Energy Dissipation Characteristics Research Articles

Seismic performance of innovative prefabricated reinforced recycled concrete shear walls

In this study, the seismic performance of innovative prefabricated recycled concrete shear walls has been investigated. Unlike the conventional grouting sleeve connections, the "button-head bars" grouting connections to connect the walls have been proposed. Four shear wall specimens with different construction types (two semi-prefabricated, one fully-prefabricated, and one cast-in-place) were tested under low-cyclic loading. The fully-prefabricated wall was connected to the foundation only using the proposed button-head bars; while for the semi-prefabricated walls, the two cast-in-place concealed columns were arranged at both edges of the wall. The failure modes, hysteretic behavior, skeleton curves, strength, ductility, stiffness and degradation process, energy dissipation, and strain characteristics were investigated. The influence of axial force ratio and construction type on the seismic performance of the shear walls was analyzed. The results showed that the seismic performance of semi-prefabricated shear walls and cast-in-place shear walls was similar. The shear slip for the cast-in-place, semi-prefabricated, and fully-prefabricated shear walls was 0.3 mm, 0.32 mm, and 0.78 mm, respectively. The cast-in-place concealed columns could effectively limit horizontal shear slip. An increase in the axial force ratio significantly enhanced the strength and energy dissipation capacity of semi-prefabricated specimens. The ultimate strength according to different design codes was calculated, with the Chinese GB-50010 design code providing the most accurate prediction of the strength of prefabricated shear walls.

Study on Dynamic Parameters and Energy Dissipation Characteristics of Coal Samples under Dynamic Load and Temperature

Coal and rock dynamic disasters such as rock burst and outburst seriously threaten the sustainable development of the coal mining industry, which are intimately correlated with the nonlinear dynamic response process of the deep coal and rock mass. This study conducts coal dynamic experiments under vibration load from room temperature to 60 °C by using the split Hopkinson bar (SHPB) with a temperature real-time control system and analyzes the variation in stress and strain and the energy dissipation characteristics of coal during the dynamic load process. The expression equation of dissipated energy of coal at different scales is established, and the judgment conditions of the macroscopic mechanical behavior of coal are analyzed theoretically. The stress curves show a multi-stress peak phenomenon when the coal samples are subjected to different temperatures and dynamic loads, and the coal’s dynamic stress and temperature show a polynomial fitting relationship at different stages. When the coal sample is subjected to temperature and dynamic load, the macroscopic changes in incident energy, reflected energy, and dissipated energy are consistent; that is, various energies gradually increase to a fixed value and tend to stabilize with the time of stress wave action. The transmission energy exhibits a rising trend in correlation with the duration of the dynamic load action, but the value is less than 0.1 J. The growth gradients of the different energies, in descending order, are: the growth gradient of incident energy, reflection energy, dissipation energy, and transmission energy. The energy inflection point appears at 60 °C. Based on the linear elastic fracture mechanics and damage mechanics theories, the expression for coal energy dissipation from the nanoscale to the microscale is established, and the relationship between energy dissipation and macroscopic mechanical behavior response of the coal samples is analyzed. The main physical components of the coal sample are calcite and kaolinite. Within the temperature range of 18–60 °C, the macroscopic failure form of the coal is horizontal tensile failure. The study results are introduced into dynamic disaster prevention and control and the surrounding rock system stability evaluation in deep mines.

The vibration energy dissipation behaviour of 3D-PAM type RVD

Considering that ordinary rubber materials have problems such as insufficient mechanical properties and poor shock absorption effect, a right-angle viscoelastic damper (RVD) based on 3D printed auxetic metamaterial (3D-PAM) is proposed in this paper. According to the refined finite element simulation, a dynamic energy dissipation study was conducted on the RVD. Firstly, the 3D-PAM was fabricated by selective laser sintering printing technique, and its material properties were demonstrated. Secondly, the 3D-PAM type RVD was simulated by ABAQUS to study the characteristics of dynamic energy dissipation and to investigate the stress distribution and displacement variation of the 3D-PAM layer. The results show that the hysteresis curve shape is smooth and full under all working conditions. The hysteresis loop shows linear characteristics under small displacement amplitude. As displacement amplitude increases, a hardening nonlinear response is observed. The maximum loss factor of the 3D-PAM type RVD reaches 0.64. Under the same thickness and loading conditions, the maximum loss factor has increased by 16.4% and 100.0% respectively compared to Polyurethane type RVD and Fluororubber type RVD. In conclusion, results indicate that the 3D-PAM type RVD designed in this project exhibits superior energy dissipation characteristics.

Analysis of energy dissipation characteristics and numerical simulation of surrounding rock control for backfill combinations with different ash/sand ratios

To reduce the economic cost of backfilling a mine, layers of cemented materials with different ash sand ratios are often used to backfill the void. In this study, we explored the damage evolution mechanism from the energy consumption point of view for backfill and rock combination with different ash sand ratios, and introduced the strength dissipation rate, damage value parameter and elastic strain energy rate to achieve the definition of damage in the specimens, as well as the characterization of the energy accumulation effect. In addition, the layered backfilling of the assemblage was simulated using FLAC 3D software. The results show that: (1) the elastic strain energy rate can reflect the accumulation ability of the strain energy of the specimen; the larger the strain energy rate, the stronger the accumulation ability; (2) the damage evolution of the backfill–backfill combination is divided into stages: initial damage repair stage, damage stable development stage, damage accelerated development stage and residual damage stage; and (3) the top layer with an ash/sand ratio of 1:4, the middle layer with an ash/sand ratio of 1:8 and the bottom layer with an ash/sand ratio of 1:10 is the optimal backfilling scheme. This study can provide a theoretical reference for the backfilling of a hollow area.

Energy Behavior of Sandstone Containing Weak Filling Joints with Multiple Angles under Dynamic Splitting Loads

The impact of weak filling joints with multiple angles on the energy dissipation mechanism is significant for surrounding rock engineering to prevent and mitigate disasters. In the present study, the sandstone samples containing weak filling joints were prefabricated, and dynamic splitting tests were conducted under three nominal loading rates with a modified Split Hopkinson Pressure Bar system. The effects of nominal loading rates and joint angles on time-based curves and energy-based curves were investigated systematically. The test results indicated that the nominal loading rate and joint angle had remarkable influences on energy dissipation characteristics. The sample containing a larger joint angle preferred brittle failure, whereas the sample with a smaller joint angle failed with a plastic feature. Moreover, the reflection energy decreased as the joint angle increased, which was opposite to the evolution tendencies of transmission energy and absorption energy. The transmission energy and absorption energy had different sensitivities to changes in joint angle and nominal loading rate. The exponential function could excellently describe the dependence of transmission energy, reflection energy, and absorption energy on joint angles. With the incremental joint angle, the energy reflection ratio had a contrary tendency to the energy transmission ratio.

Experimental and analytical studies on a novel double-stage coupling damper

A series of experimental and numerical studies on the novel double-stage coupling damper (DSCD) are presented in this paper. The effects of the damper configuration, friction-yield ratio (Rfy), and loading protocol on the hysteresis performance of the DSCD are investigated via quasi-static tests on seven specimens, and the variation in the failure mode, compression-strength adjustment factor, energy dissipation capacity, and equivalent viscous damping ratio of the DSCD is discussed. The test results demonstrate that the arrangement of ribs in the DSCD increased the average energy dissipation per loading cycle, compared to the device without these elements. The damper exhibits double-stage energy dissipation characteristics for several friction-yield ratios, however, relatively low values of this parameter (Rfy = 0.5) leads to reduced energy dissipation capacity, due to significant variations in the friction force associated with creep, ploughing, and preload effect. Furthermore, a detailed finite element model of the DSCD is conducted based on the experimental data, focusing on exploring the effectiveness of the device. Numerical analysis revealed that the cumulative energy dissipation and peak force of the DSCD reduced with increasing the length of the friction mechanism (Lf). A large clearance between the yield segment and the restraining system (Cb) reduces the stability of the equivalent viscous damping ratio of the damper under compression, but Cb has no effect in the cumulation energy dissipation of the damper, which has important implications in the design of these devices for the seismic control of structures. Based on these results design recommendations for the DSCD are provided.

Inter-stage performance and energy characteristics analysis of electric submersible pump based on entropy production theory

The electric submersible pump (ESP) is a crucial apparatus utilized for lifting in the oil extraction process. Its lifting capacity is enhanced by the multi-stage tandem structure, but variations in energy characteristics and internal flow across stages are also introduced. In this study, the inter-stage variability of energy characteristics in ESP hydraulic systems is investigated through entropy production (EP) analysis, which incorporates numerical simulations and experimental validation. The EP theory facilitates the quantification of energy loss in each computational subdomain at all ESP stages, establishing a correlation between microscopic flow structure and energy dissipation within the system. Furthermore, the underlying causes of inter-stage variability in ESP hydraulic systems are examined, and the advantages and disadvantages of applying the EP theory in this context are evaluated. Consistent energy characteristics within the ESP, aligned with the distribution of internal flow structure, are provided by the EP theory, as demonstrated by our results. The EP theory also enables the quantitative analysis of internal flow losses and complements existing performance analysis methods to map the internal flow structure to hydraulic losses. Nonetheless, an inconsistency between the energy characterization based on EP theory and the traditional efficiency index when reflecting inter-stage differences is identified. This inconsistency arises from the exclusive focus of the EP theory on flow losses within the flow field, disregarding the quantification of external energy input to the flow field. This study provides a reference for the optimization of EP theory in rotating machinery while deeply investigating the energy dissipation characteristics of multistage hydraulic system, which has certain theoretical and practical significance.

Anisotropic characteristics of layered backfill: Mechanical properties and energy dissipation

Layered backfill is commonly used in mining operations, and its mechanical behavior is strongly influenced by delamination parameters. In this study, 13 specimens with different numbers of delamination and delamination angle were prepared to investigate the anisotropic mechanical behavior, energy dissipation characteristics and crack development of backfill. P-wave velocity, uniaxial compression, scanning electron microscope (SEM), and acoustic emission (AE) experiments were conducted. The results indicate that: (1) The P-wave velocity has linear and elliptical relationships with the number of delamination surface and delamination angle, respectively; the strength, delamination parameters and P-wave velocity show a high degree of coincidence in terms of their function relationship, which can realize the rapid prediction of strength. (2) The microstructure of the delaminated surface is looser than that of the matrix, leading to a decrease in strength and an increase at the pore-fissure compaction stage. The number and angle of delamination increase linearly with the anisotropy coefficient. (3) The energy evolution in angle-cut backfill can be divided into four stages, with a decrease in the proportion of elastic energy at the initiation stress and peak stress with increasing number of delamination planes and delamination angle. (4) Crack development increases with the number of delamination surface and delamination angle, resulting in a decrease in energy dissipation coefficient and peak AE energy. These findings provide valuable insights for the design of filling materials and processes in mining operations.

MAGNETIC POLE REPULSIVE DAMPER (MPRD): A PROMISING SOLUTION FOR SEISMIC PROTECTION OF STRUCTURES

Owing to its high energy dissipation characteristics, the passive damper is an effective means of mitigating natural hazards for structures. In this study, a novel magnetic pole repulsive damper (MPRD), designed for reducing structural responses during natural hazards such as earthquakes, was developed and its performance was validated. The MPRD is an effective solution for seismic protection that works on the principle of magnetic repulsion and has a higher energy dissipation capacity than conventional dampers. The MPRD was fabricated using mild steel, neodymium magnets, and a set of helical springs. Two scaled reinforced concrete frames were tested using a 50 kN loading actuator. One frame was equipped with the MPRD, while the other served as a conventional frame for comparison. The frame with the MPRD showed reduced displacements. Compared with the conventional frame, that with the MPRD exhibited an increase in load of 40 % and an increase in energy dissipation of 6,44 %. Further, an increase in lateral stiffness, a 19,23 % increase in stiffness degradation, and changes in crack patterns were observed in the frame with MPRD compared to the conventional frame. The study's success in validating the MPRD performance in reducing structural responses in moderate to high seismicity regions makes it a promising solution for building seismic protection.

An analysis of impact load and fragmentation dimension to explore energy dissipation patterns in coal crushing

This research delineates the energy dissipation characteristics in coal crushing under impact loads, leveraging the capabilities of Separated Hopkinson Pressure Bar experimental system. A meticulous examination of both burst-prone and non-burst-prone coal samples during destruction processes was undertaken to decipher the dynamic compression mechanical attributes from perspectives of energy and fragmentatio‘s fractal dimensions. Burst-prone coal showcases a more pronounced escalation in fragmentation work in comparison to non-burst-prone samples, thereby illustrating a perceptible strain-rate dependent effect correlating with enhanced strain rates. Additionally, it was observed that incident, reflected, and transmitted energy trajectories for both sample categories follow an approximately linear ascendancy, albeit exhibiting diverse magnitudes. Burst-prone coal manifests a more rapid and focused energy growth compared to its non-burst-prone counterpart. When subjected to impact loads, a notable trend was discerned where the fragmentation’s fractional dimension escalated persistently with both the incident energy and the crushing work, portraying a prominent growth effect. The insights garnered from this study pave the way for distinguishing between impacted and unimpacted coal samples using energy perspectives and fragmentation's fractal dimensions.

A novel response-amplified shape memory alloy-based damper: Theory, experiment and numerical simulation

The energy dissipation capacity of shape memory alloy (SMA) dampers can be effectively improved owing to the success of response amplification technology. However, conventional response-amplified SMA dampers for building structures still face a risk of failure during extremely rare earthquake events. In this study, a novel response-amplified SMA damper (RASD) is proposed with the advantages of fully exploiting the energy dissipation characteristics of SMA materials and avoiding material failure. First, the components, configuration, and working principles of the proposed damper were described. Subsequently, a restoring-force model of the RASD was established, and its accuracy was verified through cyclic loading tests. Finally, seismic performance mitigation of a single-degree-of-freedom (SDOF) system under different hazard levels was conducted to evaluate the effectiveness and advantages of the proposed RASD quantitatively. The results reveal that the RASD has a good force amplification effect and excellent damping enhancement effect and thus conspicuously mitigates the seismic response of the SDOF system. In particular, the proposed RASD can effectively reduce the force and displacement demand of SMA materials without the risk of SMA failure, while significantly mitigating the structural response.

Study on the mechanical properties and energy dissipation characteristics of concrete subjected to high strain rate and sulfate attack

Marine structures, such as cross-sea bridges, port constructions, and offshore drilling platforms, are not only subjected to sulfate erosion, but also to various dynamic loads. Analyzing the damage evolution process of concrete under sulfate erosion and impact loads is the key to improving the lifespan of concrete. In order to study the damage evolution process of eroded concrete under high strain rates, the energy dissipation characteristics, basic physics and mechanical properties, and micro-fracture mechanism of sulfate-eroded concrete at different sulfate concentrations (C=0, 3%, 6%, and 9%) under high strain rate ranging from 70/s to 85/s are systematically studied by using the split Hopkinson pressure bar (SHPB) test system, X-ray diffractometer and SEM scanning electron microscope. The research results indicate that an increase in sulfate concentration leads to a decrease in Ca(OH)2 content and an increase in Ettringite (AFt) content in concrete specimens; As the sulfate concentration increases, the dynamic peak strength and dynamic elastic modulus of concrete specimens gradually decrease, while the dynamic peak strain of concrete specimens gradually increases; The degree of macroscopic fragmentation in concrete specimens subjected to impact compression becomes increasingly severe with rising sulfate concentrations; As the sulfate concentration increases, the proportion of reflected energy and dissipated energy gradually increases, while that of transmitted energy gradually decreases, and the energy absorption capacity of the sample is significantly improved; The results of the SEM test shows that with the increase of sulfate concentration, a large amount of AFt is generated at the joint fissures and the interface of cement aggregates, the expansion of AFt and the crack development of concrete reduce the integrity and stability of concrete. This study holds significant guidance for the application of concrete in impact situations under a sulfate attack environment.

Seismic performance of full-scale prefabricated semi-rigid bolted connection between RC column and composite beam

This paper presents a novel proposal for an assembled bolted joint between precast reinforced concrete (RC) column and steel-concrete composite beams, focusing on its seismic performance. To evaluate the joint's behavior, a comprehensive experimental investigation was conducted on a full-scale RC column to composite beam joint specimen subjected to pseudo-static loading. The study aimed to analyze the joint's failure mode, bearing capacity, ductility, and energy dissipation characteristics. The joint stiffness was assessed by analyzing the bending moment-rotation (M-θ) curve of the beam in accordance with the European standard BS EN 1993-1-8:2005. The experimental results demonstrate that the proposed assembled bolted joint exhibits semi-rigid behavior under positive moments and approaches rigidity under negative moments. To further enhance our understanding of the joint's performance, a finite element model was developed using ABAQUS. The stress distribution in each joint component, as well as the failure mode and ultimate bearing capacity, were analyzed in conjunction with the experimental results. Based on the findings from both the experimental and finite element analyses, an improved joint design is proposed. Additionally, parametric analysis was conducted on the enhanced joint configuration. The study findings indicate that the improved joint exhibits superior damage resistance, seismic performance, and enhanced assembly efficiency compared to the original design. This research contributes to the advancement of assembled bolted joints between precast RC columns and steel-concrete composite beams, offering valuable insights for practical applications in seismic regions.

Quantitative Study of the Weakening Effect of Drilling on the Physical and Mechanical Properties of Coal-Rock Materials.

Coal seam drilling is a simple, economical, and effective measure commonly used to prevent and control rock burst. Following rock burst, coal exhibits significant dynamic characteristics under high strain-rate loading. Our purpose was to determine the physical processes associated with impact damage to drilled coal rock, and its mitigation mechanism. An impact test was carried out on prefabricated borehole coal specimens, and the impulse signals of the incident and transmission rods were monitored. The crack initiation, expansion, and penetration of coal specimens were video-recorded to determine the mechanical properties, crack expansion, damage modes, fragmentation, and energy dissipation characteristics of coal specimens containing different boreholes. The dynamic compressive strength of the coal specimens was significantly weakened by boreholes under high strain-rate loading; the dynamic compressive strength and the dynamic modulus of elasticity of coal rock showed a decreasing trend, with increasing numbers of boreholes and a rising and decreasing trend with increasing borehole spacing; the number and spacing of boreholes appeared to be design parameters that could weaken coal-rock material under high strain-rate loading; during the loading of coal and rock, initial cracks appeared and expanded in the tensile stress zone of the borehole side, while secondary cracks, which appeared perpendicular to the main crack, expanded and connected, destroying the specimen. As the number of boreholes increased, the fractal dimension (D) and transmission energy decreased, while the reflection energy increased. As the borehole spacing was increased, D decreased while the reflective energy ratio decreased and increased, and the transmissive energy ratio increased and decreased. Drilling under high strain modifies the mechanical properties of impact damaged coal rock.

Experimental study on seismic behavior of cover-plate connections between steel beams and high strength steel box columns

As one of the beam-to-column fully restrained connections that could shift the plastic hinges of the beam away from the face of the column, cover-plate reinforced connections are expected to be a practical choice for high strength steel frame seismic applications. Five cover-plate reinforced and one unreinforced welded flange-bolted web connection specimens combined with Q355 steel I-shaped beams and Q460 or Q690 steel box columns were designed according to Chinese codes and tested under cyclic loads at full scale. Failure modes, including local buckling of the beam, complete joint penetration (CJP) weld fracture, and column web fracture, were reported. The strength, stiffness, deformation, and energy dissipation features were analyzed. The four cover-plate connections met the AISC requirements for special moment frames (SMF) with maximum story drift angles greater than 0.06 rad and exhibited satisfactory seismic behavior. According to the test results, a limit on the ratio of the diaphragm plate to column plate thickness should be considered when the electroslag welding (ESW) process is used in high strength box columns. The strong panel zone designed with a panel zone resistance ratio (γpz) greater than 1.20 was recommended for box columns with steel strength no less than 690 MPa. Additionally, other design implications of the results were discussed.

Seismic performance of an energy dissipating shear key for highway bridges using butterfly-shaped steel plates

Typical small-to-medium-span highway bridges in China are usually equipped with reinforced concrete shear keys in the transverse direction to provide lateral support for the superstructure under design earthquakes. In the 2008 Wenchuan earthquake, a large number of shear keys were severely damaged, resulting in out-of-control consequences of bearing sliding and girder unseating. The deficiency of traditional reinforced concrete shear keys has engendered a sense of urgency in China to develop novel and competent shear keys. As motivated by such a demand, this paper proposes a new kind of energy dissipating shear key (ED shear key) using butterfly-shaped steel plates based on the installation requirements of typical highway bridges in China. Eight full-scale specimens were designed and tested to examine the seismic performance of the ED shear keys under various test parameters. Based on the test results, the failure modes of the ED shear keys were identified and the energy dissipation characteristics were discussed. It was found that the ED shear keys had a stable and considerable capacity of energy dissipation even after buckling occurred to the strips. In addition, the ED shear keys exhibited very good deformation capacity and ductility, with the ultimate drift ratios ranging between 20.4 ∼ 24.3%. According to the identified failure modes of the ED shear keys, an analytical model was finally proposed. The comparison between the experimental and theoretical results demonstrated that the model can well represent the recorded force–displacement skeleton curves. It is expected that the ED shear keys can satisfy the seismic requirements of different highway bridges through adjusting the number of butterfly-shaped steel plates, and the proposed analytical model can be successfully applied to predict the seismic behavior of highway bridges in practical engineering.

Characteristics of Energy Dissipation in T-Shaped Fractured Rocks under Different Loading Rates

T-shaped fractured rocks in the engineering rock mass with different inclination angles, quantities, and cross patterns will cause slope landslides, cavern collapse, roof fall, and other disasters under the action of external forces. Deformation evolution of the T-shaped fractured rock is also significant for monitoring the stability of rock engineering structures. In this paper, the compression test of T-shaped fracture specimens was carried out under different loading rates. By modulating both the fracture inclination angle and the loading rate, the attributes pertaining to energy dissipation in the T-shaped fractured specimen were scrupulously scrutinized and subsequently expounded upon. The difference in the energy characteristics between fractured rock and intact rock was investigated to understand the deformation evolution of T-shaped fractured rock samples. The results show that when the fracture angle is 45° and 90°, the elastic strain energy and dissipated energy decrease as the secondary fracture angle increases. At the peak point, as the secondary fracture angle increases from 0°, the total absorbed energy, elastic strain energy, and dissipated energy of the T-shaped fractured rock increase, the ratio Ue/U of elastic strain energy to total energy increases, and the ratio Ud/U of dissipated energy to total energy decreases. The increase in loading rate leads to an increase in Ue/U and a decrease in Ud/U at the peak point of the T-shaped fractured rock specimen. The increase in loading rate leads to an increase in the total absorbed energy and elastic energy at the peak point of the T-shaped fractured rock, while the dissipated energy decreases. Investigative endeavors into the mechanics and energetic attributes of T-shaped fractured rocks bestow pragmatic and directive significance upon the safety assessment and stability prognostication of sundry geological undertakings.

Effect of working fluid temperature on energy dissipation characteristics of liquid ring vacuum pump

Liquid ring vacuum (LRV) pump working fluid temperature has a great influence on its energy efficiency. To improve the energy efficiency of the pump, a new model for the energy dissipation of the LRV pump was established based on the relationship between pump suction capacity, the vaporization loss rate of the working fluid and working fluid temperature. Furthermore, the theoretical model was experimentally verified and quantitatively analyzed. The results showed that the useless power increased and suction capacity decreased with increasing working fluid temperature. When the pump shaft speed was 1500r/min and the inlet pressure was 45kpa, the inlet liquid temperature increased from 15 °C to 45 °C, while the proportion of waste work dissipated by temperature rise of the working fluid significantly decreased from 78.8% to 22.1%. On the contrary, the proportion of the working fluid vaporization, the temperature rise of gas, and the convective heat transfer from the pump outer wall increased. The working fluid temperature positively correlated with the inlet fluid temperature and negative correlated with the inlet flow rate. To further reduce the pump operating temperature, it is necessary to increase the flow rate and reduce the inlet temperature.

A Robust Damping Control for Virtual Synchronous Generators Based on Energy Reshaping

Virtual synchronous generators (VSGs) have been proved to be important means to provide the inertia for future power systems. However, it suffers the issue of active power oscillation under various disturbances. In this paper, a robust damping control is proposed to mitigate the active power oscillation by reshaping the oscillation energy of VSGs. The paper first represents the power-angle dynamics of VSGs as an equivalent circuit and thus enables the understanding of oscillations from the circuit energy. It is revealed that the active power oscillation can be comprehended as an LC resonance and the damping provided by the traditional VSG is commonly insufficient. To tackle this issue, a robust damping method is proposed using interconnection and damping assignment passivity-based control (IDA-PBC). The theory of IDA-PBC is established based on the concept of energy reshaping, which guarantees the state tracking via its intrinsic energy dissipation characteristics. The IDA-PBC, when applied to VSGs, is a combination of the disturbance compensation via feedforward channels and the deviations regulation through feedback paths. Noticeably, the disturbance compensation is achieved with the support of an extended state observer (ESO), which can accurately estimate the lumped disturbance including the grid frequency variation and the model uncertainties. A guideline on the parameter selection is also provided through Bode-plot analysis. Finally, the effectiveness and merits of the proposed method is verified by hardware in the loop-based experiments with the comparison to the state of art work.

Experimental research on damage identification of fully free beams based on modal shapes

Ship damage identification is a new field of ship research, which is of great significance to damage control, life and property safety and strategic decision-making, but there is no effective method for ship damage identification. The structural system changes caused by ship damage are usually represented by the change of system mass, stiffness and energy dissipation characteristics, and then the change of structural dynamic characteristic parameters, which provides a theoretical basis for ship damage identification. In this paper, the ship is simplified as a beam model with fully free boundary conditions. Based on the dynamic characteristic parameter of the modal shape, the damage identification of the ship under six damage conditions is carried out through numerical simulation and experimental verification by using COMAC and the derived indexes of curvature mode and modal flexibility. The results show that the first four orders of curvature mode difference mean index and the curvature index of modal flexibility change rate can accurately locate the damage of hull beam structure; The damage degree of hull beam can be identified by the change of curvature mode difference index, but there are some errors in this method; The curvature index of modal flexibility change rate is positively correlated with the damage degree, which can reflect the damage degree of the structure. The research results of this paper can provide new methods and ideas for hull beam damage identification.