Measurement of the mechanical properties of a fibre-reinforced composite on the submicrometre scale

Ultramicrotomy is being used routinely as a sample preparation technique for transmission electron microscopy (TEM). TEM study of thin sections of a diketone-bis-benzocyclobutene composite reinforced with Celion (trademark of BASF Co.) carbon fibre revealed two types of periodic crack in the fibre. Coarse cracks were due to bending at knife tip in the early stage of the ultramicrotomy. Also, very fine cracks were observed near the fibre–matrix interface and believed to have been induced by the shear lags between the fibre and the matrix. A simple analysis indicated that the coarse and fine crack spacings could be used to obtain the compressive strength of the fibre and the ultimate shear stress at the fibre–matrix interface, respectively. The combination of ultramicrotomy and TEM provides a useful tool to explore the mechanical properties of a composite material on the submicrometre scale, in addition to the other microstructural and compositional information accessible by TEM. This revised version was published online in November 2006 with corrections to the Cover Date.     

Measurement of mechanical properties of rectal wall

In this paper, a pigs rectum was studied as a model biomaterial and its mechanical behaviors under tensile, compressive, and shear stresses were measured accurately using a multipurpose microtesting system. Based on the stress-strain relations of samples of different orientations, the tangential moduli were calculated through a reverse method combined with self-correlation analysis. The experimental data exhibited pronounced nonlinear and anisotropic characteristics. It was found that the effective compliance in tension along the longitudinal direction was larger than that along the circumferential direction, but smaller than that along the out-of-plane direction.     

Measurement of the parameters of mechanical oscillations by optical-interferometry methods

Conclusions Theoretical and experimental investigations have shown that the application of the Doppler effect makes it possible to measure the velocities of oscillating objects with specular reflecting surfaces over the range from 10^–6 to 160 m/sec, when the reflecting surface is several hundreds of meters distant from the measuring instrument and using a photomultiplier with a frequency resolution of up to 1 GHz. Shortening of the distance between the reflecting surface of the object and the measuring instrument to 5 to 10 m permits the amplitudes of mechanical oscillations of nonspecular surfaces to be measured over the range of a few microns to a millimeter. It is shown that the heterodyne method for reception of the data is favorably different from other interference methods. Its main advantage is the possibility of determining the sign of the velocity being measured and to carry out the analysis of an electrical signal of intermediate frequency over a frequency range above the region of low-frequency noise of the phototransducer.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 65–67, September, 1972.     

Measurement of the dynamic characteristics of machine tools by a pulse loading method mechanical measurements

A pulse loading method for estimating the dynamic characteristics of the elastic systems of machine tools is considered, which gives considerable advantages compared with harmonic loading, requires the minimum amount of measuring apparatus, is simple to use, and provides a computer representation of the results and need not be changed for tests under production conditions. The original software enables the frequency characteristics of elastic systems to be obtained rapidly and reliably. It can be used successfully for vibroacoustic diagnostics of equipment and technological processes in metal processing.     

Measurement of mechanical properties of multilayer coatings by nanoindentation

Abstract

Multilayer protective coatings of alternate aluminium and titanium diboride TiB₂ layers have been tested by nanoindentation to measure both hardness and Young's modulus values. The initial results show that the values obtained depend upon the depth of indentation. An alternative view is presented to show that by considering the percentage of each coating in contact with the indenter a single relationship between either hardness or Young's modulus and the amount of aluminium layer penetrated can be produced. This technique allows the influence of the percentage ceramic on the results obtained to be identified. Comparison of the nanoindentation results with three point bending tests show how the coating structure influences the results obtained.     

Measurement system for end face mechanical seal performance

Improving the performance of mechanical seals requires the investigation of their behaviour. In order to improve the characteristics of long service life and low leakage, operating cost, and (presumably stable) operating torque, seals must be thoroughly evaluated under service conditions. However, the measurement of operating parameters in the field is hindered by the inaccessibility of seal components and by inadequate instrumentation. Therefore, a well calibrated and fully instrumented system is required to measure the performance characteristics of seals in the laboratory. A test stand has been developed to achieve this.     

Considerations for appointing an external examiner of a PhD in the biomedical sciences in Sweden: a questionnaire-based survey

A survey of 170 Swedish mentors of PhD-students found that expertise in the research field and avoidance of conflict of interest were big motivators for finding an examiner from abroad for PhD theses. The survey also identified that concern by supervisors for facilitating the career paths of younger scientists in terms of introductions to potential labs for post-doctoral work and obtaining high quality neutral review of one’s research was also important, as was the desire to set up collaborations. An expectation from the management of one’s university of the PR-value of a foreign senior person as examiner also played a part. Although few were willing to admit that PR for one’s own group was a motivating factor. A small fraction of responders expressed concern that, as some of the costs of the PhD-examination were being shifted on to the research groups themselves, this might impact the current situation. Language also played a subordinate role. To get the best out of the visiting examiner, it was important to educate and instruct them in their role in a Swedish PhD-examination protocol. Male supervisors had had more PhD-candidates than female, but they also had used more Sweden-based examiners than their female colleagues. We conclude that using a foreign examiner was motivated by factors that are likely to prevail for the foreseeable future. This Swedish practice may also provide a template for a common standard.     

Measurement of the uniaxial mechanical properties of healthy and atherosclerotic human coronary arteries

Atherosclerosis is a common arterial disease which alters the stiffness of arterial wall. Arterial stiffness is related to many cardiovascular diseases. In this investigation, maximum stress and strain as well as physiological and maximum elastic modulus of 22 human coronary arteries are measured. In addition, the force-displacement diagram of human coronary artery is obtained to discern the alterations between the healthy and atherosclerotic arterial wall stiffness. The age of each specimen and its effect on the elastic modulus of human coronary arteries is also considered. Twenty-two human coronary arteries, including eight atherosclerotic and fourteen healthy arteries are excised within 5 hours post-mortem. Samples are mounted on a tensile-testing machine and force is applied until breakage occurs. Elastic modulus coefficient of each specimen is calculated to compare the stiffness of healthy and atherosclerotic coronary arteries. The results show that the atherosclerotic arteries bear 44.55% more stress and 34.61% less strain compared to the healthy ones. The physiological and maximum elastic moduli of healthy arteries are 2.53 and 2.91 times higher than that of atherosclerotic arteries, respectively. The age of specimens show no correlation with the arterial wall stiffness. A combination of biomechanics and mathematics is used to characterize the mechanical properties of human coronary arteries. These results could be utilized to understand the extension and rupture mechanism of coronary arteries and has implications for interventions and surgeries, including balloon-angioplasty, bypass, and stenting.     

UV-LIGA镍薄膜材料的力学性能测试与分析

利用LIGA或UV-LIGA技术制备的镍,特别适合作为微器件的结构材料。材料的力学性能在微器件的仿真设计和实际使用中起到重要作用。主要利用常规的力学试验机和自行搭建的微拉伸平台,通过单轴拉伸方法测试了电流密度为20mA/cm2的UV-LIGA镍薄膜的力学性能。3种测试方法的结果呈现了一致的规律性变化——弹性模量显著降低,强度显著提高,表明UV-LIGA镍具有与块体镍显著不同的力学性能。通过X射线衍射分析(XRD),测量了该电流密度下试样的择优取向和晶粒尺寸,通过场发射扫描电镜(SEM)观察了试样的表面形貌和拉伸断口,并初步地分析了UV-LIGA镍力学性能的变化原因。该测试结果为微器件的仿真设计提供了重要的参考依据。     

Measurement of mechanical properties of one-dimensional nanostructures with combined multi-probe platform

New materials and nanostructures with superior mechanical and electronic properties are emerging for development of novel devices. Their engineering application requires accurate mechanical characterization, which, in turn, requires novel experimental techniques. In this paper, we report a recently developed multi-probe mechanical testing system and a few of its typical applications in studying mechanical behaviors of one-dimensional (1D) nanostructures, which include analyzing clamping strength of electron beam induced deposition (EBID) for Si nanowires and the tungsten substrate, retrieving Young’s modulus of a Si nanowire using tunable resonance method, and investigating thermal fatigue behavior of nanoscale interconnect lines bearing alternating current. We find this testing system can be easily used for clamping, loading, and measuring various 1D nanostructures.     

The choice of examiner patent citations for refusals: evidence from the trilateral offices

Utilizing a novel methodology based on international family-to-family patent citation data, this paper directly compares X/Y patent citations (i.e., those cited as grounds for rejections, equivalent to “blocking patents” in the US) between major patent offices. Remarkable discrepancies between the offices were revealed, despite the common patentability criteria of novelty and inventive step to generate citations. This paper then introduces a simple cosine similarity measurement between a family of X/Y patent citations and all citations added globally to the same original application. How the discrepancies of X/Y patent citations at the European Patent Office (EPO) and the US Patent and Trademark Office (USPTO) relate to the characteristics of applications and longitudinal aspects of office actions were also examined. X/Y patent citations from both the EPO and USPTO commonly show that the range of patent application classes is positively correlated with divergent reasons for refusal, suggesting that costly examinations lead to diversified X/Y patent citations. One novel methodological feature of this paper is that examiner citations across jurisdictions are comparable if we employ family-to-family citations and common criteria for the X/Y citation category. Furthermore, unlike the normal citation-generating process where a citing document adds citations to prior art only once, this paper represents the first attempt to analyze a citation network with multiple citing opportunities from separate parties. We find that the variance of citation linkages has a negative relationship with the ease in which different citers evaluate prior art in the same way, thereby providing a new perspective on the notion of breadth in citation impact.     

基于水听器法的医用超声声场热指数和机械指数测量

介绍了医用超声设备热指数（TI）和机械指数（MI）两种声输出指数,提出一种基于水听器法测量医用超声声场参数的测量装置,可通过扫描声场实现对超声诊断设备的声输出指数的测量。以一种B型超声诊断仪为例,进行初步的测量并给出了实验数据。     

On the mechanical behaviour of a crystalline undulator

A crystalline undulator is a newly proposed compact device to generate coherent electro-magnetic waves. The crystalline undulator is a micro-electro-mechanical system that relies on silicon micro-fabrication. In the present work, the mechanical behaviour of a crystalline undulator with sub-millimetric period obtained by patterning the surfaces of a silicon lamina with alternate strips has been investigated. The anisotropy of the silicon substrate and the geometrically nonlinear behaviour of the device have been discussed. Sensitivity study has been performed for defining the optimal thickness and width of the strips. Finally, an analytical model is proposed to evaluate the displacements and local effects such as interfacial shear stress concentrations.