Papers by Keyword: Mechanical Loading

Abstract: This paper presents a metallographic and fractographic study of AISI 304 austenitic stainless steel subjected to mechanical loading in the sensitized condition. Static three-point bending tests and impact tests were carried out to evaluate how sensitization affects the mechanical response and fracture behaviour of AISI 304. The study compares the initial state of the material with its condition after sensitization at 700 °C for 10 h, with emphasis on changes in plastic deformation and fracture mechanisms. Microstructural evaluation was performed using light microscopy, while Vickers microhardness measurements provided insight into local mechanical changes. Fractographic analysis using scanning electron microscopy revealed differences in fracture surface morphology. Results demonstrate a decrease in microhardness, reduced impact energy, and noticeable differences in fracture morphology following the sensitization treatment, indicating that the heat treatment influences both the mechanical response and failure behaviour of AISI 304.

Abstract: The carbonaceous nanofillers such as graphene nanoplatelets (GN) due to their unique properties have been increasingly used as nanofillers to improve the mechanical properties of FRP composites. In the present study, unidirectional glass fiber reinforced polymer (GFRP) composites and GFRP composites with graphene nanoplatelets (GN-GFRP) are fabricated using vacuum bag process and hand layup method. The percentage of GN added in GN-GFRP composites is 0.1% and 0.5% in case of hand layup method and 0.5% in case of vacuum bag process. The specimens are tested under uniaxial tension and three-point bending to study the effect of GN on the tensile and flexural performance of GFRP composites. In case of composites fabricated using hand layup method, the tensile strength of GFRP composites increased by 35.8% and 40.4% with the addition of 0.1% and 0.5% GN respectively. The tensile modulus of GN-GFRP composites with 0.5% GN decreased by 11.8% compared to GFRP composites. The flexural strength of GN-GFRP composites with 0.1% and 0.5% GN are found to have increased by 6.5% and 5.3% respectively compared to GFRP composites. The flexural modulus of GN-GFRP with 0.1% GN increased by 11% and the same for GN-GFRP with 0.5% decreased by 8.2% compared to GFRP composites. The tensile strength and modulus of GN-GFRP composites fabricated using vacuum bag process decreased by 24.4% and 7.7% respectively compared to GFRP composites. Scanning Electron Microscope (SEM) investigation reveals that poor adhesion of resin with the fibers caused delamination in GN-GFRP composites fabricated using vacuum bag process resulting in reduction of tensile properties.

Abstract: This study presents the dynamic response analyze of a simply supported and isotropic functionally graded (FG) double curved panel under mechanical loading. The aim of the research was to investigate mechanical behavior in a FGM curved panel due to different excitation mode of dynamic loading. The novelty of this research is an investigation of von Mises equivalent stress distribution in double curved panel due to different excitation mode. Computed results are found to agree well with the results reported in the literature. Moreover, influence of volume fraction of the material is studied.

Abstract: In the present study, flat specimens from polycrystalline α-iron were monotonically and cyclically loaded at ambient temperature for the investigation of magneto-mechanical behavior. The magnetic flux density was measured by a Hall-sensor in in-situ and ex-situ experiments. For the characterization of the magnetic microstructure of α-iron Kerr microscopy was used. Additionally, Moessbauer spectroscopy of specimens in initial state and after failure was performed.

Abstract: Fire poses one of the most severe environmental conditions that can act on concrete structures as an external load and can induce severe damages (cracks, spalling) or even lead to collapse. Fire spalling of concrete is a complex phenomenon, which might occur due to pressure build-up in the pores, thermal and load-induced stresses. In this context, ordinary concrete specimens (B40-II and B40-III: fc_28days ≈ 40 MPa) were exposed to standard fire curve (ISO 834-1), while a constant uniaxial or biaxial compressive load was applied. Six different levels of uniaxial compressive stress on cubes and four different levels of biaxial compressive stress on slabs have been investigated. The test results showed that loaded specimens are more susceptible to spalling than unloaded specimens, with increasing amount of spalling for higher values of applied load. It has been found that biaxially loaded specimens are more prone to spalling than uniaxially loaded specimens. B40-II concrete (3% of slag) exhibited higher spalling than the B40-III concrete (43% of slag).

Abstract: Loss of hard dental tissues of the posterior teeth during caries removal represents an important issue for conservative dentistry. The use of direct dental biomaterials in this case have to satisfy the requirements of the restored area. The studies have shown higher values of chewing forces at the molar teeth level (20-120N) compared to other teeth [1,2]. Thus, for a long-term clinical success the dental biomaterials have to assure a good marginal sealing and a high resistance to thermal and mechanical stresses developed in the lateral zones of the oral cavity [3]. The aim of this study was carried out to assess the effect of an in vitro chewing simulation model on the adhesively-bonded resin composite restorations. Standardized extended proximal cavities were prepared and restored in forty five sound human third molars. Three in vitro aging methods: a chewing simulation model (mechanical cycling and periodontal ligament simulation) (MC+PDL), thermocycling (TC) and distilled water storage (WS), were used to test the marginal sealing behavior of two adhesive techniques (an adhesive-free flowable resin composite and a self-etch all-in-one adhesive system). A weight-controlled dual-axis chewing device (CS-4.2, SD Mechatronik, Germany) was used for mechanical testing (MC) of the samples. Significantly higher marginal leakage values were observed for the chewing simulation model (MC) compared to TC and WS groups (p<0.05). No statistical correlations were found with regard to aging methods for the tracer’s infiltration of the two adhesive techniques. The dual-axis chewing simulator (CS-4.2) due to its facile mechanical adjustment system may be used for different other in vitro aging models or simulated clinical settings.

Abstract: The aim of this paper is to investigate the effects of elastic stress for a C-ring specimen with an18.974-mm outer diameter and a 1.244-mm wall thickness. Tests are conducted on Type 304L SS material. Half-cell potential measurement specimens are used as methods of exposure and inspection The C-ring specimen for quantitatively determining the stress corrosion. Applying ASTM G38, which is a standard practice for making and using C-Ring Stress-Corrosion, was performed for elastic stress analysis. The results show that the effects of stress on the polarization curve are due to the magnitude of stress level in the specific corrosive environment.

Abstract: The paper is focused on the study of the material changes which can occur on the basis of mechanical and thermal loading in relation to the functional surfaces of the construction parts. The structural or the mechanical changes can be influenced by ambient environment and in this case, it is the influence of liquid media. The water, hot metal as well as molten glass can be the representatives of the mentioned liquid medium. In relation to the influence of the liquid medium, there is the danger of superposed wears while one of these wears is considered as dominant. Furthermore, occurrence of the corrosion process leads to the increases of the given dominant wear. In relation to the analysis and evaluation of the wear, the simulated tests under the critical conditions are necessary for the correct and precise prediction of the degradation processes. Experimental measurements can be used for the prediction of the material behaviour under the critical operation conditions. In the given work, the attention was paid to the selected materials which were exposed to the mechanical as well as mechanical-thermal loading. The important parameters were achieved with help of the testing device which was modified in a special way. Moreover, the structure changes were observed for the different time intervals or periods. On the basis of the susceptibility to the loading, the conclusions as well as recommendations were summarized for the selected materials.

Abstract: Aluminum alloys are often used as the aircraft fuselage materials. Three materials of aluminum alloys 2A16, 7A09 and titanium alloy TC11 are selected in this work. The fracture behaviors of these materials are investigated under the combination of thermal and mechanical loads. The analytical model is an infinite plate with a line crack subjected to the uniform tension stress and thermal loading. The temperature boundary condition is that the temperature remains unchanged on the crack surfaces while the uniform heat flow is imposed at infinite. The analytical solutions of temperature field, stress field, stress intensity factor, strain energy density factor are solved by the complex function method. The failure stresses under the different conditions are calculated and compared for three materials by using the strain energy density theory. It is seen that the temperature effect would play an important role for the fracture behavior of aircraft fuselage materials.

Abstract: This paper focuses on the coupled structural/thermal response of a cylindrical part of multi-layered composite vessel. Uniform and parabolic temperature distributions are chosen for the structural loads. In this work, an analytical model is proposed in which the laminate composite is assumed to be an anisotropic purely elastic material. Assuming that the interface between the core and skin are perfectly bound, continuity conditions for the displacement and stress, the suggested analytical model provides an exact solution for stresses and strains on the cylindrical section of the vessel solution submitted hygrothermal loading coupled with internal pressure with end effect.