Contact Temperature and Its Effects in an Oscillatory Sliding Contact

1989 ◽  
Vol 111 (1) ◽  
pp. 63-69 ◽  
Author(s):  
F. E. Kennedy ◽  
S. C. Cullen ◽  
J. M. Leroy
Keyword(s):  
Wear Rate ◽  
Polyethylene Wear ◽  
Contact Temperature ◽  
Element Analysis ◽  
Wear Rates ◽  
Transfer Films ◽  
Model Predictions ◽  
The Relationship ◽  
Ultra High Molecular Weight ◽  
Good Agreement

The relationship between contact temperature, friction coefficient, and wear rate was studied here for the case of dry sliding between pin and flat in small amplitude oscillatory motion. In the first part of the study, infrared radiation pyrometry and finite element analysis techniques were used to measure and model surface temperatures in an oscillatory contact. Good agreement was achieved between model predictions and experimental measurements. The model was then applied to an oscillating contact between an ultra-high molecular weight polyethylene pin and a rough stainless steel flat. Temperature predictions for that case were correlated with measured friction coefficients and wear rates. It was found that the polyethylene wear rate decreased as the contact temperature increased. The uniformity and thickness of the transfer films which formed on both counterface and polymer pin were found to be affected by contact temperature. Transfer film behavior was deemed responsible for the influence of contact temperature on wear rate.

scholarly journals Unified Creep Plasticity Damage (UCPD) Model for SAC396 Solder

2013 ◽  
Author(s):  
Michael Neilsen ◽  
Paul Vianco
Keyword(s):  
Finite Element ◽  
Solder Joints ◽  
Element Analysis ◽  
Damage Evolution Equation ◽  
Thermal Mechanical Fatigue ◽  
Model Predictions ◽  
Solder Fatigue ◽  
Solder Joint Fatigue ◽  
The Relationship ◽  
Model Crack

A unified creep plasticity damage (UCPD) model for Sn-Pb and Pb-free solders was developed and implemented into finite element analysis codes. The new model will be described along with the relationship between the model’s damage evolution equation and an empirical Coffin-Manson relationship for solder fatigue. Next, developments needed to model crack initiation and growth in solder joints will be described. Finally, experimentally observed cracks in typical solder joints subjected to thermal mechanical fatigue are compared with model predictions. Finite element based modeling is particularly suited for predicting solder joint fatigue of advanced electronics packaging, e.g. package-on-package (PoP), because it allows for evaluation of a variety of package materials and geometries.

Performance analysis of an orthopaedic biomaterial 100-station wear test system

2009 ◽  
Vol 224 (3) ◽  
pp. 697-701 ◽  
Author(s):  
V Saikko
Keyword(s):  
Wear Rate ◽  
Polyethylene Wear ◽  
Calf Serum ◽  
High Capacity ◽  
Wear Test ◽  
High Standard ◽  
Test System ◽  
Wear Rates ◽  
Two Samples ◽  
The Mean

Until recently, wear studies of orthopaedic biomaterials have suffered from inadequate testing capacity and high standard deviation (SD) of results. In the present article, the previously validated 100-station hip wear simulator, the SuperCTPOD, is evaluated with regard to its capability of producing statistically significant differences in mean wear rates. SuperCTPOD wear tests were done for 38 different types of polyethylene pins against polished CoCr discs with diluted calf serum lubrication. A total of 200 pins were worn in two consecutive tests of 6 weeks, duration each. The sample size varied from four to six. The mean wear rates of the samples ranged from 0.52 to 77.1 mg per one million cycles. On the average, the SD of the wear rate was 4.2 per cent of the mean value (range 1–8.5 per cent). A difference in the mean wear rates below 5 per cent was large enough to be statistically significant ( p <0.05) in 21 comparisons between two samples, the lowest statistically significant mean difference being 3.2 per cent. In conclusion, the high capacity and the low SD of the wear rate make the SuperCTPOD wear test system unparalleled in efficiency. The observations regarding the effect of crosslinking and molecular weight on polyethylene wear resistance were in agreement with studies published earlier.

Tribological Characteristics of Deformed Magnesium Alloy AZ61 Under Dry Conditions

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Abdel-Wahab El-Morsy ◽  
A. Abouel-Kasem
Keyword(s):  
Magnesium Alloy ◽  
Wear Rate ◽  
Deformation Process ◽  
Wear Behavior ◽  
Sliding Velocity ◽  
Wear Rates ◽  
Power Spectral ◽  
Dry Conditions ◽  
The Relationship ◽  
Applied Stresses

The wear behavior of deformed magnesium alloy AZ61 under dry conditions was evaluated. Two types of AZ61 alloy were used, extruded and rolled samples, to investigate the effect of deformation process on the wear behavior. The experiments were performed using a pin-on-ring type wear apparatus against a stainless-steel counterface under applied stresses in the range of 3–7 MPa, and within a sliding velocity range of 0.2–1.8 m/s. The topographical images of the eroded surfaces at different sliding velocity for extruded and rolled samples were quantified using fractal analysis. The results revealed that for all applied stress, the wear rates increased with increasing the sliding velocity of both samples. The wear rate of the rolled samples is greater than that of the extruded samples at the stress range from 3 to 5 MPa. However, when the stress is increased to 7 MPa the wear rate of the rolled samples is lower than that of the extruded samples. The variation of fractal value of slope of linearized power spectral density (PSD) with the sliding velocity is largely similar to the relationship between the wear rate and the sliding velocity.

Effects of Hardness on the Lifetime of Graphite Brushes Used for Aircraft Starter Generators

2012 ◽  
Author(s):  
R. Asmatulu ◽  
M. J. Holle ◽  
H. E. Misak
Keyword(s):  
Wear Rate ◽  
Surface Morphology ◽  
Optical Microscope ◽  
Excess Carbon ◽  
Wear Rates ◽  
Key Factor ◽  
Generating Mode ◽  
Starter Generator ◽  
The Relationship ◽  
Morphology Changes

This study is focused on the relationship between the hardness of three different carbon/graphite brushes (A, B and C), the wear rate of the brushes and heat generated within a 400 Amp starter generator. The method being proposed was to alternate the starter generator from the starting mode and the generating mode, and run each carbon/graphite brush in the starter generator for a set time and document the wear rates, heat generations and surface morphology changes. The hypothesis was that either excess carbon dust caused arcing, or the energy required to form the carbon dust was releasing too much heat, and thus the brush was too hard. An optical microscope, AFM, and SEM were used in the analysis of the surfaces. It was found that as the hardness of the brush went up, the wear rate decreased while the overall heat on the inside of the starter generator increased. From this research, it is evident that the hardness of the brushes is the key factor for heat, wear and morphology changes in the starter generator.

scholarly journals Aerosol Generation and Entrainment Model for Cough Simulations

2006 ◽  
Author(s):  
C. Ersahin ◽  
I. B. Celik ◽  
W. G. Lindsley ◽  
D. G. Frazer
Keyword(s):  
Physical Properties ◽  
Fluid Composition ◽  
Size Distributions ◽  
Aerosol Transport ◽  
Physical Size ◽  
Aerosol Generation ◽  
Air Stream ◽  
Model Predictions ◽  
The Relationship ◽  
Good Agreement

Coughing produces aerosols comprised of components of fluid that line the respiratory tract. These aerosols have been implicated in the transmission of many infectious diseases. Important factors that must be considered in aerosol transport include its physical size distribution, the shape and density of its components, as well as its chemical and biological composition. This study represents the initial phase of a larger project whose goal is to investigate the relationship between the generation of infectious aerosols and the dissemination of diseases in the workplace. The objective of this study was to develop a computational model representative of the generation and entrainment of an aerosol during cough. This model is composed of two sub-models; the first describes the formation of “mother” droplets and their entrainment in an air-stream and the second simulates the fragmentation of these droplets into smaller size distributions. The first sub-model is used to calculate the amount of fluid entrained in the droplets which is a function of the physical properties of the airway lining fluid and airflow patterns in the airway. The second sub-model describes the fragmentation of the droplets as a function of the physical properties of the fluid composition and a description of the flow field surrounding the droplet. Preliminary results show that, with the proper choice of model constants, it is possible to obtain relatively good agreement between model predictions and experimental measurements.

Local Head Roughening as a Factor Contributing to Variability of Total Hip Wear: A Finite Element Analysis

2002 ◽  
Vol 124 (6) ◽  
pp. 691-698 ◽  
Author(s):  
Thomas D. Brown ◽  
Kristofer J. Stewart ◽  
John C. Nieman ◽  
Douglas R. Pedersen ◽  
John J. Callaghan
Keyword(s):  
Wear Rate ◽  
Adhesive Wear ◽  
Polyethylene Wear ◽  
Bearing Surface ◽  
Third Body ◽  
Element Analysis ◽  
Wear Factor ◽  
Total Hip ◽  
Key Factor ◽  
Sliding Distance

Large inter-patient variability in wear rate and wear direction have been a ubiquitous attribute of total hip arthroplasty (THA) cohorts. Since patients at the high end of the wear spectrum are of particular concern for osteolysis and loosening, it is important to understand why some individuals experience wear at a rate far in excess of their cohort average. An established computational model of polyethylene wear was used to test the hypothesis that, other factors being equal, clinically typical variability in regions of localized femoral head roughening could account for much of the variability observed clinically in both wear magnitude and wear direction. The model implemented the Archard abrasive/adhesive wear relationship, which incorporates contact stress, sliding distance, and (implicitly) bearing surface tribology. Systematic trials were conducted to explore the influences of head roughening severity, roughened area size, and roughened area location. The results showed that, given the postulated wear factor elevations, head roughening variability (conservatively) typical of retrieval specimens led to approximately a 30° variation in wear direction, and approximately a 7-fold variation in volumetric wear rate. Since these data show that randomness in head scratching can account for otherwise-difficult-to-explain variations in wear direction and wear rate, third-body debris may be a key factor causing excessive wear in the most problematic subset of the THA population.

Permeability and porosity models of bi-fractal porous media

2017 ◽  
Vol 31 (29) ◽  
pp. 1750219 ◽  
Author(s):  
Xiao-Hua Tan ◽  
Ming-Qing Kui ◽  
Xiao-Ping Li ◽  
Zheng-Lin Mao ◽  
Heng Xiao
Keyword(s):  
Experimental Data ◽  
Porous Media ◽  
Fractal Parameters ◽  
Model Predictions ◽  
Capillary Bundle ◽  
Geometric Character ◽  
Sensitive Parameters ◽  
The Relationship ◽  
Good Agreement

In previous studies, it is found that the frame and pore in porous media both possess the fractal geometric character. So the permeability and porosity models of bi-fractal porous media are derived based on the assumption that a porous media consists of fractal solid clusters and capillary bundles. The expressions of presented models are constituted by the fractal parameters of solid cluster and those of capillary bundle. Good agreement between model predictions and experimental data is obtained. This verifies the validity of the permeability and porosity models for bi-fractal porous media. The sensitive parameters that influence the permeability and porosity are specified, and their effects on the relationship between permeability and porosity are discussed.

UCPD Model for Pb-Free Solder

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Michael K. Neilsen ◽  
Paul T. Vianco
Keyword(s):  
Finite Element ◽  
Solder Joints ◽  
Element Analysis ◽  
Damage Evolution Equation ◽  
Thermal Mechanical Fatigue ◽  
Model Predictions ◽  
Solder Fatigue ◽  
Solder Joint Fatigue ◽  
Free Solder ◽  
The Relationship

A unified creep plasticity damage (UCPD) model for eutectic Sn-Pb and Pb-free solders was developed and implemented into finite element analysis codes. The new model will be described along with the relationship between the model's damage evolution equation and an empirical Coffin–Manson relationship for solder fatigue. Next, developments needed to model crack initiation and growth in solder joints will be described. Finally, experimentally observed cracks in typical solder joints subjected to thermal mechanical fatigue are compared with model predictions. Finite element based modeling is particularly suited for predicting solder joint fatigue of advanced electronics packaging, e.g. package-on-package (PoP), because it allows for evaluation of a variety of package materials and geometries.

Theoretical and Experimental Investigation on Cross-Shear Dependency of Polyethylene Wear in Artificial Knee Implants

2008 ◽  
Author(s):  
Thorsten Schwenke ◽  
Markus A. Wimmer
Keyword(s):  
Molecular Orientation ◽  
Polyethylene Wear ◽  
Longitudinal Direction ◽  
Implant Design ◽  
Motion Path ◽  
Artificial Joints ◽  
Wear Rates ◽  
Pin On Disc ◽  
Direction Of Movement ◽  
Ultra High Molecular Weight

It has been shown that the contact motion path in artificial knee bearings is implant design dependent [1]. It is also known that multidirectional motion of artificial joints leads to higher wear rates compared to the application of unidirectional motion [2,3]. This phenomenon has been linked to “strain-hardening” of ultra-high molecular weight polyethylene (PE): the molecular chains in the surface layer align along the direction of shear. Since more energy is required to rupture the fibrils in their longitudinal direction than perpendicularly, less wear is generated if the direction of movement follows the molecular chain orientation [3]. Computer models could potentially become an important tool in wear prediction if this relationship could be quantified. A variable, defined as ‘cross-shear’ A/(A+B), with A being the fraction of motion along the molecular orientation and B being the fraction of motion perpendicular to the molecular orientation, takes this into account (Fig.1); however, pin-on-disc studies trying to validate this model found agreement for small cross-shear values only [4].

Analysis of magnetic force and dynamic characteristic for non-contact permanent magnet linear drive device

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1337-1345
Author(s):  
Chuan Zhao ◽  
Feng Sun ◽  
Junjie Jin ◽  
Mingwei Bo ◽  
Fangchao Xu ◽  
...  
Keyword(s):  
Finite Element ◽  
Permanent Magnet ◽  
Dynamic Characteristic ◽  
Driving Force ◽  
Magnetic Circuit ◽  
Response Speed ◽  
Computation Method ◽  
Element Analysis ◽  
Element Simulation ◽  
The Relationship

This paper proposes a computation method using the equivalent magnetic circuit to analyze the driving force for the non-contact permanent magnet linear drive system. In this device, the magnetic driving force is related to the rotation angle of driving wheels. The relationship is verified by finite element analysis and measuring experiments. The result of finite element simulation is in good agreement with the model established by the equivalent magnetic circuit. Then experiments of displacement control are carried out to test the dynamic characteristic of this system. The controller of the system adopts the combination control of displacement and angle. The results indicate that the system has good performance in steady-state error and response speed, while the maximum overshoot needs to be reduced.

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