Short-Term Stable Crack Propagation through Polyolefin Single- and Bilayered Structures - Influence of Welding, Composition and Direction of Crack Propagation

2016 ◽  
Vol 258 ◽  
pp. 538-541
Author(s):  
Ralf Lach ◽  
Tobias Krolopp ◽  
Pavel Hutař ◽  
Eva Nezbedova ◽  
Wolfgang Grellmann
Keyword(s):  
Fracture Mechanics ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Crack Resistance ◽  
Crack Initiation And Propagation ◽  
Short Term ◽  
Elastic Plastic ◽  
Stable Crack Propagation ◽  
Initiation And Propagation ◽  
Specimen Shape

The overall stable crack initiation and propagation behaviour of specimens cut from plastic pipes that were composed of different polyolefin materials were investigated using concepts of elastic–plastic fracture mechanics including the crack propagation kinetics. The effect of specimen shape, orientation, welding, lading rate, composition/microstructure and direction of crack propagation on the crack resistance (R) behaviour of these materials has been thereby assessed.

Investigation of Mechanical and Fracture Mechanical Properties of Elastomers Filled with Precipitated Silica and Nanofillers Based upon Layered Silicates

2004 ◽  
Vol 77 (4) ◽  
pp. 662-677 ◽  
Author(s):  
Katrin Reincke ◽  
Wolfgang Grellmann ◽  
Gert Heinrich
Keyword(s):  
Fracture Mechanics ◽  
Crack Initiation ◽  
Crack Resistance ◽  
Fracture Behavior ◽  
Loading Conditions ◽  
Crack Initiation And Propagation ◽  
Precipitated Silica ◽  
Propagation Behavior ◽  
Initiation And Propagation

Abstract The aim of this paper is to show possibilities of experimental methods of polymer diagnostics and fracture mechanics for quantitative characterization of crack initiation and propagation properties of elastomeric materials. At first, a general overview of methods of technical fracture mechanics is given. This is followed by a short discussion of some possibilities for determination of tearing energy T for elastomers. In the main part, results of various mechanical and fracture mechanics experiments on filled natural rubber vulcanizates are shown. The vulcanizates were filled with different contents (5–70 phr) of two filler types. The fillers were precipitated silica and an organic-modified nano-disperse layered silicate. Th aim of the experiments was to prove possibilities of several fracture mechanics testing methods for quantifying the influence of the filler content, filler type and additionally the specimen direction on the deformation and fracture behavior. Tear-analyzer results were used to assess the crack propagation behavior under fatigue-like loading conditions. Furthermore, instrumented tensile-impact tests were performed for the characterization of the crack resistance of the materials under impact-like loading conditions. To obtain information about the initiation and propagation of a stable crack, a quasi-static fracture mechanics test was applied, and crack resistance curves were recorded. Here, specimens with various thicknesses were investigated. Additionally, conventional tear tests were done and the results were compared to that of the fracture mechanics test. Generally, it was found that all methods are useful for the description of the fracture properties. Furthermore, the fracture behavior is influenced positively especially by high filler contents. Strong differences of several parameters were found depending on the filler type. Another important result is that again differences were found between the crack initiation and propagation behavior.

On the Topology Update of the Numerical Manifold Method for Multiple Crack Propagation

2021 ◽  
pp. 2150030
Author(s):  
Jun He ◽  
Shuling Huang ◽  
Xiuli Ding ◽  
Yuting Zhang ◽  
Dengxue Liu
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Numerical Method ◽  
Crack Tip ◽  
Search Method ◽  
Numerical Manifold Method ◽  
Crack Initiation And Propagation ◽  
Multiple Crack ◽  
Initiation And Propagation ◽  
Numerical Manifold

Crack initiation and propagation are the two key issues of concern in the geotechnical engineering. In this study, the numerical manifold method (NMM) is applied to simulate crack propagation and the topology update of the NMM for multiple crack propagation is studied. The crack-tip asymptotic interpolation function is incorporated into the NMM to increase the accuracy of the crack-tip stress field. In addition, the Mohr-Coulomb criterion with tensile cut off is adopted to be the crack propagation criterion to judge the direction of crack initiation and propagation. Then a crack tip searching method is developed to automatically update the position of the crack tips. The inapplicability of the original loop search method in the NMM is also illustrated and a novel loop search method based on manifold elements is developed for physical loop updating. Moreover, methods for the manifold element updating and physical cover updating are provided. Based on the above study, the developed numerical method is capable to simulate multiple crack propagation. At last, typical rock rupture problems are numerically simulated to manifest the effectiveness of the developed numerical method.

scholarly journals Fretting fatigue crack initiation and propagation in Ti6Al4V sheets under tribocorrosive conditions of artificial seawater and physiological solutions

2020 ◽  
Vol 234 (12) ◽  
pp. 1526-1534 ◽  
Author(s):  
Zeeshan Anjum ◽  
Masood Shah ◽  
Hassan Elahi ◽  
Mushtaq Khan ◽  
Mohammad Mujahid ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Testing Machine ◽  
Fatigue Crack Initiation ◽  
Physiological Solution ◽  
Fretting Corrosion ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Dry Conditions ◽  
Phosphate Buffered Saline

The interaction of mechanical components experiencing relative movements and cyclic loads in a corrosive environment is known as fretting corrosion or tribocorrosion. In the current work, the mechanism of crack initiation and propagation in dovetail slots of Ti6Al4V samples (in contact with carbide rods) under fretting corrosion conditions was investigated. A newly developed test rig installed on a universal testing machine was used to conduct tests at 20 Hz frequency under 5 and 7.5 kN fretting loads. Tests were conducted at room temperature in 3.5% NaCl and phosphate-buffered saline solutions. Crack propagation in all samples was examined by a metallurgical microscope, and the detailed analysis of fractured samples was carried out by a scanning electron microscope. In comparison to dry conditions, early crack initiation and faster crack propagation were observed in salt and physiological solution environments. Colored spots and large amounts of chlorine, sodium, and oxygen were found around cracks, and plastically deformed regions in the 3.5% NaCl environment provided the evidence of a corrosive attack. Large amounts of oxygen, phosphorous, chlorine, potassium, and sodium were detected in the phosphate-buffered saline environment.

scholarly journals Investigation of Low-Cycle Bending Fatigue of AISI 9310 Steel Spur Gears

2007 ◽  
Author(s):  
Robert F. Handschuh ◽  
Timothy L. Krantz ◽  
Bradley A. Lerch ◽  
Christopher S. Burke
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Test Machine ◽  
Spur Gears ◽  
Crack Initiation And Propagation ◽  
Bending Fatigue ◽  
Initiation And Propagation ◽  
Single Tooth ◽  
Relationship Of ◽  
The Relationship

An investigation of the low-cycle bending fatigue of spur gears made from AISI 9310 gear steel was completed. Tests were conducted using the single-tooth bending method to achieve crack initiation and propagation. Tests were conducted on spur gears in a fatigue test machine using a dedicated gear test fixture. Test loads were applied at the highest point of single tooth contact. Gear bending stresses for a given testing load were calculated using a linear-elastic finite element model. Test data were accumulated from 1/4 cycle to several thousand cycles depending on the test stress level. The relationship of stress and cycles for crack initiation was found to be semi-logarithmic. The relationship of stress and cycles for crack propagation was found to be linear. For the range of loads investigated, the crack propagation phase is related to the level of load being applied. Very high loads have comparable crack initiation and propagation times whereas lower loads can have a much smaller number of cycles for crack propagation cycles as compared to crack initiation.

scholarly journals Investigation on the Fracturing Permeability Characteristics of Cracked Specimens and the Formation Mechanism of Inrush Channel from Floor

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Jianning Wang ◽  
Weitao Liu ◽  
Jianjun Shen
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Formation Mechanism ◽  
Water Pressure ◽  
Water Inrush ◽  
Confining Pressure ◽  
Crack Initiation And Propagation ◽  
Initiation And Propagation ◽  
Final Failure ◽  
Cracked Specimens

To study the fracture characteristics and the permeability change law of the cracked specimens during the complete stress-strain process, a mechanical model was constructed, from which different types of crack initiation angles were obtained. The crack inclination angles under uniaxial compression, confining compression, and confining tension, and the influence of confining pressure and pore water pressure on the crack propagation and permeability of rock mass were investigated and simulated with RFPA-Flow software using prefabricated crack models with crack initiation angles of 30°, 45°, and 60°. Furthermore, the formation mechanism of inrush channel from floor was qualitatively analyzed. The results indicated that the theoretical initiation angles of wing cracks, secondary coplanar cracks, and secondary inclined antiwing cracks were found to be 70.53°, 0°, and 123.8°, which were consistent with the simulation results. The crack propagation was mainly concentrated at the postpeak stage of the complete stress-strain curve, causing the peak of seepage velocity to lag behind the stress peak. For the case with a constant confining pressure, the rate of crack initiation and propagation to final failure was positively correlated with the internal pore pressure. For the case with a constant water pressure, the speed of crack initiation and propagation to final failure decreased first and then increased as the confining pressure increased. In addition, the longitudinal propagation of wing cracks and the increase in permeability were prone to occur in the low confining pressure zone, which induced the formation of water inrush channels. The research result provides an improved understanding for predicting and preventing water inrush disasters.

Crack Initiation and Propagation as Part of Engineering Design

2012 ◽  
Author(s):  
Hans Minnebo ◽  
Marc Duflot ◽  
Eric Wyart
Keyword(s):  
Fatigue Crack ◽  
Fracture Mechanics ◽  
Crack Initiation ◽  
Crack Initiation And Propagation ◽  
Linear Elastic ◽  
Linear Fracture ◽  
Initiation And Propagation ◽  
Improve Analysis ◽  
Elastic Fracture ◽  
Analysis Design

This article deals with the interest of the analysis of cracks in order to improve analysis design. Mainly oriented around the linear elastic fracture mechanics and fatigue crack propagation, it will also address some issues in non-linear fracture mechanics and crack insertion.

Experimental Study on Crack Propagation by AE Location under Uniaxial Compression Condition

2007 ◽  
Vol 353-358 ◽  
pp. 2329-2332
Author(s):  
Xing Dong Zhao ◽  
Yuan Hui Li ◽  
Rui Fu Yuan
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Failure Mode ◽  
Uniaxial Compression ◽  
Crack Initiation And Propagation ◽  
Stress Strain ◽  
Initiation And Propagation ◽  
Ae Location ◽  
Granite Samples ◽  
Compression Condition

AE technique is proved a efficient tool for real-time monitoring of the crack initiation and propagation during rock failure process under uniaxial compression condition. In this paper, An AE system was employed to investigate the crack propagation and failure modes of three groups of granite specimens (80mm×100mm×170mm) with the same pre-existing crack. The AE sensors can be surface mounted. By using a Geiger location algorithm, AE event location can be determined by time-of-arrival times. The propagation velocities of p-wave or s-wave of granite samples were measured. Experiments on pre-existing crack propagation of granite samples were carried out on the press machine. From the testing result, failure mode of three kinds of granite samples was mainly shear failure, while the secondary crack propagated slowly and could not influence the failure mode of granite sample. By surveying the relation of accumulative AE events and stress-strain curve, AE activity represents different characters with stress-strain changing during the total loading process, microcracking contributing to fracture propagation with strain corrosion. AE location result reflected crack initiation and propagation, which is of great importance in studying rock instability and predicting rock failure mode.

scholarly journals First Steps of Crack Initiation and Propagation in Fatigue of FCC Crystals Studied by Dislocation Dynamics

2012 ◽  
Author(s):  
C. Déprés ◽  
G. V. Prasad Reddy ◽  
L. Tabourot ◽  
R. Sandhya ◽  
S. Sankaran
Keyword(s):  
Stress Field ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Crack Initiation ◽  
Crack Tip ◽  
Dislocation Dynamics ◽  
Crack Initiation And Propagation ◽  
Dislocation Dynamic ◽  
Discrete Dislocation ◽  
Initiation And Propagation

3D discrete dislocation dynamic (DDD) simulations are performed to simulate stage-I fatigue crack initiation and propagation along the surface, in the primary grain and its neighbouring grain, in 316L stainless steel. The scenario of crack propagation in primary grain and the evolution of dislocation structure ahead of crack tip are discussed, and in addition crack tip sliding displacement is estimated. Probable mechanisms of crack propagation from primary grain to neighbouring grain are evaluated. In this process, surface relief in the neighbouring-grain under the influence of crack stress field in the primary grain is studied for varying neighbouring-grain orientations. An enhanced evolution of surface extrusions in the neighbouring grain, are observed in the presence of heterogeneous stress field (i.e., in the presence of crack in the primary grain), compared to that in the case of homogeneous stress field. In addition, influence of crack stress field on prior cyclic-deformed substructure is presented.

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