Damage In Plates Research Articles

Characterization of ductile damage in polyethylene plate using ultrasonic testing

An experimental study was conducted to explore the possibility of using ultrasound to quantify deformation-induced damage in polyethylene (PE) plate. Specimens of two gauge lengths were machined from PE plates with thickness in the range from 1.5 to 10 mm. The specimens were first stretched monotonically to various prestrain levels to vary the extent of damage introduced by the stretch. Ultrasonic testing in the through transmission mode was then conducted on the prestrained specimens to determine the time of flight, based on which ultrasonic velocity was determined. The results show that the ultrasonic velocity, normalized by the speed in the virgin plate of the same thickness, decreases with the increase of prestrain. The study also shows that, with the correction of density change by the prestrain, the normalized ultrasonic velocity can be used to determine the dependence of damage level on the prestrain which, for specimens with long gauge length, is consistent with the damage determined by mechanical testing. The study concludes that ultrasonic testing can be used as a non-destructive means to quantify deformation-induced damage evolution in PE plates.

CERVICAL SPINE INSOLVENT FIXATION IN THE CASES OF ITS TRAUMAS AND DISEASES

The work represents the analysis of surgery treatment of 552 patients with traumas and degenerative diseases of cervical spine subaks level (CSSL) who were treated in Scientific Research Insnitute of Emergency Care n.a. N.V. Sklifosofsky neurosurgery department since 01.01.2001 to 31.12.2013 and who underwent 554 surgeries. 19 (3.4%) patients had complications connected with the incorrect installation of a stabilizing system and insolvent fixation of a spine. 5 other patients were moved from other hospitals with instrumental confirmed dislocation of ventral plate fragments and damages of the esophagus. The aim of this work is to define risk factors, frequency and causes of complications connected with unsatisfactory fixation of CSSL of patients with trauma and degenerative diseases of cervical spine subaks level.

Detection of damages in hybrid composite plates with the use of elastic waves generated by PZT active sensors

Detection of damages in hybrid composite plates with the use of elastic waves generated by PZT active sensors

Impact Damage Localisation with Piezoelectric Sensors under Operational and Environmental Conditions.

Guided-wave structural health monitoring (SHM) systems with piezoelectric sensors are investigated for localisation of barely visible impact damage in CFRP plates under vibration and different thermal conditions. A single baseline set is used in a delay-and-sum algorithm with temperature correction for damage localisation in a large temperature range. Damage localisation is also demonstrated under transient thermal conditions, with signals recorded while the temperature is rapidly decreased. Damage severity due to successive impact events is studied under constant temperature. Damage is also localised when the plate is subjected to random vibration.

Low-velocity impact of woven CFRE composites under different temperature levels

Low-velocity impacts are unavoidable during the assembly stages and service life of aircrafts, marine and automobiles composite structures. This work aims to study the damage resistance of woven carbon fiber reinforced epoxy (CFRE) composite laminates subjected to a wide range of low-velocity impacts (15–85J). The composite laminates were fabricated using prepreg technique. The impact tests were carried out using falling weight impact tester at room temperature (RT), 50 °C and 75 °C. The selected test temperature of 50 °C represents the summer midday temperature of some countries, while the highest temperature value (75 °C) was used to study the possible effects of unexpected temperature rise. Compression-after-impact (CAI) were undertaken to measure their residual strength. Specimens that were tested at low impact energies (15 and 35J) as well as at higher temperature level (75 °C) are not penetrated by the impactor. Therefore, part of the kinetic energy is absorbed by the specimen in the form of damages. A second part is stored in the specimen as elastic energy, which is restituted back to the impactor for its rebound. Though no penetration is observed, the highest reduction in the stiffness and strength is observed at 75 °C. This is explained in terms of the softening and plastification of the epoxy matrix, the debonding at the interfacial fiber/matrix and the increase in the interfacial stress concentration of the re-solidified matrix. The threshold energy to initiate damage in the composite plates is measured/estimated using four methods and ranges between 2.8 and 9.6J.

Current Concepts in Radial Club Hand.

Radial club hand is a complex congenital abnormality of the radial or pre-axial border of the upper extremity. It has a wide range of phenotypes from hypoplasia of the thumb to complete absence of the radius and the first ray. Centralization with tendon transfer is a popular method for maintaining the correct position of radial club hand. On the other hand, various corrections were devised, e.g. radialization after distraction to emphasize the fact that the head of the ulna is positioned under the radial carpal bones and is no longer placed in a slot in the center of the carpus, microvascular epiphysis transfer, gradual correction using Ilizarov method, for Bayne Type III or Type IV. We should pay attention to the recurrence of radial deformity or circulatory impairment with the tension. Lunate excision or ulnar shortening can be selected for tension-free correction. Radialization can be indicated for avoiding the recurrence of radial flexion. However, we should pay attention of the radial protrusion of the ulnar head. For avoiding the recurrence of radial deformity or circulatory impairment, gradual correction using Ilizarov external fixation can be indicated, especially in the cases with severe radial deviation or with short forearm. In the mild cases, Bayne Type I or Type II, radius lengthening is accompanied by a soft-tissue distraction or release at the ulnar carpal joint with keeping wrist and forearm motion without producing growth plate damage.

Non-model-based damage identification of plates using principal, mean and Gaussian curvature mode shapes

Mode shapes have been extensively used to identify structural damage. This paper presents a new non-model-based method that uses principal, mean and Gaussian curvature mode shapes (CMSs) to identify damage in plates; the method is applicable to mode shapes associated with low and high elastic modes on dense and coarse measurement grids and robust against measurement noise. A multi-scale discrete differential-geometry scheme is proposed to calculate principal, mean and Gaussian CMSs associated with a mode shape of a plate, which can alleviate adverse effects of measurement noise on calculating the CMSs. Principal, mean and Gaussian CMSs of a damaged plate and those of an undamaged one are used to yield four curvature damage indices (CDIs), including Maximum-CDIs, Minimum-CDIs, Mean-CDIs and Gaussian-CDIs. Damage can be identified near regions with consistently higher values of the CDIs. It is shown that a mode shape of an undamaged plate can be well approximated using a polynomial of a properly determined order that fits a mode shape of a damaged one, provided that the undamaged plate has a smooth geometry and is made of material that has no stiffness and mass discontinuities. Fitting and convergence indices are introduced to quantify the level of approximation of a mode shape from a polynomial fit to that of a damaged plate and to determine the proper order of the polynomial fit, respectively. A weight function is applied to the proposed CDIs to alleviate adverse effects of measurement noise on the CDIs and manifest existence of damage in the CDIs. A mode shape of an aluminum plate with damage in the form of a machined thickness reduction area was measured to experimentally investigate effectiveness of the proposed CDIs in damage identification; the damage on the plate was successfully identified. The experimental damage identification results were numerically verified by applying the proposed method to the mode shape associated with the same mode as that of the measured one from a finite element model of the damaged plate.

Lamb wave mode and frequency selection for assessment of creep damage in titanium alloy plates

Lamb wave mode and frequency selection for assessment of creep damage in titanium alloy plates

Probability Approach to the Problem of Impact-Induced Damage Simulation of Composite Plates

The probability damage and fracture model for a composite material under impact loading is proposed, within this model, the damage parameters are regarded as the probability functions of strain, strain rate, and temperature with a preset probability density. FEM numerical strength computations for fiber-reinforced plates were carried out in the range of impact velocities up to 1200 m/s. The dynamics of energy absorption and plate damage levels with the impact velocity were analyzed.

Calculus of the defect severity with EMATs by analysing the attenuation curves of the guided waves

The aim of this paper is to develop a novel method to determine the severity of a damage in a thin plate. This paper presents a novel fault detection and diagnosis approach employing a new electromagnetic acoustic transducer, called EMAT, together with a complex signal processing method. The method consists in the recognition of a fault that exists within the structure, the fault location, i.e. the identification of the geometric position of damage, and the determining the significance of the damage, which indicates the importance or severity of the defect. The main scientific novelties presented in this paper is: to develop of a new type of electromagnetic acoustic transducer; to incorporate wavelet transforms for signal representation enhancements; to investigate multi-parametric analysis for noise identification and defect classification; to study attenuation curves properties for defect localization improvement; flaw sizing and location algorithm development.

Damage effects of aluminum plate by reactive material projectile impact

This investigation describes and analyzes the damage effects of 2024-T3 aluminum plates normally impacted by cold isostatically pressed and sintered PTFE/Al/W reactive material projectiles. In the experiments, the reactive material projectiles impacted 3mm thick aluminum plates at velocities in the range from 289 to 569m/s and impacted 12mm thick aluminum plates at velocities in the range from 500 to 956m/s. The damage patterns and the corresponding penetration-induced deflagration behavior are presented and analyzed. In addition, combining theoretical considerations with experimental results, the effect of impact velocity on the extent of petal bulge and the penetration hole sizes is analyzed. Moreover, by comparing the calculated results with the experimental data, the influences of chemical energy released from the reactive materials during penetration on the extent of petal bulge and the penetration hole sizes are investigated and discussed. As the results show, the damage of aluminum plates by reactive material projectile impact not only varies with the kinetic energy, but is also significantly influenced by the chemical energy released in the penetration process.

Reverse time migration Lamb wave imaging based on mode separation

Frequency domain reverse time migration method is used to reconstruct damages in isotropic and anisotropic plates. Considering multimode overlapping, the Lamb wave signals scattered by the defects may result in artifacts in defect imaging. The scattering signals are thus pre-processed by using a mode separation method based on the vibration symmetry difference between the fundamental guided modes. Based on the multi-element array ultrasonic technique, a numerical study is carried out for defect imaging of aluminum and composite plates by using the frequency reverse time migration method. This paper is organized as follows. Firstly, in order to capture multi-directional information about damages, scattering Lamb wave signals caused by the defects are numerically collected by an annular array of transducers through using the finite element simulation. Secondly, after the pre-processing of mode separation, the separated scattering signals are time-reversed and used to stimulate the corresponding receivers. The Green's function is utilized to back-propagate the scattering Lamb signals in frequency domain, so that the back-propagated acoustic field information of monitored area can be obtained. Finally, the defect images are reconstructed by the cross-correlation between the incident acoustic field and the back-propagated acoustic field. To illustrate the influence of mode separation, the numerical experiments are carried out on an aluminum plate with single defect and on another composite plate with two adjacent identical defects. The reconstructed results from frequency domain reverse time migration method with and without mode separation are compared. The comparison indicates the importance of mode separation. Furthermore, the method is extended to detecting the double adjacent defects with different depths in the composite plate. The imaging result illustrates that the presupposed two adjacent defects with different depths are successfully identified. Numerical results demonstrate that the pre-processing of mode separation helps to effectively remove the artifacts resulting from the multimode interference in the imaging process. The proposed frequency reverse time migration method presents a strong potential for detecting and imaging defects in isotropic and anisotropic plates, which is capable of accurately measuring multi-site defects with information about geometry, size and depth.

Damage assessment and analysis of steel plate for different loading conditions

Damage is an undesired physical change formed in the structure that adversely affects its current or future performance. Damage is determined by comparing the current state of structure with its expected service state at that particular period. The process of detecting the damages and analysing its adverse effects on a structure becomes very crucial from the safety aspects. Thus Detection of damage in its early stage is essential. Hence structural health monitoring plays a major role in the field of damage assessment and rehabilitation of structures. The present study is intended on the analysis of damage of steel gusset plate in truss using MATlab software. The concept of Finite Element Method has been used to analyse the damaged plate. Two types of damages are considered in the present study i.e. damage due to corrosion and damage due to crack in a plate.

AE Global Diagnostics on Corrosion Damage in Bottom Plates of Above-ground Oil Tanks.

AE Global Diagnostics on Corrosion Damage in Bottom Plates of Above-ground Oil Tanks.

FEA Simulation of Vibrating Cantilever Plate with Transverse Surface Crack

The main objective of this research work is to investigate the effect of transverse surface crack on cantilever plate. To investigate the surface crack effect, cantilever plate with crack and without crack was analysed for result comparison. Finite Element Analysis (FEA) based Ansys has been used for numerical simulation. Modal analysis was performed to find the fundamental frequencies of plate. First 6 natural frequency and mode shapes were obtained for varying crack size. Vibration mode shape were analysed to find the total deformation value at surface of plate. Red hues show maximum deformation with chances of crack generation. Higher value of deformation shows plate damage. FEA results show small frequency value for lower crack size. As crack depth increases frequency difference increases. Fundamental frequency is 32.63 Hz when plate is without crack. The range of natural frequency is (32.63-960.92) Hz. Material properties and boundary condition remains same in all cases of FEA simulation. 3D solid modelling was performed using Pro-E.© 2016 Elsevier Ltd. All rights reserved.Selection and Peer-review under responsibility of International Conference on Recent Trends in Engineering and Material Sciences (ICEMS-2016).

Damage detection of plate-like structures using intelligent surrogate model

Cracks in plate-like structures are some of the main reasons for destruction of the entire structure. In this study, a novel two-stage methodology is proposed for damage detection of flexural plates using an optimized artificial neural network. In the first stage, location of damages in plates is investigated using curvature-moment and curvature-moment derivative concepts. After detecting the damaged areas, the equations for damage severity detection are solved via Bat Algorithm (BA). In the second stage, in order to efficiently reduce the computational cost of model updating during the optimization process of damage severity detection, multiple damage location assurance criterion index based on the frequency change vector of structures are evaluated using properly trained cascade feed-forward neural network (CFNN) as a surrogate model. In order to achieve the most generalized neural network as a surrogate model, its structure is optimized using binary version of BA. To validate this proposed solution method, two examples are presented. The results indicate that after determining the damage location based on curvature-moment derivative concept, the proposed solution method for damage severity detection leads to significant reduction of computational time compared with direct finite element method. Furthermore, integrating BA with the efficient approximation mechanism of finite element model, maintains the acceptable accuracy of damage severity detection.

Non-model-based damage identification of plates using measured mode shapes

Mode shapes (MSs) have been extensively used to detect structural damage. This paper presents a new non-model-based damage identification method that uses measured MSs to identify damage in plates. A MS damage index (MSDI) is proposed to identify damage near regions with consistently high values of MSDIs associated with MSs of different modes. A MS of a pseudo-undamaged plate can be constructed for damage identification using a polynomial of a properly determined order that fits the corresponding MS of a damaged plate, if the associated undamaged plate is geometrically smooth and made of materials that have no stiffness and mass discontinuities. It is shown that comparing a MS of a damaged plate with that of a pseudo-undamaged plate is better for damage identification than with that of an undamaged plate. Effectiveness and robustness of the proposed method for identifying damage of different positions and areas are numerically investigated using different MSs; effects of crucial factors that determine effectiveness of the proposed method are also numerically investigated. Damage in the form of a machined thickness reduction area was introduced to an aluminum plate; it was successfully identified by the proposed method using measured MSs of the damaged plate.

An elasto-plastic damage model for functionally graded plates with in-plane material properties variation: Material model and numerical implementation

The paper presents an elasto-plastic damage model based on irreversible thermodynamics for the analysis of functionally graded (FG) plates with in-plane material properties variations. The model considers a simple power law function to describe the FG plates as continua with smooth variation of material properties, such as Young’s Modulus, yield stress, plastic material constants and damage parameters. By introducing two independent plastic and damage multipliers, the model is applicable to different types of materials. Employing the operator splitting methodology, a three-step predictor/multi-corrector algorithm is developed that includes an elastic predictor, a plastic corrector, and a damage corrector. Then, the damage finite element (FE) solutions are obtained using linear hexahedral solid elements with spatially graded property distribution (at different Gauss points), and subsequently implemented by a user material subroutine (UMAT) in the ABAQUS FE software. Good agreement is shown between the analytical damage models, the FE solutions and experimental results sourced from the literature. Several numerical examples establish that the present model is not only accurate, but provides a simple approach to predicting damage of different types of materials, including those that demonstrate both elastic-brittle damage and elasto-plastic damage behaviours. Moreover, the presented model effectively describes the continuum damage of FG plates, capturing variation of the damage variable throughout the plane of the plate.

Orthotopic Autologous Chondrocyte Grafting as a Method of Treatment of Growth Plate Damage in Rabbits.

With the continuous advances in the therapy of joint cartilage injury, some of those classification systems are also being used for evaluating the quality of regenerating cartilage. Histo lo gi cal assessment of joint cartilage is a very important component in the staging of osteoarthritis and tracing therapeutic outcomes. We performed a histological assessment of regenerating growth plate in a group of New Zealand white rabbits as a component of autologous chondrocyte therapy for growth plate damage. We studied a group of 14 five-week-old in-bred white rabbits. We used a tre phine needle to harvest growth plate from the medial fourth of tibial width. The mean duration of the procedure was 25 minutes (range: 12-37 minutes). We conducted a total of 25 growth plate harvesting procedures. In 21 cases, we placed a drainage tube at the site of the defect for 22 days. After removing the tube, we introduced a cartilago-fibrinous construct containing cultured autologous chondrocytes into 14 defects, while 4 defects were left intact. Three growth plates represented non-intervention controls. Our analysis showed satisfactory graft morphology and integration; absence of inflammatory res ponse and fair restitution of growth plate architecture. 1. Growth plate damage can lead to the development of an angular deformity as a result of im paired longitudinal bone growth; 2. Autologous chondrocyte grafting is a good method of treatment for growth plate damage; 3. A weakness of autologous chondrocyte grafting is the relatively long time of chondrocyte culturing.

Blast response of geometrically asymmetric metal honeycomb sandwich plate: Experimental and theoretical investigations

Dynamic response of geometrically asymmetric sandwich plates with aluminum hexagonal honeycomb core subjected to blast loading is investigated experimentally and theoretically. Specimens of various face sheet thicknesses are tested for three blast intensities which are varied by changing the weights of cyclotrimethylene trinitramine (RDX) explosive charges at a constant standoff distance. Four edges of sandwich plates are fully clamped. The deformation and damage modes of sandwich plates are obtained. The influences of the blast loading and the core density on the dynamic response of sandwich plates are analyzed. The analytical model is developed to predict the blast response of the geometrically asymmetric sandwich plate subjected to blast loading. It is shown that the theoretical predictions of the deflection of the center point at the rear face sheet is in good agreement with the experimental results. The geometrical asymmetry due to the thicknesses of the face sheets has a significant effect on the deformation and damage of sandwich plates.