Use Of Brittle Materials Research Articles

An AI-Based Approach to Optimize Stress in Shrink Fits

AbstractThe present analytical design of shrink fits typically results in an uneven stress condition that can lead to failure in a variety of manners. With increasing loads and the use of brittle materials, the optimization of the stresses in the shrink fit hence becomes increasingly necessary. Currently existing approaches do not solve the problem satisfactorily or increase the manufacturing and design effort. This paper therefore considers the implementation of an AI-based stress optimization using reinforcement learning, which performs stress optimization by geometrically contouring the interstice.

A new approach to fitting the three-parameter Weibull distribution: An application to glass ceramics

The field of strength reliability is one of the critical factors restricting wider use of brittle materials in certain structural applications, like ceramics. In this area, the Weibull distribution is widely accepted for lifetime modeling. In essence, the brittleness of ceramic materials leads to poor toughness and low strength reliability. The statistical nature of these flaws results in a significant scatter of the measured macroscopic strength outcomes, which has a number of consequences both in the design and verification of components involving such materials. In this article, an analysis and evaluation of six existing estimation methods for a Weibull distribution are presented, as well as a new approach for fitting the Weibull distribution using neural networks (NNs). The major focus of this work is, however, the implementation of simulations in order to contrast how well the suggested techniques of the Weibull parameter estimation perform. Finally, an important implication of this study is that it shows how various estimators of the Weibull model work for wide-ranging sample sizes and different parameter values. The simulation results revealed that L-Moment estimator produces more accurate estimates, unlike those using NNs that are more robust with the lowest Root Mean Square Error.

Design substantiation of ceramic materials on fusion reactor confinement boundaries

Ceramic components will be used for electrical insulation and optical transparency on the heating and diagnostic systems of fusion reactors. As these form the boundary for the radioactive confinement, a defined procedure is required to demonstrate structural integrity. The established design codes are incompatible with ceramic materials for various reasons, predominantly the brittle nature of ceramics. CCFE and others have started to develop an in-house design code for the use of brittle materials in pressure vessels, this paper discusses the rationale behind the rules. The difficulty of reconciling the statistical nature of failure in ceramics with the deterministic nature in codes is addressed and it is suggested that the only way to achieve this is by a proof testing approach. The inherent weakness of the proof testing methodology, quantifying the strength loss during the qualification test is discussed. Further work is required to determine the validity of the rules experimentally.

Is Weibull distribution the most appropriate statistical strength distribution for brittle materials?

Strength reliability, one of the critical factors restricting wider use of brittle materials in various structural applications, is commonly characterized by Weibull strength distribution function. In the present work, the detailed statistical analysis of the strength data is carried out using a larger class of probability models including Weibull, normal, log-normal, gamma and generalized exponential distributions. Our analysis is validated using the strength data, measured with a number of structural ceramic materials and a glass material. An important implication of the present study is that the gamma or log-normal distribution function, in contrast to Weibull distribution, may describe more appropriately, in certain cases, the experimentally measured strength data.

Mechanical Performance of Thin Films in Flexible Displays

AbstractThe use of brittle materials in flexible displays requires the understanding of the mechanical limitations of the materials and the various display architectures. We discuss various approaches to mechanical bend tests for components of flexible displays and describe a new test method based on a three-axis motion. We discuss the mechanical limitations of indium tin oxide (ITO) as a transparent conductor, and present results for a more mechanically robust multilayer transparent conductor made of an ITO-metal-ITO (IMI) stack. The IMI structures showed dramatically improved mechanical properties when subjected to bending both as a function of radius of curvature as well as number of cycles to a fixed radius. Organic light emitting devices fabricated on IMI anodes showed improved performance compared with those made on ITO anodes at current densities greater than 1 mA/cm2 due to the improved conductivity of the anode. We discuss the difficulties in analysis of the mechanical failure of transparent thin film permeation barriers. We present a novel approach for etching barrier-coated polymer substrates such that film cracking is readily visible. We report on the bend test results for sputter- deposited SiOxNy films.

Material removal mechanisms in precision machining of new materials

Modern-day products are characterised by high-precision components. A wide range of materials, including metals and their alloys, ceramics, glasses and semiconductors, are finished to a given geometry, finish, accuracy and surface integrity to meet the service requirements. For advanced technology systems, demands for higher fabrication precision are complicated by the use of brittle materials. For efficient and economical machining of these materials, an understanding of the material removal mechanism is essential. This paper focuses on the different material removal mechanisms involved in machining of brittle materials.

Design considerations in the choice of materials

The designer's responsibility is to select materials and processes to best meet the performance, cost and schedule requirements of the product. Numerous technical factors influence the selection of materials, including the extent to which the material is characterized. Brittle materials may be selected when they result in improvement in performance, are lower in cost, or possess some special or unique properties which cannot be provided by a more ductile material. However, the designer is generally hesitant to select brittle materials because they often are not well characterized or service experience is lacking. Some specific actions are suggested to increase the use of brittle materials when trade-off studies show them to be justified.