Search Results (220)

Inconel 718 is widely utilized in critical engineering sectors, particularly aerospace, owing to its exceptional creep resistance, corrosion resistance, and retention of mechanical strength at elevated temperatures. However, its high hardness, low thermal conductivity, and strong work-hardening tendency make it extremely difficult to machine using conventional techniques. Ultrasonic Vibration-Assisted Machining (UVAM) has emerged as an effective strategy to overcome these limitations by superimposing high-frequency, low-amplitude vibrations onto the cutting process. Depending on the vibration direction, UVAM can significantly change chip formation, tool–workpiece interaction, and surface integrity. In this study, the influence of three UVAM modes—longitudinal (Z-UVAM), feed-directional (X-UVAM), and multi-axial (XZ-UVAM)—on the machining behavior of Inconel 718 was systematically investigated. The findings reveal that XZ-UVAM provides the most advantageous outcomes, primarily due to its intermittent cutting mechanism. Compared with Conventional Machining (CM), XZ-UVAM reduced cutting forces by up to 43% and areal surface roughness by 37%, while generating surfaces with more uniform topographies and smaller peak-to-valley variations. Furthermore, UVAM enhanced subsurface microhardness as a result of the surface hammering effect, which may improve fatigue performance. XZ-UVAM also effectively minimized burr formation, demonstrating its potential for high-quality, sustainable, and efficient machining of Inconel 718. Full article

The increased test frequency inherent in Ultrasonic Fatigue Testing (UFT) is commonly observed to result in an increased fatigue resistance for ferritic, low-carbon steels. In this investigation, the fatigue response of S275J2 ferritic structural steel is evaluated at both 20 kHz and 50 Hz. At the ultrasonic frequency, an increase in the fatigue limit of 136 MPa and an increase in the finite life region of 150 MPa was observed, alongside a reduction in the slope of the S-N curve. By combining the S275J2 results with additional data from the literature, generalised versions of previously proposed frequency sensitivity models are produced by evaluating the model coefficients as a function of different combinations of the material properties. Additionally, a new frequency sensitivity model was proposed by evaluating the empirical change in the S-N curve coefficients as a function of these material properties. For all of the models, it was found that the best correlation was against the ferrite content divided by the tensile strength. The generalised forms of these models were rearranged to produce correction factors, which allow the conventional frequency fatigue response to be estimated based on the UFT test. The most reliable correction method was found to be using the empirical change in the S-N curve exponent. Full article

Aluminium alloys are widely used across various industrial sectors due to their suitability for enhancing structural safety and reducing weight, thereby improving operational efficiency. This study investigates the feasibility of using ultrasonic techniques as an alternative to thermistors for temperature monitoring in electric vehicle motors and batteries. The extent to which ultrasonic maximum amplitude and propagation velocity are temperature-dependent was examined, and the material nonlinearity was analyzed. Step-wedge specimens of Al3003, Al6061, and Al6063—commonly used in electric vehicle components—were fabricated with thicknesses of 4, 6, 8, 10, and 12 mm to examine thickness-dependent behavior. Although the three alloys differ in composition and mechanical properties, their ultrasonic propagation characteristics were found to be highly similar. As temperature increased, ultrasonic attenuation increased while propagation velocity decreased. For intact specimens, nonlinearity increased with temperature. However, the variation remained constant beyond a certain temperature range. In contrast, tensile-fatigued specimens showed increased nonlinearity with fatigue cycles, and the variation decreased at elevated temperatures, producing a more pronounced nonlinear response. These findings suggest that ultrasonic techniques may provide a cost-effective solution for temperature measurement and defect diagnosis, potentially replacing high-cost thermistors currently used in electric vehicles. Full article

The gear transmission system is a safety-critical component in rail transit, typically designed for a service life exceeding 20 years. Failure analysis of such systems remains a key focus for railway engineers. This study systematically investigates four representative cases of premature gear failure in high-speed trains using a standardized analytical procedure that includes visual inspection, chemical analysis, metallographic examination, scanning electron microscopy, and hardness testing. The results identify four primary root causes: subsurface slag inclusions in raw materials, inadequate heat treatment leading to a non-martensitic layer (∼60 μm) at the tooth root, grinding-induced temper burns (crescent-shaped "black spots") accompanied by a hardness drop of ∼100–150 HV, and insufficient lubrication. The interdependencies between these factors and failure mechanisms, e.g., fatigue cracking, spalling, and thermal scuffing, are analyzed. This work provides an evidence-based framework for improving gear reliability and proposes targeted countermeasures, such as ultrasonic inclusion screening and real-time grinding temperature control, to extend operational lifespans. Full article

As the world increasingly gravitates towards green, environmentally friendly and low-carbon lifestyles, wind power has become one of the most technologically established renewable energy sources. However, with the continuous increase in their output power and height, wind turbine towers are subjected to higher-intensity alternating wind loads. This makes critical components more prone to fatigue failure, potentially leading to major accidents such as tower buckling or turbine collapse. High-strength bolts play a vital role in supporting towers but are susceptible to fatigue crack initiation under long-term cyclic loading, necessitating regular inspection. Types of wind turbine bolts mainly include high-strength bolts, stainless steel bolts, anchor bolts, titanium alloy bolts, and adjustable bolts. These bolts are distributed across different parts of the turbine and perform distinct functions. Among them, high-strength bolts in the tower are particularly critical for structural support, demanding prioritized periodic inspection. Compared to destructive offline inspection methods requiring bolt disassembly, non-destructive testing (NDT) has emerged as a trend in defect detection technologies. Therefore, this review comprehensively examines various types of NDT techniques for wind turbine towers’ high-strength bolts, including disassembly inspection techniques (magnetic particle inspection, penetration inspection, intelligent torque inspection, etc.) and non-disassembly inspection techniques (ultrasonic inspection, radiographic inspection, infrared thermographic inspection, etc.). For each technique, we analyze the fundamental principles, technical characteristics, and limitations, while emphasizing the interconnections between the methodologies. Finally, we discuss potential future research directions for bolt defect NDT technologies. Full article

With the rapid development of mechanical components, increasingly stringent demands are placed on steel properties—particularly tensile strength and rotating bending fatigue resistance. This study systematically investigates the effects of the electropulsing-assisted ultrasonic surface rolling process (EUSRP) on the surface microstructure and fatigue performance of 30CrNi2Mo steel. A fine-grained surface layer (depth: 80 μm) was formed. Lath martensite width decreased significantly from 7 μm to 4 μm after EUSRP treatment, which was significantly refined after electropulsing treatment and an ultrasonic surface-rolling process. Under identical stress amplitudes, the rotating bending fatigue life of EUSRP-treated specimens substantially exceeded that of the as-machined state. Fatigue cracks in the as-machined state consistently initiated at the surface, coalesced, and propagated into large cracks, leading to premature fracture. In EUSRP-treated samples, crack initiation shifted to subsurface regions, delaying failure and extending fatigue life. Full article

Ultrasonic-assisted machining (UAM) has emerged as a transformative technology for increasing material removal efficiency, improving surface quality and extending tool life in precision manufacturing. This review specifically focuses on the application of it to titanium aluminide (TiAl) alloys. These alloys are widely used in aerospace and automotive sectors due to their low density, high strength and poor machinability. This review covers various aspects of UAM, including ultrasonic vibration-assisted turning (UVAT), milling (UVAM) and grinding (UVAG), with emphasis on their influence on the machinability, tool wear behavior and surface integrity. It also highlights the limitations of single-energy field UAM, such as inconsistent energy transmission and tool fatigue, leading to the increasing demand for multi-field techniques. Therefore, the advanced machining strategies, i.e., ultrasonic plasma oxidation-assisted grinding (UPOAG), protective coating-assisted cutting, and dual-field ultrasonic integration (e.g., ultrasonic-magnetic or ultrasonic-laser machining), were discussed in terms of their potential to further improve TiAl alloys processing. In addition, the importance of predictive force models in optimizing UAM processes was also highlighted, emphasizing the role of analytical and AI-driven simulations for better process control. Overall, this review underscores the ongoing evolution of UAM as a cornerstone of high-efficiency and precision manufacturing, while providing a comprehensive outlook on its current applications and future potential in machining TiAl alloys. Full article

In the saline soil area of western China, the concrete is simultaneously subjected to cyclic loading and sulfate attack. To reveal the effect of sulfate attack on fatigue performance of normal concrete (NC) and hybrid fiber-reinforced rubber concrete (HFRRC), the uniaxial compression test and cyclic loading test were carried out on the specimens after sulfate erosion. The loading strain, plastic strain, and elastic strain of the concrete were compared and analyzed. The compressive strength, fatigue resistance, and strain energy of the concrete were compared and analyzed. Ultrasonic Pulse Velocity (UPV) measurements were also used to quantify the damage in sulfate attack tests. The results indicate that the fatigue failure stress of concrete is lower than its uniaxial compressive strength. The fatigue resistance coefficient of HFRRC is always higher than that of NC. Under the cyclic loading with the same level, the stress–strain curve of HFRRC is denser than that of NC, exhibiting good elasticity. The energy evolution is independent of whether or not sulfate attacks, but its growth rate is affected by sulfate erosion time. It can provide an experimental and theoretical foundation for the application of HFRRC in engineering structures subjected to repeated loads in sulfate environments. Full article

Cavitation-induced degradation of metallic materials presents a significant challenge for engineers and users of equipment operating with high-velocity fluids. For any metallic material, the mechanical strength and ductility characteristics are controlled by the mobility of dislocations and their interaction with other defects in the crystal lattice (such as dissolved foreign atoms, grain boundaries, phase separation surfaces, etc.). The increase in mechanical properties, and consequently the resistance to cavitation erosion, is possible through the application of heat treatments and cold plastic deformation processes. These factors induce a series of hardening mechanisms that create structural barriers limiting the mobility of dislocations. Cavitation tests involve exposing a specimen to repeated short-duration erosion cycles, followed by mass loss measurements and surface morphology examinations using optical microscopy and scanning electron microscopy (SEM). The results obtained allow for a detailed study of the actual wear processes affecting the tested material and provide a solid foundation for understanding the degradation mechanism. The tested material is the Ni-based alloy INCONEL 625, subjected to stress-relief annealing heat treatment. Experiments were conducted using an ultrasonic vibratory device operating at a frequency of 20 kHz and an amplitude of 50 µm. Microstructural analyses showed that slip bands formed due to shock wave impacts serve as preferential sites for fatigue failure of the material. Material removal occurs along these slip bands, and microjets result in pits with sizes of several micrometers. Full article

The attenuation of bolt preload is a critical factor leading to bolt fatigue failure, whereas the study of the nonlinear attenuation behavior of preload and its mechanism during installation is an inevitable challenge in engineering practice. The attenuation of the preload of a bolt is mainly related to the stiffness of the bolt body as well as the stiffness of the connected parts. This study aimed to develop an experimental system to analyze the nonlinear attenuation behavior of preload during bolt tightening. First, a simulation system replicating the bolt installation process was constructed in a laboratory setting, incorporating blade and pitch bearing specimens identical to those used in a 10 MW wind turbine, restoring the stiffness coupling characteristics of the “composite-metal bearing” heterogeneous interface at the blade root through a 1:1 full-scale simulation system for the first time. Second, ultrasonic preload measurement equipment was employed to monitor preload variations during the bolt tightening process. Finally, the instantaneous preload decay rate of the wind turbine blade-root bolts and the over-draw coefficient were quantified. Experiments have shown that the preload decay rate of commonly used M36 leaf root bolts is 11–16%. If a more precise value is required, each bolt needs to be calibrated. These findings provide valuable insights for optimizing bolt installation procedures, enabling precise preload control to mitigate fatigue failures caused by abnormal preload attenuation. Full article

Based on rolling contact fatigue life experiments, this study systematically investigates the effect of ultrasonic surface rolling processing (USRP) with a composite diamond-like carbon (DLC) coating on the rolling contact fatigue life of bearings through characterization and analysis. The results show that the USRP-composite DLC coating forms a synergistic mechanism between the coating and the substrate on the surface of specimens: the DLC coating resists surface wear with its high hardness and low friction coefficient, while USRP reduces substrate deformation and crack growth by decreasing surface roughness, increasing substrate hardness, and introducing residual compressive stress. Additionally, USRP enhances the adhesion between the coating and the substrate. The average wear volume of the USRP-composite DLC-coated specimens is 3.73 × 10¹¹ μm³, which is 30.95% lower than that of USRP-treated specimens and 85.38% lower than that of untreated specimens. The average fatigue life of the USRP-composite DLC-coated specimens is 6.55 × 10⁶ cycles, which is 94.94% higher than that of USRP-treated specimens and 208.24% higher than that of untreated specimens. Full article

In recent decades, the application of composite materials in aerostructures has significantly increased, with modern commercial aircraft progressively replacing aluminum alloys with composite components. This shift is exemplified by comparing the material compositions of the Boeing 777 and the Boeing 787 (Dreamliner). The Boeing 777 incorporates approximately 50% aluminum alloy and 12% composite materials, whereas the Dreamliner reverses this ratio, utilizing around 50% composites and 12% aluminum alloy. While metals remain advantageous due to their availability and ease of machining, composites offer greater potential for property tailoring to meet specific performance requirements. They also provide superior strength-to-weight ratios and enhanced resistance to corrosion and fatigue. To ensure the reliability of composites in aerospace applications, comprehensive testing under various loading conditions, particularly impact, is essential. Impacts were performed on quasi-isotropic (QIT) carbon-fiber reinforced epoxy panels with stainless steel, round-nosed and flat-ended impactors with rubber discs of 1-, 1.5- and 2 mm thickness, adhered to the flat-ended impactor to simulate the transition between hard and soft impact loading conditions. QIT composite panels were tested in this research employing similar lay-ups often being implemented in aircraft wings and other structures. The rubber discs were applied in the flat-ended impactor case but not for the round-nosed impactor due to the limited adhesion between the rubber and the rounded stainless-steel surface. Impact energies of 7.5, 15 and 30 J were investigated, and the performance of the panels was evaluated using force-time and force-displacement data alongside post-impact ultrasonic C-scan imaging to assess the damaged area. Damage was observed at all three energy values for the round-nosed impacts but only at the highest impact energy when using the flat-ended impactor, leading to the hardness study with adhered rubber discs being performed at 30 J. The most noticeable difference with the addition of rubber discs was the reduction in the damage in the plies nearest the top (impacted) surface. This suggests that the rubber reduces the severity of the impact, but increasing the thickness of the rubber from 1 to 2 mm does not notably increase this effect. Indentation clearly plays a significant role in promoting delamination at low-impact energies for the round-nosed impactors. Full article

Performing fatigue characterisation is often an expensive task, being both time consuming and expensive. Taking that into account, ultrasonic fatigue testing is an interesting solution, since it can be thousands of times faster than traditional experiments. In ultrasonic fatigue testing, excitation frequencies are in the order of magnitude of 20 kHz, while common fatigue testing frequencies are typically approximately a few hundreds of Hz. Although promising, ultrasonic fatigue testing has some challenges, like high strain rates, heat generation and complex specimen design. Regarding the latter, since the working principle of ultrasonic fatigue tests relies on exciting the specimen in one of its natural frequencies, finding a specimen geometry to resonate at this given frequency might be challenging. Additionally, some materials often present challenges associated with high temperature during tests. The goal of this paper is to provide guidelines for specimen design, encompassing the effects of critical factors and their impact on important test parameters, like temperature and dimensions. The proposed methodology developed a parameter able to quantify the heat generation severity during ultrasonic fatigue testing for several materials based on their physical properties. Moreover, the effects of the geometry and material properties in the temperature during loading cycles, with special focus on thermal gradients were enumerated. Full article

High-speed electrical discharge machining (EDM) is crucial for drilling aerospace components, but the fatigue effects of its recast layer are still not well understood. This study investigates the fatigue behavior of high-speed EDM-processed specimens using ultrasonic fatigue testing and microscopic analysis. The recast layer showed a 20.4% increase in hardness and a 16.5% decrease in elastic modulus compared to the base material. Fatigue cracks originated from microcracks, pores, and inclusions within the recast layer, as well as at its interface with the substrate. Microscopic crack initiation was influenced by defect interactions, while macroscopic crack initiation occurred near the maximum hole diameter perpendicular to the loading direction due to stress concentration. The specimens exhibited bimodal fatigue life: shorter lifetimes were observed when macroscopic stress concentrations overlapped with recast layer defects such as cracks and voids, while defect-free regions significantly extended durability. The non-uniform distribution of the recast layer critically links microstructural heterogeneity to variations in fatigue failure. These findings highlight how recast layer characteristics influence crack nucleation and life variability in EDM-processed components, offering valuable insights for optimizing machining parameters to reduce fatigue risks in critical aerospace applications. Full article

In this paper, we introduce an advanced AI-based solution for predicting structural damage in aircraft laminates. Our innovative approach focuses on detecting and locating fatigue damage within composite structures, thereby enhancing the assessment of aircraft health and usage. By leveraging state-of-the-art ultrasonic guided wave (UGW) inspection simulations of composite laminates integrated with piezoelectric transducers, comprehensive datasets are extracted efficiently. The signals captured by the piezoelectric sensors are utilized to engineer key features sensitive to composite structural damage, which are then used to train a deep neural network (DNN) for accurate structural damage prediction. Our findings demonstrate the significant potential of combining advanced simulation techniques with machine learning to improve the accuracy and reliability of structural health monitoring in aerospace applications. Full article