АНАЛИЗ ПОВЕДЕНИЯ ТРЕХСЛОЙНОЙ ГОФРИРОВАННОЙ КОНСТРУКЦИИ ПРИ ЛИНЕЙНОМ ЗАКОНЕ ПОДАЧИ ДАВЛЕНИЯ

There was considered regime of forming for sandwich construction from titanium alloy that represents corrugated filling, inserted between two shell plates, by means of linear law of neutral gas supply. This gas entered in the area between filling and shells. There was offered simple model of process, based on the use of torque-free shell theory. There was offered numerical procedure of the main parameters of examined process. There was offered example of special calculation for titanium alloy VT6 (Ti–6Al–4V). The results of calculations on approximate formulae are correspond to numerical solution of boundary problem of recovery creep theory, obtained by means of software ANSYS.Рассмотрен режим деформирования трехслойной конструкции из титанового сплава, представляющей собой гофрированный наполнитель, помещенный между двумя листами обшивки, при линейном законе подачи инертного газа, поступающего в область между наполнителем и обшивками. Представлена упрощенная модель процесса, основанная на использовании безмоментной теории оболочек. Предложены алгоритмы расчета основных параметров рассматриваемого процесса. Приведен пример конкретного расчета для титанового сплава ВТ6 (Ti–6Al–4V). Результаты расчетов по приближенным формулам сопоставлены с численным решением краевой задачи теории ползучести, полученным в среде программного комплекса ANSYS

МЕТОДЫ РАСЧЕТА ПРОДОЛЖИТЕЛЬНОСТИ ПРОЦЕССА СВЕРХПЛАСТИЧЕСКОЙ ФОРМОВКИ КРУГЛОЙ МЕМБРАНЫ

The process of superplastic forming of a circular membrane under constant pressure is analyzed. The analytical process model is built based on principal assumptions of the thin shell theory, and two simplified approaches known from the literature and based on the hypothesis on the uniform thickness of a shell along its profile, and the uniform stretching of a meridian passing the dome apex. The methods of calculating the duration of superplastic forming of a circular membrane are considered. The finite element modeling of the process considered is made using the educational version of ANSYS software. The paper considers two boundary value problems stated in terms of superplasticity mechanics – the theory of creep and the theory of viscoplasticity. The results of analytical formula calculations are compared with the solutions of boundary value problems in terms of the creep and viscoplasticity theories obtained in the ANSYS software environment. The material constant values are determined from the results of uniaxial tests and test forming of Ti–6Al–4V titanium alloy. It is shown that test forming used to identify the material model provides much more appropriate results with the evaluation error reduced from ~20 % (when identifying the model based on the results of standard uniaxial mechanical tests) to ~3 %.Исследован режим сверхпластической формовки круглой мембраны при постоянном давлении. Математическая модель технологического процесса построена в рамках основных предположений безмоментной теории оболочек, а также двух известных из литературы упрощенных подходов, основанных на гипотезе о равнотолщинности оболочки по ее профилю и равнорастянутости меридиана, проходящего через полюс купола. Проанализированы методы расчета продолжительности процесса сверхпластической формовки круглой мембраны. Проведено конечно-элементное моделирование рассматриваемого процесса с использованием учебной версии программного комплекса ANSYS 10ED. В данной работе рассмотрены два варианта постановки краевой задачи механики сверхпластичности – теории ползучести и вязкопластичности. Результаты вычислений по аналитическим формулам сопоставлены с решениями краевых задач теории ползучести и вязкопластичности, полученными в среде программного комплекса ANSYS. Значения материальных постоянных были определены по данным одноосных испытаний и тестовых формовок титанового сплава ВТ6 (Ti–6Al–4V). Показано, что в том случае, если для идентификации модели материала используются тестовые формовки, результаты расчетов оказываются намного более корректными, а погрешность оценки снижается с уровня ~20 % (при идентификации модели по результатам стандартных одноосных механических испытаний) до ~3 %

Emulsion sheet doublets as interface trackers for the OPERA experiment

New methods for efficient and unambiguous interconnection between electronic counters and target units based on nuclear photographic emulsion films have been developed. The application to the OPERA experiment, that aims at detecting oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is reported in this paper. In order to reduce background due to latent tracks collected before installation in the detector, on-site large-scale treatments of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd) packages, each made of a doublet of emulsion films, have been designed, assembled and coupled to the OPERA target units ("ECC bricks"). A device has been built to print X-ray spots for accurate interconnection both within the CSd and between the CSd and the related ECC brick. Sample emulsion films have been extensively scanned with state-of-the-art automated optical microscopes. Efficient track-matching and powerful background rejection have been achieved in tests with electronically tagged penetrating muons. Further improvement of in-doublet film alignment was obtained by matching the pattern of low-energy electron tracks. The commissioning of the overall OPERA alignment procedure is in progress.Comment: 19 pages, 19 figure

The detection of neutrino interactions in the emulsion/lead target of the OPERA experiment

The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode through the study of $\nu_\mu\to\nu_\tau$ oscillations. The apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2007 and 2008 with the detector fully operational with its related facilities for the emulsion handling and analysis. After a brief description of the beam and of the experimental setup we report on the collection, reconstruction and analysis procedures of first samples of neutrino interaction events

First events from the CNGS neutrino beam detected in the OPERA experiment

The OPERA neutrino detector at the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode, through the study of nu_mu to nu_tau oscillations. The apparatus consists of a lead/emulsion-film target complemented by electronic detectors. It is placed in the high-energy, long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. In August 2006 a first run with CNGS neutrinos was successfully conducted. A first sample of neutrino events was collected, statistically consistent with the integrated beam intensity. After a brief description of the beam and of the various sub-detectors, we report on the achievement of this milestone, presenting the first data and some analysis results.Comment: Submitted to the New Journal of Physic

Measurement of the atmospheric muon charge ratio with the OPERA detector

The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used to measure the atmospheric muon charge ratio in the TeV energy region. We analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime during the 2008 CNGS run. We computed separately the muon charge ratio for single and for multiple muon events in order to select different energy regions of the primary cosmic ray spectrum and to test the charge ratio dependence on the primary composition. The measured charge ratio values were corrected taking into account the charge-misidentification errors. Data have also been grouped in five bins of the "vertical surface energy". A fit to a simplified model of muon production in the atmosphere allowed the determination of the pion and kaon charge ratios weighted by the cosmic ray energy spectrum.Comment: 14 pages, 10 figure

Study of the effects induced by lead on the emulsion films of the OPERA experiment

The OPERA neutrino oscillation experiment is based on the use of the Emulsion Cloud Chamber (ECC). In the OPERA ECC, nuclear emulsion films acting as very high precision tracking detectors are interleaved with lead plates providing a massive target for neutrino interactions. We report on studies related to the effects occurring from the contact between emulsion and lead. A low radioactivity lead is required in order to minimize the number of background tracks in emulsions and to achieve the required performance in the reconstruction of neutrino events. It was observed that adding other chemical elements to the lead, in order to improve the mechanical properties, may significantly increase the level of radioactivity on the emulsions. A detailed study was made in order to choose a lead alloy with good mechanical properties and an appropriate packing technique so as to have a low enough effective radioactivity.Comment: 19 pages, 11 figure

Observation of a first ντ\nu_\tau candidate in the OPERA experiment in the CNGS beam

The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) has been designed to perform the first detection of neutrino oscillations in direct appearance mode through the study of the $\nu_\mu\rightarrow\nu_\tau$ channel. The hybrid apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2008 and 2009. After a brief description of the beam, the experimental setup and the procedures used for the analysis of the neutrino events, we describe the topology and kinematics of a first candidate $\nu_\tau$ charged-current event satisfying the kinematical selection criteria. The background calculations and their cross-check are explained in detail and the significance of the event is assessed.Comment: 19 pages, 3 figure

Model for grain boundary sliding and its relevance to optimal structural superplasticity Part 5 - A unique numerical solution and its reliability

A few of the constitutive equations used to describe the mechanical response of superplastics are examined. The problems associated with the estimation of the values of the model constants are discussed. Attention is focused on the model for grain boundary sliding controlled optimal structural superplasticity recently proposed. A numerical procedure that allows the unambiguous determination of the material constants of this model is presented and validated by analysing the experimental data pertaining to a few systems. It is shown that this method allows the determination of the material constants with a limited number of experimental points. A comparison of the predictions with the experimental results shows that this model accurately describes optimal superplastic flow, for Regions I and II up to the point of inflection in the sigmoidal ln (stress)-ln (strain rate) curve. The advantages of the present method over others available in the literature are noted