Viscoelastic model to describe mechanical response of compact heat exchangers with plate-foam structure

The miniaturization of the process equipment has lead to the development of micro-chemical and thermal systems for high tech applications. With the increase of temperature and pressure, the design of the miniature components against creep failure becomes a primary concern. However, the stress analysis of the structure is highly complicated and time-consuming by general finite element methods if a network of inter-connected dodecahedral-like cells is involved. In the present paper, the short-term mechanical properties and the viscoelastic parameters are measured by uniaxial tension experiments. Based on these parameters and small deformation theory, the time-dependent deformation and stresses of the plate-foam structures are analyzed by assuming the metal foams as elastic foundation. Using the numerical inversion of Laplace transform and the standard linear solid model, the analytic expressions of the deformation and stresses are derived. By comparison, the results show that the time-dependent deflection and bending stress along the normalized distance from the analytical method were consistent with those from the finite element method. It indicates that the proposed analytical method was feasible and accurate. Additionally the effect of the viscoelasticity on the deflection will disappear gradually if λ is much larger than 600 GPa.