In this paper, with the aim of more appropriately characterizing surface topography for tribology, the validity of Nayak's theory is assessed through a comparison with direct calculations. The summit parameters examined in this study are the areal density, mean radius of curvature, and standard deviation of height. Functions such as the probability density of summit height and summit height vs. mean radius of curvature are also discussed. Purely homogeneous, isotropic and Gaussian distributed surfaces generated with a stochastic model are used to avoid unpredictable components such as noise and local irregularities. Overall, the estimation showed good qualitative agreement with the direct calculation. The relative discrepancies range from -10 to 20% for density, -20 to -8% for curvature, and -2 to 10% for height.
This paper presents a study on effects of the pre-treatment and the heating time on the hardened layer and the bending fatigue strength of induction hardened gears. The measurement of hardened layer and the bending fatigue test of induction hardened gears made of thermally refined and as-rolled S35C and S45C steels were carried out, and then profiles of hardened layer and S-N curves were obtained. Effects of the pre-treatment and the heating time on profiles and micro structures of hardened layers of induction hardened gears were examined. The relationship between the bending fatigue strength and the profile of hardened layer was determined. An optimum heating condition for the bending fatigue strength of induction hardened S35C and S45C steel gears were indicated.
In this study, the influence of basic design parameters and tooth surface modifications on the mechanical (friction induced) power losses of a helical gear pair is studied. A helical gear mechanical efficiency model based on elastohydrodynamic lubrication (EHL) is introduced. The model is used to simulate the gear contact conditions of an example helical gear pair within the ranges of basic design parameter such as pressure and helix angles, number of teeth (module), and major diameters to quantify their impact on mechanical power losses. Variation of gear efficiency with these parameters are then weighed against other functional requirements such as transmission error amplitudes, and contact and bending stresses to demonstrate that many designs that have high efficiency might perform poorly in terms of noise, pitting, and tooth breakage. A representative design that is acceptable in all aspects is considered next with varying amounts of tooth modifications to demonstrate their impact on power losses. At the end, recommendations are made on how to reduce helical gear mechanical power losses while meeting other functional requirements as well.
Roller chains have a long history as mechanical elements for transmission. Although they have clear advantages over belts in terms of performance and efficiency, their larger weight has always been a disadvantage. In this paper, the authors propose some methods of weight saving for roller chains. These methods are based on finite element method (FEM) analysis of the stress and deformation in a link plate of a roller chain. The authors also suggest some approaches for reducing stresses and weight saving in the link plate of the roller chain. Stresses are 3% higher in the proposed design, but the weight is reduced by 10%. Tensile tests are performed on link plates made of resin, and the effectiveness of the proposed model is confirmed.
It is widely known that the electromotive force generated at the interface between the cutting tool and work material, during a metal cutting process, influences the cutting mechanism. Previously published papers describe the influence of the passage of electric current through the contact zone between cutting tool and work material, on tool life in cutting several work materials. However, few papers deal with the influence of this electric current on the behavior of a deposited layer called “belag”, observed in turning work materials such as calcium deoxidized steel and boron and nitrogen, BN added steel. This paper deals with the machinability of BN free-machining steel in turning with a supplied current of various values and different directions of flow. The test materials were, BN added steel based AISI 1045 which has good machinability at high cutting speed and standard AISI 1045. Turning was undertaken using one of three types of cutting tool; K10 and P30 carbide and cermet. The power source for additional current supply was a direct current source and the maximum current flowing in the circuit was 20milliamperes (mA). To investigate the influence of supplied current on the characteristics of the turning process, tool life, cutting force and cutting temperature were determined experimentally. When turning with carbide P30 the maximum crater depth in the tool was reduced drastically when the value of supplied current reached 5mA, regardless of its direction of flow, compared with depths at lower current values. This suggests that the additional electrical current promotes generation of the protective layer, on the rake face, in turning BN free-machining steel.
This work synthesizes the topological structures of the lost Zhang Heng's seismoscope, which was invented in ancient China in 132 AD, with cam-linkage mechanisms. Based on the study of the literature and seismology, the design specifications of Zhang Heng's seismoscope are defined and concluded. According to the concepts of generalization and specialization subject to the concluded design specifications, all feasible interior mechanisms with cams and links that meet science theories and techniques of the subject's time period are receated. Two examples, one with five members and six joints and the other with six members and eight joints, of the interior mechanism of Zhang Heng's seismoscope are derived with 2 and 11 feasible designs, respectively.