Disk Slot Research Articles

Stress concentration effect on the failure of an axial compressor first-stage rotating blades

The failure causes of a gas turbine axial compressor’s first-stage blades have been investigated in this paper. It was found that crack initiation and propagation occurred in the root region on the suction side of the blade. Under various conditions, blade stress analyses were conducted using the Abaqus software and the finite element method. The submodeling technique assessed the stress distribution in the blade root. The results revealed that the presence of the shim plate in the blade root region led to a 162.8% increase in the maximum principal stress. This increase occurs when the shim plate fills the gap in the blade assembly between the blade root and the rotor disk slot. As a result, the mentioned zones have experienced plastic strain. It was revealed that there are regions with permanent deformation on the root surface of the blade by examining the scanning electron microscope (SEM) images of crack initiation areas. These regions are located on the oblique surfaces of the blade root in the placement of the corner edges of the shim plates. Comparing the findings of the experimental study and numerical simulation shows that the crack initiation site is appropriately aligned with the plastic strain field and the maximum principal stress. Considering that the maximum principal stress distribution in the aforementioned geometrical positions is tensile, the crack initiation occurred due to the presence of shim plates and caused blade failure.

Dynamic modulation of electromagnetically induced transparency in complementary graphene metamaterial

In this paper, we use a complementary graphene metamaterial to achieve dynamic modulation of electromagnetically induced transparency. The structure consists of a disk slot graphene and a strip slot graphene corresponding to bright and dark modes, respectively. A clear transparency window appears in the transmission spectrum. In contrast to metallic metamaterials, the transmission spectrum of the complementary graphene metamaterial can be controlled by changing the Fermi energy rather than reconstructing the structure. The complementary graphene metamaterial proposed in this paper modulates the gate voltage more simply than discrete structures of a graphene metamaterial. Active control of the slow-light effect can also be realized by modulating the Fermi energy. This work demonstrates potential applications in the design of terahertz modulators, environmental sensors, and slow-light devices.

Slotting mechanization for intensive garden planting

The paper presents a structure diagram of a slot trencher when planting a garden, consisting of a frame on which working sections, a bevel gear reducer and support wheel stands are fixed. On the working section there is a shaft with a working body - a disk slot cutter. It is made in the form of a disc with teeth, one cutting edge of each tooth is straight and the other edge is parabolic. On the parabolic edge the working elements are fixed in the form of knives with a cutting edge consisting of two parts. A straight one is along the periphery; the other is in the form of a guide along the entire length of the curved edge of the tooth and equal to the width of the cutting edge of the knife. The theoretical substantiation of the main structure parameters is carried out as a result of which the length of the inclined knife is determined, which allows satisfying the operating conditions of the device.

Grinding of fir tree slots of powder metallurgy superalloy FGH96 using profiled electroplated CBN wheel

Broaching is commonly used for machining fir tree slots on turbine disk, which has outstanding advantages and disadvantages, such as high-quality machined surface, high manufacturing accuracy, and high productivity as well as fast tool wear, extremely high processing costs, long preparation time, and poor process flexibility. Utilizing the electroplated cubic boron nitride (CBN) profiled grinding wheels and single-sided local profiled grinding process, the experiments of FGH96 turbine disk slots are carried out. The results show that the high precision of slot profile can be achieved by the developed process. Using the given experimental parameters n = 48,000 rpm, ap = 0.002 mm, vf = 100 mm/min, and 600# electroplated CBN-profiled wheel, the profile error of FGH96 slots is within ±0.012 mm, and the grinding surface roughness is less than Ra 0.8 μm. After four whole slots are machined completely, the grinding wheel still has grinding capability, which proves that 600# electroplated CBN-profiled wheel can meet the grinding needs of FGH96 turbine disk slots.

Geometrical Analysis of Wire Electrochemical Machining for the Manufacture of Turbine Disc Slots

Abstract The advantages of sinking electrochemical machining (ECM), e.g. best surface integrity, are always faced with the cost-intensive initial effort for the component specific design of a machining device and its tool geometry. However, this disadvantage does not apply to wire ECM where no task-specific tool design is required for cutting 2.5-dimensional geometries like fir tree slots in turbine discs. An industrial application is still being hindered by insufficient flushing concepts. However, a previous study showed that the flushing approach of High Speed Wire Electrical Discharge Machining (HSWEDM) is also successfully transferable to wire ECM. Workpiece heights up to 40 mm could be machined with a cutting rate of Vw = 20 mm2/min. Nevertheless, these investigations were only performed with straight cuts, radii were not examined. Therefore, in this paper the geometrical accuracy of the wire ECM process is analyzed using the example of two different turbomachinery disc slot geometries with 20 mm and 40 mm heights by a coordinate measuring machine.

Improvement of fretting wear resistance of blade root made of polymer composite material

Polymer composite materials (PCM) are being increasingly used in aircraft engine industry. Development of PCM fan blade manufacturing technology that meets all the necessary strength requirements is an important task in creating Russian-made latest-generation engines. One of the problems to be faced is the wear of the blade root caused by cyclic micro-displacements in the interlock under the action of external forces. There are several engineering solutions to control surface wear of blade roots made of PCM that can basically be divided into three groups: manufacture of metal roots and the use of known methods of metal fretting prevention, use of replaceable special inserts placed between the contact surfaces of the root and the disk slot, application of elastic and damping elements. In this paper, we consider another method of controlling wear, the principal feature of which is stitching the blade pre-form with aramid thread that forms a layer with higher wear resistance on the root surface. In order to verify the efficiency of the proposed approach, model blades were made and tests were carried out on an electrodynamic shaker.

A Study of the Disc Scoring Generation Principle and Reduction(III)

<div class="section abstract"><div class="htmlview paragraph">In the latest works [12], we presented the guideline for reducing Metal pick up(MPU, the main component of disc scoring) by controlling the location of the roughness of disc, the brake pad friction coefficients and the disc slot's size. In this study, the previously studied iron transfer theory to 'Cu free' brake pad and the disc surface roughness controlling methods which are based on the mass production manufacturing process are applied. It is possible to suggest the ways to improve the scoring-free disc without reducing friction coefficient between the disc and pad, and any demerit such as increased wear and airplane noise like conventional slot discs [11].</div></div>

Substructuring for Contact Parameters Identification in Bladed-disks

Single stage bladed-disks are fundamental bricks of the rotating parts of a turbomachine. Although made of nominally identical sectors, the presence of imperfections or misalignment produces a large amplification of the forced response. Furthermore, due to their high modal density, friction dampers must be designed to mitigate resonance stresses, since a perfect detuning of the resonances from the excitation forces is impossible. Blade-root joints in these structures can provide the much-desired damping but the contact between the disk slot platform and blade-root lobes is characterized by uncertainty due to the actual locking position and machining tolerances.The cases of two simple beams and a bladed-disk test rig of an array of blades with dovetail root joints are studied to identify contact parameters. A dynamic Lagrange multiplier frequency based sub-structuring (LM-FBS) method is applied in a hybrid manner (experimental and numerical frequency response functions) to identify a parameter associated to each contact by mounting only one blade at a time. A sensitivity analysis is performed that will provide the basis for future work on non-linear frequency response prediction.

Fretting Fatigue Analysis of Additively Manufactured Blade Root Made of Intermetallic Ti-48Al-2Cr-2Nb Alloy at High Temperature.

Slots in the disk of aircraft turbines restrain the centrifugal load of blades. Contact surfaces between the blade root and the disk slot undergo high contact pressure and relative displacement that is the typical condition in which fretting occurs. The load level ranges from zero to the maximum during take-off. This cycle is repeated for each mission. In this paper, a fretting fatigue analysis of additively manufactured blades is presented. Blades are made of an intermetallic alloy γTiAl. Fretting fatigue experiments were performed at a frequency of 0.5 Hz and at a temperature of 640 °C to match the operating condition of real blades. The minimum load was fixed at 0.5 KN and three maximum loads were applied, namely 16, 18 and 20 kN. Both an analytical and a two-dimensional finite element model were used to evaluate the state of stress at the contact interfaces. The results of the analytical model showed good agreement with the numerical model. Experiments showed that cracks nucleate where the analytical model predicts the maximum contact pressure and the numerical model predicts the maximum equivalent stress. A parametric analysis performed with the analytical model indicates that there exists an optimum geometry to minimize the contact pressure. Tests showed that the component life changed dramatically with the maximum load variation. Optical topography and scanning electron microscopy (SEM) analysis reveals information about the damage mechanism.

DETERMINATION OF RUPTURE SOURCES OF TURBINE BLADE PACKETS AT PERFORMANCE OF FORENSIC EXAMINATIONS

The technique ofdetermination of rupture sources of the turbine blades packets, which can be used at performance of forensic expertise is suggested. Its distinctive feature is completeness of the account of the various factors concerning different areas of the applied physics, such as gas dynamics, heat conductivity, thermoelasticity, static and dynamic strength. The following series of calculations was made for acknowledgement of rupture sources of bladed disk. I. Calculation of a viscous compressed subsonic current. II. Calculation periodic gas-dynamic loads operating on the blades. III. Calculation of a non-stationary stress-strain state of the bladed disk under the action of periodic forces. The technique is based on use of the numerical methods of gas dynamics and dynamic strength. The steam current through a turbomachine step calculated with the help of model of the viscous, compressedfluid. The forced vibrations of the bladed disk under the action of the aerodynamic loads are analyzed by the numerical integration of the nonlinearfinite elements design model. Four cases are considered for the numerical calculations of the stress-strain state. I. The clearance in the disk slots are not accounted and the vibrations under the action ofgas-dynamic loads from ideal directing device are investigated. II. The clearance in the disk slots are not accounted and the vibrations under the action of gas- dynamic loads from defective directing device are investigated. III. The clearance in the disk slots are taken into account and the vibrations under the action of gas-dynamic loads from ideal directing device are investigated. IV. The clearance in the disk slots are taken into account and the vibrations under the action of gas-dynamic loads from defective directing device are investigated. It’s established that a source of rupture ofworking blades of a regulating step of a compartment of a high pressure of the steam turbine is damage of blades of the directing device.

Developing a new experimental set up to study fretting fatigue behavior under cyclic contact loading

The disk slot and blade attachment in the gas turbine engines are operated under both cyclic axial and contact loads simultaneously. In this investigation, a new coupon scale testing apparatus is designed and manufactured to study the fretting fatigue behavior of materials under cyclic contact loads. In this cyclic contact load fretting fatigue device (CCLFFD), a simple synchronized electro-mechanical system is used for generating cyclic contact loads with frequency of 0–200 Hz and magnitude of 0–10 kN. The CCLFFD is well instrumented for adjusting, measuring and online monitoring the contact load frequency, contact load graph, and rotation speed of the servomotors. Repeatability and reliability of the test rig were examined by experiment. The performance of the CCLFFD was verified using the experimental results reported in the literature and also by conducting a number of fretting fatigue tests on Al7075-T6 at different contact load frequencies in this work. The results showed that fretting fatigue was significantly affected by the contact load frequency particularly for high cycle fatigue regime. However, the effect was less important for low cycle fatigue regime and totally insignificant for frequencies higher than 80 Hz.

Abrasive water jet cutting methods for reducing blast-induced ground vibration in tunnel excavation

This study assessed the controlling effect of abrasive water jet cutting on blast-induced ground vibration during tunnel excavation. The abrasive water jet cutting method adopted in this study includes the notch-cutting and disc-cutting methods. The abrasive water jet notch-cutting method was applied to block the propagation of blast-induced ground vibration in the transverse direction of the tunnel face, and the disc-cutting method was applied to suppress the blast-induced ground vibration in the longitudinal direction of the tunnel. The vibration-reduction effects of both methods were quantitatively investigated through experimental and numerical studies. In the experimental study, the vibration-reduction effect of notch cutting was compared with that of the line-drilling method, whereas the vibration-reduction effect of the disc cutting was measured against the case without disc cutting. In the numerical study, the effects of notch slot length and disc slot diameter were investigated. The abrasive water jet cutting method reduced the blast-induced ground vibration and was more effective than conventional drilling and blasting method in tunnel excavation.

Mitigation of Fretting Fatigue Damage in Blade and Disk Pressure Faces With Low Plasticity Burnishing

Low plasticity burnishing (LPB) is now established as a surface enhancement technology capable of introducing through-thickness compressive residual stresses in the edges of gas turbine engine blades and vanes to mitigate foreign object damage (FOD). The “fatigue design diagram” (FDD) method has been described and demonstrated to determine the depth and magnitude of compression required to achieve the optimum high cycle fatigue strength, and to mitigate a given depth of damage characterized by the fatigue stress concentration factor, kf. LPB surface treatment technology and the FDD method have been combined to successfully mitigate a wide variety of surface damage ranging from FOD to corrosion pits in titanium and steel gas turbine engine compressor and fan components. LPB mitigation of fretting-induced damage in Ti–6Al–4V in laboratory samples has now been extended to fan and compressor components. LPB tooling technology recently developed to allow the processing of the pressure faces of fan and compressor blade dovetails and mating disk slots is described. Fretting-induced microcracks that form at the pressure face edge of bedding on both the blade dovetail and the dovetail disk slots in Ti-6-4 compressor components can now be arrested by the introduction of deep stable compression in conventional computer numerical control (CNC) machine tools during manufacture or overhaul. The compressive residual stress field design method employing the FDD approach developed at Lambda Technologies is described in application to mitigate fretting damage. The depth and magnitude of compression and the fatigue and damage tolerance achieved are presented. It was found that microcracks as deep as 0.030in.(0.75mm) large enough to be readily detected by current nondestructive inspection (NDI) technology can be fully arrested by LPB. The depth of compression achieved could allow NDI screening followed by LPB processing of critical components to reliably restore fatigue performance and extend component life.

Seal coating between rotor blade and rotor disk slot in gas turbine engine

Seal coating between rotor blade and rotor disk slot in gas turbine engine

Hydrodynamics and heat and mass transfer at chemical conversions in slot reactors

In this paper, experimental and numerical investigations of the hydrodynamics and heat transfer in a disk slot heat exchanger-reactor for a radial flow of a gas mixture reacting on the channel walls are described. Data for the coefficients of heat transfer from the wall being heated to the gas flowing inside the reactor are presented. The temperature field of a catalytically active reactor plate at heat release on it has been investigated experimentally. Calculations of the flow and heat transfer in a slot reactor element for a catalytic reaction with heat release have been performed. Partial oxidation of methane in an oxygen medium with the formation of a hydrogen-containing synthesis gas in a two-dimensional microchannel has been investigated numerically. Data for the extent of the chemical conversion of methane versus the initial mixture consumption and reaction temperature are presented.

Rotational effects of polymeric fluids on shape of filaments in melt extruded net structures

The present work deals with the net structures, which are produced by replacing the static die (spinneret) with two concentric dies rotating in opposite directions in a melt extrusion process. These dies consist of defined number of slots with non-circular geometries on their peripheries and the filaments are produced when the slots in disk and annulus are offset from each other. The effect of die rotation on the shape of filament is investigated by analysing the polymer flow inside the complex die slots including square and trapezoidal shapes, using computational fluid dynamics (CFD). The die slot shapes have also been predicted using CFD to achieve the desired filament shape.

Efficient disk replacement and data migration algorithms for large disk subsystems

Random data placement, which is efficient and scalable for large-scale storage systems, has recently emerged as an alternative to traditional data striping. In this report, we study the disk replacement problem (DRP) to find a sequence of disk additions and removals for a storage system, while migrating the data and respecting the following constraints: (1) the data is initially balanced across the existing distributed disk configuration, (2) the data must again be balanced across the new configuration, and (3) the data migration cost must be minimized. In practice, migrating data from old disks to new devices is complicated by the fact that the total number of disks connected to the storage system is often limited by a fixed number of available slots and not all the old and new disks can be connected at the same time. This article presents solutions for both cases where the number of disk slots is either unconstrained or constrained.

Efficiency of process methods for improving the surface quality and fatigue strength of gas-turbine engine disks of the KhN73MBTYu-VD alloy

The results of the present study suggest that a fatigue limit of the crown interslot projections of gas-turbine engine disks made of the KhN73MBTYu-VD alloy can be raised by subjecting the surface layer of the disk slots to ultrasonic hardening with balls. We attribute this to a removal of abrasive grits left by previous machining, to a decrease in depletion of the surface in alloying elements, and a simultaneous improvement in uniformity of the stress-strain state of various sections of the surface of a slot.

EVALUATION OF FULL FIELD AUTOMATED PHOTOELASTIC ANALYSIS BASED ON PHASE STEPPING

A full field automated polariscope for photoelastic analysis has been developed in the author's laboratory and has been described in detail elsewhere. Briefly, the system uses phase-stepping to determine both the fractional isochromatic fringes and isoclinic parameter at all points in the field of view independently of their neighbouring points. A wrapping algorithm is then employed to produce continuous ischromatic and isoclinic data, which can be subsequently be used in stress separation procedures. The idea of using phase stepping in photoelasticity is a fairly recent innovation and can be described as changing incremently the absolute phase of the reference wave by rotating the output elements of the polariscope and measuring the local light intensity after each step. In the apparatus described here, the output elements are rotated to six different positions providing six images of the specimen. Maps of the periodic values of the isoclinic and isochromatic parameters are subsequently obtained by combining, mathematically, these six images. A number of full field techniques have been developed. Poloshin and Redner have developed half fringe photoelasticity, and two laboratories in Japan are working on the technique of phase stepping. It appears, however, that no detailed evaluation has been made of the accuracy and reliability of the results generated by the technique. The objective of the work described in this paper has been provided such an evaluation. Five different models were selected for analysis using the automated system and manually using the Tardy compensation method: (a) a disk in diametral compression: (b) a constrained beam subject to a point load: (c) a tensile plate with a central hole: (d) a turbine blade; and (e) a turbine disk slot. These models provided a range of different fringe patterns, orders and stress gradients to test the performance of the system.

Conditions for the harmonic-like and efficient amplitude modulation of the cw gaussian laser beam by means of a mechanical chopper

The values of the chopping disc slot and mark space widths relative to the radius of the Gaussian beam are found, which achieve optimum harmonic-like and efficient amplitude modulation of the cw laser beam. The simple approximation for the waveform of the modulated laser power valid for these optimum or near optimum values of the chopping disc parameters is presented.