Journal of Modern Mechanical Engineering and Technology

Remarks on Solving Methods of Nonlinear Equations

2024-03-07T14:31:47+00:00

Abstract: In the field of mechanical engineering, many practical problems can be converted into nonlinear problems, such as the meshing problem of mechanical transmission. So the solution of nonlinear equations has important theoretical research and practical application significance. Whether the traditional Newton iteration method or the intelligent optimization algorithm after the popularization of computers, both them have been greatly enriched and developed through the continuous in-depth research of scholars at home and abroad, and a series of improved algorithms have emerged. This paper mainly reviews the research status of solving nonlinear equations from two aspects of traditional iterative method and intelligent optimization algorithm, systematically reviews the research achievements of domestic and foreign scholars, and puts forward prospects for future research directions.

A Flow Structure Interaction Method for Towed Cable System

2024-03-17T06:30:27+00:00

Abstract: The ocean towed cable system is a classic example of fluid-structure interaction (FSI). This interaction can exhibit stability or oscillation between a highly deformable moving cable and the surrounding turbulent flow. However, in dynamic simulations of towed cable systems, a constant drag coefficient for an infinite circular cylinder is often used based on experimental data. An innovative fluid-structure interaction method is introduced to obtain accurate drag distribution along cable to couple with towed system dynamics. A modified nodal position finite element method (NPFEM) coupled with Reynolds-averaged Navier-Stokes (RANS) approach has been utilized to predict hydrodynamic forces along the cable. A data exchange algorithm has been developed specifically for fluid-structure interaction within the towed cable system where the cable profile is transferred to construct the flow domain while hydrodynamics is interpolated for NPFEM analysis. A topology partition around cable is applied. A multiblock grid is generated around cable. The simulation results of the fluid-structure interaction of the towing system are verified. This FSI scheme reveals how strongly hydrodynamics determine cable dynamics and induce vortex structure vibrations around a towed cable system. Parametrically controlled structured grid generation and their applicability for complex flow fields have also been discussed. Detailed descriptions of boundary layer separation evolution around spatially distributed cable are provided. This FSI scheme reveals a real strongly hydrodynamic determined cable dynamics and vortex structure induced vibrations around a towed cable system. The proposed method enhances predictive accuracy of the towed system dynamics response.

Experimental Investigation of Oil Film Variation in Finite Line Contact Under Intermittent Motion

2024-09-20T09:27:36+00:00

The variation of oil film distribution in the line contact area of pin and disk was experimentally observed during a periodic intermittent motion. The study was conducted on a ball-disk optical interferometric test rig, with motion speed controlled by PLC programming. PAO40 oil was primarily used in the experiment, with the glass disk undergoing periodic motion of constant speed-deceleration-stop-acceleration, while the pin roller remained fixed. The results indicate that when the motion stops, a portion of the oil is entrapped in the center of the contact area. As the acceleration phase begins, this portion of the oil is gradually squeezed out of the contact area, and the oil film with lowest thickness at the entrance of the contact area moves towards the exit of the contact area, passing through the contact center. It can also be observed that during the entire process, an increase in speed increases the film thickness, while an increase in deceleration time, i.e., a decrease in deceleration, reduces the film thickness during the stop phase.

Application of Anal Manometry in the Planning for Anal Fistula Surgery

2024-10-31T05:23:44+00:00

Anal fistula does not heal spontaneously without surgery, and anal function should be preserved after muscle dissection, which is a challenge even to the most experienced surgeon. In order to develop a planner for anal fistula surgery, anal manometry used in the measurement of pressures in the anal canal to investigate the anal function is reviewed. In this review paper, current techniques are described and compared with each other, and technical and clinical challenges are discussed. There are four types of catheters used to measure anal sphincter pressure: water-perfused, solid-state, air-coupled, and fiber optic catheter. Parameters acquired by anal manometry and their relationship with fecal incontinence after anal fistula surgery are discussed. Vectormanometry can provide the pressure profile along the anal canal in three dimensional space, pressure vectorgram, and cross-sectional radial asymmetry, which have more advantages than the conventional method. Understanding the technology and development of anal manometry is critical for the anal fistula surgical planning. A novel design is highly desired for 3D pressure profile measurement along the entire anal canal simultaneously without pulling the catheter.

Numerical Simulation of the Multi-Roller Skew Tandem Rolling of Unequal Wall Thickness Hollow Stepped Shafts

2024-11-01T23:20:28+00:00

This paper proposes a multi-roll skew rolling forming process to address the slow forming speed of large-section shrinkage for aviation turbine shafts. Using Simufact Forming software, simulations were conducted on the GH4169 turbine shaft blank, analyzing the variations in stress, strain, and temperature fields during the forming process of a hollow shaft component with an initial wall thickness of 6mm. Additionally, we further explored the intrinsic relationship between the initial wall thickness and the depth of the concave center at the end of the workpiece. The results indicate that after multi-field coupling effects, the metal deformation of the workpiece gradually accumulates along the axial direction, reaching a peak after achieving the maximum reduction, while displaying a trend of decreasing from the outside to the inside. Additionally, there is a positive correlation between the depth of the concave center at the end of the workpiece and the initial wall thickness; as the amount of metal involved in the deformation increases, the depth of the concave center also intensifies. These findings provide an important theoretical basis for achieving flexible rolling formation of turbine shafts.