PubMed · 4436778
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J F Bavitz, N R Bohidar, J I Karr, F A Restaino. 1974. Letter: Tablet strength testing.. https://doi.org/10.1002/jps.2600631003
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BACKGROUND: Aim of the study is to compare microstructure of Titanium joints soldered with Laser and Infrared methods by performing SEM analysis, metallography and microhardness evaluation. METHODS: Wax specimens were separated in the middle area corresponding to the joint region, machined and then soldered. 40 Titanium samples were fused and divided in 2 groups of 20 samples each. First group was soldered by laser welding, second one by infrared brazing. SEM analysis and standard metallography were carried out at joined areas and unsoldered surfaces. Microhardness test was performed on longitudinally sectioned samples with 150 g load for 15 second up to 7 mm distance from the joined area. RESULTS: SEM photomicrographs revealed for group 1 a homogeneous metal-joint interface, without microporosities; for group 2 exhibited a distinct demarcation of metal joint interface. Metallography evaluation showed for laser joined samples only the presence of Titanium; infrared joined samples showed in soldered regions also Ni and Cu. Microhardness values detected at the joined surfaces seem to be higher for both considered groups. CONCLUSIONS: Laser joining method with exclusive presence of Titanium seems to be ideal for monometallism; both techniques exhibited microstructural changes in the heated surface layer.
The thrust of the present work was the development of a new modification to the ASTM E813-89 method for determining the J-integral fracture toughness, JIc, of ductile polymers. The advantages and limitations of the modification, vis a vis the ASTM E813-89 and the hysteresis methods, are presented. The modification was then applied to investigate the effect of sterilization method on the JIc of ultra-high-molecular-weight polyethylene (UHMWPE) specimens that were subsequently aged (heated, in a cylindrical pressure vessel, in oxygen gas at 507 kPa and 70 degrees C for 14 d). Relative to the unsterilized material, it was found that gamma-irradiating the polymer leads to a significant drop in its JIc, while sterilization using either ethylene oxide or gas plasma produced no effect on its JIc. The clinical implications of the present results for the in vivo performance of UHMWPE counterfaces, and, hence, hip and knee arthroplasties, are fully discussed.
Microhardnesses of five types of renal calculi: calcium apatite (82.5%)/magnesium ammonium phosphate hydrogen (10%)/calcium oxalate monohydrate (7.5%); calcium apatite (95%)/calcium oxalate monohydrate (5%); magnesium ammonium phosphate hydrogen (90%)/calcium apatite (10%); calcium oxalate monohydrate (85%)/calcium apatite (15%); and cystine (100%) were measured. Using Knoop and Vickers indenters the effects of chemical composition and microstructure on the microhardness measurement were assessed. Calcium oxalate monohydrate, magnesium ammonium phosphate hydrogen, and cystine stones, without apparent structure pattern, showed neither regional nor directional differences in their microhardness. In contrast, calcium apatite stones, with distinctly concentric laminae structure, showed regional variations which were correlated with the chemical composition of stone constituents. Scanning electron microscopy of the indenter impressions were taken to help in interpreting the directional dependence in Knoop hardness measurements with respect to the microstructure of the calculi. Vickers measurements showed the crystalline stones were isotropic within a layer. Combined results of Knoop and Vickers measurements indicate that the anisotropic Knoop hardness readings seen in the laminated regions were structural but not material-based. Implications of the results for the fragmentation of renal calculi in extracorporeal shock wave lithotripsy are discussed.