Shrink Fit Research Articles

Optimal the Process Variables of Internal Grinding for Shrink Fit Tool Holder

The goal of this study was to investigate the optimal variables settings in internal grinding for shrink fit tool holder. The effects of the main grinding variables on finishing responses were comprehensively investigated based on Taguchi method. The main process variables such as abrasive grain size (AGS), grinding wheel speed (GWS), feed rate for rough (FRR), depth for rough (DR), feed rate for finishing (FRF), depth for finishing (DF), dressing speed (DS), and workpiece rotational speed (WRS) were chosen to determine their effects on grinding performances related to roundness and surface roughness in the internal grinding of the shrink fit tool holder. The experimental response values were transferred to signal-to-noise (S/N) ratios, and then the significant process variables associated with the grinding performance were examined by analysis of variance (ANOVA). In addition, the optimal combination levels of the grinding variables were also obtained from the response graphs of S/N ratios to improve the surface quality of internal grinding. The experimental results show that the significant grinding variable affecting the roundness was FRF. In addition, the significant variables with regard to surface roughness were AGS, GWS, FRR, DR, DF, and DS. The optimal grinding variable settings were achieved. Consequently, the finishing characteristics of internal grinding could be enhanced to meet the requirements of modern manufacturing applications.

Mechanical design of rotors for permanent magnet high‐speed electric motors for turbocharger applications

Realisation of electrically boosted turbochargers requires electric motors capable of operating at very high speeds. These motors often use a permanent magnet rotor with the magnets retained within an interference fit external sleeve. Whilst it is possible to model such systems numerically, these models are an inefficient tool for design optimisation. Current analytical models of rotors typically consider the stresses induced by the shrink fit of the sleeve separately from the stresses generated by centripetal forces due to rotation. However, such an approach ignores the frictional interaction between the components in the axial direction. This paper presents an analytical model that simultaneously accounts for interaction between the magnet and outer sleeve in both the radial and axial directions at designed interference and with the assembly subjected to centripetal and thermal loads. Numerical models presented show that with only moderate coefficients of friction and rotor lengths; axial load transfer between magnet and sleeve takes place over a short distance at the ends of the assembly. This paper then demonstrates how the analytical model aids definition of a feasible set of rotor designs and selection of an optimum design.

Measurement of Partial Slip at the Interface of a Shrink Fit Assembly under Axial Load

The slip at the interface of a shrink fit between a shaft and hub under axial load has been measured by a technique where a small cross hole is drilled through the assembly and a Talysurf profilometer is used to measure the profile of the hole. The measurements suggest that the technique is capable of measuring slip of the order of 1 to 2 μm. A finite element study has been carried out to predict the magnitude of slip with adequate agreement with the experimental results. The finite element study also shows that the extraction load for shrink fit assembly does not increase linearly with the coefficient of friction or the axial length of engagement of the shrink fit, as would be expected from a straightforward analysis.

Correlation Between Rotor Vibration and Mechanical Stress in Ultra-High-Speed Permanent Magnet Synchronous Motors

This paper investigates the correlation between rotor vibration and mechanical stress in ultra-high-speed permanent magnet synchronous motors (PMSMs); the mechanical stress generated in the PM and the rotational vibration when the PMSM rotates at high speeds were evaluated. Two PM rotors that have the same performance characteristics but different shrink fits were studied, and the vibration of these two PM rotors was analyzed. Furthermore, to evaluate the correlation between mechanical stress and vibration, the rotor design parameters, such as sleeve thickness and shrink fit, were varied. Based on the analysis results, a real-world model was developed and an experiment was conducted to test the vibration of these two rotors; the validity of our results was verified by performing experiments.

Optimization of Shrink Fitting Process of Rotor Shaft for Motor Applying High Frequency Induction Heating

This research is collaborative investigation with the general-purpose motor manufacturer. In order to review construction method in production process, we applied the parameter design method of quality engineering and tried to approach the optimization of construction method. Conventionally, press fitting method has been adopted in process of fitting rotor core and shaft which is main component of motor, but quality defects such as core shaft deflection occurred at the time of press fitting. In this research, as a result of optimization design of shrink fitting method by high frequency induction heating devised as a new construction method, its construction method was feasible, and it was possible to extract the optimum processing condition.

Expanding the applicable duration for shrink fitting of the ultrathin-walled reactor coolant pump rotor-can

The rotor-can of reactor coolant pump (RCP) is generally assembled on the rotor using shrink fitting technique. The rotor-can is characterized by large height and ultrathin-walled cylinder, thus, its rigidity is weak and heat capacity is quite limited. The shrink fitting process has to be completed within a short limited-time, which makes it difficult for rotor to insert in the rotor-can completely. In order to solve this problem, a new method was proposed to extend the limited time by using a heat capacity added layer (HCAL) during the shrink fitting process. A thermal-mechanical coupled finite element (FE) model was developed to simulate the whole process. The transient heat exchange with a narrow gap between rotor and rotor-can during the shrink fitting process was taken into consideration. The limited time was predicted by calculating and analyzing the evolutions of temperature field and radial displacement field of the rotor-can. The simulation results indicate that the limited time of the shrink fitting process can be significantly extended with the increase of HCAL in thickness. Then, shrink fitting experiments were performed to confirm the extending effect of the HCAL. The experimental results of limited time show good agreement with the predicted values. The current results will certainly help the designer to improve the shrink fitting technique.

Elastic–plastic design of a rotating shrink fit with functionally graded hub

For given geometry of a shrink fit, a further essential design parameter is the interface pressure between inclusion and hub to reliably transfer a moment under all operating conditions in the specific application. Hence, in general a large interface pressure shall be achieved, and this may be facilitated by an elastic–plastic design. Furthermore, minimizing the weight of the device becomes increasingly important in engineering, too. To achieve both objectives, in the present semi-analytical study of a shrink fit with solid inclusion a combined elastic–plastic design and use of a functionally graded hub is proposed. As is shown, by appropriate grading not only the weight of the hub can be reduced noticeably as compared to a homogeneous one but also a much better behavior at rotation can be achieved, and admitting partial plasticization can further improve the performance; as an example, a shrink fit with steel/aluminum FGM-hub is discussed comprehensively.

Testing signals formation for identification of heat power objects and control systems comparison

The purpose of this study is to validate the schedule of testing impacts to compensate for uncontrolled disturbances in furnaces conditions for heating of metals before rolling. Two problems have been solved in this paper: the formation of the input testing signal effects to determine the dynamic characteristics of an object by its transient response; prompt obtaining of valid information about the effectiveness of different methods or control algorithms application. To compensate for the low-frequency and random perturbations the method of forming the signal identifying impacts on the basis of the Walsh orthogonal functions system has been proposed in this research. Uncontrolled process disturbances acting on the actual thermal energy objects distort the information on their dynamic parameters, which leads to deterioration of control quality. And it is possible to note that the characteristics of the object have considerable inertia and the frequency of perturbations is low; the characteristics have a vertical and horizontal drift. The influence of these disturbances can be reduced considerably due to the proper formation of input testing signal impacts. The influence of the signal impacts in the identification of the inertial object with delay has been tested by the authors on the developed laboratory—scale plant and has shown high efficiency. The second task is the prompt definition of the relative cost-effectiveness of two methods for the process control of metal heating before rolling. Conducted by the authors, the production experiment in which the switching of the compared systems has also been produced according to a specially formed schedule based on the system of Walsh orthogonal functions has been considered in this paper. The results obtained in the experiment give grounds to assert that the proposed formation of the switching schedule allows virtually eliminating the effect of the main disturbing random factors (production volume, the proportion of hot shrink fit metal) on a comparative indicator of the effectiveness of two methods of metal heating control.

Dynamic Response of TI2ALC Under Radial Confinement at High Temperature

Experiments were performed to evaluate the dynamic mechanical response of MAX phase material Ti2AlC at high temperature (HT) and under radial confinement. A Split Hopkinson Pressure Bar (SHPB) apparatus was employed to conduct experiments at a strain rate of 500 s−1. High speed photography was used to capture the dynamic response of unconfined specimens. An induction coil was used to heat the specimens from 25 to 1000 °C. Nickel–cobalt–ferrous alloy (Kovar) shrink fit sleeves were utilized to produce a mechanical radial pressure of 30–195 MPa. Unconfined room temperature (RT) and HT experiments revealed that Ti2AlC fails in a gradual, brittle manner (also referred to as graceful failure) with a low dependency on temperature up to 800 °C. All experiments conducted with radial confinement produced a fully plastic response without failure. The addition of hydrostatic confinement increased the maximum compressive stress for all temperatures and allowed specimens to reach strains in excess of 8% without failing. Optical and Scanning Election Microscopy (SEM) images were taken of the cross-section of recovered confined specimens. Imaging revealed conical damage patterns on each end of the specimen which facilitate the plastic response.

Performance of an ultrasonic-assisted drilling module

The ultrasonic-assisted drilling (UAD) process is a technology which applies high frequency vibrations (>20 kHz) at amplitudes of 2–20 μm in the feed direction to the drill tip in order to improve machining conditions and productivity. Past work in this field is reviewed, noting the valuable foundation provided by laboratory-based research systems. This work is aimed at the development of a robust UAD module, fully compatible with computer numerical control (CNC) systems, and able to function in a production environment, describing results of drilling tests on 4340 steel. The UAD module, designed using FEA methods, with a 16-mm carbide drill, attached by shrink fit, is used to study the effects of ultrasonics on thrust force, torque, surface quality, hole size, and the microstructure of drilled 4340 steel. In order to provide a better understanding of the performance of this module, two different test scenarios were designed and the results for each were compared with the results obtained from baseline settings for conventional drilling. The results show that ultrasonic vibrations not only can reduce the average values of thrust force and torque but also can improve the surface quality of the hole. It is also found that a major increase in productivity could be achieved by using ultrasonic vibrations. Finally, the effects of ultrasonic vibrations on hardness and microstructure of the drilled hole is assessed and the results show that high frequency vibrations do not have significant effect on dimensional accuracy or on the microstructure of the drilled holes.

Coming out prevention by stopper for the shrink fitted sandwiched shaft from the ceramic sleeve

Ceramic roller can be used in the heating furnace conveniently because of its high temperature resistance. The roller consists of sleeve and steel shaft connected only under a small shrink fitting ratio because of the brittleness. However, the coming out of the shaft may often happen from the ceramic sleeve under repeated bending load. Therefore, how to prevent the coming out failure becomes an important issue. Based on the previous study, a two-dimensional shrink fitted structure is considered by replacing the shaft with the inner plate and by replacing the sleeve with the outer plate. Then, this research focuses on preventing the inner plate coming out from the outer plate by introducing a newly designed stopper on the outer plate. The simulation results shows that the coming out phenomenon can be prevented effectively due to the contact between the inter plate and the stopper installed on the outer plate. In order to evaluate the contact force between the inner plate and the stopper, the coming out mechanism is clarified. To prevent the coming out by stopper safely, the effects of the magnitude of repeated load and the friction coefficient upon the contact compressive force are investigated under large number of loading cycles by using 2D simulation.

Experimental verification of the coming out of the shaft for the ceramic rolls/rollers with shrink fitting system

Ceramic rolls/rollers have an advantage in steel strip production because of its high wear resistance and corrosion resistance. The new rolls/rollers consist of a ceramic sleeve and two alloyed steel shafts connected to the sleeve ends only under a small shrink fitting ratio because of the brittleness. However, the alloyed steel shafts may be loosening out from the ceramic sleeve under such low shrink fitting ratio. In the some previous studies have considered the coming out mechanism was considered by the numerical simulation focusing on the displacement and the shear stress at the joint end. This phenomenon should be confirmed without experiment. In this study, therefore, in order to clarify the coming out behavior, rotating bending experiment is conducted for a small roller specimen consisting of a steel sleeve and steel shafts connected by low shrink fitting ratio. Then, it is found that the coming out can be realized in the small specimen.

Stress and deformation of ceramic rolls to produce high quality zinc coated steel sheet

Several ceramic rolls can be used efficiently to produce high quality zinc coated steel sheet used for automobiles. Those ceramics rolls may provide a longer life and reduce the cost for the maintenance because of its large heat resistance and large wear resistance. One example may be seen in sink rolls used in molten zinc bath to manufacture zinc coated steel sheet. Since the rolls are subjected to large thermal stress and mechanical loading, care should be taken for the risk of fracture due to the ceramic brittleness. Moreover, since the sleeve and shafts can be connected only by using small shrink fitting ratio, another failure risk should be considered for the separation of those components [25, 26]. In this paper, therefore, the mechanical and thermal stress and separation condition will be investigated considering the separation of the connected portion. Here, by using the finite volume method the heat transfer coefficient is discussed and by using the finite element method the thermal stress is considered.

Evaluation of Interface Defects in Inaccessible Reactor Shrink Fit Nozzle Welds Using Ultrasonic Waves

This study proposes an effective method to inspect inaccessible nuclear power reactor head nozzles using interface waves that propagate along the shrink fit boundary of a reactor head. The reactor head is relatively thick, which makes it difficult to inspect from the outside by conventional ultrasonic testing. However, interface waves can propagate a long distance from a fixed transducer position. The inside of the nuclear reactor has limited access due to the high radiation, so the transducers are located outside the nuclear reactor head, and interface waves propagate into the nuclear reactor to detect defects. A numerical simulation and experiments were carried out to validate the method. Various defect cases that simulate field failures are also presented, and the proposed technique shows satisfactory defect classification.

Design of Shrink Fit for Low Temperature Rotating Turbine Components

Design of Shrink Fit for Low Temperature Rotating Turbine Components

Impact of Mechanical Stress on Characteristics of Interior Permanent Magnet Synchronous Motors

In this paper, we investigate the impact of mechanical stress on characteristics of interior permanent magnet synchronous motors from both results of measurement and calculation. First, the basic experiments by using stator cores with/without shrink fitting of housings are carried out. The measured iron loss is compared with the calculated results obtained by combined stress and electromagnetic field finite-element analysis. Next, the measured torque and iron loss of the motor under load conditions are compared with the analysis that considers the mechanical stress caused by both the stator shrink fitting and the rotor centrifugal force. The measured and calculated results are found to be in good agreement. From these results, it is clarified that the mechanical stress causes not only an increase in the stator iron loss, but also an increase in the rotor-iron loss, and a decrease in the reluctance torque of interior permanent magnet synchronous motors.

Laser cladding of phosphor bronze

Phosphor bronze is a suitable bearing material because of its good fatigue strength and excellent wear properties under corrosive conditions, high temperatures and high loads. Bronze is usually continuously cast as bar or tube and machined into bushes, cam followers, washers or other bearing components. It is common to mount bronze bushes around shafts by means of warm shrink fitting. Laser Cladding is a manufacturing process to generate a dense a metallurgical bonded coating over a substrate and it can be employed to deposit a phosphor bronze coating directly over a shaft improving its wear properties. In this paper, the feasibility of the Laser Cladding to produce phosphor bronze coatings on alloy steel is demonstrated. Suitable processing parameters to generate phosphor bronze coatings are presented. The hardness of the bronze coating obtained is 172±12HV, 56% higher than the one reported for cast bronze. Finally, Laser Cladding is proposed as a method to create a bronze surface in an area of a shaft as a substitute of warm shrink fitting of machined bronze bushes.

打抜き歪を考慮した高精度モータ鉄損解析手法の基礎的検討

Mass productions of the motor core such as the blanking of the electromagnetic steel sheet and the shrink fit cause the residual strain in the material, processing strain, which prevents the movement of magnetic walls and increases the magnetic loss in the motor. Conventionally, the increase of the magnetic loss by the processing stress was evaluated with trial products, because it couldn't be done in the design phase. So, it was difficult to optimize the motor design considering the processing stress. Therefore, this paper studies the computing method of the magnetic loss considering the blanking press strain which is particularly estimated to be large influence on the magnetic loss as follows:

Determination of Optimal Shrink Fitting Ratio for 2-layer Compound Forging Die by Improving Fatigue Life in Backward Extrusion

Abstract Shrink fitting ratio is an important design parameter in assembling compound forging dies. However, the determination for the optimal parameter to prolong die life is often neglected in the industry. Thus, the authors propose a method to identify optimal shrink fitting ratio by the use of master fatigue diagram to achieve maximum fatigue life where the working conditions under multi-stress tension-compression mode and various oscillation amplitudes are considered. In this paper, a master fatigue diagram was made from experimental results obtained for the die insert materials SKD11 and it is then applied to determine optimal shrink fitting ratio for the 2-layer compound forging die in backward extrusion. The method shows the capability of improving fatigue life from 10 4 to 10 5 cycles or even up to higher number of cycles if optimal shrink fitting ratio can be determined.

レーザ加熱を利用したかん合に関する研究

Laser shrink fitting for shaft coupling was developed as application of laser forming. The coupling of the pipe of stainless steel and bar of carbon steel is made by laser shrink fitting. A bar is inserted into a pipe, and the pipe surface of the bar-inserted-part is irradiated and heated by 1kw class laser. Metallographic structure of the laser irradiated part of the pipe and bar is not changed. The fitted part of the pipe is shrunk in both circumferential and axial direction. The residual stress on the surface of the fitted pipe is a compressive one in the circumferential and axial direction. The tensile strength of the fitted part is nearly equal to the tensile strength of base metal of stainless steel pipe.