Assessment of trunk-pipeline survivability taking into account residual welding stresses

A method to calculate pipeline survivability (operability of a part having cracks) taking into account residual welding stresses is proposed. This method allows one to determine the pipeline’s residual life, i.e., to make a conclusion whether the pipeline may be operated after ultrasonic testing detects cracklike defects of a certain size.     

Nature of scatter of fracture toughness in static loading

The previously proposed model of unstable fatigue crack growth is used to explain a large (in comparison with other mechanical characteristics) scatter of static fracture toughness for 15Kh2MFA and 15Kh2NMFA steels at temperatures below the tactile-brittle transition temperature. The results show that for the materials for which K_fc ¹ < K_Ic the critical stress intensity factor K_Ic depends on the specific energy of inelastic strain W at the tip of the initial fatigue crack in its formation stage. The value of W is a function of the number of load cycles (in the conditions with a constant range of the stress intensity factor K) as a result of irregular fatigue crack growth. Here K_fc ¹ is the minimum cyclic fracture toughness. A method is proposed of evaluating the minimum fracture toughness of the material in static loading based on inspection of the process of irregular fatigue crack growth in the stage of crack initiation.Translated from Problemy Prochnosti, No. 2, pp. 10–16, February, 1990.     

Influence of preliminary cyclic plastic deformation on crack resistance

The influence of preliminary (before crack origin) cyclic plastic deformation by tension-compression (R = _min/_max = –1 on the brittle fracture resistance of 15Kh2MFA heat resistant steel in two conditions was investigated. The preliminary loading was done at 293 K and the fracture at 123 and 293 K. It was established that in the case of relatively short preliminary deformation the change in static fracture toughness is caused by a change in yield strength as the result of the Bauschinger effect. However, with an increase in cyclic deformation the total irreversibly dispersed specific energy of inelastic deformation and the structural changes in the material are the determining factor. A physically based method is proposed for prediction of the influence of preliminary cyclic plastic deformation on the brittle fracture resistance of cyclically softening steels.Institute of Problems of Strength of the Academy of Sciences of the Ukrainian SSR, Kiev. Leningrad. Translated from Problemy Prochnosti, No. 11, pp. 14–20, November, 1989.     

Mathematical Model of Synthetic Leather Drying

A mathematical model of synthetic leather drying for removing the organic solvent is proposed. Analytical solutions are obtained for a number of problems of heat transfer in a plate, including the problem of a moving evaporation front. The model proposed adequately describes the real processes.     

Thermal Characteristics of High-Efficiency Photovoltaic Converters of High-Power Laser Light

The influence exerted by the heat removal conditions on the extent of overheating of photovoltaic converters of high-power (>10³ W/cm²) laser light has been studied. The temperature of the p–n junction of photovoltaic cells was measured by recording the instantaneous values of the open-circuit voltage generated by laser light. The effect of cooling in high-efficiency photovoltaic cells (efficiency = 55%) via removal of a substantial part of absorbed optical power by the photocurrent into the external load was demonstrated. It was shown that, at laser radiation power of 2.5 W, the overheating of a photocell with an area of 1.7 × 10^–3 cm² relative to the copper heatsink temperature is 48°C in the no-load conditions and 30°C in operation with the optimal load.     

Topological method for analysis of periodic canards

Singularly perturbed systems of ordinary differential equations are studied. A method for analysis of canard-type trajectories in such systems based on the topological degree theory is suggested. The method does not require smoothness of the right-hand side of the system. A result on the existence of periodic canards in systems with non-smooth perturbations is obtained. The trajectories located in this way are not necessarily Lyapunov stable, and appropriate control algorithms are required to stabilize them, e.g., feedback control.     

Inhomogeneous shear flows of linear polymers

Solutions of a system of equations of nonlinear viscoelastic fluid motion describing inhomogeneous shear flows of linear polymers are indicated.Notation _ij stress tensor - p pressure - F_i mass force vector - _ij Kronecker delta - coefficient of shear viscosity - relaxation time - _ij inner parameter - _ij=vi/x_j velocity gradient tensor - ₀ initial value of the shear viscosity coefficient - ₀ initial value of the relaxation time - D dimensionless first invariant of the additional stress tensor - A, B, C constants of integration - f(D) universal function characterizing the material - r, , z cylindrical coordinates - u=v_z axial component of the velocity vector - v=v circumferential component of the velocity vector - ₁, ₂ first and second differences of the normal stress - Q volume mass flow rate - R radius of a circular tube - R₁, R₂ radii of the inner and outer cylinders, respectively - M moment per unit length Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 3, pp. 449–456, September, 1981.