Specimen Geometry Effects on Dynamic Crack Propagation

2006 ◽  
Vol 326-328 ◽  
pp. 911-914
Author(s):  
Kazuo Arakawa ◽  
Toshio Mada
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Dynamic Stress Intensity Factor ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Acceleration Process ◽  
Fracture Event ◽  
Acceleration And Deceleration ◽  
Event Dynamic ◽  
Crack Acceleration

Dynamic crack propagation in PMMA was studied using the method of caustics in combination with a Cranz-Schardin type high-speed camera. Three different types of specimen geometries were employed to achieve the crack acceleration, deceleration and re-acceleration process in one fracture event. Dynamic stress intensity factor KID and the crack velocity were evaluated in the course of crack propagation to obtain the relationship between KID and the velocity The effect of crack acceleration and deceleration on the KID -velocity relations was examined.

scholarly journals Non steady-state intersonic cracks in elastomer membranes under large static strain

2021 ◽  
Author(s):  
Thomas Corre ◽  
Michel Coret ◽  
Erwan Verron ◽  
Bruno Leblé
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Crack Path ◽  
Stretch Ratio ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Crack Speed ◽  
Propagation Regime ◽  
Acceleration And Deceleration ◽  
International Audience

International audience Dynamic crack propagation in elastomer membranes is investigated; the focus is laid on cracks reaching the speed of shear waves in the material. The specific experimental setup developed to measure crack speed is presented in details. The protocol consists in (1) stretching an elastomer membrane under planar tension loading conditions, then (2) initiating a small crack on one side of the membrane. The crack speed is measured all along the crack path in both reference and actual configurations, including both acceleration and deceleration phases, i.e. non steady-state crack propagation phases. The influence of the prescribed stretch ratio on crack speed is analysed in the light of both these new experiments and the few previously published studies. Conclusions previously drawn for steady-state crack growth are extended to non steady-state conditions: stretch perpendicular to the crack path governs crack speed in intersonic crack propagation regime, and the role of the stretch in crack direction is minor.

Numerical Simulation for Dynamic Crack Propagation by MLPG

2006 ◽  
Vol 324-325 ◽  
pp. 495-498
Author(s):  
Ying Liu ◽  
Ling Tian Gao
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Mass Matrix ◽  
Crack Edge ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Lumped Mass ◽  
Central Difference ◽  
Stress Criterion ◽  
Dynamic Propagation

In this paper, a new algorithm based on Meshless Local Petrov-Galerking (MLPG) method is presented for analyzing the crack dynamic propagation. A new modified Moving Least Squares approximation is proposed to simplify the treatment of essential boundary conditions. Explicit central difference with lumped mass matrix is adopted for the time integral. Visibility criterion with crack edge node adding technique and the maximum hoop stress criterion are used to describe the crack propagation and forecast the crack propagation direction. Based on this algorithm, three-point bend specimen for impact fracture test is investigated. Comparing the results with those obtained by the laser caustic method and high-speed photographs, the accuracy of the present algorithm is proved.

Dynamic Crack Propagation Behavior of the Mg-Li Alloys under High-Speed Impact Loading

2005 ◽  
Vol 488-489 ◽  
pp. 717-720 ◽  
Author(s):  
Gui Ying Sha ◽  
Yong Bo Xu ◽  
En Hou Han
Keyword(s):  
Crack Propagation ◽  
High Speed ◽  
Loading Rate ◽  
High Loading ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Propagation Behavior ◽  
High Loading Rate ◽  
Crack Propagation Behavior

The dynamic experiments for the Mg-Li alloys with single phase structure were carried out using the Hopkinson pressure bar. The dynamic crack propagation behavior and fracture mechanism of the alloys were investigated. The results show that the dynamic crack propagation is a deceleration process for the Mg-Li alloys under high loading rate. The fastest crack propagation velocity for Mg-3.3Li alloy is m/s 37 . 1253 , and 935.36m/s for Mg-14Li alloy. Observations of the fracture by SEM reveal that the dynamic fracture surface for Mg-3.3Li alloy mainly appears to be brittle fracture along grain boundaries. Whereas, the Mg-14Li alloy is ductile fracture mode under high loading rate. The main reason for these may be the transformation of hcp→bcc structure and the precipitation of the MgLi2Al and AlLi, as increase of Li in Mg-Li alloy.

scholarly journals Dynamic crack propagation in weak snowpack layers: insights from high-resolution, high-speed photography

2021 ◽  
Vol 15 (7) ◽  
pp. 3539-3553
Author(s):  
Bastian Bergfeld ◽  
Alec van Herwijnen ◽  
Benjamin Reuter ◽  
Grégoire Bobillier ◽  
Jürg Dual ◽  
...  
Keyword(s):  
High Resolution ◽  
Crack Propagation ◽  
Fracture Energy ◽  
High Speed ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Crack Speed ◽  
Weak Layer ◽  
Specific Fracture ◽  
Insight Into

Abstract. Dynamic crack propagation in snow is of key importance for avalanche release. Nevertheless, it has received very little experimental attention. With the introduction of the propagation saw test (PST) in the mid-2000s, a number of studies have used particle tracking analysis of high-speed video recordings of PST experiments to study crack propagation processes in snow. However, due to methodological limitations, these studies have provided limited insight into dynamical processes such as the evolution of crack speed within a PST or the touchdown distance, i.e. the length from the crack tip to the trailing point where the slab comes to rest on the crushed weak layer. To study such dynamical effects, we recorded PST experiments using a portable high-speed camera with a horizontal resolution of 1280 pixels at rates of up to 20 000 frames s−1. We then used digital image correlation (DIC) to derive high-resolution displacement and strain fields in the slab, weak layer and substrate. The high frame rates enabled us to calculate time derivatives to obtain velocity and acceleration fields. We demonstrate the versatility and accuracy of the DIC method by showing measurements from three PST experiments, resulting in slab fracture, crack arrest and full propagation. We also present a methodology to determine relevant characteristics of crack propagation, namely the crack speed (20–30 m s−1), its temporal evolution along the column and touchdown distance (2.7 m) within a PST, and the specific fracture energy of the weak layer (0.3–1.7 J m−2). To estimate the effective elastic modulus of the slab and weak layer as well as the weak layer specific fracture energy, we used a recently proposed mechanical model. A comparison to already-established methods showed good agreement. Furthermore, our methodology provides insight into the three different propagation results found with the PST and reveals intricate dynamics that are otherwise not accessible.

scholarly journals Rock Dynamic Crack Propagation under Different Loading Rates Using Improved Single Cleavage Semi-Circle Specimen

2019 ◽  
Vol 9 (22) ◽  
pp. 4944
Author(s):  
Fei Wang ◽  
Meng Wang ◽  
Mohaddeseh Mousavi Nezhad ◽  
Hao Qiu ◽  
Peng Ying ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Stress Intensity Factor ◽  
Crack Arrest ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Tight Sandstone ◽  
Crack Propagation Velocity ◽  
Loading Rates

The objective of this paper is to investigate the complete process of dynamic crack propagation in brittle materials under different loading rates. By using Improved Single Cleavage Semi-Circle (ISCSC) specimens and Split Hopkinson Pressure Bar equipment, experiments were conducted, with the fracture phenomenon and crack propagation of tight sandstone investigated. Meanwhile, the process of crack propagation behaviour was simulated. Moreover, with the experimental–numerical method, the crack propagation dynamic stress intensity factor (DSIF) was also calculated. Then, the crack propagation toughness of tight sandstone under different loading rates was investigated and illustrated elaborately. Investigation results demonstrate that ISCSC specimens can achieve the crack arrest position unchanged, and the numerical simulation could effectively deduce the actual crack propagation, as their results were well matched. During crack propagation, the crack propagation DSIF in the whole process increases with the rising loading rate, and so does the crack propagation velocity. Several significant dynamic material parameters of tight sandstone are also given, for engineering reference.

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