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A reduced-order method for parameter identification of a crystal plasticity model considering crystal symmetry

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Science China(Technological Sciences) 2019年第3期62卷 373-387页

作者： HAN ShiWei YANG XiaoGuang SHI DuoQi HUANG Jia School of Energy and Power engineering Beihang University beijing key laboratory of aero-engine structure and strength Shijiazhuang Flying College

The focus of this paper is to identify the material parameters of a crystal plasticity model for Ni-base single crystal *** facilitate the stepwise calibration of the multistage flow rules, further decoupling and simplification are implemented without compromising its simulating capability. Reduced-order kinematics in crystal plasticity, which only comprise scalar components instead of their original tensors, are derived by considering the crystal symmetry and uniaxial loading condition. The relationships between components in elastic and plastic deformation gradient are established by explicitly accounting the control quantities, which is overall load in stress-controlled creep tests or displacement of gauge section in strain-controlled experiments,respectively. In addition, their approximate forms are also given by neglecting both elastic changes in volume and section area. A new objective function based on the shortest distance was introduced to correlate data from the simulations and experiments, and an integrated optimization process without finite element computation was developed into a commercial software *** in the crystal plasticity model are successfully calibrated by the efficient reduced-order method from the experimental data in such a sequence as: elastic, plastic, primary stage and secondary to tertiary stages creep laws. The multistage weak coupling flow rules can significantly reduce the non-uniqueness of the optimal solution under the circumstance of excessive parameters but insufficient experimental data. Finally, the optimized results with the reduced-order method have been validated by the finite element method.

关键词： reduced-order crystal plasticity parameter identification finite deformation single crystal crystal symmetry

Moving Mechanism of a High-speed Insect-scale Microrobot via Electro-magnetically Induced Vibration

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Journal of Bionic engineering 2021年第3期18卷 662-673页

作者： Xinyi Liu Zhiwei Liu Yangsheng Zhu Jiaming Leng Mingjing Qi Jianmei Huang Xiaojun Yan School of Energy and Power engineering Beihang UniversityBeijing 100191China National key laboratory of Science and Technology on aero-engine aero-thermodynamics Beijing 100191China beijing key laboratory of aero-engine structure and strength Beijing 100191China Collaborative Innovation Center of Advanced aero-engine Beijing 100191China

This paper presents the moving mechanism of a high-speed insect-scale microrobot via electromagnetically induced vibration of two simply supported *** microrobot,which has a body length of 12.3 mm and a total mass of 137 mg,can achieve reciprocating lift motion of forelegs without any intermediate linkage mechanisms due to the design of an obliquely upward body tilt *** gait study shows that the body tilt angle prevents the forelegs from swinging backward when the feet contact the ground,which results in a forward friction force applied on the *** forward movement,the microrobot utilizes the elastic deformation of the simply supported beams as driving force to slide forward and its forelegs and rear legs work as pivots alternatively in a way similar to the movement of soft *** gait analysis also indicates that the moving direction of the microrobot is determined by whether its body tilt angle is obliquely upward or downward,and its moving speed is also related to the body tilt angle and as well as the body *** an applied AC voltage of 4 V,the microrobot can achieve a moving speed at 23.2 cm s1(18.9 body lengths per second),which is comparable to the fastest speed(20 cm s-1 or 20 body lengths per second)among the published insect-scale *** high-speed locomotion performance of the microrobot validates the feasibility of the presented actuation scheme and moving mechanism.

关键词： Legged microrobot electromagnetic actuation moving mechanism high-speed

Nonlinear modal electromechanical coupling factor for piezoelectric structures containing nonlinearities

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Chinese Journal of aeronautics 2023年第2期36卷 100-110页

作者： Yaguang WU Yu FAN Lin LI School of Energy and Power engineering Beihang UniversityBeijing 100191China beijing key laboratory of aero-engine structure and strength Beijing 100191China

Within the linear framework,the Modal Electromechanical Coupling Factor(MEMCF)is an important indicator to quantify the dynamic conversion of mechanical energy and electrical energy of piezoelectric *** is also an important tool to guide the piezoelectric damping design of linear *** aircraft often fly in maneuvers,and the variable working conditions induce drastic changes in the load level on *** and contact nonlinearities of thin-walled structures and joint structures are often *** achieve a good vibration reduction effect covering all working conditions,one cannot directly use linear electromechanical coupling theory to instruct the piezoelectric damping design for nonlinear ***,this paper defines the Nonlinear Modal Electromechanical Coupling Factor(NMEMCF)and proposes the corresponding numerical method for the first time to quantitatively evaluate the electromechanical coupling capability of nonlinear piezoelectric *** candidate definitions of the NMEMCF are given,including two frequency definitions and one energy *** energy definition is the most promising *** is not only applicable to both conservative and dissipative nonlinear structures but also compatible with the linear *** addition,based on the energy formula,the NMEMCF can be obtained by only performing one nonlinear modal analysis in the open-circuit *** analytical findings and the numerical tool are validated against two piezoelectric structures with different types of nonlinearities.A strong correlation among the NMEMCF,geometric parameters,and energy dissipation is *** results confirm that the proposed NMEMCF captures the physics of the electromechanical coupling phenomenon associated with nonlinear piezoelectric structures and can be used as an essential design indicator of piezoelectric damping,especially for variable working conditions.

关键词： Modal electromechanical coupling factor Multiharmonic balance method Nonlinear normal modes Piezoelectric damping Vibration control

Experimental study and numerical modeling of the damage evolution of thermal barrier coating systems under tension

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Science China(Technological Sciences) 2018年第12期61卷 1882-1888页

作者： LI ShaoLin YANG HongWei QI HongYu SONG JiaNan YANG XiaoGuang SHI DuoQi School of Energy and Power engineering Beihang University Beijing 100191 China beijing key laboratory of aero-engine structure and strength Beijing 100191 China

This study investigated the damage evolution(i.e., formation of vertical cracks, transformation of vertical cracks to interfacial crack and delamination) of thermal barrier coating systems under tension by using experimental and numerical *** results revealed that the first transverse crack that was perpendicular to the load direction occurred when the strain of the top coat reached 0.5%. The full-scale strain of the top coat layer obtained by using the Digital Image Correlation technique indicated that surface cracks formed due to the coalescence of micro-cracks. Moreover, the results of the finite element method demonstrated that the vertical cracks initiated from the coating surface and extended through the thickness of the coatings. The density of the surface cracks was used as a damage evolution indicator such that numerical simulation could predict the cracking behaviour under tension loading. The results were consistent with those of the experimental study.

关键词： damage evolution interfacial thermal barrier coating systems digital image correlation

Oxidation-induced damage of an uncoated and coated nickel-based superalloy under simulated gas environment

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Rare Metals 2018年第3期37卷 204-209页

作者： Shao-Lin Li Hong-Yu Qi Xiao-Guang Yang School Of Energy and Power engineering Beihang UniversityBeijing 100191 China beijing key laboratory of aero-engine structure and strength Beijing 100191 China

Turbine blades and vans operated in an aggressive gas environment usually suffer from combined oxidation and cycle loading effects. The surface oxide layer will result in premature failure and lead to a significant reduction in the service lifetime. The effects of prior oxidation-induced damage under a simulated combustion-gas environment on the fatigue lifetime of the directionally solidified（DS） nickel-based superalloy DZ125 with and without an oxidation-resistant coating were presented. The fatigue lifetime of uncoated samples is adversely affected by prior oxidation exposure. The deterioration of fatigue lifetime in uncoated samples is associated with surface microstructural degradation, which occurs during prior exposure. However,the presence of MCrAlY coating is beneficial for the sample＇s lifetime under high stress. Further scanning electron microscopy（SEM） analysis demonstrates that the coating does not contribute to the initiation mode of fatigue cracks.

关键词： Gas environment Fatigue Lifetime Coating Superalloy

Microstructural evolution and restoration of creep property for a damaged K403 alloy after rejuvenation heat treatments

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Rare Metals 2021年第7期40卷 1865-1871页

作者： Liang Wang Xiao-Guang Yang Hong-Yu Qi Duo-Qi Shi Shao-Lin Li School of Energy and Power engineering Beihang UniversityBeijing 100191China beijing key laboratory of aero-engine structure and strength Beijing 100191China

Rejuvenation heat treatments can restore the microstructures and mechanical properties of the degraded turbine blades in gas turbine *** we analyze the effects of rejuvenation heat treatments on the microstructural characteristics and mechanical properties of damaged and undamaged specimens of a Ni-based superalloy,*** damaged specimens were found to have degraded microstructures and shorter creep lifetime than the undamaged *** rejuvenation heat treatment proved beneficial,especially for specimens exposed to damage for 50 *** addition,the microstructure recovery and creep life were found to depend on the predamage durations of the specimens.A y’-precipitate-based creep lifetime model was established to predict the residual lifetime based on the microstructural information.

关键词： Microstructural evolution Creep property Restoration Rejuvenation heat treatments

Macro-phenomenological high-strain-rate elastic fracture model for ice-impact simulations

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Chinese Journal of aeronautics 2023年第3期36卷 146-160页

作者： Jiang FAN Qinghao YUAN Fulei JING Guangchen BAI Xiuli SHEN School of Energy and Power engineering Beihang UniversityBeijing 100191China beijing key laboratory of aero-engine structure and strength Beijing 100191China Collaborative Innovation Center of Advanced aero-engine Beijing 100191China aero-engine Academy of China Aero Engine(Group)Corporation of ChinaBeijing 101304China

The ice impact can cause a severe damage to an aircraft’s exposed structure,thus,requiring its *** numerical simulation represents an effective method to overcome this *** establishment of the ice material model is ***,ice is not a common structural material and exhibits an extremely complex material *** material models of ice reported so far are not able to accurately simulate the ice behavior at high strain *** study proposes a novel high-precision macro-phenomenological elastic fracture model based on the brittle behavior of ice at high strain *** developed model has been compared with five reported models by using the smoothed particle hydrodynamics method so as to simulate the ice-impact process with respect to the impact speeds and ice *** important metrics and phenomena(impact force history,deformation and fragmentation of the ice projectile and deflection of the target)were compared with the experimental data reported in the *** findings obtained from the developed model are observed to be most consistent with the experimental data,which demonstrates that the model represents the basic physics and phenomena governing the ice impact at high strain *** developed model includes a relatively fewer number of material ***,the used parameters have a clear physical meaning and can be directly obtained through ***,no adjustment of any material parameter is needed,and the consumption duration is also *** advantages indicate that the developed model is suitable for simulating the iceimpact process and can be applied for the anti-ice impact design in aviation.

关键词： Crack propagation Elastic fracture High strain rate Ice impact Impact force Material model

Investigation on nonlinear lateral-torsional coupled vibration of a rotor system with substantial unbalance

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Chinese Journal of aeronautics 2020年第6期33卷 1642-1660页

作者： Jie HONG Pingchao YU Yanhong MA Dayi ZHANG School of Energy and Power engineering Beihang UniversityBeijing 100083China Collaborative Innovation Center of Advanced aero-engine Beihang UniversityBeijing 100083China beijing key laboratory of aero-engine structure and strength Beijing 100083China

Substantial unbalance may be caused by fan blade off during the operation period of gas turbine engines,and related dynamic problems are very critical to the safety design of rotor system in *** article aims to understand lateral-torsional coupled vibration of the rotor system with substantial *** governing equation of a modified unbalanced rotor system is established based on Lagrangian ***,a mathematical analytical method is proposed in which a linear approximation is derived and the Floquet theory and Hill’s method are incorporated,from which the modal characteristics of the unbalanced rotor are *** modal characteristics of the unbalanced rotor system are revealed comprehensively for the first ***,the relation between the modes and responses of the unbalanced rotor is discussed in *** results show that the lateral vibration and torsional vibration of the unbalanced rotor are coupled through the inertial terms in the governing *** to the coupling,veering and lock-in phenomena occur between the frequencies of the forward whirl mode and the torsional ***,lock-in can lead to a kind of principal *** regard to the response of the unbalanced rotor,both natural vibration components and enforced vibration components appear in the lateral response,while only natural vibration components appear during torsional ***,natural vibration components play a crucial role in the response within the principal instability region and cause divergence of the vibration amplitudes in the lateral and torsional directions.

关键词： Instability Lateral-torsional coupled vibration Lock-in phenomenon Modes Unbalanced rotor

Experimental investigation on dynamic response of flat blades with underplatform dampers

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Chinese Journal of aeronautics 2019年第12期32卷 2667-2678页

作者： Dayi ZHANG Bin GAO Jie HONG Jianwei FU Xiangyun GE School of Energy and Power engineering Beihang UniversityBeijing 100083China beijing key laboratory of aero-engine structure and strength Beijing 100083China Collaborative Innovation Center of Advanced aero-engine Beihang UniversityBeijing 100083China

One test rig with three blades and two Under-Platform Dampers(UPDs) is established to better understand the dynamical behavior of blades with UPDs. A pre-loaded spring is used to simulate the centrifugal load acting on the damper, thereby achieving continuous adjustment of the pressing load. UPDs with different forms, sizes and materials are carefully designed as experimental control groups. Noncontact measurement via a laser Doppler velocimeter is employed and contact excitation which is performed by an electromagnetic exciter is adopted to directly obtain the magnitude of the excitation load by a force sensor mounted on the excitation rod. Particular attention is paid to the influence of the contact status of the contact surfaces, e.g. the pressure-sensitive paper is used to measure the effective contact area of the UPDs. The experimental variables are selected as the centrifugal force, the amplitude of the excitation force, the damper mass, the effective contact area, and the damper material. The Frequency Response Function(FRF) of the blade under different experimental parameters is obtained by slow frequency sweep under sinusoidal excitation to study the influence of each parameter on the dynamic characteristics of the blade and the mechanism analysis is carried out combined with the experimental results.

关键词： Effective contact area Forced response Friction Test rig Turbo machinery Underplatform dampers