Influences of sulphureous impurity and micro-shrinkage on hydrogen assisted cracking (HAC) and fracture behavior of the super-strength low-alloy steel 40CrMnSzMo VA have been studied in this paper.By way of scanning e...Influences of sulphureous impurity and micro-shrinkage on hydrogen assisted cracking (HAC) and fracture behavior of the super-strength low-alloy steel 40CrMnSzMo VA have been studied in this paper.By way of scanning electron microfractography (SEM)and electron probe microanalyser to investigate the fractography of material constantly strained to failure, it was found that the microscopic segregation of sulphureous impurity and micro-shrinkage not only increased strongly the susceptibility to hydrongen embrittlement (HE), but also made the HAC to initiate preferably in such regions with the assistant of stress induced diffusion of hydrogen. The microscopic observation revealed that the steel has commonly intergranular (IG) and quasi-cleavage (QC)features around the segregation of sulphureous impurity and micro-shrinkage for their strong effects of irreversible traps for hydrogen.展开更多
The irradiation of a target with high laser intensity can lead to self-generation of an intense magnetic field(B-field)on the target surface.It has therefore been suggested that the sheath-driven acceleration of high-...The irradiation of a target with high laser intensity can lead to self-generation of an intense magnetic field(B-field)on the target surface.It has therefore been suggested that the sheath-driven acceleration of high-energy protons would be significantly hampered by the magnetization effect of this self-generated B-field at high enough laser intensities.In this paper,particle-in-cell simulations are used to study this magnetization effect on sheath-driven proton acceleration.It is shown that the inhibitory effect of the B-field on ion acceleration is not as significant as previously thought.Moreover,it is shown that the magnetization effect plays a relatively limited role in high-energy proton acceleration,even at high laser intensities when the mutual coupling and competition between self-generated electric(E-)and B-fields are considered in a realistic sheath acceleration scenario.A theoretical model including the v 3 B force is presented and confirms that the rate of reduction in proton energy depends on the strength ratio between B-and E-fields rather than on the strength of the B-field alone,and that only a small percentage of the proton energy is affected by the self-generated B-field.Finally,it is shown that the degraded scaling of proton energy at high laser intensities can be explained by the decrease in acceleration time caused by the increased sheath fields at high laser intensities rather than by the magnetic inhibitory effect,because of the longer growth time scale of the latter.This understanding of the magnetization effect may pave the way to the generation of high-energy protons by sheath-driven acceleration at high laser intensities.展开更多
文摘Influences of sulphureous impurity and micro-shrinkage on hydrogen assisted cracking (HAC) and fracture behavior of the super-strength low-alloy steel 40CrMnSzMo VA have been studied in this paper.By way of scanning electron microfractography (SEM)and electron probe microanalyser to investigate the fractography of material constantly strained to failure, it was found that the microscopic segregation of sulphureous impurity and micro-shrinkage not only increased strongly the susceptibility to hydrongen embrittlement (HE), but also made the HAC to initiate preferably in such regions with the assistant of stress induced diffusion of hydrogen. The microscopic observation revealed that the steel has commonly intergranular (IG) and quasi-cleavage (QC)features around the segregation of sulphureous impurity and micro-shrinkage for their strong effects of irreversible traps for hydrogen.
基金the National Key Program for S&T Research and Development(Grant No.2018YFA0404804)the Science Challenge Project(Grant No.TZ2016005 and TZ2018005)+1 种基金the Science and Technology on Plasma Physics Laboratory(Grant No.6142A04200101)the National Natural Science Foundation of China(Grant No.11805181).
文摘The irradiation of a target with high laser intensity can lead to self-generation of an intense magnetic field(B-field)on the target surface.It has therefore been suggested that the sheath-driven acceleration of high-energy protons would be significantly hampered by the magnetization effect of this self-generated B-field at high enough laser intensities.In this paper,particle-in-cell simulations are used to study this magnetization effect on sheath-driven proton acceleration.It is shown that the inhibitory effect of the B-field on ion acceleration is not as significant as previously thought.Moreover,it is shown that the magnetization effect plays a relatively limited role in high-energy proton acceleration,even at high laser intensities when the mutual coupling and competition between self-generated electric(E-)and B-fields are considered in a realistic sheath acceleration scenario.A theoretical model including the v 3 B force is presented and confirms that the rate of reduction in proton energy depends on the strength ratio between B-and E-fields rather than on the strength of the B-field alone,and that only a small percentage of the proton energy is affected by the self-generated B-field.Finally,it is shown that the degraded scaling of proton energy at high laser intensities can be explained by the decrease in acceleration time caused by the increased sheath fields at high laser intensities rather than by the magnetic inhibitory effect,because of the longer growth time scale of the latter.This understanding of the magnetization effect may pave the way to the generation of high-energy protons by sheath-driven acceleration at high laser intensities.
