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The correlation between strain rates and the mechanical properties of HTPB propellant with 90% solid content (mass fraction) was investigated by uniaxial tensile tests at different tensile rates, and the tensile fracture surface was observed by scanning electron microscope (SEM). The effects of strain rate on the mechanical properties and failure mechanisms of the propellant were analyzed. The results show that the stress--strain curve of the propellant appears an arc segment phenomenon at low tensile rates. With the increase of tensile rates, the stress--strain curves of propellant gradually changes from 5 segment to 4 segment. The initial modulus and the maximum tensile strength of the propellant show an increasing trend with an increase in the tensile rates. The maximum elongation of the propellant decreases with an increase in the strain rate, and the maximum elongation of propellant is only 33.9% when the strain rate is 1 190.48 X 10 4s 1 . With the increase of strain rate, the failure mechanism of propellant gradually changes from particle dehumidification to matrix tearing, without particle fragmentation. [ABSTRACT FROM AUTHOR]

The Line laser gear measuring center (LLGMC) is an innovative gear measurement equipment that offers high efficiency but low accuracy. One crucial factor that influences its measurement accuracy is the presence of geometric errors. In this study, we conducted a thorough analysis of these geometric errors and proposed a method for modeling spatial errors. Instead of directly considering the geometric errors, we replaced them with the installation errors of the gear and line laser probe. This approach simplifies and improves the error transmission relationship. Subsequently, the installation errors are converted into a unified representation of the height error of the incident light from the line laser. A spatial error model that considers nine installation errors is then further established. By numerically calculating the sensitivity of different error sources, we effectively identified the errors that have a significant impact on the accuracy of LLGMC. Moreover, accuracy distribution is carried out to ensure that LLGMC can meet the measurement accuracy requirements for gears with a tolerance class of 6. This article provides a theoretical foundation for the structural design and accuracy assurance of LLGMC during the research and development phase. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive theory for wavelength modulation laser heterodyne spectroscopy is presented. Some necessary simplifications based on the Taylor series are introduced, the general formulas employed to demodulate the first harmonic signal (1f), the second harmonic signal (2f), and higher harmonic signal (nf) are derived in details, and hence the formulas are suitable for an arbitrary intensity modulation amplitude and modulation index. The purpose of this paper: an overview of how the laser heterodyne harmonic signal depends on the experimental parameters of intensity modulation amplitude and modulation index is reported. This overview is helpful to choose these parameters for the best laser heterodyne harmonic signal because it initiated a new pathway for systematically analyzing the relationships between the experimental parameters and the laser heterodyne harmonic signal. [ABSTRACT FROM AUTHOR]