Grzegorz Dymny

Remote online monitoring and measuring system for civil engineering structures

In this paper a distributed intelligent system for civil engineering structures on-line measurement, remote monitoring, and data archiving is presented. The system consists of a set of optical, full-field displacement sensors connected to a controlling server. The server conducts measurements according to a list of scheduled tasks and stores the primary data or initial results in a remote centralized database. Simultaneously the server performs checks, ordered by the operator, which may in turn result with an alert or a specific action. The structure of whole system is analyzed along with the discussion on possible fields of application and the ways to provide a relevant security during data transport. Finally, a working implementation consisting of a fringe projection, geometrical moiré, digital image correlation and grating interferometry sensors and Oracle XE database is presented. The results from database utilized for on-line monitoring of a threshold value of strain for an exemplary area of interest at the engineering structure are presented and discussed.

Design and testing of a low-cost full-field integrated optical extensometer

The paper deals with design and implementation of an optical extensometer based on grating (moire) interferometry, for large engineering construction monitoring. The paper presents the principles of the grating interferometry and the construction of miniaturized and portable version of grating interferometer and its implementation for out-door measurement directly at civil engineering structures. The paper presents also a concept of the low-cost full-field optical extensometer.

Hierarchical, multitasks optical system for health monitoring of civil engineering structures

In this paper a distributed intelligent system for civil engineering structures on-line measurement, remote monitoring, and data archiving is presented. The system consists of a set of full-field optical displacement sensors connected to a controlling server. The server conducts measurements according to a list of scheduled tasks and stores the primary data or initial results in a remote centralized database. The description of an exemplary set of full-field sensors including IP and thermovision camera, 2D and 3D digital image correlation systems, and grating interferometry based extensometers is provided. Three different measurement tasks performed by means of this systems are presented in details.

Experimental studies of mechanical joints by automated grating (moire) interferometry

Current design, analysis and control engineering applications require effective experimental methodologies and tools for determination of displacement and strain fields as well as material characterization. One of the most important problem in engineering objects is proper design and quality of joints between elements in the form of welds, glued and riveted joints and many others. Specificly the fatigue and fracture mechanics problems in joints are difficult to analyze numerically, therefore they need experimental support. In the paper we present the results of static, dynamic and fatigue experiments performed by grating (moire) interferometry systems. These full-field optical extensometers provide information about in-plane displacement field (u,v) and strain fields (εx, εy, γxy) in the region of a joint subjected to various modes of loads. It is shown that proper design of full-field extensometer (insensitivity to vibration, good quality of interferogram, automatic analysis of long series of interferograms) allows to use it efficiently directly at conventional loading machine in workshop environment and for long term fatigue tests. In the paper we present results of studies of: conventional laser welds (static, fatigue tests), friction stir weld (static tests), riveted joint (static, fatigue tests). The methodology of determination of local material constants in different zones of a joint (inc. Poisson ratio, Young’s modulus) is given. The future trends in hybrid experimental-numerical analysis of joints in conventional and novel material are discussed.

Hybrid FEM/grating interferometry analysis of displacement fields in mechanical elements

In the paper the concept of interactive implementation of grating interferometry and FEM is proposed in order to provide additional information to properly design and control both numerical and experimental procedures. At first the information from global FEM approximate model is used to design interferogram and adjust experimental setup. Having the best fitted experimental conditions, the measurement is performed. The results are used to improve the FEM parameters e.g. size and shape of FEM grid and fit local experimental data to modified FEM model. To provide the proper experimental tool, grating interferometry with two-channel acquisition module (for instantaneous u and v displacement measurement) is applied. The concept is tested on the examples of analysis of bending ceramic-to-metal joint and laser beam weldment under tensile semiaxial load.

Modified electronic speckle pattern shearing interferometry for simultaneous derivative map measurements

Electronic speckle pattern shearing interferometry (ESPSI) allows for the measurement of displacement derivative maps. To monitor the stress/strain state of an object surface and its material properties, it is necessary to measure more than one displacement derivative map. The conventional configuration of ESPSI has been modified by parallel adaptation of Michelson shearing interferometers and an optoelectronic/image processing head with the capability of simultaneous capturing of 2 images. The automatic analysis of speckle fields is performed by temporal phase stepping method with the separation of the information by orthogonal polarization states. In the paper the opto-mechanical and electronic configuration of the system is presented. The experimental results obtained in the modified ESPIS system, when applied to determination of shear strain in a tensile loaded aluminium specimen are also presented.

Optoelectronic/Image Processing Module for Enhanced Fringe Pattern Acquisition and Analysis

The paper introduces an optoelectronic/image processing module, OIMP, which enables more convenient implementation of full-field optical methods of testing into industry. OIMP consist of two miniature CCD cameras and optical wavefront modification system which recombines the beams produced by opto-mechanical measurement system and images fringe patterns on the CCD matrices. The modules makes possible simultaneous registration of there monochromatic images as R,G,B components of color video signal by means of signal frame grabber or by VCR on video tape. This enables convenient and inexpensive storage of large quantities of data which may be analyzed by spatial carrier phase shifting method of automatic fringe pattern analysis. THe usefulness of OIMP is shown by two examples: u and v in-plane displacement simultaneous analysis in grating interferometry system and complex shape determination by fringe projection systems.

Experimental Investigation of Displacement/Strain Fields in Metal Coatings Deposited on Ceramic Substrates by Thermal Spraying

The paper presents the initial results of application of the high sensitivity grating interferometry (GI) method in order to measure the displacement and strain fields in copper and titanium coatings thermally sprayed onto alumina ceramic (Al2O3). The residual stresses had been relieved by iterative cutting method, which was applied twice. The displacement maps of u and v were measured after each cut and εxx and εyy maps were calculated. The results clearly show the presence of εxx strains relieved along the second cut. The comparison of both samples confirmed that residual strains in Ti/Al2O3 are more significant than in Cu/Al2O3 system. The result after relevant postprocessing had been supplemented with the sub-surface principal residual stresses measured in the selected point by the x-ray diffraction method and curvature measurements.

Hybrid Numerical-Optical Methods for Analysis of Mechanical Structures

In conventional approach numerical and experimental solutions are independent and lack of interaction. Because each method has its own drawback, an interactive combination of numerical and experimental methods is proposed. An application of the hybrid method with Finite Element Method and optical metrology is illustrated, which demonstrates the viability of the feedback of experimental to numerical model, or numerical solutions to experimental setup and then improvement and adjustment of mathematical model and experimental setup.

Long-base optical extensometer for tensile testing machines

The principles of operation and optomechanical design of novel optical extensometer OPEX for tensile testing machines is presented. The system provider on-line strain measurements performed at an arbitrary measurement base. OPEX is integrated with a tensile loading machine so it can be used for active controlling of the machine setup. The applicability of the system is demonstrated by determination of elongation of various mechanical samples subjected to uniaxial tensile tests.