Structure and near-threshold fatigue of steels

Diagnostics of threshold characteristics of welded joints in structural steels

“…It should be taken into account that steels in which the controlling micromechanism of failure is the cleavage of cementite plates usually have higher strength and a lower hardening coefficient (m<0.1-0.13). In this case, under conditions of a severe stress state which occurs at the crack tip, [8], in the denominator from the experimental results'. " The size of cementite plates the microcleavage conditions form most probably at e, = m. 4 Therefore, a t can be efficiently determined using the expression for the exponential approximation of the deformation diagrams with an allowance made for the previously mentioned condition: a, = a T (m/0.002) m and d^ will be equal to the size of the cementite plate.…”

“…If the main mechanism is cementite microcleavage and not the grain mechanism, Ko, can also be determined from [8]. However, the method of determining a, and d, ff will differ.…”

“…The efficiency of calculations was verified for different steel grades. The initial data for the calculations and the results are presented in the Table. Comparison of the calculated and experimental data makes it possible to verify the efficiency of using [8] for determining the threshold characteristics of the different zones of welded joints in structural steels.…”

“…Taking this into account, from. [4] 47cd OT [8] where d, ff is the size of the structural member which determines the microcleavage mechanism.…”

“…Thus, the resultant dependence [8] can be used to calculate K ft on the basis of characteristics determined in simple standard mechanical tensile tests of specimens. The efficiency of calculations was verified for different steel grades.…”