Compressive Damage Evolution Research Articles

Compressive damage evolution analysis of self-healing SiC/SiC composites based on acoustic emission pattern recognition

Compressive damage evolution analysis of self-healing SiC/SiC composites based on acoustic emission pattern recognition

Numerical implementation of tension–compression asymmetry in a gradient‐extended two‐surface damage–plasticity model

AbstractBased on the spectral decomposition of the strain tensor, the tension‐compression asymmetry (TCA) in a gradient‐extended two‐surface damage‐plasticity model is considered in this study. More specifically, the gradient extension is applied in the current model as a suitable damage regularization technique to prevent pathological mesh dependence issues. Furthermore, plasticity and damage are treated as distinct but strongly coupled dissipative mechanisms by using two different types of damage and yield criteria as well as the related loading/unloading conditions, respectively. Finally, a specific material parameter is adopted to control the degree of TCA which results in a unique damage evolution in compression.

Compressive Damage and Failure Behavior of Plain-Woven GFRP Sandwich Composite L-Joints of Ships: Experiment and Simulation

This paper studies the compressive failure behavior of pw-GFRP (plain-woven glass fiber reinforced polymer) sandwich composite L-joints for ships. Six L-joint specimens were subjected to ultimate compressive tests, which show that damage and stiffness degradation started much earlier than any visible signs. A modified fiber kinking criterion is developed for the compressive failure of pw-GFRP layup structure. Moreover, a hybrid stiffness degradation model is applied to simulate the damage progression. The criterion and the degradation model are implemented in simulation through Abaqus user coding. The simulation results are compared with other existing theories, and the proposed criterion is validated by the similar damage initiation time. The combination of the proposed criterion and hybrid degradation model demonstrates a clear advantage over conventional methods in predicting the compressive damage evolution and ultimate failure behavior of the L-joint structure.

Influence of In-Situ Stress on Cut Blasting of One-Step Raise Excavation Using Numerical Analysis Based on a Modified Holmquist-Johnson-Cook Model.

Due to different tensile and compressive properties of rock material, the corresponding tensile and compressive damage evolution show major differences. To investigate the tensile and compressive damage evolution in deep cut blasting with different in-situ stresses, an improved Holmquist-Johnson-Cook (HJC) material model considers the tensile and compressive damage separately is developed. The improved HJC model is implemented into LS-DYNA via a user-defined subroutine in this study. Then, a numerical model with different in-situ stresses loading schemes is modelled. Numerical simulation results show that in-situ stress can inhibit the development of tensile damage evolution, while promote the development of compressive damage evolution. The overall damage zone presents a decreasing trend with the increase of in-situ stress, because the tensile damage is more sensitive than the compressive damage for rock material. In addition, the maximum principal stress can determine the development of the direction of damage. Further, for a field test of blind cut raise in deep, the actual in-situ stress values are loaded on the numerical model. Then, in order to overcome the difficulties caused by in-situ stress, the cut blasting design is optimized by reducing hole spacing. Subsequently, the optimized cut parameters are applied in the blind cut raise. However, the one-step raise excavation method is adjusted to two steps to ensure success due to a serious borehole deviation between drilling and design drawing. After these steps, the formation of the blind cut raise with 8.7 m depth is met the requirements of design.

Multiscale modeling for dynamic compressive behavior of polymer bonded explosives

The impact damage behavior of polymer bonded explosives (PBXs) is critical to ensure the safety of explosive systems. PBX 1314 (60 wt% RDX, 16 wt% aluminum, and 24 wt% HTPB) is a popular propellant owing to its characteristics of high energy density and low sensitivity. In this study, the compressive damage evolution rules and the strain rate effect of PBX 1314 were investigated by using a multiscale method. To acquire damage evolution data during loading, a finite element model based on real crystal morphology, with a cohesive zone model (CZM) for describing the damage, was developed. A novel hybrid/inverse optimization strategy was developed to calibrate the cohesive parameters of PBX 1314, and the accuracy of the parameters was verified basis experimental results. Using an as-developed bilinear model, the shift of damage pattern with the variation of strain rate was observed, and the nonlinearity of the stress–strain curve was presented at the mesoscale. The crack parameters and distribution of damaged elements in each mesoscopic component were acquired to quantitively characterize the strain rate dependence of PBX 1314, and the mechanism of crack propagation and the shift of damage mode under various strain rates was illustrated. The findings of this study provide insights for understanding the nonlinearity of macroscopic mechanical behavior and the influence of strain rate on the mesoscopic damage mode of PBXs with high binder content.

Deformation and damage behavior of the deep concrete cut-off wall in core earth-rock dam foundation based on plastic damage model - A case study

Concrete cut-off walls are widely used as an effective anti-seepage technique in overburden dam foundations all over the world. The deep cut-off wall in a core earth-rock dam foundation is often subjected to complex force conditions, and may have to withstand large stresses and deformations. In certain circumstances, it can even face the risk of cracking damage. Thus, it is of a great importance to clarify the mechanical properties and cracking trend of the deep cut-off wall of core earth-rock dam on the overburden foundation. In this paper, a simple plastic damage model for the damage analysis of deep cut-off wall was proposed under the framework of Lee-Fenves Model. In this model, the tensile and compressive responses of the wall were characterized by employing the tensile and compressive constitutive relations based on fracture energy, and different tensile and compressive damage evolution processes were considered based on the damage factor introduced according to the Sidoroff energy equivalence principle. Further, by taking into account the plastic damage, the wall-soil contact effect and the rock mass plasticity, a numerical model was established to investigate the stress deformation and damage properties of a 92-m-deep cut-off wall of a core earth-rock dam, in order to validate the feasibility and rationality of the proposed model in describing the nonlinear mechanical behavior and failure trend of the cut-off wall. Moreover, the impact of hidden faults and constraints on the mechanical properties of cut-off wall was also discussed in detail.

Compressive mechanical properties of self-expanding grouting materials with different densities

The compressive mechanical properties of self-expanding grouting materials with different densities are essential in evaluating the ultimate conditions of the repaired underground infrastructure. In this study, digital imaging correlation (DIC) and acoustic emission (AE) techniques were applied to monitor the compressive damage evolution process of self- expanding materials with different densities. It was found that the varied density exhibits great effect on the compressive response of self-expanding grouting materials, and that the length of the horizontal yield plateau decreases with the density. As the density increases to 0.399 g/cm3, the horizontal yield plateau diminishes and the materials present from plastic to brittle characteristics. Moreover, a statistical damage constitutive model of the ascending branch was developed and validated by experimental results.

A dynamic constitutive model of ultra high toughness cementitious composites

In this study, an explicit dynamic constitutive model was established for ultra high toughness cementitious composites (UHTCCs). The model, based on the Holmquist–Johnson–Cook (HJC) model, includes tensile and compressive damage evolution, hydrostatic pressure, strain rate, and the Lode angle effect. The proposed model was embedded in LS-DYNA software and then comprehensive tests were carried on a hexahedral brick element formulation under uniaxial, biaxial, and triaxial stress states to verify its rationality through comparisons with results determined by the HJC and Karagozian & Case (K&C) models. Finally, the proposed model was used to simulate the damage caused to UHTCC targets subjected to blast by embedded explosive and projectile penetration, and predictions were compared with corresponding experimental results. The results of the numerical simulations showed that our proposed model was more accurate than the HJC model in predicting the size of the crater, penetration depth, and the distribution of cracks inside the target following the blast or high-speed impact loading.

Observation of microscopic damage accumulation in brittle solids subjected to dynamic compressive loading

Dynamic failure of brittle materials is a fundamental physical problem that has significantly impacts to many science and engineering disciplines. As the first and the most important step towards the full understanding of this problem, one has to observe dynamic damage accumulation in brittle solids. In this work, we proposed a methodology to do that and demonstrated it by studying the dynamic compressive damage evolution of a granitic rock loaded with a modified split Hopkinson pressure bar system. To ensure consistency of the experimental results, we used cylindrical rock samples fabricated from the same rock core and subjected them to identical incident loading pulse. Using a special soft recovery technique, we stopped the dynamic loading on the samples at different strain levels, ranging from 0.3% to 1.4%. Therefore, we were able to recover intact samples loaded all the way to the post-peak deformation stage. The recovered samples were subsequently examined with X-ray micro-CT scanning machine. Three dimensional microcrack network induced by the dynamic loading was observed and the evolution of microcracks as a function of the dynamic loading strain was obtained.

Internal load transfer and damage evolution in a 3D interpenetrating metal/ceramic composite

The internal load transfer and compressive damage evolution in an interpenetrating Al2O3/AlSi12 composite have been studied in this work. The composite was fabricated by squeeze-casting eutectic aluminium–silicon alloy melt in a porous alumina preform. The preform was fabricated from a mixture of cellulose fibres and alumina particles via cold pressing and sintering. In an earlier work we reported the internal load transfer in the same composite material under monotonic compression and tension studied using energy dispersive synchrotron X-ray diffraction [20]. The current work is a continuation of this earlier study, aimed at obtaining further understanding about load transfer occurring during load reversal and damage behaviour during external compression. The micromechanical load partitioning between the three phases present in the composite is studied during one load cycle starting in compression followed by unloading and reloading in tension until failure. Average strain and stress value in each phase is calculated from several diffraction planes of each phase and as a result the reported strain and stress are representative of the bulk material behaviour. The load transfer results allow identifying the occurrence of a substantial Bauschinger effect in the Al solid solution phase and progressive damage evolution within the alumina phase. In situ compression test inside a scanning electron microscope showed that failure of the composite occurred by propagation of cracks through the ceramic rich regions, oriented at approximately 45° to the loading direction.

An incremental 2D constitutive model accounting for linear viscoelasticity and damage development in short fibre composites

SUMMARY A model accounting for linear viscoelasticity and microdamage evolution in short fibre composites is described. An incremental 2D formulation suitable for FE-simulation is derived and implemented in FE-solver ABAQUS. The implemented subroutine allows for simulation close to the final failure of the material. The formulation and subroutine is validated with analytical results and experimental data in a tensile test with constant strain rate using sheet moulding compound composites. FE-simulation of a four-point bending test is performed using shell elements. The result is compared with linear elastic solution and test data using a plot of maximum surface strain in compression and tension versus applied force. The model accounts for damage evolution due to tensile loading and neglects any damage evolution in compression, where the material has higher strength. Simulation and test results are in very good agreement regarding the slope of the load–strain curve and the slope change. Copyright 2005 John Wiley & Sons, Ltd.

Dynamic Damage Evolution of Solids in Compression: Microcracking, Plastic Flow, and Brittle-Ductile Transition

Dynamic compressive damage evolution in solids, associated with brittle microcracking and ductile plastic flow, is modeled through plastic flow and tensile microcracking, which are induced by the deformation of preexisting microflaws at grain boundaries, slip bands, and microcavities. The micromechanical aspect of this model is discussed in terms of the dominance of microcracking or plastic flow, and possible transition from microcracking to plastic flow is investigated. The effect of lateral confinement on the dynamic damage evolution is investigated, emphasizing the brittle-ductile transition.