With the resistance to stress corrosion of the base metal as a reference, the contrast result of stress corrosion cracking （ SCC） susceptibility of aluminum-copper alloy 2219 and 2014 welded joints under different w...With the resistance to stress corrosion of the base metal as a reference, the contrast result of stress corrosion cracking （ SCC） susceptibility of aluminum-copper alloy 2219 and 2014 welded joints under different welding processes （ VP-TIG welding, HF-TIG hybrid welding, laser-TIG hybrid welding and laser HF-TIG hybrid welding） is obtained via the slow strain rate testing （ SSRT） , scanning electron microscope （ SEM） and microstructure observation auxiliary technologies. Test results show that the joints of aluminum alloy 2219, welded by hybrid welding processes, have superior resistance to stress corrosion compared to those welded by the VP-TIG welding process in varying degrees, especially, the joint welded by the laser HF-TIG hybrid welding process, where the resistance to stress corrosion is almost the same as that of the base material. However, the HF or laser hybrid welding effect is not significant under the same welding conditions for welded joints of aluminum alloy 2014.展开更多
A new approach to the research into the distribution of prime pairs is developed, attached with corollaries about the distribution of prime triplets and generally about that of prime h-tuplets. It differs from the usu...A new approach to the research into the distribution of prime pairs is developed, attached with corollaries about the distribution of prime triplets and generally about that of prime h-tuplets. It differs from the usual methods(involving the sieve method) for this kind of research, and bases on Chebyshev inequality and on the computation of average concentration of all the related subsets, and leads to the proofs of following lemma and theorem, attached with four corollaries:[Lemma 1] Among all the prime-pair-subsets there exists at least one such subset (namely one of the sets of generalized prime twins) which is an infinite set.[Theorem 1] All the prime-pair-subsets (namely all sets of generalized prime twins) or infinitely many prime-pair-subsets are infinite sets.[Corollary 1] Among all the prime-triplet-subsets there exists at least one such subset which is an infinite set.[Corollary 2] All the prime-triplet-subsets or infinitely many prime-triplet-subsets are infinite sets.[Corollary 3] Among all the prime-h-tuplet-subsets there exists at least one such subset which is an infinite set, where h is an arbitrary finite integer ≥2.[Corollary 4] All the prime-h-tuplet-subsets or infinitely many prime-h-tuplet-subsets are infinite sets, where h is an arbitrary finite integer ≥2.展开更多
基金This work was supported by the National Natural Science Foundation of China （No. 50375005）.
文摘With the resistance to stress corrosion of the base metal as a reference, the contrast result of stress corrosion cracking （ SCC） susceptibility of aluminum-copper alloy 2219 and 2014 welded joints under different welding processes （ VP-TIG welding, HF-TIG hybrid welding, laser-TIG hybrid welding and laser HF-TIG hybrid welding） is obtained via the slow strain rate testing （ SSRT） , scanning electron microscope （ SEM） and microstructure observation auxiliary technologies. Test results show that the joints of aluminum alloy 2219, welded by hybrid welding processes, have superior resistance to stress corrosion compared to those welded by the VP-TIG welding process in varying degrees, especially, the joint welded by the laser HF-TIG hybrid welding process, where the resistance to stress corrosion is almost the same as that of the base material. However, the HF or laser hybrid welding effect is not significant under the same welding conditions for welded joints of aluminum alloy 2014.
文摘A new approach to the research into the distribution of prime pairs is developed, attached with corollaries about the distribution of prime triplets and generally about that of prime h-tuplets. It differs from the usual methods(involving the sieve method) for this kind of research, and bases on Chebyshev inequality and on the computation of average concentration of all the related subsets, and leads to the proofs of following lemma and theorem, attached with four corollaries:[Lemma 1] Among all the prime-pair-subsets there exists at least one such subset (namely one of the sets of generalized prime twins) which is an infinite set.[Theorem 1] All the prime-pair-subsets (namely all sets of generalized prime twins) or infinitely many prime-pair-subsets are infinite sets.[Corollary 1] Among all the prime-triplet-subsets there exists at least one such subset which is an infinite set.[Corollary 2] All the prime-triplet-subsets or infinitely many prime-triplet-subsets are infinite sets.[Corollary 3] Among all the prime-h-tuplet-subsets there exists at least one such subset which is an infinite set, where h is an arbitrary finite integer ≥2.[Corollary 4] All the prime-h-tuplet-subsets or infinitely many prime-h-tuplet-subsets are infinite sets, where h is an arbitrary finite integer ≥2.
