Jia Sun

Bio: Jia Sun is an academic researcher from Royal Institute of Technology. The author has contributed to research in topic(s): Equations of motion & Boundary value problem. The author has an hindex of 4, co-authored 6 publication(s) receiving 120 citation(s).

General shell model for a rotating pretwisted blade

Abstract: A novel dynamic model for a pretwisted rotating compressor blade mounted at an arbitrary stagger angle using general shell theory and including the rotational velocity is developed to study the eigenfrequencies and damping properties of the pretwisted rotating blade. The strain-displacement relation and constitutive model based on the general (thick) shell theory are applied to bring out the strain energy of the rotating blade. Using the Hamilton’s principle, the variational form of the total energy is derived in order to obtain the corresponding weak form for the numerical simulation. The model is validated by comparing to literature results and Ansys results, showing good agreement. Parametric analyses are carried out to study the influence of the rotation velocity, the stagger angle and the radius of the disk on the eigenfrequencies of the pretwisted blade. Proportional damping is included into the proposed model to investigate the influence of rotational velocity on the damping characteristics of the pretwisted rotating blade system. It is shown that, due to inertial and Coriolis e ects, damping decreases as the rotation velocity increases for the lower part of the velocity range considered and either decreases or increases depending on the mode order for higher velocities. Furthermore, frequency loci veering as a result of the rotation velocity is observed. The proposed model is an e cient and accurate tool for predicting the dynamic behavior of compressor blades of arbitrary thickness, stagger angle and pretwist, potentially during the early designing stage of turbomachinery.

A dynamic rotating blade model at an arbitrary stagger angle based on classical plate theory and the Hamilton's principle

Abstract: A dynamic model based on classical plate theory is presented to investigate the vibration behavior of a rotating blade at an arbitrary stagger angle and rotation speed. The Hamilton's principle is ...

Dynamic modeling of a multilayer rotating blade via quadratic layerwise theory

Abstract: A novel dynamic model for a multilayer rotating blade mounted at an arbitrary stagger angle using a quadratic layerwise theory is developed to study structural dynamics of the blade, particularly damping properties, using various coating layer configurations. A reduced two-dimensional (2D) model is used to describe the dynamic behavior of each layer in the weak form, while the quadratic layerwise theory is applied to interpolate the transverse shear stresses along the thickness direction. Results of numerical simulations with the reduced 2D model are compared to the full three-dimensional (3D) model showing an excellent agreement, comparable to the cubic layerwise theory, for both modal analysis and frequency response calculations. Moreover, damping analyses are performed on two types of multilayer blades: two-layer (free damping) and three-layer (constrained layer), in both non-rotating and rotating situations, and, parametric analyses with varying coating thickness and rotation speed are carried out. It is shown that damping decreases as the rotation speed increases due to inertial and Coriolis effects. Furthermore, frequency loci veering as a result of the rotation speed is observed. The proposed model gives an efficient and accurate way to study the dynamic behavior of rotating multilayer structures, such as compressor blades.

Coating methods to increase material damping of compressor blades : measurements and modeling

Abstract: Methods are developed to improve the damping performance of compressor blades, where hard coating technique isapplied to increase the structural damping, displaying both measurements and modeling r ...

A study of a dynamic rotating blade at an arbitrary stagger angle using Chebyshev collocation method

Abstract: A dynamic model of a straight, rotating blade is used and the equations of motion as well as the boundary conditions are extracted from the corresponding variational formulas. The Chebyshev collocation method is applied to discretize the two-dimension equations of motion on a 2D mesh grid. With an appropriate implementation on the dynamic boundary conditions, a coupled 2 nd order ordinary differential equation is obtained for the numerical simulation. A validation study with the convergence analysis is performed showing an acceptable agreement and a parametric analysis is implemented giving a Campbell diagram. Furthermore, the results archived by this method can be applied to both forced response and transient analyses.

An overview of layerwise theories for composite laminates and structures: Development, numerical implementation and application

Abstract: Over the past decades, a vast number of theories for numerical modeling of laminated composite plates and shells has been developed by various researchers and for diverse reasons. Three-dimensional elasticity theory , equivalent single-layer theories, zig-zag theories and layerwise theories are notable examples. In general, computing 3D elasticity solutions require huge computational time, the ESL theories cannot furnish satisfying results for thick laminates or laminates with distinct properties between layers, and the zig-zag theories cannot directly obtain the transverse stress fields from the constitutive model. The layerwise theory treats each layer individually and C z 0 continuity is satisfied from the beginning; therefore, it yields results comparable to 3D elasticity solutions. These attributes and advantages have driven the prosperity of layerwise theories for analysis of composite laminates and structures. The main aim of this review is to provide the recent development of layerwise theories, their numerical implementation, and application in the analysis of composite laminated structures . The main conclusions and possible future research trends are presented. We expect this review will provide a clear picture of layerwise theory for modeling of composite laminated structures and serve as a useful resource and guide to researchers who intend to extend their work into these research areas.

Free vibration of rotating pretwisted functionally graded composite cylindrical panel reinforced with graphene platelets

Abstract: This paper investigates the free vibrations of the rotating pretwisted functionally graded (FG) composite cylindrical panels reinforced with the graphene platelets (GPLs) by considering the cantilever boundary conditions. The weight fraction of the graphene platelets in each ply may be different, which leads to the layer-wise functionally graded composite cylindrical panels reinforced with the GPLs. The effective Young's modulus is calculated by the modified Halpin-Tsai model. The effective Poisson's ratio and mass density are derived by the rule of the mixture. The strain-displacement relationship is acquired by the Green strain tensor. Based on the first-order shear deformation theory, Chebyshev-Ritz method is used to obtain the natural frequencies of the rotating pretwisted functionally graded composite cylindrical panel reinforced with the GPLs. The natural frequencies are discussed by considering different material and geometry parameters of the rotating pretwisted functionally graded composite cylindrical panel reinforced with the GPLs, such as the GPL distribution pattern, the GPL weight fraction, the geometries of the GPLs, the pretwisted angle, the presetting angle and the rotating speed. Several validations are carried out, the numerical results are in good agreement with the results of the literature and ANSYS.

Vibration characteristics of rotating pretwisted composite tapered blade with graphene coating layers

Abstract: A new dynamic model of the rotating tapered cantilever cylindrical panel with the graphene coating layers is developed to investigate the vibration characteristics of the rotating pretwisted tapered blade. It is assumed that the graphene platelets (GPLs) are randomly oriented and uniformly dispersed in the top layer and the bottom layer of the rotating pretwisted composite tapered blade. The modified Halpin-Tsai model is used to estimate the effective Young's modulus. The rule of the mixture is used to calculate the effective Poisson's ratio and mass density. Based on the Green strain tensor, an accurate strain-displacement relationship is acquired. The effects of the centrifugal force and Coriolis force are considered in the formulation. The Chebyshev-Ritz method is utilized to obtain the natural frequencies and mode shapes of the rotating pretwisted composite tapered blade with the graphene coating layers. The accuracy of the proposed model is validated through several comparison studies with the results of the present literatures and ANSYS. The free vibration characteristics are analyzed by considering different material and geometry parameters of the rotating pretwisted composite tapered cantilever cylindrical panel with the graphene coating layers, such as the graphene platelet (GPL) geometry, GPL weight fraction, taper ratio, length-to-radius ratio, pretwist angle, presetting angle and rotating speed. The frequency veering and the mode shape shift phenomena are found in the rotating pretwisted tapered cantilever cylindrical panel with the graphene coating layers.

General shell model for a rotating pretwisted blade

Abstract: A novel dynamic model for a pretwisted rotating compressor blade mounted at an arbitrary stagger angle using general shell theory and including the rotational velocity is developed to study the eigenfrequencies and damping properties of the pretwisted rotating blade. The strain-displacement relation and constitutive model based on the general (thick) shell theory are applied to bring out the strain energy of the rotating blade. Using the Hamilton’s principle, the variational form of the total energy is derived in order to obtain the corresponding weak form for the numerical simulation. The model is validated by comparing to literature results and Ansys results, showing good agreement. Parametric analyses are carried out to study the influence of the rotation velocity, the stagger angle and the radius of the disk on the eigenfrequencies of the pretwisted blade. Proportional damping is included into the proposed model to investigate the influence of rotational velocity on the damping characteristics of the pretwisted rotating blade system. It is shown that, due to inertial and Coriolis e ects, damping decreases as the rotation velocity increases for the lower part of the velocity range considered and either decreases or increases depending on the mode order for higher velocities. Furthermore, frequency loci veering as a result of the rotation velocity is observed. The proposed model is an e cient and accurate tool for predicting the dynamic behavior of compressor blades of arbitrary thickness, stagger angle and pretwist, potentially during the early designing stage of turbomachinery.

A dynamic rotating blade model at an arbitrary stagger angle based on classical plate theory and the Hamilton's principle

Abstract: A dynamic model based on classical plate theory is presented to investigate the vibration behavior of a rotating blade at an arbitrary stagger angle and rotation speed. The Hamilton's principle is ...