The near-tip field at high crack velocities

1989 ◽  
pp. 1-13 ◽  
Author(s):  
K. B. Broberg
Keyword(s):  
High Crack

scholarly journals Compressive Test Characteristics and Constitutive Relationship of Wet Polypropylene Macrofiber-Reinforced Shotcrete

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Fenghui Li ◽  
Yunhai Cheng ◽  
Fei Wu ◽  
Chang Su ◽  
Gangwei Li
Keyword(s):  
Mechanical Response ◽  
Average Energy ◽  
Strain Curve ◽  
Peak Stress ◽  
Constitutive Relationship ◽  
Compression Tests ◽  
Response Characteristics ◽  
Test Characteristics ◽  
High Crack ◽  
Relationship Of

Shotcrete is often subject to poor ductility and cracking problems, particularly under high stresses. In order to deal with these issues, the feasibility of adding polypropylene macrofibers to shotcrete was verified. To ascertain the supporting effect, dry shotcrete, wet shotcrete, and wet polypropylene macrofiber-reinforced shotcrete (WPMS) were used as samples. Furthermore, the mechanical response characteristics thereof in uniaxial compression tests were compared and analyzed by acoustic emission (AE) monitoring. The results showed that the three materials were brittle, but the ductility, residual strength, and bearing capacity of polypropylene macrofiber-reinforced shotcrete were significantly enhanced. The energy absorption value of plain shotcrete was higher in the cracking stage, while that of polypropylene macrofiber-reinforced shotcrete was greater in the postpeak stage, which showed that the polypropylene macrofiber-reinforced shotcrete had the characteristics of a high crack-initiation strength and toughness. Besides, the energy release from fiber shotcrete occurred after the peak stress rather than near the peak stress. The average energy absorbed by polypropylene macrofiber-reinforced shotcrete was significantly higher than that in dry shotcrete and wet shotcrete, which implied that polypropylene macrofiber-reinforced shotcrete could mitigate the brittle instability of a shotcrete layer. A constitutive model of damage statistics was established based on the test data. The comparison between the experimental data and the fitting results can reflect the characteristics of the total stress-strain curve of such shotcrete. The results provide a basis for the optimization of polypropylene macrofiber-reinforced shotcrete layers.

The near-tip field at high crack velocities

1989 ◽  
Vol 39 (1-3) ◽  
pp. 1-13 ◽  
Author(s):  
K. B. Broberg
Keyword(s):  
High Crack

scholarly journals Structure and Mechanical Properties of Al-Li Alloys as Cast

2013 ◽  
Vol 13 (2) ◽  
pp. 5-10 ◽  
Author(s):  
J. Augustyn-Pieniążek ◽  
H. Adrian ◽  
S. Rzadkosz ◽  
M. Choroszyński
Keyword(s):  
Mechanical Properties ◽  
Specific Gravity ◽  
Light Microscopy ◽  
Aluminium Alloys ◽  
Broad Application ◽  
X Ray ◽  
High Crack ◽  
High Crack Resistance ◽  
Lithium Alloys ◽  
Ray Methods

Abstract The high mechanical properties of the Al-Li-X alloys contribute to their increasingly broad application in aeronautics, as an alternative for the aluminium alloys, which have been used so far. The aluminium-lithium alloys have a lower specific gravity, a higher nucleation and crack spread resistance, a higher Young’s module and they characterize in a high crack resistance at lower temperatures. The aim of the research planned in this work was to design an aluminium alloy with a content of lithium and other alloy elements. The research included the creation of a laboratorial melt, the microstructure analysis with the use of light microscopy, the application of X-ray methods to identify the phases existing in the alloy, and the microhardness test.

Simulative Study of Evolution Behavior of Transverse Surface Crack in Rolling Process

2011 ◽  
Vol 403-408 ◽  
pp. 88-92
Author(s):  
Ya Gao ◽  
Jian Lin Sun ◽  
Bing Yun
Keyword(s):  
Tensile Stress ◽  
Surface Crack ◽  
Rolling Direction ◽  
Crack Tip ◽  
Element Model ◽  
Rolling Process ◽  
Friction Coefficients ◽  
High Crack ◽  
Explicit Finite Difference ◽  
Evolution Behavior

Based on explicit finite difference algorithm, finite element model of steel plate with transverse surface crack in rough rolling was found. The evolution regularity of transverse surface crack in rolling process was calculated with the model, and effect of different crack sizes, different friction coefficients and different roll diameters on crack evolution were studied. The research indicated that, in rolling direction, the crack tip stress changed from tensile stress to compression stress and then tensile stress again; length and depth of crack both had effect on the healing and propagation of the crack, and mostly in the way of influencing displacement of freedom surface of the crack; different friction coefficients showed no effect on crack tip propagation, but low friction coefficient would be in favor of crack healing at crack bottom; small roll diameter would lead to high crack tip tensile stress and more propagation at crack tip.

Application of a new velocity gage to fracture at high crack velocities

1983 ◽  
Vol 23 (1) ◽  
pp. R7-R10 ◽  
Author(s):  
Ph. B�guelin ◽  
B. Sbalder ◽  
H. H. Kausch
Keyword(s):  
High Crack

Crack resistance of tool steels corresponding with the chemical composition of their matrices

2017 ◽  
Vol 1 (86) ◽  
pp. 5-14
Author(s):  
J. Pacyna
Keyword(s):  
Chemical Composition ◽  
Crack Resistance ◽  
Phase Transformations ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Tool Steels ◽  
Industrial Practice ◽  
High Crack ◽  
Secondary Precipitates ◽  
Kinetics Of

Purpose: of the presented investigations was showing that the crack resistance of tool steels depends on their hardenability and phase transformations occurring in the quenched matrix at tempering. The chemical composition of austenite decides on the steel hardenability while phase transformations after tempering can be influenced (apart from the chemical composition) by the heating method. Design/methodology/approach: of investigations was based on the analysis of dilatograms and the achieved aim was to obtain the hard tool steel (app. 500 HV30) for hot works. Samples of a diameter of 10 mm (without a notch) made of this steel were not broken by the Charpy impact test of energy of 30 kGm. Findings: of these investigations are practical. Grain boundaries of prior austenite should be protected against secondary precipitates, which constitute natural nuclei of diffusive structures. It is also possible to control phase transformations at tempering. Research limitations/implications: constitute the availability of the adequate equipment for investigating the kinetics of phase transformations of undercooled austenite and the kinetics of phase transformations after tempering. Practical implications: for the industry are such that the proposed tool steels of a high crack resistance contain molybdenum and nickel. Thus, these steels are very expensive. Originality/value: of these investigations was confirmed in the industrial practice.

Magnetic Images and NDT of the Express Train Wheel Using a High Speed Scan-Type Magnetic Camera

2009 ◽  
Vol 417-418 ◽  
pp. 169-172 ◽  
Author(s):  
Ji Seong Hwang ◽  
Jin Yi Lee
Keyword(s):  
High Speed ◽  
Crack Detection ◽  
Sensor Array ◽  
Hall Sensor ◽  
Limited Time ◽  
High Speed Train ◽  
Detection Ability ◽  
Express Train ◽  
High Crack ◽  
Magnetic Camera

Wheels are essential parts of an express train, as they support the train’s weight, but because of the limited time available for testing and repair in the maintenance factory, the 1000 wheels of each high-speed train must be tested within 1 h. Therefore it is essential to develop a new NDT system that is able to (a) detect cracks quickly and (b) provide high crack-detection ability regardless of the state of the materials. In this paper we propose a scan-type magnetic camera to satisfy this need. We use a linearly integrated Hall sensor array (LIHaS) as a magnetic sensor to make high-speed testing possible, and we use a small, yoke-type magnetizer as the magnetic source for the magnetic camera to assure high crack-detection ability. We tested the method by examining the cracks on a sample wheel traveling at 27.5km/h.

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