Predicting the Thermal Behaviour of Wood During Linear Welding Using the Finite Element Method

Abstract

A numerical model to simulate the temperature behaviour of wood welding samples during the welding process was developed to understand the influence of material parameters on the welding temperature. A finite element method and the CAST3M software were used to simulate and model the temperature changes during welding of beech wood. This model takes into account the different properties of the wood welded bondline, the geometry of the sample and the external conditions. The energy produced by the friction welding of the wood samples was determined from infrared thermography measurements for the welding process and inputted into the model. The comparison between the predicted and experimental results shows that the model is reliable. The applied pressure, the vibration, the extrusion of material and the chemical reactions, particularly exothermic reactions, are not taken into account in this model and thus probably explain the differences existing between actual and simulated values. However, this numerical simulation gives information on the distribution of the temperature in the sample. The model predicted that the temperature difference between the centre and the side of the sample is not higher than 4°C. This means that the border effects are negligible. The model was tested for different welding times. According to the model a heat flow about 70 kW/m2 is necessary at the welding line to ensure a satisfactory bonding for the chosen sample geometry. Welding of large wood pieces has also been simulated in this study.