scholarly journals Sharp V‐notches in viscoplastic solids: Strain energy rate density rule and fracture toughness

2020 ◽  
Vol 44 (1) ◽  
pp. 28-42
Author(s):  
Yanwei Dai ◽  
Luca Susmel ◽  
Fei Qin
Keyword(s):  
Fracture Toughness ◽  
Strain Energy ◽  
Energy Rate ◽  
Viscoplastic Solids

Ductile Tearing Simulation of Circumferential Cracked Pipe Under Cyclic Loading Using Damage Criteria Determined by Monotonic Pipe Test Data

2018 ◽  
Author(s):  
Jin-Ha Hwang ◽  
Gyo-Geun Youn ◽  
Naoki Miura ◽  
Yun-Jae Kim
Keyword(s):  
Fracture Toughness ◽  
Cyclic Loading ◽  
Ductile Fracture ◽  
Test Data ◽  
Strain Energy ◽  
Fracture Strain ◽  
Damage Model ◽  
Fracture Toughness Test ◽  
Ductile Tearing ◽  
Damage Criteria

To evaluate the structural integrity of nuclear power plant piping, it is important to predict ductile tearing of circumferential cracked pipe from the view point of Leak-Before-Break concept under seismic conditions. CRIEPI (Central Research Institute of Electric Power Industry) conducted fracture test on Japanese carbon steel (STS410) circumferential through-wall cracked pipes under monotonic or cyclic bending load in room temperature. Cyclic loading test conducted variable experimental conditions considering effect of stress ratio and amplitude. In the previous study, monotonic fracture pipe test was simulated by modified stress-strain ductile damage model determined by C(T) specimen fracture toughness test. And, ductile fracture of pipe under cyclic loading simulated using damage criteria based on fracture strain energy from C(T) specimen test data. In this study, monotonic pipe test result is applied to determination of damage model based on fracture strain energy, using finite element analysis, without C(T) specimen fracture toughness test. Ductile fracture of pipe under variable cyclic loading conditions simulates using determined fracture energy damage model from monotonic pipe test.

Effects of Crimped Fiber Paths on Mixed Mode Delamination Behaviors in Woven Fabric Composites

2016 ◽  
Author(s):  
Paul V. Cavallaro ◽  
Andrew Hulton ◽  
Mahmoud Salama ◽  
Melvin W. Jee
Keyword(s):  
Fracture Toughness ◽  
Energy Release ◽  
Mixed Mode ◽  
Strain Energy ◽  
Strain Energy Release ◽  
Woven Fabric ◽  
Woven Fabric Composites ◽  
Fabric Composites ◽  
Energy Release Rates ◽  
Strain Energy Release Rates

This research investigated the fracture toughness and crack propagation behaviors of woven fabric reinforced polymer (WFRP) composite laminates subjected to single and mixed mode loadings using numerical models. The objectives were to characterize the fracture behaviors and toughness properties at the fiber/matrix interfaces and to identify mechanisms that can be exploited for increasing delamination resistance. The mode-I and mode-II strain energy release rates GI and GII, the effective critical strain energy release rate, Gc_eff, (also known as the mixed mode fracture toughness) and crack growth stabilities were determined as functions of crimped fiber paths using meso-scale, 2D multi-continuum finite element models. Three variations of a plain-woven fabric architecture were considered; each having different crimped fiber paths. The presence of mixed-mode strain energy release rates at the meso-scale due to the curvilinear fiber paths was shown to influence the interlaminar fracture toughness and was explored for pure single-mode and mixed-mode global loadings. It was concluded that woven fabric composites provided a Fracture Toughness Conversion Mechanism (FTCM) and their toughness properties were dependent upon and varied with positon along the crimped fiber paths. The FTCM was identified as an advanced tailoring mechanism that can be further utilized to improve toughness and damage tolerance thresholds especially when the mode-II fracture toughness GIIc is greater than the mode-I fracture toughness GIc.

scholarly journals Numerical Investigation of the Fracture Properties of Pre-Cracked Monocrystalline/Polycrystalline Graphene Sheets

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 263 ◽  
Author(s):  
Xinliang Li ◽  
Jiangang Guo
Keyword(s):  
Fracture Toughness ◽  
Grain Boundary ◽  
Misorientation Angle ◽  
Strain Energy ◽  
Unit Area ◽  
Crack Tip ◽  
Mode I ◽  
Fracture Properties ◽  
Mode I Fracture ◽  
Mode I Fracture Toughness

The fracture properties of pre-cracked monocrystalline/polycrystalline graphene were investigated via a finite element method based on molecular structure mechanics, and the mode I critical stress intensity factor (SIF) was calculated by the Griffith criterion in classical fracture mechanics. For monocrystalline graphene, the size effects of mode I fracture toughness and the influence of crack width on the mode I fracture toughness were investigated. Moreover, it was found that the ratio of crack length to graphene width has a significant influence on the mode I fracture toughness. For polycrystalline graphene, the strain energy per unit area at different positions was calculated, and the initial fracture site (near grain boundary) was deduced from the variation tendency of the strain energy per unit area. In addition, the effects of misorientation angle of the grain boundary (GB) and the distance between the crack tip and GB on mode I fracture toughness were also analyzed. It was found that the mode I fracture toughness increases with increasing misorientation angle. As the distance between the crack tip and GB increases, the mode I fracture toughness first decreases and then tends to stabilize.

Rock Fracture Toughness Under Mode II Loading: A Theoretical Model Based on Local Strain Energy Density

2017 ◽  
Vol 51 (1) ◽  
pp. 243-253 ◽  
Author(s):  
M. Rashidi Moghaddam ◽  
M. R. Ayatollahi ◽  
F. Berto
Keyword(s):  
Fracture Toughness ◽  
Theoretical Model ◽  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Rock Fracture ◽  
Local Strain ◽  
Mode Ii ◽  
Rock Fracture Toughness ◽  
Mode Ii Loading

Biaxial load effects on the crack border elastic strain energy and strain energy rate

1977 ◽  
Vol 9 (4) ◽  
pp. 753-764 ◽  
Author(s):  
J. Eftis ◽  
N. Subramonian ◽  
H. Liebowitz
Keyword(s):  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Energy Rate ◽  
Biaxial Load ◽  
Load Effects

scholarly journals Acoustic Emission Characteristics and Failure Mechanism of Fractured Rock under Different Loading Rates

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Yongzheng Zhang ◽  
Gang Wang ◽  
Yujing Jiang ◽  
Shugang Wang ◽  
Honghua Zhao ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Failure Mechanism ◽  
Strain Energy ◽  
Loading Rate ◽  
Fractured Rock ◽  
Acoustic Emissions ◽  
Biaxial Compression ◽  
Particle Model ◽  
Energy Rate ◽  
Loading Rates

To study the loading rate dependence of acoustic emissions and the failure mechanism of fractured rock, biaxial compression tests performed on granite were numerically simulated using the bonded particle model in Particle Flow Code (PFC). Uniaxial tests on a sample containing a single open fracture were simulated under different loading rates ranging from 0.005 to 0.5 m/s. Our results demonstrate the following. (1) The overall trends of stress and strain changes are not affected by the loading rate; the loading rate only affects the strain required to reach each stage. (2) The strain energy rate and acoustic emission (AE) events are affected by the loading rate in fractured rock. With an increase in the loading rate, AE events and the strain energy rate initially increase and then decrease, forming a fluctuating trend. (3) Under an external load, the particles within a specimen are constantly squeezed, rotated, and displaced. This process is accompanied by energy dissipation via the production of internal tensile and shear cracks; their propagation and coalescence result in the formation of a macroscopic rupture zone.

Fracability evaluation of lacustrine shale by integrating brittleness and fracture toughness

2019 ◽  
Vol 7 (2) ◽  
pp. T363-T372
Author(s):  
Cheng Huang ◽  
Chao Yang ◽  
Feng Shen
Keyword(s):  
Fracture Toughness ◽  
Plastic Strain ◽  
Strain Energy ◽  
Evaluation Method ◽  
Peak Stress ◽  
Brittleness Index ◽  
Before And After ◽  
Lacustrine Shale ◽  
The Difference ◽  
The Impact

Rock brittleness and fracture toughness are important parameters for evaluating rock fracability. The stress-strain curves indicate that the lacustrine shale is strongly brittle. Brittle failure occurs rapidly when the stress of the lacustrine shale reaches its peak value. In addition, the lacustrine shale has different plastic strains before and after peak stress; this can relax the stress concentration of the crack tips. Therefore, the plastic strain that occurs before and after the peak stress can cause decreasing brittleness, which can be used to distinguish the brittleness and fracability in the formation of the lacustrine shale clearly. Moreover, this further enlarges the difference in the brittleness index. Based on the influence of plastic strain on brittleness, we have developed a new brittleness evaluation method that uses the ratio of linear elastic strain energy to the total strain energy before complete rock failure, which can indicate the difference of the lacustrine shale clearly. Fracture toughness is another important parameter that impacts the fracture extension and influences fracability. Based on the impact of brittleness and fracture toughness on the fracability, we have developed a new fracability evaluation method. The brittleness index increases with increases in the quartz content, and it decreases with increases in the albite feldspar and calcite contents. The fracture toughness decreases with increases in the quartz and clay contents, and it increases with increases in the siderite content. In addition, we established an empirical formula that can evaluate the brittleness index and the fracture toughness using mineral contents obtained from elemental logging. Using the new fracability evaluation method to optimize the fracturing stage, the preliminary field test indicates that the new approach was effective in the lacustrine shale formation.

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