Evaluation and consideration of local specimen material properties in lifetime prediction of short fibre reinforced PA6T/6I

To exploit the full material potential of short fibre reinforced PA6T/6I, specific component calculations including aniso- tropic material behaviour is necessary. For this, different failure criteria and fatigue models are used to describe the behaviour during a component service life. This paper deals with the determination and consideration of fibre orientations for failure criteria and fatigue calculations. Therefore, a novel method to determine fibre orientation (FO) distributions across injection moulded plates, is proposed. The developed method allows a forecast of FOs for different specimen extraction positions and angles on injection moulded plates by using only a few measured reference points. As a result, fatigue models can be calibrated with the strength values and the corresponding FO, calculated for fracture position. The performed tests show a non-negligible influence of failure positions, due to fibre orientation distributions along the specimens. So, the FO determination method delivers an improvement in strength values estimation.

Influence of Turn-Rolling on the Residual Stresses and Microstructure of C45E and the Effects on Fatigue Life under Cyclic Loading

The microstructure and the residual stress state have a significant influence on the service life of the component. The deep rolling process already enables a significant increase in the strength and service life of highly stressed components. By using the hybrid manufacturing process of turn rolling, the edge zone properties can be influenced to such an extent that the service life is further increased compared to conventional deep rolling. In addition to a change in the residual stress state, the use of the turning process temperature also leads to a significant grain refinement in the edge zone area, which has a positive effect on the component service life. This modification of the edge zone can be significantly influenced by the machining speed.

Evaluating a Three-Dimensional Slot Design for the Combustor-Turbine Interface

As turbine inlet temperatures are pushed ever higher in an attempt to improve efficiency and power, it has become critical to cool component surfaces. One surface that is particularly difficult to treat because of the complex flow field that surrounds it is the nozzle guide vane endwall. Past studies have indicated that leakage bypass flow emerging from the combustor-turbine junction may be effectively harnessed for cooling purposes. When combined with endwall film-coolant injection, component service life may be significantly extended. This paper presents results from a computational study investigating a three-dimensional slot geometry at the combustor-turbine interface. The downstream edge of the slot was scalloped using a simple periodic function intended to enhance thermal benefit to the endwall by manipulating coolant distribution. Effects of varying the slot geometry amplitude and phase were investigated along with the slot nominal width and upstream distance from the vane. Initial results indicate dramatic effects can be realized depending upon the scalloping used.

Robust Damage-Mitigating Control of Mechanical Systems: Experimental Validation on a Test Apparatus

The goal of damage-mitigating control is to achieve high performance of operating machinery without overstraining the mechanical structures and the potential benefit is an increase in the component service life with no significant loss of performance. This paper presents the design of a test apparatus, the synthesis of a damage-mitigating control system, and the results of experimentation where the objective is to demonstrate the concept of fatigue damage reduction as an extension of multivariable robust feedback control. The test apparatus is built upon a three-degree-of-freedom, two-input three-output mechanical structure. The methodology of the damage-mitigating control synthesis is built upon the principles of: (i) frequency-domain identification of the plant dynamics and modeling of uncertainties in the state-space setting; and (ii) robust control based on the H∞ approach by taking both plant dynamic performance and material degradation of structural components into consideration. Case studies on the test apparatus indicate that fatigue life of specimens can be substantially extended with no appreciable degradation in the dynamic performance of the mechanical system.