Recently, the steel parts used for automobiles and trains are required to be used under higher st... more Recently, the steel parts used for automobiles and trains are required to be used under higher stress than ever before in need of the weight down. In this study, high strength and superior toughness spring steels as the suspension material, used for automobile and railroad industries were utilized to carry out the following n vestigations : 1) To evluate the characteristics of fatigue crack propagtion, the experiments of fatigue crack growth were respectively carried out at the room temperature(RT), 100℃, 200℃. 2) Peening and unpeening materials at the each temperature were investigated for the effect on fracture toughness by compressive residual stress generated from the shot peening.
Fracture toughness is an important parameter in designing structure applied in low temperature. T... more Fracture toughness is an important parameter in designing structure applied in low temperature. The huge tesging machine and manufacturing of the testing specimen are the main shortages of the CTOD and FCG testing methods. Therefore, in this study the indentation tester AIS 3000 is applied to measure the fracture toughness. The experiment was conducted at RT, 0℃, -20℃ and -45℃, respectively. Furthermore, the fracture surface was observed by SEM. Through the results we can see that the fracture toughness was reducing through the temperature drop, and the highest fracture toughness in base metal and weld zone was measured at room temperature though there were a little peak at -20℃. As we expected, the highest fracture toughness in th HAZ was observed at -20℃ for procedding less brittle fracture at low temperature.
Recently, the steel parts used for automobiles and trains are required to be used under higher st... more Recently, the steel parts used for automobiles and trains are required to be used under higher stress than ever before in need of the weight down. In this study, high strength and superior toughness spring steels as the suspension material, used for automobile and railroad industries were utilized to carry out the following n vestigations : 1) To evluate the characteristics of fatigue crack propagtion, the experiments of fatigue crack growth were respectively carried out at the room temperature(RT), 100℃, 200℃. 2) Peening and unpeening materials at the each temperature were investigated for the effect on fracture toughness by compressive residual stress generated from the shot peening.
Fracture toughness is an important parameter in designing structure applied in low temperature. T... more Fracture toughness is an important parameter in designing structure applied in low temperature. The huge tesging machine and manufacturing of the testing specimen are the main shortages of the CTOD and FCG testing methods. Therefore, in this study the indentation tester AIS 3000 is applied to measure the fracture toughness. The experiment was conducted at RT, 0℃, -20℃ and -45℃, respectively. Furthermore, the fracture surface was observed by SEM. Through the results we can see that the fracture toughness was reducing through the temperature drop, and the highest fracture toughness in base metal and weld zone was measured at room temperature though there were a little peak at -20℃. As we expected, the highest fracture toughness in th HAZ was observed at -20℃ for procedding less brittle fracture at low temperature.
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