Showing papers on "Vibration fatigue published in 2021"

Dirlik and Tovo-Benasciutti Spectral Methods in Vibration Fatigue: A Review with a Historical Perspective

Abstract: The frequency domain techniques (also known as “spectral methods”) prove significantly more efficient than the time domain fatigue life calculations, especially when they are used in conjunction with finite element analysis. Frequency domain methods are now well established, and suitable commercial software is commonly available. Among the existing techniques, the methods by Dirlik and by Tovo–Benasciutti (TB) have become the most used. This study presents the historical background and the motivation behind the development of these two spectral methods, by also emphasizing their application and possible limitations. It further presents a brief review of the other spectral methods available for cycle counting directly from the power spectral density of the random loading. Finally, some ideas for future work are suggested.

Numerical investigation of the fatigue performance of elastic rail clips considering rail corrugation and dynamic axle load

Abstract: To analyze the reasons for rail clip fracture, the characteristics of rail corrugation were first measured using a rail corrugation meter. The vibration acceleration of the fastener clips at the se...

Vibration fatigue analysis of high-speed railway vehicle carbody under shaking condition

Abstract: A method called modified modal superposition method (MMSM) for calculating the vibration fatigue dynamic stress of carbody under shaking condition is proposed. In MMSM, each external load is divide...

Equivalent Spectral Method to Estimate the Fatigue Life of Composite Laminates Under Random Vibration Loadings

Abstract: The power spectral density (PSD) of an equivalent stress is proposed to analyze the fatigue life of composite laminates under random vibration loadings using the Tsai–Hill criterion. The vibration fatigue life can be estimated based on the rainflow amplitude probability density function p(S) of the equivalent stress, which is obtained from this PSD, combined with the S-N curve of the materials. The fatigue life analysis of a random vibration fatigue experiment of composite laminates was carried out, and the calculation results were in accordance with experimental data, which indicates that the fatigue life analysis model proposed gives a satisfactory prediction accuracy.

Vibration Fatigue Analysis for Structural Durability Evaluation Under Vibratory Loads

Abstract: The structural integrity of aircraft structures under vibratory loads is primarily evaluated through vibration tests, but it is necessary to predict the design life through vibration fatigue analysis at the design stage. Vibratory loads affect the durability of aircrafts by combining with the dynamic characteristics of their structures. The generation of stress spectrum in the vibratory loads, which must be calculated from power spectral density, is different from the calculations in the time domain. In this study, the stress spectrum generation and fatigue life were analyzed for various frequency bands with different characteristics. Through comparison of the fatigue life in the frequency domain and time domain, the characteristics of the stress spectrum estimation and optimal calculation methods are presented. It was confirmed that the frequency domain results tend to be more conservative in most cases than the time domain results, and Dirlik’s procedure estimates accurately in all frequency bands. A simple correction of the Narrow-band and Steinberg results could increase the accuracy of the fatigue life prediction.

Improved Damage Modeling for Solder Joints under Combined Vibration and Temperature Cycling Loading

Abstract: In this work, fatigue damage caused to solder joints in printed wiring assemblies due to the superposition of harmonic vibration and temperature is studied along with different damage superposition approaches. In this work, a non-linear interactive damage superposition method is used, with temperature-dependent vibration damage coefficients that are interpolated from isothermal vibration experiments at selected temperatures. The temperature range −40°C to 125 °C was segmented into multiple sub-segments for this interpolation. By applying these measures, a new procedure for an improved incremental damage superposition approach (IDSA) was developed in this work. This new procedure was then used to superpose the vibration and temperature cycling loads to forecast the fatigue life of SAC105 solder joints for leadless chip resistors under simultaneous vibration and temperature cycling loads. Potential failure sites of the solder joint have been successfully investigated by utilizing this new procedure. Using the developed model, accelerated testing profiles are designed such that the vibration fatigue and temperature cycling fatigue damage are comparable and cause failure in approximately 250 temperature cycles.

Numerical and Experimental Investigation of Cumulative Fatigue Damage under Random Dynamic Cyclic Loads of Lattice Structures Manufactured by Laser Powder Bed Fusion

Abstract: Lattice structures are lightweight engineering components suitable for a great variety of applications, including those in which the structural integrity under vibration fatigue is of paramount importance. In this work, we experimentally and numerically investigate the dynamic response of two distinct lattice configurations, in terms of fatigue damage and life. Specifically, Face-Centered-Cubic (FCC) and Diamond lattice-based structures are numerically studied and experimentally tested under resonant conditions and random vibrations, until their failure. To this end, Finite Element (FE) models are employed to match the dynamic behavior of the system in the neighborhood of the first natural frequency. The FE models are employed to estimate the structural integrity by way of frequency and tip acceleration drops, which allow for the identification of the failure time and a corresponding number of cycles to failure. Fatigue life under resonant conditions is well predicted by the application of conventional multiaxial high cycle fatigue criteria to the local state of stress. The same approach, combined with the Rainflow algorithm and Miner’s rule, provides good results in predicting fatigue damage under random vibrations.

Fatigue Damage Evaluation of Compressor Blade Based on Nonlinear Ultrasonic Nondestructive Testing

Abstract: Nonlinear ultrasonic testing is highly sensitive to micro-defects and can be used to detect hidden damage and defects inside materials. At present, most tests are carried out on specimens, and there are few nonlinear ultrasonic tests for fatigue damage of compressor blades. A vibration fatigue test was carried out on compressor blade steel KMN, and blade specimens with different damage degrees were obtained. Then, the nonlinear coefficients of blade specimens were obtained by nonlinear ultrasonic testing. The results showed that the nonlinear coefficient increased with the increase in the number of fatigue cycles in the early stage of fatigue, and then the nonlinear coefficient decreased. The microstructures were observed by scanning electron microscopy (SEM). It was proven that the nonlinear ultrasonic testing can be used for the detection of micro-cracks in the early stage of fatigue. Through the statistical analysis of the size of the micro-cracks inside the material, the empirical formula of the nonlinear coefficient β and the equivalent crack size were obtained. Combined with the β–S–N three-dimensional model, an evaluation method based on the nonlinear ultrasonic testing for the early fatigue damage of the blade was proposed.

Vibration Fatigue Damage Estimation by New Stress Correction Based on Kurtosis Control of Random Excitation Loadings

Abstract: In the pioneer CAE stage, life assessment is the essential part to make the product meet the life requirement. Commonly, the lives of flexible structures are determined by vibration fatigue which accrues at or close to their natural frequencies. However, existing PSD vibration fatigue damage estimation methods have two prerequisites for use: the behavior of the mechanical system must be linear and the probability density function of the response stresses must follow a Gaussian distribution. Under operating conditions, non-Gaussian signals are often recorded as excitation (usually observed through kurtosis), which will result in non-Gaussian response stresses. A new correction is needed to make the PSD approach available for the non-Gaussian vibration to deal with the inevitable extreme value of high kurtosis. This work aims to solve the vibration fatigue estimation under the non-Gaussian vibration; the key is the probability density function of response stress. This work researches the importance of non-Gaussianity numerically and experimentally. The beam specimens with two notches were used in this research. All excitation stays in the frequency range that only affects the second natural frequency, although their kurtosis is different. The results show that the probability density function of response stress under different kurtoses can be obtained by kurtosis correction based on the PSD approach of the frequency domain.

Mechanical Analysis Methods of Cantilever Gearbox Housing

Abstract: The mechanical state of cantilever gearbox housing is different from ordinary ones due to the long arm of force caused by cantilever structure. Conventional mechanical analysis methods either took cantilever gearbox housing as ordinary ones or cantilever beam. Few published papers have specially focused on mechanical analysis method for cantilever gearbox housing. This paper took a longwall shearer cutting unit gearbox (SCUG) as an example and the mechanical analysis method is investigated according to the causes of fatigue for SCUG. Force analysis model is established for finding out regions of static fatigue caused by low-frequency loads, and local resonance analysis is used for finding out regions of vibration fatigue caused by high-frequency loads. Not only bending moment but also torque caused by gear meshing forces is taken into account in the force analysis model. Vibration response is obtained from cutting experiment, and dominant frequencies of local resonance are obtained by frequency domain analysis. Finite element model of SCUG is established, and natural frequencies and strain modes are analyzed for obtaining the main vibration modes corresponding to dominant frequencies. Hence, large stress regions caused by low and high frequency loads are obtained. Results show that the worst working condition is oblique cutting, and the stress of B-B in 600 mm cutting depth can reach 166 MPa. 950 Hz, 1250 Hz, and 1400Hz are dominant frequencies of SCUG (23rd, 25th and 27th natural frequencies). Generally, this paper proposed some principles for mechanical analysis method of cantilever gearbox housing.

Vibration monitoring for composite structures using buckypaper sensors arrayed by flexible printed circuit

Abstract: Fiber-reinforced resin-based plastics are widely used in structural composites for aerospace and automotive applications, and they often face extreme load conditions in actual working environments....

A framework for the design of rotating Multiple Tuned Mass Damper

Abstract: The acoustic and vibratory analysis represent an essential research axis in the automotive industry because these phenomena directly affect the appreciation of the customer when using a vehicle. Indeed, the combustion engine represents the main source of mechanical energy but it generates an acyclic torque because of the explosions. This acyclism is responsible for noise and vibration fatigue. To reduce NVH issues, a possible mean is to use a Multiple Tuned Mass Damper (MTMD) adapted to rotating machine.

Dynamic Characteristics Analysis of Cylinders Bundle Coupling System Under Axial Flow

Abstract: Nuclear reactor fuel assemblies are mainly composed of cylinders bundle(CB), calculating the dynamics characteristics of CB under axial flow can lay a foundation for predicting fretting wear and vibration fatigue. In the paper, the CB coupling dynamic model of forced vibration under pulsating flow is established. And the stability analysis and natural frequency calculation of the CB system under steady flow are compared with the existing results to verify the model. Finally, the Runge-Kutta method is applied to solve the forced vibration equation of the CB under pulsating flow. The influence of the pulsating parameters m, w0, on the amplitude-frequency characteristics and the motion trajectory of the midspan cross section of the CB under forced vibration are analyzed and discussed. The results show that the pulsating parameters have an important influence on the vibration of the CB system.

Evaluation of tractor driving vibration fatigue based on multiple physiological parameters.

Abstract: The vibration generated by tractor field operations will seriously affect the comfort and health of the driver. The low frequency vibration generated by the engine and ground excitation is similar to the natural frequency of human organs. Long term operation in this environment will resonate with the organs and affect drivers' health. To investigate this possibility, in this paper we carried out a collection experiment of human physiological indicators relevant to vibration fatigue. Four physiological signals of surface electromyography, skin electricity, skin temperature, and photoplethysmography signal were collected while the subjects experienced vibration. Several features of physiological signals as well as the law of signal features changing with fatigue are studied. The test results show that with the increase of human fatigue, the overall physiological parameters show the following trends: The median frequency of the human body surface electromyography and the slope of skin surface temperature decreases, the value of skin conductivity and the mean value of the photoplethysmography signal increases. Furthermore, this paper proposes a vibration comfort evaluation method based on multiple physiological parameters of the human body. An artificial neural network model is trained with test samples, and the prediction accuracy rate reaches 88.9%. Finally, the vibration conditions are changed by the shock-absorbing suspension of a tractor, verifying the effectiveness of the physiological signal changing with the vibration of the human body. The established prediction model can also be used to objectively reflect the discomfort of the human body under different working conditions and provide a basis for structural design optimization.

The Status Quo of Aerospace Engine Vibration Fatigue

Abstract: In the working environment of aero engine blades, it is necessary to withstand the influence of factors such as aerodynamic stress, vibration stress, centrifugal stress, thermal stress, high temperature oxidation, thermal corrosion, etc. The blades often exhibit vibration fatigue fracture, foreign object damage, corrosion, material defects, and sports damage. This article summarizes the fatigue fracture problems of aero-engine blades, provides a systematic basic theory for the design, innovation and development of aero-engine blades, and has certain reference value.

Positioning Criteria for Automotive Headlamp Module Supports Using Transmitted Force and Natural Frequency

Abstract: Headlamps are one of the most important parts of vehicles because they contribute to the vision and safety of the driver. However, rough road conditions create harsh external excitations, which could loosen bolts in the headlamp assembly and cause improper aiming of headlight. Additionally, headlamps must be robustly designed because supporting positions of their assembly are typically determined based on the initial design of vehicle chassis without considering the occurrence of vibration fatigue. Therefore, under driving conditions, the headlamp assembly may experience excessive excitation forces, which loosen supporting bolts and arbitrarily change the aiming and adjustment of the headlight. To solve these issues, in this study, the authors propose positioning criteria for the headlamp bolts by predicting the transmitted force and natural frequency when external excitation forces are applied. First, the equations of motion for a conventional headlamp model are derived via lumped parameter modeling. Next, the transmitted force at each supporting point and natural frequency are calculated and utilized in the positioning criteria. Then, several cases are validated using experimental and computer aided engineering (CAE) results. Finally, positioning criteria for the headlamp bolts are suggested by combining the transmitted force and natural frequency.

Simulation and Experimental Verification of Sweep Frequency Vibration Fatigue for Motor Controller of Integrated Electric Drive System for Electric Vehicle

Abstract: The motor controller of the integrated drive system for electric vehicles has the risk of sweep frequency vibration fatigue (SFVF) failure in the frequency range of 100 ~ 440 Hz. In this paper, a finite element simulation method of SFVF for an integrated motor controller is introduced. The failure position of the motor controller component is predicted using this simulation method, which is consistent with the fracture position of the sweep frequency vibration fatigue test (SFVFT). This indicates that the simulation method is accurate. And the structural optimization suggestions are also put forward using this method. The optimized motor controller meets the requirements of SFVFT. This indicates that it is feasible to use this method during the design process of the motor controller for integrated drive system.