Critical Damage Research Articles

An equivalent target plate damage probability calculation mathematics model and damage evaluation method

Aiming at the requirement of damage testing and evaluation of equivalent target plate based on the explosion of intelligent ammunition, this paper proposes a novel method for damage testing and evaluation method of circumferential equivalent target plate. Leveraging the dispersion characteristics parameters of fragment, we establish a calculation model of the fragment power situation and the damage calculation model under the condition of fragment ultimate penetration equivalent target plate. The damage model of equivalent target plate involves the fragment dispersion density, the local perforation damage criterion, the tearing damage model, and the damage probability. We use the camera to obtain the image of the equivalent target plate with fragment perforation, and research the algorithm of fragment distribution position recognition and fragment perforation area calculation method on the equivalent target plate by image processing technology. Based on the obtained parameters of the breakdown position and perforation area of fragments on equivalent target plate, we apply to damage calculation model of equivalent target plate, and calculate the damage probability of each equivalent target plate, and use the combined probabilistic damage calculation method to obtain the damage evaluation results of the circumferential equivalent target plate in an intelligent ammunition explosion experiment. Through an experimental testing, we verify the feasibility and rationality of the proposed damage evaluation method by comparison, the calculation results can reflect the actual damage effect of the equivalent target plate.

Wavy approach for fluid–structure interaction with high Froude number and undamped structure

This paper addresses the fluid–structure interaction problem, with an interest on the interaction of a gravity wave with a flexible floating structure, anchored to a seabed of constant depth. To achieve this goal, we make use of the model equations, namely, the Navier–Stokes equations and the Navier–Lamé equation, as well as the associated the boundary conditions. Applying the multi-scale expansion method, these set of equations are reduced to a pair of nonlinearly coupled complex cubic Ginzburg–Landau equations (CCGLE). By applying the proposed modified expansion method, the group velocity dispersion and second-order dispersion relation are deduced. In the same vein, modulation instability (MI) is investigated as a mechanism of formation of pulse trains in fluid–structure system using a CCGLE. For the analytical analysis, we made use of the inverse scattering method to find analytical solutions to the coupled nonlinear equations. Through that method, the obtained solutions depict rogue-shaped waves. Our results suggest that uncontrolled MI within the interaction between a flexible body and gravity waves in viscous flow may be considered as the principal source of many structural ruptures, which are the first cause of critical damage due to the great energy and unpredictability of rogue waves. The present work aims to provide tools to model a wide range of physical problems regarding the interaction of surface gravity waves and an offshore-anchored structure, and it aims to be essential to our understanding of the nonlinear characteristics of offshore structures in real-sea states.

Refined simulation and verification of blast loads on curved shells

Terrorist attacks and accidental explosions pose significant challenges to the security of public buildings. This study combines detailed test data from three different curved shells to simulate different blast scenarios, effectively validating the simulation of blast loads and blast waves. Based on dynamic time warping and blast damage criteria, a similarity algorithm for blast loads based on overpressure histories of multi-gauge is proposed, and the similarity of blast loads on curved shells under four different scenarios is systematically evaluated. The spatiotemporal distribution of blast pressure around curved shells is analyzed based on simulation results. This paper provides a convenient tool for predicting blast loads on complex building shapes and optimizing blast-resistant designs.

Study and Optimization of the Punching Process of Steel Using the Johnson–Cook Damage Model

Sheet metal forming processes are widely used in applications such as those in the automotive or aerospace industries. Among them, punching is of great interest due to its high productivity and low operating cost. However, it is necessary to optimize these processes and adjust their parameters, such as clearance, shear force or tool geometry, to obtain the best finishes and minimize crack generation. Thus, the main objective of this research work is to optimize the punching process to achieve parts that do not require subsequent processes, such as deburring, by controlling the properties of the starting materials and with the help of tools such as design of experiments and simulations. In the present study, tensile tests were performed on three steels with different compositions and three sample geometries. The information obtained from these tests has allowed us to determine the parameters of the Johnson–Cook damage criteria. Moreover, punching was performed on real parts and compared with simulations to analyze the percentage of burnish surface. The results obtained show that the methodology used was correct and that it can be extrapolated to other types of die-cutting processes by reducing the percentage of surface fractures and predicting the appearance of cracks. Furthermore, it was observed that clearance has a greater influence than processing speed, while the minimum percentage of the burnish area was observed for the minimum values of clearance.

Comparative study on bending behavior and damage analysis of 3D-printed sandwich core designs with bio-inspired reinforcements

In this study, novel sandwich core designs with bio-inspired reinforcements were proposed and their bending behaviors were comparatively examined. The geometrical shapes of alligator osteoderm and chambered nautilus shell were utilized as bio-inspired reinforcements for sandwich core structures. Sandwich core structures were produced through the additive manufacturing method. Experimental tests and finite element analysis were performed to determine the bending performances of the proposed sandwich core structures. The load-carrying capacity, deformation ability, damage-tolerant capability, energy absorption, and damage mechanisms of the proposed sandwich core structures were comparatively investigated through experimental and numerical methods. The orthotropic material model and Hashin’s damage criterion were used in the numerical model of 3D-printed sandwich core structures to consider the effect of the filament raster orientation on the elastic and damage behavior of the sandwich core structures. Compared to the classical honeycomb sandwich core structure, while bio-inspired reinforcements improved the load-carrying capacity and damage-tolerant capability of sandwich core structures, they reduced the energy absorption ability of sandwich core structures due to reducing the vertical deformation ability of sandwich core structures. Bio-inspired reinforcements significantly affected the stress distribution and damage behavior of the sandwich core structures. They reduced von Mises stress level at the outer cell edges of the sandwich core structures and caused reinforcement damage instead of outer cell damage.

ADAR1 promotes cisplatin resistance in intrahepatic cholangiocarcinoma by regulating BRCA2 expression through A-to-I editing manner.

Aberrant A-to-I RNA editing, mediated by ADAR1 has been found to be associated with increased tumourigenesis and the development of chemotherapy resistance in various types of cancer. Intrahepatic cholangiocarcinoma (iCCA) is a highly aggressive malignancy with a poor prognosis, and overcoming chemotherapy resistance poses a significant clinical challenge. This study aimed to clarify the roles of ADAR1 in tumour resistance to cisplatin in iCCA. We discovered that ADAR1 expression is elevated in iCCA patients, particularly in those resistant to cisplatin, and associated with poor clinical outcomes. Downregulation of ADAR1 can increase the sensitivity of iCCA cells to cisplatin treatment, whereas its overexpression has the inverse effect. By integrating RNA sequencing and Sanger sequencing, we identified BRCA2, a critical DNA damage repair gene, as a downstream target of ADAR1 in iCCA. ADAR1 mediates the A-to-I editing in BRCA2 3'UTR, inhibiting miR-3157-5p binding, consequently increasing BRCA2 mRNA and protein levels. Furthermore, ADAR1 enhances cellular DNA damage repair ability and facilitates cisplatin resistance in iCCA cells. Combining ADAR1 targeting with cisplatin treatment markedly enhances the anticancer efficacy of cisplatin. In conclusion, ADAR1 promotes tumour progression and cisplatin resistance of iCCA. ADAR1 targeting could inform the development of innovative combination therapies for iCCA.

Combined Solution for Critical Damage Determination and Fracture Prediction in AA1050-O Alloy Sheets

Combined Solution for Critical Damage Determination and Fracture Prediction in AA1050-O Alloy Sheets

Verification of the MLP network-based current sensor fault classifier for vector-controlled AC motor drives

In modern drive systems, the aim is to ensure their operational safety. Damage can occur not only to the components of the motor itself but also to the power electronic devices included in the frequency converter and the sensors in the measurement circuit. Critical damage to the electric drive that makes its further exploitation impossible can be prevented by using fault-tolerant control (FTC) algorithms. These algorithms are very often combined with diagnostic methods that assess the degree and type of damage. In this paper, a fault classification algorithm using an artificial neural network (ANN) is analysed for stator phase current sensors in AC motor drives. The authors confirm that the investigated classification algorithm works equally well on two different AC motors without the need for significant modifications, such as retraining the neural network when transferring the algorithm to another object. The method uses a stator current estimator to replace faulty sensor measurements in a vector control structure. The measured and estimated currents are then subjected to a classification process using a multilayer perceptron (MLP), which has the advantage of a small structure size compared to deep learning structures. The uniqueness of the method lies in the use of data in the training set that are not dependent on the parameters of a specific motor. Four types of current sensor faults were studied, namely total signal loss, gain error, offset, and signal saturation. Simulations were performed in a MATLAB/SIMULINK environment for drive systems with an induction motor (IM) and a permanent magnet synchronous motor (PMSM). The results show that the algorithm correctly evaluates the type of damage in more than 99.6% of cases regardless of the type of motor. Therefore, the results presented here may help to develop universal diagnostic methods that will work on a wide variety of motors.

Micromechanical effects of substrate hardness on graphene nano-cutting quality

In the nanocutting process of graphene, the mechanism on the atomic scale of the effect of substrate hardness on the edge quality of graphene nanoribbons has not been thoroughly investigated. In this paper, we construct a diamond probe (radius of 5 Å) to cut graphene (190 Å × 113 Å) models with different substrates (silicon/sapphire/silicon carbide), molecular dynamics simulations were used to study the effect of substrate hardness and cutting depth on the atomic structure of graphene nanoribbon edges by observing the atomic morphology, the number of C-C bonds, the radial distribution function and friction. The results show that during the nanoindentation stage, when graphene is in the critical damage state, the substrate with high hardness has high deformation strength, the substrate deformation is small, and graphene undergoes deformation is also small, but the force Fz on the probe, the critical graphene stress σz and the equivalent stress are all large, and the number of C atoms with CN=3 is large; At the nano-cutting stage, the breakage of C-C bonds and the generation of edge defects are caused by local stress concentration, and the graphene stress σxx along the x-direction has a clear directionality. With the same cutting depth (critical damage depth of silicon substrate), silicon substrate hardness is small, the graphene nanoribbon obtained has less number of circular defects generated at the edge, less total number of defective atoms, more number of CN=3 atoms, large peak of radial distribution function of graphene after cutting, and graphene integrity is better. The hardness of the silicon carbide substrate is large, and the number of C-C bond breaks in graphene during the cutting process is high. Each substrate is cut at its own critical damage depth, and the substrate hardness has no significant effect on the number of C-C bond breaks, the number of circular defects, the total number of defective atoms, and the number of CN=3 atoms in graphene. When the silicon substrate was used, the stable force of the probe is small, the edge structure of graphene has little impact, the edge effect obtained is good. The cutting depth and substrate hardness have little effect on the graphene temperature during the nano-cutting process. In this paper, the atomic structure of graphene edges after cutting is analysed and investigated on the atomic scale, and the above results are combined to provide theoretical guidance for obtaining efficient and high-quality and low-damage graphene nanoribbon cutting.

A grid-based methodology for the assessment of time-dependent building damage at large scale

Leakage into underground constructions can result in time-dependent settlements in soft clays. In urban areas with spatial variability in geologic stratification, groundwater conditions and soil compressibility, differential settlements may occur, causing damage to buildings. Current methods for damage assessment that rely on 1D formulations for settlement prediction are not representative for drawdown-induced settlements in heterogeneous environments. Thus, in this paper, we propose a stand-alone approach to integrating spatially distributed, non-Gaussian settlement data into early-stage building damage assessments at a district scale. Deformations computed using a 2D coupled hydro-mechanical finite element model with an advanced constitutive model were then employed to get the time-dependent settlements computed as a 3D grid (along x- and y-directions) over a large area. Building damage was then calculated from these green-field simulations with typically used damage parameters for each building-specific settlement profile and comparing these with damage criteria. The approach was applied to 215 buildings in central Gothenburg, Sweden by simulating scenarios of 10 kPa and 40 kPa pore pressure drawdown in the lower (confined) aquifer. Several scenarios were studied, and the correlation between damage parameters and damage criteria was assessed. Finally, a sensitivity study on grid resolution was performed, as well as a validation against observed damage data. The proposed methodology offers an effective way for early-stage damage assessments at a large area for non-Gaussian settlements so that further investigations and mitigation measures can be targeted to the buildings and locations at the highest risk for damage.

Effect of bondline thickness on the mechanical performance of CFRP laminate with asymmetric damage repaired by double-sided adhesive patch

As a common CFRP repair method, double-sided adhesive patch has been widely used in the automotive and aeronautic industry. More specific research is thus needed to help better understanding the effect of repairing parameters on the mechanical performance of CFRP structures after patch bonding. In this paper, experimental and Finite Element Modelling (FEM) efforts were made on the adhesive repaired CFRP laminate with different bondline thicknesses. Artificial damage was prefabricated in the centre of the CFRP laminate, which was then repaired through double-sided adhesive patch. Quasi-static tensile tests were conducted on the repaired specimen up to failure, to obtain the load-displacement curves. With a bondline thickness of 0.5 mm, the repaired CFRP structure reached its maximum peak load, increased by 25.3% and 26.4% compared to 0.2 mm and 1.0 mm bondline thicknesses, respectively. SEM observations were used to analyse the influence of adhesive thickness on the fracture modes. Combined with Cohesive Zone Model (CZM) for the adhesive layer and Hashin damage criterion for the CFRP, the FE model of the CFRP laminate repaired with double-sided adhesive patch subjected to tensile loading was established. Finally, the damage evolution as well as the failure modes in the parent laminate and adhesive layer with different bondline thicknesses were compared and analysed. It was revealed that bondline thickness can effectively affect the mechanical performance of CFRP laminate after adhesive patch repair.

Comprehensive investigation on crushing performance and collapse mechanism of friction stir welded aluminium honeycomb by damage modeling

Aluminium honeycomb, renowned for its energy-absorption capabilities, poses significant manufacturing challenges. To address adhesive failure and premature collapse in traditional aluminium honeycomb, this study presents a novel approach - friction stir welded aluminium honeycomb. Traditional honeycombs can lose up to 50 % of their strength during low-velocity impacts, underscoring the need to comprehend the crashworthiness and crushing behaviour of this innovative solution. The study employs a robust finite element framework to predict crashworthiness parameters and deformation under flatwise compression. Enhanced with damage criterion, it offers more realistic predictions, indicating no debonding in welded regions. Most energy is dissipated through plastic folding, making it suitable for high-energy absorption applications. Damage initiates at the corner of the flanges due to stress concentration, minimized by a design modification to barrel-shaped honeycomb, boosting crushing strength by 21 %. This study aids in predicting responses of friction stir welded aluminium honeycombs for design optimization.

Assessing the relationship between landslide susceptibility and land cover change using machine learning

Landslides are natural disasters most frequent in the mountain region of Vietnam, producing critical damage to human lives and assets. Therefore, precisely identifying the landslide occurrence probability within the region is essential in supporting decision-makers or developers in establishing effective strategies for reducing the damage. This study is aimed at developing a methodology based on machine learning, namely Xgboost (XGB), lightGBM, K-Nearest Neighbors (KNN), and Bagging (BA) for assessing the connection of land cover change to landslide susceptibility in Da Lat City, Vietnam. 202 landslide locations and 13 potential drivers became input data for the model. Various statistical indices, namely the root mean square error (RMSE), the area under the curve (AUC), and mean absolute error (MAE), were used to evaluate the proposed models. Our findings indicate that the Xgboost model was better than other models, as shown by the AUC value of 0.94, followed by LightGBM (AUC=0.91), KNN (AUC=0.87), and Bagging (AUC=0.81). In addition, urban areas increased during 2017-2023 from 25 km² to 30 km² in very high landslide susceptibility areas. Our approach can be applied to test the other regions in Vietnam. Our findings might represent a necessary tool for land use planning strategies to reduce damage from natural disasters and landslides.

Exceptional load-bearing capability of Al FPCB/Cu FPCB lap joints using instantaneous laser-based large area facial soldering: Experimental and numerical investigations

This study introduces a novel method for integrating aluminum flexible printed circuit boards (FPCBs) and copper FPCBs into battery management systems (BMS) using and instantaneous large area facial laser source soldering. Achieving a robust bonding strength of 65 MPa involved applying 600 W of laser power for 2 s, enhancing atom diffusion and promoting intermetallic compound (IMC) growth. Finite Element Method (FEM) simulations revealed variations in heat transfer between Al and Cu, affecting IMC thickness at interfaces. Formation of the (Cu, Ni)3Sn4 phase within solder, and variations in laser output significantly influenced solder joint orientation and Al electrode nucleation. Excessive laser power (>800 W) caused critical damage, such as delamination at the Al-PI interface, altering fracture modes and bonding strength. Furthermore, with a detailed examination of the laser soldering phenomenon through both experimental and numerical investigations, this study provides a thorough understanding of the different soldering mechanisms in conventional reflow soldering compared to instantaneous uniform large-area heat source laser soldering. These insights provide new design and material considerations to replace the conventional wiring harness with Al/Cu FPCB lap joints which optimize the circuitry and reducing BMS volume.

A cloud model target damage effectiveness assessment algorithm based on spatio-temporal sequence finite multilayer fragments dispersion

To solve the problem of target damage assessment when fragments attack target under uncertain projectile and target intersection in an air defense intercept, this paper proposes a method for calculating target damage probability leveraging spatio-temporal finite multilayer fragments distribution and the target damage assessment algorithm based on cloud model theory. Drawing on the spatial dispersion characteristics of fragments of projectile proximity explosion, we divide into a finite number of fragments distribution planes based on the time series in space, set up a fragment layer dispersion model grounded in the time series and intersection criterion for determining the effective penetration of each layer of fragments into the target. Building on the precondition that the multilayer fragments of the time series effectively assail the target, we also establish the damage criterion of the perforation and penetration damage and deduce the damage probability calculation model. Taking the damage probability of the fragment layer in the spatio-temporal sequence to the target as the input state variable, we introduce cloud model theory to research the target damage assessment method. Combining the equivalent simulation experiment, the scientific and rational nature of the proposed method were validated through quantitative calculations and comparative analysis.

Progressive damage analysis of embedment of metal washer into timber

ABSTRACT Metal washers are widely used in joints of timber structures. Thick washers embed fully into timber, whereas thin washers partially embed into timber due to their bending deformation. For thick washers, physical models have been proposed to estimate the stiffness and strength of timber. However, for thin washers, these estimation methods are insufficient. The objective of this study is to propose a finite-element analysis (FEA)-based approach to predict the stiffness and strength of wood during washer embedding, as well as forecast plasticity and damage behaviours of timber, regardless of the washer size. The FEA used a constitutive model with plastic and damage criteria for timber. In the FEA, an explicit dynamic solution method was used to prevent solution divergence. The FEA reproduced the embedment load–displacement relation and damage behaviours of three species. In addition, the FEA predicted the initial stiffness, second stiffness, and yield load with error margins of 12%, 16%, and 7%, respectively. The influences of the loading speed and mesh fineness on the FEA were investigated numerically to validate the results. In addition, parametric studies on contact stiffness and damage constants were conducted to understand the influences of material constants on the embedment behaviours of FE models.

Numerical and analytical studies of multi-cell steel-concrete-steel sandwich panels under blast load

The steel-concrete-steel (SCS) sandwich panel possesses exceptional resistance and good integrity, making it successfully applied in protective engineering. Aiming at improving the blast resistance of the structure, a novel multi-cell steel-concrete-steel (MCSCS) sandwich panel was proposed as an alternative to the traditional SCS panel. In this paper, the finite element (FE) model of the MCSCS panel under blast load was first constructed, and the modeling method was verified to be reasonable against field blast tests. Then, an analytical model for predicting the blast response of the MCSCS panel was established based on the equivalent single-degree-of-freedom (SDOF) system, and the strain rate effect was incorporated into the analytical model via employing the material models with strain rate dependence. Finally, three damage criteria for the MCSCS panel under blast load were proposed, and Pressure-Impulse (P-I) diagrams corresponding to different damage levels were constructed via the validated analytical model. Additionally, based on the established analytical model, the accuracy of simplifying the blast pressure history into the triangle form was verified. Numerical and analytical results indicate that the blast resistance of the MCSCS panel is significantly enhanced with the increase of the steel faceplate thickness, and the MCSCS panel exhibits superior blast resistance with the load acting on the top plate rather than bottom plate. In addition, owing to the arrangement of the L-shaped and side stiffeners, the MCSCS panel possesses preferable integrity, and its blast resistance is nearly unaffected by the spacing of headed stud.

A Numerical Simulation Study on the Out-of-Plane Performance of Timber Framework–Brick Wall Systems in Traditional Residential Buildings of Northern China

To improve the out-of-plane collaborative performance of timber frames and walls, a metal connector is proposed and designed. A finite element model of the wall is established, and the composite block damage criteria and surface contact behavior are validated. Additionally, one group without metal connectors and three groups with different numbers of metal connectors placed at various positions in traditional residential wall models are established. Using static loading simulation, the influence of different numbers of metal connectors on the out-of-plane damage patterns, deformation characteristics, and shear force distribution is analyzed. The study reveals that top metal connectors significantly reduce the out-of-plane displacement of the top wall by up to 84.6%. Metal connectors have a significant impact on the deformation capacity of brick walls, with a maximum enhancement of 65.3%. The metal connectors in the middle and lower parts transfer the wall loads to the columns, increasing the horizontal shear at the column head by approximately 7%. The connectors in the middle and lower parts effectively improve the collaborative performance of brick walls and wooden frames.

Construction of a Dimensional Damage Model of Reinforced Concrete Columns under Explosion Loading

When studying the damage law of reinforced concrete building structures under explosive loading, the direct experimental cost is too high and numerical simulations take a long time. Based on the theoretical analysis, the dimensional analysis model of reinforced concrete members under explosive loading can be used to study the damage law of reinforced concrete members under explosive loading. It provides guidance, reduces the number of tests, improves the efficiency of the test, and has certain research significance. In this paper, a typical reinforced concrete column is taken as the main research object. Based on the dimensional analysis method, the relationship between the damage to the reinforced concrete column and the explosion equivalent and explosion distance under explosion loading is studied. The finite element simulation software LS-DYNA 18.2 is used to determine the function relationship between the disturbance in the column and the proportional explosion distance. The results show that when the proportional explosion distance Z is greater than 0.0693 m/kg1/3, the center disturbance of the blasting surface of the reinforced concrete column has a linear relationship with the reciprocal of the proportional explosion distance. The linear relationship can be used to predict the column’s center disturbance under partial explosion conditions, which provides guidance for studying the damage criterion of reinforced concrete under explosion loading.

Determination of Critical Damage Size of Inclined Waterproof Coal Pillar under Asymmetric Load

Quantitative determination of the critical size of an inclined coal pillar in an old goaf water-affected area is of great significance for water damage prevention and safe mining. The critical size of the inclined waterproof coal pillar is derived by using mechanical analyses, numerical calculations, and field engineering practices to determine the stability of the waterproof coal pillar in the old goaf water-affected area of the 1303 working face of Dananhu No. 1 Mine in the Xinjiang region. Firstly, a force model of the inclined waterproof coal pillar was established to reveal the law that the critical size of the coal pillar increases with the increase in coal seam inclination under the action of asymmetric load. Then, numerical simulation was applied to reveal the dynamic evolution processes of plastic deformation–destabilization of the coal pillar under the influence of mining and single-side water pressure, and the critical size of the coal pillar in the study area was determined to be 19.09 m. Finally, measures such as pumping pressure relief and slurry reinforcement were adopted to reduce the deformation rate of the roadway on the side of the coal pillar, which ensured the stability of the waterproof coal pillar and the safe mining of the working face.