Figure 6-7 shows the computed carbon concentration vs. distance from the internal wall at a point on the internal wall of the pipe. Figure 6-7: The carbon concentration distribution through the thickness of the liquid carburized film is shown at the point in time that the film growth stops. cL is the carbon concentration in […]

The pipe was 508 mm (20 in.) diameter and 7.9 mm (0.312 in.) wall API 5LX-65 ERW. Table 6-1: Composition of HSLA steel С Ni Si V Mo 0.12 0.11 0.16 0.001 0.001 W Mn Cr Си P Al 0.001 0.91 0.01 0.001 0.002 0.04 Table 6-2: Pipe material properties, from [8] Designation API-SLX65 Yield […]

The first time step computed the displacement, strain and stress due to applying the internal pressure, [10]. Then the weld pool was positioned in the deformed geometry for each subsequent time step. If a groove formed under the weld, the thermal analysis took into account this thinning of the pipe wall. When the arc was […]

The evolution of microstructure outside of the thin layer is computed using the methodology described in chapter IV. The microstructure evolution is assumed to be in equilibrium during heating, i. e., no super heating occurs. In austenite, grain growth begins after Nb and V carbo-nitrides dissolve and ceases when either delta ferrite forms on heating […]

Thermal Analysis The thermal analysis computes an FEM approximate solution to the transient 3D energy equation (3-2), see chapter III, using tf-node bricks with backward Euler time integration. It is solved on the current deformed geometry for each time step. Temperature dependent thermal conductivity and specific enthalpy, including the effect of latent heats of phase […]

The computational weld mechanics CWM analysis of the process of welding on pressurized pipelines involves several difficult problems that make this a particularly challenging problem. The greatest challenge is to develop the capability to deal with creep at temperatures in the range 900 °С (1652 °F, 1173 °K) to 1500 °С (2732 °F, 1773 °K). […]

6.1 Introduction and Synopsis It is widely known that hydrogen is extremely harmful to the safety of a metal construction. It influences the mechanical properties of base metal or a joint or, directly results in fracture during welding due to cracking, so called hydrogen induced cracking НІС or hydrogen assisted cracking НАС. While the time […]

Figure 5-17 shows the behavior of four constitutive models. Their properties are shown in Tables 5-2 and 5-3. Two models use rate independent plasticity, one uses rate dependent plasticity and one uses linear viscous plasticity. The test is uniaxial and the strain rate is 0.005 5_1in the time interval [0, 4] seconds. The strain rate […]

As stress evolves with time, a new problem is solved for each time step. Suppose that in time step n, rate dependent plasticity is used at Gauss point m. Then in time step n+1, suppose rate independent plasticity is used at Gauss point m. This discontinuity or switch of the constitutive equations does not cause […]

For steel at temperatures from 700 to 1300 °С we adopt a rate dependent plasticity model using the constitutive functions proposed by Brown [38] for the effective plastic strain rate was adopted in [31]: {Mm) £p = Aexp(-^^-) RT sinh(^—) s and for evolution of the internal variable: (5-39) s = {hc (1~) Sign( —)}£P […]