Nonlinear Resonant Ultrasound Spectroscopy (NRUS) is a fundamental technique for assessing elastic nonlinearity in materials, particularly those exhibiting elastic hysteresis. Such materials are also known to exhibit fast and slow dynamic response, which is evolving in time. In this study, we examine the interplay between slow and fast dynamic effects in NRUS measurements performed on a...
Concrete structures such as bridges and wind turbine towers are subjected to a significant number of load cycles throughout their service life. This repeated loading leads to progressive damage accumulation, commonly referred to as fatigue degradation. The evolution of fatigue damage in concrete is influenced not only by the amplitude of the applied stress or strain but also by the frequency...
Nonlinear elastic effects are ubiquitous in the Earth’s crust, often revealed by small temporal changes in seismic wave velocity. Being able to interpret these subtle changes is critical to help us assess the state of stress and associated seismic risk. The objective of this work is to unravel the physical mechanisms responsible for the nonlinear elastic response of rocks, and in particular to...
Nonlinear Coda Wave Interferometry (NCWI) is an effective technique for detecting closed cracks in complex materials such as concrete, often missed by conventional linear ultrasonic methods. Combining the sensitivity of Coda Wave Interferometry (CWI) with a nonlinear modulation effect induced by a pump wave, this method activates nonlinearities in materials. Pump waves are conventionally...
It is well known that the water saturation degree ($S_w$) can strongly affect the linear viscoelastic properties of siliciclastic sandstones, even at low values (a few % points). For example, the impacts on the linear $Q$ was already studied starting from the end of the ´970s, in relation to lunar samples measured in the lab. A decrease in linear moduli with increasing $S_w$ has been...
Rocks exhibit astonishing time dependent mechanical properties, like memory of experienced stress or slow dynamics, which refers to a transient recovery of stiffness after a softening induced by almost any type of loading. This softening and transient recovery is observed in the subsurface and in buildings after earthquake shaking, or in laboratory samples.
We investigate the anisotropy of...
Earthquakes induce transient mechanical damage in the subsurface, leading to postseismic hazards such as enhanced landsliding, with recovery often taking years to reach steady-state conditions. This behavior has been associated with relaxation, a phenomenon observed across a wide range of materials following strain perturbations. However, systematic controls on recovery duration in the shallow...
The data from numerous laboratory and field experiments demonstrate that the material recovery processes in these two cases have much in common. In particular, they may take much longer than the impact (slow time), and the recovery is mostly (not exclusively) logarithmic. The main difference is in the duration of this time. A typical recovery time in laboratory experiments is of the order of...
The Tengchong Volcanic Field (TCV), located in the southeastern margin of the Tibetan Plateau, is a large-scale active volcanic system. Geological surveys identify 68 Cenozoic volcanic centers distributed throughout the region. This volcanic system features extensive magma degassing, vigorous hydrothermal circulation, and intense volcanic and seismic activity, posing a potential threat of...
Thanks to seismic interferometry, even tiny velocity changes in the subsurface following sizeable earthquakes can be detected with increasing spatial resolution. It remains a substantial challenge to forecast such velocity (or better elastic module) changes in a quantitative way. However, it is clear that such nonlinear behavior may considerably affect the ground shaking and thus needs to be...
The Physical Acoustics Lab has a 20-year history in studying both fundamental problems in wave propagation and applied research. The applied research has an emphasis on geophysics, where our experiments on rocks in the lab contribute to our understanding of geohazards including Whakaari, White Island and the Alpine Fault, New Zealand. More recently, our rock physics supports programmes in...
Analytical results indicate that changes of elastic moduli in earthquake rupture zones produce damage-related-radiation (DRR) given by the product of the changes of elastic moduli and the elastic strain at the source. A tensorial decomposition indicates that the DRR has a large isotropic component expected to produce dynamic dilatation and enhanced P radiation. Since significant changes of...
Nonlinear resonant ultrasound spectroscopy (NRUS) is typically performed using unidirectional testing methods where one type of mode is considered in the analysis. The mode types considered are longitudinal, torsional, or flexural modes, and the response is measured at a single location. In our experimental work, we have observed coupling behavior between longitudinal and flexural modes when...
The linear and nonlinear elastodynamic responses of fractured rock depend on bulk rock’s properties (e.g., porosity size and distribution) and fracture morphology (e.g., aperture, contact area, contact size distribution), which in turn controls the hydromechanical properties of the fractured rock. We conduct a series of coupled in-situ synchrotron X-ray imaging and through-transmission...
Thermal Modulation (TM) is a non-linear technique previously applied to homogeneous materials like steel and aluminium to detect changes caused by damage. While TM has also been tested on concrete (Sun, 2019), research remains limited, making it difficult to fully understand its potential, limitations, and scalability.
TM results can be influenced by several factors, including temperature...
It is known since long that concrete, including its reinforced and prestressed variants, shows nonlinear elastic behaviour on the meso (material) and macro (construction) scale. For about two decades scientist have made connections to nonlinear acoustic properties, mostly determined by ultrasonic measurements. The focus has been on coda wave interferometry and the so-called classic...
Highly complex engineered materials, such as concrete, exhibit a systematic evolution of their elastic properties when subjected to the effects of static and dynamic loads. Such systematic evolution can be observed in phenomena like the acoustoelastic effect, when analysed as a function of stress, and in the slow dynamics—the fast softening and log-time relaxation processes—when examined as a...
Characterizing the nonlinear mechanical properties of a superficial layer in a material using ultrasounds has applications in nondestructive evaluation. Among others, nonlinear ultrasonics has proven highly sensitive to heat damage in concrete. The common approach to achieve detection is to use the second harmonic generation effect, with Rayleigh waves. This effect is however of limited use if...
One method of CO2 sequestration is to react carbonated water with ultramafic rocks to form carbonate minerals. The formation of these minerals causes cracks in the samples, which increase the available surface area for the necessary reactions, making a positive feedback loop for Carbon storage. A key question about this type of sequestration is how to monitor the progression of the...
Non-destructively monitoring plasticity-induced microstructural changes in metals can provide valuable insights into structural integrity and enable early failure detection. Conventional ultrasonic methods often lack the sensitivity to detect such early-stage changes. Nonlinear ultrasonic techniques, particularly second harmonic generation using guided waves, offer enhanced sensitivity, making...
Defects in plates significantly affect the local propagation characteristics of ultrasonic guided waves. Specifically, crack-like defects can introduce various non-classical nonlinear wave responses due to clapping, friction and hysteretic effects. These phenomena not only introduce nonlinear elastic wave components into the plate, but also lead to the emission of nonlinear acoustic wave...
The mechanical behavior of natural sites is largely guided by vibrations of the Earth and environmental exposure, but damage is rarely assessed, except empirically. Rock pillars , such as the Abraham's pillar above the Chauvet-Pont d’Arc cave, or the Tete Noire pillar overhanging the road to the Trient village (Wallis) represent shining example of fragility that would benefit from monitoring....
Landslides are difficult to predict and can therefore be a serious threat to populations and infrastructures. Understanding landslide processes and their precursor parameters is an important challenge for scientists and for public managers. Landslide monitoring is essential for determining the hazard associated with the unstable slopes. Computing seismic velocity changes from ambient seismic...
Rock fracturing plays a key role in shaping mountain landscapes and natural hazards. Weathering agents, such as daily thermal variations, rain and frost, are among the main triggers of the weathering and fracturing process. However, the mechanisms involved are not well quantified, and questions remain about stress variations in natural cliffs.
To better quantify the effect of thermal...
Ground response (GR) refers to the ability of a field site to naturally amplify and damp seismic wavefield components under linear and/or nonlinear conditions. While seismic waves are typically the main triggers of GR, explosions and strong acoustic waves can also induce it through air-to-ground coupling. As both explosive sources and unconsolidated near-surface materials are common to find in...
In the middle of the last century, few theoretical studies have considered the case of the interaction between a shock wave and an acoustic one. Initially limited to 1D, following investigation have extended the problem to oblique interaction and have been of great interest for the stability of shock waves. However, development have been performed considering only perfect gases or strong shock...
Nonlinear ultrasound higher harmonics have become increasingly useful as a nonintrusive probe
of both microstructure as well as damage of solid materials [1]. The current theoretical underpinning
of these e orts rely on a formula for the second harmonic that is proportional to the square of the
linear wave and grows linearly with distance away from the source [2]. This formula holds...
Physical reservoir computing (PRC) offers a promising path toward low-energy, brain-like computing by harnessing the inherent dynamics of physical systems. We present a novel ultrasound-based PRC system that exploits nonlinear acoustic wave propagation for classification tasks. As a proof of concept, we demonstrate performance comparable to state-of-the-art neural networks on a handwritten...
This paper investigates the interaction of weakly nonlinear waves in fiber-reinforced materials [1]. The constitutive relations consist of hyperelastic, polyconvex models incorporating a description that facilitates the modeling of mechanical dissipation. Models of this type can be used, for example, to describe membrane-shell structures made of textile materials or elastomeric bearings...
Estimates of in-situ geothermal reservoir properties are essential for many scientific, operational, and regulatory purposes, including the controlling and managing of the potentially induced seismicity. We present first results of our research that combines results from a forward 3D viscoelastic damage rheology model (DRM) with a Bayesian Optimization with Likelihood-Free Inference (BOLFI)...
Nonlinear time reversed focusing will be applied to map formation damage for the currently active progressive failure (PF) experiment in the Mont Terri underground rock laboratory (URL). This In-situ experiment monitors structurally-controlled rock mass deformation and damage. Complex shear failure occurs in the heavily instrumented 600 mm diameter micro tunnel, finding borehole breakout and...
Plastic land mines are difficult to detect using conventional metal landmine detection methods. In airborne acoustic landmine detection, subwoofers located above the ground excite the soil (gravel) which couples into structural vibration of the buried “target.” The enhanced ground vibration can be measured remotely using a scanning laser Doppler vibrometer. Using nonlinear tuning curve results...
