Key Engineering Materials Vol. 831

Abstract: The process of laser cutting by (Nozzle C 20E) can detect the roughness of the surface from the upper side, while laser cutting by (Nozzle C30E) have less roughness detection according to the ability of constant speed with different metal thickness. The width of the Kerf and surface roughness are the most factors which needs for focusing during cutting process for various plate cutting operation by CNC machine. Such machines require oxygen and propane or acetylene gases with proper pressure controls. For the gas cutting machine, the volume of oxygen gas used is more than that of propane gas. The oxygen gas is used for heating and cutting the plates. It is necessary to supply the proper amount and quality of gas to the machine to obtain a good cutting quality surfces. However; the pressure of oxygen gas depends upon the thickness of cutting plates. Stainless steel is the most important metals in the industrial and manufacturing process, so the cutting conditions are very important. Its concluded from our result, that the characteristics of the main selecting factors which effects the laser machine performance such as, the focal lens nozzle height (0.6 to 1.0mm) and the ability and speed of cutting should be fixed and not changing.

Abstract: Head forging is an indispensable part of major technical equipment, which is required to produce high quality products because of its large volume and complex structure and long service under high temperature and high pressure. By means of DEFORM-3D numerical simulation and scaling experiment, the dynamic recrystallization dynamics model of SA508-3CL steel is established. Meanwhile, the head forming scheme is designed. The effects of different blank height-diameter ratio size, punch shape size and upper and lower die matching relationship on forging forming are emphatically analyzed. Finally, the reasonable head forming scheme is determined, and the 1:8 head forming scale test is carried out. The results show that the size of the head forging basically coincides with the design size and meets the load of the hydraulic press, which proves the rationality of the forming process of the head. The study provides a theoretical basis for the manufacture of the same type of large variable wall thickness head forgings.

Abstract: In this paper, the finite element method is used to simulate and analyze the laser-MAG composite welding of 4mm thick cylinder of high strength steel 30CrMnSiA, and the variation law of welding residual stress under different technological conditions is obtained. By comparing and analyzing the welding residual stress of the actual test plate by blind hole method with theoretical calculation value, the two methods are in good agreement, and the rationality of the model is verified.

Abstract: Work presented in this article focuses on the study of the behaviour of materials from Senegalese quarries during compaction. These are Bandia Limestone (Sindia, Thiès Region) and Diack Basalt (Ngoundiane, Thiès Region). The grain size studied is 25/50 mm as for any material studied for use as railway ballast. The Proctor C-Mould for compacting large diameter materials was made for the occasion. With γ_dmax = 2.142 g/cm³ and W_OPM = 5.3%, the compaction results clearly show the poor behaviour of the limestone under the effect of repeated loads and water. It shows a reduction in fine elements of the aggregates of initial diameter 25/50, as well as a significant cohesion under the effect of water with the formation of a muddy paste. The compaction references that characterize Diack Basalt are: γ_dmax = 2.15 g/cm³ and W_OPM = 0.37%. Diack Basalt's compaction behaviour shows good performance. It does not break down into fine particles and the settling observed during compaction is similar to just tightening the grains and then stabilizing the material.

Abstract: In marine concrete structure, corrosion behaviors of reinforcing steel in atmosphere, splash, water-level-fluctuating and underwater zone are significantly different. This paper investigated and analyzed the effect of water conditions on the macro-cell corrosion potential difference and macro-cell current density of steel in concrete free of chloride and concrete contaminated by chloride. Results indicated that in concrete that is free of chloride and with low water content, its resistance becomes the limiting factor for the formation of macro-cell current. The increase of water content of concrete could promote the flow of macro-cell current. In concrete contaminated with chloride, only the water-saturated state of anode was little helpful to inhibit the macro-cell current, but the increase of water content of concrete around the cathodic steel could weaken the macro-cell corrosion. The water condition of cathode and anode could play an important role in controlling the ratio of magnitude of macro-cell current to micro-cell current.

Abstract: Usually the angle steel is attached to the bracket to withstand tensile or compressive forces. The single-angle steel section is an asymmetrical section, and the nature of the section involves a complex analysis. The load is transmitted to the single-angle steel through the steel plate, thus causing eccentric load behaviour. The eccentric load will cause the single angle steel to bear the action of the axial pressure and the bending moment. The process of design and analysis is difficult based on the asymmetry of single angle steel. The behaviour of axial force and bending moment involves warping and torsion, and the analysis and design process is complicated. The eccentric load behaviour of single angle steel is based on complex formula analysis, and the 2010 AISC specification [1] also provides a table lookup function. This study collated the analytical formula of a single angle steel with complex eccentric loads. According to the theory of beam-column interaction, different lengths and positions are considered. The article provides a reference for the correct analysis of the user and improves the correctness of the analysis of the single angle steel.

Abstract: The cemented coal gangue-fly ash backfill (CGFB) slurry has commonly been used to control subsidence damage caused by underground coal mining. This paper discusses the CGFB slurry rheological characteristic associated with the various percentage of the fly ash within the configuration of the mixture. A general description about CGFB slurry fluidity in the pipe transportation is provided. The physical, chemical and rheological characteristic of the CGFB have been determined in the test. The fly ash was mixed with 18%, 20% and 22% of solid concentration with respects to 12%, 10% and 8% for cement on various concentrated CGFB slurry ranges 76.05%, 78.05% and 80.05%. The tests verify the CGFB slurry exhibits non-Newtonian behavior in nature as Bingham plastic fluid. The experimental data show CGFB slurry rheological characteristic is noticeable influenced by the slurry solid concentration and the proportion of the fly ash, which affects the value of yield stress and viscosity. The lower value of the rheological parameters was observed on 22 % fly ash other than the 18 % case based on the same solid concentration of CGFB slurry.

Abstract: Strong earthquake affects buildings to response in huge dynamic oscillating motion. In a teaching hospital that full of patients, medical personnel and medical treatment facilities as well as many modern advanced equipment may be in very dangerous situation due to this building response. To reduce the human victims, equipments and infrastructure damages, a kind of base isolation is added to the foundation of the hospital building. Inspite of oscillation motion as a vertical cantilever, this foundation base isolation of the hospital building is applied and designed to give the response of the earthquake vibration waves in lateral motion. To find out the optimum properties of the base isolation, some calculations of the response from vibration parameters are observed. The K_eq value is 415,120,000 N/m and the total massive Mass of the hospital is 148,057,364 kg as well as the highest vibration force is 108,136,030.2 N. This study work deals with simplified modelling using FEA in ANSYS software. The aim is to see the simulation based on the calculation of the analysis and whether the response is as expected.

Abstract: The development of nanotechnology continues to grow. The use of nanocement in concrete is expected to reduce the number of pores and improve hydration in concrete and provide more strength to the concrete. The use of natural fibers, in this case, coconut fiber can prevent cracks in concrete and make fiber concrete more ductile than ordinary concrete. The effect of using nanocement on coconut fiber concrete on the strength of the concrete to be studied. Methodology to complete the research objectives, use nanocement used in concrete, which has added coconut fiber. Tests reviewed the value of slump and specific gravity. Then, testing the compressive strength at 7, 24, 28 days. The results obtained were an increase of 48.19% in the strength of concrete. Further research needs to review on mixing nanocement with other natural fibers.

Abstract: Polymer composites of polyaniline (PANI)/polyamide 6 (PA6) blends and reduced graphene oxide (rGO) were prepared via the in situ synthesis method in order to improve formability and electrical properties. Polymer blends and composites were characterized by the Fourier transform infrared spectroscopy, scanning electron microscopy, and thermal gravimetric analysis. It was found that the composites prepared by the in situ synthesis method have better compatibility between polymer blends and matrix than that prepared by the conventional dry-mix method as investigated by scanning electron microscope (SEM). The Fourier-transform infrared (FT-IR) spectrograms indicate the presence of covalent bonds between functional groups between polyaniline and reduced graphene oxide. The PA6/PANI-rGO films show the electrical conductivity of 2.970×10^-6 S/cm while PA6/PANI-GtO show electrical conductivity of 4.082×10^-7 S/cm. Thermal stability of polymer blend was characterized by the thermogravimetric analysis. The thermal stability of polyamide 6 after blending is not changed significantly.