铁基大块非晶合金的摩擦磨损性能研究

采用电弧熔炼、铜模吸铸法制备Fe基大块非晶合金,利用球-盘式摩擦磨损试验机进行干摩擦磨损试验,研究了铸态Fe基大块非晶合金的摩擦磨损行为及热处理对其耐磨性的影响,利用扫描电子显微镜观察合金磨损表面形貌,分析了Fe基大块非晶合金以及相同成分晶态合金的磨损机理.结果表明:在本试验条件下,铸态Fe基大块非晶合金的耐磨性高于相同成分的晶态合金,热处理可以有效提高铸态Fe基大块非晶合金的耐磨性,在保持完全非晶状态的前提下,退火态非晶合金的磨损率较铸态非晶合金减小约40%;材料的结构和性能对合金的摩擦系数影响不大,当进入稳定阶段后Fe基大块非晶合金的摩擦系数稳定在0.58左右;不同处理状态的Fe基大块非晶合金和相同成分晶态合金的磨损机制不同,非晶合金的磨损机制以疲劳磨损为主兼有磨粒磨损,相同成分晶态合金的磨损机制为粘着磨损和磨粒磨损共同作用的结果.     

MICROPARTICLES FOR STANDARDIZATION OF ELECTROPHORETIC DEVICES AND PROCESS CONTROL

An appreciation of the importance of particle surface charge as a determinant of the behavior of particle suspensions has stimulated interest in electrophoretic analyses of small particles. Currently available analytical particle electrophoresis equipment provide increasingly powerful techniques for probing the surface charge of small particles so that the potential of the application of the method may be realized in basic and applied research as well as in process development and control in manufacturing environments. Two recurrent issues in the application of the methods are the qualification of the instrument operation and the consistency of the reagents employed. Here we describe strategies for addressing these problems through the use of uniform detergent free, charge-stabilized polymer microspheres first as control particles for monitoring satisfactory instrument operation and secondly as sensitive ‘reporter” probes for detection of trace contaminants in the suspending media used for electrophoretie analysis.     

Particle electrophoresis for quality assurance and process control

Process control is an increasingly important issue as life science companies world-wide strive for recognition of their manufacturing and product development quality measures according to International Standards Organization (ISO) or good manufacturing practices (GMP) standards. Analytical particle electrophoresis (APE) has the potential for significant contributions, not just to basic research, but also in process development and control in manufacturing environments. An important feature of colloidal (small) particles, which controls their behavior, is their surface charge. Optimization of life science products and process conditions involving small particles (>100 nm) may be approached by a variety of strategies based upon direct measurements of the charge properties of process particles or "reporter" particles. The availability of increasingly powerful instruments and control particle preparations (National Institute of Standards and Technology ((NIST) and others) for validation of instrument operation make the method more attractive than ever. We summarize highly flexible electrophoretic strategies for assessing process consistency both from the perspective of particles being processed as well as the processing environment and describe principles for the use of polymer microspheres both as control particles for validation of instrument operation as well as for probes of the assay medium.     

A stress criterion for crack growth

A stress criterion for crack growth was developed from test results with 7075-T6 aluminum-sheet specimens containing transverse machined cracks. Stress distributions near the crack tip were obtained using strain gages and by reducing the strain data to stresses with the aid of Reuss plasticity theory. These distributions indicated the biaxial nature of stress at the crack tip, the high stress gradients a short distance from the tip, and the variation in stress-concentration factor with crack length. Crack growth was found to occur when the effective stress at the crack root reached the engineering ultimate strength.     

Pulsed microwave induced bioeffects

High-power pulsed microwave radiation, when applied to solutions containing dissolved carbon dioxide (or bicarbonate), hydrogen peroxide, and the soluble organic semi-conductor diazoluminomelanin, generates sound, pulsed luminescence, and electrical discharge. Microbes exposed to these phenomena experienced damage comparable to short-time, high-temperature insults, even though the average and measurable localized temperatures were insufficient to cause the observed effects