Papers by Keyword: Microcrack

Abstract: Electromechanical impedance (EMI) sensing with bonded piezoelectric patches is a compact option for structural health monitoring at high frequencies. This study evaluates the detectability of submillimeter microcracks in an Inconel 718 plate using a surface-bonded lead zirconate titanate (PZT) transducer through a finite element-based harmonic analysis. A two-dimensional coupled-field model represents a 20 × 20 × 5 mm³ plate and a PIC255 patch with an in-plane size of 10 × 10 × 0.5 mm³. The model performs a 10–100 kHz voltage sweep at 0.5 V to compute electrical resistance. Damage is introduced as circular notch-like defects with diameters of 0.25, 0.50, and 0.75 mm at nine locations that vary the sensor-to-defect distance. A mesh convergence study ensures numerical stability. Damage sensitivity is quantified using Root Mean Square Deviation (RMSD) of impedance signatures relative to the healthy baseline. Results show that frequency bands around local resonances provide the strongest separation between healthy and damaged states, with the most discriminative band observed near 54–57 kHz. RMSD increases monotonically with defect diameter and decreases with distance from the sensor, demonstrating an anisotropic positional sensitivity that is stronger along the patch axis.

Abstract: Magnetic abrasive finishing (MAF) is an advanced surface finishing technology that utilizes magnetic fields to control abrasive particles, enabling precise material removal and superior surface integrity. This review paper comprehensively analyzes MAF research from 2015 to 2024, focusing on key developments, process optimizations, and industrial applications. The study looks at how MAF affects different materials like titanium alloys, stainless steels, and 3D-printed parts, showing how it improves surface smoothness, leftover stress, and resistance to wear and tear. This review paper expands on the experimental investigation of MAF’s efficacy in removing crack fatigue layers for a high-cost product to give it a high performance and longer life, a critical aspect in enhancing the functional performance of components. It is synthesizing various studies that explore the principles of MAF, the preparation of magnetic abrasives, tool design, and the process’s modeling and simulation. It also examines the force measurement and material removal mechanisms, providing a comprehensive understanding of the process parameters and their optimization. It is highlighting the challenges faced ‎in the field and suggests future directions for research, aiming to contribute to the development of more efficient and precise finishing techniques in manufacturing industries. The findings of this study are expected to benefit researchers and practitioners in MAF-related fields, paving the way for innovations in surface finishing technologies.

Abstract: In the constructions and weld seals microdefects while repeated stress lead to metal structure damage, low-cycle and high-cycle fatigue, and cracks dissemination. The calculation method of operating life estimate presupposes a microcrack development hypothetical speed application. This speed in many cases is unknown. Initial speed determination suggested in this work is based on endurance limit values design analysis when considering a combined problem for the first two sections of fatigue failure kinetic diagram.

Abstract: Chromium plating is used widely in industry to enhance wear, abrasion resistance and to restore the dimensions of undersized parts. However, tensile residual stress always exists in chrome layer because of hydrogen embrittlement so it affect to mechanical properties of the chromium plating machine element, especially in fatigue strength. In this paper, effect of residual stress in chrome plating layer to fatigue strength was studied. The sample (AISI 1045 steel) was plated with 10 and 60 micrometers thicknesses and residual stress in chrome plating layer was determined by X-ray diffraction technique (Cu-Kα radiation). The results showed that chromium layer thicknesses go up, tensile residual stress decrease and microcrack density increase. Consequently, fatigue strength goes down when chromium layer thicknesses increase.

Abstract: The subsurface fatigue crack generation processes in near α type titanium alloy were divided into four steps: (1) development of a saturated dislocation structure by cyclical micro-plastic strain accumulation, (2) generation of localized slip and/or microcracking to relax the stress concentration in the vicinity of a boundary, (3) microcrack growth and transition to main crack, and (4) crack propagation. The experimentals on transgranular facets formation in Ti-Fe-O alloy were reviewed and a subsurface fatigue crack generation model was discussed. The β platelets which were aligned between the recrystallized α grain and the recovered α grain were responsible for the microcrack generation to form (0001) tansgranular facet in the recrystallized α grains. A combination of the shear stress and tensile stress normal to the basal plane may give a trigger of the (0001) microcracking in the recrystallized α grain. The localized shear stress following slip off on the basal plane was activated at the microcrack tip in the recrystallizedαgrain, and the microcrack grew into the recrystallized α grain to form (0001) transgranular facet.

Abstract: The article is devoted to the diagnosis of bearing units working with hydrocarbon mixtures. The diagnostic is based on the photometric method. This method allows you to determine the internal damage to the bearing unit at the stage of the appearance of the microcrack. The photometric method is based on changing the color of the indicator fabric. As the indicator substance, a bromine solution was used which had a dark brown color. If there is a leak, the hydrocarbon reacts with bromine molecules and a bright spot appears on the tape. Indicator fabric is applied to the bearing unit during assembling.The material of the article contains a model of the physicochemical process, which is the basis of the photometric method. Various stages of leakage of hydrocarbon mixtures through microcracks were studied. The results of the experimental studies are consistent with the theoretical propositions. The proposed diagnostic method can be used as a method for non-destructive testing of bearing units.

Abstract: The characterization of subsurface fatigue crack initiate sites of near α and α-β types titanium alloys and their cracking models proposed were reviewed. The crack initiation sites consisted of facets mostly on near basal plane of α grain, although the crystallographic orientation and surface topography of the facets presented a subtle difference. The crack initiation mechanisms were a quasi-cleavage accompanying high normal stress on the plane, a combination of basal slip and normal stress across the basal plane, and a pure slip on facet plane inclined near 45 degree to loading axis.

Abstract: Damage and microcracks formed by rolling contact fatigue (RCF) were characterized for carburized SCM420 steel. A large number of microcracks were detected beneath the contact surfaces after RCF. The microcrack generation and strain distribution beneath the contact trail depended on the slip ratios of 0 %, -20% and -40 % in the roller pitting test. Such severe slip increased shear strain in the region higher than 160 µm in depth from the contact surface. Compressive stress also gave rise to strain in the region near the surface up to 100 µm in the depth. Those strain gradients may cause a strain incompatibility at the transition layer in which a crack branching was detected.

Abstract: Many reinforced concrete structures susceptible to corrosion damage are subjected to externally applied loads, causing cracking. These cracks increase the permeability of the material, accelerating the ingress of corrosion-inducing deleterious agents. In this paper, the effect of multiple microcracking and macrocrack formation on corrosion initiation was investigated. A hybrid fiber-reinforced concrete (HyFRC), which forms ductile, distributed microcracking prior to dominant crack localization due to multiple tiers of fiber reinforcement, is being studied for its performance against corrosion damage. The effect of matrix cracking on corrosion initiation was studied with beam specimens preloaded in flexure prior to long-term corrosion exposure. Reinforced HyFRC composites were found to have a delayed corrosion initiation response due to reductions in crack widths and suppression of splitting cracks, compared to conventional reinforced concrete. The influence of microcracks on corrosion is studied using X-ray micro-computed tomography (μCT) on reinforced fiber-reinforced cementitious composites and reinforced mortar preloaded in tension.

Abstract: The paper presents the results of studies the deformation behavior of aluminium alloy D16 by acoustic emission (AE) method. The purpose of this study was to establish the deformation stages and deformation mechanisms at each stage. Studies were carried out on the samples of aluminum alloy D16 (analog 7075). This paper contains a method for the separation of AE signals. The method of AE sources identification based on the the two-parameter distribution analysis (frequency parameter K_fvs energy of AE signals). The frequency parameter Kf is based on wavelet transform of AE signals. Two-parameter distribution allows one to separate the AE signals emitted by dislocations from the signals of micro cracks. The investigation results allowed the various deformation stages to establish by the different types of AE signals. By the AE analysis shows the dislocation mechanism of hardening the aluminum alloyD16. The paper presents the results that characterize the influences of heat treatment and structural condition of aluminum alloy on the AE parameters.