Ring Material Research Articles

METHOD OF DYNAMIC TENSILE TESTING OF HIGH STRENGTH FIBERS

The work proposes and tests an experimental method for determining the high-speed tensile strength of high-strength fibers, based on a combination of the modified Kolsky compression method and the method of a thin ring made of the test material expanding under internal pressure. To create a pulsed internal pressure that causes expansion of the ring, accompanied by stretching and rupture of its constituent material, hydrodynamic loading is used in a split Hopkinson bar system under compression. To do this, between the ends of the measuring bars there is a sealed cavity with a liquid that transmits compressive pressure to the inner surface of the ring. Machine oil was used as a medium transmitting the compression impulse from the measuring rods to the inner surface of the thin-walled annular sample. The transmitting pressure bar performs the function of a dynamometer, which allows, based on the deformation pulse registered in it, to measure the amplitude of the pressure developed in the oil. Since the liquid inside the ring is practically incompressible, the measured stress transmitted into the liquid based on the transmitted pulse is equal to the pressure developed in it, which causes an axisymmetric expansion of the annular sample with the development of tangential stress in the body of the ring, leading to the rupture of high-strength reinforcing fibers. The maximum tangential stress, which corresponds to the maximum of the transmitted pulse recorded in the transmitting pressure bar, can be considered the required tensile strength of the composite ring material. To evaluate the performance of the proposed technique, samples in the form of thin rings made of four layers of carbon fibers impregnated with polymer glue were used. Trial tests of a composite material with unidirectional reinforcement were carried out. The stretching was carried out in the direction of the fiber. As a result of the tests of the ring sample, based on the transmitted pulse in the transmitting pressure bar, the time dependence of the development of circumferential stresses in the ring was obtained. The maximum value of tangential stresses in the ring, corresponding to the tensile strength of the carbon fibers, was approximately 2120 MPa. The rate of stress growth in this case is 35000 GPa/s. The combined use of the Kolsky method and the expanding ring method made it possible to obtain a characteristic of the tensile strength of the composite material.

A fuzzy logic approach for selecting bearing ring materials in pharmaceutical applications

The present market trend of prioritizing safety and dependability at competitive rates has prompted the pharmaceutical and medical sectors to search more biocompatible, sustainable, and safe supplies. This paper seeks to achieve the most demanding criteria for pharmaceutical product safety, production capabilities, and performance standards. Hence, in order to avoid contamination, these sectors have set strict controls on the materials used in the manufacture of pharmaceutical and medical equipment. The purpose of this work is to introduce the FAHP-FTOPSIS technique, which offers an innovative and systematic way to selecting pharmaceutical bearing materials, filling research gaps, and enhancing pharmaceutical equipment design. The crucial issue of selecting appropriate bearing ring materials for pharmaceutical applications is addressed in this work. This research suggests the use of fuzzy logic as an innovative and successful technique to addressing this issue. Fuzzy logic is used to handle and evaluate linguistic data linked with the performance criteria of various materials such as PEEK, PTFE, Acetal, Stainless Steel, and Nylon6. A preference-based approach was used to conduct a comprehensive analysis of five commonly used materials for bearing rings. This included a direct comparison of different polymers, which are gaining favor in the pharmaceutical device sector, and stainless steel, that have traditionally been used for pharmaceutical equipment. The assessment was performed using the FAHP (Fuzzy Analytical Hierarchy Process), which assigned performance weight criteria as follows: C1 (0.128, 0.153, 0.139), C2 (0.082, 0.041, 0.019), C3 (0.425, 0.107, 0.371), C4 (0.528, 0.215, 0.089), C5 (0.137, 0.072, 0.036), C6 (0.092, 0.153, 0.172), C7 (0.063, 0.049, 0.032), C8 (0.048, 0.25, 0.049), and so on. Then, the FTOPSIS (Fuzzy Technique for Order of Preference by Similarity to Ideal Solution) was used to rank the alternatives, with the following results revealing the order: PEEK > Acetal > Nylon 6 > Stainless Steel > PTFE. This novel technology has the potential to improve the precision of material selection, therefore enhancing the overall efficiency and safety of pharmaceutical equipment and processes. The results clearly indicate that PTFE-based bearings surpass metallic ones in several aspects, including corrosion resistance, quiet operation, and minimal routine maintenance requirements. Remarkably, the calculated weight criteria align closely with the manufacturer's provided data. This innovative hybrid approach, combining FAHP (Fuzzy Analytical Hierarchy Process) and FTOPSIS (Fuzzy Technique for Order of Preference by Similarity to Ideal Solution), has the potential to simplify and optimize new product designs for pharmaceutical devices, reducing costs in the process. These findings highlight the efficacy of the FAHP-FTOPSIS technique in addressing the hitherto unexplored challenge of selecting suitable bearing component materials for specific applications. This approach offers a promising avenue for enhancing pharmaceutical device performance and reliability, marking a significant advancement in this field.

High-Strength PPS-Polymer Composites for Hydrogen High-Pressure Applications

Hydrogen technology can be one key for a transition to sustainable energy necessary to achieve climate targets and limit global warming to 1.5 °C since the beginning of the industrial revolution. Hydrogen as a CO2 neutral energy carrier must replace fossil fuels from the existing natural gas grid and infrastructure to enable an environmentally friendly and circular economy in future societies. Batteries and e-fuels are practicable technologies for short term and quantitatively limited energy provision, with disadvantages including raw material demands and technologically complex transformation cycles. Utilizing advanced power-to-gas concepts, hydrogen will not only be most efficient technology in energy storage, but also allows adaption and reuse of existing energy transportation infrastructure.To provide volatile hydrogen gas in the required flow and energy densities, advanced compression technology needs to be developed inspired by conventional gas compression systems. Reciprocating piston compressors are developed for high-pressure hydrogen applications, providing high pressure levels and flow rates. Compression equipment must be designed for non-lubricated dry-running conditions, as high gas purity standards of hydrogen do not allow for oil-based lubricants to be introduced into the process gas. High-strength carbon fiber reinforced composites are developed as piston and packing ring materials to withstand extreme pressure differences under harsh thermo-mechanically loaded operation conditions.Promising candidates with high strength and wear resistance in the form of PPS-polymers, are developed with PTFE solid lubricants and different carbon fiber fractions to combine high strength, with low friction and wear, improve pressure operation range, and limit down times of hydrogen piston compressors. The current work describes tribological testing of advanced PPS-polymers with 10 to 30 wt.% carbon fibers in a high-velocity tribometer under hydrogen gas atmosphere. Supporting thermo-mechanical tests give new insights in deformation mechanisms of fiber reinforced polymer composites and allow conclusions on their applicability for hydrogen compression.

Wear performance of modified H-13 and H418E steels for TBM disc cutter ring

The wear failure of disc cutter rings is a crucial factor affecting the efficiency of TBM construction. At present, many tool manufacturers improve the content of the elements of the cutter ring material to improve its wear resistance and reduce the number of cutter changes. However, the enhancement of wear resistance by adjusting the elemental content in the cutter ring material relies mainly on experience, and the results can only be verified by improvements in macroscopic properties such as hardness and toughness. In contrast, the reason for the wear resistance improvement is unclear. Therefore, this study carried out scaled-down cutter ring and rock wear experiments, compares the wear behavior of the modified cutter ring material based on H13 steel, and analyzes the reasons for the improved wear resistance of the modified material by metallography and XRD. The result is obtained as follows: (1) Ni-H13 and H418E have better wear resistance than Modified H13, H418E has better abrasion resistance with a 34.9 % reduction in wear rate. (2) The wear mechanisms of Ni-H13 and H418E cutter ring samples were both micro-cutting and furrow wear. A few microscopic fracture wear mechanisms appeared in the Ni-H13 cutter ring. (3) The increased carbide content in H418E and its more refined and uniform tissue distribution are the main reasons for its excellent wear resistance. At the same time, the powder smelting material did not significantly improve the wear resistance of the cutter ring.

Dynamical Interactions and Mass Loss within the Uranian System

The origin and evolution of planetary rings and moons remains an active area of study, particularly as they relate to the impact history and volatile inventory of the outer solar system. The Uranian system contains a complex system of rings that are coplanar with the highly inclined planetary equator relative to the orbital plane. Uranus also harbors five primary regular moons that play an important role in the distribution of material that surrounds the planet. Here we present the results of a dynamical simulation suite for the Uranian system, intended to explore the interaction between the five primary regular moons and particles within the system. We identify regions of extreme mass loss within 40 planetary radii of Uranus, including eccentricity excitation of particle orbits at resonance locations that can promote moonlet formation within the rings. We calculate a total dynamical particle mass-loss rate of 35% within 0.5 × 106 yr and 40% mass loss within 107 yr. We discuss the implications for postimpact material, including dynamical truncation of stable ring locations and/or locations of moon formation promoted by dynamical excitation of ring material.

Self-lubricating rubber-matrix composite incorporated with microcapsules via co-vulcanization: Elimination of friction-induced noise under dry conditions

Under extreme conditions, rubber bearings of marine stern shafts will be in a state of poor lubrication, which could cause severe wear and abnormal noise, endangering the stealth and safety of underwater vehicles. In this paper, a self--lubricating bearing material was designed by co-vulcanization method, where the nitrile butadiene rubber (NBR) and liquid NBR (LNBR) as the co-matrix and the microcapsule as the additive, named Powder-NBR/Microcapsule/LNBR (PNML). The scanning electron microscopy and thermalgravimetric analysis showed that microcapsules were well dispersed in the matrix, and the co-matrix was thermodynamically compatible. The “block-on-ring” friction test was carried out using a tribological test machine with a high-precision vibration acceleration sensor, where the ring material was composed of ZCuSn10Zn2. The results showed that the PNML had significantly lower coefficient of friction and specific wear rate, up to 84.19 % and 73.08 %, respectively, compared to the composite Matrix-NBR/LNBR (MNL) without microcapsule. The analysis of the vibration signals demonstrated that the MNL generated strong vibration and noise during friction, while the total vibration acceleration level of the PNML was reduced by 61.44 dB, as well as the line spectra and broadband noise (3300–5700 Hz) were nearly eliminated. In addition, the mechanical properties of composite were basically maintained. The findings in this study expanded the application scope of self-lubricating microcapsules, providing ideas for the design of rubber bearing materials with engineering application prospects.

Study on Sealing Performance and Solubility of High Plastic-Soluble Aluminum-Based Sealing Ring Materials for Soluble Bridge Plugs

Study on Sealing Performance and Solubility of High Plastic-Soluble Aluminum-Based Sealing Ring Materials for Soluble Bridge Plugs

Rotifer distribution patterns in relation to dissolved organic matter in the middle reaches of Huai River Basin during the dry season.

Increased dissolved organic matter (DOM) may induce water browning and affect zooplankton communities by changing photochemical environment, microbial food web, and bioavailability of organic carbon supply. However, little is known about the relationship between DOM components and rotifers in natural rivers, relative to the cladocerans and copepods. Here, we investigated the spatial patterns of rotifer distribution in relation to DOM by collecting forty-four water samples from four areas in the middle reaches of Huai River Basin. Results revealed that DOM was described by two humic-like and two protein-like components. There were significant differences in the composition and diversity of rotifer communities among areas, which might be related to autochthonous and allochthonous DOM as well as geographical distances. Specifically, rotifer communities were mainly related to molecular weight, substituents on the aromatic ring, humification level, and protein-like materials. Autochthonous and fresh DOM was positively associated with rotifer abundance and richness, and terrigenous humic-like substances were positively associated with rotifer diversity and evenness. There was a reciprocal effect between rotifer and DOM. Our findings will contribute to the understanding of the possible effects of water browning on rotifer communities, providing new insights into the key role of DOM and rotifer in the energy transfer of aquatic systems.

Measuring impedance frequency characteristics of magnetic rings with DC-bias current

This paper reports on a comprehensive study on a measurement method for the impedance characteristics in the frequency domain of magnetic rings as a function of DC-bias current up to saturation. The reported measurements in a one-wire coil arrangement with DC-bias current reproduce the operating conditions of rings used in high-power equipment and are useful for the development of circuit models used in power system simulators. The method and its key features are shown on an example of a nanocrystalline ring with large physical dimensions relevant for heavy power equipment. Low magnetic permeability of the ring material and large size of the ring were chosen as the most challenging case with respect to measurement system arrangement, allowing us to highlight the key aspects of the method. The measurement results are reported for frequency ranging from 50 Hz to 30 MHz and for the DC-bias current up to 800 A. The problems and difficulties encountered are highlighted and discussed how they were controlled and overcome.

Nonlocal dual-phase-lag thermoelastic damping in small-sized circular cross-sectional ring resonators

The purpose of current research is to establish a theoretical size-dependent framework for estimating the amount of thermoelastic damping (TED) in miniaturized rings with circular cross section via the nonlocal dual-phase-lag (NDPL) generalized thermoelasticity theory, as one of the most exhaustive non-Fourier heat conduction models. The method used to achieve this goal is based on the definition of TED in the energy dissipation (ED) approach. To do so, after deriving heat equation in the context of NDPL model, the distribution of temperature all over the volume of the ring is specified. Then, the relations of dissipated thermal energy and strain energy in the ring are obtained. Lastly, by employing ED approach, a formula comprising the nonclassical parameters of NDPL model is rendered to determine TED value in small-scaled toroidal rings. By presenting various numerical examples, the dependence of TED on influential parameters including nonclassical thermal constants in NDPL model, ring geometry, vibrational mode number and ring material is surveyed. The Findings enlighten that the inclusion of nonlocal parameter into the model can have conspicuous impacts on TED value, especially in smaller rings or higher vibrational mode numbers. The results also reveal that among the investigated materials (i.e. silicon, copper, silver, and lead), rings made of lead and silicon exhibit the maximum and minimum TED values, respectively.

Effects of the focus ring on the ion kinetics at the wafer edge in capacitively coupled plasma reactors

The fabrication process of modern microelectronic devices faces a significant challenge regarding the uniformity of wafer processing during plasma etching. Particularly, nonuniformity is prominent at the wafer edge due to varying electrical properties, leading to sheath bending and distorted ion trajectories. To address this issue, a wafer terminating structure known as a focus ring is employed to modify the sheath structure near the edge of the wafer and ensure uniform ion fluxes. However, the focus ring is subject to erosion caused by the plasma, making it crucial to minimize the ion energy bombarding the focus ring. In light of this, this paper investigates the impact of parameters such as the wafer-focus ring gap, focus ring height, and dielectric constant of the focus ring on the ion angle onto the wafer and the ion energy onto the focus ring. To conduct the analysis, a 2D3V particle-in-cell/Monte Carlo collision model is utilized. The study reveals the existence of horizontal electric fields with opposite directions at the wafer edge and the inner edge of the focus ring. Optimizing the ion angle onto the wafer edge can be achieved by adjusting the material and geometry of the focus ring. Furthermore, reducing the ion energy at the focus ring can be accomplished by increasing the height or decreasing the dielectric constant of the focus ring.

Failure analysis on abnormal damage and corrosion of methanol distillation column in MTBE production plant

Methyl tert-butyl ether (MTBE) is a commonly used gasoline additive that improves combustion and reduces pollutant emissions. The methanol distillation column is an integral part of the recovery system in MTBE production plants, used to separate and recycle unreacted methanol from water through distillation. During regular maintenance, severe damage to the support ring and abnormal perforations in the column were discovered. Despite repair welding, the column still leaked. Various investigations were conducted to determine the root cause of the failure. The chemical composition, metallurgical structure, and hardness of the support ring and column materials were examined, and the medium in the column was characterized. The medium at the bottom of the column was unexpectedly subjected to an undesirable excessive acidity (with a pH of approximately 3.8) dominated by the upstream etherification reaction deacidification, and provided common basic conditions for localized pitting and uniform corrosion of low carbon steel. What's more, the appearance of clean and smooth corrosion pits and scour traces on the perforated column wall, as well as honeycomb pits and arc-shaped layered traces on the support ring, revealed that the corrosion failure was intensified due to the interaction of selective erosive corrosion and medium concentration accelerated corrosion caused by multiple corrosion types of the acidic medium. In addition, the unpolished surface from incomplete repair welding was another significant factor. Based on these findings, specific countermeasures were implemented and proved effective.

FEM Analysis of Buckled Dielectric Thin-Film Packaging Based on 3D Direct Numerical Simulation.

This paper presents a 3D direct numerical simulation of buckled thin-film packaging based on transferred elastic thin-film wrinkling bonded on a compliant polymer ring. The mode change of the fabricated thin-film cap is found by measuring the thin-film cap shape at different times after Si substrate debonding. The conventional linear and nonlinear buckling simulations are not adequate to understand the behavior of the thin-film buckling mechanism creating such packaging cap mode change. Direct buckling simulation is recently reported as an easy and useful numerical wrinkling simulation method. A novel 3D FEM model of a thin-film package suitable for direct 3D buckling simulation is built to reduce the mode mixture between different buckling modes. Buckling modes of the packaging cap are investigated in terms of elastic moduli of package materials and applied strain due to thermal expansion coefficient difference. Based on the simulation results, it is found that there are two main modes in the fabricated thin-film buckling package determining the shape of the transferred thin-film packaging cover depending on the elasticity ratio between the cap and sealing ring materials. The mode shift from wrinkling cap mode to out-of-plane cap mode due to applied strain along a polymeric sealing ring is found.

Analysis of Sealing Characteristics of Lip Seal Rings for Deep-Sea Separable Pressure Vessels

Deep-sea pressure vessels are specialized pressure vessels designed for automatic deployment from underwater to the surface. These vessels find extensive applications in underwater life-saving and transportation. Their interiors are furnished with a pair of sealing rings, one of which is lip-shaped, and the other is a convex shape, to ensure a dependable seal. With increasing water depth, the sealing rings experience augmented pressure, resulting in a gradual pressing of the rings into the sealing groove. Using ANSYS workbench finite element software, a two-dimensional axisymmetric lip seal finite element model using forces for overall constraint was established, the complete process of progressive pressing into the sealing groove was simulated, and the deformation, contact stress, maximum shear stress, and von Mises stress distribution was also simulated. We also conducted a comparative analysis of lip seals under low and high-water pressure sealing conditions. The findings of the study indicate that when subjected to a combined effect of the installation pre-tightening force and the working water pressure, the lip seal experiences complete compression into the sealing groove at a specific water depth. When subjected to the simultaneous influence of water pressure on the sealing ring material and friction force on the contact surface, two extremes of contact stress manifest in the primary sealing zone of the lip seal. These extremes have the capacity to elevate the contact stress and the effective sealing width, ultimately leading to an improvement in the sealing performance. Concurrently, as the water pressure gradually increases, the inner concave circle of the sealing ring experiences stretching, leading to a reduction in stress concentration, equivalent stress, and shear stress to a considerable extent. This mechanism ensures that the lip-shaped sealing ring retains sufficient strength. This study offers a viable solution for conducting sealing studies on deep-sea separable pressure vessels.

Research on variable stiffness characteristics of turntable bearing under heavy load condition based on FEM

Based on ANSYS finite element analysis software, a method of extracting stiffness matrix of four-point contact ball bearing was proposed. The finite element model of four-point contact ball bearing was established, the stress and strain of the bearing under different loads were calculated, and the relationship between load and stress and strain was analyzed, The global stiffness matrices of turntable bearing with steel and aluminum as inner ring materials are extracted and compared, and the causes of large changes in the matrix are analyzed.

Performance Analysis of the C/C Composite Cylindrical Reverse Inter-Shaft Gas Film Seal

The reverse inter-shaft gas film seal is a gas path seal used in the intermediate bearing cavity of an aero-engine, which is challenging to implement due to its special installation and usage conditions. This paper proposes a C/C (Carbon/Carbon) composite cylindrical reverse inter-shaft seal structure and carries out a performance simulation analysis based on bidirectional fluid–solid coupling technology. The results show that the cylindrical reverse inter-shaft gas film seal with double-layer C/C composite sealing rings with different material mesoscopic parameters can balance seal leakage and friction power consumption and is beneficial to improving the comprehensive performance of the seal. As the mesoscopic parameters of the inner sealing ring material increase in warp and weft density, the sealing leakage rate decreases, and the gas film force and gas friction power consumption all increase. As the pressure difference increases, the sealing leakage rate and gas film force increase. As the rotation speed of the inner and outer rotors increases, the seal leakage rate increases, and the gas film force decreases. A C/C composite sealing ring cylindrical reverse inter-shaft gas film seal has a lower leakage rate and larger gas film force than a graphite sealing ring cylindrical reverse inter-shaft seal, which confers certain performance advantages. The work in this paper can provide a reference for the design of reverse inter-shaft seals.

Large mass inflow rates in Saturn’s rings due to ballistic transport and mass loading

The Cassini mission provided key measurements needed to determine the absolute age of Saturn’s rings, including the extrinsic micrometeoroid flux at Saturn, the volume fraction of non-icy pollutants in the rings, and the total ring mass. These three factors constrain the ring age to be no more than a few 100 Myr (Kempf et al., 2022). Observations during the Cassini Grand Finale also showed that the rings are losing mass to the planet at a prodigious rate. Some of the mass flux falls as “ring rain” at high latitudes. However, the influx in ring rain is considerably less than the total measured mass influx of 4800 to 45000 kg s−1 at lower latitudes (Waite et al., 2018).In addition to polluting the rings, micrometeoroid impacts lead to ballistic transport, the mass and angular momentum transport due to net exchanges of meteoroid impact ejecta. Because the ejecta are predominantly prograde, they carry net angular momentum outward. As a result, ring material drifts inward toward the planet. Here, for the first time, we use a simple model to quantify this radial mass inflow rate for dense rings and find that, for plausible choices of parameters, ballistic transport and mass loading by meteoroids can produce a total inward flux of material in the inner B ring and in the C ring that is on the order of a few ⋅103 to a few ⋅104 kg s−1, in agreement with measurements during the Cassini Grand Finale. From these mass inflow rates, we estimate that the remaining ring lifetime is ∼ 15 to 400 Myr. Combining this with a revised pollution age of ∼ 120 Myr, we conclude that Saturn’s rings are not only young but ephemeral and probably started their evolution on a similar timescale to their pollution age with an initial mass of one to a few Mimas masses.In addition to showing that meteoroid impacts can produce a large sustained mass inflow through the B and C rings, this paper addresses various uncertainties and considers possible contributions by additional transport mechanisms and by external torques. We also map out a set of future research projects, including global simulations.

Evaluation of microstructural, tribological and tensile characteristics of AA7075 surface composites fabricated through friction stir process

Superior wear resistance and a high level of tensile strength in piston ring materials are achieved using AA7075 surface composites (SCs) that are fabricated by reinforcing the steel slag (SS) particulates through proper selection of friction stir process (FSP) parameters using the multipass technique. The optical structure elucidates that fine and equi-axed grains are ascertained in the stir zone of the processed region, and by increasing the number of passes from one to three, a homogenous dispersion of particulates and a reduced grain size (9 µm) is obtained. In particular, a clear and defect-free interface is prominent on the resulting composite surface. Field emission – scanning electron microscopy (FESEM) identifies the dispersion of reinforcements, while X-ray diffraction (XRD) technique and energy dispersive spectroscopy (EDS) mapping confirm the existence of reinforcing elements. The Orowan strengthening effect and reduced oxygen content around the SiO2 and CaO elements in the three-pass FSP SC specimen tend to increase its load-bearing capacity and result in superior hardness (353.3 VHN) and tensile strength (792.6 MPa). However, the same specimen exhibits a reduced percentage (%) elongation due to multiplied fragmentation of reinforcements, which eventually restricts the plastic movement of the AA7075 matrix. The SEM fracture morphology indicates that failure occurred through a combination of ductile and brittle modes. Furthermore, the SC specimen with two passes prominently decreases the wear rate (333 × 104 mm3/m), which can be attributed to the commendable trilayer formation, and the worn morphology indicates the abrasive wear was the dominant wear mechanism. This fabricated specimen with high-strength characteristics can be beneficial for design engineers. During piston ring design, an increased level of the factor of safety can be achieved.

Performance improvement strategy of the TBM disc cutter ring material and evaluation of impact-sliding friction and wear performance

Tunnel Boring Machine (TBM) cutter ring is prone to collapse, fracture, wear, and other types of failures when dealing with hard rock/extremely hard rock. In order to address the above issue, performance enhancement strategies including electroslag remelting and increased number of tempering cycles in the heat treatment process have been implemented. These strategies lead to improvements in the comprehensive performance of the cutter rings. To evaluate the effectiveness of these enhancements, a comparison was made between the mechanical properties of the cutter rings made by H13 and W360 steels, based on the parameters including microhardness, impact toughness, and impact-sliding resistance. The results show that the microhardness of W360 cutter ring specimen has increased by 9.99%, while the impact toughness has also increased by 54.2%. According to the impact-sliding wear experiment, the impact region of the W360 specimen has a smaller wear depth under the impact angles, reflecting that the impact resistance of the W360 specimen is better. However, when the impact angle is 60°, the wear volume of the sliding region of W360 specimen is larger than that of H13 specimen, which may be related to the fact that H13 specimen contains a higher proportion of martensite. To sum up, better comprehensive performance could be obtained by choosing a reasonable metallurgical method and an optimizing heat treatment process.

Analytical algorithm of longitudinal bending stiffness of shield tunnel considering longitudinal residual jacking force

Longitudinal bending stiffness is a fundamental parameter of shield tunnels, and its value directly affects the analysis of their longitudinal response. Existing studies have not considered the tensile stiffness of segment ring joints and longitudinal residual jacking force when determining the value of the longitudinal bending stiffness of an existing shield tunnel. Therefore, through theoretical analysis, this study considered the longitudinal bending deformation under an external load action as two parts, namely the longitudinal bending deformation of the homogeneous pipe and the longitudinal bending deformation induced by the opening of the segment ring joints. An analytical algorithm of the longitudinal bending stiffness of the shield tunnel was obtained, considering that this longitudinal bending stiffness was related to various factors such as the elastic modulus of the material of the segment ring, outer diameter of the shield tunnel, width of the segment ring, number of the segment ring joints and tensile stiffness of the connecting bolt. A scaled shield tunnel model that considered tensile stiffness of the segment ring joints and longitudinal residual jacking force was designed, and longitudinal bending stiffness tests of the model were conducted accordingly. The tests were designed to measure the longitudinal bending deformation and opening of the segment ring joints. The validation of the theoretical analysis result based on the test data demonstrates that the longitudinal residual jacking force could only reduce the longitudinal bending deformation and the opening of the segment ring joints at small loads, it had almost no effect under larger loads. The measured longitudinal bending stiffness of the shield tunnel model was generally consistent with that obtained using the theoretical algorithm. Thus, in the longitudinal response analysis of the shield tunnel, the effect of the longitudinal residual jacking force on the enhancement of the longitudinal bending stiffness need not be considered.