Interference Fit Research Articles

Research on the fretting contact fatigue strength of interference fit in high speed rail traction motor shafts

Fretting wear and gear contact fatigue belong to adhesive wear. They have similar causes, failure mechanisms, and failure appearance. Drawing inspiration from the gear contact fatigue strength theory, this article creatively proposes a calculation method for the fretting contact fatigue strength. The safety factor of fretting fatigue is calculated to be 0.34. Due to the singularity of the contact point at the edge of the oil groove, the mesh size near this point needs to be sufficiently fine to 0.025 mm. The contact pressure at the edge contact point of the oil groove is calculated by finite element method (FEM) to be 1034 MPa, which is 6.8 times the Lame theoretical value of 152 MPa. The stress concentration is very severe. The fretting contact fatigue strength at the edge of the oil groove is severely insufficient. The friction torque of the interference connection is calculated to be 3.1 times the overload torque of the motor. The fundamental cause of fretting wear is excessive interference and unreasonable design.

A Comparison of the Periprosthetic Fracture Rate of Cemented and Cementless Total Knee Arthroplasties: An Analysis of Data From the National Joint Registry

BackgroundPeriprosthetic fractures are serious complications of knee arthroplasty often requiring complex surgery. There is concern of increased periprosthetic fracture risk with cementless components given the reliance on interference fit for primary stability. It is unknown how the periprosthetic fracture risk compares between cemented and cementless total knee arthroplasties (TKAs). MethodsA total of 22,477 cemented and 22,477 cementless TKAs from the National Joint Registry and Hospital Episodes Statistics database were propensity score matched on patient and surgical factors. Cumulative periprosthetic fracture rates were calculated using Kaplan-Meier analyses and compared with Cox regressions. Subgroup analyses were performed in different age, body mass index, and sex groups. ResultsThe 3-month fracture rate in the cemented and cementless TKA groups were 0.02% and 0.04%, respectively. At 10 years, the cumulative fracture rate after cemented TKA was 1.2%, and after cementless was 1.4%. During the study period, there were no significant differences in fracture rates between cemented and cementless TKAs with a hazards ratio 1.14 (confidence interval 0.94 to 1.37, P = .20) at 10 years postoperatively. There were no significant differences in fracture rates between fixation types on subgroup analyses of sex, body mass index, and age groups. Female sex was a risk factor for fracture in both cemented (odds ratio 2.35, P < .001) and cementless TKAs (odds ratio 2.97, P < .001). ConclusionsThe periprosthetic fracture rates following cemented and cementless TKA surgery are low being approximately 1.2% and 1.4%, respectively at 10 years. There were no significant differences in periprosthetic fracture rates requiring readmission between cemented and cementless TKAs. Level of evidenceIII.

An investigation into the joint performance of interference fit rivets and failure analysis of aircraft fuselage skin in aerospace applications

An investigation into the joint performance of interference fit rivets and failure analysis of aircraft fuselage skin in aerospace applications

Structural stability design of an optical mirror mount adjustment mechanism

The stability of beam pointing in a laser system depends on the consistency of the optical mirror mount. Typically, a locking mechanism is used to secure the adjustment mechanism after beam alignment, ensuring the mount’s stability. However, this process can introduce errors, causing a drift in the optical path. To mitigate this issue, in this study, an interference fit adjustment screw was designed. This development enables the mechanism to self-lock after beam alignment, thereby preventing optical path drift and enhancing overall stability. Specifically, 14 long-term thermal shock stability tests, each lasting 2500 min, were conducted to validate the proposed design. The experimental results showed that the thermal drift of the interference fit adjustment screw was reduced by 47.16%, thermal shift was reduced by 79.59%, and the long-term stability improved by at least 48.67%.

Intelligent Robotic Electromagnetic Riveting Interference Connection Technology for Aircraft Assembly

Aiming at the problem that the existing automatic electromagnetic riveting equipment is difficult to adapt to the riveting of complex structures such as narrow space, an electromagnetic riveting interference connection technology based on intelligent robots is proposed. An industrial robot carrying an end-effector is used in electromagnetic riveting. First, the overall design of the electromagnetic riveting system with each integrated module is presented; Then the composition form of the electromagnetic riveting module and riveting operation principle is elaborated in detail, and the system process flow is designed; Finally, the test pieces are subjected to hole-making and interference bolt riveting tests, and the results show that the designed system can complete the electromagnetic riveting task, and the rivets and the riveted plates realize a better interference fit.

Fields of residual stresses near open assemblage holes of aircraft wing panel

The results of fatigue tests of two geometrically identical and similar in design models of the lower wing panel of a commercial aircraft are were analyzed. The panels differed in the way of installing mounting bolts, which connect the skin and stringers. Cold expansion of holes drilled both in the skin and stringer has been performed for the first panel before joining. The second panel includes no additional treatment after drilling pilot holes and final reaming. Bolts are mounted with an interference fit varying from 1.3 to 2.1% and from 2.9 to 3.2% for the first and the second panel, respectively. Changes in the interference fit are the consequence of a scatter attributed to the presence of a tolerance zone for the diameters of both bolts and mounting holes. A two-step comparison of both technologies is based on the experimental study of residual stress fields. The first stage, being a subject of the present study, includes the analysis of residual stress fields, which arise after removing bolts and separation of skin from stringers. Hole drilling and gradual crack growth were used to determine the components of residual stresses. Deformation response is measured by electronic speckle-pattern interferometry. High quality interferograms, which provide a reliable resolution of the interference fringes of ultimate density over the hole edge or directly along the notch borders, have been obtained for both ways of local removing the material. The first point-wise method based on drilling a probe hole, provides a quantitative determination of the residual stress components, starting from 1.4 mm distance from the assemblage hole edge. The second technique implements the crack compliance method of subsequent lengthening of the notch, starting directly from the mounting hole edge. This approach provides for a quantitative analysis of residual stress fields, related to different bolt mounting technologies, proceeding from the comparison of SIF values. A high level of compressive residual stresses near open holes is characteristic for both types of panels. Both experimental approaches showed the benefits of joints, where bolts are mounted into cold-expanded (reinforced) holes. For this case, the estimation of the relaxation parameters of the principal component of residual stresses in the direction of the external load is presented.

A simple new method for retrieving spectral changes of the refractive index of thin films from transmission spectra

A new method for calculating the refractive index spectral behaviour of thin films is presented. The method is based on introducing the idea of the order of appearance technique to accurately find the order of interference and Cauchy fitting parameters of the interference peaks observed in the transmission spectra of the thin film under investigation. A very simple mathematical relationship was found that relates the order of appearance and wavenumber of the interference peaks observed in the transmission spectrum. Fitting the data extracted from the measured transmission spectra to the newly found simple mathematical relation, we can extract the order of interference and Cauchy fitting parameters of the thin film under investigation. In addition, the thickness of the film was extracted and found to agree well with the thickness measured using the spectroscopic ellipsometery technique. The proposed method of calculation was successfully applied to five binary semiconductor samples, which are ZnO, ZnTe, ZnS, ZnSe, and SiO2. A very good agreement was found between the proposed method of calculation and the well-known method presented by Swanepoel. Finally, the effect of surface roughness on the FECO peak wavelength was discussed.

Research on ultrasonic assisted press-fit assembly of small interference fits

Interference fits are widely used in aerospace, precision instruments and other fields. Press-fit assembly is one of the traditional assembly methods for interference fitting parts. Wear during assembly will affect the performance of interference components and the service life of marine equipment. Ultrasonic assisted press-fit can significantly reduce the press-mounting force of an interference fit. However, its effect on connection quality is rarely studied. The mechanism of ultrasonic assisted press-fit is unclear. In this paper, ultrasonic assisted press-fit was simulated and experimentally studied. The effects of ultrasonic vibration on heat generation, press-mounting force, connection strength, and interface wear were analyzed and discussed. Through analogy analysis with similar ultrasonic assisted machining processes, the mechanism of ultrasonic assisted press-fit was revealed. The results show that the superimposed ultrasonic vibration can effectively reduce the joining force (up to 33.5%), and increase the connection coefficient from 10% to 40%. This is due to stress superposition, friction reduction and acoustic softening that reduces interface wear. The increase of the interface roughness Rz from 3.681 to 4.586 μm confirms this analysis. Furthermore, the ultrasonic vibration can effectively reduce the material plastic flow of contact interface. This study reveals the significant advantages of ultrasonic assisted press-fit assembly (UAPA) method and provided a basis to understand the underlying mechanisms of UAPA.

Influence of bolt dynamic installation on topography characteristics and mechanical behaviors of CFRP interference-fit bolted joints

As the controlled research of Dynamic Installation (DI) and Static Installation (SI), a new interference installation method was developed based on electromagnetic loading to enhance the mechanical properties of composite structures. Four different interference-fit sizes were considered, ranging from a net fit to 2.0%. The experiments were conducted to evaluate the installation resistance and the mechanical behavior of the joint under external loads. Meanwhile, an FEA model to model the stress distribution and damage behavior of the bolt-hole contact interface was established. The load–displacement curve and damage modes of experiments were used to verify the FEA results. The results show that the installation resistance during DI process was remarkably lower than that of SI process corresponding to all interference-fit sizes, and the stress amplitudes induced by interference were larger and widely distributed. The damage of the hole wall was positively correlated with interference fit size, but DI can significantly reduce the damage compared to SI. In performance tests, DI enhanced the static bearing capacity and extended longer fatigue life of the joints than SI. DI methods can be an effective way to achieve highly reliable interference joints in composite structures.

Effects of Stress on Loss and Magnetic Properties of Fe80Co3Si3B10P1C3 Amorphous Iron Cores

The research on how to reduce energy consumption and improve the efficiency of amorphous motors has extensive coverage. This study systematically investigates the influence of internal stress induced by impregnation curing and interference fit on the soft magnetic properties and loss characteristics of Fe80Co3Si3B10P1C3 (CAF4) amorphous alloy iron cores. The amorphous iron core samples undergo analysis through differential scanning calorimetry (DSC), transmission electron microscopy (TEM), X-ray diffraction (XRD), magnetic performance testing equipment, flexible pressure sensors, and magnetostriction testers. The CAF4 amorphous iron core after impregnation curing (AIC) exhibits the lowest loss of P1.2T,1.5 kHz = 22.8 W/kg when annealed at 260 °C, representing a 21% increase compared to the pre-impregnation curing (BIC) state. Within the commonly utilized interference fit range, the loss growth rate of CAF4 amorphous iron cores is lower than that of Fe80Si9B11 (1K101). Likewise, at a frequency of 50 Hz and an excitation of 1000 A/m, the magnetostriction coefficient of CAF4 is smaller than that of 1K101. Within the typical interference fit range, the magnetization performance of CAF4 amorphous iron cores surpasses that of 1K101, favoring lightweight and compact motor designs and reducing copper losses. Consequently, CAF4 amorphous iron cores exhibit significant advantages when employed in motors.

A Thermomechanical Model for Time-Varying Deformations of Spigot Interference Connection under Shrink-Fitting Assembly

The interference fit connection structure is widely employed in various industries. Different from the conventional connection structure, the aero-engine rotor connection has a spigot-bolt structure. The quality of the shrink-fitting assembly process directly affects the final assembly performance of the rotor. The complexity of the connection structure and the time-varying thermal deformation bring great challenges in analyzing the formation patterns of connection performance. However, existing methods of interference connection analysis are mainly used in the wide range of interference connection structures, which makes them difficult to apply in low height interference connection for aero-engine rotors. This paper introduces a thermomechanical interference fit pressure model. First, a theoretical model for interference fit pressure considering temperature-variable loads is established to obtain the time-varying pressure during the assembly process. Second, a finite element model is established to explore the influence of interference and temperature loads on the spigot pressure and the mounting edge deformation. Finally, the experiments validate the accuracy of both the theoretical model and the finite element analysis. The results indicate that during the shrink-fitting assembly process, the interference fit pressure exhibits a nonlinear evolution trend, and the warping deformation of the mounting edge is a result of the combined influence of temperature and interference fit pressure. The law found in this paper has an application prospect in the process parameter setting of shrink-fitting assembly for special structures.

Effect of Interference Size on Contact Pressure Distribution of Railway Wheel Axle Press Fitting

Mechanical couplings in engineering usually use interference fits to connect the shaft and hub. A railway wheel axle is a press fit that is connected by interference and can be subjected to bending stress. In loaded press fits, a high concentration of contact stresses can be generated in the area of the axle-fillet beam, which in most cases leads to the failure of the axle due to fatigue and fretting fatigues. Therefore, it is crucial to determine the ability of the press-fitted joints to provide sufficient frictional resistance that can withstand the loads and torques by evaluating the safety factor, especially when the mechanical or structural system is loaded. In this paper, the contact pressure and stress distribution along the radius of the wheel axle are studied using the analytical calculation of Lame’s equation, and the numerical method used is by ANSYS software. It was found that interference fits have a great influence on the connection strength of interference fits, which are directly related to the contact pressure. Increasing the interference increases the contact pressure, which allows higher torque and load capacity to be transmitted. The finite element analysis showed good agreement for the highest interference value of 230 µm with a relative error of 1.4%, while this error increased to the maximum relative error of 14.33% for a minimum interference of 100 µm.

Influence of Interference Fit and Temperature on High-Speed Permanent Magnet Motor

A high-speed permanent magnet motor is the core driving component of a centrifugal air compressor. The power of the centrifugal air compressor is output by the motor. Its safety and reliability are embodied in the stability of the rotor structure, which greatly affects the stability and working efficiency of the centrifugal air compressor. Much research has focused on the material strength, structural characteristics, and fit clearance of a high-speed rotor, whereas few research articles have focused on the influence of interference fit of high-speed and ultra-high-speed permanent magnet motors, and there is also little research on the thermal failure caused by temperature in high-speed motors. In this paper, the influence of the interference fit and temperature of the high-speed permanent magnet motor is studied. Using finite element analysis conducted by Ansys to obtain simulation data, the influencing factors of the strength of the interference are analyzed comprehensively in the centrifugal compressor rotor system. The interference value and rotational speed range are determined via numerical calculation. Under the condition of minimum interference, when the calculated speed reaches 137,628.82 rpm, the structure of the rotor is loose and fails, which is a mechanical failure caused by the relative sliding of the magnet and the sheath. The calculated speed value differs from the simulation result by about 1.2%. The simulation results show that the maximum stress of the structure can be reduced from 1186.1 MPa to 308.42 MPa by adding chamfer to the end covers in interference fit structure. The effects of interference value, rotational speed, temperature, and sheath thickness on the structure are also analyzed. From the perspective of temperature on structural reliability, the failure temperature of the structure decreases when the interference value increases. The lowest failure temperature is 182.3 °C when the interference value is 70 μm. After that, the interference value increases and the failure temperature increases. The reason for this is the interaction between radial stress and contact stress. These results are caused by the interaction between interference fit and temperature, which should be paid attention to when the structure of a high-speed permanent magnet motor is designed.

Analytical solution for the interference fit problem of functionally graded materials hollow cylinder/spherical shell

Analytical solution for the interference fit problem of functionally graded materials hollow cylinder/spherical shell

Analysis of separation mechanism and life enhancement study of lug joint with interference fit fastener

Analysis of separation mechanism and life enhancement study of lug joint with interference fit fastener

Crashworthiness analysis and structural optimization of shrink tube under interference condition

This paper aims to study the crashworthiness of shrink tubes for rail vehicles under axial impact loading. A theoretical model of shrink tube for platform force prediction under interference fit conditions was proposed. The trolley crash test was used to experimentally study the structural energy absorption and characteristics during collision, and a corresponding finite element model was constructed and validated. The finite element model validated the accuracy of the theoretical model. The influence of structural parameters on the crashworthiness of shrink tube under interference conditions was then studied. Structural design variables, including the magnitude of interference (int_pre), thickness (T), long right-angle edge (tri_x) and short right-angle edge (tri_z) were sampled using a full factorial and a Latin hypercube design method. Based on the above samples, the moving least squares method (MLSM) was used to construct an approximate model of peak force (Fmax), specific energy absorption (SEA), and platform force (Fplt). The main effects analysis illustrated that the tri_z had the most significant effects on the peak force, specific energy absorption and platform force. To minimize Fmax and maximize SEA, the global response surface method (GRSM) was employed for parameter optimization. Finally, the optimized configurations were obtained with int_pre=0.067mm, T=10.003mm, tri_x=21.485mm, and tri_z=6.101mm. Compared to the initial design, the SEA value was increased by 16.41 %, while the Fmax value was decreased by 2.21%. The error of platform force derived from the optimal solution and theoretical prediction was 3.62%, which verified that the theoretical prediction model was credible within an acceptable range.

Study on Non-linear Contact Stress and Prognosis Analysis of Lug Joints With Misfits

Components of aircraft and other large scale structures are generally made in parts in order to facilitate easy manufacturing, assembly and dis-assembly. Lug joints with fasteners are preferred in several aerospace applications where their purpose is to connect primary load carrying members. Study on structural integrity of these types of joints becomes mandatory from the safety point of view. This requires in-depth understanding of science and technology of Structural Health Monitoring (SHM) at these joints. Analysis presented here deals with the critical locations of interference and clearance fit lug joints which continuously operate under fatigue loading. Both interference and clearance fits exhibit non-linear contact-stress variation above certain load level and this effect needs to be addressed for both fatigue and monotonic loading. The maximum Pull or Push loads causes high stress concentrations at critical locations along the pin-hole interface. With continuous usage of the component, crack like damages initiate at these locations and they grow till failure of the component. The non-linear prognosis analysis is carried out to generate the data required for SHM at any stage which can be used to estimate remaining life of the component.

Project Assessment of the Reliability of the Joint of a Circulation-Loaded Ring of a Rolling Bearing with a Shaft of Tolerance Class js6

Study and assessment of the reliability of a joint of a circulation-loaded ring of a rolling bearing 50217 and a flange of the Yaroslavl Engine Plant gearbox demultiplier have been carried out. It has been found that, upon adding the dispersion of the sizes of the analyzed holes and shafts, a dispersion of gaps and interferences is formed, in which the probability of occurrence of interference fits (93%) prevails. After pressing, due to the collapsing of the roughness of the hole and the shaft, the probability of interference with a gap increases (51.7%). In addition, upon operating under the action of a load, the possibility arises that joints with an actual interference less than the smallest functional one (8.1 µm) can turn. It has been proven that, when shaft tolerance class js6 is assigned, interference with a gap will prevail in the joint, which will lead to rotation of the circulation-loaded bearing ring in more than 80% of the joints, significantly reducing the reliability of the demultiplier bearing assembly and the gearbox of the Yaroslavl Engine Plant engine as a whole.

Interference Assembly Stress of Wheel-Axle in B-type Subway

This paper aims to improve the reliability of train operation as well as to guarantee the safety of wheelset interference assembly. A finite element model of the wheel-axle interference fit is established with a metro B-type car as the research object. The finite element calculation software is used to simulate the static strength of the wheel-axle model under different working conditions, contact spots, and maximum/minimum interference. The effect of different interference and different working conditions on contact stress is studied. The study shows that the wheel meets the static strength requirements under all working conditions. The maximum equivalent stresses are located at the wheel hub bore under the maximum or minimum interference assembly. The full curved condition with maximum interference is the most dangerous condition among the working conditions.

ARTIFICIAL INTELLIGENCE TECHNIQUES FOR IMPROVING CYLINDRICAL SHRINK-FIT SHAFT-HUB COUPLINGS

AbstractDue to the continuous progress in information technology, complex problems of machine elements can be investigated using numerical methods. The focus of these investigations and optimizations often aims to reduce the stresses that occur or to increase the forces and torques that can be transmitted. Interference fit connections are an essential machine element for drive technology applications and are characterized by their economical fabrication. The transmission of external loads over a large contact surface between the shaft and hub makes it less vulnerable to impact loads. These advantages contrast with disadvantages such as the limited transmittable power, the risk of friction fatigue, and stress peaks at the hub edges, which can lead to undesirable and sudden failure, especially in the case of brittle hub materials. Analytical approaches already exist for optimizing these connections, which are expensive, time-consuming, and complex, so a high degree of expert knowledge is required to apply these methods in practice successfully. This paper presents a novel method using the example of optimizing the pressure distribution in the interface of a shrink-fit connection.