  
Nonlinear Ultrasonic ◽  
Contact Acoustic Nonlinearity

Abstract. Micro-damages such as pores, closed delamination/debonding and fiber/matrix cracks in carbon fiber reinforced plastics (CFRP) are vital factors towards the performance of composite structures, which could collapse if defects are not detected in advance. Nonlinear ultrasonic technologies, especially ones involving guided waves, have drawn increasing attention for their better sensitivity to early damages than linear acoustic ones. The combination of nonlinear acoustics and guided waves technique can promisingly provide considerable accuracy and efficiency for damage assessment and materials characterization. Herein, numerical simulations in terms of finite element method are conducted to investigate the feasibility of micro-damage detection in multi-layered CFRP plates using the second harmonic generation (SHG) of asymmetric Lamb guided wave mode. Contact acoustic nonlinearity (CAN) is introduced into the constitutive model of micro-damages in composites, which leads to the distinct SHG compared with material nonlinearity. The results suggest that the generated second order harmonics due to CAN could be received and adopted for early damage evaluation without matching the phase of the primary waves.

scholarly journals High Frequency Ultrasonic Wave Propagation in  Anisotropic Materials

2021 ◽  
Author(s):  
◽  
Andrew Paul Dawson
Keyword(s):  
Wave Propagation ◽  
Ultrasonic Wave ◽  
High Frequency ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Tissue Characterisation ◽  
Ultrasonic Wave Propagation ◽  
Matching Layer ◽  
Fibrous Tissues ◽  
Wave Modes

<p>The influence of highly regular, anisotropic, microstructured materials on high frequency ultrasonic wave propagation was investigated in this work. Microstructure, often only treated as a source of scattering, significantly influences high frequency ultrasonic waves, resulting in unexpected guided wave modes. Tissues, such as skin or muscle, are treated as homogeneous by current medical ultrasound systems, but actually consist of highly anisotropic micron-sized fibres. As these systems increase towards 100 MHz, these fibres will significantly influence propagating waves leading to guided wave modes. The effect of these modes on image quality must be considered. However, before studies can be undertaken on fibrous tissues, wave propagation in more ideal structures must be first understood. After the construction of a suitable high frequency ultrasound experimental system, finite element modelling and experimental characterisation of high frequency (20-200 MHz) ultrasonic waves in ideal, collinear, nanostructured alumina was carried out. These results revealed interesting waveguiding phenomena, and also identified the potential and significant advantages of using a microstructured material as an alternative acoustic matching layer in ultrasonic transducer design. Tailorable acoustic impedances were achieved from 4-17 MRayl, covering the impedance range of 7-12 MRayl most commonly required by transducer matching layers. Attenuation coefficients as low as 3.5 dBmm-1 were measured at 100 MHz, which is excellent when compared with 500 dBmm-1 that was measured for a state of the art loaded epoxy matching layer at the same frequency. Reception of ultrasound without the restriction of critical angles was also achieved, and no dispersion was observed in these structures (unlike current matching layers) until at least 200 MHz. In addition, to make a significant step forward towards high frequency tissue characterisation, novel microstructured poly(vinyl alcohol) tissue-mimicking phantoms were also developed. These phantoms possessed acoustic and microstructural properties representative of fibrous tissues, much more realistic than currently used homogeneous phantoms. The attenuation coefficient measured along the direction of PVA alignment in an example phantom was 8 dBmm-1 at 30 MHz, in excellent agreement with healthy human myocardium. This method will allow the fabrication of more realistic and repeatable phantoms for future high frequency tissue characterisation studies.</p>

scholarly journals Improving sensitivity and coverage of structural health monitoring using bulk ultrasonic waves

2020 ◽  
pp. 147592172096512
Author(s):  
Stefano Mariani ◽  
Yuan Liu ◽  
Peter Cawley
Keyword(s):  
Structural Health Monitoring ◽  
Health Monitoring ◽  
Temperature Compensation ◽  
Signal Amplitude ◽  
Guided Wave ◽  
Ultrasonic Waves ◽  
Back Wall ◽  
Environmental Chamber ◽  
Structural Health ◽  
Specific Temperature

Practical ultrasonic structural health monitoring systems must be able to deal with temperature changes and some signal amplitude/phase drift over time; these issues have been investigated extensively with low-frequency-guided wave systems but much less work has been done on bulk wave systems operating in the megahertz frequency range. Temperature and signal drift compensation have been investigated on a thick copper block specimen instrumented with a lead zirconate titanate disc excited at a centre frequency of 2 MHz, both in the laboratory at ambient temperature and in an environmental chamber over multiple 20°C–70°C temperature cycles. It has been shown that the location-specific temperature compensation scheme originally developed for guided wave inspection significantly out-performs the conventional combined optimum baseline selection and baseline signal stretch method. The test setup was deliberately not optimised, and the signal amplitude and phase were shown to drift with time as the system was temperature cycled in the environmental chamber. It was shown that the ratio of successive back wall reflections at a given temperature was much more stable with time than the amplitude of a single reflection and that this ratio can be used to track changes in the reflection coefficient from the back wall with time. It was also shown that the location-specific temperature compensation method can be used to compensate for changes in the back wall reflection ratio with temperature. Clear changes in back wall reflection ratio were produced by the shadow effect of simulated damage in the form of 1-mm diameter flat-bottomed holes, and the signal-to-noise ratio was such that much smaller defects would be detectable.

Measurement of Natural Vibrations and Resonant Second Higher-Harmonics Due to a Fatigue Crack

2020 ◽  
Vol 3 (4) ◽  
Author(s):  
Kosuke Kanda ◽  
Shan Lin
Keyword(s):  
Fatigue Crack ◽  
Frequency Response ◽  
Ultrasonic Testing ◽  
Characteristic Curve ◽  
Ultrasonic Waves ◽  
Local Defect ◽  
Response Characteristics ◽  
Local Defect Resonance ◽  
Nonlinear Ultrasonic ◽  
Frequency Response Characteristics

Abstract Nonlinear ultrasonic testing is considered a more promising technique for evaluating closed cracks than conventional ultrasonic testing. However, the mechanism of the generation of nonlinear ultrasonic waves has not been sufficiently explained. We first set up a system to measure the frequency–response characteristics of ultrasonic waves and experimentally investigated the mechanism of second higher-harmonic (HH) wave generation for a fatigue crack. Sweeping the frequencies of incident waves impinging on a fatigue crack introduced to a specimen, we obtained a frequency–response characteristic curve for the crack. From the curve, resonance phenomena resulting from local defect resonance were observed. We then measured the frequency response characteristics of second HH waves using the same system and consequently confirmed that second HH waves resonated when their frequencies corresponded to the eigenfrequencies of the crack. Finally, we theoretically showed that the resonant second HH waves were generated by local defect resonance and nonlinearity.

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