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Moire Analysis of Planar Elastic Contact for Understanding Wheel-Rail Traction.

PB270639

Publication Date	1977
Personal Author	Matic, P.; Kumar, S.
Page Count	41
Abstract	The nature of adhesion and creep in the contact region between two planar surfaces with normal and tangential loads is experimentally investigated with moire analysis. This study is aimed at advancing the understanding of adhesion and creep in the contact zone between a steel wheel and rail. The contact region between a silicon block (width 2.4 in., and height 1.6 in.) and a thick plexiglass plate investigated. Loads of 0.33 lbs to 5.01 lbs were applied at angles of 0 degrees to 11.1 degrees from the vertical. Gratings of 300 and 302 lines/inch were placed on the contacting surfaces of the plate and block respectively. Movement of the moire fringes yielded the displacement fields. Analysis of the displacement fields for four loads at four different inclination angles shows that the adhesion zone appears as a region of restrained displacements. It is believed that ideal adhesion (i.e. zero displacements) is possible only for optically flat surfaces, and that surface roughness, as was present in this investigation, is responsible for restrained displacements in the adhesion zone. For only vertical loads, the adhesion zone was in the middle of the contact surface and creep zones were symmetrically placed on two sides. Under increasing load the adhesion zone decreases in size. This is as predicted by theory and the finite element method. Under inclined loads, the adhesion zone moves opposite the direction of horizontal components of loading. The adhesion zone will eventually move to the edge of the contact zone when there is a large enough tangential load. The experimental results were compared with a finite element analysis conducted at I.I.T. earlier and showed good agreement.
Keywords	Railroad tracks Wheels Traction Displacement Surface roughness Adhesion Finite element analysis Loads(Forces) Rail wheel interactions
Source Agency	Federal Railroad Administration Office of the Secretary
NTIS Subject Category	85C - Metropolitan Rail Transportation 85I - Railroad Transportation
Corporate Authors	Illinois Inst. of Tech., Chicago, Dept. of Mechanics, Mechanical and Aerospace Engineering.; Association of American Railroads, Chicago, Ill.; Federal Railroad Administration, Washington, D.C.; General Motors Corp., La Grange, Ill. Electro-Motive Div.
Supplemental Notes	Prepared in cooperation with General Motors Corp., La Grange, Ill. Electro-Motive Div., and Association of American Railroads, Chicago, Ill.
Document Type	Technical Report
Title Note	Interim technical rept. no. 6.
NTIS Issue Number	197723
Contract Number	DOT-OS-40103

Moire Analysis of Planar Elastic Contact for Understanding Wheel-Rail Traction.

Moire Analysis of Planar Elastic Contact for Understanding Wheel-Rail Traction.
PB270639

Publication Date	1977
Personal Author	Matic, P.; Kumar, S.
Page Count	41
Abstract	The nature of adhesion and creep in the contact region between two planar surfaces with normal and tangential loads is experimentally investigated with moire analysis. This study is aimed at advancing the understanding of adhesion and creep in the contact zone between a steel wheel and rail. The contact region between a silicon block (width 2.4 in., and height 1.6 in.) and a thick plexiglass plate investigated. Loads of 0.33 lbs to 5.01 lbs were applied at angles of 0 degrees to 11.1 degrees from the vertical. Gratings of 300 and 302 lines/inch were placed on the contacting surfaces of the plate and block respectively. Movement of the moire fringes yielded the displacement fields. Analysis of the displacement fields for four loads at four different inclination angles shows that the adhesion zone appears as a region of restrained displacements. It is believed that ideal adhesion (i.e. zero displacements) is possible only for optically flat surfaces, and that surface roughness, as was present in this investigation, is responsible for restrained displacements in the adhesion zone. For only vertical loads, the adhesion zone was in the middle of the contact surface and creep zones were symmetrically placed on two sides. Under increasing load the adhesion zone decreases in size. This is as predicted by theory and the finite element method. Under inclined loads, the adhesion zone moves opposite the direction of horizontal components of loading. The adhesion zone will eventually move to the edge of the contact zone when there is a large enough tangential load. The experimental results were compared with a finite element analysis conducted at I.I.T. earlier and showed good agreement.
Keywords	Railroad tracks Wheels Traction Displacement Surface roughness Adhesion Finite element analysis Loads(Forces) Rail wheel interactions
Source Agency	Federal Railroad Administration Office of the Secretary
NTIS Subject Category	85C - Metropolitan Rail Transportation 85I - Railroad Transportation
Corporate Authors	Illinois Inst. of Tech., Chicago, Dept. of Mechanics, Mechanical and Aerospace Engineering.; Association of American Railroads, Chicago, Ill.; Federal Railroad Administration, Washington, D.C.; General Motors Corp., La Grange, Ill. Electro-Motive Div.
Supplemental Notes	Prepared in cooperation with General Motors Corp., La Grange, Ill. Electro-Motive Div., and Association of American Railroads, Chicago, Ill.
Document Type	Technical Report
Title Note	Interim technical rept. no. 6.
NTIS Issue Number	197723
Contract Number	DOT-OS-40103