scholarly journals Numerical and Experimental Assessment of the Effect of Residual Stresses on the Fatigue Strength of an Aircraft Blade

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5279
Author(s):  
Arkadiusz Bednarz ◽  
Wojciech Zbigniew Misiolek
Keyword(s):  
Residual Stresses ◽  
Practical Importance ◽  
Cyclic Hardening ◽  
Fatigue Analysis ◽  
Compressor Blade ◽  
Point Of View ◽  
Initial Stresses ◽  
Aviation Industry ◽  
Turbine Engine ◽  
Engine Maintenance

The work presents the results of numerical fatigue analysis of a turbine engine compressor blade, taking into account the values of initial stresses resulting from surface treatment-shot-peening. The values of the residual stresses were estimated experimentally using X-ray diffraction. The paper specifies the values of the residual stresses on both sides of the blade and their reduction due to cutting through the blade-relaxation. The obtained values of the residual stresses were used as initial stresses in the numerical fatigue analysis of the damaged compressor blade, which was subjected to resonant vibrations of known amplitude. Numerical fatigue ε-N life analysis was based on several fatigue material models: Manson’s, Mitchell’s, Baumel-Seeger’s, Muralidharan-Manson’s, Ong’s, Roessle-Fatemi’s, and Median’s, and also on the three models of cyclic hardening: Manson’s, Xianxin’s, and Fatemi’s. Because of this approach, it was possible to determine the relationship between the selection of the fatigue material ε-N model and the cyclic hardening model on the results of the numerical fatigue analysis. Additionally, the calculated results were compared with the results of experimental research, which allowed for a substantive evaluation of the obtained results. These results are of great scientific and practical importance. The problem of determining the fatigue life of blades with defects operating under resonance vibrations is one of the original tasks in the field of fracture mechanics and experimental mechanics. The results obtained are of great importance in the aviation industry and can be used during engine maintenance and inspections to assess the suitability of blades with defects in terms of the needs of further work. This aspect of engineering maintenance is of great importance from the aircraft safety point of view.

scholarly journals Numerical and Experimental Assessment of the Effect of Residual Stresses on the Fatigue Strength of an Aircraft Blade

2021 ◽  
Author(s):  
Arkadiusz Bednarz ◽  
Wojciech Z. Misiolek
Keyword(s):  
Residual Stresses ◽  
Practical Importance ◽  
Cyclic Hardening ◽  
Fatigue Analysis ◽  
Compressor Blade ◽  
Point Of View ◽  
Initial Stresses ◽  
Aviation Industry ◽  
Turbine Engine ◽  
Engine Maintenance

The work presents the results of numerical fatigue analysis of a turbine engine compressor blade, taking into account the values of initial stresses resulting from surface treatment - shot-peening. The values of the residual stresses were estimated experimentally using X-ray diffraction. The paper specifies the values of the residual stresses on both sides of the blade and their reduction due to the cutting through the blade - relaxation. The obtained values of the residual stresses were used as initial stresses in the numerical fatigue analysis of the damaged compressor blade, which is subjected to resonant vibrations of known amplitude. Numerical fatigue ε-N life analysis was based on the several fatigue material models: Manson’s, Mitchell’s, Baumel-Seeger’s, Muralidharan-Manson’s, Ong’s, Roessle-Fatemi’s and Median’s, and also on the three models of cyclic hardening: Manson’s, Xianxin’s, and Fatemi’s. Because of this approach, it was possible to determine the relationship between the selection of the fatigue material ε-N model and the cyclic hardening model on the results of the numerical fatigue analysis. Additionally, the calculated results were compared with the results of experimental research, which allowed for a substantive evaluation of the obtained results. These results are of great scientific and practical importance. The problem of determining the fatigue life of blades with defects operating under resonance vibrations is one of the original tasks in the field of fracture mechanics and experimental mechanics. The results obtained are of great importance in the aviation industry and can be used during engine maintenance and inspections to assess the suitability of blades with defects in terms of the needs of further work. This aspect of engineering maintenance is of great importance from the aircraft safety point of view.

scholarly journals On Kaufmann's theory of the impact of the pianoforte hammer

1920 ◽  
Vol 97 (682) ◽  
pp. 99-110 ◽  
Keyword(s):  
Initial Conditions ◽  
Practical Importance ◽  
Prima Facie ◽  
Point Of View ◽  
Infinite Length ◽  
Modes Of Vibration ◽  
Rigorous Treatment ◽  
The Subject ◽  
Set Up ◽  
The Impact

The theory of the vibrations of the pianoforte string put forward by Kaufmann in a well-known paper has figured prominently in recent discussions on the acoustics of this instrument. It proceeds on lines radically different from those adopted by Helmholtz in his classical treatment of the subject. While recognising that the elasticity of the pianoforte hammer is not a negligible factor, Kaufmann set out to simplify the mathematical analysis by ignoring its effect altogether, and treating the hammer as a particle possessing only inertia without spring. The motion of the string following the impact of the hammer is found from the initial conditions and from the functional solutions of the equation of wave-propagation on the string. On this basis he gave a rigorous treatment of two cases: (1) a particle impinging on a stretched string of infinite length, and (2) a particle impinging on the centre of a finite string, neither of which cases is of much interest from an acoustical point of view. The case of practical importance treated by him is that in which a particle impinges on the string near one end. For this case, he gave only an approximate theory from which the duration of contact, the motion of the point struck, and the form of the vibration-curves for various points of the string could be found. There can be no doubt of the importance of Kaufmann’s work, and it naturally becomes necessary to extend and revise his theory in various directions. In several respects, the theory awaits fuller development, especially as regards the harmonic analysis of the modes of vibration set up by impact, and the detailed discussion of the influence of the elasticity of the hammer and of varying velocities of impact. Apart from these points, the question arises whether the approximate method used by Kaufmann is sufficiently accurate for practical purposes, and whether it may be regarded as applicable when, as in the pianoforte, the point struck is distant one-eighth or one-ninth of the length of the string from one end. Kaufmann’s treatment is practically based on the assumption that the part of the string between the end and the point struck remains straight as long as the hammer and string remain in contact. Primâ facie , it is clear that this assumption would introduce error when the part of the string under reference is an appreciable fraction of the whole. For the effect of the impact would obviously be to excite the vibrations of this portion of the string, which continue so long as the hammer is in contact, and would also influence the mode of vibration of the string as a whole when the hammer loses contact. A mathematical theory which is not subject to this error, and which is applicable for any position of the striking point, thus seems called for.

Designing Forging and Die Tooling for the Manufacture of Turbine Engine Compressor Blades in Siemens NX

2016 ◽  
Vol 684 ◽  
pp. 497-506 ◽  
Author(s):  
D.S. Goryainov ◽  
V.V. Anokhin ◽  
Aleksey Shlyapugin
Keyword(s):  
Point Cloud ◽  
Compressor Blade ◽  
Compressor Blades ◽  
Turbine Engine ◽  
Direct Modeling ◽  
Engine Compressor ◽  
Data Source ◽  
Theoretical Contour ◽  
Gas Turbine Compressor ◽  
Complex Parts

For designing forging and die tooling for bulk forging a necessity in using the data of the geometry of the part produced arises. Obviously, the use as a data source for designing drawings of commonly applied in “manual alternate design” (without a computer) especially such complex parts as compressor blades is not perspective because of the complexity of developing theoretical contour specified by a point cloud. In this case the use of special tooling of direct modeling that provides changing the original model of the part developed by the designers is a perspective one. It should be taken into account during the process of forging and die tooling designing that it is necessary to register the special features of the technology, upon that, the technologist should be highly proficient in using the software. The work given describes the designing technique of gas turbine compressor blade with the account of using the potential of NX Siemens program.

The Earliest Tool-makers

Antiquity ◽  
1956 ◽  
Vol 30 (117) ◽  
pp. 4-8 ◽  
Author(s):  
Kenneth Oakley
Keyword(s):  
Practical Importance ◽  
Point Of View ◽  
Fossil Remains

Man has been defined in many ways, as the talking animal, the religious animal, and so on, but the most satisfactory definition from the scientific point of view is probably Man the Tool-maker. One might ask, why bother to define man, considering his uniqueness and self-evident characteristics? But from the standpoint of students of evolution, particularly those concerned with the interpretation of fossil remains of early man and his possible ancestors, to define man is of practical importance.

BASIN CONFIGURATION OF A SIX-DIMENSIONAL MODEL OF AN ELECTRIC POWER SYSTEM

2002 ◽  
Vol 12 (06) ◽  
pp. 1333-1356 ◽  
Author(s):  
YOSHISUKE UEDA ◽  
HIROYUKI AMANO ◽  
RALPH H. ABRAHAM ◽  
H. BRUCE STEWART
Keyword(s):  
Power Systems ◽  
Power System ◽  
Initial Conditions ◽  
Electrical Power ◽  
Practical Importance ◽  
Intervention Strategy ◽  
Basins Of Attraction ◽  
Electric Power System ◽  
Point Of View ◽  
Electrical Power System

As part of an ongoing project on the stability of massively complex electrical power systems, we discuss the global geometric structure of contacts among the basins of attraction of a six-dimensional dynamical system. This system represents a simple model of an electrical power system involving three machines and an infinite bus. Apart from the possible occurrence of attractors representing pathological states, the contacts between the basins have a practical importance, from the point of view of the operation of a real electrical power system. With the aid of a global map of basins, one could hope to design an intervention strategy to boot the power system back into its normal state. Our method involves taking two-dimensional sections of the six-dimensional state space, and then determining the basins directly by numerical simulation from a dense grid of initial conditions. The relations among all the basins are given for a specific numerical example, that is, choosing particular values for the parameters in our model.

Evaluating and Exploring Successful Disruptive Innovation in the Aviation Industry From the Perspective of Consumers

2021 ◽  
Vol 13 (4) ◽  
pp. 105-119
Author(s):  
Gang-Hoon Seo
Keyword(s):  
Word Of Mouth ◽  
Low Cost ◽  
Disruptive Innovation ◽  
Point Of View ◽  
Aviation Industry ◽  
Basic Service ◽  
Low Cost Carriers ◽  
Content Analyses ◽  
Southwest Airlines

Since Southwest Airlines' disruptive innovation was introduced, low-cost carriers (LCCs) have had a prominent impact on the aviation industry. Therefore, considerable attention has been paid to the LCC model. However, it is still not clear whether it is a successful disruptive innovation, or what factors and differentiation points for successful LCC service exist from the passengers' perspective. As this study's methodology, quantitative and qualitative content analyses are conducted using the word-of-mouth data of 1,854 passengers of 20 airlines. This study found that the LCC model is perceived as a successful disruptive innovation from the passengers' point of view. For successful LCC service, LC airlines should offer higher quality services than passengers' expectations using basic service elements. Also, good staff characteristics, leaving a professional impression, and providing good optional services could play a role as differentiation tools.

Fatigue analysis of rolled components considering transient cyclic material behaviour and residual stresses

2018 ◽  
Vol 13 (2) ◽  
pp. 189-200 ◽  
Author(s):  
David Kühne ◽  
Christina Guilleaume ◽  
Martha Seiler ◽  
Peter Hantschke ◽  
Franz Ellmer ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Fatigue Analysis ◽  
Material Behaviour

Finite Element Modelling and Measurements of Residual Stress and Phase Composition in Ferritic Welds

2010 ◽  
Author(s):  
Benjamin M. E. Pellereau ◽  
Christopher M. Gill ◽  
Matthew Dawson ◽  
Paul R. Hurrell ◽  
John Francis ◽  
...  
Keyword(s):  
Finite Element ◽  
Phase Transformation ◽  
Residual Stresses ◽  
Cyclic Hardening ◽  
Tig Welding ◽  
Transformation Model ◽  
Welding Parameters ◽  
Isotropic Hardening ◽  
Low Carbon ◽  
Fe Modelling

This paper describes finite element (FE) modelling and neutron diffraction (ND) measurements to investigate the development of residual stresses in two different geometries of ferritic weld. All specimens were produced using SA508 Grade 3 steel plates, depositing a low carbon SD3 weld filler by mechanised TIG welding. The FE analyses were carried out using Abaqus/VFT and the behaviour of the SA508 steel was modelled using a simplified (Leblond) phase transformation model with isotropic hardening using VFT’s UMAT-WELD subroutine, which includes the change in volume due to phase transformation. Single bead-on-plate specimens were manufactured using a range of mechanised TIG welding parameters. One pass and three pass groove welds were also produced, in order to investigate the cyclic hardening behaviour of the materials, as well as phase transformation effects in a multi-pass weld. FE analyses were then performed to determine how accurately these effects could be modelled. During manufacture, a number of thermocouples were attached to each of the specimens in order to calibrate the heat input to the FE models. The residual stresses in each of the bead on plate welds, as well as the groove weld after the first and the third passes, were then measured using ND at the middle of the plate. The ND measurements for the three pass weld showed no significant cyclic hardening behaviour although some was predicted by the FE analysis. Another key finding of the FE modelling that was seen in all of the models was that the phase transformation acts to reduce the stress levels in the deposited weld metal leaving the largest tensile stresses in a ring at the outer edge of the full heat affected zone (HAZ). There are plans to refine the FE studies using improved material properties when material testing of SA508 and SD3 are completed in the near future.

A regression problem

1951 ◽  
Vol 47 (2) ◽  
pp. 337-346
Author(s):  
D. V. Lindley
Keyword(s):  
Complete Solution ◽  
Practical Importance ◽  
Random Variable ◽  
Partial Solution ◽  
Point Of View ◽  
General Definition ◽  
Regression Problem ◽  
Definition Of ◽  
Regression Theory ◽  
Complete Solutions

During the Oxford Conference of the Econometric Society in September 1936, Ragnar Frisch proposed a problem in regression theory. A partial solution was found in 1938 by Miss H. V. Allen (1). A more complete solution was given by C. R. Rao (6) in 1947, and in the same year the present author (5) obtained a solution as a particular case of a more general result. These last two papers contained a flaw, and a correct solution was provided by Miss E. Fix (2). This last solution still leaves a part of the problem unanswered, and in the present paper a result of P. Lévy's (4), is used to complete the solution. At the same time further generalizations of the problem are considered and, in the cases of most practical importance, complete solutions are obtained. It is advisable, both from the point of view of rigour and simplicity of analysis, to use a general definition of the conditional expectation of a random variable. Accordingly, the paper begins with a summary of the relevant definitions. These notions were introduced by Kolmogoroff (3). It has been thought worth while giving the definitions here, in forms which are slightly different from Kolmogoroff's and seem more suitable for applications, in order to explain the notation and nomenclature used. The relevant consequences of these definitions are also stated in the form in which they are used.

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