FUNDAMENTAL OF ENGINEERING

Department of Mechanical Engineering, IIT Delhi organized a Five Days QUALITY IMPROVEMENT PROGRAM (QIP) on "Fundamentals of Engineering Tribology with Applications" from 7th – 11thDecember, 2015. Around Sixty five faculties from different technical colleges (including IIT’s, NIT’s) from India participated in this workshop. Faculty members Mr.Kumar Jyotiraditya and Mr. Vikas Sahu from Mechanical Engineering department of Dronacharya College of Engineering, Gurgaon attended the short term course.

The objective of this course is to introduce the fundamental of engineering tribology and its application in various mechanical system like bearings, shafts and all other interacting surface in relative motion that include any type of tribological applications.

The workshop was coordinated by Prof.(Dr.) Harish Hirani, Department of Mechanical Engineering, IIT DELHI. The workshop was conducted in four sessions per day and also there was a Lab session during which participants were brought to different research labs related to tribology to understand the course effectively. The session started with a basic introduction and its need by Prof. Harish Hirani followed by recent research activities going in IIT’s and other research centers in INDIA.

The speakers of the Workshop were:

1. Prof.(Dr.) Harish Hirani , Course Coordinator , Department of Mechanical Engineering, IIT DELHI

2. Dr. SM Muzakkir, Associate Professor ,Department of Mechanical Engineering, Jamia Millia Islamia, New Delhi

3. Dr. Jayshree Bijwe, ITMMEC, Indian Institute of Technology Delhi

4. Dr. Sujeet Kumar Sinha, Associate Professor, Department of Mechanical Engineering, IIT DELHI

5. Mr. Abhimanyu Sharma, KITTIWAKE technology New Delhi

6. Dr. Deepak Sharma, Asst. Prof. ITMMEC IIT DELHI

7. Dr. Satish C Sharma, Associate Professor, Department of Mechanical Engineering, IIT Roorkee

8. Dr. T Singh, BPCL

9. Dr. Lijesh, Research associates, Department of Mechanical Engineering, IIT DELHI

10. Dr. Pranav Samanta, Surface Engineering and Tribology Lab CSIR-Central Mechanical Engineering Research Institute

7th December 2015

The session started with Introduction and need of Tribology. Prof. Hirani explained the concept of Tribology. He said that Tribology is one of the oldest sciences and is still not very well understood and is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear. The tribological interactions of a solid surface's exposed face with interfacing materials and environment may result in loss of material from the surface. The process leading to loss of material is known as "wear".

Dr. SM Muzakkir explained the concept of effect of Cylindricity on the Tribological Performance of Heavily-Loaded Slow Speed Journal Bearing. He explained that theoretical and experimental studies have been conducted to analyze the effect of cylindricity on performance of a heavily loaded slow-speed journal bearing. The design of experiments has been employed to quantify the effect of bearing clearance and cylindricity on the wear. The wear coefficient was determined using the steady wear data obtained experimentally on the lubricity tester. A mathematical model was formulated to estimate wear of the bearing incorporating the actual cylindricity.

He further discussed about tribological performance of CrN and DLC coatings are oil dependent. The physical and chemical analyses of tribo-films suggest that the CrN coating responds in a similar manner to steel surfaces to the conventional additives. Optimisation of lubricant additives has been found to be immensely important, especially for the effective lubrication of non/low-hydrogenated DLC coatings. He also focussed on Design table for journal bearing and Various theories related to Tribology and applications.

8th December 2015

Dr. Jayshree Bijwe started the session on Friction theories and instability. She said that Friction instability generally occurs due to large difference in the value of static and kinetic coefficient of friction. Ideally lubricated condition having coefficient of friction equal to 0.00025 shall be preferred, but there is a possibility of variation in static and kinetic coefficient of frictions. If we assume that static coefficient of friction under lubricated conditions is equal to 0.01 and kinetic coefficient of friction is equal to 0.00025, then this lubricated contact may not be preferred.

Prof. Hirani took the next session on Online condition monitoring of high speed gears using vibration & oil analysis. He said that Online condition monitoring is an essential component of Predictive maintenance which helps in determining the condition of in-line service equipment to predict when maintenance is required. He further said that two most popular techniques to monitor the condition of gearbox are: Vibration analysis & Oil analysis. He pointed out that where sliding wear is prevalent oil analysis is very important in identifying the progressive failure of gear.

9th December 2015

Dr. Sujeet Kumar Sinha started the session by explaining the Basics of fluid film lubrication , Hydrostatic bearings. He said that three compensators are used in hydrostatic bearings -- orifice, capillary, and variable-flow restrictor. The first two are fixed-flow restrictors; the third is a valve which automatically adjusts flow as it senses pressure differentials between pads. The variable-flow restrictor provides a stiffer bearing system, but is more expensive than fixed-flow restrictors. Sizing of the orifice or capillary for optimum performance is an essential part of the design of a compensated hydrostatic bearing.

He also briefed on Hydrostatic Lubrication and discussed that it is characterized by the complete separation of the conjugated surfaces of a kinematic pair, by means of a film of fluid, which is pressurized by an external equipment like a pump.

In next session. Dr. Satish C Sharma discussed about Basics of condition monitoring and Oil condition monitoring and defined the use of condition monitoring allows maintenance to be scheduled, or other actions to be taken to avoid the consequences of failure. He further explained that there are two main methods used for condition monitoring, and these are trend monitoring and condition checking. Trend monitoring is the continuous or regular measurement and interpretation of data, collected during machine operation, to indicate variations in the condition of the machine or its components, in the interests of safe and economical operation. Condition checking is where a check measurement is taken with the machine running, using some suitable indicator.

10th December 2015

Dr. Deepak Sharma started the session on Nano Tribology for Mechanical Systems. He said that nanotribology as a field is concerned with experimental and theoretical investigations of processes ranging from atomic and molecular scales to the microscale, occurring during adhesion, friction, wear, and thin-film lubrication at sliding surfaces. Nanotribology can be defined as the investigations of interfacial processes, on scales ranging in the molecular and atomic scale, occurring during adhesion, friction, scratching, wear, nanoindentation, and thin-film lubrication at sliding surfaces.

Next session was on Boundary lubrication. There are three different types of lubrication:

1. boundary,

2. mixed

3. full film.

Boundary lubrication is found where there are frequent starts and stops, and where shock-loading conditions are present. Some oils have extreme-pressure (EP) or anti-wear (AW) additives to help protect surfaces in the event that full films cannot be achieved due to speed, load or other factors. These additives cling to metal surfaces and form a sacrificial layer that protects the metal from wear. Boundary lubrication occurs when the two surfaces are contacting in such a way that only the EP or AW layer is all that is protecting them. This is not ideal, as it causes high friction, heat and other undesirable effects.

Mixed lubrication is a cross between boundary and hydrodynamic lubrication. While the bulk of the surfaces are separated by a lubricating layer, the asperities still make contact with each other. This is where the additives again come into play.

Full-film lubrication can be broken down into two forms: hydrodynamic and elasto-hydrodynamic. Hydrodynamic lubrication occurs when two surfaces in sliding motion (relative to each other) are fully separated by a film of fluid. Elasto-hydrodynamic lubrication is similar but occurs when the surfaces are in a rolling motion (relative to each other). The film layer in elasto-hydrodynamic conditions is much thinner than that of hydrodynamic lubrication, and the pressure on the film is greater.

Dr. Lijesh then took the participants for Lab Visit where the practical aspect of tribological applications were shown

11th December 2015

Dr. T Singh conducted the session on Lubricants as Synthetic base oil, turbine oil, Grease and hydraulic oils. He said that Most lubricants are formulated with mineral base stocks that are severely refined, low-wax, heavy distillate fractions of crude oil. They are relatively low cost, generally good solvents for most additives, available in a wide viscosity range and compatible with a number of seal materials. Synthetic base stocks are made by chemical manufacturers to impart special qualities to the finished oil. Polyalphaolefin (PAO), organic esters, glycols and phosphate esters are examples of synthetics that are used to meet specific needs. Synthetics are used where the value of their special functional properties, oxidation stability, fire-resistance, etc., outweigh their cost.

Dr. Pranav Samanta then discussed on Foil bearings and Magnetic bearings. He explained that Foil bearings, also known as foil-air bearings, are a type of air bearing. A shaft is supported by a compliant, spring-loaded foil journal lining. Once the shaft is spinning fast enough, the working fluid (usually air) pushes the foil away from the shaft so that there is no contact. The shaft and foil are separated by the air's high pressure which is generated by the rotation which pulls gas into the bearing via viscosity effects. A high speed of the shaft with respect to the foil is required to initiate the air gap, and once this has been achieved, no wear occurs.

Session continued on Elasto hydrodynamic Lubrication and he defined that while rolling contact elements (bearings, gears), generated fluid film is minutely small slightly greater than irregularities of the surfaces, but serve much longer than predicted by mixed lubrication theories. Increased viscosity under the action of extreme local pressure leads the generation of thicker film.

Many times using only classical hydrodynamic lubrication theory predicts a negligible fluid film in high-pressure non-conforming contacts such as exist in rolling element bearings and gears, but on considering the influence of pressure on both elastic deformation and lubricant viscosity, a significant oil-film thickness becomes possible. Difference between elasto hydrodynamic lubrication (EHD) and hydrodynamic lubrication(HD) occurs as HD is based on the assumption of a fluid continuum, while EHD shows significant increase in local (limited to few molecular thickness) viscosity compared to bulk viscosity.

Prof. Hirani concluded the session by discussing the Future prospective of Tribology. He said that new areas of tribology have emerged, including the Nanotribology, biotribology, and green tribology. These interdisciplinary areas study the friction, wear and lubrication at the nanoscale, in biomedical applications and ecological aspects of friction, lubrication and wear.

The course concluded with a valedictory session where Prof. Hirani gave the vote of thanks. It was a very knowledgeable session and the participants came to learn a lot from the course.