BrainMap

Stefan Sorohan

- UNIVERSITATEA NAȚIONALĂ DE ȘTIINȚĂ ȘI TEHNOLOGIE POLITEHNICA BUCUREȘTI

Researcher | Teaching staff | Scientific reviewer

Expertise & keywords

Innovative, efficient and reliable integrated systems producing renewable energy, based on smart design solutions and advanced SHM approach Call name: Joint Applied Research Projects - PCCA 2013 - call
PN-II-PT-PCCA-2013-4-0737 2014 - 2017

Role in this project: Key expert

Coordinating institution: UNIVERSITATEA POLITEHNICA DIN BUCURESTI

Project partners: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO); COMPOZITE S.R.L. (RO)

Affiliation: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO)

Project website: http://www.mechstruct.tk

Abstract:

The project proposes to create integrated installations for producing renewable energy aimed to cover the various needs of small to medium houses, farms, hotels or motels and institution existing in remote areas or areas where the energy infrastructure is bad, expensive to create/refurbish or exposed to harsh climatic and geological conditions. It will combine wind and solar - thermal and photovoltaic – energy generation, in order to ensure a high degree of flexibility and reliability in power supply in various meteorological and climatic conditions. The modular conception of these installations will assure easy mounting and adaptability to various conditions/requirements existing in the wide range of addressed end users. New or improved materials and maintenance procedures will be proposed and implemented, in an innovative approach, in order to increase in service reliability, at lower costs.

For fulfilling these ambitious performances, the project will be focused on several main objectives:

I. High aerodynamic effectiveness, aimed to make possible wind energy generation at a wide range of wind velocities. Special solutions will be in view for harvesting energy from low velocity winds and from high winds, always keeping high in service reliability on the side of aerodynamic loads.

II. Important advancements in the structural performance, through the use of well adapted composite materials, like sandwiches and other light structures, in the thin walled structural parts philosophy, leading to weight saving structures, with improved functionality, able to resist to harsh environmental conditions, easy to manufacture and repair, to mount and dismantle, ready to be recycled.

III. High in service structural reliability ensured by a comprehensive structural health monitoring (SHM) management. This will include implementation of damage tolerance and predictive maintenance approaches, substantiated by the development of innovative damage tolerant, improved non-destructive testing/evaluation/ inspection (NDT/NDE/NDI) techniques and repair technologies. Adequate NDI techniques, combining global and local inspections, will lead to improved, efficient maintenance.

IV. Improved solutions for the integrated management of energy inputs, by flexible use of electric and heat generators, in combination with smart, innovative energy storage solutions, adapted to variable wind and solar exposure conditions. One solution will put in value previous innovative products made by one member of the consortium.

V. Smart design solutions, aiming to produce customer shaped configurations of the green energy units and modular structures, easy to manufacture, mount and repair in various ground conditions, with adequate combination of advanced materials and on the shelf parts, aimed to minimize costs.

VI. Realization of one integrated installation, with intended performances averaging 5 KW output power and 100 kJ/hour thermal energy, serving as test bed for assessing the proposed solutions and developing improved variants.

VII. Continuous dissemination and co-operation activities, targeting steady updating of performances and penetration of national and international markets.

In pursuing these goals, the partners to be involved in this tentative project will fully take advantage from their previous experience, skills and valuable equipment acquired during a long raw of national and international projects and grants in the relevant topics. This proposed partnership worked very well in a good number of these actions, due to complementary approaches and proved honest share of responsibilities. Additionally, the project will create opportunities for students to take part in attractive research, design and market oriented activities and further work in academic, research or industrial environment.

Performant Applications of Functionally Graded Composites Call name: Joint Applied Research Projects - PCCA 2013 - call
PN-II-PT-PCCA-2013-4-1864 2014 - 2017

Role in this project: Key expert

Coordinating institution: UNIVERSITATEA POLITEHNICA DIN BUCURESTI

Project partners: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO); INTREPRINDEREA METALURGICA PENTRU AERONAUTICA METAV SA (RO); TEHNOMAG S.A. (RO)

Affiliation: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO)

Project website: http://bit.do/comgrad

Abstract:

Today, industry needs materials with complex properties, incoporate on the same structural component. Functionally Graded Materials (FGM) and Functionally Graded Composite Materials (FGCM), developed in the ComGrad project will be processed bu metal powders characterized by the absence of chemical segregation, high purity, fine and uniformly distributed carbides and fine microstructure which will properties will provide complex properties by wear resistance, toughness, ductility and superior job performance of conventional steels..

Objectives of the project are: (1) Establish simple rules of design and design of processing technologies of typical functional gradients for structural components subject of intense abrasive wear, adhesive wear, corrosion and fatigue; (2) Development of prototype industrial applications and demonstrate increase two to three times the performance of the service compared with conventional steels; (3) Demonstration of economic benefits to potential suppliers of fabrication sevices and structural components processed FGM / FGCM as well as users of molds, punches, tools processingof these materials; (4) Implementation in production in 2015, to the SMEs partner in of the manufacture of mold, tooling, punches, processed in FGM / FGCM.

Project implementation methodology is based on the development of five Work Packages (WP), namely, (WP1) Proiectare materiale cu Gradient Functional, (WP2) Designing technologies, processes, Experimental Models;(WP3) Execution (ME) and laboratory experiments, processing components of FGM / FGCM;

(WP4) Achievement prototype mechanical components in FGM / FGCM; patent and dissemination; (WP5) Project management.

Because of the complementary partners in the project, University Polytechnic of Bucharest - Research Center of Applied Mechanics SC IMA-METAV SA Bucuresti, SC TEHNOMAG SA Cluj Napoca, development of the Work Package will generate synergies that allow transforming of the technical knowledge accumulated in project in economic effects.

Modeling and and simulation of material behavior FGM / FGCM in (WP1) will allow gradual spatial architecture optimization of microstructure and providing the information based on which will determine the design rules of these materials. Active experiments achieved in the laboratory phase in (WP2) will assume developing technologies of cold/warm compacting to pressure between 400-700 MPa, sintering and sinterhardening to proper temperature with nature and chemical composition of matrices powders (850 0C, 11000C, 13000C), represing/die closed forging of sintered preforms, extrusion profiles, treatment heat treatment and treatment specific of surface engineering will provide the opportunity for analysis of the properties FGM / FGCM

Analysis of blanks properties FGM / FGCM will require complex laboratory investigations: optical microscopy- LOM, electron microscopy-SEM / TEM, mechanical testing, tests to abrasive wear by pin-on-disk method, adhesive wear by CALO-WEAR method, corrosion in seawater , fatigue resistance, electric arc resistance.

Modeling and in simulation of microstructure in gradual architecture (WP3) in the case of structural components, will allow optimization of the microstructural architecture and processing inl phase "batch ZERO" selected industrial applications of SMEs partner in the project from its own production program.

Properties of prototype industrial applications processed FGM / FGCM will be analyzed by the same laboratory investigations carried out in (WP2), but also by introduction in manufacturing and testing in real working condition of prototype industrial applications to partner SMEs thus ensuring technical transformation technical and scientific knowledge in economic effects.

Temperature sensor based on GHz operating AlN/Si SAW structures Call name: Joint Applied Research Projects - PCCA 2013 - call
PN-II-PT-PCCA-2013-4-0677 2014 - 2017

Role in this project: Key expert

Coordinating institution: INSTITUTUL NATIONAL DE CERCETARE- DEZVOLTARE PENTRU MICROTEHNOLOGIE - IMT BUCURESTI INCD

Project partners: INSTITUTUL NATIONAL DE CERCETARE- DEZVOLTARE PENTRU MICROTEHNOLOGIE - IMT BUCURESTI INCD (RO); INSTITUTUL NATIONAL DE CERCETARE - DEZVOLTARE PENTRU FIZICA MATERIALELOR BUCURESTI RA (RO); UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO); ROM-QUARTZ S.A. (RO)

Affiliation: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO)

Project website: http://www.imt.ro/setsal

Abstract:

The main objective of this project consists in the manufacturing of the first temperature sensor based on a SAW type device on AlN/Si. The sensor is based on the variation of the SAW resonance frequency vs. temperature. The sensor will be characterized ”on wafer” in the 25-150 oC temperature range. The sensor structures mounted on a special ceramic carrier, provided with SMA connectors and cables, will be characterized in the 5-500 K temperature range inside a cryostat. We aim to obtain a sensitivity >75 ppm/oC (on-wafer measurements) and 60 ppm/ oC for measurements with connectors and cables, in the 23-150 oC temperature range.

The project corresponds to the world wide effort to obtain acoustic devices operating in the gigahertz frequency range, using wide band gap semiconductors (AlN, GaN). These materials have very good piezoelectric properties. High quality GaN and AlN layers grown or deposited on Sapphire SiC or Si substrate permits to use in the fabrication protocol nanolithography, micromachining techniques and monolithic integration. The advantage of using AlN for the SAW structure consist in the possibility to obtain a higher resonance frequency and a higher sensitivity for the sensor. The project has few objectives beyond the state of the art.

The main element will be a SAW structure on AlN/Si with the resonance frequency in the 6-9 GHz range. The highest resonance frequency obtained up to now for SAW structures on AlN/Si is 5.1 GHz and was reported by the IMT and INCD-FM groups, partners in this project, using an IDT structure with digits and interdigit spacing 300 nm wide. This project requires interdigitated transducers having the digit/interdigit spacing 80-150 nm wide, a challenge due to the major difficulties of the nanolithographyic process on materials like AlN or GaN. Up to now, the narrowest lines on AlN have been reported on an AlN/Diamond based SAW structure in 2012 (200 nm).

For the proposed sensor a „single resonator” structure will be developed. Compared with classical structures based on face-to-face resonators and delay lines, the single resonator structure offers few advantages: higher quality factor, lower losses and mainly, higher values for the sensitivity, as it was recently proved by IMT for GaN.

A two steps, low temperature, deposition process will be developed, for the synthesis of thin AlN films. The goal is to lower the FWHM of rocking curve at 1.5° for the AlN films deposited on Si.

There is a potential advantage of monolithic integration of the SAW based AlN temperature sensor in a CMOS ICs. AlN technology is CMOS compatible, due to its low deposition temperature. In such circuits fabrication protocols contain nanolithographic processes, therefore these processes for the sensor will not add significant costs.

The project consortium consists in four teams with excellent expertise and complementarity in the project topics. The IMT team has many contributions in the state of the art for acoustic devices on GaN and AlN, in nanolithography and microwave characterization. INCD-FM has an excellent expertise in high quality AlN films deposition. UPB has excellence expertise in design and modelling of high frequency devices and circuits. ROMQUARZ is the only Romanian enterprise with an authentiq experience in SAW type devices manufacturing on classical piezoelectric materials.They have been involved in SAW devices manufacturing on non-semiconductor materials (quartz, lithium niobate, etc) in the last 20 years.

Advanced Tools and Methodologies for the Multiphysics Modelling and Simulation of RF MEMS Switches Call name: Joint Applied Research Projects - PCCA-2011 call, Type 1
PN-II-PT-PCCA-2011-3.1-0842 2012 - 2016

Role in this project:

Coordinating institution: UNIVERSITATEA POLITEHNICA DIN BUCURESTI

Project partners: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO); INSTITUTUL NATIONAL DE CERCETARE- DEZVOLTARE PENTRU MICROTEHNOLOGIE - IMT BUCURESTI INCD (RO)

Affiliation: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO)

Project website: http://mems.lmn.pub.ro

Abstract:

The topic is related to the 2012 work programme for ICT of the European Commission which emphasizes the need for more integration on functionalities on chips, requiring new software development technologies and parallelisation tools. The main goal is the development of knowledge in the RF-MEMS domain by fundamental and applicative research finalized with a new modelling methodology validated by experiments, aiming to efficiently couple electromagnetic, mechanical and fluid flow phenomena for the design of RF-MEMS switches. Models of manageable size for a set of benchmarks will be manufactured and characterized. The models will account for the dependence on relevant design or operating parameters and their behaviour will be experimentally validated.

Depending on the complexity of the structures and on the target applications certain steps in the fabrication process can suffer modifications (e.g. deposition of a Benzocyclobutene (BCB) layer on the Silicon substrate, BCB representing an important determinant of package reliability), which could represent a novelty for the technological process. The target is to obtain a functional switch that can be further integrated. The structure of the switch beam must be chosen so as to produce the lowest possible insertion loss (less than -1 dB), the highest possible isolation (more than 20 dB at 20GHz), lowest possible actuation voltage (25 - 30 V) that operates up to 60 GHz. The project aims to demonstrate potential benefits of using supercomputing in the design of RF-MEMS devices, improve design capabilities for RF-MEMS MMIC technology in Romania and achieve an efficient transfer of knowledge in both directions between a research institute which is more industry oriented (IMT) and a university team specialized in high frequency modelling and high performance computing (UPB).

HIGH PERFORMANCE LIGHTWEIGHT PANELS WITH A NEW OPTIMIZED DESIGN FOR ADVANCED AIRCRAFT STRUCTURES Call name: Joint Applied Research Projects - PCCA-2011 call, Type 2
PN-II-PT-PCCA-2011-3.2-0068 2012 - 2016

Role in this project: Project coordinator

Coordinating institution: UNIVERSITATEA POLITEHNICA DIN BUCURESTI

Project partners: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO); STRAERO-(INSTITUTUL PENTRU CALCULUL SI EXPERIMENTAREA STRUCTURILOR AERO-ASTRONAUTICE) S.A. (RO); UNIVERSITATEA POLITEHNICA TIMIŞOARA (RO); INAS S.A. (RO); SMART MECHANICS S.R.L. (RO)

Affiliation: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO)

Project website: http://www.panouri-compozite-aviatie.ro

Abstract:

The aim to design a structure as light as possible, but without reducing its strength, stiffness and stability can be achieved by using sandwich composite components.The proposed project has innovative ideas based on: 1) identification of new mechanical interconnection solutions for the skins, using elements that cross the core of the sandwich, which are simpler, more cost efficient than those currently in use; 2) design of sandwich panels having an ultralight core spatially folded, or having double or triple core; 3) hybrid assembly solutions of sandwich panels having the core and skins made of dissimilar materials. Three new, original, types of lightweight plane sandwich panels, with increased strength, are proposed as follows: an aluminum one with “truss” type core, having a new geometry; a composite panel with carbon fiber reinforced skins and core having gradual properties made out of three or five layers of different polymeric foams; an orthotropic panel with core made out of polymeric tubes. The curved sandwich panels to be proposed represent innovative solutions with optimized geometries: a metallic cylindrical panel with a network type core made out of aluminum profiles intersected and built-in the polymeric foam, and a spherical panel made out of carbon fiber reinforced composite skins, joined together by using a “truss” type core. Experimental (static and cyclic testing of some joints) and numerical (linear and nonlinear 3D parametric FEM modeling for optimization) means of analysis will be used during the development of the project. Finally, the produced models made from these new sandwich composites will be tested experimentally. Registration of at least two requests of patents concerning the original construction solutions developed within the project will demonstrate the deliverables of this project. Internal homologation of the final products and technologies used by the manufacturing partner will prove the soundness of the engineering applications.

Next generation of epoxies for structural applications: nanocomposites with enhanced strength and toughness Call name: Exploratory Research Projects - PCE-2011 call
PN-II-ID-PCE-2011-3-0120 2011 - 2016

Role in this project: Key expert

Coordinating institution: Universitatea Politehnica Bucuresti

Project partners: Universitatea Politehnica Bucuresti (RO)

Affiliation: Universitatea Politehnica Bucuresti (RO)

Project website: http://www.nanocompozite.ro

Abstract:

Epoxies are used today in a variety of applications such as coatings, adhesives and composites. A major limitation of these materials is their low toughness and reduced fatigue resistance. The central objective of this project is to fundamentally modify the mechanical behavior of epoxy by controlling its structure on multiple scales via cross-link density control and filling with nanoscale additives. Carbon nanotubes, graphene and carbon black will be considered as fillers.

The resulting material will have enhanced toughness and crack growth resistance, without reduction in strength. The central concept is to exploit the interplay between the heterogeneity of the base epoxy molecular network and that due to the distribution of nanofillers to create multiscale structures which exhibit enhanced toughness and strength. To this end we propose a combined experimental and modeling and simulation program. Modeling will be used to identify the optimal structure. We will fabricate these systems and use experimental data to validate models and test predictions.

This collaboration between US and Romanian partners is based on preliminary work in this area performed over the last decade at Rensselaer Polytechnic Institute, and brings together participants with expertise in nanocomposites, multiscale modeling of polymers, testing and characterization, as well as a participant from industry. The proposal includes technology transfer and dissemination components, and a management plan.

HIGH TOUGHNESS NANOPRECIPITATED MICROALLOYED STEELS Call name: Joint Applied Research Projects - PCCA-2011 call, Type 2
PN-II-PT-PCCA-2011-3.2-1018 2012 - 2016

Role in this project: Key expert

Coordinating institution: METAV - CERCETARE DEZVOLTARE S.R.L.

Project partners: METAV - CERCETARE DEZVOLTARE S.R.L. (RO); UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO); FORJA ROTEC SRL (RO)

Affiliation: UNIVERSITATEA POLITEHNICA DIN BUCURESTI (RO)

Project website: http://www.metav-cd.ro/ToughNanoMicrAl

Abstract:

Microalloyed (MA) steels are suitable as a replacement for plain carbon steels grades due to their ability to achieve final engineering properties in as hot-rolled condition eliminating the next heat treatments. Compared to the quenched and tempered steels at the same hardness, MA steels have much lower toughness so their further use is restricted to parts not subjected to impact.

The main goal of this project is to develop new microllaoyed steel class with improved toughness and formability as a replacement for low and medium alloyed heat treatable steels. The most innovative aspect of the project will be to use deformation induced ferrite transformation (DIFT) as a way to obtain nanosized Fe3C precipitates and fine ferrite grains.

The research work will be oriented on two main direction:

1. Manipulating the chemical composition considering the factors that influence mechanical characteristics of MA steels, particularly toughness

2. Thermomechanical processing of steel bars in order to obtain advanced grain refinement, for enhanced toughness.

To achieve the project goals several stages will be performed, as follows:

-Identification of solutions to enhance toughness and development of a theoretical model for chemical composition, structure and morphology:

- Development of a laboratory technology in order to obtain high toughness microalloyed steels in specified compositional domains.

- Setting of the thermomechanical processing regime in order to conduct the forging process within warm-forging temperatures for a further enhancement of toughness.

- Industrial applications of high toughness microalloyed steels for warm-forged automotive parts

The new high toughness steels will be the choice for automotive forged parts requiring impact resistance, such as truck side rails, steering links and telescoping crane booms, replacing heat treatable steels thus eliminating the need to subsequent heat treatment with significant cost reduction.

FILE DESCRIPTION	DOCUMENT
List of research grants as project coordinator or partner team leader
Significant R&D projects for enterprises, as project manager
R&D activities in enterprises
Peer-review activity for international programs/projects