Simplified Analytical Model for Predicting Neutral Cross-Section Position of Lenticular Deployable Composite Boom in Tensile Deformation

Foldable and deployable flexible composite thin-walled structures have the characteristics of light weight, excellent mechanical properties and large deformation ability, which means they have good application prospects in the aerospace field. In this paper, a simplified theoretical model for predicting the position of the neutral section of a lenticular deployable composite boom (DCB) in tensile deformation is proposed. The three-dimensional lenticular DCB is simplified as a two-dimensional spring system and a rigid rod, distributed in parallel along the length direction. The position of the neutral cross-section can be determined by solving the balance equations and geometric relations. In order to verify the validity of the theoretical model, a finite element model of the tensile deformation of a lenticular DCB was established. The theoretical prediction results were compared with the finite element calculation results, and the two results were in good agreement.

The Absolute Torsion of Circular Shaft and Neutral Cross-Section

Mechanics of materials are based on the relative deformation to discuss the calculation of the circular shaft torsion deformation, But the relative torsion angle can not reflect the real deformation of a specific cross-section. According to the plane hypothesis, to discuss the absolute deformation of several common shaft withstand the simple torque, defined the neutral cross-section of torsion deformation and given the method to calculate absolute torsion angle, for the rational design of engineering components have a certain reference value.

Identification of longitudinal incisions of the beam from its own frequencies

The natural frequencies of bending vibrations of a prismatic beam with symmetrical bilateral longitudinal incisions are considered. A method is proposed that makes it possible to calculate the parameters of the incisions with by two frequencies taken from different spectra. These spectra belong to bending vibrations in two mutually perpendicular planes, which are chosen in such a way that in both cases the neutral cross-section line is parallel to the sides. The dependence of the natural frequency on the depth of the defect is also studied. It is proved that the values of the frequencies for the beam under consideration and the identical beam without cuts do not coincide for any value of the defects.

The use of magneto-acoustic oscillations as a plama diagnostic technique

A theoretical and experimental investigation of the forced radial magnetoacoustic oscillations of a magnetized plasma column is presented in this paper. Forced magneto-acoustic oscillations of a magnetized argon afterglow plasma are generated continuously by passing an RF current through a solenoid wrapped around the discharge tube. The radial variation of the amplitude of the magnetic field disturbance [bz(r)] associated with these oscillations is measured at various times during the decay of the afterglow plasma. A theoretical description of these oscillations is developed in which the collision frequencies between the various plasma constituents are treated as free parameters. The values of these free parameters at any given instant during the decay of the plasma are determined by fitting computed bz{r) radial profiles to the measured ones. The electron temperature Te, and the ion-neutral cross section for momentum transfer QD are deduced from these collision frequencies. The reliability of this plasma diagnostic technique is demonstrated by its ability to yield values for Te and QD which compare favourably with the results obtained by other workers.