Numerical Modeling of Plasticity in FCC Crystalline Materials Using Discrete Dislocation Dynamics
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Plasticity in crystalline solids is controlled by the microscopic line defects known as “dislocations”. Decisive role of dislocations in crystal plasticity in addition to fundamentals of plastic deformation are presented in the current thesis work. Moreover, major features of numerical modeling method “Discrete Dislocation Dynamics (DDD)” technique are described to elucidate a powerful computational method used in simulation of crystal plasticity.
First part of the work is focused on the investigation of strain rate effect on the dynamic deformation of crystalline solids. Single crystal copper is chosen as a model crystal and discrete dislocation dynamics method is used to perform numerical uniaxial tensile test on the single crystal at various high strain rates. Twenty four straight dislocations of mixed character are randomly distributed inside a model crystal with an edge length of 1 µm subjected to periodic boundary conditions. Loading of the model crystal with the considered initial dislocation microstructure at constant strain rates ranging from 103 to 105s1 leads to a significant strain rate sensitivity of the plastic flow. In addition to the flow stress, microstructure evolution of the sample crystal demonstrates a considerable strain rate dependency. Furthermore, strain rate affects the strain induce microstructure heterogeneity such that more heterogeneous microstructure emerges as strain rate increases.
Anisotropic characteristic of plasticity in single crystals is investigated in the second part of the study. Copper single crystal is selected to perform numerical tensile tests on the model crystal along two different loading directions of  and  at two high strain rates. Effect of loading orientation on the macroscopic behavior along with microstructure evolution of the model crystal is examined using DDD method. Investigation of dynamic response of single crystal to the mechanical loading demonstrates a substantial effect of loading orientation on the flow stress. Furthermore, plastic anisotropy is observed in dislocation density evolution such that more dislocations are generated as straining direction of single crystal is changed from  to  axis. Likewise, strain induced microstructure heterogeneity displays the effect of loading direction such that more heterogeneous microstructure evolve as single crystal is loaded along  direction. Formation of slip bands and consequently localization of plastic deformation are detected as model crystal is loaded along both directions.
Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2015. , x, 50 p.
Dislocations, crystal plasticity, discrete dislocation dynamics, Cu single crystal, high strain rate deformation, strain rate sensitivity, plastic anisotropy, slip band formation
Engineering and Technology Materials Engineering Metallurgy and Metallic Materials
Research subject Materials Science and Engineering
IdentifiersURN: urn:nbn:se:kth:diva-175424ISBN: 978-91-7595-705-0OAI: oai:DiVA.org:kth-175424DiVA: diva2:860893
2015-10-22, Sal Kuben N111, Brinellvägen 23, Materialvetenskap, KTH, Stockholm, 15:30 (English)
Alava, Mikko, Professor
Korzhavyi, Pavel, Assoc. ProfSandström, Rolf, Professor
QC 201510152015-10-142015-10-142015-10-14Bibliographically approved
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