2。5。Elasto-hydrodynamic model for connecting rod

of every mesh point

2。3。  Asperity contact model

We use the Greenwood & Tripp approach [23], the theory of Greenwood & Tripp is based on the contact of two nominally flat, random roughness surfaces。 The resulting asperity contact pressure is the product of elastic factor and function F5/2(H), asperity contact pressure is written as:

In order to add the deformation to the oil film thickness, the con- necting rod structure needs to be flexible。 Fig。 3 is the flexible and solid connecting rod model and bearing substructure。 The finite ele- ment mesh is very limited for the calculation。 The big-end bearing and small-end bushing are meshed with hexahedron, in this paper, the density of the finite difference mesh is 19 × 121, and the density

F5/2(H) is the switch function whether the asperity happens。 The function F5/2(H) is written as:

。 4。486 × 10−5(4 − h/o)6。804   h/o < 4

where E∗ denotes the composite elastic modulus, E∗ = ((1 − v12)/E1 + (1 − v22)/E2)−1, where vi and Ei are the Poisson ratio and Young’s modulus of the adjacent surfaces, respectively。 ys is the asperity density, ˇ is the radius of curvature of convex peak,

H is the dimensionless clearance parameter, H = H/o。 ysˇo is in the region of 0。03–0。05, o/ˇ is always in the region of 10−4–10−2。

Fig。 3。   Flexible and solid model connecting rod and bearing substructure。

Fig。 4。   Mapping process with interpolation algorithm。

of the finite element mesh is 9 × 44, then the     two-dimensional

-50

0 90 180 270 360 450 540 630 720

Crank angle/°CA

Fig。 5。  Load variations at 2200 rpm。

Table 2

Orthogonal experiment。

Influence factor Level 1(1)    Level 2(2)    Level 3(3)    Level  4(4) A    Oil hole location (◦ ) 30 60 – –

B     Modulus of bush (Gpa) 180 190 200 210

interpolation with transform matrix (as shown in Fig。 4) to realize

this function。

2。6。Engine descriptions

The engine general specifications are given in Table 1。 The deformation of the big-end bearing has great relationship with its

C

Oil supply pressure

(MPa)

DRoughness of bearing (µm)

ERoughness of journal (µm)

FJournal oil hole

diameter (mm)

0。3 0。5 0。7 0。9

0。6 0。8 1。0 1。2

0。4 0。6 0。8 1。0

4 6 8 10