Papers by Keyword: Lagrangian Analysis

Abstract: The Lagrangian analysis method is re-analyzed. It is shown that when a series of stress profiles (or strain profiles, or particle velocity profiles) are measured to determine the strain-stress relation. In this paper, the stress histories at different Lagrange positions are measured by one dimensional SHPB experiments. The variation histories of various physical quantities are fitted to least square cubic B-spline function with a sufficient accuracy definite condition. The path lines of these quantities are constructed in terms of a least square quadratic polynomial. A program for inert flow of Lagrangian analysis (IFLA) is worked out. Taking the data of experiments as the input for the IFLA, the flow field information is solved. The error analysis shows that such a method has a definite reliability and stability.

Abstract: Shock initiation experiments on the explosives pressed TNT was performed to obtain in-situ pressure/radial displacement gauge data for the purpose of determining the Ignition and Growth reaction flow model with proper modeling parameters. The pressure and radial displacement were got by manganin-constantan composite 2-D Lagrange sensor. The particle velocity, relative volume, internal energy and fraction reacted of shock initiation process has been calculated by 2-D Lagrangian analysis method.

Abstract: Heat and mass transfer in fluid flows traditionally is examined in terms of temperature and concentration fields and heat/mass-transfer coefficients at fluid-solid interfaces. However, heat/mass transfer may alternatively be considered as the transport of a passive scalar by the total advective-diffusive flux in a way analogous to the transport of fluid by the flow field. This Lagrangian approach facilitates heat/mass-transfer visualisation in a similar manner as flow visualisation and has great potential for transport problems in which insight into (interaction between) the scalar fluxes throughout the entire configuration is essential. This ansatz furthermore admits investigation of heat and mass transfer by well-established geometrical methods from laminar-mixing studies, which offers promising new research capabilities. The Lagrangian approach is introduced and demonstrated by way of representative examples.

Abstract: One-stage light gas gun is used to study the dynamic mechanical properties of reinforced concrete (SFRC) subjected to shock loading. The material of projectile is the same as of the target. The stress-time curves are recorded by three manganin pressure transducers embedded in the targets beforehand. The data of experiment are analyzed by self-designed program using the path line principle of Lagrangian analysis method. With the stress records, complete histories of particle velocity, density (and thus strain) and specific internal energy can be obtained at any point within the gaged region of the material. Moreover, the numerical constitutive relations of RC are obtained and the strain rate ranges from 104 to 105 per second. The result of experiment indicates that the stress-strain curves of SFRC present stagnant-return properties. And some other dynamic properties can be gained, such as rate dependent, waveform dissipation etc.

Abstract: The plate impact experiments have been conducted to investigate the dynamic behavior of 91W-6.3Ni-2.7Fe with three kinds grain sizes of 1− 3μm, 10 −15μmand 30 − 40μm . The stress-time history curves at different Lagrangian positions were obtained for tungsten alloys at different impact velocities. Lagrangian analysis technique was adopted to discuss the mechanical properties of the tungsten alloys under high strain rate. SEM was introduced to analyze the microstructure properties of tungsten alloys. The influence of grain size on the dynamic behavior of tungsten alloys under high strain rate was obtained and the stress-strain curves ( 4 5 1 10 ~ 10 s− ) of the tungsten alloys were given.

Abstract: Split Hopkinson pressure bar (SHPB) and one-stage light gas gun are utilized to study the dynamic mechanical properties of reinforced concrete (RC) subjected to shock loading. The former experimental results show that the strength and stiffness of RC decrease but the ductibility increases with increasing the volume fractions of reinforced fibers due to more damage in the concrete and interface. For the latter experiment, three stress-time curves are recorded by three manganin pressure transducers embedded in the targets. With the stress-time records, complete histories of particle velocity and strain etc. can be obtained at any point within the gauged regions of RC using the path line principle of Lagrangian analysis method. The stress-strain curves of RC present stagnant-return properties. And some other dynamic properties can be gained, such as strain rate hardening, wave shape dispersion effects and the rheological properties of the concrete.