Congress contributions

Insufficient mechanical properties and uncontrollable degradation rates limit the wide application of Mg alloys in bioimplant materials. Microstructure refinement is a common method to improve both the mechanical properties and the corrosion resistance of Mg alloys. In order to efficiently obtain Mg alloys with fine microstructures for potential applications in bioimplant materials, a novel constrained friction processing (CFP) was proposed. In this work, the resulting compression properties of ZX10 alloy obtained by CFP with optimized processing parameter are reported. Additionally, the microstructure evolution during CFP was studied. The results show that during CFP, materials are subjected to high shear strain at the transition zone between the stir zone and thermo-mechanical affected zone, leading to recrystallization with strong local basal fiber shear texture. As the shoulder plunges down, the fraction of recrystallized grain and grain size increase. ZX10 alloy obtained by CFP exhibited higher compressive yield strength by more than 300% and ultimate compressive strength improves by 60%, which indicates the bright prospect of CFP for Mg processing.

Multidimensional positioning, measuring and manipulation with a spatial resolution in the subatomic range are an upcoming demand in the area of nanotechnology. Nanopositioning and measuring machines (NMM) enable to measure and manipulate objects within a large addressable 3D-range of up to a few hundred millimetre in each dimension with a specified spatial resolution of down to 0.1 nm [1]. New approaches are needed to extend the potential of NMM technology to even smaller scales. In previous work [2] a proof-of-concept positioning system has been designed to achieve reproducibility and resolution for precise motion on subatomic scale. In a first approach, a scanning probe microscope will be used to measure a nanosized periodic lattice that serves as a scale for the position according to [3]. Here, we present a microsystem design with an addressable positioning range of ±100 μm that will carry the lattice structure. In order to precisely control the motion, the electrostatic drive and position sensor characteristics of the demonstrator must be calibrated thoroughly by means of an optical measuring system. A focused, range-resolved fibre-optic laser interferometer is comprised as the calibration standard. An uncertainty estimation for the measurement setup is carried out. It is shown that the desired positioning accuracy for the first tip- and grating-based setup can be achieved with the presented microsystems.

A new Kibble balance is being built at the National Institute of Standards and Technology (NIST). For the first time in one of the highly accurate versions of this type of balance, a single flexure mechanism is used for both modes of operation: the weighing mode and the velocity mode. The mechanism is at the core of the new balance design as it represents a paradigm shift for NIST away from using knife edge-based balance mechanisms, which exhibit hysteresis in the measurement procedure of the weighing mode. Mechanical hysteresis may be a limiting factor in the performance of highly accurate Kibble balances approaching single digit nanonewton repeatability on a nominal 100 g mass, as targeted in this work. Flexure-based mechanisms are known to have very good static hysteresis when used as a null detector. However, for larger and especially longer lasting deformations, flexures are known to exhibit anelastic drift. We seek to characterize, and ideally compensate for, this anelastic behavior after deflections during the velocity mode to enable a 10 accurate Kibble balancemeasurement on a nominal 100 g mass artifact with a single flexure-based balance mechanism.

Aerostatic bearings are extensively used in precision engineering applications that require high positional accuracy and low friction motion. In these bearings, externally pressurized gas is fed through a restrictor into the bearing gap. The viscous shear in the gap restricts the flow, thus forming a pressurized film between the bearing and the guide surface. In the development of models and in investigations of, for example, effects of manufacturing errors and porous material permeability properties, characterization of bearing performance is required. The performance is commonly characterized with a measurement setup, either under static or dynamic conditions. In the present study, an experimental setup for the measurement performance of aerostatic bearings is presented. The investigated measurement setup is validated with a comparison to a literature model. The results of the present study include the load capacity, stiffness, air consumption, and pressure distribution of a commercially available axisymmetric graphite thrust bearing. The results show good agreement between the measurements and the model. Thus, the results show corroborative evidence on the usability of the measurement setup in future aerostatic bearing research.

Compliant mechanisms for ultra-precision applications are often required to achieve highest accuracy over largest possible ranges of motion along multiple axes. The typical synthesis approach for such high demands is based on the substitution of the revolute joints of a suitable rigid-body model with optimized flexure hinges. However, during the transition from rigid-body model to compliant mechanism, the effects of multiple input parameters are still widely unknown. Among them are the degrees of freedom of the rigid-body model, the integration of the drive elements, as well as the coupling of mechanisms to achieve multiple motion axes. The following contribution expands the fundamentals of the synthesis of compliant mechanisms based on rigid-body models for their application in ultra-precision technologies. Based on the investigation of the aforementioned parameters as well as the knowledge gained from previous research work, a novel synthesis method has been developed.