• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 추계학술대회논문집A
• /
• pp.316-321
• /
• 2000

The role of fatigue on the surface damage of 5% chrome cold milling work roll is evaluated. Uniaxial and torsional fatigue tests are carried out, and the baseline data for fatigue life evaluation are established. An appropriate multiaxial fatigue parameter is developed from the fatigue data. Fatigue tests are also performed under compressive mean stresses, and a mean stress model is formulated. A computer program is developed to assess the interaction of fatigue and grinding of the roll. The fatigue damage is computed for selected servicing conditions. It is found that the fatigue damage can be an important issue when the effect of mean stress is ignored, however the fatigue damage is negligibly small when the effect of mean stress including the residual stresses currently used is fully accounted. The result indicates that spalling due to the growth of thermal shock cracks is more important than fatigue damage in roll surface failure.

• 소성∙가공
• /
• 제7권5호
• /
• pp.465-473
• /
• 1998

The effect of alloying elements of Ag-Cu-Zr-X brazing alloy on the microstructure and the bond strength of $Al_2O_3/Ni-Cr$ brazed steel joint was investigated. The reaction layer, $ZrO_2$ (a=5.146 ${\AA}$ , b=5.213 ${\AA}$ , c=5.311 ${\AA}$ )was formed at the interface of $Al_2O_3/Ni-Cr$ steel joint by the redox reaction between alumina and Zr. The addition of An and Al to the Ag-Cu-Zr brazing alloy gave rise to changes in the thickness of the reaction product layer and the morphology of the brazement. Sn caused the segregation of Zr was decreased b Al the $ZrO_2$ layer formed at the Ag-Cu-Zr-Al alloy was thinner than that of $ZrO_2$ formed at the Ag-Cu-Zr-An alloy. The fracture shear strength was strongly dependent on the microstructure of the brazement. Brazing with Ag-Cu-Zr-Sn alloy resulted in a better bond strength than with Ag-Cu-Zr or Ag-Cu-Zr-Al alloy.

• 한국가스학회지
• /
• 제16권5호
• /
• pp.28-34
• /
• 2012

보일러 튜브용 크롬강의 열화기구에 대해 고찰하였다. 크롬강의 열화는 경도 및 응력-파단 수명의 변화를 동반하는데, 이는 주로 탄화물 분해 거동에 의존한다. 그런데 2Cr강인 T22의 열화는 이러한 탄화물 거동에 따르지만 12Cr강인 X20의 열화는 마르텐사이트 래쓰 성장거동에 따르기도 한다. T22와 X20의 열화에 의한 경도값과 응력-파단수명 변화현상을 미세조직적인 측면에서 고찰하였다.