Analysis of interface damage heterogeneity in polycrystalline materials

The Interface Damage Function (IDF) defining fractional damage of intercrystalline interfaces in polycrystalline materials, with functional dependence upon lattice misorientation and boundary normal orientation, is described. A method of section analysis to calculate the IDF is derived; it is shown to depend upon a convolution with the Intercrystalline Structure Distribution Function (ISDF) which has been defined in previous work. This convolution is expressed in a double integral equation which is solved by the Fourier method. Application of the theory to cavitation damaged OFHC copper is described. Illustrated is a rich structure of the IDF which illuminates the mechanisms of heterogeneity in creep damage. Random high-angle boundaries are found to be remarkably damage resistant, while some special boundaries are preferentially damaged. A varied response of the damage to shear and normal components of the applied stress is also observed.     

Fe-2Ni/Fe-2Ni-xCr梯度功能材料的共烧结致密化行为和界面强度

目前共烧结工艺相容性问题是限制粉末共注射成形以及梯度功能材料制备技术的关键问题之一,由于共烧结异种材料的烧结行为不一致,极易在界面处产生烧结界面应力,造成异种材料共烧结界面变形、开裂等缺陷。因此,对共烧结进行实验研究,探索适当的工艺参数和工艺路线显得极为重要,故本文作者选用Fe-2Ni/Fe-2Ni-0.3C、Fe-2Ni/Fe-2Ni-(0.5、1、3)Cr多种共烧结材料体系进行共烧结相容性研究。结果表明共烧结后的Fe-2Ni/Fe-2Ni-0.3C、Fe-2Ni/Fe-2Ni-0.5Cr、Fe-2Ni/Fe-2Ni-1Cr试样界面结合强度较高,达到甚至超过了强度较弱端的强度,而Fe-2Ni/Fe-2Ni-3Cr共烧结则容易出现裂纹;实验结果说明共烧结会造成试样中存在密度梯度,缩小界面处相容性差异,从而提高界面结合强度。     

The fracture resistance of a model metal/ceramic interface

Crack propagation has been measured for the Al₂O₃/Au interface subject to conditions that exclude stress corrosion. Crack growth has been shown to occur with a rising resistance, governed by intact metal ligaments in the crack wake. The level of resistance also increases as the metal layer thickness increases. Crack extension occurs by a combination of plastic void growth and interface debonding. The fracture energies are much larger than the work of adhesion, but appreciably smaller than those expected for ductile interface fracture. The fracture energy is nevertheless dominated by plastic dissipation, which increases at larger metal layer thicknesses.     

Sustainability: The materials role

This lecture series began in 1971 focused on the links between materials, energy, and the environment. The issue of sustainability had emerged, but only as an exploration of the possibility of materials depletion in the face of predicted population growth. Today, sustainability implies a global economic and social system that both satisfies human needs and does not despoil the earth. What has been our role in this increasingly important arena of human concern and what should it be? Our report card is impressive. Improvements in processing, in materials substitution, in design to minimize materials usage, and in recycling of metals and polymers have all been remarkable. However, we are faced with twin dreadnoughts of change in the next decades: technological ascendency of developing nations and rising world population. Add to these the need to reduce the effluence of greenhouse gases and we must anticipate formidable technological upheaval throughout the materials cycle. Our professional societies need to step forward and play larger and significantly more visible roles in this arena. Working individually and in concert with others, the societies must broadcast our achievements, identify future areas for activity, support industrial road-mapping efforts, and join with all who will participate in clarifying the flow of materials throughout their life cycles.     

Sustainability: The materials role

This lecture series began in 1971 focused on the links between materials, energy, and the environment. The issue of sustainability had emerged, but only as an exploration of the possibility of materials depletion in the face of predicted population growth. Today, sustainability implies a global economic and social system that both satisfies human needs and does not despoil the earth. What has been our role in this increasingly important arena of human concern and what should it be? Our report card is impressive. Improvements in processing, in materials substitution, in design to minimize materials usage, and in recycling of metals and polymers have all been remarkable. However, we are faced with twin dreadnoughts of change in the next decades: technological ascendency of developing nations and rising world population. Add to these the need to reduce the effluence of greenhouse gases and we must anticipate formidable technological upheaval throughout the materials cycle. Our professional societies need to step forward and play larger and significantly more visible roles in this arena. Working individually and in concert with others, the societies must broadcast our achievements, identify future areas for activity, support industrial road-mapping efforts, and join with all who will participate in clarifying the flow of materials throughout their life cycles.     

界面对复合保温材料热学性能劣化作用机理

为了考察界面对复合保温材料热学性能的影响,成型了一组EPS含量不同的复合保温砂浆试件,并研究了这些试件在经历干湿循环和冻融循环作用后的导热系数.通过确定有机保温组分和基体的影响因子值,间接求得界面对复合保温材料热学性能的影响值.实验结果表明,当有机组分EPS的体积分数超过50%时,复合保温砂浆试件的热学性能明显劣化.结合理论分析认为,界面是影响有机-无机复合保温材料热学性能变化的重要原因.特别是当有机保温组分在复合材料中的体积分数超过一定值时,界面成为导致材料热学性能劣化的关键因素.因此,在复合保温材料开发和应用中,必须对有机保温组分的掺量加以限制.     

The growing teratoma syndrome: report of a case

We report here the first case of a one-step endosonography(EUS)-guided pseudocyst drainage. A prototype large channel curved array echo endoscope (Pentax FG-38 UX) and a prototype delivery system for placement of an endoprosthesis was used for the procedure. The delivery system (GIP MedicinTechnik GmbH/Medi-Globe Corporation) consists of a handle part with a piston, a metal ring sheath, a plastic catheter with a diathermy needle and a double pigtail endoprosthesis (8.5 Fr). When mounted on the endoscope the endoprosthesis can be advanced out of the distal end of the endoscope. The introduction of the stent as well as the stent release can be monitored entirely by ultrasound. The procedure was tested in a 76-year-old woman with a pseudocyst measuring 60 mm in diameter located in the tail of the pancreas. The procedure was well tolerated by the patient, and there were no procedural complications. The advantage of a large channel echo endoscope and our new prototype delivery system is that the endoprosthesis can be inserted in to a pancreatic cyst guided exclusively by EUS without exchange of endoscopes, catheters or guide wires. Further studies are warranted.     

Biotechnology core facilities: trends and update

A survey of 128 biotechnology core facilities has provided data on the finances, services, space requirements, and personnel. An average facility had four full-time personnel and 7.5 major instrument systems, and occupied 969 sq. ft. Average total income was $244,000/year, but annual user fee income was only $125,000. Typically, facilities required substantial institutional support or grants. Cost recovery (user fee income divided by total income) averaged 49%. During the last 5 years user fee income, total income, and cost recovery have increased. In-house charges for protein sequencing and peptide synthesis increased approximately 30%, while oligonucleotide synthesis charges decreased by 74%. The costs (charges corrected for subsidy from non-user fee income) for most services did not significantly change, except that oligonucleotide synthesis costs decreased by 25% in 1992. DNA synthesis had the highest throughout per month (116 samples), followed by amino acid analysis (86 samples) and DNA sequencing (67 samples). Other services averaged from 5 to 60 samples. DNA synthesis and purification were the services used by the greatest number of principal investigators. A number of services including DNA sequencing, mass spectrometry, capillary electrophoresis, RNA synthesis, electroblotting, and carbohydrate analysis have been introduced in the last 3 years. Although these services are characterized by high levels of methods development and non-user runs, they are offered by twice the percentage of facilities as in 1989, and are increasingly contributing to facility income.     

The Potential of Biotechnology in the Mining Industry

Abstract

Applications of biotechnology are in use or have been proposed for almost all sectors of the mining and minerals industries for metal extraction, metal recovery, and environmental control. A recently completed study in Canada reviewed the status of biotechnological process development in different sectors of the industry and by commodity. This paper provides an overview of the findings of the study including a discussion of the sectors of the industry in which biotechnology enjoys commercial success and those for which future applications are indicated. Special emphasis is given to the commercial metal extraction processes and to applications for environmental control for which future technical and economic advantages are likely as environmental regulations become more stringent.     

Deflection and penetration of cracks at an interface between two dissimilar materials

The tendency of a crack to deflect or penetrate at an interface between two dissimilar elastic materials in a finite-sized sample is investigated with the boundary element method. The ratio of the energy release rate of a deflecting crack to the maximum energy release rate of a penetrating crack is computed as a function of the Dundurs' elastic mismatch parameters for several double-edged notch specimen geometries and loading conditions.Over the entire range of material parameters, the results displayed only a weak dependence on the loading conditions imposed on the specimen, the aspect ratio of the specimen, and on Dundurs' parameter, β. For moderate differences in the relative stiffnesses of the two materials and when the crack is advancing toward a stiffer material, we find essentially no difference between the singly and doubly deflected crack, and the numerical calculations are in excellent agreement with recent analytical predictions [1]. However, when the crack is advancing into a material of much lower modulus, the numerical calculations for a doubly deflected crack are smaller than the analytical predictions.