Experimental Study Of Plastic Deformation Research Articles

Study of deformation structures maps in metals under tension

The paper considers the regularities of macroscopic inhomogeneity of plastic flow during uniaxial tension of flat samples of Fe-Cr-Ni 2 mm thick. Their tension axis was oriented along the rolling direction. The average grain size was 12.5 ± 3 mm. The plastic flow curves of the alloy had long stages of linear strain hardening over the entire test temperature range 180 K < T < 297 K. For the experimental study of plastic deformation, we used the method of accurately reconstructing the fields of displacement vectors and calculating the components of the plastic distortion tensor using speckle photography with increments of the total strain between exposures 0.001. The field of displacement vectors as a whole over the sample during loading is inhomogeneous both in the directions of the displacement vectors and in values; in some areas, the displacement vectors nonmonotonically change directions relative to the tension axis. It has been established that in the test temperature range 180 K < T < 297 K, plastic flow is localized at all stages of the process. The appearance of the a′-martensite phase during the deformation of the alloy under study leads to a change in the mechanical characteristics, the work hardening coefficient, and the deformation localization parameters. The maps of deformation structures are analyzed in the form of spatial distributions of the components of the plastic distortion tensor: local elongations, narrowings, shifts and rotations. The non-linear nature of the change in the coefficient of transverse deformation from the level of acting stresses is established. The general form and quantitative parameters of the evolution of the components of the plastic distortion tensor indicate the connection of this process with the self-organization of a defective subsystem in a deformable medium.

Numerical and Experimental Study of Plastic Deformation During Flash Butt Welding of X65 Pipeline Steel

AbstractThe plastic deformation during flash-butt welding (FBW) and its effects on weld quality are investigated by using numerical and experimental methods. The electro-thermo-mechanical coupling model of FBW is validated by comparing the calculated temperature and plastic deformation to measured one, obtaining reasonable agreement. The calculation results reveal that a thin liquid metal film forms at the contact interface during accelerating flash stage to provide temperature conditions for upsetting. The length of liquid metal (including burning and expelled losses) is 29.7 mm for one piece pipeline tube under the given condition. The stress and strain at contact surface are both almost zero at the initial stage of upsetting due to the thin liquid metal film existing at the contact interface, and they rapidly increase to 58.0 MPa and 17.7, respectively, while the liquid metal are excluded from the contact interface between two tubes to be welded. The maximum plastic deformation is 18.1 mm at the given condition under the action of upsetting force. The experimental results illustrate that the microstructure of X65 FBW joints consists of massive ferrite, grain boundary pre-eutectic ferrite, pearlite, and widmannstatten, while the microstructure in heat-affected zone is fine ferrite and pearlite. The coarse grain size and gray spots in the butt joint severely decrease the tension strength and impact toughness.

Stress measurements of deforming olivine at high pressure

Rheological properties of mantle minerals are critical for understanding the dynamics of the Earth’s deep interior. Due to limitations in experimental technique, previous quantitative studies of the rheological properties of mantle minerals are limited to either low pressure or low temperature. The present understanding of mantle flow is mostly inferred from the extrapolation of relatively low-pressure data to mantle high-pressure conditions. However, the effect of pressure (represented by activation volume) on the rheological properties of olivine is still controversial. Therefore, deformation experiments, carried out at mantle pressures, are necessary to understand and model mantle flow. Here we report an experimental study of plastic deformation of San Carlos olivine (Mg, Fe) 2SiO 4 under upper mantle conditions. Macroscopic differential stress and strain rates have been measured in situ in a large-volume high-pressure apparatus using newly developed techniques. The differential stress at high temperature and high pressure that we measured is significantly lower than that estimated by many currently accepted olivine flow laws. We document the first in situ experimental differential stress results in a multi-anvil press. Our results give direct evidence for a relatively small activation volume (less than 10 −5 m 3 mol −1). This shows that the effect of pressure on dislocation creep is small.

Reinversion of aluminium frustra

In this paper experimental study of plastic deformation of aluminum frusta when reinverted is presented. Effects of changing the angle of frustum as well as frustum wall thickness on the absorbed energy are investigated. The details of the experimental plastic inversion and reinversion are given. Obtained results show that it is possible to use the inverted aluminum frusta several times, thus they are reusable collapsible absorbers.

Influence of plastic deformation on seizure initiation in a lubricated sliding contact

This paper describes an experimental study of plastic deformation and its influence on the initiation of seizure in a boundary and mixed lubricated non-conformal sliding contact. The experiments were made in a ball-on-disc tribometer with computer controlled transient loading. Previous work has shown a strong influence of sliding velocity and surface roughness on the transition from mild to unacceptably severe conditions. The influence of plastic deformation on the transition has not been fully understood although proposed mechanisms are often based on a plasticity dominated process. The results from this study suggest that the degree of plastic deformation is not the only factor that determines the initiation of the transition from a mild sliding condition to a severe condition. Rather, the results indicate that the properties of the boundary layers and how they change with running conditions are much more important than plastic deformation.

Experimental study of plastic deformation during sintering of cubic boron nitride compacts

Abstract In this work polycrystalline cubic boron nitride compacts (PcBN), prepared with and without binder, were sintered at 8 GPa and 1850°C using different processing times. X-ray diffraction and Raman spectroscopy were used to investigate the kinetics of plastic deformation during sintering. For compacts sintered in short processing times, both Raman and X-ray diffraction linewidths increased, indicating a high plastic deformation of the grains. For longer processing times (30–120 s) the linewidth decreased, tending to the value of the pristine cBN grains. This dependence on the processing time was interpreted as a result of the competition between the plastic deformation of the grains, dominant for short processing times, and the defect annealing process, which becomes significant for longer processing times. When aluminum binder was used for sintering, it was observed that the processing time required to recover the original linewidth is longer, and the maximum broadening of the lines occurs at a longer processing time compared to the case without binder. These results indicated that the binder phase significantly affects both plastic deformation and defect annealing processes.

Directional dependence of c-plane slip in single crystals of mercuric iodide

An experimental study of plastic deformation in thin single crystals of mercuric iodide (Hgl2) subjected to (0 0 1) [1 0 0] and (0 0 1) [1 1 0] shear loadings has established a directional dependence to the phenomenon of (0 0 1) orc-plane slip in Hgl2. The average stressess c for the “onset of yielding” were 12.6 psi (86.9 kPa) for (0 0 1) [1 0 0] shear and 16.5 psi (113.8 kPa) for (0 0 1) [1 1 0] shear; the average values of the deformation parameters 0, interpreted as a “bulk yield stress”, were 24.7 psi (170.3 kPa) for (0 0 1) [1 0 0] shear and 37.7 psi (259.9 kPa) for (0 0 1) [1 1 0] shear. These values are in agreement with the theoretical relationss c(θ)=s c(0)/cosθ ands 0(θ)=s 0(0)/cosθ, whereθ is the smallest angle between 〈1 0 0〉 crystallographic axis and the direction of shear stress applied in the (0 0 1) plane.