Process modelling of weld repair in aeroengine components

Weld repair is a specific application of fusion welding processes adopted to correct defects which arise during the manufacturing process of aeroengine components and, also, to repair damage in order to extend the operative life, if safe and correctly performed. The operation is carried out by removing the anomaly and re-filling the slot with a fusion welding process. The thermal cycles induced by fusion welding processes produce undesirable residual stresses, which significantly affect the fatigue life of the component and, in some cases, they may give a larger contribution to the total stress field than the stresses caused by the service loads themselves. Based on the sequentially coupled thermo-mechanical analysis, two numerical methodologies have been implemented to simulate the residual stress field induced by weld repair operations. Differently from models presented in the literature, the modelling approaches allow taking into account the pre-existing stress in the component subjected to the weld repair. The experimental work to validate the numerical models involved a full thermal characterization of the welding apparatus used to produce the welds. Residual stress predictions were validated by means of neutron diffraction measurements using the most advanced diffractometer, ENGIN-X, available at ISIS neutron source at the Rutherford Appleton Laboratory. The model can be used a priori, in the attempt of mitigating the effects of the repair operations on the final residual stress field. It can also be used a posteriori, with the aim of determining the stress state in the component, producing the input for the analysis of the fatigue life. In order to prove the applicability of the numerical methodology in the case of aeroengine components, the model was used to study a weld repair in a demonstrative case study. The effects of number and direction of passes were investigated in the weld repair of a laser beam weld in a stainless steel pipe. It was concluded that the interaction between the pre-existing stress in a component and the stress induced by weld repair operations cannot be generalized and established a priori. Numerical models that simulate the process by neglecting the history of the components, ignore the contribution of the pre-existing stress to the final residual stress distribution. Predictions from such models approximate the global stress distribution in the component. The entire characterization of the residual stress field in a component that undergoes a weld repair operation can only be achieved by using models which take into account the pre-existing stress

Numerical simulation of residual stresses induced by weld repair in a stainless steel pipe considering the influence of an initial fabrication weld

This work presents the application of a finite element (FE) model developed to simulate the repair process in the case of components with a pre-existing stress state. The approach is tested in the case of a repair of a laser beam weld in a stainless steel pipe with the region of repair located in the heat affected zone of the original weld. The area of the repair is removed and refilled testing different approaches in terms of the number, and direction of the repair passes. The comparison between the refilling procedures is presented with the aim of evaluating the effects on the final residual stress distribution

Numerical simulation of residual stresses induced by weld repair in a stainless steel pipe considering the influence of an initial fabrication weld

This work presents the application of a finite element (FE) model developed to simulate the repair process in the case of components with a pre-existing stress state. The approach is tested in the case of a repair of a laser beam weld in a stainless steel pipe with the region of repair located in the heat affected zone of the original weld. The area of the repair is removed and refilled testing different approaches in terms of the number, and direction of the repair passes. The comparison between the refilling procedures is presented with the aim of evaluating the effects on the final residual stress distribution

FE modelling strategies of weld repair in pre-stressed thin components

Two computational procedures have been developed in the commercial finite element (FE) software codes Sysweld and Abaqus to analyse and predict the residual stress state after the repair of small weld defects in thin structural components. The numerical models allow the effects of the repair to be studied when a pre-existing residual stress field is present in the fabricated part and cannot be relieved by a thermal treatment. In this work the modelling strategies are presented and tested by simulating a repair of longitudinal welds in thin sheets of Inconel 718 (IN718). Although the numerical strategies in the two codes are intrinsically different, the results show a significant agreement, predicting a notable effect imposed by the initial residual stress

An experimental and numerical investigation on the process efficiency of the focused TIG welding of Inconel 718 thick plates

A combined experimental and numerical approach was adopted to investigate the focused tungsten inert gas (TIG) welding process by producing bead-on-plate welds in Inconel 718 plates. Experimental investigations were carried out by means of thermocouple measurements and optical macrographs of the weld cross-section. Three dimensional finite element (FE) simulations were conducted using the commercial specialized FE software Sysweld in order to predict the thermal field induced by the process in the plates. The work presents an approach to investigate the process efficiency and calibrate the heat source model in order to produce a full thermal characterization the plasmatron welding apparatus

Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an

Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation

One of the ways in which legal services are financed, and indeed shaped, is through private insurance arrangement. Two contrasting types of legal expenses insurance contracts (LEI) seem to dominate in Europe: before the event (BTE) and after the event (ATE) legal expenses insurance. Notwithstanding institutional differences between different legal systems, BTE and ATE insurance arrangements may be instrumental if government policy is geared towards strengthening a market-oriented system of financing access to justice for individuals and business. At the same time, emphasizing the role of a private industry as a keeper of the gates to justice raises issues of accountability and transparency, not readily reconcilable with demands of competition. Moreover, multiple actors (clients, lawyers, courts, insurers) are involved, causing behavioural dynamics which are not easily predicted or influenced. Against this background, this paper looks into BTE and ATE arrangements by analysing the particularities of BTE and ATE arrangements currently available in some European jurisdictions and by painting a picture of their respective markets and legal contexts. This allows for some reflection on the performance of BTE and ATE providers as both financiers and keepers. Two issues emerge from the analysis that are worthy of some further reflection. Firstly, there is the problematic long-term sustainability of some ATE products. Secondly, the challenges faced by policymakers that would like to nudge consumers into voluntarily taking out BTE LEI

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Search for stop and higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top-quark (stop) and the Higgs boson (higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 inverse femtobarns of proton-proton collision data at sqrt(s) = 8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the stop mass below 360 to 410 GeV, depending on the higgsino mass