Showing papers on "Vibration fatigue published in 2019"

Influence of multiple laser peening on vibration fatigue properties of TC6 titanium alloy

Abstract: In this study, typical TC6 titanium alloy was taken to investigate the effects of multiple laser peening (LP) on the vibration fatigue properties and microstructural evolution. The vibration fatigue experiments were conducted, while the vibration fatigue life of the specimens before and after LP was compared and the fracture morphologies were observed by scanning electron microscopy (SEM). In addition, the measurements of residual stress and microhardness were carried out. The microstructures produced by different treatments were also characterized by transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). The experimental results indicated that multiple LP could indeed enhance the vibration fatigue properties of TC6 titanium alloy. Comparing with the investigated specimen without LP, the vibration fatigue life of the specimen subjected to 5 times LP increased by 105.2%. Meanwhile, after 5 times LP, the surface residual stress transformed from tensile stress (+26 MPa) to compressive stress (−485 MPa), and the surface microhardness was 428 HV, which increased by 32.9% compared with the untreated sample. Additionally, high-density of dislocation and deformation twin were also generated after multiple LP. The improvement of vibration fatigue properties was attributed to the rewarding compressive residual stress and the beneficial microstructural evolution induced by multiple LP.

Improvement of Damping Property and Its Effects on the Vibration Fatigue in Ti6Al4V Titanium Alloy Treated by Warm Laser Shock Peening

Abstract: In order to increase the vibration life of Ti6Al4V titanium alloy, warm laser shock peening (WLSP) is used to improve the damping properties and thus decrease the vibration stress in this study. Firstly, the Ti6Al4V specimens are treated by WLSP at different treatment temperatures from 200 °C to 350 °C. Then the damping ratios of untreated and WLSPed samples are obtained by impact modal tests, and the improvement of damping properties generated by WLSP is analyzed by the microstructures in Ti6Al4V titanium alloy. Moreover, the finite element simulations are utilized to study the vibration amplitude and stress during the frequency response process. Finally, the vibration fatigue tests are carried out and the fatigue fracture morphology is observed by the scanning electron microscope. The results indicate that the damping ratios of WLSPed specimens increase with the increasing treatment temperatures. This is because elevated temperatures during WLSP can effectively increase the α phase colonies and the interphase boundaries, which can significantly increase the internal friction of materials. Moreover, due to the increasing material damping ratio, the displacement and stresses during vibration were both reduced greatly by 350 °C-WLSP, which can significantly decrease the fatigue crack growth rate and thus improve the vibration fatigue life of Ti6Al4V titanium alloy.

Research on multidisciplinary fatigue optimization design method in structural design of high speed train

Abstract: Aiming at the shortcomings of single-discipline fatigue design and life prediction optimization design method for high-speed trains, considering the characteristics of structural design integrity, a durability analysis method for key structural components based on multi-disciplinary fatigue optimization design is proposed. According to the characteristics of vibration fatigue and structural failure of key structural components of high-speed trains, the multi-disciplinary fatigue design of carbody components is carried out from the perspectives of materials, loads and structural design. In the research process, qualitative and quantitative analysis and comparison of multi-objective optimization analysis (MOO) and multi-disciplinary optimization (MDO) processes were carried out. At the same time, considering the actual example, considering the vibration characteristics of the vehicle structure, the typical load spectrum and the complex material characteristics, the failure characteristics of the structural components are analyzed in detail. The research results are shown that there are certain limitations in single-disciplinary fatigue design and analysis. In order to effectively solve the complex engineering structure failure problem, it is necessary to fully consider the vibration characteristics of the entire vehicle structure. Through the multi-disciplinary fatigue design and optimization method of high-speed train structural components, the safety and structural integrity of key structural components of rail transit can be better guaranteed.

$${\mathcal {H}}_{2}$$ H 2 optimization and numerical study of inerter-based vibration isolation system helical spring fatigue life

Abstract: This paper presents an optimization and numerical analysis of vibration-induced fatigue in a two degree-of-freedom inerter-based vibration isolation system. The system is comprised of a primary, e.g. source body, and a secondary, e.g. receiving body, mutually connected through an isolator. The isolator includes a spring, a dashpot and an inerter. Inerter is a mechanical device which produces a force proportional to relative acceleration between its terminals. A broadband frequency force excitation of the primary body is imposed throughout the study. The goal of the proposed optimization is to prolong the fatigue life of the ground connecting helical spring of the secondary body. The optimization is based on minimizing separately the displacement and velocity amplitudes. Both optimization criteria are compared with regard to spring fatigue life improvement for fair benchmark comparison. The inerter-based optimized systems, in which the $${\mathcal {H}}_{2}$$ index of the receiving body is minimized, are also compared with the optimized systems without inerter. Notable improvements are observed in inerter-based systems due to the inclusion of an optimally tuned inerter in the isolator. The proposed analytical vibration fatigue method optimization results are compared with the finite element method results, and a very good agreement is observed. Most accurate helical spring deflection and stress correction factors are discussed and determined. Furthermore, the inerter concept is successfully implemented into finite element-based dynamic solution.

Implementation of Dirlik's damage model for the vibration fatigue analysis

Abstract: Mechanical fatigue is an important phenomenon when the structures are exposed to dynamic, fluctuating loadings. Especially aerospace structures are commonly exposed to random vibration loadings. In this paper, random vibration fatigue is studied both numerically and experimentally. For this purpose, a rectangular cross-section notched beam is designed in order to conduct the vibration fatigue analysis in the frequency domain by the Dirlik’s damage model. Aluminum and steel notched beams are prepared in order to carry out the vibration fatigue tests to compare with the fatigue analysis results. The effect of modal damping on the vibration fatigue analysis results is particularly studied.

Harmonic Equivalence of the Impulse Loads in Vibration Fatigue

Abstract: Laboratory for Dynamics of Machines and Structures, Aškerčeva 6, 1000 Ljubljana, Slovenia, janko.slavic@fs.uni-lj.si 631 Strojniški vestnik Journal of Mechanical Engineering 65(2019)11-12, 631-640 Received for review: 2019-06-14 © 2019 Journal of Mechanical Engineering. All rights reserved. Received revised form: 2019-10-14 DOI:10.5545/sv-jme.2019.6197 Original Scientific Paper Accepted for publication: 2019-10-14 “template” — 2019/11/13 — 7:29 — page 631 — #1

Modified Three-Parameter Model to Predict Compressor Blade Fatigue Life under Vibration Loading

Abstract: This paper investigates steel alloy stator blade flexural vibration characteristics and fatigue properties analytically using flexural fatigue tests. First, fatigue life data reliability is...

Method for amplifying beam structure and improving amplitude ratio in blade vibration fatigue test

Abstract: The invention discloses a method for amplifying a beam structure and improving an amplitude ratio in a blade vibration fatigue test The method is applied to the blade vibration fatigue test, and comprises a base, an amplifying body and a fixture body are arranged on the base, the fixture body is fixed above the magnifying body, and the fixture body and the magnifying body are integrally arranged;and a pressing block is arranged on the fixture body, the pressing block can be fixed with a blade through a connecting component, the connecting component comprises a tenon and a mortise, the mortise is formed in the pressing block, and the blade comprises the tenon that can be embedded in the mortise The amplitude ratio in the vibration fatigue test can be improved, so that the blade vibrationfatigue test with relatively large exciting force and relatively high frequency can be implemented

Vibration Fatigue Analysis and Research of URV Shunt Reactor

Abstract: Problems of vibration fatigue in UHV reactor is mentioned, comparative analysis of several commonly used fatigue analysis methods, finally, the modal superposition method is used to calculate the structural fatigue caused by vibration. Through analysis of reactor vibration data, the reason for using frequency domain signals as fatigue frequency domain load spectrum to calculate the service life of reactors. In order to perform reactor fatigue analysis, a finite element model of the reactor was first built using ANSYS Workbench finite element integration software, the frequency response function FRF is obtained by harmonic response analysis, and then the vibration time domain signal are transformed into frequency signal as load spectrum input with the power density spectrum, finally, nCode fatigue analysis software is used to estimate the service life of the reactor.

Vibration fatigue testing device for engine shouldered fan blade

Abstract: The invention discloses a vibration fatigue testing device for an engine shouldered fan blade. Blade tenon is positioned and jacked by using a tenon ejector rod, a shoulder groove used for clamping ablade shoulder is formed in a shoulder clamping block, so that the blade shoulder is positioned and clamped, then the blade shoulder is clamped by using a shoulder ejector rod on a shoulder fixing frame, and the shoulder structure on the engine shouldered fan blade is ensured to be suspended; afterwards, a tenon positioning block and the shoulder fixing frame are both fixed on a vibrostand, and the vibration fatigue test of the shouldered fan blade is completed by using the vibrostand. According to the device, the working state of the blade can be accurately simulated, the high-cycle fatigue assessment test of the blade is completed, and reliable fatigue test data is ensured; the device is simple and compact in structure, easy to adjust and capable of flexibly adjusting the position according to the needs of the test blade; and meanwhile, the device can be widely applied to other types of blades, is wide in application range, strong in applicability and high in engineering applicationvalue.

Vibration fatigue test device for metal material axial varying stress ratio and installation method thereof

Abstract: The invention discloses a vibration fatigue test device for a metal material axial varying stress ratio. The vibration fatigue test device comprises a frame base plate, a frame, a mass block, an auxiliary sample and a locking block, wherein the frame base plate is fixedly installed on a vibration table, the frame is installed on the frame base plate, the locking block is installed on the top of the frame, the auxiliary sample is vertically installed on the frame base plate, the mass block is installed at the upper end of the auxiliary sample, and a sample is installed between the mass block and the locking block; the frame is n-shaped integrally, and an opening for installing the locking block is formed in the top of the n-shaped frame; two sides of the n-shaped bottom are fixedly connected with the frame base plate through first screws respectively; the appearance of the locking block is a T-shaped circular table, and the outer edge of the upper part of the T-shaped circular table isconnected with the frame through second screws; a central hole is formed in the T-shaped circular table, and the central hole is internally provided with a table shoulder for fixing the sample. The vibration fatigue test device has the functions of changing a test stress ratio and realizing free adjustment of the stress ratio, and control for test frequency can be realized by adjusting several parameters when different test frequency requirements need to be met.

Composite material thermal vibration fatigue test device and method based on reverse resonance

Abstract: A composite material thermal vibration fatigue test device and method based on a reverse resonance are disclosed. The test device comprises a double-cantilever-beam vibration test system, a thermal environment simulation system, an electronic acquisition system, and a measurement and control system; an eccentric motor is used to drive a beam to be tested to vibrate. Compared with a vibration exciter, the device of the invention has a small size and less energy consumption, and is convenient to carry. The reverse resonance of a double-cantilever vibration beam is used to drive the beam to be tested to vibrate, test efficiency is improved, energy is saved, and an amplitude range of the beam to be tested is widened compared with existing test equipment. A variety of precision instruments areused to measure and analyze a fatigue characteristic of a material to be tested from optical, acoustic, time domain waveforms and other aspects, and high test accuracy is achieved. A thermal environment where the composite material is located can be simulated, and the fatigue characteristic of the composite material at different temperatures can be tested. The device of the invention is simple, components adopt a detachable design, disassembling is convenient, the portability is good, and the operation is easy.

Failure of Locking Wires of an Aeroengine Component: Attributed Primarily to Over-twisting and Secondarily to Engine Vibration and Improper Material Selection

Abstract: Each of failed, working and unused (as-fabricated) locking wires used in fastening engine exhaust pipe of an aeroengine was analyzed during the course of failure investigation. Relevant background information is as follows: (1) Specification GOST 18143-72 was followed in manufacturing those wires, and (2) wires were for one-time use only. The failed and all other wire types were found to be made of as-specified AISI 321 austenitic stainless steel, based on compositional and microstructural analyses with high volume fraction of phases of Ti–C–N family. High volume fraction of Ti–C–N phases led to unacceptably higher strengths in each of the failed as well as non-failed wires (UTS value in excess of 580 MPa), while the as-specified material is supposed to have breakage strength of 520 MPa. The principle contributing factor to failure of one wire of the locking wire pair is over-twisting of the wire during fixing it to the main assembly. Effect of engine vibration in form of vibration fatigue was found to be of secondary in nature and did not cause the failure directly. It assisted in the final (propagation) stage of failure. Other wire failed by overload as a result of over-twisting of its counterpart. Temperature did not play any role in the present failure. Failure mechanism was verified by simulated experimental results on fractographs conducted with the unused wire and obtained by twisting, untwisting and retwisting. Excessively high and unspecified strength of the material and lower toughness (as manifested by Ti–C–N particles–matrix interfacial cracking) might have contributed to the present failure in a secondary way.

Experimental Study on Stepping Stress Stochastic Resonance Fatigue

Abstract: The vibration fatigue is studied from the dynamics, and the resonance fatigue test is designed and completed in this paper. The resonance fatigue test is designed by analyzing the analytic solution of the differential equation of structural vibration response. Taking C/SiC material as the experimental object, the resonance fatigue life of different stress levels should be obtained by stepping from the applied excitation. The equation of the root mean square value and fatigue life of the stress response under resonance fatigue is the conclusion. Compared with the traditional S-N curve, the resonance fatigue failure life of the material is shorter.

Bolt assembly connection vibration reliability experiment device and test method

Abstract: The invention discloses a bolt assembly connection vibration reliability experimental device andtest method.The bolt assembly connection vibration reliability experimental device andtest method comprises a base, a strain sensor, an excitation device, and a force measuring device, wherein the strain sensor, the excitation device, and the force measuring deviceare mounted on the base; the base is acasting part, a T-shaped groove is formed in the base, a working load device is arranged at the tail portion of the base,and the excitation device and the force measuring device are installed on the base through the T-shaped groove; by changing the position and size of an eccentric block on the excitation device and changing the rotational speed of a variable frequency motor, vibration loading ofdifferent amplitudes and frequencies can be realized; through a sensor of the force measuring device, the time history of a vibration load can be monitored; the change of pre-tightening force of the bolt under the vibration load can be tested throughthe strain sensor mounted on the working load device. Thebolt assembly connection vibration reliability experimental device andtest method has the characteristics of being easy to use and adjustable, the influence of the bolt layout and the bolt spacing on the connection vibration reliability can be easily tested, the change of the bolt connectionpre-tightening force under the vibration load can also be studied, anda reliable experimental platform can be provided forresearches of bolt vibration loosening and vibration fatigue test, and bolt assembly connection vibration reliability experimental device andtest method has an important research value.

Fatigue damage spectrum-based assessment of vibration standards on Battery Pack for EV’s using stress as a response metric

Abstract: Estimation of vibration severity on battery packs designed for Electric Vehicle by calculating fatigue damage spectrum for different global standards and actual vibrations in field. Review investigates factors influencing the vibration durability of HV batteries and components. The research objective of providing the underpinning knowledge that allows manufacturers to improve the mechanical durability and performance of EV battery assemblies with respect to vibration. Vibration fatigue methods uses stress as the response metric of interest, which requires Stress vs. Numbers of failure free Cycles (S-N) curve as input material property. From this "b" Basquin coefficient is evaluated for common material used for battery pack design. The damage index is plotted as a function of natural frequency, with separate curves for each Q and b pairs leads to different FDS for Global available standards ISO-12405, ISO-16750, ECE-R100 and AIS-048 etc. Fatigue damage spectrum is useful for comparing the relative damage potential between profiles. Comparison of FDS for current EV vibration test standards which apply vibration via a Swept Sine Profile and Random Profile are compared with 100,000 Miles of BEV Durability. This research also defines innovative testing techniques and characterization data, which can be employed by engineers to predict the warranty performance, of future EV battery assemblies.

CAE-based vibration fatigue simulation test method of new energy vehicle battery pack

Abstract: The invention relates to a CAE-based vibration fatigue simulation test method of a new energy vehicle battery pack.The CAE-based vibration fatigue simulation test method comprises the steps that virtual connection parts among a virtual battery pack, a virtual vibration test bench and a virtual battery pack and a virtual vibration test bench areconstructed to obtain a vibration fatigue virtual testdevice; modal calculation is performed on the virtual battery pack within the test vibration frequency range, and the natural frequency and modal matrix of the virtual battery pack are obtained; andactual vibration excitation load is applied to the vibration fatigue virtual test device under the natural frequency and modal matrix of the virtual battery pack; and the vibration fatigue parametersof the virtual battery pack under the actual vibration excitation load are calculated, whether the vibration fatigue parameters meet the vibration fatigue parameter threshold range conditions or not is determined, and if so, the initial parameters of the battery pack are stored to be taken as the design parameters of the battery pack for designing the battery pack. The CAE-based vibration fatiguesimulation test method evaluates whether the virtual battery pack is subjected to vibration fatigue damage or not during the test, and reduces the test cost of the battery pack design.

Method for monitoring local vibration of aeroengine conduit

Abstract: The invention provides a method for monitoring a local vibration of an aeroengine conduit. The assessment test of the vibration fatigue of an engine conduit performed on a tester is an ideal measuringmethod for assessing the conduit structure and the material strength, and the measuring condition is an ideal fixed boundary condition. The conduit is in an entire pipeline system state after the engine is installed. Coupling and interference exist between individual pipeline structures. Vibration interference exists between the pipeline and an adjacent installing position, such as a casing. Oilpressure and air pressure pulsation interference and other factors exist in the pipeline. The vibration testing and monitoring of the conduit is performed in a complete machine state of the aeroengine. The method for monitoring the local vibration of the aeroengine conduit has the advantages that the design is simpler and more effective. The installation space, the installation link, and the consumption cost of a sensor are saved. Compared with a traditional method, the local vibration state of a micro component can be accurately and visually reflected, the online real-time monitoring can be performed while the engine works, and the intellectualization and the automation of the vibration prevention monitoring system of the engine conduit are improved.

Effect of crack surface contact forces on vibration fatigue characteristics of beam structure

Abstract: The vibration fatigue characteristics of a beam structure with breathing cracked links are studied, with the consideration of the contact forces at the breathing crack surfaces. First, a dynamic model of the breathing cracked beam element was formulated using the finite element method (FEM) and the theory of fracture mechanics. Subsequently, the coupled dynamic equation of a beam structure with breathing cracked links was established by FEM based on the dynamic model of the breathing cracked beam element. Then, the law of opening and closing of the breathing crack in the beam element was analyzed and the expressions for contact forces at the crack surfaces were derived using FEM. The sensitivity of the breathing crack surfaces to structural parameters and crack parameters was analyzed, by which the influence of contact forces on the structural parameters and crack parameters was revealed. Finally, the dynamic stress characteristics of the beam structure with breathing cracked links were analyzed. The vibration fatigue characteristics were described by the Paris fatigue crack growth curve model, by which the effect of the contact forces at the breathing crack surfaces on the vibration fatigue life of a beam structure with breathing cracked links was studied. Some concluding remarks based on an example have also been given.

Study on Fatigue Strength of Welded Joints Subject to Intermittently Whipping Superimposed Wave Load

Abstract: The stochastic characteristics of hull vibration superimposed stress waveform experienced by 6500 TEU container ship’s deck longitudinal is examined by Non-Linear Hydro-Elasticity Analyses. It is found that the stress waveform’s characteristics can be simplified so that the slamming impact occurs once in every 4 to 5 waves and the impact stress range is comparable to the wave stress range. Based on these results, the whipping superimposed stress waveform which are applied in fatigue tests are chosen. An electric exciter-driven plate bending vibration fatigue testing machine, which can apply various hull vibration superimposed stress waveform in high speed, is newly developed. Performing the whipping superimposed fatigue tests of welded joints using this machine, the validity of rainflow cycle counting for whipping superimposed loadings is examined. It is found that rainflow counting led to conservative estimates of fatigue lives, and the fatigue damage up to the failure of intermittently superimposed cases is larger than that of constantly superimposed cases under conditions chosen.

Vibration fatigue test device for high-frequency high-stress blade

Abstract: The utility model discloses a vibration fatigue test device for a high-frequency high-stress blade. Arrangement on a vibration device, wherein the amplifying body is fixedly arranged on vibration equipment and is in an inverted U shape, and the clamp unit is arranged on the amplifying body. wherein an opening of the amplification body faces the vibration equipment, and the clamp unit comprises a clamp body used for clamping the blade and a counterweight assembly arranged on the clamp body and used for adjusting the resonant frequency of the clamp body relative to the blade. The frequency adjusting device at least has the advantages that extra additional frequency is not increased, and the frequency generated by the whole device can be adjusted.

Fretting Wear and Fatigue Life Analysis of Fuel Bundles Subjected to Turbulent Axial Flow in CEFR

Abstract: In a fast spectrum reactor, the fuel rod bundle is mainly positioned radially by the wire which can make contact with the adjacent fuel rods, and then it is inevitable that flow-induced vibration (FIV) will cause fretting wear and vibration fatigue of the fuel cladding at the contact position. Therefore, the computational model of fretting wear and fatigue life about the fuel rod bundle caused by FIV will be studied in this paper. Based on the random vibration model of the fuel rod bundle, Hertz contact theory, and Archard wear theory, the fretting wear life computational model and the fatigue life computational model of the wire-to-adjacent fuel rod (WAFR) contact have been established. Finally, taking CEFR design parameters as an example, the fretting wear life and vibration fatigue life of the cladding are calculated, and it is found that fatigue affects the service life of the fuel rod more seriously than fretting wear. The calculation model and method lay a foundation for further accurate prediction and analysis of the fuel rod life.

Blade high-temperature vibration fatigue test system

Abstract: The utility model discloses a blade high-temperature vibration fatigue test system, which comprises a temperature control box, a vibration table and a clamp for fixing a blade, and the clamp can be fixed with the vibration table; the temperature control box can cover the vibration table and the clamp, and a plurality of electric heating elements are arranged in the temperature control box so as toincrease the test temperature of the blade placed in the temperature control box; a displacement sensor and an incident hole matched with the displacement sensor are arranged on the temperature control box so as to detect the blade tip displacement of the blade; and a high-temperature strain gauge is arranged on the blade so as to detect the stress and strain of the blade. The device can measurethe fatigue life of the turbine blade in a high-temperature environment.

Investigation on the effect of microstructure and mechanical properties of laser cladded TC17 titanium alloy following laser shock peening

Abstract: This paper aims to determine the effects of microstructure and mechanical properties of laser cladding TC17 titanium alloy post laser shock peening (LSP) In this work, A 3J, 20ns, 1064nm wavelength, Nd:YAG laser was employed on laser cladded TC17 titanium alloy samples with multiple impacts. Micro-hardness, residual stress were measured. The microstructure of LSPned sample was mapped by Electron Backscattered Diffraction (EBSD). The residual stress results showed that a stable compressive residual stress has been formed on the cladded coating surface with a value of 190MPa due to LSP modification. Additionally, LSP also improves the surface microhardness of cladded TC17 samples with an increase rate of 13.1%. Vibration fatigue tests were designed and carried out to examine the effects of LSP on the fatigue strength of cladded TC17 specimens. Results show that the fatigue strength of unpeened cladded sample is 290MPa while of peened claded sample is 300MPa. This work will contribute to prolong the service life of repaired TC17 components in aero-engines thereby economizing the repairing costs.