Interaction Effect Of Cracks Research Articles

Influence of crack configurations of asphalt mortar on the loading response characteristics of cracks under low-temperature conditions

Asphalt mortar is the base material used in asphalt concrete, and its mechanical properties directly affect those of the prepared asphalt concrete. An analysis of the loading response characteristics of cracks in asphalt mortar under low-temperature conditions can help reveal the interaction effect of multiple cracks in asphalt concrete and the influence mechanism of aggregates on the crack propagation and evolution behaviors. In this study, various forms of pre-cracks were generated in asphalt mortar specimens using the water jet cutting technology. Combined with the discrete element method (DEM), an indirect tensile (IDT) test and a virtual IDT test were conducted to analyze the effects of the crack deflection angle (β) and crack length (r) on the crack propagation behavior from macro- and meso-perspectives. The main results showed that: (1) Changes in the crack shape parameters (β and r) not only induced multiple branch cracks in the asphalt mortar but also led to the development of II Mode fractures; (2) With the increase in the crack shape parameters, the low-temperature crack resistance of the asphalt mortar decreased, with β having a greater effect on the crack propagation behavior than r; (3) At the mesoscale, with the increase in the crack shape parameters, there was a gradual transformation of the fracture mode from I Mode to II Mode, and the crack propagation process accelerated, resulting in a significant decrease in the low-temperature crack resistance at the macroscale. The research results establish a theoretical foundation for revealing the characteristics of multi-crack propagation in asphalt concrete under environmental influences, and offer technical support for pavement crack repair and maintenance.

Characteristics of crack growth in brittle solids with the effects of material heterogeneity and multi-crack interaction

AbstractDespite the extensive research on crack propagation in brittle solids, numerous unexplored problems still necessitate in-depth study. In this work, we focus on numerical modeling of multi-crack growth, aiming to explore the effect of material heterogeneity and multi-crack interaction on this process. To do this, an improved singular-finite element method (singular-FEM) is proposed with incorporation of heterogeneity and crack interaction. An efficient algorithm is proposed for simulating multi-crack propagation and interaction. Stress singularity near crack tip is reproduced by the singular elements. The singular-FEM is convenient and cost-effective, as the zone far away from crack tips is directly discretized using linear elements, in contrast to the quadratic or transition elements utilized in traditional FEM. Next, the proposed method is validated through benchmark study. Numerical results demonstrate that the superiority of the singular-FEM, which combines the merits of low cost and high accuracy. Then, the mechanics of crack growth are explored in more complex scenarios, accounting for the effects of crack interaction, loading condition and heterogeneity on crack trajectory, stress field and energy release rate. The findings reveal that the combined effect of heterogeneity and crack interaction plays a critical role in the phenomenon of crack growth, and the proposed method is capable of effectively modeling the process.

Atomistic simulations of pore-crack nano-interaction in Indium-monochalcogenides monolayers

A comprehensive MD analysis of cracked and porous InX structures (X = Se, Te) is performed to elucidate the mechanical properties and fracture behavior. The results show that fracture stress degrades as crack length and pore diameter increase, inducing a power-law relationship between stress and structural integrity. The effect of nanoscale crack-pore (CP) and main crack-auxiliary crack (MC-AC) interactions shows that depending on the positions of pores/auxiliary cracks around the main crack, the ultimate tensile stress can decrease or amplify. The simulations demonstrate that the CP and AC lead to a stress reduction in the area near the crack tip, which retards the fracture process. The CP strategy can enhance fracture strength more efficiently than AC. Finally, the fracture mechanism highlights that branching predominates for applied tension in the zigzag direction. Such a study is an adequate framework towards the advanced stress-engineered based design of InX structures and their counterparts.

Numerical Investigation of Thermoelastic Crack Interactions in Various Materials using a Novel Enrichment Approach

Crack interaction studies play a crucial role in understanding and predicting the fracture behaviour of various engineering components subjected to thermomechanical loads. The present work investigates the interaction effect of multiple cracks in different types of material subjected to thermoelastic loadings using Element free Galerkin method (EFGM). These materials include isotropic material, orthotropic material, functionally graded material, and layered material. These all materials are subjected to thermoelastic loads in presence of multiple cracks to investigate the effect of crack interactions. A novel modified Intrinsic enrichment has been proposed to precisely capture the interaction effect and stress fields in the presence of multiple cracks. The proposed algorithm has been tested for a benchmark problem and it produced better stress fields in comparison to the conventional EFGM procedure. Stress intensity factors corresponding to variations in crack parameters have been evaluated concerning with the primary crack. Results reveal that presence of multiple cracks alters the crack tip stress fields owing to the interaction effect i.e shielding or amplification. Additionally, parameters such as crack length, crack orientation, distance between cracks, and domain properties greatly influence the stress intensity factor of the primary crack. These parameters exhibit varying behaviour under distinct circumstances, and their effects have been thoroughly analysed. Current work provides valuable insights into the effects of crack interactions in different media under thermoelastic loadings, thereby ensuring the structural integrity and durability of these materials for practical applications.

Facilitation effect of multiple crack interaction on fatigue life reduction and a quantitative evaluation of interactions factor of two parallel Non-coplanar cracks

Synergistic/interaction action of the multiple cracks can be clearly observed from fracture topography of the post-fatigue test specimen. Based on experimental observations, the interactions of two parallel non-coplanar cracks mounted in double-edge crack specimens under tension loading are investigated. The stress intensity factor (SIF) for a wide range of crack configurations is established using three-dimensional finite element analysis (FEA), and the effects of multiple crack interactions on the SIF values are studied. The effects of crack interactions on the SIF are strongly dependent on the crack geometry. The greater the vertical distance between the two cracks, the more strongly the stress field at the tip of the main crack is impacted. The analytical solutions for calculating SIF under effect of the multiple crack interactions were derived in a matrix form and the accuracy of the estimated equation was confirmed.

Transient heat transfer analysis of an orthotropic composite plate with oblique cracks using dual-phase-lagging model

Cracks have a significant effect on heat transfer in composites, yet the influence of oblique cracks on the temperature response of composites has not been fully investigated under strong transient thermal shock, in which the heat propagation velocity cannot be assumed to be infinite. In this work, the dual-phase-lagging heat transfer model is employed to capture the transient temperature response. By imposing different boundary conditions on the crack surface, an extended boundary correction algorithm has been derived to avoid the problem of non-convergence when dealing with large and small angle cracks. The effects of crack orientation angle and interaction between cracks on dual-phase-lagging heat conduction in orthotropic materials are analyzed at the macroscale. For the two-dimensional representative volume element (RVE) of fiber reinforced composite material, the influence of the multi-crack distribution on dual-phase-lagging heat conduction at the mesoscale is further discussed in detail.

Effect of crack interaction and friction on the dynamic strength of rock-like materials with many cracks

Rock-like materials are heterogeneous and contain numerous defects. Under compression, the widely used two-dimensional wing crack models cannot accurately describe the three-dimensional behaviour of cracks because the three-dimensional secondary crack will wrap (curl) around the disc-shaped primary crack under uniaxial loading. Moreover, experimental results have shown that a single embedded crack expands easily when the lateral compression is higher than approximately 6% of the axial compression. To describe the three-dimensional behaviour of cracks under uniaxial compressive loading accurately, we propose a three-dimensional wing crack model that incorporates the crack propagation dynamics, the inertia effect, the dependence of the friction coefficient on the slip velocity of the crack faces, and the interaction between cracks. We numerically solve the crack propagation dynamics equation, crack interaction equations, friction coefficient equations, and constitutive equation to estimate the effects of the friction coefficient and crack density on the dynamic strength of samples containing mode I cracks. The numerical results indicate that as the crack density increases, the initiation of crack growth and failure of the sample both occur earlier, while the loading stress at the initiation and failure points decreases. The inertia-induced additional axial stress increases with increasing crack density. The failure of the sample occurs earlier at a lower loading stress when considering the modified friction law than when considering a constant friction coefficient.

Influence of dynamic-strain aging due to excess Mg on fatigue crack growth rate scatter in Al6061-T6 alloy

Fatigue failure results in high industrial costs, and its mechanism requires close examination; however, current methods are costly and time-consuming due to the need for a large number of test specimens. The purposes of this study are to investigate the influence of dynamic strain aging on fatigue crack growth rate (FCGR) scatter in Al 6061-T6 alloys and to present a new approach to evaluate the scatter of FCGR using a limited number of the test specimen. Rotating bending fatigue tests of 6061-T6-based Al alloys with added Zr and excess Mg were performed under constant amplitude loading using smooth specimens. The scatter behavior of FCGR is investigated by examining the fatigue crack growth on the specimen surface and fractographic observation on the fracture surface. The accounting for the interaction effects of multiple surface cracks and fractographic examination on striation formation from previous findings revealed that excess Mg promoted small scatter in Mode I fatigue crack growth. This study showed that local plastic deformation affected the FCGR scatter of microstructurally-large fatigue cracks. These findings suggest that dynamic strain aging of Mg induces stable Mode I crack growth due to pinning of dislocation movement on slip planes during the crack growth process.

Experimental Investigation of Interactions between Double Oblique Cracks on Crack Growth Behaviours under the Fatigue Loading

In this paper, the interaction of double oblique cracks is researched experimentally and numerally. Fatigue crack growth tests of both the single crack and double crack specimens are conducted to investigate the effect of crack interactions on fatigue crack growth behaviours. Results indicate that the oblique crack has a shielding effect on the crack growth length of the dominant crack. In addition, numerical simulations show that the stress intensity factors at the dominant crack tips in the double crack specimens are smaller than those at the crack tips in the single crack specimens, which explains why the growth length of the dominant crack decreases in the present of the oblique crack.

Study of Crack Interaction Effects Under Thermal Loading by Digital Photoelasticity and Finite Elements

The effect of an interacting internal crack on the edge crack in a transient thermal stress field is evaluated using digital photothermoelastic experiments and finite element (FE) analysis. Initially, a transient thermal stress field is simulated using FE analysis for which the thermal boundary conditions are set based on the experimental isochromatic fringes. In this simulated thermal stress field, single edge crack with and without an internal short crack interacting at different configurations are modeled and the non-dimensional Stress Intensity Factor (SIF) values are evaluated at different time intervals. It is observed that the asymmetric and collinear configurations tend to increase the SIF of the edge crack whereas a parallel crack tends to decrease the SIF of the edge crack. For experimental evaluation, specimens with a single edge crack and asymmetric configuration of interacting cracks are considered and the non-dimensional SIF values are evaluated under a thermal stress field generated by edge heating and cooling. The results are compared with those obtained using the FE analysis.

Stress and energy based prediction of crack distribution pattern in general cross-ply laminates

Stress and energy based criteria are proposed to predict transverse crack distribution pattern in cross-ply laminates. A unit cell based variational approach is developed to derive the stress state of the unit cell of a general cross-ply laminate containing multi-cracked layers with arbitrary sequence. The accuracy of the stress state is investigated compared to FEM results. The inter- and intra-laminar interaction effects of matrix cracks are investigated and discussed. Having the stress state for all plausible crack distribution patterns, the energy release rates are derived and compared as an energy based criterion to predict the distribution pattern. The stress based criterion is implemented in a step by step procedure. Initial matrix cracks are considered to form in one transverse ply and the stress redistribution due to the presence of the cracks is used to predict the location of next crack. the stress redistribution due to presence of new cracks is then derived and the position of the next cracks are predicted. The procedure of stress redistribution and prediction of next crack positions is continued until a uniform distribution pattern is achieved in all transverse plies. Both energy and stress based procedures are described and implemented to predict the crack distribution patterns of some specific layups. The results are shown to be in agreement with experimental observations.

Fatigue Growth Behaviour of Two Interacting Cracks with Different Crack Offset.

Under cyclic fatigue load, multiple cracks would significantly deteriorate the service life of the components with respect to the case of a single crack owing to the crack interaction. The present study aims to explore the effect of crack interaction on the fatigue growth behaviour of samples with different crack offset. In this study, fatigue crack growth tests were performed for samples containing a single crack and non-collinear cracks of different crack offset in an aluminum–lithium alloy. It was shown that the two facing non-collinear cracks changed their growth direction when the cracks were overlapped, resulting in load mode transfers from mode I to I + II mixed mode. Then, the interaction behaviour was studied by establishing the finite element models to calculate the stress intensity factor K of samples with different crack offset. The results indicated that the K decreased, largely owing to the shielding effect as the two cracks overlapped, leading to retardation of crack growth in the position of overlap, especially for the specimens with a small crack offset. It was also shown that the interaction effect could change from positive to negative during the process of the multiple cracks’ growth, thus leading to the acceleration or deceleration of crack growth rates, suggesting that the influence of interaction on cracks’ growth behaviour could vary with the different stages of crack growth.

Effect of crack interaction on dynamic behavior of rockunder impact

<p indent="0mm">Rock contains numerous cracks, which will interact mutually under the action of external loads. This research based on the wing crack model, the interaction of Mode I cracks is considered for square and hexagonal configurations of crack distribution, and the effect of crack interaction on rock dynamic behavior is studied. Using crack motion equation and loading equation, the effect of crack concentration on dynamic deformation and fracture is investigated numerically. Numerical results show that, the greater the crack density is, the more intensive the crack interaction is, the lower the failure strength is, and the greater the inertia-induced additional axial stress is.

Effect of micro-macro crack interaction on softening behaviour of concrete fracture

During the fracture of concrete the formation of microcracks is a continuous process where new microcracks are formed in the vicinity of the macrocrack. As the fracture grows, these microcracks interact with the macrocrack and disrupt its smooth opening. In fracture mechanics based approaches; a smooth stress-crack opening softening behaviour is generally used to describe the local fracture process, where the effect of micro-macro crack interactions is lacking. This paper presents firstly an experimental study on the interaction between microcracking and the macrocrack opening (COD) in concrete using digital image correlation and acoustic emission techniques. The study reveals a transient behaviour of macrocrack opening as microcracks are formed in the surrounding. Based on the experimental results, the paper presents a new approach based on fracture mechanics to consider the effects of micro-macro crack interaction on the stress-crack opening softening behaviour. Local fracture energy is determined using the new softening model with micro-macro crack interaction for different geometrically similar sizes of the beams and at different locations on the crack profile.

Study of interaction effects of asymmetric cracks under biaxial loading using digital photoelasticity

Closely spaced asymmetric cracks in a biaxial cruciform specimen interacting at different orientations is studied by digital photoelasticity. Isochromatic fringe patterns are captured under biaxial loading conditions with varying biaxial ratios from 0 to 1, zero indicating uniaxial loading and one indicating equi-biaxial loading. Stress Intensity Factors (SIFs) are determined using corrected Atluri-Kobayashi multiparameter stress field equation in conjunction with over-deterministic least squares method. The SIF values calculated are normalized with the SIF for a single crack and compared with finite element results. The comparison is found to be good. For a single central crack in a cruciform specimen, when the biaxial ratio is increased from 0 to 1, only shielding is observed. On the other hand, for two asymmetric cracks both amplification and shielding effects are seen that are dependent on the crack-tip under consideration, crack interaction angle and biaxiality ratio. Empirical relations to estimate the normalized SIF under different biaxial ratios are also given.

On the anisotropy of cracked solids

We consider the effective elastic properties of cracked solids, and verify the hypothesis that the effect of crack interactions on the overall anisotropy – its type and orientation – is negligible (even though the effect on the overall elastic constants may be strong), provided crack centers are located randomly. This hypothesis is confirmed by computational studies on large number of 2-D crack arrays of high crack density (up to 0.8) that are realizations of several orientation distributions. Therefore, the anisotropy can be accurately determined analytically in the non-interaction approximation (NIA). Since the effective elastic properties possess the orthotropic symmetry in the NIA (for any orientation distribution of cracks, including cases when, geometrically, the crack orientation pattern does not have this symmetry), the orthotropy of cracked solids is not affected by interactions.

Interaction effect of cracks and anisotropic influence on degradation of edge stretchability in hole-expansion of advanced high strength steel

Edge stretchability has become an important performance index in automotive sheet metal component manufacturing. In this paper, a quantitative method has been introduced to evaluate effects of punching of sheet metal on the degradation of its edge stretchability with the employment of the index, Effective Failure Strain Ratio (EFSR). The magnitude of EFSR depends on the severity of damages expressed as the imperfection value in M–K model, which corresponds to the edge damage caused by preprocessing such as punching. Based on the method, numerical studies were conducted to investigate the interaction effect of cracks and anisotropy influence on the degradation of edge stretchability. Results of hole-expansion simulations with two damage zones preset showed that cracks at different locations along the edge developed with high independence. Results of simulations under different anisotropy in term of R¯ and Δr showed that the degradation of edge stretchability of materials with lower anisotropic coefficient (r-value) was more sensitive to the edge pre-damage. According to simulations, for transversely anisotropic materials, cracks were prone to appearing along the direction with the lowest r-value within the sheet plate. Punching and hole-expansion experiments using Dual Phase (DP) steel were conducted to validate the conclusions. The locations of the firstly appearing cracks on specimens were coincident with simulation results.

Interaction effect of cracks on flutter and divergence instabilities of cracked beams under subtangential forces

The dynamic stability of cracked beams under conservative and non-conservative forces and for various boundary conditions is investigated. In order to extend the formulation of a previous paper by the first two authors, here doubly cracked Euler–Bernoulli beams subjected to triangularly distributed subtangential forces are considered. Cracked sections are modelled through the theory of fracture mechanics and involve a line-spring stiffness matrix. The finite element method (FEM) is used to perform numerical computations. The stability maps, obtained from the eigenvalue analysis, define the divergence and flutter domains. The proposed procedure can also tackle general multi-cracked beams.

Evaluation of &lt;i&gt;J&lt;/i&gt; Integral for Interacting Twin Collinear Through-Wall Cracks in a Plate under Tension

The interaction behavior of twin collinear through-wall cracks in tension loaded plate under elastic-plastic condition is investigated by the finite element method (FEM). The fracture parameter J integral for interacting cracks is calculated and compared to the J integral for a single crack the same size. In this way, the interaction factor of cracks under elastic-plastic condition is defined. This interaction factor is compared to the results of analytical solution of the interaction factor under linear elastic condition. The results show that interaction factor of cracks under elastic-plastic condition is higher than interaction factor of same cracks under linear elastic condition. Also the interaction effect of cracks under elastic-plastic condition is influenced not only by the crack configurations but also by the material properties, especially the strain hardening exponent n.

A numerical creep analysis on the interastion of twin parallel edge cracks in finite width plate under tension

In many practical situations, high-temperature structures and components contain more than one crack. An interaction of such multiple cracks has significant influence on the service life of structures and components. In this paper, the interaction of two identical parallel edge cracks in a finite plate subjected to the remote tension is numerically analyzed. The results show that interaction effect of multiple cracks at creep regime is obviously greater than at linear elastic regime. The intensity of creep crack interaction increases with increasing creep exponent m. The crack intensity and the crack interaction limit at creep regime depend on crack distance ratio d/a, crack width ratio a/W and creep exponent m.