2024 alüminyum alaşımının yorulma ömrü üzerine farklı bilyalı dövme işlem parametrelerinin etkisi

Abstract

j ÖZET Bu çalışmada, farklı bilyalı dövme işlemi parametrelerinin 2024 alüminyum alaşımının yorulma özellikleri üzerindeki etkisi araştırılmıştır. 2024 alaşımı için en uygun ısıl işlem uygulamasını belirlemek üzere, solüsyona alma işleminden sonra numuneler tabii ve sun'i yaşlandırılmışlardır. Mekanik deneyler sonunda tabii yaşlandırma ısıl işleminin en uygun işlem olduğu sonucuna varılmıştır. Tabii yaşlandırılmış dönen eğmeli yorulma deneyi numuneleri HRC 45-55 sertliğinde S110, S170,'S230 çelikbilya ve 25, 30, 35, 40, 50, 75 psi nozul hava basıncı şartlarında bilyalı dövülmüştür. Her bir bilya çapı ve hava basıncı için Almen A dövme şiddeti değerleri belirlenmiş ve bu dövme şiddetleri, bilyalı dövme işlemi esnasında kullanılmıştır. Bu özel yüzey işleminden sonra bütün numunelere yorulma deneyi uygulanmıştır. Sonra, farklı dövme şartları altında dövülmüş her bir numune gurubunun yorulma deneyi sonuçlarına göre S-N eğrileri çizilmiştir. Optimum dövme şartlarını belirlemek için bütün S-N eğrileri karşılaştırılarak incelenmiştir. Ayrıca, bu ': dövme şartlarının numunelerin plastik deformasyon derinliği ve yüzey kalitesi üzerine etkileri araştırılmıştır. Bu çalışma sonunda, S110, 50 psi, 16-18 A ve %200 doyurma şartları 2024-T4 alaşımı için optimum dövme şartları olarak T lvi saturation parameters have been found to be the optimum shot peening condition for the 2024-T4 alloy. For 107 cycles, rotating bending fatigue strength of peened specimens has increased as high as 108% of that of unpeened specimens. An obvious expansion in the surface roughness has been observed after shot peening under any combination of the conditions. Increasing shot size and Almen intensity has caused more roughness on the surface. However, any glass beads peening following steel made shot peening or 200% saturation condition, certain amount of decrease in the surface roughness has been achieved. In addition, it has been seen that the depth of plastic deformation has increased in parallel to the increase in Almen A intensity. Although shot peenig is not a complete manufacturing method, it is a special surface treatment since it augments the fatigue life or strength with its beneficial effect on the surface layer of the material. Therefore, it is well-suited to refer to shot peening in order to make the sizes of mechanical parts smaller or to increase the fatigue strength for the same sizes.

ABSTRACT In this work., the effects of different shot peening parameters on the fatigue properties of 2024 aluminium alloy have been investigated. In order to determine the most convenient heat -treatment for 2024 alloy, the specimens were naturally and artificially aged after the solution heat- treatment. As a result of mechanical testings, the solution heat- treatment and natural aging has been concluded to be the most convenient treatment. The specimens of the naturally aged rotating bending fatigue testing were peened by the steel made shots with the sizes of S110, S170 and S230 and the hardness of HRC 45-55, under the nozzle air pressures of 25, 30,35,40,50 and 75 psi. For each shot size and air pressure, Almen A peening intensity was determined and these intensity values were employed during the shot peening operation. After such particular surface treatment, the fatigue testing was applied to all the speci mens. Then, S -N curves were plotted according to the results of the fatigue testing for each specimen group peened under dif - ferent conditions. To determine the optimum peening conditions all the S-N curves have been examined comparatively, In addi tion, the effects of these conditions on the depth of plastic deformation and the surface quality the specimens have been investigated. As a result of this work, S110, 50 psi, 16-18 A and 200%vi saturation parameters have been found to be the optimum shot peening condition for the 2024-T4 alloy. For 107 cycles, rotating bending fatigue strength of peened specimens has increased as high as 108% of that of unpeened specimens. An obvious expansion in the surface roughness has been observed after shot peening under any combination of the conditions. Increasing shot size and Almen intensity has caused more roughness on the surface. However, any glass beads peening following steel made shot peening or 200% saturation condition, certain amount of decrease in the surface roughness has been achieved. In addition, it has been seen that the depth of plastic deformation has increased in parallel to the increase in Almen A intensity. Although shot peenig is not a complete manufacturing method, it is a special surface treatment since it augments the fatigue life or strength with its beneficial effect on the surface layer of the material. Therefore, it is well-suited to refer to shot peening in order to make the sizes of mechanical parts smaller or to increase the fatigue strength for the same sizes.