The shape memory effect of Fe-Ni alloy would be improved with hot dip aluminum coating. There were five types of the specimens, namely #1; just after shape memory treatment (SMT), #2; Al-coated after SMT, #3; Al-coated after SMT and then annealed at 400 degree C, #4; the same but 800 degree C, and #5; annealed at 800 degree C after SMT w/o Al-coated. The shape recovery ratio of the Al-coated specimens (#2) was as much as 20% better than those of w/o Al-coated ones (#1) in V-shaped bending test. All the Al-coated specimens had the intermediate layer at the boundary of Fe-Ni and Al layers. The layer consists of solid solutions of Al dissolved by Fe and Ni with 10 – 20 μm thickness evaluated by microscopic observations. The Vickers hardness was higher than the specimens without Al coating and the specimens with Al coating might have higher yielding stress. The solid-solution layer may store the elastic strain energy during the bending test and then release it for assisting inverse martensite transformation during recovery treatment, thus the recovery may have been strengthened.
Fatigue cracks, leading to catastrophic fracture of metal structure, generally initiate by the cyclic stress even under yield stress. At the first stage of fatigue process, movement and increase of lattice defects (dislocations), namely microscopic sliding takes place, and crack initiation follows thereafter. The positron annihilation spectroscopy has been widely used for probing open volume lattice defects in various materials. In this study, rotating bending fatigue test of Type 316 stainless steel was conducted, and fatigue damage accumulation has been investigated using S parameters defined in positron annihilation spectroscopy. S-parameter increased with increasing number of loading cycles due to the fatigue damage accumulation, namely increase of dislocation density. When fatigue crack initiated, S-parameter measured at the crack initiation site became higher than that at the location without fatigue crack. The plastic deformation zones at the fatigue crack tips had extremely higher dislocation densities. Higher S parameter at the crack initiation site was attributed to those plastic zones at the fatigue crack tips.
Since residual vibration decreases lifetime of springs in the system, the profiles of spring-loaded cam and cam follower are important design factors of cam mechanism in automation machineries or engines. By simplifying the vibration by modeling it as a 1DOF oscillator, trajectory of cam follower, called pitch curve, affects the oscillation by modifying enforced displacement of the oscillator base. Although both profiles of cam and cam follower influence the pitch curve, people usually consider merely cam profile and ignore the effect from the shape of cam follower. In this report we study the effect of radius of roller follower, which contacts a periodical sinusoidal translation cam. In case the radius is smaller than the amplitude of the cam profile, almost sinusoidal enforced displacement can excite merely a resonant condition in the oscillator. However, in case the radius size cannot be ignored against the amplitude of the cam profile, higher harmonics excitations, especially 2nd harmonics, also occurs in the oscillator. Hence the radius of cam follower affects harmonics of cam mechanism, we should consider the trajectory of pitch curve as the combination of cam and cam follower profiles in design them.
For the purpose of analyzing the characteristic of spiral spring, knowing the free shape of spring is indispensable. And to get the free shape of spring needs to analyze on elasticplastic method with geometric non-linearity. But the practical importance for the spring characteristic is the liner zone without both side-ends. If extrapolating liner field to both non-linear zones asuming affine linearity,we are able to analize the spring charactristic only by elasticplastic analysis at both-ends without the necessity of considering geometric nonlinerlity . So we can analyze by easy procedure as compared with traditional integral formulation. This calculation results agree with experimental one in two kind sample springs.
In general, springs are flexible machine elements used for controlled application of force (or torque) or for storing and release of mechanical energy. A coiled wave spring (CWS), also known as a scrowave spring is a compression spring made of coiled wire or thin plate with waves giving a spring effect and offers the unique advantage of space savings when used to replace conventional coil springs. By reducing spring operating height, the coiled wave springs also offers a decreased spring cavity. A production cost savings is realized with a smaller assembly size and less material used in the manufacturing process. CWS makes it possible to accommodate higher thrust load within the limited axial space depending on the size of the wire (or plate), the number of waves, the height of waves, and the number of turns. In recent years, CWS with very high performance are widely applied to “Slip Clutch” and “Multi-Tooth Cutter”, “Retaining Ring”, “Face Seal”, and so on. However, nonlinear characteristics observed in large deformation of CWS has not been made clear yet. The large deformation analysis has been eagerly looking forward to as calculation formula. As it is, there exists no persuasive analysis. In this research, these nonlinear characteristics and spring constant for CWS are analyzed theoretically. A nonlinear large deformation theory is applied and exact analytical solutions are derived in terms of elliptic integrals, and then put into a nondimensional formula to facilitate the common understanding of large deformation phenomenon. Moreover, three concepts for the spring constant are newly proposed. In this study, some experiments were presented and the experimental results were compared with the theoretical formulas. As a results, the relation between the applied axial compression force and the nonlinear deflection obtained from the experiments is in good agreement with the relation predicted by the analytical theory.
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