應用熔射覆膜技術於摩阻型螺栓接合之滑移係數探討

Abstract

本研究旨在提升摩阻型螺栓接合之滑移係數，以熔射覆膜技術於鋼板摩擦面覆膜，使接合於滿足設計作用力時，螺栓數量與接合尺寸得以縮減。依照相關規範之滑移實驗方法設計試體，探討熔射覆膜材料、覆膜厚度、鋼板材質、螺栓種類與鋼板表面粗糙度對滑移係數之影響。實驗結果顯示連接板摩擦面以鋁鎂合金熔射覆膜處理可將滑移係數提升達0.81至1.04，平均可達0.91，為連接板未塗裝之滑移係數0.71之1.3倍。覆膜材料採用鋁鎂合金之滑移係數相較於採用純鋁更為穩定，而覆膜厚度由150 μm提升至450 μm會使鋁鎂合金覆膜之滑移係數降低11.1%，使純鋁覆膜之滑移係數降低12.9%。鋼板材質採用SM570MB相較於採用SN490B，因材質差異造成噴砂及熔射覆膜效果不同，使接合滑動摩擦行為較不穩定，但對滑移係數影響不顯著。接合若以F14T超高強度螺栓取代F10T高強度螺栓，抗滑強度可有相對應的提升，但於滑移係數則無顯著的影響。鋼板表面粗糙度影響鋼材與熔射塗層之鍵結強度，將表面粗糙度由7.1 μm提升至12.8 μm可使滑移係數略為提升。應用鋁鎂合金熔射覆膜技術於摩阻型螺栓接合時，建議滑移係數採用0.70，為規範中鋼板去除黑皮未塗裝表面之滑移係數0.33的2倍以上，可避免抗滑力喪失使接合滑移時，螺栓立即被剪斷之狀況；同時可減少接合螺栓數量與連接板尺寸皆50%以上，達到節省材料並降低施工費用及時間之目的。

The objective of this study is to increase the slip coefficient of bolted slip-critical connections by applying a thermal sprayed coating on faying surfaces, and further to reduce the number of bolts and connection’s dimension while satisfying the design force. The specimens were designed according to related specifications. The effects of the coating material, coating thickness, steel material, bolt type, and surface roughness of the steel plate on the slip coefficient were evaluated. The test results showed that the slip coefficients of the connection by thermal spraying aluminum-magnesium alloy coating on the faying surface were increased to the range of 0.81 to 1.04. The average slip coefficient is 0.91 which is 1.3 times the slip coefficient 0.71 of connections with uncoated faying surface. The slip coefficient of the aluminum-magnesium alloy coated faying surface proved to be more stable compared to that of the pure aluminum coated faying surface. However, the slip coefficients were reduced by 11.1 and 12.9% for aluminum-magnesium alloy and pure aluminum coated faying surface, respectively, when coating thickness was increased from 150 to 450 μm. Using the steel material of SM570MB instead of S490B resulted in an unstable frictional behavior that was presumed to be affected by the discrepancies caused by the blasting and thermal sprayed coating on the steel material. However, the steel material had insignificant effect on the slip coefficient. The use of the super-high strength bolt F14T on the connection led to higher slip resistance than the use of high-strength bolt F10T, but had negligible effect on the slip coefficient. The surface roughness of the steel plate might affect the bond strength between the steel plate and coating, and increasing the surface roughness from 7.1 to 12.8 μm slightly improved the slip coefficient. To prevent the bolts from shear failure after slip occurs, the slip coefficient of the bolted slip-critical connection with aluminum-magnesium coating is suggested to be 0.7 which is 2 times higher than that of the uncoated connection, having a slip coefficient of 0.33. Using the slip coefficient of 0.7 results in a reduction of more than 50% of the bolt amount and the splice plate size, and achieves the saving of the materials, and construction cost and time.