scholarly journals Effect of the Preexisting Fissure with Different Fillings in PMMA on Blast-Induced Crack Propagation

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Xin Yang ◽  
Xiangguo Zeng ◽  
Chuanjin Pu ◽  
Dingjun Xiao
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Stress Wave ◽  
Wave Energy ◽  
Dynamic Crack Propagation ◽  
Pressure Curve ◽  
Dynamic Crack ◽  
Wing Crack ◽  
Initiation Point ◽  
Peak Value

In order to study the dynamic crack propagation law in fissured rock under the different fillings, a borehole with 7 mm diameter was processed in the center of a polymethyl methacrylate (PMMA) specimen. The preexisting fissure with different angles (θ = 0°, 45°, and 90°) and different distances (L = 20, 30, 40, 50, and 60 mm) was prefabricated around the borehole. Air, soil, and water were employed as fillings in the fissure, respectively. The experiment of explosive loading was carried out by a single detonator, and the dynamic crack propagation process of the experimental specimens was simulated by nonlinear dynamics software AUTODYN. The results show that the blast-induced cracks are the most favorable and unfavorable to propagate when θ = 0° and θ = 45°, respectively. The length of the far-end wing crack decreases with the increase of the distance L, and the length of the far-end wing crack in the air-filled specimens is larger than those in soil-filled and water-filled specimens. The damage-pressure curve of the far-end wing crack initiation point shows “S”-type change, and the damage-pressure curve shows two obvious damage evolution processes of initial nonlinear and later linear stages. With the increase of the angle, the distance from the borehole to the crack initiation point decreases and the compressive stress wave peak value should increase, but the tensile force peak value decreases. Meanwhile, the relationships between pressure and average velocity of the initiation point and L, θ, and fillings are established, respectively. The numerical simulation agrees with the experimental results well. It can be seen that the fillings types, angle, and distance have a mutual restraint relationship with the reflected and absorbed stress wave energy. The phenomenon of crack propagation under different fillings can be explained well from the viewpoint of discontinuity degree and stress wave energy, which reveals the general law of blast-induced crack propagation.

Modeling Intersonic Crack Propagation in Fiber Reinforced Composites With Contact/Cohesive Laws

2001 ◽  
Author(s):  
S. K. Dwivedi ◽  
H. D. Espinosa
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Epoxy Composite ◽  
Dynamic Crack Propagation ◽  
Interface Element ◽  
Dynamic Crack ◽  
Crack Speed ◽  
Interface Elements ◽  
Intersonic Crack Propagation ◽  
The Impact

Abstract Dynamic crack propagation in an unidirectional Carbon/Epoxy composite is studied through finite element analyses in total Lagrangian co-ordinates. A finite deformation anisotropic visco-plastic model is used to describe the constitutive response of the composite. Crack initiation and propagation is simulated by embedding zero thickness interface element along the possible crack path. An irreversible cohesive law is used to describe the evolution of normal and shear tractions as a function of displacement jumps. The compressive response prior to interface failure is analyzed using contact impenetrability conditions. The failure of the first interface element at the pre-notch tip models crack initiation. Crack propagation is modeled through consecutive failure of interface elements. Dynamic crack propagation phenomena are studied in terms of crack initiation time, crack speed, mode I and mode II displacement jumps and tractions associated with the failure of interface elements, effective plastic strain at the crack tip and path independent integral J′. Analyses are first carried out for the dynamic crack propagation along bi-material interfaces. The results obtained from present analyses agree well with literature data. Detailed analyses are carried out for a pre-notched unidirectional Carbon/Epoxy composite material. The impact velocity in the analyses is an imposed velocity over an assumed impact region and remains constant throughout the analysis. Analyses are carried out at impact velocities of 5, 10, 20, 30 and 40 m/s, assuming the crack wake is frictionless. Moreover, analyses at impact velocities of 30 and 40 m/s are also carried out with a friction coefficient of 0.5 along the crack surfaces. The analyses established intersonic crack speed in the fiber reinforced composite material. Intersonic crack propagation for the impact velocities of 40 m/s is 400% of the shear wave speed and 87% of the longitudinal wave speed. Detailed discussion is given on the features of sub-sonic and intersonic crack propagation in Carbon/Epoxy composite materials. It is shown that the friction coefficient along the crack surface plays an important role by smearing the discontinuous field that develops behind the crack tip and by reducing crack speed in the intersonic regime. The analyses show that the contour integral J′ computed at near field contours are path independent and can serve as a parameter for characterizing intersonic crack propagation.

Dynamic crack propagation in matrix involving inclusions by a time-domain BEM

2012 ◽  
Vol 36 (5) ◽  
pp. 651-657 ◽  
Author(s):  
Jun Lei ◽  
Yue-Sheng Wang ◽  
Yifeng Huang ◽  
Qingsheng Yang ◽  
Chuanzeng Zhang
Keyword(s):  
Crack Propagation ◽  
Time Domain ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack

Dynamic Crack Propagation in Single-Crystalline Silicon

1998 ◽  
Vol 539 ◽  
Author(s):  
T. Cramer ◽  
A. Wanner ◽  
P. Gumbsch
Keyword(s):  
Crack Propagation ◽  
Crystalline Silicon ◽  
Potential Drop ◽  
Tensile Tests ◽  
Terminal Velocity ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Single Crystalline Silicon ◽  
Single Crystalline ◽  
Crack Propagation Velocity

AbstractTensile tests on notched plates of single-crystalline silicon were carried out at high overloads. Cracks were forced to propagate on {110} planes in a <110> direction. The dynamics of the fracture process was measured using the potential drop technique and correlated with the fracture surface morphology. Crack propagation velocity did not exceed a terminal velocity of v = 3800 m/s, which corresponds to 83%7 of the Rayleigh wave velocity vR. Specimens fractured at low stresses exhibited crystallographic cleavage whereas a transition from mirror-like smooth regions to rougher hackle zones was observed in case of the specimens fractured at high stresses. Inspection of the mirror zone at high magnification revealed a deviation of the {110} plane onto {111} crystallographic facets.

scholarly journals Dynamic crack propagation in a 2D elastic body. The out-of plane case

PAMM ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 1090801-1090802
Author(s):  
A.-M. Sändig ◽  
A. Lalegname ◽  
S. Nicaise
Keyword(s):  
Crack Propagation ◽  
Elastic Body ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Plane Case ◽  
Out Of Plane

Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method

2007 ◽  
Author(s):  
B. Prabel ◽  
S. Marie ◽  
A. Combescure
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Rate ◽  
Thermal Shock ◽  
Crack Growth ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Pressure Vessel Steel ◽  
Vessel Steel

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.

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