Current Issue : January - March Volume : 2014 Issue Number : 1 Articles : 5 Articles
We have developed a novel instrument combining a glide tester with anAtomic ForceMicroscope (AFM) for hard disk drive (HDD)\r\nmedia defect test and analysis. The sample stays on the same test spindle during both glide test and AFM imaging without losing\r\nthe relevant coordinates. This enables an in situ evaluation with the high-resolution AFM of the defects detected by the glide test.\r\nThe ability for the immediate follow-on AFM analysis solves the problem of relocating the defects quickly and accurately in the\r\ncurrent workflow. The tool is furnished with other functions such as scribing, optical imaging, and head burnishing. Typical data\r\ngenerated from the tool are shown at the end of the paper. It is further demonstrated that novel experiments can be carried out on\r\nthe platform by taking advantage of the correlative capabilities of the tool....
We investigate the normal contact stiffness in a contact of a rough sphere with an elastic half-space using 3D boundary element\r\ncalculations. For small normal forces, it is found that the stiffness behaves according to the law of Pohrt/Popov for nominally flat\r\nself-affine surfaces, while for higher normal forces, there is a transition to Hertzian behavior. A new analytical model is derived\r\ndescribing the contact behavior at any force....
Nitrogen implantation in Interstitial-Free steel was evaluated for its impact on metal transfer and 1100 Al rider wear. It was\r\ndetermined that nitrogen implantation reduced metal transfer in a trend that increased with dose; the Archard wear coefficient\r\nreductions of two orders of magnitude were achieved using a dose of 2e17 ions/cm2, 100 kV. Cold-rolling the steel and making\r\nvolumetric wear measurements of the Al-rider determined that the hardness of the harder material had little impact on volumetric\r\nwear or friction. Nitrogen implantation had chemically affected the tribological process studied in two ways: directly reducing the\r\nrider wear and reducing the fraction of rider wear that ended up sticking to the ISF steel surface. The structure of the nitrogen\r\nin the ISF steel did not affect the tribological behavior because no differences in friction/wear measurements were detected after\r\npostimplantation heat treating to decompose the as-implanted ??-Fe3N to ??-Fe4N. The fraction of rider-wear sticking to the steel\r\ndepended primarily on the near-surface nitrogen content. Covariance analysis of the debris oxygen and nitrogen contents indicated\r\nthat nitrogen implantation enhanced the tribo-oxidation process with reference to the unimplanted material. As a result, the\r\nreduction inmetal transfer was likely related to the observed tribo-oxidation in addition to the introduction of nitridewear elements\r\ninto the debris. The primary Al rider wear mechanism was stick-slip, and implantation reduced the friction and friction noise\r\nassociated with that wear mechanism. Calculations based on the Tabor junction growth formula indicate that the mitigation of the\r\nstick-slip mechanism resulted from a reduced adhesive strength at the interface during the sticking phase....
The present paper concentrates on the investigations regarding the situations of frictional shear stress of gear teeth and the relevant\r\nfrictional effects on bending stresses and transmission error in gear meshing. Sliding friction is one of themajor reasons causing gear\r\nfailure and vibration; the adequate consideration of frictional effects is essential for understanding gear contact behavior accurately.\r\nAn analysis of tooth frictional effect on gear performance in spur gear is presented using finite element method. Nonlinear finite\r\nelementmodel for gear tooth contact with rolling/sliding is then developed.Thecontact zones formultiple tooth pairs are identified\r\nand the associated integration situation is derived. The illustrated bending stress and transmission error results with static and\r\ndynamic boundary conditions indicate the significant effects due to the sliding friction between the surfaces of contacted gear teeth,\r\nand the friction effect can not be ignored. To understand the particular static and dynamic frictional effects on gear tooth contact\r\nanalysis, some significant phenomena of gained results will also be discussed. The potentially significant contribution of tooth\r\nfrictional shear stress is presented, particularly in the case of gear tooth contact analysis with both static and dynamic boundary\r\nconditions....
Analyzing wearmechanisms and developments of surface layers inWC/Co-cemented carbide cutting inserts is of great importance\r\nfor metal-cutting manufacturing. By knowing relevant processes within the surface layers of cutting tools during machining the\r\nchoice of machining parameters can be influenced to get less wear and high tool life of the cutting tool. Tool wear obviously\r\ninfluences tool life and surface integrity of the workpiece (residual stresses, surface quality, work hardening, etc.), so the choice\r\nof optimised process parameters is of great relevance. Vapour-deposited coatings onWC/Co-cemented carbide cutting inserts are\r\nknown to improve machining performance and tool life, but the mechanisms behind these improvements are not fully understood.\r\nThe interaction between commercial TiN-coated and uncoated WC/Co-cemented carbide cutting inserts and a normalised SAE\r\n1045 steel workpiece was investigated during a dry plain turning operation with constantmaterial removal under varied machining\r\nparameters. Tool wear was assessed by light-optical microscopy, scanning electron microscopy (SEM), and EDX analysis. The state\r\nof surface layer was investigated by metallographic sectioning. Microstructural changes and material transfer due to tribological\r\nprocesses in the cutting zone were examined by SEM and EDX analyses....
Loading....