Papers by Keyword: Metal

Abstract: Vat photopolymerization is one of additive manufacturing and also known as photo-curable three-dimensional printing technology. It uses light energy with the proper wavelength to expose on the liquid photo-curable resin inducing the photopolymerization process and resulting in solidification layer-by-layer. The building method is classified into two ways: free-surface and constrained-surface. The advantage and disadvantage of both methods are described and analysed according to the different material property and requirement. The basic composition for photo-curable resin consists of photo-initiator and monomer. Adding powder into photo-curable resin makes the photo-curable slurry. Literatures report that high density powder such as zirconia oxide or Inconel 718 is suitable for free-surface building method because of poor suspension. However, the volume percentage in the slurry is less than 50% causing the higher shrinkage ratio and inaccuracy after sintering process. The coupling agent may increase the suspension of powder in slurry but experimental result shows that it still cannot improve the success rate in the constrained-surface building method. Therefore, this study proposes a combination method to overcome the difficulty of making high density ceramic or metal part. In addition, the sintering process is a key factor to obtain the high dense part with no crack occurrence and desirable microstructure. The optimized sintering parameters for zirconia oxide and Inconel 718 are also introduced.

Abstract: In this work, we investigated and discussed the experimental and theoretical data of the vacancy formation energy E_v. The results of calculations in the continuum model of the solids and the model of interaction between a pair of neutral atoms, as well as the results of ab initio methods using various exchange – correlation functionals, are analyzed. It was found that the experimental and theoretical values of the vacancy formation energy have an adjusted coefficient of determination R² close to 0.80. The relationship between the calculated vacancy formation energy and the sublimation enthalpy most closely corresponds to the relation E_v = ΔH_s/3 for the results obtained on the basis of continuum model and model of interaction between a pair of atoms. The vacancy formation energy most closely correlates with the melting enthalpy ΔH_m. The adjusting coefficient of determination R² of this relation is 0.87 in comparison with 0.71 and 0.84 for the sublimation enthalpy and the evaporation enthalpy, respectively.

Abstract: The article presents the results of research on the impact of laser surface treatment on selected steel properties. The laser treatment consisted of remelting and alloying high speed steel using hard ceramic phase powders. A high-power diode laser was used in the experiment to examine the effect of parameters such as beam power and powder type on the structure and properties of the surface layer. A structural mechanism was observed consisting in obtaining, after laser processing, a super fine crystalline structure and a dendritic structure at the remelting zone. Structural changes have been found to be associated with improved properties such as hardness, microhardness and wear resistance. Steel treated with conventional heat treatment was used as a comparative material.

Abstract: This paper investigates the effect of the laser cutting parameters on the heat-affected zone, and on the boundary layer of stainless steel processing. A new analytical resolution based on the boundary layer theory is used to deduce the interaction effects of the cutting parameters on the above zones. The results revealed that, the laminar nitrogen assist gas has a negligible effect on the HAZ depth but it has a remarkable effect on the molten boundary layer. It is also noticed that the pressure gradient remains very small compared to the interface shearing and the conductive heat losses from the cutting zone towards the substrate is dominant compared to the convective heat losses towards the gas.

Abstract: The aim of this study is to develop a finite element analysis technique to characterize the distributions of temperature and stress in the process of multilayer deposition of metallic powders by laser additive manufacturing (LAM). Simulation results indicate the residual normal stress in the laser moving direction is greater than that in other directions due to a larger temperature gradient, and it increases with number of deposited layers. Highly residual stresses are present in the LAM build and at the base nearby the interface between the build and base.

Abstract: Ultrasonic welding is a suitable solid-state joining technique for producing high strength joints of similar or dissimilar materials, even of material combinations that were previously considered as not weldable. Several varieties of transmitting the ultrasound into the joining partners exist whereas the investigated torsional welding principle utilizes a ring shaped sonotrode for transmitting ultrasonic vibrations tangentially to the welding force into the workpiece. Due to the specific sonotrode geometry ultrasonic torsional welding is a remarkably gentle welding technique, allowing to join even most sensitive components e.g. sensors or brittle elements. Nevertheless, ultrasonic torsional welded joints show high tensile strengths and helium-tightness. Current investigations focus on the realization of metal/glass ceramics joints. In this project two metals with different thermal expansion coefficients have been utilized as the metal joining partner. The glass joining partner was the commercially available Li₂O-Al₂O₃-SiO₂ CERAN. For examining the microstructure light as well as scanning electron microscopy have been performed. Additionally, mechanical characterization has been carried out through tensile shear tests.

Abstract: The results of investigation of mechanical, electrical, thermoelectric and tribological properties of metal-fullerene film composites of Ni-C₆₀ and Ti-C₆₀ systems is presented. It has been found that doping of metals with fullerenes leads to a significant increase in the strength of the material, and a change in the electrical, optical, and other properties of the material. It is established that metal-fullerene films are characterized by low friction coefficients and high wear resistance. It is experimentally shown that metal-fullerene composite thin films possess a capacitive impedance, that the thermopower of Ti-C₆₀ coatings reaches the value of 30 μV/K depending on the Ti/C₆₀ ratio.

Abstract: A wetting layer with a nanophase structure was detected and identified before the first bulk phase during the formation of the metal-silicon interface by vapor-phase deposition at room temperature of the substrate. This became possible due to the developed technique for complex analysis of the structural-chemical state of the surface/ interface with help of Auger electron spectroscopy and electron energy loss spectroscopy, and also due to the method of physical vapor deposition at low temperature of vapor. The discovery this wetting layer and stage of its formation fundamentally changes the approach to the formation of contact between metal and silicon.

Abstract: In different innovative markets, such as electro mobility and flexible electronics, among others, the mechanical joining processes based on sheet metal forming technologies are gaining a significant relevance due to their low cost and ease of automation as compared to traditional joining techniques of riveting, bolting, fastening, welding, etc. In lightweight hybrid constructions, where a high production rate is required, clinching technology demonstrates a sustainable method to join hybrid metal-composite parts. However, the basic mechanisms of this hybrid joining process are not well studied at present and an accepted design theory in this area has not yet been established. The current contribution presents a parametric study of the hybrid clinching joining process. The Taguchi’s design of experiments method is used to investigate the effects of tools’ geometry on hybrid clinching joints’ quality characteristics, i.e. neck thickness, undercut and final bottom thickness. For this purpose, a 2D axisymmetric modelling approach was adopted for its simplicity. The study results are analyzed using the mean response and signal-to-noise ratio approaches. Accordingly, the relevant geometrical parameters of the tools with the highest influence on the accurate shaping of hybrid clinching joints are determined numerically.

Abstract: The bearings are widely used in the rotating machinery systems to support the mechanical, structural for system. In a high rotating speed, the spindle to be stable rotating is dependent on a high performance bearing. Therefore, the dynamic characteristic of a ball bearing is very importance and need to study. In this work, the dynamic characteristic of a ball bearing is focused to study. Because the geometric of ball bearing are so complex, the finite element analysis is employed to investigate. By using the finite element analysis software ANSYS, the bearings meshed model can be setup. The dynamic properties, natural frequency and mode shape of ball and global system, can be studied to improve the high spindle rotating stable performance. Numerical indicates that the stress, strain and dynamics of the ball bearing system can be investigated in this finite element model.