We have investigated the influence of aging conditions on fatigue strength of titanium alloy and studied the wear resistant coatings for titanium alloy. Utilizing the results, we have developed the valve spring made of titanium alloy in order to increase engine speed and lighten engine weight. The main results obtained are summarized as follows: 1) Tensile strength dependence of fatigue strength in Ti-13V-11Cr-3Al alloy is opposite to tensile strength dependence in steel. 2) Settling performance of Ti-13V-11Cr-3Al alloy is improved as increasing tensile strength, and settling performance is equivalent to steel with higher strength. 3) Ni-P electroless plating and Ni-P+Au-Ni electroless plating are excellent methods as wear resistant coating for titanium alloy. 4) Ti-13V-11Cr-3Al alloy springs with optimum tensile strength and coating by Ni-P electroless plating or Ni-P+Au-Ni electroless plating pass the motoring test. 5) Titanium alloy springs with optimum tensile strength and coating by Ni-P electroless plating or Ni-P+Au-Ni electroless plating in comparison with steel springs lead to a 13 percent decrease in free height and a 57 percent decrease in weight.
By using new technique which enables us to measure the depth of initial fatigue cracks in springs, the mechanism of fatigue on engine valve springs was made clear: (1) The initial cracks on non-electropolished springs start from the surface of wire. By contraries, on electropolished springs, they start from inside of wire. (2) On non-electropolished spring, the depth of initial cracks has certain critical values, which probably depend on applied stress. (3) When the initial crack on non-electropolished springs reaches the critical depth, failure occurs suddenly. On the other hands, when the initial crack on electropolished springs comes to surface, sudden failure takes place.
Platinum and it's alloys which own excellent characteristics such as corrosion resistance, high melting point, heat resistance and so on arewidely used for industry, for example, ammonia oxidation catalyst gauzes, thermocouples, temperature measuring resistance bulb, contact material. Noble metal alloys for springs are used for contact material. However, the fundamental data at high temperature are not enough. In this report, the tensile strength of Platinum-Rhodium alloys in the range of temperature 373-873K are examined and then compared with those of Platinum.
In the Macpherson strut type suspension, a spring offset is frequently adopted to compensate the side load acting on the damper rod with the reaction force of a spring; this offset amount is determined based on the assumption that the reaction force is directed along the spring axis. However, this is valid only for close-coiled helical springs. For helical springs of usual design, the reaction force will have the component perpendicular to the coil axis, as often pointed out by many researchers. Therefore, this component, that is the side force of the spring, should be taken into consideration to improve the riding comfort. In this paper, we first investigated the specifications of the springs which minimizes the side force. Then we studied the effect of the tilting angle of a spring seat and of the kinematic condition of the spring on the side force. In consequence, it was found that the side force periodically increases with decrease of the number of free coils, minimum values occuring at integer numbers of free coils. it was also found that the side force can be reduced by moving the upper seat of the spring in the direction of the side force acting on the upper seat. Moreover, we found that the side force is remarkably reduced by tilting the upper seat in a proper direction.
Regarding the design of stabilizer bars, the following subjects must be considered in order to obtain highly accurate calculations. (1) Bent shape between mounting areas (2) Flat section of bent area (3) Rigidity of mounting bush In this paper, Finite Element Method (FEM) was easily applied to account for the above-mentioned factors, especially for hollow stabilizer bars. And availability of FEM analysis was cleared. Considering the flat section of bent areas, an experimental equation for predicting the shape of flattened crosssections was proposed. Also the way in which these three factors influence on a stabilizer bar's charcteristics was confirmed. It was determined that taking the above three subjects into consideration FEM analysis makes it possible to achieve highly accurate calculations.
Manufacturing the solid springs by a synchronous cutting machine with a sheet of cut-off wheel, is available in respect of the working accuracy, but the process is not practical in respect of the productivity in comparison with manufacturing the solid springs by coiling machine. So we try to improve the above productivity by a multi-cut method that the synchronous cutting machine cuts several springs simultaneously with several sheets of cut-off wheel. As a result of this experiment, the productivity (i.e. volume of abrasive wear and cut-off time), the working characteristics of the solid springs (i.e. free height, inclination of coil outside face, burn mark and step), and cutting condition suited for synchronous cutting of the solid springs with multi-cut method were cleared. It was also cleared that the cut-off time for manufacturing one spring in case of two sheets of cut-off wheel (multi-cut method) decreased by approximately 40-45% in comparison with that in case of a sheet of cut-off wheel while the working accuracy in case of two sheets of cut-off wheel was held the same level as that in case of a sheet of cut-off wheel.
In order to examine the effect of shot peening on the corrosion behavior of high carbon spring steel S60C by the changes of passive state or the state of pitting formation, anodic polarization curves were measured under various applied stresses in undeairated 3%NaCl solution. The main results obtained are summerized as follows; 1) Shot peened surface becomes electrochemically more stable. 2) Shot peened is depressed the formation of deep pit above 3μm. Conseguently, the possibility of fracture caused by pitting corrosion should decreased. 3) It is supposed to be mainly because of dispersion of impurity elements segregation and residual compression stress by shot peening respectively.
Standardization of characterization methods of mechanical properties of thin plates and fine wires is reported. These plates and wires are used for electronics equipment in the variety of fields such as information, telecommunication, office automation, automatic control or transportation. Variety of mechanical properties of thin plates and fine wires were investigated in the antecedents of the research committee for electronic materials & components, the committee on strength of flat spring and the committee for characterization of spring materials in electronic use. Among these characteristics, most fundamental tests of hardness test, tensile test and fatigue test are reported. Especially, common testing methods for thin plates with less than 0.2mm thickness and fine wires with less than 0.2mm diameter are reported to propose standardization of testing method to be authorized by Japan springs manufacture's association.
Nakamura-type rotating-bending fatigue test has been widely used order to evaluate the fatigue strength of wire, because of its simplicity and rapidity. However it has been used for the relative comparison within results obtained by own institution, it was difficult to compare the results with data obtained by other institutions, because its standard testing method has not been established. Consideing these background, actural problems of the conventional method were investigated, and load-controlled method and deflection-controlled method were tested in order to compare the scattering of static bending stress and dynamic fatigue life. Furthermore, some factors which cause scattering were checked in detail. On the basis of these investigations, this comittee proposed a new standard testing method. In this study, the following facts were mainly clarified. (1) Load-controlled method has been conventionally used in many institutions, and the bending stress is calculated by using the linear solution based on the beam bending theory. (2) Bending stress should be calculated by using the equation based on the large deflection theory. (3) Deflection-controlled metod is superior to load-controlled method comparing the amounts of scattering of data. (4) By measuring the deflection, true stress can be estimated even in load-controlled method. (5) Most useful bush which has good wear resistance and low friction is made from ultra high molecule polyethylene.