Logo SFB 871 Produkt-Regeneration
Logo: SFB 871
Logo SFB 871 Produkt-Regeneration
Logo: SFB 871
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C Consideration of variability in the repair processes and in material properties

The task of Project Area C, “Consideration of variability in the repair processes and in material properties", is to develop methods which describe and assess the effects of the variability in regeneration on the functional characteristics of individual components and the overall capital good.

Based on an exhaustive inspection of the component condition before regeneration, a description of the functional characteristics is to be created after specific repair methods are applied. The special significance of Project Area C’s contribution is that the effects of this increased variance will be predicted, and thus controllable. This means that in future, deviations from the component’s new condition, which are not permitted today, could be tolerated. With the help of the methods provided by Project Area C it will be possible to describe which functional characteristics a capital good will have after regeneration is completed. In addition, minimum requirements, e.g. tolerances, can be formulated for the respective regeneration path. These requirements must be satisfied in order to ensure that a capital good has the desired functional characteristics after regeneration. Ultimately, through the methods developed by Project Area C, it will be possible to make decisions in favor of or against regeneration, based on an evaluation of the costs of production and logistics versus the benefit of a restored or even improved function.


C1 Process Design

Process Design

Simulation Based Planning of Recontouring Metal Cutting Processes
In subproject C1 experimental investigations will be performed to detect and isolate the influences of the machining process during recontouring. The expected results are used within a simulation based assessment method which enables the choice from alternative processing approaches due to defined quality criteria and process guidelines. In particular, the direct coupling of simulation and NC-programming, an automated process optimization, the extension towards nickel-based alloys and the component distortion are considered.  With further investigations on chipping and continuing simulations, strategies for the compensation of the component distortion will be developed and included in an algorithm which is used for tool path planning.


C2 Fast Measurement of Complex Geometries

Setup and result of the Inverse Fringe Projection

Fast Measurement of Complex Geometries using inverse Fringe Projection
In subproject C2 the inverse fringe projection technique is evaluated for the purpose of measuring geometry deviations of complex work pieces, i.e. blisks, even at those geometry elements, which are not easily accessible. The research program includes methods for pose-dependent calibration of the newly developed endoscopic optical setup under influence of gravity, for fast and precise pose estimation of the measurement device relative to the specimen, and for data fusion. Further research efforts cover the analysis and visualization of deviations from the individual target geometry of the work piece, which is due to its individual regeneration process, by means of image processing algorithms.


C3 Regeneration-induced Mistuning (finished 2017)

Regeneration-induced Mistuning

Influence of Regeneration-induced Mistuning on the Dynamics of Coupled Structures
In the subproject C3 the mistuning of the disk part of a blisk is considered in the reduction method developed within the first funding period in order to account for realistic dynamic properties of the blisk due to regeneration-induced disturbances of the rotational symmetry. This gives rise to a possible reduction of blade vibration amplitudes by an intentional mistuning of the disk part instead of an intentional mistuning of the blade part of the blisk. In order to predict the realistic vibrational behavior, the influence of the temperature and the aerodynamical interblade coupling is considered in the simulation model. With a modified rotating test rig, the necessary model parameters will be identified and a validation of the simulation results is conducted.


C4 Aeroelasticity of Turbine Blades

Aeroelasticity of Turbine Blades

Regeneration-induced Variance of Aeroelastic Properties of Turbine Blades
In research project C4 the upstream stator blade rows of a multistage axial turbine are geometrically varied. The Influence of these regeneration-specific variations on the aerodynamic excitation is numerically and experimentally investigated. In the second part of this project, the radial gaps of the rotor blades (tip clearances) are varied. Due to the variation of the radial gap, tip vortices of different sizes exist. These vortices are able to excite blade vibrations. This excitation mechanism is numerically investigated. Additionally, experiments are conducted to validate the numerical results.


C5 Crack Growth

Crack Growth

Prediction of Crack Growth and Fatigue Strength of Repaired Components
Subproject C5 extends the developed crack propagation model to tetrahedral elements, such that a whole blade/blisk can be modeled using the multi-scale projection method. After developing a temperature dependent elastoplatistic material model, ductile fracture is taken into account. Especially temperature induced strains cause unphysical crack face penetration, which is avoided by the implementation of an appropriate contact model. Contacting crack faces allow heat transfer through the crack face and thus have a major impact on crack growth.


C6 Aeroelasticity of Compressor Blisks

Regeneration-induced Variance of Aeroelastic Properties of Compressor Blisks
In research project C6 a 1.5-stage compressor blading for a blisk is designed, which allows flutter of the rotor blades at specific operating points. To investigate the influence of regeneration-induced variances on the aeroelastic properties, some blisks are modified by applying selected geometrical variances. Then the rotor shaft and the blisk disks are designed and manufactured. Extensive measurements are conducted to study the aeroelastic properties of the compressor blisks to derive physical relations between geometrical variance and aeroelastic behavior for flutter and forced response, respectively.