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Stiffness Reduction Strategies for Additively Manufactured Compliant MechanismsMerriam, Ezekiel G 01 April 2016 (has links)
This work develops and examines design strategies for reducing the stiffness of 3D-printed compliant mechanisms. The three aspects of a flexure that determine its stiffness are well known: material, boundary conditions, and geometry. In a highly constrained design space however, flexure stiffness may remain unacceptably high even while arriving at the limits of design constraints. In this work, changes to geometry and boundary conditions are examined that lead to drastically reduced stiffness behavior without changing flexure thickness, width, or length. Changes to geometry can result in very complex mechanisms. However, 3D printing enables almost arbitrarily complex geometries. This dissertation presents three design strategies for stiffness reduction: static balancing, lattice flexures, and compound joints. Static balancing refers to changes in the boundary conditions that result in a near-zero net change in potential energy storage over the useful deflection of a flexure. In this work, I present a method for static balancing that utilizes non-dimensional parameters to quickly synthesize a joint design with stiffness reduced by nearly 90%. This method is not only simple and straightforward, it is applicable to a wide range of flexure topologies. The only requirements on the joint to be balanced are that it must be approximated as a pin joint and torsion spring, and it must have a well-understood stiffness when subjected to a compressive load. Lattice flexures result from modifications to geometry that reduce cross-sectional area without changing width or thickness. However, the reduction in stiffness is greater than the reduction in cross sectional area. This can occur because the bending load is now carried by beams partially in torsion. Two lattice geometries are proposed and analyzed in detail using analytic and numeric techniques. It is shown that the off-axis stiffness behavior of lattice flexures can be better than that of conventional blade flexures while bending stiffness is reduced >60%. Compound joints are those that consist of arrays of flexures arranged co-axially. This arrangement provides increased range of motion, generally decreased stiffness, and improved stability. Additionally, a method is herein presented to reduce the parasitic center shift of a compound joint to nearly zero at a specified deflection. The penultimate chapter demonstrates how all three strategies can be used together, and includes new results to facilitate their combination.
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Low Loss Articulated Hauler Axle : A Conceptual Study / Lågförlustaxel till ramstyrd dumper : En konceptstudieAndersson, Patrik, Wallin, Morgan January 2017 (has links)
Volvo Construction Equipment is highly regarded for robust products, but with an increasing competition in their market, development of the product portfolio is more important than ever. One step being carried out is to reduce losses in powertrains and increase the fuel efficiency for solutions such as articulated haulers and wheel loaders. This would eventually lower the fuel costs and emissions for the end customer. With this development, Volvo CE could strengthen their position in the market while also contributing to reducing the construction industry's environmental impact. By investigating the front bogie axle of the recently introduced hauler, Volvo A60H, important information about possible reductions and the distribution of the current losses were found. The investigation focused on a front bogie axle, but some of the results are applicable for other applications such as wheel loaders as well, since a lot of the technology in the axles are similar. A conceptual study was performed where completely new ideas were generated, such as implementing a dry sump system in the axle, as well as ideas for improving the subcomponents currently found in the axle. Two cases were presented for the evaluation of concepts, one with a fully loaded dump body and low speeds, and one with an unloaded dump body and a wider speed interval. The concepts were later evaluated using calculation tools such as MATLAB and a Simulink-model was created for the losses in the axle. When combining concepts that reduces load dependent losses, a potential reduction of 64% of the axle's total losses was achieved for the case with a full dump body. The largest improvement found for the load independent losses was 8% with an unloaded hauler and the highest speed investigated, 50 km/h. A dry sump system improves the axle's efficiency with 45% in optimal working conditions, but was found to lower the efficiency at other conditions. Room for improvement of axle losses currently exists both for load dependent and load independent losses. The evaluation performed pointed towards the load dependent losses being the largest influence on the total losses, even with an unloaded dump body and high speeds. This is an interesting observation since a lot of work at Volvo CE has revolved around reducing the load independent losses since these are easier to affect with different lubrication levels and rotational speeds. A test methodology for load dependent losses should be implemented in order to validate the results of this thesis work, and also to aid further development at Volvo CE.
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