Question

1. an undulated surface that is designed to reduce friction by eliminating wear particles from the sliding interface. The interface is subjected to normal force N. The sliding speed is so low that the interfacial temperature rise is negligible relative to the melting point of the material. We are planning to use metals for the sliders.

a. Determine the optimum dimensions of the undulated topography.

b. Discuss the consequence of deviating from the optimum geometry.

2. A conical asperity is plowing the surface. Determine the coefficient of friction.

3.At the beginning of sliding, there are 10,000 particles of 1 micron in diameter between two flat Armco iron surfaces. The hardness of Armco iron is 1000MPa. After one day of sliding, the particles have agglomerated into 100 equal sized spheres. What would be the change in friction coefficient? Plowing is primarily responsible for friction. State your assumptions clearly.At the beginning of sliding, there are 10,000 particles of 1 micron in diameter between two flat Armco iron surfaces. The hardness of Armco iron is 1000MPa. After one day of sliding, the particles have agglomerated into 100 equal sized spheres. What would be the change in friction coefficient? Plowing is primarily responsible for friction. State your assumptions clearly.

4. A composite bearing material has been developed using uniaxial graphite fibers embedded in a polyurethane matrix. The fibers are perpendicular to the sliding surface. Estimate the coefficient of friction and wear rate of the composite when it is sliding against a 52100 steel sphere of 0.02 m in diameter. State your assumptions

5. You have developed a new copper alloy that has titanium diboride (TiB2) as second phase particles. The total volume fraction of TIB2 is 3 %. The particle size is uniform throughout the matrix of copper. You made five samples by varying particle size as follows: 0.05 microns, 0.1 microns, 1 microns, 10 microns, and 100 microns.

(a) Estimate the hardness of each material.

(b) Estimate the wear coefficient of each sample, assuming that they wear by delamination.

State your assumptions clearly

Answer 1

1) a) Modeling of the tribological is a complex and difficult task. It is most important for all stages of the life cycle of machine and machine component.

So the design of parts minimum contact between two bodies and for maintaining friction coefficient between two bodies use suitable lubricant according to material properties. Stability depends on a part geometry, so create parts like that way equal normal force transfer to each other and maintain the stable condition during sliding. Using this condition easily design a part. In this part friction is minimum and we eliminate wear particles from the sliding interface

b) If the geometry is not optimum that time we face some problem stability not exist and a contact area between two parts are increases and normal force does not balance proper way.

Geometry is the main parameter it plays a crucial role in this process and the second important parameter is the area of contact between two bodies or lubrication.