Regenerative Chatter in High-Speed Tandem Rolling Mills

2006 ◽  
Author(s):  
Huyue Zhao ◽  
Kornel F. Ehmann
Keyword(s):  
Mode Coupling ◽  
High Speed ◽  
Process Model ◽  
Structural Model ◽  
Rolling Process ◽  
Space Representation ◽  
Regenerative Chatter ◽  
State Space Representation ◽  
Negative Damping ◽  
Delay Differential

Third-octave-mode chatter, the most detrimental form of rolling chatter, is generated by means of negative damping, mode coupling, and regeneration. While mechanisms that include negative damping, and mode coupling have been thoroughly investigated, those associated with the regenerative effect remain elusive. In this paper, the mechanisms that may lead to regenerative chatter are studied through a state-space representation of a multi-stand mill that is constructed by coupling a homogenous dynamic rolling process model with a structural model for the mill stands in a high-speed tandem mill configuration. Stability analysis, by using the integral criterion for the stability of systems described by delay differential equations, is carried out for the regenerative mechanism in order to better understand the effects of rolling parameters on a single stand as well as the overall system. Preliminary simulation results, based on the proposed chatter model, are presented to demonstrate the feasibility and the accuracy of the chatter model, as well as to investigate chatter phenomena too complex to be studied analytically.

Stability Analysis of Chatter in Tandem Rolling Mills—Part 1: Single- and Multi-Stand Negative Damping Effect

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Huyue Zhao ◽  
Kornel F. Ehmann
Keyword(s):  
State Space ◽  
Process Model ◽  
Structural Model ◽  
Rolling Process ◽  
Space Representation ◽  
Mathematical Form ◽  
Stability Criteria ◽  
Model Stability ◽  
State Space Representation ◽  
Negative Damping

Many different modes of chatter in rolling and their possible causes have been identified after years of research, yet no clear and definite theory of their mechanics has been fully established and accepted. In this two-part paper, stability of tandem mills is investigated. In Part 1, state-space models of single- and multi-stand chatter are formulated in a rigorous and comprehensive mathematical form. Then, the stability of the rolling system is investigated in the sense of the single- and multi-stand negative damping effects. First, a single-stand chatter model in state-space representation is proposed by coupling a dynamic rolling process model with a structural model for the mill stand. Subsequently, a multi-stand chatter model is developed by incorporating the inter-stand tension variations and the time delay effect of the strip transportation based on the single-stand chatter model. Stability criteria are proposed and stability analyses are performed to create corresponding stability charts in terms of the single- and multi-stand negative damping mechanism through numerical simulations. Particularly, the effect of friction conditions on chatter is examined and an explanation is given for the existence of an optimum friction condition. In Part 2, the regenerative effect and resulting instabilities are examined. Suitable stability criteria for each mechanism are established and stability charts are demonstrated in terms of relevant rolling process parameters.

Single- and Multi-Stand Chatter Models in Tandem Rolling Mills

2008 ◽  
Author(s):  
Huyue Zhao ◽  
F. Ehmann Kornel
Keyword(s):  
Stability Analysis ◽  
State Space ◽  
Process Model ◽  
Structural Model ◽  
Work Roll ◽  
Rolling Process ◽  
Complete Analysis ◽  
Space Representation ◽  
Mathematical Form ◽  
State Space Representation

Many different modes of chatter and their possible causes have been identified after years of research, yet no clear and definite theory of their mechanics has been established. One of the most important reasons for this can be attributed to the fact that only oversimplified models with a single input and a single output were historically used to formulate chatter in rolling. Such a situation has hindered a complete analysis of the underlying mechanisms. In this paper, a state-space representation of single- and multi-stand chatter models will be proposed in a rigorous and comprehensive mathematical form for stability analysis of the various chatter mechanisms. First, a dynamic model of the rolling process that utilizes homogeneous deformation theory will be established that includes the material strain-hardening and work roll flattening effects. By coupling this dynamic rolling process model with a structural model for mill stands, a single-stand chatter model in a state-space representation will be proposed. Based on the single-stand chatter model, a multi-stand chatter model will be formulated by incorporating the inter-stand tension variations and the time delay effect of the strip transportation. A simulation program will also be presented for the study of the dynamic rolling process in the time domain and for verifying the results from stability analysis.

On the Effect and Analysis of Fluid-Structural Mode Coupling

2020 ◽  
Author(s):  
Mani Sadeghi ◽  
Ming-Ta Yang ◽  
Huan-Min Shang ◽  
Eric Grover
Keyword(s):  
Mode Coupling ◽  
Vital Role ◽  
Forced Response ◽  
Space Representation ◽  
Aerodynamic Forces ◽  
Analysis Techniques ◽  
State Space Representation ◽  
Linear Dynamic ◽  
The Impact ◽  
Structural Mode

Abstract The consideration of aeromechanics plays a vital role in the design of machines that operate under aerodynamic forces, such as turbomachinery, and aircraft. The structure of those machines is subject to aeromechanical dynamics, including forced response and flutter. The strength of aeromechanical interaction depends on the level of coupling between flow and structure. One effect that can lead to strong coupling is the interaction between eigenmodes of the structure and eigenmodes of the flow near coincidence. This paper examines the impact of modal coincidence on the linear dynamic stability of aeromechanical systems for two illustrative canonical examples, one governed by inviscid acoustics, and one by the eigenmode of a wake. Three commonly used analysis techniques are applied and ranked for various levels of coupling: The 1-way coupled work-per-cycle method, a 2-way coupled non-linear modal FSI analysis in time, and an eigenanalysis of the 2-way coupled linear system, based on a state-space representation. It is demonstrated that all three methods agree for low to moderate levels of 2-way coupling, typical in turbomachinery applications. At higher levels, the work-per-cycle assessment is insufficient, whereas the FSI and eigenvalue analysis agree well.

Stability analysis of the rolling process and regenerative chatter on 2030 tandem mills

2002 ◽  
Vol 216 (12) ◽  
pp. 1225-1235 ◽  
Author(s):  
Y Chen ◽  
S Liu ◽  
T Shi ◽  
S Yang ◽  
G Liao
Keyword(s):  
Stability Analysis ◽  
Rolling Mill ◽  
Rolling Process ◽  
Delay Effect ◽  
Regenerative Chatter ◽  
Vibration Model ◽  
Negative Damping ◽  
Time Delay Effect ◽  
Chatter Marks

Chatter in the rolling stack of high-velocity tandem mills and temper mills is a widespread problem and affects the quality of the finished product and the productivity of the rolling mill. One factor that clearly plays an important role in causing mill vibration is the inherent gap between the roll chocks and mill housings. In order to control chatter in cold rolling operations, a much deeper understanding of the basic mechanics of the problem is required. Therefore, this paper proposes a rolled piece vibration model for comprehending instability of the strip due to the variation of the friction coefficient in the roll bite. Subsequently, owing to the time delay effect of the chatter marks between the immediate stands, a regenerative chatter model is developed and stability analysis of the regenerative chatter model due to negative damping is presented. Finally, for a more detailed understanding of the regenerative chatter phenomena, a simulator is developed and industrial investigations are carried out in practice. It follows from the numerical simulations and industrial investigations that regenerative chatter is a more serious vibration phenomenon than simple chatter.

Chatter in the Strip Rolling Process, Part 3: Chatter Model

1998 ◽  
Vol 120 (2) ◽  
pp. 343-348 ◽  
Author(s):  
I-S. Yun ◽  
K. F. Ehmann ◽  
W. R. D. Wilson
Keyword(s):  
Mode Coupling ◽  
Metal Cutting ◽  
Dynamic Instability ◽  
Rolling Process ◽  
Central Problem ◽  
Strip Rolling ◽  
Basic Understanding ◽  
Negative Damping

The central problem of the analysis and prevention of chatter in rolling operations is in understanding the conditions which lead to dynamic instability. By analogy with metal cutting operations, it appears that a few basic mechanisms may be responsible for the occurrence of self-excited vibrations in rolling. The three most significant mechanisms are: negative damping, mode-coupling and regeneration. In this paper, negative damping and mode-coupling are considered separately in an “artificial” manner to make inroads toward a better basic understanding of rolling instability.

Wavelet-Based Damage Detection of Multi-Degree-of-Freedom Structures

2004 ◽  
Author(s):  
Yuito Hashimoto ◽  
Arata Masuda ◽  
Akira Sone
Keyword(s):  
Wavelet Transform ◽  
Damage Detection ◽  
Structural Model ◽  
Structural Parameters ◽  
Degree Of Freedom ◽  
Space Representation ◽  
State Space Representation ◽  
Damage Location ◽  
Propagation Of Singularities ◽  
Structural Responses

In this paper, a method is proposed to identify the occurrence and the location of damage from the responses of multi-degree-of-freedom (MDOF) structures based on the wavelet transform, which has the capacity to detect discontinuities and singularities. First, the propagation of singularities in responses is investigated qualitatively in order to explain how the structural responses are influenced by sudden changes of structural parameters (stiffness) resulting from damages. Next, in order to confirm the proposed method for complicated models, we evaluate the influence of sudden changes of structural parameters on responses quantitatively, and the relations between the wavelet transform and the damage location by the aid of the state space representation of the MDOF structures. Finally, laboratory-scale experiments are carried out to verify the performance and detectability of the proposed methods in a fourth story structural model installed by additional stiffness members.

Prediction of Surface Quality due to Chatter Vibration in Rolling of Thin Steel Strip Using ALE Finite Element Method

2011 ◽  
Vol 473 ◽  
pp. 572-578 ◽  
Author(s):  
Mohammad Reza Niroomand ◽  
Mohammad Reza Forouzan ◽  
Mahmoud Salimi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
High Speed ◽  
Steel Strip ◽  
Rolling Process ◽  
Arbitrary Lagrangian Eulerian ◽  
Computational Region ◽  
Thin Steel ◽  
Negative Damping ◽  
Element Method

Chatter is one of the most encountered vibration problems in high-speed rolling of thin steel sheets in tandem mills. Due to its negative cause on product quality and maintenance costs, chatter is a technical and economical problem in rolling mills. To study chatter in rolling, it is necessary to set up models for the rolling process as well as the mill stand. Existing models of rolling process are analytic and are based on many simplifying assumptions. In current work the finite element method is utilized for the first time to model the chatter vibrations in rolling, which relaxes many of these assumptions. The model has the benefit of mass translation to the computational region by using Arbitrary Lagrangian Eulerian (ALE) technique, which tremendously reduces huge computational requirements of common Lagrangian models. Four chatter mechanisms in rolling are reviewed in this paper, but the presented model is updated for simulating the negative damping effect by means of some online velocity sensors and signal filtering method in applying the ALE boundary conditions. Using this new model, single stand negative damping mechanism of chatter and its effect on the sheet surface is understood more accurately. Simulation results are in comprehensive agreement with the experimental and industrial observations.

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