During machining processes, materials undergo severe deformations that lead to different behavior than in the case of slow deformation. The microstructure changes, as a consequence, affect the materials properties and therefore influence the functionality of the component. Developing material models capable of capturing such changes is therefore critical to better understand the interaction process-materials. In this paper, we introduce a new physics model associating Mechanical Threshold Stress (MTS) with Dislocation Density (DD) models. The modeling and the experimental results of a series of large strain experiments on polycrystalline copper (OFHC) involving sequences of shear deformation and strain rate (varying from quasi-static to dynamic) are very similar to those observed in processes such as machining. The Kocks-Mecking model, using the mechanical threshold stress as an internal state variable, correlates well with experimental results and strain rate jump experiments. This model was compared to the well-known Johnson-Cook model that showed some shortcomings in capturing the stain jump. The results show a high effect of rate sensitivity of strain hardening at large strains. Coupling the mechanical threshold stress dislocation density (MTS-DD), material models were implemented in the Abaqus/Explicit FE code. The model shows potentialities in predicting an increase in dislocation density and a reduction in cell size. It could ideally be used in the modeling of machining processes.
The work presented in this paper resume a numerical analysis of the concrete cover effect, on the resistance of the steel-concrete interface. The effect of friction on the interface behavior is also included. For this, a brief description of the experimental steps generally used for the characterization of the steel-concrete interface is presented. Also, the CDP model, Concrete Damage Plasticity, is illustrated. The results of the numerical simulation using the Abaqus code are presented with different diameters of coatings with and without friction.
Behaviour of reinforced concrete and prestressed concrete structures subjected to fire is an important research theme in civil engineering. In addition, experiment investigations show that the concrete behavior is strongly affected by temperature. The aim of this work is to study numerically the residual behavior of steel-concrete bond after high temperature exposure. To do a numerical study, bond stress at the steel-concrete interface were developed using a concrete damage plasticity model (CDP model) implemented in the nonlinear finite element software «ABAQUS». The physical, mechanical and damage plasticity parameters (compressive damage and tensile damage) required for the model were drawn from previous literature works and the model was validated by simulating the uniaxial compression strength test under different temperatures using Abaqus code. The model was finally applied to simulate a pull-out test made on a reinforced concrete specimen heated at various temperature (105°C, 150°C, 200°C, 300°C, 400°C and 500°C.) and then cooled at room temperature. The numerical results show a good correlation with the experimental results and clearly indicate a deterioration of bond performance when temperature increased, particularly the bond stress, bond stiffness and pull-out force. The model was also used to validate the results of initiation and propagation of cracks.
This paper investigates the mechanical properties of light mortars containing coal waste of Jerada mine, as a volume replacement for sand, with different percentages of substitution: 10%, 20% and 50%. The results revealed a decrease in the mechanical properties of composite mortars, including uniaxial compression and flexural strength as well as rigidity modulus. However, the heat treatment improves their ductility, and delays the propagation of cracks. Thus, the developed material is interesting for use in construction, serving as a basis for manufacturing prefabricated blocks treated at 600°C. These elements can be used for applications with large deformations, or with mechanical or acoustic vibrations.
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