There are literature available to predict the residual stress after machining in a single phase material by ABAQUS. . But how to predict it in a two phase material (duplex stainless steel)?
Hi Rajaguru - great question!
Residual stresses can vary across different length-scales. For example they can vary at the macro-scale (so-called "Type I" stresses) and at the scale of individual crystallites ("Type II")*. Type I residual stresses are most often discussed in mechanical and structural engineering. However in many materials, including multi-phase materials but also single-phase materials, Type II stresses can have an influence on macro-scale material behaviour and on failure processes.
Abaqus is most often used for residual stress analysis at the continuum (ie. Type I) scale. In this case, you would treat a duplex steel the same as a single-phase one: by determining a suitable mechanical constitutive law which can be used to represent the material's macro-scale behaviour, and then using this as input in a finite element model of the process that creates the residual stress.
Some researchers also use Abaqus to predict Type II residual stresses in materials. This can be done by first defining a constitutive law which represents the plastic deformation behaviour of a single crystal explicitly, then using Abaqus to solve a finite element model of many differently-oriented crystallites together in a polycrystalline aggregate under load. Type II stresses which arise due to differential deformation of adjacent crystallites can be determined from the result.
*See Withers & Bhadeshia, Residual stress: Part 1 - Measurement techniques, Materials Science and Technology, 17(4):355-365, 2001.
Hi Rajaguru - great question!
Residual stresses can vary across different length-scales. For example they can vary at the macro-scale (so-called "Type I" stresses) and at the scale of individual crystallites ("Type II")*. Type I residual stresses are most often discussed in mechanical and structural engineering. However in many materials, including multi-phase materials but also single-phase materials, Type II stresses can have an influence on macro-scale material behaviour and on failure processes.
Abaqus is most often used for residual stress analysis at the continuum (ie. Type I) scale. In this case, you would treat a duplex steel the same as a single-phase one: by determining a suitable mechanical constitutive law which can be used to represent the material's macro-scale behaviour, and then using this as input in a finite element model of the process that creates the residual stress.
Some researchers also use Abaqus to predict Type II residual stresses in materials. This can be done by first defining a constitutive law which represents the plastic deformation behaviour of a single crystal explicitly, then using Abaqus to solve a finite element model of many differently-oriented crystallites together in a polycrystalline aggregate under load. Type II stresses which arise due to differential deformation of adjacent crystallites can be determined from the result.
*See Withers & Bhadeshia, Residual stress: Part 1 - Measurement techniques, Materials Science and Technology, 17(4):355-365, 2001.
Hello Rajaguru,
as Harry correctly pointed out you can see stresses as a scale-dependent quantity. By using the classification mentioned by Harry, i.e. Type I, II & III residual stresses, in one of my recent publication I have attempted separating these contributions using both FEM multi-scale modeling (macro- & micro-scale) and micro-scale residual stress experimental evaluation:Article An analysis of macro- and micro-scale residual stresses of T...
I invite you to have a look as it contains exactly an approach of simulation you can follow to obtain statistical description of the residual stresses across the scales, when considering poly-crystalline materials.
While at the macro-scale the FEM simulation can be done by knowing the cyclic behavior of your material, in the case of micro-scale (Crystal Plasticity-FEM model) simulation the parameters you need are the following: 1) ratio of phases involved; 2) material texture; 3) elastic properties of the phases; 4) Critical resolved shear stress (CRSS) coefficients, for the simulation of plastic deformations.
In your specific case of machining, the macro-scale simulation is basically what you can find in the literature as you mentioned, which describe the plastic deformation using a continuum mechanics approach. The result from such simulation will then feed the model at the micro-scale, i.e. CP-FEM.
To answer your second question, the difference lies principally in the absence of the neighbouring grains interaction, which is particularly enhanced when the single crystal behavior is highly anisotropic.
Hope this helps,
Enrico
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