The present work investigates the nature of dry-friction whip and whirl through experimental and numerical methods. Efforts of the author, Dyck, Pavalek, and coworkers enabled the design and construction of a test rig that demonstrated and recorded accurately the character of multi-mode dry-friction whip and whirl. These tests examined steady state whip and whirl characteristics for a variety of rub materials and clearances. Results provided by the test rig are unparalleled in quality and nature to those seen in literature and possess several unique characteristics that are presented and discussed. A simulation model is constructed using the Texas A and M University (TAMU) Turbomachinery Laboratory rotordynamic software suite XLTRC2 comprised of tapered Timoshenko beam finite elements to form multiple degree of freedom rotor and stator models. These models are reduced by component mode synthesis to discard highfrequency modes while retaining physical coordinates at locations for nonlinear interactions. The interaction at the rub surface is modeled using a nonlinear Hunt and Crossley contact model with coulomb friction. Dry-friction simulations are performed for specific test cases and compared against experimental data to determine the validity of the model. These comparisons are favorable, capturing accurately the nature of dryfriction whirl. Experimental and numerical analysis reveals the existence of multiple whirl and whip regions spanning the entire range of frequencies excited during whirl, despite claims of previous investigations that these regions are predicted by Black's whirl solution, but are not excited in simulations or experiments. In addition, spectral analysis illustrates the presence of harmonic sidebands that accompany the fundamental whirl solution. These sidebands are more evident in whip, and can excite higher-frequency whirl solutions. Experimental evidence also shows a strong nonlinearity present in the whirl frequency ratio, which is greater than that predicted by the measured radius-toclearance ratio at the rub location. Results include whirl frequencies 250% of that predicted by the measured radius-to-clearance ratio.

No description available.

The present work investigates the phenomena of whip and whirl for a rigid rotor contacting at two bearing locations. The idea originated from an anemometer consisting of a rotor with an elastically supported stator undergoing the phenomena of dry friction whip and whirl at the two bushing contacts. To analyze the behavior, a mathematical model similar to the anemometer is developed and analyzed assuming two possible solutions, Mode1 (normal reaction forces in phase at two contacts) and Mode 2 (normal reaction forces out of phase at two contacts). Analytical solutions are only possible for the models with same RCl (Radius to Clearance ratio) at the two rub locations. A simulation model is constructed using the Texas A&M University (TAMU) Turbomachinery Laboratory rotordynamics software suite XLTRC² comprised of Timoshenko beam finite elements to form multiple degrees of freedom rotor and stator models. The nonlinear connections at the rub surface are modeled using Hunt and Crossley‘s contact model with coulomb friction. Dry friction simulations are performed for three separate models depending on the rotor‘s mass disk location with respect to the contact locations. The three models used have (1) Disk at center location (2) Disk at 3/4 location (3) Disk at overhang location. The adequacy of the analytical solution is investigated using the above simulations. Also, cases are explored where the general assumed solution would not solve the mathematical model, e.g. different RCl ratios at the two contacts. Simulations are performed for increasing as well as decreasing running speeds. There is partial agreement between simulation predictions and the analytical solutions for the cases with the mass center at centered and at 3/4 location. First, whirl-to-whip transitions occur at near the combine rotor-stator bounce frequency for both disk at center and disk at 3/4 location. The case with overhang mass disk predicts the two contacts to whip and at different frequencies simultaneously. Neither of the analytical solutions predicts a case where precession occurs at two different frequencies at the two contact points. Predictions for models with different RCl on the Backward Precessional (BP) graph imitate whirling. The BP graph predicts increasing BP frequency with increasing rotor speeds which is a characteristic of whirling, whereas investigation of individual contact velocities suggest that they are slipping at all conditions, one of them slipping more than the other netting a whirling like motion. For the overhang model with different RCl, apart from whipping at different frequency the two contacts also whirl at different frequencies corresponding to the RCl at the respective contacts. Simulations for decreasing rotor speed predict jump down from whirl- to-whip different BP frequency as compared to the jump up from whip-to-whirl for the speed up.

One of the requirements of a safe nuclear power plant design is the postulation of the dynamic effects of a steam pipe rupture. The dynamic effects are the discharging fluid and pipe whip on structures, systems or components. A pipe rupture can be caused in the steam pipe system where a defect such as a crack exists. Multiple factors contribute to the initiation of pipe cracks during the plant’s life. Cracks may start microscopically small and over time, with the assistance of cyclic operation, fatigue may elongate the crack. When a steam pipe is cooled by water during an accident, steam condensate may accumulate and form slugs of water. This water will have an effect on the system termed condensation induced water hammer. The cause of the pipe rupture is not addressed in this dissertation. Pipe rupture can be considered to be either a circumferential or longitudinal break. For the purpose of this dissertation only a circumferential break will be considered. This research is based on the development of a pipe whip restraint structure to protect the plant environment during a steam pipe rupture event in a nuclear power plant. It focuses on a structural component required to restrain the dynamic energy to an acceptable level. Whip restraints used in the nuclear industry are typically honeycomb, U-bar and crush pipe types. In this dissertation only the U-bar and crush pipe whip restraints will be considered. The plant environment, with regards to pipe layout, plays a large role in determining the type of restraint to be used, whether it is U-bar or crush pipe. A whip towards the wall/structure will favor a crush pipe; a whip away from the wall/structure will favor a U-bar restraint. In this project the crush pipe is selected where the whip is towards a wall/structure. The crush pipe also represents a simpler design. First-order analysis is performed using the energy method to determine the conceptual geometry of the whipping component and the restraint geometry. Second-order analysis includes finite element analysis to verify the first-order results. In this dissertation the concept validation is done using LS-PrePost. for the pre- and post-processing while the analysis is performed using LS-DYNA ®. During the second-order analysis it was demonstrated that the energy is successfully absorbed by the crush pipe and thus the first-order analysis is considered adequate. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

One of the requirements of a safe nuclear power plant design is the postulation of the dynamic effects of a steam pipe rupture. The dynamic effects are the discharging fluid and pipe whip on structures, systems or components. A pipe rupture can be caused in the steam pipe system where a defect such as a crack exists. Multiple factors contribute to the initiation of pipe cracks during the plant’s life. Cracks may start microscopically small and over time, with the assistance of cyclic operation, fatigue may elongate the crack. When a steam pipe is cooled by water during an accident, steam condensate may accumulate and form slugs of water. This water will have an effect on the system termed condensation induced water hammer. The cause of the pipe rupture is not addressed in this dissertation. Pipe rupture can be considered to be either a circumferential or longitudinal break. For the purpose of this dissertation only a circumferential break will be considered. This research is based on the development of a pipe whip restraint structure to protect the plant environment during a steam pipe rupture event in a nuclear power plant. It focuses on a structural component required to restrain the dynamic energy to an acceptable level. Whip restraints used in the nuclear industry are typically honeycomb, U-bar and crush pipe types. In this dissertation only the U-bar and crush pipe whip restraints will be considered. The plant environment, with regards to pipe layout, plays a large role in determining the type of restraint to be used, whether it is U-bar or crush pipe. A whip towards the wall/structure will favor a crush pipe; a whip away from the wall/structure will favor a U-bar restraint. In this project the crush pipe is selected where the whip is towards a wall/structure. The crush pipe also represents a simpler design. First-order analysis is performed using the energy method to determine the conceptual geometry of the whipping component and the restraint geometry. Second-order analysis includes finite element analysis to verify the first-order results. In this dissertation the concept validation is done using LS-PrePost. for the pre- and post-processing while the analysis is performed using LS-DYNA ®. During the second-order analysis it was demonstrated that the energy is successfully absorbed by the crush pipe and thus the first-order analysis is considered adequate. / Thesis (MIng (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2013

No description available.

Práce se zabývá empirickým ověřením platnosti efektu biče u reálného dodavatelského řetězce. Zároveň na reálných datech ukazuje rozdíl mezi optimalizací zásob každého dílčího článku řetězce a optimalizací zásob podél celého řetězce. Součástí práce je vytvořená učební pomůcka pro ukázku optimalizace zásob (model EOQ) a Pivní hra pro demonstraci platnosti efektu biče.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The successful operation of a man-pack VHF jamming system requires a compact and efficient antenna operating over a wide bandwidth. The design of such an antenna is the focus of this thesis. The antenna should be of a practical size for a portable system and it must radiate energy efficiently across a frequency bandwidth in excess of a decade. A practical „target‟ specification of such an antenna has been drawn up based on the performance of a commercially available system. Several possible antenna topologies, each with a variety of loading section options, are tested using “Full wave” electromagnetic modelling (FEKO). Each topology/loading-section is numerically optimised for load element values by considering both its gain and reflection coefficient. Results of the „optimally loaded‟ solution for each topology are then compared to each other to arrive at the best overall design. The best result is found to be the traditional monopole whip-type antenna, with four R-L loading sections spread along its length. The simulated results show that the proposed antenna can be expected to meet the target standing wave ratio (SWR) specifications while offering a gain advantage of between 5 and 10 dBi higher than is available commercially. The selected design is constructed and its performance measured. / AFRIKAANSE OPSOMMING: Die suksesvolle werking van ʼn mobiele VHF "jammer‟ benodig ʼn kompakte antenna met ʼn bruikbare benuttingsgraad wat oor ʼn wyeband funksioneer. Die ontwerp van so ʼn antenna is die fokus van hierdie tesis. Die antenna moet kompak genoeg wees om draagbaar te wees en moet ʼn bruikbare benuttingsgraad hê oor ʼn frekwensie-bandwydte van meer as 10:1. ʼn Praktiese spesifikasie is opgestel vir die antenna deur te kyk na die sigblaaie van beskikbare stelsels. “Volgolf” elektromagnetiese modelleringsagteware is daarna gebruik om ʼn parametriese ondersoek te loods van verskillende antennas. Verskillende topologieë is getoets met ʼn verskeidenheid van belaaide seksies waar die topologieë ge-optimaliseer was vir wins en weerkaatskoëffisiënt. Die resultate vir elke optimale oplossing is vergelyk.Opgrond van hierdie resultate is bevind dat die beste topologie die tradisionele monopoolmas "whip-type‟ antenna is met vier RL lading afdelings langs die lengte versprei. Analise word gebruik om te wys dat verwag kan word dat dit aan die aanwins en staande golf verhouding (SGV) spesifikasies sal voldoen met n 10 dB verhoging in aanwins vir n laer SGV. Die geselekteerde ontwerp is gebou en gemeet om te verifieer dat dit aan die spesifikasies voldoen.

The goal of this paper is to evaluate the growth of the seedlings, in different sizes and recipients, with different types of substracts. The experiment was established and conducted on the premises of the Forestry Science Silviculture Laboratory of the Federal University in Santa Maria, located in the Central Depression Area of the State, in the municipality of Santa Maria, State of Rio Grande do Sul, and the area is at an approximate altitude of 90 to 95 meters, its geographic location is between parallels 20º43 and 29º44 latitude south, and between meridians 53º42 and 53º44 longitude west of Greenwich. Statistical delineation utilized was an entirely casualized block, and as the treatment consisted of different recipientss and different substracts, the bifactoral system was adopted, with 16 treatments and 4 repetitions. On average, 96 plants were seeded in each parcel, and with the exclusion of the two border rows, 32 useful plants were obtained. The seeds came from Afubra s Socioenvironmental Program, a sub-project of the Native Tree Seed Pouch program. Three seeds were sown into each recipient and later submitted to thinning out. Evaluations started 90 days after seeding, and were concluded in 180 days, taking into consideration stem diameter, size of seedlings, dry root weight, dry aerial weight, and the Dickson quality rate. Using the variance analysis and average comparison test, through the Tukey test, there were no significant differences in the analyzed parameters for the following variables: stem diameter; size of seedlings; dry root weight, dry aerial weight and Dickson quality rate, among the 180 cm³ and 280 cm³ cells. For the variables: stem diameter, dry root weight, and Dickson quality rate, the best media was the so-called Plantmax Agrícola. For the seedling size and dry aerial weight variables, the best media was defined as Humosolo Vida. Based on these results, it is possible to recommend 180-cm³ recipients, for their economic advantages in terms of less material, less labor and smaller transport costs. The recommended media is the Plantmax Agrícola, which has so far produced the best results in terms of seedling quality patterns. / Os objetivos desta pesquisa foram avaliar o crescimento das mudas em diferentes tamanhos de recipientes com diferentes tipos de substratos. O experimento foi instalado e conduzido no viveiro florestal, junto ao Laboratório de Silvicultura do Departamento de Ciências Florestais da Universidade Federal de Santa Maria, localizado na Depressão Central do Estado, no município de Santa Maria, no Rio Grande do Sul, cuja área possui uma altitude aproximada de 90 a 95 metros, sua localização geográfica é entre os paralelos 20º43 e 29º44 de latitude sul, e entre os meridianos 53º42 e 53º44 de longitude oeste de Greenwich. O delineamento estatístico utilizado foi bloco inteiramente casualizado, e como os tratamento se constituíram em diferentes tubetes e diferentes substratos adotou-se o sistema bifatorial, com 16 tratamentos e 4 repetições. Foram semeadas em média 96 plantas em cada parcela, excluindo-se duas linhas de bordadura, obteve-se 32 plantas úteis. As sementes foram obtidas junto ao Programa de Ação-Sócio Ambiental da Afubra, sub-projeto Bolsa de Sementes de Árvores Nativas , sendo semeadas três sementes em cada recipiente e posteriormente realizado o raleio. As avaliações iniciaram-se aos 90 dias após a semeadura, e concluídas aos 180 dias, através do diâmetro do colo, altura das mudas, peso seco de raízes, peso seco da parte aérea e o índice de qualidade de Dickson. Através da análise de variância e teste de comparação de médias, pelo teste de Tukey, não se encontraram diferenças significativas nos parâmetros analisados para as variáveis: diâmetro do colo; altura da mudas, peso seco de raízes, peso seco da parte aérea e o índice de qualidade de Dickson, entre os tubetes 180 cm³ e 280 cm³. As variáveis diâmetro do colo, peso seco de raízes e o índice de qualidade de Dickson o melhor substrato foi o definido como Plantmax Agrícola. As variáveis altura das mudas e peso seco da parte aérea o melhor substrato foi o definido como Humosolo Vida. Com base nestes resultados é possível recomendar o recipiente de 180 cm³, pelas vantagens econômicas em economia de material, mão-de-obra e transporte, quanto ao substrato a definição recomendado é pelo substrato Plantmax Agrícola pelos melhores resultados obtidos quanto aos padrões de qualidade das mudas.

Recently, the Whip-poor-will (Caprimulgus vociferous) has become focus of considerable conservation concerns as the result of evidence indicating significant population declines throughout its breeding range (Veit and Petersen 1993). The lack of quantitative data concerning much of this species natural history has delayed recovery efforts and is a fundamental shortcoming in forming effective conservation strategies. Current surveys show Pitch Pine (Pinus rigida) / Scrub Oak (Quercus illicifolia) Barrens (PPSO) as habitat with high numbers of Whip-poor-wills relative to other forest types found throughout the northeastern United States (Cavanaugh in Cink 2002), so we focused our study in these habitats in an attempt to 1) identify habitat selection within PPSO, and 2) determine characteristics of PPSO that make it relatively high quality habitat. Our Study was conducted during the 2005 and 2006 breeding seasons at the Massachusetts Military Reservation on Cape Cod, Massachusetts, USA. We used mist nets to capture adult Whip-poor-wills and affix radio-transmitters for locating individuals during night hours, using triangulation techniques. A kernel analysis of these locations was used to estimate the home range of each individual, where structural characteristics of vegetation was measured, for use in habitat selection analyses. Prey availability was estimated using captures from light traps (Leroy Koehn design, Georgetown, KY) with UV bulbs. Light traps were run on 12 different nights in each habitat during both years of the study. We assessed diet from fecal samples collected at day roost locations used by radio-marked individuals on a daily basis. Samples were dissected under a 22x stereoscope with prey fragments identified to the family when possible. Generalized Linear Mixed Models were used to model habitat selection from structural variables of the habitat collected at used and random locations within the home range, while a compositional analysis of habitat use was also done by comparing the amount of radio-locations in each habitat type to the total amount of that habitat found within the home range. A compositional analysis was also used to test for prey selection. Data from 15 Whip-poor-wills were used in our analyses. Univariate and multivariate statistics showed that there was no difference in vegetation structure between used and random sites. Ground cover was the best predictor of habitat use identified by the GLMM, but was still inefficient for determining habitat use. However, the compositional analysis of habitat use did show a preference of pitch pine – oak forests over pitch pine – scrub oak communities. The fecal analysis showed Whip-poor-wills preferred moths over scarab beetles, and “other” prey items which consisted mainly of beetles other than scarabs, along with neuropterans. Light trap captures showed prey was distributed equally among habitats at the MMR. Although our study did not show any strong relationships between vegetation structure and habitat selection, this may not be the case in habitats of lesser quality (i.e. not PPSO). The habitat preference rank from the compositional analysis directly correlated with the amount of ground cover found in each habitat, which is supporting evidence that ground cover may be an important factor in selecting habitat. Low amounts of ground cover may allow Whip-poor-wills to detect and capture prey more easily, as well as provide open area for an easy escape route from potential predators. Land management techniques such as prescribed burning that reduce understory are recommended treatments to increase habitat quality for Whip-poor-wills.