scholarly journals Static and cyclic strength properties of Mount St. Helens debris avalanche and ash cloud materials

1985 ◽  
Author(s):  
W.J. Winters ◽  
R.E. Kayen
Keyword(s):  
Debris Avalanche ◽  
Strength Properties ◽  
Cyclic Strength ◽  
Ash Cloud ◽  
Mount St Helens

Shot Peening of Brittle Materials - Status and Outlook

2010 ◽  
Vol 638-642 ◽  
pp. 799-804 ◽  
Author(s):  
Wulf Pfeiffer ◽  
Johannes Wenzel
Keyword(s):  
Shot Peening ◽  
Surface Region ◽  
Strength Properties ◽  
Cyclic Strength ◽  
Cemented Carbides ◽  
Common Procedure ◽  
Surface Strength ◽  
Crack Network ◽  
Near Surface ◽  
Compressive Stresses

Shot peening is a common procedure to improve the static and cyclic strength of metal components by a combination of work hardening and the introduction of compressive stresses into the surface region. Our investigations through the last years showed that high compressive stresses of more than 1 GPa can also be introduced in brittle ceramics under specific shot peening conditions. These stresses significantly increase the near-surface strength. Based on the findings for ceramics, shot peening procedures have now been developed for cemented carbides and hard chromium platings. Recent investigations showed that, due to the higher fracture toughness of cemented carbides, shot peening could be performed using higher peening intensities leading to a higher gain in strength properties. Although chromium platings are less brittle than ceramics, shot peening of these layers are very challenging due to the formation of a micro-crack network being typically for these coatings. Nevertheless, first results indicate the possibility of a successfully shot peening of these coatings.

scholarly journals Static and cyclic strength properties of brittle adhesives with porosity

2017 ◽  
Vol 7 ◽  
pp. 291-298
Author(s):  
G. Fernandez ◽  
D. Vandepitte ◽  
H. Usabiaga ◽  
S. Debruyne
Keyword(s):  
Strength Properties ◽  
Cyclic Strength

Wind dispersed seeds and plant recovery on the Mount St. Helens debris avalanche

1989 ◽  
Vol 67 (5) ◽  
pp. 1434-1441 ◽  
Author(s):  
Virginia H. Dale
Keyword(s):  
Plant Density ◽  
Plant Cover ◽  
Debris Avalanche ◽  
Long Distance ◽  
Spider Webs ◽  
Climate Conditions ◽  
Disturbed Areas ◽  
Successional Species ◽  
Average Plant ◽  
Mount St Helens

Seed dispersal and plant establishment were monitored for 4 years on the debris avalanche created by the 1980 eruption of Mount St. Helens. The number of plants on the deposit increased over time to a high of almost 2 plants/m2 by 1983. The number of species per 250-m2 plot has increased to a mean of 10.3 in 1983 with 76 species being present over the entire deposit. Four years after the eruption only 30% of the species present before the eruption had reestablished themselves, and average plant cover was less than 1%. The debris avalanche has been invaded primarily via wind-dispersed seed of early successional species that survived or have become established in adjacent disturbed areas. Most of the early successional species on the avalanche have plumed seeds that are adapted not only for long distance dispersal, but also for being trapped in wet areas or by spider webs. Fluctuations in the density of seeds dispersed to the deposit were related to variation in precipitation. Neither seed abundance nor plant density correlated with absolute distance to a seed source or soil texture conditions. Colonization patterns are more influenced by the available biota and prevailing climate conditions than by substrate alterations resulting from the eruption.

Understanding seismic path biases and magmatic activity at Mount St Helens volcano before its 2004 eruption

2020 ◽  
Vol 222 (1) ◽  
pp. 169-188 ◽  
Author(s):  
S Gabrielli ◽  
L De Siena ◽  
F Napolitano ◽  
E Del Pezzo
Keyword(s):  
Time Window ◽  
Debris Avalanche ◽  
Coda Waves ◽  
Source Inversion ◽  
Borehole Data ◽  
Lapse Time ◽  
Scattering Attenuation ◽  
Seismic Coda ◽  
Velocity Anomalies ◽  
Mount St Helens

SUMMARY In volcanoes, topography, shallow heterogeneity and even shallow morphology can substantially modify seismic coda signals. Coda waves are an essential tool to monitor eruption dynamics and model volcanic structures jointly and independently from velocity anomalies: it is thus fundamental to test their spatial sensitivity to seismic path effects. Here, we apply the Multiple Lapse Time Window Analysis (MLTWA) to measure the relative importance of scattering attenuation vs absorption at Mount St Helens volcano before its 2004 eruption. The results show the characteristic dominance of scattering attenuation in volcanoes at lower frequencies (3–6 Hz), while absorption is the primary attenuation mechanism at 12 and 18 Hz. Scattering attenuation is similar but seismic absorption is one order of magnitude lower than at open-conduit volcanoes, like Etna and Kilauea, a typical behaviour of a (relatively) cool magmatic plumbing system. Still, the seismic albedo (measuring the ratio between seismic energy emitted and received from the area) is anomalously high (0.95) at 3 Hz. A radiative-transfer forward model of far- and near-field envelopes confirms this is due to strong near-receiver scattering enhancing anomalous phases in the intermediate and late coda across the 1980 debris avalanche and central crater. Only above this frequency and in the far-field diffusion onsets at late lapse times. The scattering and absorption parameters derived from MLTWA are used as inputs to construct 2-D frequency-dependent bulk sensitivity kernels for the S-wave coda in the multiple-scattering (using the Energy Transport Equations—ETE) and diffusive (AD, independent of MLTWA results) regimes. At 12 Hz, high coda-attenuation anomalies characterize the eastern side of the volcano using both kernels, in spatial correlation with low-velocity anomalies from literature. At 3 Hz, the anomalous albedo, the forward modelling, and the results of the tomographic imaging confirm that shallow heterogeneity beneath the extended 1980 debris-avalanche and crater enhance anomalous intermediate and late coda phases, mapping shallow geological contrasts. We remark the effect this may have on coda-dependent source inversion and tomography, currently used across the world to image and monitor volcanoes. At Mount St Helens, higher frequencies and deep borehole data are necessary to reconstruct deep volcanic structures with coda waves.

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