Passive Material Properties of Intact Ventricular Myocardium Determined From a Cylindrical Model

1991 ◽  
Vol 113 (1) ◽  
pp. 42-55 ◽  
Author(s):  
J. M. Guccione ◽  
A. D. McCulloch ◽  
L. K. Waldman
Keyword(s):  
Residual Stress ◽  
Left Ventricle ◽  
Material Properties ◽  
Circumferential Stress ◽  
Transversely Isotropic ◽  
Ventricular Myocardium ◽  
Equatorial Region ◽  
Fiber Axis ◽  
Fiber Direction ◽  
Incompressible Hyperelastic Material

The equatorial region of the canine left ventricle was modeled as a thick-walled cylinder consisting of an incompressible hyperelastic material with homogeneous exponential properties. The anisotropic properties of the passive myocardium were assumed to be locally transversely isotropic with respect to a fiber axis whose orientation varied linearly across the wall. Simultaneous inflation, extension, and torsion were applied to the cylinder to produce epicardial strains that were measured previously in the potassium-arrested dog heart. Residual stress in the unloaded state was included by considering the stress-free configuration to be a warped cylindrical arc. In the special case of isotropic material properties, torsion and residual stress both significantly reduced the high circumferential stress peaks predicted at the endocardium by previous models. However, a resultant axial force and moment were necessary to cause the observed epicardial deformations. Therefore, the anisotropic material parameters were found that minimized these resultants and allowed the prescribed displacements to occur subject to the known ventricular pressure loads. The global minimum solution of this parameter optimization problem indicated that the stiffness of passive myocardium (defined for a 20 percent equibiaxial extension) would be 2.4 to 6.6 times greater in the fiber direction than in the transverse plane for a broad range of assumed fiber angle distributions and residual stresses. This agrees with the results of biaxial tissue testing. The predicted transmural distributions of fiber stress were relatively flat with slight peaks in the subepicardium, and the fiber strain profiles agreed closely with experimentally observed sarcomere length distributions. The results indicate that torsion, residual stress and material anisotropy associated with the fiber architecture all can act to reduce endocardial stress gradients in the passive left ventricle.

STRESSES AND STRAINS IN THE PASSIVE LEFT VENTRICLE

1996 ◽  
Vol 04 (04) ◽  
pp. 535-554 ◽  
Author(s):  
H.R. CHAUDHRY ◽  
B. BUKIET ◽  
T. FINDLEY ◽  
A.B. RITTER
Keyword(s):  
Left Ventricle ◽  
Residual Stresses ◽  
Diastolic Function ◽  
Fiber Orientation ◽  
Deformation Theory ◽  
Stress Gradient ◽  
Circumferential Stress ◽  
Equatorial Region ◽  
Hollow Cone ◽  
Lower Stress

In this paper, we estimate the stresses and strains from the equatorial region down to the apex of the heart by modeling the passive left ventricle as a frustrum of a thick hollow cone. Large deformation theory has been employed in this analysis. Furthermore, the effects of residual stresses and the anisotropy due to muscle fiber orientation have been included. It is observed that circumferential stress, which is the most important physiologically, decreases considerably at the endocardium and is more evenly distributed through the wall when residual stresses are taken into account. The stresses also decrease as we go from the equatorial region to the apex. Because heart muscles physically have residual stresses, the consequent lower stress gradient through the wall enhances the diastolic function of the left ventricle.

Anisotropic Behavior of White Matter in Shear and Implications for Transversely Isotropic Models

2013 ◽  
Author(s):  
Ruth J. Okamoto ◽  
Yuan Feng ◽  
Guy M. Genin ◽  
Philip V. Bayly
Keyword(s):  
White Matter ◽  
Strain Tensor ◽  
Experimental Studies ◽  
Transversely Isotropic ◽  
Stretch Ratio ◽  
Fiber Axis ◽  
Fiber Direction ◽  
Material Models ◽  
Green Strain ◽  
The Brain

Experimental studies [1] have shown that white matter (WM) in the brain is mechanically anisotropic. Based on its fibrous structure, transversely isotropic (TI) material models have been suggested to capture WM behavior. TI hyperelastic material models involve strain energy density functions that depend on the I4 and I5 pseudo-invariants of the Cauchy-Green strain tensor to account for the effects of stiff fibers. The pseudo-invariant I4 is the square of the stretch ratio in the fiber direction; I5 contains contributions of shear strain in planes parallel to the fiber axis. Most, if not all, published models of WM depend on I4 but not on I5.

Tensile Material Properties of Skeletal Muscle Tissue in Longitudinal and Transverse Directions

2008 ◽  
Author(s):  
Duane A. Morrow ◽  
Tammy L. Haut Donahue ◽  
Gregory M. Odegard ◽  
Kenton R. Kaufman
Keyword(s):  
Skeletal Muscle ◽  
Muscle Tissue ◽  
Material Properties ◽  
Computational Models ◽  
Muscle Length ◽  
Transversely Isotropic ◽  
Longitudinal Direction ◽  
Longitudinal Shear ◽  
Fiber Direction ◽  
Tension Properties

Since Blix noted that force varies with muscle length [1], many investigators have worked to characterize the passive length-tension properties of skeletal muscle in the tissue’s fiber direction [2]. However, few reports have examined the properties of muscle in either transverse extension or in longitudinal shear [3–4]. Material properties in these three directions are needed to fully characterize computational models, which generally describe muscle as being transversely isotropic, hyperelastic, and isovolumetric [3–6]. Further, previous studies reporting tri-planar material properties indicate that muscle tissue is stiffer in the transverse direction compared to the longitudinal direction [3–4]. This counters conventional notions of transversely isotropic materials, which are generally stiffer in the fiber direction.

Effect of residual stress on transmural sarcomere length distributions in rat left ventricle

1993 ◽  
Vol 264 (4) ◽  
pp. H1048-H1056 ◽  
Author(s):  
E. K. Rodriguez ◽  
J. H. Omens ◽  
L. K. Waldman ◽  
A. D. McCulloch
Keyword(s):  
Residual Stress ◽  
Left Ventricle ◽  
Wall Thickness ◽  
Sarcomere Length ◽  
Equatorial Region ◽  
Analysis Of Covariance ◽  
Opening Angle ◽  
Cross Sectional ◽  
Rat Hearts ◽  
Stress Free State

It has been previously shown that the myocardium in the walls of the unloaded passive left ventricle (LV) is not stress free. To assess the functional significance of residual stress in the ventricular wall, we compared the transmural distributions of sarcomere length (SL) in specimens of rat LV myocardium fixed in the unloaded (residually stressed) and stress-free states. When a cross-sectional ring cut from the equatorial region of the freshly arrested rat hearts was cut radially to relieve residual stress, it sprang open into an arc with a mean opening angle of 45 +/- 15 degrees (SD) (n = 8). During immersion fixation in glutaraldehyde, the opening angle increased 9.3 +/- 7.1 degrees (SD) overall. SLs were measured at 16 equally spaced transmural locations from the free wall in the stress-free tissue sections and were compared with control measurements from adjacent cross-sectional rings in which residual stress had not been relieved. Average SL for the stress-free tissue (n = 11) was 1.84 +/- 0.05 (SD) microns and for the unloaded tissue was 1.83 +/- 0.06 (SD) microns. However, analysis of covariance on the pooled data showed that the transmural distributions were significantly different (P < 0.0001). Whereas SL was uniform across the wall in the stress-free state with a mean gradient of -0.014 +/- 0.044 (SD) microns/total wall thickness, there was a significant decrease (P = 0.001) in SL from epicardium to endocardium in the intact unloaded tissue [slope = -0.114 +/- 0.054 (SD) microns/total wall thickness].(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Residual Stress and Heterogeneity on Circumferential Stress in the Arterial Wall

2000 ◽  
Vol 122 (4) ◽  
pp. 454-456 ◽  
Author(s):  
S. J. Peterson ◽  
R. J. Okamoto
Keyword(s):  
Residual Stress ◽  
Stress Distribution ◽  
Material Properties ◽  
Arterial Wall ◽  
Circumferential Stress ◽  
Single Species ◽  
Opening Angle ◽  
Layer Model ◽  
Multiple Sources ◽  
The Media

Quantifying the stress distribution through the arterial wall is essential to studies of arterial growth and disease. Previous studies have shown that both residual stress, as measured by opening angle, and differing material properties for the media-intima and the adventitial layers affect the transmural circumferential stress σθ distribution. Because a lack of comprehensive data on a single species and artery has led to combinations from multiple sources, this study determined the sensitivity of σθ to published variations in both opening angle and layer thickness data. We fit material properties to previously published experimental data for pressure–diameter relations and opening angles of rabbit carotid artery, and predicted σθ through the arterial wall at physiologic conditions. Using a one-layer model, the ratio of σθ at the internal wall to the mean σθ decreased from 2.34 to 0.98 as the opening angle increased from 60 to 130 deg. In a two-layer model using a 95 deg opening angle, mean σθ in the adventitia increased (112 percent for 25 percent adventitia) and mean σθ in the media decreased (47 percent for 25 percent adventitia). These results suggest that both residual stress and wall layers have important effects on transmural stress distribution. Thus, experimental measurements of loading curves, opening angles, and wall composition from the same species and artery are needed to accurately predict the transmural stress distribution in the arterial wall. [S0148-0731(00)02204-4]

scholarly journals Impact of residual stress evoked by pyramidal embossing on the magnetic material properties of non-oriented electrical steel

2021 ◽  
Author(s):  
Ines Gilch ◽  
Tobias Neuwirth ◽  
Benedikt Schauerte ◽  
Nora Leuning ◽  
Simon Sebold ◽  
...  
Keyword(s):  
Magnetic Material ◽  
Residual Stress ◽  
Magnetic Flux ◽  
Material Properties ◽  
Electrical Steel ◽  
Maximum Energy ◽  
Material Behavior ◽  
Electrical Machine ◽  
Element Analysis ◽  
Steel Sheets

AbstractTargeted magnetic flux guidance in the rotor cross section of rotational electrical machines is crucial for the machine’s efficiency. Cutouts in the electrical steel sheets are integrated in the rotor sheets for magnetic flux guidance. These cutouts create thin structures in the rotor sheets which limit the maximum achievable rotational speed under centrifugal forces and the maximum energy density of the rotating electrical machine. In this paper, embossing-induced residual stress, employing the magneto-mechanical Villari effect, is studied as an innovative and alternative flux barrier design with negligible mechanical material deterioration. The overall objective is to replace cutouts by embossings, increasing the mechanical strength of the rotor. The identification of suitable embossing geometries, distributions and methodologies for the local introduction of residual stress is a major challenge. This paper examines finely distributed pyramidal embossings and their effect on the magnetic material behavior. The study is based on simulation and measurements of specimen with a single line of twenty embossing points performed with different punch forces. The magnetic material behavior is analyzed using neutron grating interferometry and a single sheet tester. Numerical examinations using finite element analysis and microhardness measurements provide a more detailed understanding of the interaction of residual stress distribution and magnetic material properties. The results reveal that residual stress induced by embossing affects magnetic material properties. Process parameters can be applied to adjust the magnetic material deterioration and the effect of magnetic flux guidance.

Residual stress determination in surface treated alumina samples applying beam limiting masks

2009 ◽  
Vol 24 (S1) ◽  
pp. S77-S81 ◽  
Author(s):  
Thorsten Manns ◽  
André Rothkirch ◽  
Berthold Scholtes
Keyword(s):  
Residual Stress ◽  
Material Properties ◽  
Ccd Camera ◽  
Sample Surface ◽  
Real Space ◽  
Experimental Setup ◽  
Stress Determination ◽  
Small Gauge ◽  
Position Sensitive ◽  
To Receive

This paper deals with the implementation of a theoretically described method to determine residual stresses in real space directly by means of small gauge volumes. For this purpose, beam limiting masks were designed, manufactured, and investigated in first experiments. Image series taken with a position sensitive CCD camera demonstrate the ability to detect interferences from gauge volumes beneath the sample surface by defined slit geometries. The experiments show that due to the highly absorbing masks the amount of detectable photons is poor, and thus long exposure times are necessary to receive suitable data. For increasing measurement depths (altering masks) a decrease in the intensity can be detected which leads to the assumption that the diffracted photons originate from deeper regions in the material. A model was developed to simulate the diffraction conditions with different mask layouts and material properties. Modeling yields consistent results with experimental data, and thus provides a basis for further improvements of the experimental setup and the realization and assessment of residual stress measurements.

The Elastic Characterization of Composite Based on Ultrasonic Waves

2021 ◽  
Author(s):  
Y. H. Park ◽  
J. Dana
Keyword(s):  
Composite Materials ◽  
Fatigue Failure ◽  
Elastic Constants ◽  
Material Properties ◽  
Weight Ratio ◽  
Transversely Isotropic ◽  
Ultrasonic Waves ◽  
Material Strength ◽  
Isotropic Composite

Abstract Anisotropic composite materials have been extensively utilized in mechanical, automotive, aerospace and other engineering areas due to high strength-to-weight ratio, superb corrosion resistance, and exceptional thermal performance. As the use of composite materials increases, determination of material properties, mechanical analysis and failure of the structure become important for the design of composite structure. In particular, the fatigue failure is important to ensure that structures can survive in harsh environmental conditions. Despite technical advances, fatigue failure and the monitoring and prediction of component life remain major problems. In general, cyclic loadings cause the accumulation of micro-damage in the structure and material properties degrade as the number of loading cycles increases. Repeated subfailure loading cycles cause eventual fatigue failure as the material strength and stiffness fall below the applied stress level. Hence, the stiffness degradation measurement can be a good indication for damage evaluation. The elastic characterization of composite material using mechanical testing, however, is complex, destructive, and not all the elastic constants can be determined. In this work, an in-situ method to non-destructively determine the elastic constants will be studied based on the time of flight measurement of ultrasonic waves. This method will be validated on an isotropic metal sheet and a transversely isotropic composite plate.

scholarly journals Successful Surgical Treatment of Postinfarction Rupture of Left Ventricular Myocardium

2020 ◽  
Vol 9 (1) ◽  
pp. 140-147
Author(s):  
M. K. Mazanov ◽  
N. I. Kharitonova ◽  
A. A. Baranov ◽  
S. Yu. Kambarov ◽  
N. M. Bikbova ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Left Ventricle ◽  
Surgical Intervention ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Left Ventricular Myocardium ◽  
Free Wall ◽  
Fatal Complication ◽  
Widespread Availability ◽  
Complications Of Myocardial Infarction

ABSTRACT. The rupture of the left ventricle free wall is one of the most dangerous complications of myocardial infarction. Due to the widespread availability of echocardiography method, the detection of this fatal complication and the number of lives saved after surgery grew. The survival of patients depends on early diagnosis, stabilization of the patient’s condition, promptness and tactics of surgical intervention. We report a case of successful closure of a rupture of the left ventricle free wall on the 15th day after myocardial infarction.

scholarly journals Three-dimensional residual strain in midanterior canine left ventricle

1997 ◽  
Vol 273 (4) ◽  
pp. H1968-H1976 ◽  
Author(s):  
Kevin D. Costa ◽  
Karen May-Newman ◽  
Dyan Farr ◽  
Walter G. O’Dell ◽  
Andrew D. McCulloch ◽  
...  
Keyword(s):  
Residual Stress ◽  
Left Ventricle ◽  
Residual Strain ◽  
Three Dimensional ◽  
Element Analysis ◽  
Primary Mechanism ◽  
Dimensional Measurements ◽  
Residual Strains ◽  
Shear Strains ◽  
Pressure State

All previous studies of residual strain in the ventricular wall have been based on one- or two-dimensional measurements. Transmural distributions of three-dimensional (3-D) residual strains were measured by biplane radiography of columns of lead beads implanted in the midanterior free wall of the canine left ventricle (LV). 3-D bead coordinates were reconstructed with the isolated arrested LV in the zero-pressure state and again after local residual stress had been relieved by excising a transmural block of tissue. Nonhomogeneous 3-D residual strains were computed by finite element analysis. Mean ± SD ( n = 8) circumferential residual strain indicated that the intact unloaded myocardium was prestretched at the epicardium (0.07 ± 0.06) and compressed in the subendocardium (−0.04 ± 0.05). Small but significant longitudinal shortening and torsional shear residual strains were also measured. Residual fiber strain was tensile at the epicardium (0.05 ± 0.06) and compressive in the subendocardium (−0.01 ± 0.04), with residual extension and shortening, respectively, along structural axes parallel and perpendicular to the laminar myocardial sheets. Relatively small residual shear strains with respect to the myofiber sheets suggest that prestretching in the plane of the myocardial laminae may be a primary mechanism of residual stress in the LV.

Sign in / Sign up

Export Citation Format

Share Document