Transactions of the Canadian Society for Mechanical Engineering

Volume 31 (2007), Issue 3

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South Pointing Chariot is one of the important mechanical inventions in ancient China. It achieves the purpose of fixing direction by applying mechanical devices with either the fixed axis wheel system or the differential gearing system. In this study, the historical background and records of South Pointing Chariots are introduced. The characteristics of existing designs of South Pointing Chariots with a fixed axis wheel system are analyzed. Representations to identify different axial directions of joints and characteristics of members are presented. A design methodology is proposed to synthesize all feasible design concepts of South Pointing Chariots with a fixed axis wheel system systematically. And, three examples are provided.

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Whenever a simultaneous production is allowed for the entire tasks in an assembly line, the assembly line balancing (ALB) problem becomes complicated because the simultaneous assignment is performed. In this paper, a mathematical model applying the Lingo 9.0 syntax for an advanced issue called single-model assembly line balancing problem with simultaneous production (SALBPS) is developed, and a coding technique- Three-Position Code (TPC) as well as a computerized coding program are presented to make this issue solvable. In addition, the simulated analyses of the model for various cycle times are also conducted to reveal the behavior changes of the optimal solution. The traditional method always underestimates the production rate for the SALBPS problem, but our study can more accurately estimate the system production rate for such a kind of problems. This study functions as a valuable tool because of its repeated characteristic. The proposed mathematical model and its relevant computerized coding program can make other cases easily solved by changing their input data only. Moreover, our study can help line designers quickly design or redesign the assembly line to satisfy the fluctuant environments.

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The purpose of this paper is to present a systematic approach for the kinematic synthesis of the jet propulsion mechanisms with 6-link for bionic jellyfishes. The structural synthesis is carried out based on the methodology of creative mechanism design, and the dimensional synthesis is performed by the loop closure method. First, the design requirements and design constraints are specified based on the kinematics characteristic of jellyfishes. Then, the joint assortments with respect to the (6, 7) and (6, 8) chains are derived by number synthesis, and the atlas of feasible chain with one degrees of freedom is generated. After that, the atlas of specialized feasible chain is obtained. Furthermore, the atlas of the new design is obtained through the particularization process. Finally, a design example selected from the atlas is given for illustration, dimensional synthesis is performed at first, and the feasibility of the design is verified by conducting computer simulation using ADAMS software. The result shows that the proposed design can effectively mimic the contraction and relaxation motion of a jellyfish.

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In this paper, contact length, uncut chip thickness, and contact forces were studied as the wheel wore during dry surface grinding of 4130 normalized steel for three different depths of cut (0.0025, 0.005, 0.0075 mm). An aluminum oxide grinding wheel (Norton 38A46HVBE) was used for all the experiments and the work and wheel speeds were 0.22 and 32.3 m/s, respectively. In each experiment, the wear flat area, the cutting edge density, the cutting edge width and length were determined using an automated optical measurement system. The grinding forces were measured using a force dynamometer. The contact length was determined using rigid-body, smooth-body and rough-body contact assumptions. The uncut chip thickness was determined using a continuity analysis. In this approach, the average volume of material is first determined by dividing the total material removal rate by the number of cutting edges. Then an assumption of the shape of the chip is made. In this work, the uncut chip was assumed to have a triangular profile and a rectangular cross-section. The uncut chip thickness can then be determined by dividing the average chip volume by the average contact length and chip width. In the experiments, grinding forces, wear flat area, cutting edge density increased and uncut chip thickness decreased as a result of wheel wear. In addition, the wheel wear increased the contact length significantly in the rough-body assumption, marginally in the smooth-body assumption but not in the rigid-body assumption. The normal contact pressure was determined by dividing the normal force by the product of the percent wear flat area and contact area. This result suggested that the rough body assumption represented the data most accurately.

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This paper presents the design of an active suspension controller for an automotive vehicle using a genetic algorithm as the optimization technique. A four-degree-of-freedom model is used to represent a vehicle with different front and rear axes characteristics. The suspension deflection, tire deflection, vertical and angular acceleration are the performance criteria optimized. Different filters are used to model the frequency sensitivity of these criteria and the weighting is based on a passive suspension reference system. Independent front and rear controller optimization is performed with a genetic algorithm. The controllers include a linear gain matrix and a single filter. Each controller is designed to work with a minimum number of sensors and a limited order filter. To adapt the passive suspension components to the active system, the stiffness and damping of the suspension are optimized with values limited to a realistic range. Results show the impact of the various filters used to specify the critical frequency range of the inputs and outputs. This is observable for ride and handling criteria that are known to be frequency dependant. There is 38% improvement in the global performance of the active system compared to the baseline passive system.

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Fluidized bed annealing furnaces used for annealing low- and medium-carbon wire products have been used for a number of decades as an environmentally friendly alternative to more traditional heat treating systems based on molten lead. Recent investigations into heat transfer rates to wires immersed in a fluidized bed have shown that the heat transfer rate is relatively constant over a wide range of fluidizing rates, contrary to earlier thinking. As a result, it is possible to modulate air/gas flow rates in these systems without affecting product quality due to variable heat transfer rates. Typically, systems have operated at constant fluidizing air flow rates with either on/off gas control, or modulating gas only, resulting in high effective excess air operation and resulting low thermal efficiency. This work investigates the result of operating a fluidized bed with modulating air/fuel flow rates at fixed air/fuel ratios, resulting in improved thermal efficiency. Results indicate that significant fuel savings can be achieved, particularly at lower load levels.

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We make parts called tampons on which one executes grooves with different configurations as shown further in the text. These grooves allow the airflow evacuation and they will be called in the article "evacuation channels". One measure the airflow velocity at the evacuation channel exit by means of a hot wire anemometer of a DISA 55M type and one measure also the wall pressure along the channel. The main influence parameters are the δ₀ retreat of the blowing nozzle towards the tampon frontal surface, the δ distance of this last one towards the wall surface to be measured and the channel depth Pr. The used nozzle is a classical one which has a plane frontal surface, called the "Number 02 nozzle" in the industry. The width of the evacuation channels is 1.5 mm.

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A set of fixed and moving pivot loci can represent an infinite number of planar four-bar motion generator solutions for a given series of prescribed rigid-body poses. Unfortunately, given the vast number of possible mechanical solutions in a set of fixed and moving pivot loci, it is difficult for designers to arbitrarily select a fixed and moving pivot loci solution that ensures full link rotatability, produces feasible transmission angles and is a compact design. This work presents an algorithm for selecting planar four-bar motion generators with respect to Grashof conditions, transmission angle conditions and having the minimum perimeter value. This algorithm has been codified into MathCAD for enhanced analysis capabilities and ease of use. The example in this work demonstrates the synthesis of a compact planar, four-bar crank-rocker motion generator with feasible transmission angles.