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Evaluation of adhesive bond Young's modulus during crosslinking using a mechanical method and an ultrasound method B Mascaro, M K Budzik, M Castaings et al. Abstract. Structural adhesives are increasingly used in the construction of mechanical devices. Adhesive joints replace welded, soldered and other joints. The strength of the adhesive joints obtained allows the transfer of loads. The possibility of combining different materials is a significant advantage. In order to design joints, it is necessary to know the mechanical properties of adhesives. Determining them requires the use of special methods of obtaining specimens. Analytical and numerical methods of stress estimation in adhesive joints require more material data than is provided by manufacturers. The aim of the following work is to present the method of manufacturing specimens and to compare methods for determining mechanical properties based on three example structural adhesives. The paper presents two methods for determining the mechanical properties of exemplary structural adhesives: metacryl, epoxy and polyurethane adhesive. The tests were carried out on a cast and then machined specimens. Flat specimens were used in a tensile test. In compression test, round specimens were used. The results obtained from both tests were compared with the manufacturer's data. Differences and possible reasons for them were indicated. Stress distributions in the adhesive single lap joint were estimated using the Volkersen analytical method for various determined mechanical properties.

Description of fatigue crack growth in steel structural components using energy approachInfluence of the microstructure on the FCGR AIP Conference Proceedings 1780, 050003 (2016) Abstract When determining the characteristics of the fatigue crack growth rate, it is necessary, inter alia, to measure the crack length growth which must be combined with the number of accumulated load cycles. The length of the crack is determined using different testing methods. Recently, there is an increased interest in optical systems based on digital image correlation methods. These methods have however some limitations as regards, inter alia, the sharpness of pictures taken during tests e.g. at cryogenic temperatures. This paper presents a comparative analysis of the crack length "a" as a function of a crack-opening-displacement "δ" obtained by experimental and numerical method. The tests were performed under ambient temperature for CT type specimens made of Ti6Al4V titanium alloy. Numerical research was carried out by finite element method using ABAQUS software. Satisfactory results were obtained which gave the reasons for establishing a hybrid methods for the crack length determination.

The study presents an analysis of the cracking process of explosive welded layered material AA2519–AA1050–Ti6Al4V (Al–Ti laminate) at ambient (293 K) and reduced (223 and 77 K) temperatures. Fracture toughness tests were conducted for specimens made of base materials and Al–Ti laminate. As a result of loading, delamination cracking occurred in the bonding layer of specimens made from Al–Ti laminate. To define the crack mechanisms that occur at the tested temperatures, a fracture analysis was made using a scanning electron microscope. Moreover, acoustic emission (AE) signals were recorded while loading. AE signals were segregated to link their groups with respective cracking process mechanisms. Numerical models of the tested specimens were developed, taking into account the complexity of the laminate structure and the ambiguity of the cracking process. A load simulation using the finite element method FEM allowed calculating stress distributions in the local area in the crack tip of the Al–Ti laminate specimens, which enabled the explanation of significant material cracking process development aspects. Results analysis showed an influence of interlayer delamination crack growth on the process of the Al–Ti laminate specimen cracking and the level of KQ characteristics at different temperatures.

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This study presents the testing results of methacrylic adhesive single-lap joints made from elements with different stiffness and of the adhesive itself, using cast specimens. Methods for the preparation and testing of material specimens of the adhesive joints have been presented. Moreover, an attempt was undertaken to determine the strength criterion and find out which of the presented calculation methods enables the most precise assessment of strength in the tested group of single-lap joints, that differ in terms of the adhered stiffness and thickness. For this purpose, C45 steel and 5754 aluminium flat bars were bonded. Stress distributions were determined for failure forces obtained in the experiment by means of three basic analytic and numerical methods. Stress and strain states were compared, indicating the highest consistency for the value of normal peel stresses acting in the direction perpendicular to the direction of the joint tension. Reduced stresses provided by the analyses reached values higher than those which were achieved during the specimen tension testing.

The article presents the results of an analysis of the crack growth and fatigue life of CT specimens made of explosively welded AA2519–AA1050–Ti6Al4V layered material for the construction of air and space structures. The investigations were carried out for two temperature conditions: ambient temperature (293 K) and under cryogenic conditions at the temperature of liquid nitrogen (77 K). The analysis of the test results revealed the impact of cryogenic conditions on the process of fatigue cracking of a layered material. However, this impact is partly limited by a significant scatter of the test results, which may be caused by the different character of the process of cracking.