Stephen652
Mechanical
- Jul 13, 2016
- 4
Hello everyone,
I am currently working on a three-dimensional orthogonal cutting model with AISI 4340 steel as the workpiece and a Carbide cutting tool. I have constructed a preliminary model that models only the mechanical process of cutting, which runs smoothly and effectively. However, my interest lies in the thermal stresses and workpiece temperatures that result from this cutting. So, I have been attempting to construct a coupled temp-disp model in ABAQUS CAE. When I implement the coupled model, the elements that should be deleted under my damage criteria (Johnson-Cook damage and flow stress models are used) are not deleting (Despite my activation of the Element deletion option in Element Type and my selection of STATUS in Field Output Requests) and instead distorting into long, thin, plate-like shapes until the analysis is eventually aborted due to error. The error message reads: An excessive temperature rate occurs in solving the heat transfer equations. This usually indicates that some elements are badly distorted or an error exists with model definition. You can check the temperature values and see if the distorted elements exist. I am using ALE Adaptive meshing. Noticing that my contact interaction was set to General Contact, and that General Contact does not usually support Adaptive meshing techniques, I changed my interaction to Surface-to-surface contact. This did not solve the problem, and a new error resulted: The elements contained in ErrElemExcessDistortion-Step1 have distorted excessively. There is only one excessively distorted element. This critical element again lied on the plane where elements are supposed to be deleted under my damage criteria (and based on the behavior of the mechanical only model.
The changes I have made from my base mechanical-only model in order to construct the coupled analysis model are as follows:
Under materials, reference and melting temperatures were prescribed for the workpiece under Plastic (JC) and Damage (JC) tabs, and a thermal conductivity, specific heat, and inelastic heat fraction (0.9) were specified, along with a rate dependency being added to the Plastic settings. The tool's JC constitutive property values have been removed (Not concerned with flow stress through the tool), and specific heat and thermal conductivity values have been added.
Step was changed from Dynamic, Explicit to Dynamic, temp-disp, Explicit
Field output requests: Element TEMP toggled on
Interaction Props: Heat Generation added (Tangential behavior already specified)
Pre-defined temperature fields of 298 K (Same as reference temp for materials) added to tool and workpiece
Temp BCs added to top and back faces of tool (298 K; should experience no temp change throughout cutting)
Element type: C3D8R changed to C3D8RT. Options selected under Element Type include Explicit, 3D Stress, Kinematic split: Average strain, Reduced integration, Element deletion: Yes
If anyone has any ideas as to what I added above to my coupled model that could have caused these errors (Or something I left off that could prevent it), then please respond! I have been working on resolving this issue for quite some time. I have included pictures illustrating the distortion issue I have described above.
Thanks,
Stephen Mangum
I am currently working on a three-dimensional orthogonal cutting model with AISI 4340 steel as the workpiece and a Carbide cutting tool. I have constructed a preliminary model that models only the mechanical process of cutting, which runs smoothly and effectively. However, my interest lies in the thermal stresses and workpiece temperatures that result from this cutting. So, I have been attempting to construct a coupled temp-disp model in ABAQUS CAE. When I implement the coupled model, the elements that should be deleted under my damage criteria (Johnson-Cook damage and flow stress models are used) are not deleting (Despite my activation of the Element deletion option in Element Type and my selection of STATUS in Field Output Requests) and instead distorting into long, thin, plate-like shapes until the analysis is eventually aborted due to error. The error message reads: An excessive temperature rate occurs in solving the heat transfer equations. This usually indicates that some elements are badly distorted or an error exists with model definition. You can check the temperature values and see if the distorted elements exist. I am using ALE Adaptive meshing. Noticing that my contact interaction was set to General Contact, and that General Contact does not usually support Adaptive meshing techniques, I changed my interaction to Surface-to-surface contact. This did not solve the problem, and a new error resulted: The elements contained in ErrElemExcessDistortion-Step1 have distorted excessively. There is only one excessively distorted element. This critical element again lied on the plane where elements are supposed to be deleted under my damage criteria (and based on the behavior of the mechanical only model.
The changes I have made from my base mechanical-only model in order to construct the coupled analysis model are as follows:
Under materials, reference and melting temperatures were prescribed for the workpiece under Plastic (JC) and Damage (JC) tabs, and a thermal conductivity, specific heat, and inelastic heat fraction (0.9) were specified, along with a rate dependency being added to the Plastic settings. The tool's JC constitutive property values have been removed (Not concerned with flow stress through the tool), and specific heat and thermal conductivity values have been added.
Step was changed from Dynamic, Explicit to Dynamic, temp-disp, Explicit
Field output requests: Element TEMP toggled on
Interaction Props: Heat Generation added (Tangential behavior already specified)
Pre-defined temperature fields of 298 K (Same as reference temp for materials) added to tool and workpiece
Temp BCs added to top and back faces of tool (298 K; should experience no temp change throughout cutting)
Element type: C3D8R changed to C3D8RT. Options selected under Element Type include Explicit, 3D Stress, Kinematic split: Average strain, Reduced integration, Element deletion: Yes
If anyone has any ideas as to what I added above to my coupled model that could have caused these errors (Or something I left off that could prevent it), then please respond! I have been working on resolving this issue for quite some time. I have included pictures illustrating the distortion issue I have described above.
Thanks,
Stephen Mangum