连杆疲劳试验标准Connecting Rod

Connecting Rod Fatigue Test Procedure Chery NEF1–1,6L4V CBR VVT

Written by Approved by

Benjamin West Claus Knorz

Mech.Development Manager Mech.Development

1Objective

The main objective of this test is to assess the fatigue strength of a conrod.The test is carried out on a dedicated fatigue test machine,which is usually hydraulically driven and simulates the relevant loads on the conrod of a running engine.

The fatigue tests are regarded mainly as a verification of the production process of the components.Therefore the specimen should be ideally full production level.In an early phase of an engine development program it might be useful to perform a preliminary test program with prototype components.

The fatigue test will also be used to assess:

•The level of fretting at the split face between conrod and cap and between bearings/bushes and the parent bores occurring throughout a test of4million cycles

•load limits regarding buckling or yield

2Test Preparation

The tests are carried out on a dedicated fatigue test machine.

The connecting rods are tested purely under tensile-compression forces.

The test loads are applied through dummy pins that replace the original

supply of5bar is necessary for both bearings in order to avoid fretting or

It is important to prevent excessive heat build up in the

applied to the specimen to ensure that the

Generally

range of

It is normally Crack Detection Methods),if the same checks will

2.1

One specimen consists of the conrod including the bearing cap,the fitted small end bush,the big end bearing shells and the fasteners.

The clearances between the dummy pins and both bearings should be as shown below

Large end bearing diametric clearance10-20microns

Small end bearing diametric clearance20-30microns

Small end diametric clearance(large end test)-20to-40microns(without small end bearing)

The test loads for the conrod big end are at a higher tensile force level than permitted for the small end with the standard bearing clearance.This reduces the bending forces associated with the oval deformation of the small end under tensile forces and improves stiffness and strength.The dummy pin in this instance would have an interference fit in the small end parent bore(without small end bush).

Tolerances regarding the interference between the bearing shells/bush and the parent bores have an influence on the fatigue strength.Ideally the parts should be selected in order to achieve a maximum interference according to drawing tolerances at large end and small end

The bearing cap bolts should be tightened to the specification stated in drawing00001446AA