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Title :土-機械系における相乗効果を考慮した力学挙動の有限要素解析
Title alternative :Finite Element Analyses for Mechanical Interactions of The Soil-Machine System
Authors :上野, 正実
Authors alternative :Ueno, Masami
Issue Date :Mar-1991
Abstract :昭和63年度~平成2年度科学研究費補助金(一般研究(C))研究成果報告書
研究概要 : 本研究の主要な成果は次の通りである。 1) トラクタの力学的挙動に関する有限要素解析プラウ耕等におけるトラクタの力学的挙動を有限要素法を用いて合理的に解析する手法の開発をねらいとした。これは地盤とトラクタ(機械)を一つの結合力学系として相互の挙動を同時に解析することを特徴としている。まず、トラクタのプラウ耕の問題を取り上げ、次にクローラの挙動ならびに耕耘機によるロータリ耕の問題を扱った。後者は土-機械-人間系とみなすことができる。機体部をトラス、ラーメンおよびトラス・ラーメン混合要素でモデル化し、地盤を3角形要素で表した。人体に関しては骨格部と筋肉部に分けて棒要素で表した。プログラムはBASICで作成し、パソコン(16ビット)を用いた。計算では、土および機械部の材料定数、駆動力、耕盤の深さ等を様々に変化させてシミュレーションを行った。本解析法は単純ながらも地盤の力学的挙動だけでなく、トラクタ本体の各部に作用する力、あるいは他の力学特性を明確に分析しうる可能性をもっていることが明らかとなった。 2) 農用車輪の力学的挙動に関する有限要素解析土を弾塑性体とみなし、増分形式による構成式(等方硬化・下負荷面モデル)を採用して有限要素法を開発した。土と車輪との接触面における境界条件は、剛性車輪上の点の軌跡に基づいて節点に強制変位増分を与えた。これらは各ステップ毎に車輪に接する節点においてクーロンの摩擦条件によるチェックを行い、必要に応じて修正計算を行った。計算は最初に所定深さまで車輪を沈下させた後に転動させた。本解析により車輪下の応力およびひずみ分布、すべり率と推進力の関係、すべり沈下現象等についておおむね説明しえた。
研究概要 : 1) Numerical Simulations for Mechanical Interactions of a Tractor. This study aimed to develop a new method for analyzing mechanical behaviors of tractor in plowing by using Finite Element Method. This method had a distinctive feature which analyzed the interactions of machine and soil behaviors as a soil-machine combined system. At first the plowing problems were tried to simulate by this method. In addition, behaviors of a crawler shoes and problems of rotary tillage by a power tiller were analyzed by this method. The latter was categorized as a problem of soil-machine-man system. The tractor body was expressed with beam elements and the soil was done with continuous elements i. e. a triangle one. Skeleton and muscle of the operator were modeled with beam elements. Programs were written by a BASIC and personal computers (16 bits CPU machine) were used. Simulations of these systems were executed under the various conditions. These were performed to change the values of material constants, the tractive force of tractor, the depth of soil layer to the hard pan, the weight of tractor and the size of elements. The results represented qualitatively such mechanical behaviors. This method could be applied not only to the design tool such as CAD but to an educational tool in the field of tractor mechanics. 2) Finite Element Analyses for Mechanical Behaviors of a Wheel. A finite element method was developed to analyze rotating behaviors of a tractor wheel. The soil was regarded as an elastoplastic body. The constitutive equation of this FEM was based on the Subloading Surface Model which described the smooth transition process from the elastic state to the plastic one. Boundary conditions at the contact surface between the wheel and the soil which was major difficulty for a successful analysis of this problem was given by constraint displacements to these nodes. A concept of relative slip was introduced to suit such boundary conditions. The ratio of normal and tangential forces at the contact node was checked every incremental stages. If the ratio exceeded frictional coefficient, the constraint displacement increment was modified by the use of relative slip until to satisfy the frictional conditions. The motion of wheel which went down vertically at first and rotated secondary were expressed as two different stages in the calculation. The results gave useful information to the stress and strain distributions, relationships between the slip and traction, the slip sinkage and so on.
Type Local :研究報告書
Publisher :上野正実
URI :http://hdl.handle.net/20.500.12000/12207
Appears in Collections:Research Report (Faculty of Agriculture)

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