The effect of heat treatment and deep cryogenic treatment on microstructural evolution of low carbon martensitic bearing steel was investigated.The experimental results showed that the lath martensite was obtained by ...The effect of heat treatment and deep cryogenic treatment on microstructural evolution of low carbon martensitic bearing steel was investigated.The experimental results showed that the lath martensite was obtained by quenching and a few twins as substructures formed in some martensitic laths.The rudiment of sub-interfaces of martensitic lath was formed in the highdensity dislocation regions after deep cryogenic treatment;meanwhile,the number of twins increased,especially in the highdensity dislocation regions.This phenomenon is due to the increase in internal stress caused by cryogenic treatment.After tempering,the rudiment of sub-interface further evolved into the martensitic lath boundary,and thus the original martensitic laths were refined.The twins formed by cryogenic treatment did not disappear after tempering.In addition,small quantities of annealing twins formed in tempering process.Martensitic laths morphology and substructures in different stages of the heat and deep cryogenic treatment were observed by tninsmission electron microscopy.展开更多
In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete （SRC） columns, steel plate （SP） deep beams, a concrete wall and energy dissipation strips, is p...In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete （SRC） columns, steel plate （SP） deep beams, a concrete wall and energy dissipation strips, is proposed. In order to study the multi-energy dissipation behavior and restorability after an earthquake, two stages of low cyclic loading tests were carded out on ten test specimens. In the first stage, test on five specimens with different number of SP deep beams was carried out, and the test lasted until the displacement drift reached 2%. In the second stage, thin SPs were welded to both sides of the five specimens tested in the first stage, and the same test was carried out on the repaired specimens （designated as new specimens）. The load-bearing capacity, stiffness, ductility, hysteretic behavior and failure characteristics were analyzed for both stages and the results are discussed herein. Extrapolating from these results, strength calculation models and formulas are proposed herein and simulations using ABAQUS carried out, they show good agreement with the test results. The study demonstrates that SRC columns, SP deep beams, concrete wall and energy dissipation strips cooperate well and play an important role in energy dissipation. In addition, this study shows that the shear wall has good recoverability after an earthquake, and that the welding of thin SP＇s to repair a deformed wall is a practicable technique.展开更多
The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced th...The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount.In addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated ones.It was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface increases.It has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.展开更多
基金Funding was provided by Analysis and Testing Foundation of Kunming University of Science and Technology(Grant Nos.2017M20152230037,2017M20152230069).
文摘The effect of heat treatment and deep cryogenic treatment on microstructural evolution of low carbon martensitic bearing steel was investigated.The experimental results showed that the lath martensite was obtained by quenching and a few twins as substructures formed in some martensitic laths.The rudiment of sub-interfaces of martensitic lath was formed in the highdensity dislocation regions after deep cryogenic treatment;meanwhile,the number of twins increased,especially in the highdensity dislocation regions.This phenomenon is due to the increase in internal stress caused by cryogenic treatment.After tempering,the rudiment of sub-interface further evolved into the martensitic lath boundary,and thus the original martensitic laths were refined.The twins formed by cryogenic treatment did not disappear after tempering.In addition,small quantities of annealing twins formed in tempering process.Martensitic laths morphology and substructures in different stages of the heat and deep cryogenic treatment were observed by tninsmission electron microscopy.
基金Beijing Natural Science Foundation of China under Grant No.8122004the National Natural Science Foundation of China under Grant No.51178010the National Science and Technology Support Program of China under Grant No.2012BAJ13B02
文摘In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete （SRC） columns, steel plate （SP） deep beams, a concrete wall and energy dissipation strips, is proposed. In order to study the multi-energy dissipation behavior and restorability after an earthquake, two stages of low cyclic loading tests were carded out on ten test specimens. In the first stage, test on five specimens with different number of SP deep beams was carried out, and the test lasted until the displacement drift reached 2%. In the second stage, thin SPs were welded to both sides of the five specimens tested in the first stage, and the same test was carried out on the repaired specimens （designated as new specimens）. The load-bearing capacity, stiffness, ductility, hysteretic behavior and failure characteristics were analyzed for both stages and the results are discussed herein. Extrapolating from these results, strength calculation models and formulas are proposed herein and simulations using ABAQUS carried out, they show good agreement with the test results. The study demonstrates that SRC columns, SP deep beams, concrete wall and energy dissipation strips cooperate well and play an important role in energy dissipation. In addition, this study shows that the shear wall has good recoverability after an earthquake, and that the welding of thin SP＇s to repair a deformed wall is a practicable technique.
基金the Majlesi Branch,Islamic Azad University for the support of this work
文摘The effects of the deep cryogenic heat treatment on the microstructural changes,wear resistance,and hardness of carburized DIN 1.7131 grade steel were investigated.Results show that cryogenic heat treatment reduced the retained austenite and increased the carbide amount.In addition,after the cryogenic heat treatment,carbide shows a more uniform distribution,as compared to the conventionally treated ones.It was also clarified that the hardness of the cryogenically treated samples was improved,but the relative improvement decreases with the distance as the surface increases.It has been shown that the wear resistance improves due to the cryogenic heat treatment,and the predominant wear mechanism is a combination of the adhesive and tribo-chemical wear.
