Interference Fit Research Articles

The installation load prediction method of interference fit between the submarine elliptical pipeline and mechanical connector

For damaged submarine pipelines, interference fit is necessary for the repair technology by the mechanical connector. Due to manufacturing error and asymmetric load, the ovality occurs on pipeline and increases the difficulty to install the connector. For ensure safety, it is necessary to consider the interference and ovality of pipeline to predict the installation load. In this paper, the software ANSYS was used to establish the finite element model of the connector and pipeline, then the contact characteristics on the contact surface were analyzed. According to the static equilibrium equation, the installation load of interference fit is equivalent to the friction force and is proportional to the contact pressure, it could be predicted according to the contact pressure. The results indicate that, on the premise of the same equivalent interference, the contact force and contact area on the contact surface were independent of the ovality of pipeline. For the pipelines with different ovality, the installation load can be predicted based on contact force of the circular pipeline. Some cases are conducted to verify the accuracy of the established prediction formula. The load prediction formula effectively solves the problem of submarine pipeline repair connection and has high engineering application value.

Non-Destructive Disassembly of Interference Fit under Wear Conditions for Sustainable Remanufacturing

Remanufacturing has been gaining increasing attention in the last few years as a part of green engineering. It is the process of restoring the original specifications of a given product utilizing a combination of new, repaired, and old parts. The present study investigates non-destructive disassembly of an interference fit pin-hub joint to enable the reuse of worn parts with the same loading capacity. The aim is to reduce the disassembly force while preventing plastic deformation and frictional damage on the contact surface to avoid fretting failure and enable further coating. A finite element model of a shaft/hub interference fit was developed, taking into account two cases of damage to the mating parts: deformation and corrosion. The results indicate that thermal disassembly is effective in reducing breaking force by 50% in deformed joints, whereas vibration waves are more suitable for corroded parts with increased friction. In addition, applying a low-frequency oscillation force to the axis of disassembly reduces the pulling out force by 5% and plastic deformation by 99% due to acoustic softening effects. Furthermore, using a heat flux simultaneously with vibration decreases the breaking force by 85%, indicating the higher effectiveness of thermal-aided disassembly and vibration-assisted disassembly in reducing the breaking force of corroded parts with increased friction. This study provides remanufacturing designers with efficient tools to weaken the interference fit and decrease the disconnecting force, ultimately reducing the cost and time required for the disassembly process.

Fretting-fatigue of shrink fit lug-bush assemblies: Interference-fit effect

The fretting-fatigue behaviour of shrink fit lug-bush assemblies is investigated. In this paper, experimental fatigue tests are carried out on lug-bush specimens with three different levels of interference fit. It is observed that the relative movements of fretting induce tribo-oxidation phenomena at the shrink-fit interface and that the crack initiation sites correspond well to the oxides formation spots. The increase in the fatigue life with interference fit is consistent with stress analysis considering the SWT multiaxial fatigue criterion, but the predicted fatigue life is not conservative relative to material reference data. In order to account for fretting surface damage, different approaches are investigated considering homogeneous and heterogeneous distributions of the coefficient of friction.

Ensuring Tightness of Interference Fits

Ensuring Tightness of Interference Fits

Experimental Study on the Reduction Effect of Pit Texture on Disassembly Damage for Interference Fit

After remanufacturing disassembly, several kinds of friction damages can be found on the mating surface of interference fit. These damages should be repaired and the cost is closely related to the severity of damages. Inspired by the excellent performance of surface texture in wear reduction, 5 shapes of pit array textures are added to the specimens’ surface to study their reduction effect of disassembly damage for interference fit. The results of disassembly experiments show that the order of influence of texture parameters on disassembly damage is as follows: equivalent circle diameter of single texture, texture shape and texture surface density. The influence of equivalent circle diameter of single texture and texture shape are obviously more significant than that of texture surface density. The circular texture with a surface density of 30% and a diameter of 100 μm shows an excellent disassembly damage reduction effect because of its perfect ability of abrasive particle collection. And the probability of disassembly damage formation and evolution is also relatively small on this kind of textured surface. Besides, the load-carrying capacity of interference fit with the excellent texture is confirmed by load-carrying capacity experiments. The results show that the load-carrying capacity of the excellent texture surface is increased about 40% compared with that of without texture. This research provides a potential approach to reduce disassembly damage for interference fit.

Three-dimensional fretting and sliding contact model in planetary gear system: Theoretical analysis and experiments

The failure of the interference fit between the planetary gear and the bearing outer rings in planetary gear systems has received increasing attention from researchers. In this study, a three-dimensional model for determining the fretting and sliding contacts between planetary gears and these outer rings is presented. A three-dimensional fretting numerical model under oblique forces was established to investigate the fretting contact between planetary gears and bearings, and an experiment was conducted to study the relative sliding between them. The results showed that if the torque generated by the difference between two meshing forces exceeded the limit torque of the interference fit, overall relative sliding would occur. Otherwise, fretting contact would occur in some regions of the interference fit surface under oblique forces. The relative sliding between the planetary gear and outer rings of the bearings can be reproduced experimentally; the relative sliding value decreased with an increase in the size of the interference fit.

Experiments and finite element analysis on a hybrid polymer gear rack

This article presents the results of experiments and finite element analysis on a hybrid polymer gear concept. The study aimed to investigate the effectiveness of the hybrid gear concept by using a rack tooth geometry.The results of the experiments have shown that the hybrid gear concept improves the heat evacuation from the flank and root regions, potentially increasing the load-carrying capacity. Additionally, the results of the experiments were compared with those obtained from the finite element analysis to validate the numerical model. The results showed that the hybrid polymer gear rack exhibited good thermal performance, and the finite element analysis accurately predicted the behaviour of the gear rack specimens. The study also analyses the influence of the interference fit on the contact pressure and thermal contact conductance in a hybrid polymer gear concept, taking into account surface roughness and temperature. It provides insights for optimizing the press fit to ensure efficient heat dissipation in practical applications.Overall, the study provides valuable insights into the potential use of hybrid polymer–metal materials in gear applications and supports the validity of the hybrid gear concept.

Research on the vibration characteristics of the ball bearing considering the uncertain bearing-shaft interference fit

Due to the exist of the inevitable dimensional tolerance and assembling errors in the ball bearing, the interference amounts between the inner ring and the connected shaft are uncertain but bounded, which could directly affect the dynamics performance of the rotor-ball bearing system. Whereas, most of the works on the field of dynamics in a ball bearing have considered the varying compliance (VC) vibration as deterministic vibration and there are few quantitative studies considering the uncertain factors. Therefore, in this paper, an uncertain ball bearing-rotor dynamic model is presented based on the Chebyshev interval method. Firstly, the uncertain interference amounts between the bearing inner ring and the connected shaft are modeled by the Chebyshev interval method. Then the radial clearance and actual interference amounts of ball bearing are derived by the bearing-shaft interference fit model. The time-dependent ball-raceway contact probability is formulated and the influence of the average and deviation coefficient of the initial interference amounts on the vibration behaviors of the rotor under various rotational speeds are investigated based on the double degrees of freedom (2-DOF) ball bearing system. The numerical cases show that the amounts of the bearing-shaft interference fit are uncertain and could be affected by rotational speed, which have an obvious influence on the dynamic performance of the rotor-ball bearing system. Reasonable design of the interference amounts could reduce the dispersion of the displacement and time-varying stiffness. The numerical results obtained by the present study are compared to the Monte Carlo simulation (MCS), which show the validity of the study.

Dynamic behaviors and contact characteristics of ball bearings in a multi-supported rotor system under the effects of 3D clearance fit

Clearance fit is a common assembly method for bearings in rotor systems, which leads to a certain clearance between the outer ring of the bearing and the bearing pedestal, that is, the fit clearance. The nonlinear factors caused by the fit clearance may affect the mechanical properties of the bearing and rotor system. Considering the fillet and six-degree-of-freedom (6-DOF) motion of the outer ring, a three-dimensional (3D) clearance fit model is proposed. In addition, considering the interference fit between the inner ring and spindle, an analytical stiffness model of ball bearings is developed. By coupling the clearance fit model and the analytical bearing stiffness model with a finite element (FE) model of a spindle, a dynamic model of a multi-supported rotor system is established and verified by the experiment, which fully considers the nonlinear factors of ball-raceway contact and outer ring-bearing pedestal contact. The effects of fit clearance, radial force, and axial force on the vibration behaviors and contact characteristics of the ball bearing in the system are analyzed. The results indicate that the larger fit clearance of the unilateral bearing may lead to misalignment of the bearing and reduce the bearing force. Under radial force, the bearing clearance and fit clearance are eliminated, which improves the stability of the system. At this time, further application of axial force causes the load-bearing area to become larger and weakens the variable compliance (VC) characteristics of the bearing. This investigation can provide technical support for the assembly and design of the bearing-rotor system.

Effect of selective reinforcement on heat dissipation of 3D-printed poly lactic acid

Additive Manufacturing (AM) represents a sustainable means of production, reducing the need for energy and resources and thus creating eco-friendly products. Homogeneous composites based on metal, polymer, and ceramic are currently used to meet the requirements of the end product. The current investigation attempts to identify functional needs and selective reinforcing with appropriate materials. The effectiveness of heat dissipation, one of the prime requirements in many applications, in metal-integrated polymer systems is assessed using simple representative samples. Representative parts are constructed using material extrusion processing with biodegradable Polylactic Acid (PLA) parts. Given its superior thermal conductivity for selective reinforcement, aluminium (Al) is chosen as the secondary material. The dimensional accuracy of the printed parts is fine-tuned using the different layer parameters to ensure the required interface clearances. A constant heat supply is provided thus to understand the influence of metal reinforcement in interaction with the polymer at the interface. The temperature is measured through the volume to record the heat conduction and dissipation. The metal-polymer sample with the interference fit is found to have the best heat dissipation compared to other alternative geometries. Either an insulating void or the absence of metal-polymer contact reduces the heat dissipation efficiency.

Stress Analysis Around the Interference-fit Joint of CFRP/metal Stacks

Carbon fibre reinforced polymer (CFRP) composites and traditional metal alloy are both widely applied in modern aircrafts. The mechanical performances between CFRP laminate and metal alloy are totally different, the stress of CFRP/metal stacks around the interference-fit joint is severely non-uniform. Therefore, the stress distribution for the contact interface of CFRP/metal stacks was investigated by finite element simulation in detail. First, the assembly process of the interference-fit bolt with CFRP/metal stacks was partitioned into six stages. Secondly, an accurate 3D finite element model was established by ABAQUS to simulate the hi-lock bolt interference fit assembly process with CFRP/metal stacks. Finally, the stress magnitude and distribution of interference-fit interface were compared and analysed. It was observed that the interference percentages and friction coefficient were the two major factors that affected the non-uniform stress distribution. The stress on the contact interface of the stacks was less than that on the free surface and decreased with moving away from the bolt.

Simulation research on fretting wear of train axles with interference fit based on press-fitted specimen

Based on dimensional analysis and similarity theorem, this paper deduces the scaling relationship considering the fretting fatigue problem of the wheel and axle, and verifies it through finite element simulation analysis. A finite element model of a 1/10 reduction ratio press-fit specimen was established to simulate the fretting characteristics of the interference fit of the train axle, and the ABAQUS finite element software combined with the Fortran wear subroutine Umeshmotion was used to apply the rotational bending load. Only considering the cumulative effect of fretting wear in the slip zone, the variation characteristics of the wear width and depth of the specimen shaft with the number of load cycles were studied. The simulation results show that the fretting wear area and wear depth increase with the increase of the number of load cycles, and the axial width of the wear area of the contact surface is about 0.2 mm; the existence of the overlap of the specimen hub can restrain the position of the contact edge of the specimen shaft fretting wear effect. This makes the maximum wear depth of the specimen shaft occur at 0.03 mm from the contact edge, while the maximum wear depth of the specimen hub contact area occurs at the contact edge.

Application of 3D Scanning Method to Assess Mounting Holes’ Shape Instability of Pinewood

Swelling and shrinkage anisotropy affect the susceptibility to an assembly of wooden elements by changing designed clearances or interference fits. This work described the new method to measure mounting holes' moisture-induced shape instability and its verification using three sets of twin samples made of Scots pinewood. Each set of samples contained a pair with different grain patterns. All samples were conditioned under reference conditions (relative air humidity-RH = 60% and temperature 20 °C), and their moisture content (MC) reached equilibrium (10.7 ± 0.1%). On the side of each sample, the seven mounting holes of 12 mm in diameter were drilled. Immediately after drilling, Set 1 was used to measure the effective hole diameter with 15 cylindrical plug-gauges with diameters of 0.05 mm step, while Set 2 and Set 3 were separately re-seasoned by six months in two extreme conditions. Set 2 was conditioned with air at 85% RH (reached an equilibrium MC of 16.6 ± 0.5%), while Set 3 was exposed to air at 35% RH (reached an equilibrium MC of 7.6 ± 0.1%). Results of the plug gauge tests highlighted that holes in the samples subjected to swelling (Set 2) increased an effective diameter in the range of 12.2-12.3 mm (1.7-2.5%), while samples subjected to shrinking (Set 3) reduced the effective diameter to 11.9-11.95 mm (0.8-0.4%). To accurately reproduce the complex shape of the deformation, gypsum casts of holes were made. The 3D optical scanning method was used to read the gypsum casts' shape and dimensions. The 3D surface map of deviations analysis provided more detailed information than the plug-gauge test results. Both the shrinking and swelling of the samples changed the shapes and sizes of the holes, but shrinking reduced the effective diameter of the hole more than swelling increased it. The moisture-induced changes in the shape of holes are complex: the holes ovalized with a different range, depending on the wood grain pattern and hole depth, and were slightly extended in diameter at the bottom. Our study provides a new way to measure 3D hole initial shape changes in wooden elements during desorption and absorption.

Structural and technological support of tightness of interference fits

The conditions for contact interaction of mating parts in interference fit joints are considered. It is shown that the main factor determining the strength and tightness of joints is the state of the surface layer. Ways are established to control the performance of joints with an interference fit by using surfactants, both in the technological preparation of parts before assembly, and in the assembly of joints. Keywords: contact interaction of surfaces, real contact area, joint tightness, influence of surfactants. kurnosov-ne@mail.ru

Design of a New Type of Bowl Plug and Its Disassembling Device

In order to solve the problem that bowl plug and cylinder hole cavity are difficult to disassemble due to interference fit. Through designing a new type of bowl plug and its disassembly device, the disassembly device is connected with the new bowl plug by the matching shaft, and through the fixing of the support plate and the support frame, the bowl plug can be easily disassembled under the action of the automatic traction device, so as to save manpower and improve work efficiency.

Automatic identification and location method for shaft-hole interference fit crack based on deep learning

Cracking on the shaft of the interference fit joint surface is a common failure form for the shaft-hole interference fit. Because the crack is small and is located at the shaft edge, the crack signal is affected by echo and reflection signals and noise when traditional ultrasonic guided wave methods are used to detect the crack. When the crack is small-sized, the crack signal may even be submerged completely in the echo and reflection signals. Therefore, the traditional detection method is unable to obtain accurate information about the crack locations easily and thus cannot evaluate the overall safety performance of the interference fit accurately. To solve these problems, this paper presents an on-axis crack monitoring system for interference fit joints using laser ultrasound and an improved YOLOv5 network that integrates early warning, detection, positioning, and analysis functions. The system detects axial cracks at the shaft-hole interface via laser ultrasonic guided waves on the workpiece, and captures the crack information by deep learning; then, the captured crack information is analyzed to extract the essential crack location information. Finally, the method is verified experimentally. The experimental results show that this method can not only identify axial cracks at the shaft-hole interference fit surface automatically, but also can locate these cracks accurately and obtain both the number of cracks and the distance between pixels.

Fatigue life prediction of double-row tapered roller bearings considering thermal effect

Thermal effects on fatigue life were investigated by analyzing the thermomechanical behavior of double-row tapered roller bearings (DTRBs) and a fatigue life prediction model was developed. A bearing’s mechanical behavior was analyzed using a quasi-static model and its thermal behavior was analyzed using a thermal network method. Viscous drag and sliding friction at the contact area were considered as heat generation factors for DTRBs. The bearing lubrication characteristics and shape dimensions interacted with the temperature and the analysis was repeated until the entire DTRB system’s temperature converged. DTRB fatigue life was estimated using a fatigue life formula based on Gupta and Zaretsky’s statistical model. Results confirmed that the fatigue life decreased rapidly because of an interference fit that occurred at very high rotation speeds or at very low supply oil flow rates. This interference fit phenomenon is caused by thermal expansion of the bearing element. The interference fit can be prevented by designing with a large initial clearance value, but an initial clearance that is too large affects fatigue life negatively because of load distribution imbalance. Optimal design of the roller end sphere radius to minimize sliding friction for the flange part can provide additional help in preventing interference fit.

Influence of assembly clearance on vibration characteristics of angular contact ball bearings in the thermal environment

Assembly clearance has a great influence on the vibration characteristics of angular contact ball bearings. In this paper, the effect of assembly clearance variation on bearing vibration characteristics was investigated by establishing a vibration analysis model and accounting for thermal effects. The model calculation results show that when the assembly of the bearing housing and outer ring is in a clearance fit, the bearing has a high-frequency resonance with the outer ring, but this phenomenon does not occur with an interference fit. The vibration characteristics of the bearing under three different assembly clearances were investigated by experiments and the correctness of the established model was proved.

Combined analysis of stiffness and fatigue life of deep groove ball bearings under interference fits, preloads and tilting moments

Combined analysis of stiffness and fatigue life of deep groove ball bearings under interference fits, preloads and tilting moments

Influence of biological pretreatment of wooden dowels on strength of rotary welded joints

Welding wood achieves joints whose strength is comparable with the strength of glued joints. When welding, the top of the dowel is not welded because of the lack of melted lignin. To achieve satisfactory strength of a welded joint, it is necessary to optimize the main welding factors such as interference fit, frequency of dowel rotation, welding depth, welding duration, etc. There are also other ideas to increase the strength of welded joints. One of these ideas involves pre-treatment of dowels with wood decaying fungi to increase the proportion of lignin on the surface of the dowels and thus in the melt. This paper presents the results of the impact of pretreatment of beech wood dowels with the brown-rot fungus Gloeophyllum trabeum. Results showed that biological pretreatment of the dowels had a significant impact on the pull-out force of the joint. Pretreatment for 4 weeks caused a substantial increase in pull-out force, while pretreatment for 2 weeks did not have a positive effect on the strength of the welded joint. Grooved dowels exhibited an increase in pull-out force of 26.9%, while smooth dowels had an increase of 21.1% of pull-out force. Research also determined additional vibrations during welding.