Damage Evolution In Materials Research Articles

The use of curvilinear fibers for enhancement of progressive failure performance of perforated composite panels

This paper aims to examine the progressive failure performance of an open-hole variable stiffness composite (VSC) panel manufactured by the continuous tow shearing (CTS) technique under uniform edge shortening. A finite element (FE) model based on the Puck failure criterion in combination with a material stiffness degradation and damage evolution model is developed to perform the progressive failure analysis (PFA). The linear variation of the fiber orientation along a reference axis is assumed. The progressive failure performances of two constant stiffness composite (CSC) counterparts are also carried out for comparison. The results indicate that both the buckling load and the ultimate strength of the VSC panel are much higher than those of the CSC counterparts. Moreover, a significant decrease in the stiffness is observed after entering the post-buckling regime for CSC panels, while it maintains a high level for the VSC panel. Another interesting finding is that the VSC behaves notch-insensitive under the studied loading condition. The novel findings demonstrate the superior buckling, post-buckling, and failure-resistance properties of VSC fabricated by the CTS technique.

A damage phase-field model for fractional viscoelastic materials in finite strain

This paper proposes a thermodynamically consistent phase-field damage model for viscoelastic materials following the strategy developed by Boldrini et al. (Methods Appl Mech Eng 312:395–427, 2016). Suitable free-energy and pseudo-potentials of dissipation are developed to build a model leading to a stress-strain relation, under the assumption of finite strain, in terms of fractional derivatives. A novel degradation function, which properly couples stress response and damage evolution for viscoelastic materials, is proposed. We obtain a set of differential equations that accounts for the evolution of motion, damage, and temperature. In the present work, for simplicity, this model is numerically solved for isothermal cases by using a semi-implicit/explicit scheme. Several numerical tests, including fitting with experimental data, show that the developed model accounts appropriately for damage in viscoelastic materials for small and finite strains. Non-isothermal numerical simulations will be considered in future works.

Debris effect on the surface wear and damage evolution of counterpart materials subjected to contact sliding

Debris effect on the surface wear and damage evolution of counterpart materials subjected to contact sliding

Prismatic edge dislocations in graphite

Dislocations are a central concept in materials science, which dictate the plastic deformation and damage evolution in materials. Layered materials such as graphite admit two general types of interlayer dislocations: basal and prismatic dislocations, of which prismatic dislocations have been relatively less studied. Using density functional theory (DFT) calculations, we have examined different prismatic core structures in graphite and evaluated their structure, energetics and mobility. We find close energetic interplay between bonded and “free-standing” core structures in both zigzag and armchair directions, with a reconstructed stable zigzag core identified. We explore grain boundaries and prismatic dislocation pile-up, identifying metastable structures which may be important in energy storage. The role of interlayer stacking in core structure, dislocation glide and climb is also considered in-depth. Our calculations suggest that the prismatic dislocation core is stable up to high temperatures of approximately 1500 K in bulk graphite. Above this temperature, the breaking of bonds in the dislocation core can facilitate climb, grain-boundary motion, and the annealing of damage through prismatic dislocation glide.

A plasticity-based dynamic constitutive model for ultra high toughness cementitious composites

Ultra high toughness cementitious composites (UHTCC) have a wide range of application prospects in various protective structures. At present, various concrete material models have been frequently used to simulate the mechanical response of such materials subjected to high-speed impact and explosive loads. However, none of these models can accurately describe the tensile ductility, strain rate effect, and shear expansion effect of UHTCC, which may lead to inaccurate numerical simulation results. In this study, a dynamic constitutive model of UHTCC was established, which comprehensively considered damage evolution, shear expansion, strain rate, strain hardening and strain softening of such materials. It was implemented into LS-DYNA software through a user-defined interface. Then comprehensive element tests were conducted and compared with the commonly used concrete models. Finally, a set of experimental tests of the UHTCC subjected to high-speed impact and contact blast loads were simulated. It was found that the numerical prediction results were in good agreement with the experimental results.

Modeling the anisotropic plasticity and damage of AA7075 alloy in hot forming

The theory of unified visco-plastic damage constitutive equations has been frequently used to model the thermal flow behavior and damage evolution of various materials. But the anisotropic properties of materials were generally neglected in the previous studies. In this paper, a novel damage correction formula was proposed, which was expressed as a function of loading path and loading direction and used as a multiplier of a continuum damage model. By integrating a set of unified visco-plastic damage constitutive equations, the Yld2004-18p criterion and the damage correction formula, an improved anisotropic damage constitutive model was established. Anisotropic plasticity and anisotropic damage of AA7075 alloy under hot forming conditions can be properly modeled by this model. Material constants included in the three integrated functions were determined respectively based on different experimental data. The calibrated model is capable to accurately predict the forming limit curves of AA7075 alloy for different forming temperatures, strain rates and loading directions. The model was then numerically implemented in hot Nakajima simulations. The simulation results were evaluated comprehensively from the aspects of limit strain point, punch force- displacement curve, major strain field and fracture position. For further verification of the established model, hot forming simulation of a B-pillar was conducted and compared with a real B-pillar of AA7075 alloy fabricated via an industrial hot stamping process. It is concluded the anisotropic damage constitutive model can be numerically applied to accurately predict the plastic deformation and damage-induced fracture of AA7075 alloy under hot forming conditions.

Pixel-level intelligent recognition of concrete cracks based on DRACNN

Materials surface damage identification based on computer vision technology has become one of the research hotspots in the field of materials surface. Crack is one of the most common forms of material damage. It is of great significance to carry out intelligent recognition of cracks to identify and estimate evolution of material damage. In order to improve the accuracy of intelligent crack recognition, a deep residual attention convolution neural network (DRACNN) was proposed for semantic segmentation of concrete cracks. DRACNN network is based on U-Net and adds recursive residual convolution block and attention mechanism in U-Net for more accurate intelligent crack recognition at pixel-level. Through the comparison with other mainstream semantic segmentation algorithms, it is found that the proposed DRACNN can achieve better classification performance for concrete cracks, and the IoU, accuracy, precision, and recall of the DRACNN are 73.95%, 97.82%, 78.48%, and 67.95% respectively.

Heating process and damage evolution of microwave absorption and transparency materials under microwave irradiation

Heating process and damage evolution of microwave absorption and transparency materials under microwave irradiation

Cracking process and energy dissipation of sandstone under repetitive impact loading with different loading rates: From micro to macro scale

Rocks are widely used as building materials in many engineering applications. The repetitive impact loading can induce damage accumulation to rocks. To elucidate the multiscale damage and energy dissipation mechanism of sandstone under repetitive impact loading with different loading rates, dynamic compression tests were performed using Split Hopkinson pressure bar system (SHPB). In addition to the macroscopic deformation and energy absorption analysis, the optical microscope and the nuclear magnetic resonance technique were used to analyze the microstructural evolution of sandstone. A higher loading rate results in a larger number but smaller size of microcracks in sandstone sample, consequently, more macroscopic cracks and a higher energy absorption can be found in sandstone sample. In addition, despite the loading rate, the porosity shows a nearly linear relationship with the cumulative dissipated energy. The present results clarify the multi-scale damage evolution and energy dissipation of rock materials exposed to repetitive impact loading with different loading rates.

Gradient‐enhanced damage growth modeling of ductile fracture

AbstractWe present a gradient‐enhanced damage model for ductile fracture modeling, describing the degraded material response coupled to temperature. Continuum thermodynamics is used to represent components of the energy dissipation as induced by the effective material response, thermal effects, and damage evolution. The viscoplastic Johnson‐Cook constitutive model serves as prototype for the effective material. The continuum damage evolution of Lemaitre type is focusing the degradation of the shear response, eventually leading to ductile shear failure. A novel feature is the damage‐driving dissipation rate, allowing for elastic and plastic components separated by a global damage threshold for accumulation of inelastic damage‐driving energy. In the application to a dynamic split‐Hopkinson test and two quasi‐static tensile tests, the gradient damage model is compared with the corresponding local model. For isothermal conditions, the examples show that both damage models exhibit mesh convergent behavior when using the global damage threshold.

Burst capacity of reinforced thermoplastic pipes based on progressive failure criterion

This paper examines the burst capacity of reinforced thermoplastic pipes (RTPs) under the effect of internal pressure. Used the theory of the three-dimensional (3D) thick-walled cylinder, combined the 3D Hashin failure criterion with the theory of the evolution of damage in composite materials, considered the nonlinear stress-strain relationship of materials, and introduced changes in the winding angle caused by deformation to formulate a analytical model for the progressive failure analysis of RTPs. The model was used to examine the failure sequence and burst capacity of the RTPs, and analytical results agree well with the experimental ones. The results show that the ply number of the reinforced layer had a more significant effect on the burst capacity of the RTPs than the winding angle. Their burst capacity first increased and then decreased with increasing winding angle. When the winding angle was ±60°, the burst pressure reached its peak. With an increase in the ply number of the reinforced layers, the burst pressure of the RTPs increased nonlinearly and its rate of growth gradually decreased. Once a certain ply number in the reinforced layer had been reached, interlaminar separation was more likely to occur in the RTPs before they burst.

A cohesive contact algorithm to evaluate the mechanical behaviour of concrete ITZ at different roughness conditions

The capability of modelling damage evolution in concrete materials represents a topic of relevance for improving the design of concrete structures and for the recovery of existing components. The present work aims to investigate the collapsible behaviour of the Interfacial Transition Zone (ITZ) around coarse inclusions, by using a new cohesive contact law able to take into account the coupling between normal/peeling and shear stresses, specifically calibrated to take into account the roughness of various aggregate types. A series of numerical analyses have been carried out considering different material inclusions and distributions within concrete samples, so proving the capabilities of the proposed formulation.

Comparative study of strength-based damage evolution in ultra-high-performance concrete (UHPC) and conventional concrete (CC) under dynamic loading

The initiation and development of damage inside cementitious materials subjected to dynamic loadings, which is manifested by the cracking and fragmentation process, have a significant contribution to the load-bearing capacity of these materials. However, current popular concrete models hypothesize that damage only initiates after the specimen reaches its peak stress, and due in part to the lack of validation from sufficient experimental data, none of the models entertain the possibility of variation in damage evolution among different types of concretes. In this study, the evolution of damage in an ultra-high-performance concrete (UHPC) and a conventional concrete (CC), characterized by the degree of strength degradation, are comparatively investigated throughout the entire pre-/post-peak deformation process as a function of carefully measured plastic strain. Well-controlled intermittent dynamic loadings are achieved on a modified Kolsky compression bar apparatus to first introduce various degrees of damage in the concrete specimens, and then the carefully preserved specimens are tested for residual strength. Coupling with pulse shaping techniques, the incident wave profiles are tailored for UHPC and CC specimens to acquire dynamic stress equilibrium and constant strain-rate deformation. Further evaluation on the residual strength of damaged specimens reveals that damage initiates prior to the peak stress, and there is a distinct difference in damage evolution between these two types of concrete materials. This investigation demonstrates a more comprehensive view of damage evolution in concrete materials and offers novel experimental data to assist the damage model development.

A modified cohesive damage-plasticity model for distinct lattice spring model on rock fracturing

In this study, a modified cohesive damage-plasticity model (m-CDPM) is developed for a distinct lattice spring model (DLSM) to simulate the damage evolution and fracture process in quasi-brittle materials. A hyper-elastic segment is introduced into the original CDPM to enable the DLSM to handle special cases associated with negative or vanishing shear stiffness in the DLSM framework when attempting to link micro- and macro-constitutive parameters. Relationships between the macro experimental parameters and their micro counterparts are theoretically derived following the tradition of the DLSM with consideration of the particle size effect. The correctness and feasibility of the proposed model are verified through numerical examples and a comparison with available experimental or numerical solutions.

New Nonlinear Cumulative Fatigue Damage Model Based on Ecological Quality Dissipation of Materials

The failure of many aircraft structures and materials is caused by the accumulation of fatigue damage under variable-amplitude cyclic loading wherein the damage evolution of materials is complicated. Therefore, to study the cumulative fatigue damage of materials under variable-amplitude cyclic loading, a new nonlinear fatigue damage accumulation model is proposed based on the ecological quality dissipation of materials by considering the effects of load interaction and sequence. The proposed new model is validated by the test data obtained for three kinds of material under multilevel fatigue loading. Compared with the Miner model and Kwofie model, the proposed model can more effectively analyse the accumulative damage and predict fatigue life of different materials under variable-amplitude cyclic loading than others. The study provides a basis for predicting fatigue life accurately and determining reasonable maintenance periods of aircraft structures.

Coupling Peridynamics with the Classical Methods for Modeling Hydraulic Fracture Growth in Heterogeneous Reservoirs

Summary Hydraulic fracture (HF) modeling is a multiscale and multiphysics problem. It should capture various effects, including those of in-situ stresses, poroelasticity, and reservoir heterogeneities at different length scales. A peridynamics (PD)-based hydraulic fracturing simulator has been demonstrated to reproduce this physics accurately. However, accounting for such details leads to a reduction in computational speed. In this paper, we present a novel coupling of the PD-based simulator with numerically efficient finite element methods (FEMs) and finite volume methods (FVMs) to achieve a significant improvement in computational performance. Unlike classical methods, such as FEM and FVM that solve differential equations, PD uses an integral formulation to circumvent the undefined spatial derivatives at crack tips. We implemented four novel coupling schemes of our PD-based simulator with FEM and FVM: static PD region scheme, dynamic PD region scheme, adaptive mesh refinement scheme, and dynamic mesh coarsening scheme. PD equations are solved using a refined mesh close to the fracture, whereas FE/FV equations are solved using a progressively coarser mesh away from the fracture. As the fracture grows, a dynamic conversion of FE/FV cells to PD nodes and adaptive mesh refinement are incorporated. To improve the performance further, the dynamic mesh coarsening scheme additionally converts the fine PD nodes back to coarse FE/FV cells as the HF grows in length. The coupling schemes are verified against the Kristianovich-Geertsma-de Klerk (KGD) fracture propagation problem. No spurious behavior is observed near the transition between PD and FE/FV regions. In the first three coupling schemes, the computational runtime for single fracture propagation is reduced by up to 10, 20, and 50 times, respectively, compared to a pure PD model. Laboratory experiments on the interaction of an HF with a natural fracture (NF) are revisited. The model captures complex fracture behavior, such as turning in the case of low stress contrast and low angle of interaction, kinking for higher stress contrast or higher angle of interaction, and fracture crossing for near-orthogonal NFs. Moreover, several previously reported phenomena, including fracture propagation at an angle to the principal stress directions, competing fracture growth from multiple closely spaced clusters, and interaction with layers of varying mechanical properties are successfully modeled. Thus, the coupling of PD with FEM and FVM offers an innovative and fundamentally comprehensive solution to alleviate the high computational costs typically associated with the pure PD-based hydraulic fracturing simulations. At the same time, these coupling schemes retain the versatility of the nonlocal PD formulation at modeling the evolution of arbitrary material damage, commonly observed during HF propagation in complex heterogeneous reservoirs.

Novel nonlinear time-varying fatigue reliability analysis based on the probability density evolution method

The evolution of fatigue damage in materials of structures under cyclic loading is a time-varying cumulative process. Method on time-varying fatigue reliability analysis is scarce due to the popular use of Miner’s rule in defining the fatigue damage which does not consider the influence of the load sequence. A novel nonlinear time-varying fatigue reliability analysis method is presented to improve the accuracy and efficiency of time-varying reliability analysis. A nonlinear fatigue damage index is defined based on the toughness exhaustion of material, and the fatigue damage limit state function is then derived. This state function is then analyzed with the probability density evolution method (PDEM), and the generalized density evolution equation is solved numerically. The complete process of the time-varying fatigue reliability analysis is presented. Two sets of experimental results are employed to validate the proposed method. Results show that the accuracy and efficiency of time-varying fatigue reliability can be improved with the proposed method considering the effects of nonlinearity of the fatigue damage and loading sequence.

Local well-posedness for Frémond’s model of complete damage in elastic solids

We consider a model for the evolution of damage in elastic materials originally proposed by Michel Frémond. For the corresponding PDE system, we prove existence and uniqueness of a local in time strong solution. The main novelty of our result stands in the fact that, differently from previous contributions, we assume no occurrence of any type of regularising terms.

Computational Approches for Ballistic Impact Response of Stainless Steel 304

The present study introduces a numerical procedure to estimate the impact resistance of stainless steel 304 (SS 304) commonly used in producing security screens through calculation of the effective ballistic limit velocity (V50). Non-linear finite element (FE) analysis using ABAQUS FE software was performed to simulate the material response with wide variety of thicknesses under various impact scenarios. Three different techniques were employed to determine V50, including: simulation of SS 304 using material parameters obtained from coupons testings and impact residual velocity and energy based on FE analysis. The material plasticity and damage initiation and evolution under dynamic loading conditions were simulated using Johnson-Cook model, while Lambert-Jonas model was utilized in predicting the residual impact velocity and energy using robust data regression system. Very good correlation within the investigated methodologies was observed along with obvious proportional between V50and coupons’ thickness. The significance of the outcome of this investigation is the developing of feasible and economical approach to evaluate the impact resistance of SS 304 which will significantly contribute to the development of superior security screens.

Multiparameter Approach for Damage Propagation Analysis in Fiber-Reinforced Polymer Composites

Assessing the damage evolution in carbon-fiber-reinforced polymer (CFRP) composites is an intricate task due to their complex mechanical responses. The acoustic emission technique (AE) is a non-destructive evaluation tool that is based on the recording of sound waves generated inside the material as a consequence of the presence of active defects. Proper analysis of the recorded waves can be used for monitoring the damage evolution in many materials, including composites. The acoustic track associated with the entire loading history of the sample or the structures is usually followed by using some descriptors, such as the amplitude of the sound waves and the number of counts. In this study, the acoustic emission in CFRP single-lap shear joints was monitored by using a multiparameter approach based on the contemporary analysis of multiple features, such as the absolute signal level (ASL), initiation frequency, and reverberation frequency, to understand whether a proper combination of them can be adopted for a more robust description of the damage propagation in CFRP structures. For selecting the best features, principal component analysis (PCA) was used. The selected features were classified into different clusters using fuzzy c-means (FCM) data clustering for analyzing the damage modes.