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Nowadays, fracture characterization of dissimilar materials adhesively bonded structures still generally refers to standards for fiber‐reinforced plastic composites. Moreover, the calculation methods of fracture energy release rate specified in these standards often lead to great deviation due to the differences in material properties and geometry. In this paper, dissimilar materials corrected beam theory with effective crack length (DM‐CBTE) method for calculation of mode II fracture energy release rate of dissimilar materials adhesively bonded structures was proposed. The differences in material properties and geometry as well as the effect of clamp were all considered. The experimental and J‐integral numerical analysis results showed that the maximum deviation of the GIIC calculated by the methods recommended in standard from the J‐integral result is 28% while that by the DM‐CBTE method is only 5%, which proved good feasibility of the DM‐CBTE method for evaluation of mode II fracture performance of dissimilar materials adhesively bonded structures. Highlights: DM‐CBTE method for GII of dissimilar materials adhesively bonded samples was proposed.The differences in material, geometry, and clamp correction were all considered.Good feasibility of the DM‐CBTE method for evaluation of GII was validated. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical behavior of 10 and 14 vol.% SiCp/Al composites was studied with both experiments and numerical analysis. A 3D macrostructure model based on modified Gurson–Tvergaard–Needleman (GTN) model was developed to predict the elasto‐plastic response and fracture behavior of particle reinforced aluminum matrix composites (PRAMCs). The particle size effects on the plastic strengthening induced by geometrically necessary dislocations (GNDs) were introduced, and the size distribution of the SiC particles was obtained according to the statistical analysis of the microstructure. The material parameters for GTN model were determined with a parameter identification process, and the validity of the numerical results was validated by the agreement of the experimental stress–strain curve. Results reveal that particle size randomness plays an important role in the fracture morphologies. Highlights: Establish a macro‐mechanical model to predict failure behavior of PRAMCs.Modify the GTN damage model to introduce the effect of particle failure and decohesion.Identify the parameters for the modified GTN model and validate the model by comparing with experimental results.Find that particle size randomness plays an important role in fracture morphologies. [ABSTRACT FROM AUTHOR]

The present paper is dedicated to the mechanical and fracture characterization of a specific earthen material, that is, the shot‐earth 772. Although such a material has been recently characterized from a microstructural, chemical and physical point of view, the knowledge of its mechanical and fracture properties (essential for extending its use in construction industry) is still lacking. Such characterizations are here performed both experimentally, through laboratory tests, and numerically, through a FE model. The experimental tests (i.e., flexural, compression, and fracture tests) are carried out on shot‐earth specimens according to recommendations available for concrete and a method proposed by the present authors, named Modified Two‐Parameter Model. The numerical analyses are performed by employing a micromechanical model (implemented in a nonlinear 2D FE homemade code), which allows to simulate both flexural and fracture behavior of the shot‐earth examined. Finally, the obtained numerical results are compared with the experimental ones. Highlights: The mechanical and fracture characterization of shot‐earth 772 is performed.Flexural, compression and fracture tests are carried out on the shot‐earth specimens.Numerical analyses are performed by using a homemade micromechanical finite element model.Flexural behavior and fracture behavior of shot‐earth 772 are numerically simulated. [ABSTRACT FROM AUTHOR]

This paper suggests a simple loading configuration for conducting the SCB (semi‐circular bend) tests on brittle materials to produce mixed mode I/III loadings. In the suggested test setup, the SCB specimen containing an inclined crack is loaded using a conventional three‐point bending fixture, but the bottom supports touches nearly half of the specimen thickness rather than the entire thickness. It is found that various mixed mode I/III loadings can be provided by rotating the crack, and especially the SCB specimen experiences pure mode III when the crack angle is set to be 90°. Different values of the crack length, span and crack angle are then considered in the numerical analyses to further study the proposed SCB test setup. Finally, several experiments are successfully conducted on the rock samples under various mixed mode I/III and pure mode III loadings to evaluate the SCB test setup in practical point of view. Research highlights: A simple loading configuration is suggested for conducting the SCB tests.Mixed mode I/III and pure mode III tests can be performed using the SCB specimen.Effects of crack length, span and crack angle in the SCB tests are numerically explored.Mode III has a negative effect on the fracture resistance of rock materials. [ABSTRACT FROM AUTHOR]

Inclusion is one of the main causes for unqualified wire. However, the forming mechanism of drawing fracture due to inclusions is still unclear. Therefore, it is significant to figure out the forming mechanism of wire drawing fracture with inclusions for designing and manufacturing high‐quality wires. In this paper, a physical model of wire with inclusion is established based on experimental observations. Multipass drawing is simulated by using finite element method (FEM) with the developed numerical damage modeling. Numerical results demonstrate that the damage increases with the development of drawing progress, and the damage caused by high elastic modulus of inclusion is greater than that of low elastic modulus. Pen‐tip shaped fracture of wire with inclusions is mainly caused by the superposition of core and external V‐shaped damage. Furthermore, the core V‐shaped crack will propagate along the external V‐shaped damage area. [ABSTRACT FROM AUTHOR]

The paper concerns an experimental study on the crack deflection angle in a semi‐circular disc made of an alkali‐activated fine‐grained composite under mixed‐mode conditions. This study is supplemented by an extensive numerical analysis that calculates the crack deflection angles via generalized (multi‐parameter) fracture criteria. It is proved that the use of higher‐order terms of the Williams expansion for the approximation of the crack‐tip stress field leads to more accurate results. The influence of various parameters on the crack deflection angle is discussed, and recommendations on their proper choice are presented. The conclusions help in describing the crack behaviour under mixed‐mode conditions more accurately. [ABSTRACT FROM AUTHOR]

Polymeric foams have good capacity of absorbing energy in compression but are brittle in tension. Linear elastic fracture mechanics is successfully applied to assess the integrity of polymeric foam‐based composite structures. The fracture toughness represents an important parameter. The different approaches to estimate the fracture toughness of polymeric foams are reviewed: analytical and numerical micromechanical models and experimental investigations. Focus is given on the parameters influencing the fracture toughness of polymeric foams like specimen type, solid material, density, loading speed, size effect and temperature. Data on mixed‐mode loading and dynamic fracture toughness are also presented. The last part of the paper presents some results to increase the fracture toughness by reinforcing of polymeric foams. [ABSTRACT FROM AUTHOR]

This paper proposes a node release approach to estimate the fracture resistance curve, often known as the J‐R curve, for monotonic and cyclic fracture tests. The node release approach simulates the crack extension by releasing the constraints imposed on the node at the crack tip and estimates the J‐R curve by coupling the domain integral value with the corresponding crack extension. This proposed node release approach estimates closely the J‐R curve for SE(B) and SE(T) specimens subjected to monotonic loading. For SE(T) specimen under cyclic loading, this study implements the node release analysis in two approaches: (1) an equivalent monotonic analysis corresponding to the envelope of the cyclic load‐CMOD response and (2) a direct cyclic simulation. Both approaches lead to close estimations of the experimentally measured J‐R curve. The numerical analysis also confirms the path independence of the domain integral values in the direct cyclic simulation. [ABSTRACT FROM AUTHOR]

Cracking is an important phenomenon in the failure of geomaterials. The prediction of crack paths is difficult and challenging because of the randomness and uncertainty in the cracking behaviors of geomaterials. In this paper, to predict crack paths based on 2D X‐ray computed tomography (CT) images, a digital energy grade‐based approach is proposed, and the corresponding energy principle is established. Excellent consistency of crack paths is found between the predicted crack path and the real crack path of the specimen. The numerical results indicate that the proposed approach provides a useful way to predict cracking paths in geomaterials. Meanwhile, the stress and displacement fields before and after the specimen fails can be obtained by combining the proposed method with finite element (FE) analysis. In total, this proposed method can be applied not only to monitoring the health of but also to the stability analysis of engineering structures during engineering activities. [ABSTRACT FROM AUTHOR]

Abstract: This paper studies the length effect on fatigue life of longitudinal element at the macroscale. An asymptotic weakest‐link Weibull phenomenological model that incorporates a statistical length effect for the fatigue life of longitudinal element is proposed in this research. In the proposed model, the weakest‐link effect gradually becomes dominant and causes a decrease in fatigue life that increases along L ̂, the normalized length of the longitudinal element. To this end, the fatigue life under a specified stress range is divided into 3 zones according to the normalized length L ̂: (1) L ̂ ≤ 1 is the zone where length effects can be ignored, and the fatigue life can be treated as a random variable; (2) 1 < L ̂ < L ̂ ρ is the zone where the fatigue life is length dependent; and (3) L ̂ ≥ L ̂ ρ is the zone where the fatigue life follows asymptotic length dependence. The asymptotic threshold normalized length, L ̂ ρ, can be evaluated by the asymptotic weakest‐link Weibull model. To validate the proposed model, 3 previously published datasets are used: (1) the fatigue data of Picciotto yarn, (2) hipo‐eutectoid steel wire with different lengths, and (3) the fatigue data of high‐strength steel wire with different lengths and different constant stress ranges. Finally, the results obtained by the proposed model are compared with those from the literature and discussed in detail. The analytical solutions obtained using the proposed model allows for assessment of the fatigue life of certain components and structures that are beyond current testing capabilities. In particular, the length effects on the fatigue life of the high‐strength steel wire in stay cables are investigated to gain insight into issues regarding safe designs. [ABSTRACT FROM AUTHOR]

Geometrical discontinuities such as notches need to be carefully analysed by engineers because of the stress concentration generated by them. Notches become even more important when the component is subjected, in service, to very severe conditions, such as high-temperature fatigue and imposed viscoplastic behaviour such as creep. The knowledge of strains and stresses in such stress concentration zones is essential for an efficient and safe design process. The aim of the paper is to present an improvement and extension of the existing notch-tip creep stress-strain analysis method developed by Nuñez and Glinka, validated for U-notches only, to a wide variety of blunt V-notches. The key in obtaining the extension to blunt V-notches is the substitution of the Creager-Paris equations with the more generalized Lazzarin-Tovo solution, allowing a unified approach to the evaluation of linear elastic stress fields in the neighbourhood of both cracks and notches. Numerous examples have been analysed to date, and the stress fields obtained according to the proposed method were compared with appropriate finite element data, resulting in a very good agreement. In view of the promising results discussed in the paper, authors are considering possible further extension to sharp V-notches and cracks introducing the concept of the strain energy density. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on calculating and analysing the thickness and load level influence on the stress intensity factor distribution along the thickness, both individually and together. The main objective is improving the knowledge about the small region existing near the surface where the stress intensity factor results remain independent of external factor as load level or thickness. It is found that this phenomenon occurs around a pivot node within the crack front (PI) that presents advantages for the correlation of numerical and experimental studies. The work evaluates the finite element model of an Al 2024‐T35 compact tension specimen with no plastic wake effect introduced. The three‐dimensional behaviour near the crack front is simulated through numerical analysis with ANSYS code, and J‐integral method is used to determinate the curves of K evolution along the thickness. The results are studied according to a series of parameters that characterize the curves. Conclusions are presented on the areas of influence of each factor involved. [ABSTRACT FROM AUTHOR]

This paper is focused on the methodological aspects of the numerical study of stress intensity factor (SIF) evolution through thickness. The work evaluates the modelling of an Al-alloy 2024-T351 CT specimen under mode I nominal loading in fracture. No plastic wake effect is introduced to separate the influence of plasticity-induced crack closure near the surface. Numerical models have shown the complexity 3-D behaviour in the vicinity of the crack front and finite element methods (FEM) are widely used in these problems with interesting results. However, there is a lack of literature support in many simplifying assumptions. In previous studies, authors have analysed some issues as the evolution of the plastic zone, the crack closure stress or the SIF. The current work attempts to describe and justify the key aspects of the methodology developed to address these problems by the FEM. A huge effort has been made to study main parameters involved and their influence in the results, especially in order to properly capture the SIF distribution along the thickness. Recommendations about mesh density are provided, and the main procedures to obtain K are discussed. [ABSTRACT FROM AUTHOR]

In this paper, numerical methods of fatigue life prediction for elastomers subjected to multidirectional, variable amplitude loadings are presented. Because experiments and numerical methods use different stress measures in large deformation, transformation between nominal stress and the second Piola-Kirchhoff stress is performed before fatigue life calculation. In order to incorporate the Mullins effect, the material properties of elastomers are calculated after an initial transition period. An efficient interpolation scheme using load stress/strain curves under unidirectional loading is proposed based on the fatigue characteristic of elastomers. A rainflow counting method with multi-stress components is developed for variable amplitude loadings, and the critical plane method is applied to find the plane with the maximum damage parameter. Fatigue life predictions using the proposed numerical method are validated against experimental results. As a practical example, the fatigue life of a rubber engine mount is predicted using the proposed numerical method. [ABSTRACT FROM AUTHOR]

In this paper, impact damage behaviours of C/SiC rigid-felt titanium alloy three-layered plate under normal impact are investigated. First, low velocity impact experiment of the three-layered plate is performed by means of a drop weight impact apparatus. Second, the finite element model of the three-layered plate is established using a damage constitutive model; also, the influences of the initial kinetic energy (the initial velocity and the mass of the impactor) on stress distributions and damage patterns of the three-layered plate are analysed. Finally, the energy dissipation mechanisms and failure characterizations of the three-layered plate are discussed; also, the agreements of physical variables and damage morphologies between experimental and numerical results validate the reliability of numerical simulation. The results will play an important role in designing and evaluating advanced thermal protection structure. [ABSTRACT FROM AUTHOR]

In this paper, the growth of long fatigue cracks up to failure in aircraft components is studied. A deterministic model is presented, able to simulate the growth of fatigue through cracks located at rivet holes in lap-joint panels. It also includes criteria to assess the link-up of collinear adjacent cracks in a MSD scenario. To validate the model, a fatigue test campaign was carried out on riveted lap-joint specimens in order to produce experimental crack growth and link-up data. Accurate measurements of naturally occurred surface cracks were automatically performed by the Image Analysis technique, thus allowing the tests to run 24 h a day. The comparison between experimental tests and numerical simulations is good, thus confirming the model as a useful tool for the assessment of fatigue life of aircraft riveted joints. [ABSTRACT FROM AUTHOR]

ABSTRACT In fatigue design of welded joints, the local approach based on the notch stress intensity factor (NSIF) assumes that the weld toe profile is a sharp V-notch having a tip radius equal to zero, while the root side is a pre-crack in the structure. The ratio between the mode I NSIF and the linear elastic opening peak stress evaluated at the point of singularity (i.e. the V-notch tip) by the finite element (FE) method depends only on the type and size of the elements adopted in the discretization. The ratio between the mode II SIF and the linear elastic sliding peak stress evaluated at the crack tip has the same property. This useful property of the opening and sliding peak stresses evaluated by the FE method gives rise to the so-called peak stress method (PSM). In the present paper, it is adopted as an engineering, FE oriented application of the NSIF approach to fatigue design of welded joints. Originally applied to 2D FE models, the peak stress method is combined here with 3D numerical models to assess the fatigue strength of steel welded joints having complex geometry and characterised by toe as well as root cracking. A properly defined design stress, that is, the equivalent peak stress, is shown to correlate with good approximation all analysed experimental data. [ABSTRACT FROM AUTHOR]