Total Energy Dissipation Research Articles

A test rig for the experimental characterization of the mechanical energy dissipation due to the propagation of elastic waves during the impact of cylinders

The proposed work describes the design and construction of an experimental test rig used to quantify the mechanical energy dissipation due to the propagation of elastic waves during the impact of cylinders and validate the background theoretical models. Firstly, the impact of perfectly elastic cylinders is studied using finite element and lumped parameter models. The main result obtained is the coefficient of dissipation, which allows quantifying the total mechanical energy dissipation of the system. Then, the final layout of the test rig designed to reproduce the test conditions of the theoretical models is shown. Two kinds of tests are performed to obtain the energy dissipation of the system with and without impacts. The position of one cylinder during its motion is acquired with an industrial camera. Finally, the experimental results are compared with an analytical model of a nonlinear pendulum and used to quantify the coefficient of dissipation.

Hysteretic performance of self-centering buckling-restrained braces with embedded friction spring

This paper proposes an alternative configuration of an all-steel assembly self-centering buckling-restrained brace (FSBRB) fabricated by combining a buckling-restrained brace and friction spring. The hysteretic performance of the FSBRB is investigated using low-cycle fatigue tests, and the accuracy and applicability of the theoretical hysteretic model are verified by comparing the theoretical, test, and simulation results. The test results show that the hysteresis curve of the FSBRB exhibits a symmetric flag shape with stable hysteresis performance under cyclic loading. The recommended minimum pre-pressure of the friction spring is not less than four times the yield force of the buckling-restrained brace to achieve a full self-reset. The friction spring also has non-negligible energy dissipation capacity, which accounts for 60% of the total energy dissipation of the FSBRB under the zero residual displacement condition. The equivalent viscous damping ratio of the brace is approximately 20%. The parameter analysis results obtained by simulation show that the change in taper angle has the greatest influence on peak force and residual displacement. Moreover, the friction coefficient mainly affects energy consumption, and pre-pressure ratio has a strong relationship with the yield force of the brace. Accordingly, to achieve the self-centering capacity, the FSBRB design scheme with small taper angle, friction coefficient, and pre-pressure ratio is selected priority to attain the performance objective and reduce the force requirement of connecting parts.

Power-efficient in vivo brain-machine interfaces via brain-state estimation

Objective. Advances in brain–machine interfaces (BMIs) can potentially improve the quality of life of millions of users with spinal cord injury or other neurological disorders by allowing them to interact with the physical environment at their will. Approach. To reduce the power consumption of the brain-implanted interface, this article presents the first hardware realization of an in vivo intention-aware interface via brain-state estimation. Main Results. It is shown that incorporating brain-state estimation reduces the in vivo power consumption and reduces total energy dissipation by over 1.8× compared to those of the current systems, enabling longer better life for implanted circuits. The synthesized application-specific integrated circuit (ASIC) of the designed intention-aware multi-unit spike detection system in a standard 180 nm CMOS process occupies 0.03 mm2 of silicon area and consumes 0.63 µW of power per channel, which is the least power consumption among the current in vivo ASIC realizations. Significance. The proposed interface is the first practical approach towards realizing asynchronous BMIs while reducing the power consumption of the BMI interface and enhancing neural decoding performance compared to those of the conventional synchronous BMIs.

Low-cycle fatigue behavior and life prediction of TA15 titanium alloy by crystal plasticity-based modelling

It is of significance to reveal the low-cycle fatigue deformation mechanism of titanium alloy with tri-modal microstructure for improving its properties. This work developed a crystal plasticity finite element model based on realistic microstructure to predict the low-cycle fatigue behavior of TA15 titanium alloys with tri-modal microstructure containing primary α (αp), secondary lamellar α (αl) and transformed β (βt). During modelling, plastic strain accumulation (PSA) and energy dissipation were used as the fatigue indicator parameter (FIP) to predict fatigue damage and life. It is found that the fatigue deformation prefers to localize at the interfaces of αp/β, αl/β and at triple junctions, which leads to the initiation of fatigue crack. In addition, the soft geometry of αl will also contribute to the strain localization inside αl grains causing fatigue damage. This is because the local lattice rotation is more prone to occur at these locations due to the tension-compression asymmetry of lattice rotation, which induces the occurrence of the microtexture and aggravates the heterogeneity of the lattice rotation, leading to the localized PSA and the total energy dissipation. And the asymmetry of lattice rotation in each cycle also leads to the tension-compression asymmetry of flow behavior. Both of the two FIPs can effectively predict fatigue life. With the strain amplitude increasing, the PSA-based model shows a relatively higher predictive accuracy of fatigue life than that of the accumulated energy dissipation-based model. The predicted fatigue life is in accordance with the C-M model.

Acoustic transmission characteristics based on coiled-up space metamaterials

Coiled-up metamaterials with solid plate (SC) and with micro-perforated plate (MPC) are proposed for broadband low-frequency acoustic insulation and absorption. Firstly, the sound transmission theory of the double-layer plate and the impendence of the micro-perforated plate coupled with the coiled-up channel are introduced to obtain the dependence of structural parameters on the acoustic characteristics. Then, the acoustic performances of SC and MPC are investigated numerically and verified by experiments, and the effects of geometry parameters are analysed to predict the acoustic performance of SC and MPC. The minimum sound transmission loss (STL) of SC with a thickness of less than 2 cm is higher than 20 dB and the average STL reaches 45 dB at [0, 1600] Hz. The multi-order resonances of coiled-up space induce STL valleys but provide 10 dB improvement at valleys compared with double-layer plates. The MPC achieves narrow absorption at 422 Hz and 1232 Hz, which are induced by the resonances of coiled-up channels and 99.99 % of total energy dissipation is viscous dissipation mainly occurring in MPP. Coiled-up space with embedded porous materials (PTM) achieves above 0.9 absorption coefficient at [700, 1600] Hz. The optimized MPTMs, which consists of three parallel MPCs guided by the genetic algorithm (GA) and a single PTM unit, can reach a normal incident average absorption coefficient of 0.80 at [342–2000] Hz and a random incident absorption coefficient above 0.5 at [352–1862] Hz.

Experimental study on the seismic performance of steel frames with infill ALC wall panels

To explore the seismic performance of H-shaped steel frames with infill precast autoclaved lightweight concrete (ALC) wall panels, the horizontal low-cyclic loading tests were conducted under vertical load. The influence of the connector style, the arrangement, and the integrity of the wall panels on the seismic performance of the structure were analyzed depending on four specimens of H-shaped steel frames with ALC wall panels and one hollow H-shaped steel frame. The failure mode, bearing capacity, rigidity and strength degradation, and energy dissipation performance were compared and discussed. The results showed that the steel frame with infill wall panels had better ductility and energy-dissipating capacity than the hollow frame. The infill ALC wall panels greatly enhanced the seismic performance of the frames and had a significant influence on the bearing capacity, stiffness, energy dissipation capacity, and ductility performance of the specimens. The maximum ductility factors and total energy dissipation of the steel frame with ordinary infill wall panels were 1.58 times and 2.27 times larger than those of the hollow frame. Due to cooperation with the steel frame, the panels delayed the buckling and in-plane deformation of the frame. The sliding connector improved the bearing capacity, displacement ductility, and energy dissipation of the overall structure compared with the hooking connector. Moreover, the bearing capacity of the frames with the reinforced wall panels was improved further. Additionally, the equivalent compression bar model was developed to estimate the bearing capacity of the steel frames with the infill ALC wall panels. The experimental conclusions and the proposed analytical model improve the practical design of the steel frames with the infill ALC wall panels in high-rise buildings.

Large Magnetodielectric Effect of BaTiO3-BaFe12O19 Composites in a Low Magnetic Field.

A microwave sintering procedure has been developed to achieve high quality multiferroic composites of (1 - x)BaTiO3-xBaFe12O19 (x = 0.05, 0.10, 0.15, and 0.20). X-ray diffraction, scanning electron microscopy, and impedance spectra indicate that BaFe12O19 particles are isolated homogeneously by BaTiO3 particles. In a 1.8 T magnetic field, a large room temperature magnetodielectric effect over 4.3% is observed in the 0.8BaTiO3-0.2BaFe12O19 composite. The total mechanical energy dissipation (Q -1) for the BaTiO3-BaFe12O19 composites was composed of the mechanical damping of BaFe12O19, the mechanical damping of BaTiO3, and the loss at the interface. The mechanical damping of BaFe12O19 plays the dominant role in the variation of Q -1.

Shear fatigue behavior of reinforced concrete beams produced with manufactured sand as alternatives for natural sand

Compared to natural sand, manufactured sand (M-Sand) has significant differences in terms of stone powder content, particle size distribution, and particle shape. The fatigue performance of M-Sand concrete structures is a crucial problem for the application of M-Sand in significant engineering structures. In this study, four different types of fine aggregates were selected to investigate the shear fatigue behavior of reinforced concrete (RC) beams by considering the influence of the maximum load level. Next, the performance indexes of the fatigue life of M-Sand concrete beams were evaluated. The results showed that the fatigue failure processes of concrete beams produced with different sand types were similar. The fatigue life of concrete beams was found to be related to the stress or load range. At the same maximum load level, the methylene blue (MB) value is a critical index that influenced the fatigue life of concrete beams containing M-Sand. Moreover, the fatigue life showed a linear logarithmic relationship with the average permanent deflection of Stage II. The total dissipation energies of the concrete beams in Stage II were different for the various fine aggregates. Generally, the higher the total dissipation energy, the longer the fatigue life of the concrete beam. The average dissipation energy in Stage II can be used as a characteristic index for evaluating the fatigue performance of concrete beams produced with different types of fine aggregates. • Shear fatigue behaviors of sixteen reinforced concrete beams containing manufactured sand were innovative analyzed. • Three different types of manufactured as well as natural sand were used in experimentally program. • The fatigue life of manufactured sand concrete beams was found to be related to the stress or load range. • The magnitude of the dissipation energy together with permanent deflection could indicate the fatigue life of concrete beams.

Design Method for Reinforced Concrete Based on Bond-Slip Energy Consumption

To reveal the energy consumption characteristics of a steel bar and all-lightweight shale ceramsite concrete (ALWSCC), focusing on hot rolled crescent ribbed bars (CRB) and hot rolled plain steel bars (PSB), a series of pull-out tests were carried out. The bonding failure modes, the contribution of the ribs to bond-slip failure and the energy consumption characteristics were analyzed based on the curves of pull-out load F-slip displacement S and energy consumption W–slip displacement S. Results show that the splitting failure is the main failure of the CRB specimen, and the pulling out failure is the main failure of the PSB one. The ratio of the total energy dissipation of splitting failure to that of the pulling out failure is less than 30%. The mechanical bite force between CRB and concrete contributes more than 95% to the bond strength. The pull-out force is divided into four stages, such as the chemical adhesive force stage (elastic and micro-elastic strain stage), the common-effect stage of mechanical bearing force and static frictional force (plastic development stage), and the frictional force stage (crushed stage). The new design is proposed to guarantee the ductility of the reinforced concrete structure, which is based on the bond-slip energy consumption rather than the traditional strength design. The conclusions provide a reference to the reinforced concrete practice.

Seismic uplift behavior and energy dissipation mechanism of scoured bridge pile-group foundations: Quasi-static test and numerical analysis

Seismic-induced pile uplift is likely to happen in coastal bridges with scoured pile-group foundations. This study investigates the seismic performance of scoured pile-group foundations with pile uplift behavior. To this end, a quasi-static test was conducted on a reinforced concrete specimen comprising a rigid single-column pier and a 2 × 2 pile-group foundation partially embedded in homogeneous sand. Cyclic lateral loading was imposed near the top of pier to produce sufficient bending moments on the foundation for achieving the pile uplift behavior. After that, a finite element (FE) model for the quasi-static test is developed and validated using the experimental data. An in-depth comparative study is conducted on two FE models with and without pile uplift. Results show that bridge models with pile uplift show apparent self-centering behavior, while those without pile uplift do not. Pile uplift prevents the yielding of pile head sections and meanwhile delays the yielding of underground ones. Besides, bridges with or without pile uplift have quite close total energy dissipation capacity, but the contribution of soil-pile frictional interaction is greatly increased (from 24% to 76%) while the contribution of structural damage is significantly decreased (from 40% to 2%) due to pile uplift.

Comparison between RANS and 3D-PTV measurements of Newtonian and non-Newtonian fluid flows in a stirred vessel in the transitional regime

Newtonian and non-Newtonian fluid flows in a vessel (T=H=180 mm) stirred with a Rushton turbine (C=D=T/3) have been simulated in CFD using steady RANS in the transitional regime (183≤Re≤1,086). The numerical results have been compared against 3D-PTV measurements. For Newtonian fluids, the different turbulence models predicted the same mean flow, which matched well the experimental velocity data. The standard k-ε model predicted the power numbers closest to expected values and resolved 80 % (at Re=943) and 89 % (Re=86) of the total energy dissipation. Simulations of the non-Newtonian flows presented challenges. For shear thinning rheology, the simulated mean flow patterns did not correspond to the measured ones. CFD also predicted a higher mean velocity, compared to PTV. For yield stress fluids, the numerical predictions of the cavern boundaries were in reasonably good agreement with the experimental observations.

Seismic performance of earthquake-damaged corroded reinforced concrete beam-column joints retrofitted with basalt fiber-reinforced polymer sheets

This present research conducted an experimental study on the influence of different earthquake damages on the seismic performances of aged reinforced concrete (RC) beam-column joints retrofitted with basalt fiber-reinforced polymer (BFRP) sheets under cyclic loadings. Six beam-column joints included one benchmark specimen, one uncorroded specimen retrofitted with BFRP sheets, and four earthquake-damaged corroded specimens with the corrosion rates of 0% and 9% retrofitted with BFRP sheets. Test results demonstrated that the seismic performances of earthquake-damaged corroded specimens effectually improved after retrofitting with BFRP sheets, and the retrofitting effectiveness was significantly affected by the earthquake-damaged levels. The bucking of stirrups, spalling and crushing of concrete of retrofitted specimens were effectually postponed, while the ductility of corroded and uncorroded specimens under the earthquake damages increased after retrofitting with BFRP sheets. The total cumulative energy dissipation and final stiffness of retrofitted specimens considerably improved with the maximum increase of 22.3% and 14.3% comparing to those of benchmark specimen, respectively. Besides, the models for predicting the shear strength of RC beam-column joint cores considering the influences of earthquake damage, reinforcement corrosion, and FRP retrofitting were proposed.

Effect of relative phase of periodic loading on frictionally constrained joints

This paper considers a two-dimensional frictionally constrained joint to investigate the interfacial characteristics under periodic loadings with phase variations. Joints are pressed in contact by normal pressure, subjecting to tangential loading and bending moment. The tendency of contact behavior at the steady-state is investigated, subjected to various phase differences between the bending moment and the tangential loading. Total energy dissipation per cycle is obtained at steady-state to examine the overall frictional damping from the joint interface. It is found that friction damping is dominant during tensile loading, and the energy dissipates the most when the phase difference is near π / 2.

Research on Sandstone Damage Characteristics and Acoustic Emission Precursor Features under Cyclic Loading and Unloading Paths

The deformation and failure features of rock formation in deep coal mines are basic mechanical problems in the complex geology environment and complicated excavation process. Under the effect of cyclic loading and unloading, the bearing capacity weakens and damage degree exacerbates significantly, which seriously threatens the safety and stability of the working face. To study the damage characteristics of sandstone, especially the precursor characteristics of acoustic emission (AE), this paper conduct the AE response experiments on sandstone under cyclic loading and unloading. The results show that with the increasing number of cycles, the loading modulus, unloading modulus, total strain energy, elastic energy, and dissipation energy of sandstone in the cycle stage all increase continuously. In the initial loading stage, the sandstone has fewer cycles and lower stress levels, fewer AE ringing counts and energy, and less rock damage. With the increasing cyclic times and loading stress, the damage degree of sandstone increases rapidly in a very short time. The damage variable represented by ringing count is more sensitive than by energy. Just before rock failure, the ringing count and the energy value increase significantly, and the damage curve rises sharply. In addition, AE waveform signals have obvious aggregation characteristics and four main bands. Just before sandstone failure, the main frequency band becomes wider, the low frequency bands f1 and f2 become connected, and the main signal frequency appears abnormally low and high. The waveform signals before sandstone instability and failure show a phenomenon where the low-frequency amplitude is generally at a high level, the high-frequency signal decreases, the amplitude becomes low, and the multipeak phenomenon weakens. The above characteristics of the AE time domain and waveform analysis can be used as the precursor characteristics of sandstone failure and instability. This study can reveal the process of the sandstone deterioration and AE response under the cyclic loading and unloading condition, and has certain guiding significance for roof and floor control in deep roadway, instability warming monitor of working faces, and guarantees for safety production.

Single‐bit digital comparator circuit design using quantum‐dot cellular automata nanotechnology

AbstractThe large amount of secondary effects in complementary metal–oxide–semiconductor technology limits its application in the ultra‐nanoscale region. Circuit designers explore a new technology for the ultra‐nanoscale region, which is the quantum‐dot cellular automata (QCA). Low‐energy dissipation, high speed, and area efficiency are the key features of the QCA technology. This research proposes a novel, low‐complexity, QCA‐based one‐bit digital comparator circuit for the ultra‐nanoscale region. The performance of the proposed comparator circuit is presented in detail in this paper and compared with that of existing designs. The proposed QCA structure for the comparator circuit only consists of 19 QCA cells with two clock phases. QCA Designer‐E and QCA Pro tools are applied to estimate the total energy dissipation. The proposed comparator saves 24.00% QCA cells, 25.00% cell area, 37.50% layout cost, and 78.11% energy dissipation compared with the best reported similar design.

Experimental Study on Earthquake-Resilient Precast Shear Wall with Bolt-Plate Connectors

ABSTRACT Precast shear wall (PSW) has been widely applied in building structures with advantages of good mechanical behavior and construction efficiency. To improve the seismic performance and the earthquake resilience of PSW, a new earthquake-resilient precast shear wall with bolt-plate connectors (ERPSW) was developed. Experimental study was conducted to investigate the seismic performance of the proposed ERPSW, including the failure mode, shear resistance, ductility, energy dissipation capacity, degradation in stiffness, etc. Moreover, seismic-damaged ERPSW was repaired by replacing the damaged connectors and tested again to verify the earthquake resilience through the comparisons with original test. Results demonstrated that the proposed ERPSW exhibited the similar mechanical behavior compared with the cast-in-situ shear wall, while developed higher shear capacity, better ductility, and energy dissipation capacity. The damage was concentrated in the bolt-plate connectors, consuming more than 85% of the total energy dissipation, while precast concrete wall almost remained elastic with few cracks. The seismic performance of seismic-damaged ERPSW was recovered after replacing the damaged members, exhibiting as good as seismic performance with the original one. Consequently, the utilization of bolt-plate connectors could ensure the reliable connection of PSW, enhance the seismic performance as well as satisfy the requirement of earthquake resilience with convenient replacement.

Cyclic loading tests of a resilient hinged self-centering RC wall

To reduce the residual drift of the reinforced concrete shear wall (RCSW), this paper proposes a resilient hinged self-centering shear wall (RHSCSW) in which two tension–compression-symmetrical disc spring devices (TCSDSDs) and a restraint plate form a resilient bottom that prevents plastic deformation on the wallboard. Cyclic loading tests are conducted on a TCSDSD specimen, an RCSW specimen, and two RHSCSW specimens to investigate their hysteretic responses. The experimental results indicate that the TCSDSD exhibits a symmetrical flag-shaped hysteretic behavior, and its macro-mechanical properties can be described by eight stiffness variables and four force variables. Benefiting from the self-centering characteristic of the TCSDSD, the maximum residual inter-story drift ratio of the RHSCSW is only 0.37% with a maximum inter-story drift ratio of 4%, while that of the RCSW reaches 0.94% with an inter-story drift ratio of only 2%. Moreover, the total energy dissipation of the RHSCSW is found to be 25.4% higher than that of the RCSW. The equivalent viscous damping ratio of the RHSCSW is almost constant because the axial displacements of the TCSDSDs are almost linear with the lateral drift of the RHSCSW.

Experimental Investigation on Hydraulic Efficiency of Vertical Drop Equipped with Vertical Screens

In the present study, vertical screens were utilized at downstream of vertical drops to increase the energy dissipation of subcritical flow. The experiments were carried out using screens with two different porosity ratios (40% and 50%) and three different distances from the drop brink (30, 60 and 90 cm). The results reveal that drops equipped with screens increase the relative downstream depth, the relative pool depth, and the relative energy dissipation compared with a plain vertical drop. By increasing porosity ratios and the screen distance from the drop brink, the relative downstream depth and relative energy dissipation increase, whereas the relative pool depth decreases. Also, by increasing the relative critical depth, the relative energy dissipation of the vertical drop decreases, whereas the energy dissipation related to the screens increases. However, increasing the relative critical depth initially increases and then decreases the performance of the hydraulic jump in terms of total energy dissipation.

Effects of Coal Gangue Coarse Aggregate on Seismic Behavior of Columns under Cyclic Loading

Coal gangue is the rock discharged from coal mining. Using coal gangue as coarse aggregate is one of the solutions for the sustainable development of construction engineering. Five one-half scaled coal gangue concrete (CGC) frame columns with different coal gangue coarse aggregate replacement ratios were designed, and the effect of coal gangue coarse aggregate on seismic behavior of columns under cyclic loading was studied. The test results show that the failure of coal gangue coarse aggregate under cyclic loading is the main reason for the reduction in hysteretic performance of CGC specimens. Compared with natural aggregate concrete (NAC) specimen, the hysteretic behavior, deformation performance, and energy consumption of CGC columns were reduced. However, the seismic performance of CGC specimens with higher replacement ratio was better than that of CGC specimens with a lower replacement ratio. Compared with NAC specimen, the ductility and total energy dissipation of CGC specimen with r = 100% were only reduced by 8.2% and 12.8%. In addition, the test results also found that the higher the replacement ratio, the greater the shear deformation of the specimen. It is recommended to appropriately increase the stirrup ratio of CGC specimens in seismic design.

Design and energy analysis of a new fault-tolerant SRAM cell in quantum-dot cellular automata

Quantum-dot cellular automata (QCA) is an emerging technology proposed in response to the limitations of CMOS technology. Moreover, static RAM (SRAM) is crucial for memory design, and efficient RAM design can play a significant role. This paper proposes a fault-tolerant QCA SRAM cell based on QCA three- and five-input majority gates. This cell is implemented on a single layer and does not require any rotated cell, which significantly improves the manufacturability and robustness of the design. Furthermore, our design can tolerate a single omission fault. The proposed 3-input majority gate improves complexity, area, and energy dissipation, on average, by 54%, 68%, and 67% in 1 Ek, respectively, as compared to its previous counterparts. The proposed fault-tolerant SRAM cell improves the complexity, area, and total energy dissipation by almost 13%, 25%, and 35% in 1 Ek, respectively, as compared to its state-of-the-art QCA-based single-layer fault-tolerant counterpart.