**3. Material and methods**

In this study, material used for the welding simulation was SAE 1020 with the material properties vary according to the temperature history (Teng et al, 2001 and ASM, 1990). In addition, the welding parameters used in this analysis were as follows: single pass GTAW welding method, welding current, *I* = 260 A, welding voltage, *V* = 20 V, and welding speed, *ν* = 5 mm/s.

## **3.1. The variations of welding sequence**

Several welding sequences (WS) were considered in this study and the numerical investigation of the resulted temperature distribution, longitudinal and transverse residual stresses and angular distortions due to the welding sequences was then carried out. Four welding sequences considered were the one direction welding (WS-1), the contrary direction welding (WS-2), the welding from centre of one side (WS-3), and the welding from centres of two sides (WS-4), which are illustrated in Fig. 8.

**Figure 8.** Variation of welding sequence employed in this study: (a) the one direction welding (WS-1), (b) the contrary direction welding (WS-2), (c) the welding from centre of one side (WS-3), and (d) the welding from centres of two sides (WS-4).

## **3. 2. Finite element simulation of welding**

594 Numerical Simulation – From Theory to Industry

**3. Material and methods** 

**3.1. The variations of welding sequence** 

of two sides (WS-4), which are illustrated in Fig. 8.

welding from centres of two sides (WS-4).

now obtained.

*ν* = 5 mm/s.

that from the thermal analysis results, the updated stress and displacement conditions are

In this study, material used for the welding simulation was SAE 1020 with the material properties vary according to the temperature history (Teng et al, 2001 and ASM, 1990). In addition, the welding parameters used in this analysis were as follows: single pass GTAW welding method, welding current, *I* = 260 A, welding voltage, *V* = 20 V, and welding speed,

Several welding sequences (WS) were considered in this study and the numerical investigation of the resulted temperature distribution, longitudinal and transverse residual stresses and angular distortions due to the welding sequences was then carried out. Four welding sequences considered were the one direction welding (WS-1), the contrary direction welding (WS-2), the welding from centre of one side (WS-3), and the welding from centres

**Figure 8.** Variation of welding sequence employed in this study: (a) the one direction welding (WS-1), (b) the contrary direction welding (WS-2), (c) the welding from centre of one side (WS-3), and (d) the

In the present study, a thermal elasto-plastic finite element procedure was employed to simulate the thermo-mechanical response of welding problem. In the procedure, two sequenced thermal and mechanical analyses were carried out independently (uncoupled) to obtain the total or desired response of the welding structure modelled.

A transient thermal analysis of heat conduction was carried out in the first step to obtain temperature distribution histories over the structural model. In the thermal analysis, the welding heat input, *Q*a was calculated according to Masubuchi (1980) and the arc efficiency, *η*a for GTAW was assumed to be 0. 60 (Grong, 1994). Also, the values of convective heat transfer coefficient, *h*f and reference temperature were taken, respectively, to be 15 W/m2. K and 25°C (298. 15 K).

In the next step, a structural analysis was carried out to now obtain the mechanical response of the structural model, where the temperature history obtained from the first step was employed as a thermal load in the analysis. The material model of elasto-plastic based on the von Mises yield criterion and isotropic strain hardening rule was chosen, in which its response over the history was determined by the temperature-dependent material properties inputted. The boundary condition or constraint on the structural model needs also to be assigned accordingly.

Fig. 9 represents the mesh of T-joint fillet weld employed in this study along with the position of constraint assigned on the finite element model. The total number of nodes and elements utilized for the 3D model were 3654 and 2961, respectively. The analyses were implemented in ANSYS environment utilizing the element type of SOLID70 for the thermal analysis and that of SOLID45 for the structural analysis.

**Figure 9.** (a) Geometry of T-joint fillet welds, (b) Mesh of T-joint fillet weld along with its constraint position.
