Sn-3.5Ag 무연합금을 Cu 및 Alloy42 리드프레임에 납땜접합 (solder joint)하고 미세조직, 젖음성, 전단강도, 시효효과를 측정하여 비교하였다. Cu의 경우, 땜납의 Sn기지상안에 Ag(sub)3Sn과 Cu(sub)6Sn(sub)5상이, 그리고 땜납/리드프레임의 경계면에서는 1∼2㎛ 두께의 Cu(sub)6Sn(sub)5상이 형성되었다. Alloy42의 경우, 기지상내에 있는 낮은 밀도의 Ag(sub)3Sn상만이, 그리고 계면에는 0.5∼1.5㎛ 두께의 FeSn(sub)2이 형성되었다. 한편, Cu에 비해 Alloy42 리드프레임에서 퍼짐면적은 크고 접촉각은 작아 더 우수한 젖음성을 나타내었으나, 전단강도는 35%, 연신율은 75%로 낮았다. 180℃에서 1주일간 시효처리 후, Cu 리드프레임에는 계면에 η-Cu(sub)6Sn(sub)5 층외에 ξ-Cu(sub)3Sn층이 성장하였고, Alloy42 리드프레임에는 기지상내에 Ag(sub)3Sn이 구형으로 조대하게 성장하였고, 계면에는 FeSn(sub)2층만이 약 1.5㎛로 성장하였다.

Thermal damage in concrete reduce the stress resistance to external loading and then increase the risk of structural failure. This presentation is aimed to apply a nonlinear ultrasonic NDT on concrete thermally damaged. In addition, SEM images was investigated to identify the thermal damage and the feasibility of the nonlinear ultrasonic NDT.

Since thermal damage of concrete causes the formation of micro-defects according to physicochemical changes, the adoption of a sensitive nondestructive evaluation method is required. This study introduces an nondestructive evaluation method for thermally damaged concrete, which is on the baasis of nonlinear resonance characteristic. The test was investigated to evaluate thermal damage of concrete and to demonstrate the suitability of the proposed method

Nowadays, finger joints have been more popular than rail type joints due to their many merits: easiness to maintain, low noise, etc. However, finger joints have some demerits too. This paper investigates the damage of finger joints installed at a curved PSC box girder bridge. The analytical results show that the damage of finger joints of the curved bridge is caused by thermal expansion and imperfect installation of the joints.