Cold forging is used extensively as a forming method since it has several advantages like netshape manufacturing, improved mechanical properties, low operating temperatures and lower operating costs. The key to a successful cold forging operation i.e., to obtaining the desired shape and properties, is the understanding and control of metal flow. Finite element simulations are frequently used to visualize metal flow.
To perform accurate FE simulations, two important process parameters are needed:
- Flow stress of the material
- Friction factor of the lubricant being used
In the laboratory, uniform compression tests are commonly used for the determination of flow stress data of metals. These tests help to obtain the true stress vs true strain data for a large strain value. To be applicable without errors or corrections, the cylindrical sample must be upset without any barreling i.e., a uniaxial state of stress in the sample must be always maintained during the tests.
Friction can be defined as the resisting force acting tangentially to the common boundary between two bodies under the action of an external force, as one body moves or tends to move relative to the surface of the other. In cold forging, higher friction leads to higher forging load, die wear and excessively high temperatures. Lubrication is the use of one or more substances between the surfaces of sliding bodies to decrease or eliminate the direct contact. All lubricants must be tested for their effectiveness by laboratory tests. The double cup extrusion test is extensively used for testing lubricants. Different lubricants can be ranked based on their shear friction factor using this test.
Traditionally the two parameters required for FE simulations have been determined using two separate tests. In this study, an attempt is made to use a single test i.e., the double cup extrusion test, along with machine learning techniques and optimization to obtain both the parameters. As can be seen this reduces the cost and time required to run the tests. It also eliminates certain manual calculations done for curve fitting in the traditional method.
The following Altair and Altair-partner products have been used:
- AFDEX/3D – An Altair partner product, used for FE simulations of double cup extrusion tests
- Altair Twin Activate –
- romAI library – For building reduced order models of the double cup extrusion simulation
- Twin Activate – For system level model that is used for optimization
- Altair HyperStudy – For running optimization to match curves between system level model and tests
For more details, please email me at rajivd@altair.com
