Determination of mechanical properties of alloy steel 30Kh2SN2MFA according to the instrumented indentation results

Проведено комплексні дослідження механічних властивостей легованої високоміцної сталі 30Х2СН2МФА з використанням методики інструментованого індентування. З листової заготовки було виготовлено партії зразків у різних напрямках для проведення металографічних досліджень, випробувань на одновісний розтяг, інструментоване індентування та твердість. Випробування проведено на сучасному експериментальному обладнанні з використанням сучасних методик та нормативних документів. Для досліджуваного матеріалу отримано значення твердості за Брінеллем шляхом осереднення результатів десяти вимірювань на поверхнях зразків у трьох напрямках. Проведено співставлення значень умовної границі текучості σ0,2 та границі міцності σв сталі 30Х2СН2МФА, отриманих методом інструментованого індентування та за результатами випробувань на одновісний розтяг. Відхилення в отриманих результатах не перевищує 5%. При цьому відхилення значень механічних характеристик, визначених у двох взаємно перпендикулярних напрямках складає до 3,2% σ0,2 і 12% для σв. Зменшення значень мікротвердості НV, твердості НВ та границі міцності, визначеної методом інструментального індентування, в поверхневих шарах прокату зумовлене їх зневуглецюванням та відповідно іншою мікроструктурою в порівнянні з центральною зоною, що було виявлено на основі хімічного та металографічного аналізу. Отримані результати свідчать про придатність методу інструментованого індентування до визначення механічних характеристик подібного класу сталей та можуть бути використані при чисельному моделюванні відповідальних деталей та елементів складних конструкцій спеціального призначення для прогнозування їх працездатності.The possibility of using the instrumented indentation method in mechanical engineering on the example of steel 30KH2SN2MFA is substantiated. The mechanical properties obtained by the instrumented indentation method are confirmed by the results of uniaxial tension tests. The deviation of the strength properties determined using the instrumented indentation method from the results of tensile tests does not exceed 5%

High-resolution modal analysis

Usual modal analysis techniques are based on the Fourier transform. Due to the Delta T . Delta f limitation, they perform poorly when the modal overlap mu exceeds 30%. A technique based on a high-resolution analysis algorithm and an order-detection method is presented here, with the aim of filling the gap between the low- and the high-frequency domains (30%<mu<100%). A pseudo-impulse force is applied at points of interests of a structure and the response is measured at a given point. For each pair of measurements, the impulse response of the structure is retrieved by deconvolving the pseudo-impulse force and filtering the response with the result. Following conditioning treatments, the reconstructed impulse response is analysed in different frequency-bands. In each frequency-band, the number of modes is evaluated, the frequencies and damping factors are estimated, and the complex amplitudes are finally extracted. As examples of application, the separation of the twin modes of a square plate and the partial modal analyses of aluminium plates up to a modal overlap of 70% are presented. Results measured with this new method and those calculated with an improved Rayleigh method match closely

MODEL ELEMENTÓW SKOŃCZONYCH DO ANALIZY CHARAKTERYSTYK DRGAŃ ŁOPAT WIRNIKA OSŁONIĘTEGO

The paper presents the approaches to FE modelling of blade airfoil, contact between the shrouds and operational damage. The regularities are established concerning the influence of the finite element type, finite element mesh and model of contact interaction on the spectrum of natural frequencies of blade assemblies. The use of the developed computational models is substantiated to determine the forced vibration characteristics of the selected objects of investigation. Based on the performed numerical experiments it was substantiated of finite element model selection for analysis of characteristics of shrouded rotor blade vibrations.W artykule przedstawiono podejścia do modelowania elementów skończonych płata łopaty, styku osłon oraz uszkodzeń eksploatacyjnych. Ustalono prawidłowości dotyczące wpływu typu elementu skończonego, siatki elementów skończonych oraz modelu interakcji stykowej na widmo częstotliwości drgań własnych zespołów łopatek. Uzasadnione jest wykorzystanie opracowanych modeli obliczeniowych do wyznaczania charakterystyk drgań wymuszonych wybranych obiektów badań. Na podstawie przeprowadzonych eksperymentów numerycznych uzasadniono wybór modelu elementów skończonych do analizy charakterystyk drgań osłoniętych łopat wirnika

Cyclic thermal creep model for the bodies of revolution

The new method of solving thermal creep problems, accounting for cyclic variations of external force and thermal fields was put forward. Asymptotic expansions and period averagings were used to derive the systems of basic and auxiliary equations. The equation of state for cyclic thermal creep was proposed and validated. Numerical simulation of the creep of cylinders under cyclic temperature variations was carried out

A practical guide on using SPOT-GPR, a freeware tool implementing a SAP-DoA technique

This is a software paper, which main objective is to provide practical information on how to use SPOT-GPR release 1.0, a MATLAB®-based software for the analysis of ground penetrating radar (GPR) profiles. The software allows detecting targets and estimating their position in a two-dimensional scenario, it has a graphical user interface and implements an innovative sub-array processing method. SPOT-GPR was developed in the framework of the COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” and is available for free download on the website of the Action (www.GPRadar.eu)

Removal of the phase noise in the autocorrelation estimates with data windowing

13th European Signal Processing Conference, EUSIPCO 2005; Antalya; Turkey; 4 September 2005 through 8 September 2005The sinusoidal frequency estimation from short data records based on Toeplitz autocorrelation (AC) matrix estimates suffer from phase noise. This effect becomes prominent especially when additive noise vanishes becoming a nuisance, that is at high signal-to-noise ratios (SNR). Based on both analytic derivation of the AC lag terms and simulation experiments, we show that data windowing can mitigate the limitations caused by the phase noise. Thus with proper windowing, the variance of the frequency estimate is no more limited by phase noise, but it continues to decrease linearly with the SNR. The cases of the Pisarenko frequency estimator and of MUSIC, both for the single sinusoid case, are analyzed in detail

Inventions of Scientists, Engineers and Specialists from Different Countries in the Area of Nanotechnologies. Part VI

Introduction. Advanced technologies impress people\u27s imagination demonstrating the latest achievements (materials, methods, systems, technologies, devices etc.) that dramatically change the world. This, first of all, concerns nanotechnological inventions designed by scientists, engineers and specialists from different countries. Main part. The article provides an abstract overview of inventions of scientists, engineers and specialists from different countries: Russia, USA, China, Kazakhstan, Sweden. The results of the creative activity of scientists, engineers and specialists, including inventions in the field of nanotechnology and nanomaterials allow, when introduced to industry, achieving a significant effect in construction, housing and communal services, and related sectors of the economy. For example, the invention \u27A method to obtain polymer-composite material and a composite reinforcement \u3e\u3e relates to construction materials and is designed to reinforce building structures, that allows obtaining strengthened stressed composite reinforcement with improved physical-mechanical characteristics, increased resistance to aggressive environments. A method to obtain polymer-composite material is a multi-stage production of colloid solution on the basis of epoxy resin with addition of carbon nanotubes and applying heat and ultrasound impact. Introduction of modifiers (fillers) in polymer matrix in a certain ratio and fillers orientation make it possible to create a polymer strengthened for mechanical loads and with increased resistance to aggressive media (acid-resistance and alkali-resistance). The following inventions in the field of nanotechnology can also be interesting for specialists: a method to obtain biocide suspension applied on wallpaper and wall finishings, a method of aerosol spraying of nanoparticles in constant electric field, a method to obtain amorphous nanostructured diamond-like coating, a polymer composite heat-conducting paste with nanofiber modifier, a plant to provide controlled electroimpulse obtaining of nanoparticles of current conducting materials, etc. Conclusion. One of the most challenging tasks the economy of every country faces is to increase industrial competitiveness through technological upgrade. From the side of the state and companies the principal object to control in this process are the people and enterprises dealing with introduction of inventions and new technologies