Papers by Keyword: Vibration Analysis

Abstract: Cavitation is a critical issue in centrifugal pumps, leading to severe mechanical wear, reduced efficiency, and potential system failure. This study investigates cavitation in a centrifugal pump operating in a Hydrocracking Complex (HCC) using vibration analysis combined with Fast Fourier Transform (FFT) spectral diagnostics. The results reveal characteristic cavitation signatures, including Blade Pass Frequency (BPF) peaks, 1X RPM harmonics, and high-frequency random vibrations exceeding 120k CPM, with overall amplitudes ranging from 5.53 to 9.17 mm/s. Despite component replacement, vibration levels remained elevated, indicating that persistent low-flow conditions, suction-side pressure fluctuations, and deviation from the Best Efficiency Point (BEP) were the root causes of cavitation. The findings demonstrate that vibration spectrum analysis provides a quantitative and reliable tool for diagnosing cavitation severity under real industrial conditions. Unlike many laboratory-based studies, this work contributes an industrial case study from a hydrocracking unit, offering practical insights into predictive maintenance strategies for large-scale pumping systems.

Abstract: Effective condition monitoring is crucial for maintaining industrial rotating machinery. This study investigates a predictive maintenance approach to diagnose and resolve excessive vibration in a refinery’s centrifugal pump. Vibration analysis using Fast Fourier Transform (FFT) and phase difference diagnostics identified a dynamic imbalance caused by contaminant accumulation on the impeller, resulting in vibration spikes of 11.61 mm/s with a dominant FFT spectrum at 1X RPM. To mitigate this issue, dynamic balancing was performed in accordance with ISO 1925 and ISO 1940-1 standards, successfully reducing the vibration to 3.59 mm/s. The results validate vibration-based diagnostics as a proactive maintenance tool, minimizing downtime and improving reliability. This study demonstrates how predictive maintenance strategies can enhance the performance of rotating machinery, with potential applications in other industrial systems.

Abstract: This work presents a theoretical and numerical study on the nonlinear free vibrations of orthotropic laminated composite beams, with a focus on different material orientations such as cross-ply, balanced, and woven configurations. Based on the Euler-Bernoulli beam theory and Von Karman’s geometric nonlinearity, we develop an analytical and matrix formulation using Hamilton’s principle. The novelty lies in the use of a homogenization approach to derive equivalent stiffness properties, allowing the comparison between symmetrical and asymmetrical composite beams. Despite limitations inherent to Euler-Bernoulli assumptions, results show the significant influence of layer orientation on the nonlinear frequency and displacement behavior. This study is valuable for structural applications in aerospace and mechanical systems.

Abstract: There are number of different methods and procedures in vibration analysis, where the natural frequencies of the specimen or the system are one of the key parameters. It is known that these frequencies can change under load, for example in response to pre-stressing, but the effect of residual stresses is less known. By developing a suitable method, natural frequencies can be used to predetermine residual stress, therefore this method can be used for example predicting whether it will cause deformation during machining of a part, whether it requires increased attention or how to set the parameters well for vibratory stress relief. The results can be significant cost and time savings, as well as the improvements of the quality. Natural frequency is the frequency of free vibration of an undamped linear vibration system, or in other words at which a system left alone will vibrate after excited by an external force [1]. Metal castings or welded structures may have several natural frequencies which appear as frequency bands or ranges on the measurement images. Based on these, to determine the natural frequency of a component or system, we need to excite a frequency as close as possible to the natural frequency for the resonance to occur. When the resonance is reached, the amplitude of the system is at its maximum, and the natural frequencies of the workpiece can be measured. Traditionally, sensors, usually accelerometers are used to measure the natural frequency. The continuous development of information technology has made it possible to replace these sensors with an acoustic diagnostic system. During this research, we have developed an acoustic diagnostic system and procedure, which can generate the acoustic measurement images. We have evaluated the measurement images in many ways, and many different types of components and materials (mostly iron alloys) were analyzed. In addition, the changes of natural frequencies show a similar pattern in the case of parts before treating with vibratory stress relief as for load tests.

Abstract: Hybrid Fibre Metal Laminates (HFMLs) are composite materials made of alternating layers of metal and fibre-reinforced polymers. The paper discusses the development of HFMLs and their applicability in aerospace applications when compared to conventional FMLs. Experimental (Mechanical and vibrational) studies are conducted to assess the strength and vibrational properties of these materials. Mechanical and vibrational characteristics of the proposed materials are explored and presented. Aluminium 2024 T3 sheets as metal layer and hybrid (glass, carbon) polymer fibre reinforcements are used for developing hybrid lightweight laminates. SEM (scanning electron microscope), and stereomicroscopy are used for microscopic characterization studies and a universal testing machine (UTM) is employed to perform mechanical characterization. The impact behaviour of these materials is also disclosed using the Charpy impact test. An improvement in the strength and vibrational properties are clearly observed in the FMLs after fibre hybridization, which may be due to improved bonding compatibility in carbon prepregs. The outcome of the research contributes to the advancement of lightweight materials for next-generation aerospace structures.

Abstract: This study presents an analytical investigation of the vibration of fluid-conveying pipes on viscoelastic foundations using the differential transform method. The effects of a new time dependent viscosity parameter in the modified Winkler viscoelastic foundation is studied and analyzed. The governing equation is a fourth-order partial differential equation with pinned-pinned boundary conditions, which required a special analytical method for solution. The differential transform method was applied to obtain the solution of the governing partial differential equation for the fluid-conveying pipes on viscoelastic foundations. The time-dependent viscosity parameter in the modified Winkler viscoelastic model was implemented and simulated to determine the behavior of the viscoelastic foundation. The obtained analytical solution was validated with Runge-Kutta order four numerical method. The effects of foundation stiffness , coefficient of foundation damping and the frequency mass ratio on the governing model equation were investigated. In addition, the bending and deflection of the pipe on a viscoelastic foundation are compared with those on an elastic foundation. The analytical and the numerical solutions are in good agreement. From the study, it is observed that an increase in the foundation stiffness results in increase in the pipe inherent frequencies. Furthermore, the vibration of the pipe on a viscoelastic foundation shows better control and reduction compared with its vibration on an elastic foundation.

Abstract: Milling is a widely used machining process for creating intricate parts with desired dimensions and surface quality. In this study, we investigate the effects of process parameters namely spindle speed, feed rate and depth of cut on the vibration behavior of a milling machine tool. The analysis begins by selecting appropriate cutting conditions for the milling operation. Various combinations of process parameters are considered to observe their influence on vibration of the tool. A series of experiments are conducted, with each experiment using a specific set of process parameters. The experimental trials were designed according to the factorial design. Accelerometer is employed to capture the dynamic behavior of the tool and quantify the amplitude and frequency of vibrations. The results can be utilized to optimize the machining parameters for enhanced surface quality in milling operations, leading to improved productivity, reduced tool wear and increased overall process efficiency.

Abstract: The numerical model is developed to study the vibration response due to the localized defect of ball bearing in rotating machinery. In order to simulate the dynamic response, the equations of motions are developed based on the rotor-bearing system where two identical rotors mounted on symmetric flexible shaft and supported by ball bearings are considered in this model. The presence of defect is introduced on a bearing outer raceway and lubrication effect between bearing components is also included. The numerical results are obtained by applying Runge–Kutta method to solve governing equations of motions. It has been observed that the vibration spectrum of the ball pass frequency outer race and its harmonics for the defect bearing is relatively higher than the good one. Moreover, this dynamic model can effectively enhance the understanding of vibration responses for good and defective bearing.

Abstract: The three cutting edge drills are not the most common drills, nevertheless, are characterized by superior stability, excellent precision and finishing, due to the intersection of three cutting edges at one point. In general, stainless steels are considered as difficult to machine materials due to their tendency to work harden, their toughness and relatively low conductivity, leading to poor surface finish, poor chip breaking and built-up-edge formation. In the case of duplex stainless grades, the high strength, and the very good corrosion resistance, only compared with austenitic steels, make these materials as an alternative to the austenitic stainless steels, with superior mechanical properties. In this study, the performance of the drills with two and three cutting edges were evaluated in the drilling of duplex stainless steels, when low-pressure external cooling or high-pressure internal cooling were applied. Whether used drills of two or three cutting edges, the most important factor to increase the number of holes made, is the use of high-pressure internal cooling, in detriment of external low-pressure external cooling. The drills of three cutting edges have better results in roughness and dimensional tolerance of the holes. However, these drills proved to be more fragile and more sensitive to the cutting parameters. The use of three cutting edges drills is recommended for situations where hole quality is more important, while two cutting edges drills is recommended for situations where productivity is the main objective.

Abstract: The main aim of this work is to analyse the significance of cutting parameters on surface roughness and spindle vibrations while machining the AA6063 alloy. The turning experiments were carried out on a CNC lathe with a constant spindle speed of 1000rpm using carbide tool inserts coated with Tic. The cutting speed, feed rate and depth of cut are chosen as process parameters whose values are varied in between 73.51m/min to 94.24m/min, 0.02 to 0.04 mm/rev and 0.25 to 0.45 mm respectively. For each experiment, the surface roughness parameters and the amplitude plots have been noted for analysis. The output data include surface roughness parameters (R_a,R_q,R_z) measured using Talysurf and vibration parameter as vibration amplitude (mm/sec) at the front end of the spindle in transverse direction using single channel spectrum analyzer (FFT).With the collected data Regression analysis is also performed for finding the optimum parameters. The results show that significant variation of surface irregularities and vibration amplitudes were observed with cutting speed and feed. The optimum cutting speed and feed from the regression analysis were 77.0697m/min and 0.0253mm/rev. for the minimum output parameters. No significant effect of depth of cut on output parameters is identified.