The propeller is the important component of the power system in ships, the blades of which are spatial curved structures with continually changing sections. Wire arc additive manufacture (WAAM) is a ...novel technology and an effective method for manufacturing propellers. Currently, the planar slicing methods cannot form the high-accuracy propellers with complex spatial curves, a new cylindrical surface slicing method, based on the principles of conformal slicing, is applied to WAAM, the section for slicing being a cylindrical surface coaxial with the hub. Both cylindrical circumferential filling and cylindrical axial filling are used for filling the blades. In the manufacturing process, the hub is firstly formed by plane slicing and offset filling, then the blade is formed piece by piece by cylindrical slice and cylindrical axial filling and cylindrical circumferential filling alternately. A non-contact 3D measuring is conducted with a surface structure light 3D scanner after the completion of printing, and a 3D comparison is made with Geomagic qualify software. The dimensional error of the product is within ± 1.6 mm. The mechanical properties of WAAM propeller components are higher than the casting ones with the same composition.
This paper studies the temperature field, dynamic strain, and forming accuracy of the oscillate-WAAM conical shell in the forming process and manufactures the WAAM conical shell part. The results ...show that compared with the offset filling WAAM, the oscillate-WAAM conical shell shows the following characteristics: the temperature difference value between the inner and outer walls of the shell is significantly reduced, the cooling rate doubled decreased, the interlayer temperature is above 300 °C, and the average temperature gradient, the dynamic strain stability value, and deformation are reduced by about 50%. Under the same process parameters, the travel speed of oscillate-WAAM is low, which increased the heat input large and the interlayer temperature high. Meanwhile, the molten pool of oscillate-WAAM is in consistent with the width of the shell. The molten pool’s simultaneous solidifying changes the stress state of printed shell from three-dimensional to two-dimensional. All the above are conductive to stress release and reduce the strain and deformation of components. The bimetallic rocket motor shell composed of HS600 and HS950 is manufactured by oscillate-WAAM. The section roundness of the shell is 0.31 mm, and the overall forming accuracy is ± 0.625 mm. The deposited metal in HS600 part of conical shell is composed of pearlite and pro-eutectoid ferrite, while the deposited metal of HS950 is composed of pearlite, acicular ferrite, and bainite. The forming accuracy and mechanical properties of conical shell formed by oscillate-WAAM meet the requirements.
High-building multi-directional pipe joint is a complex structure. A novel technology, which is called wire and arc additive manufacture (WAAM), was used to manufacture a high-building 10-directional ...pipe joint in this paper. Because the intersecting areas of multi-directional pipe joint are space surfaces, the conventional planar slicing method of WAAM is hard to form space surface with high precision. According to the study of space surface slicing method and space path planning by WAAM, this paper used the outer cylinder surface of main pipe to slice other forming pipes of 10-directional pipe joint, and the intersecting surfaces could be divided into two kinds: smooth surface and curved surface with inflection point areas. Two different path filling schemes were proposed for different intersecting surfaces: The former was filled in rotating approaches, while the latter was filled in raster approaches. The dimensional errors of forming pipes were controlled about ± 1 mm, and the angle errors of intersecting pipes were less than ± 0.5°. Compared with the properties of the casting pipe joint, the tensile strength of 10-directional pipe joint increased by 12.4% and the impact toughness (20 °C) increased more than 100%. The microstructure mainly consisted of pearlite and ferrite, and average grain size was about 15 μm. Rare defects such as pores and cracks were found.
•Propose a new technology to improve the precision of large WAAM metal component.•The surface structure light 3D measurement technology is applied to obtain the offset of cross-section center.•The ...printing path is adjusted according to the offset cross-section center between layers.•Improving the forming accuracy of WAAM parts by controlling the offset cross-section center between layers in real time.
The marine propeller bracket is a complex core component of large ship power system. Wire Arc additive manufacturing is an effective method to manufacture propeller bracket, which consists of the hub, the support and cross arm. For obtaining high forming precision, offset filling method for printing hub and scanning filling method for printing support and cross arm are adopted. Central deviations of deposition layer are acquired by a 3D scanner and a program written by Matlab software. Adjusting print path in real time to improve forming precision of bracket. The cross section center offset of each deposition layer is within ±0.6mm while the dimensional errors of bracket are within ±0.8 mm. The microstructure of bracket is composed of ferrite, lath bainite and VC precipitates. The tensile strength of printed bracket is 796 MPa, the yield strength is 660 MPa and the impact toughness at −20°C is 53 J.
The propeller bracket is an essential structural component of the large ship, with large structural size, high precision and performance. Multi-arc collaborative additive manufacturing is an ...effective method for forming high precision and performance large-scale propeller bracket. This paper studies the high-precision and performance multi-arc collaborative additive manufacturing propeller bracket forming strategy and path planning method. In the multi-arc cooperative additive manufacturing of the bracket, the two arcs in the front are used to form the contour of the depositing layer, while the rear three arcs are used to fill the contour. Finally, the five arcs collaborated additive manufacturing bracket is formed. Based on the structural characteristics of the bracket, it is divided into four regions: the hub, support arm, cross arm and intersecting area. The hub is a rotating body of equal thickness and cross-section. The relative positions of the five arcs are fixed, and the path is calculated by adjusting the attitude angle of the device in real-time during the printing process. The intersecting area, support arm and cross arm are all curved bodies with variable thickness and cross-section. The contour torches are used to form the two sides of the contour separately, and then the filling torch is used to variable amplitude swing filling the contour. The five arcs collaborative additive manufacture propeller bracket with a length of 3.5 m is formed by the above forming strategy and path planning method. The forming accuracy of the bracket is ±0.6 mm. The microstructure is composed of pearlite and massive ferrite. The tensile strength is 774 MPa, and the yield strength is 642 MPa. The mechanical properties are higher than the castings one with the same composition, and the forming efficiency reaches 1800 cm3/h.
•Design a multi-arc WAAM system and path planning method to form the propeller bracket and analyze its accuracy and properties.
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•Screening, isolation and characterization of lysozyme-producing Bacillus subtilis strains.•Bacillus subtilis BSN314 was found to have highest biomass production capacity.•Analysis of ...results was based on two techniques; single factor and orthogonal method.•By single factor, influence of medium composition and growth conditions was determined.
Lysozyme is a naturally occurring enzyme that is ubiquitous and plays an important role in innate immunity through its potent bacteriolytic activity. The main objective of this study was to isolate, screen and identify lysozyme-producing Bacillus subtilis strains by 16S rDNA sequencing. Of the four Bacillus subtilis strains isolated (B18, B66, B70, and B124), only one (B66) was selected for further study because it exhibited the comparatively highest enzymatic activity. The 16S rDNA sequence of strain B66 was submitted to the Genbank database with accession number OM327451 and was assigned the name Bacillus subtilis BSN314. Bacillus subtilis BSN314 was selected for further study to maximize biomass production. To obtain the maximum biomass product of Bacillus subtilis BSN314, two statistical methods were applied, one related to the nutritional conditions affecting the growth medium (chemical components), called the single factor optimization method, and the other showing their effects on the cultivation conditions (orthogonal method). The results showed that the composition of the culture medium (carbon, nitrogen, inorganic salts and surfactants) and the culture conditions (temperature, pH, shaking speed and percentage of inoculum) have a specific influence on the biomass production of Bacillus subtilis BSN314. The culture medium containing the combination of A2B3C1D2 with 1.5% glucose, 2.5% soybean peptone, 0.5% K2HPO4, and 0.1% Tween-20 was determined to be the optimal medium for biomass production whereas, the order of culture media based on the effects of the selected conditions having lysozyme activity is as follows; glucose % > soyapeptone % > Tween-20 % > K2HPO4 %. The results showed that the A2B3C1D2 ratio had the highest enzyme activity of 55 U/mL.
Van der Waals heterostructure shows promising applications in next generation optoelectronics. As a kind of van der Waals heterostructure, graphene/silicon (Gr/Si) based heterostructure devices have ...been demonstrated as high performance photodetectors. Here, we studied the origin of the high performance of Gr/Si photodetectors based on photocurrent mapping technology. According to photocurrent mapping, the photocurrent in the Gr/Si and Gr/SiO
2
/Si area nearing the Si window edge is higher than that in other positions, which is attributed to the highly effective collection efficiency of photocarriers. A device with size of Gr/Si region (
r
=7.4 μm) and Gr/SiO
2
/Si region (
L
=6.1 μm) shows high sensitivity and a broadband photoresponse in the range from 420 to 1000 nm with the peak sensitivity of 52 A/W at 780 nm, and fast response speed with rise time of 16 μs and decay time of 52 μs. Our study provides a strategy for the design of high photoresponsivity Gr/Si based devices.
Van der Waals heterostructures built from two-dimensional materials on a conventional semiconductor offer novel electronic and optoelectronic properties for next-generation information devices. Here ...we report that by simply stacking a vapor-phase-synthesized multilayer n-type WS2 film onto a p-type Si substrate, a high-responsivity Zener photodiode can be achieved. We find that above a small reverse threshold voltage of 0.5 V, the fabricated heterojunction exhibits Zener tunneling behavior which was confirmed by its negative temperature coefficient of the breakdown voltage. The WS2/Si heterojunction working in the Zener breakdown regime shows a stable and linear photoresponse, a broadband photoresponse ranging from 340 to 1100 nm with a maximum photoresponsivity of 5.7 A/W at 660 nm and a fast response speed of 670 μs. Such high performance can be attributed to the ultrathin depletion layer involved in the WS2/Si p–n junction, on which a strong electric field can be created even with a small reverse voltage and thereby enabling an efficient separation of the photogenerated electron–hole pairs.
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