Metallo- and fractographic examination of reasons for failure of two-layer thin-walled bellows operating under compressive loading

Conclusions 1. The structure of the metal and the design of the fractured bellows (with the exception of the parameters D, L,a and t, which changed during service) satisfy the requirements of the normalization and technical documents.2. The main reason for failure of the bellows is its long-term service, almost four times higher than the design life.3. Failure is also caused by the presence on the surface of the bellows of technological roughness acting as regions of microcrack nucleations.4. To increase the efficiency of bellows, it is efficient to produce them from pipes/blanks with an electrochemically polished surface.5. The detected HV—running life dependence can be used to evaluate approximately the number of operating cycles of failed bellows and also their permissible service life.6. The design life of the bellows of the 44.5–15–0.18×2 type under this loading system may be increased from 3000 to 5000 cycles.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 2, No. 2, pp. 125–127, March–April, 1993.     

Fractal analysis of fracture in aluminum alloy 01450T

The fractal dimensions of rupture surfaces of specimens of aluminum alloy 01450T tested for cyclic and static tension are evaluated. The relationship between the fatigue curve and the fractal dimension as a function of stress is established. The dependence of the maximum coefficient of stress intensity on the fractal dimension is determined.Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 8, pp. 20–25, August, 1995.     

Brittle failure susceptibility of metal of a large structure

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 2, pp. 74–79, March–April, 1990.     

Special Features of Nucleation and Growth of Tin Crystals in the Temperature Range of Its Polymorphic Transformation

Special features of nucleation and growth of tin whiskers in the range of tin polymorphic transformation on galvanically tin-plated surfaces of parts of electric devices and laboratory specimens in the absence of the action of electric fields and moisture are considered. The main factors responsible for the nucleation and growth of crystals are determined. Process and maintenance recommendations are given for deceleration of formation of crystals in the period of storage and service of devices.     

Crack propagation in a pipe steel subjected to cyclic loading after long-term operation

The mechanical properties (under static and cyclic loading) and damage of a product pipeline made of 3G steel have been studied after its long-term operation. The ultrasound velocity in a damaged steel and the fatigue crack length on the sample surface are determined at various stages of macrocrack initiation. At the stage of main-crack initiation, the cumulative curves of fatigue microcrack distribution are well described by both exponential and power functions, with their exponents decreasing with increasing stress amplitude. The majority of fatigue microcracks have a length close to the average grain size.