Engineering Fracture Mechanics最新文献

Skeletal muscles are susceptible to injury during daily activities and competitive sports. Reliable prediction of tissue failure strength is a major challenge due to the large uncertainty in the mechanical behavior of skeletal muscle tissue. The present study reveals a strong correlation between histological characteristics and skeletal muscle failure strength by means of mechanical and histological experiments. We propose a data-driven hybrid modeling approach that enables an effective integration of data science and informatics tools to capture tissue failure strength. Uncertainty in the tissue failure strength is propagated into the posterior information of reduced model parameters via the Bayesian inference framework and parameter space compression. A histological enhancement to the softening hyperelasticity model is made by linking a quantified tissue-scale histological characteristic and stiff model parameters using artificial neural networks. The model is applied to skeletal muscle tissue from different species and sites to assess its predictive capabilities for physiological differences. The results show that the approach can achieve reliable predictions of skeletal muscle tissue failure strength. The proposed approach can be extended to different scales to enrich the understanding of structure–property linkages for biomaterials.

The excellent anti-corrosion resistance properties of duplex stainless steels (DSS) have made it a great choice material for engineering applications in corrosive environments. But it is still necessary to broaden the knowledge of these materials in hydrogen environments to know its susceptibility to embrittlement and the effects on mechanical properties. This paper focuses on studying the mechanical behaviour of DSS grade 2205 by means of tensile tests in pure hydrogen gas environment at different pressures (in-situ testing), avoiding electrochemical or ex-situ procedures that introduce uncertainties. Standard smooth and notched specimens following ASTM G142 have been used. Specimens have been machined in longitudinal and transversal orientations from a hot-rolled plate to study the anisotropy. The results show the influence of orientation on the mechanical properties. The tests at pressures ranging from 35 bar to 140 bar in hydrogen have a huge impact reducing the mechanical properties of DSS 2205 compared to tests in inert environments. Moreover, the failure mechanisms have been analyzed founding brittle behaviour characteristic of HE.

In industrial production, sheet metal rupture will inevitably occur in the process of forming, especially in the shape of complex, relatively small thickness of the sheet. It is vital to accurately predict the failure of ductile metals under various working conditions. To deal with the problem, an uncoupled ductile fracture criterion (DFC) for a broad range of stress states is proposed based on the micro-mechanism of ductile fracture of metals, which redefines the relationship between the number of void nucleating and the equivalent plastic strain and takes into account the different deformation modes of the voids in the growth stage. Then, in order to verify the validity and advantages of the proposed DFC, the 3D fracture surface of AA 2024-T351 and AISI 1045 steel are constructed by the new criterion based on their fracture data under various stress states, and compared with the commonly used DF2016 criterion and Hu criterion. The prediction results show that the new criterion is better than them, both in terms of the maximum prediction error and the average prediction error. Furthermore, to further prove the effectiveness of the proposed model, five samples are designed for tension tests to calibrate the new DFC using a hybrid experimental–numerical approach, and the calibrated criterion is applied to cupping simulations of AA 6061 and compared with cupping experimental results. The results indicate that the Erichsen cupping number (IE) of the cupping simulation and experiment are 6.88 mm and 7.05 mm, respectively, and the error between them is only 2.411 %, and the location of the fracture is also basically the same. Therefore, all comparison results show that the proposed DFC can forecast the fracture problem in sheet forming more accurately under various stress states.

A dynamic implementation of the coupled criterion under quasi-static loading, based only on the mean velocity during crack initiation, is proposed. It relies on a simultaneous node release method. It consists of computing the dynamic incremental energy release rate by simultaneously opening a crack of a finite length during a given time increment rather than progressively opening smaller crack increments following a velocity profile as in the progressive node release method. Both methods result in significantly different kinetic energy variations as a function of the crack length, and thus different incremental energy release rates for large enough crack velocities, for which the kinetic energy magnitude is similar to the elastic strain energy magnitude. Both simultaneous node release method and progressive node release method can however be equivalently used for small enough crack velocities since similar incremental energy release rates are obtained with both methods. Inverse identification of fracture properties based on dynamic crack initiation at a hole in Brazilian disk specimens yields critical energy release rates in the same order of magnitude as the one obtained based on dynamic crack propagation modeling.

The study tries to address Brazilian tests on a transversely isotropic rock to investigate failure conditions by using digital volume correlation (DVC). For this purpose, an in-situ Brazilian apparatus in a nano- X-ray computed tomography (CT) scanner is applied to investigate the 3D progressive failure mechanism of the schist. Two different anisotropy angles are tested. CT scans are conducted at every selected loading stage before peak load. DVC analyzes the constructed X-ray CT images to determine the effect of schistosity orientation on failure mechanism, including crack initiation and propagation. A calibration method is presented to verify DVC parameters, including the half size of the correlation window and the space between two sub-volumes. Using DVC, 3D deviatoric strain field, strain contours, and displacement increment are determined at all stages of loading. A CT value-based method (VG Studio) is also applied to validate the DVC results. It is found that the layer boundaries affect the failure pattern, with the agreement between the DVC results and VG Studio results being observed. For the specimen with horizontal layers, the crack initiates at the center part at the lower density layer and finishes out of the center. Also, for the specimen with horizontal layers, the crack initiates and propagates at the boundary of two layers out of the middle line of the specimen. These asymmetry failures are due to the heterogeneity of layers. The study also shows the type of failure using DVC by monitoring displacement increment vectors near the crack location.

Fatigue of high-strength high-ductility steel rebars under pitting corrosion and high-temperature remains largely unknown, specifically concerning temperature-dependent pit sensitivity effects, limiting their widespread adoption despite advantages. This study performs high-temperature, low-cycle fatigue tests on Fe 500D rebars with Gaussian pits. Moreover, experimental results are compared with average strain energy density method, augmented with fractography-based, temperature-dependent parameter models, including exponential pit sensitivity function. Results show accelerated cyclic softening, with up to 94% and 91% reductions in fatigue life and energy dissipation capacity in corroded rebars, respectively. The findings enhance fatigue life predictions, aiding the design of more resilient and safer structures.

The primary defects in coal are critical factors that induce geological disasters. Accurately predicting and identifying local damage in these defects is essential for the safe mining of underground engineering. In this paper, uniaxial compression tests were conducted on defective coal, and acoustic emission (AE) and electric potential (EP) were tested simultaneously. The mechanical behavior and failure characteristics were studied, the EP and AE features were analyzed, and the temporal-spatial features of the EP multifractal were revealed. The results indicate that external loads significantly stimulate both AE and EP responses in the coal sample, which correlate well with stress changes. As the defect dip angle increases, high-amplitude AE signals gradually decrease, and the main frequency distribution of AEs shifts from a full frequency range to a mid-low frequency range. The EP signals of each channel correspond closely with its corresponding strain evolutions, and the EP signals near the local damage area exhibit regions of high-value abnormal Δα_e and low-value abnormal Δf(α_e). When macroscopic fracturing occurs, Δα_e shows a fluctuating increase, while Δf(α_e) shows a fluctuating decrease. The spatiotemporal distribution of Δα_e and Δf(α_e) corresponds well with the stress levels and local damage in the sample. These research results provide significant theoretical guidance for the early warning and precise identification of geological disasters.

The main objective of this work is to propose a partial recoverable cohesive interface model, coupled with a bi-potential contact algorithm, to simulate the phenomenon of adhesion recoverability degradation under cyclic bonding–debonding between hyperelastic bodies. For this end, the proposed adhesion recoverability degradation model is constructed by defining the recovery of interface damage during the rebonding when two bodies come into contact, and a degradation factor related to the number of bonding–debonding cycles is introduced into the fully recoverable adhesion model to reduce energy dissipation after multiple cycles. Recoverability degradation includes adhesive stiffness and strength degradation, which is physically described as parallel, series and mixed arrays of adhesive bonds. Then, a finite element framework coupling the adhesion recoverability degradation model and the bi-potential contact algorithm is proposed, with Mooney–Rivlin hyperelastic material used to describe the soft matters. This framework is implemented in an in-house finite element code, with numerical examples demonstrating the model’s reliability. The proposed approach could be applied to investigate interfacial adhesion effects in fields such as flexible electronics and intelligent robotics.

Fracture failure behaviors of DZ125 directionally solidified nickel-base superalloy under combined high and low cycle fatigue (CCF) loads are investigated in this study. It is found that competitive cracking behaviors are present in DZ125 alloy while subjected to different CCF loads. An increase in the maximum low-cycle fatigue (LCF) nominal stress or high-cycle fatigue (HCF) stress amplitude results in a transition of crack initiation sites from subsurface pores or carbides to surface oxides. As the cycle ratio of HCF to LCF rises, crack initiation sites shift from subsurface carbides to surface oxides.

Creep reliability assessment of structural components at elevated temperatures is essential to guarantee the long-term safe operation of the system. Current studies are limited to continuum damage mechanics methods at the material level, while the reliability assessment method for creep design at the component level is rarely reported. In this work, the framework for creep reliability assessment of structural components is extended, where the time dependent feature of the representative stress is included. The effect of the time dependent feature of the representative stress on creep reliability assessment is discussed. Sensitivity analyses of material parameters on creep reliability assessment results are conducted based on the Sobol and Morris global methods. Results indicate that for the same creep design life, the component presents a higher failure probability when the time dependent feature of the representative stress is considered. Parameters D and d in the creep rupture life equation have more significant effects on creep rupture life than other parameters for the case studied.