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On the supply chain of automotive body market, the steel industry has played a major role as a material supplier. After the early 1990s, new technologies such as TWB(tailor welded blanks) and hydroforming have been adopted in manufacturing processes of automotive body have made a great influence on changing the traditional roles of steel and automotive industries. This paper is concerned with the role transfer of steel making companies on the supply chain management for automotive body, based on the rapid variation of managerial environment for these industries.

In order to predict and understand the slippage between the cam and roller follower, the Cummins L-10 engine valve train was modeled. A mixed lubrication model was developed to investigate the friction and oil film thickness since the valve train is operated in very severe conditions. First, the roller follower pin friction was studied because it is a significant friction source for a valve train with a roller follower.(13) Using similarity analysis of the roller pin friction from the experimental data, the correlation between the friction coefficient and the Sommerfeld variable was obtained. Second, the interface friction between the cam and roller follower was studied. Oil film thickness and the asperity load were obtained based on the mixed lubrication model. Finally, the total friction force at each cam angle was calculated and roller slippage was predicted by comparing the tractive force and the friction force.

The valve train was instrumented to record the instantaneous roller speed, roller pin friction torque, pushrod forces, and cam speed. Results are presented for one exhaust valve of a motored Cummins L-10 engine. The instantaneous cam/roller friction force was determined from the instantaneous roller speed and the pin friction torque. The pushrod force and displacement were also measured. Friction work loss was determined for both cam and roller interface as well as the upper valve train which includes the valve pushrod, rocker arm, valve guide, and valve. Roller follower slippage on the cam was also determined. A kinematic analysis with the measured data provided the normal force and contact stress at cam/roller interface.(1) Finally, the valve train friction was found to be in the mixed lubrication regime.(2) Further efforts will address the theoretical analysis of valve train friction to predict roller slippage.