Accumulated Energy Dissipation Research Articles

Seismic behavior of looseness-induced inclined mortise and tenon joints in ancient timber structures: Experimental tests, multi-scale finite element model, and behavior degradation

The inclination damage of mortise and tenon (M-T) joints, caused by the looseness between the mortise and tenon, has an detrimental impact on the overall safety of structures. To investigate the effects of varying inclination rotation on the seismic behavior of ancient M-T joints, four 1/3.2-scaled straight M-T joints with different inclination rotation, one intact joint for comparison and three looseness-induced inclined joints, were cyclically tested. Typical failure modes of the damaged joints were identified. The influence of the tilt deterioration on the joint's hysteretic and rotational behavior was evaluated. The test results showed that with an increase in the inclination rotation, the size of the hysteretic loops of the inclined joints was increasingly smaller, the negative initial slippage and pinching effects were more apparent, the ultimate moment-resisting, initial elastic stiffness, and ductility of the specimens degraded significantly. Furthermore, the multi-scale finite element models of the looseness-induced inclined M-T joints were established using the ABAQUS. Based on the validated numerical model, the parameter analysis was performed. The influence of the frictional coefficient of wood, inclined rotation, and horizontal gap between the tenon and mortise on the joint's hysteretic behavior and energy dissipation mechanism was quantified. It is found that with a friction coefficient of 0.6, the positive and negative ultimate moments-resisting of the joint improved 65.99 % and 35.89 %, respectively; the joint's slip moment and energy dissipation increased by 12.18 and 3.78 times, respectively. With a 0.043 rad inclined rotation, the positive and negative ultimate moments of the joint decreased 23.32 % and 30.46 %, respectively; the joint's positive and negative initial elastic stiffnesses and cumulative energy dissipation reduced 49.12 %, 28.96 %, and 56.33 %, respectively. When the inclined rotation remained at 0.022 rad, the positive and negative ultimate moments of the joint including a 6 mm horizontal gap reduced 26.63 % and 34.20 %, respectively; the joint's positive and negative initial elastic stiffnesses, and accumulative energy dissipation decreased 42.42 %, 59.43 %, and 79.50 %, respectively.

Experimental and numerical investigation on axial compression behaviour of prefabricated ECC shell–reinforced concrete column

To improve the mechanical behaviour of traditional reinforcement concrete (RC) column, a novel prefabricated engineered cementitious composite (ECC)–reinforced concrete composite (ECC shell–C) column was proposed in this study. Subsequently, five prefabricated ECC shell–C columns, as well as one cast–in–place (CIP) RC column and one CIP pure ECC column, were designed and manufactured. Then, axial compression tests were carried out to explore their mechanical behaviour with considering the effect of the ECC shell thickness t and stirrup ratio ρv. On this basis, a numerical analysis method for the composite column was developed and verified. And numerical parametric study was carried out to clarify the influence of the design parameters on the axial compression behaviour of the prefabricated ECC shell–RC columns, including the compressive strength of ECC (fc,ecc) and concrete (fc), as well as the longitudinal reinforcement ratio (ρs). The experimental and numerical results demonstrated that the ECC shell can improve cracking resistance, ductility capacity and energy dissipation capacity of the RC column. The accumulated energy dissipation and ductility coefficient of the prefabricated ECC shell–RC columns with different t was 2.13–2.46 times and 1.14–1.35 times greater than those of the RC column, respectively. The ρv had small influence on the bearing capacity of the prefabricated ECC shell–RC columns, which can be appropriately reduced in practical application. The numerical analysis method considering the confinement effect of ECC shell can provide reliable prediction for the axial compression behaviour of prefabricated ECC shell–RC columns. fc,ecc and fc have the positive influence on the bearing capacity of the prefabricated ECC shell–RC columns but have negative influence on the ductility; meanwhile a moderately lower ρs will not significantly reduce the ductility.

Application of nonlinear energy sink for vibration suppression of mine boring machines

The propulsion system of mine boring machines often experiences severe vibration during mining. To suppress the vibration of the main beam system of roadheader and prevent the excessive fatigue of propulsion system, a magnetic nonlinear energy sink (MNES) is designed to suppress vibration. In this paper, firstly, the structure and design principle of MNES are introduced, and the dynamic equations of the main beam-MNES system are established. On this basis, the genetic algorithm is applied to optimize the vibration suppression of MNES, and the optimal parameters are determined. In results, the accumulative energy dissipation rate of optimal MNES in transient vibration can reach 90.2% and the vibration reduction effect of the optimal MNES in steady-state vibration is about 82.2%.

Suppression of multi-modal torsional vibration of the long-shafting rotor system with nonlinear piecewise NES

Long-shafting rotor systems tend to cross multi-order natural frequencies at start up and coast down, and the multi-order modes of vibration are excited by various excitations. The bending vibration can be limited to the single rotor, but the torsional vibration is obviously coupled between each single rotor, which leads to more problems. Therefore, the current work proposes to suppress the multi-modal torsional vibration of long-shafting rotor system by a single nonlinear piecewise NES (PNES). The dynamic models of long-shafting rotor system and the long-shafting rotor-PNES system are established in which the PNES is used to suppress the first two-order torsional vibration. The genetic algorithm (GA) is used to optimize the multi-modal transient and steady-state torsional vibration suppression results of PNES to obtain optimal parameters design, respectively. And the influences of the parameters of long-shafting rotor-PNES system and the additional position of PNES on the vibration suppression effect of PNES are also discussed. The experimental verification of the suppression of the first two-order steady-state torsional vibration of the long-shafting rotor system by a PNES is carried out. In numerical simulation, the percentage of accumulated energy dissipation of the PNES can reach 52.2 % for the multi-modal transient torsional vibration, and the inhibitions of the three torsional vibrations by the PNES are about 71.6 % and 77.9 %, 67.5 % and 81.2 %, 68.5 % and 69.5 % in the multi-modal steady-state torsional vibration suppression. In the test, only the suppression of the first torsional vibration by PNES is tested, that the PNES can reduce the first two-order steady-state torsional resonances of the first torsional vibration of the long-shafting rotor system by 62.1 % and 65 % respectively.

Experimental Study on Structural Performance of Cast-in-Place Frame Printed Concrete Wall

A growing number of nations and regions have printed concrete structures thanks to the application of 3D printing technology in the field of civil engineering. However, the houses built with printed concrete are mostly printed concrete wall structures with composite load-bearing walls and cast-in-place frames. This structure solely takes into account the performance of the structure under vertical loads, which does not address its ability to withstand horizontal loads. In this paper, wall specimens were designed and tested under horizontal reciprocal loads in order to investigate the structural performance of this cast-in-place border-frame printed concrete wall structure under horizontal loads. Four factors are examined in order to determine how well the cast-in-place frame printed concrete wall structure performs when subjected to horizontal loads: column longitudinal reinforcement strain, hysteresis curve, skeleton curve, and energy dissipation capacity. According to the test results, the addition of the wall increased the bearing capacity and accumulated energy dissipation of the specimen, but the increase in stiffness also caused the structural ductility to decrease. As a result, cracks were more likely to generate at the wall–column joints, so the stiffness matching between the printed concrete wall and the cast-in-place side frame needed to be further coordinated to obtain a higher ductility. It turns out that the wall sections have little impact on the seismic performance of the members.

A crystal plasticity based methodology for crack initiation lifetime prediction of fretting fatigue in AA2024-T351 alloy

AA2024-T351 alloy finds extensive use as a component material in the fields of civil engineering, machinery and aerospace, which are prone to long-term contact loading during service that may cause catastrophic failure such as fretting fatigue. In this work, a crystal plasticity finite element (CPFE) model has been established to predict the fretting fatigue crack initiation (FFCI) lifetime of AA2024-T351 alloy. Submodel methods for frictional contact parts are adopted, and crystal plasticity theory is utilized to obtain more accurate simulation results. The hotspots for fretting fatigue crack nucleation are determined by the difference of maximum value of maximum principal strain. The accumulated plastic slip and accumulated energy dissipation are utilized as fatigue indicator parameters (FIPs) to accurately predict FFCI lifetime. The results show that both FIPs predicted crack initiation lifetime are within twice the scatter band. Furthermore, the submodel is employed to generate diverse grain orientation sets while maintaining a constant total of 800 grains. The results indicate that different sets have little effect on the prediction of FFCI lifetime, but has a significant impact on the cumulative shear strain distribution between each individual grain at the mesoscale.

The seismic behaviors of steel-concrete-steel composite walls with dumbbell-shaped connectors

In this study, quasi-static tests were conducted on six steel-concrete-steel composite wall (SCSCW) specimens with novel dumbbell-shaped connectors (DSCs) to investigate their seismic performance. The research parameters included the connector arrangement scheme and the axial load. The failure mode, load-displacement curve, and strain data were analyzed in detail. All the specimens exhibited flexural failure, and the experimental phenomena included the local buckling of external steel plates and compressive failure of internal concrete. The local buckling located between the foundation and first row of connectors, had a limited effect on the bearing capacity of the specimens. The connectors effectively controlled the buckling range of the external steel plates. With increasing axial load, the deformation capacity of the specimens decreased significantly. Under the same displacement, the greater the axial load, the greater the secant stiffness, and the higher the accumulated energy dissipation value. When the load reached its peak value, the yield range of the bottom front steel plates of specimen with large axial load was less than that of the specimen with small axial load. The theoretical formula accurately calculated the flexural bearing capacity of SCSCWs, and the maximum error and the average ratio which was defined as experimental value to calculated value were 9% and 1.02, respectively. The horizontal load-displacement relationship of the specimens was calculated using the OpenSees software, and the maximum error of the bearing capacity was 4%. The parametric analysis showed that increasing the steel plate thickness can effectively improve the bearing capacity of SCSCWs.

Structural performance of H-type shear panel damper made of hot-rolled mild steel

In this study, cyclic loading experiments were performed to understand the mechanical characteristics of SPHC (hot-rolled mild steel) H-type shear panel dampers in a stud support-type installation. The specimens evaluated had panel width-to-thickness ratios of 48.9 and 52.5. Constant amplitude deformation loading was performed using shear deformation as a variable. A stable spindle-shaped hysteresis curve was exhibited with strength reduction caused by out-of-plane deformation. Maximum strength was achieved near the second cycle for all specimens and the specimens with the lower width-to-thickness ratio exhibited slightly higher strength increase ratios. Similarly, energy absorption capacity depended on load amplitude and width-to-thickness ratio of the panel part and specimens with a smaller width-to-thickness ratios corresponding to larger accumulative energy dissipation. Based on the Manson–Coffin law, the deformation capacity of the tested specimens was found to be lower throughout the fatigue curve when compared with the relative architectural guidelines.

Numerical simulation and experimental validation of the seismic response of suspended grooved-fit piping systems

Robust internal building pipeline is one of the most important non-structural components for reducing post-earthquake secondary disasters and maintaining normal use of buildings after an earthquake. The seismic damage of piping systems can result in the loss of firefighting abilities or lead to failure of water supplies and drainage systems in a building which can have serious implications for emergency rescue, post-disaster response and reconstruction work. In this study, moment-rotation hysteresis curves of grooved-fit piping-joints are obtained by quasi-static cyclical tests. Moment-rotation hysteresis models of piping-joints are developed using the Pinching4 uniaxial constitutive in the finite element software OpenSees. The calibrated model parameters are obtained using test data. The developed hysteresis models can accurately reproduce the moment-rotation hysteresis curves obtained in the experiments and simulate moment time-history during the loading process. The predicted accumulated energy dissipation is consistent with the test results. Using this observation, generic piping-joint moment-rotation hysteresis models are further developed and parameter values used to define the generic hysteresis model are obtained. A numerical model of a piping system is then developed using the generic hysteresis model. The numerical results confirm that the model can be used to reproduce the nonlinear behavior of a piping system under cyclic loading with high accuracy. The developed numerical model was further calibrated using shaking table test results. Comparisons between numerical and experimental responses demonstrate that the developed numerical model can be used to analyze the seismic response of a suspended piping system using grooved-fit joints.

Mechanical properties of short polypropylene fiber enhanced recycled concrete under cyclic compression

AbstractThis study investigated the mechanical properties and stress–strain relationship of polypropylene fiber recycled aggregate concrete (PFRAC) subjected to uniaxial cyclic compression. A total of 78 cylindrical specimens were designed for uniaxial cyclic compression test with coarse aggregate replacement rate, polypropylene fiber volume fraction, and loading rate as variation parameters. The failure process of the specimens under cyclic loading was observed and recorded. The stress–strain curve of PFRAC was summarized. The important mechanical properties of PFRAC were obtained, such as plastic strain, accumulated energy dissipation. The microstructure of PFRAC was analyzed by scanning electron microscopy, and the crack resistance mechanism of PFRAC under cyclic loading was revealed. The results show that the PFRAC under cyclic loading appeared oblique splitting failure. The compressive stress–strain curve envelope of PFRAC subjected to cyclic loading exhibited similarity to the monotonic counterpart. The addition of polypropylene fibers can improve the peak stress, peak strain, residual stress, post‐peak ductility, and accumulated energy dissipation of the recycled concrete. In addition, a constitutive relation formula for the PFRAC stress–strain curve under cyclic loading is proposed, and the fitting result is good.

Rotational behavior of bolted post-to-beam glulam connections with friction damped knee brace

Alternative bracing systems have been widely applied in heavy timber structures due to its contribution to lateral stiffness and strength, while the improvement in the ductility and energy dissipation capability is limited. Friction damped knee brace is applied in this paper to reinforce rotational behavior of the bolted post-to-beam glulam connections. Monotonic and cyclic loading experiments were conducted on fifteen full-scale specimens. The failure modes, elastic stiffness, moment capacity, hysteresis response and energy dissipation were evaluated and analyzed. The experimental results indicated that with the installation of friction damped knee brace, extremely large initial stiffness was achieved and the moment capacity and accumulated energy dissipation of the post-to-beam connections were increased by 207% and 950%, respectively. Moreover, a multi-segment theoretical model was proposed to predict the rotational behavior of the reinforced bolted glulam connections. The theoretically predicted moment-rotation curves showed good agreement with the experimental results.

Cyclic behavior of unbonded post-tensioned precast segmental concrete columns fabricated by 3D printed concrete permanent formwork

A 3D printed concrete permanent formwork of composite unbonded post-tensioned precast segmental concrete (3DPCPSC) column is proposed in this research. Its hysteresis performance and the failure mode are researched by quasi-static experiment and compared with the precast segmental reinforced concrete (PSRC) columns. Two interface enhancement methods, stainless-steel-nails internal shear bonds and prestressed steel-hoops external active confinement are proposed, and the enhancement effect and mechanism of 3DPCPSC columns with two interface enhancement methods are studied. Furthermore, the pouring and vibration load of 3D printing concrete formwork is analyzed using a three-dimensional solid finite element model finite element model. The results indicate that the energy dissipation capacity of 3DPCPSC columns is better than that of the PSRC column when the 3DPC formwork does not spall. The largest accumulated energy dissipation of the 3DPCPSC specimen is 1.14 times of the PSRC column. The 3DPCPSC column without interface enhancement has the phenomenon of formwork spalling, the bearing capacity is lower than the PSRC column, and the bearing capacity of the 3DPCPSC columns with two interface enhancement methods is close to or higher than the PSRC column. The initial stiffness of all the 3DPCPSC specimens is larger than the PSRC column. A comprehensive evaluation factor η is proposed to evaluate the hysteretic performance of precast segmental concrete columns. The comprehensive performance of the 3DPCPSC and PSRC is compared by the comprehensive evaluation factor η.

Creep-fatigue damage mechanisms and life prediction based on crystal plasticity combined with grain boundary cavity model in a nickel-based superalloy at 650°C

In this study, a dual-scale numerical procedure is developed to reveal the creep-fatigue damage mechanisms and estimate the crack initiation life for notched structures made of Inconel 718 superalloy at 650 °C. The macro-scale simulation solves the creep-fatigue deformation behavior with viscoplastic constitutive models, and the local deformation histories are supplied to the micro-scale simulation as boundary conditions. In the micro-scale simulation, the local damage evolutions are solved based on crystal plasticity combined with grain boundary cavity model. The creep damage is calculated by a special formulation in the form of cavity nucleation, growth and coalescence. The fatigue damage is represented by accumulated energy dissipation originated from crystal plasticity finite element simulation. Experimentally, the creep-fatigue tests of notched structures are carried out for Inconel 718 superalloy at 650 °C to validate the feasibility and robustness of the proposed numerical procedure. Moreover, the crack initiation behavior, including transgranular cracks under fatigue loading and intergranular cracks under creep-fatigue loading, is explained through different types of microstructure observations together with a dual-scale numerical procedure. In detail, the crack initiation sites transferred from the grain interior at notched surface to the grain boundaries at notched subsurface with an increase in hold times can be well predicted by the proposed numerical procedure. In addition, the simulated life based on the developed life prediction approach agrees well with the experimental data within an error band of ±2. Parametric studies show that the creep damage is more sensitive to grain boundary diffusion than to the external conditions of strain level and hold time.

Seismic behaviour of I-beams bolted CFST column connection using extended TSOBs

In this paper, the structural response and design method of Extended T-head Square-neck One-side Bolts (Extended TSOBs) bolted I-beams to Concrete Filled Steel Tubular (CFST) column cruciform connection were investigated under cyclic load through experimental, numerical, and theoretical approaches. The study mainly reports the effects of H-steel stiffener on seismic performance indices such as failure mode, bending bearing capacity, strength and rigidity degradations, and energy dissipation of the connection. Test results show that: (1) The H-steel stiffener can prevent Extended TSOB pull-out failure, but the relative slippage between the upper and lower columns is introduced in the strengthened connection; (2) The H-steel stiffener improves the peak bending moment, ultimate rotation, and accumulated energy dissipation of the connection by 3.3 %∼8.3 %, 33.9 %∼63.1 %, and 100.3 %, respectively; (3) The test connections can be classified as semi-rigid and partial strength joints according to Eurocode 4. The Finite Element Model (FEM) parametric analysis results show that Extended TSOB can be replaced by TSOB in the connections with H-steel stiffener and increasing the concrete grade has little effect on improving the connection bending bearing capacity. Moreover, two analysis models for calculating the bending bearing capacity of Extended TSOBs bolted I-beams to CFST column cruciform connections are proposed based on theory and tests. The accuracy and reliability of the proposed models are verified by comparing the calculated and tested bearing capacities.

Cyclic loading test for reinforced concrete columns strengthened with high-strength engineered cementitious composite jacket

This paper intends to investigate the enhancing effect of high-strength engineered cementitious composite (HS-ECC) jacket on the seismic performance of reinforced concrete (RC) column subjected to cyclic loading. Totally eighteen column specimens were prepared, including conventional RC columns, high-performance mortar (HPM), high-strength fiber-reinforced concrete (HSFRC), and HS-ECC jacketed columns. The effect of different strengthening materials, axial compression ratio (0.2, 0.3, and 0.4), scheme of HS-ECC jacket (strengthening height, cast-in-place or prefabricate), and stirrup spacing on the hysteresis characteristics of the RC columns were explored. Three typical failure modes can be observed depending on different strengthening materials, including shear failure mode, flexural failure mode, and multiple cracking mode. The test results indicate that fiber-reinforced concrete jacketed columns exhibited both high bearing capacity and superior ductility under different axial compression ratios. In particular, HS-ECC jacketed full-column possesses the best overall performance. Under the axial compression ratio of 0.2, the ductility value and the accumulated energy absorption of the HS-ECC jacketed column were improved by 67.7% and 394.8%, respectively, compared with ith conventional RC column. The superior ductility and saturated cracking behavior of HS-ECC ensure jacketed columns have higher damage tolerance and crack closure ability. Compared with HPM and HSFRC jacketed columns, the ultimate displacement of HS-ECC jacketed column was improved by 113.4% and 26.5%, respectively. The accumulated energy dissipation was 866.6% and 111.7% higher than that of HPM and HSFRC jacketed columns. Additionally, the increase in strengthening height could significantly enhance the seismic performance of HS-ECC jacketed columns. In terms of the strengthening scheme, the deformation capacity of cast-in-place HS-ECC jacketed column was better than that of column strengthened by prefabricate HS-ECC slab.

Experimental and numerical study on seismic performance of precast segmental CFST bridge columns with non-uniform prestressed steel tendons

A precast segmental concrete-filled steel tube (PSCFST) bridge column set with non-uniform (external and internal) prestressed post-tensioned (PT) steel strands was proposed, then the seismic performance of this type of bridge column was researched in this paper. The external prestressed steel strands are arranged on the outside of the bridge column to provide re-centering force, which can facilitate to observe the damage state of the PT tendons and be rapidly replaced. Pseudo static test was carried out on three scaled specimens, including a reference monolithic reinforced concrete (MRC) column and two PSCFST columns. The test results showed that both PSCFST columns have good seismic and resilience performance, with no visible damage and little residual displacement. The PSCFST column with external and internal PT strands shows better self-centering performance. The external prestressed steel strand will yield earlier than the internal, so it can be used as an early damage warning device for the PSCFST column. Then, a detailed finite-element (FE) model was established and validated using the test specimen. The finite element calculation results are in good agreement with the experimental results, indicating that good applicability of the established FE model. Furthermore, based on the validated FE model, the non-uniform arrangement position and initial prestress level of the prestressed PT steel strand were analyzed. That is, analysis was conducted to investigate the seismic and resilience behaviors of the PSCFST specimen with different arrangements of PT strands and different ratios of initial prestress of the internal and external PT strands. Analytical results indicated that increasing the initial prestress value of the external steel strand can increase the bearing capacity of the PSCFST specimens, while the initial prestress of the external prestressed steel strand has little effect on the initial stiffness, drift ratio, or accumulative energy dissipation. Furthermore, allocating more external PT strands can increase the bearing capacity and initial stiffness of the PSCFST specimen, while decreasing the drift ratio.

Deep HystereticNet to predict hysteretic performance of RC columns against cyclic loading

This article attempts to reproduce hysteretic performance of HRB600 bar reinforced concrete columns under cyclic loading by adopting multivariate deep learning methods. Bidirectional long short-term memory (BiLSTM) and bidirectional gated recurrent units network (BiGRU) have been modified for temporal sequence related strength prediction with the consideration of multivariate parameters. To this end, a database with a 79,244 (row) × 12 (column) matrix is prepared for training, validation, and testing purposes. The inputs to the model include time intervals, loading displacement, concrete strength, axial compression ratio, longitudinal reinforcement tensile grade, longitudinal reinforcement diameter, longitudinal reinforcement ratio, stirrup tensile strength, stirrup diameter, spacing, and stirrup reinforcement ratio while the target is the cyclic load. By comparing the energy dissipation, accumulated energy dissipation, stiffness degradation and backbone curve of the hysteretic performance, the capacity of the adopted methods is compared with that of the finite element analysis. The comparison shows that the adopted method can recovery the hysteretic curves very well and the GRU method exhibits the most accurate prediction performance because of the highest R2 and the lowest MAE, MSE, and RMSE. The originality and innovation are mainly reflected in the use of time series data-driven deep learning model to replace the existing empirical formula and finite element method to reconstruct the nonlinear hysteretic behavior, so as to predict the seismic performance of the structure.

Disipasi Energi Pada Kolom Dijacketing Dengan Wire Mesh dan Self Compacting Concrete Akibat Beban Siklik

In structures located in earthquake-prone parts, energy dissipation capacity is one of the criteria that must be achieved by the structure. For old structures or built long before earthquake regulations were introduced, it becomes very vulnerable to earthquakes, so it necessitates to be anticipated to prevent collapse, and one method that can be done is by jacketing. In this subject field, testing was conducted using a cyclic load on a reinforced concrete square column measuring 300 mm x 300 mm, which jacketing using wire mesh and self-compacting concrete. From the test results, it was found that in specimens jacketed with M6 wire mesh and self-compacting concrete experienced an increase in accumulative energy dissipation by 23.32% with a relatively minor loss of strength.

Life prediction and damage analysis of creep-fatigue combined with high-low cycle loading by using a crystal plasticity-based approach

Many high-temperature rotating components are always subjected to complex loading waveforms, arising the concerns for multi-damage driving crack initiation. In this paper, a series of strain-controlled low cycle fatigue (LCF) and creep-fatigue interaction (CFI) tests as well as the novel creep-fatigue combined with high-low cycle (CF-HL) tests were performed in a nickel-based superalloy at 650 ℃. Then, post-test microstructure observations were carried out to reveal the damage mechanisms under the multi-damaged CF-HL loading based on the EBSD-TEM combinative characterizations. In this aspect, the single-slip-dominated deformation mechanism under CFI loadings transformed to double-slip-dominated one under CF-HL loading was revealed. Computationally, a numerical procedure with a combination of crystal plasticity theory and finite element implementation was constructed for predicting the CF-HL crack initiation life and quantifying the crack initiation mechanisms. With the help of the developed fatigue and creep indicator parameters represented by accumulated energy dissipation, good agreements between experimental data and simulated results were achieved within a scatter band of ± 2 on life prediction. In addition, the simulation results indicate that the combined effects of grain orientation and multiple slip system activation showed great influence on the CF-HL crack initiation.

An inerter nonlinear energy sink for torsional vibration suppression of the rotor system

To reduce size and weight of the inertial mass required in traditional nonlinear energy sink (NES), an inerter nonlinear energy sink (INES) for suppressing the torsional vibration of the rotor system is developed in this paper. The INES is a combination of a NES with piecewise linear stiffness and an inerter whose vibration can be enlarged by levers. The structure of the INES is introduced, the inerter mechanism is analyzed and the dynamic model of the INES-rotor system is built. Vibration attenuation performance of INES on the rotor system is evaluated by the transient torsional vibration and steady-state torsional vibration, both of which are optimized by the genetic algorithm (GA). It is found that the inerter mass of INES can save about 14.2 times its own rotary inertia when suppressing the torsional vibration of the rotor system. By using the inerter, a significant damping effect also appears. In transient torsional vibration suppression, the percentage of accumulated energy dissipation of INES can reach 95.1%. In steady-state torsional vibration suppression, the peak vibration eliminations of INES for the rotor system can achieve 89.1% in simulation and 80.6% in test.