Papers by Keyword: Plastic Deformation

Abstract: In this work a new method for analysis of neutron diffraction results obtained during “in situ” tensile load is proposed and tested. The methodology is based on the measurements of lattice strains during “in situ” tensile test for several hkl reflections and for different orientations of the sample with respect to the scattering vector. As the result the full stress tensor for preferred texture orientations in function of applied stress can be determined with help of crystallite group method. The experimental data are presented and compared with self-consistent model calculations performed for groups of grains corresponding to the measured hkl reflections.

Abstract: Al-Si-Al₂O₃ composites were prepared by powder metallurgy with in-situ synthesis technology. The recovery and recrystallization behavior of Al-Si-Al₂O₃ composites which underwent compression and then heat-treatment under different temperature were studied using micro-hardness tester, optical microscope (OM) and scanning electron microscopy (SEM) . The results showed that the hardness of composites increased dramatically after compression, and the sample containing 5wt% Si was increasing more evidently than the sample including 10wt%Si. Heat treatment gradually eliminated work hardening; meanwhile the fact that the hardness of composites trended to decline greatly when subjected to annealing suggested occurrence of recovery and recrystallization inside the composites. Recrystallization nucleation preferentially took place in the region near the particle, while the growth of recrystallized grains can also be hindered owning to the pining effect of particles. Depending on the analysis of microstructure and microhardness, it can be concluded that the recrystallization temperature of Al-wt.5%Si-Al₂O₃ composites was 500°C and the Al-wt.10%Si-Al₂O₃ composites was 525°C.

Abstract: It is shown that the process of-phase particles dissolution in the alloy matrix is faster at superplastic deformation than during annealing. Identify ways of 40CrNiAl alloy strengthening treatments after superplastic deformation were determined. Use after superplastic deformation re-quenching and aging leads to an effective hardening of 40CrNiAl alloy. In grains of-matrix allocated secondary lamellae of-phase intermittent mechanism.

Abstract: Controlled impact may be done if the source of additional force is placed on one of the impact bodies and this force is acting during the impact time. The use of Industrial Rocket Engine (IRE), produced in Bulgaria, enables the controlled impact technology. A laboratory set up was created in order to explore the controlled impact. Experiments on plastic deformation of lead specimens were conducted on this devise using controlled impact. An increase of the specimen deformation was obtained compared to the common free-fall impact deformation as well as a decrease of the rebound to zero (we called that a sticking impact). The results obtained make clear that the use of IRE propelled production machines for plastic deformation technologies improve those processes and decrease the production drain.

Abstract: Ice jet technology shows a promising prospect of application in surface cleaning and de-painting engineering because of its environmentally friendly feature. The main objective of this work is to present a deeply experimental study on the organic paint removal from aluminum alloy 2A12 substrates and the surface damage development using ice jets. The effects of ice blasting pressure and blasting time on de-painting and damage to the substrate were mainly concerned. It was shown that at blasting pressure of 0.2MPa, organic paint coatings were stripped from the 2A12 substrates. The paint coatings, moreover, were removed more effectively with increasing blasting pressure. Little changes of the roughness of the blasted substrate surface were observed. SEM images showed little plastic deformation at the blasting pressure of 0.5MPa existed on the surface. Whereas, a few of impact craters due to impact of high-velocity ice particles appeared at 0.7MPa for 7 seconds of exposure time with its number increasing obviously for 15seconds.

Abstract: Explosive welding experiment of T2 red copper plate and DT4C electrical pure iron plate was carried out. Microcosmic analysis and plastic deformation test of the bonding interface were also studied. Results indicate that the welded zone presents periodical wavy metallurgical interface and Cu-Fe Solid solution is distributed on the wave interface. Moreover, large amplitude variation of the ratio of Cu to Fe in the Cu-Fe Solid solution is found. No separation happens after flattening test and bending test, which shows that Cu-Fe Solid solution does no harm to the bonding properties and the welding quality of T2/DT4C laminates can meet the needs of plastic working of complicated shape workpieces.

Abstract: Crack growth under cyclic loading causes failure of machine components. Non-destructive methods that can be related to plastic deformation around crack tip are necessary to study the crack growth. In the present work, a scanning Hall probe microscope (SHPM) equipped with GaAs film sensors was used to observe the magnetic fields around the plastic deformation induced by Vicker's indentations in tool steel specimens (SKS93, JIS B 4404: 2006, equivalent to AISI W4 tool steel). The magnetic field around a 2.94N-indentation was compared to that of a 294N-indentation. It was found that the decrease in the magnetic fields depends on the plastic deformation size.

Abstract: It is proposed to study the state of deformation of the material subjected to cutting technological operations. The study is based on finite deformation theory, according to which an elementary sphere imagined in the material subjected to deformation is transformed into an elementary ellipsoid. It used the method of grids or networks division applied semi-finished which was cut by two types of punches made from improved, unused OSC 10 and used OSC 10 after 15.000 cuttings. Also are analyzed the metallographic structures of the samples that are in different stages of penetration of the active cutting tool in semi-finished material. It is observed the deformation, the appearance and the structure for the action of the both punches on the semi-finished.

Abstract: Among the rail defects, the transverse fatigue crack, which has been the most dangerous damage, is developed near the rail running face and grows perpendicular to the rail surface. Finally, the transverse fatigue crack would result in the failure of railway rail. In this paper, the rolling tests were performed using a JD-1 wheel/rail simulation facility without any lubricant. The tester is composed of a small wheel served as rail and a larger wheel served as wheel. The fatigue behavior of rail rollers with different materials and curve radius were investigated in detail by examining wear volume and wear scar using optical microscopy (OM) and scanning electronic microscopy (SEM). The results indicate that with curve radius decreasing, the wear volume of rail roller increases rapidly and the fatigue damage becomes severe. Furthermore, the cracking propagation angle increases obviously with curve radius decreasing and fatigue wear is dominating during the wear process. There appears distinct plastic deformation on the section of rail roller under small curve radius condition. For the same curve radius, the wear volume of PD3 rail is more than that of PG4 rail and the plastic deformation is more obvious. Moreover, the cracking propagation angle of PD3 rail material is smaller than that of PG4 rail. In conclusion, PG4 rail material is not suitable for the high-speed railway.

Abstract: 2-D pressure model in axial and radial direction was proposed to simulate response of copper subjected to micro laser shock peening (μLSP) according to the size effect in the propagation of shock wave induced by laser in microscale. Simulations under 1-D and 2-D pressure model were conducted respectively in order to explore the effect of pressure in radial direction. The results show that distribution of residual stress and plastic deformation in depth and width are obviously different, and response of copper under 2-D pressure model are more close to the experimental results. The pressure effect in radial direction in the propagation of shock wave shouldnt be ignored, and 2-D shock wave pressure model plays an important role in accurate simulation of μLSP.