Efficiency of the method of spectral vibrodiagnostics for fatigue damage of structural elements. Part 1. Longitudinal vibrations, analytical solution

1997 ◽  
Vol 29 (6) ◽  
pp. 561-572 ◽  
Author(s):  
V. V. Matveev
Keyword(s):  
Analytical Solution ◽  
Fatigue Damage ◽  
Structural Elements ◽  
Longitudinal Vibrations

Vibration Control of H-Shaped Planar Frames Based on the Classical Euler-Bernoulli and the Advanced Timoshenko Bending Theories

2013 ◽  
Author(s):  
C. Mei
Keyword(s):  
Bernoulli Model ◽  
Structural Elements ◽  
Longitudinal Vibrations ◽  
Timoshenko Model ◽  
Bending Vibrations ◽  
Low Frequencies ◽  
High Frequencies ◽  
Planar Frames ◽  
Shear Distortion ◽  
Control Forces

Coupled bending and longitudinal vibrations in H-shaped planar frames are controlled from a wave standpoint, in which vibrations are described as waves traveling along uniform structural waveguides, and being reflected and transmitted at structural discontinuities. Active discontinuities are created using active control forces/moments both along structural elements and at structural joints to control vibration waves. The bending vibrations are modeled and controlled using the classical Euler-Bernoulli as well as the advanced Timoshenko theories. Numerical examples are presented. Comparisons are made between the results obtained using the classical Euler-Bernoulli model and the advanced Timoshenko model. Good agreements have been reached at low frequencies. However, discrepancies are significant at higher frequencies, typically when the transverse dimensions are not negligible with respect to the wavelength. This study addresses the importance of taking into account the effects of rotary inertia and shear distortion at high frequencies.

Fatigue Damage Accumulation Prediction for Combined Sine and Random Stresses

1988 ◽  
Vol 31 (3) ◽  
pp. 53-63
Author(s):  
Ronald Lambert
Keyword(s):  
Fatigue Life ◽  
Closed Form ◽  
Fatigue Damage ◽  
Damage Accumulation ◽  
Structural Elements ◽  
Numerical Examples ◽  
Stress Situation ◽  
Fatigue Damage Accumulation ◽  
Special Cases ◽  
Parameters Of Interest

Simple closed-form expressions have been derived to predict fatigue life, damage accumulation, and other fatigue parameters of interest for structural elements with combined sinusoidal (sine) and narrowband Gaussian random stresses. These equations are expressed in common engineering terms. The sine and random only stress situations are special cases of the more general combined sine/random stress situation. They also have application for establishing vibration workmanship screens. Numerical examples are also included.

Use of fatigue-damage transducers to evaluate the loading of structural elements

1984 ◽  
Vol 16 (12) ◽  
pp. 1663-1667
Author(s):  
V. T. Troshchenko ◽  
V. A. Kuz'menko ◽  
B. Z. Kruk ◽  
V. I. Boiko
Keyword(s):  
Fatigue Damage ◽  
Structural Elements

scholarly journals BUCKLING DELAMINATION IN COMPRESSED NO-TENSION HOMOGENEOUS BRITTLE BEAM-COLUMNS REINFORCED WITH FRP

2021 ◽  
Vol 30 (1) ◽  
Author(s):  
Francesco Marchione
Keyword(s):  
Analytical Solution ◽  
Structural Elements ◽  
Structural Members ◽  
Beam Columns ◽  
Instability Problem ◽  
Frp Reinforcement ◽  
Buckling Delamination ◽  
No Tension Material ◽  
Primary Instability ◽  
Delamination Length

The main issue of this paper is the instability of no-tension structural members reinforced with FRP. This study concerns the instability of FRP reinforcement. The primary instability problem of a compressed element involves the partialization of the inflex section. In particular, in the case of a compressed slender element reinforced on both tense and compressed side FRP delamination phaenomenon could occur on the latter. This entails the loss of the reinforcement effectiveness in the compressed area for nominal load values much lower than material effective strength. Therefore, structural elements or portions thereof which absorb axial components in the direction of the reinforcement may exhibit relatively modest performance with respect to the unreinforced configuration. By employing a no-tension material linear in compression, an analytical solution for FRP buckling delamination length is provided. The main objective of this paper is to provide a simplified tool that allows to evaluate the critical load of the reinforced beam-column and to predict the tension at which delamination and the loss of effectiveness of reinforcement in the compressed area could occur.

scholarly journals Study of running engines inertial and gyroscopic properties influence on the dynamic system engine – pylon – wing structural capabilities

2020 ◽  
Vol 23 (3) ◽  
pp. 63-72
Author(s):  
V. V. Ovchinnikov ◽  
Yu. V. Petrov
Keyword(s):  
Dynamic System ◽  
Fatigue Damage ◽  
Dynamic Properties ◽  
Elastic Beam ◽  
Aircraft Engine ◽  
Basic Structure ◽  
Elastic Vibration ◽  
Rigid Bodies ◽  
Practical Implementation ◽  
Structural Elements

A modern large-sized aircraft dynamic properties analysis, determined by the specificity of its layout scheme, demonstrates that the engines on under the wing elastic pylons lightly damped oscillations cause a number of undesirable phenomena, including intense accumulation of fatigue damage of the pylon-to-the-wing attachment, in fact in the area of engine installation in the pylon and the wing. The results of theoretical and experimental research show that with some engine attachment to the pylon structural modification it becomes possible to use the engines inertial and gyroscopic properties to absorb these oscillations. In this case, the motor tones damping coefficients increase by an order of magnitude or even more, so the gyroscopic coupling of elastic vibration tones is realized. With the rational choice of the additional parameters of elastic and dissipative bonds in the engine attachments it is possible to affect the aircraft wing and engines aero elastic vibrations effectively, which has a significant effect on the aircraft elements structural capabilities. A mathematical model of aero elasticity (MMAE) with respect to the kinetic moment of the engine rotors and specially designed units for attaching the engines to the pylons was developed in order to study the influence and the selection of rational elastic-dissipative parameters of the pylons-under-the-wing aircraft engine mounts. The method of predetermined basic forms is used for the aircraft with running engines on the pylons MMAE synthesis. The given forms are considered as the aircraft basic structure forms natural vibrations in the void. This work treats the engine nacelle and the rotor as absolutely rigid bodies, the elasticity of the rotor to the nacelle attachment is neglected. The pylon is modeled by an elastic beam, and the elastic and dissipative properties of the pylon-to-the-wing and the engine-to-the-pylon attachments are correspondingly by elastic-dissipative bonds. Schematic diagrams of the engine to the pylon attachments are proposed. The results of the study devoted to the influence of the proposed attachment points modifications on the load and integral strength characteristics of the main structural elements of the engine – pylon – wing dynamic system on the example of an An-124 aircraft are presented. The practical implementation of the proposed solutions aimed to reduce the level of fatigue damage to structural elements of the aircraft feasibility is proved.

Semi-Discrete Analytical Solution of Lumped Mass Finite Element Method for the Longitudinal Vibrations of an Elastic Bar

2013 ◽  
Vol 273 ◽  
pp. 234-239
Author(s):  
Jing Song Pan ◽  
Ji Chan Wang
Keyword(s):  
Finite Element Method ◽  
Exact Solution ◽  
Finite Element ◽  
Analytical Solution ◽  
Longitudinal Vibration ◽  
Analytical Approximation ◽  
Longitudinal Vibrations ◽  
Lumped Mass ◽  
Elastic Bar ◽  
Element Method

The objective of this paper is to present semi-discrete analytical method for the longitudinal vibration of an elastic bar. Using lumped mass finite element method, we first obtain a system of second order ordinary differential equations. In terms of some transform technique we obtain the exact solution to the system, i.e. excellently semi-discrete analytical approximation to the longitudinal vibration. An example is given to illustrate the effectiveness of the proposed method.

Degradation of the surface layers of superalloys and thermal-fatigue damage to the structural elements of gas-turbine engines

2008 ◽  
Vol 40 (5) ◽  
pp. 552-559 ◽  
Author(s):  
L. V. Kravchuk ◽  
R. I. Kuriat ◽  
K. P. Buiskikh ◽  
S. G. Kiselevskaya
Keyword(s):  
Gas Turbine ◽  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Structural Elements ◽  
Surface Layers

Fatigue Damage Prediction for Combined Random and Static Mean Stresses

1993 ◽  
Vol 36 (3) ◽  
pp. 25-32
Author(s):  
Ronald Lambert
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Narrow Band ◽  
Stress Rupture ◽  
Structural Elements ◽  
Damage Prediction ◽  
Static Tensile ◽  
Analytical Expressions ◽  
Static Tensile Stress ◽  
Mean Stresses

Closed form analytical expressions have been derived and are proposed for use to predict accumulated fatigue damage and fatigue life of structural elements subjected to a combination of fully reversed narrow-band Gaussian random and static mean stresses. Such mean stresses can significantly alter fatigue life. The proposed method of combining random alternating and mean stresses shows excellent agreement with published experimental data for a steel alloy. Reasonable agreement is maintained, surprisingly, even for static tensile stress values up to near the material's yield stress where the failure mode shifts from that of typical brittle fatigue to that of stress rupture (i.c.,creep). Numerical examples are provided to illustratc the application.

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