Modeling Ground-Shell Contact Forces in NATM Tunneling Based on Three-Dimensional Displacement Measurements

2013 ◽  
Vol 139 (3) ◽  
pp. 444-457 ◽  
Author(s):  
Shafi Ullah ◽  
Bernhard Pichler ◽  
Christian Hellmich
Keyword(s):  
Three Dimensional ◽  
Contact Forces ◽  
Displacement Measurements

A Nonlinear Rail Vehicle Dynamics Computer Program SAMS/Rail: Part 1—Theory and Formulations

2009 ◽  
Author(s):  
Khaled E. Zaazaa ◽  
Brian Whitten ◽  
Brian Marquis ◽  
Erik Curtis ◽  
Magdy El-Sibaie ◽  
...  
Keyword(s):  
High Speed ◽  
Dynamic Performance ◽  
Three Dimensional ◽  
Contact Element ◽  
Contact Forces ◽  
Simulation Code ◽  
Vehicle Performance ◽  
Normal Contact ◽  
Advantages And Disadvantages ◽  
High Speed Trains

Accurate prediction of railroad vehicle performance requires detailed formulations of wheel-rail contact models. In the past, most dynamic simulation tools used an offline wheel-rail contact element based on look-up tables that are used by the main simulation solver. Nowadays, the use of an online nonlinear three-dimensional wheel-rail contact element is necessary in order to accurately predict the dynamic performance of high speed trains. Recently, the Federal Railroad Administration, Office of Research and Development has sponsored a project to develop a general multibody simulation code that uses an online nonlinear three-dimensional wheel-rail contact element to predict the contact forces between wheel and rail. In this paper, several nonlinear wheel-rail contact formulations are presented, each using the online three-dimensional approach. The methods presented are divided into two contact approaches. In the first Constraint Approach, the wheel is assumed to remain in contact with the rail. In this approach, the normal contact forces are determined by using the technique of Lagrange multipliers. In the second Elastic Approach, wheel/rail separation and penetration are allowed, and the normal contact forces are determined by using Hertz’s Theory. The advantages and disadvantages of each method are presented in this paper. In addition, this paper discusses future developments and improvements for the multibody system code. Some of these improvements are currently being implemented by the University of Illinois at Chicago (UIC). In the accompanying “Part 2” and “Part 3” to this paper, numerical examples are presented in order to demonstrate the results obtained from this research.

Three-dimensional Force Perception of Robotic Bipolar Forceps for Brain Tumor Resection

2021 ◽  
Author(s):  
Xiu-Heng Zhang ◽  
Heng Zhang ◽  
Zhen Li ◽  
Gui-Bin Bian
Keyword(s):  
Brain Tumor ◽  
Real Time ◽  
Force Measurement ◽  
Measurement Techniques ◽  
Tumor Resection ◽  
Three Dimensional ◽  
Contact Forces ◽  
Surgical Instruments ◽  
Force Perception ◽  
Brain Tumor Resection

Abstract Three-dimensional force perception is critically important in the enhancement of human force perception to minimize brain injuries resulting from excessive forces applied by surgical instruments in robot-assisted brain tumor resection. And surgeons are not responsive enough to interpret tool-tissue interaction forces. In previous studies, various force measurement techniques have been published. In neurosurgical scenarios, there are still some drawbacks to these presented approaches to forces perception. Because of the narrow, and slim configuration of bipolar forceps, three-dimensional contact forces on forceps tips is not easy to be traced in real-time. Five fundamental acts of handling bipolar forceps are poking, opposing, pressing, opening, and closing. The first three acts independently correspond to the axial force of z, x, y. So, in this paper, typical interactions between bipolar forceps and brain tissues have been analyzed. A three-dimensional force perception technique to collect force data on bipolar forceps tips by installing three Fiber Bragg Grating Sensors (FBGs) on each prong of bipolar forceps in real-time is proposed. Experiments using a tele-neurosurgical robot were performed on an in-vitro pig brain. In the experiments, three-dimensional forces were tracked in real-time. It is possible to experience forces at a minimum of 0.01 N. The three-dimensional force perception range is 0-4 N. The calibrating resolution on x, y, and z, is 0.01, 0.03, 0.1 N, separately. According to our observation, the measurement accuracy precision is over 95%.

The Effect of Body Position and Number of Supports on Wall Reaction Forces in Rock Climbing

1997 ◽  
Vol 13 (1) ◽  
pp. 14-23 ◽  
Author(s):  
Franck Quaine ◽  
Luc Martin ◽  
Jean-Pierre Blanchi
Keyword(s):  
Body Weight ◽  
Contact Force ◽  
Body Position ◽  
Three Dimensional ◽  
Rock Climbing ◽  
Contact Forces ◽  
Vertical Posture ◽  
Reaction Forces ◽  
Force Data ◽  
Lower Contact

This manuscript describes three-dimensional force data collected during postural shifts performed by individuals simulating rock-climbing skills. Starting from a quadrupedal vertical posture, 6 expert climbers had to release their right-hand holds and maintain the tripedal posture for a few seconds. The vertical and contact forces (lateral and anteroposterior forces) applied on the holds were analyzed in two positions: an “imposed” position (the trunk far from the supporting wall) and an “optimized” position (the trunk close to the wall and lower contact forces at the holds). The tripedal postures performed in the two positions were achieved by the same pattern of vertical and contact forces exerted by the limbs on the holds. In the optimized position, the transfer of the forces was less extensive than in the imposed position, so that the forces were exerted primarily on the ipsilateral hold. Moreover, a link between the contact force values and the couple due to body weight with respect to the feet was shown.

Numerical Simulation of a Floater in a Broken-Ice Field: Part II — Comparative Study of Physics Engines

2012 ◽  
Author(s):  
Ivan Metrikin ◽  
Andrey Borzov ◽  
Raed Lubbad ◽  
Sveinung Løset
Keyword(s):  
Numerical Simulation ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Contact Forces ◽  
Limited Attention ◽  
Detection Accuracy ◽  
Documentation Quality ◽  
Physics Engine ◽  
Broken Ice ◽  
Ice Floes

Numerical simulation of a floater in ice-infested waters can be performed using a physics engine. This software can dynamically detect contacts and calculate the contact forces in a three-dimensional space among various irregularly shaped bodies, e.g. the floater and the ice floes. Previously, various physics engines were successfully applied to simulate floaters in ice. However, limited attention was paid to the criteria for selecting a particular engine for the simulation of a floater in broken-ice conditions. In this paper, four publicly available physics engines (AgX Multiphysics, Open Dynamics Engine, PhysX and Vortex) are compared in terms of integration performance and contact detection accuracy. These two aspects are assumed to be the most important for simulating a floater in broken ice. Furthermore, the access to code, documentation quality and the level of technical support are evaluated and discussed. The main conclusion is that each physics engine has its own strength and weaknesses and none of the engines is perfect. These strength and weaknesses are revealed and discussed in the paper.

Thermal Stresses in a Bimaterial Joint: An Experimental Analysis

1994 ◽  
Vol 61 (1) ◽  
pp. 192-198 ◽  
Author(s):  
D. Post ◽  
J. D. Wood ◽  
B. Han ◽  
V. J. Parks ◽  
F. P. Gerstle
Keyword(s):  
Experimental Analysis ◽  
Thermal Stresses ◽  
Stress Gradient ◽  
Three Dimensional ◽  
High Sensitivity ◽  
Stress Singularities ◽  
Severe Stress ◽  
Field Displacement ◽  
Displacement Measurements ◽  
Uniform Change

An experimental analysis was conducted on a bimaterial plate subjected to a uniform change of temperature. Whole-field displacement measurements U and V were made on the free surface by means of high-sensitivity moire interferometry, and stresses were calculated from these data. Stresses resembled those of stress singularities, but they reached finite tensile and compressive peaks on opposite sides of the interface. The peaks and a severe stress gradient between them occurred in a narrow zone of about ±25 μm from the interface. The results pertain to an elastic three-dimensional body.

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