Yueming Li

Bio: Yueming Li is an academic researcher from Xi'an Jiaotong University. The author has contributed to research in topics: Computer science & Vibration. The author has an hindex of 19, co-authored 93 publications receiving 1112 citations.

Vibration and acoustic response of an orthotropic composite laminated plate in a hygroscopic environment

Abstract: This paper is a study of the vibration and acoustic response characteristics of orthotropic laminated composite plate with simple supported boundary conditions excited by a harmonic concentrated force in a hygroscopic environment. First the natural vibration of the plate with the in-plane forces induced by hygroscopic stress is obtained analytically. Secondly, the sound pressure distribution of the plate at the far field is obtained using the Rayleigh integral. Furthermore, the sound radiation efficiency is deduced. Third, different ratios of elastic modulus in material principal directions are set to research the effects of increasing stiffness of the orthotropic plate on the vibration and acoustic radiation characteristics. Finally, to verify the theoretical solution, numerical simulations are also carried out with commercial finite software. It is found that the natural frequencies decrease with the increase of the moisture content and the first two order modes interconvert at high moisture content. The dynamic response and sound pressure level float to lower frequencies with elevated moisture content. Acoustic radiation efficiency generally floats to the low frequencies and decreases with an increase of moisture content. The dynamic and acoustic responses reduce and the coincidence frequency decreases with the enhanced stiffness.

Vibration and acoustic radiation of an orthotropic composite cylindrical shell in a hygroscopic environment

Abstract: An analytical study is presented for vibration and acoustic radiation of a finite thin orthotropic composite cylindrical shell excited by a harmonic concentrated force in a hygroscopic environment....

Six degrees of freedom coupled dynamic response of rotor with a transverse breathing crack

Abstract: More coupling mechanisms between the six degrees of freedom (DOFs) are introduced by considering the contribution of the general transverse forces to stress intensity factor of mode I crack in predicting the crack additional flexibility matrix of the cracked rotor. And the obtained flexibility elements show a good agreement with the experiment result for a wide range of the crack depth ratio. Six DOFs coupled dynamic equations for cracked rotor are formulated by introducing three rotational DOFs. A response-dependent non-linear breathing crack model is applied to simulate the breathing behavior during operation in this paper. Numerical investigations are carried out to simulate the various parametric conditions on the dynamic characteristics of cracked rotor, including the crack depth, shaft slenderness ratio, and rotating speed ratio. A perturbation frequency component and its combinations with harmonic components are observed in the dynamic response obtained by six DOFs coupled models (SDCM). Some differences in evolution of whirling orbit obtained by SDCM and three DOFs coupled models are found, when the cracked rotor passes through the sub-critical speeds.

Experimental and numerical investigations on dynamic and acoustic responses of a thermal post-buckled plate

Abstract: Experiments were carried out for a clamped rectangular aluminum plate to study the dynamic and acoustic behaviors in both pre- and post-buckling ranges under thermal loads. Plate temperature was elevated from ambient value to the level above the theoretical critical buckling temperature of the plate. In the whole test temperature range, the measured frequencies decreased to the minimum values in sequence, and then turned to increase as temperature rose. The softening effect of thermal stresses played the leading role in the decreasing stage and the stiffening effect of thermal buckling deflection became the major influence factor in the increasing stage. The later one could drive the temperature equilibrium point of the heated plate to move towards lower temperature range. All the frequencies would not drop to zero due to the inherent initial deflection which provides additional stiffness to the plate. Dynamic responses state two variation trends in different temperature ranges, shifting toward the lower frequency range and closing up in the mid-frequency range. The characters of spectrum responses changed gradually as the temperature was elevated. Numerical simulations gave predictions with same variation trend as the test results.

Experimental Characterization of the Thermal Conductivity and Microstructure of Opacifier-Fiber-Aerogel Composite.

Abstract: Due to their high-porosity, nanoporous structure and pores, aerogel materials possess extremely low thermal conductivity and have broad potential in the thermal insulation field Silica aerogel materials are widely used because of their low thermal conductivity and high temperature resistance Pure silica aerogel is very fragile and nearly transparent to the infrared spectrum within 3⁻8 μm Doping fibers and opacifiers can overcome these drawbacks In this paper, the influences of opacifier type and content on the thermal conductivity of silica fiber mat-aerogel composite are experimentally studied using the transient plane source method The thermal insulation performances are compared from 100 to 750 °C at constant pressure in nitrogen atmosphere among pure fiber mat, fiber mat-aerogel, 20% SiC-fiber mat-aerogel, 30% ZrO₂-fiber mat-aerogel and 20% SiC + 30% ZrO₂-fiber mat-aerogel Fiber mat-aerogel doped with 20% SiC has the lowest thermal conductivity, 00792 W/m·K at 750 °C, which proves that the proper type and moderate content of opacifier dominates the low thermal conductivity The pore size distribution indicates that the volume fraction of the micropore and mesopore is also the key factor for reducing the thermal conductivity of porous materials

Mechanics of composite materials

Abstract: INTRODUCTION TO COMPOSITE MATERIALS Chapter Objectives Introduction Classi?cation Recycling Fiber-Reinforced Composites Mechanics Terminology Summary Key Terms Exercise Set References MACROMECHANICAL ANALYSIS OF A LAMINA Chapter Objectives Introduction Review of De?nitions Hooke's Law for Different Types of Materials Hooke's Law for a Two-Dimensional Unidirectional Lamina Hooke's Law for a Two-Dimensional Angle Lamina Engineering Constants of an Angle Lamina Invariant Form of Stiffness and Compliance Matrices for an Angle Lamina Strength Failure Theories of an Angle Lamina Hygrothermal Stresses and Strains in a Lamina Summary Key Terms Exercise Set References APPENDIX A: MATRIX ALGEBRA Key Terms APPENDIX B: TRANSFORMATION OF STRESSES AND STRAINS Transformation of Stress Transformation of Strains Key Terms MICROMECHANICAL ANALYSIS OF A LAMINA Chapter Objectives Introduction Volume and Mass Fractions, Density, and Void Content Evaluation of the Four Elastic Moduli Ultimate Strengths of a Unidirectional Lamina Coefficients of Thermal Expansion Coefficients of Moisture Expansion Summary Key Terms Exercise Set References MACROMECHANICAL ANALYSIS OF LAMINATES Chapter Objectives Introduction Laminate Code Stress-Strain Relations for a Laminate In-Plane and Flexural Modulus of a Laminate Hygrothermal Effects in a Laminate Summary Key Terms Exercise Set References FAILURE, ANALYSIS, AND DESIGN OF LAMINATES Chapter Objectives Introduction Special Cases of Laminates Failure Criterion for a Laminate Design of a Laminated Composite Other Mechanical Design Issues Summary Key Terms Exercise Set References BENDING OF BEAMS Chapter Objectives Introduction Symmetric Beams Nonsymmetric Beams Summary Key Terms Exercise Set References INDEX