scholarly journals Noise Filtering in the Synthetic Transmit Aperture Imaging by Decomposition of the Time Reversal Operator: Application to Flaw Detection in Coarse-grained Stainless Steels

2015 ◽  
Vol 70 ◽  
pp. 562-565
Author(s):  
Eduardo Rigoberto Lopez Villaverde ◽  
Sebastien Robert ◽  
Claire Prada
Keyword(s):  
Stainless Steels ◽  
Time Reversal ◽  
Flaw Detection ◽  
Coarse Grained ◽  
Noise Filtering

Ultrasonic imaging of defects in coarse-grained steels with the decomposition of the time reversal operator

2016 ◽  
Vol 140 (1) ◽  
pp. 541-550 ◽  
Author(s):  
Eduardo Lopez Villaverde ◽  
Sébastien Robert ◽  
Claire Prada
Keyword(s):  
Time Reversal ◽  
Ultrasonic Imaging ◽  
Coarse Grained

Hydrogen Embrittlement of Ultrafine-Grained Austenitic Stainless Steels

2018 ◽  
Vol 54 (1) ◽  
pp. 25-45 ◽  
Author(s):  
E. G. Astafurova ◽  
S. V. Astafurov ◽  
G. G. Maier ◽  
V. A. Moskvina ◽  
E. V. Melnikov ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Hydrogen Embrittlement ◽  
Stainless Steels ◽  
Subgrain Size ◽  
Austenitic Stainless Steels ◽  
Mechanical Twinning ◽  
Coarse Grained ◽  
Flow Strength ◽  
Hydrogen Charging ◽  
Ultrafine Grained

Abstract The effect of electrochemical hydrogen-charging on tensile properties, mechanisms of plastic deformation and fracture micromechanisms was studied using two ultrafine-grained (UFG) Cr-Ni austenitic stainless steels. UFG austenitic structures with an average subgrain size of 200 nm for CrNiMo (316L-type) and 520 nm for CrNiTi (321-type) steel were produced using hot-to-warm ABC-pressing. Hydrogen-charging up to 100 hours weakly influences stages of plastic flow, strength properties and elongation of the UFG steels. TEM analysis testifies to hydrogen-assisted partial annihilation and rearrangement of dislocations into dislocation tangles, and to hydrogen-induced variation in ratio of low- and high-angle misorientations in UFG structure of both steels. Hydrogen-alloying promotes mechanical twinning and deformation-induced γ ® e martensitic transformation in the UFG steels under tension. Ultrafine-grained CrNiTi steel with lower stacking fault energy (SFE) is more susceptible to mechanical twinning and deformation-induced γ ® e martensitic transformation in comparison with CrNiMo steel with higher SFE. The micromechanism of the fracture in hydrogen-assisted surface layers of the steels is compositional, grain-size and hydrogen content dependent characteristic. The present results demonstrate that the steels with UFG structure possess higher resistance to hydrogen embrittlement compared to coarse-grained analogues.

Fatigue damage in coarse-grained lean duplex stainless steels

2016 ◽  
Vol 659 ◽  
pp. 47-54 ◽  
Author(s):  
R. Strubbia ◽  
S. Hereñú ◽  
M.C. Marinelli ◽  
I. Alvarez-Armas
Keyword(s):  
Fatigue Damage ◽  
Stainless Steels ◽  
Duplex Stainless Steels ◽  
Coarse Grained

scholarly journals Formation of residual stresses in austenitic stainless steels by infeed and recess rotary swaging

2020 ◽  
Author(s):  
Holger Hoche ◽  
Fabian Jaeger ◽  
Alessandro Franceschi ◽  
Matthias Oechsner ◽  
Peter Groche
Keyword(s):  
Residual Stresses ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Phase Changes ◽  
Austenitic Steels ◽  
Coarse Grained ◽  
Fatigue Properties ◽  
Forming Process ◽  
Cold Forming ◽  
Rotary Swaging

The austenitic stainless steels 1.4307 and 1.4404 significantly benefit from cold forming, due to their high work hardening capability. Great potential to improve the component's fatigue properties is expected by optimizing the forming process chain such that specific residual stresses are induced in critical component areas. In this work, an analysis of the formation of residual stresses during rotary swaging is carried out. Through this incremental forming process, high strain hardening and a complex material flow history are induced in the workpieces. Therefore, measuring strategies for the residual stress measurement of cold de-formed austenitic steels by X-Ray diffraction, using the sin2Ψ-method, were developed. Here, especially the 1.4307 is a challenging material due to cold forming induced martensite formation. Despite phase changes, both cold formed materials exhibit anisotropic microstructures as well as coarse grained areas. Moreover, particular notched geometries are produced on the workpieces by rotary swaging. The measuring techniques are further developed for these complex geometries and the residual stresses are investigated.

Ultrasonic Sound Field Mapping Through Coarse Grained Cast Austenitic Stainless Steel Components

2014 ◽  
Author(s):  
Susan L. Crawford ◽  
Matthew S. Prowant ◽  
Anthony D. Cinson ◽  
Michael R. Larche ◽  
Aaron A. Diaz ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Phased Array ◽  
Flaw Detection ◽  
Sound Field ◽  
Coarse Grained ◽  
Sound Fields ◽  
Fine Grained ◽  
Ultrasonic Sound ◽  
Field Formation

The Pacific Northwest National Laboratory (PNNL) has been involved with nondestructive examination of coarse-grained cast austenitic stainless steel (CASS) components for over 30 years. More recent work has focused on mapping the ultrasonic sound fields generated by low-frequency phased-array probes that are typically used for the evaluation of CASS materials for flaw detection and characterization. The casting process results in the formation of large-grained material microstructures that are nonhomogeneous and anisotropic. The propagation of ultrasonic energy for examination of these materials results in scattering, partitioning, and redirection of these sound fields. The work reported here provides an assessment of sound field formation in these materials and provides recommendations on ultrasonic inspection parameters for flaw detection in CASS components. Confirmatory research conducted at PNNL consisted of acquiring sound field data from four CASS components containing columnar, equiaxed, and banded grain structures, and a fine-grained wrought stainless steel specimen used for benchmarking. Phased-array probes with center frequencies of 0.5, 0.8, and 1.0 MHz were used for sound field formation, with a pinducer being raster scanned over the end of the specimen face to capture the sound field energy. Data were collected at multiple refracted and skew angles, and imaging performed for analyses. A 6.4-mm (0.25-in.) thick slice of material was removed from the end of the CASS components and the beam mapping repeated. This slicing and mapping sequence was performed three times to produce multiple beam images through the specimens. Grain sizes were also measured at each mapped specimen face and compared to sound field characteristics. The acquired sound field images were characterized in terms of beam redirection from the theoretical position, beam scatter or coherence, and partitioning. A comparison of the fine-grained beam data to the CASS data is made and conclusions are presented.

Fatigue behavior of ultrafine-grained and coarse-grained Cr–Ni austenitic stainless steels

2011 ◽  
Vol 528 (10-11) ◽  
pp. 3890-3896 ◽  
Author(s):  
A.S. Hamada ◽  
L.P. Karjalainen ◽  
P.K.C. Venkata Surya ◽  
R.D.K. Misra
Keyword(s):  
Stainless Steels ◽  
Fatigue Behavior ◽  
Austenitic Stainless Steels ◽  
Coarse Grained ◽  
Ultrafine Grained
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