High Vibration Amplitudes Research Articles

Design and Uncertainty Evaluation of a Calibration Setup for Turbine Blades Vibration Measurement

Turbomachinery engines face significant failure risks due to the combination of thermal loads and high-amplitude vibrations in turbine and compressor blades. Accurate stress distribution measurements are critical for enhancing the performance and safety of these systems. Blade tip timing (BTT) has emerged as an advanced alternative to traditional measurement methods, capturing blade dynamics by detecting deviations in blade tip arrival times through sensors mounted on the stator casing. This research focuses on developing an analytical model to quantify the uncertainty budget involved in designing a calibration setup for BTT systems, ensuring targeted performance levels. Unlike existing approaches, the proposed model integrates both operational variability and sensor performance characteristics, providing a comprehensive framework for uncertainty quantification. The model incorporates various operating and measurement scenarios to create an accurate and reliable calibration tool for BTT systems. In the broader context, this advancement supports the use of BTT for qualification processes, ultimately extending the lifespan of turbomachinery through condition-based maintenance. This approach enhances performance validation and monitoring in power plants and aircraft engines, contributing to safer and more efficient operations.

Interferometric image reorganization and screening method based on phase-shift convergence criterion

To address the challenge of obtaining high-quality interferometric images in the presence of environmental disturbances, this paper proposes a method for interferometric image reorganization and screening based on the phase-shift convergence criterion. The method begins with the acquisition of multiple sets of interferometric images, which are subsequently classified and reorganized according to the amount of phase shift. A mean absolute deviation metric is then employed to systematically screen the classified images, allowing for the selection of a subset that exhibits accurate phase shifts. Finally, the screened and combined interferometric images are evaluated for phase shift centralization through the calculation of the coefficient of variation, ensuring that the screened images conform to the expected criteria. The experimental results indicate that the average coefficient of variation of the screened interferometric images obtained using the proposed method is significantly reduced by 0.1236, 0.0968, and 0.1042 when compared to the nine sets of directly acquired interferometric images subjected to high-frequency vibration, high-amplitude vibration, and transverse distortion vibration, respectively. These data demonstrate that the proposed method can effectively adapt to various vibration environments while screening interferometric images of higher quality. Consequently, this method offers a novel approach to enhancing the vibration resistance of interferometers.

Justification and implementation of the layer thickness control method in ultrasonic spraying

Relevance. The need for the development and widespread use of the ultrasonic spraying method, which has unique advantages, to solve the most pressing problems of modern industry. In particular: minimal, of all known methods, energy consumption for the implementation of the process, the possibility of forming fine droplets without the use of gas under pressure, regulating the dispersion of the formed aerosol by the parameters of the emitter, etc. However, for widespread practical use of the ultrasonic spraying method, it is necessary to ensure spraying conditions with a specified dispersion and productivity. In this regard, there is a need to develop a method for controlling and maintaining the necessary and sufficient thickness of the liquid layer on the surface of the piezoelectric transducer of the atomizer, the spraying of which will ensure, at a given spraying performance, the formation of an aerosol with the smallest deviation in the size of the formed droplets relative to the average value. It is proposed to control the thickness of the liquid layer by identifying the dependence of the resonant frequency of the piezoelectric transducer of the atomizer on the thickness of the liquid film on the oscillating surface of the atomizer. Aim. To develop a method and means for controlling the thickness of the layer of sprayed liquid by changing the resonant frequency of the ultrasonic oscillatory system and maintaining the optimal value of the layer thickness by changing the amplitude of vibrations of the surface of the ultrasonic sprayer. Objects. Liquid atomizing with ultrasonic high-amplitude vibrations. Methods. Obtaining the frequency characteristics of ultrasonic oscillatory systems, analyzing changes in the amplitude-frequency characteristics of oscillating systems and identifying criteria that allow monitoring and managing the ultrasonic spraying. Results. The authors have proposed and developed the method for indirectly monitoring the thickness of a sprayed liquid layer on the oscillating surface of an ultrasonic atomizer, based on measuring the resonant frequency of an ultrasonic oscillating system. The possibility of implementing the method and its practical application is caused by the fact that in the working range of layer thicknesses of the sprayed liquid, the change in the resonant frequency can reach 100 Hz, and with a frequency measurement accuracy of 1 Hz, the accuracy of determining the layer thickness will be no more than 2% of the working layer thickness. The identified dependencies and certain values of possible ranges of changes in the controlled parameter made it possible for the first time to develop a method for automatically controlling ultrasonic spraying, ensuring the maintenance of optimal modes of ultrasonic influence (amplitude of vibrations of the spray surface) and the thickness of the layer of sprayed liquid.

Response Analysis and Vibration Suppression of Fractional Viscoelastic Shape Memory Alloy Spring Oscillator Under Harmonic Excitation

This study investigates the dynamic behavior and vibration mitigation of a fractional single-degree-of-freedom (SDOF) viscoelastic shape memory alloy spring oscillator system subjected to harmonic external forces. A fractional derivative approach is employed to characterize the viscoelastic properties of shape memory alloy materials, leading to the development of a novel fractional viscoelastic model. The model is then theoretically examined using the averaging method, with its effectiveness being confirmed through numerical simulations. Furthermore, the impact of various parameters on the system’s low- and high-amplitude vibrations is explored through a visual response analysis. These findings offer valuable insights for applying fractional sliding mode control (SMC) theory to address the system’s vibration control challenges. Despite the high-amplitude vibrations induced by the fractional order, SMC effectively suppresses these vibrations in the shape memory alloy spring system, thereby minimizing the risk of catastrophic events.

Parametric resonance and suppression for L-shaped pipe conveying pulsating fluid

This work establishes a new dynamic model for solving parametric resonance and suppression of a L-shaped pipe conveying pulsating fluid, which can be extended to arbitrary pipe configurations. Firstly, the linear dynamic analysis for the L-shaped pipe conveying steady-state fluid is performed. The new results show that there are more wave numbers of the mode shape than those for the straight pipe. With increasing the flow velocity, the natural frequency is decreased and the mode shape is changed from symmetry to asymmetric characteristics. Subsequently, the nonlinear dynamic analysis is conducted for the L-shaped pipe conveying pulsating fluid. It is found that primary and subharmonic resonance behaviors are newly produced due to parametric excitations. At the same time, the subharmonic resonance occurs for the pipe to have much higher vibration amplitudes than the primary resonance. Finally, the strategy of adding an intermediate support is proposed to suppress vibrations of the L-shaped pipe conveying pulsating fluid. Results indicate that there is an optimal position for the L-shaped pipe to add the intermediate support, which can significantly reduce the vibration amplitude. This optimal position is exactly where the fundamental frequency of the pipe system is maximized.

Modeling of drilling tool vibration in the process of drilling blast wells

Purpose. To determine the characteristic features and model bit vibration during its interaction with rock in the process of drilling technical (blast) wells in open pit mines. Methodology. The following methods were used in the work: analysis of scientific and practical solutions; statistical methods for processing the results of experimental studies; methods of analytical synthesis; computer modeling methods for synthesis and analysis of mathematical models. Findings. The process of interaction between a drill bit and a rock was analyzed. The conditions and causes of vibration of drilling equipment are determined. The spectral analysis of the vibration signal, the formation and analysis of the map of the order of rotation of the rotating parts of the drilling rig during the drilling of technical (blast) wells were performed to identify the bit in the frequency domain of the measured concomitant integrated vibration signal as a source of high-amplitude vibration. The modulated signal measured in the time domain at the specified frequency carries information about the physical and mechanical characteristics of the drilled rock and the state of the bit. The analysis of the experimental studies and modeling of the process of interaction of the bit with the rock allows us to conclude that the obtained statistical indicators of the accompanying vibration signal really adequately characterize the process of well drilling. Originality. A method for determining the characteristics of the interaction of a drill bit with rock in the process of drilling technical (blast) wells based on measuring the parameters of the accompanying vibration signal is proposed. The method differs from the known ones in the fact that in the process of changing the operating mode of the drive of the rotating parts of the drilling rig, an order map is formed over the entire range of its revolutions, the frequency of high-amplitude vibration of the bit is determined, which corresponds to a certain peak order of revolutions, and at this frequency the statistical parameters of changes are measured. Practical value. This approach to the process of drilling wells in open pit mines makes it possible to quickly determine the physical and mechanical characteristics of the drilled rock and adjust the process parameters accordingly to increase its productivity and energy saving.

Experimental analysis of Local Defect Resonance in an aluminum plate

In the context of non-destructive evaluation and testing of structures, the use of Local Defect Resonance is promising for the detection of delamination-type defects in composites. In this context, an experimental analysis Local Defect Resonance is proposed. It is here carried out on a model system: a thin aluminum plate with a Flat Bottom Hole (FBH) defect consisting in a self-adhesive aluminum sheet (a shim) adhesively bonded over a circular through hole. First, the local defect resonance frequencies and mode shapes are analyzed assuming linear vibrations of the structure. Then, a nonlinear approach is used to compare two types of FBH defects, a first flawless one and a second one including a damaged area. For this purpose a high amplitude vibration around the resonance frequencies are used in order to generate high order harmonics. This enhancement is identified as associated with mainly quadratic nonlinearity.

A parametric study of dynamic stress in acoustic black holes

Acoustic Black Holes (ABHs) make modifications to a structure that act to reduce the speed of a wave travelling through the ABH region. The reduced wavespeed has a corresponding reduced wavelength which increases the effectiveness of damping treatment applied to the ABH. A common way in which the reduction of wavespeed can be achieved is by gradually reducing the thickness of a structure. This is commonly implemented as a beam termination, which results in a thin tip. In this case, the energy focusing effect of the ABH causes high amplitude vibrations to occur in the thin section of the structure, raising concerns about high levels of dynamic stress that could result in fatigue failure. This paper presents an investigation into the effect of changing the ABH taper length, tip height and power law on the dynamic stress in an ABH terminated beam. This is achieved via numerical model of the structure, which enables a full parametric analysis to be carried out. For each ABH parameterisation, the performance is also quantified in terms of reflection coefficient so that trade-offs between performance and stress can be observed.

Vortex-induced vibration and energy harvesting of cylinder system with nonlinear springs

Vortex-induced vibration is a common fluid–structure coupling phenomenon in ocean engineering. As a nonlinear stiffness structure caused by anisotropic deformation and support gap, nonlinear spring is of great significance in the field of vortex-induced vibration. Based on the structural dynamics equations and the wake oscillator model, the vibration model of the 2-Degree of Freedom cylinder system with the nonlinear stiffness spring is established. The stiffness ratio, mass ratio, and damping ratio of the cylinder system are changed, and the amplitude and frequency response are analyzed to obtain the effect of nonlinear spring on vortex-induced vibration. The results show that the cylinder system with a nonlinear stiffness spring can maintain a high vibration amplitude in a large Reynolds number range, and the smaller the mass ratio, the more significant the effect is. When m*=1.5, the amplitude of the cylinder system in a cross flow is greater than 0.6 at Re = 180 000–480 000. The energy harvesting in the vortex-induced vibration of cylinder systems with nonlinear stiffness springs is also studied. The efficiency depends on the damping ratio and Reynolds number. When the damping ratio is constant, the energy harvesting efficiency increases first and then decreases with the Reynolds number increases. When m*=1.5, the energy harvesting efficiency of the cylinder system is 19.27% with Re= 35 000 and damping ratio ξ=0.155. As a kind of renewable energy, energy harvesting in vortex-induced vibration is a potential development direction in the future energy field.

Aeroelastic Influence of Blade-Shaft Coupling in a 1 1/2-Stage Axial Compressor

Abstract The design process of turbomachinery, is often constraint by aeroelastic phenomena. The design choices are limited by possible structural failure, which can be caused by high vibration amplitudes. In particular, damping has an important impact on these phenomena. In the absence of friction, damping is mainly created by aerodynamics. In this paper, additional damping created by the shaft will be investigated. This becomes relevant when blade vibrations with nodal diameters 1 and -1 couple structurally with shaft vibrations. To investigate the blade-shaft coupling, a simulation process is set up based on a full structural dynamic model of the blisk-shaft assembly and a harmonic balance CFD model to account for the aeroelastic effects. In addition, mistuning identification is performed based on an experimental modal analysis at standstill. All results are incorporated into a structural reduced order model that calculates the vibrational behavior of the blading. These results are compared to damping determined during operation using an acoustic excitation system and measured forced frequency responses. The numerical results agree well with the experimental results, i.e. within the measurement uncertainty. Furthermore, the blade-shaft coupling results in significant changes of the eigenfrequencies and damping. As a consequence, damping increases by up to twelve times due to the coupling. This reduces amplitudes by a factor of nine for the mistuned blade responses. Consequently, higher structural safety factors can be achieved by taking the blade-shaft coupling into account so that the remaining potentials in the aerodynamic design could be better exploited.

Surface quality enhancement in ultrasonic vibration-assisted electrochemical machining

The aviation industry's evolution has introduced electrochemical machining (ECM) as a promising non-traditional technology for aero-engine blades. However, the surface quality of challenging-to-cut materials is compromised due to insoluble electrolytic products on the machined surface. To enhance ECM's surface quality, ultrasonic-assisted ECM (UA-ECM) was introduced for effective electrolytic product removal. This study conducted numerical simulations involving coupled flow field and cavitation models. It also performed observation experiments and a series of UA-ECM trials with varying inlet pressures (0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, and 0.5 MPa), vibration amplitudes (21 µm, 17 µm, 13 µm, 8 µm, 4 µm, and 0 µm), and current densities (31.9 A/cm2, 42.1 A/cm2, 61.1 A/cm2, 76 A/cm2, and 100.9 A/cm2). These aimed to elucidate the mechanism of tool ultrasonic vibration's influence on surface quality and corroborate the simulation findings. Notably, under conditions of low inlet pressure (0.1 MPa), high vibration amplitude (21 µm), and high current density (100.9 A/cm2), complete removal of electrolytic products, inhibition of pitting defects, and attainment of a mirror surface with a surface roughness of Ra = 0.14 µm were achieved, with no change in hardness. This clearly demonstrates that the surface quality of ECM on complex surfaces can be significantly enhanced by ultrasonic assistance.

Damping efficiency of the fractional Duffing system and an assessment of its solution accuracy

Dynamical systems with high damping efficiency in a wide frequency band can be useful on a small scale – for harvesting energy from ambient vibrations, and on a large scale – for damping harmful vibrations of mechanical structures. In this paper we present an assessment of the quality of solutions and damping efficiency of systems with fractional order derivatives. To simulate the fractional system the fourth-order Runge–Kutta method and Grünwald–Letnikov methods are used. We propose a coefficient for assessing the quality of solutions to fractional systems by reference to the quality of the calculated energy balance. As an exemplary system we study the Duffing model with embedded additional fractional-order derivative terms. Based on this coefficient, intervals of key numerical simulation parameters are determined to ensure the appropriate quality for the calculations of energy flows and energy balance. The determined values of these parameters are then used in tests of the damping efficiency of the studied system. Our results show that by modifying the fractional terms it is possible to configure a system that exhibits a “broadband effect”, i.e. a system that is characterized by high-amplitude vibrations and, consequently, high energy efficiency in a wide range of excitation frequencies.

Vibration mitigation of a model aircraft with high-aspect-ratio wings using two-dimensional nonlinear vibration absorbers

High-aspect-ratio (HAR) airplane wings have higher energy efficiency and present an economical alternative to standard airplane wings. HAR wings have a high span and a high lift-to-drag ratio, allowing the wing to require less thrust during flight. However, due to their length and construction, HAR wings exhibit low-frequency, high-amplitude vibrations in both vertical (yaw axis) and longitudinal (roll axis) directions. To combat these unwanted vibrations, a two-dimensional nonlinear vibration absorber (2D-NVA) is constructed and attached to a model HAR-wing airplane to verify its effectiveness at reducing vibrational motion. The 2D-NVA design, which was presented in a previous study, consists of two low-mass, rigid bodies namely the housing and the impactor. The housing consists of a ring-like rigid body in the shape of an ellipse, while the impactor is a solid cylindrical mass which resides inside the cavity of the housing. The 2D-NVA is designed such that the impactor can contact the inner surface of the housing under both impacts and constrained sliding motion. The present study focuses on the use of the 2D-NVA to mitigate multiple modes of vibration excited by impulsive loading of a model airplane with HAR wings in both vertical and longitudinal directions. The effectiveness of a single 2D-NVA is investigated computationally using a finite element model of the model airplane. These results are verified experimentally and the performance of two 2D-NVAs (one on each wing) is also investigated. The contributions of this work are that: 1) the 2D-NVA alters the global response of the model aircraft by mitigating all relevant modes in both directions simultaneously; 2) a single 2D-NVA is optimal for mitigating motion in the vertical direction, while two active 2D-NVAs are optimal for the longitudinal direction; and 3) the performance of the 2D-NVA is robust to changes in the frequency content of the parent structure.

Nonlinear dynamic modeling and vibration analysis for flexible tethered satellite systems under large deformations

The escalating threat posed by space debris necessitates innovative approaches for its removal. This article presents a comprehensive mathematical modeling and dynamic analysis of a flexible tethered satellite system (FTSS) in the post-capture phase, taking into account nonlinear strain effects for the flexible appendages. The FTSS consists of a rigid central body satellite, two identical flexible panels, and a towing mass that manipulates the satellite through a tether. We develop a detailed dynamic model that accurately represents the system’s three-dimensional motion, incorporating the rigid body’s 6 degrees of freedom (DOF), the tether’s 3 DOF motion, and two modal generalized coordinates for each panel. The extended Hamilton method is employed to derive this model, enabling us to investigate the conditions under which nonlinear strain considerations become critical. The findings of this article reveal that nonlinear strain effects can profoundly impact the system’s dynamics under certain geometric and forcing conditions, often overlooked in previous studies. In these scenarios, the panel strains exceed the linear regime, necessitating the use of nonlinear models for accurate representation. This work emphasizes the importance of incorporating nonlinear strain terms in the dynamic analysis of FTSSs, particularly when dealing with large deformations and high-amplitude vibrations encountered in debris removal applications.

Ultrasonic vibration-assisted single point incremental forming of hemispherical shaped component using AA3003 material

ABSTRACT Ultrasonic vibration-assisted single point incremental forming is a recent hybrid process variant of the single point incremental forming process. In this process, longitudinal ultrasonic vibration is used as an assistance in the conventional forming process. In this paper, the effect of amplitude of vibration in the ultrasonic vibration assisted single point incremental forming process have been researched. For the same, experimental work has been carried out by forming the hemispherical shaped components using multistage forming strategy. Moreover, numerical simulation work has been carried out using the LSDYNA solver and the results have been discussed in the light of depth of forming and strain distribution. The experimental fracture forming line is also developed for the AA3003 material for single point incremental forming process. High amplitude of vibration of 12 micron with 20 kHz frequency leads to poor formability; however, the lower amplitude of vibration of 8 micron with 30 kHz frequency leads to good formability.

Advanced vibrant controller results of an energetic framework structure

Abstract This research shows the influence of a new active controller technique on a parametrically energized cantilever beam (PECB) with a tip mass model. This article remains primarily concerned with regulating the system’s response using a novel control mechanism. This study describes a novel control mechanism called the nonlinear proportional-derivative cubic velocity feedback controller (NPDCVFC). The motivation of this article is to design a novel control algorithm in order to mitigate the nonlinear vibrations of a parametrically energized cantilever beam with a tip mass model. The proposed controller NPDCVFC incorporates nonlinearly second- and first-order filters into the system. The system is governed by one nonlinear differential equation having both quadratic and cubic nonlinearities within the parametric force. The controller’s efficiency in reducing framework vibrations, managing nonlinear bifurcations, and calming unstable motion is evaluated using numerical simulations of instantaneous vibrations. The perturbation technique is beneficial for solving the current model under the proposed worst resonance case ( Ω ˆ p = 2 ω ˆ 0 ) \text{(}{\hat{{\Omega }}}_{\text{p}}=2{\hat{{\omega }}}_{0}) . In order to choose the optimal controller, we have also added three more controller approaches to the configuration. Integral resonant control, positive position feedback, and nonlinear integral positive position feedback are the three controller approaches that are applied to the structure under consideration. We determine that the NPDCVFC as a new controller is the most effective for lowering the high vibration amplitudes. Over the investigated model, all numerical results were performed using the MATLAB 18.0 programmer software. The stability analysis and the effects of various elements on the controlled structure have been investigated. A comparison with recently published works of a comparable model has also been prepared. Experiment capacities for a PECB with a tip mass are obtainable to validate the results, and they demonstrate good agreement with analytical and numerical results.

A piezoelectric nonlinear energy sink shunt for vibration damping

The theoretical study and experimental validation of a nonlinear shunt circuit for piezoelectric vibration damping is investigated here. The circuit consists of a resistor, an inductor and a nonlinear cubic voltage source. The shunt acts as an electrical analog to the mechanical nonlinear energy sinks (NESs). These mechanical NESs are passive vibration absorbers that typically have a cubic nonlinear stiffness. They have attractive properties such as saturation of the host system’s vibration amplitude and strongly modulated response. This increases its operational frequency bandwidth and robustness against variations in the properties of host systems compared to linear vibration absorbers. However, the nonlinear nature may induce isolated responses in the host system that induce high vibration amplitudes. This paper investigates if these attractive properties also occur in the electric nonlinear energy sink shunt. An analytical expression for the frequency response is derived through the complexification-averaging method. Bifurcations in the frequency response reveal the occurrence of a quasi-periodic vibration energy exchange between the host system and the voltage over the electrodes of piezoelectric material. This is the main mechanism behind the amplitude saturation of the host system. Other bifurcations also reveal the existence of isolated responses. The nonlinear shunt is then realized with analog multipliers and a synthetic inductor and its performance in vibration damping is experimentally verified for a cantilever beam.

Numerical Investigation of the Excitation Characteristics of Contaminated Nozzle Rings

The deposition of combustion residues in the nozzle ring (NR) of a turbocharger turbine stage changes the NR geometry significantly in a random manner. The resultant complex and highly asymmetric geometry induces low engine order (LEO) excitation, which may lead to resonance excitation of rotor blades and high cycle fatigue (HCF) failure. Therefore, a suitable prediction workflow is of great importance for the design and validation phases. The prediction of LEO excitation is, however, computationally expensive as high-fidelity, full annulus CFD models are required. Previous investigations showed that a steady-state computational model consisting of the volute, the NR, and a radial extension is suitable to reduce the computational costs massively and to qualitatively predict the level of LEO forced response. In the current paper, the aerodynamic excitation of 69 real contaminated NRs is analyzed using this simplified approach. The results obtained by the simplified simulation model are used to select 13 contaminated NR geometries, which are then simulated with a model of the entire turbine stage, including the rotor, in a transient time-marching manner to provide high-fidelity simulation results for the verification of the simplified approach. Furthermore, two contamination patterns are analyzed in a more detailed manner regarding their aerodynamic excitation. It is found that the simplified model can be used to identify and classify contamination patterns that lead to high blade vibration amplitudes. In cases where transient effects occurring in the rotor alter the harmonic pressure field significantly, the ability of the simplified approach to predict the LEO excitation is not sufficient.

Cryogenic and ultrasonic-assisted micro-drilling of printed circuit boards using high-frequency-amplitude spindle

Printed circuit boards (PCBs) are key components in computers, 5G, 6G, and other wireless communication devices. On the other hand, the manufacture of micro-holes in PCBs faces severe challenges. Conventional micro-drilling methods often encounter challenges such as poor surface quality and limited tool life. To overcome these issues, a novel micro-drilling method called cryogenic and ultrasonic-assisted micro-drilling (CUAMD) has been developed. This study compared four drilling methods to investigate the benefits of cryogenic and ultrasonic-assisted drilling in hybrid machining processes: conventional micro-drilling (CMD), cryogenic-assisted micro-drilling (CAMD), ultrasonic-assisted micro-drilling (UAMD), and cryogenic and ultrasonic-assisted micro-drilling (CUAMD). The experimental results unequivocally indicate that the utilization of cryogenic-assisted drilling leads to a significant reduction in cutting heat during the machining process. This not only contributes to an improvement in machining accuracy but also exerts a positive influence on tool life and surface morphology. Ultrasonic-assisted drilling separates chips into smaller volumes through high-frequency-vibration, effectively reducing the cutting forces. The high frequency of 38.25 kHz and high amplitude vibration of 5.16 μm of the ultrasonic spindle induced vibrations on the drill bit. Liquid nitrogen with a pressure and temperature of 28 kPa and − 196 °C, respectively, was used in the cryogenic-assisted method. The superior machining performance of the CUAMD approach was evaluated by comparing it to various methods, including cutting forces, tool flank wear, entrance/exit hole morphology, and chip formation. The CUAMD method avoids chip entanglement, suppresses burrs, and reduces the maximum cutting force, maximum torque, and exit hole damage factor Fd by 47.7 %, 56.1 %, and 42.5 %, respectively, compared with CMD.

Effect of ultrasonic vibration on microstructural evolution, clad defects, and surface properties in laser direct energy deposition of Inconel 625

Laser direct energy deposition (DED) has some accompanying issues, such as existence of micropores, elemental segregation at grain boundaries, intergranular corrosion, etc. Therefore, the current work aims for a reduction in clad defects and enhancement in surface properties for laser direct deposition of Inconel 625 by implementing ultrasonic vibration. The acoustic streaming and cavitation effect induced by ultrasonic vibration results in the breaking of columnar grains, along with grain refinement and better elemental distribution in the matrix during the solidification process. The investigation is carried out for deposition using a 240 W Yb-fiber laser under the application of ultrasonic vibration with a variable amplitude of 6–13 μm (frequency: 33–28 kHz). A relatively higher vibration amplitude was found more efficient in converting long columnar grains into finer and uniformly distributed equiaxed grains, with a significant reduction in micropores. Further, it resulted in a shorter molten pool lifetime because of the generation of more nucleation centers, leading to better cooling. The above effects resulted in higher microhardness of the deposited layer. Further, the wear and corrosion resistance showed an improvement with the application of vibration, which may be due to the finer equiaxed grains, less porosity, and better elemental distribution at a higher vibration amplitude.