@conference{
author = "Trišović, Nataša and Petrović, Ana",
year = "2019",
abstract = "The possibilities of real constructions testing are often limited, especially in case of large
constructions. One of the solutions is to create a sub-scaled model in order to anticipate the
behavior of the real construction, regarding the behavior of the model, with sufficient
accuracy. In most cases, testing on the model instead of the actual construction results in a
great saving of money and time. The aim of this paper is to demonstrate that model testing of
complex structures is possible, from the aspects of dynamics, i.e. it is possible to predict
eigenvalue frequencies of the real structure regarding the eigenvalue frequencies of the model.
The laws of similitude and scaling are well-known and confirmed for examples of simple
structures [1]. Recommendation is, if a model is 10 times smaller (in dimensions and plate
thicknesses) than the real structure, then it should be loaded with load 100 times lower than
the real structure to obtain stress and strain on the model comparable to stress and strain on
the real structure. Also, it should be expected eigenvalue frequencies of the model to be 10
times higher than the frequencies of the real structure. In this paper will be shown that laws of
scaling can be applied on testing of complex structures, not just the simple ones.
As a test example, the construction of the substructure, the slewing platform and the lower
part of the pylons of the bucket wheel excavator SchRs 630 is taken. Bucket-wheel excavator
is a high-performance machine that works in difficult working conditions. These machines are
the first in the chain of surface coal mining so it follows that the number of failures of these
machines should be kept to the minimum possible level. From an economic point of view the
failure of those machines includes a double cost, the cost of repairs and the cost as a result of
the fact that the machine does not operate, which is crucial [2]. First reason why this
construction is obtained as a test example is that those machines are dynamically loaded and
dynamic calculation is significant from the aspects of identifying dynamic behavior.
Secondly, strength of supporting structure has a crucial importance for proper functioning of
these machines [3]. Also, dynamic calculation gives results in identifying weak construction
spots, because the dynamic behavior gives the answer how the construction would react under
some hypothetical load of arbitrary direction [4].
Nataša R. Trišović and Ana S. Petrović.
Numerical calculations of the real construction and sub-scaled model were performed
using Finite Element Method. Eigenvalue frequencies of the real construction and model are
obtained in correlation as expected. In that way scaling laws are confirmed for this structure
and similar structures. Physical model of this construction is made (from the same material as
the real structure). Static experiments on physical model validated all numerical models (of
the real structure and its sub-scaled model) and indirectly validated dynamic calculations. It
also confirmed that 10 times reduction in dimensions and thicknesses is justified. So, physical
model represents the real structure, in both dynamic and static aspects, and is ready for further
dynamic testing in the laboratory.
REFERENCES
[1] Liang Z., Reinhorn A.M., Experimental Methods in Structural Engineering, Chapter 2 -
Modeling and Similitude, http://civil.eng.buffalo.edu/cie616/2-LECTURES/Lecture 2 -
Modeling and Scaling/Chapter2.pdf
[2] Dreyer, E. (1995) “Cost-effective prevention of equipment failure in the mining
industry,” International Journal of Pressure Vessels and Piping, Vol. 61, No. 2-3, pp. 329-
347.
[3] Bošnjak, S.; Pantelić,, M.; Zrnić, N.; Gnjatović, N.; Đorđević, M. (2011) “Failure
analysis and reconstruction design of the slewing platform mantle of the bucket wheel
excavator O&K SchRs 630, ” Engineering Failure Analysis, Vol. 18, No. 2, pp. 658-669.
[4] Allaboudi, E.; Maneski, T.; Trišović, N.; Ergić, T. (2013) “Improving Structure Dynamic
Behaviour Using a Reanalysis Procedures Technique,” Technical Gazette, Vol. 20, No. 2,
pp. 297-304.",
journal = "The Symposium “Nonlinear dynamics - Scientific work of Prof. Dr Katica (Stevanovic) Hedrih”",
title = "Model testing of complex structures from the aspects of dynamics",
url = "https://hdl.handle.net/21.15107/rcub_machinery_6000"
}
