Internal Pressure Parameters Research Articles

Theoretical analysis of inflated tube wrinkling behavior under pure bending

Inflatable tubes, owing to their lightweight and foldable characteristics, have important applications in soft robots and space expandable structures. The application of a bending load to the inflated tube might induce local instability on its compressed side, leading to the formation of wrinkles that could potentially compromise the structural strength. Therefore, it is necessary to have a comprehensive understanding of the wrinkling behavior exhibited by inflated tubes under bending load. Initially, a theoretical solution is developed for the critical wrinkling behavior of inflated tubes under pure bending, drawing upon the principle of minimum potential energy. According to the energy expression of the system, the critical wrinkling behavior of inflated tubes depends on dimensionless geometrical and internal pressure parameters. The critical wrinkling load and wrinkle pattern of the system are influenced by the thickness-radius ratio and the ratio of internal air pressure to Young's modulus. Subsequently, the theoretical solutions are validated through several finite element analysis examples and a systematic investigation is conducted into the influence of dimensionless geometrical and internal pressure parameters. Finally, the evolution of morphology in post-buckling is investigated through numerical results. The findings suggest that during post-buckling, the wrinkles may undergo a secondary bifurcation and evolve into a non-axisymmetric diamond-like pattern. These results hold significant implications for understanding the bending instability and failure mechanisms of inflated tubes.

Calculation of binary phase diagrams of refractory metals, Ta, W, Tc, and Re, with liquid metals, Am, Cm, and Bk, using a regular solution theory modification

The binary phase diagrams of several refractory metals such as Ta, W, Tc, and Re with three low melting metals Am, Cm, and Bk were calculated by the modified regular solution theory. Although there are several parameters that can influence the predictions of the phase diagrams, in this present study they were limited to the internal pressure difference. The internal pressure parameters of solid metals were calculated from the internal parameters of liquid metals. The phase boundaries are then calculated from the modified regular solution theory. A HP-41C program was applied to solve the analytical equations for solubilities and then the solubilities were transferred to analytical equation formats by the Chebyshev Polynomials program. Thus, the phase boundaries can be easily obtained as a function of temperature.

Internal Pressure in Solids and Liquids

The internal pressure parameter α, first derived from the compressibility of metals and alkali-halides, is interpreted as α = dW/dV where W is the potential energy and V the volume. This expression enables the evaluation of α from measurements on thermal energy and thermal expansion. With now available experimental results α-values can in this way be obtained for most metals at ordinary temperatures and in some cases these values can be compared with values from very low temperatures and values obtained from melting and the liquid state. Though α must be expected to vary with the volume the variations do not exceed the limits of the present experimental uncertainty. The experimental α-values are used for a determination of the electron density in metals and for an interpretation of the activation energy of diffusion.