Effect on Dynamic Biaxial Fracture Behaviors by Different Heat Treatments on Magnesium Alloy

2008 ◽  
Vol 33-37 ◽  
pp. 357-362
Author(s):  
Akira Shimamoto ◽  
Ryo Kubota
Keyword(s):  
Heat Treatment ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Fracture ◽  
Dynamic Stress Intensity Factor ◽  
Treatment Temperature ◽  
Biaxial Stress ◽  
Heat Treated ◽  
Caustics Method

The dynamic fracture experiments were conducted on the heat treated magnesium alloys; AZ31B-O, AZ31B-200 °C, and AZ31B-430 °C. Cross shaped specimens with the crack on their center were used for the experiments. Dynamic fracture behavior near a crack tip under equal and unequal biaxial stress was observed by the caustics method. From the observation, the stress intensity factor and the fracture toughness value were calculated. As a result, the effect of heat treatment was found. However, no clear relation such as correlation between dynamic stress intensity factor and heat treatment temperature was deduced.

Effect of Heat Treatment on the Fracture Toughness of Glass Fibre Reinforced Polypropylene

2002 ◽  
Vol 10 (3) ◽  
pp. 211-218
Author(s):  
Jeng-Shyong Lin ◽  
Sheng-Kuen Wu
Keyword(s):  
Heat Treatment ◽  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Glass Fibre ◽  
Initial Crack ◽  
Unstable Fracture ◽  
Heat Treated ◽  
Glass Fibre Reinforced

In this work, the effect of heat treatment on the fracture toughness of glass fibre reinforced polypropylene was studied. Polypropylene blended with short glass fibres was injection-moulded. The moulded parts were heat treated at 150°C for 30 min. The crack growth resistance curve (R-curve) was measured to evaluate the effect of heat treatment on the fracture toughness, and to determine the stress intensity factor at the point of instability, KR(ins). The fracture surface was examined using scanning electron microscope to analyze the fracture mechanism. The results show that the stress intensity factor at the unstable fracture point KR(ins) increases with the initial crack length.

scholarly journals Hole Defects Affect the Dynamic Fracture Behavior of Nearby Running Cracks

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
R. S. Yang ◽  
C. X. Ding ◽  
L. Y. Yang ◽  
P. Xu ◽  
C. Chen
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Fracture ◽  
Fracture Behavior ◽  
Dynamic Stress ◽  
Crack Path ◽  
Dynamic Stress Intensity Factor ◽  
Experimental System ◽  
Intersection Area

Effects of defects on the dynamic fracture behavior of engineering materials cannot be neglected. Using the experimental system of digital laser dynamic caustics, the effects of defects on the dynamic fracture behavior of nearby running cracks are studied. When running cracks propagate near to defects, the crack path deflects toward the defect; the degree of deflection is greater for larger defect diameters. When the running crack propagates away from the defect, the degree of deflection gradually reduces and the original crack path is restored. The intersection between the caustic spot and the defect is the direct cause of the running crack deflection; the intersection area determines the degree of deflection. In addition, the defect locally inhibits the dynamic stress intensity factor of running cracks when they propagate toward the defect and locally promotes the dynamic stress intensity factor of running cracks when they propagate away from the defect.

Determination of Dynamic Fracture-Initiation Toughness Using a Novel Impact Bend Test Procedure

1993 ◽  
Vol 115 (4) ◽  
pp. 389-397 ◽  
Author(s):  
T. Yokoyama
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Dynamic Fracture ◽  
Dynamic Stress ◽  
Test Procedure ◽  
Dynamic Stress Intensity Factor ◽  
Fracture Initiation ◽  
Initiation Toughness ◽  
Bend Specimen

A novel impact bend test procedure is described/or determining the dynamic fracture-initiation toughness, KId, at a loading rate (stress intensity factor rate), K˙I, of the order of 106MPam/s. A special arrangement of the split Hopkins on pressure bar is adopted to measure accurately dynamic loads applied to a fatigue-precracked bend specimen. The dynamic stress intensity factor history for the bend specimen is evaluated by means of a dynamic finite element technique. The onset of crack initiation is detected using a strain gage attached on the side of the specimen near a crack tip. The value of KId is determined from the critical dynamic stress intensity factor at crack initiation. A series of dynamic fracture tests is carried out on a 7075-T6 aluminum alloy, a Ti-6246 alloy and an AISI 4340 steel. The KId values obtained for the three structural materials are compared with the corresponding values obtained under quasi-static loading conditions.

Study of the Dynamic Crack Growth of a Planar Crack Front in Three-Dimensional Body Subjected to Mode I Loading

2008 ◽  
Author(s):  
Felicia Stan
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Dynamic Fracture ◽  
Dynamic Stress ◽  
Dynamic Stress Intensity Factor ◽  
Three Dimensional ◽  
Dynamic Fracture Toughness

In this paper, a methodology is presented for predicting crack growth rate along three-dimensional crack fronts under mode I dynamic loading conditions. Within the present methodology, for every point along the crack front the stress intensity factor matches the dynamic fracture toughness at the onset of propagation. In order to accurately evaluate the dynamic stress intensity factor the component separation method of the dynamic J integral is used. To overcome the difficulties in three-dimensional dynamic fracture simulations, the three-dimensional dynamic moving finite element method based on three-dimensional moving 20-noded isoparametric elements is used. In the absence of experimental measurements for dynamic fracture toughness, a new methodology to estimate the dynamic fracture toughness is proposed, i.e., a hybrid experimental-numerical approach, which makes use of numerically determined histories of the dynamic stress intensity factor. The values of the dynamic stress intensity factor are converted into dynamic fracture toughness based on the Weibull distribution. The predictive ability of the developed methodology is demonstrated through the prediction of the dynamic crack growth in Double Cantilever Beam (DCB) specimen of PMMA with different thickness.

The Dynamic Stress Intensity Factor Due to Arbitrary Screw Dislocation Motion

1983 ◽  
Vol 50 (2) ◽  
pp. 383-389 ◽  
Author(s):  
L. M. Brock
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Plane Wave ◽  
Screw Dislocation ◽  
Dynamic Stress ◽  
Critical Level ◽  
Dynamic Stress Intensity Factor ◽  
Dislocation Motion ◽  
Crack Edge

The dynamic stress intensity factor for a stationary semi-infinite crack due to the motion of a screw dislocation is obtained analytically. The dislocation position, orientation, and speed are largely arbitrary. However, a dislocation traveling toward the crack surface is assumed to arrest upon arrival. It is found that discontinuities in speed and a nonsmooth path may cause discontinuities in the intensity factor and that dislocation arrest at any point causes the intensity factor to instantaneously assume a static value. Morever, explicit dependence on speed and orientation vanish when the dislocation moves directly toward or away from the crack edge. The results are applied to antiplane shear wave diffraction at the crack edge. For an incident step-stress plane wave, a stationary dislocation near the crack tip can either accelerate or delay attainment of a critical level of stress intensity, depending on the relative orientation of the crack, the dislocation, and the plane wave. However, if the incident wave also triggers dislocation motion, then the delaying effect is diminished and the acceleration is accentuated.

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