Method of assembling two hermetic threaded tubular joints comprising a local and initial added thickness, by means of plastic expansion

Assembly of two expandable threaded tubular joints, disposed symmetrically and each comprising, on the one hand, a first tubular element (EM) arranged at an end of a tube (T1, T2) and comprising a first portion (P1), provided with a male thread (FM), and a second portion (P2) extending said first portion and comprising i) a first outer surface (SE1), a first annular lip (L1) having a first axial abutment surface (SB1) and a first inner surface (SI1) and delimited by said first outer surface (SE1) over a portion of the axial length thereof, and iii) a second abutment surface (SB2), and, on the other hand, a second tubular element (EF1, EF2) comprising i) a female thread (FF), matching the first male thread (FM) and screwed thereto, ii) a second annular lip (L2), having a third abutment surface (SB3), a second outer surface (SE2), capable of being arranged to face said first inner surface (SI1), and a second inner surface (SI2), and iii) a third inner surface (SI3) and a fourth axial abutment surface (SB4) defining with the second outer surface (SE2) an annular recess (LO) matching and receiving the corresponding first lip (L1), characterised in that said second tubular elements (EF1, EF2) form two opposing ends of a female/female-type connection sleeve (M), separated by a central portion (PCM) initially provided, over an outer surface, with an annular zone (G2) having an initial reduced thickness selected such that the section of the sleeve (M) in the region of this zone (G2) is greater than or equal to the product of the section of a common portion of said tubes (T1, T2), and the efficiency of the joint, in that each second abutment surface (SB2) rests against the corresponding third abutment surface (SB3) and/or in that each abutment surface (SB1) rests against the corresponding fourth abutment surface (SB4) and in that the assembly is capable of developing, after diametral expansion in the plastic deformation region, sealing interference contacts sealing the assembly.