Fracture Mechanics of Welded Structures

For fracture mechanics the location and geometry of the crack or defect must be specified as input data. The crack geometry could be specified as an ordered set of points …

Material Properties Summary

Properties can be provided for a material or alloy or for a specific phase in a material or alloy. If properties are provided for a specific phase, then the macroscopic …

Weld Pool Solver

If there is a weld pool solver that computes the weld pool free surface, velocity and temperature in the weld pool and weld pool reinforcement, the input data should include …

Thermal Stress Analysis Outside the Weld Pool

The initial conditions include initial stress, i. e., the residual stress and initial effective plastic strain for each part in the structure if it is known. If the residual stress …

Microstructure Evolution

The composition of the base metal must be specified. We prefer the format ((Fe,*), (C, 0.12), (Mn, 1.3),...). Here (Fe,*) means the balance of the fraction is Fe. We have …

Thermal Analysis Outside the Weld Pool

For the thermal analysis, the initial temperature of each part must be specified. The interface between the moving weld pool and its complement is a Dirichlet BC on the complement. …

Weld Procedure

Associated with each weld pass in each weld joint is a weld pool. The weld pool may have any shape and size but its geometry must be specified as input …

Input Data for Computational Welding Mechanics

9.1 Introduction and Synopsis This section describes the author’s preferred input data for a Computational Welding Mechanics analysis of a welded structure. Often some desired input data will not be …

Discussion

Hot cracking is important in certain classes of alloys. This requires models of solidification, including segregation and texture modeling. The stress analysis near the melting point could be the most …

Review and Model Development

Since the 1950s, more than one hundred separate and distinct weldability tests aiming at assessing the solidification and liquation cracking susceptibility have been devised and completely new or modified tests …

Fracture Mechanics

8.1 Introduction and Synopsis The development and production of High Strength Low Alloy (HSLA) linepipe steels has been growing rapidly because of their desirable combination of high strength, low temperature …

Implications of real-time CWM

If our prediction that CWM can be done in real-time is correct then CWM is likely to be used routinely in industry. This raises the question of what will be …

Real-Time for CWM

Is real-time Computational Welding Mechanics feasible? For the question to have meaning, it is necessary to first specify what we mean by a solution and what errors in the solution …

Analysis of a Weld Structure

Figure 6-5, chapter VI, shows a composite mesh for a weld on a pressure vessel. These meshes do not always conform; i. e., nodes and element faces on either side …

Weld Joint

A weld joint usually joins two or more parts. In any case we assume that the position of any weld joint in space can be associated with a curve in …

Weld Procedure

A weld procedure is a specification for a weld joint defined on a cross-section of the weld joint. It specifies the number of weld passes, the position and shape of …

Welded Structures and Applications of Welding in Industrial Fields

7.1 Introduction and Synopsis A welded structure is usually designed by a structural engineer who designs the structure but only specifies the requirements of the welded joints. A welding engineer, …

Computational Analysis

By 3D-FEM analysis for hydrogen diffusion, the heat transfer, stress-strain analysis and transient microstructure distribution must be coupled. This FEM formulation leads to asymmetric equations. Other than that the formulation …

Preheat prediction

Several investigators have developed relationships for predicting preheat levels to avoid the HAZ hydrogen cracking problem. Bibby et al [28] present a review of the predictive methods to assist in …

Hydrogen Diffusion in Welds

Hydrogen cracking is an important cause of failures in many welded structures. Given a sufficiently sensitive microstructure, a sufficient hydrogen concentration and a high enough tensile stress state, hydrogen cracking, …

Results and Discussion

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 …

Structure and Materials

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 …

Coupling Thermal, Microstructure and Stress Analysis

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 …

Microstructure Analysis

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. …

Thermal, Microstructure and Stress Analysis

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 …

Carburization; Theory and Numerical Methods

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 …

Carburized and Hydrogen Diffusion Analysis

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 …

Numerical Experiments and Results

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 …

Changing Constitutive Equations in Time and in Space

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 …

Rate dependent isotropic plasticity (General case)

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 …

Linear Viscous Isotropic Plasticity around the melting point

The main difference in implementing a linear viscous or any other kind of rate dependent model compared to a rate independent model arises in the evolution equation for stress and …

Deformation

By introducing a reference configuration in the deformation equations, any configuration in the deformation process can be expressed in that reference configuration. Figure 5-8 shows the displacement of a particle …

Rate Independent Isotropic Plasticity

Rate independent plasticity occurs at low temperatures, roughly in the temperature range below 0.57^. The deformation is due to dislocation glide and strain rate due to thermal fluctuations plays no …

Stresses, Strains and Deformations

Thermal-elastic-plastic constitutive models decompose the total strain rate ej01 into the elastic ЄуЄ, plastic due to rate independent plasticity, thermal є* consisting of thermal expansion and creep strain rate ej. …

Properties for Modeling

Accurate modeling of the development of residual stresses and strains in welded steels requires realistic modeling of the microstructural evolution. It is possible to obtain accuracy comparable to experimental measurements. …

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