Early-stage Damage Research Articles

Interphase mechanical behavior of carbon fiber reinforced polymer exposed to cyclic loading

A micro-/nano-scale technique is presented for characterizing early stage damage formation on un-sized individual carbon fibers as well as embedded carbon fibers exposed to cyclic loads. Nanoindentation and atomic force microscopy were used to study the local mechanical properties and morphology of composite constituents before and after cyclic loading. Samples were of the type: 1) un-sized individual carbon fiber and 2) carbon fibers embedded in an epoxy matrix. Contributions from the structural compliance were isolated from the indentations in order to track variations in interphase properties due to global fatigue. When tested in the radial direction, the fiber shell was found to be approximately 50% stiffer than the fiber core. Indentations on fibers within a composite cycled to 100% of fatigue life revealed a compliance effect of roughly 5 GPa with respect to fibers within a control composite. The experimental results are compared to a finite element analysis model in order to help understand the mechanical influence of the interphase in the presence of the elastically-mismatched fibers and matrix. The work is a first step toward understanding damage precursor formation in individual microfibers and composite interphase regions; the work is expected to enable multiscale composite modeling efforts as well as the development of future self-sensing materials.

Simulations on Monitoring and Evaluation of Plasticity-Driven Material Damage Based on Second Harmonic of S₀ Mode Lamb Waves in Metallic Plates.

In this study, a numerical approach—the discontinuous Meshless Local Petrov-Galerkin-Eshelby Method (MLPGEM)—was adopted to simulate and measure material plasticity in an Al 7075-T651 plate. The plate was modeled in two dimensions by assemblies of small particles that interact with each other through bonding stiffness. The material plasticity of the model loaded to produce different levels of strain is evaluated with the Lamb waves of S0 mode. A tone burst at the center frequency of 200 kHz was used as excitation. Second-order nonlinear wave was extracted from the spectrogram of a signal receiving point. Tensile-driven plastic deformation and cumulative second harmonic generation of S0 mode were observed in the simulation. Simulated measurement of the acoustic nonlinearity increased monotonically with the level of tensile-driven plastic strain captured by MLPGEM, whereas achieving this state by other numerical methods is comparatively more difficult. This result indicates that the second harmonics of S0 mode can be employed to monitor and evaluate the material or structural early-stage damage induced by plasticity.

Multi-scale analysis of the early damage mechanics of ferritized ductile iron

A multi-scale analysis of the linear elastic and the early damage stages of ferritic ductile iron is introduced in this work. The methodology combines numerical and experimental analyses in the macro and micro scales. Experiments in the micro-scale are used for the characterization of the material micro constituents and the assessment of the micro-scale damage mechanisms; experiments in the macro-scale provide the data to calibrate and validate the models. The 2D multi-scale problem is modeled using the pre-critical regime of the Failure-Oriented Multi-Scale Variational Formulation, which is implemented via a FE $$^{2}$$ approach. Finite element analysis in the micro-scale is customized to account for plastic deformation and matrix-nodule debonding. The multi-scale model is found effective for capturing the sequence and extent of the damage mechanisms in the micro-scale and to estimate, via inverse analyses, parameters of the matrix-nodule debonding law. Results allow to develop new insights for the better understanding of the ductile iron damage mechanics and to draw conclusions related to the modeling aspects of the multi-scale simulation.

Prediction of infarct size using two-dimensional speckle tracking echocardiography in acute myocardial infarction.

This study aimed to determine the myocardial damage (infarct size provided by cardiac single-photon emission tomography) in early stages of the infarction using longitudinal strain and rotational parameters of the left ventricle. The study included 66 patients with anterior myocardial infarction (AMI) and 62 patients with inferior myocardial infarction (IMI) who underwent primary percutaneous intervention as well as a control group consisting of 50 healthy subjects. LV rotational parameters based on parasternal short-axis views in basal and apical planes and global longitudinal strain were measured with apical four-chamber, apical two-chamber, and apical long-axis views. There was a significant positive correlation between infarct size and GLPSavg (r=-.55 <.001), GTOR angle (r=-.52, P<.001), apical rotation angle (r=-.40 <.001, and EF (r=-.43, <.001). While cutoff values were GLPSavg: 11.9 (AUC=0.78), GTOR angle: 11.4° (AUC=0.77), apical rotation angle: 7.1° (AUC=0.76) for patients with an infarct size greater than 20%, the cutoff values were GLPSavg: 10.7 (AUC=0.75), GTOR angle: 8.7° (AUC=0.86), apical rotation angle: 4.35° (AUC=0.87) for those with an infarct size greater than 40%. GLPSavg, GTOR angle, and apical rotation angle values may be used to determine the extent of infarction in early post-MI period, thereby allowing precautions to be taken for remodeling in early stages.

The critical role of myeloperoxidase in Streptococcus pneumoniae clearance and tissue damage during mouse acute otitis media.

We have recently reported that neutrophils play a pivotal role in innate defense against Streptococcus pneumoniae ( Spn) during mouse acute otitis media (AOM). However, the underlying mechanism remains unclear. By constructing models of pneumococcal AOM in C57BL/6 mice and using a specific inhibitor invivo, we investigated the role of myeloperoxidase (MPO), one of the most important protein components of neutrophils. Experiment results showed a significant increase in MPO production of the recruited neutrophils in Spn-infected mice. Neutrophils killed Spn in a MPO-dependent manner. MPO facilitated the generation of reactive oxygen species (ROS), and consequently promoted Spn clearance at an early stage and exacerbated tissue damage. Moreover, MPO induced neutrophil apoptosis and necrosis, which, in turn, worsened tissue damage. In summary, our study demonstrates that neutrophil MPO plays a paradoxical role in bacterial clearance and tissue damage in pneumococcal AOM.

Neuroprotective Properties of Panax notoginseng Saponins via Preventing Oxidative Stress Injury in SAMP8 Mice.

Inhibiting oxidative damage in early stage of Alzheimer's disease (AD) is considered as a strategy for AD treatment. Our previous study has shown that Panax notoginseng saponins (PNS) have an antiaging action by increasing the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) in the serum of aged rats. In this study, we aimed to investigate the effects of PNS on antioxidant enzymes and uncoupling proteins (UCPs) involved in oxidative stress in AD mice. The results showed that PNS prevented neuronal loss in hippocampal CA1 region and alleviated pathomorphological change of neurons in CA1 region. Moreover, PNS inhibited the production of 8-hydroxydeoxyguanosine (8-OHdG), enhanced the expressions and activities of SOD, CAT, and GSH-PX, and improved the mRNA and protein levels of UCP4 and UCP5 in the brains of SAMP8 mice. Together, our study shows that PNS has the ability to protect neurons in AD brain from oxidative stress damage through attenuating the production of 8-OHdG, enhancing the activities of antioxidant enzymes and the expressions levels of UCP4 and UCP5. Accordingly, PNS may be a promising agent for AD treatment.

Composite Plate Phased Array Structural Health Monitoring Signal Reconstruction Based on Orthogonal Matching Pursuit Algorithm

In order to ensure the safety of composite components, structural health monitoring is needed to detect structural performance in real-time at the early stage of damage occurred. This is difficult to detect complex components with single sensor detection technology, so that ultrasonic phased array technology using multisensor detection will be selected. Ultrasonic phased array technology can scan the structure in all directions and angles without moving or less moving the probe and becomes the first choice of structural health monitoring. However, a large amount of data will be generated when using ultrasonic phased array with Nyquist sampling theorem for structural health monitoring and is difficult to storage, transmission, and processing. Besides, traditional Nyquist sampling cannot satisfy the sampling of large amounts of data without distortion, so a more efficient acquisition technique must be chosen. Compressive sensing theory can ensure that if the signal is sparse, it can be sampled in low sampling rate which is much less than two times of the sampling rate as defined by Nyquist sampling theorem for a large number of data and reconstructed in high probability. Then, the experiment result indicated that the orthogonal matching pursuit algorithm can reconstruct the signal completely and accurately.

Healing of Early Stage Fatigue Damage in Ionomer/Fe₃O₄ Nanoparticle Composites.

This work reports on the healing of early stage fatigue damage in ionomer/nano-particulate composites. A series of poly(ethylene-co-methacrylic acid) zinc ionomer/Fe3O4 nanoparticle composites with varying amounts of ionic clusters were developed and subjected to different levels of fatigue loading. The initiated damage was healed upon localized inductive heating of the embedded nanoparticles by exposure of the particulate composite to an alternating magnetic field. It is here demonstrated that healing of this early stage damage in ionomer particulate composites occurs in two different steps. First, the deformation is restored by the free-shrinkage of the polymer at temperatures below the melt temperature. At these temperatures, the polymer network is recovered thereby resetting the fatigue induced strain hardening. Then, at temperatures above the melting point of the polymer phase, fatigue-induced microcracks are sealed, hereby preventing crack propagation upon further loading. It is shown that the thermally induced free-shrinkage of these polymers does not depend on the presence of ionic clusters, but that the ability to heal cracks by localized melting while maintaining sufficient mechanical integrity is reserved for ionomers that contain a sufficient amount of ionic clusters guaranteeing an acceptable level of mechanical stability during healing.

Laboratory and field evaluation of cold recycling mixture with foamed asphalt

Cold recycling with foamed asphalt stabilisation has been gaining acceptance and growing steadily. This study evaluates the performance of cold recycled mixes stabilised with foamed asphalt, with respect to the effects of confining stresses, and material moisture content. An experimental test section with a foamed stabilised recycled material used as the base course was monitored through quality control and quality assurance and falling weight deflectometer (FWD) tests. In laboratory, indirect tensile strength, triaxial resilient modulus, and permanent deformation tests were performed. Based on the results obtained, one can conclude that the curing is a critical consideration in terms of timing and its influence on pavement performance. Triaxial tests showed the stress dependency of this bitumen-stabilised material, while permanent deformation results indicated some potential for damage in early stages after construction. On the field evaluation, FWD data indicated the decrease in deflection with time, as a result of the increase in the layers stiffness.

Application of objective audiological tests in bilateral tinnitus patients with normal hearing capability

Objective:To analyze the relationship of tinnitus and early stage damage of cochlear, to explore the clinical applied value of distortion product otoacoustic emission(DPOAE) and auditory brainstem response(ABR) in the bilateral tinnitus patients with normal hearing capability. Method:There are 30 cases(60 ears) in the tinnitus group with bilateral tinnitus patients with normal hearing capability, and there are 30 cases(60 ears) in the control group without tinnitus of normal hearing capability. The two groups both test the DPOAE and ABR,and compare the results of the DPOAE and ABR. Result:The passing rate of DPOAE in all frequencies was 100% in the control group,42.67% in the tinnitus group. Significant differences existed between the two groups(P<0.05).The DPOAE could be checked out at all frequencies under 2 kHz except 0.75 kHz in the tinnitus group, and the passing rates of DPOAE were significantly lower than those in control group(P<0.05).There were 3 cases could not be checked out at 0.75 kHz frequency, but there were no significant difference(P>0.05).The DPOAE amplitudes at frequencies of 3 to 8 kHz in tinnitus ears were significantly lower than those in nontinnitus ears(the P value were 0.011,0.013,0.008,0.027 ).Wave Ⅰ,Ⅲ and Ⅴcould be detected in all ears tested at 80 dB nHL. The latencies of WaveⅠin tinnitus group were obviously prolonged.The latencies of Wave Ⅲ and Ⅴ in tinnitus group were also prolonged, but there was no significant difference(P>0.05).The interval between waves Ⅰand Ⅲ,waves Ⅲ and Ⅴand wavesⅠand Ⅴ showed no difference. Conclusion:The maybe cochlear early injury in fractional bilateral tinnitus patients with normal hearing capability, DPOAE and ABR can act as an objective method for diagnosing peripheral tinnitus.

Sensing of damage and substrate stress in concrete using electro-mechanical impedance measurements of bonded PZT patches

The influence of stress and induced damage in concrete on the electro-mechanical (EM) impedance response of bonded PZT patches is evaluated for applied compressive loading. Full field displacements obtained from digital image correlation are used to evaluate the level of stress-induced damage in concrete. Stress in the substrate produces an imposed strain on the PZT. A change in the imposed strain produces a rightward frequency shift and an increase in the amplitude of the resonant peak in the EM conductance spectrum of the PZT. An increase in the substrate compliance produces a decrease in the resonant frequency and an increase in the amplitude of the resonant peak. Changes in the resonant peak in the conductance spectrum induced by increasing substrate stress are of a significant magnitude when compared with the changes induced by damage. In the early stages of damage associated with distributed microcracking, the counteracting influences of increasing level of damage and increasing stress on the resonant peak result in no shift in frequency for measurements under applied load. There is however an increase in the amplitude of the resonance peak. When the applied stress is removed, there is a net decrease in frequency resulting from damage in the form of distributed microcracks. Measures of changes in the resonant peak based on root mean square deviation (RMSD), do not show any observable change when measurements are performed under applied loading. There is a consistent increase in RMSD values and frequency shift with increasing damage when the applied stress is removed. The centroidal measure of the normalized frequency spectrum reflects changes in substrate stress. At higher applied stress levels, there is a nonlinear increase in damage, leading to localization and cracking. The influence of damage is dominant in this region and significant changes are obtained in the RMSD values in both loaded and unloaded conditions.

Diagnosis of early-stage damage to polymer - glass fibre composites using non-contact measurement of vibration signals

Ensuring reliable operation of the means of transport requires the development of methods for early detection of damage to its components made of composite materials. For diagnostic testing of composite materials during normal operation of the means of transport, the authors propose to use non-contact vibration measurement methods and their subsequent processing and analysis. The paper presents the results of laboratory tests whose aim was to assess the ability to detect early symptoms of damage to composite materials using non-contact vibration measurement methods. The measurements included mechanical curves of the glass composite samples made in a conventional manner and simultaneously their vibrations were measured in a non-contact manner using a laser vibrometer. Continuous wavelet transform was used for processing vibration signals. Calculated time-frequency scale distributions of vibration signals enabled the designation of frequency scale bands in which early, low-energy symptoms of damage to glass composites are observed. The analysis results allow to draw conclusions that the use of non-contact measurements and processing of vibration signals extends the existing range of composites research and enables detection of early, low-energy symptoms of damage to glass fibre reinforced composites.

Spectral algorithm for non-destructive damage localisation: Application to an ancient masonry arch model

Structural monitoring and vibration-based damage identification methods are fundamental tools for condition assessment and early-stage damage identification, especially when dealing with the conservation of historical constructions and the maintenance of strategic civil structures. However, although the substantial advances in the field, several issues must still be addressed to broaden the application range of such tools and to assert their reliability. This study deals with the experimental validation of a novel method for non-destructive damage identification purposes. This method is based on the use of spectral output signals and has been recently validated by the authors through a numerical simulation. After a brief insight into the basic principles of the proposed approach, the spectral-based technique is applied to identify the experimental damage induced on a masonry arch through statically increasing loading. Once the direct and cross spectral density functions of the nodal response processes are estimated, the system's output power spectrum matrix is built and decomposed in eigenvalues and eigenvectors. The present study points out how the extracted spectral eigenparameters contribute to the damage analysis allowing to detect the occurrence of damage and to locate the target points where the cracks appear during the experimental tests. The sensitivity of the spectral formulation to the level of noise in the modal data is investigated and discussed. As a final evaluation criterion, the results from the spectrum-driven method are compared with the ones obtained from existing non-model based damage identification methods.

The Podocyte Count Detected by an Improved Immunocytochemical Method has Higher Diagnostic Efficiency than Enzyme-Linked Immunosorbent Assay and Serum Cystatin C to Evaluate the Early Stage Damage of Glomerular.

In renal diseases, earlier injury to glomerular may lead to the abscission of podocyte. The number of podocyte in urine may reflect the severity of glomerular damage. Podocalyxin (PCX) was considered as a podocyte marker. Many methods were used to detect podocyte. Applications of these methods were limited by tricky, expensive, and low accuracy. Here, we improved an immunocytochemical method to count the number of podocyte in urine. In this study, we counted the numbers of podocyte in urine by our improved method and detected the PCX levels in urine by enzyme-linked immunosorbent assay (ELISA) in glomerulopathy patients and healthy controls. The serum levels of cystatin C (CysC), blood urea nitrogen (BUN), creatinine (CR), uric acid (URIC), and β2-Microglobulin (β2-MG) in all subjects were detected. Correlation analysis and diagnostic efficiencies comparisons among immuocytochemical method, ELISA, and the biochemistry index were also performed. The podocyte counts in patients were significantly higher than controls. Podocytes counts positively correlated with PCX concentrations and the serum CysC. The podocyte count had higher diagnostic efficiency than PCX concentrations detected by ELISA and serum CysC. The podocyte count detected by our improved method had higher diagnostic efficiency than ELISA and serum CysC.

Chronic intermittent hypobaric hypoxia ameliorates diabetic nephropathy through enhancing HIF1 signaling in rats

AimOur previous study demonstrated that chronic intermittent hypobaric hypoxia (CIHH) had anti-diabetes effect. The present study was to explore the renal protective effect of CIHH in diabetic rats. MethodsSprague–Dawley rats were randomly divided into three groups: diabetes mellitus group (DM, induced by high-fat diet combined with low-dose streptozotocin), diabetes plus CIHH treatment group (DM+CIHH, simulated 5000-m altitude, 6h per day for 28days, after diabetes model confirmed) and control group (CON). Systolic arterial blood pressure (SAP), blood biochemicals, urinary albumin, and histopathology of kidney were determined. The superoxide dismutase (SOD) activity, malondialdehyde (MDA) level, protein levels of hypoxia induced factors (HIFs) and transforming growth factor β1 (TGF-β1) in kidney were assayed. ResultsThe increased SAP, urinary albumin, hyperplasia of glomerular, fibrosis in mesangial and glomerular, and abnormal lipid metabolism in diabetic rats were ameliorated by CIHH treatment. And decreased superoxide dismutase (SOD) activity and increased malondialdehyde (MDA) level in diabetic kidney were reversed in CIHH-treated DM rats. In addition up-regulated TGF-β1 and down-regulated HIF1α in diabetic kidney returned back to normal level in CIHH-treated DM rats. ConclusionsThese data demonstrated for the first time that CIHH had protective effects against the early stage damage of diabetic nephropathy through activating HIF1 signaling, improving anti-oxidation and inhibiting TGF-β1 signaling in diabetic rats.

In Vivo Dual Fluorescence Imaging to Detect Joint Destruction.

Diagnosis of cartilage damage in early stages of arthritis is vital to impede the progression of disease. In this regard, considerable progress has been made in near-infrared fluorescence (NIRF) optical imaging technique. Arthritis can develop due to various mechanisms but one of the main contributors is the production of matrix metalloproteinases (MMPs), enzymes that can degrade components of the extracellular matrix. Especially, MMP-1 and MMP-13 have main roles in rheumatoid arthritis and osteoarthritis because they enhance collagen degradation in the process of arthritis. We present here a novel NIRF imaging strategy that can be used to determine the activity of MMPs and cartilage damage simultaneously by detection of exposed type II collagen in cartilage tissue. In this study, retro-orbital injection of mixed fluorescent dyes, MMPSense 750 FAST (MMP750) dye and Alexa Fluor 680 conjugated monoclonal mouse antibody immune-reactive to type II collagen, was administered in the arthritic mice. Both dyes were detected with different intensity according to degree of joint destruction in the animal. Thus, our dual fluorescence imaging method can be used to detect cartilage damage as well as MMP activity simultaneously in early stage arthritis.

Tissue damage within normal appearing white matter in early multiple sclerosis: assessment by the ratio of T1- and T2-weighted MR image intensity.

Histopathological and magnetic resonance imaging (MRI) studies have shown white matter (WM) damage in early stages of multiple sclerosis (MS) beyond the apparent T2-hyperintense lesions. These changes in normal appearing WM (NAWM) are important with regard to the clinical picture and prognosis. However, the detection of changes within NAWM has so far required special imaging techniques commonly not available in clinical routine and, hence, at large scale. The purpose of this study was to detect MS-related damage of NAWM by conventional MRI. As, within NAWM, the myelin content mainly drives the T1-weighted (T1w) signal, we scaled it by the T2w signal. We tested the hypothesis that the mean T1w/T2w ratio of NAWM is decreased in MS compared to healthy controls (HC) and that it correlates with clinical measures. We developed a pipeline to determine the individual mean values of this ratio within NAWM. We studied 244 patients in early disease stages of MS (mean age 37±10years, mean disease duration 3.1±2.3, Expanded Disability Status Scale 1.3±1), and 78 HC (mean age 31±8years). Compared to HC, the mean T1w/T2w ratio was lowered in the patient group (P<0.001). The difference remained significant after restricting the analysis to patients with a disease duration of 5years or less and without disease modifying drugs. Our measures also correlated with clinical scores. We believe that the mean T1w/T2w ratio is a promising candidate to assess MS-related tissue damage within NAWM at large scale.

Applications of smart piezoelectric materials in a wireless admittance monitoring system (WiAMS) to Structures—Tests in RC elements

The application of an innovative real-time structural health monitoring system is studied through tests performed on flexural and shear-critical reinforced concrete elements subjected to monotonic and cyclic loading. The test set-up involves a Wireless impedance/Admittance Monitoring System (WiAMS) that comprises specially manufactured small-sized portable devices to collect the voltage frequency responses of an array of smart piezoelectric transducers mounted on structural members of reinforced concrete constructions. Damage detection and evaluation is achieved using the in-situ measurements of the integrated piezoelectric sensors/actuators signals at the healthy state of the member and at various levels of damage during testing. Three different installations of Piezoelectric lead Zirconate Titanate (PZT) transducers are examined: (a) epoxy bonded PZTs on the surface of the steel reinforcing bars of the flexural elements, (b) PZTs embedded inside the concrete mass of the shear-critical beams and (c) externally epoxy bonded PZTs attached to the concrete surface of the tested elements. The smart piezoelectric materials have been pre-installed before testing based on the potential flexural and shear cracking of the elements. Quantitative assessment of the examined damage levels using values for the statistical damage index is also presented and discussed. Voltage signals and index values acquired from the PZTs’ measurements using the proposed wireless monitoring technique demonstrated obvious discrepancies between the frequency response of the healthy and the examined damage levels for every tested element. These differences clearly indicate the presence of damage, whereas their gradation reveals the magnitude of the occurred damage. Promising results concerning the prediction of the forthcoming fatal failures at early damage stages have also been derived.

Early stage damage in off-axis plies under fatigue loading

The very early stages of damage evolution under fatigue loadings were investigated by testing [45/-45/0]s glass/epoxy specimens. Microscope observations revealed that the first damage event was the initiation of micro-cracks in the 45° plies within the inter-fibre region. Off-axis cracks then formed by the coalescence of these micro-cracks and propagated along the fibres direction with the same mechanism. The orientation of the micro-cracks was proven to be normal to the direction of the local maximum principal stress in the matrix. The results presented here are the first published evidences of fatigue damage initiation at the inter-fiber scale and represent a further validation of the fatigue crack initiation criterion recently presented by the authors.

An experimental study on the applicability of acoustic emission for wind turbine gearbox health diagnosis

Condition monitoring of wind turbine gearboxes has mainly relied upon vibration, oil analysis and temperature monitoring. However, these techniques are not well suited for detecting early stage damage. Acoustic emission is gaining ground as a complementary condition monitoring technique as it offers earlier fault detection capability compared with other more established techniques. The objective of early fault detection in wind turbine gearboxes is to avoid unexpected catastrophic breakdowns, thereby reducing maintenance costs and increase safety. The aim of this investigation is to present an experimental study the impact of operational conditions (load and torque) in the acoustic emission activity generated within the wind turbine gearbox. The acoustic emission signature for a healthy wind turbine gearbox was obtained as a function of torque and power output, for the full range of operational conditions. Envelope analysis was applied to the acoustic emission signals to investigate repetitive patterns and correlate them with specific gearbox components. The analysis methodology presented herewith can be used for the reliable assessment of wind turbine gearbox subcomponents using acoustic emission.