Narrow Results

The electric impedance of a segmented beam with surface piezoelectric actuators is studied. The two layer piezoelectric actuators are in parallel in the electric circuit. The dynamics of the piezo-laminated segment and the elastic segments in the whole beam are presented by the 5 × 5 and 4 × 4 impedance matrix, respectively. Considering the mechanical-electric boundary conditions and the continuum conditions among these beam segments, the electric impedance of the whole system is obtained by solving its linear impedance equations. The experiment on a free-free segmented beam is done, the measured electric impedance of the system agrees with the theoretical value. For the resonance frequencies of such system, the relative errors between the measured and the theoretical values are smaller than 1.62% in the frequency range of 2800Hz. The parameter study of piezoelectric elements shows the change of the system impedance has the same trend with the change of their elastic modulus and absolute value of piezoelectric strain constant. However, the change of the system impedance has the opposite trend with the change of its dielectric constant.

In vehicle crashworthiness simulation analysis, anti-crash performance of the front bumper beam assembly of auto body made of 22MnB5 by hot forming and high strength steel by cold forming is compared. Software PAM-CRASH is employed to analyze the energy absorption and the acceleration value of beams with different profiles and thicknesses during the frontal impact process. And the structure of the hot forming bumper beam is optimized to get more light-weight effect. The results show that the use of hot forming beam can not only improve the energy absorption, but also can effectively reduce the weight of the body in white.

The non-linear behaviour of rubbing cylindrical rotors have been studied in several papers. In such systems rich dynamics have been found for frequencies above the natural frequency. Below natural frequency the solution was found to be stationary. In this paper the influence of blades is studied. A Jeffcott rotor with three blades is used and the contacts are described by large displacement beam theory. The model shows that no stationary point will exist and complex behaviour will occur below the natural frequency. For the studied rotor, failure due to high stresses will occur at driving frequencies below 50% of the natural frequency and instability at 80% of the natural frequency. The paper shows that the dynamics of bladed rotors differs from the dynamics of rubbing circular rotors. If a bladed rotor is used it is essential to study a model with blades. Otherwise the general conclusions on the dynamics can be wrong.

About 30 years ago, I was among several students mentored by Professor Yang at Stony Brook to enter the field of particle accelerator physics. Since then, I have been fortunate to work on several major accelerator projects in USA and in China, guided and at times directly supported by Professor Yang. The field of accelerator physics is flourishing worldwide both providing indispensable tools for fundamental physics research and covering an increasingly wide spectrum of applications beneficial to our society.