scholarly journals Compound-mode crack propagation law of PMMA semicircular-arch roadway specimens under impact loading

2021 ◽  
Author(s):  
Chengxiao Li ◽  
Dongming Guo ◽  
Yuantong Zhang ◽  
Chen An
Keyword(s):  
Crack Propagation ◽  
Numerical Simulations ◽  
Dynamic Stress Intensity Factor ◽  
Central Axis ◽  
Propagation Path ◽  
External Loading ◽  
Mode I ◽  
Propagation Law ◽  
The Impact ◽  
Semicircular Arch

AbstractAn underground roadway usually contains defects of various types, and when the roadway is subjected to external loading, the locations of those defects influence the roadway by differing degrees. In this study, to study how the locations of defects affect crack propagation in a roadway, specimens with tunnel-type voids were made using polymethyl methacrylate, and the stress wave produced by a bullet impacting an incident rod was used as the impact load. Meanwhile, the variations in crack speed, displacement, and dynamic stress intensity factor during crack propagation were obtained using an experimental system of digital laser dynamic caustics, and the commercial software ABAQUS was used for numerical simulations. From the experiments and numerical simulations, the crack propagation path was verified and the impact fracture behavior of a semicircular-arch roadway with different defect positions was presented. The results show that when the pre-fabricated crack is on the central axis of the sample, the crack propagation is purely mode I; when the pre-fabricated crack is 5 mm from the central axis, the crack propagation alternates between mode I and a mixture of modes I and II; when the pre-fabricated crack is at the edge of the semicircular-arch roadway, the crack propagation follows the I–II mixed mode.

scholarly journals Study on Compound Mode Crack Propagation Law of Semi Circular Arch Roadway Under Impact Load

2021 ◽  
Author(s):  
Chengxiao Li ◽  
Renshu Yang ◽  
Yuantong Zhang ◽  
Chen An
Keyword(s):  
Numerical Simulation ◽  
Crack Propagation ◽  
Mixed Mode ◽  
Impact Load ◽  
Central Axis ◽  
Mode I ◽  
Finite Element Software ◽  
Circular Arch ◽  
Propagation Law ◽  
The Impact

Abstract Various kinds of defects are usually contained in the underground roadway. When the roadway is impacted by external load, the location of defects will influence the roadway with different degrees. In order to study the effect of the location of defects on crack propagation in roadway, in this paper, the stress wave produced by the bullet impacting the incident rod was used as the impact load. Meanwhile, the variations of speed, displacement and dynamic stress intensity factor (DSIF) of cracks, during crack propagation, were obtained by using the experimental system of digital laser dynamic caustics (DLDC). And the extended finite element software ABAQUS is used for numerical simulation. Based on the method of experimental-numerical simulation, the crack propagation path is verified and the impact fracture behavior of semi-circular arch roadway with different defect positions is presented. It can be concluded that when the prefabricated crack is located at the central axis of sample, the crack propagation belongs to pure mode I; when the prefabricated crack is 5mm away from the central axis, the crack propagation appears between mode I and I-II mixed mode alternately; when the prefabricated crack is at the edge of semi-circular arch roadway, the crack propagation follows I-II mixed mode

scholarly journals Controlling the Crack Propagation Path of the Veil Interleaved Composite by Fusion-Bonded Dots

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1260 ◽  
Author(s):  
Guangchang Chen ◽  
Jindong Zhang ◽  
Gang Liu ◽  
Puhui Chen ◽  
Miaocai Guo
Keyword(s):  
Crack Propagation ◽  
Propagation Path ◽  
Mode I ◽  
Fiber Breakage ◽  
Fracture Path ◽  
Interlaminar Fracture ◽  
Crack Propagation Path ◽  
Pull Out ◽  
Continuous Carbon Fiber ◽  
The Veil

This study investigated the effect of the fusion-bonded dots of veil interleaves on the crack propagation path of the interlaminar fracture of continuous carbon fiber reinforced epoxy resin. Two thin fiber layers (i.e., nylon veil (NV) with fusion-bonded dots and Kevlar veil (KV) physically stacked by fibers) were used to toughen composites as interleaves. Result shows that the existence of fusion-bonded dots strongly influenced the crack propagation and changed the interlaminar fracture mechanism. The Mode I fracture path of the nylon veil interleaved composite (NVIC) could propagate in the plane where the dots were located, whereas the path of the Kevlar veil interleaved composite (KVIC) randomly deflected inside the interlayer without the pre-cracking of the dots. The improvement of Mode I toughness was mainly based on fiber bridging and the resulting fiber breakage and pull-out. Fiber breakage was often observed for NVIC, whereas fiber pull-out was the main mechanism for KVIC. For the Mode II fracture path, the fusion-bonded NV dots guided the fracture path largely deflected inside the interlayer, causing the breakage of tough nylon fibers. The fracture path of the physically stacked KVIC occurred at one carbon ply/interlayer interface and only slightly deflected at fiber overlapped regions. Moreover, the fiber pull-out was often observed.

Effect of Environmental Corrosion on Fatigue Crack Growth Morphology: A Detailed Investigation of the Boundary between Fatigue and Corrosion Control Regimes

2014 ◽  
Vol 891-892 ◽  
pp. 278-285
Author(s):  
Sandeep R. Shah ◽  
Ian L. Pryce ◽  
Todd B. St John ◽  
James M. Greer
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Driving Force ◽  
Galvanic Corrosion ◽  
Corrosion Damage ◽  
Propagation Path ◽  
Fatigue Properties ◽  
Mode I ◽  
Mode Ii ◽  
Element Analysis

Legacy 7XXX series aluminum alloys were developed primarily for their high strength with less regard for their fatigue properties, corrosion resistance and fracture toughness. The constituent alloying elements in these materials (used to achieve high strengths) markedly increased their corrosion susceptibility. Consequently, aircraft structures made from these alloys have exhibited fatigue and corrosion damage. In the present work, we have investigated a crack finding in a fuselage skin of AA7XXX series alloy. This investigation revealed the crack propagated by a combination of fatigue and corrosion. Through the use of extensive metallography, mechanical analysis and laboratory experiments, we have separated the contributions to the damage growth due to corrosion and fatigue. We have also confirmed that in-service mixed-mode failures like this, observed in these alloys, can be reproduced reliably in the laboratory. Furthermore, it was observed that the presence of corrosion can actually change the propagation of a fatigue crack from mode I, the preferable orientation for fatigue crack propagation, to mode II, the preferable orientation for corrosion propagation. Even though the mechanical driving force is enough to grow the crack in mode I, the presence of corrosion can change it to mode II by electrochemical degradation of the material. Using electrochemical measurements, we relate the change in failure mode to the frequency of cyclic loading. At slow enough cyclic frequency the electrochemical energy released due to galvanic corrosion degrades the material such that the crack turns and propagates in the orientation which has only one third the mechanical driving force as compared to the original crack propagation path. This is the first time such phenomenon has been successfully replicated in the laboratory and modeled with finite element analysis.

scholarly journals Study on Crack Propagation of the Tunnel Model under Dynamic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Chengxiao Li ◽  
Yuantong Zhang ◽  
Peng Xu ◽  
Chen An
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Dynamic Fracture ◽  
Propagation Velocity ◽  
Fracture Process ◽  
Test Results ◽  
Crack Propagation Velocity ◽  
Propagation Law ◽  
Initial Fracture ◽  
The Impact

Crack defects make it difficult to predict the dynamic fracture of tunnel specimens under an impact load. To study the impact of the velocity and crack location on a roadway under dynamic load, specimens with tunnel-type voids were made using polymethyl methacrylate. The split-Hopkinson bar was used as the loading method, and a digital laser dynamic caustics system was used to observe the fracture process of the specimens. The dynamic fracture process was evaluated by the crack propagation velocity, displacement, and dynamic stress intensity factor. To predict and verify the test results, ABAQUS was used to simulate the test process. It was found that the results of the simulated combinations of the crack propagation path and initial fracture toughness change law are consistent with the test results. The initial fracture toughness and the peak value of the crack propagation velocity increased with the increase of the impact velocity. The crack propagation law and trajectory were affected by the location of the prefabricated cracks.

An Alternative Technique to Evaluate Crack Propagation Path in Hyperelastic Materials

2012 ◽  
Vol 40 (1) ◽  
pp. 42-58 ◽  
Author(s):  
R. R. M. Ozelo ◽  
P. Sollero ◽  
A. L. A. Costa
Keyword(s):  
Constitutive Model ◽  
Crack Propagation ◽  
Experimental Tests ◽  
Growth Direction ◽  
Propagation Path ◽  
J Integral ◽  
Alternative Technique ◽  
Crack Propagation Path ◽  
Hyperelastic Materials ◽  
Material Constitutive Model

Abstract REFERENCE: R. R. M. Ozelo, P. Sollero, and A. L. A. Costa, “An Alternative Technique to Evaluate Crack Propagation Path in Hyperelastic Materials,” Tire Science and Technology, TSTCA, Vol. 40, No. 1, January–March 2012, pp. 42–58. ABSTRACT: The analysis of crack propagation in tires aims to provide safety and reliable life prediction. Tire materials are usually nonlinear and present a hyperelastic behavior. Therefore, the use of nonlinear fracture mechanics theory and a hyperelastic material constitutive model are necessary. The material constitutive model used in this work is the Mooney–Rivlin. There are many techniques available to evaluate the crack propagation path in linear elastic materials and estimate the growth direction. However, most of these techniques are not applicable to hyperelastic materials. This paper presents an alternative technique for modeling crack propagation in hyperelastic materials, based in the J-Integral, to evaluate the crack path. The J-Integral is an energy-based parameter and is applicable to nonlinear materials. The technique was applied using abaqus software and compared to experimental tests.

scholarly journals Fatigue Crack Growth Analysis with Extended Finite Element for 3D Linear Elastic Material

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 397
Author(s):  
Yahya Ali Fageehi
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Crack Growth ◽  
Mixed Mode ◽  
Propagation Path ◽  
Loading Conditions ◽  
Extended Finite Element ◽  
Linear Elastic

This paper presents computational modeling of a crack growth path under mixed-mode loadings in linear elastic materials and investigates the influence of a hole on both fatigue crack propagation and fatigue life when subjected to constant amplitude loading conditions. Though the crack propagation is inevitable, the simulation specified the crack propagation path such that the critical structure domain was not exceeded. ANSYS Mechanical APDL 19.2 was introduced with the aid of a new feature in ANSYS: Smart Crack growth technology. It predicts the propagation direction and subsequent fatigue life for structural components using the extended finite element method (XFEM). The Paris law model was used to evaluate the mixed-mode fatigue life for both a modified four-point bending beam and a cracked plate with three holes under the linear elastic fracture mechanics (LEFM) assumption. Precise estimates of the stress intensity factors (SIFs), the trajectory of crack growth, and the fatigue life by an incremental crack propagation analysis were recorded. The findings of this analysis are confirmed in published works in terms of crack propagation trajectories under mixed-mode loading conditions.

scholarly journals Experimental and Numerical Study of Fracture Behavior of Rock-Like Material Specimens with Single Pre-Set Joint under Dynamic Loading

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2690
Author(s):  
Bo Pan ◽  
Xuguang Wang ◽  
Zhenyang Xu ◽  
Lianjun Guo ◽  
Xuesong Wang
Keyword(s):  
Crack Initiation ◽  
Crack Propagation ◽  
Joint Angle ◽  
Simulation Software ◽  
Dissipated Energy ◽  
Energy Structure ◽  
Joint Angles ◽  
Crack Penetration ◽  
Before And After ◽  
The Impact

The Split Hopkinson Pressure Bar (SHPB) is an apparatus for testing the dynamic stress-strain response of the cement mortar specimen with pre-set joints at different angles to explore the influence of joint attitudes of underground rock engineering on the failure characteristics of rock mass structure. The nuclear magnetic resonance (NMR) has also been used to measure the pore distribution and internal cracks of the specimen before and after the testing. In combination with numerical analysis, the paper systematically discusses the influence of joint angles on the failure mode of rock-like materials from three aspects of energy dissipation, microscopic damage, and stress field characteristics. The result indicates that the impact energy structure of the SHPB is greatly affected by the pre-set joint angle of the specimen. With the joint angle increasing, the proportion of reflected energy moves in fluctuation, while the ratio of transmitted energy to dissipated energy varies from one to the other. NMR analysis reveals the structural variation of the pores in those cement specimens before and after the impact. Crack propagation direction is correlated with pre-set joint angles of the specimens. With the increase of the pre-set joint angles, the crack initiation angle decreases gradually. When the joint angles are around 30°–75°, the specimens develop obvious cracks. The crushing process of the specimens is simulated by LS-DYNA software. It is concluded that the stresses at the crack initiation time are concentrated between 20 and 40 MPa. The instantaneous stress curve first increases and then decreases with crack propagation, peaking at different times under various joint angles; but most of them occur when the crack penetration ratio reaches 80–90%. With the increment of joint angles in specimens through the simulation software, the changing trend of peak stress is consistent with the test results.

scholarly journals Benchmarking Quantum Computers and the Impact of Quantum Noise

2021 ◽  
Vol 54 (7) ◽  
pp. 1-35
Author(s):  
Salonik Resch ◽  
Ulya R. Karpuzcu
Keyword(s):  
Numerical Simulations ◽  
Computer Architecture ◽  
Quantum Noise ◽  
Computing System ◽  
Quantum Computers ◽  
Complicating Factors ◽  
The Impact

Benchmarking is how the performance of a computing system is determined. Surprisingly, even for classical computers this is not a straightforward process. One must choose the appropriate benchmark and metrics to extract meaningful results. Different benchmarks test the system in different ways, and each individual metric may or may not be of interest. Choosing the appropriate approach is tricky. The situation is even more open ended for quantum computers, where there is a wider range of hardware, fewer established guidelines, and additional complicating factors. Notably, quantum noise significantly impacts performance and is difficult to model accurately. Here, we discuss benchmarking of quantum computers from a computer architecture perspective and provide numerical simulations highlighting challenges that suggest caution.

scholarly journals Mode I Crack Propagation Experimental Analysis of Adhesive Bonded Joints Comprising Glass Fibre Composite Material under Impact and Constant Amplitude Fatigue Loading

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4380
Author(s):  
Alirio Andres Bautista Villamil ◽  
Juan Pablo Casas Rodriguez ◽  
Alicia Porras Holguin ◽  
Maribel Silva Barrera
Keyword(s):  
Crack Propagation ◽  
Structural Integrity ◽  
Crack Propagation Rate ◽  
Fatigue Loading ◽  
Propagation Rate ◽  
Operating Conditions ◽  
Impact Testing ◽  
Mode I ◽  
Mode I Crack ◽  
Constant Amplitude

The T-90 Calima is a low-wing monoplane aircraft. Its structure is mainly composed of different components of composite materials, which are mainly bonded by using adhesive joints of different thicknesses. The T-90 Calima is a trainer aircraft; thus, adverse operating conditions such as hard landings, which cause impact loads, may affect the structural integrity of aircrafts. As a result, in this study, the mode I crack propagation rate of a typical adhesive joint of the aircraft is estimated under impact and constant amplitude fatigue loading. To this end, effects of adhesive thickness on the mechanical performance of the joint under quasistatic loading conditions, impact and constant amplitude fatigue in double cantilever beam (DCB) specimens are experimentally investigated. Cyclic impact is induced using a drop-weight impact testing machine to obtain the crack propagation rate (da/dN) as a function of the maximum strain energy release rate (GImax) diagram; likewise, this diagram is also obtained under constant amplitude fatigue, and both diagrams are compared to determine the effect of each type of loading on the structural integrity of the joint. Results reveal that the crack propagation rate under impact fatigue is three orders of magnitude greater than that under constant amplitude fatigue.

scholarly journals The Impact of Initial Conditions in N-Body Simulations of Debris Discs

2015 ◽  
Vol 32 ◽  
Author(s):  
E. Thilliez ◽  
S. T. Maddison
Keyword(s):  
Numerical Simulations ◽  
Initial Conditions ◽  
Parent Body ◽  
Dust Trapping ◽  
Physical Context ◽  
Disc Width ◽  
Wide Range ◽  
Belt Width ◽  
New Generation ◽  
The Impact

AbstractNumerical simulations are a crucial tool to understand the relationship between debris discs and planetary companions. As debris disc observations are now reaching unprecedented levels of precision over a wide range of wavelengths, an appropriate level of accuracy and consistency is required in numerical simulations to confidently interpret this new generation of observations. However, simulations throughout the literature have been conducted with various initial conditions often with little or no justification. In this paper, we aim to study the dependence on the initial conditions of N-body simulations modelling the interaction between a massive and eccentric planet on an exterior debris disc. To achieve this, we first classify three broad approaches used in the literature and provide some physical context for when each category should be used. We then run a series of N-body simulations, that include radiation forces acting on small grains, with varying initial conditions across the three categories. We test the influence of the initial parent body belt width, eccentricity, and alignment with the planet on the resulting debris disc structure and compare the final peak emission location, disc width and offset of synthetic disc images produced with a radiative transfer code. We also track the evolution of the forced eccentricity of the dust grains induced by the planet, as well as resonance dust trapping. We find that an initially broad parent body belt always results in a broader debris disc than an initially narrow parent body belt. While simulations with a parent body belt with low initial eccentricity (e ~ 0) and high initial eccentricity (0 < e < 0.3) resulted in similar broad discs, we find that purely secular forced initial conditions, where the initial disc eccentricity is set to the forced value and the disc is aligned with the planet, always result in a narrower disc. We conclude that broad debris discs can be modelled by using either a dynamically cold or dynamically warm parent belt, while in contrast eccentric narrow debris rings are reproduced using a secularly forced parent body belt.

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