Predicting the Fatigue Limit of Surface-Hardened Parts with Stress Concentrators

Pavlov, V. F.; Букатый, А. С.; Семенова, О. В.

doi:10.3103/s1068798x19040130

Cited by 2 publications

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“…Â îáðàçöàõ ðàçëè÷íûõ äèàìåòðîâ, èñïûòàííûõ ïðè íàïðÿaeåíèÿõ, ðàâíûõ ïðåäåëó âûíîñëèâîñòè, ñðåäíÿÿ êðèòè÷åñêàÿ ãëóáèíà (t êð ) òðåùèí ñóùåñòâåííî îòëè÷àëàñü: ïðè D = 10 ìì -t êð = = 0,201 ìì (R = 0,3 ìì) è t êð = 0,197 ìì (R = = 0,5 ìì); ïðè D = 25 ìì -t êð = 0,525 ìì (R = = 0,3 ìì) è t êð = 0,523 ìì (R = 0,5 ìì); ïðè D/d = 25 ìì/15 ìì -t êð = 0,446 ìì (R = 0,3 ìì) è t êð = 0,442 ìì (R = 0,5). Ýòî ñîîòâåòñòâóåò äàííûì ðàáîòû [5] î çàâèñèìîñòè t êð îò äèàìåòðà îïàñíîãî ñå÷åíèÿ ïîâåðõíîñòíî-óïðî÷íåííûõ îáðàçöîâ è äåòàëåé, èçãîòîâëåííûõ èç äðóãèõ ñòàëåé è ñïëàâîâ.…”

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“…Âèäíî, ÷òî êîýôôèöèåíò y s èìååò íåáîëüøîå ðàññåÿíèå, ñîñòàâëÿÿ â ñðåäíåì 0,366, 0,341, 0,345 äëÿ îáðàçöîâ äèàìåòðàìè 10, 25 è 25 ìì/15 ìì ñîîòâåòñòâåííî. Îí íåçíà÷èòåëüíî îòëè÷àåòñÿ îò y s = 0,36, óñòàíîâëåííîãî â [5] äëÿ óïðî÷íåííûõ îáðàçöîâ è äåòàëåé ñ àíà-ëîãè÷íîé êîíöåíòðàöèåé íàïðÿaeåíèé. Ìåíüøåå â ñðåäíåì çíà÷åíèå êîýôôèöèåíòà y s äëÿ îáðàçöîâ äèàìåòðîì 25 ìì îáúÿñíÿåòñÿ, î÷åâèäíî, áîëüøåé êîíöåíòðàöèåé íàïðÿaeåíèé ñ óâåëè÷åíèåì äèàìåòðà îáðàçöà ïðè îäíîì è òîì aeå ðàäèóñå ïîëóêðóãëîãî íàäðåçà [16].…”

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Dependence of the limit endurance of specimens with notches from the depth of hardened surface layer

Vakulyuk¹,

Шадрин²,

Сургутанов³

2018

Zavod. lab., Diagn. mater.

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It is shown that, growth of the layer with compressive residual stresses at advanced surface plastic deformation of smooth samples leads to an increase in the endurance limit of the notched specimens due to an increase in the compressive residual stresses in their dangerous section. The study was conducted on the specimens with outer diameterDequal to 10 and 25 mm and on a 25 mm specimen with inner diameterd= 15 mm which were subjected to air shot blasting and roll-in. Residual stresses in smooth specimens were determined by the mechanical method. Circular incisions (R= 0.3 and 0.5 mm) were applied on hardened smooth samples with a shaped cutter. Residual stresses in notched specimens were determined by a numerical method calculating the redistribution of the residual stresses upon the incision. As the diameter of the samples increases with the same strengthening surface treatment,the depth of the layer with the compressive residual stresses increases due to an increase in the rigidity of the samples. The effect of surface hardening on the endurance limit of notched specimens was evaluated according to the criterion of the average integral residual stresses, which takes into account both the magnitude and completeness of the residual stresses. This criterion was calculated from the depth of the non-propagating fatigue crack that occurs in the surface layer in the dangerous section of the specimen during the fatigue test at the limit endurance. Fatigue tests are carried out in symmetrical cycle, the test base being 3 × 106cycles of loading. Estimation of the increment of the limit endurance of surface-hardened cylindrical specimens with semicircular notches gave the results acceptable for practice. The use of the proposed method can significantly reduce long-term and expensive fatigue tests.

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