Italian Group Fracture (IGF): E-Journals / Gruppo Italiano Frattura
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Guided waves with machine learning for structural health monitoring: transparent features and Monte Carlo confidence
Full text linkReliable discrimination of small damage states under operational variability requires uncertainty aware Structural Health Monitoring. A pipeline is presented that couples guided wave physics with supervised machine learning to classify damage severity in a metallic panel. The experimental platform is a 310 × 190 × 1 mm aluminum plate with one central piezoelectric actuator and three receivers, interrogated by five cycle tone bursts at 20 kHz and sampled at 250 kHz. Signals are reduced to vectors of 20 physics informed features including root mean square, peak measures, analytic envelope statistics in fundamental and second harmonic bands, band limited energies, a spectral peak near 20 kHz, inter channel correlation, and a second harmonic index that captures weak interface nonlinearity. Uncertainty is propagated with Monte Carlo waveform perturbations, 5 000 realizations per condition, using amplitude scaling around 5 percent, time of flight jitter around 20 µs, and broadband noise near 2 percent of peak. These perturbations yield prediction bands and calibrated decision scores. The method is benchmarked across four learners: random forest, support vector machine with radial basis function kernel, additive boosting, and a hierarchical screener that first detects any mass and then separates severities. A finite element model provides a physics baseline for feature design. The study is a laboratory proof of concept on one specimen and three conditions, practical implications for aerospace deployment are outlined, including transfer to composite skins and links to certification metrics such as probability of detection. Calibration against the pristine response verified timing and mode content
The influence of temperature on the deformation behavior, strength and fracture mechanism of the heat-resistant Nickel-based alloy EI698-VD
Full text linkA detailed investigation was conducted into the fracture mechanisms of cylindrical specimens made of a polycrystalline heat-resistant nickel-based alloy XH73MBTU-VD (EI698-VD), under uniaxial tension in the temperature range of 25–700°C. The presence of both surface and internal defects was identified and subsequently described. The alloy microstructure was observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy methods. In the temperature range of 650 to 700°C, it has been observed that the onset of crack formation occurs at surface defects. Conversely, at lower temperatures, failure was attributed to the process of ductile growth and the coalescence of pores, leading to the formation of an internal crack. At a test temperature of 400°C and above, the Porteven-Le Chatelier effect (serrated flow) was identified. At temperatures of 25, 400 and 550°C, fracture was accompanied by deformation in different slip planes. An increase in the test temperature was found to result in a change in the slope angle of the slip planes. It was observed that at higher temperatures, there was a significant decrease in plasticity. An excess of 90 times the nominal mass composition of Pb content was detected. A possible cause and mechanism of the steep loss of alloy plasticity with increasing temperature is explained
Effect of B₄C variation on the mechanical, fractographic and tribological performance of hybrid composites Al7075/Gr/ZrO₂
Full text linkThe current study focuses on the influence of varying levels of boron-carbide (B4C) particles on mechanical and tribological characteristics of Al7075 hybrid composites that are strengthened by fixed percentages of graphite (Gr) and zirconia (ZrO2). Hybrid composites were made by stir casting the 2 and 4 wt.% of B4C to Al7075-Gr-ZrO2 matrix in two-steps. The reinforcements were evenly spread throughout the matrix was confirmed by analysis through electron microscopy SEM together with elemental mapping through energy dispersive spectroscopy was utilized. Microstructural properties, tensile, hardness, and wear behaviour of the resulting hybrid composites were tested. The findings suggest that the adding of 4 wt.% B4C shall improve the hardness of Al7075 hybrid reinforced composites to 87 BHN, the UTS by 37% (214 MPa to 293 MPa) and vice versa slight decrease in ductility was attributed due to the addition of B4C. The tribological study revealed that the resistance to wear increased with additions of B4C as the hard ceramic particles served as load bearing phases. These results demonstrate the importance of B4C variation in improving mechanical and tribological behaviour of Al7075-Gr-ZrO2 hybrid reinforced composites in potential structural and aerospace application
Hybrid feedforward neural network for pressure vessel internal corrosion prediction: integrating chemical models with inspection data for structural integrity assessment
Full text linkThis study presents a hybrid framework integrating a physics-based corrosion model with a feedforward neural network (FNN) to predict corrosion rates and estimate the remaining useful life (RUL) of industrial pressure vessels for condition-based maintenance. Using non-destructive evaluation (NDE) wall thickness measurements from 24 inspection points over multiple years (2002–2008) and physics-based training data, a three-layer FNN with Monte Carlo dropout predicts localized corrosion rates, while exponential and linear degradation models project future wall thickness. The FNN achieved a coefficient of determination (R²) of 0.975 for corrosion rate prediction and a mean absolute error (MAE) of 0.1204 mm/year. For thickness prediction, the exponential model achieved R² = 0.99 with MAE = 0.0389 mm, outperforming the linear model (MAE) = 0.1350 mm. The framework was integrated with Fitness-for-Service (FFS) assessment based on API 579-1/ASME FFS-1 standards, enabling classification of vessel components and identification of sections requiring maintenance. This hybrid approach translates predictive analytics into standards-compliant engineering decisions for structural integrity management
Effects of machining methods on uniaxial tensile properties of 75μm thick 304L stainless steel foil
No full textConsidering the fragility of ultra-thin foil material, the machining methods might bring in undesired and non-neglectable damage, which would affect the uniaxial tensile properties of such material. This presented work systematically investigates the effect of five machining methods on the tensile performance of 75μm thick 304L stainless steel foil across four different gage width through uniaxial tension test. The yield stress and ultimate strength are found insensitive to the machining methods and gage widths. Full-field digital image correlation analysis confirmed that the fabrication method dictates the failure mode. Laser cutting and photochemical etched specimens failed in the gage central portion due to intrinsic plastic instability, while specimens fabricated by electrical discharge machining, mechanical milling, and waterjet cutting failed prematurely from process-induced edge defects. Thus, the uniform and fracture elongations were dependent on the process. Geometric size effect on material ductility was also observed for samples with good or moderate edge qualities
Effect of external operational damage on the mechanical behavior of GFRP under quasi-static and fatigue loading
No full textAn experimental study was conducted to investigate the influence of operational defects, such as surface scratches and dents, on the residual mechanical properties of glass fiber-reinforced plastic (GFRP) during quasi-static tensile and fatigue tests. Based on the results of static tests, the types of simulated defects and loading parameters for cyclic testing were determined. Fatigue tests were performed on groups of samples without defects, with a 10 kN dent, a 15 kN dent, and a scratch. The results of these tests allowed the identification of the most critical type of external damage. The failure of GFRP samples with operational defects was analyzed after both quasi-static tension and fatigue testing. Examination of the fracture surfaces of the fatigue-tested samples revealed that failure occurs primarily at the site of the applied defect due to fiber fracture
Effects of Ni-P + DLC multilayer coating on cavitation erosion behavior of AlSi10Mg produced by laser powder bed fusion
Full text linkAdditive manufacturing (AM) technologies are currently contributing to significant progress in the design of lightweight metal components. Al alloys constitute the most studied light metal, particularly the Al-Si ones, due to their high specific properties. However, surface-driven damage mechanisms represent a limitation in the lifespan of such components.
In the present work, different coatings are studied to enhance the cavitation erosion resistance of AlSi10Mg alloy manufactured via laser powder bed fusion (L-PBF). In detail, a Ni-P single layer and a Ni-P + DLC (diamond like carbon) multilayer were considered. Erosion resistance was examined by means of ultrasonic cavitation erosion tests with periodic interruptions to monitor mass loss and damage evolution. The damaged surfaces were inspected through a field emission scanning electron microscopy (FEG-SEM) to determine the damage mechanism, with the aim of evaluating the performances of the different proposed coatings
The damping influence in monitoring the tension of cable using the vibration method
Full text linkIn the maintenance work of cable configurations, which have limitations such as cables in cable-stayed bridges, suspenders in suspension bridges, and hangers in arch bridges, tension on the cables is required. The safety of the cable is confirmed by checking whether the tensile force on the cable is within the allowable value. In the current widespread practice, cable tension is estimated using the vibration method by measuring the natural frequencies of the cable. However, this method is affected by several factors, including flexural rigidity, sag, and damper. The main difference is that natural frequencies (ωn) are the theoretical frequency of vibration without any energy loss, while damped natural frequencies (ωd) are of the actual system where damping (energy loss) is present. The undamped frequency is a system's inherent property based on its mass and stiffness, while the damped frequency is a practical measurement that is always less than the undamped frequency. This paper proposes a novel method for estimating tensile force that considers global damping. To model the cable as a Rayleigh beam, a theoretical equation for a viscoelastic system has been developed to estimate the natural frequency. The solution method calculates the cable tension and the material damping simultaneously from the natural frequencies. Previous studies verified the validity of the method. The maximum error in the tension is in the range of 4.71% in all valid tests. The evidence confirms the effectiveness of the proposed methods in tension estimation. In this research, the influence of damping on the evaluation of tension is investigated through analytical model, in which the natural frequencies, determined by the damping levels and the damped natural frequencies (measured frequencies). Then, the Hierarchical Bayes model was used to find stable estimates while preserving partial pooling, under sparse data, to stabilize estimates and fully quantify uncertainty. The results show that neglecting damping can cause noticeable errors, especially in low-tension or short cables. The study emphasizes the importance of considering damping in vibration-based tensile force assessments to enhance accuracy and reliability.
Experimental study on the mechanical and tribological characteristics of pineapple leaf fiber reinforced polymer composites for biomedical applications
Full text linkNew biomedical supportive and lightweight structures require the creation of sustainable polymer composites of high strength and wear resistance. This research explores the use of alkali-treated pineapple leaf fiber (PALF) reinforced epoxy composites and determines complete structure property wear relationships using combined mechanical, tribological, and microstructural analysis. The novelty of the work is based on the correlation of fiber content with the stiffness increment, the damage tolerance, and degradation behavior under friction conditions at controlled fabrication conditions. A hand lay-up method was used to manufacture composite laminates with 5-25 wt.% PALF. The tensile strength rose to 78 MPa and Youngs modulus rose to 3.5 GPa. Flexural strength increased to 112 MPa and flexural modulus to 3.7 GPa. The energy impact decreased by 12 and dropped to 20 kJ/m2 and Shore D hardness rose by 72 and 76, respectively, which means the increase in deformation and surface damage resistance. Tribological testing revealed that coefficient of friction and wear rate decreased to 0.51 and 3.7 x 10-6 mm 3/N-m respectively by fiber-supported load distribution and establishment of protective transfer films. The scanning electron microscopy showed that there was consistent fiber dispersion, good bonding of fiber matrix, and predominance of crack-bridging and pull-out processes involving the fracture resistance. The best mechanical tribological behavior was observed with a concentration of 10-15 wt.% PALF. A further study will involve biocompatibility studies, long-lasting stability, and surface functionalization to permit biomedical assistance elements like orthotic braces, prosthetic frames, and non-load-bearing auxiliary medical components
Mechanical and morphological evaluation of jute fiber reinforced epoxy composites for sustainable structural and automotive applications
Full text linkThis study investigates jute fibre reinforced epoxy composites fabricated using a controlled vacuum bag moulding process, with emphasis on establishing reliable structure property relationships relevant to sustainable engineering applications. To address limitations in earlier jute/epoxy studies such as generic claims, limited processing transparency, and weak correlation between impact behaviour and fracture mechanisms laminates containing 5, 10, 15, 20, and 25 wt.% jute fibre were produced and systematically characterized. Tensile strength and modulus increased with fibre content, reaching peak values of 95 MPa and 4.5 GPa at 20 wt.%, while reduced elongation at break indicated enhanced stiffness. Flexural strength and modulus exhibited similar trends, attaining maximum values of 150 MPa and 4.8 GPa, respectively, consistent with improved load transfer and crack-bridging mechanisms. Hardness and low-velocity impact energy absorption were also optimized at 20 wt.% fibre loading due to strengthened fibre matrix interfacial bonding and more uniform stress distribution. A decline in mechanical performance at 25 wt.% was attributed to fibre agglomeration, micro-void formation, and localized interfacial debonding. Scanning electron microscopy revealed matrix-dominated fracture at low fibre contents 5 to 10 wt.%, optimal dispersion and interfacial integrity at intermediate contents 15 to 20 wt.%, and severe clustering at higher loading. These findings identify 15 to 20 wt.% jute fibre as the optimal range for achieving a balanced combination of stiffness, strength, and impact resistance, supporting potential application in lightweight, non-critical structural and automotive components