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Experimental characterization of the dynamic failure behavior of mortar under impact loading (2001)

Grote, D. L. ; Park, S. W. ; Zhou, M.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 89 (2001), S. 2115-2123

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ISSN: 1089-7550

Source: AIP Digital Archive

Topics: Physics

Notes: The failure behavior of mortar under dynamic impact loading is characterized through a series of plate impact experiments. The analysis focuses on the spall strength and the shear stress carrying capacity in different regions of the specimen under normal impact loading. Special attention is paid to the possible existence of a failure wave phenomenon that has been widely recognized as an important failure mechanism for glasses during plate impact. The experiments are designed to allow the strengths of the medium at locations behind and ahead of a possible failure wave front to be analyzed. The diagnostics used include velocity interferometer system for any reflector (VISAR) recording of the free surface velocities of targets and monitoring of the internal stresses via polyvinylidene fluoride (PVDF) gauges embedded in the specimen. Experiments conducted do not provide evidence for the existence of a failure wave phenomenon for mortar under plate normal impact loading. While the study suggests that a threshold impact stress must be exceeded for failure to occur, a clearly defined failure wave that propagates behind the loading wave is not observed. Instead, a gradual failure process that initiates upon the arrival of the loading wave and progresses thereafter is observed. This gradual failure process in mortar is in contrast to the well-defined failure front and complete loss of tensile strength associated with the failure wave phenomenon reported for glasses. The study also indicates that, under impact involving high levels of input stresses, attenuation of the loading wave occurs as it propagates through the failed medium. © 2001 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.1340005

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Severity of root rot on tomato plants caused by Phytophthora nicotianae under nutrient- and light-stress conditions (2001)

Grote, D. ; Claussen, W.

Oxford, UK : Blackwell Science Ltd

Plant pathology 50 (2001), S. 0

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ISSN: 1365-3059

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abiotic stress induced by three concentrations of nutrients in solution, and biotic stress caused by three inoculum densities of Phytophthora nicotianae, were imposed on tomato plants grown hydroponically under natural light in the glasshouse. The pathogen causes stem and root rot, thereby inducing water deficiency symptoms. The progress of the disease, as measured serologically by DAC–ELISA, was markedly accelerated by enhanced concentrations of nutrients. Significant differences in proline content of infected and noninfected plants were observed at a nutrient concentration equivalent to 5·0 dS m−1. Higher nutrient concentrations increased further proline concentration in leaves. Inoculation of tomatoes under two light regimes in a phytotron produced significantly more affected roots with increasing inoculum density, but disease was not affected by different light treatments. However, higher light intensity accelerated the appearance of symptoms and produced higher proline contents in tomato leaves. It is suggested that the proline content of tomato leaves is a suitable marker for stress induced by both abiotic and biotic factors.