Materials Engineering - Materiálové inžinierstvo (MEMI)
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Study of the influence of agricultural waste on the porosity of clay brick
Get PDFThis paper deals with the influence of two organic residues on the porosity of clay bricks. The insulation capacity of the brick increases with increasing the porosity. Combustible organic additions are often used to form pores. The formation of the more homogenous porous structure is favourably impacted by using the crushed rough olive stones containing oil. Plasticity, bulk density and mechanical properties were studied. The additions of organic residues have proved successful to form pores while maintaining the mechanical properties in the limits of the Algerian norms
Influence of the surface finishing on electrochemical corrosion characteristics of AISI 316L stainless steel
Get PDFStainless steels from 316 group are very often and successfully uses for medical applications where the good mechanical and chemical properties in combination with non-toxicity of the material assure its safe and long term usage. Corrosion properties of AISI 361L stainless steel are strongly influenced by surface roughness and treatment of the engineering parts (specimens) and testing temperature. Electrochemical characteristics of ground, mechanically polished and passivated AISI 316L stainless steel specimens were examined with the aim to identify the polarization resistance evolution due to the surface roughness decrease. Results obtained on mechanically prepared specimens where only natural oxide layer created due to the exposure of the material to the corrosion environment was protecting the materials were compared to the passivated specimens with artificial oxide layer. Also the influence of temperature and stabilization time before measurement were taken into account when discussing the obtained results. Positive influence of decreasing surface roughness was obtained as well as increase of polarization resistance due to the chemical passivation of the surface. Increase of the testing temperature and short stabilization time of the specimen in the corrosion environment were observed negatively influencing corrosion resistance of AISI 316L stainless steel
INFLUENCE OF PHOSPHATIZED SURFACE LAYER ON CORROSION RESISTANCE OF Mg-Al-RE ALLOY
Get PDFThis contribution deals with evaluation of the corrosion resistance of extruded Mg-2Al-1RE (AE21) magnesium alloy in the state before and after treatment of ground surface by selected phosphatizing procedure. Specimens were exposed to 0.1M NaCl solution for several time periods starting from 5 minutes up-to 168 hours at room temperature of 22 ± 1 °C. Afterwards electrochemical impedance spectroscopy was carried out on the exposed specimens. Based on the results obtained from the electrochemical tests and visual observation of corrosion attack progress, positive or negative impact of selected phosphating process on the corrosion resistance of Mg-2Al-1RE magnesium alloy under given conditions was assessed
Fatigue life analysis of die forged railway axle manufactured from C30 steel
Get PDFWith respect to the manufacturing process, different parts of one structural component can have different fatigue properties. In this study, the fatigue life of a railway axle manufactured from C30 steel by die forging is evaluated in the part of the axle bolster and axle body. According to the fatigue test results obtained at high frequency tension - compression fatigue tests (f ≈ 20 kHz, R = -1, T = 20 ± 5 °C), due to the higher level of work hardening of the axle bolster, the fatigue strength of material in this part is significantly higher than in the axle body. Different fatigue strength of these parts were observed despite the fact, that results of static tensile tests did not proved any important differences in the ultimate tensile strength, yield point and elongation.
The pseudoelasticity and the shape memory effect in CoNiAl alloys
Get PDFThe cobalt alloys (close to the CoNiAl stoichiometry) are the less known shape memory alloys. Such behavior is consequence of the martensitic transformation. The pseudoelasticity is caused by the stress-induced martensitic transformation above the equilibrium martensite start temperature from high temperature cubic phase (austenite) to lower symmetry phase (martensite). In CoNiAl the pseudoelastic behavior can be obtained by the high temperature annealing. In presented work the effect of the annealing temperature on both pseudoelastic behavior and microstructure was investigated
The degradation of lining of rotary furnaces in the production of zinc oxide
Get PDFThis paper is closely connected with the complex problem of degradation relating to the refractories of rotary furnace linings in the production of zinc oxide. Zinc oxide can be produced by variety of ways, but the most common method of production which is used in Europe is indirect, i.e. pyrolytic combustion of zinc. This method is also called "French process" of manufacturing ZnO. But this mentioned method of preparation leads to the creation of the enormous amount of zinc slag including chemical complexes of elements Fe, Zn and Al. The mechanism of degradation of the lining leads to slag rests and it is closely connected with the mutual interaction of the aggressive agents with the components of the lining. This process creates a new undesired surface layer which increased the overall thickness of zinc slag. Stuck slag has the influence on rapid degradation of the linings and moreover it also decreases the production quality of ZnO. Analysis results introduced in this paper are significant information for minimizing of degradation of rotary furnaces.
Modeling the damage of welded steel, using the GTN model
Get PDFThe aim of our work is the modeling of the damage in the weld metal according to the finite element method and the concepts of fracture mechanics based on local approaches using the code ABAQUS calculates. The use of the Gurson-Tvergaard-Needleman model axisymmetric specimens AE type to three different zones (Base metal, molten metal and heat affected Zone) with four levels of triaxiality (AE2, AE4, AE10 and AE80), we have used to model the behavior of damage to welded steel, which is described as being due to the growth and coalescence of cavities with high rates of triaxialit
Synthesis of a new 0.6PZS-0.4PLZT ceramics system, sintering and Microstructure properties characterization
Get PDFThe composition of 0.6PZS-0.4PLZT system was 0.6Pb (Zn1/3, Sb2/3) O3-0.4Pb0.98La0.02 (Zr0.48, Ti0.52) O3 were synthesized by a solid mixed-oxide solution method. The specific weight and porosity of the sintered component was measured from its mass and dimensions. The phase development and the lattice parameters of the sintered samples at 1050°C and 1200°C were analyzed and estimate by X-ray diffraction (XRD) (High score) and Celref software . The microstructure properties and morphology were characterized by scanning electron microscopy (SEM). The increasing in sintering temperature from 1050°C to 1200°C causes change for compound formation from Pb2Sb2O7 with cubic phase structure (FD3M) ,a= 10,4825°A; to another compound Zn2.3Sb0.67O4 with cubic phase structure (FD3M) ,a= 8,5354°A and slightly porous morphology
BEHAVIOR OF STEEL DP 600 UNDER DYNAMIC CONDITIONS
No full textDynamic tensile testing of sheet steels is becoming more important. Experimental dynamic tensile technique is depending on the strain rate. For experiments was used two testing method servo hydraulic and single bar method. Experiments was realized on steel grade DP 600. Steel were performed and evaluated static and dynamic tests. Was investigated substructure in static and dynamic loading conditions
Influence of mictrostructure features on the corrosion behaviourof AZ91 alloy in chloride media
Get PDFThe influence of the microstructure of as-cast AZ91 magnesium alloy, which applied to solution annealing treatment and ageing treatment respectively, was evaluated in terms of its corrosion behaviour in 0.1 M NaCl solution at room temperature. The corrosion process was monitored by electrochemical impedance spectroscopy (EIS) and the surface was characterized by scanning Kelvin probe force microscopy (SKPFM). The extent of corrosion damage was dependent on the microstructure. Surface potential maps indicated that, the surface potential of α-matrix is more positive than surface potential of β phase