Irreversible dilatancy or compressibility of viscoplastic rock-like materials and some applications

An elastic/viscoplastic constitutive equation for rock-like materials which is able to describe, besides creep, an irreversible compressibility and/or dilatancy of the volume is formulated. Mathematical definitions are used for the concepts of dilatancy, compressibility, compressibility/dilatancy boundary, and failure. Two examples of such constitutive equations are given for a hard rock and a softer rock.Two applications of this constitutive equation are presented. First the creep dilatancy and/or compressibility of the rocks surrounding an oil well or a pressure shaft are studied for various initial primary stresses. The location and the conditions under which the rock surrounding the well may become dilatant are then shown. The same problem is studied for the case of horizontal tunnels. Various depths and primary stresses are considered and it is shown where possible failure may occur. For both applications numerical examples are given.     

On dynamic relaxation

Summary One discusses the mathematical conditions to be satisfied by the coefficients entering in a quasi-linear constitutive law which can describe the phenomenon of dynamic relaxation. In the relaxation period the plastic component of the strain increases though the stress and the elastic component decrease. In this paper only one-dimensional problems are considered.Paper read at the Annual Meeting of the German Rheologists, Berlin-Dahlem June 7–10, 1966.     

Matrix assisted pulsed laser evaporation of cinnamate-pullulan and tosylate-pullulan polysaccharide derivative thin films for pharmaceutical applications

We have demonstrated the successful thin film growth of two pullulan derivatives (cinnamate-pullulan and tosylate-pullulan) using matrix assisted pulsed laser evaporation (MAPLE). Our MAPLE system consisted of a KrF* laser, a vacuum chamber, and a rotating target holder cooled with liquid nitrogen. Fused silica and silicon (1 1 1) wafers were used as substrates. The MAPLE-deposited thin films were characterized by transmission spectrometry, profilometry, atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The deposited layers ranged from 250 nm to 16.5 μm in thickness, depending on the laser fluence (0.065-0.5 J cm⁻²) and number of pulses applied for the deposition of one structure (1500-13,300). Our results confirmed that MAPLE was well-suited for the transfer of cinnamate-pullulan and tosylate-pullulan.