Abstract: The paper also presents the growth kinetics of the hard layers on the surface grade machinery steels type AISI 9840 with a boron dehydrated paste. The thermochemical treatment was performed at three different temperatures: 1173, 1223, and 1273 K, with 2, 4, 6, and 8 h treatment time for each temperature. The presence of the hard layers FeB and Fe2B formed on the surface AISI 9840 was confirmed by cross sectional observation by scanning electron microscopy (SEM), XRD analysis and the distribution of alloy elements from hard layers was confirmed by energy dispersive spectroscopy (EDS). Using the law of parabolic growth the mobility of boron was included potential influence of boron, treatment time, temperature and time incubation in hard layers. Finally, nanoindentation technique test the modulus and hardness are obtained of the FeB and Fe2B hard layers.
Abstract: In this work, the mechanical behavior on AISI 4140 with boride coating and hardened quenching-tempering was studies subsequently to boriding. The boriding is conducted at temperatures 1203 and 1233 K for 7 h, after that all samples at a temperature of 1143 K for 1 h and tempering 473 K were exposed for 1 h 30 minutes. The microstructural characterization was examined by scanning electron microscopy with saw-tooth morphology of boride coatings type Fe2B. Three-point bend test was used to study the effect of hydrogen cathodic charging on the mechanical behavior of AISI 4140 with boride coatings, the results show a reduction of ductility and 58.17% of indices of embrittlement () and show a crack on the substrate due to interaction of hydrogen atom. Also, sample boride at 1203 K with hydrogen show a low decrease of the bending stress with respectively a sample boride without hydrogen and a decrease of the parameter () with 35.32% due to the formation of boride coatings.
Abstract: Samples of partly desorbed MgH2 have been studied by the X-ray diffraction method. All samples contained two phases (Mg and MgH2) and were stable at ambient condition for several months. After fast quenching in liquid nitrogen the samples became unstable and transformed after several days into Mg. The rate of decomposition depends on the amount ratio of Mg and MgH2 phases in the sample. Destabilization of the hydride phase observed in quenched samples can be explained on the basis of different diffusion of disordered and ordered hydrogen atoms.
Abstract: One of the most used in the field of medicine for the treatment of tibial shaft fractures internal fixation methods is by osteosynthesis plates, the most common plate limited contact dynamic compression (DCP-LC) . This paper presents the results of the fracture site grade 1, where the contact plate and the bone callus area on plates made of bone (LVM stainless steel, titanium alloy different biomedical materials and cobalt alloy), in recovery conditions 1% (one week of recovery), 50% (three weeks of recovery), 75% (six weeks of recovery) and 100%. The fractured tibia bone was modeled with an ideal geometry in CAD , modeling of commercial DCP-LC plate was obtained by parameterization of the part using a coordinate machine equipment for the exact geometry.
The finite element method for the analysis of each case under the same loads and boundary conditions is used, the results were used to determine stress concentrations in the displacement plate and the fracture callus in the load direction, to have a starting point in the optimization of the geometry from a commercial plate minimizing mass while determining that the material has faster and better biocompatibility with the human body recovery.
The results obtained show that the plate under the conditions of three different types of biomaterials has a greater stress concentration in the part located in the fracture zone from stage with 1% recovery between the surfaces of the bone callus upper and lower, keeping this a significant effect on the recovery of the fracture. The compression and tension strength that occur in the intact part of the bone and the tibial fracture interface at different stages of osseous healing have been investigated, The results were compared and presented, showing that the stress distribution in the callus to 1% recovery in the stainless steel plate indicate considerable compression in the area of the callus with this causing deterioration in the area fracture because the callus is not strengthened by contact between fractured bone by increasing the recovery time, the results also indicate that the titanium plate is the one with the lower shielding effect  according to the distribution of contact stresses according to the recovery period in the part of callus, making it the material of which the best adaptability to the bone is obtained.
Abstract: When casting ECO Al alloys, Mg-Al2Ca is used as a substitute for elemental Mg during the alloying process. Several previous studies have determined the mechanical and metallurgical properties of the ECO Al 5052 alloy. In this study, the weldability of the ECO Al 5052 alloy was determined. Gas metal arc welding was performed, and the resultant mechanical and metallurgical aspects of the welds in ECO Al 5052 alloy and commercial Al 5052 alloy were examined. In comparison to the commercial Al 5052 alloy specimen, the welds produced in the ECO Al 5052 alloy exhibited a very narrow heat-affected zone and were not softened through grain coarsening. Consequently, almost 100% joint efficiencies were observed in ECO Al alloy welds, in comparison to joint efficiencies of only 82% in conventional Al 5052 alloy welds.
Abstract: This work aims to realize an experimental investigation of the drying of castor bean fruits (Ricinus communis L., “BRS Energia” variety) in oven. Results of the average moisture content and surface temperature of the product as a function of time were analyzed for different drying air temperatures (40, 50, 60, 70, 80, 90 and 100°C). Results shows that increasing drying temperature and decreasing air relative humidity we have an increases in the drying rate and more quickly the castor fruits reaches both thermal and hygroscopic equilibrium. It was found that high drying rates generates hydric and thermal stresses inside the product, causing cracks and deformations in the castor bean fruits.
Abstract: Classical surveying of the machined surface quality is performed very often with using roughness profile recording by means of contact mechanical profilometer [4-7]. Also classical attitude to the profile run elaboration is to regard it as to a curve composed of the three main components: shape – treated mostly as deterministic, waviness – treated essentially as deterministic with some probabilistic component, and roughness itself – treated to as purely probabilistic. The question is: how to estimate this three components quantitatively and extract for individual evaluation. In our works we have developed methodical procedures of profile elaboration divided into three major steps: shape estimation and extraction with using polynomials of the order fitted to the evaluated profile, waviness estimation and extraction with using spatial filtering methods employing so called notch filters, statistical roughness estimation with using the set of tests and methods devoted especially to roughness runs of the purely probabilistic type. The notch filters are filters cutting out one, well determined spatial frequency λ0 from the spectrum of frequencies related with investigated profile. The second but not less important advantage of this choose, was the phase characteristics of this filter, which tends rapidly to zero outside the “notch” band, not distorting unfiltered spatial signal. The width of cutting “notch” is controlled with using one independent variable Q. Our methodology is based upon cutting out a set of frequencies from the profile, tuned separately for to achieve as well reflection of the periodic impulse-like signal as possible, due to the well known theorem of decomposing physical, periodical signals into their harmonic components. In our researches we have employed the set of 8 filters providing us with good results even with profiles “scared” with substantial tracks of periodically acting tool. Of course, it is still possible to employ even greater number of filters, due to their low numerical complexness. Also the comparison has been performed with the profile not affected by waviness for to convince, that this type of filter simply do not affect the probabilistic roughness component. All of the profile elaboration stages have been checked due to their spatial spectrum with using classical tool – FFT transform of the roughness profile autocovariance function. As the major check of the proposed procedure correctness, i.e. proper extraction of the waviness component without disturbing of the statistical roughness parameters we assumed checking of the shape factor Rq/Ra before and after waviness extraction, which turned to be the same at the good level of accuracy. Our results, basing on simple and fundamental frequency analysis seems to be the good alternative to much complicated and time consuming analysis based on wavelet transforms in different forms.
Abstract: In this study, we analyzed weld cracking in Ni-based superalloys. Alloys with about 64 wt.% Ni and 31 wt.% Ni were used for the weld metal analysis. Phase transition predicted by thermodynamic calculation were compared with experimental results. The weld metal’s microstructure was analyzed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) mapping, and its mechanical properties tested. From EDX mapping, it was established that the alloying elements (Nb and Mo) were segregated around the weld crack as a result of the formation of a niobium carbide (NbC).
Abstract: Low-temperature nitriding of austenitic stainless steels or chromium containing alloys can produce expanded austenite, known as S-phase, with combined improvement in wear and corrosion resistance. In the paper a critical review of various models for nitrogen diffusion during nitriding is presented. A special attention is paid to the expanded austenite growth. A new model based on bi-velocity method and including stresses is presented. Basic equations and boundary conditions are discussed. Composition dependent nitrogen diffusion coefficient is assumed. Numerical solutions are obtained for the growth of the S-phase layer in steel. The results are compared with previous experiment and calculations.