Proposal of a Six-Legged Mini-Shovel and Its Mechanism Design and Walking Analysis Based on Static Analysis and a Computer-Aided Design Dynamic Model

The conventional method of movement of a mini-shovel used for interior demolition work is a crawler. However, a crawler scratches road surfaces and floors; moreover, it lacks body stability when climbing up and down stairs. In this study, we propose a six-legged mini-shovel for interior demolition work and develop it based on a mini-shovel SK09SR, which is a product for the interior demolition work market. With regard to mechanism design, first the basic sizes of the chassis and leg are determined by the reachable region of the legs that is necessary for climbing stairs. Next, the leg mechanism is designed using static analysis based on the constraints of the maximum output of the hydraulic cylinder and pump. In addition, in order to demonstrate the dynamic analysis and simulation of walking, a three-dimensional computer-aided design dynamic model of six-legged mini-shovel is produced on the mechanism analysis software DADS. Then, the servo control of the hydraulic cylinder is designed. Finally, the results of dynamic analysis and simulation of walking, such as going straight, turning, side walk, diagonal walk, lifting vehicle height and climbing stairs, show that our proposed six-legged mini-shovel is a useful and effective method of movement for interior demolition work.     

Finite element modelling: a solution to seam end cracking?

Abstract

Seam end cracking has been a common feature of many single sided seam welding installations. The crack tends to be located about 140 mm in from the plate end, but this distance has been found to be related to plate thickness. In addition, the longer cracks tend to be more prevalent in thicker plates. The incidence of cracking in this particular case was typically 38%, which incurred significant inspection and rectification costs. The present study presents a detailed FEM study of a slot run-off plate configuration that was carried out using a thermo-mechanical model. The outcome of this investigation was that the run-off plate slot angle had an effect on the potential for cracking but the slot width did not. When the slot run-off plate was used in practice, over a wide range in thickness, the transverse cracking was eliminated.     

Experimental investigation and numerical analysis of compaction behaviour of moulding sand

Abstract

The compaction behaviour of green sand was studied to assess the applicability of the Cooper–Eaton equation under conditions close to those of real foundry operations. The results indicate that the Cooper–Eaton equation describes the behaviour reasonably well, allowing prediction of the pressure required to achieve sand moulds of reasonable density. A corresponding distinct element method numerical simulation was also attempted. The study contributes useful information to the understanding of green sand compaction. It is clear that spherical sand is preferable to improve filling behaviour and that the gap between mould wall and pattern must be sufficiently large to avoid prevent weak sand compaction.     

Comparison of the stress transfer in single- and multi-fiber composite pull-out tests

Analyses of the elastic stress transfer taking place across the fiber-matrix interface are presented for single- and multi-fiber composite pull-out tests. The multi-fiber composite is treated as a three-cylinder assemblage consisting of a central fiber, a matrix annulus, and a composite medium. The forms of the fiber axial stress and the interface shear stress distributions along the embedded fiber length are determined for single- and multi-fiber composite pull-out tests and their dependences on the fiber volume fraction, the dimensions of the specimen, the fiber-to-matrix modulus ratio, and the embedded fiber aspect ratio are displayed. The stress transfer for a perfectly bonded interface for the two pull-out tests is compared and the difference is clearly shown. In addition, for the single-fiber composite pull-out test, the present theory is compared with some existing theories.     

Experimental investigation and numerical simulation of cooling process in water assisted injection moulded parts

Abstract

This report investigated, both experimentally and numerically, the cooling process in water assisted injection moulded parts. Experiments were carried out on a laboratory developed water assisted injection moulding system, which included an injection moulding machine, a water pump, a water injection pin, a water tank equipped with a temperature regulator, and a control circuit. The resin used was semi-crystalline polypropylene. The in-mould temperature of the polymeric materials during the cooling process was measured. A transient heat transfer finite element model was adopted to simulate and predict the temperature variation within water assisted injection moulded products. Simulated results matched well with the experimental data. Experimental investigation and numerical simulations of a water assisted injection moulding cooling process can provide an improved understanding of the influence of water related parameters on the cooling process of water assisted injection moulded parts.     

Numerical simulation of the ENF test for the mode-II fracture characterization of bonded joints

In this work, the End Notched Flexure (ENF) test is analyzed in order to obtain the critical strain energy release rate in mode-II fracture of bonded joints. A cohesive model based on specially developed interface elements, including a linear softening damage process, is employed. The adequacy of the experimental ENF test is evaluated by numerical simulation. The objective is to compare the critical strain energy release rate in mode-II (G _{II c} ) obtained by different data reduction schemes with the real value which is an inputted parameter in the cohesive model. The effect of the Fracture Process Zone (FPZ) ahead of the crack tip is evaluated. A crack equivalent concept is proposed in order to account for the energy dissipated in the FPZ. A data reduction scheme avoiding the need to measure crack length is proposed. A good agreement with the inputted value of G _{II c} was obtained.     

Simulating Adaptive Human Bipedal Locomotion Based on Phase Resetting Using Foot-Contact Information

Humans generate bipedal walking by cooperatively manipulating their complicated and redundant musculoskeletal systems to produce adaptive behaviors in diverse environments. To elucidate the mechanisms that generate adaptive human bipedal locomotion, we conduct numerical simulations based on a musculoskeletal model and a locomotor controller constructed from anatomical and physiological findings. In particular, we focus on the adaptive mechanism using phase resetting based on the foot-contact information that modulates the walking behavior. For that purpose, we first reconstruct walking behavior from the measured kinematic data. Next, we examine the roles of phase resetting on the generation of stable locomotion by disturbing the walking model. Our results indicate that phase resetting increases the robustness of the walking behavior against perturbations, suggesting that this mechanism contributes to the generation of adaptive human bipedal locomotion.     

Hot Corrosion Behavior of CM 247 LC Alloy in Na2SO4 and NaCl Environments

Hot corrosion studies of CM 247 LC alloy werecarried out in pure sodium sulfate, as well as sodiumchloride and sodium sulfate mixtures of differentconcentrations at various temperatures. A crucible test was employed to study the suitability of CM 247LC as a gas turbine blade material. It was observed thatbare CM 247 LC was severely corroded in just 4 hr, whileit was completely consumed in 70 hr when tested in 90% Na₂SO₄ +10% NaCl at 900°C. The results show that a chloridecontaining melt is more corrosive than pure sodiumsulfate. The weight loss is linearly related tot^1/2 (time) and temperature in the different environments studied. Thecorroded samples were characterized by EPMA, SEM, XRD,and metallographic techniques. The results show that hotcorrosion of CM 247 LC is an electrochemicalphenomenon.     

Simplified theodolite calibration for robot metrology

Theodolites represent a well-established three-dimensional-point-measuring technology. However, when used for robot applications they have to be properly calibrated to fulfil the necessary accuracy requirements. The theodolite calibration methods reported in the literature involve the use of costly sophisticated equipment not easily available to most users. Therefore, a new simplified calibration technique is presented based on the use of a graduated precision bar suspended freely to align with the vertical direction. To develop efficient mathematical models, the theodolites will be regarded as 2R open-ended mechanisms with the end-effector axis directed along the line of sight. The proposed models are then coded in a computer program designed to verify the validity of the technique presented. The simulation results will be presented at the end of the paper.     

Mechanical design and motion control of a biomimetic robotic dolphin

This paper addresses the design, construction and control issues of a novel biomimetic robotic dolphin equipped with mechanical flippers, based on an engineered propulsive model. The robotic dolphin is modeled as a three-segment organism composed of a rigid anterior body, a flexible rear body and an oscillating fluke. The dorsoventral movement of the tail produces the thrust and bending of the anterior body in the horizontal plane enables turning maneuvers. A dual-microcontroller structure is adopted to drive the oscillating multi-link rear body and the mechanical flippers. Experimental results primarily confirm the effectiveness of the dolphin-like movement in propulsion and maneuvering.