scholarly journals Modelling the dynamic contact forces during orthogonal turn‐milling

PAMM ◽  
2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Katharina Knape ◽  
Steffen Nitzschke ◽  
Elmar Woschke
Keyword(s):  
Dynamic Contact ◽  
Contact Forces ◽  
Turn Milling

Evaluation of vehicular contact force on bridge joints by vibration responses and object detection

2021 ◽  
Author(s):  
Di Su ◽  
Yuichiro Tanaka ◽  
Tomonori Nagayama
Keyword(s):  
Object Detection ◽  
Contact Force ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Expansion Joints ◽  
Cyclic Movements ◽  
Bridge Joints ◽  
Vibration Responses ◽  
On The Road ◽  
Board System

<p>Expansion joints on bridges should accommodate cyclic movements to minimize imposition of secondary stresses in the structure. However, these joints are highly susceptible to severe and repeated vehicular impact that results their inherent discontinuity. In this paper, a portable on- board system including accelerometers and a drive recorder to evaluate the vehicular contact force on bridge joints is proposed. First, from the acceleration responses of the vehicle, the contact force exerted on the road surface is estimated from a half-car model by Kalman Filter. Next, extraction of the expansion joints is performed by object detection from videos taken by the drive recorder. Finally, a relative comparison of the contact forces acting on joints is performed, with location identification on the map. The proposed system benefits to utilize the dynamic contact forces results from on-board system to detect the potential risky joints more precisely and efficiently.</p>

Influence of the Fastening Modeling on the Vehicle-Track Interaction at Singular Rail Surface Defects

2014 ◽  
Vol 9 (3) ◽  
Author(s):  
Xin Zhao ◽  
Zili Li ◽  
Rolf Dollevoet
Keyword(s):  
Kinetic Energy ◽  
High Frequency ◽  
Surface Defects ◽  
Dynamic Contact ◽  
Rolling Speed ◽  
Contact Forces ◽  
The Other ◽  
Practical Significance ◽  
Fe Model ◽  
Wide Spread

With up to 12 spring-damper groups distributed in the actual area of a rail pad, different fastening models are developed in this paper to include the nonuniform pressure distribution within a fastening system and model the constraints at the rail bottom more realistically for the purpose of high frequency dynamics between vehicle and track. Applied to a 3D transient FE model of the vehicle-track interaction, influence of the fastening modeling on the high frequency dynamic contact forces at singular rail surface defects (SRSDs) is examined. Two defect models, one is relatively large and the other is small, are employed. Such a work is of practical significance because squats, as a kind of SRSD, have become a wide spread problem. Results show that the fastening modeling plays an important role in the high frequency dynamic contact forces at SRSDs. Supports in the middle of the rail bottom, modeled as spring-damper groups located under rail web, are found to be most important. The less the rail bottom is constrained or supported, the more isolated the sleepers and substructure are from the wheel-rail interaction, and the more kinetic energy is kept in the rail after impact at a SRSD. Rolling speed is also varied to take into account its influence. Finally, based on the results of this work, influence of the service states of the fastening system on growth of relatively small SRSDs is discussed.

Analyzing characteristics of high-speed spindle bearing under constant preload

2017 ◽  
Vol 232 (5) ◽  
pp. 568-581 ◽  
Author(s):  
Thi-Thao Ngo ◽  
Van-The Than ◽  
Chi-Chang Wang ◽  
Jin H Huang
Keyword(s):  
Film Thickness ◽  
Thermal Effects ◽  
High Speed ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Lubricant Film ◽  
Contact Forces ◽  
Transfer Model ◽  
Lubricant Film Thickness ◽  
Spindle Bearing

Bearings play an important role in a high-speed spindle. Its characteristics are often influenced by speed and thermal effects. This paper presents an approach that combines an inverse method with a high-speed ball bearing model to determine the characteristics of a high-speed spindle bearing under constant preload in actual working conditions. With temperature distribution in the entire spindle obtained by the experimental inverse heat transfer model from the authors’ previous results, the change in bearing parameters is then calculated and subsequently replaced in the bearing model to analyze the change in bearing characteristics. As a result, thermal effects on a bearing’s dynamic contact angles, contact forces, contact stress, stiffness, and lubricant film thickness are presented. Moreover, analysis results indicate that a bearing’s stiffness and lubricant film thickness nonlinearly vary with the increase in speed, and the thermal effect significantly affects the lubricant film thickness. The results presented herein may be applied to develop a dynamic model for a high-speed spindle using a constant preload and provide useful information to avoid failure in lubrication.

Wheel–Rail Impact at Crossings: Relating Dynamic Frictional Contact to Degradation

2017 ◽  
Vol 12 (4) ◽  
Author(s):  
Zilong Wei ◽  
Chen Shen ◽  
Zili Li ◽  
Rolf Dollevoet
Keyword(s):  
Plastic Deformation ◽  
Contact Force ◽  
Frictional Contact ◽  
Point Contact ◽  
Strain Analysis ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Fe Method ◽  
Normal Contact ◽  
The Impact

Irregularities in the geometry and flexibility of railway crossings cause large impact forces, leading to rapid degradation of crossings. Precise stress and strain analysis is essential for understanding the behavior of dynamic frictional contact and the related failures at crossings. In this research, the wear and plastic deformation because of wheel–rail impact at railway crossings was investigated using the finite-element (FE) method. The simulated dynamic response was verified through comparisons with in situ axle box acceleration (ABA) measurements. Our focus was on the contact solution, taking account not only of the dynamic contact force but also the adhesion–slip regions, shear traction, and microslip. The contact solution was then used to calculate the plastic deformation and frictional work. The results suggest that the normal and tangential contact forces on the wing rail and crossing nose are out-of-sync during the impact, and that the maximum values of both the plastic deformation and frictional work at the crossing nose occur during two-point contact stage rather than, as widely believed, at the moment of maximum normal contact force. These findings could contribute to the analysis of nonproportional loading in the materials and lead to a deeper understanding of the damage mechanisms. The model provides a tool for both damage analysis and structure optimization of crossings.

scholarly journals Mixed Finite Element Method for Static and Dynamic Contact Problems with Friction and Initial Gaps

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Lanhao Zhao ◽  
Zhi Liu ◽  
Tongchun Li
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Mixed Finite Element ◽  
Iteration Process ◽  
Mixed Finite Element Method ◽  
Contact Problems ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Stick Slip ◽  
Element Method

A novel mixed finite element method is proposed for static and dynamic contact problems with friction and initial gaps. Based on the characteristic of local nonlinearity for the problem, the system of forces acting on the contactor is divided into two parts: external forces and contact forces. The displacement of structure is chosen as the basic variable and the nodal contact force in contact region under local coordinate system is selected as the iteration variable to confine the nonlinear iteration process in the potential contact surface which is more numerically efficient. In this way, the sophisticated contact nonlinearity is revealed by the variety of the contact forces which are determined by the external load and the contact state stick, slip, or separation. Moreover, in the case of multibody contact problem, the flexibility matrix is symmetric and sparse; thus, the iterative procedure becomes easily carried out and much more economical. In the paper, both the finite element formulations and the iteration process are given in detail for static and dynamic contact problems. Four examples are included to demonstrate the accuracy and applicability of the presented method.

Thermal Assessment of Dynamic Rotor/Auxiliary Bearing Contact Events

2006 ◽  
Vol 129 (1) ◽  
pp. 143-152 ◽  
Author(s):  
Patrick S. Keogh ◽  
Woon Yik Yong
Keyword(s):  
Contact Area ◽  
Initial Conditions ◽  
Frictional Heating ◽  
Thermal Response ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Normal Operation ◽  
Permanent Loss ◽  
Auxiliary Bearing ◽  
Transient Thermal

Under normal operation, a rotor levitated by magnetic bearings will rotate without making contact with any stator component. However, there are a number of circumstances that may lead to temporary or permanent loss of levitation. These include full rotor drop events arising from power loss, momentary fault conditions, sudden changes in unbalance, high levels of base acceleration, and other aerodynamically induced force inputs. The spinning rotor will come into dynamic contact with an auxiliary bearing. Highly localized and transient temperatures will arise from frictional heating over the dynamically varying contact area. Rotor dynamic contact forces are predicted for a range of initial conditions leading to combinations of bounce and rub motion on the auxiliary bearing. The transient heat flux from the contact area is then ascertained. A transient thermal Green’s function is developed in a form that is effective over short or long time scales and local to the source. This enables the transient thermal response of an auxiliary bearing to be assessed for a range of dynamic contact conditions. Auxiliary bearings consisting of fixed bushings and free to rotate inner races are analyzed. The results show that significant localized contact temperatures may arise from each contact event, which would accumulate for multiple contact cases. The methodology will be of relevance for the life prediction of auxiliary bearing designs.

scholarly journals Design and Calibration of a Tri-Directional Contact Force Measurement System

2021 ◽  
Vol 11 (2) ◽  
pp. 877
Author(s):  
Rizwan Ahmed ◽  
Christian Maria Firrone ◽  
Stefano Zucca
Keyword(s):  
Contact Force ◽  
Measurement System ◽  
Force Measurement ◽  
Three Dimensional ◽  
Dynamic Contact ◽  
Forced Response ◽  
Contact Forces ◽  
Blade Vibration ◽  
Contact Models ◽  
Force Measurement System

In low pressure turbine stages, adjacent blades are coupled to each other at their tip by covers, called shrouds. Three-dimensional periodic contact forces at shrouds strongly affect the blade vibration level as energy is dissipated by friction. To validate contact models developed for the prediction of nonlinear forced response of shrouded blades, direct contact force measurement during dynamic tests is mandatory. In case of shrouded blades, the existing unidirectional and bi-directional contact force measurement methods need to be improved and extended to a tri-directional measurement of shroud contact forces for a comprehensive and more reliable validation of the shroud contact models. This demands an accurate and robust measurement solution that is compatible with the nature and orientation of the contact forces at blade shrouds. This study presents a cost effective and adaptable tri-directional force measurement system to measure static and dynamic contact forces simultaneously in three directions at blade shrouds during forced response tests. The system is based on three orthogonal force transducers connected to a reference block that will eventually be put in contact with the blade shroud in the test rig. A calibration process is outlined to define a decoupling matrix and its subsequent validation is demonstrated in order to evaluate the effectiveness of the measurement system to measure the actual contact forces acting on the contact.

Analysis of a Compliant Honing Tool for Brushing Cylindrical Surfaces

1997 ◽  
Vol 119 (3) ◽  
pp. 441-444 ◽  
Author(s):  
Chih-Yuan Shia ◽  
R. J. Stango
Keyword(s):  
Steady State ◽  
Contact Force ◽  
Rotational Speed ◽  
Cylindrical Surface ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Spherical Volume ◽  
Special Cases ◽  
Flexible Honing ◽  
State Configuration

In this paper, a mechanics-based model is developed and I used for analyzing the steady-state configuration of brush fibers during concentric brushing of a cylindrical surface. The geometry of the problem is generalized in order to facilitate the analysis of flexible honing tools, that is, brushing tools having a spherical volume of abrasive compound attached at the end of each fiber. The integrity of the model is evaluated by examining two special cases that have a known solution, namely, (i) quasistatic contact, and (ii) dynamic contact associated with successively reduced fiber stiffness. In each case, correct results are obtained for the contact forces generated at the interface of the filament tip/cylindrical workpart surface. Also, special attention is given to examining the role that brush rotational speed plays in the response of each fiber of the honing tool, including filament/workpart contact force, torque, and filament stress.

Measurement of Tube-to-Support Dynamic Forces in Fretting-Wear Rigs

1989 ◽  
Vol 111 (4) ◽  
pp. 385-393 ◽  
Author(s):  
N. J. Fisher ◽  
B. Ingham
Keyword(s):  
Heat Exchangers ◽  
Force Measurement ◽  
Wear Test ◽  
Dynamic Contact ◽  
Contact Forces ◽  
Fretting Wear ◽  
Test Facility ◽  
Test Results ◽  
Flow Induced Vibration ◽  
Dynamic Forces

Tubes within tube and shell heat exchangers are supported at intermediate points by plates. Flow-induced vibration can cause tubes to impact and rub against these supports, or other tubes, and can result in tube fretting-wear. The tube-to-support dynamic interaction, which consists of dynamic contact forces and tube motion, is used to relate single-span wear data to real heat exchanger configurations consisting of multi-span tube bundles. This paper describes the technique used to measure tube-to-support dynamic forces in the Chalk River Nuclear Laboratories impact fretting-wear test facility and reports test results that validate the technique. The force measurement technique is shown to provide a reasonable measure of dynamic contact forces.

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