Eiryo Shiratori

Analysis of stress-strain relations by use of an anisotropic hardening plastic potential

Abstract A method of analyzing plastic behavior by use of an anisotropic hardening plastic potential is proposed. The plastic potential surface in deviatoric stress space is assumed to be the same as the equi-plastic-strain surface. Stress-strain relations in combined loading and in multi-axial cyclic loading are calculated by use of the anisotropic hardening plastic potential and the normality rule of the plastic strain increment vector to the plastic potential surface, which are experimentally determined or confirmed by subjecting thinwalled tubular test specimens of 60 40 brass to combined axial load, internal pressure and torsion. The calculated results agree fairly well with the experimental observations.

Experimental Studies of the Strength of an Adhesive Joint in a State of Combined Stress

The adhesive strength of a butt-type specimen of two cylinders is experimentally studied. Combined stresses are applied on the adhesive layer by subjecting the specimen to combined axial load, torsion and internal pressure. The effects of the surface roughness, the thickness of adhesive layers and the combined stresses on the adhesive strength are examined for the specimens of various metals bonded with epoxy resin. The adhesive failure locus under the combined stress state are represented by a polynominal equation of stress tensors.

Failure criterion of angle ply laminates of fibre reinforced plastics and applications to optimise the strength

Abstract The failure criterion of fibre reinforced plastics is experimentally determined by subjecting filament-wound tubes with various ply angles to axial load, torsion and internal pressure. The material of the tubes is a composite of glass rovings and epoxy resin. Expressions for the failure criterion under a combined stress state are derived for various ply angles. Using these results, the optimum ply angles are determined for the maximum strength and for the maximum strain energy. The maximum strength results are used to optimise the strength of rotating discs.

Stress and plastic strain increment after corners on strain paths

Abstract The direction and the magnitude of the stress vector were determined for the plastic deformation along the strain path with a corner by subjecting thin-walled tubular specimens made of brass to combined axial load and torsion or to combined axial load and internal pressure. The influence of the comer angle on the strain path and of the pre-strain up to the comer on the direction and the magnitude of the stress vector were experimentally investigated. Empirical relations between the stress vector and the strain path after the corner were derived.

Composite flywheels with rim and hub

Abstract The possibility of obtaining a flywheel of high energy density by increasing both rotating speed and moment of inertia of the disc is investigated. As the starting point of the search process for such a flywheel, a glass cloth-laminated disc with a hole at the center is considered. The rotating speed of the disc is improved by reinforcing the central hole of the disc with the same material as that of the disc. The large moment of inertia is obtained by attaching a rim around the disc. The rim is moulded by winding carbon fiber around it. This rim also has the usual “hoop” effect which prevents a reduction of the rotating speed of the disc because of the additional moment of inertia of the rim. The shape of the disc having a high energy density is numerically sought by varying the dimensions of the hub and the rim of the disc, and an optimal shape is proposed.

Effects of material constitutions on the strength of fiber reinforced plastic gears

Abstract The strength of various fiber reinforced plastic gears is analytically and experimentally investigated. A method to reinforce gear teeth with glass or carbon roving cloths along the tooth profile is proposed to improve the bending strength. A stress analysis using the finite element method is performed for reinforced gears subjected to bending loads. Various fiber systems are considered and strengths are estimated. From these results, the most effective reinforcing method is discussed. The strengthening effects are experimentally examined by both static bending tests and running load tests. It is shown that fiber reinforcement is useful to improve the strength of plastic gears.

Plastic Behaviours of Initially Anisotropic Metals after Multi Prestrainings

Commercially obtained industrial metallic materials are generally subjected to many processes of workings and heat treatments, and they show various initial anisotropies. The anisotroqic theories [1, 2, 4, 5, 7] for initially isotropic materials which have succeeded, in some degree, in describing the subsequent plastic behaviours of the materials after various prestrainings cannot easily be applied to those initially anisotropic materials, as the required information on the type and amount of the prestrain previously given to the materials during their manufacturing processes is generally not given to the users. Hence, the authors try to derive an anisotropic theory of plasticity for an initially anisotroqic material by experimentally studying stress-strain relations of commercially obtained metals in the reloading stages after various preloadings. The reloading stage is assumed to be divided into three regions, namely, elastic region, transitional hardening region and steady hardening region. Strain hardening characteristic is formulated for each of these regions.

Plastic Deformation Behavior of Metal for Complex Loading Paths

The relations between the stress vector and the strain path were investigated for a complex loading to which the current plastic flow theory can not be applied. It was shown that by the use of the expression which related the stress vector to the strain path with a corner, the direction and the magnitude of the stress vector in loading along the strain path having various curvatures could be calculated by means of the Hereditary Integrals with respect to the length of strain path, and the trace of the strain vector in loading along the stress path with a corner could be determined by means of the graphic method. There was good agreement between the predicted results by the above mentioned method and the experimental results. The applicability of the current flow theory to non-proportional loading of brass was investigated on the basis of the calculated results of the stress vector for the strain path having various curvatures.

A study on the reinforcing effect of fiber in the ERP screw thread.

For the development of the FRP bolt, it is essential to analyze the stress distribution in the screw thread of FRP bolt and to examine theoretically and experimentally the reinforcing effect of fiber arrangement on the static as well as fatigue strengths of the thread. This paperdescribes the results of a study on the reinforcing effect of fiber in the FRP screw thread. For the two-dimensional glass-epoxy composite model of M 8 thread magnified in 10 diameter, finite element analysis of the stress distribution in the thread, static shear test and fatigue test were made. The arrangement of the long fiber along the screw thread was found effective for the increase of the strength of thread.

Fatigue crack propagation and final fracture of high speed rotating disk under cyclic start and stop.

アルミニウム合金製のノッチ付円板の繰返し発停疲労試験およびコンパクト試験片の疲労試験を行い, 両者のき裂進展速度と応力拡大係数範囲の間の関係がほぼ一致することを実験的に確かめた. また, 最終破断のクライテリオンの適否を限界き裂長さに基づいて検討し, Klcクライテリオンがあまりにも安全側の値を与え, 平均応力説が危険側の値を与えるのに対して, 本研究で導いている剛塑性解析法が実験値にわりあいよく合うことを見出した.