| Microplane modeling of martensite reorientation in shape memory alloys (1393/3/12) |
Two main parts of the inelastic strain in deformations of shape memory alloys are
transformation- and reorientation- induced strains. In some constitutive models, a distinct
term is assigned for reorientation of the product p hase according to variations of loading di-rection. In this work, a model is proposed in which there is not any separate expression for
modeling the reorientation part. This model is based on Microplane theory and is inherently
able to account for reorientation strains in multiaxial loadings. Stress-strain diagrams for
uniaxial tension at different temperatures are simulated in order to compare the present ap-proach and another one in which the reorientation strain is separately stated. A very good
agreement is seen indicating the capability of Microplane theory to predict the main charac-teristics of the behaviors of shape memory alloys.
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| hape Memory Effect Behavior of NiTi Torque Tubes in Torsion (1393/3/12) |
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n order to simulate the torsional behavior of NiTi torque
tubes, two different 3D thermo-mechanical constitutive models
are utilized. Firstly, an available incremental constitutive model
is used in which a return mapping algorithm is implemented to
numerically calculate the strains for any applied stresses.
Secondly, Microplane theory is employed based on which 1D
constitutive laws are considered for associated stress and strain
components on any arbitrary plane passing through a material
point followed by a homogenization process to generalize the
1D equations to a 3D macroscopic model. Both of the
constitutive models are implemented in ABAQUS by
developing UMAT.
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| Microplane modeling of shape memory alloys in an alternative formulation (1393/3/12) |
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In this work, a volumetric-deviatoric split in microplane
formulation is considered for modeling of shape memory alloys.
In the microplane theory, macroscopic stress tensor is projected
into the microplane stresses that are decomposed to either
Volumetric-Deviatoric-Tangential (V-D-T) split or Volumetric-Deviatoric (V-D) split. Then 1D constitutive laws are defined
between associated microplane stress and microplane strain on
any plane. The homogenization process is used according to
which macroscopic strain tensor is obtained by integration
strains on all orientations at a point. The constitutive
formulation based on V-D-T split uses the principle of
complementary virtual work (PCVW) to derive macroscopic
strain tensor. It is shown that in the microplane models based on
V-D-T split- which are derived from the PCVW
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| Modify the Phase-Diagram to enter Effects of Loading History on Transformation Surface in Shape Memory Alloys (1393/3/12) |
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In most of the existing SMA constitutive
models, it is assumed that transformation starts when
a thermodynamic driving force reaches a specified
amount regardless of loading history. In this work, a
phenomenological approach is used to develop an
enhanced one-dimensional constitutive model in
which loading history is directly considered as one of
the main parameters affecting the transformation start
conditions. To generalize the model to three-dimensional cases, a microplane formulation based
on volumetric-deviatoric is employed. A free energy
potential is defined at the microplane level,
integratied over all orientations at a material point to
provide the macroscopic free energy.
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4.4/10 (تعداد آرا 17 نفر )
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