1990 Vol. 5, No. 4

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MEASUREMENT OF ELASTOPLASTIC STRESSES OF ROTATING DISK IN HOT STATE
Liu Xiangsheng
1990, 5(4): 292-296,370.
Abstract PDF(350KB) icon1631 icon391
Abstract:
The philosophy、the measurement scheme、the essential technological data treatment and the error analysis in the measurement of elastoplastic strains and stresses at median and high temperatures are considered in this paper.The method for identification of plastic state of the disk,as well as the approach to obtaining the secant module and transverse deformation coefficient are presented.The accuracy of the measurements is quite sufficient.The useful measuring and testing technique as well as reference data are provided for the engineering utilization and theoretical analysis.
ANALYSIS OF THERMOELASTOPLASTIC CREEP FINITE ELEMENT UNDER CYCLIC LOADING
Mu Xiaying, Hu Zhiqiang
1990, 5(4): 297-301,370-371.
Abstract PDF(412KB) icon1453 icon502
Abstract:
The incremental constitutive equations of thermoelastoplastic creep analysis has been derived under the conditions of variable temperatures and loadings.The finite element basic formulation of the plane stress state has been deduced and the program MTEPCA of its thermoelastoplastic creep analysis under cyclic loading has been worked out.Two sophisticated problems in the programming have been tackled.One is how to improve computational accuracy under the influence of various thermoelastoplastic creep factors.For this purpose the subincremental method and the Newton iteration are applied to calculation of the stress and the elastoplastic weight coefficient respectively,besides a high accurate method is proposed for yield surface correction.The other is how to deal with Δα z and Δε z of plane stress problem becauase they are not equal to zero.The solution of this problem is also provided in the program.Several numerical examples are given to check the reliability of the MTEPCA program.The stress strain hysteresis loops of the point A (danger point) on the analogue sample under cyclic loading are analysed for the structural integrity research.
VARIABLE AMPLITUDE LCF LIFE PREDICTION METHODS
Wang Lüsheng, Ru Meixiu, Cao Fenglan, Gong Mengxian
1990, 5(4): 302-306,371.
Abstract PDF(365KB) icon1648 icon503
Abstract:
This paper describes our variable amplitude LCF life prediction system based on the strain fatigue theory.The local stress strain method modified by us is more accurate than the conventional local stress strain method,This method is provided for disk life design.The presented system is also capable of accurate prediction of the variable amplitude LCF life according to the statistic data of smooth round bar specimen LCF lives to failure,so it is quite a convenient and simple experimental estimation method.Finally,the new method used in the presented system for detemining the reliability life of rotating disks is better than the method in EGD 3 stress standard.
VERTICAL ROTATING TESTER WITH VARIABLE-AMPLITUDE CYCLE FOR GAS TURBINE DISKS
Cao Fenglan, Wang Lüsheng, Huang Songling
1990, 5(4): 307-308,375.
Abstract PDF(213KB) icon1651 icon530
Abstract:
A microcomputer controlled high speed high temperature rotating tester with variable amplitude cycle has been constructed and oprerated to estimate the LCF life of gas turbine disk.So far the tester has worked about 2500 hours(total cycle index is about 50000),without essential troubles.The data of the variable amplitude LCF life for seversl disks have been obtained.These data are of high quality.It is testified that the test equipment is sufficient for preformance research of rotating disks with diameter up to 1m and weiget up to 300kg.The disk is mounted vertically on flexible shaft;an D.C.motor(125kw)drives the disk up to 25000rpm.The heater can raise the temperature of the disk up to 800±5℃.The average speed error for a run is less than 0.1%;the maximum instantaneous error is about 0.5%.A vacuum pump is used to sustain about 400 to 667Pa in the chamber of the tester.
A LOW CYCLE FATIGUE LIFE PREDICTION FOR DISK GROOVE BOTTOMS
Ru Meixiu, Cao Fenglan, Gong Mengxian
1990, 5(4): 309-310,375-376.
Abstract PDF(254KB) icon1290 icon436
Abstract:
According to the theory of local strain fatigue,the fatigue experiments for the 30CrMnSiA disk have been completed on a multichannel radial loading fatigue rig (“Ferris”whell).A good number of the crack propagation curves of the groove bottoms in the disk have been obtained.The calculations show that the median LCF life to crack initiation is 8642 (cycles).In comparison with cyclic rotating tests,the test period on a multi channel radial loading fatigue test rig can be shortened greatly and the test data can be obtained easily.A smooth round bar specimen experiment method for predicting the LCF life of groove bottom in the disk is provided,which is better than the Morrow method.For the median LCF life,the ratio of the experimental life to the predited life is 1.2.
EXPERIMENTAL ESTIMATION OF LCF LIFE FOR A COMPRESSOR DISK
Gong Mengxian, Wang Lüsheng, Cao Fenglan, Deng Jianbo, Ru Meixiu
1990, 5(4): 311-312,376.
Abstract PDF(212KB) icon1838 icon416
Abstract:
A LCF(Low Cycle Fatigue)test of a single rotor disk of a compressor is presented.The experimental results show that the location and the growth orientation of LCF crack in 9th single rotor disk reproduce those in the global compressor rotor.In addition,the LCF tests of the smooth round bar specimens are accompanied with the LCF tests of a single rotor disk,so as to estimate of the strain history of the eccentric holes in the disk.The statistical data of smooth round bar specimens tested to failure enables to estimate the LCF life to crack initiation for the eccentric holes in the disk of the global compressor rotor.
STRESS INTENSITY FACTORS AND THE PROPAGATION OF SURFACE CRACK IN TURBINE DISK
Zheng Guanghua, Xia Deyi
1990, 5(4): 313-317,371.
Abstract PDF(372KB) icon1737 icon486
Abstract:
A displacement method is provided to determine the stress intensity factors of nodes on crack surface in cracked body.The K I at the points along crack front of surface crack are obtained from the curve of KI versus r by the extrapolation.The KI of semi circular and semi elliptical surface crack in the finite thickness plates subjected to tensile load are calculated by the three dimensional finite element method.The photoelastic experiments with stress frozen method are made to examine the accuracy of the calculated results by the present method.Based on the expression proposed by Elber and Newman for the crack growth rate,the crack growth pattern and the life prediction of semi elliptical crack in a turbine disk of a jet engine are investigated.It is shown that the method presented in this paper is simple and convenient to analyse surface crack problems of engineering components.
AN EXPERIMENTAL STUDY ON DISC BURSTING SPEED
Zheng Qixuan, Hong Qilin, Hou Guichuang, Wang Ping, Zhao Changzhan
1990, 5(4): 318-320,376.
Abstract PDF(2196KB) icon1701 icon404
Abstract:
This paper discribes the experimental work on the research of disc bursting speed.The bursting speed tests for a series of disc models are made successfully.That means:such a difficult experimental technique has been mastered;and the reconstructed horizontal test rig is suitable for the research of disc bursting speed at normal atmospheric temperature and with heating.The results obtained from experiments and calculations are coincident.This work provides the basis for the further research on the bursting speed of aeroengine discs.
A LARGE ANALYTICAL DEFORMATION METHOD FOR PREDICTION OF DISK BURST SPEED
Hong Qilin, Wang Ping
1990, 5(4): 321-324,371-372.
Abstract PDF(364KB) icon1960 icon431
Abstract:
A new method has been elaborated to predict the burst speed of aeroengine disks.The disks should overspeed or even break due to malfunction of control system,shaft decoupling or afterburning failure.In order to avoid catastrophic failure of an engine,it is required to allow a margin of the disk burst speed.When the maximum rotor speed approaches to the disk burst speed,the plastic strain attains to large value in strain hardening range.So the concepts of material and geometrical nonlinearities are employed,but it is very difficult to obtain the solution of the double nonlinear problems.An approximate large deformation large analytical method is proposed firstly.The basic equations are derived according to the variable thickness and temperature of the disks.Secondly,the computational procedure is described and the burst speeds of four tested disks are obtained from the calculations.At last,the calculated results are compared with the test data,and the differences are less than four percent.Therefrom,it is proved that the new method is simple,convinent and accurate for engineering application as well as it is applicable to a wide variety of disks.
APPLICATION OF PHOTOELASTIC COATING AND PHOTOPLASTICITY TO ELASTOPLASTIC STRESS ANALYSIS OF A ROTATING DISK
Dong Benhan, Gao Pengfei
1990, 5(4): 325-330,372.
Abstract PDF(419KB) icon1793 icon542
Abstract:
A experimental method is developed for elastoplastic stress analysis of a rotating disk by means of photoelastic coating and photoplasticity.The experimental results are obtained from elastoplastic strain measurements of a model disk and a compressor disk.The isochromatic fringe fields of rotating disks are recorded by two systems which are designed by authers and composed of derotator、strobe light、photoelectric detector and camera.Strips method and difference method are proposed to separate strains in the photoelastic coating.The elastoplastic stresses of the rotating disk are calculated from experimental data according to small deformation elastoplastic theory.This experimental method has the advantage over other methods in noncontact measurement of the whole field.
A THREE-DIMENSIONAL ELASTIC STRESS ANALYSIS FOR AIR COOLED TURBINE BLADES OF ORTHOTROPIC MATERIAL WITH CONTOURED PASSAGE
Xu Heshan, Wang Zhengtao, Hao Yanhua
1990, 5(4): 331-334,372.
Abstract PDF(309KB) icon1665 icon475
Abstract:
A three dimensional elastic stress analysis method is provided for air cooled turbine blades of orthotropic material with contoured passages.The analytical results are presented for a real air cooled turbine blade.The sectional linear and nonlinear assumptions are adopted to divide a blade into elements and to form the geometrical and mechanical models,the coordinate transformation is employed to set up an elastic matrix of the elements,and the sectional linear interpolation is used to consider the effect of the temperature on the blade metal,so as to calculate the directionally solidified air cooled turbine blades with complicated contoured passages and the high temperature differences between the inner and outer walls.The method and the program have been verified and the accuracy could meet the requirements of engineering.
ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF BIRD IMPACT ON BLADES
Gao Deping, Li Qinghong
1990, 5(4): 335-338,373.
Abstract PDF(334KB) icon1759 icon407
Abstract:
Investigation on blade damage by bird impact is of great importance in the development of modern aero engines.The high speed dynamics of the bird impact on blades has been studied analytically and experimentally.The response analysis of the bird impact on the blade is a geometrical and material non linear,transient large displacement problem.A program system for the non linear transient response analysis has been developed and the loading characteristics of the bird impact are outlined.Based on the sensibility analysis of structural response to loading,a simple effective loading model of the bird impact is presented.A computer program of model analysis for the bird impact on blades is developed.The calculational results show that the bird impact on the blade at the velocity about 200m/s can be characterized as compressible fluid.The normal impact experiments with artificial birds have been completed,and the course of the bird impact was recorded by the high speed photography.It is proved again that the bird colliding against the blade behaves like compressible fluid.
EFFECT OF INLET DISTORTION ON BLADE VIBRATION AND INLET DISTORTION TOLERANCE
Chen Qun, Du Shaohui, Li Wenlan
1990, 5(4): 339-342,373.
Abstract PDF(296KB) icon1718 icon398
Abstract:
This paper examines the acceptability of inlet distortion from the angle of to the blade strength,and considers the influence of some inlet distortion patterns on the compressor blades vibration.An analytical moethod is provided.Meanwhile,the exciting forces of the circumferential distortion on the compressor blades and the blade responses to these fores are analyzed.The blade vibratory stresses caused by the distortion are calculated.The stress variation at different distortion levels is also investigated,and so the inlet distortion tollerance limit determined by the blade strength is discussed.
A SUPPLEMENTARY ALGORITHM FOR LUG TOOTH CONTACT ANALYSIS
Pen Kejian, Sheng Yuansheng, Zheng Guanghua
1990, 5(4): 343-346,374.
Abstract PDF(296KB) icon1709 icon406
Abstract:
According the principles of the inequality variations,the existence and the uniqueness of the solution have been verified for elastic contact problems,which contain friction forces between the contact surfaces.Thus the contact problems are made to be equivalent to the quardratic programming problems.By using the basic idea of supplement,the objects of a contact system is discreted and then lumped to the contact boundaries,then an resultant stiffness matrix is formed and a linear supplementary equation of non negative variables,υ adn λ,is also derived in the light of the non penetration condition of the normal displacements of the contact surfaces and the Conlumb friction law,etc.By the direct use of the Lemke algorithm of quardratic programming method,the scope of solution is limited to the contact boundaries.The whole field information is therefore obtained from further solution of the subelements.Such an algorithm enables to eliminate effectively the convergence instability which used to appear in the iteration methods in solving the problems.The results of calculations of the lug tooths contact stresses are fitted with the experimental data quite well.
MODIFICATION OF SHAPE OF DOVETAIL JOINTS FOR ANTI-FRETTING DAMAGE
Zhu Rupeng, Pan Shengcai, Dai Zhendong
1990, 5(4): 347-348,377.
Abstract PDF(249KB) icon1668 icon502
Abstract:
The fretting damage of the dovetail joints between blades and disks in turbojet engines has significant effect on fatigue life of the joints.In order to improve the resistibility to of dovetail joints fretting damage,an effective method provided,which palliates the fretting wear of the joint.By modifying the shape of the local interface to adjust the distribution of the mechanical parameters.The numerical analysis of the joints with the Boundary Element Method indicates that for the modified joints the peak reaction on the interface drops greatly but the peak stress does not rise at both the contacting and non contacting interface in elastic bodies.Comparative experiments have been carried out.The results show that the fretting wear of the modified dovetail joints is palliated,especially at the root of contact surface.The fatigure life of the appropriately modified dovetail joints increases twice.
COMPUTATION FOR CONTACT PROBLEM OF A DISK-BLADE COUPLED COMPONENT
Tang Guoan, Ding Haicheng
1990, 5(4): 349-351,377.
Abstract PDF(243KB) icon2037 icon444
Abstract:
Contact stress of a disk blade coupled component is analyzed by numerical method.The contact problem is reduced to a problem of quadratic programming with linear inequality constraints(LCQP).Objective function of the LCQP is derived from the principle of minimum potential energy of elastic bodies in combination with finite element method.In order to formulate the constrain equations,an imaginary media is introduced between the two contact surfaces.Then the displacement compatibility condition on the contact region can be considered as to make the imaginary media have non negative volume during deformation.Such geometric condition will be presribed by a set of linear inequalities after discretization.Besides,static condensation technique is also used to reduce the degree of freedoms of the LCQP problem.A practical problem is estimated by our method and SAP5 software.These two results are in good agreement.
DOUBLE COMPATIBLE MODE SYNTHESIS OF SYMMETRIC STRUCTURES WITH C_nGROUP
Wang Wenliang, Zhu Nongshi, Xu Jiahua
1990, 5(4): 352-356,374.
Abstract PDF(344KB) icon1384 icon487
Abstract:
The success of implementing the mode analysis in the structural integrity research depends to a large extent on the ability to extract normal modes of the structures.In this paper,a new technique is proposed to combine the group theory algorithm and double compatible substructure method for analyzing rotationally symmetric(Cn)structures.In this method,only one sector(1/n part of a structure)is taken and considered so as to obtain the normal modes of the whole structure.But for a large complicated structure,this sector still contains a lot of degrees of freedom(DOF)and is not suitable for direct solution by finite element method.For this reason a substructure method-double compatible mode synthesis method is employed.This technique enhance the extraction efficiency with the accuracy ensured by considerable reduction of synthetic scale through elimination of interface DOF,a numerical example is given to illustrate the merits of the presented technique.
NATURAL VIBRATION ANALYSIS OF TURBOMACHINERY DISK WITH SMALL MISTUNED BLADES
Wang Hao, Wang Wenliang
1990, 5(4): 357-360,375.
Abstract PDF(307KB) icon1504 icon1030
Abstract:
A numerical approach is developed for natural vibration analysis of turbomachinery disk with small mistuning blades by using modal synthesis technique.Due to lack of rotational periodicity,the group theory method for the tuned bladed disk assemblies is not applicable to the mistuned ones.According to the matrix peturbation theory,the modes used for synthesis in this paper are taken from a tuned bladed disk corresponding to the small mistuning one.This new technique keeps the advantages of the group theory method and makes the final eigenvalue problem of small size.A computer program has been written to analyse the natural vibration characteristics of turbomachinery disk with small mistuning blades.The computational results prove that the method is very efficient.
INFLUENCE OF SIZE FACTOR ON SCATTER DEGREE OF THE LOW CYCLE FATIGUE LIFE OF A DISK
Xu Linyao, Sun Qin
1990, 5(4): 361-363,377.
Abstract PDF(249KB) icon1383 icon402
Abstract:
From mathematical statistics of test data has been drawn the following conclusion:the low cycle fatigue life of disks scatters due to their size difference.The cylic stress strain curve and the strain life relationship of a materical must consider requirements of the survival probability and believable degree when the low cycle fatigue life of a disk is estimated with the partial stress strain method.This paper also provides an approximate correction method for the preliminary estimation of the low cycle fatigue life of a disk.
THE TREATMENT OF 1/r SINGULARITY AND DISCONTINUOUS TRACTIONS IN 3-D ELASTIC BOUNDARY ELEMENT METHOD
Wen Weidong, Gao Deping
1990, 5(4): 364-366,378.
Abstract PDF(242KB) icon1787 icon389
Abstract:
For treatment of common discontinuous tractions in 3 D elastic boundary element method,a simple and practical approach is proposed in this paper.The problem of the 1/r integral singularity and its treatment are discussed and analyzed as well.The numerical results show that the appprach in this paper is satisfactory.
ANALYSIS FOR TYPICAL STATOR BLADE STRUCTURE AND ITS IMPLEMENTATION
Qiu Chunhang, Yu Duokui, Liang Jixin, Li Dong
1990, 5(4): 367-368,378.
Abstract PDF(193KB) icon1359 icon503
Abstract:
A program named the STAP for the stator blade analysis with preprocessor and postprocessor is briefly introduced.Using the mesh generation and substructure assemblage functions of the STAP,it is possible to accomplish conveniently the stress and vibration analyses of the stator blade if only the coordinates of points on the contour of a blade and a few of mechanical properties of materials are inputted.Since mechanical properties,particularly Youngs modulus and coefficient of thermal expansion,are temperature dependent,it is very important to take this fact into account for calculating the stress of a cooled gas turbine blade.For this end the STAP provides for user a finite element methed with a temperature dependence on the properties.In structure modelling,in order to reduce the number of unknown variables and to describe the complex boundary conditions,the STAP is possessed of the function of Master Slave relations between the nodal displacements.

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