The diploma thesis deals with non-destructive testing of concrete as well as with the relationship between determined parameters and the compressive strength of concrete. The thesis is mainly focused on the ultrasonic pulse velocity method and the rebound hammer test. The experimental part of the thesis describes non-destructive tests performed on concrete blocks. The compressive strength was tested on the drill cores taken from the concrete blocks. The aim of this thesis is to find regression models of the relationship between the compressive strength and non-destructive parameters, and the subsequent analysis of the results.

This dissertation is focused on the research of the applicability of the thermographic method in the diagnosis of concrete bridges in the Czech Republic. The theoretical part characterizes selected defects of concrete structures and the principle of their detection. The practical part describes the measurements made in the laboratory on the test specimen and the field on the concrete bridge. Most attention is paid to infrared thermography, ground-penetrating radar and ultrasonic pulse-echo method. Based on the results of the dissertation, recommendations for the use of the thermographic test method in practice were developed.

This thesis deals with the rebound hammer method as a tool for approximation of the time limit for handling the concrete. The theoretical part is focused on three fields of knowledge - rebound hammer test, production of precast concrete components and statistical data analysis. The following practical part deals with the design of two single-parameter linear functions for two types of rebound hammer testers - SilverSchmidt L and SchmidtOriginal N. Statistical data processing is completed by the analysis of influential points by using the Cook’s distance. The resulting statistical models are compared with commonly used relationships.

<p>Developing a reliable in-situ non-destructive testing method to determine the strength of in-place concrete is critical because a fast-paced construction schedule exposes concrete pavement and/or structures undergoing substantial loading conditions, even at their early ages. Conventional destructive testing methods, such as compressive and flexural tests, are very time-consuming, which may cause construction delays or cost overruns. Moreover, the curing conditions of the tested cylindrical samples and the in-place concrete pavement/structures are quite different, which may result in different strength values. An NDT method that could directly correlate the mechanical properties of cementitious materials with the sensing results, regardless of the curing conditions, mix design, and size effect is needed for the in-situ application.</p><p>The piezoelectric sensor-based electromechanical impedance (EMI) technique has shown promise in addressing this challenge as it has been used to both monitor properties and detect damages on the concrete structure. Due to the direct and inverse effects of piezoelectric, this material can act as a sensor, actuator, and transducer. This research serves as a comprehensive study to investigate the feasibility and efficiency of using piezoelectric sensor-based EMI to evaluate the strength of newly poured concrete. To understand the fundamentals of this method and enhance the durability of the sensor for in-situ monitoring, this work started with sensor fabrication. It has studied two types of polymer coating on the effect of the durability of the sensor to make it practical to be used in the field.</p><p>The mortar and concrete samples with various mix designs were prepared to ascertain whether the results of the proposed sensing technique were affected by the different mixtures. The EMI measurement and compressive strength testing methods (ASTM C39, ASTM C109) were conducted in the laboratory. The experimental results of mortar samples with different water-to-cement ratios (W/C) and two types of cement (I and III) showed that the correlation coefficient (R²) is higher than 0.93 for all mixes. In the concrete experiments, the correlation coefficient between the EMI sensing index and compressive strength of all mixes is higher than 0.90. The empirical estimation function was established through a concrete slab experiment. Moreover, several trial implementations on highway construction projects (I-70, I-74, and I-465) were conducted to monitor the real-time strength development of concrete. The data processing method and the reliable index of EMI sensing were developed to establish the regression model to correlate the sensing results with the compressive strength of concrete. It has been found that the EMI sensing method and its related statistical index can effectively reflect the compressive strength gain of in-place concrete at different ages.</p><p>To further investigate the in-situ compressive strength of concrete for large-scale structures, we conducted a series of large concrete slabs with the dimension of 8 feet × 12 feet × 8 inches in depth was conducted at outdoor experiments field to simulate real-world conditions. Different types of compressive strength samples, including cast-in-place (CIP) cylinder (4” × 6”) – (ASTM C873), field molded cylinder (4” × 8”) – (ASTM C39), and core drilled sample (4” × 8”) – (ASTM C42) were prepared to compare the compressive strength of concrete. The environmental conditions, such as ambient temperatures and relative humidity, were also recorded. The in-situ EMI monitoring of concrete strength was also conducted. The testing ages in this study were started from 6 hours after the concrete cast was put in place to investigate the early age results and continued up to 365 days (one year) later for long-term monitoring. The results indicate that the strength of the CIP sample is higher than the 4” x 8” molded cylinder , and that core drilled concrete is weaker than the two aforementioned. The EMI results obtained from the slab are close to those obtained from CIP due to similar curing conditions. The EMI results collected from 4 × 8-inch cylinder samples are lower than slab and CIP, which aligns with the mechanical testing results and indicates that EMI could capture the strength gain of concrete over time.</p><p>The consequent database collected from the large slab tests was used to build a prediction model for concrete strength. The Artificial Neuron Network (ANN) was investigated and experimented with to optimize the prediction of performances. Then, a sensitivity analysis was conducted to discuss and understand the critical parameters to predict the mechanical properties of concrete using the ML model. A framework using Generative Adversarial Network (GAN) based on algorithms was then proposed to overcome real data usage restrictions. Two types of GAN algorithms were selected for the data synthesis in the research: Tabular Generative Adversarial Networks (TGAN) and Conditional Tabular Generative Adversarial Networks (CTGAN). The testing results suggested that the CTGAN-NN model shows improved testing performances and higher computational efficiency than the TGAN model. In conclusion, the AI-guided concrete strength sensing and prediction approaches developed in this dissertation will be a steppingstone towards accomplishing the reliable and intelligent assessment of in-situ concrete structures.</p><br>

Composite materials offer a high strength-to-weight ratio and directional load bearing capabilities. Compression molding of composite materials yields a superior surface finish and good dimensional stability between component lots with faster processing compared to traditional manufacturing methods. This experimental compression molding capability was developed for the ME composites lab using unidirectional carbon fiber prepreg composites. A direct comparison was drawn between autoclave and compression molding methods to validate compression molding as an alternative manufacturing method in that lab. A method of manufacturing chopped fiber from existing unidirectional prepreg materials was developed and evaluated using destructive testing methods. The results from testing both the continuous and chopped fiber were incorporated into the design of a functionally graded hybrid continuous and chopped carbon fiber component, the manufacture of which resulted in zero waste prepreg material.

Electromagnetic emission and acoustic emission are physical phenomena evoked in non-conductive material by the sudden release of energy that generate rising cracks in material structure. The significant is a fact that these emission signals are detected already in stadium of materials loading whereof can be used e.g. at non-destructive diagnostics of building materials and constructions. In the appropriate manner processing of the emitted signals then make possible to obtain valuable informations for study physical properties of cracks. Master’s thesis describes methods designed for important signal data ascertainment in time, frequency even time-frequency domain. It can be e.g. start time, maximum value, dominant frequency in spectrum etc. All these methods are implemented into main program. Next load is formularization of source signal transformation which is given by used measuring circuit. Analytical method is chosen for solving. It means finding out reserve electrical circuit with constant element values. Resultant circuit approaches original circuit with less square error than existing way. The signal transformation is described by differential equation of second order with constant coefficients. MATLAB software is used for all computations and projections.

The masers’s thesis is about the methods of non-destructive testing and about determining the properties of prestressed concrete. The first part pursues an introduction on the prestressed concrete, its essence and material properties. The next section describes the non-destructive diagnostic methods used in the practical part – the ultrasound impulse method, the resonance method and the rebound hardness test method. There are described destructive tests on the specimens for the calculation of the calibration. This is followed by a practical part, which describes the item tested - truss, its manufacturing, storage, and perform the test. Then search value are calculated from the test results and results are compared according to various procedures specified in the standards. The last section is devoted to the calculation of camber truss and loss of preload.

This master`s thesis deals with methods of turbojet engines maintenance and diagnostics. First specify and review methods. Then choose acceptable and perspective methods of non-destructive testing. Based on this choosing will be designed modern service center.

This diploma thesis resolves aplication of particular non-destructive testing methods while producing castings of steel wheels and quality control of this process. There are described fundamentals of flaw detection, determination of flaw-generation cause and suggestions for optimalization of casting process and increasing of its quality.

The presented diploma thesis is focused on defects of castings as well as optimization of production with the aim of reducing the number of defective products. The theoretical part is focused on basic information about cast iron and its production, structure and mechanical properties. Another part of this thesis describes the defects of castings and options for non-destructive testing of cast iron castings. In the experimental part are analyzed three sorts of defective casting. Castings for testing were provided by JMA s.r.o. foundry. The summary contains tests results and proposals for optimization of production.