On the Acoustic Nonlinearity of Solid-Solid Contact With Pressure-Dependent Interface Stiffness

2004 ◽  
Vol 71 (4) ◽  
pp. 508-515 ◽  
Author(s):  
S. Biwa ◽  
S. Nakajima ◽  
N. Ohno
Keyword(s):  
Contact Pressure ◽  
Power Law ◽  
Pressure Dependence ◽  
Second Harmonic ◽  
Harmonic Wave ◽  
Contact Interface ◽  
Acoustic Nonlinearity ◽  
Contact Acoustic Nonlinearity ◽  
Nonlinear Interface ◽  
Rough Surface Contact

Nonlinear interaction between elastic wave and contact interface, known to result in the so-called contact acoustic nonlinearity, is examined in a one-dimensional theoretical framework. The present analysis is based on a nonlinear interface stiffness model where the stiffness property of the contact interface is described as a function of the nominal contact pressure. The transmission/reflection coefficients for a normally incident harmonic wave, and the amplitudes of second harmonics as well as DC components arising at the contact interface are derived in terms of the interface stiffness properties and other relevant acoustic parameters. Implications of power-law relations between the linear interface stiffness and the contact pressure are examined in detail regarding the linear and nonlinear acoustic responses of the contact interface. Also, a plausible range of the relevant power-law exponent is provided from considerations based on the rough-surface contact mechanics. The analysis clarifies the qualitative contact-pressure dependence of various nonlinearity parameters based on different definitions. A particular power law is identified from existing experimental data for aluminum-aluminum contact, for which some explicit nonlinear characteristics are demonstrated. The theoretical contact-pressure dependence of the second harmonic generation at the contact interface is found to be in qualitative agreement with previous measurements.

scholarly journals Experimental Verification of Contact Acoustic Nonlinearity at Rough Contact Interfaces

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2988
Author(s):  
Youngbeom Kim ◽  
Sungho Choi ◽  
Kyung-Young Jhang ◽  
Taehyeon Kim
Keyword(s):  
Contact Pressure ◽  
Second Harmonic ◽  
Fem Simulation ◽  
Harmonic Component ◽  
Interface Roughness ◽  
Contact State ◽  
Acoustic Nonlinearity ◽  
Specific Contact ◽  
Contact Acoustic Nonlinearity ◽  
Good Agreement

When a longitudinal wave passes through a contact interface, second harmonic components are generated due to contact acoustic nonlinearity (CAN). The magnitude of the generated second harmonic is related to the contact state of the interface, of which a model has been developed using linear and nonlinear interfacial stiffness. However, this model has not been sufficiently verified experimentally for the case where the interface has a rough surface. The present study verifies this model through experiments using rough interfaces. To do this, four sets of specimens with different interface roughness values (Ra = 0.179 to 4.524 μm) were tested; one set consists of two Al6061-T6 blocks facing each other. The second harmonic component of the transmitted signal was analyzed while pressing on both sides of the specimen set to change the contact state of the interface. The experimental results showed good agreement with the theoretical prediction on the rough interface. The magnitude of the second harmonic was maximized at a specific contact pressure. As the roughness of the contact surface increased, the second harmonic was maximized at a higher contact pressure. The location of this maximal point was consistent between experiments and theory. In this study, an FEM simulation was conducted in parallel and showed good agreement with the theoretical results. Thus, the developed FEM model allows parametric studies on various states of contact interfaces.

Evaluation of Linear and Nonlinear Ultrasonic Response of Contacting Surfaces

2007 ◽  
Vol 345-346 ◽  
pp. 1315-1318 ◽  
Author(s):  
Shiro Biwa ◽  
Shunsuke Hiraiwa ◽  
Eiji Matsumoto
Keyword(s):  
Contact Pressure ◽  
Pressure Dependence ◽  
Second Harmonic ◽  
Contact Condition ◽  
Reflection Coefficients ◽  
Transverse Waves ◽  
Normal Stiffness ◽  
Longitudinal And Transverse Waves ◽  
Nonlinear Ultrasonic ◽  
Linear And Nonlinear

Linear and nonlinear ultrasonic responses of contacting surfaces were studied based on the contact-pressure dependence of the interfacial stiffnesses. To this purpose, the reflection coefficients of longitudinal and transverse waves were measured for the contacting interface between polished aluminum blocks. The normal and tangential stiffnesses of the interface were then obtained as function of the contact pressure. The reflection coefficients were found to decrease, while the interfacial stiffnesses were found to increase, with the contact pressure. It was also found that the ratio of the tangential to normal stiffness as well as the nonlinearity parameters (ratio of the second harmonic to the squared fundamental amplitudes) could be used as a parameter to characterize the contact condition.

scholarly journals Fatigue crack detection in pipes with multiple mode nonlinear guided waves

2018 ◽  
Vol 18 (1) ◽  
pp. 180-192 ◽  
Author(s):  
Ruiqi Guan ◽  
Ye Lu ◽  
Kai Wang ◽  
Zhongqing Su
Keyword(s):  
Fatigue Crack ◽  
Crack Detection ◽  
Guided Waves ◽  
Second Harmonic ◽  
Experimental Testing ◽  
Harmonic Wave ◽  
Guided Wave ◽  
Element Analysis ◽  
Fatigue Crack Detection ◽  
Wave Modes

This study elaborates fundamental differences in fatigue crack detection using nonlinear guided waves between plate and pipe structures and provides an effective approach for analysing nonlinearity in pipe structures. For this purpose, guided wave propagation and interaction with microcrack in a pipe structure, which introduced a contact acoustic nonlinearity, was analysed through a finite element analysis in which the material nonlinearity was also included. To validate the simulation results, experimental testing was performed using piezoelectric transducers to generate guided waves in a specimen with a fatigue crack. Both methods revealed that the second harmonic wave generated by the breathing behaviour of the microcrack in a pipe had multiple wave modes, unlike the plate scenario using nonlinear guided waves. Therefore, a proper index which considered all the generated wave modes due to the microcrack was developed to quantify the nonlinearity, facilitating the identification of microscale damage and further assessment of the severity of the damage in pipe structures.

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.

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