Tribology of soap powders used in dry wire drawing
File(s)
Author(s)
Schlichting, Marie-Louise
Type
Thesis
Abstract
Understanding friction and lubrication behaviour of powdered soaps used in dry wire drawing is crucial for reduced die wear, enhanced wire quality and improved energy efficiency. However, the complex tribological behaviour of powdered soaps proves to be challenging in providing a thorough understanding of the tribological interactions at the wire-die contact. In this work, lab tests were used to obtain accurate quantitative data on powdered soap friction, and to study the nature of soap lubrication.
To gain insights into the frictional behaviour of typical powdered soaps under condi-tions relevant to the wire die-contact in wire drawing, a systematic test campaign with selected soap chemistries was conducted using a high-pressure ball-on-disc tribo-meter. The impact of high sliding, speed and contact pressure on friction was explored using materials similar to die-wire materials.
Friction tests showed that powdered soaps provide a very good level of lubrication with friction coefficients (COF) being as low as 0.04 at high sliding-speeds and pressures. An increase in pressure and sliding-speed leads to a decrease in soap COF. At low speeds and low SRRs soap COFs are very variable suggesting potential effects of shear-rate. Soap formulation, particularly the amount of fatty acid content, was shown to be significant for friction performance. Measurements on a real wire drawing set-up showed that observed friction trends are in line with trends of drawing stress.
Soap lubricating films were studied using optical techniques which gave evidence of thick, residual soap layers on the rubbing track of the specimens. A high-speed optical ball-on-disc machine was used to directly observe in-contact soap film formations. Powdered soaps exhibit a very dynamic film behaviour with occasional formation of a constriction near the outlet, resembling the characteristic ‘horse-shoe’ shape of EHL fluids. It is postulated that the in-contact temperature rise has crucial effects on film formation.
To gain insights into the frictional behaviour of typical powdered soaps under condi-tions relevant to the wire die-contact in wire drawing, a systematic test campaign with selected soap chemistries was conducted using a high-pressure ball-on-disc tribo-meter. The impact of high sliding, speed and contact pressure on friction was explored using materials similar to die-wire materials.
Friction tests showed that powdered soaps provide a very good level of lubrication with friction coefficients (COF) being as low as 0.04 at high sliding-speeds and pressures. An increase in pressure and sliding-speed leads to a decrease in soap COF. At low speeds and low SRRs soap COFs are very variable suggesting potential effects of shear-rate. Soap formulation, particularly the amount of fatty acid content, was shown to be significant for friction performance. Measurements on a real wire drawing set-up showed that observed friction trends are in line with trends of drawing stress.
Soap lubricating films were studied using optical techniques which gave evidence of thick, residual soap layers on the rubbing track of the specimens. A high-speed optical ball-on-disc machine was used to directly observe in-contact soap film formations. Powdered soaps exhibit a very dynamic film behaviour with occasional formation of a constriction near the outlet, resembling the characteristic ‘horse-shoe’ shape of EHL fluids. It is postulated that the in-contact temperature rise has crucial effects on film formation.
Version
Open Access
Date Issued
2024-08-12
Date Awarded
01/01/2025
License URL
Advisor
Kadiric, Amir
Wong, Janet
Masen, Marc
Sponsor
NV Bekaert SA (Firm)
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)