The relevance of false-twist addition on ring spun yarns by means of rotary threaded surfaces

A novel concept of producing false-twist yarns by cyclical stress fluctuation was developed. The forming principle was introduced to analyze the formation process of false twists on rotary threaded contact surfaces. Geometric analysis indicates that cyclical stress variations produce extra rotations (false twists) on fiber strands in the yarn formation area, causing twist redistribution and fiber arrangement remodeling with the appearance of local fiber reversion. Theoretical analysis reveals that more false twists are produced when the spun yarn is in contact with surfaces of high traverse speeds. Then, a motion simulation model using different traverse speeds of the threaded contact surface was established to compare the yarn internal stress variation, verifying the false-twist efficiency at different traverse speeds. Finally, a systematic comparison was conducted between the yarns spun at different traverse speeds. It was shown that the yarn properties improved with higher traverse speeds of the threaded contact surface, achieving less hairiness, high yarn strength, and low residual torque.

Analysis of geometric parameters and technical requirements for pin conical joints in pump nodes

The article analyzes the causes of the situation with the appearance of manufacturing errors and the lack of the necessary technical requirements to perform a pin conical joint his intended purpose. The analysis was performed based on geometric construction of the assembly dimensional chain of two parts to be connected and a conical pin with a taper 1:50 according to GOST 9465-79, which is used in the pin joints of pumping equipment. The geometric analysis included the separation of deviations into linear dimensions and angular deviations. The values of the angular deviations were reduced to the linear values of their projections along the axis of the pin, to determine the tolerance on the end height protrusion of the pin above the surface of the connecting parts. Also, the unfoundedness of assigning the roughness index of the hole under the pin at the level of Ra 1.6 μm and its inexpediency when it is impossible to ensure the required contact length is theoretically proved and the solution of this contradiction is proposed. A detailed analysis of the technical requirements for drawings of pumping equipment units containing pin conical joints and paragraphs of the relevant standards, which resulted in the inconsistencies, and offer recommendations that will ensure the quality of the joint following its official purpose. Analysis of the geometric parameters of pin conical joints for the first time allowed to determine the dependence of the height of the pin end protrusion above the surface of the connecting parts and the tolerance for this parameter, as well as to propose mathematical dependences for their determination. The presented dependencies can be used in practice for a reasonable calculation during the design of pin conical joints in pump nodes and in machine-building enterprises where such joints are used. For the first time, the determination of the tolerance for hole size for machining conical reamers is presented, and the formula for calculating this parameter is proposed, which is given in the recommendations for their use in machine building enterprises and products containing pin conical joints.

Two-Dimensional Soil Geometric Tortuosity Model Based on Porosity and Particle Arrangement

Porosity and particle arrangement are important parameters affecting soil tortuosity, so it is of great significance to determine the intrinsic relationship between them when studying soil permeability characteristics. Theoretical derivation and geometric analysis methods are used to derive a two-dimensional geometric tortuosity model. The model is a function of particle arrangement parameters (m and θ) and porosity. An analysis of the model and its parameters shows that: (1) The arrangement of particles is one of the reasons for the different functional relationship between tortuosity and porosity, which proved that the tortuosity is not only related to the porosity but also affected by the particle arrangement. (2) The greater the anisotropy parameter m is, the greater the tortuosity is, indicating m varies when fluid passes through the soil from different sides resulting in different values of permeability. (3) The tortuosity increases with the increase in the blocking parameters θ. (4) With increasing porosity, the influence of the parameters m and θ on the tortuosity gradually decreases, suggesting that the influence of particle arrangement on tortuosity gradually decreases. The results presented here increase the understanding of the physical mechanisms controlling tortuosity and, hence, the process of fluid seepage through soil.

NON-UNIFORM RATIONAL B-SPLINE BASED ISO-GEOMETRIC ANALYSIS FOR A CLASS OF HYDRODYNAMIC PROBLEMS

Herein, we present the design and development of a ‘Non-uniform Rational B-spline (NURBS)’ based iso-geometric approach for the analysis of a number of ‘Boundary Value Problems (BVPs)’ relevant in hydrodynamics. We propose a ‘Potential Function’ based ‘Boundary Element Method (BEM)’ and show that it holds the advantage of being computationally efficient over the other known numerical methods for a wide range of external flow problems. The use of NURBS is consistent, as inspired by the ‘iso-geometric analysis’, from geometric formulation for the body surface to the potential function representation to interpolation. The control parameters of NURBS are utilised and they have been explored to arrive at some preferable values and parameters for parameterization and the knot vector selection. Also, the present paper investigates the variational strength panel method, and its computational performance is analyzed in comparison with the constant strength panel method. The two variations have been considered, e.g. linear and quadratic. Finally, to illustrate the effectiveness and efficiency of the proposed NURBS based iso-geometric approach for the analysis of boundary value problems, five different problems (i.e. flow over a sphere, effect of the knot vector selection on analysis, flow over a rectangular wing section of NACA 0012 aerofoil section, performance of DTMB 4119 propeller (un-skewed), performance of DTNSDRC 4382 propeller (skewed)) are considered. The results show that in the absence of predominant viscous effects, a ‘Potential Function’ based BEM with NURBS representation performs well with very good computational efficiency and with less complexity as compared to the results available from the existing approaches and commercial software programs, i.e. low maximum errors close to 110−3 , faster convergence with even up to 75 % reduction in the number of panels and improvements in the computational efficiency up to 32.5 % even with low number of panels.

Automatic Georeferencing of Topographic Map Sheets Using OpenCV and Tesseract

The authors developed a pipeline for the automatic georeferencing of older 1 : 25 000 topographic map sheets of Hungary. The first step is the detection of the corners of the map content, then the recognition of the sheet identifier. These maps depict geographic quadrangles whose extent can be derived from the sheet ID. The sheet corners are used as GCPs for the georeference.The whole process is implemented in Python, using various open source libraries: OpenCV for image processing, Tesseract for OCR and GDAL for georeferencing.1147 map sheets were processed with an average speed of 4 seconds per sheet. False detection of the corners is automatically filtered by geometric analysis of the detected GCPs, while the sheet IDs are validated using regular expressions. The error of corner detection is under 1% of the sheet size for 89% of the sheets, under 2% for 99%. The sheet ID recognition success rate is 75.9%.Although the system is finetuned to a specific map series, it can be easily adapted to any other map series having approximately rectangular frame.

Fracture Modelling of a Cracked Pressurized Cylindrical Structure by Using Extended Iso-Geometric Analysis (X-IGA)

In this study, a NURBS basis function-based extended iso-geometric analysis (X-IGA) has been implemented to simulate a two-dimensional crack in a pipe under uniform pressure using MATLAB code. Heaviside jump and asymptotic crack-tip enrichment functions are used to model the crack’s behaviour. The accuracy of this investigation was ensured with the stress intensity factors (SIFs) and the J-integral. The X-IGA—based SIFs of a 2-D pipe are compared using MATLAB code with the conventional finite element method available in ABAQUS FEA, and the extended finite element method is compared with a user-defined element. Therefore, the results demonstrate the possibility of using this technique as an alternative to other existing approaches to modeling cracked pipelines.