Nonlinear Stress-strain Relationship Research Articles

Effects of 3D deformation and nonlinear stress–strain relationship on the Brazilian test for a transversely isotropic rock

To improve the accuracy of indirect tensile strength for a transversely isotropic rock in the Brazilian test, this study considered the three-dimensional (3D) deformation and the nonlinear stress–strain relationship. A parametric study of a numerical Brazilian test was performed for a general range of elastic constants, revealing that the 3D modeling evaluated the indirect tensile strength up to 40% higher than the plane stress modeling. For the actual Asan gneiss, the 3D model evaluated the indirect tensile strength up to 10% higher and slightly enhanced the accuracy of deformation estimation compared with the plane stress model. The nonlinearity in stress–strain curve of Asan gneiss under uniaxial compression was then considered, such that the evaluated indirect tensile strength was affected by up to 10% and its anisotropy agreed well with the physical intuition. The estimation of deformation was significantly enhanced. The further validation on the nonlinear model is expected as future research.

Research on the bearing behavior of single pile in self-weight collapsible loess areas.

The negative skin frictional caused by loess collapse will decrease the bearing capacity of single pile, which is essential to the design of pile foundations in loess areas. In this study, a method for estimating the subsidence of soil layer at any depth is firstly proposed based on the total self-weight collapse value. Secondly, a new load transfer constitutive model for pile-soil interface is developed, which considers the nonlinear stress-strain relationship and the ultimate shear strength of soil. Then, a load transfer calculation model for pile foundation is established, which can calculate the pile axial force, the pile skin frictional, neutral point position and the settlement of a single pile. The calculation results are compared with the test data that obtained from a pile foundation on-site immersion test and the effectiveness of the calculation method is verified well. This calculation method may be useful for designing pile foundations in collapsible loess regions.

A Thermo-Electro-Viscoelastic Model for Dielectric Elastomers.

Dielectric elastomers (DEs) are a class of electro-active polymers (EAPs) that can deform under electric stimuli and have great application potential in bionic robots, biomedical devices, energy harvesters, and many other areas due to their outstanding deformation abilities. It has been found that stretching rate, temperature, and electric field have significant effects on the stress-strain relations of DEs, which may result in the failure of DEs in their applications. Thus, this paper aims to develop a thermo-electro-viscoelastic model for DEs at finite deformation and simulate the highly nonlinear stress-strain relations of DEs under various thermo-electro-mechanical loading conditions. To do so, a thermodynamically consistent continuum theoretical framework is developed for thermo-electro-mechanically coupling problems, and then specific constitutive equations are given to describe the thermo-electro-viscoelastic behaviors of DEs. Furthermore, the present model is fitted with the experimental data of VHB4905 to determine a temperature-dependent function of the equilibrium modulus. A comparison of the nonlinear loading-unloading curves between the model prediction and the experimental data of VHB4905 at various thermo-electro-mechanical loading conditions verifies the present model and shows its ability to simulate the thermo-electro-viscoelastic behaviors of DEs. Simultaneously, the results reveal the softening phenomena and the instant pre-stretch induced by temperature and the electric field, respectively. This work is conducive to analyzing the failure of DEs in functionalities and structures from theoretical aspects at various thermo-electro-mechanical conditions.

Experimental study of real-time temperature-dependent nonlinear deformation of sandstone

In contrast to thermal heating, the real-time heated rock exhibits significant nonlinearity during the elastic deformation stage. Hence, an experiment assembled by a high and low-temperature test chamber and a microcomputer-controlled rock direct shear instrument is built to evaluate the effect of real-time temperature on the nonlinear deformation behavior of rock. A set of nonlinear stress–strain relationships of forty sandstone samples under moderate real-time temperature conditions are obtained from experiments and agree well with the theoretical predictions from the two-part Hooke’s model (TPHM). The soft and hard parts respond to the real-time temperature are quite different. The ratio of the soft part (γt) increases and the elastic modulus of the hard part (Ee) decreases with the temperature below 125℃. On the contrary, γt decreases and Ee increases with the temperature above 125℃ up to 200℃. Thermally-induced and expandable microcracks (thermal weakening) incur structural damage of the hard part below 125℃, while thermal expansion (thermal strengthening) can lead to tighter compaction between grains above 125℃. Therefore, there is a threshold temperature 125℃ under real-time heating condition due to the thermal cracks and expansion. The elastic modulus of the soft part (Et) decreases continuously with increasing temperature, indicating inconsistent thermal expansion effects on the soft part with mixture of impurity particles and the hard part whose mineral particles are closely contacted at higher temperature. Based on the experimental data and TPHM, empirical relationships between the real-time temperature and nonlinear deformation are proposed. This study will provide support for the safe production and disaster prevention of geological engineering under thermo-mechanical coupling working condition.

A multiscale nonlinear fracture model for staggered composites to reveal the toughening effect of process zone

The attainment of both strength and toughness is a vital requirement for most structural materials. Unfortunately, these properties are generally mutually exclusive in synthetic materials. Natural structural materials defeat the conflict of strength versus toughness, and provide design motifs for the high-performance materials. However, there still lacks a deep understanding of the toughening mechanisms in bioinspired composites. This paper presents a microstructure-based nonlinear fracture mechanics model for staggered composites, to investigate the toughening effect of the nonlinear deformation in the process zone. Firstly, a nonlinear stress–strain relationship of staggered composites is derived, to capture the plastic deformation of the matrix. Then, a multiscale nonlinear fracture mechanics model incorporating the effect of crack bridging and process zone is established based on the above constitutive relation and HRR theory. Finally, the model is used to reveal the influence of geometric and constitutive parameters. The results demonstrate that the process zone leads to a tremendous contribution to the overall toughness. And the crack resistance curve is rising with crack extension due to the increase of the process zone. What is more, there still exists an optimal balance between toughness, stiffness, and strength in biological materials. These results can provide guidelines for the design of high-performance composites.

The change in propagation speed of natural shear waves by altering preload might differentiate patients with increased myocardial stiffness

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Research Foundation Flanders - FWO. Background Shear wave (SW) elastography (SWE) is a novel ultrasound-based technique for the assessment of myocardial stiffness. SWE tracks the propagation of SWs travelling through the myocardium, induced by e.g. mitral valve closure (MVC). The speed of SWs is related to myocardial stiffness. As myocardial stiffness is defined by a non-linear stress-strain relation, it is dependent on the operating stress levels and thus left ventricular (LV) loading. As a result, elevated SW speed values could be caused by both increased LV preload or structural remodelling of the myocardium. In this way, performing SWE measurements at different loading states could potentially provide additional information aiding with the interpretation of these measurements. Purpose to investigate if performing SWE before and after a loading change could provide more information on tissue properties of the myocardium. Methods Twelve patients [age: 76(41–82)] receiving intermittent hemodialysis (HD) and 12 age-matched healthy volunteers [age: 67(47–71); p = 0.19] were included. Patients were scanned before and 1 hour after the start of HD. Parasternal long-axis views were acquired using an experimental ultrasound scanner with an average frame rate of 1086±185 Hz. Patients were divided into 2 equal groups based on the grade of diastolic dysfunction (DD), determined using conventional echo parameters (group 1: DD grade 0–1 and group 2: DD grade 2−3). SWs after MVC were visualized on M-mode maps along the septum which were colour coded for tissue acceleration (Figure A). The speed was semi-automatically calculated by measuring the slope of the SW. Results The average ultra-filtrated volume after 1h of HD was 0.64±.27 L, which did not significantly differ between patient groups (p = 0.44). Patients in group 2 had significantly higher indexed LV wall mass compared to group 1 (128±39 g/m² vs. 72±24 g/m²; p = 0.02), indicative of LV structural remodelling. SW speed after MVC was significantly different between healthy volunteers and the patient groups at baseline (p<0.01) (Figure B). After 1h of HD, SW speed decreased in both groups, with the largest decrease in group 2 (Figure B). Furthermore, SW speed values of patient group 1 decreased to values similar to healthy volunteers, while patient group 2 still had significantly increased SW propagation speed. Conclusions Overall, myocardial stiffness, assessed using SW propagation speed, of patients with end-stage kidney disease was increased compared to healthy volunteers. This could result from increased LV preload or structural remodelling. Our data indicate that in addition to single measurements, assessing the change in SW speed by altering the loading state might aid in differentiating these causal mechanisms underlying increased myocardial stiffness. Therefore, adding a loading challenge, e.g. leg lifting, when doing SWE could provide additional information. Further research needs to confirm these initial findings.

Stability and nonlinear vibration of carbon nanotubes-reinforced composite pipes conveying fluid

This paper focuses on the stability and nonlinear vibration characteristics of carbon nanotubes-reinforced composite pipes conveying fluid, and the mechanism of the combined effects of multiple factors. Based on the assumption of Euler beam and Von-karman nonlinear stress-strain relationship, the dynamic governing equations and generalized boundary conditions of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) pipes are established by Hamiltonian variational principle. Firstly, the modal function suitable for generalized boundary conditions is derived by Galerkin method. The stability of FG-CNTRC pipes system and the relationship between natural frequency and flow velocity are analyzed in this paper. The effect of flow velocity on the natural frequency of pipelines is examined under various carbon nanomaterial distribution patterns and wall thicknesses in this research. Then, the nonlinear vibration characteristics of FG-CNTRC pipes are analyzed by multi-scale method. The method of deducing nonlinear frequency through high-order partial differential equations is also extended in nonlinear analysis. The results show that, in the case of uniform distribution of carbon nanotubes, increasing the wall thickness can improve the stability of the pipe system. The influence of amplitude on the nonlinear frequency is more obvious at the second-order frequency.

Measuring vibrations on a biofidelic brain using ferroelectret nanogenerator

Our knowledge of traumatic brain injury has been fast growing with the emergence of new markers pointing to various neurological changes that the brain undergoes during an impact or any other form of concussive event. In this work, we study the modality of deformations on a biofidelic brain system when subject to blunt impacts, highlighting the importance of the time-dependent behavior of the resulting waves propagating through the brain. This study is carried out using two different approaches involving optical (Particle Image Velocimetry) and mechanical (flexible sensors) in the biofidelic brain. Results show that the system has a natural mechanical frequency of sim 25 oscillations per second, which was confirmed by both methods, showing a positive correlation with one another. The consistency of these results with previously reported brain pathology validates the use of either technique, and establishes a new, simpler mechanism to study brain vibrations by using flexible piezoelectric patches. The visco-elastic nature of the biofidelic brain is validated by observing the the relationship between both methods at two different time intervals, by using the information of the strain and stress inside the brain from the Particle Image Velocimetry and flexible sensor, respectively. A non-linear stress-strain relationship was observed and justified to support the same.

A mechanics model of hard-magnetic soft rod with deformable cross-section under three-dimensional large deformation

Hard-magnetic soft (HMS) materials are soft active materials prepared by embedding the hard-magnetic particles (e.g. NdFeB) into soft elastomer, which can be actuated by applied magnetic fields. With the ability to retain remnant magnetism, HMS materials have many applications in soft robotics, haptic sensors and other fields. For HMS structures used in soft robotics, mechanics models have been developed for better exploiting the potential of the HMS materials. However, for rod-like structures made of soft materials, the nonlinear stress–strain relation and the areal change of the cross-section have not been considered in previous modeling work. In the present three-dimensional HMS rod model, started with the geometrically exact beam theory, the rigid cross-section assumption is replaced with a planar areal change assumption for soft rods, incompressible neo-Hookean material model is used to model the hyperelastic behavior of elastomers, which will be more accurate than linear relation under large deformation. Consistent with the deformable cross-section assumption, the magneto-elastic energy distribution is formulated and reduced to the line of centroid of the soft rod. To verify the accuracy and efficiency of the model, some simulation examples and experiments are performed. The error between the experimental results and the simulation results calculated by using 5 elements is within 10%. Our model can accurately and efficiently predict the 3D large deformation of the HMS rod, which can reduce the design and optimization cost and shorten the design cycle of HMS structure.

Local buckling resistance of bamboo scrimber plates in compression

This paper describes experimental and theoretical investigations on behaviour of short bamboo scrimber box columns under compression. In the experimental programme, six groups of short columns with different width-to-thickness ratios of plates were tested and the load capacity and failure modes of the columns were determined. Test results indicated that when the width-to-thickness ratio of plates was less than or equal to 10, box columns exhibited compression failure and the ultimate compressive strength of bamboo scrimber was reached at failure. However, local buckling of bamboo scrimber plates was observed instead of compression failure once the width-to-thickness ratio of plates exceeded 11, and the ultimate compressive stress decreased with increasing width-to-thickness ratio. Based on the experimental data, theoretical analyses were also performed by considering the nonlinear stress-strain relationship to quantify the buckling stress of bamboo scrimber plates with four simply-supported edges. Comparisons between experimental and theoretical results suggest that when the theoretical equation yields reasonably good estimations of the local buckling stress of columns with the width-to-thickness ratio of plates greater than 10.

Geomechanical performances of geocell reinforced retaining wall backfilled with magnesia-based cement stabilized marine fill

Cement-stabilized soil retaining wall structures are becoming increasingly popular for high-speed railway lines. However, the widely used Portland cement is heavily associated with carbon dioxide (CO2) emissions. Additionally, the rising cost and scarcity of sand traditionally used as fill material is becoming a concern. Besides, the geomechanical performances of the cement-stabilized soil retaining walls using three-dimensional (3-D) finite element method (FEM) numerical analysis have seldom been investigated. To address these issues, this study investigates the geomechanical performances of geocell-reinforced soil (GRS) backfilled with magnesia-based cement-stabilized marine fill using the nonlinear stress-strain relationship and 3-D FEM models as an alternative to the traditional earth GRS walls. The study finds satisfactory results regarding stability, deformation, and settlement. Only nominal facing reinforcements may be required as the magnesia cement mechanically stabilizes the fill. Moreover, the strength and stiffness properties improve with increased curing duration. The safety factors and observed displacements were within acceptable limits. However, the critical region for the cement-stabilized marine fill GRS wall showing a rupture zone was identified at the toe of the structure. Finally, the study developed a load-displacement model for settlement predictions and uncertainty interpretations, and explained the strength development and deformation mechanisms. The results suggest that cement-stabilized soil retaining walls using magnesia-based cement could be a viable alternative to traditional earth GRS walls, while mitigating environmental concerns and reducing costs.

The applicability and the low limit of the classical fracture theory at nanoscale: The fracture of graphene

Miniaturization of mechanical structures offers excellent performances of the device while has brought problems of fracture at nanoscale. However, whether the classical fracture theory is applicable at such a small scale and what is its low limit are still challenging problems. In this paper, by conducting atomistic simulation of graphene and compared with the reported in-situ experiments, the applicable range of distance from crack tip for crack-tip stress distribution models and the low limit of crack length for fracture criterion are investigated. It is found that all crack-tip stress models are invalid within fracture process zone whose dimension is 2.5 Å away from crack tip. The energy-based fracture criteria are not applicable when the crack length is less than 8 nm due to the nonlinear stress–strain relationship, while the modified Griffith criterion can be applied to low limit of crack length 5 Å. For the stress-based fracture criterion, the stress intensity factor criterion fails when the crack length is less than 8 nm due to the decreasing size of critical K-dominant zone ΛK, while the theory of critical distances and quantized fracture mechanics can accurately predict the critical fracture stress regardless of the crack length, which can be unified by a non-local stress criterion. This work will provide a mechanical basis for the reliable application of the microelectronic devices at nanoscale.

3-D coupled peridynamics and discrete element method for fracture and post-fracture behavior of soil-like materials

The present paper investigates a 3-D numerical analysis method, combining peridynamics (PD) and the discrete element method (DEM), which can simultaneously handle both the fracture and post-fracture behavior of materials assumed to be soils. With geomaterials, it is very important to treat the process from fracture to post-fracture in a continuous manner. The bond-based PD model is employed to reproduce the behavior from the initiation of cracks to fracturing. At the same time, the DEM model is also introduced so that the contact forces among the fragmented pieces can be calculated after the fracturing. The computational process of the physical contact between the wall element and the computational nodes of the PD is also solved based on the DEM so that plane geometry boundaries can be used. For the failure criteria of the connection between the computational nodes of the PD, a bilinear type of bond model is introduced to obtain a nonlinear stress–strain relationship and numerical stability when the calculation process switches from PD to the DEM. To verify the proposed approach, numerical simulations of the diametral compression test are performed on flawless cylindrical specimens, and the results are compared with theoretical solutions for the stress distribution inside the specimens. Based on the results, a simulation of the compressive failure of multiple soil-like crushable objects is performed as an example of the application of the coupled PD-DEM. The obtained results show that the proposed method will serve as a computational framework that can treat the continuous fracture behavior of soil-like materials in three dimensions.

Linear vs nonlinear ultrasonic testing of kissing bonds in adhesive joints

Kissing bonds in adhesive joints are precursors to damage and failure in materials and components used in safety-critical industries. They are zero-volume, low-contrast contact defects widely regarded as “invisible“ in conventional ultrasonic testing. In this study, the recognition of the kissing bonds is examined in automotive industry-relevant aluminum lap-joints with standard bonding procedures using epoxy- and silicone-based adhesives. The protocol to simulate kissing bonds comprised customary surface contaminants PTFE oil and PTFE spray. Preliminary destructive tests revealed brittle fracture of the bonds with typical single-peak stress-strain curves indicating ultimate strength reduction due to adding contaminants. The curves are analyzed by using nonlinear stress-strain relation with the higher-order terms containing the higher-order nonlinearity parameters. It is shown that the lower-strength bonds manifest a high nonlinearity while the high-strength contacts are candidates for a low nonlinearity. Based on that, the nonlinear approach is set side by side with linear ultrasonic testing for experimental locating of the kissing bonds fabricated in the adhesive lap-joints. The sensitivity of the linear ultrasound is shown to be adequate to detect only a substantial bonding force reduction caused by the irregular interface defects in adhesives, while a minor contact softening due to kissing bonds remains undistinguishable. On the contrary, the probing of the kissing bonds vibration with nonlinear laser vibrometry reveals dramatic growth of the higher harmonic amplitudes and thus validates highly-sensitive detectabilty of these troublesome defects.

An enhanced cutting plane algorithm of elastoplastic constitutive models for geomaterials

Integration of the nonlinear stress–strain relationship plays a critical role in the application of constitutive models to engineering practice. Aiming at the nonlinear integration problems commonly existing in elastoplastic constitutive models for geomaterials, we herein present a robust enhanced cutting plane algorithm (ECPA). This algorithm is based on the traditional cutting plane algorithm (CPA) with a new adaptive substepping technique. The accuracy of the CPA is first investigated via a series of numerical examples on a unified hardening/softening elastoplastic model with different nonlinearity degrees of yield functions and plastic potential functions. An intriguing observation is that the accuracy of CPA cannot be guaranteed as long as the plastic flow direction (i.e., ∂G/∂σ ) is not a constant during loading. To overcome this deficiency, a substepping technique for adaptively restricting substep increments solely related to the plastic flow direction was originally proposed and embedded into CPA. The robustness, including the accuracy and efficiency of the proposed ECPA, is evaluated by setting different increment steps and error tolerances. Finally, the ECPA is applied to the Modified Cam Clay (MCC) model, and the robustness of the ECPA is further assessed in element scale tests and a boundary value problem.

Redox Balance Differentially Affects Biomechanics in Permeabilized Single Muscle Fibres—Active and Passive Force Assessments with the Myorobot

An oxidizing redox state imposes unique effects on the contractile properties of muscle. Permeabilized fibres show reduced active force generation in the presence of H2O2. However, our knowledge about the muscle fibre's elasticity or flexibility is limited due to shortcomings in assessing the passive stress-strain properties, mostly due to technically limited experimental setups. The MyoRobot is an automated biomechatronics platform that is well-capable of not only investigating calcium responsiveness of active contraction but also features precise stretch actuation to examine the passive stress-strain behaviour. Both were carried out in a consecutive recording sequence on the same fibre for 10 single fibres in total. We denote a significantly diminished maximum calcium-saturated force for fibres exposed to ≥500 µM H2O2, with no marked alteration of the pCa50 value. In contrast to active contraction (e.g., maximum isometric force activation), passive restoration stress (force per area) significantly increases for fibres exposed to an oxidizing environment, as they showed a non-linear stress-strain relationship. Our data support the idea that a highly oxidizing environment promotes non-linear fibre stiffening and confirms that our MyoRobot platform is a suitable tool for investigating redox-related changes in muscle biomechanics.

Global buckling behaviour of bamboo scrimber box columns under axial compression: Experimental tests and numerical modelling

With the advancement of manufacturing technologies, bamboo scrimber members made of hot-pressed plates have been increasingly used in building structures in the form of thin-walled members. However, limited investigations have been conducted on global buckling behaviour of bamboo scrimber members. This paper presents experimental tests and numerical simulations of the global buckling behaviour of bamboo scrimber columns. Six groups of box columns with different slendernesses were tested under axial compression. The buckling resistance and failure mode of columns were obtained. Test results showed that due to the inelastic stress-strain relationship of bamboo scrimber, most of the box columns exhibited inelastic global buckling, with significant lateral deflections at failure. Comparisons were made between experimental results and design equations in existing codes for glulam structures to evaluate the applicability of the design equations to bamboo scrimber columns. Besides, numerical simulations were also performed for bamboo scrimber columns under axial compression, in which the nonlinear stress-strain relationship and geometric imperfections were incorporated. Numerical results showed that the model could predict the global buckling resistance of columns with reasonably good accuracy. Based on the numerical model, parametric studies were conducted on the effect of column slenderness on the buckling resistance. Finally, design recommendations were proposed for bamboo scrimber columns against global buckling.

A non-linear complementary energy-based constitutive model for incompressible isotropic materials

Inverse non-linear stress–strain relations between the logarithmic Hencky strain tensor and the Cauchy stress tensor are derived for incompressible isotropic materials. The constitutive model is based on a new type of complementary energy potential that considered to be the function of the second and third invariants of the deviatoric Cauchy stress tensor in a power-law form. A proper scaling of the third deviatoric stress invariant allows separate fitting to uniaxial tension and equibiaxial tension (or uniaxial compression) data. The predictive capabilities of a four- and a six-parameter model are presented through a parameter fitting procedure using Treloar’s experimental data for rubber. The performance of the new constitutive model is also demonstrated by solving the inflation problem of a spherical shell.

A modified rigid-body-spring method for modeling damage and failure of brittle rocks subjected to triaxial compression

A three-dimensional modified rigid-body-spring method (3D mRBSM) is presented to simulate the progressive damage and failure process of rocks under triaxial compressive conditions. Different from the original RBSM model, the mRBSM employs spring-set groups distributed on interfaces between blocks to approximately describe the progressive failure process of micro-cracks without increasing the size of governing equations. Firstly, the basic equations of 3D mRBSM are derived. A new randomly distributed Voronoi-based mesh technique is proposed to reproduce homogeneous and isotropic rock materials. Then, relationships between macro and micro elastic parameters are established, and a calibration procedure for parameters of failure criterion is adopted based on the trial-and-error procedure. Lastly, the new model is applied to simulate pseudo triaxial and true triaxial compression tests on brittle rocks. Results show that the proposed model correctly captures common mechanical properties of brittle rocks, such as nonlinear stress–strain relationship, brittle-ductile transition, confining pressure dependence of failure mode and medium principal stress effect. The above research demonstrates that the mRBSM is successfully upgraded to three-dimensional version. The new method is a promising tool for simulation of deformation and failure process of rocks under true triaxial stress conditions.

Impact of Loading and Myocardial Mechanical Properties on Natural Shear Waves: Comparison to Pressure-Volume Loops

BackgroundShear wave elastography (SWE) has been proposed as a novel noninvasive method for the assessment of myocardial stiffness, a relevant determinant of diastolic function. It is based on tracking the propagation of shear waves, induced, for instance, by mitral valve closure (MVC), in the myocardium. The speed of propagation is directly related to myocardial stiffness, which is defined by the local slope of the nonlinear stress-strain relation. Therefore, the operating myocardial stiffness can be altered by both changes in loading and myocardial mechanical properties. ObjectivesThis study sought to evaluate the capability of SWE to quantify myocardial stiffness changes in vivo by varying loading and myocardial tissue properties and to compare SWE against pressure-volume loop analysis, a gold standard reference method. MethodsIn 15 pigs, conventional and high–frame rate echocardiographic data sets were acquired simultaneously with pressure-volume loop data after acutely changing preload and afterload and after inducting an ischemia/reperfusion (I/R) injury. ResultsShear wave speed after MVC significantly increased by augmenting preload and afterload (3.2 ± 0.8 m/s vs 4.6 ± 1.2 m/s and 4.6 ± 1.0 m/s, respectively; P = 0.001). Preload reduction had no significant effect on shear wave speed compared to baseline (P = 0.118). I/R injury resulted in significantly higher shear wave speed after MVC (6.1 ± 1.2 m/s; P < 0.001). Shear wave speed after MVC had a strong correlation with the chamber stiffness constant β (r = 0.63; P < 0.001) and operating chamber stiffness dP/dV before induction of an I/R injury (r = 0.78; P < 0.001) and after (r = 0.83; P < 0.001). ConclusionsShear wave speed after MVC was influenced by both acute changes in loading and myocardial mechanical properties, reflecting changes in operating myocardial stiffness, and was strongly related to chamber stiffness, invasively derived by pressure-volume loop analysis. SWE provides a novel noninvasive method for the assessment of left ventricular myocardial properties.