Graphical and computer-aided approaches to plan experiments

Design of experiments is a quality technology to achieve product excellence, that is to achieve high quality at low cost. It is a tool to optimize product and process designs, to accelerate the development cycle, to reduce development costs, to improve the transition of products from R & D to manufacturing and to troubleshoot manufacturing problems effectively. It has been successfully, but sporadically, used in the United States. More recently, it has been identified as a major technological reason for the success of Japan in producing high-quality products at low cost. In the United States, the need for increased competitiveness and the emphasis on quality improvement demands a widespread use of design of experiments by engineers, scientists and quality professionals. In the past, such widespread use has been hampered by a lack of proper training and a lack of availability of tools to easily implement design of experiments in industry. Three steps are essential, and are being taken, to change this situation dramatically. First, simple graphical methods, to design and analyse experiments, need to be developed, particularly when the necessary microcomputer resources are not available. Secondly, engineers, scientists and quality professionals must have access to microcomputer-based software for design and analysis of experiments.¹ Availability of such software would allow users to concentrate on the important scientific and engineering aspects of the problem by computerizing the necessary statistical expertise. Finally, since a majority of the current workforce is expected to be working in the year 2000, a massive training effort, based upon simple graphical methods and appropriate computer software, is necessary.² The purpose of this paper is to describe a methodology based upon a new graphical method called interaction graphs and other previously known techniques, to simplify the correct design of practically important fractional factorial experiments. The essential problem in designing a fractional factorial experiment is first stated. The interaction graph for a 16-trial fractional factorial design is given to illustrate how the graphical procedure can be easily used to design a two-level fractional factorial experiment. Other previously known techniques are described to easily modify the two-level fractional factorial designs to create mixed multi-level designs. Interaction graphs for other practically useful fractional factorial designs are provided. A computer package called CADE (computer aided design of experiments), which automatically generates the appropriate fractional factorial designs based upon user specifications of factors, levels and interactions and conducts complete analyses of the designed experiments is briefly described.¹ Finally, the graphical method is compared with other available methods for designing fractional factorial experiments.     

刻蚀实现双重图形的前景

双重图形需要更新更苛刻的刻蚀能力，要求低于1.5nm CD均匀性、图形收缩和原位多层刻蚀。     

Preparation of a Porous Cermet SOFC Anode Substrate by Gelcasting of NiO–YSZ Powders

A porous NiO–YSZ substrate for anode-supported solid oxide fuel cells has been prepared by gelcasting of NiO–YSZ powders using urea–formaldehyde monomers, followed by humidity-controlled drying, binder removal, and sintering of the gelled bodies. The gelled bodies had sufficient strength to remove even 2-mm-thick samples from the mold immediately after gelation. A gelcast NiO–YSZ sample sintered at 1450°C for 2 h showed an open porosity of ∼53 vol%, and the porosity increased to ∼58% upon reduction with hydrogen. Pore sizes measured on the scanning electron microscopy photomicrograph of NiO–YSZ and Ni–YSZ cermet substrates are in the range of 2–5 μm. Urea–formaldehyde polymer, present in a high amount (∼13 wt%) in the gelcast body, acts as a template for pores.     

Isotropic Constitutive Model for Sintering Particle Packings

This paper presents an isotropic model for the effective viscosities of sintering particle packings. The relationship between the macroscopic stress and deformation rate is based on the behavior of individual interparticle contacts, represented by contact viscosities, and the statistics of the packing. The contact viscosities depend on the contact area, which is the primary variable used to describe the state of the packing. A direct consequence of this choice of state variable is that the effective viscosities are identically zero for an undeformed and unsintered packing. Specific results are presented for the case of Newtonian viscous materials. The model is compared with existing models for porous Newtonian viscous materials. Experiments conducted with spherical glass powder packings show good agreement with the model. Finite-element simulations using the model have been used to study forging of a pellet.     

Simulation of the Viscous Sintering of Two Particles

The viscous sintering of two initially spherical particles is modeled as creeping flow in response to surface tension. The governing equations are solved using the finite-element method. The condensed results of this simulation, the center-to-center approach velocity, and the rate of change of contact area were presented earlier. Some details of the flow field during sintering and the evolution of the neck geometry in the early stages of sintering are presented here. Important numerical issues are detailed.     

Determination of compressive residual stress in a doubly-clamped microbeam according to its buckled shape

In this work, an analytical relationship is derived for a doubly-clamped microbeam when it buckles after release from the substrate. In terms of the relationship, compressive residual stress in the doubly-clamped microbeam can be determined according to its buckled shape, allowing one to find the compressive residual stress directly without much experimental effort. This relationship has been used to determine compressive residual stresses in four types of doubly-clamped SiO₂ microbeams. In addition, four methods have been applied to find the elongations of these SiO₂ microbeams, and the corresponding results are compared. Finally, the residual stresses in doubly-clamped SiO₂ microbeams predicted according to the derived relationship are compared with those found in SiO₂ microcantilevers, and the results have a good match.     

Micro-measurement using grating microscopy

In this paper, two quantitative methods to measure micro-deformation using grating microscopy are proposed, a grating diffraction method and a full-field grating phase-shift method. A compact optical transmitting microscope with white light source is reconstructed by developing a loading and recording system. For direct strain measurement, a grating diffraction method is presented. With the help of a Bertrand lens, the Fourier spectrum of the grating is formed on the CCD sensor plane with high image quality. Software for precise, fast and automatic determination of the diffraction spot centroids is developed. Local strains are thus measured with high resolution. For the deformation measurement, a phase-shifting grating microscope method with high sensitivity and spatial resolution is proposed. Phase-shifting is based on the slab refraction effect and is realized via a tilting compensator. The system possesses a high spatial resolution (1 μm), and a displacement precision of 0.1–0.03 μm. The combination of the grating diffraction method and the phase-shifting method in the same test provides simultaneous measurement of strain and displacement, thus demonstrating that the grating techniques are viable in the microscope environment.