Large-Scale Yielding Failure Prediction of Notched Ductile Plates by Means of the Linear Elastic Notch Fracture Mechanics

Abstract

à Ëàáîðàòîðèÿ èññëåäîâàíèÿ ðàçðóøåíèÿ, Ôàêóëüòåò èííîâàöèîííûõ òåõíîëîãèé, Òåãåðàíñêèé óíèâåðñèòåò, Òåãåðàí, Èðàí á Ôàêóëüòåò îðãàíèçàöèè ïðîèçâîäñòâà, Ïàäóàíñêèé óíèâåðñèòåò, Ïàäóÿ, Èòàëèÿ â Ôàêóëüòåò ìåíåäaeìåíòà è èíaeèíèðèíãà, Ïàäóàíñêèé óíèâåðñèòåò, Âè÷åíöà, Èòàëèÿ ã Ìåõàíèêî-ìàøèíîñòðîèòåëüíûé ôàêóëüòåò, Íîðâåaeñêèé óíèâåðñèòåò åñòåñòâåííûõ è òåõíè-÷åñêèõ íàóê, Òðîíõåéì, Íîðâåãèÿ Ïðåäëîaeåí êðèòåðèé ðàçðóøåíèÿ, îñíîâàííûé íà ëèíåéíîé óïðóãîé ìåõàíèêå ðàçðóøåíèÿ, äëÿ ïðîãíîçèðîâàíèÿ èíèöèèðîâàíèÿ òðåùèíû ðàñòÿaeåíèÿ îò çàòóïëåííîãî V-îáðàçíîãî íàäðåçà ïðè áîëüøîé ïëàñòè÷íîñòè âáëèçè íàäðåçà. Îïèñàíû íåêîòîðûå ñîâðåìåííûå ýêñïåðèìåíòàëüíûå ðåçóëüòàòû ïî ðàçðóøåíèþ ïðè ðàñòÿaeåíèè ïëàñòè÷íûõ àëþìèíèåâûõ ïëàñòèí ñ V-îáðàçíûì íàäðåçîì. Ñ öåëüþ èçáåaeàíèÿ ñëîaeíîãî è òðóäîåìêîãî óïðóãîïëàñòè÷åñêîãî àíàëèçà äëÿ ïðîãíîçèðîâàíèÿ íåñóùåé ñïîñîáíîñòè àëþìèíèåâûõ ïëàñòèí ñ V-îáðàçíûì íàäðåçîì èñïîëüçóþòñÿ êîíöåïöèÿ ýêâèâàëåíòíîãî ìàòåðèàëà è êðèòåðèé óñðåäíåííîé ïëîòíîñòè ýíåðãèè äåôîðìàöèè, áàçèðóþùèéñÿ íà ëèíåéíîé óïðóãîé ìåõàíèêå ðàçðóøåíèÿ. Ïîêàçàíî õîðîøåå ñîîòâåòñòâèå ìåaeäó ýêñïåðèìåíòàëüíûìè äàííûìè è ðåçóëüòàòàìè ïðîãíîçèðîâàíèÿ íà îñíîâå êîíöåïöèè ýêâèâàëåíòíîãî ìàòåðèàëà è êðèòåðèÿ óñðåäíåííîé ïëîòíîñòè ýíåðãèè äåôîðìàöèè.Êëþ÷åâûå ñëîâà: íàäðåç, ïëàñòè÷íûé ìàòåðèàë, çàðîaeäåíèå òðåùèíû, ïîíÿòèå ýêâèâàëåíòíîãî ìàòåðèàëà, êðèòåðèé óñðåäíåííîé ïëîòíîñòè ýíåðãèè äåôîðìàöèè, ïîëíîìàñøòàáíîå òå÷åíèå.Introduction. In general, ductile metallic materials are divided into two main categories. The first and second categories involve those materials exhibiting negligible and considerable strain-hardening in the plastic zone, respectively. An accurate factor to realize the category is normally the difference between the yield and tensile strengths of the material. The fracture mechanics analyses for the two categories are really different. The

J‐integral evaluation for V‐notched ductile plates subjected to tension

“…As illustrated in Table , there are the discrepancies between the experimental results and theoretical estimations, which are useful to realize the strong and weak points of each ductile failure model, especially those of EMC‐J model investigated in the present contribution. Additionally, failure prediction results based on the EMC‐ASED criterion for these experimental data have been reported in Table . As is evident in Table , for Al 7075‐T6 specimens, a good agreement with an average accuracy of about 88% can be found between the experimental results and the theoretical predictions obtained from EMC‐ASED criterion, while an average accuracy of about 84% is observed for EMC‐J criterion.…”

“…It has been reported in Torabi et al that the mode I crack initiation from the blunt V‐notches in Al 7075‐T6 and Al 6061‐T6 plates has taken place the LSY regime. Thus, the failure models in the context of the notch fracture mechanics (NFM) based on the linear elastic material behavior cannot basically be used for predicting LCCs of the tested ductile samples.…”

“…By properly substituting the data from Table in Equation , values of can be calculated for the aluminum alloys assessed in Torabi et al These values are calculated to be approximately 1845 MPa for Al 7075‐T6 and also 1066 MPa for Al 6061‐T6. After calculating the values of , the LCCs of the tested ductile samples with notches could be estimated via substituting such values together with the fracture toughness values ( K c ) into various brittle fracture criteria, such as the linear elastic J‐integral model.…”

Notch ductile failure with significant strain‐hardening: The modified equivalent material concept

“…The calculation process of the tensile strength value for the equivalent material in MEMC is absolutely the same as that in EMC . In the previous works, a power‐law expression has been used to relate stress to strain in the plastic region, and the closed‐form expression for the tensile strength of the equivalent material, σ f * , has been proposed as follows: …”

“…In the literature and some other research works dealing with EMC, it can be clearly found that EMC has been based on an important assumption that a valid fracture thoughness (ie, K Ic or K c ) exists for the ductile material which can be obtained according to ASTM E399 . Such an assumption has been shown to be satisfied in those ductile materials, for which the ultimate and yield strengths are not so different . Because of needing ductile materials with considerable strain‐hardening in design process of engineering structures, eg, the sheet metals in automobile and ship structures etc., LCC prediction for such materials weakened by notches of various shapes is necessary.…”