Wyniki wyszukiwania - BazTech

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Effect of non-zero mean stress bending-torsion fatigue on fracture surface parameters of 34CrNiMo6 steel notched bars

Macek Wojciech, Szala Mirosław, Trembacz Jarosław, Branco Ricardo, Costa José

Production Engineering Archives

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2020

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Vol. 26, Iss. 4

167--173

EN

Modern methods of testing materials require the use of the latest technologies and combining measurement and calculation methods. It is important to find a quantitative way of describing, among other things, the failures so that it can help to design with high accuracy. This paper studies loading orientations on crack shape and fracture surface changes. The advantage of the entire fracture surface method is simplicity and applicability in studies on other materials, shapes and loadings. A higher values of fracture surface parameters (Sx, Vx) was observed in failure specimens with lower σ/τ (B/T) ratios. It has been observed that largest crack lengths with a small number of cycles occur for loading combinations different then B=T. As well as analyzed surface parameters Sx, Vx, are higher for larger number of cycles to crack initiation (Ni) values.

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Analysis of stress and strain concentrations in notched members made of alloys D16 and 1460

Śnieżek L., Małachowski J.

Technical Sciences / University of Warmia and Mazury in Olsztyn

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2006

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nr 9

93-109

EN

The aim of the study was to present findings on the effect of the presence of a notch upon stress and strain concentrations in model members for aeronautical structures, made of selected aluminum alloys, i.e. D16 and 1460. Flat specimens with centrally positioned holes and side cuts, loaded with some bending moment of stress ratio R = 1, were tested. Specialized FEM software (MSC.Patran and MSC.Nastran) was applied to examine stress and strain distributions. The findings are presented in the form of σ[max] and ε[max] values as well as functions of the following factors: α σ, α ε, and αk, computed on the grounds of these values for both different distances from the bottom of the notch and assumed levels of load put on the specimens. Theoretical analysis was supplemented with experimental investigations into the microstructure of fatigue-fracture surfaces in the area of crack initiation and in that of fatigue of a propagating crack.

PL

Przedstawiono wyniki badań wpływu działania karbu na spiętrzenie naprężenia i odkształcenia w elementach modelowych wykonanych z wybranych lotniczych stopów aluminium D16 i 1460. Badaniom poddano próbki płaskie z otworem centralnym z nacięciami bocznymi, obciążone momentem zginającym o współczynniku asymetrii cyklu R = -1. Do badań rozkładu naprężenia i odkształcenia zastosowano specjalizowane oprogramowanie MES (MSC. Patran i MSC. Nastran). Wyniki obliczeń przedstawiono w postaci zestawienia wartości σ[max], ε[max] oraz wyliczonych na ich podstawie przebiegów współczynników α σ, α ε i αk, w różnej odległości od dna karbu i dla przyjętych poziomów obciążenia próbek. Analizę teoretyczną uzupełniono doświadczalnymi badaniami mikrobudowy powierzchni przełomów zmęczeniowych w strefie inicjacji oraz w strefie zmęczeniowej propagującego pęknięcia.

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Wpływ karbu na wytrzymałość zaprawy cementowej modyfikowanej polimerem

Kulpiński J.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2000

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z. 32[180], cz.1

319-326

EN

In this article have been presented results of flexure strength of polymer-modified mortars. There was used the mortars with 1:2,5 ratio and silica fume in amount 5 % weight of cement. Water/cement ratio in mortars has been taken between 0,30 and 0,42. Mortars were modified with epoxy resin emulsified in water. Polymer amount was 0-10 % weight of cement. In bending test were used 4x4x16 cm beams and 4x8x36 cm beams with notch. The addition of polymer has increased flexural strength for beams without notch, while the flexural strength for beams with notch was independent on the addition of polymer. The attempt of obtained result explanation has been taken based on fracture mechanics. Critical stress intensity factor K slc and critical CTODc have been investigated according to TC-89 RILEM recommendation. K slc for all mortars (with and without polymer) were similar. High flexural strength for mortars with polymer may be caused by less defective structure. Less defective structure is the effect of polymer addition probably.