Grinding Depths Research Articles

Characterization of the mechanical properties and structural integrity of T-welded connections repaired by grinding and wet welding

This paper presents an experimental methodology to characterize the structural integrity and mechanical properties of repaired T-welded connections using in fixed offshore structures. Grinding is employed to remove localized damage like cracking and corrosion and subsequent wet welding can be used to fill the grinded material. But it is important to define the grinding depth and profile in order to maintain structural integrity during the repair. Therefore, in this work different grinding depths were performed, for damage material removal, at the weld toe of the T-welded connections. The grinding was filled by wet welding in a hyperbaric chamber, simulating three different water depths: 50m, 70m and 100m. The electrodes were coated with vinilic varnish, which is cheap and easy to apply. The characterization of the mechanical properties of the T-welded connections was done with standard tensile, hardness and Charpy tests; microstructure and porosity analysis were also performed. The samples were obtained from the welded connections in regions of the wet weld beads. The test results were compared with the mechanical properties of the T-welded connections welded in air conditions performed by other authors. The results showed that the wet welding technique performed in this work produced good mechanical properties of the repaired T-welded connection. The mechanical properties, measured in wet conditions, for 6mm grinding depth, were similar for the 3 different water depths measured in air conditions. But for 10mm grinding depth, the values of the mechanical properties measured in wet conditions were quite lower than that for air conditions for the 3 water depths. However a porosity analysis, performed with a Scanning Electronic Microscopy (SEM), showed that the level of porosity in the resulted wet weld beads is in the range of that published in the literature and some samples revealed lower level of porosity. The main resulting microstructure was polygonal ferrite, followed by ferrite with second aligned phases and ferrite with second phases not aligned in the welding bead, which are typical microstructures of wet welding of A36 steel and electrodes E6013. The results also showed that with the methodology present in this work, one can restore the mechanical properties of localized damage in offshore structures when damage occurs at different water depths.

Thermal Study on the Grinding Special-Shaped Surface of Granite Material

The heat released from grinding process plays a very important role for the machining quality, so studying the temperature distributions on the machined surfaces of granite is necessary. For grasping the influencing factors of temperature, the experimental analysis basing on the infrared imaging method were carried out. The grinding temperatures for two kinds of granite materials (Qilu Red and Jinan Green) are measured. In the results, there are obvious variations of the highest temperatures with different grinding depths, spindle speeds and feed velocities on the machined surfaces. Then, it is suggested that the degree of difficulty is affected by property of granite material to a great extent.

The effect of compressed cold air and vegetable oil on the subsurface residual stress of ground tool steel

This paper investigates experimentally the effect of compressed cold air (CCA) and vegetable oil on the surface integrity and residual stresses of ground tool steel components. It shows that CCA can reduce grinding temperature and produce a compressive residual stress up to the grinding depth of 30 μm. CCA can also improve surface finish while keeping grinding forces low. Oil was found to be more effective in reducing grinding heating and improving surface finish at small grinding depths.

Some observations in grinding unidirectional carbon fibre-reinforced plastics

This paper investigates the grinding performance of epoxy matrix composites reinforced by unidirectional carbon fibres, using an alumina grinding wheel. Emphasis was placed on understanding the effect of fibre orientations and grinding depths on the grinding force and surface integrity, and on understanding the grinding mechanisms, with a comparison to orthogonal cutting. It was found that greater grinding forces occurred at a fibre orientation between 60° and 90°, but poorer grinding surface finish took place between 120° and 180°. The surface integrity was highly dependent on the fibre orientation and the depth of grinding, which is very similar to the results of orthogonal cutting.