Cylindrical Texture Research Articles

Effect of texture parameters on the lubrication performance of static and dynamic pressure thrust bearings and multi-objective optimization

PurposeThis paper aims to study the influence of cylindrical texture parameters on the lubrication performance of static and dynamic pressure thrust bearings (hereinafter referred to as thrust bearings) and to optimize their lubrication performance using multiobjective optimization.Design/methodology/approachThe influence of texture parameters on the lubrication performance of thrust bearings was studied based on the modified Reynolds equation. The objective functions are predicted through the BP neural network, and the texture parameters were optimized using the improved multiobjective ant lion algorithm (MOALA).FindingsCompared with smooth surface, the introduction of texture can improve the lubrication properties. Under the optimization of the improved algorithm, when the texture diameter, depth, spacing and number are approximately 0.2 mm, 0.5 mm, 5 mm and 34, respectively, the loading capacity is increased by around 27.7% and the temperature is reduced by around 1.55°C.Originality/valueThis paper studies the effect of texture parameters on the lubrication properties of thrust bearings based on the modified Reynolds equation and performs multiobjective optimization through an improved MOALA.

Thermohydrodynamic Lubrication Characteristics of Piston Rings in Diesel Engine Considering Transient Heat Transfer under the Parameterized Surface Texture of Cylinder Liners

The cylinder liner and piston ring form the most crucial friction pair in the diesel engine, contributing 35–40% of its overall friction losses. Recent research indicates that transient heat transfer significantly affects piston ring lubrication. However, the impact of such a transfer on varying surface textures and lubrication traits remains unclear. This paper takes the piston ring–cylinder liner of a certain diesel engine as the research object, which is based on a two-dimensional averaged Reynolds function and Greenwood–Tripp micro convex body contact model; establishes a numerical calculation model of the transient heat fluid lubrication characteristics of a vertical piston ring–cylinder liner assembly by combining the oil film thickness equation, energy equation, lubricating oil viscosity–temperature, and viscosity pressure characteristics; avoids large errors associated with assuming different temperature values for lubricants; and also uses the cylinder liner surface texturing technique to examine the effects of surface texturing on lubrication properties in the presence of transient thermal fluids. The findings indicate that employing transient thermal fluid for determining the mean value of the oil film temperature in isothermal lubrication calculations yields comparable values for minimum oil film thickness and frictional power consumption, while the friction power consumption calculated by the transient thermal fluid is slightly lower. The depth of the recesses on the surface of the cylinder liner should be minimized, while the radius of the texture should be maximized, taking into consideration the current circumstances. Compared with a cylindrical texture, a spherical texture achieves lower friction with good lubrication indexes.

Micro-crystallographically revealing the plasticity-evolved behaviors of thick Ti–6Al–4V laser-arc hybrid welded joint

Revealing the plasticity-evolved behaviors is of great significance for developing high-reliability thick Ti–6Al–4V welded joint for deep-sea exploration equipment. This research effort entailed a collaborative utilization of transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques to reveal the evolution behaviors of microstructure, weld texture, and grain boundaries for thick Ti–6Al–4V laser-arc hybrid welded joint with thickness of up to 40 mm. The discerned outcomes of this study underscored that the mixture strategy of large-sized lath martensite, densely entangled dislocations, and dislocations pile up at grain boundaries in distinct welding layers significantly enlarged the inhomogeneous plasticity of thick Ti–6Al–4V welded joint. Besides, the intensified cylindrical-texture within the weld leads to a substantial augmentation in the occurrence of Schmidt Factor concentrations above 0.3, indicative of a larger fraction of grains assuming a soft-orientation. Furthermore, the investigation unveiled an increase in the proportion of low angle grain boundaries demonstrably augmented the distribution density of geometrically necessary dislocations (GNDs) within the welds, which in conjunction with the enhanced cylindrical texture substantially elevated the grains deformability, consequently reinforcing the plasticity of welded joint. This work has provided insights into the evolution behavior of thick Ti–6Al–4V welded joint for greatly improving the plastic properties of welded structure, and substantially enhancing the service safety for deep-sea exploration equipment.

Friction and Wear Behavior of G20CrMo with Cylindrical Texture Filled with Sn-Ag-Cu under Different Conditions

Friction and Wear Behavior of G20CrMo with Cylindrical Texture Filled with Sn-Ag-Cu under Different Conditions

Small fatigue crack growth in an extruded dual-phase Mg-Li alloy

This study investigated the high-cycle fatigue behavior of an extruded dual-phase magnesium-lithium (Mg-Li) alloy using ultrasonic fatigue experiments and surface replica techniques. Specimens along the extrusion and transverse directions were compared. The α-Mg phase was found to significantly affect fatigue crack behaviors, with different deformation textures and microstructures in ED and TD specimens. ED specimens exhibited a stronger cylindrical texture, which impeded crack initiation within the basal plane of the α-Mg grain, resulting in higher fatigue strength than TD specimens. This study highlights the importance of microstructure and deformation texture in determining the fatigue behavior of dual-phase Mg-Li alloys.

Performance of hydrodynamic textured journal bearing with the combined influence of elastic deformation and pseudo-plastic lubricant

This study outlines the performances of finite-length journal bearing with textured liner, shear-thinning Rabinowitsch lubricants, and considers the elastic deformation of the bearing liner. The yielded nonlinear Rabinowitsch-Reynolds PDE system has been solved using the finite difference method combined with Elrod’s algorithm for the case of cylindrical textures. The static performance of hydrodynamic lubrication, in this case, involves different parameters such as depth of texture, eccentricity ratio, elastic deformation factor, rheological index, etc. Results showed that, at a fixed eccentricity ratio, texturing of the bearing’s converging area enhances significantly the load-carrying capacity and reduces the friction coefficient compared to the smooth bearing surface (up to [Formula: see text] in load capacity and [Formula: see text] in friction coefficient). On the other hand, using a lubricant with more pronounced shear-thinning behavior and/or elastic liner reduces the journal bearing performances (up to [Formula: see text] in load capacity and [Formula: see text] in pressure). By applying the optimization technique (particle swarm optimization), an optimal arrangement of textures that can compensate for these losses in performance even at high eccentricity has been found. This optimal texture with dimensionless dimple’s depth set to 1 [Formula: see text] improves the load capacity with [Formula: see text] for a lubricant with a rheological index [Formula: see text] and elastic bearing liner with deformation parameter [Formula: see text].

Numerical Study on the Bearing Capacity of Lubricant Film in Journal Bearing with Micro-textured Surface

For studying the hydrodynamic lubrication performance of micro-textured radial journal bearings, a numerical model of hydrodynamic lubrication for journal bearings was established first. Solve the established numerical model using FDM, and the lubricant film pressure distribution and static characteristics of bearings were obtained. Considering the processing cost and feasibility of the processing technology, the cylindrical texture arranged in the radial of the bearing shell surface is applied, the lubricant film thickness equation considering the micro-texture is introduced into the Reynolds equation. According to the height and distribution density of microstructure, the bearing capacity parameters were obtained. The load-carrying capacity of micro structure journal bearing is significantly higher than that of plain bearing. In this paper, a practical model with cylindrical micro-textured surface is given for journal bearing applications with high capacity demand.

Oil Cavitation Morphology Analysis of Textured Cylindrical Rotating Friction Pair on Circular-Disk End Faces

Cavitation is a destructive hydraulic phenomenon; it causes damage to small hydraulic machinery and large water-conservancy projects, and cavitation and cavitation corrosion problems are long-standing problems for hydraulic machinery experts. Micro-textures are often machined onto the end face near the indirect contact point to increase the oil film bearing capacity and reduce the transfer torque in hydraulic machinery, but the pressure disturbance caused by the texture dimple and boundary can induce cavitation. To delay or eliminate cavitation on the textured surface of equipment such as mechanical seals and dynamic bearings, the cavitation effect of a cylindrical texture on a rotating frictional pair was investigated from theoretical, imitational, and experimental perspectives. Low pressure is extremely important for inducing cavitation; once cavitation conditions are met, a full bubble can be formed in about 0.015 s. Cavitation mainly occurs at the outer radius of the rotating end face, i.e., in the high-speed region. There is a mutual mass transfer between gas and liquid phases when cavitation occurs, but the generation of cavitation bubbles is faster than its collapse, thus causing an increasing cavitation region.

Molecular dynamics simulations of friction behaviours on nano-textured silicon surfaces

ABSTRACT Molecular dynamics simulations have been applied to study the friction behaviours of nano-textured silicon surfaces. The effects of texture shape, texture pitch and indenter size on forces, temperature, stress and plastic deformation are investigated. It is found that the presence of the texture facilitates the reduction of friction due to the decrease the contact area. The texture shape significantly influences the tribological properties of the textured surface. The hemispherical texture has the optimum friction reduction effect, followed by cylindrical texture and lastly by cubic texture. The number of atoms that undergo phase transformation in the scratching is the maximal for the cubic texture while the smallest for the hemispherical texture. However, the texture pitch has little effect on the tribological properties of the textured surface. In addition, it is interesting to observe the indenter size effect that a larger indenter causes a smaller force and wear volume at the initial stage of scratching. The indenter size effect on tribological properties results from the variation of contact area in the scratching. The insights gained can shed light on the friction mechanism of nanoscale textured silicon surface and are beneficial to the design of micro/nanoscale devices such as micro/nanoelectromechanical systems with surface textures.

Effect of Texture on Total Energy Consumption of High Frequency Hydraulic Impact Piston Pair

Limited by the influence of the traditional clearance seal structure on the leakage and friction loss of piston pair, the energy utilization ratio of the hydraulic impactor is difficult to improve effectively. To solve this problem, a novel micro-texture clearance seal structure of impact piston cylinder was proposed, and an integrated energy consumption evaluation index considering leakage and friction loss of impact piston pair was proposed. Based on the average Reynolds equation, a comprehensive energy consumption analysis model for a textured high-frequency hydraulic impact piston pair was established, and the influence of piston texture parameters on the comprehensive energy consumption under rated working conditions was studied. The results show that the cylindrical texture clearance seal structure provided an effective way to improve the energy utilization ratio of hydraulic impactor, with energy consumption 13~15% less than the traditional structure. Variation of area rates textured made the amplitude value of integrated energy consumption of the piston pair decrease by 4~15%, and the optimum area rate was 0.2~0.4. Depth ratio of texture could also reduce the integrated energy consumption of the piston pair, but the reduction range was small.

Effect of texture geometry on the performance of noncircular aerodynamic journal bearings

Today, considerable uses of aerodynamic journal bearings have attracted the attention of many researchers in the field of tribology. Therefore, the theoretical and experimental analysis of their performance has been the subject of many researches. Growing application of the gas journal bearings is due to their capability in various engineering fields such as instrumentation and high-speed machines like spindles, small-scale turbomachines, and precision gyroscopes, dental milling machines, and many other rotor-bearing systems. Upgrading the performance of gas bearings by changing their geometry or using new compressible lubricants has always been one of the suggestions proposed by the tribology researchers. Recently, the development of new technologies such as laser milling and lithography increased the possibility of creating textured surfaces as a way to improve the performance of journal bearings. So, in this study, the effects of texture geometry on the steady-state performance of two-lobe noncircular aerodynamic journal bearings are presented. For this purpose, the governing Reynolds equation of hydrodynamic gas lubrication is analyzed by finite element method according to the changes of the lubricant film thickness in presence of the cubical, cylindrical, and ellipsoidal surface textures. Results show that the creation of textures on the lower lobe compared to the upper lobe or the whole surface is more effective on the performance of two-lobe aerodynamic bearings. Also, increasing both the dimple depth and the amount of bearings noncircularity, especially at shallow texture depth, cause more significant changes in the lubricant film pressure distribution and the bearing performance parameters such as load-carrying capacity, attitude angle, and frictional power loss. Further, it is obvious that the creation of cubical, cylindrical and ellipsoidal textures especially at shallow depth with an increase in the noncircularity of bearings’ geometry have a higher impact on the steady-state performance of the studied rotor-bearing system, respectively.

Effect of Deformation on the Microstructure of Cold-Rolled TA2 Alloy after Low-Temperature Nitriding

In order to improve the low hardness and poor wear resistance of TA2, this paper proposes a composite process of cold-rolling and low-temperature plasma nitriding with recrystallization. This composite modification process can effectively achieve the dual goals of modifying the matrix structure and surface of TA2 alloy simultaneously. The cold-rolling experimental results indicate that when the deformation rate increases, the small-sized grains in the sample increase significantly, and the grain orientation changes from TD (transverse direction) to RD (rolling direction) and then to TD. The nitriding experimental results indicate that the {0001} basal surface texture deflected from the TD direction to the RD direction, {10-10} cylindrical texture components gradually increased, and the special orientation phenomenon of cylindrical and conical texture disappeared, it can be seen that an increase in the deformation rate promotes recrystallization. The XRD test results indicate that after low-temperature nitriding, metastable nitriding phase TiN0.26 is formed on the surface of TA2. The SEM morphology of the cross-section shows that a relatively special nitrided zone is formed, and mechanical performance test results indicate the wear resistance and hardness of the alloy increased.

Synergistic effect of textured piston ring and nano-lubricant on performance parameters and emissions of IC engine

Internal combustion (IC) engine is a prime emitter of greenhouse gases. The piston ring-cylinder liner pair plays a critical role in engine performance and exhaust emissions. Moreover, it accounts for major engine losses. The texturing on the piston ring and nano-material blended engine oil (nano-lubricant) have demonstrated promising results in their respective investigations on the IC engine. So far, most of the studies have been conducted on one of these approaches. Therefore, in this study synergistic effect of textured piston ring and nano-lubricant is investigated on performance parameters (fuel consumption, brake thermal efficiency, and brake specific fuel consumption) and engine emissions. The upper top compression piston ring is textured partially, and the nano-lubricant is prepared using silicate complexes nano-material [Mg6SiO10(OH)8] of 1% by weight with multi-grade engine oil (20W-40). The laser surface texturing technique (LST) is used to produce cylindrical textures on the piston ring with 6% texture density and 7.5% aspect ratio. Experiments have been conducted on a single-cylinder, direct injection, air-cooled, naturally aspirated compression ignition engine. All tests have been performed under different loading conditions (20%, 40%, 60%, 80% and 100% of full load). The synergistic effect of partially textured piston ring and nano-lubricant showed lower fuel consumption up to 4.58%, and nano-lubricant showed fuel reduction up to 3.23%. Furthermore, the exhaust emissions (CO, HC, and NOx) demonstrated a reduction that ranges from 0.24% to 10% compared to baseline data.

Effect of Multidirectional Forging on Microstructure and Properties of AZ40 Alloy

AZ40 alloy was operated with the plastic deformation by multidirectional forging (MDF). The evolution rules of microstructure and texture during forging were analyzed by means of metallographic microscope and electron backscattering diffraction (EBSD), and the evolution mechanism of texture during forging is explored. The results show that, with the increase of passes of forging, the strength of the basal texture decreases. After four passes of forging, the original {0001} basal texture is changed to {101̄0} and {21̄1̄0} cylindrical texture, and the Schmind factor of the alloy reaches the maximum. Through multidirectional forging, the anisotropy of the alloy is weakened, and the mechanical properties of each texture are improved compared with that of the extruded state. After four passes of forging, the plasticity of the alloy is the best and the elongation ratio reaches the maximum, which is 32.0%, 29.2% and 27.0%, respectively.

Behaviour of hydrodynamic journal bearing under the combined influence of textured surface and Non-Newtonian Rabinowitsch fluid model

In the present study, the static characteristics of hydrodynamic circular journal bearings of finite length are highlighted, using the combined influences of textured surface and non-Newtonian lubricants behavior, obeying to the Rabinowitsch fluid model. The associated nonlinear Rabinowitsch-Reynolds equation has been discretized using finite differences scheme and solved by the mean of Elrod’s algorithm taking into account the presence of cylindrical textures on full/optimum bearing surface. Following to the absence of textures on the bearing surface or the non-Newtonian fluid behavior, the obtained results are in good agreement with the reference ones. The hydrodynamic lubrication static performances are computed for various parameters such as textures location; eccentricity ratio and the rheological coeffcient. The results suggest that texturing the bearing’s convergent zone enhances significantly the load carrying capacity and reduces the friction coeffcient, whereas texturing the full bearing surface may leads to bad performances. It is also noticed that the pseudoplastic lubricant coeffcient decreases the bearing performances (load capacity and pressure) compared to Newtonian fluid cases. Considering the optimal arrangement of textures on the contact surface, a significant improvement in terms of load capacity and friction can be achieved, especially at low pseudoplasticity effect.

Optimal design of the slip–texture on a journal-bearing surface

Purpose This work aims to explore the combined effects of boundary slip and texturing on hydrodynamic journal bearings and identifies optimized slip and texture patterns to improve the performance of journal bearings. Design/methodology/approach The quadratic programming technique is used to study the influence of boundary slip on the lubrication performance of a two-dimensional journal bearing. A numerical model is used to analyze the effect of the cylindrical texture shape on the characteristics of journal bearings. It is concluded that the combination of slip and texture can be an effective approach to improve the performance of hydrodynamic journal bearings. Findings The results show that there is an interfacial shear stress (perfect slip surface) and that the role of the slip regime is to reduce friction. Numerical analyses indicate that the location and size of the slip and texture zone have a large effect on journal bearings. A comparison of the distribution forms of various texture–slip combinations indicates that the full texture–slip combination can prominently reduce the load-carrying capacity and that the “forward-slip backward-texture” configuration can considerably improve the performance of journal bearings. Originality/value The combined effects of boundary slip and texture on hydrodynamic journal bearings are meticulously examined. The patterns of the slip and texture are optimized, which can substantially improve the journal bearing performance.

Tribological Properties of Rock Bit Journal Bearings for Journal with Nanosecond Laser Surface Texture

One of the urgent problems that has yet to be addressed in the field of drilling engineering is how to further improve the working performance of rock bit journal bearings (RBJBs) and prolong their service life under complicated conditions of low speed, heavy load, and high temperature. Generally, reasonable surface texture parameters serve as an effective means for enhancing the lubrication and antiwear performance of the sliding surface under harsh lubrication conditions. This study combines the geometric similarity with Sommerfeld similarity and designs an RBJBs scaling experiment; then, experimental studies are performed using an improved journal bearing test bench. The effects of nanosecond laser-textured shape, geometric parameters, and angle factors on the tribological properties of RBJBs are discussed. The results indicate that cylindrical, elliptical, and chevron textures with appropriate parameters can significantly reduce the wear and improve the lubrication performance of RBJBs under the simulated test conditions.

Effect of Surface Texture on the Output Performance of Lateral Sliding-Mode Triboelectric Nanogenerator

In the working process of textured sliding-mode Triboelectric Nanogenerator (TENG), triboelectrification and wear occur simultaneously. At present, there is no systematic research on how the size of surface texture affects surface wear and output performance. In this paper, polymer surface with cylindrical texture of different pitches was prepared by photolithography and replication technology. According to the experimental results, the relationship between surface charge density and normal load of textured PI films was determined. Then the wear and electrostatic field of textured sliding-mode TENG were simulated by finite element method. The results show that the surface charge density increases with the contact load. And the open-circuit voltage of the sliding-mode TENG increases with the sliding distance given in this paper. The reason is that the height of textures in the separation zone is higher, which is caused by the shorter in-friction time and less wear, leading to the increased contact load in the next full-contact state. Therefore, more charges caused by the increased contact load tend to induce the higher output voltage. Moreover, textured surface with small pitch has better wear resistance and output characteristics. This research can provide an analytical method and basis for designing of surface texture in sliding-mode TENG.

Influence of dimple location and depth on the performance characteristics of the hydrodynamic journal bearing system

This paper concerns with theoretical investigation to predict the influence of cylindrical textures on the static and dynamic performance characteristics of hydrodynamic journal bearing system and the performance is compared with smooth surface bearing. The Reynolds equation governing the fluid–film between the journal and the bearing surface is solved numerically with the assistance of finite element method and the performance characteristics are evaluated as a function of eccentricity ratio, dimple depth and its location. In this study, four journal bearing configurations viz: smooth (non-textured), full-textured, partially textured-I, and partially textured-II are considered for the evaluation of theoretical results. The simulated results indicate that the influence of surface textures is more significant when the textures were created in upstream zone of 126°–286° and dimple aspect ratio nearly 1.0.

Computational investigation on the performance of hydrodynamic micro-textured journal bearing lubricated with micropolar fluid using mass-conserving numerical approach

The tribological characteristic of journal bearing systems can be enhanced with the integrating of textures in the contact interfaces, or using the lubricating effect of non-Newtonian fluids. In this study, the combined effects of bearing surface texturing and non-Newtonian lubricants behavior, using micropolar fluid model, on static characteristics of hydrodynamic circular journal bearings of finite length are highlighted. The modified Reynolds equation of micropolar lubrication theory is solved using finite differences scheme and Elrod's mass conservation algorithm, taking into account the presence of the cylindrical texture shape on full and optimum bearing surfaces. The optimization textured area is carried out through particle swarm optimization algorithm, in order to increase the load lifting capacity. Preliminary results are in good agreement with the reference ones, and present an enhancement in the performances of micro-textured journal bearings (load carrying capacity and friction). The results suggest that texturing the bearing convergent zone significantly increases the load carrying capacity and reduce friction coefficient, while fully texturing causes bad performances. It is also shown that the micropolar fluids exhibit better performances for smooth journal bearings than a Newtonian fluid depending on the size of material characteristic length and the coupling number. The combined effects of fully surface textured with micropolar fluids reduce the performance of journal bearing, especially at lower eccentricity ratios. Considering the optimal arrangement of textures on the contact surface, a significant improvement in terms of load capacity and friction can be achieved, particularly at high eccentricity ratios, high material characteristic lengths and high values of the coupling numbers of micropolar fluids.