Propagation Criterion Research Articles

Security Analysis of Arbiter PUF and Its Lightweight Compositions Under Predictability Test

Unpredictability is an important security property of Physically Unclonable Function (PUF) in the context of statistical attacks, where the correlation between challenge-response pairs is explicitly exploited. In the existing literature on PUFs, the Hamming Distance Test, denoted by HDT( t ), was proposed to evaluate the unpredictability of PUFs, which is a simplified case of the Propagation Criterion test PC( t ). The objective of these test schemes is to estimate the output transition probability when there are t or fewer than t bits flips, and ideally this probability value should be 0.5. In this work, we show that aforementioned two test schemes are not enough to ensure the unpredictability of a PUF design. We propose a new test, which is denoted as HDT( e , t ). This test scheme is a fine-tuned version of the previous schemes, as it considers the flipping bit pattern vector e along with parameter t . As a contribution, we provide a comprehensive discussion and analytic interpretation of HDT( t ), PC( t ), and HDT( e , t ) test schemes for Arbiter PUF (APUF), Exclusive-OR (XOR) PUF, and Lightweight Secure PUF (LSPUF). Our analysis establishes that HDT( e , t ) test is more general in comparison with HDT( t ) and PC( t ) tests. In addition, we demonstrate a few scenarios where the adversary can exploit the information obtained from the analysis of HDT( e , t ) properties of APUF, XOR PUF, and LSPUF to develop statistical attacks on them, if the ideal value of HDT( e , t ) = 0.5 is not achieved for a given PUF. We validate our theoretical observations using the simulated and Field Programmable Gate Array (FPGA) implemented APUF, XOR PUF, and LSPUF designs.

Experimental and numerical investigations on fracture process zone of rock–concrete interface

AbstractA crack propagation criterion for a rock–concrete interface is employed to investigate the evolution of the fracture process zone (FPZ) in rock–concrete composite beams under three‐point bending (TPB). According to the criterion, cracking initiates along the interface when the difference between the mode I stress intensity factor at the crack tip caused by external loading and the one caused by the cohesive stress acting on the fictitious crack surfaces reaches the initial fracture toughness of a rock–concrete interface. From the experimental results of the composite beams with various initial crack lengths but equal depths under TPB, the interface fracture parameters are determined. In addition, the FPZ evolution in a TPB specimen is investigated by using a digital image correlation technique. Thus, the fracture processes of the rock–concrete composite beams can be simulated by introducing the initial fracture criterion to determine the crack propagation. By comparing the load versus crack mouth opening displacement curves and FPZ evolution, the numerical and experimental results show a reasonable agreement, which verifies the numerical method developed in this study for analysing the crack propagation along the rock–concrete interface. Finally, based on the numerical results, the effect of ligament length on the FPZ evolution and the variations of the fracture model during crack propagation are discussed for the rock–concrete interface fracture under TPB. The results indicate that ligament length significantly affects the FPZ evolution at the rock–concrete interface under TPB and the stress intensity factor ratio of modes II to I is influenced by the specimen size during the propagation of the interfacial crack.

Discrete model of hydraulic fracture crack propagation in homogeneous isotropic elastic media

An infinite homogeneous and isotropic elastic medium with a penny shape crack is considered. The crack is subjected to the pressure of fluid injected in the crack center. Description of the crack growth is based on the lubrication equation (balance of the injected fluid and the crack volume), equation for crack opening caused by fluid pressure on the crack surface, the Poiseullie equation related local fluid flux with the crack opening and pressure gradient, and classical criterion of crack propagation of linear fracture mechanics. The crack growth is simulated by a discrete process consisting of three basic stages: increasing the crack volume by a constant crack size, crack jump to a new size defined by the fracture criterion, and filling the appeared crack volume by the fluid. It is shown that the model results a reasonable dependence of the crack size on the time as well as the pressure distribution of fluid on the crack surface. Comparisons with the solutions of hydraulic fracture problems existing in the literature are presented.

Simple criteria for ploughing and runout in post-failure evolution of submarine landslides

This paper extends shear band propagation analysis of slope failures to the investigation of ploughing and runout phenomena in submarine landslides. The ability to predict the two different modes of post-failure landslide evolution is critical for determining the tsunami hazard and type of landslide impact on offshore structures. The proposed analysis is based on the analogy between ploughing and spreading failures. It uses the energy balance approach to develop the criterion for progressive shear band propagation driven by accumulation of sliding material on top of the stable slope. This criterion is then combined with the kinematic passive block mechanism to produce analytical ploughing failure criteria formulated in terms of the critical rise in the seabed level. If the minimum rise of the seabed level at which ploughing can take place is larger than the maximum possible free-standing step in the seabed surface, the first passive failure block will start crumbling over top the stable zone causing the landslide to runout. Application of the derived criteria to the analysis of observed geomorphological features is demonstrated using an example of a paleolandslide complex in the Caspian Sea.

Geophysical criterion of pre-outburst crack propagation in coal beds

The process of crack propagation in the coal face area is considered as an informative sign of coal and gas outburst hazard. In the known condition of crack growth at a certain distance from a coal face, it is suggested to replace mechanical parameters by geophysical data through application of different evaluation approaches: actual stresses—by spectral–acoustic method relative to amplitudes of highfrequency and low-frequency components of acoustic signal generated by mining machines in coal face area; pore pressure—by analysis of methane concentration in mine air in coal face area; strength of the most folded coal bed—by measuring strength based on penetration depth of a steel cone. The author analyzes the influence of acoustic, strength and permeability and porosity properties of coal face area on limit value of geophysical pre-outburst crack propagation criterion.

EXPERIMENTAL STUDY OF COMBUSTION CHARACTERISTICS OF ISOLATED POCKETS OF HYDROGEN-AIR MIXTURES

This paper examines the dynamics of unconfined hydrogen–air flames and the criterion for flame propagation between neighbouring pockets of reactive gas separated by air using the soap bubble technique. The combustion events were visualized using high-speed schlieren or large-scale shadowgraph systems. It was revealed that for sufficiently lean hydrogen–air mixtures characterized by low flame speeds, buoyancy effects become important at small scales. The critical radius of hemispherical flame that will rise due to buoyancy is highly sensitive to the hydrogen concentration. The test results demonstrate that for transition of a flame between neighbouring pockets, the separation distance between the bubbles is mainly determined by the expansion ratio for near stoichiometric mixture, but it becomes much smaller for leaner mixtures because the flame kernel rises due to buoyant effects before the flame can reach the second bubble, thus the separation distance is no longer governed by the expansion ratio.

Double layers and double wells in arbitrary degenerate plasmas

Using the generalized hydrodynamic model, the possibility of variety of large amplitude nonlinear excitations is examined in electron-ion plasma with arbitrary electron degeneracy considering also the ion temperature effect. A new energy-density relation is proposed for plasmas with arbitrary electron degeneracy which reduces to the classical Boltzmann and quantum Thomas-Fermi counterparts in the extreme limits. The pseudopotential method is employed to find the criteria for existence of nonlinear structures such as solitons, periodic nonlinear structures, and double-layers for different cases of adiabatic and isothermal ion fluids for a whole range of normalized electron chemical potential, η0, ranging from dilute classical to completely degenerate electron fluids. It is observed that there is a Mach-speed gap in which no large amplitude localized or periodic nonlinear excitations can propagate in the plasma under consideration. It is further revealed that the plasma under investigation supports propagation of double-wells and double-layers the chemical potential and Mach number ranges of which are studied in terms of other plasma parameters. The Mach number criteria for nonlinear waves are shown to significantly differ for cases of classical with η0 < 0 and quantum with η0 > 0 regimes. It is also shown that the localized structure propagation criteria possess significant dissimilarities for plasmas with adiabatic and isothermal ions. Current research may be generalized to study the nonlinear structures in plasma containing positrons, multiple ions with different charge states, and charged dust grains.

Dynamic localization of damage and microstructural length influence

In the present contribution a localization analysis is performed for a two-scale dynamic damage model. The damage evolution law considered here results by homogenization from micro-crack propagation criteria and involve a characteristic length of the microstructure. For the one-dimensional dynamic system, we study the localization of strain and damage using analytical and numerical methods. An instability analysis based on harmonic perturbations of a homogeneous state for the linearized equations reveals wave dispersion properties and an intrinsic length of the model is deduced in the high frequency regime. The explicit dependence of this intrinsic length on the microstructural length and the damage level is obtained. Numerical simulations of dynamic tests illustrate the localization of damage, strain-rate sensitivity of the tensile strength and the influence of the size of the microstructure. The model predictions are compared with experimental results for spalling tests on concrete specimens. It is shown that the damage model is able to reproduce the observed influences of the strain rate and the size of the microstructure on the dynamic tensile strength.

Experimental and numerical analysis of sandwich panels with hybrid core

The paper presents the experimental and numerical studies of sandwich panels with a hybrid core. The sandwich panel consists of external steel facings and a core, which is made of polyurethane foam or mineral wool or a combination of those two materials. The polyurethane foam material has a low weight and high thermal insulation properties, while the mineral wool material can provide high acoustic insulation and excellent fire resistance. Various proportions of the core materials are taken into account. It is assumed that a proper combination can provide the benefits of both materials. The structural behavior of a sandwich structure with a hybrid core is observed during laboratory tests. The failure mechanism is investigated in a four-point bending test. The material parameters of the core and facings are determined in standardized tests. The obtained parameters are used for FE simulations of the four-point bending tests. The criteria of damage initiation and propagation are defined in the interface layer of the numerical model. A satisfactory correlation between laboratory tests and numerical results is reported. Additionally, the sensitivity analysis of the numerical model response to the variation of the parameters of the interface is presented.

A Dugdale-Barenblatt Crack Between Dissimilar Media

The problem of a Dugdale-Barenblatt crack between dissimilar media is treated. The corresponding singular integral equation of the second kind is solved numerically. The crack propagation criteria is deduced using the revisited Griffith theory (Francfort and Marigo in J. Mech. Phys. Solids 46(8), 1319–1342, 1998). A parametric study is performed. An important result is the absence of the non physical phenomenon of overlapping of the crack faces near the ends observed in (England in J. Appl. Mech. 32(2), 400–402, 1965).

Out-of-plane deviation of a mode I+III crack encountering a tougher obstacle

One possible explanation of out-of-plane deviations of cracks loaded in mode I+III was suggested by Gao and Rice in 1986. These authors noted that small in-plane undulations of the crack front, arising from fluctuations of the fracture toughness, should generate a small local mode-II component, causing the crack to depart from planarity. Their analysis is completed here by explicitly calculating the evolution in time of the out-of-plane deviation of a mode-I+III crack encountering a tougher obstacle. The calculation is based on (i) first-order formulae for the stress intensity factors of a crack slightly perturbed within and out of its plane; and (ii) a “double” propagation criterion combining a Griffith condition on the local energy-release rate and a Goldstein–Salganik condition on the local stress intensity factor of mode II. It is predicted that the crack must evolve toward a stationary state, wherein the orthogonal distance from the average fracture plane to the perturbed crack front is constant outside the obstacle and varies linearly across it. We hope that this theoretical prediction will encourage comparison with experiments, and propose a fracture test involving propagation of a mode-I+III crack through a 3D-printed specimen containing some designed obstacle.

Dynamic propagation criteria for catastrophic failure in planar landslides

SummaryQuantitative assessment of the risk of submarine landslides is an essential part of the design process for offshore oil and gas developments in deep water, beyond the continental shelf. Landslides may be triggered by a reduction in shear strength of subsea sediments over a given zone, caused for example by seismic activity. Simple criteria are then needed to identify critical conditions whereby the zone of weakness could grow catastrophically to cause a landslide. A number of such criteria have been developed over the last decade, based either on ideas drawn from fracture mechanics, or considering the equilibrium of the initial weakened zone and adjacent process zones of gradually softening material. Accounting for the history of the weak zone initiation is critical for derivation of reliable propagation criteria, in particular considering dynamic effects arising from accumulating kinetic energy of the failing material, which will allow the failure to propagate from a smaller initial zone of weakened sediments. Criteria are developed here for planar conditions, taking full account of such dynamic effects, which are shown to be capable of reducing the critical length of the softened zone by 20% or more compared with criteria based on static conditions. A numerical approach is used to solve the governing dynamic equations for the sliding material, the results from which justify assumptions that allow analytical criteria to be developed for the case where the initial softening occurs instantaneously. The effect of more gradual softening is also explored. Copyright © 2016 John Wiley & Sons, Ltd.

Comparison of toughness propagation criteria for blade-like and pseudo-3D hydraulic fractures

The goal of this study is to compare and evaluate the accuracy of different approaches to incorporating the effect of lateral fracture toughness into reduced models for blade-like and pseudo-3D hydraulic fractures. The following three methods are used for the comparison: (i) a classical model with a plane strain (or local) elasticity assumption and a pressure boundary condition calculated based on energetic considerations, (ii) a classical model with local elasticity and pressure boundary condition originating from “stitching” a radial fracture tip to the rest of the fracture, and (iii) a novel model with non-local elasticity and a boundary condition at the tip that is consistent with the linear elastic fracture mechanics propagation criterion. Predictions of all three approaches are compared to a reference solution calculated using a fully planar hydraulic fracturing simulator. The results indicate that the reduced model with non-local elasticity is able to provide an accurate approximation for a wide range of fracture toughness values. The models that feature the local elasticity assumption are able to provide reasonably accurate results for moderate values of fracture toughness, while they become less accurate for blade-like geometries and significantly less accurate (and in some cases unstable) for the pseudo-3D geometry for large values of the fracture toughness.

Numerical evaluation of crack growth in polymer electrolyte fuel cell membranes based on plastically dissipated energy

Understanding the mechanisms of growth of defects in polymer electrolyte membrane (PEM) fuel cells is essential for improving cell longevity. Characterizing the crack growth in PEM fuel cell membrane under relative humidity (RH) cycling is an important step towards establishing strategies essential for developing more durable membrane electrode assemblies (MEA). In this study, a crack propagation criterion based on plastically dissipated energy is investigated numerically. The accumulation of plastically dissipated energy under cyclical RH loading ahead of the crack tip is calculated and compared to a critical value, presumed to be a material parameter. Once the accumulation reaches the critical value, the crack propagates via a node release algorithm. From the literature, it is well established experimentally that membranes reinforced with expanded polytetrafluoroethylene (ePTFE) reinforced perfluorosulfonic acid (PFSA) have better durability than unreinforced membranes, and through-thickness cracks are generally found under the flow channel regions but not land regions in unreinforced PFSA membranes. We show that the proposed plastically dissipated energy criterion captures these experimental observations and provides a framework for investigating failure mechanisms in ionomer membranes subjected to similar environmental loads.

Improved Strength Criterion and Numerical Manifold Method for Fracture Initiation and Propagation

AbstractThis paper develops a novel empirical strength criterion and proposes a manifold method for fracture initiation and propagation. First, to investigate the influencing factors of fractured rock mass strength, a set of uniaxial and biaxial compression tests were performed on gypsum specimens. According to the experimental results, rock mass strength is attributable to nonlinear relationships with fracture inclination angle, length, and lateral pressure. Then, on the basis of strength theory and tests, an improved empirical strength criterion, which can describe the multi-influence of fracture inclination angle, fragmentation degree, and lateral pressure on strength of the rock mass and the path of fracture propagation, was established. Moreover, the critical conditions of tensile and shear fracture for fracture propagation are proposed and used with a numerical manifold method to simulate fracture propagation. Furthermore, in the modeling, the manifold element is regarded as the basic failure elemen...

A comparative study on two stress intensity factor-based criteria for prediction of mode-I crack propagation in concrete

In the analysis of mode-I crack propagation of normal strength concrete at a crack tip, the initial fracture toughness and nil-stress intensity factor (nil-SIF) are two distinguished and widely adopted types of crack propagation criteria. However, there is little information reported on the difference resulting from the two criteria when they are employed to analyze concrete with different strength grades. Aiming at this objective, three-point bending tests are carried out on notched concrete beams of five strength grades, i.e. C20, C40, C60, C80 and C100, and an arrange of initial crack length/depth ratios as 0.2, 0.3 and 0.4, to investigate initial fracture toughness, fracture energy and load–crack mouth opening displacement (P–CMOD) relationship. Meanwhile, the three-point bending tests are also conducted on notched concrete beams of four specimen heights, i.e. 60, 90, 120, and 150mm. The two aforementioned types of concrete crack propagation criteria are introduced to determine crack propagation and predict the P–CMOD curves of a series of notched concrete beams under a three-point bending test. It has been found that the P–CMOD curves calculated using the initial fracture toughness criterion show a better agreement with experimental results than the ones calculated using the nil SIF criterion. With the increase of concrete strength, the difference between the peak loads from experiment and those from analyses based on the nil-SIF criterion becomes increasingly larger than the scenarios based on the initial fracture toughness criterion. Therefore, it can be reasonably concluded that for the two types of concrete crack propagation criteria, the initial fracture toughness is more appropriate for describing the fracture behavior of concrete, especially for high strength concrete.

Numerical investigation of fracture spacing and sequencing effects on multiple hydraulic fracture interference and coalescence in brittle and ductile reservoir rocks

For unconventional resources exploration and development, hydraulic fracture pattern and associated dimensions are critical in determining well stimulation efficiency and ultimate recovery. When creating arrays of hydraulic fractures along horizontal wells, stress field changes induced by hydraulic fractures themselves can lead to fracture interference and coalescence. The resulting complex fracture geometry may compromise or improve the effectiveness of the stimulation job, depending on the nature of the context. Currently, the prevailing approach for hydraulic fracture modeling also relies on Linear Elastic Fracture Mechanics (LEFM), which uses stress intensity factor at the fracture tip as fracture propagation criteria. Even though LEFM can predict hard rock hydraulic fracturing processes reasonably, but often fails to give accurate predictions of fracture geometry and propagation pressure in quasi-brittle and ductile rocks, such as poorly consolidated sands and clay-rich shales. In this study, a fully coupled hydraulic fracture propagation model based on the Extended Finite Element Method (XFEM), Cohesive Zone Method (CZM) and Mohr–Coulomb theory of plasticity is presented, to investigate the interference and coalescence of fluid-driven hydraulic fractures that initiated from horizontal wells. The results indicate that fracture spacing and the relative timing of fracture initiation control whether the fractures compete against each other to form a divergent pattern or coalesce into a single, primary fracture. Fracture growth can be arrested after fracture tips pass by when simultaneously fracturing adjacent horizontal wells. Even though the in-elastic rock deformation due to shear failure can strongly impact fracture geometry and fracturing pressure, it has limited influence on hydraulic fracture interaction patterns.

Growth by Optimization of Work (GROW): A new modeling tool that predicts fault growth through work minimization

Growth by Optimization of Work (GROW) is a new modeling tool that automates fracture initiation, propagation, interaction, and linkage. GROW predicts fracture growth by finding the propagation path and fracture geometry that optimizes the global external work of the system. This implementation of work optimization is able to simulate more complex paths of fracture growth than energy release rate methods. In addition, whereas a Coulomb stress analysis determines two conjugate planes of potential failure, GROW identifies a single failure surface for each increment of growth. GROW also eliminates ambiguity in determining whether shear or tensile failure will occur at a fracture tip by assessing both modes of failure by the same propagation criterion. Here we describe the underlying algorithm of the program and present GROW models of two propagating faults separated by a releasing step. The discretization error of these models demonstrates that GROW can predict fault propagation paths within the numerical uncertainty produced by discretization. Model element size moderately influences the propagation paths, however, the final fault geometry remains similar between models with significantly different element sizes. The propagation power of the fault system, calculated from the change in work due to fault propagation, indicates when model faults interact through both soft- and hard-linkage.

An XFEM Model for Hydraulic Fracturing in Partially Saturated Rocks

Hydraulic fracturing is a complex multi-physics phenomenon. Numerous analytical and numerical models of hydraulic fracturing processes have been proposed. Analytical solutions commonly are able to model the growth of a single hydraulic fracture into an initially intact, homogeneous rock mass. Numerical models are able to analyse complex problems such as multiple hydraulic fractures and fracturing in heterogeneous media. However, majority of available models are restricted to single-phase flow through fracture and permeable porous rock. This is not compatible with actual field conditions where the injected fluid does not have similar properties as the host fluid. In this study we present a fully coupled hydro-poroelastic model which incorporates two fluids i.e. fracturing fluid and host fluid. Flow through fracture is defined based on lubrication assumption, while flow through matrix is defined as Darcy flow. The fracture discontinuity in the mechanical model is captured using eXtended Finite Element Method (XFEM) while the fracture propagation criterion is defined through cohesive fracture model. The discontinuous matrix fluid velocity across fracture is modelled using leak-off loading which couples fracture flow and matrix flow. The proposed model has been discretised using standard Galerkin method, implemented in Matlab and verified against several published solutions. Multiple hydraulic fracturing simulations are performed to show the model robustness and to illustrate how problem parameters such as injection rate and rock permeability affect the hydraulic fracturing variables i.e. injection pressure, fracture aperture and fracture length. The results show the impact of partial saturation on leak-off and the fact that single-phase models may underestimate the leak-off.

Theoretical research on the propagation of the crack normal to and dwelling on the interface of the cermet cladding material structure

The interface crack propagation problem in the cermet cladding material structure was studied. A comparative propagation property parameter (CP) suitable to judge the propagation direction of the interface crack in the cermet cladding material structure was proposed. The interface crack propagation criterion was established. Theoretical models of the CPs for the crack normal to and dwelling on the interface deflecting separately into the clad, the interface and the substrate were built, and the relations between the CPs and the load action angle, the clad thickness ratio and the load were investigated with an example. The research results show that, under the research conditions, the interface crack will more easily propagate into the clad layer than into the substrate.