Authors: Minoru Yamashita, Tomohito Okuyama, Naoya Nishimura, Toshio Hattori
Abstract: The method for prescribing the site of the first buckling lobe in the axial impact of the
tubular structure is proposed. The inertia force induced by the solid mass attached to the tube during
the impact is exploited to trigger the first buckling lobe. When the tube with the solid mass
undergoes a large acceleration, the inertia force of the solid mass is expected to bend on the tube
wall. In the experiment, the rectangular solid mass was attached to the aluminum alloy square tube.
The tube fixed to the drop-hammer was impacted against the stationary rigid plate at the velocity of
5 or 7.7 m/s. For the case of the tube without the solid mass, the site of the first buckling lobe varied
and the slight wavy plastic deformation remained further than the buckling lobes. On the other hand,
when the tube with the solid mass was impacted, the onset of the first buckling lobe was observed at
the portion where the solid mass was attached and the wavy deformation stated above was
suppressed. The corresponding computation was also conducted using the dynamic explicit finite
element method. The result showed a good agreement with the experimental one.
173
Authors: Naoya Nishimura, Toshio Hattori, Minoru Yamashita, Naoyuki Hayakawa
Abstract: In this paper, we have evaluated the sliding and the loosening behavior of thread joints
under transverse loading. Firstly, the critical relative slippage (Scr), less than which the thread joints
can keep the fastening, is obtained by the cyclic loading tests. Then, this critical relative slippage is
estimated according to the theoretically obtained equation considering the bending deformation of
bolt and the geometrical constraint condition. The inclination compliance (kw) of the bolt head used
in this equation is evaluated by comparing the experimental result with the corresponding analytical
one. In consideration of the nonlinearity of kw with respect to the bolt axial tension, the Scr is well
estimated by this equation.
894
Authors: Toshio Hattori, Naoya Nishimura, Minoru Yamashita
Abstract: In this paper we present the estimation methods of fretting wear process and fretting
fatigue life using this wear process. Firstly the fretting-wear process was estimated using contact
pressure and relative slippage. And then the stress intensity factor for cracking due to fretting
fatigue was calculated by using contact pressure and frictional stress distributions, which were
analyzed by the finite element method. The S-N curves of fretting fatigue were predicted by using
the relationship between the calculated stress intensity factor range ( #K) with the threshold stress
intensity factor range ( #Kth) and the crack propagation rate (da/dN) obtained using CT specimens
of the material. Finaly fretting fatigue tests were conducted on Ni-Mo-V steel specimens. The S-N
curves of our experimental results were in good agreement with the analytical results obtained by
considering fretting wear process. Using these estimation methods we can explain many fretting
troubles in industrial fields.
882
Authors: Naoya Nishimura, Toshio Hattori, Minoru Yamashita, Naoyuki Hayakawa
Abstract: Considering the productivity and the maintenance, most of machine and product has
many joints (fastening, welding and adhesive joint). Especially, the thread joint has been used the
most mainly as a machine element. However, many troubles on strength and reliability of these
machine and product are generating in these joints. In this paper, we have evaluated the sliding and
the self loosening behavior of thread joints under transverse loading, where the entire response of
the thread joint portion exhibits an inelastic one. The finite element analysis using a simple model
of thread joints with respect to the relative sliding motion between the parts was performed and
compared with the experimental results under quasi-static loading. The critical relative slippage
(Scr), less than the value which thread joints can keep the fastening, was obtained by the result of
cyclic loading tests. In addition, this critical relative slippage was estimated according to the
theoretically obtained equation considering the bolt bending and the geometrical constraint
condition. The inclination compliance (kw) of the bolt head used in this equation was evaluated by
the comparison of experimental and analytical results from theoretical equation. In consideration of
the nonlinearity of kw with respect to the bolt axial tension, the Scr is well estimated by this
equation.
1467
Authors: Minoru Yamashita, Toshio Hattori, Naoya Nishimura, Y. Tange
Abstract: Various polygonal tubes were compressed in the axial direction under quasi-static and
dynamic loading conditions. The effect of the polygonal shape and the wall thickness on the crush
behavior is investigated, in which the cyclic buckling takes place. The numbers of polygonal edges
were 3, 4, 5, 6 and 7 in the experiment. A circular tube was also tested for comparison. The tubes
were machined from aluminum alloy A5056 bar. Crush strength is estimated as an index of the
energy absorption capacity of the tube. It increases with increasing the number of polygonal edges
of the tube, although it almost saturates when the number of polygonal edges is more than 6. For the
wider variety of polygonal tubes than that in the experiment, numerical simulation is performed
using the dynamic explicit finite element code DYNA3D. The computed crush behavior well agrees
with the corresponding experimental one, however, the difference in collapse mode arises due to the
slight imperfections in experiment. The deformation pattern becomes more irregular for the
thinner-walled tube. Further, it is presumed that the large hardening exponent in the plastic property
of the material could prevent the buckling switching from the symmetric mode to asymmetric one
in the crushing of circular tube.
1399
Authors: Manabu Gomi, K. Ban, Naoya Nishimura, Takeshi Yokota
Abstract: Magnetic, dielectric properties and magnetoelectric effect of ceramics with a composition
of 0.9 BaTiO3-0.1 LaMnO3 have been investigated. X-ray diffraction measurements showed that
the sintered ceramics are composites containing a small amount of (La, Ba)MnO3 phase in the
BaTiO3 matrix. These composites were multiferroic, having ferromagnetic and ferroelectric Curie
temperatures of 330 K and 392 K respectively. We found that the composite sintered at 1150 °C
exhibits a reduction of spontaneous magnetization as large as 55 % at room temperature when an
electric field of 1.4 KV/mm is applied. This reduction is probably ascribed to a change of hole
concentration distribution in the precipitated ferromagnetic (La, Ba)MnO3 and the resultant
decrease of ferromagnetic Curie temperature.
2514
Authors: Naoya Nishimura, M. Ozaki, F. Masuyama
297
Authors: R. El-Sheikhy, Naoya Nishimura
581