The stresses and strains introduced by low-temperature autofrettage of smooth thick-walled tubes made of the austenitic stainless steel AISI 304 L were modelled by the finite-element (FE) method. The objective was to show that low-temperature autofrettage is much more efficient than autofrettage at room temperature in enhancing the fatigue resistance by introducing a higher beneficial tangential (hoop) residual compressive stress at the inner part of the tube. Attention was paid to the influences of the autofrettage temperature and pressure, the work hardening and the reverse yielding on the residual stress components and on the total strain components of the tube. The FE calculations confirmed that more beneficial residual stress patterns can be attained by autofrettage at low rather than at room temperature. From the quantitative calculations, the optimal autofrettage temperature and pressure of the tube were concluded to be about and 4000 bar, respectively. The results of the calculations were shown to be in good agreement with recently measured data.
The purpose of this research was to study effects of microwave treatment on China aster seed germination, vigour and infestation with fungi, at temperature 20?C. The seeds were treated in microwave oven (power 850 W heating power) in dry conditions and in water for 10, 20, 30, 40, 50, 60, 90, 120 and 180 s respectively
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