Laser Based Manufacturing of Ti6Al4V: A Comparison of LENS and Selective Laser Melting

The laser engineered net shaping (LENS) system was used for the laser based manufacturing of a test geometry used to assess the performance of additive manufacturing systems. This system was preferred over a selective laser melting (SLM) system due to certain inherent benefits that would promote the manufacture of the test geometry where the SLM system had failed due to part delamination. The test geometry was successfully manufactured on the LENS system and machined to produce test specimen for mechanical testing and microstructural evaluation. Investigations revealed that the α-β lamellar microstructure was formed via in situ martensitic decomposition of the α’ structure. This resulted in promising yield and tensile strengths in excess of 900 MPa and high tensile elongation up to 13%.

Influence of the Extent of Fracture on the Resistance against Chloride Penetration into Cementitious Composite

The paper presents data obtained in own experimental campaign focused on the investigation of the effect of fracture propagation on the change in values of electrical resistivity and ultrasound pulse passing time in notched beam specimens. Test geometry of three-point bending was utilized to propagate the crack through the specimen ligament in several loading−unloading cycles, between which the electrical resistivity and ultrasonic measurements over the fractured region in the centre of the beam were performed. Equivalent elastic crack length was estimated at those loading stages. Relationships among the changes in the investigated, non-destructively gained parameters, the effective crack length and the distance from crack tip are discussed with respect to two variants of treatment of the specimens’ surface during testing: the pre-dried and the wet one.

Optimization of the Modified Yoshida Buckling Test to Investigate the Influence of Curvature

During deep drawing process compressive stresses are induced in the sheet metal, which can cause undesirable wrinkling. On the other hand a high sheet thickness and high local surface curvature counteract the wrinkling tendency by stabilizing the blank. To investigate these factors influencing the wrinkling initiation experimentally, a modified and the requirements customized test form based on a simple test geometry, the so called Yoshida buckling test, is created. This enables to take into account surface curvature in the region of instability.