Papers by Keyword: Non-Destructive Testing

Abstract: Although extrusion is a well-established and widely used manufacturing process, charge weld seams remain a persistent challenge due to oxides, contaminants, and unfavorable material flow conditions at billet-to-billet transitions. In lateral angular co-extrusion (LACE), the material flow becomes more complex because it is redirected orthogonally to the ram movement and the metal is segmented into four separate streams in the die. This results in charge weld seams developing in more intricate shapes and locations than in conventional forward extrusion. Knowing the position of these seams along the profile is therefore essential for ensuring the structural integrity of co-extruded hybrid profiles, such as aluminum alloy hollow profiles reinforced by an inner titanium alloy tube. This study investigated the formation of charge weld seams in LACE through controlled billet-on-billet experiments. A hybrid profile was produced consisting of EN AW-6082 aluminum alloy as the lightweight component and a reinforcement element made of titanium grade 5 (Ti-6Al-4V). To enable accurate detection of the charge weld seam within the aluminum alloy part of the profile using non-destructive testing methods, a thin iron foil was inserted as a robust marker prior to extrusion between two parts of a split billet. Eddy-current testing (ET) and ultrasonic testing (UT) were applied to detect and map the charge weld seam along the extruded profile. ET enabled robust, high-resolution circumferential mapping of the weld propagation, while UT provided depth-resolved information. Complementary cross sections were prepared to validate the NDT results and characterize seam morphology. This combined approach provides a clearer picture of the formation of charge weld seams in LACE and demonstrates that NDT techniques can be used to reliably identify and assess these features in complex hybrid profiles.

Abstract: Carbon fiber reinforced polymer (CFRP) composites are highly valued in aerospace for their superior strength and fatigue resistance. However, the structural complexity of CFRP components leads to inevitable internal defects during manufacturing, with complex geometry being a key factor hindering detection. This paper investigates the ultrasonic propagation characteristics in CFRP multidirectional plates with complex geometries via finite element simulations, focusing on the multifactor coupling effects in CFRP members. Acoustic tracing is conducted for the anisotropic and multilayered CFRP multidirectional plates. Through bottom reflection method and full-focus imaging inspection experiments, the propagation behaviors of ultrasonic waves in CFRP are systematically analyzed. Results reveal that the material’s multilayer structure, elastic anisotropy, and complex geometry significantly affect the imaging quality, defect localization accuracy, and defect distribution range in full-focus ultrasonic array inspection. The optimized algorithm achieves accurate detection of hole defects in complex-shaped CFRP multidirectional plates, reducing the imaging array performance indicator (API) value to 0.7 and the defect localization error to less than 0.3 mm. Keyword: CFRP components; complex geometries; non-destructive testing; acoustic tracing; full-focus imaging;

Abstract: This study analyzes the impact of high temperatures on the physico-chemical properties of concrete, highlighting a marked decrease in strength and material integrity. Among the mechanical non-destructive testing methods, the rebound hammer technique was selected for its accessibility, speed, and capacity to deliver preliminary on-site results. Field data obtained at fire-damaged sites reflect the extent of material degradation and enable the identification of critical heat-affected zones and potential fire origin points. By comparing the strength of concrete in damaged versus intact areas, the most severely affected zones can be identified.

Abstract: This study investigates the impact of high temperatures on the structural and physico-chemical properties of concrete, emphasizing the degradation of material strength under fire exposure. Through a review of reference data, it was confirmed that elevated temperatures significantly reduce concrete strength, potentially leading to structural failure. The rebound hammer method, a mechanical non-destructive testing technique, was selected for on-site evaluation due to its accessibility, speed, and ability to provide immediate preliminary results. Field measurements conducted at fire-affected sites allowed for the identification of temperature zones and heat flow directions based on variations in concrete strength. Comparative analysis between intact and damaged areas enabled the identification of critically affected zones and the estimation of structural degradation. The study demonstrates that using the Schmidt hammer, with proper calibration and error consideration, provides reliable data for determining the origin of the fire and for making informed decisions on structural repair or reinforcement.

Abstract: One of the critical components in the rehabilitation of lower limb amputees is the prosthetic foot. The solid ankle cushion heel (SACH) foot is commonly prescribed to patients due to its ability to reduce impact loading at heel strike, as well as its durability and cost-effectiveness. This research focuses on developing a composite SACH foot using two different polymers. The keel was constructed from Nylon fiber, while the shell, designed to resemble an amputee's foot, was made from Polyurethane (PU) foam. The keel functions as a surrogate for the amputee's bone and is therefore specifically designed and embedded within the shell. The developed SACH foot underwent static testing according to the ISO 10328:2016 standard at various angles. Additionally, it was modeled and analyzed using the finite element method (FEM). Material tests were conducted on both the keel and shell to establish their material models for FEM. The finite element analysis (FEA) demonstrated an average error of less than 15.22%. Moreover, the FEA provided insights into the deformation and stress experienced by both the keel and the shell. This detailed investigation into the structural behavior of both SACH components offers valuable guidance for the future design and development of composite SACH feet.

Abstract: This study aims to explore the correlation between the dimensions of concrete specimens and their compressive strength. In the field of engineering, it is essential to determine concrete strength. Besides the standard cylindrical compressive strength test, core samples are often required for compressive strength testing to verify the quality of concrete. However, coring requires significant time and energy, and the number of available samples is limited. Some projects may not be suitable for coring, necessitating the use of non-destructive testing methods to assess in-situ concrete strength. This research project aims to investigate the correspondence between various specimen sizes and the compressive strength of concrete, establishing corresponding curves for compressive strength of concrete core specimens of different sizes. The results of this research reveal that smaller specimen sizes tend to exhibit slightly higher compressive strength, provided that the concrete mixture is well-blended, and the specimen diameter and the proportion of the largest coarse aggregate nominal diameter comply with specifications. Regardless of specimen size, representative compressive strength values can be obtained. In lower-strength concrete specimens, the quality control aspects have a more substantial influence on compressive strength than specimen size effects.

Abstract: Fiber-reinforced plastics (FRP) are a type of composite material consisting of a reinforcing structure and a plastic matrix. When compared to traditional construction materials, FRP has higher strength and stiffness due to the high mechanical properties of reinforcing fibers such as carbon or glass. However, the properties of FRP are dependent on the alignment of fibers within the composite, with deviations leading to reduced strength and stiffness. Eddy current testing is a non-destructive technique used to visualize carbon fibers in the composite and assess the impact of local fiber orientation on the structural properties of FRP. This study aims to understand the influence of local fiber orientation on tensile strength and elastic modulus by producing composites with defined fiber orientations, analyzing them with eddy current testing, and assessing their mechanical properties through tensile tests. The measured fiber orientations are then used to validate a finite element model, in which the actual, measured fiber orientation is applied to the simulation and correlated with the mechanical properties. In contrast to previous published studies measured fiber orientation is used, which as shown in this work, differs from the theoretically implemented fiber orientation.

Abstract: The purpose of this research is to use an electrochemical method to evaluate corrosion conditions of steel bars in concrete. According to the description of ASTM C876, when the corrosion potential measurement values of the steel bar are below -350 mV, there may be a greater than 90 percent chance of corrosion. If the current impedance of the concrete is below 10 kΩ-cm, there is a possibility of corrosion in the steel bar. The test plan is as follows: to use concrete with different concentrations of chloride ions or applying an electric current to the steel bars to accelerate the corrosion reaction. In addition, we plan to use a solution of chloride ions to simulate sea tidal erosion on reinforced concrete structures by spraying. According to the experimental observations, concrete containing chloride ions is very likely to cause internal corrosion of the steel bar. The current impedance of the concrete can be used as the basis for assessing the internal humidity and moisture content of concrete. With an increase in curing time, the concrete's resistance correspondingly increases.

Abstract: The main purpose of this study is to develop non-destructive testing techniques for assessing the repair condition of concrete structures. Concrete is a building material commonly used in engineering, such as dams, bridges, retaining walls, houses, etc.. Concrete structures frequently exist various types of cracks due to inferior environments and excessive loading. There are several crack-repairing techniques used in concrete construction. The most common method is to use epoxy. The proposed research will perform a series of numerical and experimental studies to investigate the feasibility of developing a new technique for quantitative evaluation of the concrete surface crack repairing status degree. The results of the studies will form the experimental study for establishing the experimental procedure and signal analysis criteria for further field application in the nondestructive evaluation of concrete surface crack repairing status.

Abstract: The aim of this work is the evaluation by non-destructive impulse excitation tests, the modulus of elasticity (E) and the transversal deformation modulus (G) of cross laminated bamboo (CLB). Tests were performed on twenty-three CLB specimens measuring: 12 mm (height), 40 mm (width) and 12 mm (length). Twelve specimens have two lamellas with fibers at 0 °, longitudinal direction, and one layer with fibers at 90 °, normal direction (N) and the other eleven specimens have two layers in the normal direction and one in the longitudinal direction (L). The tests were performed using the Sonelastic apparatus indicated for the estimation of the dynamic modulus of elasticity and the damping of materials by the impulse excitation technique. A software attached to the apparatus analyzes the acoustic wave generated, and from it, the dynamic modulus of elasticity is determined. In order to verify the significance of this estimation, semi-destructive, three-point bending tests were performed in a universal test machine, determining E and G. It was concluded that the estimation of the modulus of elasticity is very significant when compared with the semi-destructive tests, and this method can be used to estimate the elasticity modulus of the CLB with high precision (R² = 99% and p-value <0.001). Modulus of elasticity in the longitudinal direction were five times larger than those in the normal direction.