Shrink Fitted Joints Research Articles

Temperature response of LOCTITE 648 anaerobic adhesive and hoop channels to enhance its effectiveness under high interference

ABSTRACT The strength of a shaft-hub hybrid joint is affected by several factors, such as working temperature, interference level and coupling procedure. The first part of this study deals with temperature effect on the static response of shaft-hub hybrid joints. LOCTITE 648 anaerobic adhesive was applied for coupling 42CrMo4 tempered steel shafts to 16CrNi4Pb hardening steel hubs. The performance up to 100°C was experimentally investigated, involving press-fitted as well as shrink-fitted joints with interference up to 0.2%. Adhesive stripping upon coupling, adhesive degradation at high temperature and also frictional contribution decrease were highlighted. Afterwards, in the second part, the question of the adhesive being teared off under high interference was tackled. A hoop-channeled geometry was proposed, to increase the amount of adhesive remaining trapped at the joint interface. Hoop channels in the shafts proved to act as adhesive reservoir, thus facilitating adhesive dragging over the entire engagement length. Their effects on the joint strength were experimentally determined for both press-fitting and shrink-fitting coupling methods. The results, processed by the statistical tools of Analysis of Variance, orthogonality and pairwise tests, indicate the modified geometry is significantly beneficial for high interference press-fitted joints. Conversely, it may even be detrimental for shrink-fitted ones.

Creep Analysis of Plastically Deformed Shrink-Fitted Joints

Creep Analysis of Plastically Deformed Shrink-Fitted Joints

Residual stress and deformation analysis on thermal shrink-fitted joint in the semi built-up marine crankshaft

Interference and deformation of the shrink fitting connection have a significant influence on the local stress state at the contact area. To improve its assembly quality, an optimized induction heating method with an arc-shaped frame coil and a cylinder type coil was developed. The effects of shrink fitting parameters such as residual contact stress and dimensional deformation were researched using finite element analysis (FEA). A thermal-structure coupling model of crankshaft shrink fitting was built, and contact stress evaluations of the measurement points in the shrinkage were obtained by numerical simulation. In addition, contact stress and deformation analysis under different interferences were also carried out to determine the range of values. The simulation and comparative analysis results show that the optimized multiple induction heating method with an arc-shaped frame coil and a cylinder type coil would be helpful to improve the uniformity and sustainability of contact.

Influence of the interference level and of the assembly process on the shear strength of loctite 648 anaerobic adhesive

ABSTRACTThe aim of this research is to study the effect of the interference level and of the coupling procedure on the shear strength of Loctite 648 anaerobic adhesive. The tests involved shaft-hub joints with a quite large interference range and joined by a broad range of coupling strategies, which is one of the main issues of novelty of this research. 42CrMo4 tempered steel shaft specimens and 16CrNi4Pb hardening steel hub samples were used. Two factors were considered: the interference level and the assembly strategy. Four different levels of specific interference were analyzed up to a maximum value of 0.22%, performing five replications per level. Experimental trials were carried out with different coupling procedures: using press-fitted and shrink-fitted joints. Using the first procedure, a high level of interference induces scratches on the sample surfaces. These are conversely not produced by shrink-fitting. Some tests were devoted to friction coefficient estimation, thus also assessing the lubricating properties of the adhesive. Particularly, dry couplings and couplings and de-couplings with not yet cured adhesive were run to address this point. The results were processed by statistical methods, to assess the influence of the studied factors on the adhesive strength.

Shrink-fitted joint behavior using three-dimensional solid finite elements in rotor dynamics with inclusion of stress-stiffening effect

In this article, the contact behavior of a shrink-fitted joint in a rotor assembly at different spin speeds is studied, using the three-dimensional solid finite element approach. A custom frictionless contact model is proposed and extensively tested by means of simulation. The theory for solving pre-stressed damped eigenvalue problem is presented and implemented, and the results are presented in Campbell diagram form. Two sample rotor assemblies are studied. In addition, experimental modal analysis results of a shrink-fitted joint with various interferences are presented and numerically studied. The reduction of the interference of the shrink-fitted joint due to centrifugal forces at high-speed operation as well as the contact status are updated at each rotational speed step. The inclusion of stress-stiffening effect is studied in detail. The comparison of the Campbell diagram results with the results obtained using a commercial finite element software (Ansys) shows a good agreement.

Influence of the Thermal Assembly Process on the Stress Distributions in Shrink Fit Joints

One of the most widespread procedures used for building a shrink fit consists in a thermal process in which the hub is heated and lately cooled while the shaft is placed at the assembly final position, so the joint is radialy set. In this paper the contact pressure in a shrink fit is analyzed by means of the numerical simulations using FEA method. We compare the results with those obtained by the alternative building fit process, i.e., the axial press insertion, and, with the ones given by the pressure cylinders theory. Relevant information revealed from numerical simulations, as the stress and strain state after the assembly process, could be useful in the design of shrink fitted joints improving their performance during their life in service.

Parametric excitation of a thin ring under time-varying initial stress; theoretical and numerical analysis

Initial stress in rings is one of the destructive effects which is almost inevitable due to various reasons such as being subsystems of a shrink-fitted joint, imperfections in the manufacturing, assembly or misalignment of the supporting mounts, and unbalancing in rotating condition. So, in this paper we focus on the effect of the initial stress and its variation with time on the dynamics of the pre-stressed ring. For this purpose, the equation of motion for in-plane bending vibration of a thin ring is derived using Hamilton’s principle. It is assumed that the initial stress is due to the distributed radially time-varying pressure. By representing the dynamic initial stress in the coefficients of the equation of motion; the equation is converted to Mathieu’s equation. The strained parameters method has been used to obtain the stability regions of motion and transition curves. Furthermore, to validate the obtained stability regions, numerical solutions of the equation of motion and Floquet theorem are used in some selected values of the parameters of the initial stress (magnitude of static and dynamic components of the initial stress). The fourth-order Runge-Kutta algorithm is used for numerical analysis of the equation of motion. The results show that the parameters of initial stress have direct impact on the stability of dynamic response. The obtained results from theoretical and numerical methods which are notably consistent with each other demonstrate that the initial stress, which has been almost always neglected in dynamic models of the systems, has a significant effect on the dynamics of the system, and it may even lead to an unstable dynamic response, while the excitation frequency is far enough from resonance region. So this paper can present the other application of modal analysis to non-destructive measure of initial stress.

Parametric vibration of two shrink-fitted thin rings with time-varying interface pressure; nonlinear analysis and experimental study

In a shrink-fitted joint, the interface pressure plays an important role as it is the main source of the joint and it keeps the joining components together. However, time-variation of the interface pressure causes parametric instability in the system. In this paper, the effect of time-variant interface pressure on the dynamics of two shrink-fitted rings has been studied. Deriving a dynamic equation of motion of the joint of two shrink-fitted rings and substituting time-variant interface pressure in the equation, the problem extends to nonlinear vibration. The obtained equation of motion, which contains parametrically excited terms, is a general form of Mathieu’s equation. A perturbation method, to determine the instability regions of motion, is applied to obtain the transition curves. To validate the obtained stability regions, an experiment has been performed. Both the analytical and experimental results demonstrate that by increasing the value of the interface pressure, the natural frequencies of the joint increase.

Growth of fretting fatigue cracks in a shrink-fitted joint subjected to rotating bending

Crack growth in a shrink-fit assembly subjected to rotating bending was studied. Two finite element (FE) models and a numerical routine were implemented to evaluate the contribution of the fretting load and to compute the crack growth. Numerical results for the crack propagation were compared to each other and to experimental data from the literature. Good agreements were found for the stress intensity factor (SIF) computations and for the crack propagation life. A significant reduction in the fatigue crack propagation life, up to 50%, was found as compared to an equivalent pure bending case.

ICS-09: Axisymmetric Stress Analysis and Strength of Bonded Shrink-fitted Joints of Solid Shafts subjected to Torsional Loads(ICS-II: INTERFACES AND CONTACT SURFACE MECHANICS)

ICS-09: Axisymmetric Stress Analysis and Strength of Bonded Shrink-fitted Joints of Solid Shafts subjected to Torsional Loads(ICS-II: INTERFACES AND CONTACT SURFACE MECHANICS)

Stress analysis of shrink-fitted joints for various fit forms via finite element method

Abstract The stresses and deformations in the shrink-fitted hub–shaft joint for various fit forms have been analysed using finite element method. First, the results of finite element method (FEM) were compared with the results of Lame’s equations along central radial line of one shrink fit type for accuracy of model and it was proved by these results. Then, the most appropriate fit type was investigated. It was observed that the most effective parameter to determine appropriate fit type is to be stepped or not for shaft and the geometries of hub of which edges were wasted have been found as more appropriate to reduce the stresses and deformations. Finally, it was also observed that the each point of the shaft or the hub at the moment of the first meeting to its partner during fit can enter the plastic region, and this situation must be taken into consideration as design parameter.

A shrink-fitted peg subjected to cyclic loading

The plane problem of a peg, shrink fitted into a cavity and subjected to an oscillating/fluctuating axial load, is studied. Firstly, the conditions ensuing complete adhesion, analogous to the elastic limit in plasticity, are found. For conditions where adhesion is not achieved everywhere in the first cycle, the stick-slip regime is tracked and the conditions under which frictional shakedown will occur are deduced. A frictional equivalent to the Melan principle is then applied to give identical results. The results summarized are of practical relevance to the design of shrink-fitted joints, and demonstrate the extension of plastic shakedown to frictional problems.

Axisymmetric Stress Analysis and Strength of Bonded Shrink-Fitted Joints of Solid Shaft Subjected to Torsional Loads.

Recently, joints that combine a shrink fit with anaerobic adhesives have been used in order to increase joint strength. In this study we deal with the stress analysis and strength evaluation of bonded shrink fitted joints subjected to torsional loads. The stress distributions in the adhesive layer of bonded shrink fitted joints are analyzed by using the axisymmetric theory of elasticity when an external torsion is applied to the upper end of the shaft. The effects of the outer diameter and the stiffness of rings on the interface stress distributions are analyzed by the numerical calculations. Using the interface stress distributions, the joint strength was predicted. In addition, the value of the joint strength was obtained experimentally. It is seen that a rupture in the adhesive is initiated from the upper edge of the interfaces when a torsion is applied to the upper end of the shaft. The numerical results show more conservative values than the experimental results. It is found that the joint strength of bonded shrink-fitted joints is greater than that of shrink-fitted joints.

Axisymmetric Stress Analysis and Strength of Bonded Shrink-Fitted Joints Subjected to Push-Off Forces.

Shrink fit has been used commonly for joining the cylindrical components such as shaft and gears. It is noted recently the shrink fitted joint with anaerobic adhesives is adopted in order to improve it's joint strength. In a reliable design of bonded shrink fitted joints, it is necessary to know the contact stress distributions at the interfaces. In this paper, the interface stress distribution of bonded shrink fitted joint under push-off force is analyzed by using axisymmetric theory of elasticity as four-body contact problem. Analogical test is conducted to determine the relationship between the normal stress and the shear stress. Using the interface stress distribution and analogical test results, a method for estimating the joint strength is proposed. In the numerical calculations, the effect of the outer diameter and Young's modulus of the rings and the engagement length on the contact stress distributions at the interfaces are clarified. Push-off force measurement was carried out for bonded shrink fitted joints. In the experiments, the effect of shrink fit interference and the outer diameter of ring on the joint strength are examined. The numerical results are in a fairly good agreement with the experimental results. It is found that the strength of the bonded shrink fitted joint is greater than that of shrink fitted joint.

Axisymmetric Stress Analysis and strength of Bonded Shrink-Fitted Joints of Solid Shafts Subjected to Push-Off Forces.

This paper deals with analysis of stress in the adhesive layer of bonded shrink-fitted joints subjected to push off forces. The stress distributions in the adhesive layer of bonded shrink-fitted joints and those when the joints are subjected to push-off forces are analyzed as a four-body contact problem using the axisymmetrical theory of elasticity. The effects of the outer diameter and the stiffness of rings on the stress distributions in the adhesive layer are clarified by numerical calculation. Using the stress distributions in the adhesive layer, a method for predicting joint strength is proposed. It is seen that a rupture initiates from the lower edge of the outside surface in an adhesive layer. Experiments on joint strength were performed. The numerical results are in fairly good agreement with the experimental results. It is found that the joint strength increases as the outer diameler and Young's modulus of rings increase. In addition, it is found that the joint strength of bonded shrink-fitted joints is greater than that of unbonded shrink fitted joints.

Axisymmetric Stress Analysis and Strength of Bonded Shrink-fitted Joints of Solid Shafts Subjected to Torsional Loads.

Axisymmetric Stress Analysis and Strength of Bonded Shrink-fitted Joints of Solid Shafts Subjected to Torsional Loads.

The static and dynamic stiffness of interference shrink-fitted joints

The main objective of this work is to investigate the effect of size, surface roughness and the interference value on the static and dynamic stiffness of shrink-fitted joints. Most of the previous research has been concerned with the joint holding load under static conditions without consideration of many of the applications in which the joints are exposed to dynamic loading. The dynamic performance of a machine tool is greatly affected by the collected response of its joints. In many applications in which shrink-fitted joints are used, such as engines and machine tools, their dynamic characteristics can be an important factor in deciding the overall performance of the machine. Hence, studying the joints' stiffness characteristics under static and dynamic conditions is of importance.

The development of prow and wedge type junctions in shrink-fitted torsion joints

During an investigation into the torsional strengths of shrink-fitted joints some interesting features related to the interface friction of the joints were observed. These had a scuff-like appearance and junction growth with sliding was evident. Numerous scores which had not developed into scuffs may indicate that there are optimum load/contact area conditions for the initiation of scuffs. Scuffs and scores appear to be randomly distributed over the surfaces and not related to the stress distribution. A surface scratch on one surface can initiate scuffs on both mating surfaces. Owing to the strictly limited degree of freedom perpendicular to the surfaces, sliding conditions in a shrink fit are severe compared with those of a normal sliding pair. However, junction deformation appears to be similar to that found by Cocks & Antler in their investigations of junction shearing and development. But the junction growth is different and seems to be due to progressive shearing along spherical boundaries. There was no detectable evidence of junction welding between the shrink-fit components.