The shearing of the chips in a blind hole thread presents a particular problem in machining industry. The tap geometry plays an important role in the tool's durability, influencing the forces during the tapping process and also the way in which the chips are evacuated. This paper analyzes the influence of the tap geometry on the cutting of materials such as C45, 42CrMo4 and X5CrNi8. An adequate geometry will extend the tap durability by controlling the chip when the tap reverses while still engaged in the tapping process. It relates to the improvement of a spiral tap drill, which discharges chips towards the shank via a helical flute. The article contains details about the tap geometries and the results obtained in this research. Based on the results obtained in this research, the purpose of this paper was achieved. The tap durability was improved, the chip deposition on the rake surface was reduced and the torsion torque has a smaller value compared to the standard tap geometry.

The improvement of the microgeometry became a subject of a great interest in cutting tools optimization. This paper approaches the process of cutting edge preparation of solid carbide reamers. It has been analyzed the evolution of cutting edge wear resistance in the material GGG 40 using the scanning electron microscope (SEM). The work also compared the rounded cutting edge reamers realized using wet abrasive jet machining with standard unprepared cutting edge. To obtain different microgeometries were experienced a number of machining strategies, which resulted in four combinations of roundness and forms for the cutting edge. In order to validate the results, the author studied the wear resistance during the reaming tests, the influence of prepared surface of the cutting edge on metallic coating layer adhesion. The final purpose was to determinate the optimal strategy of cutting edge preparation considering the evolution of wear during the reaming process.

This study aims to presents the importance of end constrains, boundary conditions and position of the applied forces regarding the design of precast/prestressed concrete box girders. The study is based on a destructive test which was performed on a 37.1 m span single-cell prestressed concrete box girder. The scope of the test was to certify the usage of such girders for the new Transylvania motorway bridges. The test is numerically reproduced through a full 3D FEM model implemented in SAP2000. The influence of the end diaphragms is considered by analysing the beam's behaviour to six loading conditions: one of which is replicating the loadings during the test, while the others are conceived as real vertical and horizontally loading scenarios. The results obtained for the girders with and without end constrains are compared. The performances of both design solutions in the presence of prestressing are highlighted where applicable. It is considered that the results of this study may provide very important data if considering that Romania has an urgent need to realize a modern and an adequate transport infrastructure.

A common problem when casting reinforced concrete structures is to have a lower concrete compressive strength as opposed to what has been assumed in design. The deflections that may occur under the serviceability conditions can exceed the maximum allowed. Although less frequent nowadays, there is still an ongoing demand to offer simple and practical retrofitting solutions for such situations. To cast a new concrete layer above an existing waffle slab facing these problems is sometimes, only by appearance, the simplest retrofitting method. The major disadvantages reside in the growth of the overall steel consumption and overall weight of the structure. Additional reinforcement is needed for the new slab and at the interface of the two concretes. Interventions that are not always simple and accessible to the builder may still be needed to satisfy the strength demands of the already cast elements. Therefore, a post-tensioning system placed bellow the existing concrete seems to be a better solution. The present study refers to a real-case investigation on a 5-level residual building where a low concrete class was identified for several waffle slabs. Casting an overall top concrete slab or applying an exterior post-tensioning system were the two main retrofitting solutions offered by the designer. Both solutions are compared in terms of structural performance and cost efficiency.

The article presents the research of a cutting tap that has a geometry that extends the cutting tool's life by reducing chipping when the tap reverses while still engaged in cutting a thread. It relates to the improvement of a spiral tap which discharges chips toward a shank via a helical flute. The article contains details about the tap geometries and the results obtained in this research, such as: tool life, chips comparison after cutting 1000 threads, surface comparison after processing 1000 threads and torsion moment analysis. Chip removal is an important factor in the process of threading blind holes which influences the life of the tool.