Industrial Lubrication and Tribology

Müller, Martina; Hild, Rafael; Trauth, Daniel; Bergs, Thomas

2019 Industrial Lubrication and Tribology

doi: 10.1108/ilt-08-2019-0316

The modification of the tribological system is an essential aspect of the implementation of resource-saving processes in cold forming. As a result, the focus of this contribution is the influence of the tribological system on the full forward impact extrusion of aluminum alloy EN AW 6082 (T6) with regard to reduction of friction and wear.Design/methodology/approachThe investigations included a variation of lubricant and die treatment. Friction, wear and the mean arithmetic height Sa were used as evaluation criteria. The aim was to find a suitable die surface treatment and a suitable lubricant on the basis of the evaluation criteria.FindingsThe experiments indicated that each of the selected tribological systems prevents physical metallic contact between tool and workpiece and thus prevents the formation of wear. Nevertheless, differences were found in the areas of smoothing of workpiece surfaces and adhesive strength of lubricants.Originality/valueAs general cause effect relationships between die coating and lubricant are not known in the field of bulk metal forming of aluminum, fundamental investigations are described below. The investigations focus on the influence of the material and the tribological system on friction as well as wear.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-08-2019-0316

Klocke, Fritz; Broeckmann, Christoph; Löpenhaus, Christoph; Bezold, Alexander; Frech, Tim; Hajeck, Marko; Scholzen, Philipp; Gebhardt, Christian

2019 Industrial Lubrication and Tribology

doi: 10.1108/ilt-06-2018-0248

The purpose of this study is to optimize high-strength gears produced by powder metallurgical process and to provide a material model to predict the tooth root bending fatigue strength. Powder metal (PM) technology offers great opportunities for the reduction of the carbon footprint and improvement of the cost efficiency of gear production. PM gears can achieve flank load-carrying capacities comparable to wrought steel gears if the loaded volume is fully densified. Still, the tooth root strength is of particular importance.Design/methodology/approachThe tooth root stresses can be minimized by optimizing the tooth root geometry. This usually leads to a target conflict, as fully optimized tooth root geometries cannot be manufactured by generating processes such as hobbing, generating-grinding or rolling. To use the increase in tooth root load-carrying capacity of fully optimized root geometry on PM gears, a non-generating method for surface densifying is needed. The shot-peening process is used as an alternative densification process for PM gears. The properties of both shot peened and cold-rolled PM gears are analyzed and compared. To quantify the effect of both manufacturing processes, the tooth root bending fatigue strength will be evaluated and compared to wrought gears.FindingsFrom the fatigue strength perspective, a material model is developed, which is able to predict local endurable stress amplitudes. The model is gained through regression varying carbon content, density and size effect on bending specimens.Originality/valueIt is transferable to PM gears of the same material using a load transfer coefficient.

Fan, Yujie; Xue, Feng; Zhou, Yuankai; Dai, Yibin; Cui, Pengfei; Su, Yu; Liu, Zhiqiang

2019 Industrial Lubrication and Tribology

doi: 10.1108/ilt-04-2019-0136

As a key basic component used in machining, high-speed steel (HSS) tools often prone to wear and failure during machining. Therefore, the purpose of this study is to adopt a suitable approach to improve the stability of the cutting force, the service life and the wear resistance.Design/methodology/approachLaser shock processing (LSP) was used to process the tool rake face and the tribological test was performed with ball-on-disk wear tester.FindingsExperimental results show that cutting force of the LSP-treated tool is lower than untreated tool under the same cutting conditions. Wear rate of the tool nose treated by LSP decreases obviously and the tool life increases by 40 per cent.Originality/valueHSS is often used in the manufacture of complex cutting tools. The main value of this article is to improve the tool surface wear resistance, thereby extending the service life of cutter. This paper is valuable not only in theory but also with reference value in engineering practice.

Zhao, Yuanfang; Jianxi, Yang

2019 Industrial Lubrication and Tribology

doi: 10.1108/ilt-01-2018-0032

The purpose of this paper is to explore the sensitive parameters affecting the friction resistance of sliding bearings under different interface slip conditions and the influence of the texture position of circular pits on the friction force of sliding bearings.Design/methodology/approachBased on the mechanical equilibrium equation and Newton's viscous fluid mechanics formula and wedge oil film model, the calculation model of sliding bearing friction resistance under interface slip state is established, and the influence of interface slip on friction resistance under different slip conditions is analyzed by means of ANSYS. Friction simulation model of circular pit textured journal bearing under different interface slip conditions.FindingsThe friction resistance of bearings is mainly determined by journal linear velocity, oil film slip ratio, pressure of inlet and outlet of bearings, oil film thickness and bearing capacity. When both the upper and lower surfaces of the oil film slip, the friction resistance decreases significantly, which is only 4-17 per cent of that without slip. And the friction force of the texture model of circular pit at the exit is better than that at the entrance and the middle of the pit.Originality/valueRelevant research results will lay a new theoretical foundation for friction reduction and optimization design of sliding bearings.