ˇ∗ = arctan (εz/εx) [22]。

2。2。Lubrication characteristics evolution indexes

2。2。1。Oil leakage

The lubricant flow-rate Q1 from the front-end plane of the bear- ing and the lubricant flow-rate Q2 from rear end plane of the bearing are given by:

displacement of composite soil-nailing wall。 Chang [15] presents a systematic  and

cost-effective approach for process optimization with minimal experimental runs, all the optimization is based on neural network model and orthogonal arrays, and the proposed approach provides an effective and economical solution for process

optimization。

From the literatures review, many researchers focused on the effect of param-

eters on lubrication, the dynamic lubrication characteristics or lubrication model。 The purpose of this study is to numerically and roughly quantify the impact of each variable on the power loss, the flow rate, the MOFT and the MOFP。 The knowledge required for this particular task implies a good understanding of the connecting rod。 The orthogonal experiment is designed to do the research about the lubrica- tion, parameters which response to the oil film thickness, the oil film pressure, the oil leakage and the friction loss are gained, the regression method is used to estab- lish the prediction model which can bridge the gap between the recent numerical simulations and the need for a better understanding of the connecting rod bearing functioning。 Considering the asperity contact can cause the friction loss to increase and the bearing to be failure earlier, the SVM technology is carried out to the asperity contact identification, which can help us to avoid asperity contact in the design。

12y ·  ∂y 。

0 0 。y=L

where Q1 is the flow-rate from the front-end plane of the bearing,

Q2 is flow-rate from rear end of the bearing。

The total end leakage flow rate of lubricant is then calculated by:

Q  = Q1 + Q2 (5)

Q is the total end leakage flow rate of lubricant。

Fig。 1。   Connecting rod。

Fig。 2。  Bearing failure modes [19]。

2。2。2。Friction loss

The friction loss is partitioned into hydrodynamic friction loss and asperity contact friction loss。 The frictional force on the journal surface can be computed by:

¸ ¸

f = (ıa  + ıh)dA (6)

where ıa is the asperity contact shear force, ıh is the fluid shear force。

The friction power is the sum of the friction force that multiplies with its velocity at every time step and it is written as:

n

2。4。

Asperity contact for connecting rod description

Connecting rod consists of rod, cap, bolts, big-end bearing and small-end bushing。 In this paper, the lubrication performances of the big-end bearing are analyzed, according realistic structure of the big-end bearing, there is no oil groove in the bearing, the oil supplied by the oil hole located in the crank-pin, so the effect of the oil groove on the lubrication performances is neglected, but the special oil groove in small-end bushing, in the future work, we will do the insight research to the groove, more detail results will be gained (Fig。 1)。

According to the Ref。 [24], there are many failure modes which exist in the connecting rod lubrication and dynamic motion, three

figures in the below (as shown in Fig。 2) are very typical   failure

mode, the asperity contact appears in the bearing。

i=1

where fi  is the friction force of every mesh point, u∗  is the velocity