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Stress-strain state of a welded high-strength steel pipeline in the presence of surface defects
Get PDFThe construction of main pipelines is now predominantly carried out using high-strength steels. This makes it possible to increase pipeline capacity while maintaining the existing pipe geometry. However, the issue of ensuring the strength of such pipelines in the presence of surface defects is still relevant. This is especially true for pipeline segments that are located in hard-to-reach places, and therefore, it is difficult to repair and restore. At the same time, the introduction of high-strength steels involves a complex system of material alloying and special thermo-mechanical strengthening technologies. As a result, special structures of increased strength can be produced, but they are sensitive to reheating, in particular when welding technologies are used. This is due to the formation of a special zone of thermal deformation influence in the vicinity of the weld. Material properties of the pipes differ from their original characteristics. The stress-strain state is formed, which also affects the strength of the welded pipeline. The nature of the stress-strain state of welded joints of pipes made of high-strength materials differs from the well-studied stress distributions in pipelines built in the past sixty-eighty years of the past century. In particular, several localized maxima of stresses can be located not only on the weld axis but also in the zone of thermal deformation influence. Therefore, it is important to evaluate the effect of weld stresses in welded joints of high-strength steel pipes on the strength of the pipeline in the presence of surface defects. Since the defect may be located at an arbitrary distance from the weld axis, the predicted strength of the welded pipeline segment can vary significantly
Dual-stator ultrasonic motor achieving 2-DOF linear and rotary motion with single-phase excitation
Get PDFThis study proposes a novel dual-stator linear-rotary ultrasonic motor. The piezoelectric ceramic excites both out-of-plane and in-plane vibration modes within the stator. These distinct vibration modes independently drive the slider (rotor), generating reciprocating linear and rotational motions, respectively. Finite element analysis and laser vibrometer-based vibration testing validated the motor's operational principle. The close agreement between simulated and measured resonant frequencies for both vibration modes, with mere discrepancies of 3 % and 4 %, respectively, underscores the accuracy of the stator’s vibrational characteristics. Subsequently, two stators are fabricated and assembled to the ultrasonic motor prototype. Experimental results demonstrate the motor’s impressive performance, achieving a maximum linear velocity of 265 mm/s and a peak rotational speed of 1600 rpm. Furthermore, the motor delivers a maximum thrust force of 0.18 N and a stalling torque of 1.8 mN·m
Research on fault diagnosis of electric motor rolling bearings based on CMFSE-SVM
Get PDFRolling bearings are key components of rotating machinery such as electric motors, and their health status directly affects the reliability and safety of the equipment. In order to improve the fault classification accuracy of electric motor rolling bearing, this paper proposes a diagnostic method based on CMFSE-SVM. Firstly, the composite multi-scale fuzzy slope entropy (CMFSE) method proposed in this paper is used to extract the characteristics of the vibration signal of the motor rolling bearings. Finally, the obtained feature vectors are sent to the support vector machine (SVM) for fault classification. This paper verifies the classification accuracy of the method proposed in this paper on two publicly available datasets of electric motor rolling bearing faults. The experimental results show that the method proposed in this paper achieves average classification accuracies of 100 % and 99.6 % respectively on all working conditions corresponding to these two datasets. And the classification accuracies were 2.4 % and 2.8 % higher respectively than those of the compared methods
Research progress on 3D printed geopolymer materials
Get PDFThe integration of 3D printing technology with geopolymer materials offers a sustainable alternative to conventional construction methods, significantly reducing CO2 emissions. However, challenges such as rapid setting, limited workability, and weak interlayer bonding limit their broader application. This review summarizes recent progress in 3D printed geopolymer composites, focusing on materials selection, rheological optimization, buildability, and mechanical performance enhancement. Strategies including the use of rheology modifiers, fiber reinforcements, nano-additives, and process optimization have shown promise in improving printability and structural performance. Remaining challenges, such as balancing setting time and printability and enhancing interlayer adhesion, are also discussed. Future research directions are proposed to further advance the development of high-performance, low-carbon geopolymer 3D printing materials for sustainable construction
The design and finite element analysis of the mushroom picking flexible robotic arm
Get PDFThis article presents a robotic arm designed for mushroom picking in a greenhouse environment, taking into consideration the specific characteristics of Agaricus bisporus. The robotic arm was equipped with self-lifting and self-stretching functions, allowing it to move effectively within the restricted space of the greenhouse, while picking and placing Agaricus bisporus without causing any damage. The mechanical arm and flexible gripper were designed according to the growth environment and size of Agaricus bisporus. A finite element analysis was carried out on the flexible gripper, with the use of ABAQUS to construct a simulation model. The Yeoh model and the Mooney-Rivlin model are used as the research models, and tetrahedral linear elements C3D4H were used for meshing. By changing the positive and negative pressure of the gas inside the flexible gripper's airbag to simulate gripping and releasing actions, it was demonstrated that the deformation of the flexible gripper meets the requirements for picking actions under both the Yeoh model and the Mooney-Rivlin model. It was shown that a shear force greater than 3.2N is needed for the gripping and twisting of Agaricus bisporus within the flexible gripper to successfully complete the picking action. Finally, the experimental verification was carried out, proving the stability and feasibility of the mushroom picking robotic arm. And the design of flexible gripper control system, through the distributed computing and I/O structure, CANopen communication protocol, etc. makes the flexible gripper can perform accurate gripping tasks in complex environments, with high efficiency, reliable, flexible control performance, adaptable, and easy to expand and optimize
Finite element analysis of grouted cylindrical wedge anchors for prestressed CFRP plates
Get PDFIn current research, the anchoring performance of prestressed Carbon Fiber Reinforced Polymer (CFRP) plate anchors is primarily acquired through experimental methods, which makes it difficult to capture the internal deformation and stress distribution of the anchor. In this paper, a model of a grouted cylindrical wedge anchor for prestressed CFRP plates is established using the finite element analysis software ABAQUS. The simulation replicates the processes of anchor relaxation at the release end and the second tensioning at the tensioning end, using a geometrically nonlinear static general analysis step. This approach yields the shear stress distribution at the interface between the internal adhesive and the carbon fiber plate, as well as the deformation and normal stress distribution within the carbon fiber plate. The analysis results provide technical support and theoretical backing for experiments and research on prestressed CFRP plate grouted cylindrical wedge anchors
Modal analysis of harmonic drive reducer based on ANSYS
Get PDFModal characteristics are critical indicators for assessing the stability of harmonic reducer and serve as an essential basis for structural optimization. Based on the structure and working principle, the finite element model of harmonic reducer was systematically established and appropriately simplified. According to Block Lanczos method, the natural frequencies and mode shapes of the flexible gear and rigid gear under free boundary conditions were obtained by ANSYS. The single-factor analysis method was employed to investigate the influence of structural parameters of the flexible gear on its natural frequency and torsional stiffness. Results indicate that the natural frequency of the flexible gear increases with the length and wall thickness of the cylindrical section. Although the natural frequency of the flexible gear is lower than that of the rigid gear, it remains higher than the working excitation frequency, thus avoiding resonance. Additionally, the maximum stress in the flexible gear decreases with increasing tube length and wall thickness, which contrasts with the trend observed for torsional stiffness
The mechanism and control of low-frequency road noise in a certain hatchback Car
Get PDFDuring the development of a hatchback car, a problem of ear-pressing noise caused by low-frequency road noise was encountered. Through the analysis of the vehicle’s transmission path, the mechanism of the problem, and experimental verification, it was confirmed that the low-frequency road noise problem inside the car was mainly caused by the road exciting the tire, transmitted through the suspension system to the subframe, arms, and other bottom plate components, and then transmitted to the body, causing the rear door bending mode to be excited and generate resonance, the body panel deformation squeezing the interior cavity, causing air pressure fluctuations in the car, and ultimately causing the low-frequency road noise ear-pressing problem. To solve the low-frequency road noise problem during vehicle operation, this paper studied the noise optimization scheme for the hatchback rear door, proposed a low-frequency road noise control solution, and successfully solved the low-frequency road noise problem of the hatchback car through in-vehicle verification, proving the effectiveness of the low-frequency road noise control solution and improving the driving comfort of the car, providing important guidance for NVH low-frequency road noise control
Influence of shield tunnel construction on building foundation based on mathematical modeling
Get PDFThrough field measurement, numerical simulation and theoretical analysis, the influence of shield tunnel construction on the deformation of ceramic soil layer strip foundation is discussed. A three-dimensional numerical model of strip foundation in ceramic soil layer is established, and the effects of different shield types and parameters on the longitudinal deformation of strip foundation are analyzed using Timoshenko beam model. The increase of thrust of shield, torque of cutter head and speed of driving led to an increase of about 25 %, 28 % and 32 %, respectively, while the decrease of pressure of synchronous grouting and pressure of shield opening also aggravated the settlement. The study quantified the leading role of pressure of shield opening for the first time, revealed the double-sided effect of excavation pressure, and proposed a multi-parameter collaborative optimization strategy
Application of structural damage curve in seismic resistance: a case study of the Türkiye earthquake in February 2023
Get PDFThe degradation of structural stiffness is quantifiable through changes in the natural vibration period of the structure, facilitating the assessment of damage severity. The structural damage curve is defined by the variation in the natural vibration period of a structural system attributable to member stiffness degradation during severe earthquakes. In this study, two representative earthquake records from the February 2023 Mw 7.8 earthquake in Türkiye were selected for the elastoplastic time-history analysis of a standard ten-story reinforced concrete frame structure. Additionally, a method for defining the plastic hinge was employed to derive the structural damage curve. Analysis of varying damage levels under the influence of two seismic waves was conducted using the T-f response spectrum. The analysis results reveal: (a) Structural damage curves effectively reflect the plastic development via natural vibration period variations. (b) The T-f response spectrum encompasses amplitude, spectrum, and duration characteristics of ground motion, which, when integrated with damage curves, more intuitively delineates the structural damage mechanism. (c) Diverse impacts on the structure by seismic waves, even with identical peak values, are attributed to their distinct time-frequency characteristics. Additionally, five seismic records matching the site type of the representative records of the Mw 7.8 earthquake in Türkiye were selected from the Pacific Earthquake Engineering Research Center ground motion database in the United States. Regression analysis was utilized to derive the proposed structural damage curves at peak ground motion accelerations of 125 gal, 220 gal, 400 gal, and 620 gal. The study also includes a validation of the elastoplastic time-history analysis results with experimental data, enhancing the credibility of the findings