Tribological Properties of Cold Gas Spraying FeMnCrSi Alloy

FeMnCrSi and 316L alloy coatings were deposited on carbon steel substrates via high-pressure cold gas spraying and their microstructure, hardness, and wear resistance were obtained. Ball-on-disk testing (ASTM G99) was used to measure sliding wear behaviors. The mechanism of wear was found to be the same for both coatings, although FeMnCrSi had a higher coefficient of friction while 316L had less volume loss.

Tribological and percolation properties of polypropylene/nanodiamond soot composites

The relationship between surface- and bulk-related physical and mechanical characteristics of polypropylene (PP)-based composites filled with nanodiamond soot (NDS) particles was investigated. The tribological properties of a composite were considered as surface properties. Wear and friction coefficient values were measured using a steel pin-on-composite disk testing procedure under the justified set of test parameters. Loading of NDS particles to the PP matrix resulted in a drastic increase in the composite’s wear resistance. A significant increase in friction coefficient and contact temperature was observed for the composites with NDS content below a certain value assumed to be the percolation threshold for the selected processing method and components used. After the percolation threshold is reached, the friction coefficient decreases sharply and returns to the value characteristic of a filler-free PP. The effects observed were attributed to changes in properties of polymer matrix and composite melt.

Evaluation of Wear Resistance of Copper at Sliding against TiC Based Coatings under Load

An evaluation of the adhesion interaction of copper and TiC-based coatings formed by electrospark deposition using TiC based electrodes (SHIM mark) was carried out. Tribological tests of the samples were carried out using Pin-on-Disk testing machine. It is established that the least (0.07) coefficient of friction has a electrospark coating deposited of electrode material contained tungsten additives. After tests on the optical profilometer, it was found out that some coatings do not have adherence of the wear products of the copper counterbody. So, it was found two different types of interaction of the copper counterbody with the coatings - with adherence and without adherence (so called wear less sliding behavior) which is perspective to develop novel deforming tools.

Nucleus Implantation: The Biomechanics of Augmentation Versus Replacement With Varying Degrees of Nucleotomy

Nucleus pulposus replacement and augmentation has been proposed to restore disk mechanics in early stages of degeneration with the option of providing a minimally invasive procedure for pain relief to patients with an earlier stage of degeneration. The goal of this paper is to examine compressive stability of the intervertebral disk after either partial nucleus replacement or nuclear augmentation in the absence of denucleation. Thirteen human cadaver lumbar anterior column units were used to study the effects of denucleation and augmentation on the compressive mechanical behavior of the human intervertebral disk. Testing was performed in axial compression after incremental steps of partial denucleation and subsequent implantation of a synthetic hydrogel nucleus replacement. In a separate set of experiments, the disks were not denucleated but augmented with the same synthetic hydrogel nucleus replacement. Neutral zone, range of motion, and stiffness were measured. The results showed that compressive stabilization of the disk can be re-established with nucleus replacement even for partial denucleation. Augmentation of the disk resulted in an increase in disk height and intradiskal pressure that were linearly related to the volume of polymer implanted. Intervertebral disk instability, evidenced by increased neutral zone and ranges of motion, associated with degeneration can be restored by volume filling of the nucleus pulposus using the hydrogel device presented here.

Numerical Simulation of Spin Testing for Turbo Machine Disks Using Energy-Based Fracture Criteria

The results of numerical simulation of spin testing of disks of different structures including those made from different alloys are presented. Stress strain state (SSS) of disk during loading was determined using the MSC.Software and ANSYS commercial finite element method (FEM) software. As an integral assessment of disk burst speed, it has been suggested that a local energy fracture criterion be used. The results of calculation made using this criterion were compared with the results of disk testing carried out at special spin test rigs and also with the results of calculations made using different local strain and stress fracture criteria. Numerical simulation is effectively usable to assess the load-carrying capability of disks taking into account possible adverse combination of mechanical material properties and other factors and also to optimize structures of rotors including the welded ones.