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[9000471.] رقم البحث : 9000471 - |
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CHARACTERISTICS OF FINISHED HOLES BY BALLIZING PROCESS / |
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قطاع الدراسات الهندسية / قسم هندسة الإنتاج والتصميم الميكانيكى |
| تخصص البحث : قسم هندسة الإنتاج والتصميم الميكانيكى |
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Engineering Research Journal \ |
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محمد فتوح عبد الحميد داود ( m.fattouh46@hotmail.com - ) |
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Ballizing, Surface roughness, Residual stresses, Microhardness andTaguchi method. |
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Ballizing is a method of burnishing an internal diameter by forcing a precision ground steel or a tungsten carbide ball through a slightly undersized pre-machined hole. This plastic deformation process produces a smooth surface with favorable mechanical properties and negative residual stresses. The objective of this investigation is to determine the optimal setting of the ballizing parameters while ballizing 70/30 cu-zn brass alloy. The parameters considered are interference, wall thickness of the hole, number of passes, ball speed and initial surface roughness of the hole, whereas the responses are surface roughness, residual stresses and microhardness variation of the ballized hole. The optimal setting of the parameters is determined through experimental planning, conducted and analyzed using Taguchi method. It is found that the initial surface roughness of the hole exerted the greatest effect on surface roughness of the ballized hole, followed by interference and wall thickness of the hole. The No. of passes and ball speed were found to have only a slight influence on the surface finish. A critical interference (300 ?m) exists for maximum improvement in roughness. Based on the experimental results, the optimal ballizing for compressive residual stresses were obtained at 4 mm wall thickness, 400 ?m interference and 2 mm/sec ball speed.The initial surface roughness and No. of passes were found to have no significant effect on the residual stresses. The optimum conditions for surface roughness and residual stresses are different. The microhardness just below the ballized surface was improved up to 65%. The maximum depth of the plastically deformed layer was observed at 300 ?m below the ballized surface. Generally, it was observed that the maximum value of the strain hardening increases with the increase in both interference and wall thickness. The results of confirmation experiment agree will with the predicted optimal settings. |
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