Simulated Damage Research Articles

Evaluation and Simulation of HTHA Damaged Specimen using UT Advanced Techniques

High Temperature Hydrogen Attack (HTHA) is a wellknown phenomenon that impacts the design, operation, and maintenance for syngas production facilities (e.g., hydrogen and carbon monoxide plants). Recommendations regarding material selection and inspection are given by API 941 and API RP 586 [1], that is currently under revision after Tesoro accident. The new rules have highlighted the need to adapt inspection with more advanced NDT methodology, improving the detection of early stage HTHA damage, then supporting a Fitness for Service approach. This paper makes an overview of various projects funded by Materials Technology Institute (MTI) regarding the assessment and improvement of the performance of such UT advanced NDT for HTHA detection, by means of CIVA UT simulations after a detailed metallographic review and statistical modeling of material inclusions and HTHA damage distributions of field samples. HTHA damage inputs and comparisons between experimental and simulated UT images are consistent for different damaged samples (different levels and types of damage, especially for welded samples), different UT acquisition settings and different inspection frequencies. The unprecedented use of HTHA damage distribution laws and NDT simulations of nonmetallic defects and HTHA damage are promising tools which may then used to assess the limits of existing NDT and to define optimized probes and procedures relying on advanced ultrasonic examinations.

Automatic Rail Detection Technology Based on PointNet++ Using 3D Point Cloud Data of Railway Bridges

Recently, railway maintenance has been receiving significant attention to prevent railway accidents. Accordingly, various methods are being developed that apply IT to railroad maintenance, and digital models can be used for an efficient management. To develop a railroad digital model, current status information of the rail is required. However, the existing method consumes considerable time and cost. Therefore, in this study, we proposed a system to scan the railroad using a UAV and automatically detect the rail using PointNet++. The proposed system consisted of Phase 1 (structure from motion) and Phase 2 (rail detection). To verify the performance of the proposed system, the railroad bridge of the Osong test track in Nojang-ri, Jeondong-myeon, Sejong City, South Korea, was targeted. The proposed system is expected to be utilized in various fields such as damage detection, simulation, predictive maintenance, and efficient operation management.

Large-scale machine-learning molecular dynamics simulation of primary radiation damage in tungsten

Large-scale machine-learning molecular dynamics simulation of primary radiation damage in tungsten

Phase-field modeling of stochastic fracture in heterogeneous quasi-brittle solids

Owing to the random nature of heterogeneity, damage and fracture behavior of quasi-brittle materials exhibits a considerable degree of uncertainty. Computational modeling of stochastic fracture in quasi-brittle materials has become an indispensable tool for analysis and design of engineering structures. To this end, we present in this paper a computational framework to capture probabilistic fracture in heterogeneous quasi-brittle solids by combining the random field theory and the phase-field cohesive zone model (PF-CZM). The spatial variation of the material strength and fracture energy is represented by a cross-correlated bivariate random field generated by the Karhunen–Loève expansion. The recently proposed PF-CZM is employed to simulate the stochastic crack nucleation and propagation in quasi-brittle solids. The objectivity of the Monte-Carlo simulation is achieved by imposing a specific condition on the phase-field length scale parameter and the correlation length of the random field. In particular, upon this condition the width of the fracture process zone (FPZ) is considerably smaller than the correlation length of the random field such that the material inside the FPZ does not exhibit significant spatial variations of mechanical properties. As the fracture energy is intrinsically incorporated in the PF-CZM, it is unnecessary in this case to explicitly consider the FPZ width. The resulting probabilistic PF-CZM together is applied to the Monte-Carlo simulations of fracture in concrete structures of different geometries. It is shown that the stochastic simulation results are insensitive to both the phase-field length scale parameter and the finite element mesh discretization as in the previous deterministic analyses. Enhanced with the specific condition on the involved characteristic lengths, the PF-CZM provides a viable tool for stochastic simulations of damage and fracture in quasi-brittle structures.

Numerical Simulation of Severe Damage to a Historical Masonry Building by Soil Settlement

Historical masonry structures, which constitute an important part of the historical heritage, exhibit brittle behavior under tensile stresses due to earthquakes or soil movements/settlements. Therefore, they are sensitive to deformation. The soil–structure interaction problems play an important role in the damage to historical masonry structures. Different settlements, slips, and deformations in foundations causes damage to, and/or partial collapse the load-bearing walls. This study provides a numerical simulation of a historic masonry building on the north coast of Turkey, dating from 19th century, which suffered severe damage due to soil settlement by excavation activity near the building. FE models of the building with and without the soil–structure system were created to identify the damage to the building following soil settlement. The height of the soil domain (bounded as a fixed boundary condition) was accepted in the range of 1.5 m to 15 m. The damage propagation between the numerically obtained damage and the existing damage to the building was detailed and compared. In terms of displacement, the maximum vertical and horizontal displacement values reflecting the existing damage to the building were determined as 22 mm and 85 mm, respectively. The soil depth of 6 m was also considered acceptable for deciding the soil–structure interaction. For this, the sum of the rigid basement and the soil depth can be selected to be equal to the total height of the building participating in free vibration. It was concluded that the numerical procedure employed provided an effective representation of existing damage to a building due to soil settlement. Moreover, the procedure described can be adopted for possible collapse simulation.

Simulation and analysis of fire and pressure reducing valve damage in on-board liquid hydrogen system of heavy-duty fuel cell trucks

Simulation and analysis of fire and pressure reducing valve damage in on-board liquid hydrogen system of heavy-duty fuel cell trucks

Damage threshold of LiF crystal irradiated by femtosecond hard XFEL pulse sequence.

Here we demonstrate the results of investigating the damage threshold of a LiF crystal after irradiating it with a sequence of coherent femtosecond pulses using the European X-ray Free Electron Laser (EuXFEL). The laser fluxes on the crystal surface varied in the range ∼ 0.015-13 kJ/cm2 per pulse when irradiated with a sequence of 1-100 pulses (tpulse ∼ 20 fs, Eph = 9 keV). Analysis of the surface of the irradiated crystal using different reading systems allowed the damage areas and the topology of the craters formed to be accurately determined. It was found that the ablation threshold decreases with increasing number of X-ray pulses, while the depth of the formed craters increases non-linearly and reaches several hundred nanometers. The obtained results have been compared with data already available in the literature for nano- and picosecond pulses from lasers in the soft X-ray/VUV and optical ranges. A failure model of lithium fluoride is developed and verified with simulation of material damage under single-pulse irradiation. The obtained damage threshold is in reasonably good agreement with the experimentally measured one.

Study of the Influence of the Irradiation Flux Density on the Formation of a Defect Structure in AlN in the Case of the Effect of Overlapping of the Heavy Ion Motion Trajectories in the Near-Surface Layer.

The aim of this paper is to test the previously stated hypothesis and several experimental facts about the effect of the ion flux or ion beam current under irradiation with heavy ions on the radiation damage formation in the ceramic near-surface layer and their concentration. The hypothesis is that, when considering the possibilities of using ion irradiation (usually with heavy ions) for radiation damage simulation at a given depth, comparable to neutron irradiation, it is necessary to consider the rate factor for the set of atomic displacements and their accumulation. Using the methods of X-ray diffraction analysis, Raman and UV-Vis spectroscopy, alongside photoluminescence, the mechanisms of defect formation in the damaged layer were studied by varying the current of the Xe23+ ion beam with an energy of 230 MeV. As a result of the experimental data obtained, it was found that, with the ion beam current elevation upon the irradiation of nitride ceramics (AlN) with heavy Xe23+ ions, structural changes have a pronounced dependence on the damage accumulation rate. At the same time, the variation of the ion beam current affects the main mechanisms of defect formation in the near-surface layer. It has been found that at high values of flux ions, the dominant mechanism in damage to the surface layer is the mechanism of the formation of vacancy defects associated with the replacement of nitrogen atoms by oxygen atoms, as well as the formation of ON-VAl complexes.

Simulation of Brittle Materials Based on Ordinary State-based Peridynamics

We present a coupled model for brittle materials based on the ordinary state-based peridynamics. The ordinary state-based peridynamics theory is suitable for describing the plastic incompressibility problem and has good application prospects in the fracture damage simulation of brittle materials. The brittle material is a material with a compressive load-bearing capacity greater than the tensile load-bearing capacity and has the characteristics of incompressibility, which is consistent with the application scope of ordinary state-based peridynamics. The mechanical behavior of brittle materials is simulated and analyzed using the ordinary state-based peridynamics theory coupled with brittle materials, and the validity of the model is verified using the finite element method. The results show that the model can effectively capture the displacement field distribution of the brittle material, and the comparison of the finite element results displacement field is consistent. Finally, crack extension analysis is performed on the brittle material plate with prefabricated defects, where the cracks extend along the defect location, bifurcate, and finally penetrate the upper and lower surfaces of the material. The results show that the model can effectively predict the crack expansion path of the material, which provides a new research idea for the simulation of crack expansion in brittle materials.

Simulation of sandstone formation damage caused by solid particle invasion

During the drilling and completion process, the invasion of solid particles can have a serious impact on reservoir permeability, but there is a lack of effective prediction models for its impact. We developed a prediction model of solid particle invasion damage in response to the issue of reservoir damage induced by solid particle invasion during the exploitation of sandstone reservoirs. By considering the changes in pore permeability characteristics, particle migration and rock stress-strain state are coupled. The findings reveal that as filtration duration increases, the concentration of suspended particles and sediment particles increases, resulting in a progressive reduction in formation permeability around the wellbore. The greater the filtration coefficient, the greater the quantity of particle deposition, however, this also leads to a slowdown in the growth in deposition quantity. As the diffusion rate increases, particles are more likely to deposit. The concentration of suspended particles decreases progressively as tortuosity increases, as does the concentration of sediment particles. Large saturation sedimentation in the pore throat may cause more suspended particles to deposit, lower the effective seepage channel of the pore throat, and drastically impair formation permeability. The results of the impact factor comparison showed that filtration coefficient and medium tortuosity are the key factors. Improving the temporary plugging effect of solid particles in formations with large tortuosity of pore throats can effectively reduce reservoir damage. The findings of this study can help for optimization design of solid particles in drilling fluid for reservoir protection.

Micromechanical Finite Element Simulation of Low Cycle Fatigue Damage Occurring During Sliding Wear Test of ECAP-Processed AA7075 Alloy

Micromechanical Finite Element Simulation of Low Cycle Fatigue Damage Occurring During Sliding Wear Test of ECAP-Processed AA7075 Alloy

A gradient-based non-local GTN model: Explicit finite element simulation of ductile damage and fracture

Non-local models have over the years been established as an effective approach to solve the pathological mesh dependency problem observed in finite element simulation of strain-softening materials. This paper presents the formulation, implementation, and application of a gradient-based non-local Gurson–Tvergaard–Needleman (GTN) model for explicit finite element analysis. The porosity is taken as the non-local variable where the increment in porosity is averaged over the volume using an implicit gradient model. The gradient model is implemented in Abaqus/Explicit by utilising the coupled thermal–mechanical solver, which proves to be both a simple and computationally efficient approach. Due to the use of an explicit integration scheme, a transient term is introduced to the partial differential equation of the gradient formulation. The non-local GTN model is compared to the local counterpart for increasing mesh refinements using a plane strain shear band specimen, a plane strain tension specimen, and a plane strain compact tension specimen. The proposed approach can remedy the pathological mesh dependency problem. For the plane strain tension specimen, it is shown that the non-local GTN model will preserve the fracture mode (slant versus cup–cup fracture mode) when the mesh is refined. The non-local GTN model is also able to predict the same fracture mode as observed in ductile tearing experiments. However, non-local averaging can over-smooth the fields and exclude the slant fracture mode from occurring if the material length Lc is too large.

Bayesian parameter estimation for the inclusion of uncertainty in progressive damage simulation of composites

Despite gradual progress over the past decades, the simulation of progressive damage in composite laminates remains a challenging task, in part due to inherent uncertainties of material properties. This paper combines three computational methods — finite element analysis (FEA), machine learning and Markov Chain Monte Carlo — to estimate the probability density of FEA input parameters while accounting for the variation of mechanical properties. First, 15,000 FEA simulations of open-hole tension tests are carried out with randomly varying input parameters by applying continuum damage mechanics material models. This synthetically-generated data is then used to train and validate a neural network consisting of five hidden layers and 32 nodes per layer to develop a highly efficient surrogate model. With this surrogate model and the incorporation of statistical test data from experiments, the application of Markov Chain Monte Carlo algorithms enables Bayesian parameter estimation to learn the probability density of input parameters for the simulation of progressive damage evolution in fibre reinforced composites. This methodology is validated against various open-hole tension test geometries enabling the determination of virtual design allowables.

Probing radiation resistance in simulated metallic core–shell nanoparticles

We present molecular dynamics (MD) simulations of radiation damage in Fe nanoparticles (NP) and bimetallic FeCu core–shell nanoparticles (CSNP). The CSNP includes a perfect body-centered cubic (bcc) Fe core coated with a face-centered cubic (fcc) Cu shell. Irradiation with Fe Primary Knock-on Atoms (PKA) with energies between 1 and 7 keV leads to point defects, without clustering beyond divacancies and very few slightly larger vacancy clusters, and without interstitial clusters, unlike what happens in bulk at the same PKA energies. The Fe-Cu interface and shell can act as a defect sink, absorbing radiation-induced damage and, therefore, the final number of defects in the Fe core is significantly lower than in the Fe NP. In addition, the Cu shell substantially diminishes the number of sputtered Fe atoms, acting as a barrier for recoil ejection. Structurally, the Cu shell responds to the stress generated by the collision cascade by creating and destroying stacking faults across the shell width, which could also accommodate further irradiation defects. We compare our MD results to Monte Carlo Binary Collision Approximation (BCA) simulations using the SRIM code, for the irradiation of an amorphous 3-layer thin film with a thickness equal to the CSNP diameter. BCA does not include defect recombination, so the number of Frenkel pairs is significantly higher than in MD, as expected. Sputtering yield (Y) is underestimated by BCA, which is also expected since the simulation is for a thin film at normal incidence. We also compare MD defect production to bulk predictions of the analytic Athermal Recombination Corrected Displacements Per Atom (arc-dpa) model. The number of vacancies in the Fe core is only slightly lower than arc-dpa predictions, but the number of interstitials is reduced by about one order of magnitude compared to vacancies, at 5 keV. According to the radiation resistance found for FeCu CSNP in our simulations, this class of nanomaterial could be suitable for developing new radiation-resistant coatings, nanostructured components, and shields for use in extreme environments, for instance, in nuclear energy and astrophysical applications.

Simulation and Analysis of Damage of UAV-borne Kinetic Interceptor to Cluster Warhead based on AUTODYN

The UAV-Brone Kinetic Kill Vehicle (KKV) can effectively enhance the defense capability at low and medium altitude by intercepting missiles and other aircrafts in a reverse orbit manner. This paper mainly studies the interception and damage effectiveness of the typical KKV energy interceptors to cluster warheads. Based on the equivalent principle of “the main material remains unchanged, the mass remains unchanged, and the size remains unchanged”, the equivalent models of interceptors and cluster warheads are established respectively. The damage effects under different interception states are simulated and analyzed using ANSYS AUTODYN software. The conclusion of simulation analysis has a certain supporting effect on equipment development, and also provides ideas for other numerical simulation analysis.

Numerical Simulation of Shock Wave Damage to Medium-Range and Long-Range Targets

In order to accurately analyze the effect of a shock wave on a missile launch vehicle as a whole and on its components when the launch vehicle is at a medium or long distance from the detonation center, a simulation method based on the empirical algorithm and numerical analysis was carried out in this study. The method significantly reduced the computational cost while ensuring computational accuracy. Based on the simulation method, a finite element model for a typical missile launch vehicle was established that consisted of 2.5 million elements. Based on the structured arbitrary Lagrangian-Eulerian method and the fluid-structure coupling algorithm, it took the model only a few hours to simulate the second-level physical process. Next, a shock wave load model was built with a 2000 kg TNT equivalent detonation condition, and the degree of damage to the launch vehicle within 25–45 m from the detonation center was analyzed. The results showed that the joint action of the shock wave overpressure and the dynamic pressure was the main source of damage. Specifically, the missile launcher, the cab, and the fuel tank were the key vulnerable parts. The effective damage radius of the 2000 kg TNT equivalent detonation to the missile launch vehicle was 35 m.

Study on impact damage mechanism of gun propellant based on bonding contact model

As the main launch energy of barrel weapon, the dynamic mechanical properties of gun propellant is very important to evaluate the launch safety. Through the transverse drop hammer impact damage test at room temperature and the initial dynamic vivacity ratio test of the propellant, the crack growth law and the fracture degree of the damaged propellant were obtained separately. Based on the Hertz-Mindlin bonding contact model, the discrete element mechanical model of the rosette 19-hole gun propellant was established, and the transverse drop hammer impact damage simulation was carried out. The damage mechanism of the bonding contact model and the fracture degree of the damaged propellant were acquired, which were also verified by tests. The results show that the bonding contact model can accurately describe the impact damage law of propellant. The research results of this paper can be used to predict the abnormal chamber pressure caused by fracture of propellant, provides a research means for mechanical property evaluation of 3D printing gun propellant, and lays a theoretical foundation for quantitative evaluation of launch safety.

The effect of mesenchymal stromal cells of different origin on morphological parameters in the somatosensory cortex of rats with acute cerebral ischemia

Ischemic stroke is the second leading cause of death and the leading cause of disability worldwide. So far, promising experimental data have been obtained regarding the elimination of neurological dysfunction and the reduction of the area of ischemic damage when using mesenchymal stromal cells (MSCs). Purpose: to characterize the influence of MSCs of different origin, MSC lysate of human Wharton cells and citicoline on the dynamics of destructive changes in the somatosensory cortex of rats with acute cerebrovascular accident according to light microscopy and micromorphometry data. Materials and methods. An experiment was performed using 190 -4-month-old male Wistar rats weighing 160-190 g, which were subjected to transient bilateral 20-minute ischemia-reperfusion (IR) of the internal carotid arteries. After modeling the pathology, the animals were injected into the femoral vein with obtained from human umbilical cord Wharton’s jelly-derived MSCs, human and rat adipose tissue-derived MSCs at a dose of 106 cells/animal. Other groups of experimental animals were intravenously injected with fetal rat fibroblasts at a dose of 106 cells/animal in 0.2 ml of physiological solution and lysate of human umbilical cord Wharton’s jelly-derived MSCs at a dose of 0.2 ml/animal. Control animals were injected IV with 0.2 ml of physiological solution. The last group of rats received a single dose of the reference drug citicoline at a dose of 250 mg/kg. The studies were conducted on the 7th and 14th day. In the somatosensory cortex, the total number of neuron nuclei per 1 mm2 was counted, and the ratio of the number of intact neuron nuclei and nuclei with pathological changes (karyorrhexis and karyopyknosis) was also determined. Results: The transplantation of stem cells, lysate of human umbilical cord Wharton’s jelly-derived MSCs, or citicoline contributed to an increase in the number of neurons with nuclei in the somatosensory cortex, as well as an increase in the number of nuclei that did not undergo pathological changes. The transplantation of human umbilical cord Wharton’s jelly-derived MSCs had the most positive effect. The number of neuron nuclei in 1 mm2 that did not undergo pathological changes in the somatosensory cortex in this group of animals approached the number of nuclei in the group of pseudo-operated animals, while the number of nuclei that did not undergo pathological changes significantly exceeded the number of nuclei with signs of destruction. Conclusion: A significant increase in the number of neurons without signs of pathological changes was observed in all experimental groups of rats during the simulation of ischemic brain damage after the introduction of various types of studied mesenchymal stromal cells, lysate or citicoline. The most positive result in the somatosensory cortex was achieved after the introduction of human umbilical cord Wharton’s jelly-derived MSCs.

Research on Wind Turbine Blade Damage Fault Diagnosis Based on GH Bladed

With the increasing installed capacity of wind turbines, ensuring the safe operation of wind turbines is of great significance. However, the failure of wind turbines is still a severe problem, especially as blade damage can cause serious harm. To detect blade damage in time and prevent the accumulation of microdamage of blades evolving into severe injury, a damage dataset based on GH Bladed simulation of blade damage is proposed. Then, based on the wavelet packet analysis theory method, the MATLAB software can automatically analyze and extract the energy characteristics of the signal to identify the damage. Finally, the GH Bladed simulation software and MATLAB software are combined for fault diagnosis analysis. The results show that the proposed method based on GH Bladed to simulate blade damage and wavelet packet analysis can extract damage characteristics and identify single-unit damage, multiple-unit damage, and different degrees of damage. This method can quickly and effectively judge the damage to wind turbine blades; it provides a basis for further research on wind turbine blade damage fault diagnosis.

Progressive Classifier Mechanism for Bridge Expansion Joint Health Status Monitoring System Based on Acoustic Sensors.

The application of IoT (Internet of Things) technology to the health monitoring of expansion joints is of great importance in enhancing the efficiency of bridge expansion joint maintenance. In this study, a low-power, high-efficiency, end-to-cloud coordinated monitoring system analyzes acoustic signals to identify faults in bridge expansion joints. To address the issue of scarce authentic data related to bridge expansion joint failures, an expansion joint damage simulation data collection platform is established for well-annotated datasets. Based on this, a progressive two-level classifier mechanism is proposed, combining template matching based on AMPD (Automatic Peak Detection) and deep learning algorithms based on VMD (Variational Mode Decomposition), denoising, and utilizing edge and cloud computing power efficiently. The simulation-based datasets were used to test the two-level algorithm, with the first-level edge-end template matching algorithm achieving fault detection rates of 93.3% and the second-level cloud-based deep learning algorithm achieving classification accuracy of 98.4%. The proposed system in this paper has demonstrated efficient performance in monitoring the health of expansion joints, according to the aforementioned results.