Mechanics of Machining Processes

In the Advanced Machining Laboratory, research projects are being undertaken to study various fundamental mechanics of machining processes and to develop predictive models.  The topics include mechanistic modeling of cutting processes, prediction of tool wear effect on cutting forces, FEM modeling of machining processes, investigation of relationships between machining conditions and surface integrity, constitutive modeling of materials by machining processes, investigation of chip flow angles in three dimensional cutting, and analysis of cutting temperatures.  Please see the published papers for details.  Some highlights of these projects are briefly described below.

  Mechanistic Modeling of Cutting Processes

• Dynamic mechanistic models of various machining processes provide prediction of cutting forces, vibration of workpiece and cutting tool, and chatter.
• The models and corresponding software (IDMS) have been developed for facemilling, endmilling, longitudinal turning, face turning, boring and grinding processes.
• The models consider dynamics of the structure, three dimensional cutting tool geometry and material properties of the workpiece.
• The recent addition to the mechanistic model is the effect of tool wear and process damping.  This allows for prediction of force and vibration as well as stability lobes as a function of tool wear.

  Finite Element Modeling of Machining Processes  

• Effective coupled Eulerian-Lagrangian approach for improved computation cfficiency
• Dislocation density-based model with strain gradient plasticity  (SPG) model for predicting size effects and grain refinement
• Three dimensional cutting process modeling for turning and milling
• Prediction of tool wear

Simulation of milling  

  Multiscale Modeling of Composite Machining

• Molecular Dynamics model + Micro mechanics model + Continuum model
• Prediction of sub surface damage such as delamination
• Tool wear prediction

  Effect of Tool Wear on Cutting Force

• Three dimensional cutting process model for ploughing force separation.
• Indentation model for ploughing force prediction which allows for analytical prediction of cutting force change due to too wear.
• Considers hardness of cutting tool material and tool wear geometry.
• Effects of tool wear on process damping and hence stability.

  Development of Material Constitutive Models

    Strains and strain rates encountered during machining processes often far exceed what one can get from standard mechanical tests.   Therefore, in order to predict material deformation during machining, conventional constitutive models cannot be extrapolated and used.   To develop a suitable constitutive model, controlled orthogonal machining experiments are used to develop a constitutive model.

Stresses are obtained in terms of strain, strain rate and temperature from orthogonal machining tests based a new shear zone model.

Calculated shear strain rate using new shear zone model	Comparison of calculated flow stress with Oxley's results for 1020  steel

  Thermo-mechanical Modeling of Machining Processes

Numerical simulation of machining processes has been performed to obtain coupled solutions of plastic deformation and thermal field. Temperature dependent material properties are used and adaptive meshing is adopted to avoid numerical errors associated with large deformation.

Tool-Chip Temperature Analysis

• Use of the thermo-couple EMF technique to experimentally measure chip-tool interface temperature.
• Investigation of the relationship between machining parameters and tool-chip interface temperature.
• Analysis of the tool wear effect on temperature.
• Analytical model validation and empirical model development.
• Tool-chip interface temperature for different materials.

  Comparison of measured tool-work interface temperatures with model prediction

  Workpiece Temperature Analysis

• Workpiece temperature monitoring by a radiation thermometer.
• Modeling of workpiece temperature distribution by finite difference models.
• Prediction of workpiece temperature during thermally-assisted machining.

Temperature measured by an IR system during machining

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