Fahad Al-Mufadi

Calculation of the machining time of cutting tools from captured images of machined parts using image texture features

Quality of machined surfaces and its integrity are strongly dependent on tool wear, which consequently depends on the tool life or machining time. Therefore, prediction of the machining time of the cutting tool during machining processes is very important in order to obtain high precision parts and to reduce manual fit operations and production cost. In this work, the relationship between texture features of the gray-level co-occurrence matrix and the machining time of the cutting tool in turning operations has been investigated, and the results show that four texture features are highly correlated with machining time. These highly correlated texture features were utilized to calculate machining time of the cutting tool from captured images of machined parts. The verification results showed that the maximum percentage of error between the actual and calculated machining time ranged between −4.65% and 7.79%.

Cold deformation of dezincification resistant yellow brass for plumbing applications

ABSTRACT In the present work, the room temperature deformation behavior of dezincification-resistant (DZR) brass was performed by varying strain rates (1 × 10−4 s−1, 0.55 × 10−3 s−1, 1 × 10−3 s−1, 0.55 × 10−2 s−1, 1 × 10−2 s−1) and percent cold works (15 to 65% with step of 10%). These parameters are important to plumbing parts of its forming. Room temperature deformation workability map was developed that provides the selection of safe deformation parameters without cracking. The as-received and deformed DZR brass samples were carefully characterized by various microscopes. The results revealed that more dislocations lines and twinning were observed through transmission electron microscope images as the strain rate (SR) increases which led to early failure of the sample before reaching the set height reduction. It was determined that more amount of strain hardening with designed height reduction was achieved at lower SR whereas less amount of strain hardening was achieved at higher SR due to strain mismatching phenomenon and various deformation mechanisms.

Contact Stiffness of Polymer with Nominally Flat Surfaces

The normal contact stiffness between two polymer blocks with nominally flat surfaces in contact is investigated. Contact stiffness is experimentally determined on a tension-compression machine at small loading steps from zero to about 15 kN. The contact stiffness of steel specimens with the same dimensions as those of the polymer blocks is also investigated to examine the differences between polymers and metals. The three-dimensional surface parameters of the samples are obtained by using an optical profiler. The experimentally measured contact stiffness of Nylon shows a trend similar to that of steel, whereas Teflon and Polyimide show different trends. This discrepancy is shown to be related to the non-homogeneous distribution of surface summits on the contact area. Such a distribution may reduce the real elastic contact area, which in turn changes the surface condition from a rough to smooth contact. Keywords: contact stiffness, polymer, elastic contact area, surface roughness