Elastic Slope Research Articles

Effect of Composition Characteristics on Mechanical Properties of UHPMC Based on Response Surface Methodology and Acoustic Emission Monitoring.

Manufactured sand (MS) is a promising alternative aggregate to quartz sand (QS) in ultra-high-performance concrete (UHPC) in the preparation of ultra-high-performance manufactured sand concrete (UHPMC), which possesses the characteristics of high strength, low cost, and environmental friendliness. In this study, the effects of variable compositional characteristics including the water-binder ratio, the stone powder (SP) content, and the MS replacement ratio on the mechanical and flexural strength of UHPMC were compared and analyzed based on response surface methodology (RSM). Meanwhile, the damage characteristics of UHPMC during compressive and flexural stress were monitored and evaluated using acoustic emission (AE) technology. The results reveal that the compressive and flexural strengths of UHPMC are both negatively correlated with the water-binder ratio, while they are positively correlated with the MS replacement rate. They tend to firstly increase and subsequently decrease with the increase in the stone powder content. In the load-displacement curve of concrete with a high MS replacement ratio and a low water-binder ratio, the slope in the elastic stage is steeper, the stiffness is higher, and the bending toughness and ductility are also better. The specimens with a 10% to 0% stone powder content present a steeper elastic phase slope, a slightly higher stiffness, and superior ductility. The specimens with a low MS replacement ratio and a high water-binder ratio display earlier cracking and weaker resistance, and the destruction process is complex and very unstable. The damage mode analysis based on RA-AF shows that an increase in the MS replacement ratio and a decrease in the water-binder ratio can both reduce the tensile cracking of UHPMC specimens under a four-point bending test. Although 10% stone powder can marginally slow down crack growth, the failure mode is not significantly affected.

Optimization technology of hydroelectric power plant unit speed control based on the constriction coefficient-based particle swarm gravitational search algorithm fusion model

In recent years, the integration of wind power into hydropower networks has become a trend. But after wind power is connected to the grid, its unstable power will have an impact on the stability of the power grid. In order to improve the impact of wind power grid connection on the stability of the power supply network, a water motor speed control fusion model considering wind power interference is proposed. Firstly, analyze the impact of wind power grid connection and construct a speed regulation model for grid connected units. Secondly, the gravity search algorithm is introduced to optimize the unit speed control parameters. Considering that the algorithm is prone to local convergence, the convergence factor particle swarm optimization algorithm is adopted to optimize the gravity search algorithm. In addition, considering the impact of wind power interference on unit regulation, the Hopf bifurcation theory is introduced to analyze the dynamic regulation parameter range of hydropower units, in order to meet the requirements of stable operation of the power grid. The research contribution is mainly reflected in suppressing wind power grid connection interference through the speed regulation of hydroelectric units. At the same time, considering the impact of multiple interferences on grid connection, an intelligent model is introduced to optimize the speed control parameters of the unit, thereby improving the stable impact of wind power grid connection on the water conservancy grid. In the simulation analysis of hydroelectric unit speed regulation, after adding 5 % disturbance signal, the proposed model under rigid water hammer disturbance could stabilize the unit's stable control within 15 s, which is superior to other models. In the simulation analysis of speed regulation under wind power disturbance, the proposed model could achieve the fastest and most stable speed regulation under rigid water hammer step wind power disturbance, with a duration of 60 s. The proposed model could respond quickly to small overshoot and overshoot in elastic water hammer slope type wind power disturbances. Therefore, the proposed speed regulation technology for hydropower units has excellent application effects in practical scenarios, which will provide effective technical references for wind power grid connection and hydropower unit regulation.

Method for identifying the main factors controlling landslides based on a particle coupling algorithm simulating the ultimate state of a gas pipeline

To determine the ultimate load of buried gas pipelines under different working conditions under landslide action and provide a quick decision-making tool for landslide risk management, a pipe–soil coupling model is established based on smoothed particle hydrodynamics and the finite element method. The double elastic slope criterion and fault tree analysis method are used to perform limit and failure analyses on the pipelines. The research results indicate that pipeline stress and strain during oblique crossing are positively correlated with the crossing angle. The upper section of the pipeline exhibits tensile bending, whereas the lower section exhibits compressive bending. Local stress is concentrated at the elbows at both ends of the pipeline during longitudinal crossing, which is similar to the force applied during oblique crossing. The ultimate pipeline bearing capacity is negatively correlated with its burial depth and pressure. There is a positive correlation between the distance from the pipeline to the rear edge of the landslide and the width of the landslide. There is also an optimal value for the moisture content of landslides. Fault tree analysis reveals that, to prevent pipeline failure under the action of landslides, priority should be given to determining a reasonable pipeline laying method, reducing the moisture content of the sliding body, controlling the thickness and width of the landslide body, controlling the displacement and inclination angle of the sliding body, timely eliminating soil and soil pressure, and avoiding the failure of drainage systems and support facilities. Based on the research results, we propose a method that can preliminarily identify the main control factors affecting pipeline integrity. This method provides a reference for studying and developing engineering mitigation measures, identification procedures, and operation guidance documents for geological disaster risks for pipelines crossing landslide sections.

Limit load evaluation for healthy elbows and elbows with notch at intrados under in-plane bending moment

Elbows are critical parts of any piping system used in nuclear power plant industry. These elbows experience internal pressure and also undergoes in-plane bending due to external loading. In the present study, limit load for two types of elbows, viz., healthy elbow and elbow having circumferential through-wall notch at intrados, with and without internal pressure subjected to in-plane bending moment is determined. Limit load is dependent on the parameters, namely, thickness, mean radius, bent radius, internal pressure, yield stress, notch size and deformed diameter of the elbow. Based on the experimental and numerical studies, the expressions for limit load evaluation were proposed by various researchers. In the present study, the limit load evaluation expressions proposed by Chattopadhyay and Tomar (2006), Chang-Sik and Kim (2006) and Hong et al. (2010) are considered. The general approach followed is to arrive at a weakening factor for considering the effects of bend geometry, internal pressure and presence of notch. Limit load obtained by using the above expressions have been compared with the twice elastic slope (TES) method and experimental measured maximum load (EMML) values. For elbows without any defect, limit load of TES method are about one-third approximately compared to EMML values. But for elbows with defect, it is lesser than EMML values by 20%. Predicted limit load for healthy elbows with and without internal pressure using the different expressions, found to vary less than 10% compared to TES method. For the elbows with circumferential through-wall crack at intrados without internal pressure, limit load obtained using TES method is around 15% more compared to the values obtained using the expressions.

Abstract 15773: The Forgotten Ventricle: Insight Into Dynamic Effects of Left Ventricular Assist Device Ramp on Right Ventricle Function

Introduction: Left ventricular assist devices (LVAD) with magnetically levitated impellers have become standard due to hemocompatibility and survival profile. To optimize LVAD speeds, we previously introduced simultaneous right and left heart (RH/LH) catheterization during ramp studies. Here, we report pairing of this approach with pressure-volume (PV) assessment in a patient with a HeartMate 3 LVAD with mitral regurgitation (MR). The combined approach evaluated left ventricular (LV) hemodynamics and right ventricular (RV) PV-relationships during ramp testing. Methods: A 68-year-old male with ischemic cardiomyopathy, two years following HeartMate3 implantation, presented with NYHA class III symptoms. To evaluate for dyspnea, he underwent a RH/LH catheterization ramp study. RV PV-loops were created by use of a conductance catheter system, allowing creation of PV loops. Results: At the baseline LVAD speed of 5300 rotations per minute (RPM), right atrial pressure was elevated at 16 mmHg and pulmonary artery (PA) pressure of 26 mmHg. Left-end diastolic pressure (LVEDP) was elevated (16mmHg). Baseline cardiac index (CI) was 2.01 L/min/m 2 . Ramp testing was performed, increasing speeds from 5300 to 5800 RPM. Progressive LV unloading was observed with a 5 mmHg drop in LVEDP and a 3 mmHg drop in PA pressure. However, RV PV loop monitoring revealed a negative impact on RV contractility with the maximal elastance (Emax) slope demonstrating a 22% reduction. Furthermore, a 17% reduction in RV stroke volume was documented, while diastolic function remained unchanged. Thus, despite excellent LV offloading and diminishment of RV afterload, the significant negative impact on Emax resulted in no net increase in CI (+0.04 L/min/m 2 ) during the ramp evaluation. Inotrope therapy was initiated for RV function with increased LVAD RPM to outcompete MR. Conclusions: While RH/LH catheterization provides a real-time perspective of the interventricular relationship during ramp, the impact of increasing LVAD speeds on RV function has yet to be directly measured. Here, the RV PV loop relationship during LVAD ramp showed that although LVAD speed increases in the setting of MR may facilitate LV unloading, a drop in RV afterload did not compensate for reduction in RV contractility.

An Improved Correlation for the Estimation of the Yield Strength from Small Punch Testing

This study aims at improving the empirical correlation for estimating the yield strength from small punch tests. The currently used procedure in the European standard EN 10371 to determine the elastic–plastic transition force—based on bi-linear fitting—involves a dependency not only on the onset of plastic flow but also on the work hardening of the material. Consequently, the yield strength correlation factor is not universal but depends on the material properties and on the geometry of the small punch set-up, leading to a significant uncertainty in the yield strength estimation. In this study, an alternative definition of the elastic–plastic transition force is proposed, which depends significantly less on the work hardening of the material and on the small punch geometry. The approach is based on extensive elastic–plastic finite element simulations with generic material properties, including a systematic variation of the yield strength, ultimate tensile strength, and uniform elongation. The new definition of the transition force is based on the deviation of the force-deflection curve from the analytical elastic slope derived by Reissner’s plate theory. A significant reduction of the uncertainty of the yield strength estimation is demonstrated.

Elastic Adaptively Parametric Compounded Units for Convolutional Neural Network

The activation function introduces nonlinearity into convolutional neural network, which greatly promotes the development of computer vision tasks. This paper proposes elastic adaptively parametric compounded units to improve the performance of convolutional neural networks for image recognition. The activation function takes the structural advantages of two mainstream functions as the function’s fundamental architecture. The SENet model is embedded in the proposed activation function to adaptively recalibrate the feature mapping weight in each channel, thereby enhancing the fitting capability of the activation function. In addition, the function has an elastic slope in the positive input region by simulating random noise to improve the generalization capability of neural networks. To prevent the generated noise from producing overly large variations during training, a special protection mechanism is adopted. In order to verify the effectiveness of the activation function, this paper uses CIFAR-10 and CIFAR-100 image datasets to conduct comparative experiments of the activation function under the exact same model. Experimental results show that the proposed activation function showed superior performance beyond other functions.

A 1D Spring-Slider Model with a Simple Poly-Linear Failure Law Produces Rich Variations in Slip Behavior

ABSTRACT The failure law prescribed along the fault surface and the elastic stiffness of the surrounding medium play important roles in determining the characteristics of earthquakes. Here we use a 1D spring-slider model that includes inertia, along with a simple poly-linear failure law composed of multiple linear segments to provide insight into earthquake initiation and growth. The poly-linear failure law, which parameterizes shear resistance as a function of slip, allows analytical solutions describing the system for each failure law segment. Analytical solutions facilitate investigation of the effects of the slopes of the different failure law segments in relation to the slope of the elastic loading curve determined by the spring stiffness. Depending on the relation between the slope of the failure law segment and the elastic loading slope, there are three stability regimes in the system: harmonic oscillations, exponential growth, and cubic growth. By combining the different solution regimes within one earthquake cycle, we observe a wide range of behaviors of this simple system: interseismic oscillatory creep, precursory signals before the main event, a shorter or a much longer acceleration phase before the onset of instability, and varying durations of the preseismic and coseismic phases. These results provide a potential explanation for some seismic observations, including increased levels of “seismic noise” prior to an earthquake, precursory events, tremor and low-frequency earthquakes.

A New High‐Speed Biaxial Testing System for Rodent Myocardium Viscoelastic Measurement under Dynamic Loadings

IntroductionMyocardium stiffening is well known in heart failure (HF) development, and it contributes to cardiac dysfunction. Myocardium is viscoelastic, which means that both elastic and viscous resistance exist under dynamic loading. There are limited studies of myocardium viscoelasticity, particularly for the right ventricle (RV). Because viscoelasticity is a time‐ and strain‐dependent mechanical behavior, the measurement at physiological rates & non‐linear deformation is critical. This study aims to develop a high‐speed biaxial tester that induces physiological deformation to characterize RV viscoelasticity in rats.MethodsTo enable the viscoelasticity measurement at physiological conditions, we built a biaxial tester that induces non‐linear, cyclic stretch of myocardium at rodent heart rates. Biaxial sinusoidal stretches were induced by actuators (1400mm/s) (Zaber), forces were recorded by load cells (Honeywell) at 1 kHz, and strains were obtained by a high‐speed camera (Baumer) at up to 200 fps. The LabVIEW and MATLAB codes were developed for performing biaxial tests at various frequencies with synchronized force and image data acquisition. To validate the biaxial tester, isotropic polydimethylsiloxane (PDMS) was used due to its similar viscoelasticity to cardiovascular tissues. PDMS sheets were prepared (Sylgard 184) for equibiaxial tests. Then, consistency between different axes’ measurements, synchronization of the axes’ movement, and accurate viscoelastic measurement were evaluated. Next, we performed equibiaxial cyclic sinusoidal tests on healthy rat RVs. After euthanasia, RV free wall was dissected and mounted. The outflow track direction was defined as the longitudinal direction. The RV was placed in a relaxant solution prior to testing, then preloaded by ~0.1 N and preconditioned by 15 cycles. Stress‐strain loops were derived for viscoelastic analysis.ResultsFirst, we examined if the biaxial tester could achieve planar biaxial tests at desired frequencies. The equibiaxial data obtained from PDMS sheets showed that the tester induced cyclic sinusoidal stretch at various frequencies up to 8 Hz (Fig. 1a), and the viscoelastic behavior measured at two axes were very close (Fig. 1b), thus confirming the tester’s accurate biaxial measurement of the isotropic material. The PDMS clearly showed frequency‐dependent changes in the hysteresis loops (Fig. 1c), with trends of increasing elasticity (slope of loop) and viscosity (area of loop) at higher frequencies. We further derived the viscosity by measuring Tan(δ) (Fig. 1d). The frequency‐dependent elasticity and viscosity of the PDMS sheet were consistent with literature data. Next, we obtained preliminary viscoelasticity data of healthy rat RVs (at 0.1‐2 Hz). Our data showed strain‐rate dependent changes in the hysteresis loops (Fig. 2). The dissipated energy (loop area) as well as the stiffness (loop slope) of the RV tended to increase with increasing frequency. The RV tissue showed similar viscoelastic behavior in both directions at all frequencies.ConclusionOur data showed that this novel testing system enables biaxial viscoelastic measurement of myocardium under physiological conditions (0.1‐8Hz) across small and large animal species. The establishment of this system allows further exploration of RV tissues at higher frequencies (5‐8 Hz) and in diseased states, which will improve the understanding of cardiac biomechanics in HF progression.

Investigation on structural integrity of shape distorted 90° back-to-back pipe bends under in-plane closing bending moment

PurposeThe aim of this study is to ensure the structural integrity of 90° back-to-back (B2B) pipe bends by developing a closed-form numerical solution for estimating the collapse load of shape distorted 90° B2B pipe bends using non-linear finite element (FE) analysis.Design/methodology/approachThe collapse behaviour of 90° B2B pipe bends with ovality (Co) and thinning (Ct) has been evaluated by non-linear FE approach. Moment load is applied in the form of in-plane closing moment (IPCM). The current FE approach was evaluated by the numerical solution for the plastic collapse moment of pipe bends, which has been published in the literature. The collapse moments were obtained from the twice elastic slope (TES) method using the moment-rotation curve of every individual model.FindingsThe implication of Ct/Cth on collapse load is found to be highly insignificant in terms of increasing bend radius and Co. Co weakens the geometry, and its effect on the collapse load is substantial. A closed-form numerical solution has been proposed to calculate the collapse load of 90° B2B pipe bend with shape imperfections.Originality/valueThe implications of shape distortion (Co and Ct) in the failure analysis (collapse load) of 90° B2B pipe bends has not been investigated and reported.

Underwater strengthening and repairing of tubular offshore structural members using Carbon Fibre Reinforced Polymers with different consolidation methods

Offshore structural steel members will need strengthening or repairing due to various reasons. Strengthening is often required due to work over demands or increased environmental loads. Repairing becomes essential as the steel members are usually severely corroded due to the marine conditions. Conventional hot work strengthening and repairing solutions become very expensive and retrofitting using Fibre Reinforced Polymers (FRPs) is an economical alternative. This paper investigates strengthening and repairing of offshore steel tubular members using Carbon Fibre Reinforced Polymers (CFRPs) with the help of experimental testing and an analytical study. Two different specimen sizes which were representative of members in offshore structures namely leg and brace were examined in the study. Partial length strengthening of steel tubular members subject to combined loading of axial compression and bending was carried out using different curing environments (in air and underwater curing). Strengthening and repairing of leg and brace specimens with multiple layers of CFRP retrofitted in underwater conditions were also investigated. Two different consolidation methods (underwater vacuum consolidation and underwater stricture consolidation) were compared with the help of full length strengthening of leg specimens. Although partial length strengthening proved to be less effective, partial length repairing of corroded tubular members were successful in restoring their intact capacity. Full length strengthening for underwater leg specimens were experimentally tested and it was found to improve the structural behaviour in many aspects like ultimate strength, load displacement behaviour, elastic slope, energy absorption, and ductility. A novel technique of underwater vacuum consolidation of retrofit laminates was demonstrated through a set of full length strengthened leg specimens. Underwater vacuum consolidation proved to be advantageous compared to the normal underwater stricture consolidation. An analytical check to identify whether a retrofitted tubular member would reach its target section properties was also introduced. Overall, the paper demonstrates multiple successful applications of FRP composites for underwater strengthening and repairing of offshore steel tubular members. Studies like this expanding the current knowledge on how the FRP retrofitted steel tubular behave within a real offshore structure are essential to increase the uptake of this technology in the oil and gas industry.

Determination of temperature dependent static Young's modulus of refractory ceramics using RUL tests

AbstractRefractory linings are, in addition to loads due to corrosion and creep processes, particularly affected by thermomechanical stresses caused by the restricted thermal expansion of the lining. These stresses can occur within individual components as well as in bricks and can lead to plastic deformation, cracks, and material failure. Thus, comprehensive knowledge about thermomechanical behavior is mandatory for an accurate prediction of occurring stresses to design load‐optimized linings. This paper presents a method for utilizing refractoriness under load (RUL) tests to determine a temperature dependent static Young's modulus for refractories. In a first step, RUL tests with a negligible load are carried out in order to determine the materials temperature dependent thermal expansion coefficient. Afterwards, several RUL tests with higher loads are carried out. The measured data of change in temperature and length are then corrected by the thermal expansion and used to construct elastic lines for several temperatures, where the elastic slope is determined using the change in length and the respective load. Thus, Young's modulus for several temperatures can be determined. The obtained values for the Young's modulus are then compared to resonant frequency damping analysis measurements and validated using a finite element (FE) model of the RUL test.

Effect of welded joint imperfection on the load-carrying capacity of pipe elbows subjected to in – plane bending moment

The defects in pipe elbows can, depending on their size and position, affect the integrity and safe service, as well as deformation ability of the piping systems in exploitation. Incompletely filled groove, which is the type of defect examined here, was observed by ultrasonic measurement on the pipeline in the regulation system of the hydro power plant Djerdap. Three-dimensional finite element analysis is performed using Simulia Abaqus software package. First, the models with dimensions of the defects observed by non-destructive examination are formed. Stress and strain fields for different loading types are shown and commented. The influence of the defect dimensions on the pipe elbow load-carrying capacity is determined through plastic collapse loads, which are obtained from bending moment - rotation angle diagrams. Twice elastic slope (TES) technique is applied. Additionally, some more severe defects are considered, in the form of sharp pre-cracks at the bottom of the defect; plastic collapse loads are also determined for these geometries. Both opening and closing bending moments are taken into consideration and the results are discussed and compared to two closed-form solutions from the literature. The influence of the boundary conditions applied for examination of the pipe elbows is commented.

Efficacy of shear wave elastography for assessment of liver function in patients with heart failure.

AimsLiver dysfunction is important for prognosis in heart failure (HF). Shear wave elastography (SWE), which is a novel ultrasound technique for charactering tissues, has been used in liver diseases. However, clinical implication of SWE, including dispersion slope, remains unknown in heart diseases. This study aimed to evaluate the efficacy of SWE assessing liver function in the severity of HF.Methods and resultsWe enrolled 316 consecutive patients with or suspected heart diseases, who were classified according to the American College of Cardiology Foundation/American Heart Association stage of HF, including 37 with Stage A, 139 with Stage B, 114 with Stage C, and 26 with Stage D, and 45 normal subjects. Elasticity and dispersion slope of shear wave were assessed according to the HF stage. Elasticity and dispersion slope were not elevated in normal subjects and patients with Stage A. Elasticity was slightly increased from Stage A to Stage C and was remarkably elevated in Stage D (normal: 5.2 ± 1.1 kPa, Stage A: 5.4 ± 1.2 kPa, Stage B: 6.4 ± 1.8 kPa, Stage C: 7.8 ± 3.5 kPa, and Stage D: 17.7 ± 12.7 kPa), whereas dispersion slope was gradually increased from Stage A to Stage D (normal: 9.7 ± 1.7m/s/kHz, Stage A: 10.4 ± 1.6m/s/kHz, Stage B: 11.7 ± 2.4m/s/kHz, Stage C: 13.2 ± 3.4m/s/kHz, and Stage D: 17.6 ± 5.6 m/s/kHz). In the early HF stage, dispersion slope was elevated. In the advanced HF stage, both elasticity and dispersion slope were elevated. Liver function test abnormalities were observed only from Stage C or Stage D.ConclusionsDispersion slope could detect early liver damage, and the combination of elasticity and dispersion slope could clarify the progression of liver dysfunction in HF. SWE may be valuable to manage therapeutic strategies in patients with HF.

An initial trial of quantitative evaluation of autoimmune pancreatitis using shear wave elastography and shear wave dispersion in transabdominal ultrasound

Background/ObjectivesWe aimed to examine therapeutic efficacy and prognosis prediction of autoimmune pancreatitis (AIP) using shear wave elastography (SWE) and shear wave dispersion (SWD) in transabdominal ultrasound (US). MethodsThe subjects were 23 patients with diffuse type 1 AIP who underwent SWE and SWD, and 34 controls with a normal pancreas. Elasticity and dispersion were defined as the pancreatic elastic modulus (PEM) and dispersion slope, respectively. PEM and dispersion slope were compared between AIP and control cases, and the short-term therapeutic effect and long-term prognosis were examined. ResultsPEM (30.9 vs. 6.6 kPa, P < 0.001) and dispersion slope (15.3 vs. 13.0 (m/sec)/kHz, P = 0.011) were significantly higher in AIP cases than in controls. Among the 17 AIP patients followed-up in two weeks after treatment, these parameters were 12.7 kPa and 10.5 (m/sec)/kHz with median decrease rate of 37.2% and 32.8%, respectively, which were significantly higher than the change in the size of pancreatic parenchyma (14.4%, P = 0.026). Fourteen of these subjects were followed up for >12 months, during which 2 had relapse; diabetes improved in 5 and worsened in 2; in 60% of cases, the pancreatic parenchyma was atrophied. The % change in PEM after two weeks was tended to be higher in non-atrophy cases. ConclusionSWE and SWD measurement in US may be useful for quantitative assessment of AIP and evaluation of short-term treatment efficacy.

Efficacy of shear wave elastography for evaluating right ventricular myocardial fibrosis in monocrotaline-induced pulmonary hypertension rats

BackgroundRight ventricular (RV) function is important for outcomes in pulmonary hypertension. Evaluation of RV myocardial characteristics is useful to assess the disease severity. Shear wave elastography (SWE) provides information of shear wave (SW) elasticity, which is related to tissue hardness, and SW dispersion slope, which reflects tissue viscosity. This study aimed to test the hypothesis that SW elasticity is increased and SW dispersion slope is decreased in the right ventricle of monocrotaline (MCT)-induced pulmonary hypertension rats. MethodsRats were divided into MCT-induced pulmonary hypertension group (n = 10) and control group (n = 10). SW elasticity and SW dispersion slope were measured on excised hearts. Myocardial fibrosis was evaluated histologically. ResultsRV hypertrophy was observed in the MCT group. SW elasticity of right ventricle was higher in the MCT group than in the control group (3.5 ± 0.9 kPa vs. 2.5 ± 0.4 kPa, p < 0.01). SW dispersion slope of right ventricle was lower in the MCT group than in the control group (5.3 ± 1.7 m/s/kHz vs. 7.7 ± 1.5 m/s/kHz, p < 0.01). The fibrosis area of right ventricle was increased in MCT group compared with control group (18 ± 5% vs. 8 ± 3%, p < 0.01), and was positively related to SW elasticity and negatively related to SW dispersion slope. ConclusionsHigher SW elasticity and lower SW dispersion slope were observed in the fibrotic myocardium of right ventricle in MCT-induced pulmonary hypertension rats. SWE may have the potential to evaluate RV function by assessing myocardial characteristics.

Stability, Stress and Strain Analysis of Very Slender Pinned Thin-Walled Box Columns according to FEM, Euler and TSTh

In this study, a Finite Element Method (FEM) analysis is presented for the loss of stability in elastic states of very slender pinned without friction box-section thin-walled column axially compressed. From the FEM buckling linear stress analyses are determined the compressing critical forces for 36 cases, presented in tables and as the surface functions in dependence on the slenderness ratio and cross-section. Also are presented graphs obtained from the FEM post-buckling linear stress analysis for the elastic central line, slope, deflection and states of the stresses and strains of the box-section column 20×28×1×2500 mm made of steel, by the assumption that a maximal deflection equals the half of a side dimension. The obtained from the FEM computing function and surface graphs are compared and then discussed with graphs corresponding to Euler’s and Technical Stability Theory (TSTh) results. Finally are compared graphs of the stresses and strains of box-section thin-walled column 20×28×1×2500 obtained from FEM and TSTh, but under compressing critical force determined according to TSTh.

Experimental and Numerical Analysis of the Mechanical Properties of a Pretreated Shape Memory Alloy Wire in a Self-Centering Steel Brace

As a stimulus-sensitive material, the difference in composition, fabrication process, and influencing factors will have a great effect on the mechanical properties of a superelastic Ni-Ti shape memory alloy (SMA) wire, so the seismic performance of the self-centering steel brace with SMA wires may not be accurately obtained. In this paper, the cyclic tensile tests of a kind of SMA wire with a 1 mm diameter and special element composition were tested under multi-working conditions, which were pretreated by first tensioning to the 0.06 strain amplitude for 40 cycles, so the mechanical properties of the pretreated SMA wires can be simulated in detail. The accuracy of the numerical results with the improved model of Graesser’s theory was verified by a comparison to the experimental results. The experimental results show that the number of cycles has no significant effect on the mechanical properties of SMA wires after a certain number of cyclic tensile training. With the loading rate increasing, the pinch effect of the hysteresis curves will be enlarged, while the effective elastic modulus and slope of the transformation stresses in the process of loading and unloading are also increased, and the maximum energy dissipation capacity of the SMA wires appears at a loading rate of 0.675 mm/s. Moreover, with the initial strain increasing, the slope of the transformation stresses in the process of loading is increased, while the effective elastic modulus and slope of the transformation stresses in the process of unloading are decreased, and the maximum energy dissipation capacity appears at the initial strain of 0.0075. In addition, a good agreement between the test and numerical results is obtained by comparing with the hysteresis curves and energy dissipation values, so the numerical model is useful to predict the stress–strain relations at different stages. The test and numerical results will also provide a basis for the design of corresponding self-centering steel dampers.

Influence of structural distortion and bend angle on the collapse load of non-pressurized pipe bends under in-plane closing and opening moments

This research quantifies the implications of structural distortions and bend angle on the collapse load of non-pressurized different bend angle pipe bends. The analysis was carried out for two loading cases namely pipe bends subjected to in-plane closing bending (IPCB) and in-plane opening bending (IPOB). The method used was a three-dimensional (3D) non-linear finite element analysis with a large strain formulation. The chosen material was considered to be Elastic-perfectly plastic (EPP). Bend angle was varied from 30° to 90° with an increment of 30° while structural distortion (ovality) was varied from 0 to 15% at a span of 5%. The twice elastic slope (TES) method was adopted to determine the collapse load of all the considered pipe bend models from their rotation-moment curves. The results show that ovality impact decreased with an increase in the bend angle. When comparing pipe bends with smaller bend radii and smaller bend angles with those having larger bend radii, massive ovality impact was observed. This effect was found to be greater in IPCB compared to IPOB.

Ultimate bearing capacities of large diameter pipeline elbows with ellipsoidal pits

Defects significantly affect the carrying capacity of pipe elbows. Accurately estimating the capacity permits fewer pipe inspections and replacements, saving time and reducing costs. To study the effect of defects, a 90° pipe elbow model with a 1016 mm-diameter and 19.9 mm wall thickness was built. The material is API X80 steel and the curvature radius is 6D. The plastic failure criterion and twice elastic slope method were adopted to determine the limit internal pressure load. Using the commercial finite element software, Abaqus, the influences of defect location, defect depth, defect length, defect width and pipe wall thickness on the ultimate bearing capacity of an pipe elbow with ellipsoidal pits was studied. Through multiple nonlinear regression analysis and nonlinear fitting, formulas for calculating the ultimate internal pressure load of large-diameter elbows with defects under various influencing factors were obtained. The formulas can provide guidance and reference for evaluating the residual strength of large-diameter elbows with defects.