tailieunhanh - Engineering Tribology Episode 1 Part 4

Tham khảo tài liệu 'engineering tribology episode 1 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 50 Engineering Tribology TEAM LRN LUBRICANTS AND THEIR COMPOSITION INTRODUCTION In the previous chapter physical properties of lubricants specifically oils and greases have been outlined. The questions which remain however are what is the chemical composition of the lubricant Will the lubricant s composition differ depending on its application What is the basic make up of the oil used to lubricate machinery It is readily appreciated that oil manufacturers are so circumspect about the formulation of their products. The oil ingredients are not listed on the lubricant containers as they are listed on the packaging of most other products. How then can one differentiate between various oils What are the differences between mineral and synthetic oils What are the typical additives used in oils What is their purpose and mechanism of action What is the composition and properties of grease lubricants In what applications are greases usually used An engineer as a potential user of lubricants should know the answers to these questions. Oils can be of two different origins biological and non-biological and this provides a vast array of hydrocarbon compounds. These substances are usually present as complex mixtures and can be used for many other purposes besides lubrication that is the control of wear and friction. Modern technology places severe and varied demands on lubricants so the selection and formulation of appropriate mixtures of hydrocarbons for the purposes of lubrication is a skilled and complex process. Most natural oils contain substances which can hinder their lubrication properties but they also contain compounds essential to the lubrication process. Lubricants made from natural or mineral oils are partly refined and partly impure. The balance between impurity and purity is critical to the oxidation stability of the oil and it varies depending on the application of the lubricant. Chemicals which are deliberately added to an oil in order to improve its .