Dr. YANHU ZHANG was born in Gansu, China in 1985. He received the B.S. degree from North China University of Water Resources and Electric Power, China, in 2008, and the M.S. degree in mechanical engineering from Jiangsu University, China, in 2011, respectively. He obtained the Ph.D. Degree in Mechanical Engineering from Harbin Institute of Technology in 2016. He joined School of Mechanical Engineering (Institute of Advanced Manufacturing and Equipment Technology), Jiangsu University in March 2017, and works currently as an associate professor at SME, Jiangsu University. His research interests include piezoelectric motors, service performances and friction materials.
International Journal of Mechanics and Materials in Design, Jul 25, 2021
Conform and non-conformal contact problem in the face of piezoelectric motors can be hard to gras... more Conform and non-conformal contact problem in the face of piezoelectric motors can be hard to grasp, especially both the friction drive and wear lifespan are considered. Flowing the classical contact issue, an elastic brittle flat punch as the driving tip of the stator for piezoelectric devices is chosen and the contact behaviour under elliptical ultrasonic vibration is investigated using finite element method. A limited stress analysis is conducted after the quasi-static contact of the driving tip and the slider of the linear ultrasonic motors. After the analytical traces and experimental test on the fracture failure induced by the stress actions, the failure criteria of the elastic brittle driving tip are discussed. Results show that this quasi-static method can be applied to the complex contact analysis of an elliptical vibration device, and the failure characteristics induced by stress and strain can be obtained by FEM simulation and experiment verification. The pre-fracture stress map provides an important basis for the design of the geometrical mutation edge (e.g. edge fillet) of the elastic brittle punch and the composite structure for strength capacity. The failure analysis of brittle materials under ultrasonic vibration requires attention on quasi-brittle and quasi-plastic strength criterions. This study focus on determination of the contact stresses and the limited states during the elliptical vibration of a stator tip against slider. It also is important for the analysis on failure modes of frictional materials of ultrasonic devices, fretting wear of high-frequency connecting parts and machining process assisted with ultrasonic vibration.
Ionic liquids have received wide attention due to their novel optoelectronic structures and devic... more Ionic liquids have received wide attention due to their novel optoelectronic structures and devices as an optical means of regulating electricity. However, the quantitative testing and analysis of refractive index of ionic liquids under electric field are rarely carried out. In the present study, an experimental apparatus including a hollow prism is designed to measure the refractive indices of ionic liquids under different electric fields. Five groups of imidazole ionic liquids are experimentally investigated and an inversion is performed to determine the refractive indices under electric fields. The error propagation analysis of the apex angle and the minimum deflection angle are conducted, and the machining accuracy requirements of the hollow prism are determined. The results show that the refractive indices of imidazole ionic liquids change with the light wavelength, following a downward convex parabola. Furthermore, the refractive index decreases with the carbon chain length of ionic liquid at a given wavelength, presenting an order of C3MImI > C4MImI > C5MImI > C3MImBr > C3MImBF4. Notably, the refractive index of imidazole ionic liquid exhibits a nonlinear change with the applied voltage at 546 nm and a monotonical decrease at 1529 nm. Besides, the variation of refractive index at 1529 nm with the applied voltage is larger than that at 546 nm and 1013 nm. Importantly, the variation of refractive index is contrary to that of absorption coefficient under electric field. This study illustrates that the theory of electrode and carrier transport can be used to explain the law of variation of n–k value of ionic liquid under the electric field, and provides the support for the evaluation of physical properties of ionic liquids, the measurement of optical functional parameters and the regulation of electric–optic performances of optical devices.
Piezoelectric materials directly convert energy between electrical and mechanical domains, and ha... more Piezoelectric materials directly convert energy between electrical and mechanical domains, and have been widely employed in electronic devices as sensors and energy harvesters. Recent research endeavors are mainly devoted to dealing with problems such as high stiffness, brittleness, toxicity, poor durability, and low piezoelectric coefficients. Among developed strategies, chemical modification captures much attention. However, the exact physical properties and direct experimental evidence of chemical modification remain elusive or controversial thus far. In this review, we discuss the recently developed piezoelectric modification strategies for piezoelectric composites and assess the effect of different chemical modification approaches on piezoelectric properties. Moreover, we outline existing challenges and new applications of piezoelectric composites.
In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatel... more In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatelet (GPL)-reinforced composite multilayer cylindrical shell panel is studied for the first time. The shell is stiffened by both stringers and rings. Additionally, the effect of reinforcing the shell panel, ring and stinger with GPLs is independently studied. Halpin–Tsai relations are employed to evaluate the mechanical properties of the shell panel, rings and stringers. The first-order shear deformation shell theory, accompanied by the Lekhnitsky smeared stiffener model, using the numerical finite element method and Hamilton principle, is employed to develop the governing motion equations of the shell panel. Four different types of GPL patterns, including FG-A, FG-X, FG-O and UD, are assumed across the thickness of the shell panel, rings and stringers. The effects of different factors, including various weight fractions and patterns of GPLs nanofillers, the geometry of the shell panel and...
Ultrashort-pulse laser is widely used in drilling micro-hole (diameter<100μm) because of its h... more Ultrashort-pulse laser is widely used in drilling micro-hole (diameter<100μm) because of its higher energy density and less thermal effect. However, ultrashort-pulse laser drilling still has some defects, such as taper, poor entrance edge quality, etc. In this paper, the method of trepanning drilling was used to process micro-holes (the entrance diameter was about 55μm) on the stainless steel sheet (the thickness was 80μm) with a picosecond laser. The taper (7.63º ~ -1.8º) of the micro-hole was successfully adjusted by changing the laser angle of incidence (AOI) and laser energy. The experimental results showed that the entrance roundness increased from 85.2% to 94.1% with the increase of the AOI. In addition, the entrance roundness decreased with the rise of the laser fluence. Observing the hole wall surface showed that the remelts and micro-cracks on the hole wall surface increased with the increase of the AOI. The remelts and micro-cracks on the hole wall surface were obviousl...
International Journal of Mechanics and Materials in Design, Jul 25, 2021
Conform and non-conformal contact problem in the face of piezoelectric motors can be hard to gras... more Conform and non-conformal contact problem in the face of piezoelectric motors can be hard to grasp, especially both the friction drive and wear lifespan are considered. Flowing the classical contact issue, an elastic brittle flat punch as the driving tip of the stator for piezoelectric devices is chosen and the contact behaviour under elliptical ultrasonic vibration is investigated using finite element method. A limited stress analysis is conducted after the quasi-static contact of the driving tip and the slider of the linear ultrasonic motors. After the analytical traces and experimental test on the fracture failure induced by the stress actions, the failure criteria of the elastic brittle driving tip are discussed. Results show that this quasi-static method can be applied to the complex contact analysis of an elliptical vibration device, and the failure characteristics induced by stress and strain can be obtained by FEM simulation and experiment verification. The pre-fracture stress map provides an important basis for the design of the geometrical mutation edge (e.g. edge fillet) of the elastic brittle punch and the composite structure for strength capacity. The failure analysis of brittle materials under ultrasonic vibration requires attention on quasi-brittle and quasi-plastic strength criterions. This study focus on determination of the contact stresses and the limited states during the elliptical vibration of a stator tip against slider. It also is important for the analysis on failure modes of frictional materials of ultrasonic devices, fretting wear of high-frequency connecting parts and machining process assisted with ultrasonic vibration.
Ionic liquids have received wide attention due to their novel optoelectronic structures and devic... more Ionic liquids have received wide attention due to their novel optoelectronic structures and devices as an optical means of regulating electricity. However, the quantitative testing and analysis of refractive index of ionic liquids under electric field are rarely carried out. In the present study, an experimental apparatus including a hollow prism is designed to measure the refractive indices of ionic liquids under different electric fields. Five groups of imidazole ionic liquids are experimentally investigated and an inversion is performed to determine the refractive indices under electric fields. The error propagation analysis of the apex angle and the minimum deflection angle are conducted, and the machining accuracy requirements of the hollow prism are determined. The results show that the refractive indices of imidazole ionic liquids change with the light wavelength, following a downward convex parabola. Furthermore, the refractive index decreases with the carbon chain length of ionic liquid at a given wavelength, presenting an order of C3MImI &gt; C4MImI &gt; C5MImI &gt; C3MImBr &gt; C3MImBF4. Notably, the refractive index of imidazole ionic liquid exhibits a nonlinear change with the applied voltage at 546 nm and a monotonical decrease at 1529 nm. Besides, the variation of refractive index at 1529 nm with the applied voltage is larger than that at 546 nm and 1013 nm. Importantly, the variation of refractive index is contrary to that of absorption coefficient under electric field. This study illustrates that the theory of electrode and carrier transport can be used to explain the law of variation of n–k value of ionic liquid under the electric field, and provides the support for the evaluation of physical properties of ionic liquids, the measurement of optical functional parameters and the regulation of electric–optic performances of optical devices.
Piezoelectric materials directly convert energy between electrical and mechanical domains, and ha... more Piezoelectric materials directly convert energy between electrical and mechanical domains, and have been widely employed in electronic devices as sensors and energy harvesters. Recent research endeavors are mainly devoted to dealing with problems such as high stiffness, brittleness, toxicity, poor durability, and low piezoelectric coefficients. Among developed strategies, chemical modification captures much attention. However, the exact physical properties and direct experimental evidence of chemical modification remain elusive or controversial thus far. In this review, we discuss the recently developed piezoelectric modification strategies for piezoelectric composites and assess the effect of different chemical modification approaches on piezoelectric properties. Moreover, we outline existing challenges and new applications of piezoelectric composites.
In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatel... more In this paper, the free vibration response of a stiffened functionally graded graphene nanoplatelet (GPL)-reinforced composite multilayer cylindrical shell panel is studied for the first time. The shell is stiffened by both stringers and rings. Additionally, the effect of reinforcing the shell panel, ring and stinger with GPLs is independently studied. Halpin–Tsai relations are employed to evaluate the mechanical properties of the shell panel, rings and stringers. The first-order shear deformation shell theory, accompanied by the Lekhnitsky smeared stiffener model, using the numerical finite element method and Hamilton principle, is employed to develop the governing motion equations of the shell panel. Four different types of GPL patterns, including FG-A, FG-X, FG-O and UD, are assumed across the thickness of the shell panel, rings and stringers. The effects of different factors, including various weight fractions and patterns of GPLs nanofillers, the geometry of the shell panel and...
Ultrashort-pulse laser is widely used in drilling micro-hole (diameter<100μm) because of its h... more Ultrashort-pulse laser is widely used in drilling micro-hole (diameter<100μm) because of its higher energy density and less thermal effect. However, ultrashort-pulse laser drilling still has some defects, such as taper, poor entrance edge quality, etc. In this paper, the method of trepanning drilling was used to process micro-holes (the entrance diameter was about 55μm) on the stainless steel sheet (the thickness was 80μm) with a picosecond laser. The taper (7.63º ~ -1.8º) of the micro-hole was successfully adjusted by changing the laser angle of incidence (AOI) and laser energy. The experimental results showed that the entrance roundness increased from 85.2% to 94.1% with the increase of the AOI. In addition, the entrance roundness decreased with the rise of the laser fluence. Observing the hole wall surface showed that the remelts and micro-cracks on the hole wall surface increased with the increase of the AOI. The remelts and micro-cracks on the hole wall surface were obviousl...
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