Observation of crack propagation in saline ice and freshwater ice with fluid inclusion

2003 ◽  
Vol 81 (1-2) ◽  
pp. 159-166
Author(s):  
M Arakawa ◽  
V F Petrenko
Keyword(s):  
Crack Propagation ◽  
Electrical Resistance ◽  
Crack Velocity ◽  
High Speed ◽  
High Speed Photography ◽  
Low Density ◽  
Conductive Liquid ◽  
Freshwater Ice ◽  
Maximum Crack ◽  
Very High

A key process of crack propagation in saline ice is the interaction between the crack and fluid inclusions. We observed their interaction in freshwater ice using very high-speed photography (VHSP) and found that the low-density fluids (air and inert liquid, Fluorinert, 1.78 g/cm3) could not impede the crack effectively, interrupting the propagation for less than 10 µs. The high-density liquid mercury, (13.8 g/cm3) impeded the crack more effectively, stalling the development of the crack for more than 20 µs. The crack velocity in saline ice was measured using two different methods: electrical resistance method (ERM) and VHSP. These two methods returned very different mean velocities, 15 m/s for the ERM and 250 m/s for the VHSP. We found that in ice with conductive liquid inclusions, the ERM measured the time it took to break liquid bridges stretched across a crack rather than the crack velocity. Results from the VHSP show that the maximum crack velocity in saline ice was 500 m/s, which is one-half of that found in freshwater ice. From our results using freshwater ice with inclusions, we conclude that liquid inclusions in saline ice may play a role in this retardation. PACS No.: 62.20Mk

Crack Propagation in Freshwater and Saline Ice

1999 ◽  
Vol 578 ◽  
Author(s):  
Patrick J. Donovan ◽  
Masahiko Arakawa ◽  
Victor Petrenko
Keyword(s):  
Crack Propagation ◽  
Crack Velocity ◽  
High Speed ◽  
Acoustic Emissions ◽  
Crack Tip ◽  
High Speed Photography ◽  
Propagation Time ◽  
Reliable Technique ◽  
Resistance Method ◽  
Freshwater Ice

AbstractCrack propagation in columnar saline and freshwater ice has been investigated with high-speed photography, acoustic emission detection and the resistance method. High-speed photography was found to be a single reliable technique. The resistance method proved effective for freshwater ice samples, but not for saline ice samples due to the presence of conductive fluid inclusions. Acoustic emissions pinpointed the moment of crack initiation, but did not correspond to the crack propagation time. Crack velocity has been characterized over a temperature range of -5°C to -30 °C for freshwater and saline ice. Freshwater ice exhibited an overall average velocity of 198 m/s, and did not vary with temperature. Crack velocity in saline ice demonstrated temperature dependence, increasing from an average of 86 m/s in the -5°C to -20°C range, to 131 m/s at -30°C. The crack velocity was also shown to have a general dependence on fracture toughness K' of the material, however, the microstructural variation between samples is also shown to influence significantly the crack behavior in both saline and freshwater ice. Nonuniform crack tip advance and crack reorientation were observed as crack slowing mechanisms in freshwater ice, while in saline ice fracture crack tip blunting on voids greatly reduced average crack velocities.

Experimental Study of Dynamic Fracture Behavior of PVB Laminated Glass by High-Speed Photography

2010 ◽  
Vol 34-35 ◽  
pp. 636-640 ◽  
Author(s):  
Meng Yi Zhu ◽  
Bo Han Liu ◽  
Yue Ting Sun ◽  
Jun Xu ◽  
Xue Feng Yao ◽  
...  
Keyword(s):  
Experimental Study ◽  
Finite Element ◽  
Dynamic Fracture ◽  
Crack Velocity ◽  
High Speed ◽  
Fracture Behavior ◽  
High Speed Photography ◽  
Laminated Glass ◽  
Fracture Characteristics ◽  
Photography Method

The dynamic fracture behavior of PVB laminated glass during impact has been studied by both theoretic and finite element approaches. To make the analysis of cracking on PVB laminated glass more accurate and direct, high-speed photography method is introduced in this paper. Different crack patterns as well as their sequences of appearance are visualized. Finally, typical crack is measured in order to obtain important fracture characteristics such as crack velocity and acceleration.

Analysis of Cracking Processes of Sandstone in Rockburst Test

2012 ◽  
Vol 256-259 ◽  
pp. 1052-1059
Author(s):  
De Jian Li ◽  
Fei Zhao ◽  
Run Jie Ma ◽  
Li Qiang Han ◽  
Xiao Hu Wu
Keyword(s):  
Growth Rate ◽  
Fractal Dimension ◽  
Crack Propagation ◽  
High Speed ◽  
Fractal Dimensions ◽  
Rock Surface ◽  
Horizontal Line ◽  
High Speed Camera ◽  
Camera System ◽  
Very High

High speed camera system is used to record crack propagation on rock surface during the lab rocburst experiment. This paper presents the specific analytical method of crack propagation with high speed images. Crack propagation types and directions are briefly described, and the lengths, growth rate and fractal dimension of cracks are calculated. The results show that the crack grows mainly along the horizontal line on the unloading surface, at a low speed before rockburst and reaches a very high speed abruptly near the burst point. The fractal dimensions demonstrated that the crack turns to be rough when rockburst happens. The study on the crack propagation is benefit to the understanding on the mechanism of rockburst.

The effect of the geometry of extrusion head flow channels on the adiabatic extrusion of low density polyethylene

2015 ◽  
Vol 35 (6) ◽  
pp. 605-610 ◽  
Author(s):  
Janusz W. Sikora ◽  
Tomasz Garbacz
Keyword(s):  
High Speed ◽  
Thermal Power ◽  
Circular Cross Section ◽  
Energy Conditions ◽  
Low Density Polyethylene ◽  
Total Power ◽  
Low Density ◽  
Extrusion Head ◽  
Flow Channels ◽  
Very High

Abstract Plastics extrusion can be divided into the following types: conventional extrusion (run at low speed of the rotating screw), adiabatic extrusion (screw speed is relatively high, yet the process requires the use of heaters) and high speed extrusion (extruder barrel requires cooling due to very high screw speeds). This paper presents the results of a study undertaken to investigate the adiabatic extrusion of low density polyethylene using heads with circular cross-section nozzles and different geometries of flow channels. In the experiments, we examined the temperature and pressure of the polymer in the plasticizing unit, as well as the relationships between the output, thermal power conveyed by the plastic, total power supplied to the extruder, extrusion efficiency, unit consumption of the total energy supplied to the extruder as well as the rotational speed of the screw and the extruder’s head geometry. It was found that the most favorable energy conditions, i.e., the highest efficiency of the adiabatic extrusion of low density polyethylene in the whole range of the tested screw speeds, are ensured when the head with the highest diameter and length nozzle is applied.

scholarly journals Effect of Specimen Placement on Model Rock Blasting

2021 ◽  
Author(s):  
Zong-Xian Zhang ◽  
Li Yuan Chi ◽  
Qingbin Zhang
Keyword(s):  
Kinetic Energy ◽  
High Speed ◽  
Rock Specimen ◽  
Base Material ◽  
Scale Model ◽  
Small Scale ◽  
High Speed Photography ◽  
Rock Blasting ◽  
Ground Material ◽  
Very High

AbstractSmall-scale model blasting plays an important role in understanding mechanism of rock fragmentation by blasting and improving blast technology in rock and mining engineering. Because a specimen (or model) often needs to be placed on either a ground or another material in model blasting, an additional interface appears between the specimen and the ground (or material), compared with an engineering blast that does not have such an interface. In this paper, four model blasts with high-speed photography were presented. The results showed that: (1) as the impedance of a rock specimen was smaller than that of the ground material, the specimen was thrown up and a certain amount of kinetic energy was brought with such a bounce. Thus, this placement should be avoided in model blasts. (2) As a rock specimen was placed on three blocks of the same type of rock as the specimen the specimen was not bounced up during blasting. Correspondingly, no kinetic energy was induced by specimen bounce. Therefore, this placement is recommended for model blasting. If very high specific charge must be used in model blasting, the above-recommended method will not work well due to possible breakage of the base material during blasting. In this case, the rock specimen can be placed on a material with smaller impedance than that of the rock specimen so that specimen bounce can be reduced. Accordingly, such a possible specimen bounce should be estimated by stress wave analysis.

New crack generation phenomena by crack collision in 10 mm thick tempered glass

2021 ◽  
pp. 1-13
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Tensile Stress ◽  
Crack Propagation ◽  
High Speed ◽  
Crack Tip ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Crack Generation ◽  
Caustics Method ◽  
Thick Glass ◽  
Collision Angle

High speed photography by Caustics method using Cranz–Schardin camera was used to study crack propagation and divergence in thermally tempered glass. Tempered 10 mm thick glass plates were used as a specimen. New crack generation by two crack collision was observed. Regarding the presence/absence of new cracks, the dependence of the two cracks on the collision angle was confirmed. Considering that it is based on the synthesis of stress 𝜎CR generated at the crack tip, tensile stress necessary for the generation of new cracks could be created.

Indentation and Splitting of Freshwater Ice Floes

1995 ◽  
Vol 117 (1) ◽  
pp. 63-69
Author(s):  
D. S. Sodhi ◽  
S. N. Chin
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Small Scale ◽  
Effective Pressure ◽  
Deformation And Failure ◽  
Low Speed ◽  
Freshwater Ice ◽  
Compressive Stresses ◽  
Ice Floes

Small-scale indentation and floe-splitting experiments were conducted on columnar ice floes of various sizes and at different speeds. During low-speed indentation (0.2–8 mm s−1), the ice floes always split apart, while at higher indentation speeds (> 100 mm s−1) they did not. The reason is attributed to differences in the process of deformation and failure. At low speed, a large zone of microcracked ice forms in front of the indentor. Development of compressive stresses in the microcracked ice zone leads to buildup of transverse forces that drive crack propagation. These zones of microcracked ice are not observed during high-speed indentation. Rather, the ice fails by continuous crushing. The theoretical effective pressure required to split an ice floe, as predicted by Bhat (1988), agrees to some extent with those measured during experiments.

Crack propagation and divergence phenomena observed by Caustics method in tempered glass

2021 ◽  
pp. 1-18
Author(s):  
Shin’ichi Aratani
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
High Speed Photography ◽  
Tempered Glass ◽  
Glass Plates ◽  
The Difference ◽  
Caustics Method ◽  
Thick Glass

High speed photography by Caustics method using Cranz-Schardin camera was studied for crack propagation and divergence in thermally tempered glass. Tempered 10 mm thick glass plates were used as a specimen. Two types of bifurcation and branching as the crack divergence could be observed and clarified even in 10 mm thick tempered glass. The difference of the shadow spot sizes between bifurcation type and branching type could be confirmed.

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