Morphology and Performance Characterizations of 316 Stainless Steel Additively Fabricated by Laser Thermal-Joule Heating Composite Process

The Laser Thermal-Joule Heating Composite Process was studied by orthogonal tests based on an analysis of fabrication parameters such as the laser power, wire feeding speed, and electric current. Temperature profiles and the geometric morphology of deposited layers under different process parameters were analyzed, and the overlaps between the layers and the substrate were observed. Results show that when the temperature at the bottom layer of the additive manufacturing is higher than the melting point of the substrate, and the highest temperature at the top layer does not exceed the over-firing temperature, good morphology and close bonding with the substrate can be obtained. Finally, appropriate process parameters were identified and verified to print multiple layers continuously.

A Rapid Method for the Determination of SBS Content Based on the Principle of Orthogonal Testing

The performance of Styrene-butadiene-styrene (SBS) modified asphalt is closely related to the content of SBS modifier. In the production process of modified asphalt, a certain amount of additive such as sulfur and rubber oil may be added to reduce the segregation and promote the swelling of the polymer, but the effect of these additives on determining SBS content in asphalt is not yet clear. This paper presents the calibration curves of SBS content based on rutting factor and creep slope and points out its defects according to the temperature scanning test and the bending beam rheometer test. Subsequently, using Fourier transform infrared spectroscopy (FTIR) for rapid determination of polymer content in SBS modified asphalt based on orthogonal test and then the effects of additives such as asphalt type, SBS content, rubber oil and sulfur on the accuracy of polymer content determination by FTIR were investigated. Moreover, in the orthogonal tests of adding sulfur and rubber oil, the multivariate analysis of variance (MANOVA) was firstly used to analyze the additives influence on the test accuracy of FITR. Results indicated that the influencing degree of different additives is different. The influence of sulfur on the determination accuracy is greater than that of rubber oil. Therefore, the rapid determination method needs further improvement.

Orthogonal tests of the lubricating performance of SnO2 nanoparticles in poly-alfa-olefine oil

The tribological properties of SnO2 nanofluids were investigated using ball-on-plate reciprocating sliding wear tests. It was found that the coefficient of friction was reduced by 34.9% using 3 wt% SnO2 nanoparticles. The wear width and wear depth were reduced by 42% and 50.1%, respectively, using 2 wt% SnO2 nanoparticles. In the orthogonal tests, the frequency had the greatest influence on the friction and wear loss. Additionally, the optimal working conditions were a normal load of 50 N, a motion frequency of 1 Hz, and a surface roughness of 500–600 nm. Additionally, the excellent tribological performance of SnO2 nanofluids could be attributed to the formation of a tribo-film with a low shearing resistance due to the oleic acid and a protective layer due to the embedment of SnO2 nanoparticles.

Investigation of Characteristics of a Novel Torque Motor Based on an Annulus Air Gap

Although a two-dimensional (2D) valve has excellent performance, the processing of its spiral groove has a high cost and is time-consuming. This paper proposes a novel torque motor based on an annulus air gap (TMAAG) to replace the negative feedback function of the spiral groove to reduce the machining difficulty. In order to study the torque change law of the TMAAG, the air gap permeance was analyzed, and then a qualitative analytical model was established. Orthogonal tests were carried out to initially select the crucial parameters, which were further optimized through a back propagation (BP) neural network and genetic algorithm. The prototype of TMAAG was machined, and a special experimental platform was built, and experiment results are similar to the simulation values, which verifies the accuracy of the air gap analysis and qualitative model. For torque-angle characteristics, the output torque increases with both current and rotation angle and reaches about 0.754 N·m with 2 A and 1.5°. While for torque-displacement characteristics, due to the negative feedback mechanism, the output torque decreases with increasing armature displacement, which is about 0.084 N·m with 2 A and 1 mm. The research validates the unique negative feedback mechanism of the TMAAG and indicates that it can be potentially used as an electro-mechanical converter of a 2D valve.

Research on Catalytic Denitrification by Zero-Valent Iron (Fe0) and Pd-Ag Catalyst

This study primarily focused on how to effectively remove nitrate by catalytic denitrification through zero-valent iron (Fe0) and Pd-Ag catalyst. In order to get better catalytic performance, response surface methodology (RSM), instead of the single factor experiments and orthogonal tests, was firstly applied to optimize the condition parameters of the catalytic process. Results indicated that RSM is accurate and feasible for the condition optimization of catalytic denitrification. Better catalytic performance (71.6% N2 Selectivity) was obtained under the following conditions: 5.1 pH, 127 min reaction time, 3.2 mass ration (Pd: Ag), and 4.2 g/L Fe0, which was higher than the previous study designed by the single factor experiments (68.1%) and orthogonal tests (68.7%). However, under the optimal conditions, N2 selectivity showed a mild decrease (69.3%), when the real wastewater was used as the influent. Further study revealed that the cations (e.g., K+, Na+, Ca2+, Mg2+, and Al3+) and anions (e.g., Cl-, HCO3-, and SO42-) exist in wastewater may have distinctive influence on N2 selectivity. Finally, the reaction mechanism and kinetic model of catalytic denitrification were further studied.

Seepage Mechanism of Tight Sandstone Reservoir Based on Digital Core Simulation Method

Recently, tight sandstone oil has played an increasingly important role in the energy strategies of countries around the world. However, the understanding of a microscopic mechanism is still not clear enough, which has been affecting the improvement of the recovery of tight sandstone oil. In this article, a digital core model was established to simulate the pore network of a physical core with CT scan and difference equations were verified by Fourier counting. Then, a combination of orthogonal tests and cubic digital cores was used to experimentally investigate various parameters including pressure, length, permeability, viscosity, and time. By combining the physical experiments with the digital core methods, it can be observed that the state of the micro-crack affects the conductivity of the core, which may be the decisive reason for changing the pressure gradient. The orthogonal test showed that the sensitivity of the parameters was pressure, length, permeability, time, and viscosity in order. The results of the numerical simulations showed that this method can reveal the seepage mechanism of a tight sandstone reservoir, greatly shortening the experimental time and improving flexibility.

Multiobjective Hydraulic Design and Performance Analysis of a Vortex Pump Based on Orthogonal Tests

We design optimization on the overall blade structure of a vortex pump conducted by using the orthogonal test method to clarify the matching relationship of impeller and casing structures and then improve the hydraulic performance of the vortex pump. Based on two different impeller structures of forward-deflecting (denoted as R1 − F2) and backward-deflecting (denoted as F1 − R2), key parameters describing the impeller structure are calculated through optimization for the objective function of hydraulic efficiency by means of orthogonal tests and computational fluid dynamic simulations. Optimization computations show that the forward-deflecting blade impeller is superior to the backward-deflecting one. Model test of the optimized vortex pump is carried out calculating the error from the comparison of pump efficiencies calculated by model test and numerical simulation is calculated to be less than 6%. The experimental verification shows that the flow simulation has some errors. The weight of structure parameters such as the blade installation angle (α), the blade deflecting angle (β), the position of blade deflecting point (L), the radius (r) of smoothing arc at the deflecting point, the wedge type (W) of blade, to the lift head, the flow rate, and the efficiency of the pump is investigated, through multiparameter optimizations. Visualization observation of flows in the model pump consisted of a back-placed impeller and a front vaneless chamber is further performed. The characteristic of vortex formation predicted by flow simulation agrees with the result of visualization observation. The above results demonstrate that the optimum impeller type of vortex pump is forward-deflecting blade impeller. The optimum combination of the key structure parameters is that the deflection angle of the blade inlet (α) equals 30°, the position of blade deflecting point lM = 2/3 L, the chamfering radius (r) at the deflecting point r = 3 mm, and the best wedge type is axial deflecting blade.

Study of Dieless Radial Spinning for Thick-Walled Cylindrical Parts With External Grooves

Thick-walled cylindrical parts with external grooves are common components in the automobile and aviation fields. Such components can be produced by pressing the outer surface of a spinning thick-walled aluminum alloy tube by the dieless radial spinning process. The forming characteristics in the spinning process and the effects of various process parameters on forming were studied by using orthogonal tests and finite element simulations. During the forming process, bulge and thickness reductions occur because of material flow. The results of an investigation of process parameter effects show that the stress yield ratio (ξ) had no significant effect on forming. However, the feed thickness ratio (η) and initial wall thickness of the tube (t0) crucially affected the forming quality (e.g., the heights of bulges and thickness reduction in the groove area). Thick-walled tubes presented different phenomena compared to the thin-walled.

Performance of Heat-Insulating Materials Doped with Basalt Fibres for Use in Mines

To solve high-temperature-induced hazards in mines, heat-insulating materials were prepared by utilising basalt fibres and high-strength ceramsite combined with cementing materials. Through orthogonal tests and data analyses, the optimal combination of the heat-insulating materials doped with basalt fibres was determined as A1B1C1, that is, doping with 45% basalt fibres, a length of the basalt fibres of 6 mm, and doping with 20% ceramsite. The performance indices corresponding to the optimal comprehensive combination of the heat-insulating materials doped with basalt fibres included a density of 1200 kg/m3, thermal conductivity of 0.151 W/(mK), compressive strength of 9.7 MPa, flexural strength of 3.6 MPa, and a water-seepage depth of 25.4 mm. Numerical simulations verified that the materials presented favourable thermal insulation performance.