Soichiro Kawahara

Comparison between centrifugal and vertical vibro-compaction of high-lifted decomposed weathered granite sandy soil using a tracked vehicle

The aim of this research was to develop a new vibro-compaction machine by comparing experimentally and theoretically the effects of a tracked vehicle of total weight 9.8 kN mounted with a centrifugal or vertical oscillator on a high lifted decomposed weathered granite sandy soil. By measuring the amount of sinkage of the terrain surface, the dry density distribution with depth, the normal earth pressure distribution with depth, and the vertical and horizontal acceleration distribution with depth, the compacting effect of centrifugal and vertical vibro-tracked vehicles on the increment of dry density in a deep soil stratum were compared for a frequency of about 54 Hz. It was observed that the centrifugal vibro-tracked vehicle showed a 25% increase in the final amount of sinkage and a 11.3% increase in the maximum dry density of compacted soil compared to the vertical vibro-tracked vehicle. We believe that the centrifugal vibro-tracked vehicle can be shown from the analysis of the stress and acceleration propagation to be a better compaction machine at a high frequency of oscillation for a high lifted soil stratum when compared to conventional vertical vibro-tracked vehicles.

An optimum design method for robotic tracked-vehicles operating over fresh concrete during straight-line motion

This paper addresses the general problem of the design of tracked base travel systems for special purpose vehicles and/or robotic machines that may be required to move over weak surfaces or over a lightly bonded terrain composed of fresh concrete. For the special case of a vehicle travelling on a very soft fresh concrete during construction, the paper presents detailed comparative studies of the tractive performance of several tracked vehicles with alternative slump values and mean contact pressure configurations. To complete these studies a detailed simulation-analytical method was used. From this, it was established that the simulation analysis method is useful for predicting land locomotion performance of specially designed small tracked vehicles running over fresh concrete of different consistencies during driving and braking action. This work was done for straight-line motion. Some possibilities for the real-time optimum control method of the tractive and braking performance of automated and robotic vehicles are also outlined.

EVALUATION OF CUTTING RESISTANCE OF RUBBER FOR CONSTRUCTION MACHINERY

ダンプトラックやホイールローダのORタイヤは, 転石や岩砕による偶発的なカットが原因で廃棄される割合が大きい. カットをできるだけ抑制し, 完摩に至らせることで, ORタイヤに代表されるゴム製の足回りの寿命は大きく向上する. ここでは, 建設機械用ゴム材の耐カット性を解明することを目的とした. そのため, 新たに製作した試験装置を使用し, 転石や岩砕に見立てた切断刃の刃物角およびゴム厚の条件を組み合わせ, 代表的な耐摩耗性ゴム材からなる試験片に対する静的および動的切断実験を行い, ゴム材の耐カット性を定量的に評価した. さらに, 静的と動的切断の関連性, 耐摩耗性にもバランスのとれたゴム材についても言及した.

FRICTIONAL CHARACTERISTICS BETWEEN FRESH ROLLER COMPACTED CONCRETE AND METAL MATERIAL

本研究ではRCC舗装機械に使用されている金属材料とまだ固まらないRCC材の間の摩擦特性について室内実験を行い, その動的相互作用について理論解析を行った, とくに, RCC材と金属板の間の外部摩擦特性 (摩擦力, 付着力及び摩擦係数) の滑り速度依存性と時間依存性について考察を行い, RCC材の流動性と外部摩擦特性を解明した. これからのRCC舗装施工法とRCC舗装機械の開発に対して, 有益な指針を与えると考える.

WEAR CHARACTERISTICS OF RUBBER MATERIAL AND ITS APPLICATION TO THE PREDICTION OF WEAR LIFE OF TRACK BELT ON ROUGH TERRAIN

ブルドーザの履帯用ゴム材の摩耗特性を解明するため, 代表的な耐摩耗ゴムからなる試験片に対して砂岩からなる砕石路面における摩耗試験を行った. ここではゴム材の摩耗特性に及ぼすゴムの材質, 接地圧, 摩耗に関する雰囲気 (乾燥, 水浸), ならびに路面粗さの影響について考察を加えた. さらに, この結果を利用してブルドーザのゴム履帯の摩耗寿命予測を行う手法を提案した.

EFFECT OF GROUSER SHAPE ON THE TRACTIVE PERFORMANCE OF A RUBBER TRACKED VEHICLE

ゆるく堆積したまさ土地盤上を走行するゴム製履帯式車向の走行性能について, 履帝形状がその牽引力に及ぼす影響を厳密なシミュレーション解析により調査し, 登坂駆動時, 下降制動時, 平地旋回時それぞれにおいて最適な履帯形状であるグラウサ横切刃角βを決定した. その結果, 登坂駆動時及び旋回時には,β=π/6radが, また下降制動時にはβ=0radが最適であり, 履帯形状設計の際にはその使用目的に応じた選択が必要であることが解った.