scholarly journals Towards a field test for fracture propagation propensity in weak snowpack layers

2006 ◽  
Vol 52 (176) ◽  
pp. 164-168 ◽  
Author(s):  
Dave Gauthier ◽  
Bruce Jamieson
Keyword(s):  
Field Test ◽  
Fracture Propagation ◽  
Field Tests ◽  
Fracture Initiation ◽  
Bimodal Distribution ◽  
Test Method ◽  
Flexural Wave ◽  
Weak Layer ◽  
Columbia Mountains ◽  
Initiation And Propagation

AbstractSlab avalanche release requires fracture initiation and propagation in a weak snowpack layer. While field tests of weak-layer strength are useful for fracture initiation, the challenge remains to find a verified field test for fracture propagation. We introduce the two current versions of a field test for fracture propagation propensity, and report results of testing conducted in the Columbia Mountains of British Columbia, Canada, during the winter of 2005. By extending the column of a stability test approximately 3 m in the downslope direction, the test method allows for the development of a flexural wave in the slab, and thereby maintains the contribution of this wave and the associated weak-layer collapse to the fracture process. Fracture lengths collected on a day and location where the propagation propensity of the snowpack was locally high show a bimodal distribution, with approximately 50% of observed fractures similar to those collected in stable snowpacks, and approximately 50% with much longer fracture lengths.

The importance of aerodynamics for prosthetic limb design used by competitive cyclists with an amputation: An introduction

2014 ◽  
Vol 39 (3) ◽  
pp. 232-237 ◽  
Author(s):  
Bryce Dyer
Keyword(s):  
Field Test ◽  
Aerodynamic Drag ◽  
Field Tests ◽  
Field Testing ◽  
Test Method ◽  
Limb Amputation ◽  
Small Scale ◽  
Prosthetic Limb ◽  
Testing Method ◽  
Competitive Cyclists

Background/Objectives: This study introduces the importance of the aerodynamics to prosthetic limb design for athletes with either a lower-limb or upper-limb amputation. Study design: The study comprises two elements: 1) An initial experiment investigating the stability of outdoor velodrome-based field tests, and 2) An experiment evaluating the application of outdoor velodrome aerodynamic field tests to detect small-scale changes in aerodynamic drag respective of prosthetic limb componentry changes. Methods: An outdoor field-testing method is used to detect small and repeatable changes in the aerodynamic drag of an able-bodied cyclist. These changes were made at levels typical of alterations in prosthetic componentry. The field-based test method of assessment is used at a smaller level of resolution than previously reported. Results: With a carefully applied protocol, the field test method proved to be statistically stable. The results of the field test experiments demonstrate a noticeable change in overall athlete performance. Aerodynamic refinement of artificial limbs is worthwhile for athletes looking to maximise their competitive performance. Conclusion: A field-testing method illustrates the importance of the aerodynamic optimisation of prosthetic limb components. The field-testing protocol undertaken in this study gives an accessible and affordable means of doing so by prosthetists and sports engineers. Clinical relevance Using simple and accessible field-testing methods, this exploratory experiment demonstrates how small changes to riders’ equipment, consummate of the scale of a small change in prosthetics componentry, can affect the performance of an athlete. Prosthetists should consider such opportunities for performance enhancement when possible.

scholarly journals The propagation saw test: slope scale validation and alternative test methods

2012 ◽  
Vol 58 (208) ◽  
pp. 407-416 ◽  
Author(s):  
Cameron K.H. Ross ◽  
Bruce Jamieson
Keyword(s):  
Scale Validation ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Test Methods ◽  
Alternative Methods ◽  
Column Length ◽  
Layer Depth ◽  
Weak Layer ◽  
Predictive Skill ◽  
Alternative Test

AbstractThe propagation saw test (PST) is a recently developed snowpack test that enables assessment of the fracture propagation propensity of selected persistent weak-layer and slab combinations, which are known to release dry-slab avalanches. In this paper, we assess the slope- scale accuracy of the standard PST method at validated sites of observed weak-layer fracture initiation, with or without propagation. We also report on experiments with alternative test methods and varying saw thicknesses. Results show the standard PST method is comparably accurate to other common snowpack tests in predictive skill when predicting propagation propensity on the slope scale. Although a slight but significant dependence on saw thickness was found, it did not affect the interpretation in our validation study. Alternative methods such as scaling the test column length with weak-layer depth or leaving the upslope end of the column attached to the surrounding snowpack did not improve slope- scale accuracy and these tests were often more difficult to interpret.

scholarly journals Predicting the durability of zinc coatings based on laboratory and field tests

2019 ◽  
Vol 121 ◽  
pp. 01008
Author(s):  
Mark Kovalev ◽  
Ekaterina Alekseeva ◽  
Nikita Shaposhnikov ◽  
Anton Povyshev
Keyword(s):  
Corrosion Rate ◽  
Thermal Diffusion ◽  
Field Test ◽  
Laboratory Tests ◽  
Field Tests ◽  
Test Method ◽  
Laboratory Studies ◽  
Corrosion Rates ◽  
Zinc Coatings ◽  
Salt Fog

Galvanizing is one of the most common methods of corrosion protection. For the deposition of zinc coatings used such methods as gas-thermal deposition, thermal diffusion saturation in powder, hot-dip galvanizing, cladding, and galvanic precipitating during electrolysis. The hot-dip galvanizing is the most common method, which is used in construction, automotive and other industries. Paper presents the results of research of zinc coatings used in sea conditions. The aim of the work was to determine an acceleration factor by comparing the corrosion rate in laboratory conditions with the data from field tests. Laboratory studies were carried out in a salt fog chamber. Samples were periodically removed from chamber to build the dependence of the corrosion rate on the exposure time. Field tests were carried out at the exploitation area. Result of the work is a guide that allows to predict the corrosion rates of zinc coatings using laboratory tests. The advantage of this test method is shorter time of exposure in comparison with field test.

Full Fluid–Solid Cohesive Finite-Element Model to Simulate Near Wellbore Fractures

2014 ◽  
Vol 137 (1) ◽  
Author(s):  
Saeed Salehi ◽  
Runar Nygaard
Keyword(s):  
Finite Element ◽  
Hoop Stress ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Element Model ◽  
Cohesive Elements ◽  
Element Simulation ◽  
Initiation And Propagation ◽  
Fracture Sealing ◽  
Wellbore Strengthening

This paper presents finite-element simulation for hydraulic fracture's initiation, propagation, and sealing in the near wellbore region. A full fluid solid coupling module is developed by using pore pressure cohesive elements. The main objective of this study is to investigate the hypothesis of wellbore hoop stress increase by fracture sealing. Anisotropic stress state has been used with assignment of individual criteria for fracture initiation and propagation. Our results demonstrate that fracture sealing in “wellbore strengthening” cannot increase the wellbore hoop stress beyond its upper limit when no fractures exist. However, this will help to restore part or all of the wellbore hoop stress lost during fracture propagation.

scholarly journals Field Test and Analysis of Energy-Saving Effects of Energy-Recovery Ventilators on Heat-Pump Electricity Consumption in a Classroom

2019 ◽  
Vol 11 (7) ◽  
pp. 2069
Author(s):  
Jae-Sol Choi ◽  
Eui-Jong Kim
Keyword(s):  
Energy Saving ◽  
Field Test ◽  
Energy Recovery ◽  
Field Tests ◽  
High Energy ◽  
Heat Pumps ◽  
Test Method ◽  
Actual System ◽  
Experimental Conditions ◽  
Saving Rates

Energy-recovery ventilators (ERVs) are regarded as important energy-saving systems in buildings. It has been reported that they have high energy-saving rates compared with conventional ventilators that operate without energy recovery, but the saving rates have been obtained typically by employing chamber tests and simulations. In this work, a field-test method is proposed that uses a single test room but alternates the tested ventilation modes hourly. This proposed method is useful because an additional comparison room is not always available and can be a source of uncertainty for field tests. The test is performed in a classroom during a heating period, and the results are calibrated to account for different experimental conditions during the test period. The calibrated energy-saving rates indicate the effectiveness of the ERV; however, they are lower in the early hours of the system operation, for two reasons: (1) the maximum power control schemes of the heat pumps are applied for cases where the indoor temperatures are far lower than the set-point temperature; (2) the ventilation load seemingly represents a decreasing proportion of the total heating load in early hours owing to the thermal-capacity effects for the building, which was cooled for many hours. The findings are verified via a chamber test and simulations. As a consequence, it is important to account for actual system characteristics affected by the thermal behaviors of classrooms when the overall performance of a system is evaluated.

scholarly journals Model of Fracture Propagation in Hydraulic Isolation of the Wellbore

2020 ◽  
Vol 18 (1) ◽  
pp. 36-49
Author(s):  
V. N. Lapin
Keyword(s):  
Propagation Velocity ◽  
Numerical Experiments ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Reservoir Pressure ◽  
Initiation And Propagation ◽  
The Stability ◽  
Prestressed State ◽  
Cement Plug

A model of fracture initiation and propagation along the boundary of a cement plug and a steel casing in a plugged wellbore is proposed. The model allows predicting the conditions of hydraulic isolation failure of a cement plug induced by reservoir pressure. The model describes the stress state of the cement and it’s breakaway from the steel casing caused by the pressure of the pore fluid flowing into the fracture. Numerical experiments show that the fracture propagation velocity and the stability of the hydraulic isolation are sensitive to the reservoir pressure and to the prestressed state of the cement. It is shown also that the quality of cement adhesion to steel and the size of the initial cementing defects have little effect on the initiation conditions and fracture propagation velocity.

Effect of Intermetallic β-Mg17Al12 on Fracture of Ultralight Magnesium Alloy

2013 ◽  
Vol 535-536 ◽  
pp. 160-163
Author(s):  
Ying Chun Guan ◽  
Wei Zhou
Keyword(s):  
Magnesium Alloy ◽  
Intermetallic Compounds ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Tensile Loading ◽  
Az91d Magnesium Alloy ◽  
Initiation And Propagation ◽  
Microcrack Propagation ◽  
Plastic Zones

An AZ91D magnesium alloy was tested in either compression or tension, and extensive observation of the tested samples was carefully carried out to understand the fracture initiation and propagation processes. Cracking of β-Mg17Al12 intermetallic compounds was found to occur easily in plastic zones under either compressive or tensile loading. However, the cracking did not necessarily result in fracture propagation. It is argued that the fracture is controlled by the microcrack propagation.

scholarly journals The Analysis of Shuttlecock Velocity Based on the Field Test Method of The Home Industry Products in Indonesia

2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Ucup Yusup ◽  
Agus Rusdiana
Keyword(s):  
Field Test ◽  
Initial Velocity ◽  
Field Tests ◽  
Test Method ◽  
Final Velocity ◽  
3D Motion Analysis ◽  
Analysis System ◽  
Main Components ◽  
Home Industries

One of the main components of badminton games is shuttlecock. The shuttlecock home industries in Indonesia mainly employ for about 20-40 freelance workers. The workers in the home industries are able to produce 500-100 slops of shuttlecock daily. The guarantee of the shuttlecock quality produced by home industries, either through the laboratory tests or field tests, is rarely conducted formally. Therefore, we are interested in conducting an academic study on the velocity of the shuttlecocks produced by the workers of the shuttlecock home industries that have been distributed in Indonesia markets. There are eight widely distributed shuttlecock brands produced by the home industries in Indonesia, including Taiso, Saporate, Netra, Arjuna, Kuda Mas, Rivals, Purnama, and Spin. The purpose of this study was to examine the quality of aerodynamics rate of the shuttlecock produced by home industries by comparing the rate of motion of the shuttlecock in different distances started from the initial velocity to the final velocity when the shuttlecocks impact to the ground. The method used in this study was a descriptive qualitative study. The instruments used were three high resolution handy cams, a set of calibration, and the 3D motion analysis system software (Frame Diaz IV). The result of this study showed that the average velocity of the shuttlecock, started from the initial velocity to the final velocity with 5 meter distance, reached 85.0 m/s., while the average final velocity reached 29.8m/s at 5 meter distance. From all of the shuttlecock types tested in the field test for their velocity, it was found that the Spin brand moved with a high velocity with 12.8% of percentage. Meanwhile, the lowest velocity of the shuttlecock was found in the Taiso brand where the percentage was 15.3% in 9 meter and12 meter distances. The study concludes that the average of various shuttlecock brands’ speeds are in the normal category except for the Taiso and Spin brands.

Numerical simulation of failure in a layered thin snowpack under skier load

2010 ◽  
Vol 51 (54) ◽  
pp. 169-175 ◽  
Author(s):  
P. Mahajan ◽  
R. Kalakuntla ◽  
C. Chandel
Keyword(s):  
Slope Angle ◽  
Fracture Initiation ◽  
Middle Layer ◽  
Interface Energy ◽  
The Self ◽  
Cohesive Elements ◽  
Weak Layer ◽  
Shear Loads ◽  
Initiation And Propagation ◽  
Explicit Dynamic

AbstractFracture initiation and propagation in a snowpack due to compressive and shear loads, generated by the self-weight of the snow and a skier, is modeled. The snowpack has three layers, with a weak layer sandwiched between two strong layers. The height of the snowpack above the weak layer is such that failure occurs only because of additional stresses generated by the skier. A static analysis is performed to determine stresses due to the self-weight of snow, followed by an explicit dynamic analysis to determine additional stresses and subsequent failure due to skier load. The failure is either due to interface crack growth or due to middle-layer failure accompanied by slope-normal displacements. The former is modeled using cohesive elements, while a softening stress–displacement relation is used for the latter. Both mechanisms are active in the snowpack, although one may be predominant depending on slope angle, shear strength and interface energy.

scholarly journals Numerical simulation on the effect of pore pressure gradient on the rules of hydraulic fracture propagation

2021 ◽  
pp. 014459872110093
Author(s):  
Weiyong Lu ◽  
Changchun He
Keyword(s):  
Pressure Gradient ◽  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
Fracture Initiation ◽  
Hydraulic Fractures ◽  
Initiation And Propagation ◽  
Hydraulic Fracture Propagation ◽  
Pore Pressure Gradient ◽  
Stress Damage

To clarify the influence of pore pressure gradient on hydraulic fracture propagation, the stress distribution in and around the borehole is explained by theoretical analysis method in this paper. A mechanical model of hydraulic fracture initiation under the action of pore pressure gradient is established. Then coupled seepage-stress-damage software is used to simulate the initiation and propagation of hydraulic fractures in rock samples under the action of pore pressure gradient. Finally, the influence of the number and spatial position of the induction holes on the initiation and propagation of hydraulic fractures is analyzed. It is shown that: (1) Pore pressure gradient can effectively reduce the initiation pressure of hydraulic fractures. (2) The greater the pore pressure gradient is, the easier the hydraulic fracture is to spread to the region with high pore pressure. (3) With the action of pore pressure gradient, the hydraulic fracture is shaped as ‘丨’, ‘丿’ and ‘S’ types and can be represented by the four abstract conceptual models.

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