where  E is the bearing pitch diameter  and ν is the l ubricant viscosity  in centistokes . 

A recent review of the literature revealed that there are new models of viscous drag that take into account  significant progress in the understanding of EHD film formation that occurred during the late 1970’s [ 9]. A  review of these models is underway, but beyond the scope of this paper .    All the values required for  calculation of the torques and heat generation are known from bearing  geometries, materials properties, operational conditions, and temperature measurem ents, except for the  LQF. Thus, we use Equations 1 through 3 to determine Q int, and 4 through 6 to solve for LQF . Using this  method, we conducted a series of parametric studies to explore the impact of various factors on LQF . The  effect of operational conditions such as average temperature , temperature gradient,  and axial load , for  instance, was separated using a test matrix . The method of separating variables using this test matrix will  be explained next.    A test matrix is cre ated of LQF for various thermal and mechanical conditions . Separation of each variable’s  influence can be ascertained by maintaining one operational condition const ant while changing the other .  For instance, axial load is held constant through a series of tests, where  either the heat input (heat lamp  voltage) or heat sink temperatures (Outer Heat Meter chiller setting) settings are changed. Measurements  are made at steady state conditions . Once a matrix of thermal boundary conditions are tested at a given  axial load, the load itself is changed and measurements are taken for a matrix of thermal boundary conditions for the new mechanical state. Since the precise bearing temperature is not controlled, we use  linear interpolation to ascertain the value of LQF for a precise temperature. All tests are taken for a bearing  with an inner race rotating at a constant 6000 rpm.    All the LQF values are normalized by dividing the value by the maximum measured value of LQF (designated as LQFn) measured for a 305- sized all -steel bearing .  

 𝑛𝑛𝑛𝑛𝑟𝑟 𝑟𝑟𝑛𝑛𝑛𝑛𝑛𝑛𝑛𝑛 𝑛𝑛𝑛𝑛 𝐿𝐿𝑄𝑄𝐿𝐿=𝐿𝐿𝑄𝑄𝐿𝐿/𝐿𝐿𝑄𝑄𝐿𝐿𝑛𝑛 (7)  Test Bearing Specifications   Two different angular contact bearings were used in the experiments shown below . The primary difference  between the two bearings was the material composition of t he balls, which were 52100 steel in the first set  of experiments, and Silicon Nitride in the second. Pennzane 2001 oil  was used in all test data collected .  This is a fully synthetic multipl e-alkylated cyclopentane (MAC), formulated with a phosphate wear inhibiting  additive and anti -oxidants . Both bearings were manufactured by Barden. Specifications of both bearings  are provided in Table 1.  

Table 1. Test Bearing Specifications   Description  305 size all -steel  305 size hybrid   Bore size 25 mm  25 mm   Outer diameter  62 mm  62 mm   Width  17 mm  17 mm   Number of balls  10 10  Ball size  11.91 mm (15/32 inch)  11.91 mm (15/32 inch)   Contact angle  15 degree  15 degree   Ball material  52100 steel  52100 steel   Race material  52100 steel  Silicon Nitride   ABEC rating  7 7  Manufacturer  Barden  Barden   Lubricant  Formulated MAC  Formulated MAC  

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