### 8th European Workshop On Structural Health Monitoring (EWSHM 2016)

5-8 July 2016, Spain, Bilbao

Right Now in Bilbao 02:04 Wed 27

15:40 Wednesday 6. Jul - A4

### A damage detection approach based on wavelet analysis and noise estimation of mode shapes

Abstract »A major challenge for damage detection in structures is to achieve the maximum sensitivity to damage, reducing as much as possible the influence of the experimental noise.
This paper uses wavelet analysis as a sensitive tool to detect changes induced by damage in beams.
It applies the Continuous Wavelet Transform to the difference in mode shapes from a healthy and a damaged state. Depending on the position of the damage, some mode shapes are more sensitive to damage than others, so the effect damage may not be clear for some modes. On the other hand, the mode shapes are contaminated by experimental noise and the effect of noise can be even erroneously considered as a damage effect. The paper includes a methodology to estimate the level of noise of each mode shape based on a standard Signal to Noise Ratio considering an estimated reference noise-free mode shape. The least contaminated mode shapes are considered as the most reliable ones for damage detection.
The paper also considers the addition of a non-structural mass to enhance the sensitivity to damage of modal parameters. Modal analysis is performed for different positions of the mass along the beam so the influence of damage is emphasized at certain positions of the mass. Moreover, the results obtained for all the positions of the mass are combined so an averaging process is implicitly applied and consequently the effect of noise is reduced.
The paper presents the results obtained for a steel cantilever beam. Damage is artificially induced by a saw cut. The beam has a rectangular cross section and three different levels of damage severity are considered. They can be defined in terms of percentage of the depth of the notch relative to the height of the beam as 10%, 20% and 50%. The paper shows how the effect of damage is very small even for the most severe damage scenario. In addition to that, the damage is located between two adjacent sensors so the damage detection becomes even more challenging.
The damage is succesfully identified using a rather small numer of sensors. The dynamic response of the beam is obtained at 32 measuring points, and the modal information is extended to a larger number of points by using a cubic spline interpolation.

#### Authors

Solis, Mario***Solis, Mario***

msolis@us.es

0034 954 48 72 93

*Biography:*

Associate Professor at the Department oc Continuum Mechanics of the University of Sevilla.\\r\\nPhD about fracture mechanics on piezoelectric materials.\\r\\nResearch topics: damage detection, Structural Health Monitoring, structural dynamics, earthquake engineering for low cost adobe structures

*Affiliation:*

University of Sevilla

Department of Continuum Mechanics

41092 Sevilla

Spain

0034 954487293

*Other Presentations:*

Wed 6. 16:00, A1

Session: POSTERS-2

Title: Monitoring of the Curing Process in Laminates of Composite Materials

**Algaba, Mario**

marioalgaba@gmail.com

*Affiliation:*

University of Sevilla

Department of Continuum Mechanics

Sevilla

SpainGalvin, Pedro

**Galvin, Pedro**

pedrogalvin@us.es

*Affiliation:*

University of Sevilla

Sevilla

SpainBenjumea, Antonio J.

**Benjumea, Antonio J.**

*Affiliation:*

Escuela Técnica Superior de Ingeniería, Universidad de Sevilla

Department of Continuum Mechanics

Śevilla

Spain

**Contact*