Andrea Sili | University of Messina (original) (raw)
Papers by Andrea Sili
Welding International, 2005
ABSTRACT The aim of this study was to identify the appropriate parameters for laser welding of st... more ABSTRACT The aim of this study was to identify the appropriate parameters for laser welding of steel plates. The mechanical characteristics and metallurgical microstructures of the joints were analysed experimentally. Welded joints were made using two different types of steel (Cr–Mo low-alloy steel and austenitic stainless steel). Samples were cut from the welds and examined macrographically and micrographically; tensile and microhardness tests were also performed. Observation of these samples showed the beneficial effects of narrower molten and heat-affected zones and the consequent advantageous reductions in distortions and residual stresses. On the basis of these experimental results we conclude that both ferritic and austenitic steels can be properly welded, with good mechanical and metallurgical results, using consumable inserts pre-fitted to the edges before welding, provided that suitable welding parameters are chosen.
Archive: Proceedings of The Institution of Mechanical Engineers, Part D: Transport Engineering 1984-1988 (vols 198-202), 1988
ABSTRACT When evaluating the performances of railway brake discs, the ability to accumulate and s... more ABSTRACT When evaluating the performances of railway brake discs, the ability to accumulate and spread heat to the air plays a major role, since wear of synthetic lining and disc deterioration are strongly dependent on maximum temperatures attained on the surface in contact with the friction pad.
Journal of Nuclear Materials, 1996
This work deals with a non-destructive method for mechanical tests which is based on the indentat... more This work deals with a non-destructive method for mechanical tests which is based on the indentation of materials at a constant rate by means of a cylinder with a small radius and penetrating flat surface. The load versus penetration depth curves obtained using this method have shown correspondences with those of tensile tests and have given indications about the mechanical properties on a reduced scale. In this work penetration tests have been carried out on various kinds of Cr martensitic steels (MANET-2, BATMAN and modified F82H) which are of interest for first wall and structural applications in future fusion reactors. The load versus penetration depth curves have been examined with reference to data obtained in tensile tests and to microhardness measurements. Penetration tests have been performed at various temperature (from -180 to 100°C). Conclusions, which can be drawn for the ductile to brittle transition, are discussed for MANET-2 steel. Preliminary results obtained on BATIVIAN and modified F82H steels are reported. The characteristics of the indenter imprints have been studied by scanning electron microscopy. cations in future fusion reactors, are presented and discussed.
Fusion Engineering and Design, 2001
FIMEC is an indentation test, which permits the evaluation of yield and ultimate tensile stress a... more FIMEC is an indentation test, which permits the evaluation of yield and ultimate tensile stress and to draw indication about the ductile to brittle transition temperature. The apparatus has been recently implemented with a feedback system to maintain strictly constant the penetration speed of cylindrical punch during the test. So, experiments performed on several materials, as those for first wall
Journal of Nuclear Materials, 1994
By the use of suitable cylindrical indenters with flat surface and constant penetration rates, lo... more By the use of suitable cylindrical indenters with flat surface and constant penetration rates, load versus penetration depth curves are obtained which show correspondence with the stress-strain curves of the tensile tests for some materials examined. After an initial linear stage, a limit load of uu is reached after which a stage of work-hardening occurs with a trend comparable to the one of the tensile test. The limit load uu z 3u,,, uY being the yielding load of the tensile test. For penetration rates = 100 km/min, the loads of the work-hadening stage above (+" tend to saturation values comparable to the loads of hardness only for some of the materials examined. With larger penetration rates, loads are reached well in excess above those of hardness. With metal-matrix composite alloys a stage with drops of load has been observed at the level of the loads of hardness.
Nondestructive Testing and Evaluation, 1993
... PRIMO GONDI*, GIANLUCA MATIOGNO and ANDREA SILl Mechanical Engineering Department, II Univers... more ... PRIMO GONDI*, GIANLUCA MATIOGNO and ANDREA SILl Mechanical Engineering Department, II University of Rome, 00173 Italy ... 256 P. GONDI ET AL monitoring by BN of stressed regions allowance has to be made for accompanying variations of the local microstructure. ...
Journal of Nuclear Materials, 1994
The effects of heat treatments at 700°C on the toughness behaviour have been investigated in MANE... more The effects of heat treatments at 700°C on the toughness behaviour have been investigated in MANET steel by means of Charpy impact tests and SEM observations with microanalysis. The ductile to brittle transition temperature, the upper shelf energy and the slope in the ductile to brittle transition depend strongly on the time of heating as a consequence of the different fracture mechanisms evolving with the thermal treatment. The transition, from fracture mainly conditioned by lath boundaries to fracture depending mainly on processes at the PAG boundaries, appears correlated with the specific characteristics of the distribution of the Cr atoms in solution.
Journal of Nuclear Materials, 1998
From Flat-top Cylinder Indenter for Mechanical Characterization (FIMEC) test yield stress and ten... more From Flat-top Cylinder Indenter for Mechanical Characterization (FIMEC) test yield stress and tensile strength can be obtained. Results regarding different materials, most of them of fusion interest, show the general validity of the method. Moreover, indication on the ductile to brittle transition temperature (DBTT) of martensitic steels has been drawn by performing tests at different temperatures. FIMEC offers the possibility
Key Engineering Materials, 2000
Journal of Nuclear Materials, 1996
The effect of the cooling rate ? from austenitic field on the microstructural evolution and the m... more The effect of the cooling rate ? from austenitic field on the microstructural evolution and the mechanical stability of MANET steel for increasing times of tempering at 700°C has been studied by means of Charpy tests, SEM observations with EDS microanalysis and X-ray diffraction analysis. The investigated rates f range from 150 to 36OO"C/min. The ductile to brittle transition temperature, the upper shelf energy and the slope A E/AT in the transition region depend on the time of treatment with variations more pronounced in samples slowly cooled. After tempering times of about 20 h at 700°C the samples cooled with f= lSO"C/min show a mixed mode of brittle fracture (quasi-cleavage and intercrystalline) with good correspondence between Cr-enriched zones and surfaces fractured in intercrystalline mode. Only quasi-cleavage mechanism is operative in samples quenched with f = 3600"C/min, which present fracture surfaces with uniform Cr distribution. The results are discussed on the basis of C-Cr associate distributions determined by internal friction tests.
Welding International, 2005
ABSTRACT The aim of this study was to identify the appropriate parameters for laser welding of st... more ABSTRACT The aim of this study was to identify the appropriate parameters for laser welding of steel plates. The mechanical characteristics and metallurgical microstructures of the joints were analysed experimentally. Welded joints were made using two different types of steel (Cr–Mo low-alloy steel and austenitic stainless steel). Samples were cut from the welds and examined macrographically and micrographically; tensile and microhardness tests were also performed. Observation of these samples showed the beneficial effects of narrower molten and heat-affected zones and the consequent advantageous reductions in distortions and residual stresses. On the basis of these experimental results we conclude that both ferritic and austenitic steels can be properly welded, with good mechanical and metallurgical results, using consumable inserts pre-fitted to the edges before welding, provided that suitable welding parameters are chosen.
Archive: Proceedings of The Institution of Mechanical Engineers, Part D: Transport Engineering 1984-1988 (vols 198-202), 1988
ABSTRACT When evaluating the performances of railway brake discs, the ability to accumulate and s... more ABSTRACT When evaluating the performances of railway brake discs, the ability to accumulate and spread heat to the air plays a major role, since wear of synthetic lining and disc deterioration are strongly dependent on maximum temperatures attained on the surface in contact with the friction pad.
Journal of Nuclear Materials, 1996
This work deals with a non-destructive method for mechanical tests which is based on the indentat... more This work deals with a non-destructive method for mechanical tests which is based on the indentation of materials at a constant rate by means of a cylinder with a small radius and penetrating flat surface. The load versus penetration depth curves obtained using this method have shown correspondences with those of tensile tests and have given indications about the mechanical properties on a reduced scale. In this work penetration tests have been carried out on various kinds of Cr martensitic steels (MANET-2, BATMAN and modified F82H) which are of interest for first wall and structural applications in future fusion reactors. The load versus penetration depth curves have been examined with reference to data obtained in tensile tests and to microhardness measurements. Penetration tests have been performed at various temperature (from -180 to 100°C). Conclusions, which can be drawn for the ductile to brittle transition, are discussed for MANET-2 steel. Preliminary results obtained on BATIVIAN and modified F82H steels are reported. The characteristics of the indenter imprints have been studied by scanning electron microscopy. cations in future fusion reactors, are presented and discussed.
Fusion Engineering and Design, 2001
FIMEC is an indentation test, which permits the evaluation of yield and ultimate tensile stress a... more FIMEC is an indentation test, which permits the evaluation of yield and ultimate tensile stress and to draw indication about the ductile to brittle transition temperature. The apparatus has been recently implemented with a feedback system to maintain strictly constant the penetration speed of cylindrical punch during the test. So, experiments performed on several materials, as those for first wall
Journal of Nuclear Materials, 1994
By the use of suitable cylindrical indenters with flat surface and constant penetration rates, lo... more By the use of suitable cylindrical indenters with flat surface and constant penetration rates, load versus penetration depth curves are obtained which show correspondence with the stress-strain curves of the tensile tests for some materials examined. After an initial linear stage, a limit load of uu is reached after which a stage of work-hardening occurs with a trend comparable to the one of the tensile test. The limit load uu z 3u,,, uY being the yielding load of the tensile test. For penetration rates = 100 km/min, the loads of the work-hadening stage above (+" tend to saturation values comparable to the loads of hardness only for some of the materials examined. With larger penetration rates, loads are reached well in excess above those of hardness. With metal-matrix composite alloys a stage with drops of load has been observed at the level of the loads of hardness.
Nondestructive Testing and Evaluation, 1993
... PRIMO GONDI*, GIANLUCA MATIOGNO and ANDREA SILl Mechanical Engineering Department, II Univers... more ... PRIMO GONDI*, GIANLUCA MATIOGNO and ANDREA SILl Mechanical Engineering Department, II University of Rome, 00173 Italy ... 256 P. GONDI ET AL monitoring by BN of stressed regions allowance has to be made for accompanying variations of the local microstructure. ...
Journal of Nuclear Materials, 1994
The effects of heat treatments at 700°C on the toughness behaviour have been investigated in MANE... more The effects of heat treatments at 700°C on the toughness behaviour have been investigated in MANET steel by means of Charpy impact tests and SEM observations with microanalysis. The ductile to brittle transition temperature, the upper shelf energy and the slope in the ductile to brittle transition depend strongly on the time of heating as a consequence of the different fracture mechanisms evolving with the thermal treatment. The transition, from fracture mainly conditioned by lath boundaries to fracture depending mainly on processes at the PAG boundaries, appears correlated with the specific characteristics of the distribution of the Cr atoms in solution.
Journal of Nuclear Materials, 1998
From Flat-top Cylinder Indenter for Mechanical Characterization (FIMEC) test yield stress and ten... more From Flat-top Cylinder Indenter for Mechanical Characterization (FIMEC) test yield stress and tensile strength can be obtained. Results regarding different materials, most of them of fusion interest, show the general validity of the method. Moreover, indication on the ductile to brittle transition temperature (DBTT) of martensitic steels has been drawn by performing tests at different temperatures. FIMEC offers the possibility
Key Engineering Materials, 2000
Journal of Nuclear Materials, 1996
The effect of the cooling rate ? from austenitic field on the microstructural evolution and the m... more The effect of the cooling rate ? from austenitic field on the microstructural evolution and the mechanical stability of MANET steel for increasing times of tempering at 700°C has been studied by means of Charpy tests, SEM observations with EDS microanalysis and X-ray diffraction analysis. The investigated rates f range from 150 to 36OO"C/min. The ductile to brittle transition temperature, the upper shelf energy and the slope A E/AT in the transition region depend on the time of treatment with variations more pronounced in samples slowly cooled. After tempering times of about 20 h at 700°C the samples cooled with f= lSO"C/min show a mixed mode of brittle fracture (quasi-cleavage and intercrystalline) with good correspondence between Cr-enriched zones and surfaces fractured in intercrystalline mode. Only quasi-cleavage mechanism is operative in samples quenched with f = 3600"C/min, which present fracture surfaces with uniform Cr distribution. The results are discussed on the basis of C-Cr associate distributions determined by internal friction tests.