Damage In Plates Research Articles

Influence of fireproof damage on structural performance of post-installed anchor joint subjected to post-earthquake fire

To study explore the influence of post-earthquake fireproof coating damage on structural behaviour of steel-concrete post-installed joint, a three-dimensional FE model has been established by ABAQUS software. Parametric analysis has been carried out and the earthquake level on fireproof coating of post-installed joint by changing thickness of fireproof coating is analyzed under the condition of thermal-force coupling. By damage degree variation of fireproof coating, the influence of fireproof coating damage of anchor plate on fire endurance and bearing capacity of post-installed joint is further analyzed.

In Vivo Response of Growth Plate to Biodegradable Mg-Ca-Zn Alloys Depending on the Surface Modification

Because Mg-Ca-Zn alloys are biodegradable and obviate secondary implant removal, they are especially beneficial for pediatric patients. We examined the degradation performance of Mg-Ca-Zn alloys depending on the surface modification and investigated the in vivo effects on the growth plate in a skeletally immature rabbit model. Either plasma electrolyte oxidation (PEO)-coated (n = 18) or non-coated (n = 18) Mg-Ca-Zn alloy was inserted at the distal femoral physis. We measured the degradation performance and femoral segment lengths using micro-CT. In addition, we analyzed the histomorphometric and histopathologic characteristics of the growth plate. Although there were no acute, chronic inflammatory reactions in either group, they differed significantly in the tissue reactions to their degradation performance and physeal responses. Compared to non-coated alloys, PEO-coated alloys degraded significantly slowly with diminished hydrogen gas formation. Depending on the degradation rate, large bone bridge formation and premature physeal arrest occurred primarily in the non-coated group, whereas only a small-sized bone bridge formed in the PEO-coated group. This difference ultimately led to significant shortening of the femoral segment in the non-coated group. This study suggests that optimal degradation could be achieved with PEO-coated Mg-Ca-Zn alloys, making them promising and safe biodegradable materials with no growth plate damage.

Improved Damage Localization and Quantification of CFRP Using Lamb Waves and Convolution Neural Network

A novel method is proposed in this paper for simultaneously locating and quantifying damage in composite plates by employing Lamb waves and the algorithm of convolution neural network. The interaction between Lamb wave and damage of different degrees is also studied by simulation. The experiments on Lamb wave are carried out by employing a square array which is composed of four piezoelectric wafers. First of all, the sensor array collects response signals of Lamb wave as training data, and then de-noises them adopting the method of the wavelet transform. In the process, the damage caused to the composite can be realized through mass blocks. Besides, the Fourier transform is applied for the extraction of the characteristics shown by the signals. After that, the spectrum with the characteristics of damage and corresponding damage modes are employed as input and output of the convolutional neural network, respectively, and accordingly, the model of damage identification is established. Finally, 191 samples (from a total of 192) were identified accurately and the correct recognition rate achieved is 99.5%, which consequently demonstrates that the convolution neural network can be employed to establish the complex mapping relationship between signal and damage, and further proves that the proposed method performs well in high accuracy and great potential in simultaneous localization and quantitative identification of damage existing in composite plate.

An analytical model to predict the compressive damage of concrete plates under contact detonation

Explosions threaten the safety of buildings and occupants by inducing severe damage to concrete structural elements. The effects of close-in and contact loading situations on RC plates have been investigated in literature and the common approaches employ field test results condensed in engineering charts based on cube-root scaling. In this paper, a new analytical model based on a physical framework is developed to (a) investigate shock wave attenuation along the depth of the concrete plate and (b) predict the size of crater damage. The analytical model for shock wave pressure is discussed in comparison to prediction data from established numerical models and existing experimental results. Moreover, consistency of the newly proposed model with established scaling rules is verified with respect to crater size.

On large deformation, damage and failure of ductile plates to blast loading

This paper concerns the irreversible deformation and failure of metal plates to brief, but intense, dynamic (impulsive) load encountered in an air-blast. Hitherto, nearly all of the dynamic structural plasticity models of ‘fully-clamped’ plate only calculates its inelastic (mode I) deformation but have largely ignored damage and failure – exemplified by the partial and/or complete detachment (modes II*, II and III) of a plate from its support through material rupture – that occurs when the blast load is sufficiently intense. An analytical model that captures all three modes of the plate deformation is developed in this paper where emphasis shall be on providing the simplest formulation that contains all the essence of a material and deformation effect needed to quantify the problem. The proposed model adopts an energy density failure criterion of Shen and Jones [19] to delineate the various inelastic failure modes; employs the constitutive framework of limit analysis for simplicity; accounts for the simultaneous influence of bending, membrane stretch and transverse shear through an interaction yield criterion; and, include the effects of strain rate on the material flow stress through the Cowper–Symonds relation. Accuracy of model predictions for square mild-steel plates are assessed through comparison with results from finite element analysis, and experimental data compiled from the literature for a range of impulsive load intensities – they will be shown to be in good general agreement. Design maps delineating the different deformation régimes for different combinations of blast impulse and length versus thickness ratio are constructed for plates of equal mass.

Damage of multi-layer spaced metallic target plates impacted by radial layered PELE

Abstract Three different kinds of PELE (the penetrator with lateral efficiency) were launched by ballistic artillery to impact the multi-layer spaced metal target plates. The impact velocities of the projectiles were measured by the velocity measuring system. The damage degree and process of each layer of target plate impacted by the three kinds of projectiles were analyzed. The experimental results show that all the three kinds of projectiles have the effect of expanding holes on the multi-layer spaced metal target plates. For the normal structure PELE(without layered) with tungsten alloy jacket and the radial layered PELE with tungsten alloy jacket, the diameters of holes on the second layer of plates are 3.36 times and 3.76 times of the diameter of the projectile, respectively. For radial layered PELE with W/Zr-based amorphous composite jacket, due to the large number of tungsten wires dispersed after the impact, the diameter of the holes on the four-layer spaced plates can reach 2.4 times, 3.04 times, 5.36 times and 2.68 times of the diameter of the projectile. Besides, the normal structure PELE with tungsten alloy jacket and the radial layered PELE whit tungsten alloy jacket formed a large number of fragments impact marks on the third target plate. Although the number of fragments penetrating the third target plate is not as large as that of the normal structure PELE, the area of dispersion of fragments impact craters on the third target plate is larger by the radial layered PELE. The radial layered PELE with W/Zr-based amorphous composite jacket released a lot of heat energy due to the impact of the matrix material, and formed a large area of ablation marks on the last three target plates.

A Comprehensive Study on Detection of Hidden Delamination Damage in a Composite Plate Using Curvatures of Operating Deflection Shapes

The aim of this work is to investigate the accuracy and sensitivity of a continuously scanning laser Doppler vibrometer (CSLDV) for detection of hidden delamination damage in composite plates. Some work on using a CSLDV for detection of damage in aluminum beams and plates has been done by the authors. The current work is related to a worldwide round robin study sponsored by the Society of Experimental Mechanics. The main difference between the current work and previous work is that the damaged composite plate was provided by the organizer of the round robin study instead of being made by the authors. Hence, the authors have no information about locations of the damage, which means this is more like a blind test. The most significant advantage of using a CSLDV for vibration measurement of a structure is that a spatially dense operating deflection shape (ODS) of the structure can be obtained and further used to calculate the curvature of the ODS (CODS). A comprehensive study to detect the hidden damage in the composite plate by using the first seven CODSs from the corresponding ODSs of the plate is conducted. The study shows that different CODSs have different sensitivities to local anomaly induced by the damage and only two of the seven CODSs can be used to detect the locations of the hidden damage.

Vibration-Based Damage Identification Using Wavelet Transform and a Numerical Model of Shearography

This paper presents a method for the identification of damage in plates based on the post-processing with wavelets of modal rotation fields. These modal rotation fields are obtained by use of a numerical model of shearography, which includes the simulation of noise in the data generated. The discrete wavelet transform was chosen because of its high sensitivity to perturbations in the modal rotations. Distinct damage scenarios, defined by regions where the thickness of a plate is reduced, are considered in this paper. A study on the differences in the natural frequencies and the changes in modal rotation fields due to the damage is carried out. The order of the B-spline wavelets used in the post-processing of the modal rotation fields is discussed. The damage detectability in terms of its intensity, the selected mode, and the type of rotation field and wavelet coefficient is also studied. Finally, a scheme for the damage detectability enhancement, in particular for multiple damage scenarios, is proposed.

A damage identification method for a thin plate structure based on PVDF sensors and strain mode

Damage identification methods for engineering structures based on vibration parameters have the advantages of easy detection and high precision; however, structural strain information is more sensitive to structural damage than displacement information. Traditional resistance strain sensors have low accuracy and poor stability when measuring structural strains. Therefore, this paper uses a highly sensitive polyvinylidene fluoride dynamic strain sensor to identify structural damage in a thin plate. The polyvinylidene fluoride sensor is used to obtain structural strain response information, and structural modal parameters are identified using operational modal identification methods based on the natural excitation technique and the eigensystem realization algorithm. This paper uses a damage index based on mode shape and flexibility. A new damage index based on the LU decomposition of the flexibility matrix is used to identify the damage of the thin plate structure. The effectiveness of the modal identification methods and the new damage index is validated via an elastic thin plate experiment. The results show that the modal identification method and the new damage index proposed in this paper can identify damage in a thin plate structure. Sensor comparison experiments also show that compared with a resistance strain sensor, the polyvinylidene fluoride sensor has higher damage sensitivity, better damage recognition and the ability to recognize farther from the sensor.

Influence of the stacking sequence on the low-energy impact resistance of flax/PA11 composite

In this paper, the low-energy impact behavior of a fully biobased composite made of bio-sourced polyamide 11 resin reinforced with flax fibers was investigated. Different composite laminates were studied in order to determine the stacking sequence effects on the impact behavior of these composites. Four stacking sequences were manufactured: unidirectional [0°]8, cross-ply [0°/90°]2s, sandwich-like [02°/902°]s and quasi-isotropic [45°/0/−45°/90°]s. A low impact energy of 3.6 J was applied on these laminates by means of a drop weight impact tower. The impact properties of these lay-ups were ascertained by analysing the impact load history, the maximal displacement of the impactor and the absorbed energy. Damage after impact was further assessed by visual inspections, topographic measurements, C-scan and X-ray micro-tomography observations. The results show that impact damage of composite plates is highly influenced by fiber orientation. The impact test data are in good agreement with damage analysis after impact and indicate that stacking plies in the same orientation lead to a larger induced damage, which is responsible for energy dissipation. The quasi-isotropic composite has the smallest induced damage and the highest peak load. Otherwise, the sandwich-like sequence shows the lowest peak load, the highest energy absorption and significant induced damage. Therefore, it is necessary to choose the most suitable lay-up, in terms of impact behavior, for each considered industrial application.

Non-uniform crack identification in plate-like structures using wavelet 2D modal curvature under noisy conditions

Abstract Non-uniform crack identification in plate-like structures is of significance in mechanical, aerospace, and civil engineering. The 2D modal curvature is often utilized to identify damage in plates, but its capability to precisely characterize non-uniform cracks has not been resolved well, largely due to two noticeable deficiencies, lack of sensitivity to cracks and susceptibility to noise interference. With this concern, this study formulates the wavelet 2D modal curvatures by ameliorating the 2D modal curvature using the real and complex wavelet transform, respectively. Crack-caused singular peaks appear in crack locations can designate the presence and locations of cracks. Superior to the 2D modal curvature, the real-wavelet 2D modal curvature and complex-wavelet 2D modal curvature enjoy the multiscale analysis capability introduced by the wavelet transform, whereby noise interference can be eliminated. Moreover, the complex-wavelet 2D modal curvature is capable of synchronously eliminating noise and characterizing cracks, which endows it with the capability to identify and characterize non-uniform cracks under noisy conditions. The capability of the complex-wavelet 2D modal curvature is analytically and experimentally validated on plates with non-uniform cracks; its applicability is further explored in a numerical scenario of a plate-like sluice gate with non-uniform cracks. The results show the complex-wavelet 2D modal curvature can characterize the length, extent, and non-uniformity of non-uniform cracks, providing an appropriate tool for identifying and characterizing such cracks in plate-like structures under noisy conditions.

Failure analysis of adhesive surface damage in sandwich plates under compressed loads

Failures of honeycomb sandwich plates are analyzed using experiments and three-dimensional (3D) finite element simulations to understand the failure mechanism. Meanwhile, correlations of the critical load and various physical parameters (e.g., height and thickness of the core) are investigated. The results demonstrated that the core height and skin thickness have significant effects on the compressed load buckling of the honeycomb sandwich plates, the core density is a sub-critical sensitive factor, while wall thickness and spacing of the cell, and the sandwich modulus have negligible effects. Cracking on the adhesive surface is the dominant factor to reduce the buckling critical load of the laminated plate, which leads to failures of sandwich plates. The ultimate failure of the sandwich panel is attributed to severe deformations that lead to local cracking of the entire cemented adhesive surface. Due to the bonding of the adhesive surface defects, the actual loads related to the core height are large enough to cause compressions with local buckling. Hence, the actual loads cannot reflect the performance of the sandwich panels. It is recommended to use panels with appropriate thicknesses below the sandwich and moderate grid density in the design.

Damage and fatigue analysis of AA7050-T7451 plate with cold expanded hole based on a micro-void evolution model

The ultimate tensile strength and fatigue life of plate with cold worked hole under high loading are always key designing parameters in engineering field. In this article, different cold expanded degrees (ranging from 1.69% to 11.11%) are applied to plate specimens with a central hole, made of 7050-T7451 aluminum alloy. The damage and fatigue properties are investigated by the three-dimensional finite element method with a user subroutine embedded into a void evolution model under complex stress states. The damage analysis indicates that plastic damage becomes critical when the cold expanded degree is larger than 7.14%, which does not suit for further service due to the loss of toughness. The cold expanded degree of 5.26% is identified as the best. It can be found that the fatigue life improves with the increased cold expanded degree. The small cold expanded degree leads to poor strengthening effect because of lacking sufficient residual stress, while large cold expanded degree makes micro-cracks emerge, which is beneficial to the increase in strengthening. All these results prove that the numerical analysis can accurately predict fatigue behavior of AA7050-T7451 plate based on our proposed approach, which is expected to be a powerful method in engineering field.

Design and Fatigue Analysis of High Pressure Shell and Plate Heat Exchanger

As a kind of widely used industrial equipment for energy exchange, heat exchanger is widely used in daily life. It is a key equipment for heat recovery and is of great significance for energy saving. In this paper, firstly, the heat transfer characteristics of the heat exchanger were analysed. Then the structure, material and performance parameters of the heat exchanger were analysed for the typical titanium alloy shell and plate heat exchanger, and the heat exchanger was checked by ASPEN software. At last, the fatigue analysis under the pressure of 2MPa was carried out for the heat exchanger, and the life, damage, safety factor and fatigue sensitivity curve of the shell plate were obtained, which provides certain reference basis for the structural design and optimization of the heat exchanger.

Recent Advances in Piezoelectric Wafer Active Sensors for Structural Health Monitoring Applications.

In this paper, some recent piezoelectric wafer active sensors (PWAS) progress achieved in our laboratory for active materials and smart structures (LAMSS) at the University of South Carolina: http: //www.me.sc.edu/research/lamss/ group is presented. First, the characterization of the PWAS materials shows that no significant change in the microstructure after exposure to high temperature and nuclear radiation, and the PWAS transducer can be used in harsh environments for structural health monitoring (SHM) applications. Next, PWAS active sensing of various damage types in aluminum and composite structures are explored. PWAS transducers can successfully detect the simulated crack and corrosion damage in aluminum plates through the wavefield analysis, and the simulated delamination damage in composite plates through the damage imaging method. Finally, the novel use of PWAS transducers as acoustic emission (AE) sensors for in situ AE detection during fatigue crack growth is presented. The time of arrival of AE signals at multiple PWAS transducers confirms that the AE signals are originating from the crack, and that the amplitude decay due to geometric spreading is observed.

Multi-Mode Guided Waves Based Reference-Free Damage Diagnostic Imaging in Plates

Probability-based diagnostic imaging (PDI) is one of the most well-known damage identification methods using guided waves. It is usually applied to diagnose damage in plates. The previous studies were dependent on the certain... | Find, read and cite all the research you need on Tech Science Press

Detecting Damage in Thin Plates by Processing Infrared Thermographic Data with Topological Derivatives

A thermogram is a color image produced by a thermal camera where each color level represents a different radiation intensity (temperature). In this paper, we study the use of steady and time-harmonic thermograms for structural health monitoring of thin plates. Since conductive heat transfer is short range and the associated signal–to–noise ratio is not much favorable, efficient data processing tools are required to successfully interpret thermograms. We will process thermograms by a mathematical tool called topological derivative, showing its efficiency in very demanding situations where thermograms are highly polluted by noise, and/or when the parameters of the medium fluctuate randomly. An exhaustive gallery of numerical simulations will be presented to assess the performance and limitations of this tool.

Prediction of impact damage in composite sandwich plates

This study tracks the development of an analytical model, designed to investigate the dynamic response of a composite sandwich plate subjected to a low-velocity impact. The model is based on the thick anisotropic plate theory, developed by Reddy and Pagano, which takes into account a through-thickness shear. An indentation law, as proposed by Hertz, is used to model the local response under the impactor. The good correlation between the shock and the simulation results testifies the validity of the method as far as the prediction of the contact force and the shear deformation in the core are concerned.

Recurrence of Basal Plate Myofibers, with Further Consideration of Pathogenesis

Objectives: Basal plate myofibers (BPMF) may indicate morbid adherence. We assessed recurrence and clinical progression of BPMF. Methods: In 5 years, 135 BPMF placentas were reported. Controls were the first 50 placentas in 2009, none of which had reported BPMF. Results: 32% of BPMF patients had other placentas, with a recurrence rate of 100%. Actin stains were needed for diagnosis in 117/179 cases (65%). These cases had clinical features suggestive of morbid adherence in 69/117 (59%). 23/47 (49%) of BPMF recurrences progressed in severity, 5 to hysterectomy (11%). Thinning of the basal plate, perforating vessels, gaps in the basal plate, and villi under the basal plate were observed in BPMF placentas. Conclusions: These findings appear to validate screening for BPMF. The 100% recurrence rate suggests evaluation for a heritable factor, i.e., protease inhibitor deficiency, which may explain pre-delivery basal plate damage.

Modeling Analysis of Guided Ultrasonic Waves in Composite Plates with Impact Damage

This paper investigates the propagation of guided ultrasonic waves and the interaction with impact damage in composite plates using a full three-dimensional Finite Element analysis. Impact damage in the composite plate was modeled as rectangular- and T-shaped delaminations. In order to provide guidelines for extending the modeling of realistic multimode impact damage, the impact damage was modeled as a combination of the delamination and reduced materials properties. The information obtained from these methods was compared to the experimental results around the damage area for a validation. There was a reasonable similarity between the experimental and FE results. The FE simulations can effectively model the scattering characteristics of the A0 mode wave propagation in anisotropic composite plates. This suggests that the simplified and easy-to-implement FE model could be used to represent the complex impact damage in composite plates. This could be useful for the improvement of the FE modeling and performance of guided wave methods for the in-situ NDE of large composite structures.