Implantation indentation

Impingement mixing, 200 Implants, bioresorbable, 27 Indentation force deflection (IFD) test, 244 Infrared (IR) spectroscopy, 91, 162, 300, 490. See also Fourier transform infrared (FTIR) spectrometry Ingold s classification, 60-61 Inherent viscosity, 161-162 Injection molding, of polyamides, 136,... 

Microhardness tests upon the same worn hip cups have provided direct supporting evidence for the changed nature of PE adjacent to the wear surface (Flores et al, 2000). An increased microhardness of the used cups, at their wear surfaces, in comparison to the control was apparent. Attention turned, accordingly, to the lateral surfaces of the cups (Fig. 7.16) which did possess the smooth planar condition required for optimum microhardness measurements. Figure 7.16 shows microhardness measured as a function of the radial distance, h, from the indent to the edge of the concave surface. The microhardness of the control sample H 57 MPa) does not vary with h. however, H for the hip cups, after implantation and removal from... 

The hardening and embrittlement of polyimides by ion implantation has been also studied (Pivin, 1994). Nanoindentation tests performed using a sharp diamond pyramid of apical angle 35° provided very quantitative depth profiles of microhardness in polyimides implanted with C, N, O, Ne or Si ions. In all cases the microhardness increased steeply when the amount of deposited energy reached the order of 20 eV atom". For energies of 200 eV atom" the polymer is transformed into an amorphous hydrocarbon and the microhardening factor saturates at a value of 13-20. However, the carbonized layer is poorly adherent, as is evidenced by reproducible discontinuities in the depth vs load curves, when the indenter tip reached the interface. 

The nanoindentation technique was developed in the 1980s because of the need to determine the mechanical properties of thin films and surfaces that had been modified, for example, by ion implantation. To avoid the influence of the substrate the penetration depth of the indenter must be less than 10% of the film thickness. Consequently penetration depths are on the order of nanometers rather than millimeters, which is common for conventional indentation tests. 

Clearly all indents made with a pyramidal indenter should have the same shape regardless of their size. Thus, since we take pressure used to make this shape to be a measure of hardness—see equations (1.6) and (1.7)—we would expect hardness to be the same and there to be no load effect. Therefore when hardness increases as the applied load decreases, as shown in Figure 1.3, it must be because the volume of material used to yield is smaller and the mechanism for yielding is dependent on a volume term which becomes more significant as the indent size decreases. The most obvious development of this idea is that the shallow near-surface volume of the deformation zone can become a significant fraction of the total affected volume when a very small load is used to make the indent. Thus, work hardened layers, surface compressed layers, ion-implanted layers, and the possibility of chemical reactions between the atmosphere and the surface can dominate the yielding mechanism to produce nonstandard hardness values. Conversely we can say that these phenomena could be studied by measuring the ISE of a ceramic. 

Lessons learned from the SCF experiments also aided the drafting of the test method standards ASTM C1421 and ISO 18756. We confirmed that it did not matter whether the tiny Knoop precrack was implanted in the narrow 3 mm face or the wider 4 mm face. The formal test standards allow both indentation and loading configurations. Slight (0.5 % 1.0 %) discrepancies in our SCF outcomes early in the project... 

The microhardness of a surface is an indication of the resistance to abrasive wear that of the surface of unimplanted Ti6A14V has a value of 3000 N/mm-(136). The hardness values obtained under load with a Vickers indentor are summarized in Fig. 12, where the hardness is plotted as function of the applied indentation load. The sample implanted with N showed a more pronounced increase in hardness than those implanted with C. Implantation of N at two energies led to an even greater increase than that at only one energy and also to a thicker layer of increased hardness. 

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