Strength Of Blades Research Articles

Calculating the hardening factor in GTE ball-hardened components in an ultrasonic field

We present results from research into the fatigue strength of GTE specimens and blades, ball hardened in an ultrasonic field. Using the theory of similarity and dimensional analysis we derive a model for the hardening factor which allows us to select efficient regimes and to refine the calculation of the strength reserve in the production design stage.

Experimental studies for the thrust of the horizontal-axis wind turbine.

The accurate prediction of rotor thrust is important when analyzing the strength of the rotor blades and supporting tower of the horizontal-axis wind turbines. In the present work, a series of model wind turbines were tested in a wind tunnel to ascertain the thrust of the rotor. The effect of three design parameters on the thrust ; i.e the number of blades, the pitch angle, and the up-tilt angle of the rotor plane, were tested for several wind speeds. The result of the experiments show that, on the condition of keeping two of the three design parameters unchanged, the thrust on the rotor decreases with increasing the pitch angle and up-tilt angle, and increases with increasing the number of blades. The results uncovered by the experimental analysis correlate well with the theoretical values. Moreover, the relationship between the thrust coefficient and the torque coefficient were also clarified.

Impact strength of gas turbine engine blades

A description is presented for a centrifugal impact-testing machine, which makes it possible to conduct impact tests of blades of gas-turbine engines with partial modeling of the conditions under which collision occurs with foreign objects. It is established that ball hardening of the blades of the second stage of a high-pressure compressor in an ultrasound field makes it possible to increase their resistance to impact failure significantly due to the favorable effect of residual compressive stresses.

Influence of technological and service factors on static strength of blades with rims

Influence of technological and service factors on static strength of blades with rims

実船に装備された遊転プロペラについて

Various attentions have been paid to improvement of propeller efficiency. Among these devices, the free rotating propeller (vane wheel) to be fitted additionally behind conventional main propeller is the most attractive one. However the design method, blade strength, etc. of the free rotating propeller are not specified.The authors designed the free rotating propeller for the ship by applying the momentum theory and the blade element theory that are used for designing the hydraulic machineries. In this report, the design accuracy is compared with full-scale measurements and as the results, the following conclusions are obtained.(1) The calculated revolutions and energy saving rate of the free rotating propeller show a similarity to those of measurements.(2) Measured energy saving rate is 6-8.5% at same speed condition.(3) The mean blade stress is 2.6kgf/mm2 {25 MPa} and the fluctuation of blade stress for a rotation is 8.8kgf/mm2 {86 MPa} in peak-to-peak value.(4) The pressure fluctuation caused by main propeller is reduced by 20% at the blade frequency components.

Determination of loads and evaluation of the strength of rotor blades in a high-speed liquid flow

This paper presents results of measurements of pressure and strain in blades of a VVN2-50 liquid piston rotary compressor (LRC). The rotor of the compressor is described. Strains from centrifugal forces were measured with rotation of the rotor in nominal regimes without liquid. A compensating resistor, acting as a strain gage, was glued to the cover of the hole in the outlet manifold to provide for automatic compensation of temperature changes. The distribution of maximum stress intensity on the concave side of the blade is shown. The first experiment conducted under service conditions showed that the blades of a liquid-piston pump experience complex loading under conditions of high-speed liquid flow. Such a study is necessary to ensure adequate strength in smaller-volume blades of variable thickness that have been proposed to further improve pump designs. Together with a decrease in material content and unit electric power consumption, this modification will increase the productivity of liquid-piston pumps in both the pump and the compressor regimes.

Damage of VZhL12U alloy turbine blades

1. The strength and plastic properties of turbine blades of VZhL12U alloy are determined to a significant degree by the carbide transformations, the redistribution of alloy elements, the precipitation of new phases, and the change in morphology of the γ′-phase particles occurring in service. 2. One of the basic causes promoting the start of fatigue failure of blades of VZhL12U alloy is thermal fatigue cracking of the coating applied to these blades.

航洋中の自動車運搬船における実船計測及びプロペラ翼の強度

航洋中の自動車運搬船における実船計測及びプロペラ翼の強度

ハイリースキュードプロペラの翼応力実測解析

In recent years, the highly skewed propellers tend to be used for the prevention of the growth of ship vibration and noise. On the other hand, however, the blade strength of the highly skewed propeller under the ship operating condition has not been measured up to the present time, in spite of the need for the judgement on the blade strength. Therefore, the authors measured the blade stresses of the highly skewed propeller which was fitted on a' Pure Car Carrier.After analyzing the measured data, it has been found that the maximum principal stress induced on the pressure surface of the blade at the point of 0.4 R with 90% camber length from leading edge became maximum in value when the propeller chip clearance became minimum.Furthermore, the measured principal stress mode within one revolution has been compared with the calculated result by the FEM analysis and the both have a similar tendency in the mode.

Calcul du champ d'écoulement dans une turbine Kaplan et calcul des contraintes dans les pales

It was planned to study two aspects of a KAPLAN-type hydraulic turbine: - a hydrodynamic study to determine the characteristics of the flow, - a mechanical study to check blade strength. The flow calculation was made by a quasi-three-dimensional method. (1) The fluid was incompressible and non-viscous ; the flow was stationary ; the calculation surfaces were axisymetrical. Matrix methods based on diagrams of finite differences were used both on the meridian surface and on the blade-toblade surfaces. The coupling was initiated by a meridian calculation and after the ca1culations on five blade-to-blade surfaces the average current lines permited the definition of a new meridian surface. The theoretical and experimental values for the flow characteristics matched well, in the middle of the water-vein, for the axial and tangential velocities upstream of the runner. Downstream of the runner, the axial-velocity curves matched in the middle of the water-vein but the tangential velocity curves differed slightly though they had the same pattern. Differences appeared at the hub and the casing both upstream and downstream because the viscosity effects were not taken into account in the calculation. The distributions of static pressure on the blade systems were introduced into the calculation of stresses. This calculation was made using a finite-elements code, the material being assumed to be homogeneous and elastic in this case. The forces taken into account were : the pressure load, the centrifugal force, and the weight of the blade itse1f. The results of these calcu1ations were compared with the experimental values obtained by the Hydraulic Production Department firstly on a blade under actual operating conditions and secondly on a real blade subjected to forces produced by three jacks. Comparison of the theoretical and experirnental results shows a good match for the distribution of radial stresses. However a difference appears between the experirnental and theoretical distributions of circumferential stresses. This difference is probably associated with that found for the circumferential velocities. The results obtained from this study are eneouraging : they show that it is possible to couple up calculation of the flow and ca1culation of the stresses in present-day hydraulic machinery. The comparison between calculation and experirnental concerning the flow characteristics however emphasies the need to take account of the boundary layers and losses in the calculation.

Stress-strain state of Francis turbine blades

1. Theoretical and experimental investigations made it possible to establish the level of static and dynamic stresses in blades under various operating conditions. 2. The results of the blade strength calculated by the finite-element method are in satisfactory agreement with the experimental data.

Fatigue strength of gas turbine engine rotor blades in connection with structural changes in service

Fatigue strength of gas turbine engine rotor blades in connection with structural changes in service

Pulverization characteristics of clay soil

Soil pulverization and failures during chip formation using rotating simple wedge-shaped blades for microsite preparation were analyzed to determine soil cutting characteristics. Equations were developed for soil bite size and blade projected area, and a new term was proposed relating the power requirement for rotating the pulverizer blade to the power required for penetrating the soil profile. The results of this study indicated that the rotational power requirements, in general, increased with increases in rotational and downward speeds, and the penetration power was slightly affected by the rotational speeds and was very small in comparison with the rotational power. The soil bite size appeared to play a great role in identifying the power requirements of a pulverizer blade. A substantial increase in rotational power requirement at the same rotational speeds was required due to increases in bite sizes; this increase might be due to the increases in soil-blade friction forces. During soil pulverization, chip dimensions were affected by the operational speeds, soil strength, blade geometry, and number of pulverizer blades. The pulverizer shaft diameter has little influence on the total power requirements but definitely affects the soil packing sequence of the planting cycle when the soil pulverizer for microsite preparation is incorporated into the planting head. An example illustrating the use of the data presented in this study is included to assist in the selection and sizing of a soil pulverizer's power unit.

舶用プロペラ翼の疲労強度に関する研究 Ｉ プロペラ材料の疲労強度

Marine propeller blades have been designed so far mainly with the object of obtaining higher propulsion efficiency. Meanwhile, fatigue failure of marine propeller blades lately has increased. The reason is thought to be that the recent tendency toward higher power for engines and higher speed for ships has increased the load on blades and the fatigue strength of propeller blades has become the critical point in their design. Accordingly, the establishment of fatigue design rules for marine propeller blades is necessary. For this purpose, the fatigue strength of blade materials must be determined. However, only a few data have been available on the fatigue strength of blade materials and most of those data have been obtained by rotating bending fatigue tests in which stress conditions differ greatly from those in full-size propeller blades. In general, fatigue strength is affected considerably by the stress conditions, so that those data are not sufficient to give a basis for fatigue design rules for marine propeller blades. From this point of view, fatigue tests and crack propagation tests were conducted on two kinds of propeller blade material, Ni·Al-bronze and Mn-bronze. The stress and environmental conditions of the tests were selected carefully to be close to those of full-size propellers in use. The effects of stress ratio, stress frequency and so on on the fatigue strength and the fatigue crack propagation characteristics of the blade materials were examined.

Increasing the strength and reliability of turbine blades by thermoplastic hardening methods

7. G. N. Tret'yachenko and B. S. Karpinos, "The thermal state of hollow cylinders upon internal one-sided heating," Probl. Prochn., No. 5, 56-58 (1977). G. N. Tret'yachenko, B. S. Karpinos, and L. E. Kiyashko, "State of thermal stress of hollow cylinders upon internal one-sided heating," Probl. Prochn., No. 9, 21-24 (1977). N. F. Krasnov, Aerodynamics of Solids of Revolution [in Russian], Mashinostroenie, Moscow (1964).

Investigation of the dynamic strength and the effect of accrued operating time on the fatigue strength of the rotor blades of atomic power plant gas turbines

1. The endurance characteristics of the investigated blades operate up to 1000 h at first increase, and then gradually decrease. 2. The accumulation of damages in pair-shrouded blades of the same rotor occurs at a different rate, the latter determined by the level of dynamic stresses of the blade and by the time of service of the engine. 3. An evaluation of the amplitude of stresses in tested blades according to the range of vibrations, without accounting for the variation in the dynamic rigidity of the plates in the sample, may yield an error in stresses of ±6.5%, and an error in endurance of ±37%, which may be comparable with the effect of the factors being investigated.

A method of calculating the erosion strength of moist steam turbine blades

A method of calculating the erosion strength of moist steam turbine blades

Estimating the strength of turbine rotor blades taking into account operational damage

1. The law of equality of the action of opposite forces was used as the basis for determining the ratio of residual surface compressive stresses to subsurface tensile stresses in a hardened compressor rotor blade for the case of thin and thick cross sections. 2. Equations were derived which relate components of the stress state due to service loads to components of the initial stress field in the shaped portion of compressor and fan rotor blades. 3. An experimental and analytic method of determining the optimum level of compressive stresses in the hardened shaped portion of compressor rotor blades was developed and scientifically substantiated, the possible damage of the blade during its exploitation being taken into account in the development of the method. 4. Analysis of the problem showed that compressor and fan rotor blades must be thermally stabilized (before they are hardened by shot blasting) to produce complete relaxation of the nonuniform field of initial stresses induced in the shaped part of the blade during the mechanical treatment, since otherwise it is impossible to obtain a uniform initial stress field after the hardening treatment. 5. Compressor rotor blades hardened by shot blasting should be thermally stabilized at a temperature 10–15°C higher than the working temperature of the compressor blade at the given stage with a view to ensuring the optimum level of the uniform field of initial stresses in the shaped portion of the blade. 6. When actual rotor blades are fatigue tested to failure under laboratory conditions, their fatigue fracture will be analogous to that observed under actual working conditions only if the shaped part of the blade is subjected to the combined influence of alternating bending and an axial load simulating stresses due to centrifugal forces.

Methods of design valuation of the strength of gas turbine engine disks and blades under thermocyclic operating conditions

Methods of design valuation of the strength of gas turbine engine disks and blades under thermocyclic operating conditions

The Effects of Residual Magnetism on the Corrosion Fatigue Properties of Type 410 Stainless Steel Compressor Blades

Abstract Residual magnetism is beneficial in improving the corrosion fatigue strength of Type AISI-410 stainless steel compressor blades tested in a synthetic sea water atmosphere. The corrosion fatigue strength of magnetized blades is improved 56% and survival time is increased 357% as compared with non-magnetized blades. The improvement is attributed to a reduction in the rate at which dislocations cross slip to broaden slip planes which are preferentially attacked by the corrosion media. X-ray diffraction studies confirm an interaction of dislocations and magnetic domain walls.