Study of initial shock wave in exhausted flow field by use of a Laser Moire Deflectometry instrument

The initial show wave is a non-stationary phenomenon in the initial stage of an exhausted flow field. Its movement characteristic and development process cannot be mastered accurately with the use of contact-type measurement methods, such as pressure and velocity measurements. An experimental study of the shock wave field by use of a Laser Moire Deflectometry instrument is introduced in this paper. The instrument has a large caliber, high sensitivity and high precision. A serial photograph of shock wave field is also presented. The formation mechanism and development trend of the initial shock wave can be drawn from analysis of flow field display photographs.     

Stiffness and Damping Identification from Full Field Measurements on Vibrating Plates

The paper presents an experimental application of a method leading to the identification of the elastic and damping material properties of isotropic vibrating plates. The theory assumes that the searched parameters can be extracted from curvature and deflection fields measured on the whole surface of the plate at two particular instants of the vibrating motion. The experimental application consists in an original excitation fixture, a particular adaptation of an optical full-field measurement technique, a data preprocessing giving the curvature and deflection fields and finally in the identification process using the Virtual Fields Method (VFM). The principle of the deflectometry technique used for the measurements is presented. First results of identification on an acrylic plate are presented and compared to reference values. Results are discussed and improvements of the method are proposed.