Engel, Bernd
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Publication Access status: Metadata only , Additive manufacturing of polymeric pressure die for rotary draw bending process3D printing or additive manufacturing (AM) possesses enormous potential to benefit the manufacturing industry. Presently, rotary draw bending (RDB) is one of the most commonly used cold-forming industrial process for bending metal tubes. Pressure die is a fundamental forming tool in RDB processes, and it is conventionally made by various grades of comparatively expensive alloy steels. This research presents a novel design of a pressure die which can be 3D printed by using inexpensive polymeric filaments. In this research paper, the 3D-printed pressure die is named as “FFF-pressure die.” The material used to fabricate the FFF-pressure die is a thermoplastic polymer known as “ecoPLA.” The mechanical properties of ecoPLA are studied in relation to the process conditions of a RDB process. Firstly, an initial feasibility of using the FFF-pressure die in a RDB process is obtained by conducting a quick static stress analysis with actual process conditions. After initial feasibility, a complete RDB process is developed and simulated with actual process conditions and material properties. The FFF-pressure die is then practically fabricated by FFF 3D printer and experimentally tested on an industrial RDB machine. The results of practical experiments are compared with the simulation results. In order to make a comparison of the FFF-pressure die with the conventional metal pressure die, the simulation and practical process is also conducted with the conventional metal pressure die. A performance and cost comparison is made between the polymeric FFF-pressure die and the conventional metal pressure die. Von Mises stresses, contact forces, failure risk, and elastic deformations are analyzed. The advantages and limitations of using the FFF-pressure die in a RDB process are discussed in the end. This research intends to widen the avenue of using cost-effective and lightweight forming tools in metal forming industries.Source Type:Article5 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Defect Detection in Bidirectional Glass Fabric Reinforced Thermoplastics Based on 3-D-THz ImagingNon-homogeneous, bi-directional glass fabric reinforced thermoplastic (GFRT) composites are used in the automobile industry to produce economic and environmentally friendly vehicles. Despite the fact that GFRT materials have superior mechanical characteristics and lower manufacturing cost compared with traditional materials, they are prone to significant deformation and defect emergence during the forming/manufacturing of parts from prefabricated laminates. Some defects, especially hidden ones like delamination and consolidation defects, can significantly reduce the mechanical properties of the final parts. It is essential to use 3D non-destructive testing (NDT) technology to detect and identify such hidden defects. This research investigates the ability of 3D THz imaging to detect hidden defects (i.e., delamination and consolidation) in GFRT composite materials. Frequency modulated continuous wave (FMCW) technique is used to generate 3D-THz cross-sectional images. Non-defective and defective samples with a thickness of 1.5mm have been measured with two 3D THz imaging systems operating in the frequency range from 238 to 316GHz and from 499 to 733 GHz. In addition, a simulation of the reflected FMCW spectrum is presented to analyze the measurements and intercompare the performance of the two imaging systems. A systematic analysis in a large sample set demonstrates that a delamination defect with a thickness of 125μm as well as a consolidation defect with a difference in thickness less than 0.4mm can be successfully detected by the 700-GHz imaging system.Source Type:Article5 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Embedding optical fiber with laser metal depositionIn contrast to other additive manufacturing technologies, laser metal deposition (LMD) allows printing on existing metal parts. For smart tools, it would be advantageous to place fiber optics closely beneath surfaces in order to measure parameters, such as temperature and strains. This work presents a novel method to weld in fiber optical cables beneath sheet metal surfaces with LMD. Results show that the fiber optical cable can be enclosed in the metal, confirming the possibility of using LMD to embed fiber optical sensors in the metals. An applicable scan speed for welding has been identified. A need for a metallic strip on the surface of fiber has been identified, which prevents the fiber from being melted. Ceramic sleeve and multiple plastic layers around the cable successfully prevent the fiber from being destroyed. Further research on effects on the optical characteristics of the fibers is proposed.Source Type:Article3 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Fracture behavior of double edge notch AlSi10Mg alloy fabricated by laser powder bed fusion(2024); ; Reinicke, TamaraIn the present study, the fracture behavior of additively manufactured (AM) metal parts has been investigated. To this aim, double edge notch tension (DENT) specimens have been printed using AlSi10Mg alloy based on the laser powder bed fusion (PBF) technique. Particularly, DENT specimens have been fabricated with three different ligament lengths and three different printing directions for each ligament length. In this study, we used the concept of essential work of fracture to describe the fracture behavior AMed parts. According to a series of tests under static loading conditions, influences of the ligament length and printing direction on the structural integrity of the DENT specimens have been determined. According to the experimental practices, levels of ductility and size of plastic zone in the ligament region have been documented. Here, we utilized digital image correlation technique to measure strain fields on the surface of the examined samples. Moreover, numerical simulations have been conducted to simulate the stress distribution from DENT specimens. In addition, visual inspection of the fracture surfaces has been conducted using a free-angle observation system. The outcome of this study can be used for future designs of PBF printed parts with a better structural performance.Source Type:Article3 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Improvement of strength in single-lap adhesive joints of AlSi10Mg alloys fabricated by laser powder bed fusion(2024); ; Reinicke, TamaraSource Type:Article3 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , 4 - Some of the metrics are blocked by yourconsent settings
Publication Access status: Metadata only , Surface roughness and coefficients of friction of 3D-printed clamp tools made from selective laser meltingThe practical use of 3D-printed metal tools in production industries requires accurate characterization of tool behaviour. In metal forming industries, the efficacy of clamp tools largely depends on surface roughness and friction behaviour of tool surfaces. This research is aimed to investigate surface roughness and friction behaviour of 3D-printed clamp tools made from selective laser melting process. Gas atomized powdered tool steel-X3NiCoTi1895 (EN 1.2709) is used to 3D print clamp tools. A mechanical setup determines the friction coefficients of 3D-printed samples under practical loading conditions. The effect of raster angle on surface roughness of 3D-printed clamp tools is determined. These findings serve as the basis of a broader project in which metal-3D-printed forming tools are developed and tested in actual production setups.Source Type:Article4