International Journal of Fracture最新文献

Key microstructural features such as grain size, grain shape, crystallographic orientations, and grain boundary properties strongly influence fracture resistance of ceramics. Well-designed microstructural features contribute to the materials’ ability to withstand dynamic loading and deformation by facilitating mechanisms that dissipate energy and prevent catastrophic failure. In this research, a microstructure-explicit and fracture process-explicit computational framework is employed to better understand how these microstructural features impact the dynamic fracture response of SiC during high-rate compression loading and spallation. Utilizing the cohesive finite element method (CFEM), the model incorporates anisotropic bulk constitutive and fracture behaviors of grains and misorientation angle-dependent grain boundary properties to resolve complex crack paths and fracture patterns. The model also captures the effects of intergranular and transgranular fracture, and friction between crack faces. A key observation is that grain size gradient can be utilized to balance and optimize both compressional energy dissipation and spall strength. Additionally, it was shown that the effect of crystallographic texture on spall strength is strongly dependent on both the volume fraction and orientation of preferentially aligned grains. Lastly, the study finds that the anisotropic fracture behavior of the grain boundary has a more pronounced effect on both spall strength and energy dissipation than the degree to which anisotropy changes as a function of misorientation angle. The findings provide insight into microstructural features that optimize energy dissipation and spall strength under specific loading conditions. Furthermore, the model framework can be extended to guide the microstructural design of other ceramics and ceramic composites.

Stair-like wavy cracking commonly arises in brittle laminated materials due to the interplay between heterogeneous mechanical properties of layered structures and external boundary conditions. Based on the energy release rate (ERR) criterion and the straight-crack equivalence assumption, we derive an explicit solution for the continual kinking conditions under which crack propagation in brittle laminates through repeated kinking (stair cracking) governed by three parameterized factors. The theoretical solution yields phase diagrams mapping three fracture modes determined by (1) the ratio between the critical fracture toughness when cracking along the interface (({G}_{text{dc}})) and that during traversing fracture (({G}_{text{mc}})), (2) the angle between the initial crack and interfaces, and (3) the stress ratios of boundary conditions. Such an efficient engineering approach, with ERR playing the central role, achieves high accuracy in predicting crack path patterns, as validated through finite-element simulations.

The mechanisms of void-mediated dynamic ductile failure are discussed in the context of a recently proposed indicator of void coalescence. The indicator is developed based on unit cell calculations within the confines of a continuum description and inertial effects. Here, it is shown that this indicator may inevitably be satisfied in a loading program as a mere consequence of pressure-sensitive plastic flow. Furthermore, insofar as an indicator is not just meant to interpret unit cell results, but rather be used in structural simulations of dynamic failure, the proposed indicator cannot be used as basis to develop a void coalescence criterion. When interpreted in light of recent advances in micromechanical modeling of void growth and coalescence, the reported on unit cell calculations are found to confirm the conclusions of prior work in the literature, the most important of which being that dynamic loading may frustrate internal necking as a potent mode of void coalescence such that the latter would rather occur by mere impingement. A basic formulation of concurrent failure criteria (internal necking versus impingement) under dynamic loading conditions is presented with open questions highlighted for future research.

The aim of this study is to develop and apply a semi-analytical approach to determine the critical parameters of stability loss under compression of a bilayer consisting of a thin film on a semi-infinite substrate in the presence of an interface delamination of a given length. Using the methods of three-dimensional linearized stability theory, the corresponding boundary value problem is reduced to an eigenvalue problem with respect to the parameters of the compressive loading for a system of Fredholm integral equations of the first kind, which is solved numerically. Since the components of the bilayer are considered as hyperelastic materials with an arbitrary form of elastic potential, the obtained results cover a wide range of mechanical characteristics – both in the small and finite (large) deformation modes. Based on examples involving specific types of elastic potentials, the influence of the constitutive model on the critical parameters of stability loss is investigated. For cases of relatively short and relatively long delaminations, a comparison of the results obtained using the proposed approach is made with the results obtained using known approximate approaches used to estimate critical wrinkling and buckling deformations, respectively. In the case of intermediate-length delaminations, it is shown that due to the interaction of wrinkling and buckling mechanisms, the critical values of relative compression in the bilayer are significantly lower than those predicted by the approximate models. At the same time, the obtained results are in good agreement with the results of numerical simulations reported in previous studies and, thus, can be used to predict the onset of interfacial failure in compressed bilayers with thin films.

This study introduces a theoretical and numerical model for the spontaneous nucleation and propagation of distributed brittle fractures in initially intact materials. The formulation adopts a kinematic description of nested discontinuities characterized by a micromechanical interface law accounting for cohesion, unilateral contact and friction. The model allows for a unified treatment of the mixed-mode frictional fracture. The implementation of the model into a finite element framework is validated against benchmark tests, exhibiting independence of the discretization. The solution of selected quasi-static boundary value problems demonstrates the predictive capabilities of the framework in capturing key features observed in laboratory tests and in field problems involving confined quasi-brittle materials.

In the present work, macro-mechanical modelling of reinforced concrete structures under corrosion is performed. A traction based damage model is adopted. A discrete crack approach is used to model the fracture behaviour of concrete. The bond-slip relation between reinforcement steel and concrete is continuously evolving under corrosion, as a function of corrosion level and stress state. This is a non trivial issue, which is dealt with taking into account a total approach. Other corrosion aspects considered in this work are the reduction of the sane cross section of the reinforcement steel as well as spalling of the concrete cover. Bending tests are performed to evaluate the influence of corrosion at structural level, namely the increase of deformation as well as the decrease of the strength of the structure, leading to premature failure. Furthermore, stirrup confinement, in association with spalling, and slippage of the anchorage zone are analyzed.

In recent years, there has been growing interest in using acoustic emission (AE) time series data to develop fracture precursors for predicting imminent failure in cementitious materials. In this context, natural time (NT) analysis used in seismology has proven to be a useful tool, offering insights into the critical stage, namely the region of criticality, that precedes the mainshock event. Therefore, in the present study, the occurrence of impending macroscopic fracture in cementitious composites is predicted using the NT analysis of acoustic emission. To achieve this, the parameters of natural time, namely the variance, (kappa _{1}), the change in entropy, (Delta S), and the complexity measure, (Lambda _{i}), were utilized as precursors. Furthermore, the Tsallis q-index, obtained from the non-extensive statistical mechanics framework, was used in conjunction with the NT parameters. It was observed that the NT parameters, (kappa _{1}) reached a critical value of 0.07, (Delta S) attained a global minimum, and (Lambda _i) exhibited an abrupt increase before the mainshock event, similar to that observed in seismicity prior to major earthquakes. Furthermore, a sudden drop in Tsallis q-index was observed before the mainshock event. In addition, the behavior of the cementitious composite material closely resembled that of the Olami–Feder–Christensen earthquake model, as evidenced by the significant increase in cumulative AE energy observed after the region of criticality. Therefore, (kappa _{1}), (Delta S), and (Lambda _i) in combination with the q-index could be utilized as precursors for detecting impending macroscopic fracture in cementitious composites.

Fracture mechanics, originating from Griffith’s pioneering theory, has evolved into a foundational framework for understanding and predicting material failure across scales. Over the past century, it has expanded from linear elasticity to encompass nonlinear, dynamic, and stochastic behaviors—capturing fracture, fatigue, rupture, damage, and fragmentation in materials ranging from metals and ceramics to polymers, composites, soft matter, and biological tissues. Despite these advances, the field is far from complete. As modern materials and structures operate under unprecedented extremes of size, rate, and environment, classical assumptions—continuum validity, small-scale yielding, and singular field dominance—are increasingly challenged.

This Perspective identifies 25 outstanding issues that delineate the current and emerging frontiers of fracture mechanics. Organized across three interrelated domains—theoretical foundations, material behavior, and engineering applications—these issues span the limits of continuum theory, attainable fracture toughness, multiscale crack coalescence, fracture under extreme environments, and the integration of artificial intelligence for data-driven modeling. Collectively, they highlight a paradigm shift toward multiscale, multiphysics, and information-rich approaches that bridge atomistic processes and macroscopic failure. Far from a mature or closed discipline, fracture mechanics remains an evolving science—one that will continue to play a central role in designing materials and structures with unprecedented strength, toughness, and resilience in the century ahead.

In this work, a new damage model for cohesive fracture is presented. The concept of damage driving mechanism is introduced, from which the damage evolution law is derived. Special attention is paid to non pure mode-I and mode-II fracture modes, such as mixed-mode fracture and mode-II fracture under compression. Conversely to the previous traction-based damage model (Alfaiate et al. 2023), where the damage variables are derived from uniaxial tensile and shear relationships, the damage variables are now obtained explicitly from reference traction-jump displacement relationships, leading to an integration of fracture mechanics concepts with a damage mechanics approach. In this way, it is possible to explicitly control the dissipation of energy. The model is aimed at the simulation of the behaviour of reinforced concrete structures under corrosion. Corrosion affects i) cracking, which is modelled with a discrete crack approach, ii) bond-slip degradation between steel and concrete, iii) the reduction of the sane cross section of the reinforcement steel and iv) spalling of the concrete cover. In this work some illustrative examples of the performance of the model are shown. In part II, examples of reinforced concrete structures with and without corrosion are presented.

Laser powder bed fusion (LPBF) imposes steep thermal gradients, resulting in distortion and the formation of significant residual stresses, which often precipitate in-situ cracking at support interfaces and sharp geometric features. To isolate their influence on structural integrity, we combined fracture mechanics testing with residual stress evaluation on as-built compact tension specimens printed in two orthogonal orientations. The experimentally measured apparent stress-intensity factor was deconvolved into mechanical and residual-stress components, yielding a residual-stress-free fracture toughness (({K}_{ICeff})). Apparent fracture toughness (({K}_{IC})) ranged from 25 to 35 MPa m^1/2, whereas ({K}_{ICeff}) increased to 45–52 MPa m^1/2. Residual stresses, therefore, depress the material’s residual-stress-free resistance by up to ~ 50% and accentuate orientation-dependent anisotropy. The framework presented offers a route for quantifying process-induced toughness degradation in LPBF alloys.