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Crystal Plasticity Based Polycrystalline Cyclic Constitutive Model And Its Finite Element Implementation

Posted on:2015-02-02Degree:MasterType:Thesis
Country:ChinaCandidate:J LuoFull Text:PDF
GTID:2251330428977388Subject:Solid mechanics
Abstract/Summary:PDF Full Text Request
In the framework of crystal plasticity, a systematic study on the polycrystalline cyclic constitutive model and its numerical implementation was conducted. The main contents of this thesis involve:1. The cyclic deformation of rolled5083H111aluminum alloy plate was experimentally investigated by uniaxial cyclic loading tests, and the cyclic softening/hardening feature and ratchetting behaviour of the alloy were discussed. Some significant conclusions, which are helpful to construct the corresponding cyclic constitutive model of polycrystalline alloy, are obtained.2. Based on crystal plasticity theory, the dislocation slipping of the face centered cubic (FCC) metal was considered, and a cyclic polycrystalline constitutive model was constructed. The developed model was adopted to describe the cyclic deformation of rolled5083H111aluminum alloy plate, a face centered cubic (FCC) metal. Comparison between simulated and experimental results shows that the proposed model describes the cyclic hardening and ratchetting behavior of the prescribed FCC metal reasonably.3. From the polycrystalline cyclic constitutive model for the FCC metal, a new model describing the uniaxial ratchetting behavior of the polycrystalline body centered cubic (BCC) metal was developed. The simulations to the cyclic deformation of annealed42CrMo steel indicate that the developed model gives a reasonable prediction to the cyclic stabilizing feature and ratchetting behavior of the prescribed BCC metal. In the meantime, the remarkable dependence of the cyclic deformation of BCC single crystal grains on the crystallographic orientation is revealed correctly.4. For the finite element implementation of the cyclic crystal plasticity constitutive model, a simplified cyclic constitutive model addressing the ratchetting behavior of single crystals was proposed based on the previous work. Meanwhile, the implicit stress integration algorithm and consistent tangent modulus for the proposed simplified constitutive model were deduced, and then the proposed single crystal constitutive model was implemented numerically into the finite element software ABAQUS through a user material subroutine (UMAT). 5. A two-dimensional polycrystalline finite element model considering the randomness of grains’ geometric shapes and crystallographic orientations was constructed, which was used to simulate the uniaxial cyclic deformation behavior of rolled5083H111aluminum alloy plate. The simulated results agree quite well with the experimental ones, which verify the capacity of the proposed constitutive model to predict the cyclic deformation of the prescribed FCC polycrystalline metal. Furthermore, the simulation results show that, the crystal plasticity based finite element method can reveal the cyclic deformation mechanisms of polycrystalline metals in more details than the polycrystalline constitutive model based on the scale transition rules, because the finite element method can predict the local and heterogeneous deformation in the scale of grains, which plays an important role in the macroscopic cyclic deformation of polycrystalline aggregates.
Keywords/Search Tags:crystal plasticity, ratcheting behavior, constitutive model, finite element, facecentered cubic crystal, body centered cubic crystal
PDF Full Text Request
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