Contribution of bending energy losses to the apparent tear energy

When a strip is torn, energy is expended both in tearing it and in propagating a bend along each torn section. Estimates are given of the contribution of bending energy losses to the apparent tear energy. Experiments with highly-dissipative semi-crystalline polymers, torn with controlled amounts of bending, are then described. The bending energy losses ranged from 5 to 70 percent of the total tear energy, depending upon the degree of bending imposed, the thickness of the strip, and the extent to which it had been partly cut through before tearing. These results were in satisfactory agreement with approximate theoretical estimates. When the torn strips were allowed to take up naturally bent configurations under the action of the tearing force, then the contribution of bending energy losses to the apparent tear energy became rather independent of the strip dimensions and depended principally upon the dissipative nature of the material, represented by the fraction H of deformation energy that is not recovered. A general relationship is proposed between the apparent (G _c) and true (G _c) tear energies in this case: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaGqaciaa-Deada% qhaaWcbaGaa83yaaqaaiaa-DcaaaGccqGH9aqpcaWFhbWaaSbaaSqa% aiaa-ngaaeqaaOGaai4laiaacIcacaaIXaGaeyOeI0Iaa8hsaGqaai% aa+Lcaaaa!415E!\[G_c^' = G_c /(1 - H)\]. Values of H for the materials examined ranged from 30 to 70 percent. Thus, bending energy losses are expected to increase the tear energy by a factor of 1.4 × to 3.3 × for unconstrained tearing of these semi-crystalline polymers. Somewhat smaller increases were actually observed, ranging from 1.1× to 2×.

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Résumé Lorsque l'on déchire une bande, l'énergie est dépensée à la fois dans le déchirement et dans la propagation d'une flexion sur chacun des bords de la déchirure.On donne des estimations de la contribution des pertes d'énergie associées à ces flexions, à l'énergie apparente de déchirement. On décrit ensuite des expériences de déchirement de bandes en polymères semi-cristallins à haute dissipation, sous des conditions de flexion contrôlées. On a établi que la dissipation d'énergie associées à la flexion vaut de 5 à 70% de l'énergie totale de déchirement, selon le degré de flexion imposé, l'épaisseur de la bande, et la longueur de la coupe réalisée avant déchirure. Ces résultats ont été trouvés en accord satisfaisant avec les estimations théoriques. Lorsque les portions déchirées adoptent la configuration de flexion qui correspond à une situation naturelle sous l'effet des forces de déchirement, les pertes dues à l'énergie de flexion contribuent à l'énergie apparente de déchirement de manière relativement indépendante des dimensions de la bande, mais principalement dépendante de la nature dissipatoire du matériau, représentée par la fraction H de l'énergie de déformation non récupérée.Une relation générale est proposée dans ce cas entre l'énergie apparente (G _c) et réelle (G _c) de déchirement: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaciaacaqabeaadaqaaqaaaOqaaGqaciaa-Deada% qhaaWcbaGaa83yaaqaaiaa-DcaaaGccqGH9aqpcaWFhbWaaSbaaSqa% aiaa-ngaaeqaaOGaai4laiaacIcacaaIXaGaeyOeI0Iaa8hsaGqaai% aa+Lcaaaa!415E!\[G_c^' = G_c /(1 - H)\]Les valeurs de H varieront de 0,3 à 0,7 selon les matériaux examinés. Dès lors, on s'attend à ce que les pertes par énergie de flexion accroissent l'énergie de déchirement d'un facteur 4,4× à 3,3× dans le cas d'un déchirement sans rétreint des polymères semi-cristallins étudiés.Dans la réalité, on a observé des accroissements un peu plus faibles, variant de 1,1× à 2×.

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Department of Aerospace Engineering and Mechanics, University of Minnesota     

Status of the energy saver

The one-TeV proton synchrotron which has been under construction at Fermilab is nearly complete and is now entering the commissioning phase. The assembly and testing of the ring of more than 1000 superconducting magnets with its associated cryogenic, vacuum, power, R.F., controls and safety systems has gone extremely well.     

贯彻《节能法》推动节能工作

近年来我国能源消费增长快、利用效率低的问题比较突出,原有《节能法》已经不能适应当前节能工作的要求。为了推动全社会的节约能源工作,全国人大今年修订了这部法律。文章介绍了修订后的《节能法》基本思路、主要内容和实施后的初步效果。     

Transforming the energy sector: the evolution of technological systems in renewable energy technology

This paper analyses the development and diffusion of technologiesthat utilize renewable energy sources in Germany, Sweden andthe Netherlands. The analysis enlarges the life cycle modelof industry evolution to one where the focus is on the formationand evolution of new technological systems. Particular focusis on explaining success and failures in shifting from a formativephase into one characterized by positive feedbacks. A set ofchallenges is identified for policy makers attempting to influencethe process of transforming the energy sector.     

Promotion of wind energy in isolated energy systems: the case of the Orites wind farm

With the establishment of the first wind farm on the island, Cyprus has made progress to satisfy the European Union’s 2020 renewable energy targets. Operational since September 2010, the 174 M€ Orites wind farm is currently the largest wind project in the Mediterranean region. In this article, the main characteristics of the project with regard to Cyprus’s national action plan for the promotion of renewable energy sources are presented. The socio-economic impacts of the project and its feasibility in the context of an isolated energy system are also examined. The results of a public survey to identify the attitudes of surrounding households and neighbouring cities towards the wind farm are presented. The assessment was based on face-to-face interviews conducted with 50 households from the surrounding communities and 100 interviewees from neighbouring cities. According to the survey, the public opinion on the wind farm was generally positive, and the majority of the respondents considered the wind farm to be acceptable as of no considerable environmental impact.     

Efficiency of transformation of heat energy into electric energy due to the thermovoltaic effect

Direct measurements of the efficiency of the transformation of heat energy to electric energy on the basis of the thermovoltaic effect are carried out for the first time. Experiments are performed using samarium sulfide specimens. The values of efficiency vary from 7.5 to 28%.     

Cryogenics and the energy crisis

This paper reviews some of the ways cryogenics can help solve the energy crisis.Five specific areas are covered: the use of LNG, the conversion of coal to fuel gas using oxygen from air separation plants, the use of superconductors in power plants and electrical transmission lines, superconducting instruments for geophysical exploration of new energy resources, and the Hydrogen Economy.     

中国节能/节水产品认证制度为节能减排护航

1998年,我国依据《中华人民共和国节约能源法》建立了中国节能产品认证制度,成立了中国节能产品认证管理委员会和中国节能产品认证中心(现已并入中国质量认证中心),颁布了《中国节能产品认证管理办法》和节能产品认证标志,正式启动了中国的节能产品认证工作。2009年是我国开展节能节水产品认证的第10个年头。10多年来,这一认证制度的开展和推广工作取得了长足发展。节能产品认证制度的实施,以及节能产品的推广和普及,带来了良好的经     

Embodied energy of detached houses built to the nearly‐zero energy standard

Until now, the standards framework for the energy‐related balancing of buildings has concentrated on the operating/use phase of the building by using energy consumption or demand values as the essential parameters. Energy used for the production of the building materials, the building of the building and finally any disposal required are not included. The German government therefore formulated the target in their climate protection plan 2050 [1], published at the end of 2016, to further the use of sustainable building and insulation materials. Climate protection aspects before and after the period of use, i.e. emissions caused by the production, processing and disposal or recycling of the building materials, were to be taken into account on the basis of freely available eco‐balance data. In addition, instruments for the greater integration of the lifecycle (”Cradle to Grave“ or ”Cradle to Cradle“) of building materials were to be investigated and included more in building design practice.     

动能定理的应用分析

通过对动能定理、功能原理和机械能守恒定律的简明推导,总结出动能定理、功能原理和机械能守恒定律三者之间的相互关系及各自的应用条件。重点阐述了动能定理与机械能守恒定律应用的区别。     

On the energy characteristics of ball lightning

A compilation of 17 observations of ball lightning showing the most energetic effects is presented along with estimates of their energy content. These observations were chosen from several thousand for the much stronger interaction of each ball lightning on its surroundings, and the method of energy estimation outlined. The case is put that some of the observations show a higher energy than self-contained chemical energy could provide. Comments have been added to the paper, arguing that the energy estimations themselves should be consistent with whatever model is used for ball lightning. For example, the presence of reacting nanoparticles releasing chemical energy may bring about the same observed effects with lower estimated energy.     

On the free energy of liquid-metal plasma

The free energy of simple liquid metal in the approximation of the integral smallness of the electron–ion interaction has been found on the basis of the model of single-component plasma as the initial system. The result obtained holds at the equivalency of correlation functions determined within Gibbs canonical and large canonical distributions.     

Theory of the temperature dependence of the roton energy

The temperature dependence of the roton energy is examined considering its collision with another thermally excited roton and the interaction between one excitation and two rotons. The strong final state interaction strongly modifies the two-roton density of states, and therefore the Hartree-Fock approximation is not valid for the roton-roton scattering. Using the point interaction model for the roton-roton coupling and examining only the self-energy processes for the one-particle Green function linear in the number of rotons, it is shown that the amplitude of this temperature dependence changes sign as the roton-roton coupling strength is increased and an upper bound is obtained for the temperature dependence of the roton energy. As this upper bound is only one-seventh of the experimental result, they can be interpreted only by assuming more than seven independent channels with different angular dependence.This work is based on part of the author's Ph.D. thesis (Roland Eötvös University, Budapest). The support of the Central Research Institute for Physics is acknowledged.