Circumferential Deformation Research Articles

Spatial Oscillations of a Pipeline with Vibrating Supports

Spatial oscillations of a section of a pipeline with a liquid contained in it during the translational vibrational movements of the supports are investigated. Oscillations of both supports occur with equal amplitudes, frequencies and phases. Pipe deformations associated with the exit of its axis from the bending plane are assumed to be small. The interactions of internal constant pressure and changes in the curvature of the axial line, longitudinal and circumferential deformations of the pipe are taken into account. Its flexural-rotational vibrations are described by a system of two non-linear differential equations. By applying the Bubnov-Galerkin method, this system is reduced to the Cauchy problem, which is then solved numerically by the Runge-Kutta method. In the case of small bending and angular motions of the pipe, a comparison of the analytical and numerical solutions is given. An analysis is given of periodic and non-periodic oscillations of steel, titanium and composite pipes, for which, in particular, frequency spectra and Poincare mappings are constructed.

Model test investigation on the longitudinal mechanical property of shield tunnels considering internal structure

Reasonable evaluation of longitudinal mechanical property of shield tunnel is critical to the design and maintenance of tunnel structures. Traditionally, the internal structure has not been involved in the existing studies on the longitudinal mechanical properties of shield tunnels, of which the effect on the longitudinal mechanical properties of shield tunnels remains unknown. In this study, a series of physical similar model tests were conducted on homogeneous model (HM), non-homogeneous model (NHM) and non-homogeneous model with internal structure (NHMI), the effect of internal structure and longitudinal force on the longitudinal mechanical properties of road-metro shield tunnels were investigated. The longitudinal strain, displacement, curvature, and circumferential joint deformation of the tunnels were analyzed in depth. The experimental results show that the internal structure can reduce the longitudinal deformation of shield tunnels greatly, and the maximum displacement of tunnels with internal structure can be reduced by 70.58 %, the curvature radius can be increased by 1.73 to 2.36 times, the dislocation of the circumferential joint can be reduced by up to 70.4 %, and the opening of the circumferential joint can be reduced by up to 67.37 %. The longitudinal bending stiffness efficiency of tunnels ranges from 0.66 to 0.86 after taking into account the effect of internal structures. Increasing the longitudinal force from 0 MPa to 0.3 MPa significantly improves the longitudinal bending stiffness efficiency of tunnels, after which increasing the longitudinal force has no significant effect on the longitudinal mechanical properties of the tunnel.

Deformable hard tissue with high fatigue resistance in the hinge of bivalve Cristaria plicata.

The hinge of bivalve shells can sustain hundreds of thousands of repeating opening-and-closing valve motions throughout their lifetime. We studied the hierarchical design of the mineralized tissue in the hinge of the bivalve Cristaria plicata, which endows the tissue with deformability and fatigue resistance and consequently underlies the repeating motion capability. This folding fan-shaped tissue consists of radially aligned, brittle aragonite nanowires embedded in a resilient matrix and can translate external radial loads to circumferential deformation. The hard-soft complex microstructure can suppress stress concentration within the tissue. Coherent nanotwin boundaries along the longitudinal direction of the nanowires increase their resistance to bending fracture. The unusual biomineral, which exploits the inherent properties of each component through multiscale structural design, provides insights into the evolution of antifatigue structural materials.

Measurement of three-dimensional shrinkage deformations and volumes of stabilised soft clay during drying with Structure from Motion photogrammetry

The paper applies the Structure from Motion photogrammetry technique to measure three-dimensional shrinkage deformations of a cylindrical specimen during drying. A clay–binder mixture was statically compacted, and its shrinkage behaviour was observed for four weeks with a newly established photogrammetric system. The complete surface information including XYZ coordinates and RGB values was then reconstructed and formed into dense point cloud data, with which the volume change and shrinkage deformations are computed. In volume change determination, the reconstructed dense point cloud achieves a fine reproduction of the specimen surface, leading to satisfactory accuracy. The computed volume deviation was within 495.3 mm3 (0.24%) and 4170 mm3 (1.83%) for the dummy cylinder and clay specimen, respectively. Both values are significantly smaller than the volume deviations computed with a classical approach that involves artificially creating markers on the specimen surface. In the computation of shrinkage deformations, the paper proposes a novel method that detects the fast point feature histogram of the point clouds and then matches the detected descriptors, leading to an improvement in three-dimensional deformation determination. The compacted sample shrinks, and the computed axial deformations increase quasi-linearly with height. However, due to the noticeable tilt that occurred during drying, the calculated radial deformations are scattered at the same height and appear misleading. Circumferential deformations and strains are therefore adopted to represent the true material behaviour.

Mechanical Behavior of Cross-Winding Steel-Wire–Reinforced Thermoplastics Pipe under Internal Pressure

Cross-winding steel-wire–reinforced thermoplastic pipes (CSWRTPs) have been widely applied in oilfield gathering environments in China because of their excellent physical properties. In this study, the failure mode, short-term burst pressure, and strain for a CSWRTP with an external diameter of 75 mm and a wall thickness of 10 mm under internal pressure are investigated through experimental measurements conducted with a burst test system and simulations completed with ANSYS software. A new three-dimensional finite-element burst failure model of CSWRTPs is proposed. Simulation results are in good agreement with the measurements. An axial ductile crack was found on the tested pipe with an uneven circumferential expansion deformation. The simulated short-term burst pressure is in a good agreement with the measured value (19.7 MPa) with an error of +8.7%. The growth of the strain is initially zero, followed by a linear growth, rapid growth, and a clifflike drop when the crack is generated. The effective plastic strain within the inner polyethylene liner is greater than that within the outer polyethylene sheath, and the effective stress within the inner steel wire is greater than that within the outer steel wire. The ultimate pressure–bearing capacity decreases linearly as the strength of the steel wire decreases. Therefore, reduction of the ultimate pressure–bearing capacity of CSWRTP results from the decrease of steel wire strength from corrosion when applied in oilfield gathering systems. This finite-element analysis method can provide a reference to optimize the structural design of CSWRTP.

Tri-layered constitutive modelling unveils functional differences between the pig ascending and lower thoracic aorta

The arterial wall's tri-layered macroscopic and layer-specific microscopic structure determine its mechanical properties, which vary at different arterial locations. Combining layer-specific mechanical data and tri-layered modelling, this study aimed to characterise functional differences between the pig ascending (AA) and lower thoracic aorta (LTA).AA and LTA segments were obtained for n=9 pigs. For each location, circumferentially and axially oriented intact wall and isolated layer strips were tested uniaxially and the layer-specific mechanical response modelled using a hyperelastic strain energy function. Then, layer-specific constitutive relations and intact wall mechanical data were combined to develop a tri-layered model of an AA and LTA cylindrical vessel, accounting for the layer-specific residual stresses. AA and LTA behaviours were then characterised for in vivo pressure ranges while stretched axially to in vivo length.The media dominated the AA response, bearing>2/3 of the circumferential load both at physiological (100 mmHg) and hypertensive pressures (160 mmHg). The LTA media bore most of the circumferential load at physiological pressure only (57±7% at 100 mmHg), while adventitia and media load bearings were comparable at 160 mmHg. Furthermore, increased axial elongation affected the media/adventitia load-bearing only at the LTA.The pig AA and LTA presented strong functional differences, likely reflecting their different roles in the circulation. The media-dominated compliant and anisotropic AA stores large amounts of elastic energy in response to both circumferential and axial deformations, which maximises diastolic recoiling function. This function is reduced at the LTA, where the adventitia shields the artery against supra-physiological circumferential and axial loads.

INVESTIGATING THE STRESS - STRAIN STATE OF ALUMINIUM ALLOYS AT HOT EXTRUSION AND REGULARITIES OF STRUCTURE AND PROPERTY FORMATION

The stress strain state, as well as the process of formation of structure and features of aluminium alloys at hot extrusion are investigated. It has been shown that during hot extrusion, the ring layers of an extruded element experience not only longitudinal and transverse deformations but also a slip. The slip increases at passing from inner layers to the surface. The tensile principal stresses and the sum of slip deformations also increase. It has been also shown that at the exit of the pressing part, the tensile principal stresses have different directions, forming an angle with the extruder axis, which also increases towards the surface. As a conclusion, it has been stated that the main radial and circumferential deformations act as restraining deformations.

Structural Performance of Additively Manufactured Cylinder Liner—A Numerical Study

Climate change is exacerbated by vehicle emissions. Furthermore, vehicle pollution contributes to respiratory and cardiopulmonary diseases, as well as lung cancer. This requires a drastic reduction in global greenhouse gas emissions for the automobile industry. To address this issue, researchers are required to reduce friction, which is one of the most important aspects of improving the efficiency of internal combustion engines. One of the most important parts of an engine that contributes to friction is the piston ring cylinder liner (PRCL) coupling. Controlling the linear deformation enhances the performance of the engine and, as a result, contributes positively to its performance. The majority of the tests to study the conformability between cylinder liner and piston were carried out on cylinder liners made of cast iron. It is possible to improve the performance of piston ring cylinder liner couplings by implementing new and advanced manufacturing techniques. In this work, a validated finite element model was used to simulate the performance when advanced manufactured materials were adapted. The deformation of the cylinder liner due to thermal and mechanical loads is simulated with five different additive manufactured materials (Inconel 625, Inconel 718, 17-4PH stainless steel, AlSi10Mg, Ti6Al4V). Simulated roundness and straightness errors, as well as maximum deformation, are compared with conventional grey cast iron liner deformation. Some additive manufactured materials, especially Ti6Al4V, show a significant reduction in deformation compared to grey cast iron, both in bore and circumferential deformation. Results show that Ti6Al4V can reduce maximum liner deformation by 36%. In addition, the roundness improved by 36%. The straightness error when Ti6Al4V was used also improved by 44% on one side, with an average of 20% over the four sides. Numerical results indicate that additive manufactured materials have the potential to reduce friction within the piston liner arrangement of internal combustion engines.

Longitudinal, radial, circumferential and rotational mechanics in acute myocarditis; a 2D speckle-tracking echocardiography study

Abstract Objectives The aim of our study was to assess the utility of echocardiographic deformation imaging of the left ventricle in patients with CMR-proven acute myocarditis (AM). Background Often conventional echocardiography reveals no obvious abnormalities in AM. While longitudinal strain is known to reflect the subendocardial muscle layer deformation, in AM myocardial damage is predominantly confined to the subepicardium. The latter is involved in circumferential deformation and rotational mechanics. Methods Data were obtained from a prospectively maintained database of patients (n=44) with AM who had an echocardiography and CMR within 2 weeks of hospital presentation. All patients underwent a comprehensive echocardiographic study including measurement of left ventricular (LV) global longitudinal strain (GLS), basal and apical radial strain (RS), basal and apical circumferential strain (CS), basal and apical rotation, peak twist and peak twist rate. Furthermore, LV deformation was analysed in an age-matched control group (CG) of individuals (n=27) with no evidence of cardiovascular disease. Results There was no significant difference in demographics and most echocardiographic parameters (Table 1). LV EF (57±11% vs 63±4%, p=0.005) was lower in AM. Difference in wall thickness (LVPWd 10.6±1.9mm vs 9.5±1.5mm, p=0.002) and diastolic function (E/E' lateral 6.7±3.1 vs 4.9±0.9, p=0.015) were significant but not specific. Deformation imaging revealed significant differences between the 2 groups in parameters reflecting longitudinal and circumferential deformation, and rotational mechanics (Table 2); GLS (−15.4±4.2% vs −18.9±2.1%, p<0.001), apical CS (−26.1±10.2% vs −34.8±9.4%, p<0.001), basal CS (−20.8±7.4% vs −24.4±6.0%, p=0.017), apical rotation (4.5±3.2° vs 7.9±4.0°, p<0.001), peak twist (9.8±5.8° vs 14.5±5.1°, p<0.001) and peak twist rate (69.5±32.7deg/sec vs 89.3±32.7deg/sec, p<0.001). In patients with preserved systolic function (EF ≥50%, n=35) the only statistically significant 2D parameter between groups was LVPWd thickness (10.8±1.7mm vs 9.2±1.5mm, p=0.001), whereas differences in most strain and rotational parameters persisted; GLS (−16.5±3.3% vs −18.9±2.2%, p=0.003), apical CS (−28.0±8.2% vs −34.8±9.4%, p=0.030), apical rotation (4.7±3.2° vs 7.9±4.0°, p<0.001), peak twist (10.3±6.2° vs 14.5±5.5°, p=0.008), peak twist rate (71.1±33.3 deg/sec vs 89.3±32.7 deg/sec, p=0.048). ROC analysis showed fair classification accuracy for apical rotation (0.760, p<0.001), LV PWd (AUC 0.760, p<0.001), peak twist (0.752, p=0.01) and GLS (AUC 0.706, p<0.001). Conclusion Apical rotation and myocardial twist can objectively quantify myocardial mechanics in AM. Circumferential and rotational mechanics are mostly affected, even in patients with preserved ejection fraction, possibly reflecting subclinical LV dysfunction associated with subepicardial muscle layer inflammation. Funding Acknowledgement Type of funding sources: None.

Increased circumferential deformation predicts cardiac events when left ventricular ejection fraction is normal

Abstract Background Recent research suggests that early left ventricular (LV) systolic dysfunction is characterized by compromised longitudinal function and a concomitant augmentation of circumferential deformation expressed as increased global circumferential strain (GCS). It is hypothesized that increased GCS could be used to identify people at higher risk of cardiovascular events when left ventricular ejection fraction (LVEF) is preserved. Purpose The present study aimed to investigate whether elevated GCS in individuals with preserved LVEF predicts major adverse cardiovascular events (MACE). Methods A total of 2,874 participants from the general population were included in this prospective cohort study. All participants had echocardiography performed and analyzed. Exclusion criteria were HF at baseline, non-sinus rhythm during echocardiography, and inadequate image quality for GCS assessment. Outcome was MACE including incident heart failure, myocardial infarction, and/or cardiovascular death. Absolute values of strain were used. To determine the optimal transition point of a potential effect modification, Cox regression models with different LVEF thresholds were created. The model with the optimal hazard ratio (HR) and P values of the interaction terms and Akaike information criterion was chosen. Results Mean age was 53±18 years and 60% were female. Mean LVEF and GCS were 57±6% and 21.6±4.0%, respectively. Median follow-up was 3.5 years [IQR: 2.6; 4.4] and a total of 92 (3.2%) developed MACE. A U-shaped relationship was observed between GCS and MACE. The lowest incidence rate was within the GCS range of 20 to 25% (Figure 1a). A significant interaction (P<0.001) between GCS and LVEF was observed regarding MACE. The optimal transition point for this effect modification was determined to be LVEF=50%. In multivariable Cox regressions (including conventional cardiovascular risk factors and global longitudinal strain (GLS)), increasing GCS was significantly associated with future MACE in participants with LVEF ≥50% (HR=1.09 [95% CI: 1.01; 1.17] per 1% increase, n=2420) while decreasing GCS were associated with a higher risk of MACE in individuals with abnormal LVEF (HR=1.16 [95% CI: 1.04; 1.29] per 1% decrease, n=289) (Figure 1b). A total of 50 (2.1%) developed the MACE amongst the participants with LVEF ≥50%. This group had significantly lower GLS (19.0±2.7% vs 19.9±2.0%, P=0.013) and ratio of peak early transmitral filling velocity to peak early diastolic tissue velocity (E/e') (10.7 [IQR: 7.9; 14.3] vs 6.5 [5.3; 8.4], P<0.001) compared to the participants that did not develop MACE with normal LVEF. Figure 2 illustrates a model of the development of GCS, LVEF, GLS, and E/e' as LV function declines. Conclusion In the general population, the prognostic value of GCS is modified by LVEF. In participants with normal LVEF, higher GCS was associated with increased risk of MACE, while the opposite was observed in participants with abnormal LVEF. Funding Acknowledgement Type of funding sources: Foundation. Main funding source(s): The Copenhagen City Heart Study is funded by The Danish Heart FoundationThe Metropolitan Region of Denmark (public funding).

Novel exact layerwise analytical solution for anisotropic multi-layer magneto-piezo-elastic hollow spheres under asymmetric magneto-electro-hygro-thermo-mechanical loads

In the present article, a novel analytical layer-dependent closed-form solution is proposed for multilayer magneto-piezo-elastic hollow spheres with anisotropic layers under asymmetric 2D magneto-electro-hygro-thermo-mechanical loads. The sphere is assumed to be fabricated from piezomagnetic materials and encounters steady-state Fikean and Fourier moisture and heat diffusions. The proposed solution satisfies the layerwise continuity conditions of the stresses and especially, heat and moisture fluxes (derivatives of the main quantities) at the interfaces between layers, in addition to continuity of the main magneto-electro-thermo-elastic quantities. In contrast to the common wrong usage of the Lorentz body force concept in the static and creep analyses, the magneto-electric, hygro-electric, pyro-magnetic, and hygro-magnetic interactions are taken into consideration as well. The governing equations are derived based on the general magneto-electro-hygro-thermo-elasticity. The analytical solution contains new ideas as a special change of variables was used to enable solving the resulting system of equations Legendre series. The coefficients of the mentioned Legendre series are in turn, obtained by solving a system of Eulerian partial differential equations. Effects of various material and environmental factors on the 2D radial and circumferential distributions of the radial and circumferential deformations, stress components, and the induced electrical and magnetic fields are evaluated in the results section. From the accomplished parametric studies, it is found that due to the differences in the various material properties of the successive layers, the gradients of the variations of the responses are not only quite different within the distinct layers but also cannot be estimated without numerical derivations.

A comparative study on mechanical and vibroacoustic performance of sandwich cylindrical shells with positive, negative, and zero Poisson's ratio cellular cores

Deep-sea submersibles are significant mobile platforms requiring multi-functional capabilities that are strongly determined by the constituent materials. Their cylindrical protective cover can be advanced by designing their sandwiched cellular materials whose physical properties can be readily parameterized and flexibly tuned. Porous honeycomb materials are capable of possessing tuned positive, negative, or zero Poisson's ratios (PPR, NPR, and ZPR), which is expected to produce distinct physical performance when utilized as a cellular core of cylindrical shells for the deep-sea submersibles. A novel cylindrical meta-structure sandwiched with the semi-re-entrant ZPR metamaterial has been designed as well as its similarly-shaped sandwich cylindrical shell structures with PPR and NPR honeycombs. The mechanical and vibroacoustic performance of sandwich cylindrical shells with cellular materials featuring a full characteristic range of Poisson's ratios are then compared systematically to explore their potential for engineering applications on submerged pressure-resistant structures. The respective unit cells are designed to feature an equivalent load-bearing capability. Physical properties of pressure resistance, buckling, and sound insulation are simulated, respectively, and the orders of each property are then generalized by systematic comparison. The results indicate that the PPR honeycomb core takes advantage of higher structural strength and stability while the ZPR one yields better energy absorption and sound insulation behavior. The NPR one yields moderate properties and has the potential for lower circumferential deformation. The work explores the application of cellular materials with varied Poisson's ratios and provides guidance for the multi-functional design of sandwich cylindrical meta-structures.

Assessment of ballistic impact damage on aluminum and magnesium alloys against high velocity bullets by dynamic FE simulations

Abstract The shape of the projectile seems to determine the effect of a ballistic impact and failure mechanism. In this study, the numerical analysis of ballistic impact with different projectile shapes, i.e., ogive, blunt, conical, and hemispherical is performed. The target is a circular sandwich plate with an outer diameter of 315 mm, which is composed of three layers with a thickness of 1 mm for each layer. These layers will be filled with different materials such as 1100-H12 aluminum alloy, ZK61m magnesium alloy, and 6061-T651 aluminum alloy. The target plate in the numerical analysis consists of two parts: the inner and outer zones. In the inner zone, the selected element size is set to fine, while in the outer zone, it is set to be coarser, and the size will increase along with the direction and the diameter of the circle. This numerical simulation uses the Johnson–Cook material model and is applied to ABAQUS/Explicit software. The simulation configurations are validated based on previous experiments by comparing the residual velocity values after the projectile has penetrated the target plate. The simulation results will obtain energy absorption values for each variation of the target plate. The energy absorption values are affected by stress and strain in radial, circumferential, axial, and shear deformation. The energy absorption value determines the strength of each variation of the target plate. Then the target plate will compare which arrangement is the strongest when receiving ballistic loads.

Experimental study of permeability evolution in modified desulfurization gypsum under complete stress–strain process

In the context of low-carbon economy and sustainable development, industrial by-products are being gradually converted into green building materials. The effect of groundwater on the properties of modified desulfurization gypsum must be examined to increase its application in shotcrete supporting structures in underground engineering. In this study, triaxial compression tests with permeability measurements were carried out for modified desulfurization gypsum by simulating underground engineering conditions. The peak strength, permeability-deformation curves, and permeability-stress curves were obtained. The results showed that an increase in pore water pressure promoted internal crack propagation and enhanced the connectivity between cracks. This decreased the specimen strength and increased the initial permeability. As axial deformation and circumferential deformation increased, the variation in the permeability showed five stages: decline, gradual rise, rapid rise, rapid decline, and gradual decline. The permeability was more sensitive to circumferential deformation compared to axial deformation. The critical impermeability strength and abrupt permeability were defined according to the permeability-stress curves. These parameters can be used to evaluate the seepage problems in shotcrete supporting structures in underground engineering.

Deformation and stress analysis of cup on pipeline inspection gauge based on reverse measurement

AbstractThe pipeline inspection gauge (PIG) is one of the most significant gauges in the field of oil–gas storage and transportation. It is essential to use PIG to clean and detect petroleum and natural gas pipelines. Predicting the deformation and stress distribution of the cup on the PIG is essential before pigging. To enhance these predictions, especially the deformation of the cup, a method for measuring the deformation of the cup based on reverse measurement was introduced and a novel finite element (FE) simulation model for investigation of the deformation of cups was proposed and verified in this paper. The point cloud data of the cup before and after entering the pipe can be obtained by the three‐dimensional (3D) laser scanner. Comparing the obtained point cloud data can measure the deformation of the cup. In addition, a 3D FE model was created to predict the deformation of the cup and the effective stress on the contact area. The result shows that there is a linear relationship between circumferential deformation and interference, while there is a nonlinear relationship between axial deformation, effective stress, and interference. These results provide a better understanding of the complex behavior of PIG during pigging.

Wall thinning characteristics and prediction in numerical control bending of high strength Ti-3Al-2.5V tube

Owing to the unique properties of high strength Ti-3Al-2.5V tube, wall thinning is prone to happen in tube bending. To accomplish tube precision bending forming, the wall thinning needs to be precisely predicted and effectively controlled. A theoretical model considering circumferential deformation was presented to reveal the inherent relationship for wall thickness distribution versus tube geometrical parameters, and its reliability was validated by published experimental results. Using finite element (FE) simulation combined with orthogonal test, the effect rules and significances of process parameters on wall thinning in numerical control (NC) bending for high strength Ti-3Al-2.5V tube were investigated. The results show that the significant factors sort from the largest to the smallest for wall thinning in tube bending as the clearance of tube versus mandrel C m, axial feed of mandrel e, friction of tube versus mandrel f m, clearance of tube versus bending die C b, clearance of tube versus wiper die C w and push assistant speed of pressure die v p; the wall thinning decreases for the larger C m and v p, while increases for the larger C b, C w, f m, and e. Furthermore, the prediction model of maximum wall thinning ratio was established based on the significant process parameters by multiple linear regression method. Compared with the results of orthogonal test, the relative error of that is less than 6.5%, which can be employed for rapidly predicting the wall thinning in tube bending.

Evaluation of Cross-Sectional Deformation in Pipes Using Reflection of Fundamental Guided-Waves

Ultrasonic guided-wave technology has been successfully applied to detect multiple types of defects in pipes. However, cross-sectional deformation, which is a common defect, is less studied when compared with structural discontinuity defects in pipes. In this paper, the guided wave is employed to detect cross-sectional deformation. First, the effect of sectional deformation parameters on the reflection of guided waves is analyzed using a series of three-dimensional (3D) finite-element (FE) models, and the deformation parameters affecting the reflection are examined in light of the physics of the guided waves based on the FE results. The results show that the reflection occurs at the start of the cross-sectional deformation, while the subsequent gradual deformation region does not cause reflection. The reflection coefficient is dependent on the axial deformation severity, and the mode conversion ratio is dependent on the circumferential deformation extent. Second, an experimental study was conducted to evaluate guided-wave reflection characteristics due to pipe cross-sectional deformation in a realistic situation. Test pipes with local and overall deformations were manufactured, and the reflection from both types of deformation was investigated experimentally. The results show good agreement between the experimental measurement and the FE prediction. Two quantitative parameters, axial deformation rate δ and circumferential deformation rate β, are defined to represent the cross-sectional deformation, and are found to correlate well with the reflection coefficient and mode conversion ratio. The ratio of δ/β is suitable to be used to judge the deformation type.

Experimental Study on the Mechanical Characteristics of Saturated Granite under Conventional Triaxial Loading and Unloading Tests

It is essential to study the mechanical properties of saturated rock under different loading and unloading paths for strength calculation, safety assessment and disaster prevention; however, current literature rarely mentions conventional triaxial loading and unloading conditions. To analyze the mechanical properties, strain energy evolution characteristics and failure mode, a series of conventional triaxial unloading tests (with axial loading rate va of 0.06–6 mm/min and circumferential unloading rate vu of 0.1–10 MPa/s) and conventional triaxial compression tests were carried out on saturated granite. The test results showed that the damage sources of specimens in the conventional triaxial unloading test were mainly related to circumferential deformation, while in the conventional triaxial compression test, it was related to the axial deformation. Under the same va, the confining pressure and axial stress at the failure point decreased with the increase of vu, and the stress coordinate of the failure point was located outside the conventional triaxial compression envelope of σ1–σ3. As vu increases, except for the variation of circumferential strain energy ΔUc decreasing slowly, the trend of strain energy changes must be determined together with va. As va increases, the relationship between the magnitude of each energy changes from ΔUa > ΔU > ΔUd > ΔUe > ΔUc to ΔUd > ΔUa > ΔU > ΔUe > ΔUc, while the change of dissipated energy is dominated by vu and va together to become dominated by va. In addition, with the increase of vu and va, the damage pattern of the specimen also changes from shear damage in a single shear plane to mixed damage with tensile strain failure and shear plane during which the dilation angle of the specimen increases in total except for vu = 10 MPa/s, va = 0.6 mm/min and 6 mm/min.

A Miniature Mixing Device for Polymer Blends Dominated by Biaxial Extensional Deformations

AbstractA new miniature mixing device called the “vane mixer” dominated by the synergic action of axial and circumferential extensional deformations is developed for polymer blends. The structure and working principle of the vane mixer are introduced in detail. The effects of mixing time and rotational speed on the morphology, mechanical properties, and crystallization behavior of the high‐density polyethylene (HDPE)/graphene (GR) composites are comprehensively investigated, revealing that properly increasing mixing time and rotational speed can promote the dispersion of GR in the HDPE matrix, improve mechanical properties, and reduce the degree of crystallinity. The morphology of blends prepared by the vane mixer is compared with those prepared by the Brabender mixer to evaluate the mixing performance. The experimental results show that the new equipment has excellent mixing efficiency and performance.

Strain-volume loops for assessment of diastolic function in hypertrophic cardiomyopathy

Abstract Funding Acknowledgements Type of funding sources: None. Background Diastolic function assessment in patients with hypertrophic hearts and preserved ejection fraction (EF) is a rather challenging task, necessitating the introduction of new parameters. Strain-volume loops (SVLs), based on simultaneous frame-by-frame strain and volume changes’ recordings acquired by means of three-dimensional (3D) speckle tracking imaging, is an innovative tool which has been applied in various substrates. The ability of SVLs to assess diastolic function in hypertrophic cardiomyopathy (HCM) has not been investigated until now. Purpose Aim of this study was to investigate potential correlations between SVLs, traditional diastolic function indices and phenotypic features of HCM (thickness, obstruction and fibrosis) that may also reflect myocardial "stiffness". Methods We included 40 HCM patients (54.1 ± 14.3 years, 82.5% male, maximum wall thickness 19.3 ± 4.8mm) who have consecutively undergone 3D-speckle tracking echocardiography (panel A) and cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE). Values of 3D strain were plotted vs. volume for each frame to build an SVL. Peak of radial, longitudinal and circumferential systolic strain (Rsp, Lsp, and Csp, respectively), systolic slopes of the loops (RsSl, LsSl, CsSl), strain to end-diastolic volume (EDV) ratios (Rs/V, Ls/V, Cs/V) as well as the extent of systolic-diastolic uncoupling (difference between systolic and diastolic strain for the same volume) were computed for the analysis. Left atrial volume index (LAVI), E/E’ and tricuspid regurgitation velocity (TRvel) were measured to define diastolic dysfunction (DD) stage. Burden of fibrosis was evaluated by LGE extent in CMR slices. Results All HCM patients had preserved EF (60.5 ± 5,7%), while 16 (40%) had LV outflow tract obstruction (LVOTO > 30 mm Hg at rest). Mean LV mass index was 78.9 ± 14.5 g (evaluated by 3D echocardiography). LGE was observed in 23 patients (57.5%) occupying 5.2 ± 4.5% of LV mass. Concerning SVLs the following values were recorded for radial (Rsp 30.8 ± 9.8%, RsSl 0.4 ± 0.13 and Rs/V 0.25 ± 0.09), longitudinal (Lsp -9.4 ± 3.7%, LsSl 0.12 ± 0.06 and Ls/V 0.08 ± 0.04) and circumferential deformation (Csp -14.2 ± 3.5%, CsSl 0.18 ± 0.05 and Cs/V 0.11 ± 0.03). Traditional isolated diastolic indices (E/E’, LAVI, TRvel and DD stage) did not present significant correlations with SVL parameters or HCM phenotypic features. However, potentially "stiffer" hearts (combination of increased LVMI and fibrosis) presented a leftward transition of longitudinal SVLs, which also became wider (greater uncoupling) (panel B). Conclusions Traditional diastolic indices show modest only correlations with SVLs or HCM phenotypic characteristics, necessitating new approaches to DD of HCM patients. SVLs seem to be a promising-innovative tool for indirect assessment of myocardial "stiffness" and diastolic function. Abstract Figure.