Wiera Oliferuk

Rate of energy storage and microstructure evolution during the tensile deformation of austenitic steel

Abstract The results of investigations of the energy storage process in austenitic stainless steel deformed in tension are reported. Conclusive evidence is presented for the existence at the initial stage of deformation of the maximum in the instantaneous rate of energy storage defined as des/dew, where es is the stored energy and ew is the mechanical energy expended in plastic deformation. Its occurrence is interpreted in terms of the evolution of the microstructure during deformation.

Energy storage during the tensile deformation of Armco iron and austenitic steel

Abstract A modification of the single-step method based on continuous detection of IR radiation emitted directly from a strained sample was employed to study energy storage during the initial stage of plastic deformation of Armco iron and austenitic stainless steel. The existence of a maximum in the dependence of the ratio of stored energy to expended energy on strain was confirmed for both materials in the range of homogeneous deformation and was interpreted in terms of variations in the contributions of endo-energetic and exo-energetic processes; the contribution of endo-energetic processes is related to the increase in the dislocation density due to the generation of dislocations and the contribution of exo-energetic processes is related to energy dissipation due to movement, rearrangement and annihilation of dislocations.

Effect of the grain size on the rate of energy storage during the tensile deformation of an austenitic steel

Abstract The effect of the grain size on the energy storage process in a low carbon austenitic steel deformed in tension is studied. The energy conversion at each instant of the deformation process is characterized by the instantaneous rate of energy storage, d e s d e w , where e s is the stored energy and e w is the mechanical energy expended on the plastic deformation. It has been shown experimentally that, in the initial stage of plastic deformation in this austenitic steel, the dependence of the rate d e s d e w on e w exhibits a maximum. The location of the maximum depends on the grain size of the material. In fine-grained samples, the maximum appears at smaller strains. After reaching a certain degree of deformation, plots of d e s d e w vs. the strain for the samples of both groups are practically the same. These results are interpreted in terms of the microstructural evolution during deformation. It has been shown that the grain boundaries favour the formation and affect the evolution of low energy dislocation structures.

Energy balance and identification of hardening moduli in plastic deformation processes

Abstract The hardening moduli H r and H d of plastic deformation associated with the free energy and dissipation function in a representative material element are defined analytically and specified experimentally for three materials. Besides the stress–strain curve and work expended during the deformation process, variation of the hardening moduli with plastic deformation is also determined for austenitic steel, austenitic-ferritic steel and Fe–Si alloy.

Energy balance and macroscopic strain localization during plastic deformation of polycrystalline metals

Abstract The energy balance during uniaxial test of the annealed FeSi sheet and the rolled one has been studied. The method of estimation of the energy storage rate in the stage of macroscopic strain localization has been presented. Heterogeneous temperature distribution on the surface of the loaded sample as an experimental indicator of the macroscopic localization of strain was used. The experimental evidence for the existence of recovery process during a development of the localized plastic deformation has been provided.

Mode of deformation and the rate of energy storage during uniaxial tensile deformation of austenitic steel

The mechanism of slip and its consequence in the process of energy storage during uniaxial tension of austenitic steel was studied. The interpretation of the energy storage process in terms of the slip development and microscopic shear band formation is presented.

Slip behaviour and energy storage process during uniaxial tensile deformation of austenitic steel

The mechanism of slip and its consequence in the process of energy storage during uniaxial tension of austenitic steel were studied. Interpretation of the energy storage process in terms of slip development and microscopic shear band formation is presented.

Distributions of energy storage rate and microstructural evolution in the area of plastic strain localization during uniaxial tension of austenitic steel

The presented work is devoted to an experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using Transmission Electron Microscopy (TEM) and Electron Back Scattered Diffraction (EBSC) were performed. On the basis of microstructural studies it is believed that a 0 value of energy storage rate corresponds to the state in which only two dominant components of the texture appear, creating conditions for crystallographic shear banding.

Distribution of energy storage rate in area of strain localization during tension of austenitic steel

The present work is devoted to experimental determination of the energy storage rate in the area of strain localization. The experimental procedure involves two complementary techniques: i.e. infrared thermography (IRT) and visible light imaging. The results of experiments have shown that during the evolution of plastic strain localization the energy storage rate in some areas of the deformed specimen drops to zero. To interpret the decrease of the energy storage rate in terms of micro-mechanisms, microstructural observations using electron back scattered diffraction (EBSC) were performed.

Identification of energy storage rate components. Theoretical and experimental approach

The subject of the present paper is decomposition of energy storage rate into terms related to different mode of deformation. The stored energy is the change in internal energy due to plastic deformation after specimen unloading. Hence, this energy describes the state of the cold-worked material. Whereas, the ratio of the stored energy increment to the appropriate increment of plastic work is the measure of energy conversion process. This ratio is called the energy storage rate. Experimental results show that the energy storage rate is dependent on plastic strain. This dependence is influenced by different microscopic deformation mechanisms. It has been shown that the energy storage rate can be presented as a sum of particular components. Each of them is related to the separate internal microscopic mechanism. Two of the components are identified. One of them is the storage rate of statistically stored dislocation energy related to uniform deformation. Another one is connected with non-uniform deformation at the grain level. It is the storage rate of the long range stresses energy and geometrically necessary dislocation energy. The maximum of energy storage rate, that appeared at initial stage of plastic deformation is discussed in terms of internal micro-stresses.