Analysis of dynamics of bladed discs with monocrystalline anisotropic blades

The present study aims to quantify the effect of material anisotropic orientations on the dynamics of a gas turbine bladed disc with monocrystalline anisotropic blades (nickel-based superalloy DZ125). In consequence, a single blade finite element model has been created to analyse the effect of material anisotropy on the modal properties of a single blade of a gas turbine. Correspondingly, a finite element sector model with cyclic symmetry has been generated to analyse the influence of anisotropic material orientations on the natural frequency and mode shapes of a tuned bladed disc. Moreover, a whole bladed disc finite element model (tubed and mistuned) has been created to investigate the effect of anisotropic material orientations on the forced responses of a mistuned bladed disc of a gas turbine. Finally, 2D and 3D response charts have been plotted for different cases to analyse the variation of the natural frequency of a single blade and a tuned bladed disc respectively due to the variation of anisotropic orientations of the blade material. Also, normalised forced responses of the mistuned bladed disc with four different mistuning patterns have been plotted against a number of blades of the whole bladed disc. The outcome of these analyses indicates that the material anisotropy has a significant effect on the dynamic properties of a gas turbine bladed disc. In the case of a single blade, maximum frequency variation due to material anisotropy is found to be 5.3 % among the analysed cases. For tuned bladed disc, maximum frequency variation is found to be 5.1 % amongst the examined cases. Also, a discussion has been accomplished in terms of how Eulerian angles (primary and secondary angles) affects the natural frequency variations for different analysed cases of anisotropic orientations. Furthermore, amplification factor or normalised maximum forced responses are found to be within the range of 0.66 to 1.85 for the investigated cases of mistuned bladed disc with monocrystalline anisotropic blade material

Correction: Boruah, D.; Zhang, X. Effect of Post-Deposition Solution Treatment and Ageing on Improving Interfacial Adhesion Strength of Cold Sprayed Ti6Al4V Coatings. Metals 2021, 11, 2038

The authors wish to make the following corrections to this paper [...

Effect of post-deposition solution treatment and ageing on improving interfacial adhesion strength of cold sprayed Ti6Al4V coatings

This study aims at investigating the effect of post-deposition solution treatment and ageing (STA) on improving the interfacial adhesion strength in cold spray (CS) Ti6Al4V coatings deposited on Ti6Al4V substrates, measured by the adhesive-free collar-pin pull-off (CPP) test. Solution treatment was performed at 940 °C for 1 h and ageing was carried out at 480 °C for 8 h. Investigations were carried out for specimens with three different pre-treatments of the substrate surface, namely grit-blasted, as-machined (faced on lathe machine), and ground. Additionally, the effect of post-deposition STA was studied in terms of phase analysis, microstructure, and porosity level. It was observed that STA led to complete interfacial mixing resulting in significantly improved adhesion strength (by more than 520%) with the maximum measured value of greater than 766 MPa for ground substrates, reaching 81% of the ultimate tensile strength of mill annealed Ti6Al4V

An analytical method for predicting residual stress distribution in selective laser melted/sintered alloys

Residual stresses that build up during selective laser melting or sintering (SLM/SLS) process can influence the dimensional accuracy, mechanical properties and in-service performance of SLM/SLS parts. Therefore, it is crucial to understand, predict and effectively control residual stresses in a part. The present study aims at developing an analytical model to predict the through-thickness distribution of residual stresses in an SLM part-substrate system. The proposed model demonstrates how residual stresses built up in the substrate and previously deposited layers are related to the stress induced by a newly deposited layer, based on the stress and moment equilibrium requirements. The model has been validated by published experimental measurements and verified with existing analytical/numerical models. The outcomes of the study suggest that the proposed analytical model can be used for quick estimation of residual stress distribution and the order of magnitude

Theoretical prediction of residual stresses induced by cold spray with experimental validation

Purpose: The purpose of this paper is to develop a simple analytical model for predicting the through-thickness distribution of residual stresses in a cold spray (CS) deposit-substrate assembly. Design/methodology/approach: Layer-by-layer build-up of residual stresses induced by both the peening dominant and thermal mismatch dominant CS processes, taking into account the force and moment equilibrium requirements. The proposed model has been validated with the neutron diffraction measurements, taken from the published literature for different combinations of deposit-substrate assemblies comprising Cu, Mg, Ti, Al and Al alloys. Findings: Through a parametric study, the influence of geometrical variables (number of layers, substrate height and individual layer height) on the through-thickness residual stress distribution and magnitude are elucidated. Both the number of deposited layers and substrate height affect residual stress magnitude, whereas the individual layer height has little effect. A good agreement has been achieved between the experimentally measured stress distributions and predictions by the proposed model. Originality/value: The proposed model provides a more thorough explanation of residual stress development mechanisms by the CS process along with mathematical representation. Comparing to existing analytical and finite element methods, it provides a quicker estimation of the residual stress distribution and magnitude. This paper provides comparisons and contrast of the two different residual stress mechanisms: the peening dominant and the thermal mismatch dominant. The proposed model allows parametric studies of geometric variables, and can potentially contribute to CS process optimisation aiming at residual stress control

Artificial neural network based modelling of internal combustion engine performance

The present study aims to quantify the applicability of artificial neural network as a black-box model for internal combustion engine performance. In consequence, an artificial neural network (ANN) based model for a four cylinder, four stroke internal combustion diesel engine has been developed on the basis of specific input and output factors, which have been taken from experimental readings for different load and engine speed circumstances. The input parameters that have been used to create the model are load, engine speed (RPM), fuel flow rate (FFR) & air flow rate (AFR); contrariwise the output parameters that have been used are brake power (BP), brake thermal efficiency (BTE), volumetric efficiency (VE), brake mean effective pressure (BMEP) and brake specific fuel consumption (BSFC). To begin with, databank has been alienated into training sets and testing sets. At that juncture, an ANN based model has been developed using training dataset which is based on standard back-propagation algorithm. Subsequently, performance and validation of the ANN based models have been measured by relating the predictions with the experimental results. Correspondingly, four different statistical functions have been used to examine the performance and reliability of the ANN based models. Moreover, Garson equation has been used to estimate the relative importance of the four different input variables towards their specific output. The results of the model suggests that, ANN based model is impressively successful to forecast the performance parameters of diesel engines for different input variables with a greater degree of accurateness and to evaluate relative impact of input variables

Experimental investigation on the suitability of Karanja (Pongamia pinatta) biodiesel blends for engine application

It is now an established fact that bio-energy has the potential to augment a major part of the projected renewable energy provisions of the future. As the resources of petroleum are depleting with the increasing demand for fuels, bio-energy has come up as an effective means to supplement this energy demand as well as to mitigate the problem of environmental pollution. In respect of engine derived energy, biofuels viz. biodiesel is gaining prominence as alternative diesel fuel for its good quality exhaust, biodegradability and sustainability. Many feedstocks for biodiesel production have been investigated and experimented with. The feedstock characteristics, which are spatially varying, have a considerable effect on the biodiesel characteristics as well as the engine performance. In this study, fuel characteristics of bio-oil extracted from locally available Karanja (Pongamia pinnata) were evaluated and compared with petroleum diesel. Various fuel properties were evaluated according to ASTM standards. An experimental study was then undertaken to investigate the performance of a diesel engine using blends (B5, B20, B40, B60) of the extracted bio-oil. A comparative study of the engine performance, using different blends of the bio-oil and diesel, in terms of fuel power, indicated power, brake power, frictional power, brake thermal efficiency, indicated thermal efficiency, volumetric efficiency, relative efficiency, mean effective pressure, fuel consumption, specific fuel consumption, air consumption and specific output, was carried out. It was observed that the use of the biodiesel blends resulted in engine performance comparable to pure diesel, which suggests the suitability of Karanja biodiesel blends for engine application