Tribological characteristics of polymer materials used for slide bearings

The automotive industry uses a variety of technologies and construction materials in production process. Knowledge of the characteristics of tribological material pairs cooperating with each other is useful for their selection from the safety point of view sliding pairs, in means of transport, and other machines. The aim of the contribution is the analysis of the characteristics of tribological ball-on-disc wear of polymeric materials used as sliding bearings. Tribological tests were carried out under dry friction for a polymer–metal pair of three types of materials. Among all three groups of the tested materials statistically significant differences (p < 0.05 in Student’s t-test) in wear were observed. The wear rate and friction coefficient of the sample were tested, and the signs of wear were submitted to SEM observations.

Beneficial Interface Geometry for Laser Joining of NiTi to Stainless Steel Wires

Joining the dissimilar metal pair of NiTi to stainless steel is of great interest for implantable medical applications. Formation of brittle intermetallic phases requires that the joining processes used for this dissimilar pair limits the amount of over-melting and mixing along the interface. Thus, because of its ability to precisely control heat input, laser joining is a preferred method. This study explores a method of using a cup and cone interfacial geometry, with no filler material, to increase the tensile strength of the joint. Not only does the cup and cone geometry increase the surface area of the interface, but it also introduces a shear stress component, which is shown to be beneficial to tensile strength of the wire as well. The fracture strength for various cone apex angles and laser powers is determined. Compositional profiles of the interfaces are analyzed. A numerical model is used for explanation of the processing parameters.

Effects of Interfacial Geometry on Laser Joining of Dissimilar NiTi to Stainless Steel Wires

Joining of the dissimilar metal pair NiTi to stainless steel is of great interest for implantable biomedical applications. Formation of brittle intermetallic phases requires that the joining processes limit the amount of over-melting and mixing along the interface. Thus, laser joining is a preferred method due to its ability to precisely control heat input. This study explores a method of using a cup and cone interfacial geometry, with no filler material, to increase the tensile strength of the joint. Not only does the cup and cone geometry increase the surface area of the interface, but it also introduces a shear component, which is shown to be beneficial to tensile strength of the wire as well. The fracture strength for various cone apex angles and laser powers is determined. Compositional profiles of the interfaces are analyzed. A numerical model is used for explanation of the processing.

Metal Pollution Indices of Surface Sediment and Water from the Upper Reaches of Sombriero River, Niger Delta, Nigeria

Metal pollution indices of the surface sediments and water of the upper reaches of Sombriero river was investigated using Absorption Spectrophotometery. The data obtained for the metals- Cd, Pb, V, Fe, Ni, Cu and Zn showed consistency in the metal pollution indices of the various stations of the study area. The stations with higher pollution indices were related to areas of intense activities. Several metal pair correlations were obtained in the surface sediments than in the surface water. Both media had Zn-Cd and Cu-Fe metal pair correlations. The pattern of the metals in the surface water at 95% significant level is Fe>Zn = Cu = Pb = N = Cd = V while that of the sediment is Fe>Zn = Cu = Ni = Pb = V = Cd. Each of the metals differed significantly between the media (P<0.05) sediment > water, indicating the former to be a better monitoring index of aquatic pollution by these metals. In comparison to other related work the degree of contamination of the upper reaches of the Sombriero River is low but a gradual enrichment of these pollutants could have a deleterious effect on the aquatic resources of the area and the consumers thereof.DOI: http://dx.doi.org/10.3126/on.v10i1.7783