Optimization Design of Surface Wave Electromagnetic Acoustic Transducers Based on Simulation Analysis and Orthogonal Test Method

The energy conversion of electromagnetic acoustic transducers (EMATs) is typically lower, which seriously restricts the application of EMATs in the field of non-destructive testing and evaluation. In this work, parameters of surface wave EMATs, including structural parameters and electrical parameters, are investigated using the orthogonal test method to improve the transducer’s energy conversion efficiency. Based on the established finite element 2-D model of EMATs, the amplitude of the displacement components at the observation point of a plate is the optimization objective to be maximized with five parameters pertaining to the magnets, meander-line coils, and excitation signal as design variables. Results show that the signal amplitude of EMATs is 3.48 times on in-plane and 3.49 times on out-of-plane, respectively, compared with the original model. Furthermore, a new material (amorphous nanocrystalline material of type 1K107) is applied to optimize the magnetic circuit of EMATs and enhance the eddy current in an aluminum plate to increase the signal amplitude. Finally, the signal amplitudes obtained from the three types of models, that is, the original one, the optimization one after an orthogonal test, and the optimization one with the addition of magnetic concentrators, are analyzed and compared, indicating that the signal amplitude, compared with the original one, is 6.02 times on in-plane and 6.20 times on out-of-plane, respectively.

The Effect of 3D Printing Process Parameters on the Mechanical Properties of PLA Parts

Taking the PLA molded by FDM as the research object, the influence of various process parameters on mechanical properties is investigated through comparative experiments, which provides reference and help for the promotion and application of FDM molding technology. During the molding process, the PLA material undergoes the process of melting to solidification, thus the performance of the molded part is worse than the original due to thermal shrinkage and other reasons. To improve the quality and mechanical properties of the molded parts, the experiment is designed using an orthogonal test method in parallel with nine different sets of process parameters (layer thickness, build direction, filling speed, and infill density, etc.). Ultimately, the mechanical properties of PLA are tested and the results are analyzed respectively to determine the main factors affecting the mechanical properties and their optimal level combination. Among them, fill rate is the crucial factor in compressive property, while build direction has a significant effect on surface roughness, tensile property and bending property.

Starved lubrication analysis for the top ring and cylinder liner of a two-stroke marine diesel engine considering the thermal effect of friction

The thermal effect of friction plays an important role in friction pairs working under heavy load and starved lubrication conditions, such as the piston ring and cylinder liner (PRCL) system of two-stroke marine diesel engines. Friction heat will degrade the lubrication and increase the scuffing risk. In this study, considering the thermal effect of friction, the tribological characteristics of the top ring and cylinder liner of a two-stroke marine diesel engine under starved lubrication are studied. It is found that the temperature rise due to friction is significant and has a strong influence on the tribological characteristics of the PRCL system. Moreover, based on the orthogonal test method, the effects of groove textures under different oil supplies are also explored. Only well-designed groove textures can reduce friction and wear at the same time.

Analysis of Factors Affecting Creep of Wood–Plastic Composites

Wood–plastic composite (WPC) materials are mainly used as flooring in buildings or as structural load-bearing plates, and will undergo creep deformation during use, resulting in structural failure and safety problems. Therefore, this work adopted the orthogonal test method to carry out creep tests on wood–plastic composites. We used the range method and variance analysis method to process the creep data and analyze the influence of the load, temperature, and relative humidity on the creep strain in specimens of wood–plastic composites. The results showed that the creep strain of the WPC specimens changed significantly with a change in the load stress, while a change in relative humidity had no significant effect on the creep strain. When the relative humidity was increased from 55% to 65%, the creep strain increased by 0.03%, but when the temperature was increased from 30 °C to 35 °C, there was no significant difference in the creep strain. However, when the temperature was increased from 30 °C to 40 °C and from 35 °C to 40 °C, a significant difference in the creep strain of the WPC specimens was observed.

Fracture Characteristics of Polyurethane Grouting Materials Based on Acoustic Emission Monitoring

In this study, 16 groups of tests were designed by the orthogonal test method, and a PU grouting material was prepared, which can be used for the construction of sealing wall in mined-out area of coal mine. The basic properties of the material were measured. Firstly, the viscosity of four groups of samples with different polyether polyol contents was measured by a dynamic rheometer. Secondly, the uniaxial compressive strength of pure slurry samples and sand-containing samples was measured by a universal testing machine. Finally, the failure process of sand-containing samples was monitored by acoustic emission equipment. Through the above research and analysis, a PU grouting material with excellent performance has been obtained. That is, when the ratio of polyether triol:polyether tetraol:catalyst:surfactant:chain extender:plasticizer is 11 : 9 : 0.5 : 1.0 : 1.2 : 6.0, PU grouting material has higher injectability and ideal compressive strength, which has been proved in grouting experiments.

Research on Thermal Inkjet Technology Based on CFD

In this paper, a thermal inkjet printing simulation model is established in the CFD simulation platform, and the influence of inkjet driver parameters and ink physical parameters on the printing process is studied by numerical simulation. The evaporation-condensation model is coupled with the VOF multiphase flow model in Fluent software to establish a thermal inkjet printing process simulation model. Based on the orthogonal test method, we investigate the influence of fluid physical parameters (ink viscosity, surface tension) and inkjet driver parameters (heater temperature value) on droplet formation by changing the physical parameters of the material and the boundary conditions of the model. Through the comparison of the results, exploring the adjustment rules of thermal inkjet technology and obtaining the optimal combination of material and process parameters for high-quality ink drop formation.