Wear debris analysis

Hunt, T.M., Handbook of Wear Debris Analysis and Particle Detection in Liquids, Elsevier Applied Science, New York, 1993. 

Wear Debris Analysis When machine surfaces wear, they generate metallic particles that enter the lubricant. Monitoring and analyzing the generated debris enables analysts to detect and evaluate abnormal conditions to assist in directing needed maintenance activities. 

Tests were carried out in 25% (v/v) newborn calf serum (Harlan Seralabs, UK) with 0.1% (w/v) sodium azide to retard bacterial growth. The lubricant was changed every 330,000 cycles and stored frozen at —20°C until required for wear debris analysis. Wear was determined volumetri-cally every million cycles. The three-dimensional geometry of the cups was determined before the test and every million cycles using a coordinate measuring machine (Kemco 400 3D, Keeley Measurement Co., UK). 

Wear measurements were determined gravimetrically every million cycles using unloaded soak controls as a comparison. Serum lubricants were stored frozen at — 20°C until required for wear debris analysis. 

J. Sugimura, M. Takesue and Y. Yamamoto, Wear debris analysis for condition monitoring of gears. Tribology for Energy Conservation, D. Dowson et al. eds., Elsevier (1998) 431-442. 

Oil-related analysis encompasses a variety of physical and chemical tests such as viscosity, total acid number and particulate contamination. This is often extended to include the identification of wear debris, as an early warning of component failure, by either spectrographic... 

Some fundamental aspects of tribochemistry of ZDDP have been investigated using an ultrahigh vacuum UHV analytical tribometer on chemisorbed films previously formed on a steel surface (Martin et al., 1996). The steel surface was immersed in a solution of ZDDP at a concentration of 2 wt.% in PAO synthetic lubricant base at 130°C for 24 hours. The chemistry of the treated steel surfaces was investigated by XPS and AES, and friction tests were carried out in UHV just after the analysis. At the end of the friction tests, AES microanalysis was performed both inside and outside the wear scar. The AES analysis showed that sulfide was present inside the wear scar and phosphorus was eliminated from the surface, presumably as wear debris. Summary data of the tribofilm composition after ZDDP degradation are presented in Table 4.1. 

As in the case of corrosion failures, the sequence of steps involved in analyzing wear failures are initial examination of the failed component including service conditions to establish the mode or combination of modes of wear failure, metallographic examination to check if the microstructure of the worn part met the specification, both in the base material and in the hardened case or applied surface coatings, existence of localized phase transformations, shear or cold worked surfaces, macroscopic and microscopic hardness testing to determine the proper heat treatment, X-ray and electron diffraction analysis to determine the composition of abrasives, wear debris, surface elements and microstructural features such as retained austenite, chemical analysis of wear debris surface films and physical properties such as viscosity and infrared spectral determination of the integrity of lubricants and abrasive characteristics of soils or minerals in the cases of wear failures of tillage tools. 

What you monitor Particles, moisture, viscosity, temperature, additives, oxidation, AN/BN, soot, glycol, FTIR, RPVOT Wear debris density, temperature, particle count, moisture, elemental analysis, viscosity, analytical ferrography Wear debris, elemental analysis, moisture, particle count, temperature, viscosity, anal5fiical ferrography, vibration analysis Elemental analysis, analytical ferrography, vibration analysis, temperature Analytical ferrography, ferrous density, elemental analysis... 

Oil sampling is a critical factor in successful lubricant analysis. Errors in obtaining a representative sample can impair all further analytical efforts. There are two primary goals in obtaining a representative oil sample. The first is to sample in a way that the information density in the oil is maximized, which is often referred to as maximizing data density. The data could be particles from dust, moisture, additive levels, and wear debris. 

Static or low-damage secondary ion mass spectrometry (SIMS) can be used to characterize polymers and also detect very small amounts of metals transferred to polymers or in polymer wear debris. While SIMS uses an ion beam to sputter remove surface species and is therefore inherently destructive, damage can be minimized by using low ion beam fluxes (3x10 A/cm ). This allows for monolayer analysis. 

Measurements Normal load, cartilage deformation, friction cartilage wear and damage, biochemical analysis of cartilage specimens, synovial fluid, and wear debris sub-surface changes... 

Firkins P.J., J.L. Tipper, M.R. Saadatzadeh, et al. 2001. Quantitative analysis of wear and wear debris from metal-on-metal hip prostheses tested in a physiological hip joint simulator. Biomed Mater Eng 11 143-157. 

The fracture of ceramic balls in ceramic UHMWPE combination has been virtually zero. Fritsch and Gleitz (30) published a failure analysis on 4341 alumina ceramic heads articulating with 2693 alumina ceramic and 1464 polymer sockets implanted over 20 years (1974 to 1994), and concluded that the use of ball type neckless heads brought the fracture rate close to zero. The success rate of 10 years follow-up is normally above 90% for the elderly patient population. Stem and cup loosening are the causes of failure, where the consistent wear debris from UHMWPE and bone cement remain the problems. 

Transmission electron microscopy performed on wear particles collected on the flat after the friction test reveals the presence of flake-like wear debris (Figure 3.64). EDS analyses of these flake-like debris show the presence of catalytic particles. An EELS analysis clarifies nature of the carbon constituting this debris. The peak characteristic of an sp hybridization, visible on the spectra of graphite and nanotubes, does not exist on the spectrum of the wear particles (Figure 3.65). Therefore, this flake-like wear debris is made of amorphous carbon. An EELS analysis of the peak of inelastic losses provided the evaluation of the thickness to 60 nm [40]. 

Dimensional criterion. In tribological contact processes both lateral and depth dimensions are important, the former because of the size and shape of wear debris and the latter because of the presence of thin films. It is therefore vital to match the characteristics of a technique to the dimensions of the analysis. 

The solid wear particles from ZDDP films produced in lubricated contacts contain phosphorus, sulfur and zinc from the ZDDP molecule and oxygen mainly from the surrounding air environment. They also have a low iron content. Ex situ examination by XAS, EELS and CEMS of these particles (configuration shown in Fig. 5a) has been carried out to provide local analysis of the iron atoms, since their localized environment in the surface film is of great interest it is related directly to the wear of the steel surface and can also play a key role in the adhesion mechanisms of the film. In order to investigate this aspect, a study was made by XAS (EXAFS plus XANES) of a collection of wear debris from two lubricated tests, with and without ZDDP in the lubricant base, respectively. The processed EXAFS data presented in Fig. 8 show the RDFs of iron atoms (noncorrected phase shifts) in four samples data from the standards, pure crystalline iron and iron oxide have been included for comparison. From this EXAFS study, some important results can be deduced [4] ... 

Further analysis of the type of wear in UHMWPE glenoid components has also been conducted by examining the wear debris generated in the shoulder. Isolation and characterization of the UHMWPE wear debris generated in failed shoulder, hip, and knee arthroplasties gives added... 

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