Influence of Natural Serpentine on the Tribological Performance of Phosphate Bonded Solid Coatings

Natural serpentine powders were incorporated into phosphate bonded solid coatings to promote the anti-wear performance of the phosphate coatings. Optimal mass percent of natural serpentine in phosphate coatings was firstly explored. Thereafter, in order to stimulate layer slip of natural serpentine and strengthen interfacial interaction between natural serpentine and counterface during the friction process, tribological performance of the composite coatings under different friction condition was properly investigated. The experimental result indicated that the optimal incorporation of natural serpentine in phosphate coatings was 10 wt.%, through which anti-wear performance of phosphate coatings was significantly elevated. Additionally, accompanied by the increase of applied load and sliding speed, natural serpentine was activated by friction force and local friction heat, and simultaneously interfacial interactions between naturals serpentine and counterface were intensified. As a result, a continuous protective tribo-film was in-situ formed on the counterface, through which anti-wear performance of phosphate coatings were significantly promoted. At the same time, serious furrows generated on the counterface were also effectively self-repaired during the friction process, and further abrasion on the counterface was greatly restrained.

Numerical modeling and optimization of process parameters in continuous extrusion process through response surface methodology, artificial neural network & genetic algorithm

The product of high complex profile, high strength, high productivity and excellent material properties with infinite length can be produced by Continuous Extrusion (CE) process. The numerical simulation of Aluminum (AA 1100) feedstock material at different wheel velocities, product diameter, feedstock temperature, die temperature and friction condition has been carried out using 3D simulation tool Design Environment for Forming (DEFORM-3D) in this paper. The development of mathematical model is carried out to investigate the influence of wheel velocity, extrusion ratio, feedstock temperature, die temperature and friction conditions on total load required for the deformation and extrusion of feedstock material through Response Surface Methodology (RSM). The statistical significance of mathematical model is verified through analysis of variance (ANOVA). The most optimum value of extrusion load has been found to be 136.4[Formula: see text]kN through iterative process of Genetic Algorithm (GA) using Artificial Neural Network (ANN). The optimized value of input process variables for minimum value of extrusion load obtained has been found to be 13 Revolutions per Minute (RPM) as wheel velocity, 5[Formula: see text]mm as product diameter, 0.95 as friction condition, 650[Formula: see text]C as feedstock temperature and 550[Formula: see text]C as die temperature. This paper with proposed methodology will be helpful for industries working in the area of CE in terms of minimizing energy consumption during production process of bus bars, tubes, wires, cables, sheets, plates, strips, etc.

Shock Characteristics of the Opposed Disc Springs (ODS) Shock Isolator with Pretightening under Boundary Friction Condition

In this study, to solve the problems of shock environment and shock isolation, about which there is still a lack of reasonable description, an isokinetic shock distinguishing method (ISDM), which can quantitatively distinguish between shock and forced vibration state, is presented. And the shock isolation performance of an opposed disc springs (ODS) shock isolator with pretightening under boundary friction condition is investigated. The static and dynamic stiffness properties of the ODS shock isolator are discussed. Relying on ISDM, a shock dynamic model of the ODS shock isolator with pretightening under boundary friction condition is established. The average method is adopted to solve the model theoretically. The shock acceleration ratio (SAR), shock displacement ratio (SDR), and relative displacement ratio (RDR) of the model are calculated using the numerical method and verified by experiments. Both numerical and experimental results show that ISDM is effective. And the effects on isolation efficiency of the number of disc springs, additional supporting force, pretightening force, load, and the shock velocity constant of the ODS shock isolator are discussed, which provide guidelines for its further practical application.

The Effect of Fullerene Soot Nanoparticles on the Microstructure and Properties of Copper-Based Composites

Copper-based composite materials strengthened with nanosized fullerene soot particles were produced by mechanical milling and hot pressing technology with a content of carbon up to 5 wt. %. The microstructure of the composite powders and the compacts prepared using them were examined by light microscopy, SEM, EDS, XRD, and XPS; hardness, heat conductivity, and tribological characteristics were measured. The interesting feature of the observed microstructure was a “marble” pattern formed by a white boundary net. The study shows homogeneous distribution of carbon inside the copper grains and its lower concentration in the grain boundaries. The effect was caused by a reaction of carbon with oxygen adsorbed by the copper particles surface. The maximal hardness of the material is 160 HB for the sample with 0.5 wt. % of fullerene soot; this material has the minimal friction coefficient (0.12) and wear in a dry friction condition. Heat conductivity of the material (Cu-0.5 wt. % C) is 288 W/m*K.