Welding analysis with Abaqus using amplitudes

Hello everyone,

I know that there are some posts about welding simulation with Abaqus and i looked at them already and I couldn't find something similar to my problem. I model a moving heat source with amplitudes and sets in Abaqus/Standard. I define body heat flux loads and give them amplitudes and magnitudes. The model is meshed with DS4 shell elements. The problem is that ater the simulation it is visible (with temperatures visualization) that the heat flux is not inputed linearly in the model. I mean to say that there is no linear movement of the heat source that is typical to welding, although all fluxes are inputed at the specified time. I'm uploading three pictures so you can see what the problem is. Picture with time 14.73 shows one active flux. Picture with time 15.42 shows the time in which active flux shuts down and a new one starts (visible bigger red area, not linearly moving flux). Picture with the time 17.47 shows one active flux after the previous one shuts down. Please help as soon as you can because this is a part of my master thesis and I have limited time.

Thank you!