Browse Prior Art Database

METHOD FOR IMPROVING FATIGUE AND FRETTING STRENGTH OF SERRATED SURFACES IN AN ENGINE CONNECTING ROD

IP.com Disclosure Number: IPCOM000246317D
Publication Date: 2016-May-27
Document File: 3 page(s) / 84K

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention proposes a method for improving fatigue and fretting strength of serrated surfaces in a reciprocating engine connecting rod by laser shock peening. The laser shock peening method is used to impart compressive stress into the serrated region of the engine connecting rod. The laser beam bombards the processed surface and generates shock waves that propagate into the material. The intensity of the laser beam is configured so that this shock wave is above the dynamic yield strength of the material, which yields and plastically deforms, generating compressive stresses. Compressive residual stresses introduced in the serrated region of the connecting rod increase the fatigue life and reduce fretting damage during service. The laser shock peening method could be precise in regards to size of processed spot, and intensity could be controlled in case of small surfaces to be processed.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 51% of the total text.

Page 01 of 3

METHOD FOR IMPROVING FATIGUE AND FRETTING STRENGTH OF SERRATED SURFACES IN AN ENGINE CONNECTING ROD

BACKGROUND

The invention is in general related to material and process engineering and in particular to a method for improving fatigue and fretting strength of reciprocating engine components. During testing of connecting rod component in the engine, it is observed that serration design is sensitive to uneven loading. This creates a possibility of fretting and inducing fatigue cracking leading to failure of the rod. Generally, shot peening at critical locations is used to improve fatigue fretting resistance of components. This method is difficult to apply on small parts, or on recessed surfaces. Furthermore, this method provides poor control of the process. It is also necessary to mask the remaining portion of the part that need not be treated. Thus, there is a need for an improved method of improving fatigue and fretting strength of components such as engine connecting rod. A typical connecting rod of a reciprocating engine is shown in FIG. 1, where the larger end in two halves encloses the crankshaft through a bearing. The bottom end bearing cap is attached to the lower shell by bolts. The faying surfaces of the bearing cap and the upper shell are serrated to prevent relative movement. The invention proposes use of laser shock peening for local hardening of the serrated surfaces as indicated in Detail A.

FIG. 1: Serrated section of the engine connecting rod

BRIEF DESCRIPTION OF DRAWINGS

The invention discloses a method for improving fatigue and fretting strength of serrated surfaces in reciprocating engine connecting rod, wherein:

FIG. 1 shows serrated surfaces of the engine connecting rod.

 


Page 02 of 3

DETAILED DESCRIPTION

The invention proposes a method for improving fatigue and fretting strength of serrated surfaces in a reciprocating engine connecting rod by laser shock peening (LSP). The laser shock peening method is used to impart compressive stress into the serrated region A of the heavy loaded reciprocating engine connecting rod, as indicated in FIG. 1. The laser beam bombards the processed surface and generates shock wave creates local material distortion and introduce compressive stress preventing fatigue crack propagation. Additionally, slightly distorted surface slow down the occurrence of fretting phenomenon observed on the working mating surfaces.

The area to be treated on a part - in this case the serrated surface - is locally covered with two types of overlays: an opaque overlay and over this a transparent overlay. The opaque overlay could be any material opaque to the laser beam, for example, a black coating is commonly used. The transparent overlay can be any material tran...