Fatigue crack growth characteristics of nitrogen-alloyed type 347 stainless steel under operating conditions of a pressurized water reactor
Abstract The fatigue crack growth behavior of Type 347 (S347) and Type 347N (S347N) stainless steel was evaluated under the operating conditions of a pressurized water reactor (PWR). These two materials showed different fatigue crack growth rates (FCGRs) according to the changes in dissolved oxygen content and frequency. Under the simulated PWR conditions for normal operation, the FCGR of S347N was lower than that of S347 and insensitive to the changes in PWR water conditions. The higher yield strength and better corrosion resistance of the nitrogen-alloyed Type 347 stainless steel might be a main cause of slower FCGR and more stable properties against changes in environmental conditions.
Effects of prior cold work and sensitization heat treatment on chloride stress corrosion cracking in type 304 stainless steels
Abstract The effects of prior cold work (CW) and sensitization treatment on the stress corrosion cracking (SCC) behaviour of Type 304 stainless steels have been studied in chloride solutions using electrochemical tests and magnesium chloride tests with U-bend specimen. The results indicated that the SCC behaviour of the CW steel was essentially different from that of the solution-annealed steel. Intergranular stress corrosion cracking (IGSCC) of solution-annealed material changed into a mixed mode or dominant transgranular stress corrosion cracking (TGSCC) when the degree of CW was increased. The sensitization treatment enhanced IGSCC susceptibility by shortening failure time and accelerating crack initiation and propagation rates, but this effect was different for several other degrees of CW. These effects were revised taking into consideration the electrochemical and microstructural phenomena. The most dangerous degrees of deformation for different sensitization conditions for the development of IGSCC and TGSCC processes have been determined.
Engineering bio-inks for 3D bioprinting cell mechanical microenvironment
Three-dimensional (3D) bioprinting has become a promising approach to construct­ing functional biomimetic tissues for tissue engineering and regenerative medicine. In 3D bioprinting, bio-inks are essential for the construction of cell microenviron­ment, thus affecting the biomimetic design and regenerative efficiency. Mechanical properties are one of the essential aspects of microenvironment, which can be char­acterized by matrix stiffness, viscoelasticity, topography, and dynamic mechanical stimulation. With the recent advances in functional biomaterials, various engineered bio-inks have realized the possibility of engineering cell mechanical microenviron­ment in vivo. In this review, we summarize the critical mechanical cues of cell micro­environments, review the engineered bio-inks while focusing on the selection princi­ples for constructing cell mechanical microenvironments, and discuss the challenges facing this field and the possible solutions for them.