Design and Experiment of Hydraulic Scouring System of Wide-Width Lotus Root Digging Machine

In response to the problems of small working width and low operating efficiency of existing hydraulic scouring lotus root harvesters, a wide-width hydraulic scouring system was designed based on a wide-width self-propelled lotus root harvester. The main parameters of the key components were determined through theoretical analysis of the water flow energy of the hydraulic scouring system pipelines. An experimental study was also carried out on the main factors affecting the working performance of this hydraulic scouring system. Through hydrodynamic simulation tests, the effect of nozzle type and constriction section structure on the turbulence intensity at the nozzle outlet and the pressure loss per unit mass of fluid between the nozzle inlet and outlet sections were compared and analysed. The test yielded conical-cylindrical nozzle geometry parameters for nozzle inlet diameter of 40 mm, shrinkage angle of 30°, nozzle outlet straight section length of 20 mm, nozzle outlet diameter of 16 mm, the nozzle had better flushing performance. Single-factor tests were carried out with nozzle outlet pressure, scouring angle and nozzle height from the mud surface as influencing factors. Based on the optimum effective scour depth, a three-factor, three-level Box–Behnken central combination design test was completed. The primary and secondary factors affecting the effective scouring depth were obtained in the following order: nozzle height from the mud surface, nozzle outlet pressure, and scouring angle. Finally, the performance test of the hydraulic scouring system was completed. Results showed that when the nozzle outlet pressure of 0.30 MPa, the scouring angle of 60° and the nozzle height from the mud surface of 0 mm, the effective scouring depth was 395 mm, the lotus root floating rate was 90% and the damage rate was 5%, which meet the requirements of lotus root harvesting operations.

Strand-Morphology-Based Process Optimization for Extrusion-Based Silicone Additive Manufacturing

In the silicone material extrusion (MEX) process, product profile error and performance defects are common problems due to changes in strand shape. A process optimization method considering strand morphology, denoted as SMO, which allows adjustment of the strand shape by adjusting process parameters during the printing process is presented. The relation between process parameters (extrusion speed, moving speed, nozzle height, and nozzle radius) and the geometric parameters (strand width and strand height) of the cross-section, as well as the relationship between strand spacing, layer height, and process parameters in no void constraint is discussed and verified. SMO was utilized to produce specimens with tunable strand width and strand height. Tensile tests and profile scans were performed to compare SMO with other methods to verify its feasibility. Specimens fabricated using the SMO method have up to a 7% increase in tensile strength, up to a 10% reduction in processing time, and about a 60% reduction in strand height error over unused ones. The results show that the SMO method with adjustable strand width can effectively balance efficiency and mechanical properties compared to uniform infill, and the SMO method with adjustable strand height can provide higher accuracy compared to uniform strand height. The proposed method is validated and improves the efficiency and accuracy of silicone MEX.

Study on Direct Writing of Gallium Metal for the Flexible Sensor

There is an urgent need for a simple and effective method to manufacture flexible sensors composed of liquid metal. Gallium (Ga) metal has become an ideal flexible conductive material due to its high conductivity, low melting point, and high flow characteristics. In this paper, liquid Ga metal is directly written on the polyvinyl alcohol (PVA) film through the driving mode of piston extrusion; then, the Ga metal wire is transferred and sealed with silica gel. The advantages of piston mode are studied, and the direct writing parameters of the liquid Ga metal, including extrusion speed, nozzle height, printing speed, and nozzle inner diameter, are systematically optimized. The flexible sensor based on the sealed liquid Ga metal has good resilience under the external load. This work provides a specific reference for direct writing of liquid Ga metal and its sealing technology for the flexible sensor.

Joint improvements of radar/infrared stealth for exhaust system of unmanned aircraft based on sorting factor Pareto solution

In order to reduce the radar cross section (RCS) of the unmanned aircraft while suppressing its infrared signature, a comprehensive design method (CDM) based on sorting factor Pareto solution is presented. The physical optics and physical diffraction theory are used to evaluate the electromagnetic scattering characteristics of the aircraft, and the Monte Carlo and ray tracing method are used to evaluate the infrared radiation intensity of the exhaust system. CDM is used to evaluate and screen each individual in each offspring, and the design parameters and sub-models of the aircraft exhaust system are continuously improved. The results show that the exhaust port model, lower baffle and nozzle height are the main factors affecting the RCS indicators, nozzle stages, exhaust port model, lower baffle and outer width make the main contribution to infrared radiation suppression. The presented CDM is efficient and effective in enhancing the radar/infrared integrated stealth performance of the aircraft.

Bonding widths of Deposited Polymer Strands in Additive Manufacturing

In this study, we explore the deformation of a polymer extrudate upon the deposition on a build platform, to determine the bonding widths between stacked strands in fused-filament fabrication. The considered polymer melt has an extremely high viscosity, which dominates in its deformation. Mainly considering the viscous effect, we derive analytical expressions of the flat width, compressed depth, bonding width and cross-sectional profile of the filament in four special cases, which have different combinations of extrusion speed, print speed and nozzle height. We further validate the derived relations, using our experimental results on acrylonitrile butadiene styrene (ABS), as well as existing experimental and numerical results on ABS and polylactic acid (PLA). Compared with existing theoretical and numerical results, our derived analytic relations are simple, which need less calculations. They can be used to quickly predict the geometries of the deposited strands, including the bonding widths.

Investigation of Nozzle Height Control to Improve Dispenser Printing of E-Textiles

Dispenser printing is a versatile way of manufacturing prototype and bespoke e-textiles that uses a robotically actuated nozzle to dispense pastes. Investigation of printing on a flat substrate, however, revealed that the nozzle must be kept between 50 and 200 µm above the material’s surface in order to print effectively. In order to maintain this clearance when printing on uneven materials, the surface topography of the substrate must be measured and compensated for. However, the accuracy of the laser displacement meter used here was reduced when measuring the translucent interface layer necessary when printing on textiles. Adding various concentrations of dye to the interface was explored. A single layer of interface with 20 mg of dye added per gram showed significantly improved results with an average error of 146 µm compared to the 550 µm for the clear interface. Crucially, the standard deviation in the error was only 31 µm, down from 101 µm, meaning that an offset could be applied to get measurements that would keep the nozzle’s clearance within the necessary 150 µm range.

Joint Improvements of Radar/infrared Stealth for Exhaust System of Unmanned Aircraft Based on Sorting Factor Pareto Solution

In order to reduce the radar cross section (RCS) of the unmanned aircraft while suppressing its infrared signature, a comprehensive design method (CDM) based on sorting factor Pareto solution is presented. The physical optics and physical diffraction theory are used to evaluate the electromagnetic scattering characteristics of the aircraft, and the Monte Carlo and ray tracing method are used to evaluate the infrared radiation intensity of the exhaust system. CDM is used to evaluate and screen each individual in each offspring, and the design parameters and sub-models of the aircraft exhaust system are continuously improved. The results show that the exhaust port model, lower baffle and nozzle height are the main factors affecting the RCS indicators, nozzle stages, exhaust port model, lower baffle and outer width make the main contribution to infrared radiation suppression. The presented CDM is efficient and effective in enhancing the radar/infrared integrated stealth performance of the aircraft.