The endurance test described in NAS1675 section 4.6.7 option 1, more commonly known in the fastener industry as the “boomer banger test”, has been a commonly accepted test to examine the vibration endurance of fasteners since its approval in 1964. This paper seeks to provide a better understanding of the vibration characteristics of this test apparatus by using accelerometers attached directly to the test plate. Details from this test were analyzed for possible ambiguous setup factors which were not well defined in the specification. Those factors were then used to evaluate their effect on the test. The results from the evaluation indicates that the inherent variations are larger than what the setup factors could produce. The data obtained from the accelerometers shows the test to be closer to a repetitive shock test, with large variation in G-force measured by the accelerometers.
Gluing is an essential fastening step in the field of aircraft assembly except for riveting and bolting. Generally, the robotic programs of gluing are generated in CAM environment. Due to the positioning errors and deformation of the workpiece to be glued in the fixture, the nominal pose and the actual pose of the workpiece are no longer consistent with each other. The Robot trajectory of dispensing glue are adjusted manually according to the actual pose of the workpiece by robot teaching. In this paper, an on-line gluing path correction method is developed by 2D laser profile measurement. A pose calibration method for 2D laser profiler integrated into a gluing robot by measuring a fixed center point of a standard ball is proposed to identify the position and orientation of the laser sensor, which enables the accurate transforming coordinates between the robot frame and the sensor frame. Meanwhile, the pose of the gluing tool mounted on the end of the robot is calibrated.
Several conventional methods on preparation of exfoliated graphite are in practice. However, their major limitations are poor quality of exfoliated graphite, lower yield, more expensive with higher processing time. To address these issues, a unique method for development of exfoliation of graphite using tri-solvents namely Water, Ethanol and Acetic acid is attempted in the present work. Ethanol acts as a supporting group for the long term stable dispersions of ex-graphite nanosheets. Glacial acetic acid, which readily dissolves in water, penetrates through the layers of graphite sheets and breaks the -C=C bond force between layers with the help of stirring and sonication resulting in exfoliation of graphite layers. Exfoliated graphite nanosheets were produced by using optimized mixtures of water, acetic acid and ethanol. XRD, SEM and FTIR studies have been carried out on the developed exfoliated graphite.
This paper presents the efforts made in numerical simulation of residual stresses that are induced in Direct Metal Laser Sintering (DMLS) of Ti-6Al-4V alloy structures. The DMLS process is one of the Additive manufacturing processes that is widely used in the manufacturing of metal bodies used in automotive, aerospace and medical applications. However, the major challenge faced in this process is residual stresses that are caused by large thermal gradients. The DMLS manufactured Ti-6Al-4V has lower ductility when compared to hot work ad martensite structure formed due to the rapid solidification. Residual stresses imposed in them are a key contributor to these characteristics, Despite the fact that post-processing techniques such as hot working can alleviate some of the stresses, Some residual stress effects, like as warping and thermal stress-related cracking, are unaffected by post-processing.
The aerospace sector is challenged to produce airplanes more efficiently and resiliently in the future. This leads to an increasing demand for improving productivity and flexibility as well as providing solutions for sustainable developments. A bottleneck in production is the machining of large-scale components. Apart from the machining tasks, non-productive tasks like fixture adjustment, component handling, referencing and localization are performed within the machining station and can constitute up to 50% of the overall workload. In the UniFix project, Fraunhofer IFAM is participating in the development of a mobile fixture system for large-scale aircraft components, like vertical tail plane and landing flap components of the single aisle aircrafts.