REMOTE IDENTIFICATION OF IMPACT FORCES ON LOOSELY SUPPORTED TUBES: PART 1—BASIC THEORY AND EXPERIMENTS

1998 ◽  
Vol 215 (5) ◽  
pp. 1015-1041 ◽  
Author(s):  
M. De Araújo ◽  
J. Antunes ◽  
P. Piteau
Keyword(s):  
Basic Theory ◽  
Impact Forces ◽  
Remote Identification ◽  
Theory And Experiments

Modal Techniques for Remote Identification of Nonlinear Reactions at Gap-Supported Tubes Under Turbulent Excitation

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Xavier Delaune ◽  
José Antunes ◽  
Vincent Debut ◽  
Philippe Piteau ◽  
Laurent Borsoi
Keyword(s):  
Transfer Functions ◽  
Contact Forces ◽  
Modal Parameters ◽  
Continuous Systems ◽  
Nonlinear Dynamical ◽  
Impact Forces ◽  
Vibratory Response ◽  
Imperfect Knowledge ◽  
Active Research ◽  
Remote Identification

Predictive computation of the nonlinear dynamical responses of gap-supported tubes subjected to flow excitation has been the subject of very active research. Nevertheless, experimental results are still very important, for validation of the theoretical predictions as well as for asserting the integrity of field components. Because carefully instrumented test tubes and tube-supports are seldom possible, due to space limitations and to the severe environment conditions, there is a need for robust techniques capable of extracting, from the actual vibratory response data, information that is relevant for asserting the components integrity. The dynamical contact/impact (vibro-impact) forces are of paramount significance, as are the tube/support gaps. Following our previous studies in this area using wave-propagation techniques (De Araújo, Antunes, and Piteau, 1998, “Remote Identification of Impact Forces on Loosely Supported Tubes: Part 1—Basic Theory and Experiments,” J. Sound Vib., 215, pp. 1015–1041; Antunes, Paulino, and Piteau, 1998, “Remote Identification of Impact Forces on Loosely Supported Tubes: Part 2—Complex Vibro-Impact Motions,” J. Sound Vib., 215, pp. 1043–1064; Paulino, Antunes, and Izquierdo, 1999, “Remote Identification of Impact Forces on Loosely Supported Tubes: Analysis of Multi-Supported Systems,” ASME J. Pressure Vessel Technol., 121, pp. 61–70), we apply modal methods in the present paper for extracting such information. The dynamical support forces, as well as the vibratory responses at the support locations, are identified from one or several vibratory response measurements at remote transducers, from which the support gaps can be inferred. As for most inverse problems, the identification results may prove quite sensitive to noise and modeling errors. Therefore, topics discussed in the paper include regularization techniques to mitigate the effects of nonmeasured noise perturbations. In particular, a method is proposed to improve the identification of contact forces at the supports when the system is excited by an unknown distributed turbulence force field. The extensive identification results presented are based on realistic numerical simulations of gap-supported tubes subjected to flow turbulence excitation. We can thus confront the identified dynamical support contact forces and vibratory motions at the gap-support with the actual values stemming from the original nonlinear computations. The important topic of dealing with the imperfect knowledge of the modal parameters used to build the inverted transfer functions is thoroughly addressed elsewhere (Debut, Delaune, and Antunes, 2009, “Identification of Nonlinear Interaction Forces Acting on Continuous Systems Using Remote Measurements of the Vibratory Responses,” Proceedings of the Seventh EUROMECH Solids Mechanics Conference (ESMC2009), Lisbon, Portugal, Sept. 7–11). Nevertheless, identifications are performed in this paper based on both the exact modes and also on randomly perturbed modal parameters. Our results show that, for the system addressed here, deterioration of the identifications is moderate when realistic errors are introduced in the modal parameters. In all cases, the identified results compare reasonably well with the real contact forces and motions at the gap-supports.

Remote Identification of Impact Forces on Loosely Supported Tubes: Analysis of Multi-Supported Systems

1999 ◽  
Vol 121 (1) ◽  
pp. 61-70 ◽  
Author(s):  
M. Paulino ◽  
J. Antunes ◽  
P. Izquierdo
Keyword(s):  
Traveling Waves ◽  
Heat Exchangers ◽  
Difficult Problem ◽  
Force Identification ◽  
Dissipative Effects ◽  
Impact Forces ◽  
Random Forces ◽  
Direct Measurements ◽  
Remote Identification ◽  
The Impact

Impact forces are useful information in field monitoring of many industrial components, such as heat exchangers, condensers, etc. In two previous papers we presented techniques—based on vibratory measurements remote from the actual impact locations—for the experimental identification of isolated impacts (Arau´jo et al., 1996) and complex rattling forces (Antunes et al., 1997). In both papers a single gap support was assumed. Those results concern systems which are simpler than the actual multi-supported tube bundles found in heat exchangers. Impact force identification is a difficult problem for such systems, because 1) when sensed by the remote motion transducers, the traveling waves generated at several impact supports are mixed, and there is no obvious way to isolate the contribution of each support; 2) multi-supported tubes may be quite long, with significant dissipative effects (by interacting flows or by frictional phenomena at the clearance supports), leading to some loss of the information carried by the traveling waves; 3) in multi-supported systems, some of the supports are often in permanent contact, leading to nonimpulsive forces which are difficult to identify. In this paper, we move closer towards force identification under realistic conditions. Only the first problem of wave isolation is addressed, assuming that damping effects are small and also that all clearance supports are impacting. An iterative multiple-identification method is introduced, which operates in an alternate fashion between the time and frequency domains. This technique proved to be effective in isolating the impact forces generated at each gap support. Experiments were performed on a long beam with three clearance supports, excited by random forces. Beam motions were planar, with complex rattling at the supports. Experimental results are quite satisfactory, as the identified impact forces compare favorably with the direct measurements.

Trend of KP Continuous Digesters and the Related Basic Theory

2015 ◽  
Vol 69 (8) ◽  
pp. 799-808
Author(s):  
Makoto Iwasaki
Keyword(s):  
Basic Theory
Sign in / Sign up

Export Citation Format

Share Document