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The role of water content in rate dependence of tensile strength of a fine-grained sandstone

Cai Xin, Cheng Chuanqing, Zhao Yuan, Zhou Zilong, Wang Shaofeng

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 1

art. no. e58, 2022

EN

Rocks in nature are commonly in partially saturated conditions and exposed to dynamic loads. In this study, to explore the coupled effects of water content and loading rate, dynamic Brazilian disc experiments were conducted on Yunnan sandstone samples with four levels of water content (from air-dried to water-saturated) under various loading rates (from 100 to 600 GPa/s) using a split Hopkinson pressure bar. The test results show that for each water content, the dynamic tensile strength of sandstone is positively sensitive to loading rate. The rate dependence of tensile strength increases as the rise of water content. The change trends of tensile strength against water content depend on loading rate: as water content rises, the tensile strength displays the manner of “no change followed by fast drop” at loading rates of 10–4 and 100 GPa/s. However, when the loading rate is above 200 GPa/s, the tensile strength increases first and then declines. The turning point occurs at water content between 1.0 and 2.0%. These observations can be interpreted with the competition between water weakening and enhancing effects under different loading conditions.

2

Warunki obciążania jako czynnik rzutujący na odkształcalność osadów deltowych z zachodniej części Żuław Wiślanych

Białobrzeski T., Dobak P., Szczepański T., Zawrzykraj P.

Przegląd Geologiczny

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2017

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Vol. 65, nr 10/2

756--764

EN

Results of a series of CRL-type consolidation tests on alluvial deposits form Vistula Delta "Żuławy ”, conducted with diverse load rates are shown. Such approach revealed diversified strain response of tested material. Dividing loading into stages has made increasing of stiffness, which may be applicable on the practice field.

3

Investigation on compressive behavior of Cu-35Ni-15Al alloy at high temperatures

Li C., Chen J., Li W., Hu Y., Ren Y., Qiu W., He Junjie, Chen J.

Materials Science Poland

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2014

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Vol. 32, No. 3

341--349

EN

Microstructures and mechanical properties of Cu–35Ni–15Al alloy in cast and porous states were studied by scanning electron microscopy and compression tests. The influence of porosity, deformation temperature and loading rate on mechanical properties of the two kinds of alloys was investigated. The results show that the as cast alloy and porous alloys have almost the same phase constitution: Cu rich phase, Ni rich phase and K intermetallics. The yield strength of porous alloys increases continuously with decreasing porosity, the relationship between porosity and yield stress follows Gibson-Ashby equation.With decreasing deformation temperature, the yield strength of as cast alloy and porous alloy increase. With the increase of loading rate, the yield strength of these alloys shows an increasing trend. After compression, the microstructure of as cast alloy is more uniform, and porous alloys are more prone to have localized deformations.

4

Loading rate effect on mechanical properties of cervical spine ligaments

Trajkovski A., Omerovic S., Krasna S., Prebil I.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 3

13--20

EN

Mechanical properties of cervical spine ligaments are of great importance for an accurate finite element model when analyzing the injury mechanism. However, there is still little experimental data in literature regarding fresh human cervical spine ligaments under physiological conditions. The focus of the presented study is placed on three cervical spine ligaments that stabilize the spine and protect the spinal cord: the anterior longitudinal ligament, the posterior longitudinal ligament and the ligamentum flavum. The ligaments were tested within 24-48 hours after death, under two different loading rates. An increase trend in failure load, failure stress, stiffness and modulus was observed, but proved not to be significant for all ligament types. The loading rate had the highest impact on failure forces for all three ligaments (a 39.1 % average increase was found). The observed increase trend, compared to the existing increase trends reported in literature, indicates the importance of carefully applying the existing experimental data, especially when creating scaling factors. A better understanding of the loading rate effect on ligaments properties would enable better case-specific human modelling.

5

Wpływ szybkości obciążania na twardość wyznaczaną metodą DSI dla aluminium, miedzi i ich stopów

Pokorska I.

Inżynieria Powierzchni

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2013

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nr 4

66-71

PL

W ostatnich latach szeroko stosowaną metodą pomiaru twardości jest metoda DSI (Depth Sensing Indentation). W metodzie tej zastosowana siła obciążająca jest rejestrowana w funkcji głębokości odcisku podczas cyklu obciążania i odciążania. W pracy badano wpływ szybkości obciążania na twardość Martensa, twardość indentacyjną HIT i wartość pełzania. Zastosowano obciążanie liniowe. Szybkość obciążania zastosowana w pomiarze twardości metodą DSI nie wywiera znaczącego wpływu na wartość twardości indentacyjnej HIT oraz twardości Martensa materiałów plastycznych. Wartość pełzania wzrasta wraz z szybkością obciążania w określonych zakresach właściwych dla danego materiału.

EN

Recently, the depth sensing indentation (DSI) test became a widely used method of hardness determination. In DSI method the applied load is registered as a function of indentation depth both during loading and unloading. The influence of loading rate on Martens hardness, indentation hardness and value of creep was investigated in this work. Linear loading was applied. Not significant effect of loading rate on DSI hardness of plastic materials was observed. The value of creep increases with the loading rate in the specified ranges appropriate for the material.

6

Wpływ szybkości obciążania na twardość wyznaczaną metodą DSI

Pokorska I.

Inżynieria Materiałowa

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2011

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Vol. 32, nr 4

672-675

PL

W ostatnich latach szeroko stosowaną metodą pomiaru twardości jest metoda DSI (Depth Sensing Indentation). W metodzie tej zastosowana siła obciążająca jest rejestrowana w funkcji głębokości odcisku podczas cyklu obciążania i odciążania. W pracy badano wpływ szybkości obciążania na twardość Martensa i twardość indentacyjną HIT. Zastosowano obciążanie liniowe. Szybkość obciążania wpływa na twardość HIT. Nie zaobserwowano natomiast znaczącego wpływu szybkości obciążania na twardość Martensa HM.

EN

Recently, the depth sensing indentation (DSI) test became a widely used method of hardness determination. In DSI method the applied load is registered as a function of indentation depth both during loading and unloading. The influence of loading rate on Martens hardness and indentation hardness was investigated in this work. Linear loading was applied. The loading rate influences on indentation hardness HIT. Not significant effect of loading rate on Martens hardness HM was observed.

7

Wpływ prędkości obciążania na odpowiedź próbek skał ze złoża ZG RUDNA w fazie pokrytycznej.

Cyrul T.

Rudy i Metale Nieżelazne

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2003

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R. 48, nr 8

358-363

PL

Zaprezentowano wyniki badań zachowania skał ze złoża ZG RUDNA, które przeprowadzone zostały w Instytucie Mechaniki Górotworu PAN w Krakowie. Celem badań było poznanie wpływu prędkości obciążania próbek skalnych w próbie jednoosiowego ściskania na pełną charakterystykę odkształcenie-naprężenie. Badania przeprowadzono na czterech seriach skał. Zbadano dwie serie piaskowca o różnym spoiwie oraz dwie serie dolomitu. Prędkość obciążenia zmieniano w zakresie od 10 do -6 l/s do 2,5 x 10 do -3 l/s. Stwierdzono istotny wpływ warunków obciążania na zachowanie badanych skał. W przypadku jednej serii dolomitu stwierdzono zmianę klasy zachowania skał ze wzrostem prędkości obciążenia.

EN

Behaviour of the rocks from the Rudna mine deposit has been investigated at the Strata Mechanics Research Institute of The Polish Academy of Sciences in Cracow. Investigation was carried out to determine an effect of a loading rate of rock samples during uniaxial compression test on a full strain-stress characteristics. Four batches of rock samples were used in this investigation, including two batches of a sandstone with different binders and two batches of a dolomite. The loading rate ranged from 10 to -6 l/s to 2.5 x 10 to -3 l/s. It was found that loading conditions had significant effect on the behaviour of the rocks examined. In the case of a single batch of dolomite an increase of a loading rate appeared to result in a change of a class of rock behaviour.