Preload Method Research Articles

A Review of Machine Tool Motorized Spindle Variable Pressure Preload Technology Research

High-precision spindles are a vital study topic because of the growing demand for highspeed, high-precision, reliable, and long-lasting machine tools. Bearing preload is the primary means of improving the accuracy of the spindle rotor system. This study aims to summarize the research results, systematically analyze and evaluate the machine tool motorized spindle variable pressure preload technology, and provide a scientific basis for the practical application of the motor spindle variable pressure preload technology. This study is an in-depth analysis of the basic principles of the electric spindle preloading technology, the study of its influence mechanism on the thermal deformation, stiffness, slewing error, and life of the spindle system, and a discussion of the current shortcomings in the field of spindle preloading to provide a reference for the subsequent optimization. In the spindle system, the performance of rolling bearings and the design of bearing preload have an important impact on the spindle's accuracy and stability. The traditional preload method has yet to meet the requirements of modern high-speed machine tools. Real-time controllable preload has become the new direction of development, but the current preload technology still has certain limitations and needs to be further improved. In the future, the spindle bearing variable pressure preload technology will be more efficient and intelligent.

Application of micro-bolus injection and piezoelectric sensors to improve the safety of radiopharmaceuticals bolus injection

Radiopharmaceutical dynamic imaging typically necessitates intravenous injection via the bolus method. However, manual bolus injection carries the risk of handling errors as well as radiological injuries. Hence, there is potential for automated injection devices to replace manual injection methods. In this study, the effect of micro-bolus pulse injection technology was compared and verified by radioactive experiments using a programmable injection pump, and the overall bubble recognition experiment and rat tail vein simulation injection verification were performed using the piezoelectric sensor preloading method. The results showed that at the same injection peak speed, the effective flushing volume of micro-bolus pulse flushing (about 83 μL/pulse) was 49.65% lower than that of uniform injection and 25.77% lower than that of manual flushing. In order to avoid the dilution effect of long pipe on the volume of liquid, the use of piezoelectric sensor for sealing preloading detection could accurately predict the bubbles of more than 100 μL in the syringe. In the simulated injection experiment of rat tail vein, when the needle was placed in different tissues by preloading 100 μL normal saline, the piezoelectric sensor fed back a large difference in pressure attenuation rate within one second, which was 2.78% in muscle, 17.28% in subcutaneous and 54.71% in vein. Micro-bolus pulse injection method and piezoelectric sensor sealing preloading method have application potential in improving the safety of radiopharmaceutical automatic bolus injection.

Reinforcement effect and mechanism analysis of dredged sludge treated by alternating prefabricated radiant drain vacuum preloading method

The vacuum preloading method is widely applied in dredged sludge reinforcement, however, prefabricated vertical drain (PVD) clogging affects the effectiveness of ground reinforcement and leads to significant uneven settlement. To alleviate these deficiencies, this paper proposed an alternating prefabricated radiant drain vacuum preloading (APRD-VP) method considering the advantages of the alternating vacuum preloading (A-VP) method (delaying clogging) and prefabricated radiant drain vacuum preloading (PRD-VP) method (combining horizontal drainage and alleviating uneven settlement). The laboratory model experiments were conducted to explore the treatment effect of APRD-VP method, and the particle image velocimetry technology was employed to observe clogging range surrounding PVD. The experimental results demonstrate that APRD-VP method displayed a better reinforcement effect than the traditional method by analysis of water discharge, settlement, pore water pressure, water content, and vane shear strength. By investigating the clogging formation development for APRD-VP method, the maximum clogging range on both sides of the drainage board has been reduced by 3.15% and 14.02%. In addition, the empirical relationship between clogging range and settlement was established to can better judge and predict clogging range, which can lay the foundation for establishing the theory of computation of soft soil ground design suitable for APRD-VP method.

Recycling dredged mud slurry using vacuum-solidification combined method with sustainable alkali-activated binder

Dredged sediments with high water content is difficult to be treated and beneficially reused because of their poor engineering characteristics. To treat those slurry, this paper introduces a novel mechanical-chemical combined method, i.e., vacuum-solidification (VS) combined method, and investigates its performance in dewatering and strength improvement. Corresponding model tests using vacuum-only preloading method and binder-only solidification method, respectively, were conducted. Ground granulated blast-furnace slag, an industrial by-product, activated by hydrated lime, magnesium oxide or carbide slag was used as the binder in the proposed method. The mass of discharged water due to vacuum consolidation was measured during the model test. Soil samples were taken after vacuum preloading for unconfined compression test, permeability test, X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry to analyze the strength development, hydraulic and microstructural properties of the treated soil. The results indicate that the VS combined method exhibits a remarkable enhancement in both volume reduction efficiency and the strength improvement effectiveness. The type and content of activators have an obvious influence on the performance of the combined method. This study preliminarily revealed the mechanism and effect of using the VS combined method with alkali-activated GGBS as binder to treat high water content dredged mud.

Vacuum preloading combined with surcharge preloading method for consolidation of clay-slurry ground: A case study

A reclamation project was undertaken in Zhuhai, China, covering an area of 11.35 km2 with a clay-slurry thickness of 30 m. It is interesting to find a good reinforcement method, which is more suitable for strengthening such a large-scale dredged clay-slurry ground. Evidence from engineering practice shows that vacuum preloading or vacuum preloading combined with surcharge preloading method technology has certain advantages. However, further data is required to verify their performance in the field. This paper presents a case study using the conventional vacuum preloading and vacuum preloading combined with surcharge preloading method (vacuum pressure of 90 kPa, surcharge height of 3 m) to improve the thick clay-slurry ground for a subgrade engineering project in Zhuhai, China. A series of field monitoring, in-situ tests, and laboratory tests were performed to evaluate their treatment effect by analysis of vacuum degree, ground surface settlement, layered settlement, consolidation degree, lateral displacement, excess pore water pressure dissipation, and vane shear strength. The results showed that the ground treated via vacuum preloading combined with surcharge preloading method was more effective than conventional vacuum preloading. The vacuum degree of vacuum preloading combined with surcharge preloading method was slightly lower than that of conventional vacuum preloading, decreasing with depth. The settlement is increased by 55.56%, average consolidation degree is enlarged by 40.9%, lateral displacement can be augmented by 2.4 times, pore water pressure coefficient is less than 0.6, and undrained shear strength is amplified by 22.2%. These findings can be used to guide the design of the combined preloading method of the subgrade engineering project along the east coast of China.

Rapid Treatment Using Vacuum-surcharge Preloading with Dynamic Consolidation Method: Laboratory Model Test

This study presents an experimental investigation of reinforcement effect of dredged fill obtained from the Oufei project of Wenzhou, China using improved method of vacuum-surcharge preloading with dynamic consolidation by five parallel laboratory model tests: four model tests with different tamping energy combinations and a control group of vacuum-surcharge preloading method. The water content after treatment of the vacuum-surcharge preloading method was close to the optimal water content obtained from standard compaction test. The treatment of improved method of vacuum-surcharge preloading with dynamic consolidation can improve reinforcement effect and shorten consolidation time. The tests with higher tamping energy have a higher range of improvement. Under the condition of the identical level of tamping energy, compared with the drop height, the weight of hammer plays a greater role in foundation reinforcement, embodying concretely in water discharge, crater depth, and dissipation of pore water pressure, water content, vane shear strength, and porosity. The findings from this study may benefit the engineering application and further research of the combined method.

Anti-clogging mechanism of freeze-thaw combined with step vacuum preloading in treating landfill sludge

Globally, landfill sludge (LS) has accumulated in large quantities, and its reduction and dewatering are urgently needed. To address pollution problems and clogging of drainage boards caused by chemical conditioning combined with traditional vacuum preloading (TVP), a freeze-thaw combined with step vacuum preloading (F/T-SVP) method is proposed. A comparative experimental study was carried out between TVP and SVP to explore the anti-clogging mechanism of F/T-SVP in treating LS. As a result, the water discharge for the original sludge (OS) is 1840 ml, the water discharge for TVP is 8830 ml and for SVP is 10,010 ml; The total settlement of SVP is 16% higher than that of TVP; TVP has a volume reduction ratio of 57.6%, while SVP has 66.8%; the OS's water content was 86%, which was reduced to 57.6% by F/T-SVP; The center of the drainage board of TVP is seriously clogged, while the particles of SVP are evenly distributed; The tendency for small particles to undergo transport is relatively low at the beginning of SVP, which can effectively reduce clogging; TVP mainly focuses on the compression of large pores into small pores, and SVP mainly focuses on the compression of large into small pores and micropores. In SVP, there is more consolidation and a more compact structure. When F/T-SVP is used to treat LS, the pores are gradually penetrated, effectively avoiding the generation of clogging and improving LS's drainage and consolidation.

Study of long-time levitation performance of high temperature superconducting maglev under vertical vibration

In order to explore the long-time evolution of the high-temperature superconducting (HTS) maglev levitation force (LF), this paper uses the self-developed HTS dynamic maglev measurement device to conduct a long-time dynamic experiment. Limited by the experimental conditions, further working conditions are conducted based on the dynamic simulation model which is constructed based on COMSOL Multiphysics by using the magnetic field intensity H method and the basic electromagnetic formula of superconductors. The accuracy of the simulation model is verified by 9.5 h of experiment. Based on the simulation model, the LF change and levitation height decay of HTS maglev under the vehicle vibration excitation for a long time are explored. Firstly, considering the self-oscillation frequency of HTS maglev, a comparison of the different working conditions from 0.5 Hz to 10 Hz shows that there is no direct relationship between the LF and frequency in the self-oscillation frequency range. Secondly, a 30 days operation under 0.1 Hz external excitation is calculated to simulate long-time evolution and regularity of HTS maglev, which shows the LF decay has a logarithmic decay regularity with time. Furthermore, to investigate the influencing factors and improve the LF decay, the preload method was carried out. The work can provide a predictive model and data reference for the long-time performance of the HTS maglev engineering vehicle.

Modifikasi Perbaikan Tanah Dasar Tol Semarang–Demak: Metode Vacuum Preloading dengan Prefabricated Vertical Drain

The Semarang-Demak Toll Road Development Project provides information that conditions in these areas were dominated by rice fields and swamps with high groundwater levels. At STA 21+000 to 22+350, the subgrade was very soft to a depth of 24 m, so subgrade improvement needs to be done to eliminate soil compression. The soil improvement method used was Vacuum Preloading with Prefabricated Vertical Drain. The results of the planning showed that the installation of a vacuum pump at the project site has a pressure of 101.28 kPa. The effectiveness of the pump was 80%, making the vacuum pressure 81.02 kPa or the equivalent of 4.89 meters of soil pile. The square PVD installation pattern with a distance of 100 cm was chosen on the basis of consideration of the consolidation time. This design reduces the time it takes for the soil to reach a 90% degree of consolidation, from 256 years to 16 weeks. The Vacuum Preloading method reduces the heap height, as in STA 21+950. This method also creates a subgrade embankment of only 7,767 m.

Mesenchymal stem cells-derived extracellular vesicles as ‘natural’ drug delivery system for tissue regeneration

Mesenchymal stem cells (MSCs) have abilities to mediate tissue protection through mechanisms of anti-apoptosis, anti-oxidative stress and anti-fibrosis as well as tissue regeneration through mechanisms of cell proliferation, differentiation and angiogenesis. These effects by MSCs are mediated by a variety of factors, including growth factors, cytokines and extracellular vesicles (EVs). Among these factors, EVs, containing proteins, mRNA and microRNAs (miRNA), may carry their contents into distant tissues with high stability. Therefore, the treatment with MSC-derived EVs may be promising as ‘natural’ drug delivery systems (DDS). Especially, the treatment of MSC-derived EVs with the manipulation of specific miRNAs expression has been reported to be beneficial under a variety of diseases and tissue injuries. The overexpression of specific miRNAs in the EVs might be through pre-loading method using the gene editing system by plasmid vector or post-loading method to load miRNA mimics into EVs by electroporation or calcium chloride-mediated transfection. Despite current several challenges for clinical use, it should open the next era of regenerative medicine for a variety of diseases. In this article, we highlight the therapeutic potential of MSC-derived EVs as ‘natural’ DDS and current challenges.

Comparison of in vitro transformation efficiency methods for Plasmodium falciparum

Poor efficiency plagues conventional methods to transfect Plasmodium falciparum with genetic modifications, impeding research aimed at limiting the damage wrought by this agent of severe malaria. Here, we sought and documented improvements, using fluoresce imaging, cell sorting, and drug selection as means to measure efficiency. Through the transfection of EGFP plasmid, the transfection efficiency of the three methods used in this study was as high as 10-3. A method that pre-loaded uninfected erythrocytes with plasmids using the Bio-Rad Gene Pulser Xcell achieved the highest efficiency (0.48%±0.06%), twice the efficiency of a method using nuclear transfection of ring stages employing the 4D-NucleofectorTM X Kit L. We also evaluated an approach using the Nucleofactor system to transform schizont stages. We considered efficiency and the time required to complete drug screening experiments when evaluating transfection methods. Fluorescence measurements confirmed greater efficiencies for the Pre-load method (52.4% vs. 25%; P < 0.0001), but the Nuc-Ring method required less time to complete drug selection experiments following CRISPR/Cas9 editing. These data should benefit future studies seeking to remove or modify genes of P. falciparum.

ALTERNATIVE IMPROVEMENT OF SUBGRADE AND REINFORCEMENT OF EMBANKMENT ON PELABUHAN KUALA TANJUNG TOLL ROAD, INDERAPURA - KUALA TANJUNG SECTION IN NORTH SUMATRA (STA 0+000 S/D STA 3+500)

Planning the Kuala Tanjung Ruas Port of Inderapura - Kuala Tanjung Toll Road is one of the efforts to support economic growth in North Sumatra. The toll road will be built on a pile with a height of 2 ms / 9 m at STA 0 + 000 to STA 3 + 500. Due to limited land, the toll road section must be built on the poor subgrade. Based on the N-SPT test results, it is known that the subsoil consists of a clay layer with a thickness reaching 36 meters and a layer of sand at the top and bottom with a low N-SPT value. If the soft subgrade is burdened with a high heap, it is estimated that the subgrade will experience landslides, so it is necessary to plan the improvement of the subgrade and reinforcement of the pile.The soil improvement method chosen is the pre-loading method with a combination of the prefabricated vertical drain (PVD). Pre-loading method aims to spend the compression that occurs on the subgrade so that there is no compression during the service life of the road. The combination with PVD is intended to speed up the compression time in thick clay layers. The stability of the embankment will be calculated using a computer-assisted program, and geotextile reinforcement planning will be carried out if the value of the safety factor does not meet the requirements.Based on the analysis of compression computation will be divided into five zones. The amount of compression obtained under various piles of 2 ms / d 9 m was 2.25 m, 1.49 m, 1.75 m, 2.57 m, 3.65 m, 4.3 m, 4.69 m, and 5.06 m with an initial heap height of 5.02 m, 5.26 m, 6.51 m, 8.34 m, 10.41 m, 12.07 m, 13.46 m, and 14.83 m. Compression time required for subgrade is relatively long with a period of more than five years so that the planned acceleration with PVD. To accelerate the compression time to 5-6 weeks, a triangular PVD installation pattern is used with a spacing between PVD of 1.5 m and a depth of PVD installation as thick as a soft soil layer. From the results of the pile stability control, it is predicted that the pile will experience slides so that the reinforcement is installed with geotextile.Rp1.598,213,522,582.08.

Recent Patents for the Motorized Spindle Preload Mechanism

Background: The motorized spindle preload technology is one of the motorized spindle key technologies, and adjusting the preload according to the working conditions can effectively improve the dynamic performance of the motorized spindle and enhance the machining accuracy. Objectives: Review the preload mechanism development, introduce various preload mechanisms, and show research status in recent years. Then to explore and predict the future development of preload technology through the analysis of the overall preload mechanism. Methods: Search for different kinds of patents and literature about spindle preload structure in recent years. Through structural research and comparison with the traditional preload mechanism, to review the structure principle of various preload mechanisms at the present stage, then shown the advantages and disadvantages of each structure. Result: According to the patents and research of the preload mechanism in recent years, classification introduced the piezoelectric ceramic preload device, electromagnetic preload device, and hydraulic preload device, and so on. Introduce their advantages and existing problems in detail, then comprehensively compare the advantages and disadvantages of various mechanisms in control and mechanism. Finally, discuss the prospects and development directions of preload technology. Conclusion: With the further development of technology, high-precision products have higher requirements for machine tools, such as low latency, low heat generation, high efficiency, and long life. People use electromagnetic force, air pressure, hydraulic pressure, and other methods, to control the magnitude of the preload, maintain the performance of the motorized spindle at a high level. Compared with the traditional quantitative preload, their applicable working conditions are more extensive and accuracy is higher. However, various new preload methods still have certain shortcomings and need further improvement.

Clogging effect of prefabricated horizontal drains in dredged soil by air booster vacuum consolidation

The typical problem that occurs when the conventional vacuum preloading (CVP) method is applied to dredged soil is that the drainage is impeded, permeability is progressively reduced, and clogging occurs in prefabricated horizontal drains (PHDs). This paper proposes a method in which air booster through PHDs under vacuum preloading to reinforce newly dredged soil, and thereby solve the clogging problem. To evaluate the proposed method, several experiments were conducted using soils with variable degrees of consolidation and the effect on clogging determined. Furthermore, the proposed method was compared to the CVP method considering several variables monitored during consolidation and after consolidation. The results indicate that the proposed method is superior to the CVP as it more effectively alleviates the clogging problem. These findings could provide design criteria for dredged soil consolidation in similar projects and for scientific research and engineering practice.

Preload Optimization Method for Traveling-Wave Rotary Ultrasonic Motor

Preload optimization is very important for ultrasonic motors’ design and application. In this paper, a novel method for a traveling-wave rotary ultrasonic motor is proposed. Firstly, based on linear regression and the analytic hierarchy process (AHP), the mapping between the drive characteristics, mechanical characteristics, speed stability, and preload of the traveling-wave-type rotary ultrasonic motor was established. Then, the characteristic curves of stalling torque, no-load speed, maximum efficiency, and speed stability with the change of preload method were measured with a new test platform. Finally, three traveling-wave rotary ultrasonic motors with optimized preload were used in a cooperative manipulator for validation. The experimental results showed that when the preload was optimized from 200 N to 310 N, the stalling torque of the motor increased by 20.7%, the maximum efficiency increased by 15.3%, the standard deviation of the speed decreased by 53.8%, and the no-load speed decreased by 5.5%. Therefore, it can be seen that the new preload optimization approach can significantly improve the performance indexes of ultrasonic motors and meet the practical requirements of direct-drive cooperative manipulators in engineering applications. The new preload optimization method offers advantages in motor output performance compared to conventional methods.

Research on Innovation of Experimental System Based on Vacuum Preloading Method

Aiming at the problems of traditional vacuum pre-compression technology, which is difficult to visually observe the material curing effect and low sampling accuracy, this paper independently developed a set of new modular transparent model barrels and controllable vacuum pressure manifolds. Based on traditional experimental methods, Improve the model barrels and vacuum dividers in the experimental system. Experimental research shows that the improved experimental system not only solves the shortcomings of the traditional experimental system, but also can be assembled on site, which is beneficial to the areas with abundant water resources. The project of reclaiming land from the sea provides support, which has certain production and economic benefits.

Adaptive preload controller design and analysis for electrostatic suspension system

The electrostatic suspension control system (ESCS) is the core component of the inertial sensor in space gravitational wave detection. To adapt to the changes in orbit environment and satellite platform vibration, the test mass stable is kept in the center of the electrode cage, the ESCS requires high-precision parameters calibration and high-stability verification of the control system. This paper studied the ESCS method, an adaptive controller with variable preload was proposed, and the stability conditions of the control system are given to provide a theoretical basis for the design of the controller. The structure and working principle of the system were also introduced. The electrostatic control system model was derived, and the performance of adaptive preload controller was analyzed. Finally, a simulation was conducted under different disturbance conditions. The results show that the control method proposed in this paper can achieve stable control in difference disturbance, and the preload voltage will change with the conditions. Compared with the traditional fixed preload method, we can see that our method has significantly improved the stability margin and the control quality during the process of dynamic response. This paper provides a solid foundation for the future exploration of space gravitational waves in China and clears the optimization direction for the next step.

A novel preloading method for foundation underpinning for the remodeling of an existing building

The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load–displacement behavior of piles, the pile–soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.

Experimntal study on sludge solidification in a landfill site in Shenzhen

As urban land use is relatively tight, the rational use of sludge landfills has become a problem that must be solved. Because the sludge has the characteristics of high water content, poor permeability, strong flocculation, high combined water content, and high organic matter content, the traditional vacuum preloading method, stacking preloading method and other curing methods are too inefficient and can not meet engineering requirements. In this paper, an indoor electroosmosis drainage consolidation test was designed for sludge in a sludge landfill area in Shenzhen. The test results show that the reasonable drainage method, stacking method and shortening the electrode spacing increase the strength of solidified sludge by 1.1 times, 1.6 times and 2.8 times. The water content is reduced by 19.8%, 25.5% and 55.6%.The drainage rate is linear with the current.

Design and control of precision work stage with air bearing for large size optical grating fabrication

Scanning Beam Interference Lithography (SBIL) is an advanced large-diameter and high-precision plane grating manufacturing solution, which has very high requirements for the positioning accuracy and running speed of the work stage carrying the substrate. In order to improve the size and accuracy of optical grating manufacturing in scanning interference lithography further, air bearing with high precision, high loading capacity and high stiffness is one of the key components for the work stage. In this paper, in order to design a large stroke work stage which meets the demand, firstly, the air bearing, the core part of the work stage, is analyzed and calculated by finite element method, and the pressure distribution curve of the air bearing of the work stage is obtained. On this basis, the linear air bearing with high bearing capacity and high stiffness is designed by using the omni-directional preloading analysis method of high-precision motion platform. Based on the high-precision position feedback of grating encoder, the high-precision closed-loop control of 20nm (3σ) is realized by using PID control and trap filter, which meets the design and requirements, and provides technical and engineering support for the manufacture of large-scale optical grating.