Deformation Hysteresis Research Articles

Influence of aggregate content and strain rate on dynamic behaviour and energy consumption characteristics of concrete

Concrete's dynamic performance and energy dissipation are critical areas of interest that are significantly influenced by strain rate and aggregate content. This study investigated concrete's dynamic deformation, strength development and energy dissipation characteristics from specimens containing 0, 32%, 37% and 42% aggregate. These specimens were subjected to impact compression tests using a split Hopkinson compression apparatus, which allowed the effects of strain rate and aggregate content on the deformation, strength and energy dissipation of the concrete to be analysed. The results show that the concrete exhibits deformation hysteresis under impact loading, with splitting tensile failure as the predominant damage mechanism. Dynamic strength was more sensitive to strain rate than aggregate content. The dynamic increase factor (DIF) varied with aggregate content at different strain rates. The extent of specimen damage significantly influenced the energy distribution ratio, with absorbed energy showing a more pronounced strain rate effect than transmitted and reflected energy. Conversely, the amount of transmitted energy had a more pronounced impact on aggregate content than the amount of absorbed and reflected energy.

Numerical simulation of deformation hysteresis effect of the bristles of brush seals

Because of their good sealing performance, brush seals are used widely in turbomachinery as alternatives to traditional labyrinth seals. However, obstructed by friction, the flexible bristles cannot recover fully after deformation, resulting in a hysteresis effect and decreased sealing performance. In the present study, a three-dimensional multi-row bristle model is established that considers the friction between the neighbouring bristles and back plate. Then the deformation and recovery of the bristles during the radial reciprocating offset of the rotor in the presence of a pressure difference are studied. To evaluate the hysteresis effect, analysis is directed at the unrecovered bristle deformation in the radial direction affected by bristle diameter, bristle lay angle, fence height and width of pressure relief chamber. The results show that the larger the bristle diameter and fence height, the weaker the hysteresis effect and the larger the bristle lay angle, the stronger the hysteresis effect. With increasing width of the pressure relief chamber, the hysteresis effect weakens and then strengthens, meaning that the pressure relief chamber has an optimal axial width that departure from enhances the hysteresis effect. The present results offer a reference for selecting the structural parameters of brush seals in engineering design.

Cross-scale static/dynamic shear damage evolution mechanism of 2D C/SiC ceramic matrix composite with transient hysteresis effect

The intricate woven structure of two-dimensional woven carbon fiber-reinforced silicon carbide (2D C/SiC) poses challenges to the investigation of damage failure mechanisms and the prediction of material performance, thereby limiting its further application in aerospace engineering. In this work, static/dynamic short beam shear tests with different densities of 2D C/SiC were carried out. It was observed that high-density specimens with fewer microporous defects exhibited better strength characteristics than those with lower density. Specifically, the shear strength of 2D C/SiC with a density of 2.07 g/cm³ increased by 18.6% compared to that of the specimen with a density of 1.94 g/cm³. The transient hysteresis strengthening effect of materials at high strain rates was discovered through cross scale research methods. It was found that deformation coordination ability of 2D C/SiC under dynamic loading was weaker than that under quasi-static conditions. Moreover, the deformation hysteresis in temporal and spatial distributions induced significant fiber plucking, further accelerating dislocation movement within the internal lattice and thereby enhancing strength of the material. The failure path of materials often follows the direction of pore defects, and stress concentration leads to cracking behavior of fiber bundles. Furthermore, microcracks within the matrix, caused by residual stress, resulted in localized regions of reduced strength. This induced the matrix cracking failure with further crack expansion within the material structure under external loads. To provide technical references for practical engineering applications and design, a realistic and effective finite element prediction model was developed for 2D C/SiC composites based on their structural characteristics.

Experimental investigations of beam-column joints with replaceable BRFCPs using sliding restraint plates

This paper proposes a replaceable buckling-restrained flange cover plate (BRFCP) for steel beam-column joints with cantilever beam segments, in which a sliding restraint plate (SRP) with slotted holes is used to constrain the core plate buckling deformation and simultaneously control the restraint plate without significant damage. First, theoretical analyses and design considerations were presented for this joint. Second, cyclic loading tests were conducted on five joints with different BRFCP configurations, including different formats of restraint plates (discontinued or sliding restraint plates), filling plates (discontinued or sliding filling plates), and restraining gaps with different sizes. The test results showed that the damage of the proposed joint was visually observed only on the replaceable core plates and was not observed at any other structural components. The SRP can effectively constrain the buckling deformation of the core plate in comparison to the discontinued restraint plates; thus, the proposed joint showed more stable force–deformation hysteresis. The continuity of the filling plates and the restraining gap size had little influence on the overall hysteretic response of the joint. However, a larger restraining gap caused larger stress in the restraint plates. Finally, numerical models of the test joints were established in ABAQUS and validated by the test results, which can serve as a reference for further research.

Dynamic Response of Infinite Beam Resting on a Fractional Pasternak Viscoelastic Foundation Subjected to Moving Load

In this paper, the dynamic response of an infinite Euler beam that was mounted on a fractional-order Pasternak viscoelastic foundation subjected to a moving point load was investigated. An analytical solution to the problem was derived using Fourier and Laplace transforms. Numerical results obtained by numerical Laplace inversion were analyzed to explore the impact of various parameters on the system’s response. The findings indicated that increasing system damping led to a decrease in maximum deflection and a more visible deformation hysteresis with an increase in fractional derivative orders. Additionally, all parameters of the foundation and shear layer were observed to have a significant effect on the deflection. The study confirmed that the fractional-order model predicted damping and dynamic deflection more accurately than the conventional integer-order foundation model. The research contributed to the understanding of the behavior of Euler beams mounted on viscoelastic foundations and provided valuable insights into the design of such systems.

A deep ensemble learning-driven method for the intelligent construction of structural hysteresis models

Accurate force–deformation hysteretic models for structures, components, and materials are essential for structural analysis. The development of an explicit mathematical model for hysteresis poses challenges in the fields of artificial model selection and precise and efficient calibration of key parameters. In recent years, deep learning-based implicit hysteresis model construction methods have been widely recognized. However, such methods exhibit instability and lack of generalization. By combining deep neural network feature extraction with physics-based explicit hysteresis models, it is possible to efficiently construct an accurate and stable force–deformation hysteresis model purely based on test data. Therefore, in this study, a sensitivity-guided long short-term memory neural networks (LSTM) method is proposed to extract the features of structural behaviors and predict the key parameters of explicit hysteresis models accurately and efficiently. Furthermore, an adaptive ensemble learning method based on multiple explicit hysteresis models is proposed to improve the generalization ability. Case studies on test results demonstrate that this method can accurately predict structural behaviors, which is more efficient than manual construction and has better generalization ability than classical data-driven hysteresis models.

Effect of hydraulic fracture deformation hysteresis on CO2 huff-n-puff performance in shale gas reservoirs

Effect of hydraulic fracture deformation hysteresis on CO2 huff-n-puff performance in shale gas reservoirs

Experimental investigation of a low‐prestressed self‐centering energy dissipative brace

AbstractSelf‐centering energy dissipative (SCED) braces have the potential to contribute greatly to building resiliency, because the braces can limit both maximum and residual story drifts during earthquakes. An obstacle to widespread adoption of existing SCED systems is that they require high prestressing forces, corresponding to more than half of the brace yield strength. To address this problem, a new low‐prestressed SCED (LP‐SCED) system has been proposed, which has a flag‐shaped force–deformation hysteresis but needs only a low level of prestressing force. This paper presents the results of an experimental investigation to establish the properties of the new system's key components, as well as prototypes of the full brace specimen. The tested system had a prestressing force equal to only 3∼4% of the brace yield force. The tested systems had a stable, flag‐shaped force–deformation hysteresis relationship, even after being subjected to deformations corresponding to 3.4% story drift. Eventually, when the imposed deformations were sufficiently large, the brace stiffness increased dramatically, which helps to reduce drift concentrations that may be critical in braced‐frame structures under extreme earthquakes. The yielding and damage were restricted to the mild‐steel dissipaters, which could be replaced easily after each test, and in practice, they could be replaced easily after an earthquake.

Effect of cold rolling degree on texture evolution, eccentricity, and yielding anisotropy of GH4145 alloy tubes

The effects of the area reductions on the crystal orientation, eccentricity, and mechanical properties of GH4145 alloy tubes prepared by three-roller cold rolling were studied. Electron backscattered diffraction analysis showed that the equiaxed grains of the annealed tube blank gradually changed into elongated crystals along the axial direction (AD) with increased deformation. In addition, the grain orientations rotated from random distribution towards the <101>//radial direction (RD), <111>//AD, and <101> + <111>//tangential direction (TD). Brass, copper, S, and {123}<111‾ > textures formed and increased in strength with increasing strain. Room-temperature tensile tests loaded along the AD and TD demonstrated yielding anisotropy of the tubes. With increasing strain, the work hardening increased continuously, and the dislocations slipped in three directions and then transformed into slip bands and dislocation cells, whereas a few deformation twins formed as the reduction reached 64%, and then slipped in two directions. When the reduction was 64%, the activated slip system transformed from {111}<110> to {110}<001> in most grains under applied AD loading, which was consistent with the loading in both directions at a reduction of 72%. As the grains in the preferential deformation zone near the inner and outer walls rotated to the <101>//RD orientation, the tubes plastically deformed, and the grains in the central layer then gradually begin to rotate. The ratio of radial length in the deformation hysteresis zone to wall thickness was used to represent the degree of non-uniformity of the deformation. A direct correlation was found between the eccentricity of the wall thickness and the non-uniformity of tube deformation as the area reduction increased from 13% to 50%. In addition, the radial delamination of the tubes disappeared, deformation became uniform, and the eccentricity decreased significantly as the area reduction increase up to 64%. Therefore, the dimensional accuracy and uniformity of the tubes can be further improved by controlling the strain of the tube.

Formation of structure of TiNiCu alloys with high copper content upon producing by planar flow casting

The rapidly quenched alloys of the quasibinary intermetallic TiNi-TiCu system with a high copper content (more than 25 at.%) are of great interest as shape memory materials due to the possibility of a significant decrease in the temperature and deformation hysteresis in comparison with the binary TiNi alloy. To obtain alloys with a copper content of 25 to 40 at.%, the planar flow casting technique was used. The alloys were fabricated at a melt cooling rate of about 106 K/s in the form of ribbons 30-50 μm thick and wide in the range from 7 to 20 mm. The study of the structure of the alloys was carried out using X-ray diffraction analysis, scanning and transmission electron microscopy. It was shown that from the ribbon side, contacting the quenching wheel, all alloys are amorphous, while on the non-contact side of the ribbons of alloys with 25 and 30 at.% Cu, a thin surface crystalline layer with a B2 structure is observed. Using energy dispersive X-ray spectroscopy, it was found that the content of the alloy components in the amorphous and crystalline phases coincides.

PSO-SVM-based deep displacement prediction of Majiagou landslide considering the deformation hysteresis effect

The accuracy of landslide displacement prediction can effectively prevent casualties and economic losses. To achieve accurate prediction of the Majiagou landslide displacement in the Three Gorges Reservoir (TGR), China, a hybrid machine learning prediction model considering the deformation hysteresis effect is proposed. The real-time deep displacement measurements were captured by using in-place inclinometers with Fiber Bragg grating (FBG) sensors. The time series method was adopted to divide the total displacement into a trend term and periodic term. Trend displacement was determined by the geological condition and predicted by the fitting method. Periodic displacement was controlled by external factors such as rainfall and fluctuation of reservoir water level. Before making the prediction, the grey correlation analysis was adopted to confirm that the fluctuation of the reservoir water level was the main influence factor. In view of the deficiency that current prediction methods could not quantitatively determine the lag time of landslide deformation and thus select the influencing factors empirically, the dynamic analysis of the correlation between periodic influence factors and periodic displacement was carried out in this paper, and the deformation lag time was identified to be 18 days by using set pair analysis (SPA) method. Finally, the optimal influence factors were selected and the prediction model of Majiagou landslide based on support vector machine optimized by particle swarm optimization (SPA-PSO-SVM) was established. Results showed that the root mean square error (RMSE) and the mean absolute percentage error (MAPE) of the proposed SPA-PSO-SVM prediction model are 0.28 and 12.8, respectively. Compared with the PSO-SVM model, the prediction accuracy of the proposed model had been improved significantly. The reliability and effectiveness of the SPA-PSO-SVM prediction model is verified and it has apparent advantages while predicting landslide displacement with deformation hysteresis effect involved.

Mechanistic study of cyclic water injection to enhance oil recovery in tight reservoirs with fracture deformation hysteresis

As an effective enhanced oil recovery (EOR) technique in tight reservoirs, cyclic water injection has been extensively studied recently. However, very few studies have considered the impacts of loading-path dependent fracture deformation, i.e. deformation hysteresis. In this study, an efficient coupled two-phase flow and geomechanics model is developed to simulate cyclic water injection in a tight oil reservoir with the consideration of fracture deformation hysteresis. The embedded discrete fracture model (EDFM) is applied to handle complex fracture geometries. Different loading-path dependent constitutive models are used to describe the deformations of hydraulic fractures and natural fractures, respectively. Then simulation studies are performed to demonstrate the impacts of deformation hysteresis of hydraulic fractures and natural fractures on EOR performance. The sensitivities to injection rate, depletion pressure and soaking time are examined. The results show that the deformation hysteresis of hydraulic fracture has significant effect on oil production, while that of natural fracture has negligible impact. The effects of fracture deformation hysteresis are more pronounced under high injection rate and depletion pressure, but less sensitive to soaking time.

Bounding surface constitutive model for unsaturated soils considering microscopic pore structure and bonding effect

This article presents a bounding surface model for unsaturated soils by using skeleton stress and bonding variable based on microcosmic pore structure as constitutive variables. A Hydraulic hysteresis soil-water characteristic curve model considering deformation and hydraulic hysteresis is combined to achieve hydraulic coupling. The proposed model can capture the change of the inter-particles bonding effect in the deformation process of unsaturated soils and accurately predict the hydraulic mechanical behavior of unsaturated soils under complicated loading paths and wetting-drying cycles. The validity of the proposed model is confirmed by the results of unsaturated isotropic compression tests, wetting-drying cycles tests and unsaturated triaxial shear tests reported in the literature.

Deformation hysteresis of a water nano-droplet in an electric field.

Electric field is an effective method to manipulate droplets in micro/nano-scale, and various physical phenomena have been found due to the interaction of electric field and fluid flow. In this study, we developed a molecular dynamic model to investigate the deforming behavior of a nano-droplet in a uniform electric field. The nano-droplet was initially confined between two plates and then wetted on the lower plate (i.e., substrate) until an equilibrium state, after that a uniform electric field in vertical direction was imposed to the system. Due to the electrical force, the droplet started to deform until achieving a new equilibrium state and the dynamic process is recorded. By comparing the equilibrium state under different electric field strength, we found a deformation hysteresis phenomenon, i.e., different deformations were obtained when increasing and decreasing the electric field. To be specific, a large electric field (E = 0.57 V ·nm^-1) is needed to stretch the nano-droplet to touch the upper plate, while a relatively lower field (E = 0.40 V ·nm^-1) is adequate to keep it contacting with the plate. Accompanied by the deformation hysteresis, a distribution hysteresis of the average dipole orientations of water molecules in the nano-droplet is also found. Such a hysteresis phenomenon is caused by the electrohydrodynamic interactions between droplet and plates, and the findings of this study could enhance our understanding of droplet deformation in an electric field.

Establishment of rubber thermo-viscoelastic constitutive model and analysis of temperature field

Rubber has strong nonlinear viscoelastic behavior. Under the periodically changing external forces, it show deformation hysteresis, mechanical loss and heat generation. In this work, a pair of extruding and rotating steel-rubber rollers was researched. Stress relaxation data at different temperatures were obtained through dynamic thermomechanical analysis experiments. A thermo-viscoelastic rubber constitutive model with temperature factor was obtained by combining the generalized Maxwell model where parameters of rubber viscoelastic were fitted with Prony series. Then, the temperature experiment of structure was conducted on the experimental platform. Based on thermo-viscoelastic constitutive model, simulation and analysis of temperature distribution of steel-rubber roller was obtained. The results of experimental data were consistent with simulation results. Further, the rubber constitutive models of pure elasticity, the superposition of elasticity and viscoelasticity with non-temperature factors, the superposition of elasticity and viscoelasticity with temperature factors were simulated respectively. The results show that the third model was more consistent with the actual experimental results, which verifies the accuracy of constitutive model building by this work. Through numerical comparison and analysis, it was proved that viscoelastic hysteretic heat generation is an indispensable source of heat generation in rubber structure movement.

Reversible morphological switching and deformation hysteresis in electric field mediated instability of thin elastic films.

Reversible morphology switching in a soft elastic film sandwiched between two parallel electrodes when subject to an externally applied electric field is reported herein. In contrast to electric field mediated instability of a thin liquid film, where the instability patterns remain permanent, in the present case the patterns debond completely or partially when the electric field is switched off, depending on whether the gap spacing (dG) between the film and the top electrode is >100 nm or not. The onset of instability is marked with the appearance of isotropic columns when the applied field strength (U) exceeds a critical value (Uc). The subsequent increase in U leads to the gradual transition of the instability patterns from pillars to bi-continuous labyrinths to an array of holes. Complete conformal contact is established between the film and the top electrode at U = UF. When U is reduced, the morphology changes in a reverse sequence. There is a significant level of hysteresis between the bonding and debonding stages, including persistence of the features at much lower voltages due to pinning of the patterns to the top electrode. Complete detachment occurs at a lower voltage UD when dG > 100 nm. The holes fluctuate before complete contact between the film and the top electrode due to competition between the destabilizing electric field and restoring forces due to stretching of the crosslinked polymer matrix.

Mullins Effect and its Reversibility for Zinc Dimethacrylate-Reinforced Thermoplastic Vulcanizates Based on a Ethylene-Vinyl Acetate Copolymer/Nitrile-Butadiene Rubber Blend

The Mullins effect during uniaxial compression tests, together with its reversibility, of ethylene-vinyl acetate copolymer (EVA)/nitrile-butadiene rubber (NBR)/zinc dimethacrylate (ZDMA) thermoplastic vulcanizates (TPVs) were investigated systematically. The experimental results indicated that the Mullins effect could be observed during the cyclic uniaxial compression tests and was accompanied with stress softening, residual deformation accumulation and hysteresis. The reversibility of the Mullins effect showed a temperature-dependent feature and was enhanced with increasing temperature.

Cyclic plastic behavior of unidirectional SiC fibre-reinforced copper composites under uniaxial loads: An experimental and computational study

Silicon carbide continuous fiber-reinforced copper matrix composites (Cu/SiCf) offer huge potential as heat sink material for high-heat-flux applications at elevated temperatures (>300 °C) owing to the beneficial combination of strong, stiff and refractory SiC fibers with a highly conductive and ductile copper matrix. As high-heat-flux components are normally subjected to large temperature fluctuations combined with thermal strain variations, degradation of the Cu/SiCf composites caused by fatigue damages under cyclic loads may affect the structural integrity of the component. In this study, the robustness of the Cu/SiCf composites under cyclic loads at different temperatures was evaluated by means of uniaxial cyclic loading tests. The stability of the cyclic deformation hysteresis curves was used as a measure of material’s durability. The experimentally observed global deformation behavior was interpreted with the help of a micromechanics-based theoretical model. It was shown that the Mori-Tanaka type mean field theory could describe the cyclic loading behavior of the composite quite well with a good fitting quality between the measured and simulated saturated cyclic curves. The effects of fiber content, applied strain range and test temperature are discussed.

Shake table test of a full-scale four-story reinforced concrete structure and numerical representation of overall response with modified IMK model

This paper mainly addresses the validity and verification of our current code-based knowledge through the utilization of test data of benchmark structure in Japan. A full-scale, four-story reinforced concrete building within the 2010 E-Defense test program is revisited to assess the capability of the current state of practice for the prediction of the actual seismic response of reinforced concrete structures by taking advantage of invaluable data and high-quality measurement techniques applied during the tests. The detailing of the structural elements was in compliant with the Japanese seismic design code whereas minor modifications were applied to the final design of the structure to bring it closer to the selectively well-known US design practice. A series of full-scale shake table tests were performed by gradually increasing the two ground motions of the 1995 Hyogo-Ken Nanbu earthquake for reaching to the near collapse limit state. Global dynamic response characteristics of the structure due to damage accumulation were derived from the test data to trace the strength and stiffness deterioration in the force–deformation hysteresis. Even though the story drift angles were exceeded the critical 0.04 level beyond the limitations of code-provisions, the structure has preserved dynamic stability and its intact form. Based on the surveys and measurements performed at the end of each test, shear walls and beam–column joints were sustained the severe damage while the beams and columns were maintained their structural integrity during the entire test program. Parameters of advanced hysteretic models in the moment-resisting and shear wall frames were calibrated using test data for developing analytical models that can represent all modes of the cyclic deterioration under pinching action as an alternative to the customarily used Takeda model in Japan. For the transformation of MDOF system to equivalent SDOF system, a straightforward procedure is applied to adopt the global response characteristics to the versatile hysteretic model. Moreover, the capability of capturing the seismic response of RC system through advanced hysteretic models is justified. The test results and numerical analyses implied the necessity of further improvements on MLIT and US design provisions for the reduction of observed damages on structural elements particularly in shear walls and beam–column joints to achieve reparability goals.

Friction Behavior at the Interface Between Surgical Sutures and Tissues

In the process of surgical suturing, friction phenomena at the interface between sutures and tissues can seriously affect the suturing efficiency. However, few studies have assessed the detailed effects of types of sutures or tissues and stitching parameters on the friction behavior. In this paper, the different factors affecting the friction behaviors between sutures and tissues were studied. The unidirectional sliding wear mode in a line-on-flat configuration was selected to simulate the real surgical suturing by using a UMT-II Micro-Tribometer. Artificial skin, porcine muscle and porcine liver were used as experimental samples. Three different surface morphology and structure sutures: multifilament suture (silk), monofilament suture (prolene) and multifilament suture with coating (vicryl), were investigated in this study. The normal load was from 0.1 to 0.5 N, and the unidirectional sliding (suturing) speed was from 5 to 25 mm/s to simulate the suturing operation. Results showed that the friction coefficient at the suture–tissue interface decreased with the increase in normal load and increased with the increase in suturing speed due to the nonlinear viscoelasticity and deformation hysteresis of the soft tissues. The sutures with monofilament structure or coating could effectively reduce the friction coefficient of the suture–tissue interface. Compared to the artificial skin, the porcine tissues had the lower friction coefficients because of 30% blood and 17% interstitial fluid filled in liver and muscle, respectively, which acted as lubricants and reduced the adhesion friction coefficient of the suture–tissue interface. The results can provide guidance for the surgical suture manufacture and the surgical manipulation skills.