Decrease In Energy Dissipation Research Articles

Preparation and energy absorption of flexible polyurethane foam with hollow glass microsphere

This paper presents the preparation of a partially open-cell and partially closed-cell flexible polyurethane foam material (flex-PUF), which exhibits improved cushioning performance compared to conventional protective materials. Hollow Glass Microspheres (HGM) were used as a filling material to enhance the compressibility of the material. In order to investigate the effects of HGM on the multi-impact protection and vibration damping performance of flex-PUF with different thicknesses, flex-PUF samples filled with varying volume fractions of HGM were subjected to multi-impact testing and dynamic viscoelasticity experiments. The destructive mechanism of HGM under impact was observed using scanning electron microscopy (SEM). The experimental results revealed that, under the same impact energy conditions, filling flex-PUF with HGM reduced the maximum impact displacement while enhancing energy absorption, although at the expense of cushioning performance. As the number of impact increases, the stiffness of flex-PUF decreased. In the vibration experiments, as the frequency increased, the proportion of flex-PUF’s viscous damping energy dissipation decreases.

Experimental investigation on a new method for modifying the geometry of a vertical drop edge equipped with a screen on the amount of energy dissipation

Abstract The aim of the current research is to investigate the effect of geometry and different angles (180°, 150°, 120° and 90°) of the edge of a vertical drop with a height of 0.15 m with and without a vertical screen on energy dissipation. The finding showed that the triangulation plane forms a vertical drop at different angles of 180°, 150°, 120° and 90° without a screen that increases the energy dissipation of the drop, which is highest at an angle of 90°, by 50.5%. In the vertical drop with a screen, reducing the angle also leads to a decrease in energy dissipation, so the highest energy dissipation occurs at an angle of 180° with a 45.2% increase in energy dissipation compared to the vertical drop without a screen. The relative depth of the edge and the relative depth of the vertical drop pool of the triangular plane are different at the angle vertex and its wings, in such a way that the relative depth of the edge at the vertex is less than the wings and the relative depth of the pool at the vertex is greater than the wings.

Mucopolysaccharidosis (MPS IIIA) mice have increased lung compliance and airway resistance, decreased diaphragm strength, and no change in alveolar structure.

Mucopolysaccharidosis type IIIA (MPS IIIA) is characterized by neurological and skeletal pathologies caused by reduced activity of the lysosomal hydrolase, sulfamidase, and the subsequent primary accumulation of undegraded heparan sulfate (HS). Respiratory pathology is considered secondary in MPS IIIA and the mechanisms are not well understood. Changes in the amount, metabolism, and function of pulmonary surfactant, the substance that regulates alveolar interfacial surface tension and modulates lung compliance and elastance, have been reported in MPS IIIA mice. Here we investigated changes in lung function in 20-wk-old control and MPS IIIA mice with a closed and open thoracic cage, diaphragm contractile properties, and potential parenchymal remodeling. MPS IIIA mice had increased compliance and airway resistance and reduced tissue damping and elastance compared with control mice. The chest wall impacted lung function as observed by an increase in airway resistance and a decrease in peripheral energy dissipation in the open compared with the closed thoracic cage state in MPS IIIA mice. Diaphragm contractile forces showed a decrease in peak twitch force, maximum specific force, and the force-frequency relationship but no change in muscle fiber cross-sectional area in MPS IIIA mice compared with control mice. Design-based stereology did not reveal any parenchymal remodeling or destruction of alveolar septa in the MPS IIIA mouse lung. In conclusion, the increased storage of HS which leads to biochemical and biophysical changes in pulmonary surfactant also affects lung and diaphragm function, but has no impact on lung or diaphragm structure at this stage of the disease.NEW & NOTEWORTHY Heparan sulfate storage in the lungs of mucopolysaccharidosis type IIIA (MPS IIIA) mice leads to changes in lung function consistent with those of an obstructive lung disease and includes an increase in lung compliance and airway resistance and a decrease in tissue elastance. In addition, diaphragm muscle contractile strength is reduced, potentially further contributing to lung function impairment. However, no changes in parenchymal lung structure were observed in mice at 20 wk of age.

Shear performance of four-corner connected shear wall considering plate-frame connection ratio

The four-corner connection is an innovative way to connect the wall plate and frame of the steel plate shear wall (SPSW). Differing from the traditional four-side connected SPSW, this method mitigates the dependence of the wall plate on boundary elements. Through quasi-static cyclic loading tests, a comparison is made between a four-side connected SPSW with a plate-frame connection ratio of 100% and a four-corner connected SPSW with a plate-frame connection ratio of 65%. Subsequently, using finite element (FE) models validated by experiments, the impact of the connection ratio and the flexural stiffness of vertical boundary elements (VBEs) on structural mechanics is explored. Formulas for calculating the shear bearing capacity of the four-corner connected SPSW and the minimum flexural stiffness of VBEs considering the connection ratio are proposed and validated by FE results. The test results indicate that, when the connection ratio decreases to 65%, the ultimate bearing capacity, yield bearing capacity, initial stiffness and cumulative energy dissipation decrease by 32.7%, 28.8%, 27.9% and 35.3%, respectively. Additionally, The FE results demonstrate that decreasing the connection ratio effectively mitigates adverse effects on internal forces and deflection of VBEs.

Experimental and numerical studies on friction energy-dissipating combination chord of staggered truss

Staggered truss framing systems have the problem of insufficient energy dissipation capacity in high intensity areas. To improve this situation, this paper proposes to replace the top chord of the staggered truss with a combination chord for frictional energy dissipation. Two groups and a total of four 1:2 scaled friction energy-dissipating combination top chord specimens were designed and fabricated, and hysteretic performance tests were carried out on them under low cycle reciprocating loads. It was investigated how high-strength bolt pre-tightening force and bolt layout affected the capacity of the combination chord to dissipate energy. The experimental results show that the hysteresis curve of the combination top chord for friction energy dissipation almost presents an ideal rectangle, and its energy-dissipating capacity is very strong. The combination top chord's capacity for friction energy dissipation increases with the increasing pre-tightening force of the high-strength bolt, but its stability for energy dissipation decreases. When the bolt layout is the staggered arrangement of single and double bolts, the initial energy dissipation and cumulative energy dissipation are weaker than that of the uniform arrangement of double bolts. Then, the friction energy-dissipating staggered truss with a sliding bottom chord was proposed to improve the load state of the diagonal web member in the staggered truss. The numerical simulation results show that the overall energy dissipation capacity and lateral bearing capacity of the staggered truss with the bottom chord sliding are 4.0% and 24.5% higher than those of the staggered truss with the top chord sliding.

Trans-scale dynamic shear-lag model for the impact performance of fiber-reinforced composites

This study proposes a new trans-scale dynamic shear-lag model that integrates the strain gradient linear viscoelasticity theory to investigate the effects of size and viscous softening on the dynamic mechanical properties and energy absorption characteristics of fiber-reinforced composites with micro- and nano-structures. The proposed model clarifies how the strain gradient effect can decrease energy dissipation in the matrix. Our investigation suggests that both classical and higher-order viscosities of the submicron-scale matrix can synergistically optimize energy dissipation. Furthermore, parametric studies demonstrate that the attenuation efficiency of absorbed energy changes non-monotonically with microstructure and constituent properties, such as matrix thickness, strain gradient elasticity parameter, classical viscosity, and high-order viscosity. The trans-scale dynamic shear-lag model advances our understanding of the energy dissipation in the submicron-scale viscoelastic matrix of fiber-reinforced composites and provides valuable guidance for developing composites with micro- and nano-structures that display exceptional dynamic properties.

Residual Strength and Crack Propagation of Reinforced Concrete Columns under High Temperatures

In the present study, reinforced concrete columns with dimensions of 200×200×1200 mm were tested under static loading and high temperatures. In the experimental work, square cross-section columns with compressive strength of 28 MPa were tested up to failure. Mechanical properties such as compressive strength, were examined under static load and then under temperatures such as 500 and 800 °C. Column specimens with the same geometry and with concrete covers of 10 and 17 mm were also put under test. Mode of failure, ductility, stiffness, and energy dissipation for all tested specimens are discussed. The test results showed that the strength capacity of reinforced concrete columns was affected by the column cover. The increment in temperature led to a reduction in the strength-carrying capacity of the columns and increased the axial and lateral displacements. The static compressive strength was reduced by 36.84 and 48.81% when the applied temperature was 500 and 800 °C, respectively. The stiffness of the specimen with 17 mm cover was 29.27 and 46.86% less than that of 10 mm cover for axial and lateral displacement, respectively. Also, the specimen with 10 mm cover exhibited decreased energy dissipation by 1.69 and 12.54% for axial and lateral displacement.

Spillway deflector designs for mitigating supersaturated total dissolved gases

Supersaturated total dissolved gas (TDG) produced by dams can have negative ecological consequences and development of appropriate mitigation requires facility specific information. In this study, a computational fluid dynamics (CFD) model and an analytical model for air entrainment were used to investigate how different flow deflector designs influence TDG production. Specifically, an evaluation was conducted to assess the influence of various flow deflector designs and installation positions within the spillways at the Hugh Keenleyside Dam, B.C, Canada, on both the production of TDG supersaturation and energy dissipation. Model results indicate that the CFD model incorporating an air entrainment model reliably predicts the production of TDG supersaturation. While the installation of a straight submerged deflector can successfully reduce TDG production by up to 16%, it also results in a significant decrease in energy dissipation rate, which can be up to 25%. After installing baffle blocks below water surface, the production of TDG supersaturation can be decreased by about 9%, with little decrease of energy dissipation (7%). The effectiveness of flow deflectors in enhancing energy dissipation and reducing TDG production depends on their depth placement, with optimal results achieved at a specific depth below the water surface. Nevertheless, beyond this depth, both TDG production and energy dissipation exhibit a significant decline. This study provides an advanced tool capable of accurately predicting TDG production under different operational conditions and mitigative alternatives. Results from this study offer insights for spillway design or retrofitting to optimize the mitigation of TDG supersaturation while maintaining energy dissipation.

Seismic behavior of self-centering concrete-filled square steel tubular frame with slit steel plate shear walls

A self-centering concrete-filled square steel tubular frame with slit steel plate shear walls (SC-SSPSW) adopting post-tensioned (PT) column base was proposed in this study. The slit steel plate shear walls (SSPSWs) with edge stiffeners were only connected to the beams. Cycle tests were conducted on three 1/3 scaled single-span two-story specimens to investigate their mechanical and seismic behavior, and the formulas for beam and column internal forces considering frame expansion effects were derived. Finite element (FE) models of SC-SSPSWs were established, and the FE results agreed well with the test results. The results indicate that the hysteretic curves of specimens exhibit a typical double flag shape, and the residual deformation of all specimens is approximately 0.20% when loading to 2.0% story drift. Damage is primarily concentrated in the SSPSWs while other structural members remain elastic, and favorable resilience and energy dissipation capacity are achieved. With an increase in the width-to-thickness ratio or aspect ratio of links while keeping the thickness of SSPSWs unchanged, the energy dissipation decreases, and the self-centering capacity improves. The column that expands in the same direction as the loading direction bears more lateral loads. The theoretical gap opening value, PT tendons force, as well as beam axial force agree well with the test and FE results.

Sill Role Effect on the Flow Characteristics (Experimental and Regression Model Analytical)

This study investigates the effects of gate openings and different sill widths on the sluice gate’s energy dissipation and discharge coefficient (Cd). The physical model of the sills includes rectangular sills of different dimensions. The results show that the gate opening size is inversely related to the Cd for a gate without a sill. In addition, increasing the gate opening size for a given discharge decreases the relative energy dissipation, and increasing the Froude number increases the relative energy dissipation. The results also show that the Cd and relative energy dissipation decrease when the width of the sill is decreased, thus increasing the total area of the flux flowing through the sluice gate and vice versa. According to the experimental results, the relative energy dissipation and the Cd of the sluice gate are larger for all sill widths than without the sill. Finally, non-linear polynomial relationships are presented based on dimensionless parameters for predicting the relative energy dissipation and outflow coefficient.

An ultra-efficient design of fault-tolerant 3-input majority gate (FTMG) with an error probability model based on quantum-dots

Quantum-dot cellular automata (QCA) has recently attracted significant notice thanks to their inherent ability to decrease energy dissipation and decreasing area, which is the primary need of digital circuits. However, the lack of resistance of QCA circuits under defects in previous works is a vital challenge affecting the stability of the circuit and output production. In addition, with the high defect rate in QCA, suggesting resistance and stable structures is critical. Furthermore, the 3-input majority gate is a fundamental component of QCA circuits; therefore, improving this essential gate would enable the development of fault-tolerant circuits. This paper recommends a 3-input majority gate which is 100% fault-tolerant against single-cell omission defects. Moreover, the fundamental gates are introduced based on the proposed gate. In addition, an adder and a 1:2 decoder are also designed. Using QCADesigner 2.0.3 and QCAPro software, simulations of structures and analysis of power consumption are performed.

Hydraulic characteristics of flow at grid drop-type dissipators with the upstream supercritical approach flow

Through installing a grid drop-type dissipator at the edge of the vertical drops with an upstream supercritical approach flow, the present study investigates hydraulic characteristics of flow up- and downstream of the drop, based on model experimentation. Experiments were conducted on three different drop heights, considering eight different grid drop-type dissipators with certain grids dimensions. Results demonstrate that assembling this type of dissipator at the edge of a vertical drop increases the rate of energy dissipation up to about 70%, compared to a plain vertical drop. Owing to the increase in flow momentum and the falling jets’ collision with bottom of the downstream channel, for a given flow discharge, while the porosity of the grid drop-type dissipator is increased, the wetted length of the dissipator and the energy dissipation decrease; however, the length and depth of the pool at the drop base increase. The relative length of the pool is significantly affected by air entrainment, caused by the spaces between the separated falling jets. By increasing flow discharge, pressure fluctuations decrease and trend of the variation of average pressure becomes smoother. Although the former researchers reported a hydraulic jump downstream of the grid drop-type dissipators with an upstream subcritical approach flow, it was not the case in some tests of the present study with an upstream supercritical approach flow. Finally, based on statistical and error analyses, empirical relationships were derived to predict the flow hydraulic characteristics, to be used by design engineers in practice.

Dynamic characterization of 3D printed bolted joints

The paper deals with the effect of different parameters on the frictional energy dissipated by 3D-printed bolted joints of different configurations. A test rig is developed using the accelerometers and shaker to perform this task. The shaker provides the force that induces a relative displacement between plates. The induced relative displacement is measured using the accelerometer. The bolted plate samples are 3D printed with polylactic acid (PLA) fibre using fused deposition modelling (FDM) and joined together using a metal bolt. The four different configurations of bolted joints are developed. A single bolt flat contact, a double bolt flat contact (90°orientation), a single bolt slanted contact (1°angle on both surfaces), and a single bolt flat and curved contact. The effect of bolt preload, excitation frequency, and excitation amplitude on the experimental frictional energy dissipation of the bolted joint is studied. The energy dissipation increases with the increase in excitation amplitude and the bolt preload. However, with increasing excitation frequency, the energy dissipation decreases. The type of contact between bolted plates also seems to affect the frictional energy dissipation.

Effects of nonlinear hyper‐viscoelasticity and matrix/fiber debonding on the mechanical properties of short carbon fiber/styrene‐butadiene rubber composites under cyclic uniaxial loading using a multiscale finite element model

AbstractA multiscale finite element analysis was performed for short carbon fiber (SCF) reinforced rubber composites under uniaxial tensile loading with periodic geometries and random distributions of the short fibers. Three different zones were considered, including the rubber matrix, SCF as the inclusion phase, and a thin matrix layer as the interphase. A nonlinear hyper‐viscoelastic model was selected for the matrix, while linear viscoelastic and elastic models were considered for the interphase and reinforcing phases, respectively. The analyses were carried out on an incremental basis from a lower loading‐unloading rate of 10 mm/min to a higher rate of 100 mm/min. Two interface conditions were considered between the polymer matrix and the SCF phases: perfect bonding and partial debonding. The partial debonding was modeled via extended FEM (XFEM) with a crack initiation criterion. An integral averaging technique was employed to predict stress and strain at the macro‐scale. Based on the observations in this work, hysteresis and energy dissipation decrease with the addition of the short fibers to the neat rubber and surface modification of the fibers under three‐cycle loading. For example, in the first cycle and for a constant stress of 0.45 MPa, the strain value decreases from 0.25 to 0.17 MPa at the loading‐unloading rate of 10 mm/min. The high‐fidelity model developed in this work for short fiber/rubber composites is able to predict the stress and strain responses of the SCF/SBR composites, confirming the accuracy of the utilized multiscale approach.

Microscopic Origins of the Nonlinear Behavior of Particle-Filled Rubber Probed with Dynamic Strain XPCS.

The underlying microscopic response of filler networks in reinforced rubber to dynamic strain is not well understood due to the experimental difficulty of directly measuring filler network behavior in samples undergoing dynamic strain. This difficulty can be overcome with in situ X-ray photon correlation spectroscopy (XPCS) measurements. The contrast between the silica filler and the rubber matrix for X-ray scattering allows us to isolate the filler network behavior from the overall response of the rubber. This in situ XPCS technique probes the microscopic breakdown and reforming of the filler network structure, which are responsible for the nonlinear dependence of modulus on strain, known in the rubber science community as the Payne effect. These microscopic changes in the filler network structure have consequences for the macroscopic material performance, especially for the fuel efficiency of tire tread compounds. Here, we elucidate the behavior with in situ dynamic strain XPCS experiments on industrially relevant, vulcanized rubbers filled (13 vol %) with novel air-milled silica of ultrahigh-surface area (UHSA) (250 m2/g). The addition of a silane coupling agent to rubber containing this silica causes an unexpected and counterintuitive increase in the Payne effect and decrease in energy dissipation. For this rubber, we observe a nearly two-fold enhancement of the storage modulus and virtually equivalent loss tangent compared to a rubber containing a coupling agent and conventional silica. Interpretation of our in situ XPCS results simultaneously with interpretation of traditional dynamic mechanical analysis (DMA) strain sweep experiments reveals that the debonding or yielding of bridged bound rubber layers is key to understanding the behavior of rubber formulations containing the silane coupling agent and high-surface area silica. These results demonstrate that the combination of XPCS and DMA is a powerful method for unraveling the microscale filler response to strain which dictates the dynamic mechanical properties of reinforced soft matter composites. With this combination of techniques, we have elucidated the great promise of UHSA silica when used in concert with a silane coupling agent in filled rubber. Such composites simultaneously exhibit large moduli and low hysteresis under dynamic strain.

Effect of water saturation on dynamic behavior of sandstone after wetting-drying cycles

Fully understanding the influence of water on the rock materials' mechanical properties is of great significance to the safety design and evaluation in rock engineering. In this study, sandstone was pretreated with different wetting-drying cycles (0-15), and its pore characteristics were characterized by low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM) methods. Then, the split Hopkinson pressure bar (SHPB) tests with the same impact velocity were carried out in its dry and saturated states, respectively. The effects of water saturation on the dynamic behavior of sandstone under different porosity conditions and their mechanisms were emphasized. The results show that with the increase of cycle numbers, the porosity of sandstone increases, the dynamic strength and the total energy dissipation decreases. Moreover, the proportion of post-peak energy dissipation rises, and the degree of fragmentation intensifies. With the increase of porosity, the effect of water saturation on dynamic strength changes from enhancement to weakening. This may be related to the competition between the the Stefan effect and the contribution of pore water pressure. Finally, a dynamic damage constitutive model considering the coupling effect of the wetting-drying cycles and dynamic loads was established, and its effectiveness was verified.

Numerical Modelling of Flow in Fluidic Oscillator

The systems with fluidic oscillators are intensively studied nowadays because the oscillatory flow can increase heat and mass transfer and decrease energy dissipation. Fluidic oscillators produce an active-type mixing enhancement but in a passive manner as they do not require any moving parts. They convert steady pressurized inlet flow to oscillatory or pulsatile flow at an outlet without the need for external power. In general, there are many types of fluidic oscillators, categorized by the underlying mechanism to create oscillatory output behaviour. The fluidic oscillator with the single feedback loop is analysed in this paper. A numerical simulation of oscillating flow is performed and two approaches for modelling flow, RANS, and LES are applied especially. The results of numerical simulation are compared with experimental measurement. The analysis is focused on pressure drop and oscillation frequency dependent on the inlet conditions. The energy spectrum of oscillating flow is analysed using discrete Fourier transform.

Seismic behavior of reinforced concrete beam-column joints with unstressed steel strands fully or partially used for beam longitudinal reinforcement

Five beam-column joint specimens: three exterior and two interior specimens were subjected to cyclic loading to investigate the effectiveness of using unstressed Grade 1860 MPa steel strands as full/partial replacement for the conventional Grade 420 MPa deformed bars as beam longitudinal reinforcement. The study also developed a special hooked anchorage detail to anchor the steel strands in the joint region. The test specimens failed by beam plastic hinge formation near the column face as intended in design, with drift capacities between 5.12% and 7.57%. However, the full (100%) and partial (50%) replacement of deformed bars by strands led to a 58% and 28% decrease in average relative energy dissipation. Despite this, the full/partial replacement of deformed bars by strands as beam longitudinal reinforcement resulted in enhanced reentering capabilities. Fracture of longitudinal steel strands observed in the beam plastic hinge region at the end of the test indicated the effectiveness of the special hooked anchorage detail in allowing steel strands to develop their capacity. Further, the flexural strength of the beams of test specimens was evaluated through a detailed moment-curvature analysis, which predicted the beam flexural strength with high accuracy and less variation (mean = 1.01, standard deviation = 0.02). After that, beam flexural strengths were evaluated following the ACI 318–19 procedure modified to include the proposed bilinear strand model, which produced conservative estimates of beam flexural strength (mean = 1.15) suitable for design. Also, the procedure to estimate the beam's probable flexural strength is presented. Finally, required modifications to the conventional seismic design procedure were proposed to incorporate the use of strands as beam longitudinal reinforcement.

Deformation behaviour and notch sensitivity of a super duplex stainless steel at different strain rates and temperatures

For the successful development of a structure, understanding of mechanical behaviour of the selected material is an important issue to prevent damage or accidents. Mechanics of the material failure depends on its chemical composition, heat treatment, grain size, strain rate, type of loadings etc. Apart from material properties, the performance of the structure is also affected by its geometry, crack/notch/hole/groove and manufacturing processes. In construction of offshore, marine, power plant and oil-gas industry structures, super duplex stainless steel is one of the suitable materials. Therefore, the objective of the paper is to study the deformation behaviour and notch sensitivity of a super duplex stainless steel, SDSS 2507 at different strain rates (0.0001–0.1s−1) and temperatures (25–200 °C) under tensile, compressive and flexural (three-point bending) loads. Heating rate and soaking time are 8 °C/min and 15 min respectively. Experiments are conducted on electromechanical universal testing machine using suitable fixtures. The steel is found positive sensitive to the strain rate and temperature, where the phenomenon of dynamic strain ageing (DSA) is observed during thermal effects. Fractography analysis is correlated with the typical stress-strain curves. Heat treatment (heating rate 12 °C/min and soaking time 1–3 h) enhances the tensile strength of the steel upto 18% at 400–600 °C for strain rate 0.001s−1, whereas at 700 °C, the strength decreases by 31% and the energy dissipation decreases by 88% due to its brittle behaviour. Notch profiles (C, U and V) on the flat tensile specimens of the steel decreases the energy dissipation by nearly 67–74% at 0.001s−1. Ductile-brittle transition temperature exists between 600℃-700℃ in tensile tests. Compression tests are conducted for varying geometries of cylindrical specimens. Flexural behaviour of the steel is investigated for 120–160 mm span lengths and flat-transverse orientations. Existing material models (Cowper-Symonds and Johnson-Cook) are evaluated.

Experimental investigation on submerged water jet wrapped in an annular gas jet

To reduce the energy dissipation of the submerged water jet, a series of experiments of the submerged water jet wrapped in an annular gas jet are performed under different gas ventilation rates, annular sizes, water jet nozzle diameters, and water jet velocities in a transparent water tank. In the experiments, a ventilated cavity is created by the annular gas jet that encloses the submerged water jet. The submerged water jet is separated from the surrounding water within a certain distance after leaving the nozzle exit by the ventilated cavity, which contributes to the effective working length of the submerged water jet significantly increasing, referring to the energy dissipation decrease. Furthermore, the geometry of the ventilated cavity changes periodically, i.e., the cavity length and diameter decrease after increasing to the peak values in each cycle. Moreover, the ventilated cavity development process can be mainly divided into formation, collapse, and intermission stages. The maximum cavity length of the ventilated cavity decrease with the per unit time momentum ratio between the water jet and the gas jet. Namely, the per unit time momentum ratio between the water jet and the gas jet is the dominating parameter of the cavity geometry.