Fatigue Analysis of CVC Type Rolling Mill Rolls

Authors: Yukio Shigaki (CEFET – MG)

Eduardo Araujo (ESSS)

PRESENTATION TOPICS

• Introduction

• Description of the Problem

• Methodology

• Conclusion and Next Steps

Introduction

The Federal Centers of Technological

Education (Portuguese: "Centro Federal de Educação

Tecnológica", shortened CEFET) are Brazilian educational

institutes which are directly linked to the Ministry of

Education. They are focused on high school, technical high

school and academic degrees linked to technology.

Introduction

This work is part of a research program in progress by CEFET-MG – by

the Applied Computational Mechanics Research Group (MeCA)

Description of Problem

• Motivation: More investment and more development

in efficient manufacturing equipment has been done

due to the increasing demand from different

industries for flat steel production, as well as, other

rolled products.

• Among other aspects, one expects to have a steel

strip with uniform thickness, as well as, a

transversal uniform profile along the length of the

strip.

Description of the Problem

Description of the problem

• New types of rolling mills have been

developed to guarantee flatness and

thickness of the product.

• Among them, the CVC (Continously Variable

Crown) rolling rolls were developed by SMS

Siemag.

Description of the problem

• Crown of the plate/strip Cj:

C hh h

j c

j j

( )' ' '

2

hc: thickness of the strip at center

hj: thichnesses of the strip at position j

Description of the Problem

Description of the problem

• Out of flatness:

Description of the problem

Support rolls bi-directional axial

displacement

Intermmediate rolls bi-directional

axial displacement

Working rolls bi-directional axial

displacement

Description of the problem

• Simulation may be used to study the behavior

of different aspects of working of equipment.

• This work presents a stress analysis and

fatigue life estimation of working rolling roll.

Methodology: Finite Element Method

Methodology: Finite Element Method

Methodology: Finite Element Method

Working Roll Length (desk) 1.950 mm

Intermediate Roll Length 1.500 mm

Intermediate Roll Diameter 300 mm

Support Roll Diameter 800 mm

Table 1 – Dimensions of rolls

Methodology : Loading Function

Equation of Loading

Bland-Ford solution

Loading p depends on the reduction of thickness of

strip, roll diameter , material and friction .

Methodology: Iterative Method

• i – One applies a uniformily distributed loading on the working roll;

• ii – Vertical displacement are extracted from the central contact line

between working roll and strip;

• iii – Based on this results, the strip profile is generated;

• iv – Assuming a tolerance and a previous iteration, the generated

profile (iii) is compared with a previous obtained profile. In case they

are equal or differences are within tolerance, a solution is achieved.

Otherwise proceed to item v;

• v – One may obtain the thickness reduction in the strip with the

profile calculated in (iii);

• vi – Re-calculate rolling loading with this new thickness reduction

profile;

• vii – Aplply these loadings (item vi) on the finite element model and

proceed to item ii;

Methodology: Iterative Method

• Current model and loading were obtained from

[1].

• 3 iterations were performed to achieve results.

• Ansys 14.5 was used to perform the stress

analysis.

• Reduction applied: 4.5 to 3.0 mm

• Width of the strip: 1500 mm

• Material of the strip: mild steel

Methodology: Iterative Method

Methodology: Iterative Method Iteration 1: Vertical displacement on contact center line

Methodology: Iterative Method Iteration 2: Vertical displacement on contact center line

Methodology: Iterative Method Iteration 3: Vertical displacement on contact center line

Methodology: Iterative Method Iteration 3: Equivalent Stresses

Methodology: Iterative Method Iteration 3: Equivalent Stress of Working Roll

Methodology: Iterative Method Iteration 3: Y Displacements

Methodology: Iterative Method

Fast convergence of the model:

Fatigue Analysis

• A Fatigue analysis was performed regarding:

– Stresses and Strain from structural analysis 3rd

Interaction

– Material of the rolls: steel with UTS 400 MPa (steel)

– Geometry: BUR_roll and CVC_roll were included in the

analysis

– Loading: constant amplitude loading. It corresponds to

one complete rotation of the roll.

– S-N method was used to estimate life

S-N Curve

UTS 400 MPa

Extracted from nCode

Material Library

E-N Curve

UTS 400 MPa

Extracted from nCode

Material Library

Fatigue Analysis : Ansys Design Life Model

Fatigue Analysis: Estimated Life

Fatigue Analysis: Estimated Life

Conclusions and Next Step

• Estimated Life is Infinite

• Next steps:

– One can include a notch or a chamfer in the roll .

The presence of a notch will reduce the life of the

roll.

– Apply other shifts on the work roll

– Compare with industrial results

References

• [1] Yukio Shigaki DESENVOLVIMENTO DE UM MODELO

MATEMÁTICO-NUMÉRICO PARA SIMULAÇÃO DE LAMINADORES DE

PRODUTOS PLANOS COM CILINDROS COM PERFIS CVC

Presentation performed on 49º Rolling Seminar – Processes, Rolled and

Coated Products (2012)

• [2] nCode - DesignLife Worked Examples:

3 AN-NC-DL-WE 14.50.083 © 2012 HBM UK Ltd

• [3] Ginzburg,V. Azzam, M. Selection of optimum strip profile

and flatness technology for rolling mills

1. Ansys Mechanical 14.5

2. Design Life - GlyphWorks V8.0 ISR3 Release Build 125

Used Software

Aknowledgment

The authors thank the support from

CEFET-MG and ESSS.

OBRIGADO!!

THANK YOU