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. …
