Investigation on the effects of process Parameters for fatigue life improvement Using turn-assisted deep cold rolling process

Prabhu, Raghavendra P (2014) Investigation on the effects of process Parameters for fatigue life improvement Using turn-assisted deep cold rolling process. Phd. Thesis thesis, Manipal Institute of Technology, Manipal.

[img] Archive (ZIP) - Published Version
Restricted to Registered users only

Download (9MB) | Request a copy


Mechanical surface enhancement (MSE) techniques have been used successfully over the years to increase the fatigue life of metallic components. These techniques impart compressive residual stresses on component surfaces to counter, damage-inducing tensile stresses experienced under service loading. Deep cold rolling (DCR) is one of the mechanical surface enhancement techniques used predominantly in the automobile industry to achieve better component lives. Despite its wide application, the process is done with special purpose high cost machines. Also DCR process is not explored because the process has many parameters governing the fatigue life of components. Development of a simplified DCR process with parameters optimized to achieve fair levels of multiple responses is a need of the hour for industry and is attempted in the present work. This present research aims to study the effects of a simple turn-assisted deep cold rolling process on parts of AISI 4140 steel, which is commonly used in automobile industry with design of experiments and response surface methodology. In the preliminary study, two tools are developed which could be mounted on a lathe to implement DCR for turned parts. The tool and the set-up combination are expected to impart compressive residual stresses on the part surface and improve fatigue life and is termed “turn-assisted deep cold rolling” (TADCR). At the end of preliminary study, the set-up is improvised by providing a back rest to reduce bending of the part. Initially, screening experiments conducted at 2 levels of seven different process parameters for surface compressive stress, surface hardness and surface finish indicate that four factors rolling force, ball diameter, initial roughness of the workpiece and number of tool passes have significant effect on the TADCR process. The effect of these process parameters on residual compressive stress which is responsible for enhancing fatigue life is studied alternately with finite element model of TADCR process. The results of residual compressive stress values obtained experimentally after TADCR and the results of finite element analysis supported the existence of surface compressive stress and the distribution of this stress from both analyses is found to be similar. Variation of residual compressive stress observed along the depth registers a maximum residual compressive stress of 569 MPa at a depth of 300 μm from surface. Also, it could be noted from both results that, a higher deep cold rolling force drives residual compressive stresses to a greater magnitude and depth. Thus, development of a residual compressive stress of favorable magnitude and distribution for improvement in fatigue life is obtained with these approaches and the same could be visualized as gain elongation with study of microstructure.

Item Type: Thesis (Phd. Thesis)
Subjects: Engineering > MIT Manipal > Mechanical and Manufacturing
Depositing User: MIT Library
Date Deposited: 28 Jun 2016 14:50
Last Modified: 28 Jun 2016 14:50

Actions (login required)

View Item View Item