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论述了山区地形、水文、地质和气候特点,探讨了山区高速公路选线的影响因素和选线原则,力求从总体上寻求工程量小、造价低、运营安全可靠的路线方案。 相似文献
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Microstructure and forming quality of friction stir welding joints of 7075Al and AZ31BMg with different welding parameters were analyzed. The results show that, good welded joint is obtained when the rotating frequency is 13 r/s and the welding speed is 30 mm/min. An irregular area is formed in the welding center. Meanwhile, the river pattern and eddy-like distribution are found in the weld nugget zone. Besides, brittle intermetallic compounds Al12Mg17 and Al3Mg2 are found in the welded joint. They cause the increase of microhardness of welded joint. The maximum tension stress of welded joint is 112MPa. 相似文献