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1

Infuence of CO2–water–rock interactions on the fracture properties of sandstone from the Triassic Xujiahe Formation, Sichuan Basin

Li Hongfei, Xie Lingzhi, Ren Li, He Bo, Liu Yang, Liu Jun

Acta Geophysica

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2021

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Vol. 69, no. 1

135--147

EN

Carbon dioxide (CO2) storage in deep saline aquifers has been lauded as one of the most efective techniques to mitigate greenhouse efects globally. Nevertheless, despite many investigations, clarifying the infuence of CO2–water–rock inter actions on the fracture characteristics of sandstone remains a challenge. In this work, the fracture properties of sandstone collected from the Triassic Xujiahe Formation are systematically studied in tests simulating CO2 sequestration. The results indicate that the water–rock interactions occur in a system of sandstone and CO2 solution. Due to the interactions, the poros ity of sandstone specimens slightly increases from 8.24 to 8.45% when immersed in CO2 solution and from 8.20 to 8.40% in pure water after 28 days. In addition, the parameters of fracture toughness, tensile strength, uniaxial compressive strength and elastic modulus are reduced by 24.12%, 27.16%, 31.78% and 33.21% after immersion in pure water, while they are reduced by 24.05%, 29.72%, 30.75% and 25.79% after immersion in CO2 solution, respectively. These results suggest that the mechanical properties of the Xujiahe sandstone deteriorate after soaking. The results also show that the critical fracture energy of sandstone specimens after immersion in the CO2 solution is 10.4% lower than that in pure water and 24.1% lower than that under natural drying conditions. These research results have great signifcance for understanding the dissolution processes during CO2 sequestration and their infuence on the fracture properties of sandstone, which may be theoretically instructive for CO2 storage in the Xujiahe Formation in the Sichuan Basin.

2

Investigation on flexural behaviors of i-shaped jointed composite plates

Altan Gurkan

Advances in Science and Technology. Research Journal

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2018

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Vol. 12, no 2

65--70

EN

In this study, the flexural behaviors of a composite plate jointed with I profile jointing element have been carried out experimentally and numerically. As a load type, four point flexural tests have been used in order to study performances of jointed composite plates under bending load. The effects of jointing geometry parameters ratio of the width of lock to width of semi-specimen (b/W), lock middle/end width to the width of lock (z/b) and the length of lock to the width of semi-specimen (h/2W) have been investigated. According to the investigation optimum jointing parameters have been found with the h/2w ratio of 0.5, b/w ratio of 0.5 and z/b ratio of 0.5. Abaqus 6.11 finite element program has been used in order to support the results obtained from the experiments. Damages have been mostly seen on jointing lock elements.

3

Microstructural study of failure phenomena in WC 94%-Co 6% hard metal alloy tips of radial picks

Nahak S., Chattopadhyaya S., Dewangan S., Hloch S., Krolczyk G., Legutko S.

Advances in Science and Technology. Research Journal

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2017

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Vol. 11, no 1

36--47

EN

An excellent combination of hardness, strength, stiffness and high melting point has proved the WC-Co as an ideal material for tools that are used for metal cutting, coal mining, oil drilling, etc. The ongoing research in WC-Co is focussed on enhancing its wear resistant properties as much as possible. For the purpose, many attempts have been made to study the tribological behaviour of WC-Co for a long time. Researchers have used various grades of WC-Co in different working environments and accordingly they have characterized the wear phenomena involved there within. In this direction of research, the present paper makes an attempt to understand various wear behaviours in WC 94%-Co 6% hard metal alloy. WC-Co was used as a tip of the coal cutting tool named radial pick. Two radial picks have been taken for critical analysis through field emission scanning electron microscopy (FESEM) attached with energy dispersive X-ray spectroscopy (EDS). In this work, the failure behaviours in the tools have been divided into five categories: (1) Abrasion on individual grain; (2) Corrosion in carbide grains; (3) Fragmentation and removal of WC grains; (4) Pores in WC grains; and (5) Coal and rock embedding. The most possible reasons behind each failure phenomenon have been explained comprehensively with the help of high-resolution microscopic images. However, it is usually observed that, initially, the tool gets minor cracks due to sudden impact. These cracks provide a path to the rock and coal particles to get entrenched inside the microstructure of cemented carbide. Finally, the intermixed external elements degrade the binder content (i.e. cobalt) and the tool becomes useless.

4

Regarding the importance of the mileage distribution for reliability prognoses in automotive industry

Althaus D., Braasch A., Schlummer M., Meyna A.

Journal of KONBiN

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2010

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No. 1 (13)

17-28

EN

In automotive industry there are few information about the load of a car in use. Therefore, the available data needs to be used and looked at carefully. Data that is nearly always available is the time in field, given by the date of registration and the date when failure occurred, and the driving distance. The driving distance can be used to describe the load of a car because in most cases the operating time is not known. This data can be used to calculate the mileage distribution of a car, which contains much additional information for safety and reliability analysis. Furthermore, it is useful to adopt testing routines and lifetime distances that are written down in specifications.

PL

Przemysł samochodowy nie posiada wielu danych o obciążeniu eksploatowanego samochodu, a zatem należy korzystać z tych danych, które posiadamy i dokładnie się im przyglądać. Danymi, które są zawsze dostępne, jest czas eksploatacji określony przez datę rejestracji i datę awarii oraz przejechany kilometraż. Przejechana odległość może służyć do określenia obciążenia samochodu, ponieważ czas jego użytkowania jest w większości wypadków nieznany. Parametr ten może posłużyć do obliczenia rozkładu przebiegu samochodu, który zawiera wiele dodatkowych informacji przydatnych w analizie bezpieczeństwa i niezawodności. Ponadto ma on zanaczenie w przyjęciu programów badań okresowych i formułowaniu założeń dotyczących trwałości/ całowitego przebiegu.

5

Safety Studies on Hydraulic Proportional Valves With Electrical Position Feedback

Reinert D., Kimura T., Gorgs K.- J.

International Journal of Occupational Safety and Ergonomics

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2006

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Vol. 12, No. 1

105--115

EN

The authors analysed a proportional valve with electrical position feedback for its failure behaviour. Several failures were introduced into the feedback loop, especially into the 2 solenoids and the inductive position transducer. The behaviour of the valve for square and ramp reference signals was recorded and systematically analysed. It was shown that failures could be detected by monitoring the residual signal from the equipment under control or the residual signal from the sensor. It was possible to achieve the safe position within twice the normal response time of the valve by switching off the current of both solenoids. The application of these results for a new generation of safe proportional valves is discussed. The use of the results of these investigations obviates the need for redundancy of the electrical position monitoring arrangement in a safe proportional valve.

6

Failure analysis of textile-reinforced ceramic matrix composites

Hufenbach W., Langkamp A., Kroll L., Błażejewski W.

Kompozyty

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2003

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R. 3, nr 7

250-254

EN

The high lightweight potential of modern long-fibre reinforced ceramics for the application in components under complex thermo-mechanical loads can only be used optimally, if the anisotropic fibre reinforcement is designed according to the acting loads. For the component optimisation adapted analytical and numerical simulation techniques as well as suitable realistic failure criteria are required. By applying analytical and numerical computing methods developed so far for fibre- and textile-reinforced ceramics, the thermo-mechanical induced stresses and strains can be sufficiently determined. In contrast, undertaking the failure analysis adapted to textile ceramic structures still remains a source of considerable difficulty. One principal reason for this is that the use of the ,,homogenisation technique" in the sense of a ,,blurred" continuum is not permissible for a realistic description of the fracture behaviour of textile-reinforced ceramics. The often applied generalising fracture criteria, such as, for example, the quadratic failure criteria of Sacharov and Tsai-Wu cannot be used to simulate the actual fracture behaviour realistically and there remains a great uncertainties in the interpretation of the results of fracture tests. Only the development of a new type of so-called fracture mode criteria can enable a physically based description of the prevailing failure modes of fibre- and textil-reinforced ceramics. Subsequently, the action plane criterion of Hashin-Puck and the invariant criterion of Cuntze are applied to the failure analysis of fibre- and textile-reinforced SiC ceramics and correspondingly modified. The objective of this paper is to improve the strength analysis of fibre- and textile-reinforced ceramic structures applying novel fracture mode related failure criteria. By means of multi-axial failure tests carried out on reinforced ceramics, the failure mode criteria were able to be verified in the stress planes.

PL

Właściwości nowoczesnych materiałów ceramicznych wzmocnionych włóknami tekstylnymi stwarzają potencjalne możliwości konstruowania ultralekkich elementów, podlegających złożonym naprężeniom termomechanicznym. Potencjał tych materiałów może być optymalnie wykorzystany tylko wtedy, jeżeli cechy ich anizotropowego wzmocnienia włóknistego dobrane zostaną na podstawie występującego stanu naprężeń. Optymalizacja konstrukcji wymienionych elementów wymaga zastosowania odpowiednich analitycznych i numerycznych technik symulacji oraz realistycznych kryteriów zniszczenia. Istniejące metody obliczeń naprężeń i odkształceń pozwalają na ich wystarczająco dokładne określenie. W odróżnieniu od tego analiza pękania rozważanych materiałów stwarza istotne problemy. Wynika to z faktu, że zastosowanie „technik homogenizacji" nie pozwala na rzeczywisty opis zniszczenia w tych materiałach. Często stosowane uogólniające kryteria zniszczenia, takie jak np. kwadratowe kryterium Sacharowa i Tsai-Wu również nie pozwalają na uzyskanie dokładnych wyników. Jedynie rozwój nowego typu kryteriów zniszczenia uwzględniających tzw. tryby pękania może prowadzić do uzasadnionego fizycznie opisu materiałów ceramicznych wzmacnianych włóknami i tkaninami w realnych warunkach zniszczenia. Następnie, zastosowano kryteria Hashin-Puck i kryterium wartości niezmiennych według Cuntze do analizy uszkodzeń zaistniałych we wzmacnianych włóknami i tkaninami SiC i odpowiednio je zmodyfikowano. W artykule przedstawiono ulepszoną metodę weryfikacji wytrzymałości jedno- i wielowarstwowo wzmocnionych struktur ceramicznych przy zastosowaniu nowych kryteriów zniszczenia uwzględniających różne rodzaje pękania materiału. Wieloosiowe próby wytrzymałościowe, przeprowadzone na kompozytach ceramicznych, pozwoliły zweryfikować wyżej wymienione kryteria w płaszczyznach naprężeń.

7

Failure behaviour of alumina cutting ceramics.

Szutkowska M.

Inżynieria Materiałowa

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2001

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R. XXII, nr 5

912-915

PL

Artykuł przedstawia zwięzły przegląd ważniejszych zagadnień dotyczących badania odporności na pękanie ceramiki na bazie tlenku glinu z uwzględnieniem ich praktycznego wykorzystania do sterowania jakością oraz jako wielkość dostarczającej użytecznych informacji w pracach badawczych. Przedstawiono niektóre metody doświadczalne bazujące na trójpunktowym lub czteropunktowym obciążaniu belek ze wstępnym pęknięciem oraz technice wciskania penetratora twardości Vickersa, stosowane do oceny zachowania się badanych materiałów podczas zniszczenia. Przeprowadzono również obserwację odporności na pękanie w funkcji rozwijającego się peknięcia (krzywa R).

EN

This paper has briefly reviewed some of the major concerns in testing of fracture toughness of alumina ceramics with their practical usage for a quality control and an informative quantity in research works. Some experimental methods based on the precracked beams loaded by three or four-point bending and Vickers hardness indentation technique have been presented to assessment the failure behaviour of tested materials. The crack growth resistance curve (R-curve) has been observed as well.