{"id":165208,"date":"2023-03-17T08:59:40","date_gmt":"2023-03-17T08:59:40","guid":{"rendered":"\/knowledge\/forums\/topic\/why-is-the-temperature-higher-than-the-melting-temperature-for-the-first-step-of-the-transient-thermal-phase-of-an-additive-simulation\/"},"modified":"2023-07-31T12:30:48","modified_gmt":"2023-07-31T12:30:48","slug":"why-is-the-temperature-higher-than-the-melting-temperature-for-the-first-step-of-the-transient-thermal-phase-of-an-additive-simulation","status":"publish","type":"topic","link":"https:\/\/innovationspace.ansys.com\/knowledge\/forums\/topic\/why-is-the-temperature-higher-than-the-melting-temperature-for-the-first-step-of-the-transient-thermal-phase-of-an-additive-simulation\/","title":{"rendered":"Why is the temperature higher than the melting temperature for the first step of the transient thermal phase of an Additive Simulation?"},"content":{"rendered":"

That is often due to the fast application of a temperature boundary condition. This is a known theoretical limitation of thermal transients using the FEA method; see the MAPDL Thermal Analysis Guide->Transient->Applying Loads (https:\/\/ansyshelp.ansys.com\/account\/secured?returnurl=\/Views\/Secured\/corp\/v192\/ans_the\/Hlp_G_THE3_5.html) for a description of how element size and thermal diffusivity relate to the maximum time step size that can be used. Basically, the time step must be small enough for the heat to travel from one side of the element to the other. If the time step is too large, then you get oscillations in the temperature solution leading to some nodes above melt and some below ambient. When we apply the temperatures to a new layer, the time step used respects this condition for the *layer* thickness, so we rarely see oscillations above the build plate. However, for the first layer where the build plate is composed of much larger element sizes, we can see these fictitious temperatures. Since we are taking relatively large time steps in additive (in order to keep the run times reasonable), we violate this condition. They can be safely ignored as they have no influence on the overall deformations and stresses in the part.<\/p>\n","protected":false},"template":"","class_list":["post-165208","topic","type-topic","status-publish","hentry","topic-tag-additive-manufacturing","topic-tag-analysis-techniques","topic-tag-mechanical","topic-tag-structural-mechanics"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t