Advanced Materials Research Vols. 941-944

Abstract: In this research, a new ultrasonic horn is designed and fabricated for welding thin Ni plates by vibration analysis. Two types of the horn tip are fabricated to evaluate the effect of horn’s tip on the weldability. Modal analysis, harmonic response analysis and FFT analysis are carried out for verifying the adequacy of the developed horn. To evaluate weldability of two types of horn tip, welding strength and the microstructure of the weld surface are experimentally investigated with various welding parameters such as pressure, time and vibration amplitude. Finally, the new horn with resonant frequency of 40 kHz is developed, and it is shown that welding strength and the microstructure of the weld surface are largely affected by horn’s tip shape.

Abstract: AC A-TIG welding on 5052 aluminum alloy was investigated. The single component of oxide TiO₂, SiO₂, Cr₂O₃, V₂O₅ and halide CaF₂ was served as activating fluxes to study the effect on weld penetration and weld forming. The experimental results show that weld penetration can be increased and welding productivity can be improved in A-TIG welding. Activating fluxes, especially TiO₂ and SiO₂, have more significant effect on weld penetration than conventional TIG welding, moreover the better weld shape formed after coating activating flux is obtained, weld width has slight decrease that makes HAZ of A-TIG welding smaller.

Abstract: Welded components of low alloy steels are widely used in various applications. Stress reliving is very important to these welded structures. Vibration stress relief (VSR) is an relatively new method for this purpose. In this study, Q235 and Q345 steel plates were welded. Then they were treated by VSR. The microstructure of the welded lines were investigated and the residual stresses in two directions in these welded structures were measured. The difference of the efficiency of VSR on the two materials were investigate. It is found that, the decreasing amplitude of the residual stress in the Q235 welded structures significantly exceeded that in the Q345 welded structures. The grain size in the area near the weld lines is the main factor that affects the efficiency of the VSR treatment.

Abstract: In this paper, structural adhesive SikaPower-498 is associated with spot welds to produce weld bonded joint with KS2 specimens. The specimens are tested under tension, shear and peeling loading. Weld bonded joint ultimate strength and energy absorption are compared with single spot welded joints and adhesively bonded joints tests. In order to investigate the facture mechanism of weld bonded joint, optical microscopy and scanning electronic microscopy are used to check the material structure and the facture surfaces respectively. Weld bonded joints show the highest ultimate strength and energy absorption under tension and peeling test among the three tests while it has intermediate ultimate strength and the lowest energy absorption under shear. Fracture analysis shows that spot welds fail in ductile fracture. The results can be used to design weld bonded joint in car body-in-white and to calibrate modeling parameters for weld bonded joint modeling in finite element calculations.

Abstract: Sapphire/metal soldering joints are widely needed in various optical instruments. Traditional soldering methods are expensive and time consuming, because they usually involve a sapphire surface metallization procedure and a vacuum soldering procedure. In this study, we sealed infrared sapphire windows using a novel ultrasonic soldering method in the ambient atmosphere, with Sn-Zn-Al alloy as the solder. The wetting and bonding at the sapphire/solder and solder/metal-tube interfaces were realized by ultrasound. The microstructure of the joints was revealed by means of scanning electron microscope (SEM). The gas impermeability of the samples was investigated. This new method is very simple and cost-saving. The reliability of the samples made by this new method is equal to that made by traditional method. This is the first application of the ultrasonic interfacial deposition brazing and soldering (UIDBS) method to a practical device. We hope this method to be applied to other optical devices.

Abstract: This paper mainly introduces the properties of welded joints of supercritical boilers, combined with the actual construction of a power plant, of these new type heat-resistant steel we Ultra supercritical unit; heat resistant steel; weldability al exploration.

Abstract: Since the oil price has been significantly jumped for recent some years, the diesel engine of the merchant ship has been mainly used the heavy oil of low quality. Thus, it has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of the enginet parts surrounded with combustion chamber is more serious compared to the other parts of the engine. Therefore, an optimum repair welding for these parts is very important to prolong their lifetime in a economical point of view. In this study, Inconel 718 filler metal were welded with GTAW method in the cast steel which would be generally used with piston crown material. In this case, the mechanical and corrosion properties between weld metal zone (WM) welded to the groove which were artificially made in the base metal and deposited metal zone (DM) only welded on the surface of the base metal by Inconel 718 filler metal were investigated using electrochemical methods, such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H₂SO₄ solution. The deposited metal zone exhibited a lower value of hardness compared to the weld metal zone. Moreover, the corrosion current density also indicated significantly a lower value in the deposited metal zone compared to the weld metal zone, showing a nobler corrosion potential than the weld metal zone. The corrosive products was not observed both in the weld and deposited metal zones. The microstructure of the pearlite with black color was hardly observed in the weld metal zone, while, the microstructure of ferrite with white color indicated nearly mostly in the weld metal zone. However, ferrite microstructure considerably appeared in the deposited metal zone with crystal pattern, and pearlite microstructure was more or less observed in the deposited metal zone. In particular, the polarization characteristics such as impedance, polarization curve and cyclic voltammogram associated with corrosion resistance property were well in good agreement with each other.

Abstract: Damage modeling approach is increasingly used to simulate fracture and debonding processes in adhesively bonded joint. In order to understand the relation between the delamination behavior of different types of adhesives and the type of cohesive zone models (CZMs), the pure tension and pure shear experiments were conducted used two distinct adhesives, an epoxy-based adhesive in a brittle manner and VHB^TM tape adhesive in a ductile manner. The traction-separation relations of the two adhesives were extracted from the tension and shear experimental results. Three types of cohesive zone models (CZMs) are adopted, including the exponential, bilinear, and trapezoidal models. VUMAT subroutine of CZMs as the adhesive layer is used to simulate the specimen tension and shear debonding procedures. The results demonstrate that (i) the bilinear CZM more suitably describes the brittle adhesive and the exponential CZM suitably describes the ductile adhesive to simulate the tension and shear failure. (ii) cohesive strength and work of separation are the significant affections on the simulation results. and (iii) the shape of CZM is a significant affections on the simulation the pure tension and shear debonding procedure.

Abstract: To improve the wear resistance of A6061 plate, Fe alloy cladding layers consisting of FeAl₃ intermetallic compound were synthesized by resistance seam welding with high carbon iron alloy powder (SHA). The effect of welding speed on the macrostructures, phase compositions, hardness, and wear resistance of the cladding layers were investigated. The results showed the hardness of the cladding layers were significantly improved to 455, 469, 479 and 615 HV in response to the welding speed of 0.1, 0.5, 1.0 and 1.5 m/min as compared with 60 HV of the A6061 substrate. The wear resistance of the cladding layer was also enhanced with decreasing the welding speed.

Abstract: Many factors have an essential impact on the air purification efficiency. Very important for a lot of industries is to choose right air purification system. Especially important is to take into account manufacturing including generation of combustible and explosive dust. One of the way to prevent possibilities of fire and explosion is using reverse flow cyclone as a pre-cleaning system. In the article the efficiency of such precleaner is showed and experimentally proved.