Evaluation of the Influence of a Planned Interference Fit on the Expected Fatigue Life of a Conjugate Cam Mechanism- A Case Study

2013 ◽  
Vol 135 (8) ◽  
Author(s):  
Pau Català ◽  
Maria Antònia De los Santos ◽  
Joaquim M. Veciana ◽  
Salvador Cardona
Keyword(s):  
Fatigue Life ◽  
Dynamic Model ◽  
Contact Forces ◽  
Surface Finishing ◽  
Automatic Process ◽  
Interference Fit ◽  
Cam Mechanism ◽  
Experimental Apparatus ◽  
Manufacturing Errors ◽  
Lubrication Conditions

Due to dynamic effects, clearances, manufacturing and assembly errors in form-closed cam mechanisms, the follower jump can also occur. For conjugate cam mechanisms a technique to avoid the follower jump without the use of a spring involves making the conjugate cam profiles bigger than the kinematical ones by adding an external offset. This strategy produces an interference fit between the conjugate cam profiles and the follower train. This paper presents an ordered procedure to study the influence that the planned interference fit has on the evaluation of the contact forces, the expected fatigue life of the rollers, contact pressures and the lubrication conditions. The study is based on a conjugate cam mechanism with translational roller followers used in a real automatic process for manufacturing muselets. A three-degree-of-freedom dynamic model is proposed and the Hertzian theory for general profiles is used to model the nonlinear contact stiffness between the cams and the crowned rollers. The dynamic model predicts that it is difficult to obtain conjugate cam mechanisms with an infinite expected fatigue life of the rollers just by considering typical achievable manufacturing errors or clearances, and as happens in reality, a set-up process is highly recommended. The procedure is also tested with measured manufacturing errors on a coordinate measure machine—CMM—and with measured radial internal clearances for the rollers measured by an experimental apparatus. Also, to evaluate lubrication conditions, surface finishing measurements have been taken of the cams and the rollers with a surface profiler.

Avoiding Early Failures in Conjugate Cam Mechanism by Means of Different Design Strategies

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Pau Català ◽  
Maria Antònia De los Santos ◽  
Joaquim M. Veciana ◽  
Salvador Cardona
Keyword(s):  
Fatigue Life ◽  
Dynamic Models ◽  
Design Strategies ◽  
Premature Failure ◽  
Interference Fit ◽  
Cam Mechanism ◽  
Surface Fatigue ◽  
Lumped Parameter ◽  
Lumped Parameter Models ◽  
Early Failures

To solve the indetermination of forces existing in a form-closed cam mechanism formed by conjugate cams, where the contact between the cams and the follower rollers is constantly ensured by only the geometry of the elements, dynamic models that consider the elasticity of the elements must be proposed. Because the stiffness of the main elements is associated with the elasticity of the solids, tight variations in manufacturing and assembly errors modify the effective interference fit, which significantly affects the expected fatigue life of the mechanism, leading to a premature failure of the elements due to surface fatigue. Based on a real industrial application of a conjugate cam mechanism and using lumped-parameter models, the objectives of this paper are: first, to show that it is difficult to achieve a pure form-closed conjugate cam mechanism, with the expected fatigue life of the mechanism, by using only standard tolerance specifications; second, to compare the expected fatigue life and motor torque with other cam mechanism design strategies such as force-closed and the combination of force-closed and form-closed strategies, known as force-closed conjugate cam strategy. This paper based on simulation results demonstrates that this latest strategy can, thanks to a better control of the preload, easily achieve results very similar to the theoretical ones of a form-closed conjugate cam mechanism. A prototype of the mechanism of the force-closed conjugate cam strategy is also built.

Random impact FEM simulation of irregularly-shaped media for parametric study of vibratory surface enhancement

2021 ◽  
pp. 095440542199012
Author(s):  
Jing Zhang ◽  
Joselito Yam Alcaraz ◽  
Swee-Hock Yeo ◽  
Arun Prasanth Nagalingam ◽  
Abhay Gopinath
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Parametric Study ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Fem Simulation ◽  
Surface Finishing ◽  
Aerospace Materials ◽  
Surface Enhancement ◽  
Steel Balls

Aerospace materials experience high levels of mechanical and thermal loading, high/low cycle fatigue, and damage from foreign objects during service, which can lead to premature retirement. Mechanical surface treatments of metallic components, for example, fan blades and blisks, are proven to improve fatigue life, improve wear resistance and avoid stress corrosion by introducing work hardening, compressive residual stresses of sub-surface, and surface finishing. Vibropeening can enhance aerospace materials’ fatigue life involving the kinetic agitation of hardened steel media in a vibratory finishing machine that induces compressive stresses into the component sub-layers while keeping a finished surface. Spherical steel balls are the most widely used shape among steel-based media and have been explored for decades. However, they are not always versatile, which cannot access deep grooves, sharp corners, and intricate profiles. Steel ballcones or satellites, when mixed with round steel balls and other steel media (diagonals, pins, eclipses, cones), works very well in such areas that ball-shaped media are unable to reach. However, a methodology of study the effect of irregularly-shaped media in surface enhancement processes has not been established. This paper proposes a finite element-based model to present a methodology for the parametric study of vibratory surface enhancement with irregularly-shaped media and investigates residual stress profiles within a treated area of an Inconel component. The methodology is discussed in detail, which involves a stochastic simulation of orientation, impact force, and impact location. The contrasting effects of a high aspect ratio, or an edge contact, as opposed to rounded and oblique contacts are demonstrated, with further analysis on the superposition of these effects. Finally, the simulation results are compared with actual residual stress measurements and was found to have a max percent difference of 34% up to 20 [Formula: see text]m below the media surface.

Multibody Dynamic Model of Web Guiding System With Moving Web

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Lei Yu ◽  
Zhihua Zhao ◽  
Gexue Ren
Keyword(s):  
Dynamic Model ◽  
Lateral Displacement ◽  
Dynamical Behavior ◽  
Contact Forces ◽  
Lagrangian Formulation ◽  
Pi Control ◽  
Control Law ◽  
Reference Surface ◽  
Multibody Dynamic ◽  
Guiding System

In this paper, a multibody dynamic model is established to simulate the dynamics and control of moving web with its guiding system, where the term moving web is used to describe thin materials, which are manufactured and processed in a continuous, flexible strip form. In contrast with available researches based on Eulerian description and beam assumption, webs are described by Lagrangian formulation with the absolute nodal coordinate formulation (ANCF) plate element, which is based on Kirchhoff’s assumptions that material normals to the original reference surface remain straight and normal to the deformed reference surface, and the nonlinear elasticity theory that accounts for large displacement, large rotation, and large deformation. The rollers and guiding mechanism are modeled as rigid bodies. The distributed frictional contact forces between rollers and web are considered by Hertz contact model and are evaluated by Gauss quadrature. The proportional integral (PI) control law for web guiding is also embedded in the multibody model. A series of simulations on a typical web-guide system is carried out using the multibody dynamics approach for web guiding system presented in this study. System dynamical information, for example, lateral displacement, stress distribution, and driving moment for web guiding, are obtained from simulations. Parameter sensitivity analysis illustrates the effect of influence variables and effectiveness of the PI control law for lateral movement control of web that are verified under different gains. The present Lagrangian formulation of web element, i.e., ANCF element, is not only capable of describing the large movement and deformation but also easily adapted to capture the distributed contact forces between web and rollers. The dynamical behavior of the moving web can be accurately described by a small number of ANCF thin plate elements. Simulations carried out in this paper show that the present approach is an effective method to assess the design of web guiding system with easily available desktop computers.

scholarly journals Modeling and Dynamic Analysis of Spherical Roller Bearing with Localized Defects: Analytical Formulation to Calculate Defect Depth and Stiffness

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Behnam Ghalamchi ◽  
Jussi Sopanen ◽  
Aki Mikkola
Keyword(s):  
Dynamic Model ◽  
Contact Stiffness ◽  
Roller Bearing ◽  
Measurement Data ◽  
Contact Forces ◽  
Hertzian Contact ◽  
Radial Clearance ◽  
Outer Race ◽  
Rolling Elements ◽  
Localized Defects

Since spherical roller bearings can carry high load in both axial and radial direction, they are increasingly used in industrial machineries and it is becoming important to understand the dynamic behavior of SRBs, especially when they are affected by internal imperfections. This paper introduces a dynamic model for an SRB that includes an inner and outer race surface defect. The proposed model shows the behavior of the bearing as a function of defect location and size. The new dynamic model describes the contact forces between bearing rolling elements and race surfaces as nonlinear Hertzian contact deformations, taking radial clearance into account. Two defect cases were simulated: an elliptical surface on the inner and outer races. In elliptical surface concavity, it is assumed that roller-to-race-surface contact is continuous as each roller passes over the defect. Contact stiffness in the defect area varies as a function of the defect contact geometry. Compared to measurement data, the results obtained using the simulation are highly accurate.

scholarly journals Influence of Weld Parameters on the Fatigue Life of Deck-Rib Welding Details in Orthotropic Steel Decks Based on the Improved Stress Integration Approach

2019 ◽  
Vol 9 (18) ◽  
pp. 3917 ◽  
Author(s):  
Baoya Cao ◽  
Youliang Ding ◽  
Zhao Fang ◽  
Fangfang Geng ◽  
Yongsheng Song
Keyword(s):  
Fatigue Life ◽  
Mesh Size ◽  
Structural Stress ◽  
Partial Penetration ◽  
Full Penetration ◽  
Integration Approach ◽  
Treatment Type ◽  
Manufacturing Errors ◽  
Stress Integration ◽  
Orthotropic Steel Decks

Fatigue cracks in orthotropic steel decks (OSDs) have been a serious problem of steel bridges for a long time. The structural stress approach is an important approach for fatigue life evaluation of welded structures. Firstly, two parameters and the mesh sensitivity of the stress-based integration equivalent structural stress approach (stress integration approach for short) are analyzed in this paper. Then, the applicability of the master S-N curve is verified based on experimental data of the deck-rib welding details in OSDs. Finally, the multi-scale finite element model (FEM) of Jiangyin Bridge is established, and the bridge fatigue life calculation steps based on the stress integration approach are given. The influence of the slope of the master S-N curve at high cycles on the bridge fatigue life is discussed. Further, the weld parameter influences on the bridge fatigue life are analyzed, as including the following: (1) The determination of the influence of the weld size changes caused by weld manufacturing errors on the bridge fatigue life; (2) the proposal of a new grinding treatment type, and the analysis of influence of the grinding radius on fatigue life; and (3) a comparison of the fatigue life of the deck-rib welding details under 80% partial penetration and 100% full penetration. The results show that the structural stress calculated by the stress integration approach does not change significantly with the parameters of the isolation body width w and the distance δ between the crack propagation surface and the reference surface. To simplify the calculation, δ is set as 0, and w can be set as the mesh size along the weld length direction. The mesh size of the stress integration approach is recommended as 0.25 times the deck thickness. The slope of the master S-N curve at high cycles significantly affects the bridge fatigue life, and a slope of 5 is reasonable. The weld parameter studies for the deck-rib welding details in the OSD of Jiangyin Bridge show that the change of weld size caused by manufacturing errors can obviously affect the bridge fatigue life, and the fatigue life of five different weld types varies from 51 years to 113 years. The new grinding treatment type, without weakening the deck, is beneficial to improving the bridge fatigue life. The fatigue life increases by approximately 5% with an increase of the grinding radius of 2 mm. The fatigue life of 80% partial penetration is slightly higher than that of 100% full penetration.

Detailed Finite Element Modeling of a High Capacity Mooring Steel Wire Rope: Calculation of the Stress Concentration Near the Connection

2020 ◽  
Author(s):  
Michaël Martinez ◽  
Sébastien Montalvo
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Finite Element Model ◽  
Steel Wire ◽  
High Capacity ◽  
Element Model ◽  
Wire Rope ◽  
Contact Forces ◽  
Life Assessment

Abstract The mooring of floating platforms is an important challenge for the offshore industry. It is an important part of the design engineering and, often, a critical point for the fatigue life assessment. A solution that could improve the fatigue life is to directly connect the mooring rope to the platform, without an intermediate chain. However this solution is not widespread and the behavior of a rope near such a connection is little known. The present paper proposes to better understand this behavior, thanks to a detailed finite element model of the rope. The study case is a steel wire rope directly connected to a floating wind turbine. A local finite element model of the rope has been built, where the wires are individually modeled with beam elements. One end of the rope is clamped, simulating the connection, while tension and cyclic bending oscillations are applied to the other end. A localized bending takes place near the connection, leading to stress concentration in the wires. The stress concentration and the local contact forces are calculated for each wire. These data are important entry parameters for a local failure or fatigue analysis. This latter is however not presented here. Despite IFPEN experience in the development of local finite element models of steel wire ropes, it is the first time that such a high capacity rope (MBL = 12 500 kN) is modeled. This is challenging because of the large diameter of the rope and the large number of wires. However this modeling approach is very valuable for such ropes, because the experimental tests are rare and very expensive.

The Use of an Interference-Fit Bush to Improve the Fatigue Life of a Pin-Jointed Connection

1962 ◽  
Vol 13 (3) ◽  
pp. 275-284 ◽  
Author(s):  
T. H. Lambert ◽  
R. J. Brailey
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Interference Fit ◽  
Light Interference ◽  
Maximum Benefit ◽  
High Degree

SummaryThe fatigue life of a pin-jointed connection can be optimised by using a moderately high degree of interference between the loading pin and plate. Where a joint has to be assembled in confined conditions, difficulty may be experienced in inserting the interference-fit pin and one possible solution is to use a pre-assembled interference-fit bush in the plate, leaving only a light interference-fit pin to be pressed in on assembly of the joint. It is shown that a relatively thick bush of diametral ratio 4/3 will give a reduction in shear stress concentration factor for the plate comparable with that obtained with a solid pin, but that maximum benefit is not obtained with a thinner bush of diametral ratio 8/7. Where thin bushes are essential in order to maintain the ultimate tensile and fatigue strengths of the plate and /or the ultimate and fatigue strengths of the pin, the shear stress concentration factor for the plate is reduced as the modular ratio of bush to plate is increased and as the interference fit of the loading pin in the bush is increased.

Analysis of assembly defects in the cam curved groove mechanism

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Weibin Lan ◽  
Shouwen Fan ◽  
Shuai Fan
Keyword(s):  
Dynamic Characteristics ◽  
Contact Point ◽  
Contact Theory ◽  
Analysis Method ◽  
The Finite Element Method ◽  
Interference Fit ◽  
Content Type ◽  
Cam Mechanism ◽  
Contact Points ◽  
General Mathematical Model

Purpose This paper aims to propose an elementary approach toward the identification of assembly defects of a cam curved groove mechanism. Design/methodology/approach A numerical analysis method for identifying the assembly defects of the cam curved groove mechanism is proposed by resorting to Hertz contact theory. A general mathematical model is established to analyze the kinematic and dynamic characteristics with an interference fit between the main roller and cam curved groove, including the contact points of the external and internal ring. Findings The analysis method of the contact point characteristics of the cam curved groove mechanism is given in this paper, and the kinematic and dynamic characteristics of the main roller can be analyzed. The numerical examples presented in this paper are implemented in MATLAB, feasibility and validity of the above algorithm are verified by the finite element method. Originality/value Regarding the defects of the interference fit, the findings of this paper can serve as a reference for researchers in reducing the defects in the design process of the cam mechanism.

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