Behavior of concrete cylinders confined by carbon-composite tapes and prestressed yarns 1. Experimental data

The results of a comprehensive test program for the mechanical behavior of round concrete specimens confined by carbon-fiber epoxy tapes and prestressed carbon yarns are reported. Five different concrete batches of compressive strength from 20 to 100 MPa and the confinement of various thickness and pretension level were investigated. The specimens, which were subjected to monotonic or repeated compressive loadings, showed a nonlinear stress-strain behavior with a significant ductility and increased ultimate strength, in contrary to the brittle behavior of plain concrete. The limit of linearity on the stress-strain diagrams of the confined concrete roughly coincided with the ultimate strength of plain concrete. Above this limit, the damage accumulation and plastic deformations proceeded in the confined specimens. This fact was evidenced by the increasing slope of deformation diagrams in unloadings and repeated loadings and by the pronounced residual strains. The limit of linearity could be raised significantly by pretension of the carbon yarns during their winding. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 42, No. 1, pp. 21–44, January–February, 2006.     

Determination of the guanosine content of technical preparations

A method is proposed for the quantitative determination of the guanosine contents of technical preparations using the Folin reagent. The sensitivity of the method is 2.5 µg/ml, and the error of the determination does not exceed ±2.3%.All-Union Scientific-Research Institute of Applied Biochemistry, Olaine. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 504–507, July–August, 1983.     

Creep of compact human bony tissue under tension

The behavior of compact bony tissue from a human tibia with time at various levels of a constant lengthwise stretching load has been studied. The limits of application of the linear viscoelastic theory for bony tissue have been established. Characteristics of the material have been determined which make it possible to describe both active and also retrograde creep.     

Nonlinear creep in high-density polyethylene under time-dependent stresses

The authors have performed experiments on the creep of specimens of high-density poly-ethylene in states of plane stress which vary linearly with time. The theoretical curves are calculated from equations of two types, namely the cubic and principal cubic theories of viscoelasticity [3]. The parameters of the material are taken from a previous paper [1].Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 5, pp. 796–803, September–October, 1973.     

Characteristics of the creep and repeat creep deformation process for polymers in uniaxial tension. Part 2

Physical relations for approximating the creep deformation and recovery have been worked out for a material in the physically nonlinear state with a nonmonotonic θ (t) dependence. It has been shown experimentally that for filled low-density polyethylene and fluoroplastic there is no time similarity for the processes of longitudinal and transverse deformation, deformation under primary and repeat loading, and creep deformation and recovery.