Post-Machining Deformations of Thin-Walled Elements Made of EN AW-2024 T351 Aluminum Alloy as Regards the Mechanical Properties of the Applied, Rolled Semi-Finished Products

The paper presents an evaluation of post-machining deformations of thin-walled elements as regards the mechanical properties of the applied, rolled semi-finished products. Nowadays, wrought aluminum alloys, supplied primarily in the form of rolled plates, are widely applied in the production of thin-walled integral parts. Considering the high requirements for materials, especially in the aviation sector, it is important to be aware of their mechanical properties and for semi-finished products delivered after plastic working to take into account the so-called “technological history” concerning, inter alia, the direction of rolling. The study focused on determining the influence of the ratio of the tension direction to the rolling direction on the selected mechanical properties of the EN AW-2024 T351 aluminum alloy depending on the sample thickness and its relation to the deformation of thin-walled parts. Based on the obtained results, it was found that the sample thickness and the ratio of the tension direction to the rolling direction affected the mechanical properties of the selected aluminum alloy, which in turn translated into post-machining deformations. Summarizing, the textured surface layer had a significant impact on the mentioned deformation. Greater deformations were noted for samples made of a semi-finished product with a thickness of 5 mm in comparison to 12 mm. It was the result of the influence of the surface layer, which at lower thickness had a higher percentage of contents than in thicker samples.

Tension distribution shaping via reconfigurable attachment in planar mobile cable robots

SUMMARYTraditional cable robots derive their manipulation capabilities using spooling winches at fixed base locations. In our previous work, we examined enhancing manipulation capabilities of cable robots by the addition of base mobility to spooling winches (allowing a group of mobile robots to cooperatively manipulate a payload using cables). Base mobility facilitated the regulation of the tension-direction (via active coordination of mobile bases) and allowed for better conditioning of the wrench-feasible workspace. In this paper we explore putting idler pulleys on the payload attachment as alternate means to simplify the design and enable practical deployment. We examine analysis of the system using ellipse geometry and develop a virtual cable-subsystem formulation (which also facilitates subsumption into the previously developed mobile cable robot analysis framework). We also seek improvement of the tension distribution by utilizing configuration space redundancy to shape the tension null space. This tension distribution shaping is implemented in the form of a tension factor optimization problem over the workspace and explored via both simulation and experimental studies.

Wrench Reconfigurability via Attachment Point Design in Mobile Cable Robots

In our previous paper [1], we examined enhancing manipulation capabilities of cable robots by addition of base mobility to the spooling-winches. Base mobility facilitated the regulation of the tension-direction (via active repositioning of the mobile bases) and allowed for better conditioning of the wrench feasible workspace. In this paper, we explore design-modifications on the attachment to the common payload (merging multiple cables, attachment via pulleys) as alternate means to improve quality of the wrench-feasible workspace. Specifically we systematically examine the role played by attachment-modality and location, focusing on the benefits/drawbacks of the ensuing natural mechanical averaging behavior. Further, by using the notion of virtual cable subsystems, we illustrate the subsumption of this case into our previous mobile-cable-robot analysis framework. We seek improvement of the overall tension distribution by utilizing configuration space redundancy to shape the tension null-space. This is implemented computationally within the framework of a Tension Factor optimization problem over the workspace and explored via both simulation and experiments.

Anisotropy of Mechanical Properties and Microstructure Evolutions of Tensile AZ80 Magnesiumat Room Temperature

It is obviously different mechanical properties of the rolled magnesium alloy plate when stretched along different directions at room temperature. In this study, three groups of samples for uniaxial tension were cut from the as-rolled AZ80 plate with their tension directions either at 0°, 45°or 90°to the rolled direction (RD) of the sheet. Results show that the ductility of the 45°samples was significantly better than that of 0°and 90°samples. The electron backscatter diffraction (EBSD) technique was used to investigate the microstructure and textures evolution. Along with the increase of deformation, more low-angle grain boundaries arise in the 0°and 45°samples than the 90°samples. At the same time, the texture components that {10-10} prismatic plane perpendicular to the tension direction were significantly enhanced in three groups of samples.

Holographic interferometry method for assessment of static load stress distribution in dog mandible

This study compared the transmission of tensions in fresh, fixed and macerated dog mandibles in order to clarify the diversity of behavior of bone tissues under dry and moist conditions. Double-exposure holographic interferometry was applied and holograms were obtained from 12 fresh hemi-mandibles under static load (control group), which were randomly assigned to 2 groups: 6 were fixed in 10% formalin and 6 were macerated. The specimens were submitted to the same initial force and their respective holograms were obtained. Analysis of the holograms showed that the fresh specimens transmitted significantly less tension than the fixed and macerated ones (p<0.05), and the tension direction was different. An average two-fold tension increment was observed in the experimental conditions. The holographic interferometry method was efficient in quantifying and qualifying tension transmission. However, depending on the type of analysis, the anatomical specimens must be fresh because macerated specimens will produce different results.