The objective of this study is to develop a new spiral spring that exhibits unique deformation behavior. The properties of the spiral spring make it suitable for use not only as an energy storage element but also as an actuator or similar device. In the present study, a process for manufacturing a spiral spring made of Ti-Ni superelastic alloy wires was proposed. In addition, torque characteristics of the manufactured spiral spring were investigated by torque measurement tests. Rotational torque during wind and rewind processes at a constant rotational speed was monitored. In addition, torque measurement tests were repeated to investigate the effect of the number of wind and rewind processes on the torque characteristics. Two main results were obtained. First, the torque characteristics of the spiral spring show torque plateau behaviors, which are expected to produce a constant energy output. Second, the torque characteristic depends on the number of torque measurement tests. Torque values decrease with increasing number of repeated tests. These results for the spiral spring correspond to the superelastic behavior of the Ti-Ni alloy.

The delayed fracture properties were evaluated by conducting constant load test using notched round bar specimens with different stress concentration factor (K_t) of gas carburized JIS SCM420H. The amount of hydrogen added to specimens after gas carburizing were almost same regardless of K_t value. The testing method employed was a weight-lever method with constant load application, and the displacement of the specimen during the test was measured with a laser displacement meter. Both the deformation rate and the fracture time did not depend on K_t, but the delayed fracture limit decreased as K_t increased. Based on the morphology of fracture surface analysis and the distribution of hydrostatic stress (σ_m), this study was conducted in two cases for the carburizing region near the notch where hydrogen accumulated and for the internal non-carburizing region obtaining the averaged σ_m in each area, σ_mC and σ_mNC. The presented stresses could evaluate the delayed fracture limit and the fracture time.

The need for conductor materials such as copper alloys is increasing as the IoT of society progresses. The properties required for conductor materials are diverse, including high strength, light weight, high flexibility, and elasticity, therefore copper alloys that match the required properties are selected. However, many copper alloys have a trade- off relationship between strength and conductivity. Since conductivity has the higher priority, the strength of selected material has the tendency of being short of the required level. Among them, copper beryllium alloy is a conductive material that has both strength and conductivity, and has excellent spring properties, but there are still problems such as the possibility of adverse effects on the human body and the high cost. In this paper, we report the physical properties of TCC wire, a high-strength conductor developed to solve these problems.

The shape memory alloy (SMA) element that shows superelastic behavior exbibits negative stiffness during post-buckling deformation. Buckling deformation recover during unloading due to the shape memory effect. Thus, the negative stiffness region can be used continuously by the buckling of the shape memory alloy. The continuous availability of a negative stiffness region makes it possible to fabricate a passive vibration isolation mechanism with a quasi-zero stiffness structure composed of the combination of SMA elements and regular spring. Therefore, we devised and fabricated the passive vibration isolator using tape-shaped Ti-Ni SMA elements, and this isolator shows the excellent vibration characteristic. However, the physical properties of the Ti-Ni alloy strongly depend on the environmental temperature, which makes the operating temperature range of this vibration isolator very narrow. In this study, we focused on Cu-Al-Mn SMA with lower temperature dependence than Ti-Ni SMA and investigated their buckling characteristics and fatigue characteristics to evaluate their performance as vibration isolators. From the experimental results, it is considered that Cu-Al-Mn SMA exhibits favorable vibration-isolation properties over a wide environmental temperature range because of its smaller temperature dependence of buckling property and smaller stress hysteresis compared to Ti-Ni SMA. However, Cu-Al-Mn SMA has tendency of rapid decrease in reaction force after tens of thousands of cycles of buckling deformation fracturing shortly thereafter. This fracture was caused by intergranular fracture at the position where tensile stress is applied due to buckling deformation.

Since the metal texture of springs is related to fatigue, creep, and especially strength, we investigated the microstructure in order to clarify the changes of the texture during the manufacturing process of the springs, and to contribute to further strengthening of springs. In this study, the crystal structure of the austenitized and oil-tempered wires was observed by electron backscattering diffraction (EBSD) and confirmed that axial direction of the specimen was 〈110〉. We simulated the texture of a wire produced by drawing in the spring manufacturing process according to the predictive theory of crystal rotation presented by Katoh, which is based on the theorem of minimizing resultant of shear strain and maximizing plastic work and the result shows that the crystal orientation of axial direction rotates toward 〈110〉. Comparing the simulation results with the experimental results, it was confirmed that the metal structure of spring formed 〈110〉//RD texture, which is produced during drawing in the manufacturing process. Furthermore, austenitizing and oil-tempering have almost no effect on the texture.

Large deformations with contact area occurring in flexible beams such as bellows used for zigzag springs and flexible vessels, pipes etc., have a structure that absorbs large relative displacements. Large deformations with contact area occurs in folding process of paper and woven fabric, and are investigated both theoretically and experimentally. The analysis is based on an assumption that geometrical nonlinearity arises as the result of large deformations, while the material remains in linearly elastic status. In this paper, a slender beam is subjected to compressive forces at spring-hinged ends. Several theoretical solutions are obtained in terms of elliptic integrals. Representative parameters such as the arc length, deflection, curvature, bending moment and bending stress are presented in terms of these integrals. The predicted results are compared with the experimental data and both are found to be in fairly good agreement with each other.

The large deformation behavior of flexible thin wires when subjected to axial compressive load has already been analyzed and applied to Young’s modulus measuring method for thin wires. However, from the viewpoint of material testing, it is necessary to analyze the effect of offset compression on Young’s modulus measurement. Therefore, this paper deals with a nonlinear analysis on large deformation when axial compression is applied to an offset beam fixed at both ends. Using the elliptic integral, analytical solutions of relations among arc length s, horizontal distance ξ, deflection η, curvature 1/R, bending moment M and bending stress σ, etc. were derived. Furthermore, the large deformation state was theoretically calculated using the analytical theory, and the effect of the offset amount on the buckling load was clarified. In addition, in order to confirm the effectiveness of the analytical theory, a large deformation experiment using a PVC (polyvinyl chloride) thin plate beam was carried out. As a result, the analytical theory' prediction and the large deformation experiment result were in good agreement. On the other hand, some typical deformation states are represented graphically so that the large deformation can be easily understood visually. In this paper, the offset beam is defined as the condition where both fulcrums are not on the same straight line.

Multiplexing dynamic vibration absorber (DVA) provide better vibration control force compared to classical single-mass DVA. In fact, previous studies have shown that the vibration suppression performance of double-mass DVAs is superior to that of the single-mass DVA. In the optimal design of a parallel-type double-mass DVA, five dimensionless design parameters must be optimized. One of them is the mass ratio of two DVAs arranged in parallel. However, in many cases, especially in the parallel-type, the mass ratio of two DVAs cannot be set to the optimal value, because existing structures and machine parts are often used as DVA. This article investigates how the optimal values of other design parameters vary when the two DVA masses are set equal, and finally, how much the vibration suppression performance of the DVA deteriorates. The results of this study revealed that the performance degradation of the DVA was slight, and that few practical problems would arise. However, since this approximation reduces the number of parameters for the DVA from five to four, we had hoped the an algebraic solution rather than a numerical solution could be derived, but this was not possible.

To reduce surging of a valve spring in a reciprocal engine, we design cam functions that simultaneously damp two natural frequencies of the spring by modeling it into a series undamped 2DOF bead-spring-chain system. The cam functions are defined from a finite-time-settling function termed vibration manipulation function (VMF), which consists of half-integer trigonal functions in an arbitrary rising time. The obtained analytical conditions of the valve spring decide specific rising times of the cam. In simulations, we ascertained simultaneous suppression of the residual vibrations of two natural frequencies during translational motions of the 2DOF valve spring lifted with a designed two-dwell cam.

In this study we aim to realize an actuator that is comparable with a natural muscle from a viewpoint of flexibility, the output force and the responses. We constructed the Shape Memory Alloy (SMA) actuator protected by“a Rolled Film Tube”with the high heat resistance and the high flexibility. In this report we made a coil spring made of SMA wire with rectangular cross section. The characteristics are investigated by the experiments of the load/displacement measurement, the step response and the pulse response. The results of the load/displacement tests are investigated by the theoretical analysis and got two equations of low and high temperature. The results of the step response tests show that a coil spring made of SMA wire with rectangular cross section has time constants of output force shorter than a coil spring made of SMA wire with circler cross section. The results of pulse response testes show that a coil spring made of SMA wire with rectangular cross section has characteristics of nearly equivalent to a natural muscle.

There are two types of contact-type spiral springs: a spring without a primary winding in which the free state has a spiral shape and an S-shaped spring in which the free state has an S-shape. In order to accurately predict the torque characteristics of these springs, it is essential to estimate the free state by highly accurate elastic-plastic analysis. However, it is difficult to create a highly accurate material model because the amount of change in strain varies from the inner end to the outer end of the spring. It is also necessary to consider the effects of the primary winding process and the heat treatment process. In this paper, we first clarify the elastic-plastic deformation behavior of contact-type spiral springs during winding. For contact-type spiral springs with various dimensions or different primary windings, the deformation during winding was collected as the curvature during winding and the curvature in the free state after winding. These data are converted from curvature to surface strain to make non-dimensional parameter, and then organized considering the initial curvature derived from the primary winding of S-shaped spring. As a result, it was found that the elastic-plastic deformation in winding can be comprehensively expressed without depending on the type of spring.

The present paper proposes new remaining creep life prediction methods that can be used in situ as an in-service inspection tool for the condition-based monitoring of high-temperature structural components of modified 9Cr-1Mo steel. The methods were based on two types of the modified theta methods and the combination of the modified theta and modified omega methods and were applied to creep deformation data during creep tests made at different applied stress levels at 823K and 923 K in air. Creep lives were predicted by the proposed three methods at arbitrary time in the continuous measurement of deformation during the creep tests. The results show that the combination of the modified theta and modified omega methods gives the most accurate prediction of creep rupture time at the two levels of test temperature for different applied stress levels.

In this study, the authors proposed a functionally-graded TiNi shape memory alloy to expand the application range of TiNi shape memory alloys. The manufacturing process of the functionally-graded TiNi shape memory alloy consists of powder metallurgy, hot rolling, and ultrasonic shot peening. The effects of the hot rolling and the ultrasonic shot peening on various properties were clarified. The main results obtained in this study are as follows: (1) Vickers hardness is increased by the hot rolling and the ultrasonic shot peening. The main causes of this phenomenon are consolidation of hot rolling and work hardening effect in the ultrasonic shot peening. (2) The ultrasonic shot peening introduces compressive residual stress of up to 300 MPa in the surface layer of the sintered material. (3) Each peak obtained by differential scanning calorimetry shifts to lower temperatures side with increasing Ni composition. This is consistent with the well-known trend in a general TiNi shape memory alloy. Furthermore, the ultrasonic shot peening hardly changes this trend. In other words, the ultrasonic shot peening has almost no effect on the transformation properties of the TiNi shape memory alloy. (4) The ultrasonic shot peening work-hardens the hot-rolled sintered TiNi shape memory alloy. The effect is higher especially in the Ni-rich region, and as a result, the functionally-graded property of the deformation resistance becomes clearly visible.