Composite Bushings Research Articles

Damage and failure mechanisms of carbon fiber reinforced composite thin-walled bushings under hygrothermal-mechanical loadings

Numerous thin-walled bushings, injection-molded from AS4 short carbon fiber reinforced polyetherketone (AS4/PEK) composites, are employed in the chains of stenter heat-setting machines. These bushings rapidly deteriorate under the hygrothermal-mechanical loadings prevalent in their service conditions. This necessitates regular replacements, critically limiting machine efficiency. In this paper, considering hygrothermal-mechanical loadings, the macro–micro dual-scale damage model of composite bushings is established. The wet and thermal effects are introduced into constitutive models and damage criteria based on the macro–micro mechanics of composites and their constituents. The micro-damage and macro-destruction phenomena in the bushing are analyzed, and the related measures are proposed to delay its failure. Comparing the simulation results with the test, the macro–micro damage and failure behavior are discussed for the failed bushing. It reveals that stress concentrations near AS4 fibers initiate interfacial damage and microcracks in the PEK matrix, inciting interface debonding and matrix fragmentation, ultimately provoking composites failure. Increasing the interface thickness can delay the onset of damage. Fiber tension failure, matrix tensile, and compressive failure induce destruction at the component extremities. According to the influence of hygrothermal performance, within the glass transition temperature range of 160 °C to 240 °C, selecting composites with higher glass transition temperatures can enhance the failure strength of bushings by 19 %. Conversely, within a moisture absorption range of 0.5 % to 0.8 %, opting for materials with lower moisture absorption decreases the failure strength of bushings by 37 %. Optimal failure strength is achieved with composites having a 0.5 % moisture absorption rate and a 240 °C glass transition temperature.

Preliminary Study on Mechanical Aspects of 3D-Printed PLA-TPU Composites.

Additive technologies using Fused Deposition Modeling (FDM) technology are currently a promising tool for the production of polymeric multicomposites. This paper presents the results of a static 3-point bending test carried out on 3D printed samples of the PLA-TPU composite. The article also discusses initial vibrodiagnostic research and Finite Element Method (FEM) analysis of the 3D-printed composite bushings. The data obtained from FEM analysis served as input data for motion simulation analysis, where the influence of the stiffness of the suspension on the trajectory has been verified.

Organomorphic carbon–carbon composite for hot pressing molds

AbstractOrganomorphic composites are obtained by pyrolysis of heat‐treated molded polymer fibers followed by compacting the resulting Ipresskon® preform using carbon or silicon carbide. The structure of these materials features the most uniform volume distribution of a fiber and a matrix. The carbon–carbon (C/C) composite bushings made in this way show a very high compressive strength (up to 390 MPa) and a radial tensile strength (150 MPa). These characteristics ensure high performance of hot pressing molds for ceramics conventionally made of isostatic graphite characterized by much lesser tensile strength. This paper describes the microstructure and properties of C/C‐Ipresskon® composite that was used instead of graphite as a hot pressing mold die. The material structure was found to show a slight transformation after 22 cycles of high‐temperature thermal/mechanical loading at a temperature up to 2000°C and 30–35 MPa.

Modeling of friction engagement in a joint with carbon-carbon composite bushings in the atmosphere of Venus

The issues of the friction engagement of a carbon-carbon composite with steel under conditions of temperature and composition of the atmosphere of the planet Venus are studied in the article. The statement on the admissibility of using a carbon-carbon composite in friction units in an open atmosphere is substantiated. Antifriction properties of a carbon-carbon composite are investigated for friction against steel in the speed range 0.05 - 0.25 m / s and a contact pressure of 1 MPa. Tribological tests were carried out in sliding conditions according to the pin-on-disk scheme on a high-temperature test bench with a temperature range of 300-600 ° C. It has been shown experimentally that for given parameters of friction, there is no seizure of surfaces. Based on the study, it was found that the average value of the friction coefficient is 0.25, and the experimental data spread is less than 20%.

Development of a system for diagnosing bearing assemblies with polymer parts during operation

The object of research is the process of monitoring the limiting wear of polymer-composite bushings of the bearing unit of the parallelogram mechanism of seeding machines. This process is clearly manifested in determining the good condition of the moving joints of machines operating in severe operating conditions. The studies performed are based on the principle of breaking the active link. The diagnostics is based on this principle, which makes it possible to assert with sufficient accuracy about the failure of the control link of the mates of parts. The main hypothesis of the study is that by developing a diagnostic system based on the control of composite bushings, it is possible to determine the boundaries of the normal functioning of the sowing sections as a whole. The solution of this issue without intervention in the design of the sowing section itself is impossible. Since the material of the sleeve is a polymer composite, which has sufficient resistance not to pass an electric current, conditions are created for the implementation of the proposed diagnostic system. In this work, a regression model is built to control and identify changes in the lateral backlash from the operating time of the seeding complex. By analyzing the data obtained, it is possible to establish the relationship between the diagnostic parameter, namely, the fixation of the rupture of the active link passing near the working surface of the composite sleeve. The main limitations in the development of this diagnostic system are the boundaries of the control gaps in the mates, as well as the presence of dielectric materials for the control parts. In the case of a significant occurrence of an active rupture link or an incorrect selection of its required diameter, then this diagnostic method may work inappropriately and the diagnostic system becomes ineffective. The work reflects the timeliness and rationality of the developed diagnostic system. On the basis of such a diagnostic system, it is possible to create an automated diagnostic complex for monitoring the state of the parallelogram mechanisms of the seeding complex as a whole.

Optimal design of multiple annular tuned liquid dampers for seismic reduction of 1,100-kV composite bushing

It is of great significance to perform seismic mitigation for the 1,100-kV composite bushings because they are vulnerable to damage during earthquakes. In this paper, a new design process of multiple tuned liquid dampers (MTLDs), utilizing the displacement transfer function curves and the equivalent mechanical model of annular tuned liquid damper (ATLD), is proposed for seismic reduction of the 1,100-kV composite bushing. At first, the equivalent mechanical model of ATLD is derived based on the linear wave theory. The effects of the radius ratio and the liquid-filled depth ratio on the equivalent sloshing mass are discussed. The accuracy of the equivalent mechanical model is also verified by comparing the results with those from the Housner's model and the finite element model. And then, the transfer functions of the structure with MATLD attached are formulated in the frequency domain. The parameters, including the frequency ratio, the mass ratio, and the damping ratio, that influence the transfer function curves are also investigated. Based on these transfer function curves, the new design process of MATLD is presented. Combining with the equivalent mechanical model of ATLD, a dynamic analysis of the bushing equipped with MATLD in the dome is performed under the real earthquake records. It is concluded that the MATLD performs better than the ATLD and the bushing equipped with 5ATLD in the dome is the optimal design for seismic reduction.

Application of X-ray Detection Technology in Routine Tests of High Voltage Bushings and Arresters

The improper control of the production process can easily cause defects in the power equipment that cannot be found by routine tests. In this paper, X-ray detection technology was used to test high voltage porcelain bushings, high voltage composite bushings and metal oxide surge arresters polymeric with series gaps, which are prior to working. It is found that there are air gaps between the waterproof glue on the flange and the body of bushings, which will increase the vibration frequency of the porcelain bushings and will cause the bushings to be abnormally stressed. There is a misalignment or poor contact between the contact surface of internal valve pieces of the MOA, which will reduce the flow capacity of the series valve pieces. The above phenomena will reduce the reliability of the power grid operation. This paper believe that the current routine tests should be improved, X-ray detection technology should be used as a new routine test for high-voltage bushings and arresters to improve the reliability of equipment operation.

Sloshing characteristics of annular tuned liquid damper (ATLD) for applications in composite bushings

Sloshing characteristics of annular tuned liquid damper (ATLD) for applications in composite bushings

Расчетная оценка возможности применения подшипников скольжения из пористого стеклопластика в составе опорного катка гусеничного движителя

Currently, antifriction bushings for sliding bearings made of expensive non-ferrous metal alloys are used in low-speed caterpillar track rollers. Composite bushings based on porous GFRP obtained by radial winding is a cheap alternative for metal ones. They can withstand high radial compressive loads and successfully work without lubrication supply system using only selflubricating modifiers in their open porosity. The bushings have a low stiffness in the radial direction due to the porous structure. Low stiffness contributes to the formation of a significant contact area between interacting surfaces. Low contact normal and tangential stresses lead to a shaft wear reduction. Low interlaminar strength is the main factor limiting the use of composite bushings. Determination of the maximum radial and shear stresses emerging in the operational process of a friction unit is a very important problem. First part of the work is devoted to determination of the static and sliding friction coefficients for composite bushing. Combination of static tests up to fracture and numerical analysis was used to determine the critical interlayer shear stress. In the second part of the work, numerical model of a support roller with antifriction bushing was developed. This model was used to determine the stress-strain state of antifriction bushings of the support roller of pipe-laying machine TR-20. Distribution of normal stresses on the contact surface with the shaft for GFRP and bronze bushings were found. The relations between the maximum normal stress value and the radial clearance in pair “shaft-bushings” were obtained for both types of bushings. It was shown, that the value of the local normal stresses is significantly affected by the skew-symmetry of the roller support, clearance in pair “shaft-bushings” after assembly and after exploitation. The maximum reasonable value of the radial clearance between the shaft and the bronze and GFRP bushings were0.25 mm and 1 mm respectively. The use of antifriction composite bushings allows increasing the value of the maximum permissible clearance of friction unit more than two times in comparison with metal one. The paper shows the possibility of replacing antifriction bronze bushings on porous GFRP bushings.

Литые биметаллические втулки с износостойким композиционным слоем

The purpose of the work is developing of composite material for the functional layers of cast bimetallic bushings for operate in friction units and to explore its tribological properties.The main results – the design of the sliding bushing was designed with respect to obtain structure where soft matrix areas alternated with harder ones of the reinforcing inserts the exactly after the machining. Composite bushings made of AK12 alloy with an internal diameter of 50 mm reinforced by inserts of wires 2 mm in diameter made of stainless steel (08Х18Н10Т) and carbon steel (Ст. 45). It is stated that the wear of the composite bushings is lower than AK12 alloy has in 1,3…1,7 times. And the best result was achieved when reinforcing inserts of carbon steel (Ст. 45) where used. It can be explained by the optimal hardness ratio of reinforcing component and the matrix 3,09. In the case when reinforcing inserts are made of stainless steel hardness ratio is 3,27.

Design optimization of high voltage bushing using electric field computations

This paper illustrates the use of electric field computation to optimize the design of gas filled high voltage composite bushings. The United States Navy employs these bushings in high power very low frequency/low frequency transmitting stations. Commercially available 2D and 3D computational packages based on the boundary element method were employed to analyze the electric fields. The optimized design uses both internal and external elements for electric stress grading at critical parts of the bushing. It has been shown that the location and magnitude of the maximum electric field have been optimized which should result in a substantially higher corona free operating voltage

A study of electrical stress grading of composite bushings by means of a resistive silicone rubber coating

Local discharges in the vicinity of the mounting flange of composite bushings due to the electric field enhancement can cause insulating material degradation and finally lead to failure. In this paper, a proposed solution to this problem by employing a resistive silicone rubber coating on composite HV bushings was investigated. Finite Element Method (FEM) analysis of the electric field distribution along the surface of bushings by FEMLAB ® simulation and potential measurements by an electrostatic probe (ESP) technique confirmed that the stress grading effect of a 100 MΩ resistive coating results in a linear potential distribution and the tangential field is significantly reduced in the region of the mounting flange.

A metal-plastics antifriction material for the manufacture of composite bushings operating under dry friction conditions

A description is given of the manufacture of metal-plastics antifriction material for composite bushings. The optimum sintering condition are chosen, the technique employed for the production of metal-plastics busing is described. Tests have shown that bushing made by the process described have a high surface finish and secure the required clearance between the shaft and the inner bushing diameter.