scholarly journals Visualization of dynamic stress conditions in elastic solids utilizing high frequency stroboscopic LED arrays

2019 ◽  
Author(s):  
Jian Shi ◽  
Hendrik Ohrdes ◽  
Michael Weinstein ◽  
Jens Twiefel
Keyword(s):  
High Frequency ◽  
Dynamic Stress ◽  
Stress Conditions ◽  
Elastic Solids ◽  
Led Arrays

A dynamic model for far-field acceleration

1982 ◽  
Vol 72 (4) ◽  
pp. 1049-1068
Author(s):  
John Boatwright
Keyword(s):  
Stress Drop ◽  
High Frequency ◽  
Dynamic Stress ◽  
The Body ◽  
Body Waves ◽  
Far Field ◽  
Rupture Velocity ◽  
Frequency Level ◽  
Average Change ◽  
Dynamic Stress Drop

abstract A model for the far-field acceleration radiated by an incoherent rupture is constructed by combining Madariaga's (1977) theory for the high-frequency radiation from crack models of faulting with a simple statistical source model. By extending Madariaga's results to acceleration pulses with finite durations, the peak acceleration of a pulse radiated by a single stop or start of a crack tip is shown to depend on the dynamic stress drop of the subevent, the total change in rupture velocity, and the ratio of the subevent radius to the acceleration pulse width. An incoherent rupture is approximated by a sample from a self-similar distribution of coherent subevents. Assuming the subevents fit together without overlapping, the high-frequency level of the acceleration spectra depends linearly on the rms dynamic stress drop, the average change in rupture velocity, and the square root of the overall rupture area. The high-frequency level is independent, to first order, of the rupture complexity. Following Hanks (1979), simple approximations are derived for the relation between the rms dynamic stress drop and the rms acceleration, averaged over the pulse duration. This relation necessarily depends on the shape of the body-wave spectra. The body waves radiated by 10 small earthquakes near Monticello Dam, South Carolina, are analyzed to test these results. The average change of rupture velocity of Δv = 0.8β associated with the radiation of the acceleration pulses is estimated by comparing the rms acceleration contained in the P waves to that in the S waves. The rms dynamic stress drops of the 10 events, estimated from the rms accelerations, range from 0.4 to 1.9 bars and are strongly correlated with estimates of the apparent stress.

Behavior of materials at dynamic stress conditions using laser-induced shock waves

1993 ◽  
Author(s):  
Irith Gilath ◽  
S. Eliezer ◽  
T. Bar-Noy ◽  
R. Englman ◽  
Z. Jaeger
Keyword(s):  
Shock Waves ◽  
Dynamic Stress ◽  
Stress Conditions

Dynamic Stress—Strain Properties of a Steel and a Brass at Strain Rates up to 104 Per Second

1975 ◽  
Vol 189 (1) ◽  
pp. 107-115 ◽  
Author(s):  
R. L. Woodward ◽  
R. H. Brown
Keyword(s):  
Mild Steel ◽  
High Frequency ◽  
Dynamic Stress ◽  
High Strain ◽  
Strain Rates ◽  
Electric Load ◽  
Compression Tests ◽  
Initial Flow ◽  
High Frequency Response ◽  
Yield Point Phenomenon

Results of compression tests on 70:30 brass and a mild steel at strain rates from 10-3 to 104 per second are reported. The tests were carried out on a reactionless gas forging rig, using a high-frequency response piezo-electric load cell. The brass is shown to be relatively insensitive to strain rate over the range of the tests. The mild steel in the ‘as-received’ condition showed a marked increase in initial flow stress at high strain rates; pre-straining removed the phenomenon and ageing re-established it so that the rise in yield stress can be attributed to a ‘yield-point phenomenon’. The strain associated with the drop in stress following yielding is noted to be large and it is demonstrated that this results from the finite time for yielding to propagate along the specimen.

scholarly journals Investigations into the Potential Abrasive Release of Nanomaterials due to Material Stress Conditions-Part A: Carbon Black Nano-Particulates in Plastic and Rubber Composites

2019 ◽  
Vol 9 (2) ◽  
pp. 214 ◽  
Author(s):  
Johannes Bott ◽  
Roland Franz
Keyword(s):  
Carbon Black ◽  
Dynamic Stress ◽  
Laser Light ◽  
Stress Test ◽  
Stress Conditions ◽  
Rubber Composites ◽  
Test Protocol ◽  
Rubber Compounds ◽  
Plastic Materials ◽  
Surface Particle

Plastic and rubber based composites containing carbon black (CB) were investigated for the potential to release CB nano-particulates under stress conditions into food simulants. Nanocomposites were exposed to thermal, chemical, and mechanical stress, followed by mechanical abrasion of their surface. Particle sensitive asymmetric flow field-flow fractionation (AF4) with multi angle laser light scattering (MALLS) detection was used to detect and quantify CB nano-particulates. This study demonstrates that, even under dynamic stress conditions, CB nano-particulates are not released from the plastic or rubber compounds into food. This study intends also to propose a general nano-release stress test protocol for plastic materials coming into contact with foodstuff.

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