scholarly journals Influence of Strain Rate on Fracture Characteristics and Diffusible Hydrogen of High Tensile Steel under Hydrogen Charging

2019 ◽  
Vol 68 (2) ◽  
pp. 46-52 ◽  
Author(s):  
Gaku Kitahara ◽  
Aya Tsuji ◽  
Takashi Asada ◽  
Tomohiro Suzuki ◽  
Keitaro Horikawa ◽  
...  
Keyword(s):  
Strain Rate ◽  
Diffusible Hydrogen ◽  
Fracture Characteristics ◽  
Hydrogen Charging

Strain rate response of a Ni–Ti shape memory alloy after hydrogen charging

2013 ◽  
Vol 94 (1) ◽  
pp. 30-36 ◽  
Author(s):  
Fehmi Gamaoun ◽  
Tarak Hassine ◽  
Tarak Bouraoui
Keyword(s):  
Shape Memory Alloy ◽  
Strain Rate ◽  
Shape Memory ◽  
Hydrogen Charging

scholarly journals Hydrogen Effect on the Cyclic Behavior of a Superelastic NiTi Archwire

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 316 ◽  
Author(s):  
Rihem Sarraj ◽  
Amir Kessentini ◽  
Tarek Hassine ◽  
Ali Algahtani ◽  
Fehmi Gamaoun
Keyword(s):  
Strain Rate ◽  
Parent Phase ◽  
Residual Deformation ◽  
Cyclic Behavior ◽  
Hydrogen Effect ◽  
Strain Rates ◽  
Hydrogen Charging ◽  
Lower Strain ◽  
Superelastic Behavior ◽  
Number Of Cycles

In this work, we are interested in examining the strain rate effect on the mechanical behavior of Ni–Ti superelastic wires after hydrogen charging and ageing for 24 h. Specimens underwent 50 cycles of loading-unloading, reaching an imposed deformation of 7.6%. During loading, strain rates from 10−4 s−1 to 10−2 s−1 were achieved. With a strain rate of 10−2 s−1, the specimens were charged by hydrogen for 6 h and aged for one day showed a superelastic behavior marked by an increase in the residual deformation as a function of the number of cycles. In contrast, after a few number of cycles with a strain rate of 10−4 s−1, the Ni-Ti alloy archwire specimens fractured in a brittle manner during the martensite transformation stage. The thermal desorption analysis showed that, for immersed specimens, the desorption peak of hydrogen appeared at 320 °C. However, after annealing the charged specimens by hydrogen at 400 °C for 1 h, an embrittlement took place at the last cycles for the lower strain rates of 10−4 s−1. The present study suggests that the embrittlement can be due to the development of an internal stress in the subsurface of the parent phase during hydrogen charging and due to the creation of cracks and local zones of plasticity after desorption.

EFFECT OF HYDROGEN ON UNIAXIAL TENSILE BEHAVIORS OF A DUCTILE CAST IRON

2012 ◽  
Vol 06 ◽  
pp. 407-412
Author(s):  
K. Matsuno ◽  
H. Matsunaga ◽  
M. Endo ◽  
K. Yanase
Keyword(s):  
Cast Iron ◽  
Strain Rate ◽  
Crack Growth ◽  
Crack Tip ◽  
Thermal Desorption Spectroscopy ◽  
Ductile Cast Iron ◽  
Uniaxial Tensile ◽  
Matrix Interface ◽  
Hydrogen Charging ◽  
Graphite Matrix

Effect of the hydrogen-charging on the uniaxial tensile behaviors of a ductile cast iron was investigated. It was found that the hydrogen-charging accelerated the process of crack growth from graphite in the uniaxial tensile loading condition. Further, the accelerated crack growth had a marked influence on the reduction of area at the final fracture (RA) of specimens. For instance, for the uncharged specimens, the RA was nearly constant irrespective of the strain rate. In contrast, for the hydrogen-charged specimens, the RA gradually decreased as the strain rate decreased. Thermal desorption spectroscopy and hydrogen microprint technique revealed that, in the hydrogen-charged specimen, most of solute hydrogen was diffusive one, which was mainly segregated at graphite, graphite/matrix interface zone and pearlite. Based on these experimental observations, we consider that the hydrogen-induced degradation behavior was caused mainly by a combination of the following three mechanisms: (i) supplement of hydrogen to the crack tip from graphite and graphite–matrix interface, (ii) hydrogen-enhanced pearlite cracking and, (iii) successive hydrogen-emission from graphite and additional hydrogen-supplement to the crack tip.

Hydrogen Charging of High Strength Steel Specimens and Physical Simulation of Cold Cracking under Laser Beam Welding Conditions

2012 ◽  
Vol 706-709 ◽  
pp. 1391-1396
Author(s):  
Ossama Dreibati ◽  
R. Ossenbrink ◽  
Vesselin Michailov
Keyword(s):  
Laser Beam ◽  
High Strength Steel ◽  
Physical Simulation ◽  
Laser Beam Welding ◽  
High Strength ◽  
Cold Cracking ◽  
Tension Stress ◽  
Pure Hydrogen ◽  
Diffusible Hydrogen ◽  
Hydrogen Charging

Cold cracks occur during the cooling down of welded joint at low temperatures or later at room temperature after the end of welding. It is associated with the formation of brittle microstructures as martensite in the presence of diffusible hydrogen as well as of tension stresses. By using an enhanced Simulation-und Testing Center Gleeble 3500, a procedure for physical simulation of cold cracking under laser beam welding conditions is suggested. The approach reproduces combinations of the cold crack main parameters, a brittle microstructure, tension stress and high local hydrogen concentration under welding conditions which induce a cold crack. A specimen geometry and technique were developed to enable the gaseous hydrogen charging from pure hydrogen atmosphere. The amount of charged hydrogen can be adjusted through varying the charging parameters like temperature, gas pressure and charging time. The hydrogen charging technique and the cold crack testing procedure were proven with high strength steel specimens.

Comparison of Behaviour of Different Variants of Hydrogenated TRIP Steels at Slow Strain Rate Tests

2019 ◽  
Vol 810 ◽  
pp. 70-75
Author(s):  
Petra Váňová ◽  
Jaroslav Sojka ◽  
Kateřina Konečná ◽  
Taťána Radkovská
Keyword(s):  
Hydrogen Embrittlement ◽  
Hydrogen Absorption ◽  
Potassium Thiocyanate ◽  
Tensile Tests ◽  
Fracture Characteristics ◽  
Trip Steels ◽  
Hydrogen Charging ◽  
Metallic Inclusions ◽  
Significant Difference ◽  
Fracture Micromechanism

The paper describes effect of hydrogen on mechanical properties and fracture characteristics of two types of C-Mn-Si TRIP steel; laboratory prepared steel TRIP 800 and commercially manufactured steel TRIP 780. TRIP steels are very promising materials thanks to their combination of a very good strength and toughness. However, these steels can be embrittled by hydrogen during technological operations related to galvanizing. That is why the knowledge of effects of hydrogen on the properties and fracture characteristics of the TRIP steels is of particular importance. In the presented study, effects of hydrogen were studied by tensile tests after electrolytical hydrogen charging. Electrolytical hydrogen charging was performed in 0.05 M solution of sulfuric acid with addition of potassium thiocyanate to promote hydrogen absorption. Hydrogen provoked embrittlement in both steel variants and changed their fracture micromechanism. Hydrogen embrittlement manifested itself mainly by a loss of plasticity. Index of hydrogen embrittlement, expressed on the basic of a relative drop of elongation to fracture, reached values about 77 % for the steel variant TRIP 800, resp. 83 % for the steel variant TRIP 780. No significant difference was observed between two steel variants studied. Concerning fractographic characteristics, steels containing hydrogen displayed quasi-cleavage fracture mostly on the edges of the sample and around elongated non-metallic inclusions.

Effects of Strain Rate on the Mechanical Properties and Fracture Characteristics of a Dual Phase 980 Steel

2019 ◽  
pp. 152-165
Author(s):  
Sukanya M. Sharma ◽  
Kishlay Mishra ◽  
Shrikant P. Bhat ◽  
Naresh N. Thadhani ◽  
Arun M. Gokhale
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Dual Phase ◽  
Fracture Characteristics
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