我々は, X線極点図形回折装置を用いて, ロール延伸高密度ポリエチレンフィルムのoff-Angle再延伸時の各面法線の配向分布関数を評価した. これらの分布関数を多結晶の集合体と仮定することによって, この再延伸時の結晶の配向のシュミレーションと比較した. 我々は, により, 三つのchain slip 系の内で, {110} の〈001〉滑り系が支配するこの再延伸過程の再配向機構を解析した.

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筆者らは, X線極点図形回折装置を用いて, シンジオタクチック1, 2-ポリブタジエンフィルムの幅拘束1軸延伸に伴う各結晶面法線の配向分布関数を評価した. これらの分布関数を多結晶の集合体と仮定することにより, 結晶の配向のシミュレーションと比較した. そして, により, 7個の滑り系のうちで, (210) 〈001〉, (100) 〈001〉, (110) 〈001〉, (010) 〈001〉の滑り系の支配する幅拘束1軸延伸の配向機構を解析した.

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我々は, ロール延伸高密度ポリエチレンフィルムを, 多結晶集合体と仮定し, off-angle再延伸に際して, 結晶の配向に, シュミレーションモデルを導入した. この評価は, off-angle再延伸において, 塑性変形を引き起こす結晶各面の塑性滑りにより考慮される. この報告で, 我々は, ポリエチレン結晶の結晶単位胞に8種類の滑り系を採用した. 結晶単位の方位の回転は, 常に, を応用して, 塑性変形の個々の滑り系が選択される.

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Slip rotations of crystals undergoing constrained plastic deformation have been interpreted by utilizing the concept of grain boundary disclinations. It was considered that the plastic deformation of crystals is caused by the creation and motion of lattice dislocations and the slip rotations correspond to the creation and motion of grain boundary disclinations. From a general equation for force on disclination loops continuously distributed on a grain boundary defined as a closed surface, a yield criterion for the slip rotations, which defines the state of stress which determines the onset of rotations, was established. This yield criterion was defined by a scalor function that could be expressed in terms of the anti-symmetric parts of stress tensor. Therefore, in the proposed theory it was considered that the finite number of yield surfaces for slip systems and slip rotation were simultaneously activated in nine-dimensional stress space.
By using the proposed yield criterion of rotations, the maximum work procedure of Bishop-Hill was developed for analysis of lattice rotations under constrained deformation. The proposed procedure was applied to calculations of lattice rotations of fcc metals deformed by axisymmetric flow, employing the computational technique for optimization problems with nonlinear constraints. The computed results were in reasonable agreement with the experimental ones of tension and compression textures of fcc metals.

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筆者らは, シンジオタクチックポリプロピレンフィルム (st-PP) で多結晶集合体を仮定して, 幅拘束1軸延伸の微結晶の配向分布をシミュレーションするモデルを導いた. これらの評価法は, 幅拘束1軸延伸中に生ずる塑性変形によって結晶単位の各面の塑性滑りを評価することによって行われた. 本報では, 筆者らはシンジオタクチックポリプロピレン微結晶の結晶単位に5種類の滑り系を採用した. 結晶単位の方位回転は, を適用して, 塑性変形の場合, 個々の滑り系が絶えず選択された.

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We have evaluated the orientation distribution function of each plane for strip-biaxial stretching in syndiotactic polypropylene films. The pole figure device familiar in X-ray diffraction was used. These distribution functions were compared with a simulation of orientation in crystallites after strip-biaxial stretching, by assuming polycrystalline aggregations. We analyzed the mechanism of orientation for the strip-biaxial stretching process in which the {110}, ‹001› and (100), ‹001› slip systems dominated in five types of slip systems by applying the maximum plastic work principle.

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筆者らは, シンジオタクチックポリプロピレン (st-PP) フィルムの幅拘束1軸延伸における各面の配向分布関数を評価した. X線回折の極点図形解析装置が用いられた. これらの分布関数は, 多結晶集合体を仮定して, 幅拘束1軸延伸後の微結晶の配向シミュレーションと比較された. 筆者らは, 延伸した試料の測定およびシミュレートした分布関数から計算されるR因子を評価した. また, を適用して, 5個の滑り系のなかで, {110}, 〈001〉および (100), 〈001〉滑り系が支配する幅拘束1軸延伸過程の配向機構を解析した.

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The Cosserat medium supporting the asymmetric stresses and couple stresses and having a rigid microstructure was employed as a continuum model of crystals deforming by slip and rotations. And, a new theory of crystal plasticity, generalizing the maximum external work and minimum internal work principles of Bishop-Hill, was formulated on the basis of the Cosserat theory. The method for obtaining the solution of lattice rotations under constrained plastic deformation was introduced by using a mathematical technique of non-linear optimization problems. The proposed theory was applied to predict the development of shear deformation texture in fcc metals. Finally, the physical mechanism of lattice rotations during plastic deformation was discussed in terms of the concept of disclinations which are rotational type of Volterra’s dislocations.

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The prediction of the stress distribution in the powder bed is important for the design of the storage vessel and the unit operation of the powder. We calculated the stress distributions in a plane stress field by using the constitutive equation of powder based on the plastic potential and Coulomb-Mohr criteria, and the incremental finite element method.
We also measured the wall stress distributions and compared them with the calculated results. They agree with each other in the horizontal stress distribution of the side wall as well as in the vertical stress of the bottom. Hence, the constitutive equation and our simulation method are reasonable and would be useful for the design of the powder storage vessel.

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Plastic deformation being essentially a hysteresis phenomenon, real metals usually exhibit anisotropy and the Bauschinger effect as well as work-hardening due to strain history. The existing theory of plasticity limited to the description of ideal plastic solid, is not capable of describing the plastic deformation of such real metals. In the present paper, a new theory "The Strain History Theory of Plasticity" proposed by one of the authors being applied to the general loading processes of combined stress of tensiontorsion after simple tension and torsion respectively, the yield condition, the rate of work-hardening and the stress-strain increment relation proper to a metal and their dependence on the strain history are deduced.

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This paper deals with a rigid-plastic finite element method (FEM) of chip formation process in an orthogonal cutting of single crystal metals. Yield function of single crystal based on the Schmid's law is introduced in the rigid-plastic FEM by applying maximum plastic work principle. A new FEM model is proposed to analyze the chip formation process from the initial state to steady state on the basis of both crystal characteristics and cutting conditions. In the model, the elements of the workpiece are remeshed when the tool moves against the workpieces in order to simulate the chip separation during the cutting process. The FEM model proposed here is applied to the analysis of the micro cutting process of single crystal copper, and the results are compared with the experimental results. The results of FEM analysis, such as shapes of chips, shear angles and specific cutting forces, are in good agreement with the experimental results.

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The problem of constrained deformation of crystals based on the Bishop-Hill’s maximum work principle or Taylor’s minimum shear principle is interpreted as a constrained optimization problem for a process system consisting of many elementary processes such as simple glides on a crystallographic slip system. The mathematical method for analysis of crystal rotations under constrained deformation is introduced based on the consideration that when the plastic distortion components are prescribed, the corresponding stress and rotation vector components are the optimized responses of its process. The proposed method is applied to the simulation of rolling texture development in bcc metals deformed by the ⟨111⟩ pencil glide, using a function minimization program capable of dealing with multimodal function and non-linear constraints.
The predicted rolling textures of bcc metals are in good agreement with the experimentally determined ones of iron. Therefore, this computational method can be expected to yield realistic information about other deformation texture problems.

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