Experimental Study of Particles Induced by Screw Tightening Process for Hard Disc Drive Assembly: Effects of ‘Bit’ Speed

The morphology of particles generated during screw tightening process in hard disc drive assembly was studied using a media installing tool kit under a class 100 clean room condition. The screws were made of martensitic 410 stainless steel and the ‘bit’ was made of S2 tool steel. The ‘bit’ speeds used during the screw tightening process can be divided into two steps: the beginning and the final speeds. The effect of both speeds on the morphology of particles generated was investigated. The studied parameters were the aspect ratio and the appearance cross-sectional area of particles. Particles with different sizes were found suggesting that there were different wear mechanisms. Small particles were caused by adhesive wear, while the larger particles were generated by fatigue wear. The appearance cross-sectional area of particles was found to decrease with increase in both speeds within the speed of 250 r/min, after which the appearance crosssectional area appeared to be constant. The effect of cold-weld at asperities was obvious resulting in an increase in aspect ratio at a higher speed. The understanding of the effect of bit speed on the particles morphology during the screw tightening processes could be very useful in the design of the cleaning system in hard disc drive production.The morphology of particles generated during screw tightening process in hard disc drive assembly was studied using a media installing tool kit under a class 100 clean room condition. The screws were made of martensitic 410 stainless steel and the ‘bit’ was made of S2 tool steel. The ‘bit’ speeds used during the screw tightening process can be divided into two steps: the beginning and the final speeds. The effect of both speeds on the morphology of particles generated was investigated. The studied parameters were the aspect ratio and the appearance cross-sectional area of particles. Particles with different sizes were found suggesting that there were different wear mechanisms. Small particles were caused by adhesive wear, while the larger particles were generated by fatigue wear. The appearance cross-sectional area of particles was found to decrease with increase in both speeds within the speed of 250 r/min, after which the appearance crosssectional area appeared to be constant. The effect of cold-weld at asperities was obvious resulting in an increase in aspect ratio at a higher speed. The understanding of the effect of bit speed on the particles morphology during the screw tightening processes could be very useful in the design of the cleaning system in hard disc drive production

Materials Challenges and Testing for Manufacturing, Mobility, Biomedical Applications and Climate

X, 245 p. 120 illus., 67 illus. in color.online r

Fretting Fatigue with Cylindrical-On-Flat Contact: Crack Nucleation, Crack Path and Fatigue Life

Fretting fatigue experiments and finite element analysis were carried out to investigate the influence of cylindrical-on-flat contact on crack nucleation, crack path and fatigue life of medium-carbon steel. The location of crack nucleation was predicted using the maximum shear stress range criterion and the maximum relative slip amplitude criterion. The prediction using the maximum relative slip amplitude criterion gave the better agreement with the experimental result, and should be used for the prediction of the location of crack nucleation. Crack openings under compressive bulk stresses were found in the fretting fatigues with flat-on-flat contact and cylindrical-on-flat contacts, i.e., fretting-contact-induced crack openings. The crack opening stress of specimen with flat-on-flat contact was lower than those of specimens with cylindrical-on-flat contacts, while that of specimen with 60-mm radius contact pad was lower than that of specimen with 15-mm radius contact pad. The fretting fatigue lives were estimated by integrating the fatigue crack growth curve from an initial propagating crack length to a critical crack length. The predictions of fretting fatigue life with consideration of crack opening were in good agreement with the experimental results