The effect of loading rate on static friction and the rate of fault healing during the earthquake cycle

Chris Marone

doi:10.1038/34157

Analysis of physicochemical and thermo-mechanical characteristics of Iranian black seed (Nigella oxypetala Boiss)

International Journal of Food Engineering ◽

10.1515/1556-3758.2703 ◽

2012 ◽

Vol 8 (3) ◽

Cited By ~ 5

Author(s):

Seyed Mohammad Taghi Gharibzahedi ◽

Seyed Mohammad Mousavi ◽

Mohammad Jouki ◽

Mohammad Ghahderijani

Keyword(s):

Nutritional Value ◽

Mineral Content ◽

Mechanical Characteristics ◽

Loading Rate ◽

Static Friction ◽

Terminal Velocity ◽

Angle Of Repose ◽

Engineering Properties ◽

Mean Values ◽

Black Seed

Abstract The study experimentally scrutinized nutritional and engineering properties of Iranian black seed at a moisture content of 5.1% (w.b.) in order to design processing equipment and machinery for various post-harvest operations. Analysis of chemical composition, mineral content and fatty acid profile illustrated that the seeds had high nutritional value. Bulk density, true density and porosity were 539.3 kg/m3, 1009.4 kg/m3 and 46.5%, respectively. Mean values for angle of repose and terminal velocity were 5.6 m/s and 32.5°, respectively. Static friction coefficient on plywood, mild steel, aluminum and galvanized iron sheet were 0.53, 0.36, 0.32 and 0.37, respectively. Specific heat, thermal conductivity and thermal diffusivity varied from 1642 to 2035 J/kgK, 0.17 to 0.22 W/mK and 9.3 to 10.4 × 10-8 m2/s, respectively. The force required for initiating seed rupture decreased from 57.36 to 35.1 N and 55.7 to 30.24 N, and the energy absorbed at seed rupture decreased from 51.24 to 21.31 mJ and 26.67 to 6.31 mJ, with increase in loading rate from 1 to 10mm/min, for vertical and horizontal orientations, respectively.

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Measurement of Adhesion of Sternal Wires to a Novel Bioactive Glass-Based Adhesive

Journal of Functional Biomaterials ◽

10.3390/jfb10030037 ◽

2019 ◽

Vol 10 (3) ◽

pp. 37

Author(s):

Varinder Pal Singh Sidhu ◽

Mark R. Towler ◽

Marcello Papini

Keyword(s):

Loading Rate ◽

Static Friction ◽

Healing Time ◽

Strain Rates ◽

Scanning Electron Micrographs ◽

The Novel ◽

Sternal Closure ◽

Pull Out ◽

Steel Wires ◽

Significant Difference

Stainless steel wires are the standard method for sternal closure because of their strength and rigidity, the simplicity of the process, and the short healing time that results from their application. Despite this, problems still exist with sternal stability due to micromotion between the two halves of the dissected and wired sternum. Recently, a novel glass-based adhesive was developed which, in cadaveric trials and in conjunction with wiring, was shown to restrict this micromotion. However, in order to avoid complications during resternotomy, the adhesive should adhere only to the bone and not the sternal wire. In this study, sternal wires were embedded in 8 mm discs manufactured from the novel glass-based adhesive and the constructs were then incubated at 37 °C for one, seven, and 30 days. The discs were manufactured in two different thicknesses: 2 and 3 mm. Wire pull-out tests were then performed on the constructs at three different strain rates (1, 0.1, and 0.01 mm/min). No statistically significant difference in pull-out force was found regardless of incubation time, loading rate, or construct thickness. The pull-out forces recorded were consistent with static friction between the wire and adhesive, rather than the adhesion between them. Scanning electron micrographs provided further proof of this. These results indicate that the novel adhesive may be suitable for sternal fixation without complicating a potential resternotomy.

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From Elastic Deformation Loading Rates to Heat Flow Anomalies: Constraints on Seismic Efficiency and Friction Coefficient

10.5194/egusphere-egu2020-18763 ◽

2020 ◽

Author(s):

Malte J. Ziebarth ◽

John G. Anderson ◽

Sebastian von Specht ◽

Oliver Heidbach ◽

Fabrice Cotton

Keyword(s):

Friction Coefficient ◽

Heat Flow ◽

Elastic Deformation ◽

Loading Rate ◽

San Andreas Fault ◽

Static Friction ◽

Deformation Energy ◽

Loading Rates ◽

Static Friction Coefficient ◽

San Andreas

A long standing debate in seismology revolves around the nonexistent heat flow anomaly across the San Andreas fault. Given the fault&#8217;s average slip rate and age, a strong San Andreas fault, i.e. characterized by a relatively high static friction coefficient of &#181;>=0.6, should produce a significant local heat flow anomaly across the fault [1]. Since the work of Lachenbruch and Sass [1], this anomaly has not been observed and although many possible causes for the lack of a heat flow anomaly have been explored, the static or dynamic weakness of the San Andreas fault remains a favorable explanation [2,3].Recently, we have introduced the ENergy COnserving Seismicity (ENCOS) framework that relates elastic deformation energy loading rates to the long-term average energy release of the seismic process. Within the presented implementation of ENCOS for Southern California with an elastic loading rate between 300 MW and 1.9 GW, the two most significant parameters are the static friction coefficient and the average efficiency. In particular, they are the most significant sources of uncertainty in harnessing the GPS-derived strain rates and the stress data within the ENCOS framework.Here, we show how ENCOS can be leveraged in combination with the constraints from heat flow measurements and observed seismicity to restrict the parameter space of the average efficiency and the static friction coefficient. This can help to reduce the uncertainty of the ENCOS model parameters, such as the elastic deformation energy loading rate, and opens a new viewpoint on the heat flow paradox.[1] Lachenbruch, A. H., and Sass, J. H. (1980), Heat flow and energetics of the San Andreas Fault Zone, J. Geophys. Res., 85(B11), 6185&#8211;6222.[2] Scholz, C. H. (2013). The Strength of the San Andreas Fault: A Critical Analysis. In Earthquakes: Radiated Energy and the Physics of Faulting (eds R. Abercrombie, A. McGarr, G. Di Toro and H. Kanamori).[3] E. E. Brodsky et al. (2020), The State of Stress on the Fault Before, During, and After a Major Earthquake, Annu. Rev. Earth Planet. Sci. 48:2.1&#8211;2.26.

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Discrete dislocation plasticity analysis of loading rate-dependent static friction

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2015.0877 ◽

2016 ◽

Vol 472 (2192) ◽

pp. 20150877 ◽

Cited By ~ 3

Author(s):

H. Song ◽

V. S. Deshpande ◽

E. Van der Giessen

Keyword(s):

Loading Rate ◽

Static Friction ◽

Contact Length ◽

Point Of View ◽

Size Dependent ◽

Rate Dependent ◽

Discrete Dislocation ◽

Dislocation Plasticity ◽

Shear Yield ◽

Contact Size

From a microscopic point of view, the frictional force associated with the relative sliding of rough surfaces originates from deformation of the material in contact, by adhesion in the contact interface or both. We know that plastic deformation at the size scale of micrometres is not only dependent on the size of the contact, but also on the rate of deformation. Moreover, depending on its physical origin, adhesion can also be size and rate dependent, albeit different from plasticity. We present a two-dimensional model that incorporates both discrete dislocation plasticity inside a face-centred cubic crystal and adhesion in the interface to understand the rate dependence of friction caused by micrometre-size asperities. The friction strength is the outcome of the competition between adhesion and discrete dislocation plasticity. As a function of contact size, the friction strength contains two plateaus: at small contact length ( ≲ 0.6 μ m ) , the onset of sliding is fully controlled by adhesion while for large contact length ( ≳ 10 μ m ) , the friction strength approaches the size-independent plastic shear yield strength. The transition regime at intermediate contact size is a result of partial de-cohesion and size-dependent dislocation plasticity, and is determined by dislocation properties, interfacial properties as well as by the loading rate.

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Repeating earthquakes record fault weakening and healing in areas of megathrust postseismic slip

Science Advances ◽

10.1126/sciadv.aaz9317 ◽

2020 ◽

Vol 6 (32) ◽

pp. eaaz9317 ◽

Cited By ~ 1

Author(s):

E. J. Chaves ◽

S. Y. Schwartz ◽

R. E. Abercrombie

Keyword(s):

Loading Rate ◽

Temporal Variations ◽

Earthquake Cycle ◽

Repeating Earthquakes ◽

Seismic Slip ◽

Rupture Area ◽

Recurrence Intervals ◽

Large Earthquakes ◽

Constant Moment ◽

Postseismic Slip

Repeating earthquakes (REs) rupture the same fault patches at different times allowing temporal variations in the mechanical behavior of specific areas of the fault to be interrogated over the earthquake cycle. We study REs that reveal fault weakening after a large megathrust earthquake in Costa Rica, followed by fault recovery. We find shorter RE recurrence intervals and larger slip areas immediately following the mainshock that both gradually return to pre-earthquake values. RE seismic moments remain nearly constant throughout the earthquake cycle. This implies a balance between fault weakening (reducing slip) and transient embrittlement (increasing rupture area by converting regions from aseismic to seismic slip), induced by the increased loading rate following the mainshock. This interpretation is consistent with positive, negative, and constant moment versus RE recurrence interval trends reported in other studies following large earthquakes and with experimental work showing slip amplitudes and stress drop decrease with loading rate.

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