IFMASS10

237

MODERN APPROACH TO CONTROL AND NONDESTRUCTIVE

TESTING METHODS

Miodrag Kirić

Innovation Center of Mechanical Engineering Faculty, Belgrade, Serbia

Milesa Srećković

Business and Technology Incubator of Technical Faculties, Belgrade, Serbia

1. INTRODUCTION

Non-destructive inspection (NDI) is an important procedure for quality control and

safe operation of structures and also for the assessment of its life span. Important defects

may be cracks or corrosion pits in welds and castings, or variations in material properties

that can lead to loss of strength or in-service failure.

Improper design may lead to excessive stress in component. Variable and impact

loadings must also be considered since they contribute to failure by fracture or fatigue.

Classical non-destructive testing (NDT) methods have been properly applied for

inspection during manufacturing, maintenance and repairing of structures and equipment

in Serbia. Anyhow, permanent development offers new NDT methods. Special attention

is paid here to three of them: global positioning system (GPS), ultrasonic testing (UT) and

laser techniques, but some other are also discussed.

The construction of planned structures in Belgrade and Serbia, such as high buildings,

bridges and metro, as well their maintenance, demand for monitoring using proven, but

also some new techniques. The primary function of monitoring is to ensure the safety and

long life of a structure, including high management and maintenance level. Monitoring

must enable the timely detection of any damage of the structure, assess its significance

and, if necessary, to implement corrective measures. The monitoring program is also

important in construction phase, enabling verification of design concept and construction

process, having in mind that defects are induced mostly during construction. Frequently,

monitoring data are necessary for controlled life extension of structures approaching the

end of their use or in the case of major repair, enabling safe operation of structures and

the postponement of major investments.

Accordingly, monitoring includes various NDI methods during:

1. construction of a new structure;

2. testing for the structure acceptance;

3. exploitation for regular and requested exceptional inspection;

4. disassembling of the structure.

The choice of NDT and NDI methods should take into the account the structure type,

loads and materials used. In the case of bridges, introducing data today are based almost

entirely upon a visual inspection. In that, deterioration that does not manifest visible form

is neither detected nor quantified. Quantitative data of NDT and NDI about structure state

are required in the form which can be transmitted wireless to the server. This is important

for hidden damages, like corrosion of reinforcement in concrete or cumulative fatigue

cracks in steel bridges. Vibrations, deflection and distorsion should also be monitored.