Damage Evolution Research Articles

Research on the static and dynamic tensile damage mechanism of concrete based on fuzzy sets

The quantitative analysis of microscopic damage mechanisms in concrete and the formulation of damage evolution equations using mathematical theory and computerized tomography (CT) imaging are still emerging fields. The test data from CT scans have yet to be fully exploited. This study proposes a method for quantitatively characterizing mesoscale damage evolution in concrete. By segmenting CT images from static and dynamic tensile tests, we define metrics such as the aggregate rate, mortar rate, and porosity to examine the damage progression under both stress conditions. We then establish a damage evolution model based on porosity changes. Our findings reveal that crack growth in concrete is slower under static tension, with cracks navigating around aggregates towards weaker regions. Conversely, under dynamic loads, cracks propagate more rapidly and directly through aggregates, following paths of quicker energy dispersion. Static loading results in less aggregate damage than does dynamic loading, with a notable increase in porosity and a more varied change in the mortar rate. The damage to the finer components of concrete increases as the crack-adjacent region diminishes. Damage is generally more extensive under static loading than under dynamic loading. The proposed porosity-based damage evolution model effectively describes concrete damage under static tension, leveraging CT technology to enhance the universality of the research and offering a microscopic-level theoretical foundation for studying concrete mechanical properties.

Damage evolution in Plasma Facing Materials by a sequential multiscale approach

Abstract Describing the time evolution of Plasma Facing Materials (PFMs),
meaning quantitative evaluation of erosion, roughness, and physical properties
degradation, is one of the difficult challenges to reach the goal of efficient energy
production by nuclear fusion.
To follow all the aging-connected physical and chemical phenomena through
their characteristic dimensional scale, and to estimate the PFM microstructural
transformation over time, we propose a predictive sequential multiscale methodology,
consisting of two database-provided coupled codes. The first is a time-dependent,
volume-averaged, plasma simulator which describes completely this system, in terms of
thermodynamics, composition and evaluation of the sheath potential. Plasma solutions
are geometrically rearranged by adding surface reactions and 3D geometric features.
To increase sensitivity, plasma information is provided to the second code as an initial
condition. Such a code is a 3D kinetic Monte Carlo (3D-KMC) in-cell algorithm
for nanoscale erosion describing the PFM interactions through an extendable set of
physical phenomena, such as sticking, sputtering, ion enhanced removals and ion
penetration.
In this paper, we perform simulations for the case of study of Hydrogen (H) plasmas
produced in linear devices, reaching the quasi-atomic detail of the plasma induced
material modification of tungsten (W) as PFM.

Monitoring damage evolution of SiCf/PyC/SiC mini-composites using electrical resistivity: Crack opening distance and interphase retention rate based electromechanical modeling

Electrical resistance is closely related to the damage of ceramic matrix composites (CMC) such as matrix crack, crack opening distance (COD), and interphase retention rate, giving it the potential to become a new non-destructive testing (NDT) technique. An electro-mechanical experiment method was designed for the tensile test of ceramic matrix mini-composites (CMMC). An optical in-situ tensile test was performed to obtain the pattern of matrix crack propagation. The result confirms that matrix crack saturation may not occur before the material fractures. An electromechanical model considering the COD was established to identify the damage situations. A new method for preparing ceramic matrix micro-composites composed of a single fiber and a single-layer pyrolytic carbon (PyC) interphase was realized. The accurate in-situ resistivity of the PyC was measured based on the micro-composites.

Shaking table test on progressive collapse of the double-layer cylindrical reticulated shell with infilled wall

Double-layer cylindrical reticulated shell has made rapid development in recent decades in China, which is widely used in the large-scale public buildings such as gymnasiums, airplane terminal, Shopping mall, etc. Stability and progressive collapse mechanism have been attracting a lot of attention because the large span space structure is largely affected by the geometry nonlinear, which makes it sensitive to the local damages. The infilled wall has a greater impact on the stiffness of the lower supporting structure due to sparse column grid. However, the influence of infilled walls on the collapse mechanism of large-span spatial structures is very complex due to the coupling of upper and lower structures. Therefore, the effects of infilled walls on double-layer cylindrical reticulated shell was investigated by a series of progressive collapse tests with shaking table. In order to evaluate the seismic performance and the capacity of resisting progressive collapse, the structural dynamic characteristics and response laws were obtained under different ground motions and input principal directions. The results indicated that the existence of infilled wall made the coupling between the lower supporting structure and the upper roof structure more complicated. The infilled walls influenced the structural damage evolution and development, mitigated the damage from the earthquake and changed the progressive collapse pattern, which made the catenary collapse mechanism occur when the structure collapsed. Although the further quantitative study is still needed, this paper provides lots of useful test data and conclusions, which gives references to the infilled wall design and seismic performance evaluation for double-layer cylindrical reticulated shell.

Phase field modelling of elastic-plastic fatigue fracture of oil and gas pipeline

This paper established a fatigue fracture phase-field model (PFM) to evaluate fatigue damage evolution and crack propagation in oil and gas pipeline. To address inaccuracies in damage evolution, a threshold of the elastic-plastic fracture energy was introduced in the proposed PFM. Using the finite element method, the PFM was applied to simulate fatigue crack growth. Results from compact tension (CT) specimen of the X56 gas pipeline steel demonstrated that the da/dN-ΔK curve from the current PFM, accounting for plasticity, aligned more closely with experimental results than the elastic PFM. The fatigue crack propagation and fatigue life of the X80 gas pipeline with different defects of the same depth were also analyzed. The results indicated that triangular defects significantly impacted the fatigue life of the X80 gas pipeline. Finally, a model of X60 pipeline with various initial defects was developed to validate the effectiveness of the proposed PFM for full-scale pipeline fatigue fracture by comparing it to experimental a-N curves. The simulation results indicated that the distance and angle between two initial defects in the pipeline significantly influenced the propagation of fatigue cracks and the pipeline’s service life. These findings of this paper can serve as a reference for estimating the service life of gas and oil pipelines.

An efficient multi-scale method for failure mechanism analysis of SiCf/Ti composites with experimental validation

This study focuses on developing and validating a high-precision concurrent multi-scale finite element model considering the progressive damage model (PDM) and the cohesive zone model (CZM) for predicting the damage evolution of SiCf/Ti composites. At the macro-scale, a constitutive model describing the anisotropic damage criterion of SiCf/Ti composites was implemented by means of a user-defined subroutine (VUMAT). Meanwhile, based on the submodelling, a representative volume element (RVE) model was developed to systematically analyze the failure modes of the SiC fibers, the matrix, and the interface, respectively. Specifically, the crack initiation and propagation in the stress concentration zones were further discussed. Simultaneously, the experimental methods were employed to verify the feasibility of the current model. During the uniaxial compression, the brittle fracture of the SiC fibers and ductile fracture of the matrix are the predominant failure modes of SiCf/Ti composites, with fiber fracture being the dominant factor. The crack initiates at the fibers, propagates rapidly to the fiber-matrix interface, and then extends into the matrix. Moreover, the fracture locations are prone to stress concentrations, leading to the crack initiation and propagation. The predicted results show that the multi-scale model is able to reproduce the observed behavior, indicating that local damage evolution is a serious mechanism affecting the performance of SiCf/Ti composites.

Anisotropic damage evolution in solid fractures: A novel phase field approach with multiple failure criteria and directional-dependent structural tensor

This study proposes a novel phase-field fracture model based on unified phase field theory, aiming to overcome current limitations in simulating material complex fracture behaviors. Through this model, analytical solutions for two-dimensional bars subjected to tensile or compressive stresses are provided, enabling the coupling of multiple failure criteria and further proficient simulation of mode-I, mode-II, and mixed mode-I/II fractures, effectively addressing challenges faced in modelling materials with different or complex failure modes under various loading conditions. Furthermore, to account for the strong anisotropic failure behavior of materials, a novel directional-dependent structural tensor is proposed. The tensor correlates fracture energy with crack surface orientation, facilitating precise characterization of material damage evolution with multiple potential crack orientations. This tensor ensures the consistency of phase-field fracture evolution with predefined fracture patterns. The effectiveness of the proposed model is validated through case studies, emphasizing its robustness and superior predictive capability in capturing fracture behavior under various conditions. This research provides a more accurate and universally applicable approach for simulating material failure, particularly for complex or multiple failure mode material failure simulations.

Seismic Analysis of a Self-Centering Braced Frame in Pseudodynamic Tests: Response Characteristics, Brace Contribution, and Damage Evolution

Seismic Analysis of a Self-Centering Braced Frame in Pseudodynamic Tests: Response Characteristics, Brace Contribution, and Damage Evolution

Changes in the cardiovascular risk profile in children approaching kidney replacement therapy

Despite significant cardiovascular (CV) morbidity in children on dialysis and after kidney transplantation, data on the evolution of CV damage in children with chronic kidney disease (CKD) approaching kidney replacement therapy (KRT) is unknown. The burden, progression, and predictors of CV damage before KRT onset were explored in two prospective multicenter cohorts from Europe and Canada: Cardiovascular Comorbidity in Children with CKD (4C) and Haemodiafiltration, Heart and Height (3H) studies, conducted from 2009-19 and 2013-16, respectively. CV damage and risk factors were evaluated (i) cross sectionally at KRT-start (n=248), and (ii) longitudinally over the 2-years preceding KRT start (n=157; 331 patient-visits). Longitudinal analyses with mixed-effects models estimated associations of modifiable CV risk factors with change in carotid intima-media thickness (cIMT) standard deviation score (SDS), pulse wave velocity (PWV-SDS), left ventricular (LV) mass and systolic dysfunction. 248 patients, age 14.3 (12.2, 16.2) years were evaluated at median 35 (28-114) days before KRT start. Elevated cIMT-SDS and PWV-SDS were present in 43% and 25%, and LV hypertrophy and systolic dysfunction in 49% and 33%. Aortic stiffness and LV hypertrophy significantly increased, especially in the year before KRT start (adjusted odds ratio, OR 0.33, P=0.002 and OR 0.54, P=0.01, respectively). 79% of children had >3 modifiable CV risk factors at KRT onset. Diastolic BP and BMI were strongly associated with a linear increase in all CV measures. After controlling for CV risk factors, the time to KRT onset no longer predicted the burden of CV damage. This comprehensive CV evaluation shows the progressive accrual of modifiable risk factors and a high burden of CV damage in the years preceding KRT onset. CV damage in the pre-KRT period is preventable. Supported by EU4Health Programme (101085068) and Kidney Research UK (RP39/2013).

Severe Thoracic Trauma Indications and Contraindications for Non-operative and Operative Treatment Strategies

Severe thoracic trauma can occur as a penetrating or blunt mono-injury or as part of a polytrauma. Almost half of all severely injured patients documented in the TraumaRegister DGU were diagnosed with severe chest trauma, defined according to the Abbreviated Injury Scale (AIS) as ≥3. In our own collective, the proportion was even higher with 60%. Emergency surgical treatment with a thoracotomy within the Trauma Resuscitation Unit or within the first hour of admission is an extremely rare intervention in Germany, accounting for 0.9% of severe thoracic injuries. The management of complex polytraumas and extensive pathophysiological reactions to the trauma, as well as knowledge about the development of secondary damage have led to the conclusion that minimally invasive procedures such as video-assisted thoracoscopy (VATS) or inserting a chest drain can resolve most severe thoracic injuries. At <4%, penetrating injuries to the thorax are a rarity. Among blunt thoracic injuries, >6% show an unstable thoracic wall that requires surgical reconstruction. The demographic development in Germany leads to a shift in injury pattern. Low-energy trauma results have lower incidence than higher-grade chest wall injuries with penetrating rib fractures in the pleura, lungs, peri-/myocardium and diaphragm. Sometimes this results in instability of the chest wall with severe restriction of respiratory mechanics, which leads to fulminant pneumonia and even ARDS (Acute Respiratory Distress Syndrome). With this background, surgical chest wall reconstruction has become increasingly important over the past decade. Together with the underlying strong evidence, the assessment of the extend and severity of the trauma and the degree of respiratory impairment are the basis for a structured decision on a non-surgical or surgical-reconstructive strategy, as well as the timing, type and extent of surgery. Early surgery within 72 hours can reduce morbidity (pneumonia rate, duration of intensive care and ventilation) and mortality. In the following article, evidence-based algorithms for surgical and non-operative strategies are discussed in the context on the management of severe thoracic injuries. Thus, a selective literature search was carried out for the leading publications on indications, treatment strategy and therapy recommendations for severe thoracic injury, chest wall reconstruction.

Effect of stress ratio and welding residual stresses on the fatigue crack growth behaviour of Weldox-700 steel using LGDM

In this work, numerical simulations of high-cycle fatigue and fatigue crack growth have been performed using localizing gradient damage methodology (LGDM) for base and welded weldox-700 steel. LGDM models crack growth phenomenon by avoiding any non-physical widening of damage bands. The effect of stress ratio is included in the strain-based damage evolution in the present work. Accordingly, the generalized expressions of damage parameters have been derived. Experimental fatigue tests are performed on the base material and the welded joints. In order to numerically investigate the welded joints, residual stresses developed during welding are obtained through sequentially coupled thermo-mechanical finite element analysis. Subsequently, the fatigue-life and crack-propagation are simulated by applying the residual stresses as a pre-existing field in the LGDM framework, which uses full coupling between deformations and non-local equivalent strains in the finite element analysis. The simulated results and experimental fatigue data are found to be in good agreement.

Effects of aggregate's type and orientation on stress concentration and crack propagation of modeled concrete applied a shear force

This study focused on planarizing natural modeled aggregate concrete (NMC), recycled modeled aggregate concrete (RMC), and brick modeled aggregate concrete (BMC) for analyzing the influences of aggregates on shearing failure mechanism. A designed apparatus was used to load a shear force for the specimens and analyzed the global and local strain fields near the interface transition zone (ITZ) using digital image correlation (DIC) analysis. Additionally, we employed COMSOL software simulation to understand the crack initiation process and damage evolution mechanism of related concrete. Our findings revealed that the brick aggregate leaded to the lowest modulus of elasticity and compressive strength, resulting in poor shear resistance. However, the recycled aggregate model exhibited the highest shear resistance, primarily due to the old mortar acting as a buffer layer in the ITZ. During loading, the stress in the NMC model concentrated in the load transfer zone and gradually moved to the left and right sides of the built-in aggregate model until fracture, as observed through DIC analysis. The stress distribution of the RMC was similar with those of the NMC, but the BMC showed a distinct stress distribution pattern. Furthermore, the corner of the built-in modeled aggregate significantly influenced the crack propagating path and stress distribution. Therefore, the modeled aggregate corner plays a crucial role in the shear behavior of concrete, affecting both crack propagation and overall mechanical performance. The practical implications of our study can inform the design and application of recycled concrete.

Study on mechanical properties and damage mechanism of alkali-activated slag concrete

The cement industry has become one of the important sources of greenhouse gas emissions, and the alkali-activated slag (AAS) has the same mechanical properties and lower carbon emissions as cement in the production process. Therefore, it can be used as an alternative binder for low-carbon buildings. The effect of alkali concentration (mass ratio of Na2O to binder) on the macro-mechanical properties and meso-damage mechanism of alkali-activated slag concrete (AASC) under uniaxial compression was investigated in this work. Six kinds of concrete with alkali concentration of 2%, 4%, 6%, 8%, 10% and 12% were prepared. The microscopic characteristics of AASC were characterized by nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray energy dispersive spectroscopy (EDS); the meso-damage evolution mechanism of AASC was discussed by statistical damage theory. The results showed that the peak stress and elastic modulus of AASC specimens increased, and the microstructure became denser with the increase of alkali concentration. However, the mechanical properties of the specimen deteriorated to some extent when the alkali concentration exceeded 6%; for example, the peak stress decreased by 24.00 MPa when the alkali concentration was increased from 6% to 12% at the age of 28d. Based on the statistical damage theory, the effective stress concept was introduced to quantitatively analyze the mesoscopic damage evolution of AASC. Both fracture and yielding damage modes were considered. By exploring the regular changes of the mesoscopic parameters, the connection between the macroscopic mechanical properties and the mesoscopic damage mechanism was established. Based on the above mechanical properties and mesoscopic damage results, the alkali concentration of 6% can be used as the best mixture proportions of AASC.

Description of step loads at high temperature creep of metallic materials

Abstract In metallic materials under high-temperature creep conditions, the damage evolution occurs. To describe it, Kachanov and Rabotnov proposed the concept of damage. In this paper, the damage parameter is defined as the relative change in material density, serving as an integral measure of damage. By incorporating the damage parameter and the mass conservation law, are we formulated interrelated kinetic equations for rate of creep deformation and the damage parameter. The case of variable loads is crucial both theoretically and practically, as most structural components typically operate under such conditions. Therefore, solutions of considered equations are derived for the case of two-stage loading. The received solutions and experimental results on the creep of titanium alloy under variable loads at 500°C were compared. There is a good agreement between the theoretical results and experimental data.

A profound study of damage behavior for Al 2024-T3 alloy worksheet produced by constrained groove pressing in the superior practical condition

Constrained groove pressing (CGP) process is one of the most efficient and novel methods of severe plastic deformation to manufacture ultra-fine sheet metal. The present research work is related to the study of CGP process of 2024-T3 Aluminum alloy sheet. The empirical and numerical simulation of CGPed- specimens have been examined at both room and elevated temperatures. In order to simulate the constrained groove pressing process in Abaqus software, the Johnson–Cook material model has been employed. The geometrical variables of the CGP process include the teeth number, teeth angle, and sheet thickness, and the criterion for the superiority of the numerical test is the maximum reduction of two equivalent strain and equivalent force factors, simultaneously. To determine the weight’s coefficients of the target factors and select the superior test, the Shannon’s Entropy and Simple Additive Weighting (SAW) methods have been used, respectively. After validating the numerical findings, the variation of damage parameter, stress triaxiality and the equivalent plastic strain distribution in the superior practical condition have been evaluated in detail. Based on the Entropy-SAW hybrid technique, the weight’s coefficients of equivalent strain and equivalent force target factors were computed to, in turn, 0.38 and 0.62. Also, the results revealed that the CGP process could not be performed at room temperature based on high damage evolution. But, at elevated temperature, the damage parameter (D) doesn't exceed 0.26. Also, the maximum stress triaxiality and equivalent plastic strain (PEEQ) at this process temperature reached to 0.5 and 0.1, respectively.

Damage evolution and fracture characteristics of coal rock impacted by self‐excited pulse water jet under different stress loading conditions

AbstractIn this paper, based on smoothed‐particle hydrodynamics‐finite element method, numerical models of plunger squeezing water at a sinusoidal velocity were established to simulate self‐excited pulse water jet (SEPWJ). RHT constitutive model was adopted to describe the damage and failure of coal rock impacted by water jet. The morphological evolutions of broken pits and timeliness of rock‐breaking efficiency of SEPWJ and continuous water jet (CWJ) under the conditions with and without stress loadings were obtained and compared. The evolution laws of damage and stress inner coal rock induced by jet impact, and the failure mechanism were revealed. And the influences of different stress loading magnitudes on the fracture characteristics of coal rock were investigated. The results show that the morphologies of broken pits formed by self‐excited pulse jet undergo changes in a semi‐circular, U‐shaped, V‐shaped, and bullet shaped in sequence under the stress‐free loading condition. When applying one‐dimensional (1D) and 2D stress loadings, the shallow but wide broken pits with laminar main cracks along the stress loading direction and the inverted trapezoidal bowl broken pits are formed, respectively. With the increase of 1D stress, the depth and width of broken pits slightly decrease as a quadratic parabolic function and linearly increase, respectively. And the broken pit width and area both show an exponential slow decreasing trends with the increasing 2D stress. SEPWJ can induce higher stresses to cause the earlier occurrence of initial damage and the shorter duration of damage accumulation to coal rock than CWJ, which leads to a better rock‐breaking effect. The surface and deeper coal rock elements are broken mainly due to compressive shear stresses. The 2D stress loading delays the initial damage occurrence and prolongs the damage accumulation duration due to inhibitory effect of stress loading on jet impact.

Acoustic emission characteristics of damage evolution of multi-scale fiber reinforced rubberized concrete under uniaxial compression and tension after being subjected to high temperatures

Acoustic emission characteristics of damage evolution of multi-scale fiber reinforced rubberized concrete under uniaxial compression and tension after being subjected to high temperatures

Characterization of energy-driven damage mechanism and gas seepage in coal under mining-induced stress conditions

Gas seepage and progressive failure of coal are common energy-driven mining phenomena. A comprehensive understanding of the energy-driving mechanism behind the catastrophic behavior of mining-induced coal is fundamental to innovating the technology of coal and gas co-mining. Thus, this study simulated three typical mining stress evolution process in protective coal-seam mining (PCM), top-coal caving mining (TCM), and non-pillar mining (NM) to investigate the energy evolution and distribution patterns of coal. The results indicate a strong correlation between energy dissipation and gas seepage. By transitioning from PCM and TCM to NM, the peak elastic strain energy of gas-bearing coal increased by 155.92 %, and the ratio of peak dissipative energy decreased from 51 % to 41 %. Under the PCM stress path, gas seepage decreased the energy storage by 13.52 %, whereas the pre-mining pressure relief and enhanced permeability simulation increased in peak dissipation energy by 49.66 %. Using the cumulative dissipative energy as a damage variable reveals that the degree of coal damage evolution under PCM is higher than other mining methods. Based on the energy-driven damage mechanism, a new coal permeability model was established, and its comparison with classical permeability model demonstrated its excellent fitting effectiveness.

Apply frequency response function schemes for damage detection in composite nanoscale-pipes under transient conditions

Knowledge of Nanoscale-structures sustainability is strongly associated with the reliability and the performances of Nano-electro-mechanical systems such as Nanoactuators and Nano-sensors that are widely used in bio-applications. Therefore, the damages in these types of infinitesimal systems must be quickly and accurately detected, located, and repaired. In this study, a novel damage detection framework in Carbon Fiber Reinforced Polymer (CFRP) composite Nanoscale-Pipes (CNP) subjected to the fatigue effect of water internal pressure and thermal effect via Nanoscale-electrical capacitance sensors (NECS). First, a finite element model (FEM) of CNP damage is established, then the electrical potential difference (EPD) between the Nanoscale-electrodes (NEs) pairs before and after damage is measured. The distributed NECS measuring nano-electrodes are installed around the CNP and load the transient external excitations between each other. It is proposed and applied the transfer function (TF) of the CNP as an "open loop control" system to reflect the evolution of damage. The accuracy and reliability of the suggested technology are verified through the experimental results available in the literature. The results show that when the damage under NEs pairs has begun to grow, the signal amplitude value will change suddenly and sensitively, which demonstrates the effectiveness of the proposed method and the good potential for engineering applications.

Active mechanical cloaking for unsupervised damage resilience in programmable elastic metamaterials.

Owing to the architected void-filled low-density configurations, metamaterials are prone to defects during the complex manufacturing process, or damages under operational conditions. Recently mechanical cloaking has been proposed to shield the effect of such disorders in terms of homogenized mechanical responses. The major drawback in these studies are that the damage location should be known a priori, and the cloak is designed around that damaged zone before manufacturing. Such postulation does not allow unsupervised damage resilience during the manufacturing and service life of metamaterials by active reconfiguration of the stress field depending on the random and unpredictable evolution of damage. Here, we propose a radically different approach by introducing piezoelectric lattices where the effect of random appearance of any single or multiple disorders and damages with complex shapes, sizes and distributions can be shielded through active multi-physically controlled cloaks by voltage-dependent modulation of the stress fields within the cloaking region. Notably, this can be achieved without breaking periodicity and any additional material in the cloaking region unlike earlier studies concerning mechanical cloaks. The proposed active class of elastic metamaterials will bring a step-change in the on-demand mechanical performance of critically important structural components and unsupervised damage resilience for enhanced durability and sustainability.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.