scholarly journals Phase-transformation-induced lubrication of earthquake sliding

2017 ◽  
Vol 375 (2103) ◽  
pp. 20160008 ◽  
Author(s):  
Harry W. Green
Keyword(s):  
Phase Transformation ◽  
Dry Friction ◽  
High Speed ◽  
Frictional Resistance ◽  
Low Pressure ◽  
Self Healing ◽  
Strength Recovery ◽  
Endothermic Reactions ◽  
Shear Heating ◽  
Fast Motion

Frictional failure is not possible at depth in Earth, hence earthquakes deeper than 30–50 km cannot initiate by overcoming dry friction. Moreover, the frequency distribution of earthquakes with depth is bimodal, suggesting another change of mechanism at about 350 km. Here I suggest that the change at 30–50 km is from overcoming dry friction to reduction of effective stress by dehydration embrittlement and that the change at 350 km is due to desiccation of slabs and initiation by phase-transformation-induced faulting. High-speed friction experiments at low pressure indicate that exceeding dry friction provokes shear heating that leads to endothermic reactions and pronounced weakening. Higher-pressure studies show nanocrystalline gouge accompanying dehydration and the highest pressure experiments initiate by exothermic polymorphic phase transformation. Here I discuss the characteristic nanostructures of experiments on high-speed friction and high-pressure faulting and show that all simulated earthquake systems yield very weak transformation-induced lubrication, most commonly nanometric gouge or melt. I also show that phase-transformation-induced faulting of olivine to spinel can propagate into material previously transformed to spinel, apparently by triggering melting analogous to high-speed friction studies at low pressure. These experiments taken as a whole suggest that earthquakes at all depths slide at low frictional resistance by a self-healing pulse mechanism with rapid strength recovery. This article is part of the themed issue ‘Faulting, friction and weakening: from slow to fast motion’.

scholarly journals Influencing Factors on the Healing Performance of Microcapsule Self-Healing Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4139
Author(s):  
Yanju Wang ◽  
Zhiyang Lin ◽  
Can Tang ◽  
Wenfeng Hao
Keyword(s):  
Compressive Strength ◽  
Sodium Silicate ◽  
Recovery Rate ◽  
Sound Speed ◽  
Orthogonal Experimental Design ◽  
Self Healing ◽  
Damage Degree ◽  
Strength Recovery ◽  
Healing System ◽  
Recovery Performance

The amounts of the components in a microcapsule self-healing system significantly impact the basic performance and self-healing performance of concrete. In this paper, an orthogonal experimental design is used to investigate the healing performance of microcapsule self-healing concrete under different pre-damage loads. The strength recovery performance and sound speed recovery performance under extensive damage are analyzed. The optimum factor combination of the microcapsule self-healing concrete is obtained. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are carried out on the concrete samples before and after healing to determine the healing mechanism. The results show that the healing effect of self-healing concrete decreases with an increase in the pre-damage load, and the sound speed recovery rate increases with an increase in the damage degree. The influence of the sodium silicate content on the compressive strength and compressive strength recovery rate of the self-healing concrete increases, followed by a decrease. The optimum combination of factors of the microcapsule self-healing system is 3% microcapsules, 30% sodium silicate, and 15% sodium fluosilicate. The results can be used for the design and preparation of self-healing concrete.

Highly Loaded Low-Pressure Turbine: Design, Numerical, and Experimental Analysis

2010 ◽  
Author(s):  
J. T. Schmitz ◽  
S. C. Morris ◽  
R. Ma ◽  
T. C. Corke ◽  
J. P. Clark ◽  
...  
Keyword(s):  
High Speed ◽  
Numerical Solutions ◽  
Pressure Ratio ◽  
Low Pressure ◽  
Boundary Layer Transition ◽  
Layer Transition ◽  
Free Stream Turbulence ◽  
Low Pressure Turbine ◽  
The Mean ◽  
Highly Loaded

The performance and detailed flow physics of a highly loaded, transonic, low-pressure turbine stage has been investigated numerically and experimentally. The mean rotor Zweifel coefficient was 1.35, with dh/U2 = 2.8, and a total pressure ratio of 1.75. The aerodynamic design was based on recent developments in boundary layer transition modeling. Steady and unsteady numerical solutions were used to design the blade geometry as well as to predict the design and off-design performance. Measurements were acquired in a recently developed, high-speed, rotating turbine facility. The nozzle-vane only and full stage characteristics were measured with varied mass flow, Reynolds number, and free-stream turbulence. The efficiency calculated from torque at the design speed and pressure ratio of the turbine was found to be 90.6%. This compared favorably to the mean line target value of 90.5%. This paper will describe the measurements and numerical solutions in detail for both design and off-design conditions.

scholarly journals Liquid Film Flow Generated by High-speed Droplet Impact in Low-pressure Environment

2015 ◽  
Vol 28 (5) ◽  
pp. 531-537
Author(s):  
Masaya KATO ◽  
Masao WATANABE ◽  
Kazumichi KOBAYASHI ◽  
Toshiyuki SANADA
Keyword(s):  
Liquid Film ◽  
High Speed ◽  
Film Flow ◽  
Low Pressure ◽  
Droplet Impact ◽  
Liquid Film Flow

scholarly journals Biaxial Shear Load Capacity of Anchor System for Quick-Hardening Track on Railway Bridges

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Kyoung Chan Lee ◽  
Il-Wha Lee ◽  
Seong-Cheol Lee
Keyword(s):  
High Speed ◽  
Ride Comfort ◽  
Load Capacity ◽  
Frictional Resistance ◽  
Shear Capacity ◽  
Railway Track ◽  
Railway Bridges ◽  
Anchor System ◽  
Ballast Track ◽  
Anchor Systems

Quick-hardening railway track was developed to rapidly convert old-style ballast track to slab track in order to improve its maintainability and ride comfort. On bridges, quick-hardening track is applied in a segmented structure to reduce the temperature constraint, and anchors at the centers of the segments securely couple the track to the bridge. In this study, an anchor system is proposed that facilitates fast construction, and two designs for the proposed anchor systems are provided along with experimental test results of the same. Two anchor system designs were developed to allow for the maximum possible longitudinal and transverse loads in high-speed railways while considering the frictional resistance between the track slab and bridge deck. The biaxial shear capacity of each design was investigated experimentally, and the structural capacity for biaxial shear loads was evaluated using an elliptical curve to represent the longitudinal and transverse shear capacities. The minimum friction coefficient was determined based on the results of the evaluation to minimize damage to the anchor. The results obtained from the experiments confirmed that the proposed anchor systems possess sufficient shear capacity for application on high-speed railway bridges.

Some Limitations in Applying Classical EHD Film Thickness Formulas to a High-Speed Bearing

1981 ◽  
Vol 103 (2) ◽  
pp. 295-301 ◽  
Author(s):  
J. J. Coy ◽  
E. V. Zaretsky
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Heating Effects ◽  
Theoretical Predictions ◽  
Traction Fluid ◽  
Shear Heating ◽  
Thickness Measurements ◽  
Inner Race ◽  
Maximum Stresses ◽  
Good Agreement

Elastohydrodynamic film thickness was measured for a 20-mm ball bearing using the capacitance technique. The bearing was thrust loaded to 90, 448, and 778 N (20, 100, and 175 lb). The corresponding maximum stresses on the inner race were 1.28, 2.09, and 2.45 GPa (185,000, 303,000, and 356,000 psi). Test speeds ranged from 400 to 14,000 rpm. Film thickness measurements were taken with four different lubricants: (a) synthetic paraffinic, (b) synthetic paraffinic with additives, (c) neopentylpolyol (tetra) ester meeting MIL-L-23699A specifications, and (d) synthetic cycloaliphatic hydrocarbon traction fluid. The test bearing was mist lubricated. Test temperatures were 300, 338, and 393 K. The measured results were compared to theoretical predictions using the formulae of Grubin, Archard and Cowking, Dowson and Higginson, and Hamrock and Dowson. There was good agreement with theory at low dimensionless speed, but the film was much smaller than theory predicts at higher speeds. This was due to kinematic starvation and inlet shear heating effects. Comparisons with Chiu’s theory on starvation and Cheng’s theory on inlet shear heating were made.

Structural changes in the surface layers of sealing material S-137 in high-speed dry friction

1974 ◽  
Vol 7 (6) ◽  
pp. 660-663
Author(s):  
N. L. Golego ◽  
M. E. Belitskii ◽  
A. D. Gaidarenko ◽  
V. A. Lyashko
Keyword(s):  
Dry Friction ◽  
High Speed ◽  
Structural Changes ◽  
Surface Layers ◽  
Sealing Material

The Effects of Inlet Boundary Layer Condition and Periodically Incoming Wakes on Secondary Flow in a Low Pressure Turbine Cascade

2020 ◽  
Author(s):  
Tobias Schubert ◽  
Silvio Chemnitz ◽  
Reinhard Niehuis
Keyword(s):  
Boundary Layer ◽  
Secondary Flow ◽  
High Speed ◽  
Low Pressure ◽  
Experimental Investigations ◽  
Turbine Cascade ◽  
Flow Conditions ◽  
Low Pressure Turbine ◽  
Speed Flow ◽  
Unsteady Inflow

Abstract A particular turbine cascade design is presented with the goal of providing a basis for high quality investigations of endwall flow at high-speed flow conditions and unsteady inflow. The key feature of the design is an integrated two-part flat plate serving as a cascade endwall at part-span, which enables a variation of the inlet endwall boundary layer conditions. The new design is applied to the T106A low pressure turbine cascade for endwall flow investigations in the High-Speed Cascade Wind Tunnel of the Institute of Jet Propulsion at the Bundeswehr University Munich. Measurements are conducted at realistic flow conditions (M2th = 0.59, Re2th = 2·105) in three cases of different endwall boundary layer conditions with and without periodically incoming wakes. The endwall boundary layer is characterized by 1D-CTA measurements upstream of the blade passage. Secondary flow is evaluated by Five-hole-probe measurements in the turbine exit flow. A strong similarity is found between the time-averaged effects of unsteady inflow conditions and the effects of changing inlet endwall boundary layer conditions regarding the attenuation of secondary flow. Furthermore, the experimental investigations show, that all design goals for the improved T106A cascade are met.

Experimental Study of the Low-Pressure Water Jet Assisted Laser Processing of W6Mo5Cr4V2 High-Speed Steel

Applied laser ◽  
2013 ◽  
Vol 33 (2) ◽  
pp. 181-185
Author(s):  
王金华 Wang Jinhua ◽  
袁根福 Yuan Genfu ◽  
逄志伟 Pang Zhiwei ◽  
陈春映 Chen Chunying
Keyword(s):  
Experimental Study ◽  
Laser Processing ◽  
High Speed ◽  
High Speed Steel ◽  
Low Pressure ◽  
Water Jet ◽  
Pressure Water

scholarly journals Design of a High-Speed Prosthetic Finger Driven by Peano-HASEL Actuators

2020 ◽  
Vol 7 ◽  
Author(s):  
Zachary Yoder ◽  
Nicholas Kellaris ◽  
Christina Chase-Markopoulou ◽  
Devon Ricken ◽  
Shane K. Mitchell ◽  
...  
Keyword(s):  
High Speed ◽  
Kinematic Model ◽  
Electrical Energy ◽  
Dc Motor ◽  
Self Healing ◽  
Force Output ◽  
Prosthetic Limbs ◽  
Neuromuscular Systems ◽  
Soft Actuators ◽  
Prosthetic Finger

Current designs of powered prosthetic limbs are limited by the nearly exclusive use of DC motor technology. Soft actuators promise new design freedom to create prosthetic limbs which more closely mimic intact neuromuscular systems and improve the capabilities of prosthetic users. This work evaluates the performance of a hydraulically amplified self-healing electrostatic (HASEL) soft actuator for use in a prosthetic hand. We compare a linearly-contracting HASEL actuator, termed a Peano-HASEL, to an existing actuator (DC motor) when driving a prosthetic finger like those utilized in multi-functional prosthetic hands. A kinematic model of the prosthetic finger is developed and validated, and is used to customize a prosthetic finger that is tuned to complement the force-strain characteristics of the Peano-HASEL actuators. An analytical model is used to inform the design of an improved Peano-HASEL actuator with the goal of increasing the fingertip pinch force of the prosthetic finger. When compared to a weight-matched DC motor actuator, the Peano-HASEL and custom finger is 10.6 times faster, has 11.1 times higher bandwidth, and consumes 8.7 times less electrical energy to grasp. It reaches 91% of the maximum range of motion of the original finger. However, the DC motor actuator produces 10 times the fingertip force at a relevant grip position. In this body of work, we present ways to further increase the force output of the Peano-HASEL driven prosthetic finger system, and discuss the significance of the unique properties of Peano-HASELs when applied to the field of upper-limb prosthetic design. This approach toward clinically-relevant actuator performance paired with a substantially different form-factor compared to DC motors presents new opportunities to advance the field of prosthetic limb design.

scholarly journals A Concept of Integration of a Vactrain Underground Station with the Solidarity Transport Hub Poland

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5737
Author(s):  
Olena Stryhunivska ◽  
Katarzyna Gdowska ◽  
Rafał Rumin
Keyword(s):  
High Speed ◽  
Low Pressure ◽  
Advanced Technology ◽  
Planning Stage ◽  
Safety Standards ◽  
Planning And Design ◽  
Railway Infrastructure ◽  
Critical Issues ◽  
High Speed Trains ◽  
Underground Station

This paper provides an analysis of a designed underground station infrastructure for vacuum tube high-speed trains for the planned mega transport hub in Poland. The potential of integrating the infrastructure of the station building with sealed low-pressure tubes system is analyzed. The Solidarity Transport Hub Poland is a planned mega hub to be located in Baranów Municipality, Poland, which is comprised of an airport, an airport city, a road, and railway infrastructure. It is to be integrated with the first route of vactrains in Poland. The aim of this paper is to design a hyperloop station building adequate for the advanced technology of low-pressure high-speed trains. Designing a hyperloop station is not trivial, due to technological aspects which have not been hitherto present in airport or railway planning and design, such as low-pressure zones or airlocks which determine possible passenger paths and evacuation roads. Both the mega airport and Polish hyperloop are in the planning stage, therefore, in this paper, available models and designs of the hyperloop station building and infrastructure are used in order to formulate recommendations for further development and identify critical issues related to the safety and reduction of passenger transit time. The main contribution of this paper is a model of the hyperloop station building which respects the principles of spatial planning and safety standards.

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