Yancey, E J; Dikeman, M E; Addis, P B; Katsanidis, E; Pullen, M
2002-04-01
Two groups of 18 grain-finished steers were utilized. Nine from one group were infused via the carotid artery immediately after jugular vein exsanguination with an aqueous solution containing saccharides, NaCl, and phosphates (MPSC; MPSC, Inc., Eden Prairie, MN, USA). Nine steers served as non-infused controls (CON). An additional 18 steers were infused with either MPSC (n=9) or MPSC plus 1000 ppm vitamin C (MPSC+C, n=9) solutions. Steers infused with MPSC had higher dressing percentages and organ weights than CON steers. Vascular infusion with MPSC had no effects on USDA yield or quality grade traits, descriptive-attribute sensory panel evaluations, or Warner-Bratzler shear force of longissimus lumborum and semitendinosus muscles. Vascular infusion with MPSC resulted in some significant, but inconsistent effects on flavor-profile characteristics of cooked beef. The addition of vitamin C to the MPSC solution did not provide any benefit. PMID:22063636
Measurements of texture properties related to tenderness at different locations within deboned broiler breast fillets have been used to validate techniques for texture analysis and establish correlations between different texture evaluation methods. However, it has been demonstrated that meat text...
Directory of Open Access Journals (Sweden)
Marcos Franke Pinto
2010-06-01
Full Text Available A padronização da textura é um dos principais problemas relacionados à qualidade da carne bovina. Por isso, a avaliação objetiva da maciez, por métodos mecânicos, vem sendo estudada há muitos anos. Para que a avaliação instrumental da textura seja uma ferramenta efetiva nos estudos envolvendo a maciez da carne, é necessário minimizar as causas de variação envolvidas na análise. Atualmente, a força de cisalhamento Warner-Bratzler é o método mais amplamente empregado para essa finalidade. O protocolo padrão dessa técnica analítica preconiza a utilização de uma lâmina de cisalhamento de 1,016mm de espessura. Neste trabalho, foram comparados dados de textura de carne bovina obtidos com a lâmina de cisalhamento padrão Warner-Bratzler, de 1,016mm de espessura, e uma lâmina mais grossa, de 3,05mm de espessura. Após o abate, amostras de músculo Longissimus dorsi, semelhantes em relação aos teores de umidade, lipídeos e proteínas, foram submetidas a duas diferentes temperaturas de resfriamento, atingindo diferentes velocidades de queda de temperatura e, consequentemente, diferentes graus de contração do tecido muscular, o que foi confirmado pela determinação do comprimento dos sarcômeros. Os resultados demonstraram uma maior sensibilidade da lâmina padrão Warner-Bratzler na detecção de variações da textura da carne, em função da velocidade de resfriamento.Standardization of texture is one of the main problems related to beef quality. Because of that, objective evaluation of tenderness performed by mechanic methodologies has been studied for years. In order to count on instrumental texture evaluation as a valuable tool in meat tenderness studies, it is necessary to minimize the causes of variation that might be involved in the trial. Nowadays, Warner-Bratzler shear force is widely used for meat tenderness determination. The standard protocol of this methodology establishes the utilization of shear blade 1.016mm tick. The aim of this study was to compare beef texture data provided by Warner-Bratzler standard shear blade, 1.016mm thick, with those provided by a thicker one, 3.05mm thick. After slaughtering, Longissimus dorsi muscle samples with similar contents of moisture, lipids and proteins were subjected to two different cooling temperatures,reaching different rates of temperature drop and hence different muscle contraction extents, which were confirmed by the determination of sarcomere length. Results indicated the superior sensibility of the Warner-Bratzler standard shear blade to detect variations in meat texture due to cooling velocity.
Lean, Ian J.; Thompson, John M.; Dunshea, Frank R
2014-01-01
This study is a meta-analysis of the effects of the beta-agonists zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RAC) on feedlot performance, carcase characteristics of cattle and Warner Bratzler shear force (WBSF) of muscles. It was conducted to evaluate the effect of the use of these agents on beef production and meat quality and to provide data that would be useful in considerations on the effect of these agents on meat quality in Meat Standards Australia evaluations. We cond...
Scientific Electronic Library Online (English)
C., Gomes; L.B., Karam; R.E.F., Macedo.
2013-04-01
Full Text Available Avaliaram-se as características sensoriais e determinou-se a força de cisalhamento de cortes de carne de paca (Agouti paca). As análises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por cocção até a temperatura interna de 70ºC. A avaliação de aspecto, co [...] r, sabor, odor e maciez foi realizada pela aplicação de teste afetivo a 146 provadores, utilizando-se escala hedônica, e a força de cisalhamento foi determinada pela técnica Warner Bratzler. Na avaliação sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferença significativa (p0,05) entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante à carne suína e com boa aceitação pelos consumidores. O estudo evidenciou o potencial da paca como uma espécie silvestre para a produção comercial de carne para o mercado de carnes vermelhas ou exóticas. Abstract in english Sensory characteristics and shear force of paca meat (Agouti paca) were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70°C. The evaluation of flavor, aroma, color, appea [...] rance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05) among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca) asa wild species for meat production in the red or exotic meat market.
Directory of Open Access Journals (Sweden)
C. Gomes
2013-04-01
Full Text Available Avaliaram-se as características sensoriais e determinou-se a força de cisalhamento de cortes de carne de paca (Agouti paca. As análises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por cocção até a temperatura interna de 70ºC. A avaliação de aspecto, cor, sabor, odor e maciez foi realizada pela aplicação de teste afetivo a 146 provadores, utilizando-se escala hedônica, e a força de cisalhamento foi determinada pela técnica Warner Bratzler. Na avaliação sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferença significativa (p0,05 entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante à carne suína e com boa aceitação pelos consumidores. O estudo evidenciou o potencial da paca como uma espécie silvestre para a produção comercial de carne para o mercado de carnes vermelhas ou exóticas.Sensory characteristics and shear force of paca meat (Agouti paca were assessed in this study. Analyses were performed in the bonelessshoulder,loin andhamobtained from nine paca carcassesprepared by cookinguntil reaching the internal temperatureof 70°C. The evaluation of flavor, aroma, color, appearance and tenderness was carried out by the application of an affective test using the hedonic scaleand a 146 consumer panel. Shear force was determined by the Warner-Bratzler technique. Shoulder, loin and ham had significant differences (p 0.05 among the cuts, which were similarly tender. Paca meat was found to resemble pork meat in sensory evaluation and had good acceptance by consumers. This study showed the potential of paca (Agouti paca asa wild species for meat production in the red or exotic meat market.
2004-01-01
It is with great sadness that we learned that our friend and former colleague, David Warner, passed away on Christmas Eve. The funeral was held the following Monday. David was a "linac man". His career centred around linacs, but with a multitude of different subjects. He began at CERN by building the 3 MeV linac in the extension of the South Hall. He did pioneering work on this machine, which paved the way towards the design of the Alvarez cavities for the CERN Linac 2, for which he was responsible. After this challenge was successfully finished, David was the first member of the small but growing team, that was in charge of building the LEP Injector Linacs (LIL). After having been recognised as a proton linac expert, he quickly converted to electron linacs where he soon became the respected key expert for the design, parameters and ultimate performance of LIL. His predilection for precise and detailed documentation, and his vision that the know-how acquired with LIL should be preserved a...
DEFF Research Database (Denmark)
Christensen, L.; Andersen, L.
2011-01-01
Long term heat treatment at low temperature (LTLT) is known to decrease toughness of meat. However, the contribution from the connective tissue to the toughness of LTLT treated meat is not clear. The aim of the present study was to investigate the effect of LTLT treatments on shear force and cooking loss in semitendinosus from cows (4-6 years) and young bulls (12-14 months), representing 2 categories of beef with varying thermal strength of connective tissue. Vacuum packed muscle samples were heat treated at 53°C, 55°C, 58°C and 63°C in water baths for 2½, 7½ and 19½ h. Cooking loss and Warner-Bratzler shear force were measured after heat treatment and subsequent cooling. Shear force of semitendinosus from young bulls heated at 53°C for 2½ h was significantly higher compared with all other heat treatments. A decrease of app. 40 N was observed when increasing the heating temperature from 53°C to 55°C, or when increasing heating time from 2½ to 7½ h at 53°C. In semitendinosus from cows shear force decreased significantly with increasing temperature, and with increasing heating time from 2½ to 19½ h at 55°C and 63°C. Cooking loss increased with increasing heating temperature in both beef categories. The results show that prolonged heating at low temperatures reduce toughness in beef semitendinosus, and that a reduction in toughness require higher temperatures and longer heating times in semitendinosus from cows compared with young bulls.
Garmyn, A J; Brooks, J C; Hodgen, J M; Nichols, W T; Hutcheson, J P; Rathmann, R J; Miller, M F
2014-08-01
Beef steers (n = 1,914) were assigned to 1 of 3 ?-adrenergic agonist (?AA) supplementation treatments-zilpaterol hydrochloride (ZH; 8.3 mg/kg of DM for 20 d with 3-d withdrawal), ractopamine hydrochloride (RH; 308 mg·head(-1)·d(-1) for 28 d), or no ?AA (CON)-to determine the effects on consumer eating quality. Strip loins (n = 1,101; CON = 400, RH = 355, and ZH = 346) were obtained and fabricated into 2.5-cm-thick steaks for proximate, Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer analyses; steaks were aged until 14 or 21 d postmortem. Fat and moisture contents were not affected by ?AA supplementation (P > 0.05), but strip steaks from steers fed ZH had more protein (P 0.05). In steaks aged 21 d, feeding ?AA influenced (P 0.05) acceptability. Quality grade impacted (P < 0.01) all traits and acceptability in steaks aged 14 and 21 d. In 14-d steaks, Premium Choice typically was scored higher than Low Choice or Select; however, consumers rated 21-d Low Choice and Premium Choice similarly-both receiving greater scores than Select. Consumers detected several differences in eating quality at 14 d because of ?AA supplementation. Increasing aging from 14 to 21 d mitigated differences in shear force and tenderness scores because of feeding ZH, so that tenderness and overall acceptability were similar between ZH, RH, and CON. PMID:24879757
Arp, T S; Howard, S T; Woerner, D R; Scanga, J A; McKenna, D R; Kolath, W H; Chapman, P L; Tatum, J D; Belk, K E
2013-12-01
Effect of ractopamine hydrochloride (RH) and zilpaterol hydrochloride (ZH) on LM shear force and sensory attributes was determined using pens (n = 40) British × Continental crossbred steers randomly allocated to one of the following treatments: control; RH fed at 200 (RH 200) or 300 mg • steer(-1) • d(-1) (RH 300), or 400 mg • steer(-1) • d(-1) (RH 400) top-dressed for the final 30 d of feeding; or ZH fed at 7.5 mg/kg, beginning 23 d before slaughter with a 3-d withdrawal. Two replicates (pens) per treatment were represented in four blocks. Eighteen carcasses per pen were randomly selected and one 5-cm LM sample was removed from both carcass sides to be used for shear force and sensory evaluation. Samples were aged for 14 d, frozen at -28.8 °C, and cut into 2.5-cm steaks. All steaks were cooked to an internal temperature of 71.1 °C before being evaluated for Warner-Bratzler shear force (WBSF), slice shear force (SSF), or being fed to trained sensory panelists. Increasing dose and potency of ?-agonist increased WBSF by 4 to 17% and SSF by 5 to 24% (P 0.05). Probability of steaks failing to meet shear force standards to be certified tender (WBSF 0.05). Steaks from steers fed RH 300 and RH 400 were comparable for all sensory attributes; however, both RH 300 and RH 400 were rated lower for overall tenderness than controls (P 0.05). Results from this study indicated ?-agonists negatively affected beef tenderness and these effects may be more noticeable in steers supplemented with ZH and higher doses of RH. PMID:24166996
Corbin, C H; O'Quinn, T G; Garmyn, A J; Legako, J F; Hunt, M R; Dinh, T T N; Rathmann, R J; Brooks, J C; Miller, M F
2015-02-01
The palatability of tender [Warner-Bratzler shear force values umami (r=0.59) flavors. Fat level was the primary driver of beef flavor acceptability in all samples when no undesirable off-flavors were present. PMID:25299587
Lean, Ian J; Thompson, John M; Dunshea, Frank R
2014-01-01
This study is a meta-analysis of the effects of the beta-agonists zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RAC) on feedlot performance, carcase characteristics of cattle and Warner Bratzler shear force (WBSF) of muscles. It was conducted to evaluate the effect of the use of these agents on beef production and meat quality and to provide data that would be useful in considerations on the effect of these agents on meat quality in Meat Standards Australia evaluations. We conducted a comprehensive literature search and study assessment using PubMed, Google Scholar, ScienceDirect, Scirus, and CAB and identification of other studies from reference lists in papers and searches. Searches were based on the key words: zilpaterol, zilmax, ractopamine, optaflexx, cattle and beef. Studies from theses obtained were included. Data were extracted from more than 50 comparisons for both agents and analysed using meta-analysis and meta-regression. Both agents markedly increased weight gain, hot carcase weight and longissimus muscle area and increased the efficiency of gain:feed. These effects were particularly large for ZH, however, fat thickness was decreased by ZH, but not RAC. Zilpaterol also markedly increased WBSF by 1.2 standard deviations and more than 0.8 kg, while RAC increased WBSF by 0.43 standard deviations and 0.2 kg. There is evidence in the ZH studies, in particular, of profound re-partitioning of nutrients from fat to protein depots. This work has provided critically needed information on the effects of ZH and RAC on production, efficiency and meat quality. PMID:25548908
Morfología de Neochetina eichhorniae (Warner (Coleoptera: Curculionidae
Directory of Open Access Journals (Sweden)
Oscar Martínez-Morales
2014-01-01
Full Text Available En este trabajo se describen e ilustran características morfológicas de Neochetina eichhorniae (Warner, 1970. Esta especie se ha utilizado para el control biológico del lirio acuático (Eichhornia crassipes (Mart. Solms-Laubach, 1883. En el huevo, el aspecto cambiante del corion es dado por el desarrollo embrionario. En la larva se realizó una descripción de la quetotaxia de la cápsula cefálica y se identificaron tres ínstares larvales con la medición de su anchura; también se revisó la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en tórax y abdomen, también se observaron dos tipos de espiráculos; el más característico es el espiráculo abdominal por su posición dorsal, que además de ser esclerosado, posee órganos sensoriales en su ápice. La morfología externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Además se proporciona una descripción de las alas, proventrículo y genitalia, estructuras importantes en la taxonomía. Las características morfológicas de N. eichhorniae encontradas en éste trabajo pueden ser útiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926, la cual ha sido liberada en muchos países. Es el primer trabajo de morfología N. eichhorniae en México.
Scientific Electronic Library Online (English)
Oscar, Martínez-Morales; Edith G., Estrada-Venegas; Armando, Equihua-Martínez; Jorge, Valdez-Carrasco.
Full Text Available En este trabajo se describen e ilustran características morfológicas de Neochetina eichhorniae (Warner, 1970). Esta especie se ha utilizado para el control biológico del lirio acuático (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). En el huevo, el aspecto cambiante del corion es dado por el des [...] arrollo embrionario. En la larva se realizó una descripción de la quetotaxia de la cápsula cefálica y se identificaron tres ínstares larvales con la medición de su anchura; también se revisó la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en tórax y abdomen, también se observaron dos tipos de espiráculos; el más característico es el espiráculo abdominal por su posición dorsal, que además de ser esclerosado, posee órganos sensoriales en su ápice. La morfología externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Además se proporciona una descripción de las alas, proventrículo y genitalia, estructuras importantes en la taxonomía. Las características morfológicas de N. eichhorniae encontradas en éste trabajo pueden ser útiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926), la cual ha sido liberada en muchos países. Es el primer trabajo de morfología N. eichhorniae en México. Abstract in english In this study morphological characteristics of Neochetina eichhorniae (Warner, 1970) are described and illustrated. This species has been used for the Biological Control of waterhyacinth (Eichhornia crassipes (Mart.) Solms-Laubach, 1883). In the egg, the changing appearance of the chorion is given b [...] y the embryonic development. Description of larval head capsule chaetotaxy was done. Three larval instars were identified by measuring the head capsule width; microsculpture of the body larva was studied, microspines were evident with different arrangements in thorax and abdomen, two types of spiracles were found; the more distinctive was the dorsal spiracle in the abdomen, which is sclerotized, with sensory organs at its apex. The external morphology of N. eichorniae adult is very similar in both sexes, the main difference among them is the rostrum. Description of the wings, proventriculus and genitalia, important structures in the taxonomy, is provided. The morphological characteristics of N. eichhorniae found in this study can be use to separate from N. bruchi (Hustache) which has been released in many countries. This is the first morphological study of N. eichhorniae in Mexico.
ESTIMATED GENETIC PARAMETERS FOR PALATABILITY TRAITS OF STEAKS FROM BRAHMAN CATTLE
Heritabilities and genetic and phenotypic correlations were estimated from carcass and beef palatability data collected from Brahman calves (n = 504) born in central Florida from 1996 to 2000. Traits evaluated included Warner-Bratzler shear force (after 7, 14, and 21 d of aging), panel tenderness sc...
Ecological investigation of a hazardous waste site, Warner Robins, Georgia
Energy Technology Data Exchange (ETDEWEB)
Wade, M. [Oak Ridge National Lab., TN (United States); Billig, P. [Camp Dresser and McKee, Inc., Denver, CO (United States)
1993-05-01
Landfill No. 4 and the sludge lagoon at Robins Air Force Base, Warner Robins, Georgia, were added to the United States Environmental Protection Agency (EPA) National Priorities List in 1987 because of highpotential for contaminant migration. Warner Robins is located approximately 90 miles southeast of Atlanta. In 1990 CH2M HILL conducted a Remedial Investigation at the base that recommended that further ecological assessment investigations be conducted (CH2M HILL 1990). The subject paper is the result of this recommendation. The ecological study was carried out by the Hazardous Waste Remedial Actions Program (HAZWRAP)Division of Martin Marietta Energy Systems, Inc., working jointly with its subcontractor CDM (CDM 1992a). The primary area of investigation (Zone 1) included the sludge lagoon, Landfill No. 4, the wetland area east of the landfill and west of Hannah Road (including two sewage treatment ponds), and the area between Hannah Road and Horse Creek (Fig. 1). The bottomland forest wetlands of Zone 1 extend from the landfill east to Horse Creek. Surface water and groundwater flow across Zone 1 is generally in an easterly direction toward Horse Creek. Horse Creek is a south-flowing tributary of the Ocmulgee River Floodplain. The objective of the study was to perform a quantitative analysis of ecological risk associated with the ecosystems present in Zone 1. This investigation was unique because the assessment was to be based upon many measurement endpoints resulting in both location-specific data and data that would assess the condition of the overall ecosystem. The study was segregated into five distinct field investigations: hydrology, surface water and sediment, aquatic biology, wetlands ecology, and wildlife biology.
Geothermal hydrology of Warner Valley, Oregon: a reconnaissance study
Energy Technology Data Exchange (ETDEWEB)
Sammel, E.A.; Craig, R.W.
1981-01-01
Warner Valley and its southern extension, Coleman Valley, are two of several high-desert valleys in the Basin and Range province of south-central Oregon that contain thermal waters. At least 20 thermal springs, defined as having temperatures of 20/sup 0/C or more, issue from Tertiary basaltic flows and tuffs in and near the valleys. Many shallow wells also produce thermal waters. The highest measured temperature is 127/sup 0/C, reported from a well known as Crump geyser, at a depth of 200 meters. The hottest spring, located near Crump geyser, has a surface temperature of 78/sup 0/C. The occurrence of these thermal waters is closely related to faults and fault intersections in the graben and horst structure of the valleys. Chemical analyses show that the thermal waters are of two types: sodium chloride and sodium bicarbonate waters. Chemical indicators show that the geothermal system is a hot-water rather than a vapor-dominated system. Conductive heat flow in areas of the valley unaffected by hydrothermal convection is probably about 75 milliwatts per square meter. The normal thermal gradient in valley-fill dpeosits in these areas may be about 40/sup 0/C per kilometer. Geothermometers and mixing models indicate that temperatures of equilibration are at least 170/sup 0/C for the thermal components of the hotter waters. The size and location of geothermal reservoirs are unknown.
AOL Time Warner Playing a Part in Bridging the Technology Gap.
Roach, Ronald
2001-01-01
Presents an interview with B. Keith Fulton, recognized authority on the digital divide, vice president of the AOL Time Warner Foundation, and senior director for social innovations for the company's corporate relations division. He discusses efforts to develop and manage domestic and international programs that promote digital opportunity. (EV)
DEFF Research Database (Denmark)
Christensen, M.; Torngren, M. A.; Gunvig, A.; Rozlosnik, Noemi; Lametsch, R.; Karlsson, A. H.; Ertbjerg, P.
2009-01-01
BACKGROUND: Marination of beef muscles with brine solutions containing proteolytic enzymes from fruit extracts has been shown to tenderize meat. However, the effect of marination with actinidin on tenderness of pork muscles has not been investigated. Tenderness and eating quality of porcine M. biceps femoris was investigated by Warner-Bratzler (WB) shear test and sensory evaluation after injection of brine containing up to 11 g L-1 actinidin-containing kiwi fruit powder and 2, 5 or 9 days of sto...
Functional Genomic Analysis of Variation on Beef Tenderness Induced by Acute Stress in Angus Cattle
George Liu; Linsen Zan; Juan Luo; Fei Zhan; Yali Hou; Apratim Mitra; Ying Yu; Jiuzhou Song; M. Scott Updike; Fei Tian; Chunping Zhao
2012-01-01
Beef is one of the leading sources of protein, B vitamins, iron, and zinc in human food. Beef palatability is based on three general criteria: tenderness, juiciness, and flavor, of which tenderness is thought to be the most important factor. In this study, we found that beef tenderness, measured by the Warner-Bratzler shear force (WBSF), was dramatically increased by acute stress. Microarray analysis and qPCR identified a variety of genes that were differentially expressed. Pathway analysis s...
Non-abelian T-duality of Pilch-Warner background
Dimov, H; Rashkov, R C; Vetsov, T
2015-01-01
In this work we obtain the non-abelian T-dual geometry of the well-known Pilch-Warner supergravity solution. We derive the dual metric and the NS two-form by gauging the isometry group of the initial theory and integrating out the introduced auxiliary gauge fields. Then we use the Fourier-Mukai transform from algebraic geometry to find the transformation rules of the R-R fields. Finally, we argue that the dual theory inherit the supersymmetry of the original one by considering the general dependence of the Killing spinor on the spacetime coordinates.
Mergers and acquisitions : the case of Comcast and Time Warner Cable
Chissamba, Victor Chia
2014-01-01
Comcast and Time Warner Cable (TWC) merger has been a daily headline in the US business press since the merger announcement in last February 13th of 2014. Meanwhile many questions are raised about the transaction, either in terms of legal issues or in terms related to the strategy fit and financial accretive. These questions are motivated due to the size of both companies in industry where they operate, that leads to witness the largest merger in such industry and the emergence of a potential...
Walter Miles, Pop Warner, B. C. Graves, and the psychology of football.
Baugh, Frank G; Benjamin, Ludy T
2006-01-01
In 1926-1927, a graduate student, B. C. Graves, working with Stanford University psychologist Walter Miles and legendary football coach Pop Warner, conducted an investigation of variations in signal calling as they affected the charging times of football players. The study was one of two that involved Miles and the ingenious multiple chronograph that he had invented to time the reactions of seven players simultaneously. These studies represented a brief digression in the career of Miles, who certainly was no sport psychologist. They tell of an interesting collaboration between scientist and coaches that produced one of the richest studies in sport psychology in the first half of the twentieth century. PMID:16345007
Shelf-life and Microbiological Profiler of Chicken Wing Products Following Sous vide Treatment
Wang, S H; M. H. Chang; Chen, T.C.
2004-01-01
Chicken wings were vacuum-packaged and cooked (sous vide) at 75 and 90°C until the internal temperature reached 73.8°C was reached. The cooked samples were stored at 2 and 7°C, separately. The TBA values, aerobic plate count, aerobic and anaerobic plate counts and Warner-Bratzler (WB) shear force of the samples were evaluated weekly for 7 wk. The sous vide treatment chicken wings had lower TBA values, aerobic and anaerobic plate counts throughout the 7 wk of storage when compared with the con...
Use of near infrared spectroscopy for assessment of beef quality traits
Directory of Open Access Journals (Sweden)
L. Gallo
2010-04-01
Full Text Available Chemical and physical traits and fatty acid composition of meat samples from 148 Piemontese beef samples were predicted by near infrared spectroscopy. Coefficients of determination in calibration (R2 ranged between 0.44 and 0.99 for chemical composition and between 0.02 and 0.98 for fatty acid (FA profile, being in general more accurate for the major FA. The calibration results gave inaccurate prediction for cholesterol and collagen content and for most physical traits, such as Warner-Bratzler shear force, cooking loss, drip loss, colour (L, a, b and pH.
Bronstein, Carolyn
2008-04-01
In the mid-1970s, Women Against Violence Against Women (WAVAW), the first national feminist organization to protest mediated sexual violence against women, pressured the music industry to cease using images of violence against women in its advertising. This article presents a case study of WAVAW's national boycott of Warner Communications, Inc. and documents the activists' successful consumer campaign. The study reveals that media violence was central to feminist organizing efforts, and that WAVAW and related organizations helped establish a climate of concern about violence that motivated scientific research on the relationship between exposure to media violence and subsequent aggression. PMID:18359878
Directory of Open Access Journals (Sweden)
M. Ern
2006-06-01
Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. Still, even global features of the measurements remain unmatched, and it is inevitable to provide a globally varying source distribution in future.
Directory of Open Access Journals (Sweden)
M. Ern
2006-01-01
Full Text Available In order to incorporate the effect of gravity waves (GWs on the atmospheric circulation most global circulation models (GCMs employ gravity wave parameterization schemes. To date, GW parameterization schemes in GCMs are used without experimental validation of the set of global parameters assumed for the GW launch spectrum. This paper focuses on the Warner and McIntyre GW parameterization scheme. Ranges of parameters compatible with absolute values of gravity wave momentum flux (GW-MF derived from CRISTA-1 and CRISTA-2 satellite measurements are deduced for several of the parameters and the limitations of both model and measurements are discussed. The findings presented in this paper show that the initial guess of spectral parameters provided by by Warner and McIntyre (2001 are some kind of compromise with respect to agreement of absolute values and agreement of the horizontal structures found in both measurements and model results. Better agreement can be achieved by using a vertical wavenumber launch spectrum with a wider saturated spectral range and reduced spectral power in the unsaturated part. However, even with this optimized set of global launch parameters not all features of the measurements are matched. This indicates that for further improvement spatial and seasonal variations of the launch parameters should be included in GW parameterization schemes.
Epstein, M; Wingate, D L
2007-01-01
The recently published Report of the AHAG on the Operation of NHS Research Ethics Committees (the Warner Report) advocates major reforms of the NHS research ethics committees system. The main implications of the proposed changes and their probable effects on the major stakeholders are described. PMID:17209111
Directory of Open Access Journals (Sweden)
Ebrahim Alfaig
2014-05-01
Full Text Available A study was conducted to determine the effect of probiotics and thyme essential oil (TEO as feed additives on the sensory attributes, cooking loss and the texture of broiler chicken meat. Day-old broilers Ross 308 (n = 400 were randomly divided into four groups based on the feed supplement as follows: control, probiotics 0.05%, TEO 0.05% and combination of probiotics and TEO, while the fattening period was 42 days. Warner Bratzler shear force, cooking loss and the following sensory attributes (colour, odour, taste, texture, meat decomposing and overall acceptability were tested. The obtained results of the Warner Bratzler shear force show that there was significant different (P < 0.05 between control and TEO group and for the cooking loss there was no significant difference between groups. The descriptive sensory analysis results show that the probiotics group results were somewhat similar to that obtained by control while the TEO group and the combination group results were similar. Regarding the sensory analysis we can state that the combination of the probiotics and TEO have a positive effect on the chicken meat sensory characteristics.
Energy Technology Data Exchange (ETDEWEB)
Dodelson, Scott; /Fermilab /Chicago U., Astron. Astrophys. Ctr. /Northwestern U.; Shapiro, Charles; /Chicago U. /KICP, Chicago; White, Martin J.; /UC, Berkeley, Astron.
2005-08-01
Measurements of ellipticities of background galaxies are sensitive to the reduced shear, the cosmic shear divided by (1-{kappa}) where {kappa} is the projected density field. They compute the difference between shear and reduced shear both analytically and with simulations. The difference becomes more important an smaller scales, and will impact cosmological parameter estimation from upcoming experiments. A simple recipe is presented to carry out the required correction.
Scientific Electronic Library Online (English)
Lindon W, Mamani-Linares; Carmen, Gallo.
2011-12-01
Full Text Available Se comparó la composición química y calidad instrumental de carne de bovino, llama, y caballo finalizados bajo pastoreo. Los bovinos (n=31), llamas (n=21) y caballos (n=27) fueron faenados bajo procedimientos estándares de Chile. Las canales fueron refrigeradas durante 24 horas a 4 ºC. En el músculo [...] Longissimus lumborum (LL) se determinó la composición proximal, contenido de colesterol y colágeno, pH, color (L*, a*, b*, H*, C*), capacidad de retención de agua (WHC), pérdida de cocción, pérdida del descongelado y fuerza de corte Warner-Bratzler (WBSF). La carne de llama presentó mayores niveles de proteína y colágenos totales (p Abstract in english This study compared the chemical composition and instrumental meat quality of bovine, llama and horse from animals finished under grazing systems. The bovines (n=31), llamas (n=21) and horses (n=27) were slaughtered using Chilean standard procedures. Carcasses were stored for 24 h in a cold room (4 [...] ºC). The Longissimus lumborum muscle (LL) was collected for determining the chemical composition, cholesterol, collagen content, pH, colour (L*, a*, b*, H*, C*), water holding capacity (WHC) and Warner-Bratzler shear-force (WBSF). Llama meat had higher levels of protein and total collagen (p
Energy Technology Data Exchange (ETDEWEB)
Ohira, Yutaka, E-mail: ohira@phys.aoyama.ac.jp [Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara 252-5258 (Japan)
2013-04-10
We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.
Plasticity Approach to Shear Design
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1998-01-01
The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothes...
Scientific Electronic Library Online (English)
María C., Miquel; Edgardo, Villarreal; Carlos, Mezzadra; Lilia, Melucci; Liliana, Soria; Pablo, Corva; Alejandro, Schor.
Full Text Available The objective of this paper was to determine the association of a SNP in the µ-calpain gene at position 316 with growth and quality of meat traits of steers grown on pasture. Fifty-nine Brangus and 20 Angus steers were genotyped for CAPN1 316. Warner Bratzler shear force was measured in l. lumborum [...] samples after a 7-day aging period. A multivariate analysis of variance was performed, including shear force (WBSF), final weight (FW), average daily gain (ADG), backfat thickness (BFT), average monthly fat thickness gain (AMFTG), rib-eye area (REA), and beef rib-eye depth (RED) as dependent variables. The CAPN1 316 genotype was statistically significant. Univariate analyses were done with these variables. The marker genotype was statistically significant (p
Piórkowska, K; Nowak, J; Po?towicz, K
2015-08-01
The aim of this study was to assess mRNA abundance of calpain 1 (CAPN1) and calpain 3 (CAPN3) in breast muscle of 80 fast-growing (FG) and slow-growing broilers (SG) and relate gene expression in relation to growth and Warner Bratzler (WB) shear force of breast muscle. The expression of CAPN1 and CAPN3 genes was higher in the FG compared to the SG line, but significant results were obtained only for CAPN1. The CAPN1 mRNA level was strongly dependent on line and gender interaction. Lower values of shear force were observed in the FG line, where a higher level of calpain expression was shown. A new panel of housekeeping genes (RPL4 and SDHA) for normalisation of gene expression in muscle tissues could be used in other studies of gene expression in chicken. PMID:26042540
Tenderness assessments of top loin steaks from retail markets in four U.S. cities.
Igo, M W; Arnold, A N; Miller, R K; Gehring, K B; Mehall, L N; Lorenzen, C L; Delmore, R J; Woerner, D R; Wasser, B E; Savell, J W
2015-10-01
The purpose of this study was to evaluate the tenderness of beef loin steaks from retail markets in 4 U.S. cities. Beef top loin steaks ( = 1,613) were obtained for Warner-Bratzler shear force (WBSF), slice shear force (SSF), and consumer sensory determinations. Personnel at 4 universities (California Polytechnic State University, Colorado State University, University of Missouri, and Texas A&M University) conducted the study over a 12-mo period. Enhanced/blade-tenderized top loin steaks had the lowest ( 0.05) steaks that were enhanced/blade tenderized. The WBSF values and consumer sensory values for top loin steaks were comparable to the 2010 National Beef Tenderness Survey, signifying that no drastic changes in tenderness have occurred due to changes in antemortem or postmortem conditions. PMID:26523552
Annular electroconvection with shear
Daya, Z A; Morris, S W; De Bruyn, J R; Daya, Zahir A.; Morris, Stephen W.; Bruyn, John R. de
1998-01-01
We report experiments on convection driven by a radial electrical force in suspended annular smectic A liquid crystal films. In the absence of an externally imposed azimuthal shear, a stationary one-dimensional (1D) pattern consisting of symmetric vortex pairs is formed via a supercritical transition at the onset of convection. Shearing reduces the symmetries of the base state and produces a traveling 1D pattern whose basic periodic unit is a pair of asymmetric vortices. For a sufficiently large shear, the primary bifurcation changes from supercritical to subcritical. We describe measurements of the resulting hysteresis as a function of the shear at radius ratio $\\eta \\sim 0.8$. This simple pattern forming system has an unusual combination of symmetries and control parameters and should be amenable to quantitative theoretical analysis.
Rusconi, Roberto; Guasto, Jeffrey S.; Stocker, Roman
2012-11-01
Bacteria are ubiquitously exposed to flow, both in natural environments and artificial devices (e.g., catheters), where confining surfaces create non-uniform shear. While the effects of shear on passive particles are well understood, little is known about the consequences of shear on motile bacteria. We exposed bacteria having different motility strategies (e.g., run-and-tumble, run-and-reverse) to microfluidic Poiseuille flows and quantified the swimming kinematics and cell distribution in the channel using video-microscopy. We discovered that the coupling of motility and a spatially varying shear results in a dramatic trapping of motile cells in high-shear regions, and conversely a strong depletion in the low-shear portion of the channel. We demonstrate experimentally that this trapping process is robust across species such as Bacillus subtilis and Pseudomonas aeruginosa, and can have far-reaching consequences on bacterial transport, by (i) counteracting bacterial chemotactic responses; and (ii) enhancing surface attachment and thus biofilm formation by trapping cells near walls. More generally, this work shows that-despite the low Reynolds number-the coupling of flow and self-propulsion can be nonlinear and not simply a superposition of the two effects.
Shear thickening of cornstarch suspensions
Fall, Abdoulaye; Bertrand, François; Ovarlez, Guillaume; Bonn, Daniel
We study the rheology of cornstarch suspensions, a non-Brownian particle system that exhibits discontinuous shear thickening. Using magnetic resonance imaging (MRI), the local properties of the flow are obtained by the determination of local velocity profiles and concentrations in a Couette cell. For low rotational rates, we observe shear localization characteristic of yield stress fluids. When the overall shear rate is increased, the width of the sheared region increases. The discontinuous shear thickening is found to set in at the end of this shear localization regime when all of the fluid is sheared: the existence of a nonflowing region, thus, seems to prevent or delay shear thickening. Macroscopic observations using different measurement geometries show that the smaller the gap of the shear cell, the lower the shear rate at which shear thickening sets in. We, thus, propose that the discontinuous shear thickening of cornstarch suspensions is a consequence of dilatancy: the system under flow attempts to dilate but instead undergoes a jamming transition, because it is confined. This proposition is confirmed by an independent measurement of the dilation of the suspension as a function of the shear rate. It is also explains the MRI observations: when flow is localized, the nonflowing region plays the role of a "dilatancy reservoir" which allows the material to be sheared without jamming.
Shear thinning and shear thickening characteristics in electrorheological fluids
Jiang, Jile; Liu, YingDan; Shan, Lei; Zhang, Xiangjun; Meng, Yonggang; Choi, Hyoung Jin; Tian, Yu
2014-01-01
The electrorheology (ER) of suspensions based on polystyrene/polyaniline (PS/PANI) core/shell structured microspheres and those based on disk-like zeolite particles at different electric fields and particle volume fractions have been studied, respectively. Both types of ER fluids showed abrupt shear thickening under high electric fields and low shear rates, as well as shear thinning when the shear rate increased. A normalized method that considers the effects of electric field strength, shear rate and particle volume fraction was proposed to compare the rheological curves of the two ER fluids. The curves evaluated from the normalization method showed similar shear thinning at low shear rates and the hydrodynamic effect at high shear rates. Shear thinning represents the structure destroyed by shearing, and shear thickening at low shear regions indicates the dramatic structure change. The particle volume fraction and structure factor effects demonstrate that the mechanical contact between particles and the wall of the electrodes is crucial to the shear strength of ER fluids, indicating an electric/magnetic field modulated friction mechanism of the ER and magnetorheological (MR) effects.
Hillary Clinton / Judith Warner
Warner, Judith
1994-01-01
Kõige mõjuvõimsam naine maailmas - algus EA 22. veebruar 1994. May/4,11,18,25 lk. 22;22;22;21; Jun/1,8,15,22,29 lk. 21; Jul/6,13,20,27 21; Aug/3,10,17,24,31 lk. 21; Sep/7,14,21,28 lk. 21; Oct/5,12,19 lk. 21
Indian Academy of Sciences (India)
Akira Onuki; Akira Furukawa; Akihiko Minami
2005-05-01
We present a time-dependent Ginzburg–Landau model of nonlinear elasticity in solid materials. We assume that the elastic energy density is a periodic function of the shear and tetragonal strains owing to the underlying lattice structure. With this new ingredient, solving the equations yields formation of dislocation dipoles or slips. In plastic flow high-density dislocations emerge at large strains to accumulate and grow into shear bands where the strains are localized. In addition to the elastic displacement, we also introduce the local free volume . For very small the defect structures are metastable and long-lived where the dislocations are pinned by the Peierls potential barrier. However, if the shear modulus decreases with increasing , accumulation of around dislocation cores eventually breaks the Peierls potential leading to slow relaxations in the stress and the free energy (aging). As another application of our scheme, we also study dislocation formation in two-phase alloys (coherency loss) under shear strains, where dislocations glide preferentially in the softer regions and are trapped at the interfaces.
Meacham, Stephen P.; Flierl, Glenn R.; Send, Uwe
1989-01-01
The nature and stability of Kida's exact, time-dependent solutions for uniform, elliptical vortices in an ambient strain field are investigated. In addition to the classical Love mode of instability, we discover a class of resonant instabilities. Our linearized analysis is supplemented by numerical simulations of vortices in shear which follow the non-linear development of some of these instabilities.
DEFF Research Database (Denmark)
Hansen, Klaus
1976-01-01
This report gives a summary of the present information on the behaviour of vertical keyed shear joints in large panel structures. An attemp is made to outline the implications which this information might have on the analysis and design of a complete wall. The publications also gives a short presentation of test series carried out in Denmark and outside.
Shearing behavior of polydisperse media
Wackenhut, M; Herrmann, H; Wackenhut, Martin; Namara, Sean Mc; Herrmann, Hans
2004-01-01
We study the shearing of polydisperse and bidisperse media with a size ratio of 10. Simulations are performed with a the two dimensional shear cell using contact dynamics. With a truncated power law for the polydisperse media we find that they show a stronger dilatancy and greater resistance to shearing than bidisperse mixtures. Motivated by the practical problem of reducing the energy needed to shear granular media, we introduce "point-like particles" representing charged particles in the distribution. Even though changing the kinematic behavior very little, they reduce the force necessary to maintain a fixed shearing velocity.
Energy Technology Data Exchange (ETDEWEB)
Butler, B.D.; Hanley, H.J.M.; Straty, G.C. [National Institute of Standards and Technology, Boulder, CO (United States); Muzny, C.D. [Univ. of Colorado, Boulder, CO (United States)
1995-12-31
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions {theta} is discussed. Provided that {theta}{approx_lt}0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t {yields} {infinity}) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with {theta}>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included.
International Nuclear Information System (INIS)
An experimental small angle neutron scattering (SANS) study of dense silica gels, prepared from suspensions of 24 nm colloidal silica particles at several volume fractions ? is discussed. Provided that ? approx-lt 0.18, the scattered intensity at small wave vectors q increases as the gelation proceeds, and the structure factor S(q, t ? ?) of the gel exhibits apparent power law behavior. Power law behavior is also observed, even for samples with ?>0.18, when the gel is formed under an applied shear. Shear also enhances the diffraction maximum corresponding to the inter-particle contact distance of the gel. Difficulties encountered when trying to interpret SANS data from these dense systems are outlined. Results of computer simulations intended to mimic gel formation, including computations of S(q, t), are discussed. Comments on a method to extract a fractal dimension characterizing the gel are included
Oltra, O R; Farmer, L J; Gordon, A W; Moss, B W; Birnie, J; Devlin, D J; Tolland, E L C; Tollerton, I J; Beattie, A M; Kennedy, J T; Farrell, D
2015-02-01
In this study, important eating quality attributes that influence consumer liking for grilled lamb loin have been identified using preference mapping techniques. The eating quality attributes identified as driving the consumer liking of lamb loin steaks were “tenderness”, “sweet flavour”, “meaty aftertaste”, “roast lamb flavour” and “roast lamb aftertaste”. In contrast, the texture attribute “rubbery” and the flavour attributes “bitter flavour” and "bitter aftertaste" had a negative influence on consumer perceptions. Associations were observed between eating quality and a number of instrumental and chemical measurements. Warner Bratzler Shear Force showed an association with “rubbery” texture and a negative association with “tenderness” and consumer liking scores. The compounds, glucose, glucose-6-phosphate, inosine, inosine monophosphate and adenosine monophosphate were associated with the attributes, “sweet flavour”,“meaty aftertaste”, “roast lamb flavour”, “roast lamb aftertaste” and with consumer scores for liking of lamb which is probably caused by the role some of these compounds play as precursors of flavour and as taste compounds. PMID:25460112
Directory of Open Access Journals (Sweden)
A. Girolami
2010-04-01
Full Text Available The experiment was performed with thirty-two Altamurana and Trimeticcio lambs slaughtered at 42 and at 70 days of age. Meat organoleptic characteristics were determined on samples of M. Longissimus lumborum and Longissimus thoracis. Colour parameters were not affected by genotype, while L* value and index of yellow decreased (P<0.01 and P<0.05, respectively as age of slaughtering increased. Meat from Altamurana lambs showed lower juiciness (P<0.01 and fatness (P<0.05 than Trimeticcio lambs. No genotype and age of slaughtering effects were found for Warner-Bratzler shear force (WBSF values. Meat from younger lambs was more tender and chewable (P<0.01 but less juicy (P<0.001 and fatty (P<0.05 than meat from lambs slaughterd at 70 days.
Comparison of textural atributes of selected meat sausages using instrumental analysis
Directory of Open Access Journals (Sweden)
Vladimír Vietoris
2013-03-01
Full Text Available Normal 0 21 false false false SK X-NONE X-NONE The aim of the study was to compare textural atributes of selected meat sausages using instrumental analysis. For this purpose, seven different meat sausage samples were treated by instrumental analysis, by the use of Warner-Bratzler probe, to find differences for two selected textural parameter firmness and work of shear. As expected, various values of mentioned atributes were obtained for different samples tested in fresh stage and after storage under controlled conditions (48 hrs., 30 °C temp., and 60 % R.H. before and after cooking. For statistical evaluation of results, paired T test was used, statistically significant differences were taken at pdoi:10.5219/273
Akit, H; Collins, C L; Fahri, F T; Hung, A T; D'Souza, D N; Leury, B J; Dunshea, F R
2014-03-01
The influence of dietary lecithin at doses of 0, 4, 20 or 80 g/kg fed to finisher gilts for six weeks prior to slaughter on growth performance, carcass quality and pork quality was investigated. M. longissimus lumborum (loin) was removed from 36 pig carcasses at 24h post-mortem for Warner-Bratzler shear force, compression, collagen content and colour analyses. Dietary lecithin increased dressing percentage (P=0.009). Pork chewiness and collagen content were decreased by dietary lecithin (P0.05, respectively). Dietary lecithin reduced loin muscle L* values and increased a* values (P<0.05, respectively) but no changes on b* values (P=0.56). The data showed that dietary lecithin improved dressing percentage and resulted in less chewy and less pale pork. PMID:24334033
Matsukawa, T; Tilakaratne, N; Buvanendran, V
1976-08-01
Growth and carcass characteristics were measured on calves from three cattle breeds-the Sinhala, Red Sindhi and Friesian-and two buffalo breeds-the local buffalo and Murrah. The growth study was carried out on Brachiaria brizantha pasture over a period of 48 weeks. The two buffalo breeds grew fastest followed by the two Bos indicus breeds. The Friesian cattle grew at the slowest rate. The Sinhala and local buffalo had normal haematocrit values while the values for all other breeds were lower. The Sinhala and local buffalo had the highest carcass dressing percentages and the highest muscle; bone ratios. Tenderness measured by Warner-Bratzler shear force values and palatability scores by a taste panel were similar for meat from cattle and buffalo. PMID:968951
The Hypertrophic Marchigiana: physical and biochemical parameters for meat quality evaluation
Directory of Open Access Journals (Sweden)
F. M. Sarti
2010-04-01
Full Text Available The aim of this study was to evaluate the meat quality of double muscled Marchigiana young bulls characterized by different genotypes for the hypertrophy: normal and mutated (heterozygous. Calpain and calpastatin activities were determined to verify the state of aging meat on a sample of Longissimus thoracis muscle (XIII thoracic rib taken at slaughtering (0h and after 24 hours (24h. After 14 days of aging, another sample of muscle was taken to evaluate physical and chemical parameters of meat quality. The results showed a better meat quality of mutated animals respect normal animals. Another interesting result was the correlation between the biochemical parameters and some physical parameters, such as WBS (Warner Bratzler Shear Force, CL (Cooking loss. These results showed the relationship between the proteolytic activity of calpain system and meat tenderness.
Plasticity Approach to Shear Design
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1998-01-01
The paper presents some plastic models for shear design of reinforced concrete beams. Distinction is made between two shear failure modes, namely web crushing and crack sliding. The first mentioned mode is met in beams with large shear reinforcement degrees. The mode of crack sliding is met in non-shear reinforced beams as well as in lightly shear reinforced beams. For such beams the shear strength is determined by the recently developed crack sliding model. This model is based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed in uncracked concrete. Good agree between theory and tests has been found.Keywords: dsign, plasticity, reinforced concrete, reinforcement, shear, web crushing.
Tempo de cozimento e textura de raízes de mandioca / Cooking time and texture of cassava roots
Scientific Electronic Library Online (English)
Simone Vilela, Talma; Selma Bergara, Almeida; Rozana Moreira Pereira, Lima; Henrique Duarte, Vieira; Pedro Amorim, Bebert.
2013-06-01
Full Text Available O objetivo deste trabalho foi avaliar a adequação de medidas instrumentais de textura como índice de qualidade de raízes da mandioca de mesa e sua correlação com o tempo de cozimento. Quinze raízes de mandioca foram colhidas no 11.º mês de cultivo na região noroeste fluminense. Pedaços de raízes for [...] am cozidos em água, sendo o tempo de cozimento determinado, em triplicata, quando se observou pouca resistência à penetração do garfo. A resistência ao corte foi realizada nas polpas cruas e cozidas, em cinco a nove repetições, operando o texturômetro TA. XT Plus Texture Analyser com probe Warner-Bratzler Blade HDP/BSW, velocidades de pré-teste de 0,2 cm/s, de pós-teste e de teste de 0,5 cm/s, e distância de 5 cm. Os dados foram analisados por ANOVA e teste de média Tukey (tempo de cozimento); GLM, LSMEANS e PDIFF (resistência ao corte) e análise de correlação de Pearson (p Abstract in english The objective of this work was to evaluate the adequacy of instrumental texture analyses as a quality index for cassava roots for direct consumption, and the correlation with cooking time. Fifteen cassava roots were harvested in the eleventh month of growth in the northwest of the State of Rio de Ja [...] neiro. Pieces of roots were boiled in water and the cooking time determined in triplicate, to the point where there was little resistance to penetration by a fork. The shear strength was determined in the raw and cooked pulps with five to nine replicates, using the texturometer TA-XT Plus Texture Analyser with the Warner-Bratzler Blade HDP / BSW probe, a pre-test speed of 0.2 cm/s, post-test and test speed of 0.5 cm/s and distance of 5 cm. The data were analyzed by ANOVA and Tukey (cooking time), GLM, LSMEANS and PDIFF (shear resistance) and Pearson's correlation analysis (p
Effect of probiotics and thyme essential oil on the texture of cooked chicken breast meat
Directory of Open Access Journals (Sweden)
Ebrahim Alfaig
2013-12-01
Full Text Available Background. Texture is probably the single most critical quality factor associated with the consumers’ ultimate satisfaction with a poultry meat product and can be affected by several factors including the type of feed used for chickens fattening. The use of probiotics for meat and carcass quality improvement has been questioned, while the possibility of deposition of essential oils in various muscle tissues can alter the sensory attributes of the chicken’s meat. Material and methods. Probiotics and thyme essential oil in the percentage of 0.05% were used as feed supplements for Ross 308 broiler chickens, as the broilers were reared in four separated groups based on the feed supplement as follows: control, probiotics, thyme essential oil and combination of probiotics and thyme essential oil group, while the fattening period was 42 days. TA.XT Plus-Texture analyser apparatus was used for determination of the texture profile and Warner Bratzler shear force for the cooked breast meat. Results. Warner Bratzler shear test results showed that the tested feed additives were not affecting the texture of the chicken breast meat, while probiotic appears to have moderately effect on the hardness, cohesiveness, springiness and chewiness attributes of the cooked breast meat compared with the other groups, this effect of probiotics considered as negligible, as the results showed that all the tested groups meat were very tender according to the tenderness scale. Conclusions. According to the obtained results it can be concluded the combination of probiotics and thyme group resulted in the lowest score for the hardness, cohesiveness, springiness and chewiness attributes, while probiotics group scored the highest compared with the control.
Scaling of Entropic Shear Rigidity
Xing, X; Goldbart, P M
2004-01-01
The scaling of the shear modulus near the gelation/vulcanization transition is explored heuristically and analytically. It is found that in a dense melt the effective chains of the infinite cluster have sizes that scale sub-linearly with their contour length. Consequently, each contributes k_B T to the rigidity, which leads to a shear modulus exponent d\
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange. The position of the crack in which sliding takes place is determined by the crack sliding model developed by Jin-Ping Zhang. The theoretical calculations are compared with test results reported in the l...
Scientific Electronic Library Online (English)
Lindon W., Mamani-Linares; Faustina, Cayo; Carmen, Gallo.
2013-04-01
Full Text Available Se compararon las características tecnológicas de doce músculos de llamas que fueron criadas al pastoreo. Las llamas (n=10) fueron faenadas bajo procedimientos estándares de Bolivia. Las canales fueron refrigeradas durante 24 horas a 4 ºC. Los músculos fueron removidos de cada canal después del desp [...] oste. Cinco bifes de 2.54 cm de espesor fueron cortados de cada músculo. En cada músculo se determinó el pH24, color (L*, a*, b*), capacidad de retención de agua y fuerza de corte Warner-Bratzler (WBSF). No se observaron diferencias estadísticas en el pH entre los músculos. Los valores de L* (luminosidad) y b* (tenor de amarrillo) de los músculos L. thoracis, L. lumborum y Semimembranosus fueron mayores que en Triceps brachii y Psoas major (p Abstract in english This study compared the technological quality of twelve muscles of llama that were raised in a grazing system. The llamas (n=10) were slaughtered using Bolivian standard procedures. Carcasses were stored for 24 h in a cold room (4 ºC). Muscles were removed from the left side of each carcass in the s [...] laughter house. Five steaks (2.54 cm thick) were cut from each muscle. In each muscle was determined pH, colour (L*, a*, b*), water holding capacity (WHC) and Warner-Bratzler shear-force (WBSF). No statistical difference was found in pH between muscles. Values of L* (lightness) and b* (tenor of yellow) in L. thoracis, L. lumborum and Semimembranosus were higher than those in Triceps brachii and Psoas major (p
Macroscopic Discontinuous Shear Thickening versus Local Shear Jamming in Cornstarch
Fall, A.; Bertrand, F.; Hautemayou, D.; Mezière, C.; Moucheront, P.; Lemaître, A.; Ovarlez, G.
2015-03-01
We study the emergence of discontinuous shear thickening (DST) in cornstarch by combining macroscopic rheometry with local magnetic resonance imaging measurements. We bring evidence that macroscopic DST is observed only when the flow separates into a low-density flowing and a high-density jammed region. In the shear-thickened steady state, the local rheology in the flowing region is not DST but, strikingly, is often shear thinning. Our data thus show that the stress jump measured during DST, in cornstarch, does not capture a secondary, high-viscosity branch of the local steady rheology but results from the existence of a shear jamming limit at volume fractions quite significantly below random close packing.
Localized states in sheared electroconvection
Tsai, Peichun; Daya, Zahir A
2008-01-01
Electroconvection in a thin, sheared fluid film displays a rich sequence of bifurcations between different flow states as the driving voltage is increased. We present a numerical study of an annular film in which a radial potential difference acts on induced surface charges to drive convection. The film is also sheared by independently rotating the inner edge of the annulus. This simulation models laboratory experiments on electroconvection in sheared smectic liquid crystal films. The applied shear competes with the electrical forces, resulting in oscillatory and strongly subcritical bifurcations between localized vortex states close to onset. At higher forcing, the flow becomes chaotic via a Ruelle-Takens-Newhouse scenario. The simulation allows flow visualization not available in the physical experiments, and sheds light on previously observed transitions in the current-voltage characteristics of electroconvecting smectic films.
Shear Alfven waves in tokamaks
International Nuclear Information System (INIS)
Shear Alfven waves in an axisymmetric tokamak are examined within the framework of the linearized ideal MHD equations. Properties of the shear Alfven continuous spectrum are studied both analytically and numerically. Implications of these results in regards to low frequency rf heating of toroidally confined plasmas are discussed. The structure of the spatial singularities associated with these waves is determined. A reduced set of ideal MHD equations is derived to describe these waves in a very low beta plasma
Shear shocks in fragile networks.
Ulrich, Stephan; Upadhyaya, Nitin; van Opheusden, Bas; Vitelli, Vincenzo
2013-12-24
A minimal model for studying the mechanical properties of amorphous solids is a disordered network of point masses connected by unbreakable springs. At a critical value of its mean connectivity, such a network becomes fragile: it undergoes a rigidity transition signaled by a vanishing shear modulus and transverse sound speed. We investigate analytically and numerically the linear and nonlinear visco-elastic response of these fragile solids by probing how shear fronts propagate through them. Our approach, which we tentatively label shear front rheology, provides an alternative route to standard oscillatory rheology. In the linear regime, we observe at late times a diffusive broadening of the fronts controlled by an effective shear viscosity that diverges at the critical point. No matter how small the microscopic coefficient of dissipation, strongly disordered networks behave as if they were overdamped because energy is irreversibly leaked into diverging nonaffine fluctuations. Close to the transition, the regime of linear response becomes vanishingly small: the tiniest shear strains generate strongly nonlinear shear shock waves qualitatively different from their compressional counterparts in granular media. The inherent nonlinearities trigger an energy cascade from low to high frequency components that keep the network away from attaining the quasi-static limit. This mechanism, reminiscent of acoustic turbulence, causes a superdiffusive broadening of the shock width. PMID:24309379
Bicontinuous Microemulsions under Steady Shear Flow
Kodama, Hiroya; Komura, Shigeyuki
1997-01-01
Dynamic response of microemulsions to shear deformation on the basis of two-order-parameter time dependent Ginzburg-Landau model is investigated by means of cell dynamical system approach. Time evolution of anisotropic factor and excess shear stress under steady shear flow is studied by changing shear rate and total amount of surfactant. As the surfactant concentration is increased, overshoot peak height of the anisotropic factor increases whereas that of the excess shear stress is almost unc...
Scientific Electronic Library Online (English)
Wesley Oliveira de, Sousa; Germano Henrique, Rosado-Neto; Marinêz Isaac, Marques.
2012-09-01
Full Text Available A teoria plastrão foi testada em adultos de Neochetina eichhorniae Warner, 1970, por meio da análise da estrutura que reveste o tegumento destes insetos e em experimentos laboratoriais de submersão. Os processos tegumentares foram reconhecidos em três tipos: escamas aglutinadas e com perfurações lar [...] gas; escamas plumosas de tamanhos e formas variadas; e pêlos. Os experimentos realizados com 264 indivíduos adultos os quais permaneciam submersos por diferentes intervalos de tempo (n = 11) e em dois tratamentos, água natural não aerada e água previamente fervida, com quatro repetições para cada tratamento, revelaram uma mortalidade máxima após 24 horas de mergulho no tratamento água previamente fervida. A sobrevivência dos adultos foi negativa e significativamente correlacionada com os tratamentos empregados e entre os diferentes intervalos de tempo. Os valores de oxigênio dissolvido (mg/l) na água diferiram significativamente entre os tratamentos aplicados, sendo positivamente correlacionado com a sobrevivência dos adultos nos dois tratamentos, embora mais acentuadamente no tratamento com água previamente fervida. A mortalidade dos adultos após 24 horas de mergulho no tratamento com água previamente fervida pode estar associada às condições físico-químicas da água não testadas neste estudo, como, por exemplo, baixa tensão superficial e concentração de solutos. Estes resultados sugerem uma funcionalidade do plastrão nos adultos desta espécie. Abstract in english The plastron theory was tested in adults of Neochetina eichhorniae Warner, 1970, through the analysis of the structure that coats these insects' integument and also through submersion laboratorial experiments. The tegument processes were recognized in three types: agglutinated scales with large perf [...] orations, plumose scales of varied sizes and shapes, and hairs. The experiments were carried out on 264 adult individuals which were kept submerged at different time intervals (n = 11) and in two types of treatment, natural non-aerated water and previously boiled water, with four repetitions for each treatment. The tests showed a maximum mortality after 24 hours of immersion in the previously boiled water treatment. The survival of the adults was negative and significantly correlated with the types of treatment employed and within the different time intervals. The values of oxygen dissolved in water (mg/l) differed significantly within the types of treatment employed. They were positively correlated with the survival of the adults in the two types of treatment, although more markedly in the treatment with previously boiled water. The mortality of adults after 24 hours of submersion in the treatment with previously boiled water may be associated with the physical-chemical conditions of the non-tested water in this study, such as low surface tension and concentration of solutes. These results suggest plastron functionality in the adults of this species.
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding model developed by Jin-Ping Zhang. The model takes into account the resistance against formation of cracks due to prestressing as well as the variation of the prestressing force in the transfer zone.Du...
Shear loading of costal cartilage
Subit, Damien
2014-01-01
A series of tests were performed on a single post-mortem human subject at various length scales. First, tabletop tests were performed. Next, the ribs and intercostal muscles were tested with the view to characterize the load transfer between the ribs. Finally, the costal cartilage was tested under shear loading, as it plays an important in the transfer of the load between the ribs and the sternum. This paper reports the results of dynamic shear loading tests performed on three samples of costal cartilage harvested from a single post-mortem human subject, as well as the quantification of the effective Young's modulus estimated from the amount of cartilage calcification.
Shear transfer across cracks in reinforced concrete
International Nuclear Information System (INIS)
An experimental and analytical investigation was conducted to assess the transfer of cyclic shear forces in cracked reinforced concrete by means of the interface shear transfer and dowel action mechanisms. Two test series evaluated the transfer of shear forces by the combination of the interface shear transfer and dowel action mechanisms, and the dowel action mechanism alone. The initial crack width and the reinforcement ratios provided at the shear plane, the number of loading cycles, and the cyclic shear stress intensity were the main variables studied using a test specimen modeled after an idealized section of the cracked structure. The average shear displacement, crack width, and reinforcement strains were measured in each specimen for all load increments. Simplified equations were developed to describe the first loading cycle stiffness exhibited by both the interface shear transfer and dowel action mechanism. A bilinear idealization was proposed for the experimental hysteresis curve of each mechanism together with the corresponding stiffness coefficients. Equations were derived from a nonlinear regression analysis for the splitting failure force for axial or dowel forces, and for their interaction. An equation was also proposed for the ultimate shear stress that can be transferred across a precracked shear plane. The research concluded that shear forces can be efficiently transferred across cracked surfaces by the combined action of the interface shear transfer and dowel action mechanisms. The investigation was motivated by the desire to assess the behavior of the shear transfer mechanism in cracked secondary nuclear containment vessels
Shear history effect of magnetorheological fluids
Shan, Lei; Chen, Kaikai; Zhou, Ming; Zhang, Xiangjun; Meng, Yonggang; Tian, Yu
2015-10-01
The rheological properties of magnetorheological (MR) fluids are usually determined by particle structures and polarized particle interactions. However, the particle structures may undergo various evolutions at different shear states and history; this evolution leads to shear stress hysteresis. Therefore, the shear history effect of MR fluids was experimentally investigated in this study. In a shear rate ramp test, the shear stress at low shear rate was higher in the shear rate ramp-down process than in the shear rate ramp-up process. If the next shear test started after a rest time, the start shear stress decayed slowly and approached the original value of the first test when the interval was long enough. The MR fluids also displayed obvious hysteresis loops during the current ramp test. A high shear rate and magnetic field could reduce the shear history effect by accelerating particle structure evolutions, and then hysteresis decreased. This effect was ascribed to the evolution of particle structures during different test modes and durations, and the evolution is governed by interparticle interactions, viscous forces, and the Brownian motions of particles. These results indicated that the accuracy of the force control of MR fluids could be enhanced under high magnetic fields and high shear rates. Thus, these factors should be considered in MR actuator designs.
Shear modulus of elasticity of the esophagus
DEFF Research Database (Denmark)
Yang, Jian; Liao, Donghua; Zhao, Jingbo; Gregersen, Hans
2004-01-01
Experimental and diagnostic procedures like distension of a balloon catheter, bougie, and esophagogastroduodenoscopy can induce shear deformation in the esophageal wall. However, the shear modulus of the esophagus is yet unknown. The aim of this study was to determine the esophageal shear modulus and its dependence on the circumferential and longitudinal stresses and strains in the rat. The constitutive equation including the shear deformation based on a pseudo-strain-energy function was generat...
Kinematics and shear heat pattern of ductile simple shear zones with `slip boundary condition'
Mulchrone, Kieran F.; Mukherjee, Soumyajit
2015-06-01
Extrusion by Poiseuille flow and simple shear of hot lower crust has been deciphered from large hot orogens, and partial-slip boundary condition has been encountered in analogue models. Shear heat and velocity profiles are deduced from a simplified form of Navier-Stokes equation for simple shear together with extrusive Poiseuille flow and slip boundary condition for Newtonian viscous rheology. A higher velocity at the upper boundary of the shear zone promotes higher slip velocity at the lower boundary. The other parameters that affect the slip are viscosity and thickness of the shear zone and the resultant pressure gradient that drives extrusion. In the partial-slip case, depending on flow parameters (resultant pressure gradient, density and viscosity) and thickness of the shear zone, the velocity profiles can curve and indicate opposite shear senses. The corresponding shear heat profiles can indicate temperature maximum inside shear zones near either boundaries of the shear zone, or equidistant from them.
Shear Viscosity and Shear Thinning in Two-Dimensional Yukawa Liquids
International Nuclear Information System (INIS)
A two-dimensional Yukawa liquid is studied using two different nonequilibrium molecular dynamics simulation methods. Shear viscosity values in the limit of small shear rates are reported for a wide range of Coulomb coupling parameter and screening lengths. At high shear rates it is demonstrated that this liquid exhibits shear thinning; i.e., the viscosity ? diminishes with increasing shear rate. It is expected that two-dimensional dusty plasmas will exhibit this effect
Punching shear capacity of reinforced concrete slabs with headed shear studs
DEFF Research Database (Denmark)
Hoang, Linh Cao; Pop, Anamaria
2015-01-01
Punching shear in slabs is analogous to shear in beams. Despite this similarity, current design codes provide distinctly different methods for the design of shear reinforcement in the two situations. For example, the Eurocode method for beam shear design is founded on the theory of rigid plasticity. To design shear reinforcement in slabs, on the other hand, the engineer must settle for an empirical equation. The aim of the study reported is to demonstrate that it is possible in a simple manner t...
Shear piezoelectricity of optically active polysuccinimides
Tanimoto, Kazuhiro; Saihara, Shota; Adachi, Yu; Harada, Yuhei; Shiomi, Yuki; Tajitsu, Yoshiro
2015-10-01
Optically active crystalline polymers have shear piezoelectricity owing to their asymmetric crystal structure. In this study, to explore a novel shear piezoelectric polymer, we have focused on an imide ring structure and synthesized optically active polysuccinimides (PSIs), the minimum structure of optically active polyimides. As a result, optically active PSIs were obtained, and we observed that oriented optically active PSI films show shear piezoelectricity. Furthermore, both optical purity and molecular weight are significant factors in piezoelectric performance. This is the first report of the shear piezoelectricity of optically active polyimides, and we identify herein a novel category of a shear piezoelectric polymer.
Apparatus for shearing spent nuclear fuel assemblies
International Nuclear Information System (INIS)
A method and apparatus are described for shearing spent nuclear fuel assemblies of the type comprising an array of fuel pins disposed within an outer metal shell or shroud. A spent fuel assembly is first compacted in a known manner and then incrementally sheared using fixed and movable shear blades having matched laterally projecting teeth which slidably intermesh to provide the desired shearing action. Incremental advancement of the fuel assembly after each shear cycle is limited to a distance corresponding to the lateral projection of the teeth to ensure fuel assembly breakup into small uniform segments which are amenable to remote chemical processing
Pure shear axes and elastic strain energy
Norris, Andrew N.
2006-01-01
It is well known that a state of pure shear has distinct sets of basis vectors or coordinate systems: the principal axes, in which the stress is diagonal, and pure shear bases, in which diag(stress)=0. The latter is commonly taken as the definition of pure shear, although a state of pure shear is more generally defined by tr(stress)=0. New results are presented that characterize all possible pure shear bases. A pair of vector functions are derived which generate a set of pur...
Ideal stability limits of reverse shear equilibria
International Nuclear Information System (INIS)
The dependence on various plasma parameters of the ideal stability limit of reverse shear current profiles in TFTR and other tokamaks has been thoroughly explored. Profiles with reverse shear allow core access to the second ballooning stability region. In addition, for sufficient shear reversal, modes with n = 2 and greater are also stabilized. The n = 1 stability threshold is only slightly affected by reverse shear and becomes the limiting instability. The mode is predominately an infernal mode with a significant external contribution. Particular emphasis will be on analysis of recent experimental results of enhanced reverse shear (ERS) profiles in TFTR and a study of those profile characteristics which optimize TFTR performance
Shear instability in skin tissue
Ciarletta, Pasquale; Gower, Artur L
2013-01-01
We propose two toy-models to describe, predict, and interpret the wrinkles appearing on the surface of skin when it is sheared. With the first model, we account for the lines of greatest tension present in human skin by subjecting a layer of soft tissue to a pre-stretch, and for the epidermis by endowing one of the layer's faces with a surface tension. For the second model, we consider an anisotropic model for the skin, to reflect the presence of stiff collagen fibres in a softer elastic matrix. In both cases, we find an explicit bifurcation criterion, linking geometrical and material parameters to a critical shear deformation accompanied by small static wrinkles, with decaying amplitudes normal to the free surface of skin.
Anisotropic diffusion and shear instabilities
Talon, S.; Zahn, J. -P.
1996-01-01
We examine the role of anisotropic turbulence on the shear instabilities in a stratified flow. Such turbulence is expected to occur in the radiative interiors of stars, due to their differential rotation and their strong stratification, and the turbulent transport associated with it will be much stronger in the horizontal than in the vertical direction. It will thus weaken the restoring force which is caused by the gradient of mean molecular weight ($\\mu$). We find that the ...
Statistical Model of Extreme Shear
DEFF Research Database (Denmark)
Hansen, Kurt Schaldemose; Larsen, Gunner Chr.
2005-01-01
In order to continue cost-optimisation of modern large wind turbines, it is important to continuously increase the knowledge of wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function (PDF) of turbulence driven short-term extreme wind shear events, conditioned on the mean wind speed, for an arbitrary recurrence period. The model is based on an asymptotic expansion, and only a few and ...
Statistical Model of Extreme Shear
DEFF Research Database (Denmark)
Larsen, Gunner Chr.; Hansen, Kurt Schaldemose
2004-01-01
In order to continue cost-optimisation of modern large wind turbines, it is important to continously increase the knowledge on wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function (PDF) of turbulence driven short-term extreme wind shear events, conditioned on the mean wind speed, for an arbitrary recurrence period. The model is based on an asymptotic expansion, and only a few and e...
Causality in strong shear flows
Narayan, R; Kumar, P; Ramesh Narayan; Loeb, Abraham
1994-01-01
It is well known that the standard transport equations violate causality when gradients are large or when temporal variations are rapid. We derive a modified set of transport equations that satisfy causality. These equations are obtained from the underlying Boltzmann equation. We use a simple model for particle collisions which enables us to derive moment equations non-perturbatively, i.e. without making the usual assumption that the distribution function deviates only slightly from its equilibrium value. We apply the model to two problems: particle diffusion and viscous transport. In both cases we show that signals propagate at a finite speed and therefore that the formalism obeys causality. When the velocity gradient is large on the scale of a mean free path, the viscous shear stress is suppressed relative to the prediction of the standard diffusion approximation. The shear stress reaches a maximum at a finite value of the shear amplitude and then decreases as the velocity gradient increases. In the case of...
Shear Stabilization in the Levitron
International Nuclear Information System (INIS)
The levitron is a toroidal hard-core tube of 30-cm minor diameter, with a ring core left unsupported for 20 msec. A 5-kG toroidal field, and a comparable poloidal field based on a ring-core current, are pulsed on with 60-to 16,000-?sec rise times. The magnetic shear is always large, insuring infinite-conductivity hydromagnetic stability. Finite-resistivity and non-hydromagnetic instabilities are expected, however; and their study is the object of the experiment. Levitron experiments in the high-current regime (for example, ?50-kA induced current, lasting 1 to 2 msec, at ?3 x 1013 -cm-3 plasma density and electron temperatures in the 100-eV range) show a small-scale ''magnetic flutter'' (?5 G, ?100 kc/sec) of flutelike structure. The stability analysis for the hard-core geometry, however, proves categorically that the observed mode cannot be of the finite-resistivity ''tearing'' type. To what extent shear stabilization is valid even in the absence of directed current, is theoretically still disputed. In this context we are studying electron-cyclotron heating at 10 Gc/sec. Hot-electron plasmas with the usual dilute high-energy (10 to 1000 keV) and dense (?1012 cm-3) low-energy components have been contained for 1 to 10 msec times after ?-wave cut off. When the initially generated high-energy component is left by itself, it proves highly unstable to cross-field transport, with or without shear, due partly to the mirror localization associated with the hard-core field in toroidal geometry. In the absence of shear (pure poloidal field), the flute instability limits the electron temperature of the dense-plasma component to ? 5 eV. With an additional toroidal field ?150 G, electron temperatures of 50 eV are attained, but they are still limited by a (presumably resistive) flute instability that is insensitive to a further 10-fold increase in shear. (author)
Evolution of twist-shear and dip-shear in Faring active region NOAA 10930
Gosain, Sanjay
2010-01-01
We study the evolution of magnetic shear angle in a flare productive active region NOAA 10930. The magnetic shear angle is defined as the deviation in the orientation of the observed magnetic field vector with respect to the potential field vector. The shear angle is measured in horizontal as well as vertical plane. The former is computed by taking the difference between the azimuth angles of the observed and potential field and is called the twist-shear, while the latter is computed by taking the difference between the inclination angles of the observed and potential field and is called the dip-shear. The evolution of the two shear angles is then tracked over a small region located over the sheared penumbra of the delta sunspot in NOAA 10930. We find that, while the twist-shear shows an increasing trend after the flare the dip-shear shows a significant drop after the flare.
Directory of Open Access Journals (Sweden)
T. Suryati
2004-12-01
Full Text Available Effect of low voltage electrical stimulation (LVES; 45 volt, 3 amps for approx 100 sec and calcium chloride (CaCl2 injection on physical properties of meat were evaluated. Six mutton were devided into 3 groups. One carcass of each group was subjected to within 30 min postmortem (PM. After LVES, longissimi thoracis et lumbarum muscles were removed and treated: without CaCl2 injection, CaCl2 injection (200 mM, 5% w/w at about 2 h and 24 h PM. Samples were stored in vacuum pack at 1 ± 1o C. Physical properties evaluated were Warner–Bratzler (WB shear force, cooking loss and sarcomere length. The LVES had no significant effect on WB shear force, cooking loss and sarcomere length. There wasn’t interaction effect between LVES and CaCl2 injection on WB shear force, cooking loss and sarcomere length. CaCl2 injection decreased sarcomere length (P<0.01, therefore resulted in tougher meat with higher cooking loss.
DEFF Research Database (Denmark)
Christensen, M.; Torngren, M. A.
2009-01-01
BACKGROUND: Marination of beef muscles with brine solutions containing proteolytic enzymes from fruit extracts has been shown to tenderize meat. However, the effect of marination with actinidin on tenderness of pork muscles has not been investigated. Tenderness and eating quality of porcine M. biceps femoris was investigated by Warner-Bratzler (WB) shear test and sensory evaluation after injection of brine containing up to 11 g L-1 actinidin-containing kiwi fruit powder and 2, 5 or 9 days of storage. RESULTS: actinidin decreased WB shear force, increased tenderness and did not affect flavour and juiciness. Injection of 2.8g L-1 actinidin powder and storage for 2 days resulted in WB shear force values similar to control samples stored for 5 or 9 days. In samples injected with 10 g L-1 actinidin powder, degradation of desmin and percentage of heat-soluble collagen (P <0.05) increased compared to control samples. Myofibrillar particle size tended to decrease (P <0.1) with increasing actinidin concentration. No major changes were observed by proteome analysis. Atomic force microscopy showed actinidin-induced damage of endomysium surrounding isolated single muscle fibres. CONCLUSION: Our results indicate that actinidin tenderizes pork M. biceps femoris by affecting both the myofibrils and connective tissue.
Shear Strain Localization in Elastodynamic Rupture Simulations
Daub, E. G.; Carlson, J. M.
2007-12-01
We study how shear strain localization affects the propagation and dynamics of earthquake rupture. We model the fault as a layer of gouge governed by Shear Transformation Zone Theory, which provides a microscopic physical model for plastic deformation of the gouge, and a state variable for effective temperature. The effective temperature represents the local disorder in the gouge, and regions with higher effective temperature become more susceptible to plastic deformation. When strain is allowed to vary normal to the fault plane, a shear band instability permits sustained shear strain localization. We examine both homogeneous shear and localized shear in the spontaneous propagation of elastodynamic ruptures, and study how localization affects the stress dynamics, energy balance, and slip rate of earthquakes.
Anisotropic thermal conductivity in sheared polypropylene
Energy Technology Data Exchange (ETDEWEB)
Dai, Shao Cong; Tanner, Roger I. [The University of Sydney, Rheology Research Group, School of Aerospace, Mechanical and Mechatronic Engineering, Sydney, NSW (Australia)
2006-01-01
We discuss the anisotropy of the thermal conductivity tensor in polymer flow in this paper. Isotactic polypropylene (iPP) specimens were deformed by injection moulding at high shear rates and by steady shear at low shear rates, and were then quenched. The thermal conductivities parallel and perpendicular to the shear direction were measured using modulated differential scanning calorimetry (MDSC) in accordance with the ASTM E1952-01. The measured results showed that the thermal conductivity of the sheared polymer was anisotropic with an increase in the shear direction. The thermal conductivity can be regarded as varying either with the strain or the stress, as suggested by Van den Brule (1989). In addition to the Van den Brule mechanism, crystallization during flow also changes the thermal conductivity and this effect may often be dominant. Suggestions for procedures in processing computations, based on both effects, are given. (orig.)
Hierarchical Cosmic Shear Power Spectrum Inference
Alsing, Justin; Jaffe, Andrew H; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2015-01-01
We develop a Bayesian hierarchical modelling approach for cosmic shear power spectrum inference, jointly sampling from the posterior distribution of the cosmic shear field and its (tomographic) power spectra. Inference of the shear power spectrum is a powerful intermediate product for a cosmic shear analysis, since it requires very few model assumptions and can be used to perform inference on a wide range of cosmological models \\emph{a posteriori} without loss of information. We show that joint posterior for the shear map and power spectrum can be sampled effectively by Gibbs sampling, iteratively drawing samples from the map and power spectrum, each conditional on the other. This approach neatly circumvents difficulties associated with complicated survey geometry and masks that plague frequentist power spectrum estimators, since the power spectrum inference provides prior information about the field in masked regions at every sampling step. We demonstrate this approach for inference of tomographic shear $E$-...
Shear Thickening and Migration in Granular Suspensions
Fall, Abdoulaye; Lemaître, Anaël; Bertrand, François; Bonn, Daniel; Ovarlez, Guillaume
2010-12-01
We study the emergence of shear thickening in dense suspensions of non-Brownian particles. We combine local velocity and concentration measurements using magnetic resonance imaging with macroscopic rheometry experiments. In steady state, we observe that the material is heterogeneous, and we find that the local rheology presents a continuous transition at low shear rate from a viscous to a shear thickening, Bagnoldian, behavior with shear stresses proportional to the shear rate squared, as predicted by a scaling analysis. We show that the heterogeneity results from an unexpectedly fast migration of grains, which we attribute to the emergence of the Bagnoldian rheology. The migration process is observed to be accompanied by macroscopic transient discontinuous shear thickening, which is consequently not an intrinsic property of granular suspensions.
The Sheared Central Venous Catheter?
Hegde, Harihar V; Yaliwal, Vijay G.; Shyamsundar K. Joshi; P. Raghavendra Rao
2011-01-01
A fractured central venous catheter (CVC) with embolization of the distal fragment may lead to life-threatening complications. We had inserted a right subclavian CVC in a 68-year-old female which upon a follow-up chest X-ray appeared to have been sheared. A guidewire was inserted through the CVC until the J-tip was just beyond the tip of the CVC which were then withdrawn as a single assembly. We suspected that the tip of the guidewire might have been entrapped in the opening of the middle por...
Mixing in shear thinning fluids
Scientific Electronic Library Online (English)
H., Ameur; M., Bouzit.
2012-06-01
Full Text Available In the present study, a CFD characterization of the flow generated by curved-blade impellers in a cylindrical unbaffled vessel was carried out. The tank diameter was 300 mm, with a flat bottom. The liquid height was equal to the vessel diameter. The fluids simulated have a shear thinning behavior. A [...] nalyses concern the effect of the impeller speed, the fluid rheology and the number of impeller blades on the induced flow patterns and the power consumption. The predictions were compared with literature data and a satisfactory agreement was found.
Interfacial Slip in Sheared Polymer Blends
Lo, Tak Shing; Mihajlovic, Maja; Shnidman, Yitzhak; Li, Wentao; Gersappe, Dilip
2004-01-01
We have developed a dynamic self-consistent field theory, without any adjustable parameters, for unentangled polymer blends under shear. Our model accounts for the interaction between polymers, and enables one to compute the evolution of the local rheology, microstructure and the conformations of the polymer chains under shear self-consistently. We use this model to study the interfacial dynamics in sheared polymer blends and make a quantitative comparison between this model...
Collision statistics in sheared inelastic hard spheres
Bannerman, Marcus N.; Green, Thomas E.; Grassia, Paul; Lue, Leo
2009-01-01
The dynamics of sheared inelastic-hard-sphere systems are studied using non-equilibrium molecular dynamics simulations and direct simulation Monte Carlo. In the molecular dynamics simulations Lees-Edwards boundary conditions are used to impose the shear. The dimensions of the simulation box are chosen to ensure that the systems are homogeneous and that the shear is applied uniformly. Various system properties are monitored, including the one-particle velocity distribution, g...
Developments in Plasticity Approach to Shear
DEFF Research Database (Denmark)
Hoang, Cao Linh; Nielsen, Mogens Peter
1999-01-01
The paper deals with plastic methods applied to shear design of reinforced concrete beams. Emphasis is put on the recently developed crack sliding model applicable to non-shear reinforced and lightly shear reinforced beams and slabs. The model, which is an upper bound plasticity approach, takes into account the mechanism of crack formation followed by crack sliding. Comparisons between the model and test results are carried out. Good agreement has been found over a wide range of cases.
Residual Shear Deformations in the Coronary Artery
Wang, Ruoya; Gleason, Rudolph L.
2014-01-01
Quantifying arterial residual deformations is critical for understanding the stresses and strains within the arterial wall during physiological and pathophysiological conditions. This study presents novel findings on residual shear deformations in the left anterior descending coronary artery. Residual shear deformations are most evident when thin, long axial strips are cut from the artery. These strips deform into helical configurations when placed in isotonic solution. A residual shear angle...
Shear alters motility of Escherichia coli
Molaei, Mehdi; Jalali, Maryam; Sheng, Jian
2013-11-01
Understanding of locomotion of microorganisms in shear flows drew a wide range of interests in microbial related topics such as biological process including pathogenic infection and biophysical interactions like biofilm formation on engineering surfaces. We employed microfluidics and digital holography microscopy to study motility of E. coli in shear flows. We controlled the shear flow in three different shear rates: 0.28 s-1, 2.8 s-1, and 28 s-1 in a straight channel with the depth of 200 ?m. Magnified holograms, recorded at 15 fps with a CCD camera over more than 20 minutes, are analyzed to obtain 3D swimming trajectories and subsequently used to extract shear responses of E.coli. Thousands of 3-D bacterial trajectories are tracked. The change of bacteria swimming characteristics including swimming velocity, reorientation, and dispersion coefficient are computed directly for individual trajectory and ensemble averaged over thousands of realizations. The results show that shear suppresses the bacterial dispersions in bulk but promote dispersions near the surface contrary to those in quiescent flow condition. Ongoing analyses are focusing to quantify effect of shear rates on tumbling frequency and reorientation of cell body, and its implication in locating the hydrodynamic mechanisms for shear enhanced angular scattering. Understanding of locomotion of microorganisms in shear flows drew a wide range of interests in microbial related topics such as biological process including pathogenic infection and biophysical interactions like biofilm formation on engineering surfaces. We employed microfluidics and digital holography microscopy to study motility of E. coli in shear flows. We controlled the shear flow in three different shear rates: 0.28 s-1, 2.8 s-1, and 28 s-1 in a straight channel with the depth of 200 ?m. Magnified holograms, recorded at 15 fps with a CCD camera over more than 20 minutes, are analyzed to obtain 3D swimming trajectories and subsequently used to extract shear responses of E.coli. Thousands of 3-D bacterial trajectories are tracked. The change of bacteria swimming characteristics including swimming velocity, reorientation, and dispersion coefficient are computed directly for individual trajectory and ensemble averaged over thousands of realizations. The results show that shear suppresses the bacterial dispersions in bulk but promote dispersions near the surface contrary to those in quiescent flow condition. Ongoing analyses are focusing to quantify effect of shear rates on tumbling frequency and reorientation of cell body, and its implication in locating the hydrodynamic mechanisms for shear enhanced angular scattering. NIH, NSF, GoMRI.
Novel shear mechanism in nanolayered composites
Energy Technology Data Exchange (ETDEWEB)
Mara, Nathan [Los Alamos National Laboratory; Bhattacharyya, Dhriti [Los Alamos National Laboratory; Hirth, John P [Los Alamos National Laboratory; Dickerson, Patricia O [Los Alamos National Laboratory; Misra, Amit [Los Alamos National Laboratory
2009-01-01
Recent studies have shown that two-phase nanocomposite materials with semicoherent interfaces exhibit enhanced strength, deformability, and radiation damage resistance. The remarkable behavior exhibited by these materials has been attributed to the atomistic structure of the bi-metal interface that results in interfaces with low shear strength and hence, strong barriers for slip transmission due to dislocation core spreading along the weak interfaces. In this work, the low interfacial shear strength of Cu/Nb nanoscale multilayers dictates a new mechanism for shear banding and strain softening during micropillar compression. Previous work investigating shear band formation in nanocrystalline materials has shown a connection between insufficient strain hardening and the onset of shear banding in Fe and Fe-10% Cu, but has also shown that hardening does not necessarily offset shear banding in Pd nanomaterials. Therefore, the mechanisms behind shear localization in nanocrystalline materials are not completely understood. Our findings, supported by molecular dynamics simulations, provide insight on the design of nanocomposites with tailored interface structures and geometry to obtain a combination of high strength and deformability. High strength is derived from the ability of the interfaces to trap dislocations through relative ease of interfacial shear, while deformability can be maximized by controlling the effects of loading geometry on shear band formation.
Calcite fabrics in experimental shear zones
Friedman, M.; Higgs, N. G.
Cylindrical specimens of Tennessee sandstone, with dry crushed calcite along 35° precut surfaces, are deformed at 200-MPa confining pressure, from 25° to 910°C, and at a shear strain rate of 10-2 s-1. Under these conditions the inelastic deformations are contained within the calcite layer. Shear displacements range between 1.5 and 3.0 mm, with engineering shear strain ? reformed during the shearing. The smaller strain-free neoblasts are probably due to annealing late in each experiment.
Low-rise shear wall failure modes
International Nuclear Information System (INIS)
A summary of the data that are available concerning the structural response of low-rise shear walls is presented. This data will be used to address two failure modes associated with the shear wall structures. First, data concerning the seismic capacity of the shear walls with emphasis on excessive deformations that can cause equipment failure are examined. Second, data concerning the dynamic properties of shear walls (stiffness and damping) that are necessary to compute the seismic inputs to attached equipment are summarized. This case addresses the failure of equipment when the structure remains functional. 23 refs
Shear wall ultimate drift limits
International Nuclear Information System (INIS)
Drift limits for reinforced-concrete shear walls are investigated by reviewing the open literature for appropriate experimental data. Drift values at ultimate are determined for walls with aspect ratios ranging up to a maximum of 3.53 and undergoing different types of lateral loading (cyclic static, monotonic static, and dynamic). Based on the geometry of actual nuclear power plant structures exclusive of containments and concerns regarding their response during seismic (i.e.,cyclic) loading, data are obtained from pertinent references for which the wall aspect ratio is less than or equal to approximately 1, and for which testing is cyclic in nature (typically displacement controlled). In particular, lateral deflections at ultimate load, and at points in the softening region beyond ultimate for which the load has dropped to 90, 80, 70, 60, and 50 percent of its ultimate value, are obtained and converted to drift information. The statistical nature of the data is also investigated. These data are shown to be lognormally distributed, and an analysis of variance is performed. The use of statistics to estimate Probability of Failure for a shear wall structure is illustrated
Shear strength in one- and two-way slabs according to the critical shear crack theory
Muttoni, Aurelio; Fernández Ruiz, Miguel
2008-01-01
Currently, there is no generally-accepted theory giving a physical explanation of the shear strength in one- and two-way slabs. Furthermore, for members without transverse reinforcement, shear strength is estimated in most codes of practice following empirical or semi-empirical approaches. In this paper, the fundamentals of the Critical Shear Crack Theory (CSCT) are introduced. This theory, based on a mechanical model, is shown to provide a unified approach for one- and two-way shear in...
Turbulence suppression by E x B shear in JET optimized shear pulses
International Nuclear Information System (INIS)
The authors calculate microinstability growth rates in JET optimized shear plasmas with a comprehensive gyrofluid model, including sheared E x B flows, trapped electrons, and all dominant ion species in realistic magnetic geometry. They find good correlation between E x B shear suppression of microinstabilities and both the formation and collapse of the internal transport barrier
Shear induced transitions in vortex matter
Miguel, M C; Zapperi, Stefano
2003-01-01
We analyze the transport properties of a type II superconductor in the Corbino disk geometry by molecular dynamics simulations of the vortex lattice. The shear stress induced by the applied current yields a transition from rigid rotation to plastic flow above a threshold value $I_0$. This threshold current is shown to be proportional to the shear modulus $c_{66}$ of the vortex lattice.
Solvable groups and a shear construction
DEFF Research Database (Denmark)
Freibert, Marco; Swann, Andrew Francis
2015-01-01
The twist construction is a geometric model of T-duality that includes constructions of nilmanifolds from tori. This paper shows how one-dimensional foliations on manifolds may be used in a shear construction, which in algebraic form builds certain solvable Lie groups from Abelian ones. We discuss other examples of geometric structures that may be obtained from the shear construction.
Plastic deformation: Shearing mountains atom by atom
Energy Technology Data Exchange (ETDEWEB)
Müllner, Peter, E-mail: petermullner@boisestate.edu [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States)
2013-11-15
Highlights: ? Rocks, wood, ceramics, semiconductors, and metals all deform in the same way, namely by heterogeneous shear banding via hierarchical orthogonal shear modes. ? While the governing principles of deformation are the same for rocks, wood, ceramics, semiconductors, and metals, these materialsdiffer in their microscopic deformation mechanisms and in the width of the shear band, which covers twelve orders of magnitude from angstroms to hundreds of meters. ? Microscopic deformation mechanisms couple to macroscopic deformation mechanisms, i.e. shear banding, through the collective properties of defect groups on the mesoscale. -- Abstract: Conventional wisdom established atomistic defects, dislocations, as agents of plastic deformation. On macroscopic scale, rock, wood, steel, tough ceramics, fiber reinforced composites, and silicon all deform in the same way and produce the same pattern; shear bands. The argumentation presented here, starts on the largest length scale of the problem at hand and leads through a number of hierarchical levels down to the atomistic mechanism. Shear bands develop discontinuously by the motion of a process zone. Locally, i.e. in the process zone, deformation proceeds perpendicularly to the macroscopic shear, in combination with a rotation. The microscopic shear itself may occur again in a discontinuous manner and again orthogonally to the intermediate level and so on at ever smaller scale. Material properties come into play at the highest hierarchical level, i.e. at the smallest length scale where they control the well-known micromechanisms.
Effect of Friction on Shear Jamming
Wang, Dong; Ren, Jie; Dijksman, Joshua; Bares, Jonathan; Behringer, Robert
2015-03-01
Shear jamming of granular materials was first found for systems of frictional disks, with a static friction coefficient ? ~ 0 . 6 (Bi et al. Nature (2011)). Jamming by shear is obtained by starting from a zero-stress state with a packing fraction ? between ?J (isotropic jamming) and a lowest ?S for shear jamming. This phenomenon is associated with strong anisotropy in stress and the contact network in the form of force chains, which are stabilized and/or enhanced by the presence of friction. Whether shear jamming occurs for frictionless particles is under debate. The issue we address experimentally is how reducing friction affects shear jamming. We put the Teflon-wrapped photoelastic disks, lowering the friction substantially from previous experiments, in a well-studied 2D shear apparatus (Ren et al. PRL (2013)), which provides a uniform simple shear. Shear jamming is still observed; however, the difference ?J -?S is smaller with lower friction. We also observe larger anisotropies in fragile states compared to experiments with higher friction particles at the same density. In ongoing work we are studying systems using photoelastic disks with fine gears on the edge to generate very large effective friction. We acknowledge support from NSF Grant DMR1206351, NSF Grant DMS-1248071, NASA Grant NNX10AU01G and William M. Keck Foundation.
Shear Flows and Shear Viscosity in a Two-Dimensional Yukawa System (Dusty Plasma)
Nosenko, V
2004-01-01
The shear viscosity of a two-dimensional liquid-state dusty plasma was measured experimentally. A monolayer of highly charged polymer microspheres, with a Yukawa interaction, was suspended in a plasma sheath. Two counter-propagating Ar laser beams pushed the particles, causing shear-induced melting of the monolayer and a shear flow in a planar Couette configuration. By fitting the particle velocity profiles in the shear flow to a Navier-Stokes model, the kinematic viscosity was calculated; it was of order 1 mm^2/s, depending on the monolayer's parameters and shear stress applied.
Inverse Magnetic/Shear Catalysis
McInnes, Brett
2015-01-01
It is well known that very large magnetic fields are generated when the Quark-Gluon Plasma is formed during peripheral heavy-ion collisions. Lattice, holographic, and other studies strongly suggest that these fields may, for observationally relevant field values, induce ``inverse magnetic catalysis'', signalled by a lowering of the critical temperature for the chiral/deconfinement transition. The theoretical basis of this effect has recently attracted much attention; yet so far these investigations have not included another, equally dramatic consequence of the peripheral collision geometry: the QGP acquires a large angular momentum vector, parallel to the magnetic field. Here we use holographic techniques to argue that the angular momentum can also, independently, have an effect on transition temperatures, and we obtain a rough estimate of the relative effects of the presence of both a magnetic field and an angular momentum density. We find that the shearing angular momentum reinforces the effect of the magne...
Piping shear lug stress analysis
International Nuclear Information System (INIS)
Due to space limitations present in many of the current nuclear power plants, it is frequently necessary to apply restraints skewed to a piping system's axis in order to restrain the piping against hydraulic transient and seismic loads. In order to assure that the restraints function as required, shear lugs are often used to eliminate relative motion between the pipe and the restraint. Detailed stress analyses of the pipe-lug system are presented and expressions for the needed indices are deduced. The analyses are accomplished through use of three-dimensional finite-element modeling employing the computer program SAP IV. Eight node brick elements are used to represent both the pipe and the lug. The resulting mesh consists of 316 elements and 558 nodes and incorporates the symmetry aspects of the physical system. The mesh is a graded one with small elements employed in the area of the lug. A check on the expected accuracy is obtained through a comparison with both an approximate elasticity solution and a proprietary computer program ISOPAR-SHL. The latter allows local stress concentration regions to be modeled by using higher order three-dimensional elements (36 nodes) while the remaining structure is represented by curved shell elements, with transition elements connecting the two. Numerical results are carried out for typical pipe diameters and loadings are then interpreted and recast in terms of the Code design criteria. They are furthermore compared with the results obtained by employing the procedure given in WRC Bulletin 198. This comparison illustrates the conservativeness of the WRC approach, especially for small lugs and lugs whose long dimension is in the circumferential direction. In particular, for a circumferential lug on a 12 in. diameter pipe subjected to loading representative of the up set condition, use of the WRC procedure yields results which are larger by a factor of four for the shear term and by 1.5 for the bending term
Trapped Electron Precession Shear Induced Fluctuation Decorrelation
Energy Technology Data Exchange (ETDEWEB)
T.S. Hahm; P.H. Diamond; E.-J. Kim
2002-07-29
We consider the effects of trapped electron precession shear on the microturbulence. In a similar way the strong E x B shear reduces the radial correlation length of ambient fluctuations, the radial variation of the trapped electron precession frequency can reduce the radial correlation length of fluctuations associated with trapped electrons. In reversed shear plasmas, with the explicit dependence of the trapped electron precession shearing rate on B(subscript)theta, the sharp radial gradient of T(subscript)e due to local electron heating inside qmin can make the precession shearing mechanism more effective, and reduce the electron thermal transport constructing a positive feedback loop for the T(subscript)e barrier formation.
Experimental study on the adiabatic shear bands
International Nuclear Information System (INIS)
Four martensitic steels (Z50CDV5 steel, 28CND8 steel, 35NCDV16 steel and 4340 steel) with different hardness between 190 and 600 Hsub(B) (Brinell hardness), have been studied by means of dynamic compressive tests on split Hopkinson pressure bar. Microscopic observations show that the fracture are associated to the development of adiabatic shear bands (except 4340 steel with 190 Hsub(B) hardness). By means of tests for which the deformation is stopped at predetermined levels, the measurement of shear and hardness inside the band and the matrix indicates the chronology of this phenomenon: first the localization of shear, followed by the formation of adiabatic shear band and ultimatly crack initiation and propagation. These results correlated with few simulations by finite elements have permitted to suggest two mecanisms of deformation leading to the formation of adiabatic shear bands in this specific test
Squirming through shear-thinning fluids
Datt, Charu; Elfring, Gwynn J; Pak, On Shun
2015-01-01
Many microorganisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in nontrivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problemat...
Statistical properties of the linear tidal shear
Desjacques, Vincent
2008-01-01
Large-scale structures originate from coherent motions induced by inhomogeneities in the primeval gravitational potential. Here, we investigate the two-point statistics of the second derivative of the potential, the tidal shear, under the assumption of Gaussianity. We derive an exact closed form expression for the angular averaged, two-point distribution of the shear components which is valid for an arbitrary Lagrangian separation. This result is used to write down the two-point statistics of the shear eigenvalues in compact form. Next, we examine the large-scale asymptotics of the correlation of the shear eigenvalues, and the alignment of the principal axes. The analytic results are in good agreement with measurements obtained from random realizations of the gravitational potential. Finally, we show that a number of two-point distributions of the shear eigenvalues are well approximated by Gaussian bivariates over a wide range of separation and smoothing scales. We speculate that the Gaussian approximation al...
Shear Senses and Viscous Dissipation of Layered Ductile Simple Shear Zones
Mulchrone, Kieran F.; Mukherjee, Soumyajit
2015-02-01
Velocity profiles and shear heat profiles for inclined, layered Newtonian simple shear zones are considered. Reverse fault-like simple shear of the boundaries and upward net pressure gradient act together in such shear zones. As the velocity of the boundary increases, the point of highest velocity shifts from the lower layer of less viscosity into the upper layer. The shear heat profile shows a temperature peak inside the lower layer. For a more viscous upper layer, the point of highest velocity is located inside the upper layer and shifts towards the upper boundary of the shear zone. The shear heat profile shows a maximum temperature within the upper layer. Depending on the flow parameters of the two layers, the slip rate of the boundary, and the dip and thickness of the shear zone, a shear sense in reverse to the relative movement of the shear zone boundaries may develop. These models can decipher thermo-kinematics of layered shear zones in plate-scale hot orogens.
Ring shear characteristics of waste rock materials in response to drainage and shear velocity
Lee, Choonoh; Jeong, Sueng Won; Cho, Yong-Chan
2015-04-01
The ring shear characteristics of Imgi waste materials collected from an abandoned mine deposit, Busan Metropolitan city, were investigated to examine the slope stability and mobility of failed masses. A series of ring shear tests were carried out to investigate the shear stress characteristics of waste materials under different drainage, consolidation and shearing speed conditions. The tests are performed at the same normal stress (16 kPa), but different drainage (drained and undrained conditions) and shearing speed (0.01, 0.1, 1, 10, 100 mm/sec) conditions. From the test results, we found that a ring shear stress is dependent on the drainage and the shearing speed conditions at the same normal stress. The materials tested typically exhibited a strain softening behavior. However, at the same shearing speed (especially for V crushing is also dependent on the drainage condition. Under drained conditions, the grain crushing has been observed in the shearing zone from the shearing surface to the bottom (i.e., ? 3.5 cm), but under undrained condition it has been observed only at the shearing surface (i.e., ? 1 cm).
Shear stress distribution due to shear and Rayleigh wave propagation at deep soil sites
International Nuclear Information System (INIS)
Earthquake strong motion at ground surface may be described as the combined result of body (compression and shear) waves and surface waves. In the course of earthquake engineering site response analyses, it is usually assumed that surface motions are a result of vertically propagating body waves. In studies of liquefaction potential, it is assumed that soil shear strains are a result of vertically propagating shear waves. However, shear strains are also caused by surface Rayleigh waves and solutions to strains from each source are derived and compared in the paper, and the results for shear strain in terms of surface acceleration and wave length are presented in non-dimensional form. The results of this investigation show that the distribution of soil shear strain as a function of depth below the ground surface is different depending upon whether shear waves or Rayleigh waves are assumed to be the source of horizontal motions at the ground surface. (Auth.)
Bartz, B; Collins, M; Stoddard, G; Appleton, A; Livingood, R; Sobcynski, H; Vogel, K D
2015-09-01
The purpose of this study was to evaluate the impact of nonpenetrating captive bolt stunning followed by electrical induction of cardiac arrest on veal calf welfare, veal quality, and blood yield. Ninety calves from the same farm were randomly assigned to 1 of 2 treatment groups in a balanced unpaired comparison design. The first treatment group (the "head-only" method-application of the pneumatic nonpenetrating stun to the frontal plate of the skull at the intersection of 2 imaginary lines extending from the lateral canthus to the opposite poll [CONTROL]) was stunned with a nonpenetrating captive bolt gun ( = 45). The second group ( = 45) was stunned with a nonpenetrating captive bolt gun followed by secondary electrical induction of cardiac arrest (the "head/heart" method-initial application of the pneumatic nonpenetrating captive bolt stun followed by 1 s application of an electrical stun to the ventral region of the ribcage directly caudal to the junction of the humerus and scapula while the stunned calf was in lateral recumbence [HEAD/HEART]). Stunning efficacy was the indicator of animal welfare used in this study. All calves were instantly rendered insensible by the initial stun and did not display common indicators of return to consciousness. For meat quality evaluation, all samples were collected from the 12th rib region of the longissimus thoracis. Meat samples were evaluated for color, drip loss, ultimate pH, cook loss, and Warner-Bratzler shear force. The L* values (measure of meat color lightness) were darker ( CONTROL group (47.10 ± 0.72). There were no differences ( > 0.05) observed in a* (redness) and b* (yellowness) values between treatments. No differences ( > 0.05) were observed in drip loss, ultimate pH, cook loss, and Warner-Bratzler shear force. The blood yield from the CONTROL group (7,217.9 ± 143.5 g) was greater ( CONTROL and HEAD/HEART groups with regard to animal welfare because the initial stun was effective in all calves. However, longissimus thoracis L* and blood yield were negatively impacted by the HEAD/HEART method. The data in this study suggest that secondary induction of cardiac arrest is not necessary with effective nonpenetrating captive bolt stunning in veal calves. PMID:26440354
IMAGE ANALYSIS FOR MODELLING SHEAR BEHAVIOUR
Directory of Open Access Journals (Sweden)
Philippe Lopez
2011-05-01
Full Text Available Through laboratory research performed over the past ten years, many of the critical links between fracture characteristics and hydromechanical and mechanical behaviour have been made for individual fractures. One of the remaining challenges at the laboratory scale is to directly link fracture morphology of shear behaviour with changes in stress and shear direction. A series of laboratory experiments were performed on cement mortar replicas of a granite sample with a natural fracture perpendicular to the axis of the core. Results show that there is a strong relationship between the fracture's geometry and its mechanical behaviour under shear stress and the resulting damage. Image analysis, geostatistical, stereological and directional data techniques are applied in combination to experimental data. The results highlight the role of geometric characteristics of the fracture surfaces (surface roughness, size, shape, locations and orientations of asperities to be damaged in shear behaviour. A notable improvement in shear understanding is that shear behaviour is controlled by the apparent dip in the shear direction of elementary facets forming the fracture.
Shear modulus of elasticity of the esophagus
DEFF Research Database (Denmark)
Yang, Jian; Liao, Donghua
2004-01-01
Experimental and diagnostic procedures like distension of a balloon catheter, bougie, and esophagogastroduodenoscopy can induce shear deformation in the esophageal wall. However, the shear modulus of the esophagus is yet unknown. The aim of this study was to determine the esophageal shear modulus and its dependence on the circumferential and longitudinal stresses and strains in the rat. The constitutive equation including the shear deformation based on a pseudo-strain-energy function was generated. Results were obtained using a new triaxial instrument to perform simultaneous torsion, inflation, and longitudinal stretching tests. The shear modulus varied with the inflation pressure and the longitudinal stretch ratio. The shear modulus at the longitudinal stretch ratio of 1.5 and between inflation pressures of 0 and 2.0 kPa ranged from 5.43 to 185.01 kPa. The mechanical constant of the esophagus showed that the esophageal wall was anisotropic with different stiffness in the circumferential, longitudinal, and the shear directions. The stiffness in the longitudinal direction was higher than in the circumferential direction (P < 0.001). This test can be extended for further mechanical remodeling experiments and for other tubular organs such as the small intestine or blood vessels.
A magnetorheological elastomer compressive and shear sensor
Ghafoorianfar, Nima; Gordaninejad, Faramarz
2015-04-01
A magnetorheological elastomer (MRE)-based wireless sensor is designed, developed and tested, which is capable of sensing compression and shear forces. The MRE wireless sensor system consists of a disk-shape MRE sample with two thin steel electrodes attached to both sides and two wires connected to electrodes. Electrical resistance of MRE sensor samples changes due to piezoresistance behavior of MRE as various axial and shear stresses are applied. Electrical resistance decreases as the applied compressive axial forces increases, on the other hand, the electrical resistance increases as the applied shear force increases. Different MRE sensor configurations are evaluated for design optimization.
Interfacial Slip in Sheared Polymer Blends
Lo, T S; Shnidman, Y; Li, W; Gersappe, D; Lo, Tak Shing; Mihajlovic, Maja; Shnidman, Yitzhak; Li, Wentao; Gersappe, Dilip
2004-01-01
We have developed a dynamic self-consistent field theory, without any adjustable parameters, for unentangled polymer blends under shear. Our model accounts for the interaction between polymers, and enables one to compute the evolution of the local rheology, microstructure and the conformations of the polymer chains under shear self-consistently. We use this model to study the interfacial dynamics in sheared polymer blends and make a quantitative comparison between this model and Molecular Dynamics simulations. We find good agreement between the two methods.
Shear viscosity of liquid mixtures: Mass dependence
International Nuclear Information System (INIS)
Expressions for zeroth, second, and fourth sum rules of transverse stress autocorrelation function of two component fluid have been derived. These sum rules and Mori's memory function formalism have been used to study shear viscosity of Ar-Kr and isotopic mixtures. It has been found that theoretical result is in good agreement with the computer simulation result for the Ar-Kr mixture. The mass dependence of shear viscosity for different mole fraction shows that deviation from ideal linear model comes even from mass difference in two species of fluid mixture. At higher mass ratio shear viscosity of mixture is not explained by any of the emperical model. (author)
Shear Excitation of Confined Colloidal Suspensions
Cohen, I; Weitz, D A; Cohen, Itai; Mason, Thomas G.; Weitz, David A.
2004-01-01
We show that geometric confinement dramatically affects the shear-induced configurations of dense mono-disperse colloidal suspensions; a new structure emerges, where layers of particles buckle to stack in a more efficient packing. The volume fraction in the shear zone is controlled by a balance between the viscous stresses and the osmotic pressure of a contacting reservoir of unsheared particles. We present a model that accounts for our observations and helps elucidate the complex interplay between particle packing and shear stress for confined suspensions.
Shear effects on crystalline structures of poly(L-lactide)
DEFF Research Database (Denmark)
Xiao, Peitao; Li, Hongfei
2013-01-01
The shearing effects of sheared polymer melts on their finally formed crystalline structures of poly(L-lactide) (PLLA) were investigated by means of small angle X-ray scattering (SAXS) and wide angle X-ray diffraction (WAXD). The results of WAXD prove that shear has no effects on the crystal structure of PLLA. The SAXS results demonstrate that both of the long period and the thickness of crystalline lamellae increase with rising shear rates when vertical to the shear direction, but remains constant when being parallel to the shear direction. The structural changes for samples prepared with different shear temperature or under the same shear strain but different shear rate were investigated. The mesophase of polymer melts and shearing effects on their pre-ordered phase turned out to be the key factor affecting the crystal structure of PLLA under different shearing conditions.
Shear thickening, frictionless and frictional rheologies
Mari, Romain; Morris, Jeffrey F; Denn, Morton M
2014-01-01
Particles suspended in a Newtonian fluid raise the viscosity and also generally give rise to a shear-rate dependent rheology. In particular, pronounced shear thickening is observed at large solid volume fractions. In a recent article (R. Seto, R. Mari, J. F. Morris, and M. M. Denn., Phys. Rev. Lett., 111:218301, 2013) we have considered the minimum set of components to reproduce the experimentally observed shear thickening behavior, including Discontinuous Shear Thickening (DST). We have found frictional contact forces to be essential, and were able to reproduce the experimental behavior by a simulation including this physical ingredient. In the present article, we thoroughly investigate the effect of friction and express it in the framework of the jamming transition. The viscosity divergence at the jamming transition has been a well known phenomenon in suspension rheology, as reflected in many empirical laws for the viscosity. Friction can affect this divergence, and in particular the jamming packing fractio...
Immiscible blend morphology after shear and elongation
Batch, Gibson L.; Trifkovic, Milana; Hedegaard, Aaron; Macosko, Christopher W.
2015-05-01
This work examines the role of shear and extensional strain on immiscible blend morphology, namely domain size, orientation, and co-continuity. The domain size reduces with surface tension similar to what is observed with isolated droplets. The domain size is shown to increase with shear strain due to coalescence. Hence the best mixing is found with low shear strains, i.e. low rates of shear and short durations of time. Extensional strain (extrusion draw ratio DR) reduces phase width and thickness with a DR-0.5 dependence, suggesting the transformation to a fibrilar morphology. The critical draw ratio for morphology transformation is approximately 7, in agreement with observations by Grace for droplet breakup in elongation. Fibrilar morphology is also consistent with a large increase in strain-to-break in the drawn film and with observed creep and optical scattering behavior.
Mesoscale Elucidation of Biofilm Shear Behavior
Barai, Pallab; Mukherjee, Partha P
2015-01-01
Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under externally applied shear load is analyzed. Strain stiffening type behavior is readily observed under high strain loads due to the unfolding of chains within soft polymeric substrate. Sustained shear loading of the biofilm network results in strain localization along the diagonal direction. Rupture of the soft polymeric matrix can potentially reduce the intercellular interaction between the bacterial cells. Evolution of stiffness within the biofilm network under shear reveals two regions: a) initial increase in stiffness due to strain stiffe...
Shear Flow induced Electrical Current Generation
Ohl, Claus-Dieter; Gonzalez Avila, Silvestre Roberto; Song, Chaolong; Dung, Luong Trung
2013-11-01
Electro-osmotic flows are driven by an electric potential difference along a channel where the driving force is acting very close to the boundary at the electric double layer (EDL). The charge separation within the EDL gives rise to an electric current. Conversely, one may expect that a strong shear flow can induce an electric current that could be picked up with electrodes and a closed circuit. Previous experiments relied on a steady free jet at a nozzle exit driven by a strong pressure gradient. Here we utilize a laser induced cavitation bubble near an electrode equipped surface to generate strong shear from the impinging jet. Correlation of high-speed recordings of the spreading jet with current measurements reveals that the shear stress is causing the electric current. We make an attempt to calibrate this sensor in a better defined shear flow within a microfluidic channel.
Torsion and shear stresses in ships
Shama, Mohamed
2010-01-01
This book covers an area of ship structure analysis and design that has not been exhaustively examined by other references. It presents the basic concepts of the methods and procedures required to calculate torsion and shear stresses in ship structures.
Shear stress distribution due to shear and Rayleigh wave propagation at deep soil sites
International Nuclear Information System (INIS)
Earthquake strong motion at ground surface may be described as the combined result of body (compression and shear) waves and surface waves. In the course of earthquake engineering site response analyses, it is usually assumed that surface motions are a result of vertically propagating body waves. In studies of liquefaction potential, it is assumed that soil shear strains are a result of vertically propagating shear waves. However, shear strains are also caused by surface Rayleigh waves and solutions to strains from each source are derived and compared in the paper, and the results for shear strain in terms of surface acceleration and wave length are presented in non-dimensional form. The results of this investigation show that the distribution of soil shear strain as a function of depth below the gound surface is different depending upon whether shear waves or Rayleigh waves are assumed to be the source of horizontal motions at the ground surface. It is shown that the shear strains derived from Rayleigh waves are greater near the surface but decrease faster with depth than the shear strains derived from vertically propagating shear waves. It is noted that the more rapid attenuation of shear strains with depth as predicted by Rayleigh wave theory is more consistent with observed cases of soil liquefaction which are usually limited to shallow depths, generally not in excess of 10 to 20 meters. On the contrary, vertical shear propagation theory predicts liquefaction occurring at loose sand sites at much greater depths. The differences are significant enough to influence the decision regarding liquefaction potential of a soil site
Wittmer, J. P.; Xu, H; Benzerara, O.; Baschnagel, J
2015-01-01
The shear stress relaxation modulus $G(t)$ may be determined from the shear stress $\\tau(t)$ after switching on a tiny step strain $\\gamma$ or by inverse Fourier transformation of the storage modulus $G^{\\prime}(\\omega)$ or the loss modulus $G^{\\prime\\prime}(\\omega)$ obtained in a standard oscillatory shear experiment at angular frequency $\\omega$. It is widely assumed that $G(t)$ is equivalent in general to the equilibrium stress autocorrelation function $C(t) = \\beta V \\la...
Sheared-flow Modes in Toroidal Geometry
International Nuclear Information System (INIS)
Using a Fourier-Bessel representation for the fluctuating (turbulent) electrostatic potential, an equation governing the sheared-flow modes in toroidal geometry is derived from the gyrokinetic Poisson equation, where both the adiabatic and non-adiabatic responses of the electrons are taken into account. It is shown that the principal geometrical effect on sheared-flow modes of the electrostatic potential is due to the flux-surface average of 1/B, where B is the magnetic field strength
Adiabatic shearing study by dynamic compression
International Nuclear Information System (INIS)
The adiabatic shearing study was carried out by dynamic compression tests made on a Hopkinson's rod. The deformation rate is around 2x103 s-1; the materials studied are in martensitic steel and a titanium alloy, at ambient temperature and up to 5000C. Microscopic observations show how the break appears, associated with the development of adiabatic shearing bands. The mechanical results are discussed and compared against the theoretical approaches
Shear viscosity in antikaon condensed matter
Nandi, Rana; Banik, Sarmistha; Bandyopadhyay, Debades
2009-01-01
We investigate the shear viscosity of neutron star matter in the presence of an antikaon condensate. The electron and muon number densities are reduced due to the appearance of a $K^-$ condensate in neutron star matter, whereas the proton number density increases. Consequently the shear viscosity due to scatterings of electrons and muons with themselves and protons is lowered compared to the case without the condensate. On the other hand, the contribution of proton-proton co...
Critical packing in granular shear bands
Fazekas, S.; Török, J.; Kertész, J.
2006-01-01
In a realistic three-dimensional setup, we simulate the slow deformation of idealized granular media composed of spheres undergoing an axisymmetric triaxial shear test. We follow the self-organization of the spontaneous strain localization process leading to a shear band and demonstrate the existence of a critical packing density inside this failure zone. The asymptotic criticality arising from the dynamic equilibrium of dilation and compaction is found to be restricted to t...
Shear viscosity of degenerate electron matter
International Nuclear Information System (INIS)
We calculate the partial electron shear viscosity ?ee limited by electron-electron collisions in a strongly degenerate electron gas taking into account the Landau damping of transverse plasmons. The Landau damping strongly suppresses ?ee in the domain of ultrarelativistic degenerate electrons and modifies its temperature behavior. The efficiency of the electron shear viscosity in the cores of white dwarfs and envelopes of neutron stars is analyzed
Assessment of Shear Strength in Silty Soils
Directory of Open Access Journals (Sweden)
Stefaniak Katarzyna
2015-06-01
Full Text Available The article presents a comparison of shear strength values in silty soils from the area of Pozna?, determined based on selected Nkt values recommended in literature, with values of shear strength established on the basis of Nkt values recommended by the author. Analysed silty soils are characterized by the carbonate cementation zone, which made it possible to compare selected empirical coefficients both in normally consolidated and overconsolidated soils
Shear turbulence beneath the solar tachocline
Schatzman, E.; Zahn, J. -P.; Morel, P.
2000-01-01
Helioseismic inversions of the Sun's internal angular velocity profile show that the rotation changes from differential in latitude in the convection zone to almost uniform in the radiative region below. The transition occurs in a thin layer, the tachocline, which is the seat of strong shear in the vertical direction. In this Note we examine whether this rotation profile can lead to shear turbulence at the top of the radiation zone. By using the standard solar model, we show...
Poloidal Rotation in TFTR Reversed Shear Plasmas
Bell, R. E.; Levinton, F. M.; Batha, S. H.; Synakowski, E. J.; Zarnstorff, M. C.
1998-08-01
A bifurcation in the core poloidal rotation of carbon impurity ions in the Tokamak Fusion Test Reactor (TFTR) has been observed prior to the transport bifurcation associated with enhanced reverse shear plasmas. In a narrow radial region of the plasma, the impurity ion poloidal rotation reverses direction. This poloidal flow is associated with the establishment of a large negative radial electric field with strong shear. The measured poloidal velocities before, during, and after this precursor differ from neoclassical predictions.
Banded spatiotemporal chaos in sheared nematogenic fluids
Chakraborty, Debarshini; Dasgupta, Chandan; Sood, A. K.
2010-01-01
We present the results of a numerical study of a model of the hydrodynamics of a sheared nematogenic fluid, taking into account the effects of order parameter stresses on the velocity profile, but allowing spatial variations only in the gradient direction. When parameter values are such that the stress from orientational distortions is comparable to the bare viscous stress, the system exhibits steady states with the characteristics of shear banding. In addition, nonlinearity...
Wrinkling of microcapsules in shear flow
Finken, R; Finken, Reimar; Seifert, Udo
2006-01-01
Elastic capsules can exhibit short wavelength wrinkling in external shear flow. We analyse this instability of the capsule shape and use the length scale separation between the capsule radius and the wrinkling wavelength to derive analytical results both for the threshold value of the shear rate and for the critical wave-length of the wrinkling. These results can be used to deduce elastic parameters from experiments.
Avalanches in anisotropic sheared granular media
Peña, Andrés A.; Mcnamara, Sean; Lind, Pedro G.; Herrmann, Hans J.
2008-01-01
We study the influence of particle shape anisotropy on the occurrence of avalanches in sheared granular media. We use molecular dynamic simulations to calculate the relative movement of two tectonic plates. % with transform boundaries. Our model considers irregular polygonal particles constituting the material within the shear zone. We find that the magnitude of the avalanches is approximately independent on particle shape and in good agreement with the Gutenberg-Richter law...
Critical packing in granular shear bands
Fazekas, S; Kertész, J
2006-01-01
Relying on three-dimensional distinct element simulations of axisymmetric triaxial shear tests with spherical grains we demonstrate the existence of a critical volume fraction inside shear bands. This critical state is found to be independent of the initial conditions but dependent on the microscopic friction coefficient. We show that at high friction coefficient the critical packing density converges to a value which can be identified with a \\emph{dynamic random loose packing} limit.
Shear reinforced beams in autoclaved aerated concrete
DEFF Research Database (Denmark)
Cornelius, Thomas
2010-01-01
Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different combinations of reinforcement and for variable slenderness ratios. Theoretical approaches will be evaluated and compared with the test results of several test series. The load bearing capacity of shear reinforce...
Shear instability of a gyroid diblock copolymer
DEFF Research Database (Denmark)
Eskimergen, Rüya; Mortensen, Kell; Vigild, Martin Etchells
2005-01-01
The stability of the gyroid phase of diblock copolymers has been studied using combined oscillatory shear and small-angle neutron scattering (SANS) techniques. It is shown that the gyroid phase of polystyrene-polyisoprene (PS-PI) is unstable when exposed to combined large-amplitude and high-frequency shear deformations. The bicontinuous cubic gyroid structure (G) transforms to the hexagonally cylinder phase (HEX). The transition is perfectly reversible, but with a significant difference in time ...
Punching shear capacity of reinforced concrete slabs with headed shear studs
DEFF Research Database (Denmark)
Hoang, Linh Cao; Pop, Anamaria
2015-01-01
Punching shear in slabs is analogous to shear in beams. Despite this similarity, current design codes provide distinctly different methods for the design of shear reinforcement in the two situations. For example, the Eurocode method for beam shear design is founded on the theory of rigid plasticity. To design shear reinforcement in slabs, on the other hand, the engineer must settle for an empirical equation. The aim of the study reported is to demonstrate that it is possible in a simple manner to design shear reinforcement in slabs based on the same rigid-plasticity foundation as for beam shear design. For this purpose, an extension of the upper-bound crack sliding model is proposed. This involves analysis of sliding mechanisms in yield lines developed both within and outside the zone with shear reinforcement. Various types of headed shear studs were considered. The results obtained using the model were compared with a large number of published test results, and satisfactory agreements were found.
Shear strength of non-shear reinforced concrete elements : Part 2. T- beams
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the plastic shear strength of non shear reinforced T-beams.The influence of an un-reinforced flange on the shear capacity is investigated by considering a failure mechanism involving crack sliding in the web and a kind of membrane action over an effective width of the flange. The position of the crack in which sliding takes place is determined by the crack sliding model developed by Jin-Ping Zhang. The theoretical calculations are compared with test results reported in the literature. A good agreement has been found.A simplified method to calculate the shear capacity of T-beams is presented.
Two-state shear diagrams for complex fluids in shear flow
Olmsted, P D
1999-01-01
The possible ``phase diagrams'' for shear-induced phase transitions between two phases are collected. We consider shear-thickening and shear-thinning fluids, under conditions of both common strain rate and common stress in the two phases, and present the four fundamental shear stress vs. strain-rate curves and discuss their concentration dependence. We outline how to construct more complicated phase diagrams, discuss in which class various experimental systems fall, and sketch how to reconstruct the phase diagrams from rheological measurements.
Influence of Shear on Rotation Capacity of Reinforced Concrete Members Without Shear Reinforcement
Vaz Rodrigues, Rui; Muttoni, Aurelio; Fernández Ruiz, Miguel
2010-01-01
The influence of shear on the rotation capacity of one-way slabs without shear reinforcement is investigated in this paper by means of an experimental study. The experimental program consisted of 11 slab strips 8400 mm (331 in.) long and 450 mm (17.7 in.) thick with a flexural reinforcement ratio of 0.79%. The rotation capacity was investigated for various values of the shear span and for two types of flexural reinforcement (hot-rolled and cold-worked bars). The specimens developed shear fail...
Fan-structure shear rupture mechanism as a source of shear rupture rockbursts
Scientific Electronic Library Online (English)
B.G., Tarasov.
2014-10-01
Full Text Available This paper proposes the further development of a recently identified shear rupture mechanism (fan mechanism) that elucidates a paradoxical feature of hard rocks - the possibility of shear rupture propagation through a highly confined intact rock mass at shear stresses that can be significantly less [...] than frictional strength. In the fan mechanism, failure is associated with consecutive creation of small slabs (known as 'domino blocks') from the intact rock in the rupture tip, driven by a fan-shaped domino structure representing the rupture head. The fan head combines such unique features as extremely low shear resistance, self-sustaining stress intensification, and self-unbalancing conditions. Consequently, the failure process caused by the mechanism is inevitably spontaneous and violent. Physical and mathematical models explain unique and paradoxical features of the mechanism, which can be generated in primary ruptures and segmented faults. The fan mechanism provides a novel point of view for understanding the nature of spontaneous failure processes, including shear rupture rockbursts. The process explains, in particular, features of shear rupture rockbursts such as activation at great depths, generation of new shear ruptures in intact rock mass, nucleation of hypocentres at significant distances from the excavation, shear rupture development at low shear stresses, and abnormal rupture violence.
Shear at the Base of the Oceanic Mixed Layer Generated by Wind Shear Alignment
Brannigan, Liam; Lenn, Yueng-Djern; Rippeth, Tom P.; McDonagh, Elaine; Teresa K. Chereskin; Sprintall, Janet
2013-01-01
Observations are used to evaluate a simple theoretical model for the generation of near-inertial shear spikes at the base of the open ocean mixed layer when the upper ocean displays a two-layer structure. The model predicts that large changes in shear squared can be produced by the alignment of the wind and shear vectors. A climatology of stratification and shear variance in Drake Passage is presented, which shows that these assumptions are most applicable to summer, fall, and spring but are ...
A Controlled Shear Decorrelation Experiment (CSDX)
Tynan, George
1999-11-01
The controlled shear de-correlation experiment (CSDX) is being designed to study the effect of sheared flows on: (1) known linear pressure gradient-driven drift and/or effective gravity-driven flute eigenmodes; (2) the nonlinear three-wave coupling of a finite number of large amplitude coherent modes; and (3) on the rate of electrostatic turbulent fluctuation energy cascades. This research is motivated by magnetic confinement experiments and theory which suggest that sheared E x B shear flows lead to a nonlinear de-correlation of plasma turbulence. The plasma state (i.e. quiescent, single small-amplitude drift wave, nonlinearly coupled modes, or strongly turbulent) will be controlled by varying the magnetic field strength, collisionality, parallel current, and/or effective gravity due to solid-body plasma rotation driven by azimuthal ExB drifts. The radial electric field strength and shear rate will be controlled independently of the plasma state by the application of externally controlled voltages to concentric annular rings which will form the ends of the experimental region. Diagnostics include azimuthal, radial, and axial Langmuir probe arrays, laser induced flourescence (LIF) for ion temperature and equilibrium ExB flow velocities. Bi-spectral analysis techniques will be used to measure k-space resolved linear growth rates and nonlinear energy cascading due to three-wave coupling in the presence of flow shear. Designs and experimental plans will be presented and discussed.
Analysis of shear banding in twelve materials
Batra, R. C.; Kim, C. H.
The problem of the initiation and growth of shear bands in 12 different materials, namely, OFHC copper, Cartridge brass, Nickel 200, Armco IF (interstitial free) iron, Carpenter electric iron, 1006 steel, 2024-T351 aluminum, 7039 aluminum, low alloy steel, S-7 tool steel, Tungsten alloy, and Depleted Uranium (DU -0.75 Ti) is studied with the objectives of finding out when a shear band initiates, and upon what parameters does the band width depend. The nonlinear coupled partial differential equations governing the overall simple shearing deformations of a thermally softening viscoplastic block are analyzed. It is assumed that the thermomechanical response of these materials can be adequately represented by the Johnson-Cook law, and the only inhomogeneity present in the block is the variation in its thickness. The effect of the defect size on the initiation and subsequent growth of the band is also studied. It is found that, for each one of these 12 materials, the deformation has become nonhomogeneous by the time the maximum shear stress occurs. Also the band width, computed when the shear stress has dropped to 85 percent of its peak value, does not correlate well with the thermal conductivity of the material. The band begins to grow rapidly when the shear stress has dropped to 90 percent of its maximum value.
Wall shear stress in collapsed tubes
Naili, S.; Ribreau, C.
1999-01-01
A small flexural wall rigidity brings unique features to cross-sectional shapes and blood flow within veins, which are characterised by a non-uniform hemodynamical environment acting upon endothelial cells. Velocity fields and related wall shear stress were numerically determined for a large number of conditions, assuming a fully developed, steady, incompressible laminar flow through an uniform smooth pipe with a constant cross-section. It was shown that the flatness greatly influences the resulting distribution of the wall shear stresses along the lumen perimeter. For instance, under a steady longitudinal pressure gradient at about 500 Pascal per meter inside a constant oval-shaped tube, with a lumen perimeter of the order of 5 × 10^{-2} meter, the maximum wall shear stress is found at about 2 Pascal where the local curvature is minimal. On the other hand, the minimal wall shear stress of the order of 1 Pascal is found where the local curvature is maximal. Clear indications have been reported showing that the hemodynamical wall shear stress does alter endothelial cell morphology and orientation. These results are being used for developing an experimental set-up in order to locally map out the characteristic shear stresses looking for endothelial shape modifications whenever a viscous fluid flow is applied.
Surface instability of sheared soft tissues
Destrade, M; Prikazchikov, D A; Saccomandi, G
2008-01-01
When a block made of an elastomer is subjected to large shear, its surface remains flat. When a block of biological soft tissue is subjected to large shear, it is likely that its surface in the plane of shear will buckle (apparition of wrinkles). One factor that distinguishes soft tissues from rubber-like solids is the presence -- sometimes visible to the naked eye -- of oriented collagen fibre bundles, which are stiffer than the elastin matrix into which they are embedded but are nonetheless flexible and extensible. Here we show that the simplest model of isotropic nonlinear elasticity, namely the incompressible neo-Hookean model, suffers surface instability in shear only at tremendous amounts of shear, i.e., above 3.09, which corresponds to a 72 degrees angle of shear. Next we incorporate a family of parallel fibres in the model and show that the resulting solid can be either reinforced or strongly weakened with respect to surface instability, depending on the angle between the fibres and the direction of s...
Accurate shear measurement with faint sources
Energy Technology Data Exchange (ETDEWEB)
Zhang, Jun; Foucaud, Sebastien [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, 955 Jianchuan road, Shanghai, 200240 (China); Luo, Wentao, E-mail: betajzhang@sjtu.edu.cn, E-mail: walt@shao.ac.cn, E-mail: foucaud@sjtu.edu.cn [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai, 200030 (China)
2015-01-01
For cosmic shear to become an accurate cosmological probe, systematic errors in the shear measurement method must be unambiguously identified and corrected for. Previous work of this series has demonstrated that cosmic shears can be measured accurately in Fourier space in the presence of background noise and finite pixel size, without assumptions on the morphologies of galaxy and PSF. The remaining major source of error is source Poisson noise, due to the finiteness of source photon number. This problem is particularly important for faint galaxies in space-based weak lensing measurements, and for ground-based images of short exposure times. In this work, we propose a simple and rigorous way of removing the shear bias from the source Poisson noise. Our noise treatment can be generalized for images made of multiple exposures through MultiDrizzle. This is demonstrated with the SDSS and COSMOS/ACS data. With a large ensemble of mock galaxy images of unrestricted morphologies, we show that our shear measurement method can achieve sub-percent level accuracy even for images of signal-to-noise ratio less than 5 in general, making it the most promising technique for cosmic shear measurement in the ongoing and upcoming large scale galaxy surveys.
Shear induced structures in crystallizing cocoa butter
Mazzanti, Gianfranco; Guthrie, Sarah E.; Sirota, Eric B.; Marangoni, Alejandro G.; Idziak, Stefan H. J.
2004-03-01
Cocoa butter is the main structural component of chocolate and many cosmetics. It crystallizes in several polymorphs, called phases I to VI. We used Synchrotron X-ray diffraction to study the effect of shear on its crystallization. A previously unreported phase (phase X) was found and a crystallization path through phase IV under shear was observed. Samples were crystallized under shear from the melt in temperature controlled Couette cells, at final crystallization temperatures of 17.5^oC, 20^oC and 22.5^oC in Beamline X10A of NSLS. The formation of phase X was observed at low shear rates (90 s-1) and low crystallization temperature (17.5^oC), but was absent at high shear (720 s-1) and high temperature (20^oC). The d-spacing and melting point suggest that this new phase is a mixture rich on two of the three major components of cocoa butter. We also found that, contrary to previous reports, the transition from phase II to phase V can happen through the intermediate phase IV, at high shear rates and temperature.
Magnetized stratified rotating shear waves
Salhi, A.; Lehner, T.; Godeferd, F.; Cambon, C.
2012-02-01
We present a spectral linear analysis in terms of advected Fourier modes to describe the behavior of a fluid submitted to four constraints: shear (with rate S), rotation (with angular velocity ?), stratification, and magnetic field within the linear spectral theory or the shearing box model in astrophysics. As a consequence of the fact that the base flow must be a solution of the Euler-Boussinesq equations, only radial and/or vertical density gradients can be taken into account. Ertel's theorem no longer is valid to show the conservation of potential vorticity, in the presence of the Lorentz force, but a similar theorem can be applied to a potential magnetic induction: The scalar product of the density gradient by the magnetic field is a Lagrangian invariant for an inviscid and nondiffusive fluid. The linear system with a minimal number of solenoidal components, two for both velocity and magnetic disturbance fields, is eventually expressed as a four-component inhomogeneous linear differential system in which the buoyancy scalar is a combination of solenoidal components (variables) and the (constant) potential magnetic induction. We study the stability of such a system for both an infinite streamwise wavelength (k1=0, axisymmetric disturbances) and a finite one (k1?0, nonaxisymmetric disturbances). In the former case (k1=0), we recover and extend previous results characterizing the magnetorotational instability (MRI) for combined effects of radial and vertical magnetic fields and combined effects of radial and vertical density gradients. We derive an expression for the MRI growth rate in terms of the stratification strength, which indicates that purely radial stratification can inhibit the MRI instability, while purely vertical stratification cannot completely suppress the MRI instability. In the case of nonaxisymmetric disturbances (k1?0), we only consider the effect of vertical stratification, and we use Levinson's theorem to demonstrate the stability of the solution at infinite vertical wavelength (k3=0): There is an oscillatory behavior for ?>1+|K2/k1|, where ?=St is a dimensionless time and K2 is the radial component of the wave vector at ?=0. The model is suitable to describe instabilities leading to turbulence by the bypass mechanism that can be relevant for the analysis of magnetized stratified Keplerian disks with a purely azimuthal field. For initial isotropic conditions, the time evolution of the spectral density of total energy (kinetic + magnetic + potential) is considered. At k3=0, the vertical motion is purely oscillatory, and the sum of the vertical (kinetic + magnetic) energy plus the potential energy does not evolve with time and remains equal to its initial value. The horizontal motion can induce a rapid transient growth provided K2/k1?1. This rapid growth is due to the aperiodic velocity vortex mode that behaves like Kh/kh where kh(?)=[k12+(K2-k1?)2]1/2 and Kh=kh(0). After the leading phase (?>K2/k1?1), the horizontal magnetic energy and the horizontal kinetic energy exhibit a similar (oscillatory) behavior yielding a high level of total energy. The contribution to energies coming from the modes k1=0 and k3=0 is addressed by investigating the one-dimensional spectra for an initial Gaussian dense spectrum. For a magnetized Keplerian disk with a purely vertical field, it is found that an important contribution to magnetic and kinetic energies comes from the region near k1=0. The limit at k1=0 of the streamwise one-dimensional spectra of energies, or equivalently, the streamwise two-dimensional (2D) energy, is then computed. The comparison of the ratios of these 2D quantities with their three-dimensional counterparts provided by previous direct numerical simulations shows a quantitative agreement.
Evolution of circular shear layers
International Nuclear Information System (INIS)
The Kelvin-Helmholtz instability is a generic pathway for the formation of coherent vortical structures in quasi-neutral and non-neutral plasmas, as well as in ordinary fluids. Both plasma and fluid experiments have demonstrated rich bifurcation sequences accompanied by topological changes in the distribution of the coherent structures, in addition to various oscillating, quasiperiodic or chaotic states. The authors have performed both analytical and numerical studies which demonstrate that such transitions can be accurately described by reducing the system of slightly viscous, forced Navier-Stokes equations to a system of ordinary differential equations of few degrees of freedom. The simplest case studied so far in detail leads to an equation of the Landau type describing the saturation of the Kelvin-Helmholtz instability in terms of the amplitude A(?) of the most unstable mode, with ? a slow time scale. In this case the dynamical equation assumes the form ?A?= ?A + ?A2A*. The complex coefficients of this reduced equation are computed by numerical solution of appropriate eigenvalue problems. In conjunction with these analytical calculations, a highly accurate spectral code has been used to directly simulate the forced, circular shear flows. Both the analytical and the numerical results are in excellent agreement with fluid experiments and show the same qualitative behavior as the plasma experiments where a detailed quantitative comparison is difficult due to limitations in the experimental information. The two approaches supplement each other in predicting the transition to states of ever increasing complexity, even beyond regimes that have so far been experimentally accessible
Shear-enhanced compaction in viscoplastic rocks
Yarushina, V. M.; Podladchikov, Y. Y.
2012-04-01
The phenomenon of mutual influence of compaction and shear deformation was repeatedly reported in the literature over the past years. Dilatancy and shear-enhanced compaction of porous rocks were experimentally observed during both rate-independent and rate-dependent inelastic deformation. Plastic pore collapse was preceding the onset of dilatancy and shear-enhanced compaction. Effective bulk viscosity is commonly used to describe compaction driven fluid flow in porous rocks. Experimental data suggest that bulk viscosity of a fluid saturated rock might be a function of both the effective pressure and the shear stress. Dilatancy and shear-enhanced compaction can alter the transport properties of rocks through their influence on permeability and compaction length scale. Recent investigations show that shear stresses in deep mantle rocks can be responsible for spontaneous development of localized melt-rich bands and segregation of small amounts of melt from the solid rock matrix through shear channeling instability. Usually it is assumed that effective viscosity is a function of porosity only. Thus coupling between compaction and shear deformation is ignored. Spherical model which considers a hollow sphere subjected to homogeneous tractions on the outer boundary as a representative elementary volume succeeded in predicting the volumetric compaction behavior of porous rocks and metals to a hydrostatic pressure in a wide range of porosities. Following the success of this simple model we propose a cylindrical model of void compaction and decompaction due to the non-hydrostatic load. The infinite viscoplastic layer with a cylindrical hole is considered as a representative volume element. The remote boundary of the volume is subjected to a homogeneous non-hydrostatic load such that plane strain conditions are fulfilled through the volume. At some critical values of remote stresses plastic zone develops around the hole. The dependence of the effective bulk viscosity on the properties of individual components as well as on the stress state is examined. We show that bulk viscosity is a function of porosity, effective pressure and shear stress. Decreasing porosity tends to increase bulk viscosity whereas increasing shear stress and increasing effective pressure reduce it.
Shear Localization and Comminution of Granular and Fragmented Silicon Carbide
Shih, C.; Nesterenko, V.; Meyers, M.
1997-01-01
Granular and pre-fractured bulk silicon carbide were subjected to high strain, high-strain-rate deformation by radial symmetric collapse of a thick-wall cylinder. Profuse shear-band formation was observed, indicating the deformation had inhomogeneous characteristics. The granular silicon carbide had lower shear-band displacement, spacing between shear bands and thickness of shear bands than the pre-factured silicon carbide. Bimodal particle size distribution was seen inside the shear bands fo...
Scientific Electronic Library Online (English)
Gaspar Manuel, Parra-Bracamonte; Ana María, Sifuentes-Rincón; Williams, Arellano-Vera; Juan Gabriel, Magaña-Monforte; José Alberto, Ramírez-De León; Gonzalo, Velázquez.
2014-04-01
Full Text Available La suavidad de la carne bovina es un rasgo importante para la satisfacción del consumidor y es la principal característica asociada a su palatabilidad, por lo que es importante evaluar su variabilidad en diferentes razas bovinas. Un experimento fue diseñado para evaluar la Fuerza de Corte de Warner- [...] Bratzler (FCWB) de carne del ojo de la costilla de bovinos Brangus rojos y su aceptabilidad. La suavidad de la carne fue evaluada mediante la FCWB; además, se realizó una evaluación de preferencia de consumo para estimar cuantitativamente la suavidad, jugosidad, sabor, término y aceptación general de los cortes evaluados. La media de la FCWB fue 5.03 kg ± 0.93 kg, lo que teóricamente representa una carne dura. En la distribución de las muestras se registraron 21 % y 11 % de cortes, respectivamente, de carne moderadamente suave y suave. La condición de los animales (toros o novillos) no fue significativa para la FCWB (p > 0.5). Todas las características evaluadas en la evaluación hedónica tuvieron alrededor de 6 puntos de un total de 8 (8 era mejor). La suavidad, jugosidad y sabor mostraron una correlación alta y significativa (p Abstract in english Beef tenderness is an important trait in consumer satisfaction and has been considered as the main trait for palatability, for which reason it is important to evaluate its variability in different cattle breeds. An experiment was designed to evaluate the Warner Bratzler Shear Force (WBSF) of Red Bra [...] ngus cattle rib eye steaks and consumer acceptance. The tenderness of beef rib eye steaks was evaluated by the WBSF. A consumer preference evaluation test was carried out to quantitatively estimate tenderness, juiciness, flavor, doneness and general acceptance of the evaluated steaks. Mean WBSF was 5.03 kg ± 0.93 kg, theoretically indicating a tough beef. The distribution of the samples showed 21 % and 11 % of moderately tender and tender beef cuts, respectively. Cattle condition (bulls and steers) was not significant for the WBSF (p > 0.5). All the traits evaluated in the hedonic evaluation had approximately 6 points of a total of 8 (8 was best). Tenderness, juiciness and flavor presented a high and significant correlation (p
Shear flexoelectric coefficient ?1211 in polyvinylidene fluoride
Zhang, Shuwen; Xu, Minglong; Liang, Xu; Shen, Shengping
2015-05-01
Defined as a strain gradient-induced electric polarization, flexoelectricity exists in all dielectric materials. The coefficient that exists between the strain gradient and the electric polarization defines the flexoelectric coefficient tensor. The tensor components along the longitudinal and transverse directions have been studied widely. However, little progress has been reported on flexoelectric properties in the shear direction to date. In this work, a novel method for measurement of the shear flexoelectric coefficient ?1211 of polyvinylidene fluoride is presented. An experiment is conducted on a tubular unpolarized specimen, where shear strain gradient is generated along the radial direction by applying torque to the ends of the tube-shaped specimen. Dynamic torque is exerted on specimens with a static bias value and at different frequencies. The generated shear strain gradient is calculated via finite element analysis and the corresponding induced electrical polarization is measured using a charge amplifier. The shear flexoelectric coefficient ?1211 is found to have an average value of 7.318 × 10-10 C/m at room temperature. The experimental results show good agreement with the theoretical predictions and indicate the potential value of this material property for electromechanical device fabrication.
Review article: Cosmology with cosmic shear observations
Kilbinger, Martin
2014-01-01
Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...
Pressure-shear experiments on granular materials.
Energy Technology Data Exchange (ETDEWEB)
Reinhart, William Dodd (Sandia National Laboratories, Albuquerque, NM); Thornhill, Tom Finley, III (, Sandia National Laboratories, Albuquerque, NM); Vogler, Tracy John; Alexander, C. Scott (Sandia National Laboratories, Albuquerque, NM)
2011-10-01
Pressure-shear experiments were performed on granular tungsten carbide and sand using a newly-refurbished slotted barrel gun. The sample is a thin layer of the granular material sandwiched between driver and anvil plates that remain elastic. Because of the obliquity, impact generates both a longitudinal wave, which compresses the sample, and a shear wave that probes the strength of the sample. Laser velocity interferometry is employed to measure the velocity history of the free surface of the anvil. Since the driver and anvil remain elastic, analysis of the results is, in principal, straightforward. Experiments were performed at pressures up to nearly 2 GPa using titanium plates and at higher pressure using zirconium plates. Those done with the titanium plates produced values of shear stress of 0.1-0.2 GPa, with the value increasing with pressure. On the other hand, those experiments conducted with zirconia anvils display results that may be related to slipping at an interface and shear stresses mostly at 0.1 GPa or less. Recovered samples display much greater particle fracture than is observed in planar loading, suggesting that shearing is a very effective mechanism for comminution of the grains.
Shear melting of confined solid monolayer films
International Nuclear Information System (INIS)
Strain-induced melting of solid phases in a prototypal slit pore [a monatomic fluid constrained between two plane-parallel walls made up like atoms fixed in the configuration of the (100) plane of the face-centered cubic lattice] is investigated by Monte Carlo calculations in the ''isostress-isostrain'' ensemble where the thermodynamic state of the pore phase is uniquely determined by a fixed number of molecules, constant load or normal stress and constant temperature. If the walls are properly aligned laterally, a commensurate solid phase can form epitaxially. Moving the walls out of alignment (shear strain) creates a distorted solid, which reacts (shear stress) by tending to realign the walls. If the shear strain is increased beyond a critical value, the solid begins to melt. However, melting is a continuous transition which does not immediately lead to a normal liquid, but rather a disordered phase that sustains a non-negligible shear stress. Shear melting is contrasted to ordinary melting at constant normal stress, which appears to be a first-order transition
Colloidal Aggregate Structure under Shear by USANS
Chatterjee, Tirtha; van Dyk, Antony K.; Ginzburg, Valeriy V.; Nakatani, Alan I.
2015-03-01
Paints are complex formulations of polymeric binders, inorganic pigments, dispersants, surfactants, colorants, rheology modifiers, and other additives. A commercially successful paint exhibits a desired viscosity profile over a wide shear rate range from 10-5 s-1 for settling to >104 s-1 for rolling, and spray applications. Understanding paint formulation structure is critical as it governs the paint viscosity profile. However, probing paint formulation structure under shear is a challenging task due to the formulation complexity containing structures with different hierarchical length scales and their alterations under the influence of an external flow field. In this work mesoscale structures of paint formulations under shear are investigated using Ultra Small-Angle Neutron Scattering (rheo-USANS). Contrast match conditions were utilized to independently probe the structure of latex binder particle aggregates and the TiO2 pigment particle aggregates. Rheo-USANS data revealed that the aggregates are fractal in nature and their self-similarity dimensions and correlations lengths depend on the chemistry of the binder particles, the type of rheology modifier present and the shear stress imposed upon the formulation. These results can be explained in the framework of diffusion and reaction limited transient aggregates structure evolution under simple shear.
Dynamic Modes of Red Blood Cells in Oscillatory Shear Flow
Noguchi, Hiroshi
2010-01-01
The dynamics of red blood cells (RBCs) in oscillatory shear flow was studied using differential equations of three variables: a shape parameter, the inclination angle $\\theta$, and phase angle $\\phi$ of the membrane rotation. In steady shear flow, three types of dynamics occur depending on the shear rate and viscosity ratio. i) tank-treading (TT): $\\phi$ rotates while the shape and $\\theta$ oscillate. ii) tumbling (TB): $\\theta$ rotates while the shape and $\\phi$ oscillate. iii) intermediate motion: both $\\phi$ and $\\theta$ rotate synchronously or intermittently. In oscillatory shear flow, RBCs show various dynamics based on these three motions. For a low shear frequency with zero mean shear rate, a limit-cycle oscillation occurs, based on the TT or TB rotation at a high or low shear amplitude, respectively. This TT-based oscillation well explains recent experiments. In the middle shear amplitude, RBCs show an intermittent or synchronized oscillation. As shear frequency increases, the vesicle oscillation beco...
Experimental and 3D Numerical Simulation of Reinforced Shear Joints
Jalalifar, Hossein; Aziz, N.
2010-02-01
The load transfer capacity and failure mechanism of a fully grouted bolt installed across a joint in shear is investigated, both experimentally and numerically, in five types of bolt. The double-shearing testing of bolts were studied in concrete blocks of 20, 40 and 100 MPa strengths, subjected to different pretension loads of 0, 5, 10, 20, 50 and 80 KN, respectively. The parameters examined include: shear resistance, shear displacement, induced strains and stresses during the bolt-bending process, and its ultimate failure across the sheared joint planes. The conclusions drawn from the study were that the strength of the concrete, bolt profile configuration and bolt pretension load played a significant influence on the shear resistance, shear displacement and failure mechanism of the reinforced medium. Experimental and numerical simulations showed that the failure occurs as a result of the induced axial and shear stresses acting between the hinge point distances in the vicinity of the shear joint plane.
Mitigating shear lag in tall buildings
Gaur, Himanshu; Goliya, Ravindra K.
2015-09-01
As the height of building increases, effect of shear lag also becomes considerable in the design of high-rise buildings. In this paper, shear lag effect in tall buildings of heights, i.e., 120, 96, 72, 48 and 36 stories of which aspect ratio ranges from 3 to 10 is studied. Tube-in-tube structural system with façade bracing is used for designing the building of height 120 story. It is found that bracing system considerably reduces the shear lag effect and hence increases the building stiffness to withstand lateral loads. Different geometric patterns of bracing system are considered. The best effective geometric configuration of bracing system is concluded in this study. Lateral force, as wind load is applied on the buildings as it is the most dominating lateral force for such heights. Wind load is set as per Indian standard code of practice IS 875 Part-3. For analysis purpose SAP 2000 software program is used.
Progress of simulations for reacting shear layers
Yu, Sheng-Tao
1991-10-01
An attempt was made to develop a high speed, chemically reactive shear layer test rig. The purpose of the experiment was to study the mixing of oxidizer and fuel streams in reacting shear layers for various density, velocity, and Mach number. The primary goal was to understand the effects of the compressibility upon mixing and combustion in a fundamental way. Therefore, a two-dimensional shear layer is highly desirable for its simplicity to quantify the compressibility effects. The RPLUS 2D code is used to calculate the flow fields of different sections of the test rig. The emphasis was on the supersonic nozzle design, the vitiation process for the hot air stream and the overall thermodynamic conditions of the test matrix. The k-epsilon turbulence model with wall function was successfully implemented in the RPLUS code. The k and epsilon equations are solved simultaneously and the LU scheme is used to make it compatible with the flow solver.
Transversely Compressed- and Restrained Shear Joints
DEFF Research Database (Denmark)
Schmidt, Jacob Wittrup; Hansen, Christian Skodborg
2013-01-01
Anchorage of FRP strengthening systems where the deformation perpendicular to the FRP material is restrained or a compressive force is applied on the strengthening, seems to provide ductility, increased utilization of the FRP and failure modes which can be controlled through the anchorage method. This paper presents theoretical model which can predict the response of transversely compressed and restrained single- and double lap shear joints. The interface material model is based on a cohesive law in the shear-slip plane with a descending branch and a uniform frictional stress added due to the friction in the crack, emanating from the transverse pressure or restraint. The theoretical model is compared with experimental results from transversely compressed single- and double shear joints. Also theoretical predictions of a mechanical integrated sleeve-wedge anchorage load capacity are carried out and compared with tests. It is seen that the theory correlates well with the experimental results.
Shear viscosity in magnetized neutron star crust
Ofengeim, D D
2015-01-01
The electron shear viscosity due to Coulomb scattering of degenerate electrons by atomic nuclei throughout a magnetized neutron star crust is calculated. The theory is based on the shear viscosity coefficient calculated neglecting magnetic fields but taking into account gaseous, liquid and solid states of atomic nuclei, multiphonon scattering processes, and finite sizes of the nuclei albeit neglecting the effects of electron band structure. The effects of strong magnetic fields are included in the relaxation time approximation with the effective electron relaxation time taken from the field-free theory. The viscosity in a magnetized matter is described by five shear viscosity coefficients. They are calculated and their dependence on the magnetic field and other parameters of dense matter is analyzed. Possible applications and open problems are outlined.
Transport Physics in Reversed Shear Plasmas
Energy Technology Data Exchange (ETDEWEB)
Levinton, F.M.; Batha, S.H. [Fusion Physics and Technology, Inc., Torrance, CA (United States); Beer, M.A.; Bell, M.G.; Budny, R.V.; Efthimion, P.C.; Mazzucato, E.; Nazikian, R.; Park, H.K.; Ramsey, A.T.; Schmidt, G.L.; Scott, S.D.; Synakowski, E.J.; Taylor, G.; Von Goeler, S.; Zarnstorff, M.C. [Princeton University, NJ (United States). Plasma Physics Laboratory; Bush, C.E. [Oak Ridge National Lab., TN (United States)
1997-12-31
Reversed magnetic shear is considered a good candidate for improving the tokamak concept because it has the potential to stabilize MHD instabilities and reduce particle and energy transport. With reduced transport the high pressure gradient would generate a strong off-axis bootstrap current and could sustain a hollow current density profile. Such a combination of favorable conditions could lead to an attractive steady-state tokamak configuration. Indeed, a new tokamak confinement regime with reversed magnetic shear has been observed on the Tokamak Fusion Test Reactor (TFTR) where the particle, momentum, and ion thermal diffusivities drop precipitously, by over an order of magnitude. The particle diffusivity drops to the neoclassical level and the ion thermal diffusivity drops to much less than the neoclassical value in the region with reversed shear. This enhanced reversed shear (ERS) confinement mode is characterized by an abrupt transition with a large rate of rise of the density in the reversed shear region during neutral beam injection, resulting in nearly a factor of three increase in the central density to 1.2 X 10(exp 20) cube m. At the same time the density fluctuation level in the reversed shear region dramatically decreases. The ion and electron temperatures, which are about 20 keV and 7 keV respectively, change little during the ERS mode. The transport and transition into and out of the ERS mode have been studied on TFTR with plasma currents in the range 0.9-2.2 MA, with a toroidal magnetic field of 2.7-4.6 T, and the radius of the q(r) minimum, q{sub min}, has been varied from r/a = 0.35 to 0.55. Toroidal field and co/counter neutral beam injection toroidal rotation variations have been used to elucidate the underlying physics of the transition mechanism and power threshold of the ERS mode.
Shear Rheology of Interfaces: Micro Rheological Methods
Mendoza, A. J.; Jordán, R. C.; Pedrero, F. M.; Agogo, H.; Rubio, R. G.; Ortega, F.; Velarde, M. G.
Microrheology offers several advantages over traditional macroscopic surface rheology: the use of very small samples, the possibility of studying heterogeneous samples and the broad range of frequency that can be explored. In this Chapter the microrheology of fluid interfaces is discussed, with special emphasis on particle tracking and optical tweezer techniques. We comment the main results and the assumptions of one of the recent theories aiming to describe the hydrodynamics of a particle trapped at a monolayer, and to obtain the interfacial shear modulus over a broad frequency range not available to macroscopic interfacial shear rheometers. Experimental results for a variety of systems are discussed.
Shear band angles in FCC metals
International Nuclear Information System (INIS)
The model proposed by Yeung and Duggan has been tested by comparison with recently published results for a nickel single crystal and a complex aluminium alloy. The observed shear band angles agree well with those predicted by an analysis based on an effective Taylor factor for shearing and slip localisation on a limited number of systems. Further data have become available for two more systems, viz. rolled single crystals of nickel and a rolled multiphase Al-Cu-Li-Mg-Zr alloy. In both cases, theoretical analysis has been made possible by the development of a strong deformation texture containing only a few major orientations
Poloidal Rotation in TFTR Reversed Shear Plasmas
Energy Technology Data Exchange (ETDEWEB)
Bell, R. E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Levinton, F. M. [Fusion Physics Technology, Torrance, California 90503 (United States); Batha, S. H. [Science Research Laboratory, 15 Ward Street, Somerville, Massachusetts 02144 (United States); Synakowski, E. J. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Zarnstorff, M. C. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
1998-08-01
A bifurcation in the core poloidal rotation of carbon impurity ions in the Tokamak Fusion Test Reactor (TFTR) has been observed prior to the transport bifurcation associated with enhanced reverse shear plasmas. In a narrow radial region of the plasma, the impurity ion poloidal rotation reverses direction. This poloidal flow is associated with the establishment of a large negative radial electric field with strong shear. The measured poloidal velocities before, during, and after this precursor differ from neoclassical predictions. © 1998 The American Physical Society
Shear viscosity coefficient of liquid lanthanides
Patel, H. P.; Sonvane, Y. A.; Thakor, P. B.; Prajapati, A. V.
2015-05-01
Present paper deals with the computation of shear viscosity coefficient (?) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (?) of liquid lanthanides.
Halo abundances and shear in void models
DEFF Research Database (Denmark)
Alonso, David; García-Bellido, Juan
2012-01-01
We study the non-linear gravitational collapse of dark matter into halos through numerical N-body simulations of Lemaitre-Tolman-Bondi void models. We extend the halo mass function formalism to these models in a consistent way. This extension not only compares well with the simulated data at all times and radii, but it also gives interesting clues about the impact of the background shear on the growth of perturbations. Our results give hints about the possibility of constraining the background shear via cluster number counts, which could then give rise to strong constraints on general inhomogeneous models, of any scale.
Shear viscosity coefficient of liquid lanthanides
Energy Technology Data Exchange (ETDEWEB)
Patel, H. P., E-mail: patel.harshal2@gmail.com; Thakor, P. B., E-mail: pbthakore@rediffmail.com; Prajapati, A. V., E-mail: anand0prajapati@gmail.com [Department of Physics, Veer Narmad South Gujarat University, Surat 395 007, Gujarat (India); Sonvane, Y. A., E-mail: yas@ashd.svnit.ac.in [Department of Applied Physics, S. V. National Institute of Technology, Surat 395 007, Gujarat (India)
2015-05-15
Present paper deals with the computation of shear viscosity coefficient (?) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (?) of liquid lanthanides.
Shear viscosity coefficient of liquid lanthanides
International Nuclear Information System (INIS)
Present paper deals with the computation of shear viscosity coefficient (?) of liquid lanthanides. The effective pair potential v(r) is calculated through our newly constructed model potential. The Pair distribution function g(r) is calculated from PYHS reference system. To see the influence of local field correction function, Hartree (H), Tailor (T) and Sarkar et al (S) local field correction function are used. Present results are compared with available experimental as well as theoretical data. Lastly, we found that our newly constructed model potential successfully explains the shear viscosity coefficient (?) of liquid lanthanides
Hydrodynamic and contact contributions to shear thickening in colloidal suspensions
Lin, Neil Y C; Hermes, Michiel; Ness, Chris; Sun, Jin; Poon, Wilson C K; Cohen, Itai
2015-01-01
Shear thickening is a widespread phenomenon in suspension flow that, despite sustained study, is still the subject of much debate. The longstanding view that shear thickening is due to hydrodynamic clusters has been challenged by recent theory and simulations suggesting that contact forces dominate, not only in discontinuous, but also in continuous shear thickening. Here, we settle this dispute using shear reversal experiments on micron-sized silica and latex colloidal particles to measure directly the hydrodynamic and contact force contributions to shear thickening. We find that contact forces dominate even continuous shear thickening. Computer simulations show that these forces most likely arise from frictional interactions.
Shear-induced conformation change in ?-crystalline nylon6
International Nuclear Information System (INIS)
A study of shear deformation of ?-crystalline nylon6 is undertaken, using dispersion-corrected density functional theory. The shear stress-strain relationship and shear strength for interlayer shear deformation are computed. A conformation change induced by shear is identified along twinning deformation, whereby the conformation of chains, specifically the location of non-H-bonded hydrogen atoms, changes continuously. This paves a way for the modulation of properties of this group of materials by small shear deformation, if the non-H-bonded hydrogens are chemically substituted to form non-equivalent conformations when deformed
Yamakoshi, Yoshiki; Yamamoto, Atsushi; Kasahara, Toshihiro; Iijima, Tomohiro; Yuminaka, Yasushi
2015-07-01
We have proposed a quantitative shear wave imaging technique for continuous shear wave excitation. Shear wave wavefront is observed directly by color flow imaging using a general-purpose ultrasonic imaging system. In this study, the proposed method is applied to experiments in vivo, and shear wave maps, namely, the shear wave phase map, which shows the shear wave propagation inside the medium, and the shear wave velocity map, are observed for the skeletal muscle in the shoulder. To excite the shear wave inside the skeletal muscle of the shoulder, a hybrid ultrasonic wave transducer, which combines a small vibrator with an ultrasonic wave probe, is adopted. The shear wave velocity of supraspinatus muscle, which is measured by the proposed method, is 4.11 ± 0.06 m/s (N = 4). This value is consistent with those obtained by the acoustic radiation force impulse method.
Jacobson, William R.; Hooyer, Thomas S.
2015-12-01
Herein we present data on the shearing rate (glacier velocity) and effective pressure (difference between the ice-overburden pressure and pore-water pressure) in the development of magnetic fabric (anisotropy of magnetic susceptibility) using a rotary ring-shear device. A Wisconsin-age basal till was used in the experiments and deformed to its critical state at shear strains as high as 93. We also present data from hysteresis and high temperature susceptibility experiments to identify the magnetic carrier in the basal till. Results showed little change in fabric strength when varying the shearing rate in the speed range of 110-860 m year- 1. Moreover, the effective pressure tests also showed an inconsistency in fabric between 30 and 150 kPa; however, a slight strengthening effect was documented. Thus, the k1 magnetic fabric strength is independent of the shearing rate and effective pressure. This suggests that the fabric strength upon these variables cannot be used as a benchmark for estimating shear deformation to the geological record. The k1 fabric strength in this study; however, remained consistent with respect to other till particle fabric methods (e.g., sand and pebble) in which the same conclusion was drawn; all particles align parallel to the direction of shear and plunge mildly up glacier.
Fuhrmann, Alexander; Engler, Adam J.
2015-02-01
Several methods have been developed to quantify population level changes in cell attachment strength given its large heterogeneity. One such method is the rotating disk chamber or ‘spinning disk’ in which a range of shear forces are applied to attached cells to quantify detachment force, i.e. attachment strength, which can be heterogeneous within cell populations. However, computing the exact force vectors that act upon cells is complicated by complex flow fields and variable cell morphologies. Recent observations suggest that cells may remodel their morphology and align during acute shear exposure, but contrary to intuition, shear is not orthogonal to the radial direction. Here we theoretically derive the magnitude and direction of applied shear and demonstrate that cells, under certain physiological conditions, align in this direction within minutes. Shear force magnitude is also experimentally verified which validates that for spread cells shear forces and not torque or drag dominate in this assay, and demonstrates that the applied force per cell area is largely independent of initial morphology. These findings suggest that direct quantified comparison of the effects of shear on a wide array of cell types and conditions can be made with confidence using this assay without the need for computational or numerical modeling.
Computer simulation of three dimensional shearing of granular materials: Formation of shear bands
Fazekas, S; Kertész, J; Wolf, D E
2006-01-01
We used computer simulations to study spontaneous strain localization in granular materials, as a result of symmetry breaking non-homogeneous deformations. Axisymmetric triaxial shear tests were simulated by means of standard three-dimensional Distinct Element Method (DEM) with spherical grains. Carefully prepared dense specimens were compressed between two platens and, in order to mimic the experimental conditions, stress controlled, (initially) axisymmetric boundary conditions were constructed. Strain localization gave rise to visible shear bands, previously found experimentally under similar conditions by several groups, and different morphologies could be reproduced. We examined the stress-strain relation during the process and found good agreement with experiments. Formation mechanism of shear bands is discussed.
Wittmer, Joachim Paul; Kriuchevskyi, Ivan; Baschnagel, Joerg; Xu, Hong
2015-09-01
Shear-strain and shear-stress correlations in isotropic elastic bodies are investigated both theoretically and numerically at either imposed mean shear-stress ? ( ? = 0) or shear-strain ? ( ? = 1) and for more general values of a dimensionless parameter ? characterizing the generalized Gaussian ensemble. It allows to tune the strain fluctuations ? _{? ? } ? ? Vstress fluctuations ? _{? ? } ? ? Vstress) that ? ?? | ? = ? A - ? G eq with ? A = ? ?? | ? = 0 being the affine shear-elasticity. For the stress autocorrelation function C_{? ? } (t) ? ? Vstress barostat) to generalize to C ?? ( t)| ? = G( t) - ? G eq with G( t) = C ?? ( t) | ? = 0 being the shear-stress relaxation modulus.
Pereira, Fabíola Manhas Verbi; Bertelli Pflanzer, Sérgio; Gomig, Thaísa; Lugnani Gomes, Carolina; de Felício, Pedro Eduardo; Colnago, Luiz Alberto
2013-04-15
The noteworthy of this study is to predict seven quality parameters for beef samples using time-domain nuclear magnetic resonance (TD-NMR) relaxometry data and multivariate models. Samples from 61 Bonsmara heifers were separated into five groups based on genetic (breeding composition) and feed system (grain and grass feed). Seven sample parameters were analyzed by reference methods; among them, three sensorial parameters, flavor, juiciness and tenderness and four physicochemical parameters, cooking loss, fat and moisture content and instrumental tenderness using Warner Bratzler shear force (WBSF). The raw beef samples of the same animals were analyzed by TD-NMR relaxometry using Carr-Purcell-Meiboom-Gill (CPMG) and Continuous Wave-Free Precession (CWFP) sequences. Regression models computed by partial least squares (PLS) chemometric technique using CPMG and CWFP data and the results of the classical analysis were constructed. The results allowed for the prediction of aforementioned seven properties. The predictive ability of the method was evaluated using the root mean square error (RMSE) for the calibration (RMSEC) and validation (RMSEP) data sets. The reference and predicted values showed no significant differences at a 95% confidence level. PMID:23601874
Scientific Electronic Library Online (English)
Mayka Reghiany, Pedrão; Fernanda, Lassance; Nilson Evelazio de, Souza; Makoto, Matsushita; Paulo, Telles; Massami, Shimokomaki.
2009-06-01
Full Text Available A composição química percentual aproximada do cupim m. Rhomboideus (RB) derivado de Nelore (Bos indicus) de 24 meses de idade mostrou ser um músculo diferenciado. Há uma maior fração de material lipídico em RB chegando a ser 14 vezes proporcionalmente maior em comparação ao m. Longissimus dorsi (LD) [...] (p Abstract in english The proximate chemical composition of hump, known in Brazil as cupim, Rhomboideus m. (RB), of Nelore (Bos indicus) aged 24 months revealed it to be a unique beef muscle. It presents a lipid fraction 14-fold as high as that of Longissimus dorsi m. (LD) taken from the same animal (p[...] value reported so far. This was unequivocally observed by the histological evaluation. Proportionally more protein fraction and conversely less moisture were also observed in RB. Analysis of collagen and its crosslinking with hydroxylysylpyridinium (HP) showed there to be 22.9% more collagen and 14-fold as much HP in RB as in LD. Contrary to the expectations, the tenderness of fresh samples evaluated by Warner Bratzler shear force measurements led to values of 8.05 and 5.81 kgf for LD and RB, respectively (p
Scientific Electronic Library Online (English)
Lauren L. Hulsman, Hanna; Dorian J., Garrick; Clare A., Gill; Andy D., Herring; James O., Sanders; David G., Riley.
2014-12-01
Full Text Available The objectives of this study were to 1) compare four models for breeding value prediction using genomic or pedigree information and 2) evaluate the impact of fixed effects that account for family structure. Comparisons were made in a Nellore-Angus population comprising F2, F3 and half-siblings to em [...] bryo transfer F2 calves with records for overall temperament at weaning (TEMP; n = 769) and Warner-Bratzler shear force (WBSF; n = 387). After quality control, there were 34,913 whole genome SNP markers remaining. Bayesian methods employed were BayesB ( ? = 0.995 or 0.997 for WBSF or TEMP, respectively) and BayesC (? = 0 and ?), where ? is the ideal proportion of markers not included. Direct genomic values (DGV) from single trait Bayesian analyses were compared to conventional pedigree-based animal model breeding values. Numerically, BayesC procedures (using ?) had the highest accuracy of all models for WBSF and TEMP ( ?gg = 0.843 and 0.923, respectively), but BayesB had the least bias (regression of performance on prediction closest to 1, ?y,x = 2.886 and 1.755, respectively). Accounting for family structure decreased accuracy and increased bias in prediction of DGV indicating a detrimental impact when used in these prediction methods that simultaneously fit many markers.
Scientific Electronic Library Online (English)
Isabella Dias Barbosa, Silveira; Vivian, Fischer; Luis Henrique Ebling, Farinatti; João, Restle; Dari Celestino, Alves Filho; Luís Fernando Glasenapp de, Menezes.
2012-06-01
Full Text Available The relation between temperament with performance and meat quality was determined in 79 Charolais × Nellore steers kept in feedlot. Temperament was evaluated according to exit velocity, scale composite score and flight distance four times in the finishing phase, along with body weight, intake and fe [...] ed conversion measures. Cattle were classified as calm, intermediate and excited according to exit velocity measures at the beginning of the trial. Excited cattle presented larger values for composite score and flight distance. Irrespective of genotype, excited cattle presented lower average daily gain, dry matter intake and worse feed conversion. Temperament categories did not affect most of beef quality traits, except for calm Bos indicus steers, which presented greater pH measured 1 hour post mortem compared with more reactive steers. However, moderate but negative correlations were detected between exit velocity, flight distance and composite score and beef quality as well as Warner-Bratzler shear value, luminosity, pH measured 24 hours post mortem, although they were not consistent between genotypes raised under the same conditions.
Cottrell, J J; McDonagh, M B; Dunshea, F R; Warner, R D
2008-10-01
The aim of this experiment was to determine the effect of inhibiting the release of nitric oxide (NO) pre-slaughter in lambs on post-slaughter muscle metabolism and meat quality. Exercise was used as a positive control as NO is known to be released in skeletal muscle during exercise. Forty Border Leicester×Merino lambs were assigned to the treatments L-NAME (NO synthase inhibitor) infusion (0mg/kg vs. 30mg/kg, 135min pre-slaughter) and exercise (none vs. 15min immediately pre-slaughter). The inhibition of NO release using L-NAME reduced Warner-Bratzler shear force (WBSF) in the longissimus thoracis et lumborum (LTL) after 3days of ageing, while the Semimembranosous (SM) was unaffected. Inhibition of NO release with L-NAME resulted in altered glucose metabolism as indicated by reduced plasma glucose pre-slaughter particularly in exercised lambs, reduced LTL and SM glycogen of non-exercised lambs post-slaughter and increased SM lactate in exercised lambs post-slaughter. In conclusion, inhibition of NO Synthase with L-NAME pre-slaughter increases post-mortem glycolysis and improves tenderness in the loin muscle. PMID:22063360
Scientific Electronic Library Online (English)
S., Y& #252; ksel; M., Yanar; L., Turgut; A., & #214; zl& #252; t& #252; rk; S., Kopuzlu; E., Sezgin.
Full Text Available Fifteen young Holstein Friesian bulls (18 mo of age) were divided into three groups of five. All groups were fed a diet consisting of 60% concentrate and 40% roughage. The control (C) group received a mixture of dry meadow hay, dry lucerne and wheat straw as roughage. The second and third treatment [...] groups were fed a similar mixture of roughage partially substituting wheat straw with wet sugar beet pulp (SBP) at levels of 4% and 8% on a dry matter (DM) basis, respectively. Dry matter intake and feed efficiency ratio (kg DM intake/kg weight gain) of the C group were significantly higher than those of the 4% SBP and 8% SBP groups. Slaughter and carcass traits indicated that there were no significant differences between dietary treatments. The inclusion of 8% SBP significantly improved panel ratings for tenderness, juiciness, beef flavour intensity and general acceptance, as well as number of chews before swallowing and the Warner Bratzler Shear value. Proximate analysis of the meat did not demonstrate differences between meat from the bulls fed C and the SBP diets. It was concluded that wheat straw could be replaced by 8% SBP in the finishing diet for young Holstein Friesian bulls in order to improve feed efficiency and sensory quality characteristics of their meat.
Commercial application of high-dose irradiation to produce shelf-stable meat products. Part 3 - Effect of polyphosphates on the tenderness and sensory properties of beef silverside sterilised at 45 kGy
International Nuclear Information System (INIS)
The effect of five mixtures of sodium chloride, sodium tripolyphosphate and tetrasodiumpyrophosphate on the texture and sensory properties of irradiated beef M. biceps femoris and M. semitendinosus muscles sterilised at 45 kGy were evaluated using pH after injection, drip loss measurement, Instron texture measurement and descriptive sensory analysis. The effect of cattle race was also investigated. Three breeds of cattle namely Afrikaner (Bos indicus), Hereford (Bos taurus) and Simmentaler (Bos taurus) were used. Steers were fed and raised in a controlled environment until 18 months of age, followed by slaughtering using the same procedure for each carcass. It was found that cattle breed had a significant influence on irradiated meat tenderness and juiciness. Afrikaner breed meat was the most tender and the most juicy. The Energy to break point measured using a Warner Bratzler Shear cell correlated with the ease of fragmentation (using fingers) as well as Initial Juiciness and Sustained Juiciness. Using polyphosphate levels of 13.2 mmol/kg produced undesirable flavours in the meat. The same tenderness was obtained using levels of 8.2 mmol/kg in the meat without undesirable taste. No differences were found between sodium tripolyphosphate and tetrasodium pyrophosphate treatments. Warmed Over Flavour was a significant factor influencing the quality of the products. (author)
Effect of bleeding method and low voltage electrical stimulation on meat quality of ostriches
Scientific Electronic Library Online (English)
L.C., Hoffman; S.W.P., Cloete; S.J., van Schalkwyk; S.St.C., Botha.
Full Text Available The effect on ostrich muscle quality of an additional thoracic stick (TS) to the normal ventral throat slit to bleed ostriches after electrical stunning was evaluated. The additional TS had no negative or positive effect on the drip loss, cooking loss, colour or pH and temperature readings of the fi [...] llet (Muscularis iliofibularis), big drum (M. gastrocnemius, pars interna) and inside loin (M. iliotibialis cranialis). None the less, personal observations would recommend the use of TS due to ethical considerations. An early post mortem low voltage electrical stimulation (ES) of the carcasses also had no influence on the cooking loss, drip loss and colour of these muscles. Electrical stimulation did result in a lower pH45 in both the fillet and big drum muscles. However, after 24 h the pH of the muscles did not differ. Electrical stimulation also caused elevated initial muscle temperatures, although this effect was only temporary due to the efficient cooling mechanism used in the abattoir. Electrical stimulation also had no effect on the Warner Bratzler shear force values in the fillet. It can be concluded that low voltage ES has no advantage pertaining to physical quality characteristics of importance in an ostrich abattoir.
González-Rios, H; Peña-Ramos, A; Valenzuela, M; Zamorano-García, L; Cumplido-Barbeitia, G; González-Méndez, N F; Huerta-Leidenz, N
2010-01-01
To compare beef from Northwestern Mexico (NMEX) and that imported from the United States in physical-chemical (PC) and sensory traits, samples of ribeye (m. Longissimus dorsi thoracis, LDT) and knuckle (m. Vastus lateralis, VL) of Mexican (64 LDT; 51 VL) and U.S. (28 LDT; 25 VL) origin were purchased randomly from select retail stores located in 3 cities of NMEX. PC evaluation measured contents of moisture, fat and cholesterol, Warner-Bratzler shear force (WBSF), pH, CIE L*, a*, and b*, cooking loss, and normalized fatty acid profile (FAP). Trained panelists evaluated raw and cooked samples for 2 and 6 different organoleptic traits, respectively. Mexican and U.S.-imported LDT steaks did not differ (P>0.05) in PC traits. VL samples differed in L*, b*, hue*, WBSF, and fat content by country of origin (COO). The WBSF for cooked VL samples from the United States was lower (P fat content was greater (Pdifferences with U.S.-imported samples were detected (P > 0.05). Results indicated that domestic and U.S. retail steaks sold in the NMEX are similar in eating quality and PC, whereas differences observed in FAP deserve further attention from a nutritional standpoint. PMID:21535586
Directory of Open Access Journals (Sweden)
Abdullah N. Al-Owaimer
2014-07-01
Full Text Available The current study was performed to investigate the influence of probiotics or antibiotic on breast quality characteristics of broiler chickens that were subjected to Salmonella challenge. Two hundred, one-day-old Cobb 500 chicks were allocated in five experimental treatments for 42 d. Ten cages of birds received one of the following treatments: T1=positive control (+CONT, unsupplemented, unchallenged; T2=negative control (-CONT, unsupplemented, challenged; T3=supplemented with antibiotic neoxyval (NEOX, challenged; T4=supplemented with probiotic Toyocerin (TOYO, challenged; and T5=supplemented with probiotic CloSTATTM (CLOS, challenged. Birds in treatments T2 to T5 were challenged with 3×109 CFU/mL of Salmonella enterica subsp. typhimurium on day 16. Nine birds per treatment were sampled at the end of the trial for breast characteristics. Overall, pH and temperature values of the breast muscle were similar among all groups tested. Cooking loss results indicated that breasts from T3 birds had the highest degree of shrinkage upon cooking while those of the probiotic group had similar control values (P<0.0001. Probiotic supplementation reduced the extent of destruction of myofibrils caused by homogenisation (P<0.0001. Warner-Bratzler shear test and texture profile analysis showed that neither treatments nor Salmonella challenge had any negative impact on texture or sensory attributes of chicken breast. In conclusion, results show that breast characteristics were better when probiotics were supplemented in the diets.
Rapid detection of frozen pork quality without thawing by Vis-NIR hyperspectral imaging technique.
Xie, Anguo; Sun, Da-Wen; Xu, Zhongyue; Zhu, Zhiwei
2015-07-01
Quality determination of frozen food is a time-consuming and laborious work as it normally takes a long time to thaw the frozen samples before measurements can be carried out. In this research, a rapid and non-destructive determination technique for frozen pork quality was tested with a hyperspectral imaging (HSI) system. In this study, 120 pieces of pork meat were frozen by four kinds of methods with various freezing temperatures from -20 to -120°C. The hyperspectral images of the samples were acquired at the frozen state. Quality indicators including drip loss, pH value, color, cooking loss and Warner-Bratzler shear force (WBSF) of the samples were measured after thawing. The spectral characteristics of the frozen meat samples were studied and it was revealed that the reflectance at 1100nm had a close relationship with the freezing temperature (R=-0.832, pquality indicators. The coefficients of determination for prediction (Rp(2)) for L*, cooking loss, b*, drip loss and a* were 0.907, 0.845, 0.814, 0.762, and 0.716, respectively. However there were low correlations (Rp(2)) for pH and WBSF measurements. The current study indicated that HSI had the potential for non-destructive determination of frozen meat quality without thawing. PMID:25882428
Effect of feeding food waste-broiler litter and bakery by-product mixture to pigs.
Kwak, W S; Kang, J S
2006-01-01
This study was conducted to evaluate the effects of feeding aerobically processed and vacuum-dried food waste-broiler litter and bakery by-product mixture to finishing pigs on performance, carcass characteristics, meat quality and taste panel test. A corn-soy diet (Control) was replaced with food waste mixture (FWM) at dietary levels of 25% (25% FWM) and 50% (50% FWM) on a dry matter (DM) basis. Diets were fed to a total of 45 pigs (mean body weight 69.4kg) during the eight wk of finishing period. After slaughtering, longissmus muscle at 24h postmortem was used for meat quality analysis. Restaurant food waste was high in protein (22.0%) and fat (23.9%). Supplementing a corn-soy diet with FWM increased (P0.05) average daily gain, decreased (P0.05) carcass characteristics (carcass weight, dressing percentage, backfat thickness and carcass grade), meat fatty acid composition, meat quality (marbling score, pH, water holding capacity, drip loss, L*, a*, b* values, Warner-Bratzler shear force, cooking loss), and taste panel test (flavor, taste, tenderness, juiciness, and overall acceptance) compared with feeding a corn-soy diet. However, meat color was paler (Pfood waste-broiler litter and bakery by-product mixture was similar to a corn-soy diet in feed value for finishing pigs. PMID:16171681
Needham, T; Hoffman, L C
2015-12-01
Physical and chemical attributes of the Longissimus thoracis (LT) of 96 PIC(©) entire (E) and immunocastrated (C) pigs were evaluated. The study followed a 2×2×3 factorial design where three diets of low, medium and high proteins (7.50, 9.79 and 12.07g digestible lysine/kg) were fed either with (10mg/kg) or without ractopamine (RAC) for the last 28days of growth. Vaccination of C occurred at 16 and 20weeks and slaughtering at 24weeks of age. The LTs were analysed for moisture, protein, fat and ash contents as well as CIE L*, a*, b* colour, drip loss, cooking loss and Warner-Bratzler shear force (WBSF). Various sex and protein interactions were observed for LT protein content, L* values and WBSF. Cooking loss was decreased in C and by the medium protein diet. Feeding RAC increased WBSF values, whilst decreasing a* and b* values. However, the differences observed are minor and might be considered negligible when evaluated by a consumer. PMID:26201695
Shear stress in magnetorheological finishing for glasses.
Miao, Chunlin; Shafrir, Shai N; Lambropoulos, John C; Mici, Joni; Jacobs, Stephen D
2009-05-01
We report in situ, simultaneous measurements of both drag and normal forces in magnetorheological finishing (MRF) for what is believed to be the first time, using a spot taking machine (STM) as a test bed to take MRF spots on stationary parts. The measurements are carried out over the entire area where material is being removed, i.e., the projected area of the MRF removal function/spot on the part surface, using a dual force sensor. This approach experimentally addresses the mechanisms governing material removal in MRF for optical glasses in terms of the hydrodynamic pressure and shear stress, applied by the hydrodynamic flow of magnetorheological fluid at the gap between the part surface and the STM wheel. This work demonstrates that the volumetric removal rate shows a positive linear dependence on shear stress. Shear stress exhibits a positive linear dependence on a material figure of merit that depends upon Young's modulus, fracture toughness, and hardness. A modified Preston's equation is proposed that better estimates MRF material removal rate for optical glasses by incorporating mechanical properties, shear stress, and velocity. PMID:19412219
Modeling of Turbulent Free Shear Flows
Yoder, Dennis A.; DeBonis, James R.; Georgiadis, Nicolas J.
2013-01-01
The modeling of turbulent free shear flows is crucial to the simulation of many aerospace applications, yet often receives less attention than the modeling of wall boundary layers. Thus, while turbulence model development in general has proceeded very slowly in the past twenty years, progress for free shear flows has been even more so. This paper highlights some of the fundamental issues in modeling free shear flows for propulsion applications, presents a review of past modeling efforts, and identifies areas where further research is needed. Among the topics discussed are differences between planar and axisymmetric flows, development versus self-similar regions, the effect of compressibility and the evolution of compressibility corrections, the effect of temperature on jets, and the significance of turbulent Prandtl and Schmidt numbers for reacting shear flows. Large eddy simulation greatly reduces the amount of empiricism in the physical modeling, but is sensitive to a number of numerical issues. This paper includes an overview of the importance of numerical scheme, mesh resolution, boundary treatment, sub-grid modeling, and filtering in conducting a successful simulation.
Equilibrium states of homogeneous sheared compressible turbulence
Directory of Open Access Journals (Sweden)
M. Riahi
2011-06-01
Full Text Available Equilibrium states of homogeneous compressible turbulence subjected to rapid shear is studied using rapid distortion theory (RDT. The purpose of this study is to determine the numerical solutions of unsteady linearized equations governing double correlations spectra evolution. In this work, RDT code developed by authors solves these equations for compressible homogeneous shear flows. Numerical integration of these equations is carried out using a second-order simple and accurate scheme. The two Mach numbers relevant to homogeneous shear flow are the turbulent Mach number Mt, given by the root mean square turbulent velocity fluctuations divided by the speed of sound, and the gradient Mach number Mg which is the mean shear rate times the transverse integral scale of the turbulence divided by the speed of sound. Validation of this code is performed by comparing RDT results with direct numerical simulation (DNS of [A. Simone, G.N. Coleman, and C. Cambon, Fluid Mech. 330, 307 (1997] and [S. Sarkar, J. Fluid Mech. 282, 163 (1995] for various values of initial gradient Mach number Mg0. It was found that RDT is valid for small values of the non-dimensional times St (St 10 in particular for large values of Mg0. This essential feature justifies the resort to RDT in order to determine equilibrium states in the compressible regime.
Stability of a compressible shear flow
Bakas, N.
2012-04-01
A comprehensive understanding of the stability of compressible shear flows has been the subject of both theoretical and practical interest in astrophysics. Applications include the maintenance of turbulence in accretion disks around massive bodies and stability of supersonic shear layers in astrophysical jets. In this work, we study non-modal mechanisms underlying transient growth of propagating acoustic waves and non-propagating vorticity perturbations in an unbounded compressible shear flow, and investigate their potential of instigating a transition to turbulence. Propagating acoustic waves amplify mainly due to two mechanisms: growth due to advection of streamwise velocity and growth due to the downgradient irrotational component of the Reynolds stress. Synergy between these mechanisms along with the downgradient solenoidal component of the Reynolds stress produces large and robust energy amplification. On the other hand, non-propagating vorticity perturbations amplify due to kinematic deformation of vorticity by the shear flow. For moderate Mach numbers, a strong coupling between vorticity perturbations and acoustic waves is found with the energy gained by vorticity perturbations being transferred to acoustic waves that are abruptly excited by the vortex. Calculation of the optimal perturbations for a viscous flow showed that for low Mach numbers, acoustic wave excitation by vorticity perturbations and the subsequent growth of acoustic waves leads to robust energy growth of the order of Reynolds number, while for large Mach numbers, synergy between the lift-up mechanism and the downgradient solenoidal component of the Reynolds stress dominates the growth and leads to a comparable large amplification of streamwise velocity.
Shear bands as bottlenecks in force transmission
Tordesillas, Antoinette; Pucilowski, Sebastian; Tobin, Steven; Kuhn, Matthew R.; Andò, Edward; Viggiani, Gioacchino; Druckrey, Andrew; Alshibli, Khalid
2015-06-01
The formation of shear bands is a key attribute of degradation and failure in soil, rocks, and many other forms of amorphous and crystalline materials. Previous studies of dense sand under triaxial compression and two-dimensional analogues from simulations have shown that the ultimate shear band pattern may be detected in the nascent stages of loading, well before the band's known nucleation point (i.e., around peak stress ratio), as reported in the published literature. Here we construct a network flow model of force transmission to identify the bottlenecks in the contact networks of dense granular media: triaxial compression of Caicos ooid and Ottawa sand and a discrete element simulation of simple shear. The bottlenecks localise in the nascent stages of loading —in the location where the persistent shear band ultimately forms. This corroborates recent findings on vortices that suggest localised failure is a progressive process of degradation, initiating early in the loading history at sites spanning the full extent, yet confined to a subregion, of the sample. Bottlenecks are governed by the local and global properties of the sample fabric and the grain kinematics. Grains with large rotations and/or contacts having minimal load-bearing capacities per se do not identify the bottlenecks early in the loading history.
Crossing of shears bands in 196Pb
International Nuclear Information System (INIS)
High-spin states in 196Pb have been populated using the reaction 170Er(30Si, 4n). The previously observed shear bands in this nucleus have been extended and some of their transitions have been reordered. They now form regular bands with band crossings. One of the bands splits into two pathways at high spin. (orig.)
SHEARED FLOWS AND TURBULENCE IN FUSION PLASMAS.
Czech Academy of Sciences Publication Activity Database
Pedrosa, M. A.; Carreras, B.A.; Silva, C.; Hron, Martin; Hidalgo, C.; Alonso, J.A.; García, L.; Calvo, I.; de Pablos, J.L.; Stöckel, Jan
Varšava, 2007. -. [EPS Conference on Plasma Physics/34th./. 02.07.2007-06.07.2007, Varšava] Institutional research plan: CEZ:AV0Z20430508 Keywords : tokamak * sheared flows * turbulence Subject RIV: BL - Plasma and Gas Discharge Physics http://www.eps2007.ifpilm.waw.pl/abstracts_all.zip
Hydrodynamic Modeling and the QGP Shear Viscosity
Song, Huichao
2012-01-01
In this article, we will briefly review the recent progress on hydrodynamic modeling and the extraction of the quark-gluon plasma (QGP) specific shear viscosity with an emphasis on results obtained from the hybrid model VISHNU that couples viscous hydrodynamics for the macroscopic expansion of the QGP to the hadron cascade model for the microscopic evolution of the late hadronic stage.
Wall Shear Stress Measurements in Microfluidic Systems.
Czech Academy of Sciences Publication Activity Database
Tihon, Jaroslav; P?nkavová, V?ra; Stanovský, Petr; Vejražka, Ji?í
- : -, 2014, s. 607. ISBN N. [European Fluid Mechanics Conference EFMC10 /10./. Copenhagen (DK), 15.09.2014-18.09.2014] R&D Projects: GA ?R(CZ) GAP101/12/0585 Institutional support: RVO:67985858 Keywords : microfluidics * electrodiffusion method * wall shear stress Subject RIV: CI - Industrial Chemistry, Chemical Engineering http://www.efmc10.org/
Vorticity dynamics of inviscid shear layers
Yokota, Jeffrey W.
1992-01-01
The inviscid evolution of a two-dimensional shear layer is simulated numerically by a scheme based on a kinematic decomposition of the unsteady flow. Lagrangian and Weber transformations of the incompressible Euler equations result in a Clebsch representation that separates the flowfield into rotational and irrotational components. These transformations produce the initial construction of the flowfield and define its subsequent evolution.
Size Segregation in Sheared Jammed Colloids
Mbi, Armstrong; Blair, Daniel
2013-03-01
It is well known that granular materials can spontaneously size segregate when continuously driven. However, in jammed colloidal suspensions, this phenomenon is not well understood. Colloidal dispersions provide a unique system to study the structure and dynamics of jammed matter. In this talk, we present results of size segregation of a continuously sheared binary colloidal suspension well above point J. Our colloidal system is comprised of indexed-matched bi-disperse silica particles with diameters a = { 2 . 3 ?m and 3 . 2 ?m } and at ? 61 % , well above the colloidal glass transition. We apply a highly controlled shear at a constant shear rate through the use of a rheometer. By coupling our rheometer with a high-speed laser scanning confocal microscope, we directly image the structure and flow profiles of the suspension as it un-jams. We observe migration of the small and large species; large particles move to the top while the small particles move toward the bottom conserving the total volume fraction in all regions. Moreover, we find that an associating feature of segregation is a sustained shear band. Our results are consistent with a recently proposed void filling and squeeze expulsion mechanism. Funding is provided by NSF DMR #0847490.
Variational bounds for the shear viscosity of gelling melts
K"ohler, C H; Müller, P; Zippelius, A; K\\"ohler, Claas H.; L\\"owe, Henning; M\\"uller, Peter; Zippelius, Annette
2007-01-01
We study shear stress relaxation for a gelling melt of randomly crosslinked, interacting monomers. We derive a lower bound for the static shear viscosity $\\eta$, which implies that it diverges algebraically with a critical exponent $k\\ge 2\
Shear crack formation and propagation in reinforced Engineered Cementitious Composites
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2011-01-01
This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventional reinforced concrete (R/C) counterparts for comparison. The shear crack formation mechanism of ECC is investigated in detail and can be characterized by an opening and sliding of the crack. Photogrammetry was utilized to monitor the shear deformations of the specimens. Multiple shear cracking and strain hardening of ECC was observed under shear loading and based upon photogrammetric results fundamental descriptions of shear crack opening, sliding and subsequent failure are presented.
Transient Response of an Electrorheological Fluid in Shear Flow
International Nuclear Information System (INIS)
The transient shear stress response of an electrorheological fluid is investigated experimentally. The characteristic time constants of an electrorheological fluid sheared between two concentric cylinders were obtained under various electric field strengths and shear rates. Also, two experimental modes are adopted to investigate the effect of the shear flow on the dynamic behavior of the fluid; one is that the electric field is induced before shearing, and the other is the electric field is induced after shearing. From the difference in the response time between two modes, the cluster formation time were obtained. The response times were decreased with the increase of the shear rate, irrelatively of the electric field strength. The cluster formation time were monotonically increased with increase of shear rate, and thereafter, were converged with a certain value
Predicting km-scale shear zone formation
Gerbi, Christopher; Culshaw, Nicholas; Shulman, Deborah; Foley, Maura; Marsh, Jeffrey
2015-04-01
Because km-scale shear zones play a first-order role in lithospheric kinematics, accurate conceptual and numerical models of orogenic development require predicting when and where they form. Although a strain-based algorithm in the upper crust for weakening due to faulting appears to succeed (e.g., Koons et al., 2010, doi:10.1029/2009TC002463), a comparable general rule for the viscous crust remains unestablished. Here we consider two aspects of the geological argument for a similar algorithm in the viscous regime, namely (1) whether predicting km-scale shear zone development based on a single parameter (such as strain or shear heating) is reasonable; and (2) whether lithologic variability inherent in most orogenic systems precludes a simple predictive rule. A review of tectonically significant shear zones worldwide and more detailed investigations in the Central Gneiss belt of the Ontario segment of the Grenville Province reveals that most km-scale shear zones occur at lithological boundaries and involve mass transfer, but have fairly little else in common. As examples, the relatively flat-lying Twelve Mile Bay shear zone in the western Central Gneiss belt bounds the Parry Sound domain and is likely the product of both localized anatexis and later retrograde hydration with attendant metamorphism. Moderately dipping shear zones in granitoids of the Grenville Front Tectonic Zone apparently resulted from cooperation among several complementary microstructural processes, such as grain size reduction, enhanced diffusion, and a small degree of metamorphic reaction. Localization into shear zones requires the operation of some spatially restricted processes such as stress concentration, metamorphism/fluid access, textural evolution, and thermal perturbation. All of these could be due in part to strain, but not necessarily linearly related to strain. Stress concentrations, such as those that form at rheological boundaries, may be sufficient to nucleate high strain gradients but are insufficient to maintain them because the stress perturbations will dissipate with deformation. Metamorphism can unquestionably cause sufficient rheological change, but only in certain rock types: for example, granitoids have much less capacity for metamorphically induced rheologic change than do mafic rocks. The magnitude of phase geometry variation observed in natural systems suggests that morphological change (e.g., interconnection of weak phases) likely has little direct affect on strength changes, although other textural factors related to diffusion paths and crystallographic orientation could play a significant role. Thermal perturbation, mainly in the form of shear heating, remains potentially powerful but inconclusive. Taken together, these observations indicate that a simple algorithm predicting shear zone formation will not succeed in many geologically relevant instances. One significant reason may be that the inherent lithologic variation at the km scale, such as observed in the Central Gneiss belt, prevents the development of self-organized strain patterns that would form in more rheologically uniform systems.
Wright, T.
1991-01-01
A phenomenological model of a rigid, work hardening, plastic material, with rate hardening and thermal softening, is analysed to determine susceptibility to the formation of adiabatic shear bands. Emphasis is placed on the influence of finite thermal conductivity.
Spurious Shear in Weak Lensing with LSST
Energy Technology Data Exchange (ETDEWEB)
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
2012-09-19
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
Koo Lee Feng; Nik Mohd Asri Nik Long; Eshkuvatov Zainidin K; Wong Tze Jin
2013-01-01
Maximum shear stress intensity for nearly circular cracks subjected to equal and opposite shear stresses are considered. A hypersingular integral equation containing the crack opening displacement is formulated. Conformal mapping technique is employed to transform the obtained hypersingular equation into a similar equation over a circular crack. A suitable collocation points are chosen to reduce the hypersingular integral equation into a system of linear equations. Numerical solution of the l...
Shear flow effect on ion temperature gradient vortices in plasmas with sheared magnetic field
DEFF Research Database (Denmark)
Chakrabarti, N.; Juul Rasmussen, J.
1999-01-01
The effect of velocity shear on ion temperature gradient (ITG) driven vortices in a nonuniform plasma in a curved, sheared magnetic field is investigated. In absence of parallel ion dynamics, vortex solutions for the ITG mode are studied analytically. It is shown that under certain conditions the coupled equations for potential and pressure exhibit special tripolar vortex-like structures. For the general case, however, parallel ion dynamics is included and the equation describing the stationary ...
López-Barrón, Carlos R.; Gurnon, A. Kate; Eberle, Aaron P. R.; Porcar, Lionel; Wagner, Norman J.
2014-04-01
We present direct measurements of the evolution of the segmental-level microstructure of a stable shear-banding polymerlike micelle solution during flow startup and cessation in the plane of flow. These measurements provide a definitive, quantitative microstructural understanding of the stages observed during flow startup: an initial elastic response with limited alignment that yields with a large stress overshoot to a homogeneous flow with associated micellar alignment that persists for approximately three relaxation times. This transient is followed by a shear (kink) band formation with a flow-aligned low-viscosity band that exhibits shear-induced concentration fluctuations and coexists with a nearly isotropic band of homogenous, highly viscoelastic micellar solution. Stable, steady banding flow is achieved only after approximately two reptation times. Flow cessation from this shear-banded state is also found to be nontrivial, exhibiting an initial fast relaxation with only minor structural relaxation, followed by a slower relaxation of the aligned micellar fluid with the equilibrium fluid's characteristic relaxation time. These measurements resolve a controversy in the literature surrounding the mechanism of shear banding in entangled wormlike micelles and, by means of comparison to existing literature, provide further insights into the mechanisms driving shear-banding instabilities in related systems. The methods and instrumentation described should find broad use in exploring complex fluid rheology and testing microstructure-based constitutive equations.
Mohajeri, Arash; Finzi, Yaron; Muhlhaus, Hans; Rosenbaum, Gideon
2013-05-01
We present a linear instability analysis and numerical simulations describing deformation and melt patterns in pure shear extension of a partly molten rock. Our models implement numerical techniques that enable strong strain localization and are applied to study melt-strain interactions during continental rifting. Our results show that instabilities can initiate with either strain localization or melt localization, followed by a coupled evolution of melt and shear bands driven by a strong melt-viscosity-shear feedback. This indicates that a local increase in melt fraction due to segregation and/or local melting promotes strain localization and may lead to the formation of large shear bands. Melt-shear interactions can therefore enable rifting where tectonic forces are not sufficient to induce melt-free rifting, resulting in lubricated faults, but not necessarily observed volcanism. Finally, our simulations reveal significant asymmetry in melt segregation around localized shear bands, providing new insights into melt distribution across rift boundary faults and other extensional structures.
Estimation of seabed shear-wave velocity profiles using shear-wave source data.
Dong, Hefeng; Nguyen, Thanh-Duong; Duffaut, Kenneth
2013-07-01
This paper estimates seabed shear-wave velocity profiles and their uncertainties using interface-wave dispersion curves extracted from data generated by a shear-wave source. The shear-wave source generated a seismic signature over a frequency range between 2 and 60 Hz and was polarized in both in-line and cross-line orientations. Low-frequency Scholte- and Love-waves were recorded. Dispersion curves of the Scholte- and Love-waves for the fundamental mode and higher-order modes are extracted by three time-frequency analysis methods. Both the vertically and horizontally polarized shear-wave velocity profiles in the sediment are estimated by the Scholte- and Love-wave dispersion curves, respectively. A Bayesian approach is utilized for the inversion. Differential evolution, a global search algorithm is applied to estimate the most-probable shear-velocity models. Marginal posterior probability profiles are computed by Metropolis-Hastings sampling. The estimated vertically and horizontally polarized shear-wave velocity profiles fit well with the core and in situ measurements. PMID:23862796
Fluid Effects on Shear Waves in Finely Layered Porous Media
International Nuclear Information System (INIS)
Although there are five effective shear moduli for any layered VTI medium, one and only one effective shear modulus for the layered system contains all the dependence of pore fluids on the elastic or poroelastic constants that can be observed in vertically polarized shear waves. Pore fluids can increase the magnitude the shear energy stored by this modulus by a term that ranges from the smallest to the largest shear moduli of the VTI system. But, since there are five shear moduli in play, the increase in shear energy overall is reduced by a factor of about 5 in general. We can therefore give definite bounds on the maximum increase of shear modulus, being about 20% of the permitted range, when gas is fully replaced by liquid. An attendant increase of density (depending on porosity and fluid density) by approximately 5 to 10% partially offsets the effect of this shear modulus increase. Thus, an increase of shear wave speed on the order of 5 to 10% is shown to be possible when circumstances are favorable - i.e., when the shear modulus fluctuations are large (resulting in strong anisotropy), and the medium behaves in an undrained fashion due to fluid trapping. At frequencies higher than seismic (such as sonic and ultrasonic waves for well-logging or laboratory experiments), short response times also produce the requisite undrained behavior and, therefore, fluids also affect shear waves at high frequencies by increasing rigidity
Dong, Xia; Zou, Fasheng; Han, Charles C.
2012-02-01
The domain structure and shear viscosity of a phase-separated polymer blend of polybutadiene /polyisopreneare investigated with optical microscopy, light scattering, and rheometry. At the steady shear state, the shear-induced structures can be the nearly spherical droplets, the partially interconnected domains, the typical string-like domains, or the string-like domains with blurred interface, depending on the shear rate. The steady shear viscosity displays a rather non-Newtonian fluid behavior. In the transient flow experiments, the time dependence of viscosity and morphology after a stepwise increase of shear rate is studied and found to mainly depend on the final shear rate. In particular, as long as the final structures are the partially interconnected domains, the morphology evolution proceeds in the same way and the behaviors of the corresponding shear viscosity are similar.
Swinging of red blood cells under shear flow
Abkarian, M; Viallat, A; Abkarian, Manouk; Faivre, Magalie; Viallat, Annie
2007-01-01
We reveal that under moderate shear stress (of the order of 0.1 Pa) red blood cells present an oscillation of their inclination (swinging) superimposed to the long-observed steady tanktreading (TT) motion. A model based on a fluid ellipsoid surrounded by a visco-elastic membrane initially unstrained (shape memory) predicts all observed features of the motion: an increase of both swinging amplitude and period (1/2 the TT period) upon decreasing the shear stress, a shear stress-triggered transition towards a narrow shear stress-range intermittent regime of successive swinging and tumbling, and a pure tumbling motion at lower shear stress-values.
On the origin of shear bands in textured polycrystals
International Nuclear Information System (INIS)
The relaxation of constraints in nonequiaxed grains, which is the basis of a new theory of polycrystal deformation, permits the development of strain heterogeneities on a grain scale. Shear bands are then expected to form when there is sufficient textural softening. This was evaluated for an idealized rolling process, in which shears in the transverse plane were allowed. The result is that grain-scale shear bands should be inclined to the rolling direction preferentially at angles of 230 and 370. An analysis of the degree of textural softening incurred by sample-scale shear bands as a function of hypothetical angles indicates that such shear bands should occur preferentially at +-450
Shear zones in granular media: 3D Contact Dynamics simulation
Ries, Alexander; Unger, Tamas; Wolf, Dietrich E
2007-01-01
Shear zone formation is investigated in slow 3D shear flows. We simulate the linear version of the split-bottom shear cell. It is shown that the same type of wide shear zones is achieved in the presence as well as in the absence of gravity. We investigate the relaxation of the material towards a stationary flow and analyze the stress and the velocity fields. We provide the functional form of the widening of the shear zone inside the bulk. We discuss the growth of the region ...
Velocity profiles in shear-banding wormlike micelles
Salmon, J B; Manneville, S; Molino, F; Salmon, Jean-Baptiste; Colin, Annie; Manneville, Sebastien; Molino, Francois
2003-01-01
Using Dynamic Light Scattering in heterodyne mode, we measure velocity profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to exhibit both shear-banding and stress plateau behavior. Our data provide evidence for the simplest shear-banding scenario, according to which the effective viscosity drop in the system is due to the nucleation and growth of a highly sheared band in the gap, whose thickness linearly increases with the imposed shear rate. We discuss various details of the velocity profiles in all the regions of the flow curve and emphasize on the complex, non-Newtonian nature of the flow in the highly sheared band.
Direct measurement of shear properties of microfibers
Energy Technology Data Exchange (ETDEWEB)
Behlow, H.; Saini, D.; Durham, L.; Simpson, J.; Skove, M. J.; Rao, A. M. [Department of Physics and Astronomy, and Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina 29634 (United States); Oliveira, L. [School of Materials Science and Engineering, Clemson University, Clemson, South Carolina 29634 (United States); Serkiz, S. M. [Department of Physics and Astronomy, and Clemson Nanomaterials Center, Clemson University, Clemson, South Carolina 29634 (United States); Savannah River National Laboratory, Aiken, South Carolina 29808 (United States)
2014-09-15
As novel fibers with enhanced mechanical properties continue to be synthesized and developed, the ability to easily and accurately characterize these materials becomes increasingly important. Here we present a design for an inexpensive tabletop instrument to measure shear modulus (G) and other longitudinal shear properties of a micrometer-sized monofilament fiber sample, such as nonlinearities and hysteresis. This automated system applies twist to the sample and measures the resulting torque using a sensitive optical detector that tracks a torsion reference. The accuracy of the instrument was verified by measuring G for high purity copper and tungsten fibers, for which G is well known. Two industrially important fibers, IM7 carbon fiber and Kevlar{sup ®} 119, were also characterized with this system and were found to have G = 16.5 ± 2.1 and 2.42 ± 0.32 GPa, respectively.
Shear induced instabilities in layered liquids
Auernhammer, G K; Pleiner, H; Auernhammer, Guenter K.; Brand, Helmut R.; Pleiner, Harald
2002-01-01
Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic A like systems, we consider an extended formulation of smectic A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normal p) and the director n of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in non equilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle between n and p, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers. We generalize our earlier approach [Rheol. Acta, vol.39(3), 15] and include the cross couplings with the velocity field and the order parameters for orientational and positional order and show...
Shear instabilities in shallow-water magnetohydrodynamics
Mak, Julian; Hughes, D W
2015-01-01
Within the framework of shallow-water magnetohydrodynamics, we investigate the linear instability of horizontal shear flows, influenced by an aligned magnetic field and stratification. Various classical instability results, such as H{\\o}iland's growth rate bound and Howard's semi-circle theorem, are extended to this shallow-water system for quite general profiles. Two specific piecewise-constant velocity profiles, the vortex sheet and the rectangular jet, are studied analytically and asymptotically; it is found that the magnetic field and stratification (as measured by the Froude number) are generally both stabilising, but weak instabilities can be found at arbitrarily large Froude number. Numerical solutions are computed for corresponding smooth velocity profiles, the hyperbolic-tangent shear layer and the Bickley jet, for a uniform background field. A generalisation of the long-wave asymptotic analysis of Drazin & Howard (1962) is employed in order to understand the instability characteristics for both ...
Shear and Compression Viscoelasticity in Polymer Monolayers
Ferenczi, T A M; Ferenczi, Toby A. M.; Cicuta, Pietro
2005-01-01
Poly-vinlyacetate (PVAc) forms very stable and reproducible monolayers on the surface of water, a model system to understand polymer physics on two dimensions. A recently introduced technique is applied here to to study viscoelasticity of PVAc monolayers. The method is based on measurement of surface tension in two orthogonal directions during anisotropic deformation. Compression and shear moduli are explored over a very large concentration range, highlighting a series of four different regimes. At low concentration the polymers are in a dilute gas. Above the overlap concentration $\\Gamma^\\ast$ there is a fluid semi-dilute region, where the monolayer properties are described by scaling laws. At a threshold concentration $\\Gamma^{\\ast\\ast}$, a decrease in the gradient of pressure with concentration is observed, and we argue that there is still a large fraction of free area on the surface. Compressing further, we then identify close packing as the point where the pressure gradient rises sharply and a shear modu...
Undulatory swimming in shear-thinning fluids
Gagnon, David A; Arratia, Paulo E
2014-01-01
The swimming behaviour of microorganisms can be strongly influenced by the rheology of their fluid environment. In this manuscript, we experimentally investigate the effects of shear-thinning viscosity on the swimming behaviour of an undulatory swimmer, the nematode Caenorhabditis elegans. Tracking methods are used to measure the swimmer's kinematic data (including propulsion speed) and velocity fields. We find that shear-thinning viscosity modifies the velocity fields produced by the swimming nematode but does not modify the nematode's speed and beating kinematics. Velocimetry data show significant enhancement in local vorticity and circulation, and an increase in fluid velocity near the nematode's tail, compared to Newtonian fluids of similar effective viscosity. These findings are in good agreement with recent theoretical and numerical results.
Holographic Chiral Shear Waves from Anomaly
International Nuclear Information System (INIS)
We study dispersion relations of hydrodynamic waves of hot N=4 SYM plasma at strong coupling with a finite U(1) R-charge chemical potential via holography. We first provide complete equations of motion of linearized fluctuations out of a charged AdS blackhole background according to their helicity, and observe that helicity ±1 transverse shear modes receive a new parity-odd contribution from the 5D Chern-Simons term, which is dual to 4D U(1)3 anomaly. We present a systematic solution of the helicity ±1 wave equations in long wave-length expansion, and obtain the corresponding dispersion relations. The results depen d on the sign of helicity, which may be called chiral shear waves. (author)
Implications of Orientation in Sheared Cocoa Butter
Guthrie, Sarah E.; Mazzanti, Gianfranco; Marangoni, Alejandro; Idziak, Stefan H. J.
2004-03-01
We will present x-ray and mechanical studies of oriented phases of cocoa butter. The structural elements of foods play an important role in determining such things as quality and shelf stability. The specific structure and properties of cocoa butter, however, are complicated due to the ability of the cocoa butter to form crystals in six polymorphic forms. Recent work has shown that the application of shear not only accelerates the transitions to more stable polymorphs, but also causes orientation of the crystallites[1]. The implications of orientation on the structures formed under conditions of shear and cooling will be described using x-ray diffraction and mechanical measurements. 1 G. Mazzanti, S. E. Guthrie, E. B. Sirota et al., Crystal Growth & Design 3 (5), 721 (2003).
Super-diffusion in sheared suspensions
Souzy, Mathieu; Yin, Xiaolong; Villermaux, Emmanuel; Abid, Chérifa; Metzger, Bloen
2015-04-01
We investigate the dispersion of a layer of dye initially applied at the outer wall of a cylindrical Couette-cell into a sheared suspension of non-Brownian spherical particles. The process is directly visualized and quantified at the particle scale. A "rolling-coating" mechanism is found to convectively transport the dye at a constant rate directly from the wall towards the bulk. The fluid velocity fluctuations, u', measured with particle image velocimetry, and the imposed shear-rate, ? ? , are used to define a diffusion coefficient, D ? / ? ? , which is found to increase linearly with the distance from the wall. A solution of the transport equation accounting for this inhomogeneous stirring field describes quantitatively the concentration profiles measured experimentally. It exhibits a super-diffusive character, a consequence of the increase of the stirring strength with distance from the wall. Movies are available with the online version of the paper.
Shear banding in soft glassy materials
Fielding, Suzanne M.
2013-01-01
Many soft materials, including foams, dense emulsions, micro gel bead suspensions, star polymers, dense packing of surfactant onion micelles, and textured morphologies of liquid crystals, share the basic "glassy" features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material b...
Standing shear waves in anisotropic viscoelastic media
Krit, T.; Golubkova, I.; Andreev, V.
2015-10-01
We studied standing shear waves in anisotropic resonator represented by a rectangular parallelepiped (layer) fixed without slipping between two wooden plates of finite mass. The viscoelastic layer with edges of 70 mm × 40 mm × 15 mm was made of a rubber-like polymer plastisol with rubber bands inside. The bands were placed vertical between the top and the bottom plate. Mechanical properties of the plastisol itself were carefully measured previously. It was found that plastisol shows a cubic nonlinear behavior, i.e. the stress-strain curve could be represented as: ? = ?? + ???3, where ? stands for shear strain and ? is an applied shear stress. The value of shear modulus ? depends on frequency and was found to be several kilopascals which is common for such soft solids. Nonlinear parameter ? is frequency dependent too and varies in range from tenths to unity at 1-100 Hz frequency range, decreasing with frequency growth. Stretching the rubber bands inside the layer leads to change of elastic properties in resonator. Such effect could be noticed due to frequency response of the resonator. The numerical model of the resonator was based on finite elements method (FEM) and performed in MatLab. The resonator was cut in hundreds of right triangular prisms. Each prism was provided with viscoelastic properties of the layer except for the top prisms provided with the wooden plate properties and the prisms at the site of the rubber bands provided with the rubber properties. The boundary conditions on each prism satisfied the requirements that resonator is inseparable and all its boundaries but bottom are free. The bottom boundary was set to move horizontally with constant acceleration amplitude. It was shown numerically that the resonator shows anisotropic behavior expressed in different frequency response to oscillations applied to a bottom boundary in different directions.
Structures and shear response of lipid monolayers
International Nuclear Information System (INIS)
This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases
On the persistence of adiabatic shear bands
Bassim M.N.; Boakye-Yiadom S.; Al-Ameeri S.
2012-01-01
It is generally agreed that the initiation and development of adiabatic shear bands (ASBs) are manifestations of damage in metallic materials subjected to high strain rates and large strains as those due to impact in a Hopkinson Bar system. Models for evolution of these bands have been described in the literature. One question that has not received attention is how persistent these bands are and whether their presence and effect can be reversed or eliminated by using a process of thermal (hea...
Timescales in shear banding of wormlike micelles
Radulescu, O.; Olmsted, P. D.; Decruppe, J. P.; Lerouge, S.; Berret, J.F.; Porte, G.
2002-01-01
We show the existence of three well defined time scales in the dynamics of wormlike micelles after a step between two shear rates on the stress plateau. These time scales are compatible with the presence of a structured interface between bands of different viscosities and correspond to the isotropic band destabilization during the stress overshoot, reconstruction of the interface after the overshoot and travel of a fully formed interface. The last stage can be used to estima...
Testing modified gravity with cosmic shear
Harnois-Déraps, J.; Munshi, D.; Valageas, P.; van Waerbeke, L.; Brax, P.; Coles, P.; Rizzo, L.
2015-12-01
We use the cosmic shear data from the Canada-France-Hawaii Telescope Lensing Survey to place constraints on f(R) and Generalized Dilaton models of modified gravity. This is highly complementary to other probes since the constraints mainly come from the non-linear scales: maximal deviations with respects to the General Relativity (GR) + ? cold dark matter (?CDM) scenario occurs at k ˜ 1 h Mpc-1. At these scales, it becomes necessary to account for known degeneracies with baryon feedback and massive neutrinos, hence we place constraints jointly on these three physical effects. To achieve this, we formulate these modified gravity theories within a common tomographic parametrization, we compute their impact on the clustering properties relative to a GR universe, and propagate the observed modifications into the weak lensing ?± quantity. Confronted against the cosmic shear data, we reject the f(R) \\lbrace |f_{R_0}| = 10^{-4}, n = 1\\rbrace model with more than 99.9 per cent confidence interval (CI) when assuming a ?CDM dark matter only model. In the presence of baryonic feedback processes and massive neutrinos with total mass up to 0.2 eV, the model is disfavoured with at least 94 per cent CI in all different combinations studied. Constraints on the \\lbrace |f_{R_0}| = 10^{-4}, n = 2\\rbrace model are weaker, but nevertheless disfavoured with at least 89 per cent CI. We identify several specific combinations of neutrino mass, baryon feedback and f(R) or Dilaton gravity models that are excluded by the current cosmic shear data. Notably, universes with three massless neutrinos and no baryon feedback are strongly disfavoured in all modified gravity scenarios studied. These results indicate that competitive constraints may be achieved with future cosmic shear data.
Plasticity Approach to HSC Shear Wall Design
DEFF Research Database (Denmark)
Liu, Lunying; Nielsen, Mogens Peter
1998-01-01
The paper describes a simple theory for determining the ultimate strength of shear walls. It is based on application of the theory of perfectly plastic materials. When applied to concrete the theoretical solutions must be modified by inserting into the solutions a reduced compressive strength of concrete. The reduced strength is named the effective strength. The paper describes simple lower bound solutions. They consist of pure strut action or strut action combined with diagonal compression fiel...
Shear and Compression Viscoelasticity in Polymer Monolayers
Ferenczi, Toby A. M.; Cicuta, Pietro
2005-01-01
Poly-vinlyacetate (PVAc) forms very stable and reproducible monolayers on the surface of water, a model system to understand polymer physics on two dimensions. A recently introduced technique is applied here to to study viscoelasticity of PVAc monolayers. The method is based on measurement of surface tension in two orthogonal directions during anisotropic deformation. Compression and shear moduli are explored over a very large concentration range, highlighting a series of fo...
On statistically stationary homogeneous shear turbulence
Schumacher, J; Schumacher, Joerg; Eckhardt, Bruno
2000-01-01
A statistically stationary turbulence with a mean shear gradient is realized in a flow driven by suitable body forces. The flow domain is periodic in downstream and spanwise direction and bounded by stress free surfaces in the normal direction. Except for small layers near the surfaces the flow is homogeneous. The fluctuations in turbulent energy are less violent than in the simulations using remeshing and the anisotropy on small scales as measured by the skewness of derivatives is smaller.
Turbulence spreading in reversed shear plasmas
International Nuclear Information System (INIS)
Turbulence spreading in reversed shear plasmas is investigated using a simple, multi-fluid model of ITG turbulence in toroidal geometry. The temperature profile modification is accompanied by avalanche processes. In addition, it is found that the turbulence spreads inwards and outwards, owing to the nonlinear interactions of turbulence. Analysis of the simulation results indicates that the spatio-temporal propagation of the turbulence front is quantitatively consistent with the scaling of speed predicted by the Fisher front theory
Mesoscale Elucidation of Biofilm Shear Behavior
Barai, Pallab; Kumar, Aloke; Partha P. Mukherjee
2015-01-01
Formation of bacterial colonies as biofilm on the surface/interface of various objects has the potential to impact not only human health and disease but also energy and environmental considerations. Biofilms can be regarded as soft materials, and comprehension of their shear response to external forces is a key element to the fundamental understanding. A mesoscale model has been presented in this article based on digitization of a biofilm microstructure. Its response under e...
Faults (shear zones) in the mantle (Invited)
Tommasi, A.; Vauchez, A. R.; Mainprice, D.
2013-12-01
A variety of evidence, from direct observations of deformed peridotites in orogenic massifs, ophiolites, and mantle xenoliths to seismic reflectors and seismic anisotropy beneath major fault zones, consistently supports prolongation of major faults into the lithospheric mantle. However, the geometry of these mantle faults and the mechanisms accommodating this deformation remain poorly understood. Coupling between deformation in frictional faults in the uppermost crust and localized shearing in the ductile crust and mantle is required to explain post-seismic deformation, but mantle viscosities deduced from geodetic data and extrapolated from laboratory experiments are only reconciled if temperatures in the shallow lithospheric mantle are high (>800 °C at the Moho). There is a large discrepancy between the scale at which deformation processes are studied (a few kilometers, at most, due to the limited size of continuous mantle exposures at the Earth's surface) and the scale inferred for strain localization in the mantle from geophysical observations (tens of kilometers), combining structural and seismic properties data for naturally deformed peridotites and seismological observations allows discussing strain localization and development of shear zones in the lithospheric mantle. Seismic anisotropy, especially shear wave splitting, provides strong evidence for coherent deformation over domains several tens of km wide in the lithospheric mantle beneath major transcurrent faults, but it cannot detect narrow strain localization zones or shallowly dipping faults. Shallow-dipping seismic reflectors imaged by seismic profiles in the lithospheric mantle are interpreted as the continuation of normal or, less frequently, inverse faults in the mantle. Subhorizontal reflectors deep in the mantle lithosphere are also reported by receiver function studies. However, the nature of these reflectors (compositional or anisotropy gradients) is poorly understood, as illustrated by forward models of the seismic properties of mantle shear zones.
Transversely Compressed- and Restrained Shear Joints
DEFF Research Database (Denmark)
Schmidt, Jacob Wittrup; Hansen, Christian Skodborg
2013-01-01
Anchorage of FRP strengthening systems where the deformation perpendicular to the FRP material is restrained or a compressive force is applied on the strengthening, seems to provide ductility, increased utilization of the FRP and failure modes which can be controlled through the anchorage method. This paper presents theoretical model which can predict the response of transversely compressed and restrained single- and double lap shear joints. The interface material model is based on a cohesive la...
Self-organization in circular shear layers
DEFF Research Database (Denmark)
Bergeron, K.; Coutsias, E.A.; Lynov, Jens-Peter; Nielsen, A.H.
1996-01-01
Experiments on forced circular shear layers performed in both magnetized plasmas and in rotating fluids reveal qualitatively similar self-organization processes leading to the formation of patterns of coherent vortical structures with varying complexity. In this paper results are presented from both weakly nonlinear analysis and full numerical simulations that closely reproduce the experimental observations. Varying the Reynolds number leads to bifurcation sequences accompanied by topological ch...
Optimisation and control of shear flows
Monokrousos, Antonios
2011-01-01
Transition to turbulence and flow control are studied by means of numerical simulations for different simple shear flows. Linear and non-linear optimisation methods using the Lagrange multiplier technique are employed. In the linear framework as objective function the standard disturbance kinetic energy is chosen and the constraints involve the linearised Navier–Stokes equations. We consider both the optimal initial condition leading to the largest disturbance energy growth at finite times an...
Quasi phase transition model of shear bands in metallic glasses
International Nuclear Information System (INIS)
A quasi phase transition model of shear bands in metallic glasses (MGs) is presented from the thermodynamic viewpoint. Energy changes during shear banding in a sample-machine system are analyzed following fundamental energy theorems. Three characteristic parameters, i.e. the critical initiation energy ?Gc, the shear band stability index k0, and the critical shear band length lc, are derived to elucidate the initiation and propagation of shear bands. The criteria for good plasticity in MGs with predominant thermodynamic arrest of shear bands are proposed as low ?Gc, large k0, and small lc. The model, combined with experimental results, is used to analyze some controversial phenomena of deformation behavior in MGs, such as the size effect, the effect of testing machine stiffness and the relationship between elastic modulus and plasticity. This study has important implications for a fundamental understanding of shear banding as well as deformation mechanisms in MGs and provides a theoretical basis for improving the ductility of MGs.
Microphase transitions of block copolymer/homopolymer under shear flow
Directory of Open Access Journals (Sweden)
Y. Guo
2015-06-01
Full Text Available Cell dynamics simulation is used to investigate the phase behavior of block copolymer/homopolymer mixture subjected to a steady shear flow. Phase transitions occur from transverse to parallel and then to perpendicular lamellar structure with an increase of shear rate and this is the result of interaction between the shear flow and the concentration fluctuation. Rheological properties, such as normal stress differences and shear viscosity, are all closely related with the direction of the lamellae. Furthermore, we specifically explore the phase behavior and the order parameter under weak and strong shear of two different initial states, and realize the importance of the thermal history. It is necessary to apply the shear field at the appropriate time if we want to get what we want. These results provide an easy method to create ordered, defect-free materials in experiment and engineering technology through imposing shear flow.
Shear sensing based on a microstrip patch antenna
International Nuclear Information System (INIS)
A microstrip patch antenna sensor was studied for shear sensing with a targeted application of measuring plantar shear distribution on a diabetic foot. The antenna shear sensor consists of three components, namely an antenna patch, a soft foam substrate and a slotted ground plane. The resonant frequency of the antenna sensor is sensitive to the overlapping length between the slot in the ground plane and the antenna patch. A shear force applied along the direction of the slot deforms the foam substrate and causes a change in the overlapping length, which can be detected from the antenna frequency shift. The antenna shear sensor was designed based on simulated antenna frequency response and validated by experiments. Experimental results indicated that the antenna sensor exhibits high sensitivity to shear deformation and responds to the applied shear loads with excellent linearity and repeatability. (paper)
Shear strength of oil palm shell foamed concrete beams
International Nuclear Information System (INIS)
Four reinforced oil palm shell foamed concrete (OPSFC) beams were fabricated, and their shear behaviour was tested. The OPSFC has a target density of approximately 1600 kg/m3 and a 28-day compressive strength of about 20 MPa. Two beams were cast with shear reinforcements while the other two were cast without such reinforcements. For comparison, four reinforced normal weight concrete (NWC) beams were also cast. The beams that contained shear links failed in flexure mode, while those without links failed in shear mode. The experimental results indicated that the shear capacities of OPSFC beams without shear links are higher than those of the NWC beams and exhibit more flexural and shear cracks.
A bilateral shear layer between two parallel Couette flows
Narasimhamurthy, Vagesh D; Andersson, Helge I
2012-01-01
We consider a shear layer of a kind not previously studied to our knowledge. Contrary to the classical free shear layer, the width of the shear zone does not vary in the streamwise direction but rather exhibits a lateral variation. Based on some simplifying assumptions, an analytic solution has been derived for the new shear layer. These assumptions have been justified by a comparison with numerical solutions of the full Navier-Stokes equations, which accord with the analytical solution to better than $1\\%$ in the entire domain. An explicit formula is found for the width of the shear zone as a function of wall-normal coordinate. This width is independent of wall velocities in the laminar regime. Preliminary results for a co-current laminar-turbulent shear layer in the same geometry are also presented. Shear-layer instabilities were then developed and resulted in an unsteady mixing zone at the interface between the two co-current streams.
Shear Stress Sensing using Elastomer Micropillar Arrays
Wohl, Christopher J.; Palmieri, Frank L.; Lin, Yi; Jackson, Allen M.; Cissoto, Alexxandra; Sheplak, Mark; Connell, John W.
2013-01-01
The measurement of shear stress developed as a fluid moves around a solid body is difficult to measure. Stresses at the fluid-solid interface are very small and the nature of the fluid flow is easily disturbed by introducing sensor components to the interface. To address these challenges, an array of direct and indirect techniques have been investigated with various advantages and challenges. Hot wire sensors and other indirect sensors all protrude significantly into the fluid flow. Microelectromechanical systems (MEMS) devices, although facilitating very accurate measurements, are not durable, are prone to contamination, and are difficult to implement into existing model geometries. One promising approach is the use of engineered surfaces that interact with fluid flow in a detectable manner. To this end, standard lithographic techniques have been utilized to generate elastomeric micropillar arrays of various lengths and diameters. Micropillars of controlled length and width were generated in polydimethylsiloxane (PDMS) elastomer using a soft-lithography technique. The 3D mold for micropillar replication was fabricated using laser ablative micromachining and contact lithography. Micropillar dimensions and mechanical properties were characterized and compared to shear sensing requirements. The results of this characterization as well as shear stress detection techniques will be discussed.
Shear bond strengths of orthodontic plastic brackets.
Guan, G; Takano-Yamamoto, T; Miyamoto, M; Hattori, T; Ishikawa, K; Suzuki, K
2000-04-01
The purpose of the present study was to evaluate the shear bond strengths of plastic brackets and the influences of the bracket filler contents on the bonding. The shear bond strengths of 4 plastic brackets (Spirit; Spirit MB; Clear Bracket; Aesthetic-Line) bonded to enamel with 4 orthodontic adhesives (Orthomite Superbond; System 1+; Transbond XT; and Kurasper-F) were compared with the strength of a conventional metal bracket. The findings of this study indicated the following: (1) shear bond strength of the 4 plastic brackets was significantly lower than that of the conventional metal brackets (P brackets, Aesthetic-Line had the largest value followed by Spirit MB, Spirit, and Clear Bracket, and when the plastic brackets were bonded with Orthomite Superbond, they showed relatively stronger bond strengths than when bonded with the other adhesives. Clear Bracket showed relatively lower values especially when bonded with System 1+; (3) the application of primer did not increase the durability of the bond strengths when bonding Spirit and Clear brackets; and (4) fillers contained in each plastic bracket ranging from 9.18% to 19. 52% were fairly well distributed and showed the same morphology of a fiber type 10 microm in diameter with different lengths. The filler concentration tended to correlate with the bond strength. The exposed fillers on the bracket base surface may play a more important role in plastic bracket adhesion than the macro-morphology of the base surface. PMID:10756269
High-shear-rate optical rheometer
Mriziq, K. S.; Dai, H. J.; Dadmun, M. D.; Jellison, G. E.; Cochran, H. D.
2004-06-01
We have developed a parallel-plate rheometer in a magnetic-disk drive configuration constructed of optically transparent materials and operating with a very small gap for measurements at very high shear rates. The friction force at the disk-slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating. Both disk and slider have been made of optically transparent material to allow optical measurements simultaneously with the rheological measurements. In the present mode, the apparatus is set up for simultaneous rheometery and birefringence measurements on a thin film of polymer lubricant. Rheology and birefringence measurements were made on a perfluoropolyether lubricant over a range of strain rate from 103 s-1 to greater than 106 s-1 with 800 nm, 400 nm, and 200 nm film thicknesses.
Density-shear instability in electron MHD
Wood, Toby S; Lyutikov, Maxim
2014-01-01
We discuss a novel instability in inertia-less electron magneto-hydrodynamics (EMHD), which arises from a combination of electron velocity shear and electron density gradients. The unstable modes have a lengthscale longer than the transverse density scale, and a growth-rate of the order of the inverse Hall timescale. We suggest that this density-shear instability may be of importance in magnetic reconnection regions on scales smaller than the ion skin depth, and in neutron star crusts. We demonstrate that the so-called Hall drift instability, previously argued to be relevant in neutron star crusts, is a resistive tearing instability rather than an instability of the Hall term itself. We argue that the density-shear instability is of greater significance in neutron stars than the tearing instability, because it generally has a faster growth-rate and is less sensitive to geometry and boundary conditions. We prove that, for uniform electron density, EMHD is "at least as stable" as regular, incompressible MHD, in...
Shear measurements of bulk solid ^4He
Day, James; Beamish, John
2007-03-01
Recent torsional oscillator experiments indicate that the non-classical rotational inertia (NCRI) fraction depends on isotopic purity and on the details of crystal growth and annealing, suggesting that defects may be involved. While solid helium does not flow in response to pressure gradients at low temperatures, plastic deformation of solid helium closer to melting creates defects and pressure gradients which are not easily eliminated by thermal annealing. Similar defects must be created during crystal growth by the blocked capillary method or by large thermal gradients. Given the theoretical arguments against supersolidity in defect-free crystals and the preliminary experimental evidence linking NCRI to annealing, it is important to control and study defects in solid helium more directly. To that effect, we have begun to study the static and low frequency shear deformation of crystals grown by different methods. This is a direct measure of the shear modulus of the crystal and should allow us to separate elastic from inertial effects. We can also compare the elastic to the plastic deformation response by increasing the magnitude of the shear stress applied to the crystal. We will describe our experimental design and present preliminary results.
Singular eigenfunctions for shearing fluids I
Energy Technology Data Exchange (ETDEWEB)
Balmforth, N.J.; Morrison, P.J.
1995-02-01
The authors construct singular eigenfunctions corresponding to the continuous spectrum of eigenvalues for shear flow in a channel. These modes are irregular as a result of a singularity in the eigenvalue problem at the critical layer of each mode. They consider flows with monotonic shear, so there is only a single critical layer for each mode. They then solve the initial-value problem to establish that these continuum modes, together with any discrete, growing/decaying pairs of modes, comprise a complete basis. They also view the problem within the framework of Hamiltonian theory. In that context, the singular solutions can be viewed as the kernel of an integral, canonical transformation that allows us to write the fluid system, an infinite-dimensional Hamiltonian system, in action-angle form. This yields an expression for the energy in terms of the continuum modes and provides a means for attaching a characteristic signature (sign) to the energy associate with each eigenfunction. They follow on to consider shear-flow stability within the Hamiltonian framework. Next, the authors show the equivalence of integral superpositions of the singular eigenfunctions with the solution derived with Laplace transform techniques. In the long-time limit, such superpositions have decaying integral averages across the channel, revealing phase mixing or continuum damping. Under some conditions, this decay is exponential and is then the fluid analogue of Landau damping. Finally, the authors discuss the energetics of continuum damping.
Shear flow in smectic A liquid crystals
International Nuclear Information System (INIS)
This paper considers the onset of a shear-induced instability in a sample of smectic A liquid crystal. Unlike many previous models, the usual director n need not necessarily coincide with the local smectic layer normal a; the traditional Oseen constraint (?xa=0) is not imposed when flow is present. A recent dynamic theory for smectic A (Stewart 2007 Contin. Mech. Thermodyn. 18 343-60) will be used to examine a stationary instability in a simple model when the director reorientation and smectic layer distortions are, firstly, assumed not to be coupled to the velocity and, secondly, are supposed coupled to the velocity. A critical shear rate at which the onset of the instability occurs will be identified, together with an accompanying critical director tilt angle and critical wavenumber for the associated smectic layer undulations. Despite some critical phenomena being largely unaffected by any coupling to the flow, it will be shown that the influence of some material parameters, especially the smectic layer compression constant B0 and the coupling constant B1, upon the critical shear rate and critical tilt angle can be greatly affected by flow.
Horizontal Shear Wave Imaging of Large Optics
Energy Technology Data Exchange (ETDEWEB)
Quarry, M J
2007-09-05
When complete the National Ignition Facility (NIF) will be the world's largest and most energetic laser and will be capable of achieving for the first time fusion ignition in the laboratory. Detecting optics features within the laser beamlines and sizing them at diameters of 0.1 mm to 10 mm allows timely decisions concerning refurbishment and will help with the routine operation of the system. Horizontally polarized shear waves at 10 MHz were shown to accurately detect, locate, and size features created by laser operations from 0.5 mm to 8 mm by placing sensors at the edge of the optic. The shear wave technique utilizes highly directed beams. The outer edge of an optic can be covered with shear wave transducers on four sides. Each transducer sends a pulse into the optic and any damage reflects the pulse back to the transmitter. The transducers are multiplexed, and the collected time waveforms are enveloped and replicated across the width of the element. Multiplying the data sets from four directions produces a map of reflected amplitude to the fourth power, which images the surface of the optic. Surface area can be measured directly from the image, and maximum depth was shown to be correlated to maximum amplitude of the reflected waveform.
Microscopic Order Parameter for Shear Anisotropy for Systems near Shear Jamming
Ren, Jie; Dijksman, Joshua; Behringer, Robert
2013-11-01
Sheared granular systems at packing fractions between ?s stress. A system, prepared in a stress-free states in this density range, upon being sheared exhibits first fragile, then shear jammed states, both having high stress and fabric anisotropy. The onset of shear jammed states resembles an order-disorder transition. In recent work, we showed that the order appears in a force space (Bi et al. to appear, PRL). Here, we identify an order parameter associated with individual particles, making it possible to construct correlations in physical space. We identify local (particle-scale) order with ?, the deviatoric part of the force-moment tensor. This is a real symmetric, traceless matrix characterized by two coefficients, a and b, such that ? = aU1 + bU2 , and where U1 is diagonal with elements +/- 1 , and U2 has 0's on the diagonal, and 1 for the off-diagonal elements. The Ui's are orthogonal under an appropriate scalar product. Then, (a , b) provides a vector particle-scale order parameter. ? is additive over all particles, and is analogous to the magnetization in a spin system. Also, particles with orthogonal shear stresses now correspond to anti-parallel vectors. We use this representation to investigate both the collective order of the system and also correlations. This talk presents analysis of experimental data that explore the properties of this new order parameter.
Shear flow effect on ion temperature gradient vortices in plasmas with sheared magnetic field
DEFF Research Database (Denmark)
Chakrabarti, N.; Juul Rasmussen, J.
1999-01-01
The effect of velocity shear on ion temperature gradient (ITG) driven vortices in a nonuniform plasma in a curved, sheared magnetic field is investigated. In absence of parallel ion dynamics, vortex solutions for the ITG mode are studied analytically. It is shown that under certain conditions the coupled equations for potential and pressure exhibit special tripolar vortex-like structures. For the general case, however, parallel ion dynamics is included and the equation describing the stationary ITG vortex has the structure of a nonlinear Poisson-type equation. Analytical as well as numerical solutions of this equation are presented for various possible cases. It is shown that, for a critical value of the velocity shear asymmetric dipolar vortices can arise which are strongly modified as a localized vortex chain at resonance. For strong velocity shear these structures are destroyed and ultimately lead to a dominating monopolar form. The effects of magnetic shear indicate it may destroy these structures. (C) 1999 American Institute of Physics.
Shear strength and permeability evolution during shear-holding in single rock fracture
International Nuclear Information System (INIS)
This paper presents direct shear test results for single jointed granite and mortar specimens to investigate effects of long-term load holding on mechanical and hydrological properties of rock joints. From the test results, it was confirmed that shear strength increased and permeability decreased for mortar specimens through three days load holding. For granite specimens, however, significant change was not confirmed on mechanical and hydrological properties through up to twenty days load holding due to smallness of confining pressure compared with the strength of granite and shortness of load holding. Relationship between the time of shear holding (th) and the growth of shear strength during shear holding (??) was examined for mortar specimens. When tn was shorter than 106sec, ?? increased in proportional to the logarithm of th as Dieterich's log-linear model, which explains the time-dependency of ?? as increase of contact area of fracture surface due to asperity creep. When th was about 106sec, however, ?? was larger than the value predicted by the Dieterich's log-linear model. This result implies growth of adhesion driven by chemical action at contact area of fracture surface such as pressure solution and precipitation. (author)
Energy Technology Data Exchange (ETDEWEB)
Roar Skartlien; Espen Sollum; Andreas Akselsen; Paul Meakin
2012-07-01
A 3D lattice Boltzmann model for two-phase flow with amphiphilic surfactant was used to investigate the evolution of emulsion morphology and shear stress in starting shear flow. The interfacial contributions were analyzed for low and high volume fractions and varying surfactant activity. A transient viscoelastic contribution to the emulsion rheology under constant strain rate conditions was attributed to the interfacial stress. For droplet volume fractions below 0.3 and an average capillary number of about 0.25, highly elliptical droplets formed. Consistent with affine deformation models, gradual elongation of the droplets increased the shear stress at early times and reduced it at later times. Lower interfacial tension with increased surfactant activity counterbalanced the effect of increased interfacial area, and the net shear stress did not change significantly. For higher volume fractions, co-continuous phases with a complex topology were formed. The surfactant decreased the interfacial shear stress due mainly to advection of surfactant to higher curvature areas. Our results are in qualitative agreement with experimental data for polymer blends in terms of transient interfacial stresses and limited enhancement of the emulsion viscosity at larger volume fractions where the phases are co-continuous.
Distribution functions of a simple fluid under shear. II. High shear rates
International Nuclear Information System (INIS)
The distortion of structure of a simple, inverse 12 soft-sphere fluid undergoing plane Couette flow is studied by nonequilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) with a high-shear-rate version of the nonequilibrium (NE) potential obtained recently from the NE distribution function theory of Gan and Eu [Phys. Rev. A 45, 3670; 46, 6344 (1992)]. The theory suggests a NE potential under which the equilibrium structure of the fluid is that of a NE fluid, and also suggests a corresponding Ornstein-Zernike equation with its closure relations. As in the low-shear-rate case [Yu. V. Kalyuzhnyi, S. T. Cui, P. T. Cummings, and H. D. Cochran, Phys. Rev. E 60, 1716 (1999)] the agreement between EMD and the modified hypernetted chain version of the theory is good. Although the high-shear-rate version of the NE potential improves the agreement between NEMD and EMD results (in comparison with the low-shear-rate version), its predictions are still unsatisfactory. With the high-shear-rate NE potential, EMD gives qualitatively correct predictions only for the shift of the position of the first maximum of the NE distribution function. The corresponding changes in the magnitude of the first maximum predicted by EMD have an opposite direction in comparison with those predicted by NEMD. It is concluded that the NE potential used is not very successful, and more accurate models for the potential are needed
Dynamic Modes of Microcapsules in Steady Shear Flow: Effects of Bending and Shear Elasticities
Noguchi, Hiroshi
2010-01-01
The dynamics of microcapsules in steady shear flow was studied using a theoretical approach based on three variables: The Taylor deformation parameter $\\alpha_{\\rm D}$, the inclination angle $\\theta$, and the phase angle $\\phi$ of the membrane rotation. It is found that the dynamic phase diagram shows a remarkable change with an increase in the ratio of the membrane shear and bending elasticities. A fluid vesicle (no shear elasticity) exhibits three dynamic modes: (i) Tank-treading (TT) at low viscosity $\\eta_{\\rm {in}}$ of internal fluid ($\\alpha_{\\rm D}$ and $\\theta$ relaxes to constant values), (ii) Tumbling (TB) at high $\\eta_{\\rm {in}}$ ($\\theta$ rotates), and (iii) Swinging (SW) at middle $\\eta_{\\rm {in}}$ and high shear rate $\\dot\\gamma$ ($\\theta$ oscillates). All of three modes are accompanied by a membrane ($\\phi$) rotation. For microcapsules with low shear elasticity, the TB phase with no $\\phi$ rotation and the coexistence phase of SW and TB motions are induced by the energy barrier of $\\phi$ rotat...
Skorski, Stanislav
2011-01-01
Edge fracture occurs frequently in non-Newtonian fluids. A similar instability has often been reported at the free surface of fluids undergoing shear banding, and leads to expulsion of the sample. In this paper the distortion of the free surface of such a shear banding fluid is calculated by balancing the surface tension against the second normal stresses induced in the two shear bands, and simultaneously requiring a continuous and smooth meniscus. We show that wormlike micelles typically retain meniscus integrity when shear banding, but in some cases can lose integrity for a range of average applied shear rates during which one expects shear banding. This meniscus fracture would lead to ejection of the sample as the shear banding region is swept through. We further show that entangled polymer solutions are expected to display a propensity for fracture, because of their much larger second normal stresses. These calculations are consistent with available data in the literature. We also estimate the meniscus di...
A minimal model for chaotic shear-banding in shear-thickening fluids
Aradian, A
2005-01-01
We present a minimal model for spatiotemporal oscillation and rheochaos in shear-thickening complex fluids at zero Reynolds number. In the model, a tendency towards inhomogeneous flows in the form of shear bands combines with a slow structural dynamics, modelled by delayed stress relaxation. Using Fourier-space numerics, we study the nonequilibrium `phase diagram' of the fluid as a function of a steady mean (spatially averaged) stress, and of the relaxation time for structural relaxation. We find several distinct regions of periodic behavior (oscillating bands, travelling bands, and more complex oscillations) and also regions of spatiotemporal rheochaos. A low-dimensional truncation of the model retains the important physical features of the full model (including rheochaos) despite the suppression of sharply defined interfaces between shear bands. Our model maps onto the FitzHugh-Nagumo model for neural network dynamics, with an unusual form of long-range coupling.
Shear strength of non-shear reinforced concrete elements : Part 3. Prestressed hollow-core slabs
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
The paper deals with the shear strength of prestressed hollow-core slabs determined by the theory of plasticity. Two failure mechanisms are considered in order to derive the solutions.In the case of sliding failure in a diagonal crack, the shear strength is determined by means of the crack sliding model developed by Jin-Ping Zhang. The model takes into account the resistance against formation of cracks due to prestressing as well as the variation of the prestressing force in the transfer zone.Due to the fact that the anchorage of the reinforcement takes place by bond, a rotation failure, which is induced by a crack formed at the support with subsequent slip of the reinforcement, is also considered. This failure mode is likely to occur in cases with a high prestressing force combined with a short shear span.The theoretical calculations are compared with test results from the literature. A good agreement has been found.
Turbulence reduction and poloidal shear steepening in reversed shear plasmas on Tore Supra
International Nuclear Information System (INIS)
Infra-red light scattering is used to characterize turbulence during reversed shear scenario obtained by a fast current ramp-up on Tore Supra. The preformed hollow profile is frozen using ion cyclotron resonance frequency minority heating (ICRH). Turbulence intensity is recorded to dramatically decrease during the ramp-up and to recover smoothly as the discharge is ended. The core reduction, deduced from the light scattering measurements, is confirmed by the effective heat diffusivity behaviour. Turbulence reduction is shown to occur simultaneously with the steepening of the radial electric field shear, deduced from the frequency spectra, as well as with the negative or flat magnetic shear. In consequence, a confinement improvement of about 40% is achieved for about two seconds. (authors)
Kornuta, Jeffrey A; Nepiyushchikh, Zhanna; Gasheva, Olga Y; Mukherjee, Anish; Zawieja, David C; Dixon, J Brandon
2015-11-01
Given the known mechanosensitivity of the lymphatic vasculature, we sought to investigate the effects of dynamic wall shear stress (WSS) on collecting lymphatic vessels while controlling for transmural pressure. Using a previously developed ex vivo lymphatic perfusion system (ELPS) capable of independently controlling both transaxial pressure gradient and average transmural pressure on an isolated lymphatic vessel, we imposed a multitude of flow conditions on rat thoracic ducts, while controlling for transmural pressure and measuring diameter changes. By gradually increasing the imposed flow through a vessel, we determined the WSS at which the vessel first shows sign of contraction inhibition, defining this point as the shear stress sensitivity of the vessel. The shear stress threshold that triggered a contractile response was significantly greater at a transmural pressure of 5 cmH2O (0.97 dyne/cm(2)) than at 3 cmH2O (0.64 dyne/cm(2)). While contraction frequency was reduced when a steady WSS was applied, this inhibition was reversed when the applied WSS oscillated, even though the mean wall shear stresses between the conditions were not significantly different. When the applied oscillatory WSS was large enough, flow itself synchronized the lymphatic contractions to the exact frequency of the applied waveform. Both transmural pressure and the rate of change of WSS have significant impacts on the contractile response of lymphatic vessels to flow. Specifically, time-varying shear stress can alter the inhibition of phasic contraction frequency and even coordinate contractions, providing evidence that dynamic shear could play an important role in the contractile function of collecting lymphatic vessels. PMID:26333787
Jaishankar, Aditya; Wee, May; Matia-Merino, Lara; Goh, Kelvin K T; McKinley, Gareth H
2015-06-01
Mamaku gum is a polysaccharide extracted from the fronds of the black tree fern found in New Zealand. The cooked pith has traditionally been used for various medicinal purposes and as a food source by the Maori people of New Zealand. It has potential applications as a thickener in the food industry and as a palliative for patients with dysphagia. Studies on the shear rheology of Mamaku gum have revealed that the gum exhibits shear thickening at a critical shear rate due to a transition from intra- to inter-molecular chain interactions upon shear-induced chain elongation. In this paper, we demonstrate that these interactions are primarily due to hydrogen bonding. We perform extensional rheology on mixtures of Mamaku gum and urea (a known disruptor of hydrogen bonds) to quantify the nature of these interactions. Capillary Breakup Extensional Rheometry (CaBER) performed on the pure Mamaku gum solutions yield plateau values of the Trouton ratio as high as ?10(4), showing that the viscoelasticity of the gum in uniaxial elongation is much higher than in shear. For all Mamaku concentrations tested, the extensional viscosity decreases upon increasing urea concentration. Furthermore, the relaxation time decreases exponentially with increasing urea concentration. This exponential relationship is independent of the Mamaku concentration, and is identical to the relationships between urea concentration and characteristic timescales measured in nonlinear shear rheology. We show using the sticky reptation model for polymers with multiple sticker groups along the backbone how such a relationship is consistent with a linear decrease in the free energy for hydrogen bond dissociation. We then demonstrate that a time-concentration superposition principle can be used to collapse the viscoelastic properties of the Mamaku-gum/urea mixtures. PMID:25843844
Evolution of thermal ion transport barriers in reversed shear/optimised shear plasmas
International Nuclear Information System (INIS)
The effects of the magnetic and ExB rotation shears on the thermal ion transport in advanced tokamak scenarios are analyzed through the predictive modelling of the evolution of internal transport barriers. Such a modelling is performed with an experimentally validated L-mode thermal diffusivity completed with a semi-empirical shear correction which is based on simple theoretical arguments from turbulence studies. A multi-machine test of the model on relevant discharges from the ITER Data Base (TFTR, DIII-D and JET) is presented. (author)
Establishment of the Deep-sea Soft Sediments Shearing Strength-Shearing Displacement Model
Hongyun Wu; Jiangsan He; Xinming Chen; Yuqing Gao; Shaojun Liu
2009-01-01
The shearing strength-shearing displacement model of deep-sea soft sediments is very important to predict the traction and slip ratio of nodule collector, and optimize the running mechanism of nodule collector. According to the physical mechanics characters of the deep-sea soft sediments, the 400 sodium molybdate swell soils are selected as the preparation materials of the deep-sea soft sediments, and the demixion preparation method is adopted to simulate the deep-sea soft sediments in the la...
Directory of Open Access Journals (Sweden)
María C. Miquel
2009-01-01
Full Text Available The objective of this paper was to determine the association of a SNP in the µ-calpain gene at position 316 with growth and quality of meat traits of steers grown on pasture. Fifty-nine Brangus and 20 Angus steers were genotyped for CAPN1 316. Warner Bratzler shear force was measured in l. lumborum samples after a 7-day aging period. A multivariate analysis of variance was performed, including shear force (WBSF, final weight (FW, average daily gain (ADG, backfat thickness (BFT, average monthly fat thickness gain (AMFTG, rib-eye area (REA, and beef rib-eye depth (RED as dependent variables. The CAPN1 316 genotype was statistically significant. Univariate analyses were done with these variables. The marker genotype was statistically significant (p < 0.05 for WBSF (kg: CC: 4.41 ± 0.57; CG: 5.58 ± 0.20; GG: 6.29 ± 0.18, FW (kg: CC: 360.23 ± 14.71; CG: 381.34 ± 5.26; GG: 399.23 ± 4.68, and ADG (kg/d: CC: 0.675 ± 0.046; CG: 0.705 ± 0.016; GG: 0.765 ± 0.014 Shear force, final weight and average daily gain were significantly different according to the CAPN1 316 marker genotypes. The marker genotype was statistically significant in the multivariate analysis (p = 0.001. The first characteristic root explained 89% of the differences among genotypes. WBSF, FW and ADG were the most important traits in the first vector, indicating that animals with the marker genotype for lowest WBSF also have the lowest FW and ADG.
Shear flow generation in stellarators - Configurational variations
International Nuclear Information System (INIS)
Plasma momentum transport within magnetic surfaces plays a fundamental role in a number of toroidal plasma physics issues, such as: turbulence suppression, impurity transport, bootstrap current generation, and the shielding of resonant magnetic error field perturbations. Stellarators provide opportunities for improved understanding of plasma flow effects because (a) new forms of quasi-symmetry (e.g., helical, poloidal) can be produced that differ significantly from the tokamak; and (b) symmetry breaking effects (always present to some degree) remove the degeneracy between parallel and cross-field transport characteristic of symmetric systems. Furthermore, external control coils can be used to further enhance or suppress such effects. A method has been developed to evaluate the variation of neoclassical self-generated plasma flows in stellarators both within and across magnetic surfaces. This introduces a new dimension into both the optimization of stellarators and to the improved understanding of the existing confinement database. Application of this model to a range of configurations indicates that flow directionality and shearing rates are significantly influenced by the magnetic structure; flexibility variations within each configuration provide further control over flow characteristics. The stellarator confinement database contains evidence of machine-dependent effects that can be related to neoclassical transport physics. However, the measured cross-field transport rates are clearly anomalous. The possibility that neoclassical flow shearing effects are playing a role in these effects has become an important focus for applications of our model. For example, a recent analysis of a series of inwardly shifted LHD discharges has indicated that decreases of up to a factor of 10 in the neoclassical viscosity (allowing greater flow shearing) were correlated with the experimentally observed improved confinement times. (author)
Faults (shear zones) in the Earth's mantle
Vauchez, Alain; Tommasi, Andréa; Mainprice, David
2012-08-01
Geodetic data support a short-term continental deformation localized in faults bounding lithospheric blocks. Whether major "faults" observed at the surface affect the lithospheric mantle and, if so, how strain is distributed are major issues for understanding the mechanical behavior of lithospheric plates. A variety of evidence, from direct observations of deformed peridotites in orogenic massifs, ophiolites, and mantle xenoliths to seismic reflectors and seismic anisotropy beneath major fault zones, consistently supports prolongation of major faults into the lithospheric mantle. This review highlights that many aspects of the lithospheric mantle deformation remain however poorly understood. Coupling between deformation in frictional faults in the uppermost crust and localized shearing in the ductile crust and mantle is required to explain the post-seismic deformation, but mantle viscosities deduced from geodetic data and extrapolated from laboratory experiments are only reconciled if temperatures in the shallow lithospheric mantle are high (> 800 °C at the Moho). Seismic anisotropy, especially shear wave splitting, provides strong evidence for coherent deformation over domains several tens of km wide in the lithospheric mantle beneath major transcurrent faults. Yet it cannot detect narrow strain localization zones or shallowly dipping faults. Seismic profiling images shallow-dipping seismic reflectors in the lithospheric mantle interpreted as the continuation of normal or, less frequently, inverse faults in the mantle. However the nature of these reflectors is poorly understood. There is a large discrepancy between the scale at which deformation processes are studied (a few kilometers, at most, due to the limited size of continuous mantle exposures at the Earth's surface) and the scale inferred for strain localization in the mantle from geophysical observations (tens of kilometers). Combining data on deformation microstructures and crystal preferred orientations in naturally deformed peridotites and seismologic observations allows nevertheless discussing strain localization processes that may play a role on the development of mantle shear zones.
Transient shear banding in entangled polymers: A study using the Rolie-Poly model
Adams, JM; Fielding, SM; Olmsted, PD
2011-01-01
Spatially inhomogeneous shear flow occurs in entangled polymer solutions, both as steady state shear banding and transiently after a large step strain or during start up to a steady uniform shear rate. Steady state shear banding is a hallmark of models with a non-monotonic constitutive relation between total shear stress and applied shear rate, but transient banding is sometimes seen in fluids that do not shear band at steady state. We model this behavior using the diffusive...
Shear Strengthening of Reinforced Concrete Beams Using GFRP Wraps
Directory of Open Access Journals (Sweden)
M. A. A. Saafan
2006-01-01
Full Text Available The objective of the experimental work described in this paper was to investigate the efficiency of GFRP composites in strengthening simply supported reinforced concrete beams designed with insufficient shear capacity. Using the hand lay-up technique, successive layers of a woven fiberglass fabric were bonded along the shear span to increase the shear capacity and to avoid catastrophic premature failure modes. The strengthened beams were fabricated with no web reinforcement to explore the efficiency of the proposed strengthening technique using the results of control beams with closed stirrups as a web reinforcement. The test results of 18 beams are reported, addressing the influence of different shear strengthening schemes and variable longitudinal reinforcement ratios on the structural behavior. The results indicated that significant increases in the shear strength and improvements in the overall structural behavior of beams with insufficient shear capacity could be achieved by proper application of GFRP wraps.
Shear band formation in granular media as a variational problem
Unger, T; Kertész, J; Wolf, D E
2004-01-01
Strain in sheared dense granular material is often localized in a narrow region called shear band. Recent experiments in a modified Couette cell provided localized shear flow in the bulk away from the confining walls. The non-trivial shape of the shear band was measured as the function of the cell geometry. First we present a geometric argument for narrow shear bands which connects the function of their surface position with the shape in the bulk. Assuming a simple dissipation mechanism we show that the principle of minimum dissipation of energy provides a good description of the shape function. Furthermore, we discuss the possibility and behavior of shear bands which are detached from the free surface and are entirely covered in the bulk.
Negative pressure in shear thickening band of a dilatant fluid
Nagahiro, Shin-ichiro
2015-01-01
We perform experiments and numerical simulations to investigate spatial distribution of pressure in a sheared dilatant fluid of the Taylor-Couette flow under a constant external shear stress. In a certain range of shear stress, the flow undergoes the shear thickening oscillation around 20 Hz. The pressure measurement during the oscillation at the wall of the outer cylinder indicates that a localized negative pressure region rotates around the axis with the flow. The maximum negative pressure is close to the Laplace pressure of the grain radius and nearly independent of the applied shear stress. Simulations of a phenomenological model reveal that the thickened region is dominated by a negative pressure band, which extends along the tensile direction in the flow. Such shear thickening with negative pressure contradicts a naive picture of jamming mechanism, where thickening is expected in the compressing direction with the positive pressure.
Shear-induced displacement of isotropic-nematic spinodals
Lenstra, T. A. J.; Dogic, Z.; Dhont, J. K. G.
2001-06-01
The shear dependent location of the isotropic-nematic spinodals in suspensions of bacteriophage fd is studied by means of time resolved birefringence experiments. The hysteresis in the birefringence on increasing and subsequently decreasing the shear-rate allows the determination of the location of points in the shear-rate vs concentration phase diagram between the isotropic-to-nematic and the nematic-to-isotropic spinodals. Experimental hysteresis curves are interpreted on the basis of an equation of motion for the orientational order parameter tensor, as derived from the N-particle Smoluchowski equation. The spinodals are found to shift to lower concentrations on increasing the shear-rate. Above a critical shear-rate, where shear forces dominate over thermodynamic forces, no spinodal instability could be detected.
Two-axis direct fluid shear stress sensor
Bajikar, Sateesh (Inventor); Scott, Michael A. (Inventor); Adcock, Edward E. (Inventor)
2011-01-01
A micro sized multi-axis semiconductor skin friction/wall shear stress induced by fluid flow. The sensor design includes a shear/strain transduction gimble connected to a force collecting plate located at the flow boundary surface. The shear force collecting plate is interconnected by an arm to offset the tortional hinges from the fluid flow. The arm is connected to the shear force collecting plate through dual axis torsional hinges with piezoresistive torsional strain gauges. These gauges are disposed on the tortional hinges and provide a voltage output indicative of applied shear stress acting on the force collection plate proximate the flow boundary surface. Offsetting the torsional hinges creates a force concentration and resolution structure that enables the generation of a large stress on the strain gauge from small shear stress, or small displacement of the collecting plate. The design also isolates the torsional sensors from exposure to the fluid flow.
Hysteresis and Lubrication in Shear Thickening of Cornstarch Suspensions
Chu, Clarence E; Sieber, Hannah L; Miller, James G; Okamoto, Ruth J; Katz, Jonathan I
2014-01-01
Aqueous and brine suspensions of corn starch show striking discontinuous shear thickening. We have found that a suspension shear-thickened throughout may remain in the jammed thickened state as the strain rate is reduced, but an unjamming front may propagate from any unjammed regions. Transient shear thickening is observed at strain rates below the thickening threshold, and above it the stress fluctuates. The jammed shear-thickened state may persist to low strain rates, with stresses resembling sliding friction and effective viscosity inversely proportional to the strain rate. At the thickening threshold fluid pressure depins the suspension's contact lines on solid boundaries so that it slides, shears, dilates and jams. In oil suspensions lubrication and complete wetting of confining surfaces eliminate contact line forces and prevent jamming and shear thickening, as does addition of immiscible liquid surfactant to brine suspensions. Starch suspensions in glycerin-water solutions, viscous but incompletely wett...
Assessment of susceptibility of rape stems to shearing
Directory of Open Access Journals (Sweden)
Vielikanov L.
2000-12-01
Full Text Available In the present study, the authors used a dynamic shearing and densitometric method for the asses- sment of susceptibility of stems of winter rape, vars Mar, Bolko, Leo, Ceres and Libravo to shearing. They determi- ned dynamic shearing energy per a unit of the stem cross section area, in the natural state as well as after the removed of parenchyma, density and DOD parameter, indicating the amount of X-ray energy absorbed by the stems. It was found that susceptibility of rape stems to shearing depends on their structure. A strict correlation was shown to exist between the dynamic shearing energy and the amount of X-ray radiation energy absorbed by the stem. Moreover, in study showed that the application of the X-ray method greatly enhanced the possibility to determine of the suscep- tibility of rape stems to shearing.
Shear banding deformation in Cu/Ta nano-multilayers
International Nuclear Information System (INIS)
Highlights: ? Formation of shear bands in Cu/Ta multilayers is layer thickness dependent. ? Unique layer-morphology with prevalent mismatched laminate structure was observed. ? A new physical mechanism that dominates shear band formation is suggested. - Abstract: Nanoscale Cu/Ta multilayers with individual layer thickness ranging from 3 to 70 nm were deformed under nanoindentation at room temperature. Shear bands can be observed only when individual layer thickness is reduced to 9 nm or below, indicating formation of shear bands in the Cu/Ta multilayers is layer thickness dependent. By observing the cross sectional transmission electron microscope images of the indentation fabricated through focused ion beam technique, shear banding deformation causing a unique layer-morphology with prevalent mismatched laminate structure has been reported for the first time. By capturing and analyzing a series of typical indentation-induced deformed microstructures, a new physical mechanism of shear banding behavior in metallic nano-multilayers is suggested.
On nonlinear physics of shear Alfvén waves
Energy Technology Data Exchange (ETDEWEB)
Chen, Liu [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Department of Physics and Astronomy, University of California, Irvine, California 92697-4575 (United States); Zonca, Fulvio [Associazione EURATOM-ENEA sulla Fusione, CP 65-00044 Frascati (Italy); Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)
2013-05-15
Shear Alfvén waves (SAW) are electromagnetic oscillations prevalent in laboratory and nature magnetized plasmas. Due to their anisotropic nature, it is well known that the linear wave propagation and dispersiveness of SAW are fundamentally affected by plasma nonuniformities and magnetic field geometries, such as the existence of continuous spectrum, spectral gaps, and discrete eigenmodes in toroidal plasmas. This work discusses the pure Alfvénic state and demonstrates the crucial roles that finite ion compressibility, non-ideal kinetic effects, and geometry play in breaking it and, thereby, the nonlinear physics of SAW wave-wave interactions.
The SDSS Coadd: Cosmic Shear Measurement
Lin, Huan; Seo, Hee-Jong; Soares-Santos, Marcelle; Annis, James; Hao, Jiangang; Johnston, David; Kubo, Jeffrey M; Reis, Ribamar R R; Simet, Melanie
2011-01-01
Stripe 82 in the Sloan Digital Sky Survey was observed multiple times, allowing deeper images to be constructed by coadding the data. Here we analyze the ellipticities of background galaxies in this 275 square degree region, searching for evidence of distortions due to cosmic shear. The E-mode is detected in both real and Fourier space with $>5$-$\\sigma$ significance on degree scales, while the B-mode is consistent with zero as expected. The amplitude of the signal constrains the combination of the matter density $\\Omega_m$ and fluctuation amplitude $\\sigma_8$ to be $\\Omega_m^{0.7}\\sigma_8 = 0.276^{+0.036}_{-0.050}$.
Structural relaxation monitored by instantaneous shear modulus
DEFF Research Database (Denmark)
Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil
1998-01-01
This paper reports on aging of the silicone oil MS704 for sudden changes of temperature from 210.5 to 209.0 K and from 207.5 to 209.0 K studied by continuously monitoring the instantaneous shear modulus G [infinity]. The results are interpreted within the Tool-Narayanaswamy formalism with a reduced time definition based on a recently proposed expression for the relaxation time, where G [infinity] reflects the fictive temperature. All parameters entering the reduced time were determined from inde...
Waves in Turbulent Stably Stratified Shear Flow
Jacobitz, F. G.; Rogers, M. M.; Ferziger, J. H.; Parks, John W. (Technical Monitor)
2002-01-01
Two approaches for the identification of internal gravity waves in sheared and unsheared homogeneous stratified turbulence are investigated. First, the phase angle between the vertical velocity and density fluctuations is considered. It was found, however, that a continuous distribution of the phase angle is present in weakly and strongly stratified flow. Second, a projection onto the solution of the linearized inviscid equations of motion of unsheared stratified flow is investigated. It was found that a solution of the fully nonlinear viscous Navier-Stokes equations can be represented by the linearized inviscid solution. The projection yields a decomposition into vertical wave modes and horizontal vortical modes.
Aeolian and subaqueous bedforms in shear flows.
Andreotti, Bruno; Claudin, Philippe
2013-12-13
A sediment bed sheared by an unbounded flow is unconditionally unstable towards the growth of bedforms called ripples under water and dunes in the aeolian case. We review here the dynamical mechanisms controlling this linear instability, putting the emphasis on testing models against field and laboratory measurements. We then discuss the role of nonlinearities and the influence of finite size effects, namely the depth of the atmospheric boundary layer in the aeolian case and the water depth in the case of rivers. PMID:24471263
Steady State of microemulsions in shear flow
Corberi, F; Suppa, D
2001-01-01
Steady-state properties of microemulsions in shear flow are studied in the context of a Ginzburg-Landau free-energy approach. Explicit expressions are given for the structure factor and the time correlation function at the one loop level of approximation. Our results predict a four-peak pattern for the structure factor, implying the simultaneous presence of interfaces aligned with two different orientations. Due to the peculiar interface structure a non-monotonous relaxation of the time correlator is also found.
A New Annular Shear Piezoelectric Accelerometer
DEFF Research Database (Denmark)
Liu, Bin; Kriegbaum, B.
2000-01-01
This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass is made of tungsten. All processes and materials comply with MIL-STD-11268. The mounted resonance frequency exceeds 40kHz. The sensitivity is 10mV/g ±5%. During the design process, the new design is evaluate...
Interface instability in shear banding flow
Lerouge, S; Decruppe, J P
2006-01-01
We report on the spatio-temporal dynamics of the interface in shear-banding flow of a wormlike micellar system (cetyltrimethylammonium bromide and sodium nitrate in water) during a start-up experiment. Using the scattering properties of the induced structures, we demonstrate the existence of an instability of the interface between bands along the vorticity direction. Different regimes of spatio-temporal dynamics of the interface are indentified along the stress plateau. We build a model based on the flow symetry which qualitatively describes the observed patterns.
Free vibration of arches flexible in shear.
Austin, W. J.; Veletsos, A. S.
1973-01-01
An analysis reported by Veletsos et al. (1972) concerning the free vibrational characteristics of circular arches vibrating in their own planes is considered. The analysis was based on a theory which neglects the effects of rotatory inertia and shearing deformation. A supplementary investigation is conducted to assess the effects of the previously neglected factors and to identify the conditions under which these effects are of practical significance or may be neglected. A simple approximate procedure is developed for estimating the natural frequencies of arches, giving due consideration to the effects of the previously neglected factors.
Propagation of waves in shear flows
Fabrikant, A L
1998-01-01
The state of the art in a theory of oscillatory and wave phenomena in hydrodynamical flows is presented in this book. A unified approach is used for waves of different physical origins. A characteristic feature of this approach is that hydrodynamical phenomena are considered in terms of physics; that is, the complement of the conventionally employed formal mathematical approach. Some physical concepts such as wave energy and momentum in a moving fluid are analysed, taking into account induced mean flow. The physical mechanisms responsible for hydrodynamic instability of shear flows are conside
Dilatancy and Friction in sheared granular media
Lacombe, F; Herrmann, H J
2000-01-01
We introduce a simple model to describe the frictional properties of granular media under shear. We model the friction force in term of the horizontal velocity v and the vertical position z of the slider, interpreting z as a constitutive variable characterizing the contact. Dilatancy is shown to play an essential role in the dynamic, inducing a stick-slip instability at low velocity. We compute the phase diagram, analyze numerically the model for a wide range of parameters and compare our results with experiments on dry and wet granular media, obtaining a good agreement. In particular, we reproduce the hysteretic velocity dependence of the frictional force.
Rejuvenation and overaging in a colloidal glass under shear
Viasnoff, V; Viasnoff, Virgile; Lequeux, Francois
2002-01-01
We report the modifications of the microscopic dynamics of a colloidal glass submitted to shear. We use multispeckle diffusing wave spectroscopy to monitor the evolution of the spontaneous slow relaxation processes after the sample have been submitted to various straining. We show that high shear rejuvenates the system and accelerates its dynamics whereas moderate shear overage the system. We analyze this phenomena within the frame of the Bouchaud's trap model.
On the route to shear jamming, are fragile states real?
Zhang, Ling; Zheng, Jie; Zhang, Jie
2015-01-01
Starting from an unjammed initial state, applying shear to a granular material of a fixed packing fraction below $\\phi_J$, i.e. the isotropic jamming density of frictionless spheres can produce shear jamming states, as have been discovered recently. In addition, it has also been discovered that the system will first experience a bulk fragile state before evolving into a shear jammed state. Due to the existence of friction between the system and the third dimension in the pre...
Shear rheology of lipid monolayers and insights on membrane fluidity
Espinosa, Gabriel; López-Montero, Iván; Monroy, Francisco; Langevin, Dominique
2011-01-01
The concept of membrane fluidity usually refers to a high molecular mobility inside the lipid bilayer which enables lateral diffusion of embedded proteins. Fluids have the ability to flow under an applied shear stress whereas solids resist shear deformations. Biological membranes require both properties for their function: high lateral fluidity and structural rigidity. Consequently, an adequate account must include, in addition to viscosity, the possibility for a nonzero shear modulus. This k...
Shear Jamming in Granular Experiments without Basal Friction
Zheng, Hu; Dijksman, Joshua A.; Behringer, Robert P.
2014-01-01
Jammed states of frictional granular systems can be induced by shear strain at densities below the isostatic jamming density ($\\phi_c$). It remains unclear, however, how much friction affects this so-called shear-jamming. Friction appears in two ways in this type of experiment: friction between particles, and friction between particles and the base on which they rest. Here, we study how particle-bottom friction, or basal friction, affects shear jamming in quasi-two dimension...
Shear stress activation of nuclear receptor PXR in endothelial detoxification
Wang, Xiaohong; Fang, Xi; Zhou, Jing; Chen, Zhen; Zhao, Beilei; XIAO Lei; Liu, Ao; Li, Yi-Shuan J.; Shyy, John Y.-J.; Guan, Youfei; Chien, Shu; Wang, Nanping
2013-01-01
Endothelial cells (ECs) are constantly exposed to xenobiotics and endobiotics or their metabolites, which perturb EC function, as well as to shear stress, which plays a crucial role in vascular homeostasis. Pregnane X receptor (PXR) is a nuclear receptor and a key regulator of the detoxification of xeno- and endobiotics. Here we show that laminar shear stress (LSS), the atheroprotective flow, activates PXR in ECs, whereas oscillatory shear stress, the atheroprone flow, suppresses PXR. LSS act...
Shear banding and rheochaos in associative polymer networks
Sprakel, J.H.B.; Spruijt, E (Evan); Cohen Stuart, M. A.; Besseling, N.A.M.; Lettinga, M. P.; Gucht, J. van der
2008-01-01
We present experimental evidence of an instability in the shear flow of transient networks formed by telechelic associative polymers. Velocimetry experiments show the formation of shear bands, following a complex pattern upon increasing the overall shear rate. The chaotic nature of the stress response in transient flow is indicative of spatiotemporal fluctuations of the banded structure. This is supported by time-resolved velocimetry measurements.
Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2010-01-01
This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers af...
Shear zones between rock units with no relative movement
DEFF Research Database (Denmark)
Koyi, Hemin; Schmeling, Harro
2013-01-01
Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two “blocks” that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such deformation zones, which we call wakes, form due to the movement of exotic blocks within a viscous medium (denser blocks sinking within a salt structure, (the paths) between separated boudins), melt in partially molten surroundings (melt movement during migmatisation), or solid blocks sinking through a partially molten magma body (stoping). From the fluid dynamics perspective these shear zones can be regarded as low Reynolds number deformation zones within the wake of a body moving through a viscous medium. While compact moving bodies (aspect ratio 1:1:1) generate axial symmetric (cone like) shear zones or wakes, elongated bodies (vertical plates or horizontal rod-like bodies) produce tabular shear zones or wakes. Unlike conventional shear zones across which shear indicators usually display consistent symmetries, shear indicators on either side of the shear zone or wake reported here show reverse kinematics. Thus profiles exhibit shear zones with opposed senses of movement across their center-lines or -planes. We have used field observations and results from analytical and numerical models to suggest that examples of wakes are the transit paths that develop where denser blocks sink within salt structures, bodies of melt rise through migmatites, between boudins separated by progressive extension and (perhaps) where slabs of subducted oceanic lithosphere delaminate from the continental crust and sink into the asthenosphere. We also argue that such shear zones may be more common than they have been given credit for and may be responsible for some reverse kinematics reported in shear zones.
Rheology of concentrated suspensions and shear-induced migration
Dbouk, Talib
2011-01-01
This thesis deals with an experimental and numerical investigation of the phenomenon of shear-induced particle migration in inhomogeneous shear flows of mono-dispersed non-colloidal suspensions at neglected inertia. Variety of diffusion flux models that predict the shear-induced migration were presented. However, in this work, the Suspension Balance Model (SBM) is adopted. The latter describes the migration flux of particles as the divergence of the particle Stress tensor. According to the ne...
Critical wall shear stress for the EHEDG test method
DEFF Research Database (Denmark)
Jensen, Bo Boye Busk; Friis, Alan
2004-01-01
In order to simulate the results of practical cleaning tests on closed processing equipment, based on wall shear stress predicted by computational fluid dynamics, a critical wall shear stress is required for that particular cleaning method. This work presents investigations that provide a critical wall shear stress of 3 Pa for the standardised EHEDG cleaning test method. The cleaning tests were performed on a test disc placed in a radial flowcell assay. Turbulent flow conditions were generated a...
Systematic effects on dark energy from 3D weak shear
Kitching, T. D.; Taylor, A N; A.F. Heavens
2008-01-01
We present an investigation into the potential effect of systematics inherent in multi-band wide field surveys on the dark energy equation of state determination for two 3D weak lensing methods. The weak lensing methods are a geometric shear-ratio method and 3D cosmic shear. The analysis here uses an extension of the Fisher matrix framework to jointly include photometric redshift systematics, shear distortion systematics and intrinsic alignments. We present results for DUNE ...
Inplane shear capacity of reinforced composite masonry block walls
International Nuclear Information System (INIS)
The objective of this paper is to describe a test program performed to determine the inplane shear capacity, stiffness and ductility of composite masonry walls subjected to earthquake type loadings. Specimens were simultaneously subjected to a range of compressive loads to simulate dead load; and inplane shear loads with full load reversal to simulate the earthquake cycling load. The influence of horizontal and vertical reinforcing steel percentages on the inplane shear capacity, stiffness and ductility was also investigated. (orig./HP)
Low-n shear Alfven spectra in axisymmetric toroidal plasmas
Energy Technology Data Exchange (ETDEWEB)
Cheng, C.Z.; Chance, M.S.
1985-11-01
In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs.
Shear band dynamics from a mesoscopic modeling of plasticity
Jagla, E. A.
2010-01-01
The ubiquitous appearance of regions of localized deformation (shear bands) in different kinds of disordered materials under shear is studied in the context of a mesoscopic model of plasticity. The model may or may not include relaxational (aging) effects. In the absence of relaxational effects the model displays a monotonously increasing dependence of stress on strain-rate, and stationary shear bands do not occur. However, in start up experiments transient (although long li...
Role of Chronic Shear Stress in Endothelial Form and Function
Potter, Claire
2013-01-01
Endothelial cells in vivo exist in a dynamic environment, subject to the physical forces of blood flow as it is regulated through the cardiac cycle. Arguably, the most important force endothelial cells are subject to is shear stress, the frictional force of blood flow across the cell surface. Areas of the vasculature that experience laminar shear stress appear resistant to the development of atherosclerotic plaques, whereas those that experience low shear stress, due to complex...
Cyclic testing of shear keys for the ITER magnet system
International Nuclear Information System (INIS)
Shear keys are to be used to support the out-of-plane loading of the toroidal field (TF) coils during a plasma pulse in ITER. At the inner intercoil structures (IIS) a set of poloidal shear keys is used to take the shear load at each connection between adjacent TF coils. Solid circular keys have been selected as reference. At the outer intercoil structures (OIS) adjustable conical shear keys and friction joint based shear panels are used to take the shear load. Low voltage electrical insulation is required at the flanges of the IIS and OIS, plus for all the bolts, poloidal keys and adjustable keys. This electrical insulation has to withstand large compression associated with some shear or slippage. A ceramic coating was selected for this purpose. The main scope of the experimental campaign was the mechanical testing of the shear keys and the electrical insulation in operational conditions relevant to ITER. Both keys were made of Inconel 718, provided with a ceramic alumina coating and inserted into flanges made of cast AISI 316 LN. The adjustable conical shear key was pre-loaded at room temperature and subject to cyclic shear loads of 2.5 MN for a large number of cycles (about 30,000) at cryogenic temperature (77 K). The conical key and the alumina coating remained undamaged after the test. Another test campaign was then performed with higher shear loads (up to 3 MN) to reach a sufficient safety margin even with the friction effect due to the pre-load. A set of 15,000 cycles were completed followed by some cycles at higher loads to reach the ultimate limit, which is the shear load to be experienced by the key in case of a poloidal field (PF) coil short
Lensing magnification effects on the cosmic shear statistics
Hamana, Takashi
2001-01-01
Gravitational lensing causes a correlation between a population of foreground large-scale structures and the observed number density of the background distant galaxies as a consequence of the flux magnification and the lensing area distortion. This correlation has not been taken into account in calculations of the theoretical predictions of the cosmic shear statistics but may cause a systematic error in a cosmic shear measurement. We examine its impact on the cosmic shear st...
Effects of magnetic shear on current penetration in a tokamak
International Nuclear Information System (INIS)
The penetrations of the parallel and perpendicular components of plasma currents are interrelated to each other due to the existence of magnetic shear in a tokamak configuration. Effects of the shear on the penetration of Fourier components of toroidal plasma current are analysed in a cylindrical column model. The current penetration is obviously strengthened by the shear for a bell-bike conductivity profile and low safety factor and low aspect ratio
Rheological properties for inelastic Maxwell mixtures under shear flow
Garzo, Vicente; Trizac, Emmanuel
2009-01-01
The Boltzmann equation for inelastic Maxwell models is considered to determine the rheological properties in a granular binary mixture in the simple shear flow state. The transport coefficients (shear viscosity and viscometric functions) are {\\em exactly} evaluated in terms of the coefficients of restitution, the (reduced) shear rate and the parameters of the mixture (particle masses, diameters and concentration). The results show that in general, for a given value of the co...
Tension, compression and shear fatigue of a closed cell foam
Zenkert, Dan; Burman, Magnus
2007-01-01
A closed cell foam of Polymetacrylimide (Rohacell) with three different densities is studied. The foam is tested quasistatically in tension, compression and shear. The tensile properties scale very well with the relative density of the foam, but the compression and shear properties do not. It is believed to be due to cell edge and cell wall buckling being the dominated deformation mechanism in compression and shear for lower densities that does not occur for higher densities. Fatigue testing ...
Low-n shear Alfven spectra in axisymmetric toroidal plasmas
International Nuclear Information System (INIS)
In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfven continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfven eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfven eigenmodes on plasma heating and instabilities are addressed. 17 refs., 4 figs
Shear crack formation and propagation in reinforced Engineered Cementitious Composites
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2011-01-01
This paper describes an experimental investigation of the shear behaviour of beams consisting of steel reinforced Engineered Cementitious Composites (R/ECC). Based on the strain hardening and multiple cracking behaviour of ECC, this study investigates the extent to which ECC influences the shear capacity of beams loaded primarily in shear. The experimental program consists of ECC with short randomly distributed polyvinyl alcohol (PVA) fiber beams with different stirrup arrangements and conventio...
Colors Of Liquid Crystals Used To Measure Surface Shear Stresses
Reda, D. C.; Muratore, J. J., Jr.
1996-01-01
Developmental method of mapping shear stresses on aerodynamic surfaces involves observation, at multiple viewing angles, of colors of liquid-crystal surface coats illuminated by white light. Report describing method referenced in "Liquid Crystals Indicate Directions Of Surface Shear Stresses" (ARC-13379). Resulting maps of surface shear stresses contain valuable data on magnitudes and directions of skin friction forces associated with surface flows; data used to refine mathematical models of aerodynamics for research and design purposes.
Thermal analysis of isotropic plates using hyperbolic shear deformation theory
Shinde B.M.; Sayyad A. S.; Kawade A.B.
2013-01-01
In this paper, thermal analysis of a thick isotropic rectangular plate is carried out using the hyperbolic shear deformation theory (HYSDT). The displacement field of the theory contains three variables. The hyperbolic sine and cosine functions are used in the displacement field in-terms of thickness coordinate to represent the effect of shear deformation. The most important feature of the theory is that, the transverse shear stresses can be obtained directly from the use of constitutive rela...
Shear-induced assembly of lambda-phage DNA.
Haber, C.; Wirtz, D
2000-01-01
Recombinant DNA technology, which is based on the assembly of DNA fragments, forms the backbone of biological and biomedical research. Here we demonstrate that a uniform shear flow can induce and control the assembly of lambda-phage DNA molecules: increasing shear rates form integral DNA multimers of increasing molecular weight. Spontaneous assembly and grouping of end-blunted lambda-phage DNA molecules are negligible. It is suggested that shear-induced DNA assembly is caused by increasing th...
Viscous shear heating instabilities in a 1-D viscoelastic shear zone
Homburg, J. M.; Coon, E. T.; Spiegelman, M.; Kelemen, P. B.; Hirth, G.
2010-12-01
Viscous shear instabilities may provide a possible mechanism for some intermediate depth earthquakes where high confining pressure makes it difficult to achieve frictional failure. While many studies have explored the feedback between temperature-dependent strain rate and strain-rate dependent shear heating (e.g. Braeck and Podladchikov, 2007), most have used thermal anomalies to initiate a shear instability or have imposed a low viscosity region in their model domain (John et al., 2009). By contrast, Kelemen and Hirth (2007) relied on an initial grain size contrast between a predetermined fine-grained shear zone and coarse grained host rock to initiate an instability. This choice is supported by observations of numerous fine grained ductile shear zones in shallow mantle massifs as well as the possibility that annealed fine grained fault gouge, formed at oceanic transforms, subduction related thrusts and ‘outer rise’ faults, could be carried below the brittle/ductile transition by subduction. Improving upon the work of Kelemen and Hirth (2007), we have developed a 1-D numerical model that describes the behavior of a Maxwell viscoelastic body with the rheology of dry olivine being driven at a constant velocity at its boundary. We include diffusion and dislocation creep, dislocation accommodated grain boundary sliding, and low-temperature plasticity (Peierls mechanism). Initial results suggest that including low-temperature plasticity inhibits the ability of the system to undergo an instability, similar to the results of Kameyama et al. (1999). This is due to increased deformation in the background allowing more shear heating to take place, and thus softening the system prior to reaching the peak stress. However if the applied strain rate is high enough (e.g. greater than 0.5 x 10-11 s-1 for a domain size of 2 km, an 8 m wide shear zone, a background grain size of 1 mm, a shear zone grain size of 150 ?m, and an initial temperature of 650°C) dramatic instabilities can occur. The instability is enhanced by the development of a self-localizing thermal perturbation in the fine grained zone that is narrower than the original width of the fine-grained zone. To examine the effect of melting, we include a parameterization of partially molten rock viscosity as a function of temperature assuming a simple relationship between melt fraction and temperature. At T > ~1400°C, all other deformation mechanisms are deactivated but shear heating continues, allowing for continued temperature evolution. In addition a strain rate cap proportional to the shear wave velocity in olivine has been imposed, reflecting the maximum rate that changes in stress can be communicated through the system. While Kelemen and Hirth (2007) allowed for grain size evolution, this has not yet been implemented in our model. Adding grain size evolution as an additional strain softening mechanism would probably allow instabilities to develop at more geologically reasonable applied strain rates. In addition to discussing the stability of the olivine only system, we will explore grain size evolution during system evolution and evaluate the consequences that the grain size evolution and lithology have on the stability of the system.
Notes on shear viscosity bound violation in anisotropic models
Ge, Xian-Hui
2015-01-01
The shear viscosity bound violation in Einstein gravity for anisotropic black branes is discussed, with the aim of constraining the deviation of the shear viscosity-entropy density ratio from the shear viscosity bound using causality and thermodynamics analysis. The results show that no stringent constraints can be imposed. The diffusion bound in anisotropic phases is also studied. Ultimately, it is concluded that shear viscosity violation always occurs in cases where the equation of motion of the metric fluctuations cannot be written in a form identical to that of the minimally coupled massless scalar fields.
Shear banding in commercial pure titanium deformed by dynamic compression
International Nuclear Information System (INIS)
A cylindrical hexagonal-close-packed Ti sample was pre-deformed by dynamic compression to produce coarse-grained and ultrafine-grained structures in different parts of the sample followed by further dynamic compression to failure, making it possible to explore the effect of stored strain and grain boundary energy on shear banding in the material. A long shear band that formed during the final compression process passed through a complete diagonal of the sample. Electron backscattered diffraction was used to systematically investigate the shear-banding-induced structural evolution. Results show that the original stored energy in the matrix plays a significant role in the competition between deformation-induced grain refinement and grain growth, which determines the final average grain size in a shear band. Shear banding leads to grain reorientation such that one close-packed ?112¯0? direction and one ?101¯0? direction in most grains are parallel to the local shear direction and the normal direction to the local shear plane, respectively. The grain orientation in the shear band favours prismatic ?a? slip, while the texture in the matrix, which is a stable compression texture, benefits the basal ?a? slip. The results advance our understanding of the shear banding behaviour in heterogeneous deformation conditions and also the overall mechanical behaviour of materials under dynamic compression
Diagonal Cracking and Shear Strength of Reinforced Concrete Beams
DEFF Research Database (Denmark)
Zhang, Jin-Ping
1997-01-01
The shear failure of non-shear-reinforced concrete beams with normal shear span ratios is observed to be governed in general by the formation of a critical diagonal crack. Under the hypothesis that the cracking of concrete introduces potential yield lines which may be more dangerous than the ones found by the usual plastic theory, a physical explanation is given for this phenomenon and a way to estimate the shear capacity of reinforced concrete beams, based on the theory of plasticity, is described. The theoretical calculations are shown to be in fairly good agreement with test results from a large number of experiments carried out by previous investigators.
Aerosol penetration through a seismically loaded shear wall
International Nuclear Information System (INIS)
An experimental study was performed to measure the aerosol penetration through a reinforced concrete shear wall after simulated seismic damage. Static load-cycle testing, to stress levels sufficient to induce visible shear cracking, was used to simulate the earthquake loading. Air permeability tests were performed both before and after the simulated seismic loading damaged the structure. Aerosol penetration measurements were conducted on the cracked shear wall structure using 0.10 ?m monodisperse particles. The measured aerosol number penetration through the cracked shear wall was 0.5%. 7 refs
Compression Enhanced Shear Yield Stress of Electrorheological Fluid
International Nuclear Information System (INIS)
Shear tests of an electrorheological fluid with pre-applied electric field and compression along the field direction are carried out. The results show that pre-compressions can increase the shear yield stress up to ten times. Under the same external electric field strength, a higher compressive strain corresponds to a larger shear yield stress enhancement but with slight current density decrease, which shows that the particle interaction potentials are not increased by compressions but the compression-induced chain aggregation dominates the shear yield stress improvement. This pre-compression technique might be useful for developing high performance flexible ER or magnetorheological couplings
Direct visualization of shear waves in viscoelastic fluid using microspheres.
Labuda, C; Tierney, C M; Dayavansha, E G Sunethra K; Gladden, J R
2015-06-01
Wormlike micellar fluids, being viscoelastic, support shear waves. Shear waves in 500?mM CTAB-NaSal micellar fluid were visualized by seeding the fluid with 212-250??m diameter polyethylene microspheres. This method was compared to visualization through birefringence induced by shear stress in the fluid. Measured shear wave speeds were 733 and 722?mm/s, respectively, for each technique. Particle displacement was a sinusoidal function of time and displacement amplitude decreased quadratically with distance from the source. This supports the possibility of using particle amplitude measurements as a measure of attenuation even at low fluid concentration where birefringence visualization techniques fail. PMID:26093455
Shear bands in metallic glasses are not necessarily hot
Stephanie K. Slaughter; Felicitee Kertis; Erin Deda; Xiaojun Gu; Wendelin J. Wright; T. C. Hufnagel
2014-01-01
We have used the fusible tin coating method to detect shear band heating in amorphous Zr57Ti5Cu20Ni8Al10 loaded under quasi-static uniaxial compression. High-rate load data allowed a precise determination of the duration of shearing events and final fracture. When loading was halted prior to fracture we saw no evidence of melted tin despite the presence of shear offsets up to 6??m on some shear bands. Samples loaded to fracture showed evidence of tin melting near the fracture surface. We attr...
Permeability changes during shear deformation of fractured rock
International Nuclear Information System (INIS)
The effect of shear deformation on the permeability of fractured rock has been investigated in drained triaxial compression experiments on prefractured samples of Coconino sandstone. These experiments show that permeability across a fracture decreases with increasing shear deformation because of localized deformation along the fractures and the evolution of a gouge zone. Petrographic observations show a progressive decrease in grain size and porosity of the gouge zone with increasing shear displacement. With increasing normal stress there is a more rapid reduction in grain size and a higher degree of compaction of the gouge per increment of shear displacement, which results in a faster decline in permeability during sliding
Interface shear and pressure characteristics of wheelchair seat cushions
Directory of Open Access Journals (Sweden)
Jonathan S. Akins
2011-03-01
Full Text Available Pressure ulcer incidence rates have remained constant despite advances in support surface technology. Interface shear stress is recognized as a risk factor for pressure ulcer development and is the focus of many shear reduction technologies incorporated into wheelchair cushions; however, shear reduction has not been quantified in the literature. We evaluated 21 commercial wheelchair seat cushions using a new methodology developed to quantify interface shear stress, interface pressure, and horizontal stiffness. Interface shear stress increased significantly with applied horizontal indenter displacement, while no significant difference was found for interface pressure. Material of construction resulted in significant differences in interface shear stress, interface pressure, and horizontal stiffness. This study shows that the existing International Organization for Standardization (ISO 16840-2 horizontal stiffness measure provides similar information to the new horizontal stiffness measure. The lack of a relationship between interface shear stress and the overall horizontal stiffness measure, however, suggests that a pressure and shear force sensor should be used with the ISO 16840-2 horizontal stiffness measure to fully quantify a cushion's ability to reduce interface shear stress at the patient's bony prominences.
Turbulent bands in a planar shear flow without walls
Chantry, Matthew; Barkley, Dwight
2015-01-01
Turbulent bands are a ubiquitous feature of transition in wall-bounded shear flows. We show that these are also a robust feature of Waleffe flow -- a shear flow driven by a sinusoidal body force between stress-free boundaries -- thus demonstrating that rigid walls are not a prerequisite for band formation. Exploiting the Fourier dependence of Waleffe forcing, we construct a model flow that uses only four wavenumbers in the shear direction and yet captures uniform turbulence, turbulent bands, and spot expansion. The model is simultaneously a reduction of the full Navier-Stokes equations and an extension of minimal models of the self-sustaining process of shear turbulence.
Morphologies of three-dimensional shear bands in granular media
Fazekas, S; Kertész, J; Wolf, D E
2005-01-01
Using three-dimensional Distinct Element Method with spherical particles we simulated shear band formation of granular materials in axisymmetric triaxial shear test. The calculated three-dimensinoal shear band morphologies are in good agreement with those found experimentally. We observed spontaneous symmetry braking strain localization provided it was allowed by the boundaries. If the symmetry was enforced, we found strain hardening. We discuss the formation mechanism of shear bands in the light of our observations and compare our results with high resolution NMR experiments.
Shear viscosity in neutron star cores
International Nuclear Information System (INIS)
We calculate the shear viscosity ???e?+?n in a neutron star core composed of nucleons, electrons, and muons (?e? being the electron-muon viscosity, mediated by collisions of electrons and muons with charged particles, and ?n the neutron viscosity, mediated by neutron-neutron and neutron-proton collisions). Deriving ?e?, we take into account the Landau damping in collisions of electrons and muons with charged particles via the exchange of transverse plasmons. It lowers ?e? and leads to the nonstandard temperature behavior ?e??T-5/3. The viscosity ?n is calculated taking into account that in-medium effects modify nucleon effective masses in dense matter. Both viscosities, ?e? and ?n, can be important, and both are calculated including the effects of proton superfluidity. They are presented in the form valid for any equation of state of nucleon dense matter. We analyze the density and temperature dependence of ? for different equations of state in neutron star cores, and compare ? with the bulk viscosity in the core and with the shear viscosity in the crust.
Vortices in shear: a Hamiltonian moment description
Meacham, Steve; Morrison, Phil; Flierl, Glenn
1996-11-01
A general method, which is based upon the noncanonical Hamiltonian structure of the ideal fluid and which uses special functionals of the vorticity as dynamical variables, is presented for extracting exact or approximate finite degree-of-freedom Hamiltonian systems from the partial differential equations that describe vortex dynamics. In our examples, the functionals are chosen to be spatial moments of the vorticity. The method gives rise to constants of motion known as Casimir invariants and provides a classification scheme, of the global phase space structure of the reduced finite systems, based upon Lie algebra theory. The method is illustrated by application to the Kida vortex and to the problem of the quasigeostrophic evolution of an ellipsoid of uniform vorticity, embedded in a background flow containing horizontal and vertical shear. The dynamics of the ellipsoidal vortex in shear are represented, without further approximation beyond the assumption of quasigeostrophy, by a finite degree-of-freedom system in canonical variables. Various types of motion exhibited by the vortex, including chaotic tumbling, are described.
Shear and compression viscoelasticity in polymer monolayers
International Nuclear Information System (INIS)
Poly-vinlyacetate (PVAc) forms very stable and reproducible monolayers on the surface of water, a model system to understand polymer physics on two dimensions. A recently introduced technique is applied here to to study viscoelasticity of PVAc monolayers. The method is based on measurement of surface tension in two orthogonal directions during anisotropic deformation. Compression and shear moduli are explored over a very large concentration range, highlighting a series of four different regimes. At low concentration the polymers are in a dilute gas. Above the overlap concentration ?* there is a fluid semi-dilute region, where the monolayer properties are described by scaling laws. At a threshold concentration ?**, a decrease in the gradient of pressure with concentration is observed, and we argue that there is still a large fraction of free area on the surface. Compressing further, we then identify close packing as the point where the pressure gradient rises sharply and a shear modulus emerges. This is interpreted as a transition to a soft-solid due to the kinetic arrest of close-packed monomers. The rheological properties of PVAc above ?** have not been studied previously. Discussion includes possible explanations for the observed behaviour in terms of both equilibrium and non-equilibrium conditions, and the relation to microscopic chain properties. Temperature dependent effects around ?** are also observed and described
Leakage through cracks in RC shear walls
International Nuclear Information System (INIS)
The negative pressure inside BWR buildings and in the annular zone of PWRs should be maintained under control even in the case that an S1 design earthquake occurs after LOCA. The leakage through the cracks in a reinforced concrete shear wall is one of the important problems when the air tightness of these structures after earthquakes is considered. In order to obtain the methods for estimating the leakage, two types of the model tests were carried out. In the basic test, 20 specimens were tested for examining the air flow rate through the single cracks having different crack width under the pressure difference of 20 - 1000 mm Aq. In the application test, four flat plate specimens were tested for examining the air flow rate through the multiple residual shear cracks of different stress intensity under the pressure difference of approximately 20, 100 and 200 mm Aq. The specimens, the methods of loading and measurement, the test results and the evaluation of the test results are reported. Based on the basic test results, a simplified formula for estimating the flow rate through a single crack was obtained. (K.I.)
DSMC Simulations of Transiently Decaying Shear Flow
Torczynski, J. R.; Gallis, M. A.; Rader, D. J.
2006-11-01
The accuracy of the Direct Simulation Monte Carlo (DSMC) method is investigated for simulating the transient decay of a shear flow between two parallel specular walls. In the continuum limit, the exact solution is determined numerically from the Navier-Stokes equations, and an approximate closed-form solution is determined for linear isothermal flow (i.e., small shear stress). DSMC simulations are performed using hard-sphere argon from free-molecular to continuum conditions. Initially, the tangential velocity component varies spatially according to one half-cycle of a cosine wave. The velocity amplitude is low enough to ensure that the flow remains linear and isothermal. Simulations are performed with various cell sizes and time steps while using an extremely large number of molecules (10 million). For each continuum case, the effective viscosity is determined by matching the closed-form solution for the velocity profile to the simulation results. The Chapman-Enskog value of the viscosity is obtained to within 0.3% in the resolved limit, and the departures at finite spatial and temporal resolution are in reasonable agreement with Green-Kubo theory. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.
Plasticity Approach to HSC Shear Wall Design
DEFF Research Database (Denmark)
Liu, Lunying; Nielsen, Mogens Peter
1998-01-01
The paper describes a simple theory for determining the ultimate strength of shear walls. It is based on application of the theory of perfectly plastic materials. When applied to concrete the theoretical solutions must be modified by inserting into the solutions a reduced compressive strength of concrete. The reduced strength is named the effective strength. The paper describes simple lower bound solutions. They consist of pure strut action or strut action combined with diagonal compression fields outside the struts. Near moment maximum and near supports the stress fields are modified to save longitudinal reinforcement. Upper bound solutions are summarized briefly. The lower bound method has been compared with around 200 tests taken from the literature. With very simple formulas for the effectiveness factor, excellent agreement has been obtained. The testscover concrete compressive strengths up to 140 MPa and reinforcement yield strengths up to 1420 MPa. The work was carried out as a Ph.D. study by the first author, the second author supervising the study.Keywords: shear wall, plasticity, strut and tie, load-carrying capacity, concrete, reinforcement.
Reproducibility of MRE shear modulus estimates
Weaver, John B.; Miller, Timothy B.; Doyley, Marvin D.; Wang, Huifang; Perrinez, Phillip R.; Cheung, Yvonne Y.; Kennedy, Francis E.; Paulsen, Keith D.
2007-03-01
A significant effort has been expended to measure the accuracy of the shear modulus estimates. Conversely, very little effort has been expended to establish the reproducibility of the method in a clinical context. Previously we established the reproducibility in phantoms to be 3% for repeated measurements without moving the phantom and 5% when the phantom was moved,however, the clinical reproducibility has not been demonstrated. The reproducibility of the method was estimated by scanning subjects' heels repeatedly on a GE 1.5T scanner using previously described methods. Three subjects were scanned three times on different days (termed non-consecutive) and three subjects were scanned three times in the same session without changing the position of the foot (termed consecutive). The average difference between mean values within the field of view for the non-consecutive group was 7.75% +/- 3.76% and for the consecutive group it was 5.30% +/- 4.16%. These values represent remarkably good reproducibility considering the 20% variation in shear modulus observed within individual heels and the several hundred percent changes observed between normal and pathologic tissues. The variation in repeated examinations was caused by four factors: positioning error between examinations accounted for 4.8%, computational noise 3.0%, and the combination of MR noise and patient motion during the examination, 5.3%. Each of these sources of variation can be reduced in relatively straightforward ways if necessary but the current level of reproducibility is sufficient for most current applications.
Coupling effects in multiphase free shear flows
International Nuclear Information System (INIS)
The primary goal of this research program is to examine the effects of two-way multiphase coupling on the development of organized vortex structures in free shear flows and the resultant multiphase dispersion. Previous research studies have determined that one-way coupled particle dispersion in free shear flows is strongly dependent on the vortex structures present in these flows and their interactions as well as the ratio of the particle aerodynamic response time to the time scale of the dominant vortex structures. Current research efforts are directed towards exploring the effects that two-way momentum, mass and energy coupling have on the multiphase dispersion processes previously uncovered. These efforts involve analytical, numerical and experimental investigations. Recent analytical and numerical results indicate that momentum coupling effects can significantly alter the global stability and potentially the large scale features of the multiphase flow field. These multiphase coupling effects may have significant importance with regard to predicting the performance of many energy conversion systems
Shear-induced instabilities in layered liquids
Auernhammer, Günter K.; Brand, Helmut R.; Pleiner, Harald
2002-12-01
Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic-A-like systems, we consider an extended formulation of smectic-A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normal pcirc) and the director ncirc of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in nonequilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle between ncirc and pcirc, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers. We generalize our earlier approach [G. K. Auernhammer, H. R. Brand, and H. Pleiner, Rheol. Acta 39, 215 (2000)] and include the cross couplings with the velocity field and the order parameters for orientational and positional order and show how the order parameters interact with the undulation instability. We explore the influence of various material parameters on the instability. Comparing our results to recent experiments and molecular dynamic simulations, we find a good qualitative agreement.
Zaccone, Alessio; Gentili, Daniele; Wu, Hua; Morbidelli, Massimo
2009-01-01
Using a novel approximation scheme within the convective diffusion (two body Smoluchowski) equation framework, we unveil the shear-driven aggregation mechanism at the origin of structure-formation in sheared colloidal systems. The theory, verified against numerics and experiments, explains the induction time followed by explosive (irreversible) rise of viscosity observed in charge-stabilized colloidal and protein systems under steady shear. The Arrhenius-type equation with s...
Zhu, Jiang; Qu, Yueqiao; Ma, Teng; Li, Rui; Du, Yongzhao; Huang, Shenghai; Shung, K Kirk; Zhou, Qifa; Chen, Zhongping
2015-05-01
We report on a novel acoustic radiation force orthogonal excitation optical coherence elastography (ARFOE-OCE) technique for imaging shear wave and quantifying shear modulus under orthogonal acoustic radiation force (ARF) excitation using the optical coherence tomography (OCT) Doppler variance method. The ARF perpendicular to the OCT beam is produced by a remote ultrasonic transducer. A shear wave induced by ARF excitation propagates parallel to the OCT beam. The OCT Doppler variance method, which is sensitive to the transverse vibration, is used to measure the ARF-induced vibration. For analysis of the shear modulus, the Doppler variance method is utilized to visualize shear wave propagation instead of Doppler OCT method, and the propagation velocity of the shear wave is measured at different depths of one location with the M scan. In order to quantify shear modulus beyond the OCT imaging depth, we move ARF to a deeper layer at a known step and measure the time delay of the shear wave propagating to the same OCT imaging depth. We also quantitatively map the shear modulus of a cross-section in a tissue-equivalent phantom after employing the B scan. PMID:25927794
Structure and rheology of model-ferrofluids under shear flow
International Nuclear Information System (INIS)
Nonequilibrium simulations of ferromagnetic colloids in the presence of a magnetic field and plane shear flow are performed. Results for the nonequilibrium magnetization and the nonequilibrium structure factor are presented. We observe that the nonequilibrium magnetization and the magnetoviscosity are enhanced due to dipolar interactions. Structure formation due to magnetic field and shear flow are observed in qualitative agreement with experimental results
Behavior of MR Fluids at High Shear Rate
Hu, Wei; Wereley, Norman M.
The high shear rate behavior of MR fluids is investigated using a concentric rotational cylinder viscometer fabricated in-house. The rotational cylinder viscometer is designed such that a high shear rate of up to 30,000 s-1 can be applied to the MR fluid in a pure shear flow mode. As a comparison, the maximum shear rate of a commercially available parallel disk type rheometer is only up to 1,000 s-1. To determine the shear rate of the MR fluid in the viscometer, an exact expression between torque and angular velocity is established. The yield stress and viscosity of the MR fluid is determined by fitting the expression into the measured torque and angular velocities, and the shear stress as a function of the shear rate is further derived. The magnetic filed strength across the fluid gap is determined based on an electromagnetic field analysis, and the yield stress and viscosity of the fluid as a function of the magnetic filed is established. Specifically, the stability of the MR fluid at high shear rate is also evaluated. Two commercially available MR fluids, i.e., Lord's MRF-132DG and MRF-140CG, are investigated using the rotational cylinder viscometer, and the testing results are compared to the manufacturer's data.
Large-scale direct shear testing of municipal solid waste.
Zekkos, Dimitrios; Athanasopoulos, George A; Bray, Jonathan D; Grizi, Athena; Theodoratos, Andreas
2010-01-01
Large direct shear testing (300 mm x 300 mm box) of municipal solid waste (MSW) collected from a landfill located in the San Francisco Bay area was performed to gain insight on the shear response of MSW. The study investigated the effects of waste composition, confining stress, unit weight, and loading rate on the stress-displacement response and shear strength of MSW. The amount and orientation of the fibrous waste materials in the MSW were found to play a critical role. The fibrous material had little effect on the MSW's strength when it was oriented parallel to the shear surface, as is typically the case when waste material is compressed vertically and then tested in a direct shear apparatus. Tests in which the fibrous material was oriented perpendicular to the horizontal shear surface produced significantly stronger MSW specimens. The test results indicate that confining stress and loading rate are also important factors. Based on 109 large-scale direct shear tests, the shear strength of MSW at low moisture contents is best characterized by cohesion=15 kPa, friction angle=36 degrees at a normal stress of 1 atmosphere, and a decrease in the friction angle of 5 degrees for every log-cycle increase in normal stress. PMID:20153160
Research Concerning the Shearing Strength of Black Locust Wood
Directory of Open Access Journals (Sweden)
Mihaela POROJAN
2011-06-01
Full Text Available The paper presents the experimental resultsobtained for the shearing strength of black locustwood (Robinia pseudacacia L. harvested from twogeographical areas (North and South of Romania.Wood is subjected to shearing stress when usedwithin different fields, and especially inconstructions. Tangential stresses are produced inthe shearing sections and they are influenced by thestructure of wood through the position of theshearing plane and of the force direction towards thegrain. Accordingly, several shearing types arepossible. The shearing strengths for the three mainshearing types, both on radial and tangentialdirection were determined within the present study.The evaluation of data was achieved by using theANOVA analysis, in order to test the level ofsignificance depending on the shearing planeorientation and the harvesting area. The obtainedresults were compared to the values mentionedwithin reference literature for this wood species andtwo other hardwood species with similar density. It isworth to be mentioned that the shearing strengths ofblack locust wood from Romania (both from Northand South are generally higher than those indicatedby reference literature for oak and beech. Thisrecommends black locust wood as constructionwood and for other applications where wood issubjected to shearing stress.
Sheared and unsheared rotation of driven dust clusters
Energy Technology Data Exchange (ETDEWEB)
Schablinski, Jan; Block, Dietmar; Carstensen, Jan; Greiner, Franko; Piel, Alexander [Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet Kiel, Leibnizstraße 19-Kiel, SH 24098 (Germany)
2014-07-15
Finite size plasma crystals confined in an anisotropic potential well were studied under a rotating and radially unsheared drive in experiment and simulation at moderate rotational frequencies. A radially sheared rotation of these strongly coupled systems is observed for most cluster configurations with a low symmetry. The results show that a differential rotation can be effected by a non-sheared driving force.
Chemotactic Motility of Sperm in Shear
Guasto, Jeffrey S.; Riffell, Jeffrey A.; Zimmer, Richard K.; Stocker, Roman
2011-11-01
Chemical gradients are utilized by plants and animals in sexual reproduction to guide swimming sperm cells toward the egg. This process (``chemotaxis''), which can greatly increase the success of fertilization, is subject to interference by fluid flow, both in the bodily conduits of internal fertilizers (e.g. mammals) and in the aquatic environment of external fertilizers (e.g. benthic invertebrates). We studied the biomechanics of chemotaxing sea urchin spermatozoa using microfluidic devices, which allow for the precise and independent control of attractant gradients and fluid shear. We captured swimming trajectories and flagellar beat patterns using high-speed video-microscopy, to detect chemotactic responses and measure the effect of fluid forces on swimming. This work will ultimately help us to understand how swimming sperm cells actively navigate natural chemoattractant gradients for successful fertilization.
Entanglements in Quiescent and Sheared Polymer Melts
Yamamoto, R; Yamamoto, Ryoichi; Onuki, Akira
2004-01-01
We visualize entanglements in polymer melts using molecular dynamics simulation. A bead at an entanglement interacts persistently for long times with the non-bonded beads (those excluding the adjacent ones in the same chain). The interaction energy of each bead with the non-bonded beads is averaged over a time interval $\\tau$ much longer than microscopic times but shorter than the onset time of tube constraints $\\tau_{\\rm e}$. Entanglements can then be detected as hot spots consisting of several beads with relatively large values of the time-averaged interaction energy. We next apply a shear flow with rate much faster than the entangle motion. With increasing strain the chains take zigzag shapes and a half of the hot spots become bent. The chains are first stretched as a network but, as the bends approach the chain ends, disentanglements subsequently occur, leading to stress overshoot observed experimentally.
Friction welding; Magnesium; Finite element; Shear test.
Directory of Open Access Journals (Sweden)
Leonardo Contri Campanelli
2013-06-01
Full Text Available Friction spot welding (FSpW is one of the most recently developed solid state joining technologies. In this work, based on former publications, a computer aided draft and engineering resource is used to model a FSpW joint on AZ31 magnesium alloy sheets and subsequently submit the assembly to a typical shear test loading, using a linear elastic model, in order to conceive mechanical tests results. Finite element analysis shows that the plastic flow is concentrated on the welded zone periphery where yield strength is reached. It is supposed that “through the weld” and “circumferential pull-out” variants should be the main failure behaviors, although mechanical testing may provide other types of fracture due to metallurgical features.
Shear-induced demixing of glassy suspension
van de Laar, Ties; Sprakel, Joris; Schroen, Karin
2015-03-01
The ground state of a binary suspension composed of particles of incommensurate size is that of two demixed crystal phases. However this has never been experimentally observed, due to the prohibitively long time scales associated with diffusion in a glass. Here we show that enhancing particle mobility in a glass, by means of flow, can lead to this type of solid-solid demixing. We study this phenomenon at the scale of single particles by means of high speed confocal imaging of suspensions flowing through microfluidic channels. By systematically varying the applied pressures and volume fractions we intend to bridge the gap between classical shear-induced migration at dilute concentrations and deformation of glasses.
The SDSS Coadd: Cosmic Shear Measurement
Energy Technology Data Exchange (ETDEWEB)
Lin, Huan; /Fermilab; Dodelson, Scott; /Fermilab /Chicago U., EFI /Chicago U., KICP; Seo, Hee-Jong; /UC, Berkeley; Soares-Santos, Marcelle; /Fermilab; Annis, James; /Fermilab; Hao, Jiangang; /Fermilab; Johnston, David; /Fermilab; Kubo, Jeffrey M.; /Fermilab; Reis, Ribamar R.R.; /Fermilab /Rio de Janeiro Federal U.; Simet, Melanie; /Chicago U., EFI /Chicago U., KICP
2011-11-01
Stripe 82 in the Sloan Digital Sky Survey was observed multiple times, allowing deeper images to be constructed by coadding the data. Here we analyze the ellipticities of background galaxies in this 275 square degree region, searching for evidence of distortions due to cosmic shear. The E-mode is detected in both real and Fourier space with > 5-{sigma} significance on degree scales, while the B-mode is consistent with zero as expected. The amplitude of the signal constrains the combination of the matter density {Omega}{sub m} and fluctuation amplitude {sigma}{sub 8} to be {Omega}{sub m}{sup 0.7} {sigma}{sub 8} = 0.276{sub -0.050}{sup +0.036}.
Shear Adhesive Connections for Glass Structures
Machalická, K.; Hor?i?ková, I.; Eliášová, M.
2015-11-01
Unique aesthetical properties of glass - not only transparency but also smooth, glossy and primarily reflective surface - give this material special importance in the contemporary architecture. In every structural application of glass it is necessary to solve the problem associated with connections between glass pane and other part from a different material or between two glass elements. Moreover, there are many types of hybrid structures that combine glass and different materials to achieve safe failure behaviour and high degree of transparency at the same time. Connection of brittle glass and reinforcing material is an essential part of these structures, where composite action between two parts is beneficially ensured by a glued joint. The current paper deals with the experimental analysis focused on the determination of mechanical characteristics of adhesives applied in planar connections under shear loading.
Shear Modulus Anomaly in Solid Helium
Beamish, John; Day, James; Syshchenko, Alexander
2008-03-01
The search for supersolidity was given impetus by recent experiments in which solid helium appeared to decouple from a torsional oscillator, but other phenomena which characterize superflow have not yet been observed. Both experiments and theory indicate that defects are involved in supersolidity and these should also affect the solid's mechanical behavior. We have measured the shear modulus of solid helium at extremely low frequencies and strains, using a new method, and observe anomalous stiffening at temperatures below 200 mK. It has the same dependence on temperature, measurement amplitude, ^3He impurity concentration and annealing as the torsional oscillator decoupling. This elastic behavior is explained in terms of a dislocation network which is pinned by ^3He at the lowest temperatures but becomes mobile above 100 mK. Moving dislocations appear eliminate the decoupling and disrupt possible supersolidity.
Spatially localized solutions of shear flows
Gibson, J F
2013-01-01
We present several new spatially localized equilibrium and traveling-wave solutions of plane Couette and channel flows. The solutions exhibit strikingly concentrated regions of vorticity that are flanked on either side by high-speed streaks. For several traveling-wave solutions of channel flow, the concentrated vortex structures are confined to the near-wall region and form particularly isolated and elemental coherent structures in the near-wall region of shear flows. The solutions are constructed by a variety of methods: application of windowing functions to previously known spatially periodic solutions, continuation from plane Couette to channel flow conditions, and from initial guesses obtained from turbulent simulation data. We show how the symmetries of localized solutions derive from the symmetries of their periodic counterparts, analyze the exponential decay of their tails, examine the scale separation and scaling of their streamwise Fourier modes, and show that they develop critical layers for large R...
Lattice shear distortions in fluorite structure oxides
International Nuclear Information System (INIS)
Crystallographic shear distortions have been observed in fluorite structure, single crystals of UO2 and Zr(Ca)O2/sub-x/ by neutron-diffraction techniques. These distortions localize on the oxygen sublattice and do not require the presence of an external strain. The internal rearrangement mode in UO2 is a transverse, zone boundary q vector = 2?/a (0.5, 0.0) deformation with amplitude 0.014 A. In Zr(Ca)O/sub 2-x/, the mode is a longitudinal, q vector = 2-/a (0,0,0.5) deformation with amplitude 0.23 A. Cation-anion elastic interactions dominate in selecting the nature of the internal distortion
Particle segregation in monodisperse sheared suspensions
International Nuclear Information System (INIS)
It has been known for a long time that many mixtures of granular materials tend to segregate when tumbled in a rotating horizontal cylinder, with the different components separating into bands of relatively pure single concentration along the rotational axis [Mixing of Solids, Advances in Chemical Eng., edited by T. B. Drew and J. W. Hoopes (Academic Press, New York, 1952), Vol. 2, p. 211]. Here we report a phenomenon that seems to be analogous, but in suspensions of monodisperse neutrally buoyant spherical particles in a Newtonian liquid medium being sheared in a partially filled horizontal Couette device in which the suspension separates itself into alternating regions of high and low particle concentration along the length of the tube. The experiment is mostly qualitative, the aim at this stage being primarily to provide photographic evidence of a curious and as yet unexplained phenomenon. copyright 1999 American Institute of Physics
High-frequency ultrasonic speckle velocimetry in sheared complex fluids
Manneville, S; Colin, A
2003-01-01
High-frequency ultrasonic pulses at 36 MHz are used to measure velocity profiles in a complex fluid sheared in the Couette geometry. Our technique is based on time-domain cross-correlation of ultrasonic speckle signals backscattered by the moving medium. Post-processing of acoustic data allows us to record a velocity profile in 0.02--2 s with a spatial resolution of 40 $\\mu$m over 1 mm. After a careful calibration using a Newtonian suspension, the technique is applied to a sheared lyotropic lamellar phase seeded with polystyrene spheres of diameter 3--10 $\\mu$m. Time-averaged velocity profiles reveal the existence of inhomogeneous flows, with both wall slip and shear bands, in the vicinity of a shear-induced ``layering'' transition. Slow transient regimes and/or temporal fluctuations can also be resolved and exhibit complex spatio-temporal flow behaviors with sometimes more than two shear bands.
Impact of Vertical Wind Shear on Tropical Cyclone Rainfall
Cecil, Dan; Marchok, Tim
2014-01-01
While tropical cyclone rainfall has a large axisymmetric component, previous observational and theoretical studies have shown that environmental vertical wind shear leads to an asymmetric component of the vertical motion and precipitation fields. Composites consistently depict a precipitation enhancement downshear and also cyclonically downwind from the downshear direction. For consistence with much of the literature and with Northern Hemisphere observations, this is subsequently referred to as "Downshear-Left". Stronger shear magnitudes are associated with greater amplitude precipitation asymmetries. Recent work has reinforced the prior findings, and explored details of the response of the precipitation and kinematic fields to environmental vertical wind shear. Much of this research has focused on tropical cyclones away from land, to limit the influence of other processes that might distort the signal related to vertical wind shear. Recent evidence does suggest vertical wind shear can also play a major role in precipitation asymmetries during and after landfall.
Smoothing and roughening of slip surfaces in direct shear experiments
Sagy, Amir; Badt, Nir; Hatzor, Yossef H.
2015-04-01
Faults in the upper crust contain discrete slip surfaces which have absorbed a significant part of the shear displacement along them. Field measurements demonstrate that these surfaces are rough at all measurable scales and indicate that surfaces of relatively large-slip faults are statistically smoother than those of small-slip faults. However, post faulting and surface erosion process that might affect the geometry of outcrops cannot be discounted in such measurements. Here we present experimental results for the evolution of shear surface topography as function of slip distance and normal stress in direct shear experiments. A single prismatic fine grain limestone block is first fractured in tension mode using the four-point bending test methodology and then the fracture surface topography is scanned using a laser profilometer. We then shear the obtained tensile fracture surfaces in direct shear, ensuring the original fracture surfaces are in a perfectly matching configuration at the beginning of the shear test. First, shearing is conducted to distances varying from 5 to 15 mm under constant normal stress of 2MPa and a constant displacement rate of 0.05 mm/s using two closed-loop servo controlled hydraulic pistons, supplying normal and shear forces (Davidesko et al., 2014). In the tested configuration peak shear stress is typically attained after a shear displacement of about 2-3 mm, beyond which lower shear stress is required to continue shearing at the preset displacement rate of 0.05 mm/s as is typical for initially rough joints. Following some initial compression the interface begins to dilate and continues to do so until the end of the test. The sheared tensile fracture surface is then scanned again and the geometrical evolution, in term of RMS roughness and power spectral density (PSD) is analyzed. We show that shearing smooth the surface along all our measurements scales. The roughness ratio, measured by initial PSD / final PSD for each wavelength, increases as a function of slip amount. The roughness measured after slip can be fitted by a power-law similar to that of the initial tensile surface. In the next series of experiments a similar procedure is applied when the roughness evolution is measured as a function of increasing normal stress for a fixed displacement amount of 10 mm. While samples sheared under a constant normal stress of 5 MPa generated surface smoothing, shearing under normal stress of 7.5 MPa to 15 MPa exhibited surface roughening at the measured range of scales. We find that roughening is correlated with the attained peak shear stress values, stress drop (peak shear stress minus residual shear stress) and with wear accumulation, a novel measurement procedure of which is developed here. Analysis of the sheared samples shows that roughening is generated by sets of dense fractures that significantly damaged the sample in the immediate proximity to large asperities. This roughening is related to penetrative damage during transient wear in rough surfaces.
The DES Science Verification Weak Lensing Shear Catalogs
Energy Technology Data Exchange (ETDEWEB)
Jarvis, M. [Univ. of Pennsylvania, Philadelphia, PA (United States). et al.
2015-07-20
We present weak lensing shear catalogs for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogs of 2.12 million and 3.44 million galaxies respectively. We also detail a set of null tests for the shear measurements and find that they pass the requirements for systematic errors at the level necessary for weak lensing science applications using the SV data. Furthermore, we discuss some of the planned algorithmic improvements that will be necessary to produce sufficiently accurate shear catalogs for the full 5-year DES, which is expected to cover 5000 square degrees.
The Mercier criterion in reversed-shear tokamak plasmas
International Nuclear Information System (INIS)
A recent numerical study has found that, contrary to conventional theoretical and experimental expectations, reversed-shear plasmas are unstable primarily because the term proportional to the shear in the Mercier criterion is destabilizing. In the present study, the role of the magnetic shear, both local and global, is examined for various tokamak configurations with monotonic and non-monotonic safety factor profiles. The enhancement of the local shear due to the outward shift of the magnetic axis suggests that the latter are less susceptible to interchanges. Furthermore, by regrouping the terms in the criterion, the V'' term when differentiated instead with respect to the toroidal flux, is shown to absorb the dominant shear term. No Mercier instability is found for similar profiles as in the previous study. (author)
Image reconstruction with acoustic radiation force induced shear waves
McAleavey, Stephen A.; Nightingale, Kathryn R.; Stutz, Deborah L.; Hsu, Stephen J.; Trahey, Gregg E.
2003-05-01
Acoustic radiation force may be used to induce localized displacements within tissue. This phenomenon is used in Acoustic Radiation Force Impulse Imaging (ARFI), where short bursts of ultrasound deliver an impulsive force to a small region. The application of this transient force launches shear waves which propagate normally to the ultrasound beam axis. Measurements of the displacements induced by the propagating shear wave allow reconstruction of the local shear modulus, by wave tracking and inversion techniques. Here we present in vitro, ex vivo and in vivo measurements and images of shear modulus. Data were obtained with a single transducer, a conventional ultrasound scanner and specialized pulse sequences. Young's modulus values of 4 kPa, 13 kPa and 14 kPa were observed for fat, breast fibroadenoma, and skin. Shear modulus anisotropy in beef muscle was observed.
High shear microfluidics and its application in rheological measurement
Energy Technology Data Exchange (ETDEWEB)
Kang, Kai; Lee, L.James; Koelling, Kurt W. [The Ohio State University, Department of Chemical Engineering, Columbus, OH (United States)
2005-02-01
High shear rheology was explored experimentally in microchannels (150 x 150 {mu}m). Two aqueous polymer solutions, polyethylene oxide (viscoelastic fluid) and hydroxyethyl cellulose (viscous fluid) were tested. Bagley correction was applied to remove the end effect. Wall slip was investigated with Mooney's analysis. Shear rates as high as 10{sup 6} s {sup -1} were obtained in the pressure-driven microchannel flow, allowing a smooth extension of the low shear rheological data obtained from the conventional rheometers. At high shear rates, polymer degradation was observed for PEO solutions at a critical microchannel wall shear stress of 4.1 x 10 {sup 3} Pa. Stresses at the ends of the microchannel also contributed to PEO degradation significantly. (orig.)
High shear microfluidics and its application in rheological measurement
Kang, Kai; Lee, L. James; Koelling, Kurt W.
2005-02-01
High shear rheology was explored experimentally in microchannels (150×150 ?m). Two aqueous polymer solutions, polyethylene oxide (viscoelastic fluid) and hydroxyethyl cellulose (viscous fluid) were tested. Bagley correction was applied to remove the end effect. Wall slip was investigated with Mooney’s analysis. Shear rates as high as 106 s-1 were obtained in the pressure-driven microchannel flow, allowing a smooth extension of the low shear rheological data obtained from the conventional rheometers. At high shear rates, polymer degradation was observed for PEO solutions at a critical microchannel wall shear stress of 4.1×103 Pa. Stresses at the ends of the microchannel also contributed to PEO degradation significantly.
The DES Science Verification Weak Lensing Shear Catalogs
Jarvis, M; Zuntz, J; Kacprzak, T; Bridle, S L; Amara, A; Armstrong, R; Becker, M R; Bernstein, G M; Bonnett, C; Chang, C; Das, R; Dietrich, J P; Drlica-Wagner, A; Eifler, T F; Gangkofner, C; Gruen, D; Hirsch, M; Huff, E M; Jain, B; Kent, S; MacCrann, N; Melchior, P; Plazas, A A; Refregier, A; Rowe, B; Rykoff, E S; Samuroff, S; Sánchez, C; Suchyta, E; Troxel, M A; Vikram, V; Abbott, T; Abdalla, F B; Allam, S; Annis, J; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Gaztanaga, E; Gerdes, D W; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; March, M; Martini, P; Miquel, R; Mohr, J J; Neilsen, E; Nord, B; Ogando, R; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Walker, A R; Wechsler, R H
2015-01-01
We present weak lensing shear catalogs for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogs of 2.12 million and 3.44 million galaxies respectively. We detail a set of null tests for the shear measurements and find that they pass the requirements for systematic errors at the level necessary for weak lensing science applications using the SV data. We also discuss some of the planned algorithmic improvements that will be necessary to produce sufficiently accurate shear catalogs for the full 5-year DES, which is expected to cover 5000 square degrees.
On the origin of shear bands in textured polycrystals
Energy Technology Data Exchange (ETDEWEB)
Canova, G.R.; Kocks, U.F.; Stout, M.G.
1984-05-01
The relaxation of constraints in nonequiaxed grains, which is the basis of a new theory of polycrystal deformation, permits the development of strain heterogeneities on a grain scale. Shear bands are then expected to form when there is sufficient textural softening. This was evaluated for an idealized rolling process, in which shears in the transverse plane were allowed. The result is that grain-scale shear bands should be inclined to the rolling direction preferentially at angles of 23/sup 0/ and 37/sup 0/. An analysis of the degree of textural softening incurred by sample-scale shear bands as a function of hypothetical angles indicates that such shear bands should occur preferentially at +-45/sup 0/.
Shear waves in inhomogeneous, compressible fluids in a gravity field.
Godin, Oleg A
2014-03-01
While elastic solids support compressional and shear waves, waves in ideal compressible fluids are usually thought of as compressional waves. Here, a class of acoustic-gravity waves is studied in which the dilatation is identically zero, and the pressure and density remain constant in each fluid particle. These shear waves are described by an exact analytic solution of linearized hydrodynamics equations in inhomogeneous, quiescent, inviscid, compressible fluids with piecewise continuous parameters in a uniform gravity field. It is demonstrated that the shear acoustic-gravity waves also can be supported by moving fluids as well as quiescent, viscous fluids with and without thermal conductivity. Excitation of a shear-wave normal mode by a point source and the normal mode distortion in realistic environmental models are considered. The shear acoustic-gravity waves are likely to play a significant role in coupling wave processes in the ocean and atmosphere. PMID:24606251
Scale by scale budget and similarity laws for shear turbulence
Casciola, C M; Benzi, R; Piva, R
2002-01-01
Turbulent shear flows, such as those occurring in the wall region of turbulent boundary layers, manifest a substantial increase of intermittency with respect to isotropic conditions. This suggests a close link between anisotropy and intermittency. However, a rigorous statistical description of anisotropic flows is, in most cases, hampered by the inhomogeneity of the field. This difficulty is absent for the homogeneous shear flow. For this flow the scale by scale budget is discussed here by using the appropriate form of the Karman-Howarth equation, to determine the range of scales where the shear is dominant. The issuing generalization of the four-fifths law is then used as the guideline to extend to shear dominated flows the Kolmogorov-Obhukhov theory of intermittency. The procedure leads naturally to the formulation of generalized structure functions and the description of intermittency thus obtained reduces to the K62 theory for vanishing shear. Also here the intermittency corrections to the scaling exponen...
Shear bands in metallic glasses are not necessarily hot
Directory of Open Access Journals (Sweden)
Stephanie K. Slaughter
2014-09-01
Full Text Available We have used the fusible tin coating method to detect shear band heating in amorphous Zr57Ti5Cu20Ni8Al10 loaded under quasi-static uniaxial compression. High-rate load data allowed a precise determination of the duration of shearing events and final fracture. When loading was halted prior to fracture we saw no evidence of melted tin despite the presence of shear offsets up to 6??m on some shear bands. Samples loaded to fracture showed evidence of tin melting near the fracture surface. We attribute the difference to the duration of the events, which is much longer for shear banding (milliseconds than for fracture (microseconds.
Elasto-plastic impact response analysis of shear-failure-type RC beams with shear rebars
International Nuclear Information System (INIS)
In this paper, to establish a simple elasto-plastic impact analysis method for shear-failure-type reinforced concrete (RC) beams, falling-weight impact tests and three-dimensional finite element (FE) analyses were conducted. Here, twelve simply supported rectangular RC beams were used, each with dimensions of (width x depth x length) 200 x 400 x 2,400 mm. Shear rebar ratio and impact velocity were taken as variables. Impact load was applied at the mid-span of RC beam by dropping a 400 kg steel weight from pre-determined position. LS-DYNA nonlinear transient finite element analysis code was used for this research. From this study, it is seen that the time histories of impact force, reaction force and mid-span displacement, and crack patterns on the side-surface of RC beam can be predicted accurately by using the proposed FE analysis method
Standard Test Method for Shear Strength and Shear Modulus of Aerospace Glazing Interlayer Materials
American Society for Testing and Materials. Philadelphia
2009-01-01
1.1 This test method covers the determination of the shear strength and shear modulus of interlayer materials that are restrained by relatively high modulus plies in laminated transparencies. This test method can be used with single or multiple plies of the same interlayer materials. 1.2 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
International Nuclear Information System (INIS)
The main vessel of a fast breeder reactor (FBR) is a relatively thin-walled cylindrical shell with a reactor core, coolant and shallow-dished head at one end. In this paper, imperfection effects of cylinders on buckling in shear and in bending were clarified with regard to degradation of buckling strength and energy absorption capacity under seismic loads. The imperfections considered here were (1) boundary condition (end closure), (2) geometric imperfections in the manufacturing process and (3) geometrical imperfections in operating conditions (ratcheting deformations). Static and pseudo-dynamic buckling tests for nearly perfect cylinders and cylinders with intentional imperfections made by press-working technique were carried out under transverse shearing loads. These imperfection effects were clarified from test results and FEM and nonlinear SDOF response analyses
Strengthening of flat slabs against punching shear using post-installed shear reinforcement
Fernández Ruiz, Miguel; Muttoni, Aurelio; Kunz
2010-01-01
A significant number of existing flat slabs currently require strengthening against punching shear for safety reasons (the increase of applied loads and deficiencies during design or construction) or to comply with more stringent code requirements. Available strengthening methods are, however, not completely satisfactory, or they cannot be applied in many cases (depending on the possibilities to enlarge column sizes or to intervene on the upper face of slabs). In this paper, an innovative sys...
Shear behavior of reinforced Engineered Cementitious Composites (ECC) beams
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
2010-01-01
This paper describes an experimental investigation of the shear behavior of beams consisting of steel reinforced Engineered Cementitious Composites (ECC). Based on the strain hardening and multiple cracking behavior of ECC, this study investigates the extent to which ECC can improve the shear capacity of beams loaded primarily in shear and if ECC can partially or fully replace the conventional transverse steel reinforcement in beams. However, there is a lack of understanding of how the fibers affect the shear carrying capacity and deformation behavior of structural members if used either in combination with conventional transverse reinforcement or exclusively to provide shear resistance. The experimental investigation focuses on the influence of fibers on the shear caring capacity and the crack development in ECC beams subjected to shear. The experimental program consists of ECC with short randomly distributed PVA (polyvinyl alcohol) fiber beams with different stirrup spacing and reinforced concrete (RC) beams for comparison. Displacement and strain measurements taken using the ARAMIS photogrammetric data acquisition system by means of processing at high frame rate captured images of applied a high contrast speckle pattern to the beams surface. The multiple micro cracking resulting from the strain-hardening response of ECC in tension develop in a di-agonal between the load and support point. The formation of multiple micro cracks is highly dependent on the tensile stress-strain behavior of the ECC. The shear crack formation mechanism of ECC is investigated and found to be characterized by an opening of the cracks prior to sliding. Several analytical models on shear de-sign of ECC and concrete beams are evaluated and compared to the experimentally obtained results. The pro-visions of the Eurocode and ACI Code are found to be over-conservative but can be modified by utilizing the tensile strength of ECC. An expression for the load carrying capacity is proposed by expressing the ECC shear strength in terms of the crack angle.
Numerical simulations of pattern evolution of shear bands during pure shear of geomaterials
Chen, Tielin; Liu, Jingjing; Jie, Yuxin; Zhang, Dingli
2015-07-01
Numerical simulations with finite element method were carried out and five types of patterns of shear bands and their process of self-organization were obtained. The elasto-plastic theory of constitutive relationship with the non-associated flow rule, vertex-like yielding surfaces and strain softening of strength were adopted to describe the mechanical behavior of geomaterials of rock or soil. The non-symmetrical matrix due to the adoption of the non-associated flow rule was solved with the algorithm of dynamical relaxation of finite element method. The discrete or banded patterns of shear strain in the form of superlattice, parallel strips, super lattice turned parallel strips, rhomboid net and concentric rhomboid loops, were gradually formed as the loading increased. The mechanism of the structural pattern generation and the process of pattern self-organization in geomaterials of rock and soil were a process of mechanical equilibrium of stresses and the allocation of material deformation between the elastic sites and plastic sites. The approach provided a way for researching mechanical origin of shear band pattern.
Directory of Open Access Journals (Sweden)
Ammar N. HANOON
2014-12-01
Full Text Available Self-compacting concrete (SCC is a new generation of high-performance concrete, known for its excellent deformability and high resistance to segregation and bleeding. Nonetheless, SCC may be incapable of resisting shear because the shear resistance mechanisms of this concrete are uncertain, especially the aggregate interlock mechanism. This uncertainty is attributed to the fact that SCC contains a smaller amount of coarse aggregates than normal concrete (NC does. This study focuses on the shear strength of self-compacting reinforced concrete (RC beams with and without shear reinforcement. A total of 16 RC beam specimens was manufactured and tested in terms of shear span-to-depth ratio and flexural and shear reinforcement ratio. The test results were compared with those of the shear design equations developed by ACI, BS, CAN and NZ codes. Results show that an increase in web reinforcement enhanced cracking strength and ultimate load. Shear-tension failure was the control failure in all tested beams.
Improved Shear Performance of Bent-Up Bars in Reinforced Concrete Beams .
Abdul Qader S. Najmi; Moayyad M. Al-Nasra; Naiem M. Asha
2013-01-01
Shear failure of reinforced concrete beams is often sudden and catastrophic. This sudden failure, due to shear, made it necessary to explore more effective ways to design reinforced concrete beam for shear. The reinforced concrete beams show different behavior at the failure stage in shear compare to the bending, which is considered to be unsafe mode of failure. The shear cracks progressive rapidly without sufficient advanced warning, and the diagonal cracks that develop due to excess shear f...
Directory of Open Access Journals (Sweden)
Marielen de Lima Silva
2007-09-01
Full Text Available O presente experimento foi realizado para determinar a efetividade do tratamento térmico em água e vapor a 80 °C tendo como objetivo a inativação do Clostridium botulinum tipo E, utilizando-se amostras de Semintendinosus. Foram realizadas ainda a avaliação da maciez objetiva, utilizando-se a análise de força de cisalhamento, e a avaliação sensorial dos atributos de suculência, maciez subjetiva, "flavor" e presença de colágeno. O tratamento a 80 °C foi efetivo na eliminação do microrganismo, contudo não houve diferença significativa no atributo maciez objetiva (força de cisalhamento avaliado nos dois tratamentos utilizados. A avaliação sensorial apresentou correlação positiva entre os atributos maciez e suculência, enquanto o colágeno apresentou correlação negativa com a maciez. O "flavor" não apresentou correlação com os atributos maciez, suculência e presença de colágeno.The purpose of the experiment reported here was to determine the effectiveness of heat treatments in water and in steam at 80 °C to inactivate the bacterium Clostridium botulinum type E in samples of beef Semitendinosus muscle. The product’s tenderness was evaluated based on a Warner-Bratzler Shear Force (WBSF analysis and its attributes of juiciness, subjective tenderness, flavor and connective tissue were evaluated sensorially. The treatment at 80 °C effectively killed the bacterium, but no significant difference was found in the attribute of objective tenderness (shear force evaluated after the two treatments. The sensorial analysis indicated a positive correlation between the attributes of juiciness and tenderness, while the connective tissue showed a negative correlation to tenderness. Flavor proved uncorrelated with tenderness, juiciness and connective tissue.
Scientific Electronic Library Online (English)
Marielen de Lima, Silva; Carmen Josefina, Contreras-Castillo; Edwin Moisés Marcos, Ortega.
2007-09-01
Full Text Available O presente experimento foi realizado para determinar a efetividade do tratamento térmico em água e vapor a 80 °C tendo como objetivo a inativação do Clostridium botulinum tipo E, utilizando-se amostras de Semintendinosus. Foram realizadas ainda a avaliação da maciez objetiva, utilizando-se a análise [...] de força de cisalhamento, e a avaliação sensorial dos atributos de suculência, maciez subjetiva, "flavor" e presença de colágeno. O tratamento a 80 °C foi efetivo na eliminação do microrganismo, contudo não houve diferença significativa no atributo maciez objetiva (força de cisalhamento) avaliado nos dois tratamentos utilizados. A avaliação sensorial apresentou correlação positiva entre os atributos maciez e suculência, enquanto o colágeno apresentou correlação negativa com a maciez. O "flavor" não apresentou correlação com os atributos maciez, suculência e presença de colágeno. Abstract in english The purpose of the experiment reported here was to determine the effectiveness of heat treatments in water and in steam at 80 °C to inactivate the bacterium Clostridium botulinum type E in samples of beef Semitendinosus muscle. The product’s tenderness was evaluated based on a Warner-Bratzler Shear [...] Force (WBSF) analysis and its attributes of juiciness, subjective tenderness, flavor and connective tissue were evaluated sensorially. The treatment at 80 °C effectively killed the bacterium, but no significant difference was found in the attribute of objective tenderness (shear force) evaluated after the two treatments. The sensorial analysis indicated a positive correlation between the attributes of juiciness and tenderness, while the connective tissue showed a negative correlation to tenderness. Flavor proved uncorrelated with tenderness, juiciness and connective tissue.
Directory of Open Access Journals (Sweden)
Ivona ?urkin
2009-12-01
Full Text Available The present study was performed in order to investigate a relationship between polymorphisms on the calpastatin gene (CAST and pig meat quality traits. The investigation was carried out on 29 gilts and barrows, crosses of Large White x German Landrace randomly selected at slaughter line. Pigs were slaughtered at 130-150 kg of live weight and blood samples were taken for genomic DNA analysis. The following indicators of meat quality and meat chemical composition were evaluated: pH and electric conductivity measured 45 minutes post mortem in m. Longissimus dorsi (LD muscle and in M. Semimembranosus (SM muscle; electric conductivity measured at the same locations after 24h of cooling; drip loss (determined by “bag method”; colour (measured with Minolta chromameter and expressed as Hunter L, a, b values; instrumental tenderness assessed as Warner-Bratzler (WB shear force and moisture, fat, protein and collagen content (% determined on cooked LD muscle after 24h of thawing. The amplification products of the CAST gene were digested with HinfI restriction endonuclease and three genotypes (AA, BB and AB were revealed. Statistical analysis showed that meat originated from pigs of AB genotype had the lowest WB shear force and the highest protein content of cooked LD muscle. As for the indicators of technological meat quality, statistically significant differences (p<0.05 were found between genotype AA and both BB and AB genotype for electric conductivity measured in LD muscle after 24h of cooling, as well as between BB and both AA and AB genotypes for drip loss.
Imaging Faults and Shear Zones Using Receiver Functions
Schulte-Pelkum, Vera; Mahan, Kevin H.
2014-11-01
The geometry of faults at seismogenic depths and their continuation into the ductile zone is of interest for a number of applications ranging from earthquake hazard to modes of lithospheric deformation. Teleseismic passive source imaging of faults and shear zones can be useful particularly where faults are not outlined by local seismicity. Passive seismic signatures of faults may arise from abrupt changes in lithology or foliation orientation in the upper crust, and from mylonitic shear zones at greater depths. Faults and shear zones with less than near-vertical dip lend themselves to detection with teleseismic mode-converted waves (receiver functions) provided that they have either a contrast in isotropic shear velocity ( V s), or a contrast in orientation or strength of anisotropic compressional velocity ( V p). We introduce a detection method for faults and shear zones based on receiver functions. We use synthetic seismograms to demonstrate common features of dipping isotropic interfaces and contrasts in dipping foliation that allows determination of their strike and depth without making further assumptions about the model. We proceed with two applications. We first image a Laramide thrust fault in the western U.S. (the Wind River thrust fault) as a steeply dipping isotropic velocity contrast in the middle crust near the surface trace of the fault; further downdip and across the range, where basin geometry suggests the fault may sole into a subhorizontal shear zone, we identify a candidate shear zone signal from midcrustal depths. The second application is the use of microstructural data from exhumed ductile shear zones in Scotland and in the western Canadian Shield to predict the character of seismic signatures of present-day deep crustal shear zones. Realistic anisotropy in observed shear fabrics generates a signal in receiver functions that is comparable in amplitude to first-order features like the Moho. Observables that can be robustly constrained without significant tradeoffs are foliation strike and the depth of the foliation contrast. We find that an anisotropy of only a few percent in the shear zone is sufficient to generate a strong signal, but that the shear zone width is required to be >2 km for typical frequencies used in receiver function analysis to avoid destructive interference due to the signals from the boundaries of the shear zone.
International Nuclear Information System (INIS)
An experiment conducted to shear two dummy PWR subassemblies is described. Results pertain to the removal of end hardware by shearing, spacer grid fragmentation, the character of sheared product, product leachability, shearing force requirements, and the effects of compaction
Je?ábek, Petr; Bukovská, Zita
2015-04-01
The South Armorican Shear Zone in France represents a major right-lateral strike slip shear zone formed in the late stages of Variscan orogeny. The active deformation in this shear zone is associated with the development of S-C fabrics in granitoids where thin shear bands (C) overprint an earlier higher grade metamorphic foliation (S). In the studied samples covering low to high intensity of shear band overprint, we identified three stages of shear band evolution associated with distinct microstructures and deformation mechanisms. The initiation of shear bands stage I is associated with the formation of microcracks crosscutting the S fabric and detected namely in the recrystallized quartz aggregates. The microcracks of suitable orientation are filled by microcline, albite, muscovite and chlorite which is a typical assemblage also for the well developed shear bands. Phase equilibrium modeling in PERPLEX indicates that this assemblage formed at pressure-temperature range of 0.1-0.4 GPa and 300-340 °C. Stage II of shear band evolution is characterized by dynamic recrystallization and grain size reduction of quartz aggregates along the microcracks and replacement of quartz by microcline along grain boundaries. This process leads to disintegration of quartz aggregate fabric and phase mixing in the shear bands. The inferred deformation mechanism for this stage is solution-precipitation creep although recrystallization of quartz is still active at the contact between quartz aggregates and shear bands. The coarse grained microstructure of quartz aggregates with ca ~250 microns average grain size reduces to ~10 microns grain size when recrystallized along extremely thin shear bands/microcracks and to ~20 microns grain size when recrystallized along the thicker shear bands. By using the flow law of Patterson and Luan (1990) for dislocation creep in quartz and the quartz piezometer of Stipp and Tullis (2003) corrected after Holyoke and Kronenberg (2010), the quartz recrystallization along thin shear bands records strain rates of ~10^-14 whereas the recrystallization along thick shear bands records strain rates of ~10^-15. The contemporaneous operation of solution-precipitation creep in shear bands and dislocation creep in quartz along the shear band boundary suggests low viscosity contrast between the mixed phase shear band matrix and pure quartz aggregate implying that the solution-precipitation creep reflect similar stress and strain rate conditions as the dislocation creep in quartz. Stage III of shear band evolution is characterized by interconnection of dispersed muscovite grains and the deformation becomes accommodated by dislocation creep in thin muscovite bands separating the inactive domains of stage II microstructure. References: Holyoke III, C. W., & Kronenberg, A. K. (2010). Accurate differential stress measurement using the molten salt cell and solid salt assemblies in the Griggs apparatus with applications to strength, piezometers and rheology. Tectonophysics, 494(1-2), 17-31. Paterson, M. S., & Luan, F. C. (1990). Quartzite rheology under geological conditions. In R. J. Knipe & E. H. Rutter (Eds.), Deformation Mechanisms, Rheology and Tectonics (pp. 299-307). London: Geological Society Special Publications. Stipp, M., & Tullis, J. (2003). The recrystallized grain size piezometer for quartz. Geophysical Research Letters, 30(21), 1-5.
Extreme shearing interferometry: theoretical limits with practical consequences.
Servin, M; Cywiak, M; Dávila, A
2007-12-24
In this work we analyze the frequency response, the spatial distribution and continuity of the recovered phase in Lateral Shearing Interferometry (LSI). This frequency content and topology of the recovered phase is analyzed for the forward LSI operator as well as its inverse LSI operator using one, two, or n two-dimensional sheared interferograms. The spatial frequency response of the shearing interferometer is well known and for the reader's convenience, it is briefly revisited in a new perspective. It is however less well-known and more interesting to analyze the spatial distribution of the sheared data as well as the spatial topology of the recovered phase produced by some inverse LSI operators. Also we define a useful space of functions S with the property that any sheared data available, along any direction, may be used to recovered a smooth continuous phase with the bonus property of fully covering the pupil of the wavefront being tested. These combined aspects allow us to find the best possible wave-front reconstruction from the available sheared data using one, two or n sheared interferograms. PMID:19551077
Yielding of colloidal gels under steady and oscillatory shear
Petekidis, George; Moghimi, Esmaeel; Koumakis, Nick; Forth Team
2015-03-01
The structural and rheological properties of intermediate volume fraction colloid polymer gels are examined during and after steady and oscillatory shear flow using rheometry, confocal microscopy, light scattering and Brownian Dynamics simulations. Our main objective is to rationalize the microscopic mechanisms through which one can tune the mechanical properties of such metastable colloidal gels by imposing different types of external shear and flow. Experimentally, the gels consist of model hard sphere particle dispersions of ? = 0.44 with the addition of non-adsorbing linear chains, while BD simulations are conducted for hard spheres with the superposition of an AO potential for depletion attractions. Structural analysis shows that variation of the applied shear rate produces strong changes in the structure of the gels both when under shear and during gel reformation at cessation. Larger rates are characterized by disperse particles and the total breakage of structures at rest, which after cessation evolve with time into strong solids with relatively homogeneous structures. However, smaller rates show large inhomogeneous structures under flow, which do not evolve after cessation and additionally exhibit reduced elasticity and as such are weaker solids. Furthermore oscillatory shear is far more efficient than steady shear creating gels with stronger differences in their elastic modulus. Thus by tuning the way a gel is sheared, one may vary the final strength and structure of the resulting gel. Work in collaboration with R. Besseling, W. C. K. Poon and J. F. Brady
Shear strength of palm oil clinker concrete beams
International Nuclear Information System (INIS)
Highlights: ? Palm oil clinker can be used as lightweight aggregate for the production of structural concrete. ? The palm oil clinker concrete can be classified as lightweight concrete. ? Full scale reinforced palm oil clinker concrete beams without shear reinforcement were tested. ? The CSA based design equation can be used for the prediction of shear capacity with a limit. - Abstract: This paper presents experimental results on the shear behavior of reinforced concrete beams made of palm oil clinker concrete (POCC). Palm oil clinker (POC) is a by-product of palm oil industry and its utilization in concrete production not only solves the problem of disposing this solid waste but also helps to conserve natural resources. Seven reinforced POCC beams without shear reinforcement were fabricated and their shear behavior was tested. POCC has been classified as a lightweight structural concrete with air dry density less than 1850 kg/m3 and a 28-day compressive strength more than 20 MPa. The experimental variables which have been considered in this study were the POCC compressive strength, shear span–depth ratio (a/d) and the ratio of tensile reinforcement (?). The results show that the failure mode of the reinforced POCC beam is similar to that of conventional reinforced concrete beam. In addition, the shear equation of the Canadian Standard Association (CSA) can be used in designing reinforced POCC beam with ? ? 1. However, a 0.5 safety factor should be included in the formula for ? < 1
Rayleigh-Taylor instabilities with sheared magnetic fields
International Nuclear Information System (INIS)
Magnetic Rayleigh-Taylor (MRT) instabilities may play a relevant role in many astrophysical problems. In this work the effect of magnetic shear on the growth rate of the MRT instability is investigated. The eigenmodes of an interface and a slab model under the presence of gravity are analytically calculated assuming that the orientation of the magnetic field changes in the equilibrium, i.e., there is magnetic shear. We solve the linearized magnetohydrodynamic equations in the incompressible regime. We find that the growth rate is bounded under the presence of magnetic shear. We have derived simple analytical expressions for the maximum growth rate, corresponding to the most unstable mode of the system. These expressions provide the explicit dependence of the growth rate on the various equilibrium parameters. For small angles the growth time is linearly proportional to the shear angle, and in this regime the single interface problem and the slab problem tend to the same result. On the contrary, in the limit of large angles and for the interface problem the growth time is essentially independent of the shear angle. In this regime we have also been able to calculate an approximate expression for the growth time for the slab configuration. Magnetic shear can have a strong effect on the growth rates of the instability. As an application of the results found in this paper we have indirectly determined the shear angle in solar prominence threads using their lifetimes and the estimation of the Alfvén speed of the structure.
Electromagnetic effects in the stabilization of turbulence by sheared flow
Cole, M. D. J.; Newton, S. L.; Cowley, S. C.; Loureiro, N. F.; Dickinson, D.; Roach, C.; Connor, J. W.
2014-01-01
We have extended our study of the competition between the drive and stabilization of plasma microinstabilities by sheared flow to include electromagnetic effects at low plasma ? (the ratio of plasma to magnetic pressure). The extended system of characteristic equations is formulated, for a dissipative fluid model developed from the gyrokinetic equation, using a twisting mode representation in sheared slab geometry and focusing on the ion temperature gradient mode. Perpendicular flow shear convects perturbations along the field at the speed we denote as Mcs (where cs is the sound speed). M \\gt 1/ \\sqrt{\\beta} is required to make the system characteristics unidirectional and inhibit eigenmode formation, leaving only transitory perturbations in the system. This typically represents a much larger flow shear than in the electrostatic case, which only needs M > 1. Numerical investigation of the region M \\lt 1/\\sqrt{\\beta} shows the driving terms can conflict, as in the electrostatic case, giving low growth rates over a range of parameters. Also, at modest drive strengths and low ? values typical of experiments, including electromagnetic effects does not significantly alter the growth rates. For stronger flow shear and higher ?, geometry characteristic of the spherical tokamak mitigates the effect of an instability of the shear Alfvén wave, driven by the parallel flow shear.
Tenderness charactherization of ostrich meat commercial cuts
Directory of Open Access Journals (Sweden)
Janaina Conte Hadlich
2012-12-01
Full Text Available The ostrich meat has become an interesting source of protein as well as being an alternative to red meat, because of its healthy fatty acid profile, with a high content of polyunsaturated fatty acids and low content of intramuscular fat, which arouses the interest of people who want a low animal fat diet. Ostrich meat is also appreciated by the tenderness, since it is one of the larger impact characteristics on the acceptance of a meat product for consumers. The aim of this study was to evaluate the tenderness of different ostrich meat commercial cuts and certificate that all studied cuts present tenderness acceptable by consumers. The laboratory tests were performed at the Laboratory of Biochemistry of Proteins (FMVZ, being measured shear force of seven commercial cuts of ostrich meat. The cuts were: internal thigh, external thigh, filet plan, filet out, filet small, rump and filet fan. The samples were boiled in water bath controlled by time and temperature. After chilling, fragments of 1.0 x 1.0 x 3.0 cm were removed from samples. Shear force measurements were performed using a mechanical Warner-Bratzler Shear Force equipment. The shear force means were: internal thigh (3.5 kg, external thigh (2.8 kg, filet plan (2.4 kg, filet out (1.6 kg, filet small (3.5 kg, rump (3.3 kg and filet fan (2.0 kg. All the commercial cuts evaluated had very low values of shear force, denoting meat extremely tender. The classification of meat tenderness is based on shear force values, being values below 4.6 kg considered meat with desirable tenderness. All ostrich meat commercial cuts analyzed had shear force values lower than 4.6 kg, being classified as meat of extreme tenderness. The results found in this work allow concluding that ostrich meat can be considered tender. These findings lead us to consider the ostrich meat as an interesting alternative to red meat, in relation to tenderness and healthy fatty acid profile, being favorable for people suffering from heart disease.
Stimulated bioluminescence by fluid shear stress associated with pipe flow
Energy Technology Data Exchange (ETDEWEB)
Cao Jing; Wang Jiangan; Wu Ronghua, E-mail: caojing981@126.com [Col. of Electronic Eng., Naval University of Engineering, Wuhan 430033 (China)
2011-01-01
Dinoflagellate can be stimulated bioluminescence by hydrodynamic agitation. Two typical dinoflagellate (Lingulodinium polyedrum and Pyrocystis noctiluca) was choosed to research stimulated bioluminescence. The bioluminescence intensity and shear stress intensity were measured using fully developed pipe flow. There is shear stress threshold to agitate organism bioluminescence. From these experiment, the response thresholds of the stimulated bioluminscence always occurred in laminar flows at a shear stress level of 0.6-3 dyn/cm{sup 2}. At the same time, the spectral characteristc of dinoflagellate was recorded, the wavelength of them is about 470nm, and the full width at half maximum is approximate 30nm.
Testing of Undrained Shear Strength in a Hollow Cylinder Apparatus
Directory of Open Access Journals (Sweden)
Wrzesi?ski Grzegorz
2015-06-01
Full Text Available The paper presents the results of tests performed in a Torsional Shear Hollow Cylinder Apparatus on undisturbed cohesive soils. The tests were performed on lightly overconsolidated clay (Cl and sandy silty clay (sasiCl. The main objective of the tests was to determine the undrained shear strength at different angles of rotation of the principal stress directions. The results of laboratory tests allow assessing the influence of rotation of the principal stress directions on the value of undrained shear strength that should be used during designing structure foundations
Profile control studies for JET optimised shear regime
Energy Technology Data Exchange (ETDEWEB)
Litaudon, X.; Becoulet, A.; Eriksson, L.G.; Fuchs, V.; Huysmans, G.; How, J.; Moreau, D.; Rochard, F.; Tresset, G.; Zwingmann, W. [Association Euratom-CEA, CEA/Cadarache, Dept. de Recherches sur la Fusion Controlee, DRFC, 13 - Saint-Paul-lez-Durance (France); Bayetti, P.; Joffrin, E.; Maget, P.; Mayorat, M.L.; Mazon, D.; Sarazin, Y. [JET Abingdon, Oxfordshire (United Kingdom); Voitsekhovitch, I. [Universite de Provence, LPIIM, Aix-Marseille 1, 13 (France)
2000-03-01
This report summarises the profile control studies, i.e. preparation and analysis of JET Optimised Shear plasmas, carried out during the year 1999 within the framework of the Task-Agreement (RF/CEA/02) between JET and the Association Euratom-CEA/Cadarache. We report on our participation in the preparation of the JET Optimised Shear experiments together with their comprehensive analyses and the modelling. Emphasis is put on the various aspects of pressure profile control (core and edge pressure) together with detailed studies of current profile control by non-inductive means, in the prospects of achieving steady, high performance, Optimised Shear plasmas. (authors)
Profile control studies for JET optimised shear regime
International Nuclear Information System (INIS)
This report summarises the profile control studies, i.e. preparation and analysis of JET Optimised Shear plasmas, carried out during the year 1999 within the framework of the Task-Agreement (RF/CEA/02) between JET and the Association Euratom-CEA/Cadarache. We report on our participation in the preparation of the JET Optimised Shear experiments together with their comprehensive analyses and the modelling. Emphasis is put on the various aspects of pressure profile control (core and edge pressure) together with detailed studies of current profile control by non-inductive means, in the prospects of achieving steady, high performance, Optimised Shear plasmas. (authors)
Fracture propagation in dissimilar steel welded joints at transverse shear
International Nuclear Information System (INIS)
Fracture propagation regularities in dissimilar steel fusion zone under conditions of transverse shear are considered. It is shown that resistance to fusion zone fracture and crack propagation kinetics at transverse shear depend considerably on a material embrittlement degree. At that in a lower tail area values of a static crack resistance parameter KIIc for the fusion zone coincide practically with values KIc for 15Kh2NMFA steel welded joints. It is established that phase-structural heterogeneity of fusion zone metal affects the fracture propagation process. Fracture origin according to the shear mechanism occurs in base metal in regions of silicate inclusion concentration
Thermonuclear instability of global-type shear Alfven modes
International Nuclear Information System (INIS)
The effects of thermonuclear alpha particles on the stability of global-type shear Alfven waves in toroidal geometry in an ignition tokamak experiment are described. The presence of finite toroidicity can lead to stabilization of the so-called global shear Alfven eigenmode. However, toroidicity induces a new global shear Alfven eigenmode, which can be strongly destabilized via transit resonance with alpha particles. In the proposed International Thermonuclear Experimental Reactor, due to its large size and low density, this latter mode is found to be benign. 17 refs., 10 figs
Shear waves in a ?uid saturated elastic plate
Indian Academy of Sciences (India)
A Pradhan; S K Samal; N C Mahanti
2002-12-01
In the present context, we consider the propagation of shear waves in the transverse isotropic ?uid saturated porous plate. The frequency spectrum for SH-modes in the plate has been studied. It is observed that the frequency of the propagation is damped due to the two-phase character of the porous medium. The dimensionless phase velocities of the shear waves have also been calculated and presented graphically. It is interesting to note that the frequency and phase velocity of shear waves in porous media differ signi?cantly in comparison to that in isotropic elastic media.
Integration through transients for Brownian particles under steady shear
Fuchs, M; Fuchs, Matthias; Cates, Michael E.
2005-01-01
Starting from the microscopic Smoluchowski equation for interacting Brownian particles under stationary shearing, exact expressions for shear-dependent steady-state averages, correlation and structure functions, and susceptibilities are obtained, which take the form of generalized Green-Kubo relations. They require integration of transient dynamics. Equations of motion with memory effects for transient density fluctuation functions are derived from the same microscopic starting point. We argue that the derived formal expressions provide useful starting points for approximations in order to describe the stationary non-equilibrium state of steadily sheared dense colloidal dispersions.
Piezoelectric shear wave resonator and method of making same
Wang, J.S.; Lakin, K.M.; Landin, A.R.
1985-05-20
An acoustic shear wave resonator comprising a piezoelectric film having its C-axis substantially inclined from the film normal such that the shear wave coupling coefficient significantly exceeds the longitudinal wave coupling coefficient, whereby the film is capable of shear wave resonance, and means for exciting said film to resonate. The film is prepared by deposition in a dc planar magnetron sputtering system to which a supplemental electric field is applied. The resonator structure may also include a semiconductor material having a positive temperature coefficient of resonance such that the resonator has a temperature coefficient of resonance approaching 0 ppM//sup 0/C.
Influence of microfluidic shear on keratin networks in living cells
Nolting, Jens-Friedrich; Köster, Sarah
2013-04-01
Intermediate filaments play a key role in cell mechanics, providing cells with compliance to small deformations and reinforcing them when large forces are applied. Here, we present a study of networks of keratin intermediate filaments in living cells under the influence of external forces. We expose the cells to controlled shear forces applied by microflow and investigate the response of the keratin network in situ. Our results show that bundle dynamics are reduced upon the application of shear flow. It is likely that cytoskeletal cross-talk is involved in this shear stress response via actin-keratin coupling.
Coherent structures in compressible free-shear-layer flows
Energy Technology Data Exchange (ETDEWEB)
Aeschliman, D.P.; Baty, R.S. [Sandia National Labs., Albuquerque, NM (United States). Engineering Sciences Center; Kennedy, C.A.; Chen, J.H. [Sandia National Labs., Livermore, CA (United States). Combustion and Physical Sciences Center
1997-08-01
Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.
Turbulent Fluctuations in TFTR Configurations with Reversed Magnetic Shear
International Nuclear Information System (INIS)
Turbulent fluctuations in plasmas with reversed magnetic shear have been investigated on the Tokamak Fusion Test Reactor. Under intense auxiliary heating, these plasmas are observed to bifurcate into two states with different transport properties. In the state with better confinement, it has been found that the level of fluctuations is very small throughout most of the region with negative shear. By contrast, the state with lower confinement is characterized by large bursts of fluctuations which suggest a competition between the driving and the suppression of turbulence. These results are consistent with the suppression of turbulence by the ExB velocity shear. copyright 1996 The American Physical Society
Turbulent Fluctuations in TFTR Configurations with Reversed Magnetic Shear
Energy Technology Data Exchange (ETDEWEB)
Mazzucato, E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Batha, S. H. [Fusion Physics and Technology, Torrance, California (United States); Beer, M. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bell, M. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bell, R. E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Budny, R. V. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bush, C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hahm, T. S. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Hammett, G. W. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Levinton, F M [Fusion Physics and Technology, Torrance, California (United States); Nazikian, R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Park, H. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Rewoldt, G. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Schmidt, G. L. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Synakowski, E. J. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Tang, W. M. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Taylor, G. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Zarnstorff, M. C. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
1996-10-01
Turbulent fluctuations in plasmas with reversed magnetic shear have been investigated on the Tokamak Fusion Test Reactor. Under intense auxiliary heating, these plasmas are observed to bifurcate into two states with different transport properties. In the state with better confinement, it has been found that the level of fluctuations is very small throughout most of the region with negative shear. By contrast, the state with lower confinement is characterized by large bursts of fluctuations which suggest a competition between the driving and the suppression of turbulence. These results are consistent with the suppression of turbulence by the E x B velocity shear.
Stimulated bioluminescence by fluid shear stress associated with pipe flow
International Nuclear Information System (INIS)
Dinoflagellate can be stimulated bioluminescence by hydrodynamic agitation. Two typical dinoflagellate (Lingulodinium polyedrum and Pyrocystis noctiluca) was choosed to research stimulated bioluminescence. The bioluminescence intensity and shear stress intensity were measured using fully developed pipe flow. There is shear stress threshold to agitate organism bioluminescence. From these experiment, the response thresholds of the stimulated bioluminscence always occurred in laminar flows at a shear stress level of 0.6-3 dyn/cm2. At the same time, the spectral characteristc of dinoflagellate was recorded, the wavelength of them is about 470nm, and the full width at half maximum is approximate 30nm.
Aggregates relaxation in a jamming colloidal suspension after shear cessation
Ianni, F; Sarcia, R; Hébraud, P
2005-01-01
The reversible aggregates formation in a shear thickening, concentrated colloidal suspension is investigated through speckle visibility spectroscopy, a dynamic light scattering technique recently introduced [P.K. Dixon and D.J. Durian, Phys. Rev. Lett. 90, 184302 (2003)]. Formation of particles aggregates is observed in the jamming regime, and their relaxation after shear cessation is monitored as a function of the applied shear stress. The aggregates relaxation time increases when a larger stress is applied. Several phenomena have been proposed to interpret this behavior: an increase of the aggregates size and volume fraction, or a closer packing of the particles in the aggregates.
Surface flow visualization with shear stress sensitivive liquid crystals
Pengel, K.
The use of non-capsulated liquid crystals, which react directly to wall shear forces, for surface flow visualization, is presented. The temperature sensitivity is avoided by producing a mixture with an event temperature (first red indication temperature) above the expected investigation temperature range. Below the event temperature the liquid crystals are only sensitive to shear stress, resulting in a wavelength variation of the reflected light. The analysis of video pictures from a low speed wind tunnel lead to information about the wall shear stress distribution on an Airbus wing, and in particular about the detection of the laminar to turbulent boundary layer transition.
The Palomares brittle—ductile Shear Zone of southern Spain
Weijermars, Ruud
The Palomares Shear Zone is a major Neogene-Quaternary strike—slip zone which transects the crust of the Betic Cordillera in SE Spain. The shear zone and the mechanisms that led to its formation are discussed and illustrated on the basis of detailed compilations of both the local and regional geology. It is emphasized that the formation of the Palomares Shear Zone was not an isolated tectonic event, but part of a complex Neogene tectonic history. The Neogene evolution of the Betic-Rif orogen and its central Alboran Basin is characterised by the following events: (1) emplacement of the Alboran Diapir with resulting nappe-shedding from the overlying crust between 25 and 20 Ma ago; (2) onset of the subsidence of the Alboran Basin between 20 and 15 Ma ago due to cooling of the Alboran Diapir and the overlying crust; (3) formation of the Cabo de Gata Volcanic Chain between 15 and 8 Ma ago; and (4) refolding of the nappe sheets in the Betic-Rif orogen into a basin and range structure about 7 Ma ago. Continuous activity of the Crevillente Fault of southern Spain may have occured over a period from 20 Ma ago up to the present. The interrelated Palomare Fault in SE Spain was probably formed between 15 and 8 Ma ago and seem to be active still. The Palomares Shear Zone affects a rock volume 44 km wide, at least 80 km long and 30 km deep. A shear strain—distance diagram constructed across the Palomares Shear Zone and its axial Palomares Fault involves a new method to estimate or constrain the shear strain magnitude along brittle-ductile shears. The typical tensor shear strain rates in the approximately 20 km thick ductilely deformed walls of the Palomares Fault are of the order 10 -13-10 -14 s -1. The tensor shear strain rate along the Palomares Fault itself is of the order 10 -12s -1 and the time averaged relative displacement rate of its walls is about 2 mm a -1. The range of strain rates within the Palomares Shear Zone are interpreted to be due to a combination of various flow-softening mechanisms: geometric, structural, thermal and strain-rate softening. These softening mechanisms might explain the difference in vertically averaged viscosities of 10 20 Pa s and 10 25 Pa s or lower suggested for the crustal rocks in the Palomares Fault proper and that of the relatively rigid boundaries of the Palomares Shear Zone, respectively.
Relationship between swelling and the shear modulus of irradiated metal
International Nuclear Information System (INIS)
In three alloy systems, AISI 316, the Ni-Al binary system, and the Fe-Cr-Ni ternary system, a relationship exists between the shear modulus of the unirradiated alloys and the resultant swelling observed. An alloying addition which reduces the shear modulus will subsequently reduce the irradiation-induced swelling in a solid solution hardened alloy system. The reduction in swelling is thought to be associated with the void nucleation phase of the swelling phenomenon. Thus, relative high temperature swelling behavior of the solid solution hardened alloys can be described with reasonable certainty from room temperature shear modulus measurement
Seismic behavior of semi-supported steel shear walls
DEFF Research Database (Denmark)
Jahanpour, A.; Jönsson, J.; Moharrami, H.
2012-01-01
During the recent past decade semi-supported steel shear walls (SSSW) have been introduced as an alternative to the traditional type of steel plate shear walls. In this system the shear wall does not connect directly to the main columns of the building frame; instead it is connected to a pair of secondary columns that do not carry vertical gravity loads. In this paper, the interaction between the wall plate and the surrounding frame is investigated experimentally for typical SSSW systems in whic...
Shear behaviors of single crystal nickel at different temperatures: molecular dynamics simulations
Li, Lili; Han, Ming
2015-06-01
Shear behaviors of a single crystal nickel along the [], [], [] and [] directions in the (111) crystallographic plane have been investigated at different temperatures by performing molecular dynamics simulations with an embedded atom method potential. Results show that shear stress-shear strain curves and atomic trajectory during shear process exhibit periodic behaviors, while the periods are varied for different shear directions. It sheds light on the inherent relationship between shear displacement for a period of the curve and the atomic configuration in corresponding crystallographic direction. Furthermore, shear modulus is extracted from the curves over a temperature range from 0 to 1700 K. It is demonstrated that the modulus is independent from the size of shear models and the shear directions, and that the modulus decreases with increasing temperature. In addition, this work also demonstrates that the classical description of shear modulus is still valid at the nanoscale, which might suggest a simple and direct way to obtain shear modulus at the atomic scale.
Song, Shaozhen; Joy, Joyce; Wang, Ruikang K.; Huang, Zhihong
2015-03-01
A quantitative measurement of the mechanical properties of biological tissue is a useful assessment of its physiologic conditions, which may aid medical diagnosis and treatment of, e.g., scleroderma and skin cancer. Traditional elastography techniques such as magnetic resonance elastography and ultrasound elastography have limited scope of application on skin due to insufficient spatial resolution. Recently, dynamic / transient elastography are attracting more applications with the advantage of non-destructive measurements, and revealing the absolute moduli values of tissue mechanical properties. Shear wave optical coherence elastography (SW-OCE) is a novel transient elastography method, which lays emphasis on the propagation of dynamic mechanical waves. In this study, high speed shear wave imaging technique was applied to a range of soft-embalmed mouse skin, where 3 kHz shear waves were launched with a piezoelectric actuator as an external excitation. The shear wave velocity was estimated from the shear wave images, and used to recover a shear modulus map in the same OCT imaging range. Results revealed significant difference in shear modulus and structure in compliance with gender, and images on fresh mouse skin are also compared. Thiel embalming technique is also proven to present the ability to furthest preserve the mechanical property of biological tissue. The experiment results suggest that SW-OCE is an effective technique for quantitative estimation of skin tissue biomechanical status.
The Lamella High Shear Rate REFLUX™ Classifier
Scientific Electronic Library Online (English)
T, Orupold; D, Starr; T, Kenefick.
2014-07-01
Full Text Available This paper covers the commercial development of gravity separation of fine particles using a Lamella High Shear Rate REFLUX™ Classifier (REFLUX™ Classifier), focusing primarily on coal applications. The REFLUX™ Classifier is a fluidized bed device that incorporates a system of closely spaced paralle [...] l inclined channels located above the fluidized bed. These channels make it possible to achieve a significant suppression of the effects of particle size, resulting in a highly effective separation on the basis of density. The improved gravity separation performance is shown to be remarkably high, with a significant reduction in the variation of separation density with particle size, and a significant reduction in the change in Ecart probable error (Ep) with size. The first full commercial-sized units of the REFLUX™ Classifier were field-tested in late 2009 in coal applications. More recently, the technology has been applied in fine particle separation in minerals applications and there are a number of full-sized units operating in chrome applications in South Africa. Initially, pilot-scaled units (typically the RC™300) were trialled in iron ore, mineral sands, and manganese plants amongst other minerals, typically after other technologies failed to achieve the desired results. Currently a number of laboratories globally are carrying out more testing in minerals applications. More than 50 RC™ units are now operating in coal and minerals applications. This paper introduces the REFLUX™ Classifier technology, identifies commercial applications, and gives some commercial results.
A New Annular Shear Piezoelectric Accelerometer
DEFF Research Database (Denmark)
Liu, Bin; Kriegbaum, B.
2000-01-01
This paper describes the construction and performance of a recently introduced Annular Shear piezoelectric accelerometer, Type 4511. The design has insulated and double-shielded case. The accelerometer housing is made of stainless steel, AISI 316L. Piezoceramic PZ23 is used. The seismic mass is made of tungsten. All processes and materials comply with MIL-STD-11268. The mounted resonance frequency exceeds 40kHz. The sensitivity is 10mV/g ±5%. During the design process, the new design is evaluated and sufficiently optimized by using the Finite Element (FE) simulation before making actual prototype. Reasonable agreement between the experimental results of the physical prototype and the simulation results is achieved. The design becomes more efficient. In addition, Type 4511 has a built in DeltaTronâ charge amplifier with ID and complies with IEEE-P1451.4 standard, which is a smart transducer interface for sensors including mixed-mode communication protocols and transducer electronic data sheet (TEDS).
On the persistence of adiabatic shear bands
Directory of Open Access Journals (Sweden)
Bassim M.N.
2012-08-01
Full Text Available It is generally agreed that the initiation and development of adiabatic shear bands (ASBs are manifestations of damage in metallic materials subjected to high strain rates and large strains as those due to impact in a Hopkinson Bar system. Models for evolution of these bands have been described in the literature. One question that has not received attention is how persistent these bands are and whether their presence and effect can be reversed or eliminated by using a process of thermal (heat treatment or thermo-mechanical treatment that would relieve the material from the high strain associated with ASBs and their role as precursors to crack initiation and subsequent failure. Since ASBs are more prevalent and more defined in BCC metals including steels, a study was conducted to investigate the best conditions of generating ASBs in a heat treatable steel, followed by determining the best conditions for heat treatment of specimens already damaged by the presence of ASBs in order to relieve the strains due to ASBs and restore the material to an apparent microstructure without the “scars” due to the previous presence of ASBs. It was found that heat treatment achieves the curing from ASBs. This presentation documents the process undertaken to achieve this objective.
Shear rheology of a cell monolayer
International Nuclear Information System (INIS)
We report a systematic investigation of the mechanical properties of fibroblast cells using a novel cell monolayer rheology (CMR) technique. The new technique provides quantitative rheological parameters averaged over ?106 cells making the experiments highly reproducible. Using this method, we are able to explore a broad range of cell responses not accessible using other present day techniques. We perform harmonic oscillation experiments and step shear or step stress experiments to reveal different viscoelastic regimes. The evolution of the live cells under externally imposed cyclic loading and unloading is also studied. Remarkably, the initially nonlinear response becomes linear at long timescales as well as at large amplitudes. Within the explored rates, nonlinear behaviour is only revealed by the effect of a nonzero average stress on the response to small, fast deformations. When the cell cytoskeletal crosslinks are made permanent using a fixing agent, the large amplitude linear response disappears and the cells exhibit a stress stiffening response instead. This result shows that the dynamic nature of the cross-links and/or filaments is responsible for the linear stress-strain response seen under large deformations. We rule out the involvement of myosin motors in this using the inhibitor drug blebbistatin. These experiments provide a broad framework for understanding the mechanical responses of the cortical actin cytoskeleton of fibroblasts to different imposed mechanical stimuli
Energy Technology Data Exchange (ETDEWEB)
Burrell, K.H.
1996-11-01
One of the scientific success stories of fusion research over the past decade is the development of the ExB shear stabilization model to explain the formation of transport barriers in magnetic confinement devices. This model was originally developed to explain the transport barrier formed at the plasma edge in tokamaks after the L (low) to H (high) transition. This concept has the universality needed to explain the edge transport barriers seen in limiter and divertor tokamaks, stellarators, and mirror machines. More recently, this model has been applied to explain the further confinement improvement from H (high)-mode to VH (very high)-mode seen in some tokamaks, where the edge transport barrier becomes wider. Most recently, this paradigm has been applied to the core transport barriers formed in plasmas with negative or low magnetic shear in the plasma core. These examples of confinement improvement are of considerable physical interest; it is not often that a system self-organizes to a higher energy state with reduced turbulence and transport when an additional source of free energy is applied to it. The transport decrease that is associated with ExB velocity shear effects also has significant practical consequences for fusion research. The fundamental physics involved in transport reduction is the effect of ExB shear on the growth, radial extent and phase correlation of turbulent eddies in the plasma. The same fundamental transport reduction process can be operational in various portions of the plasma because there are a number ways to change the radial electric field Er. An important theme in this area is the synergistic effect of ExB velocity shear and magnetic shear. Although the ExB velocity shear appears to have an effect on broader classes of microturbulence, magnetic shear can mitigate some potentially harmful effects of ExB velocity shear and facilitate turbulence stabilization.
Glavatskiy, Kirill S; Dalton, Benjamin A; Daivis, Peter J; Todd, B D
2015-06-01
We present theoretical expressions for the density, strain rate, and shear pressure profiles in strongly inhomogeneous fluids undergoing steady shear flow with periodic boundary conditions. The expressions that we obtain take the form of truncated functional expansions. In these functional expansions, the independent variables are the spatially sinusoidal longitudinal and transverse forces that we apply in nonequilibrium molecular-dynamics simulations. The longitudinal force produces strong density inhomogeneity, and the transverse force produces sinusoidal shear. The functional expansions define new material properties, the response functions, which characterize the system's nonlocal response to the longitudinal force and the transverse force. We find that the sinusoidal longitudinal force, which is mainly responsible for the generation of density inhomogeneity, also modulates the strain rate and shear pressure profiles. Likewise, we find that the sinusoidal transverse force, which is mainly responsible for the generation of sinusoidal shear flow, can also modify the density. These cross couplings between density inhomogeneity and shear flow are also characterized by nonlocal response functions. We conduct nonequilibrium molecular-dynamics simulations to calculate all of the response functions needed to describe the response of the system for weak shear flow in the presence of strong density inhomogeneity up to the third order in the functional expansion. The response functions are then substituted directly into the truncated functional expansions and used to predict the density, velocity, and shear pressure profiles. The results are compared to the directly evaluated profiles from molecular-dynamics simulations, and we find that the predicted profiles from the truncated functional expansions are in excellent agreement with the directly computed density, velocity, and shear pressure profiles. PMID:26172686
Palberg, Thomas; Biehi, Ralf
2003-01-01
We constructed an optical plate-plate shear cell suitable for the study of aqueous suspensions of charged colloidal spheres under low electrolyte concentrations (10(-6) M). The variable gap height was adjusted to 30 microm corresponding to 15-30 interparticle distances. The concentration of 300 microm diameter polystyrene spheres was chosen around 1 microm(-1) where previous studies had revealed the equilibrium structure to be fluid or body centred cubic. Under shear, layer structures of hexagonal symmetry form, often coexistent with a fluid phase. We used an adapted high resolution video microscope to perform a detailed study of the structure. The central ray of light was prevented from entering the objective and the images are constructed from higher order scattered light. The cover glass correction was adjusted in such a way that several layers of particles were visible simultaneously. The effective depth of sharpness was thus increased to several microm. From the 2D video frames we constructed time averaged 2D particle correlation diagrams (PCD) which correspond to the distribution functions for the projections of particle positions into the x y-plane. They allow us to discriminate different layers and to analyse their structure and their relative position. Layer structures showed approximately hexagonal symmetry bat with an elongation in the flow direction. They were always observed to be wall based. Melting in the z-direction occurred before in-plane melting and with a different mechanism. The resulting salt concentration-shear rate phase diagram is discussed in comparison with results from computer simulation. PMID:12638859
Order-disorder transitions in a sheared many body system
Pfeifer, Jens C; Ehlers, Georg; Eckhardt, Bruno
2015-01-01
Motivated by experiments on sheared suspensions that show a transition between ordered and disordered phases, we here study the long-time behavior of a sheared and overdamped 2-d system of particles interacting by repulsive forces. As a function of interaction strength and shear rate we find transitions between phases with vanishing and large single-particle diffusion. In the phases with vanishing single-particle diffusion, the system evolves towards regular lattices, usually on very slow time scales. Different lattices can be approached, depending on interaction strength and forcing amplitude. The disordered state appears in parameter regions where the regular lattices are unstable. Correlation functions between the particles reveal the formation of shear bands. In contrast to single particle densities, the spatially resolved two-particle correlation functions vary with time and allow to determine the phase within a period. As in the case of the suspensions, motion in the state with low diffusivity is essent...
Vibrational stability of graphene under combined shear and axial strains
Cocco, Giulio; Fiorentini, Vincenzo
2015-07-01
We study the vibrational properties of graphene under combined shear and uniaxial tensile strain using density-functional perturbation theory. Shear strain always causes rippling instabilities with strain-dependent direction and wavelength; armchair strain contrasts this instability, enabling graphene stability in a large range of combined strains. A complementary description based on membrane elasticity theory nicely clarifies the competition of shear-induced instability and uniaxial tension. We also report the large strain-induced shifts of the split components of the G optical phonon line, which may serve as a shear diagnostic. As to the electronic properties, we find that conical intersections move away from the Brillouin zone border under strain, and they tend to coalesce at large strains, making the opening of gaps difficult to assess. By a detailed search, we find that even at large strains, only small gaps in the tens-of-meV range open at the former Dirac points.
Measuring shear strength of soft-tissue adhesives.
Wang, Muzhou; Kornfield, Julia A
2012-04-01
A method for evaluating strength of adhesives for hydrogels and soft tissues is presented. Quantitative measurements of shear strength for applications in tissue engineering and biomedicine are performed in torsion using a rheometer. Small, disk shaped specimens of soft biological tissues and/or hydrogels (8 mm diameter, 1-2 mm thick) are mounted onto rheometer tools and then bonded together using the adhesive to be tested. The torsional loading geometry imposes simple shear without deforming the planar adhesive bond, in contrast to the lap-shear test. It retains the advantages of the napkin ring test while reducing artifacts due to cutting and handling soft specimens. The method is demonstrated by measuring the shear strength of two types of biomedical adhesives (cyanoacrylate and polyethylene glycol-based) between model hydrogels (gelatin) and tissues (corneal stroma and skin). PMID:22323271
Transient rheology of a polyethylene melt under shear
International Nuclear Information System (INIS)
Using nonequilibrium molecular dynamics simulation, we have studied the response of a C100 model polymer melt to a step change from equilibrium to a constant, high shear rate flow. The transient shear stress of the model polymer melt exhibits pronounced overshoot at the strain value predicted by the reptation model, in striking similarity to melts of longer, entangled polymer governed by reptation motion. At the maximum of shear stress overshoot, the molecular orientational order and the alignment angle are found to be midway between those characteristic of Newtonian flow and full alignment with the flow. The Doi-Edwards theory is found to be applicable but only by taking into account the shear-rate-dependence of the terminal relaxation time. We further analyze the molecular origins of such behavior in short polymer chains by decomposing the total stress into the contributions from various molecular interactions. (c) 1999 The American Physical Society
Production of functional proteins: balance of shear stress and gravity
Goodwin, Thomas John (Inventor); Hammond, Timothy Grant (Inventor); Kaysen, James Howard (Inventor)
2011-01-01
A method for the production of functional proteins including hormones by renal cells in a three dimensional culturing process responsive to shear stress uses a rotating wall vessel. Natural mixture of renal cells expresses the enzyme 1-.alpha.-hydroxylase which can be used to generate the active form of vitamin D: 1,25-diOH vitamin D.sub.3. The fibroblast cultures and co-culture of renal cortical cells express the gene for erythropoietin and secrete erythropoietin into the culture supernatant. Other shear stress response genes are also modulated by shear stress, such as toxin receptors megalin and cubulin (gp280). Also provided is a method of treating an in-need individual with the functional proteins produced in a three dimensional co-culture process responsive to shear stress using a rotating wall vessel.
Three-dimensional imaging of colloidal glasses under steady shear
Besseling, R; Schofield, A B; Poon, W C K; Weeks, Eric R.
2006-01-01
Using fast confocal microscopy we image the three-dimensional dynamics of particles in a colloidal glass under continuous, steady shear. The quiescent glass, with particles permanently caged by neighbors, shear-melts into an ergodic state in which successive plastic cage rearrangements lead to nearly isotropic diffusion at long times. For small shear rate $\\dot{\\gamma}$ the inverse structural relaxation time $\\tau_\\alpha^{-1}(\\dot{\\gamma})$ and diffusivity increase linearly with $\\dot{\\gamma}$ (`ideal' shear thinning), but for larger $\\dot{\\gamma}$ they increase only {\\it sub-linearly}, as predicted theoretically and seen in simulations of model glasses. Microscopically, the plastic rearrangements are heterogeneous for $t \\lesssim \\tau_{\\alpha}$ and appear cooperative in nature.
Finite element analyses for Seismic Shear Wall International Standard Problem
Energy Technology Data Exchange (ETDEWEB)
Park, Y.; Hofmayer, C. [Brookhaven National Lab., Upton, NY (United States); Chokshi, N. [Nuclear Regulatory Commission, Washington, DC (United States)
1997-04-01
In the seismic design of shear wall structures, e.g., nuclear reactor buildings, a linear FEM analysis is frequently used to quantify the stresses under the design loading condition. The final design decisions, however, are still based on empirical design rules established over decades from accumulated laboratory test data. This paper presents an overview of the state-of-the-art on the application of nonlinear FEM analysis to reinforced concrete (RC) shear wall structures under severe earthquake loadings based on the findings obtained during the Seismic Shear Wall International Standard Problem (SSWISP) Workshop in 1996. Also, BNL`s analysis results of the International Standard Problem (ISP) shear walls under monotonic static, cyclic static and dynamic loading conditions are described.
Transverse electron-scale instability in relativistic shear flows
Alves, E. P.; Grismayer, T.; Fonseca, R. A.; Silva, L. O.
2015-08-01
Electron-scale surface waves are shown to be unstable in the transverse plane of a sheared flow in an initially unmagnetized collisionless plasma, not captured by (magneto)hydrodynamics. It is found that these unstable modes have a higher growth rate than the closely related electron-scale Kelvin-Helmholtz instability in relativistic shears. Multidimensional particle-in-cell simulations verify the analytic results and further reveal the emergence of mushroomlike electron density structures in the nonlinear phase of the instability, similar to those observed in the Rayleigh Taylor instability despite the great disparity in scales and different underlying physics. This transverse electron-scale instability may play an important role in relativistic and supersonic sheared flow scenarios, which are stable at the (magneto)hydrodynamic level. Macroscopic (?c /?p e ) fields are shown to be generated by this microscopic shear instability, which are relevant for particle acceleration, radiation emission, and to seed magnetohydrodynamic processes at long time scales.
Fatigue detection by 2D folding shear interferometry with magnification
Sainov, Ventseslav C.; Shulev, Assen; Ossikovska, Sonja N.; Irving, Andrew D.
2003-05-01
Fatigue detection by two dimensional folding shear interferometry of subjected to cycling loading (pressure) composite vessel is presented. As the sensitivity of the applied method is higher in comparison with the other speckle-shear techniques, inspection of the small zone over the surface with magnification for the maximum permissible loading of the object is realized. The first step is measurement of a large surface area by lateral shear interferometry for selection of the zone with unusual mechanical response in loading, due to cracks, voids, impurities or other stress concentrators. At small lateral shear (1% over the object in our case) the obtained phase map modulus 2? coincides to derivatives of normal displacements. The moment hierarchy approach to time-series analysis is used for assessment of experimental results, as mechanical behavior of composite materials as a rule is non-linear and time depending. Further improvements of the techniques to application in fracture mechanics, lifetime and sudden (catastrophic) failures prediction are discussed.
Recovery of fluctuation spectrum evolution from tomographic shear spectra
Bonometto, Silvio A
2013-01-01
Forthcoming large angle surveys are planned to obtain high precision tomographic shear data. In principle, they will allow us to recover the spectra of matter density fluctuation, at various redshift, through the inversion of the expressions yielding shear from fluctuation spectra. This was discussed in previous work, where SVD techniques for matrix inversion were also shown to be the optimal tool to this aim. Here we show the significant improvements obtainable by using a 7 bin tomography, as allowed by future Euclid data, as well as the question of error propagation from shear to fluctuation spectra. We find that the technique is a promising tool, namely for the analysis of baryon physics throug high-l shear spectra and to test the consistency between expansion rate and fluctuation growth.
Interfacial stresses in strengthened beam with shear cohesive zone model
Indian Academy of Sciences (India)
Zergua Abdesselam
2015-02-01
The failure of strengthened beams with fibre-reinforced polymer (FRP) materials is due to high stress concentration of FRP–concrete interface. Understanding the cause and mechanism of the debonding of the FRP plate and the prediction of the stress distribution at the concrete–FRP interface are important for more effective strengthening technique. This paper presents an analytical solution, based on Smith and Teng’s equations, for interfacial shear and normal stresses in reinforced concrete (RC) beams strengthened with a fibre reinforced polymer (FRP) plate. However, the shear stress–strain relationship is considered to be bilinear curve. The effects of the shear deformations are calculated in an RC beam, an adhesive layer, and an FRP plate. The results of parametric study are compared with those of Smith and Teng. They confirm the accuracy of the proposed approach in predicting both interfacial shear and normal stresses.
Experimental investigation on shear fracture at high strain rates
Roth, Christian C.; Mohr, Dirk
2015-09-01
Adiabatic shear banding is a well-understood failure mechanism of metals at high strain rates. In addition, recent research on the ductile fracture of metals has demonstrated that shear localization at the microscale is also an important precursor of fracture initiation at low strain rates. This talk presents a new shear fracture specimen which is used to conduct fracture experiments on advanced high strength steel sheets at strain rates of up to 1/s in a hydraulic testing machine and for strain rates of up to 2500/s in a Split Hopkinson Bar system. The experimental result for a 22 MnB5 steel show a significant increase in ductility as a function of strain rate. Results from scanning electron microscopy are also shown to provide insight into the effect of the strain rate on the shear localization at the microscale.
Dissipation in quasistatically sheared wet and dry sand under confinement
Fiscina, J. E.; Pakpour, M.; Fall, A.; Vandewalle, N.; Wagner, C.; Bonn, D.
2012-08-01
We investigated the stress-strain behavior of sand with and without small amounts of liquid under steady and oscillatory shear. Since dry sand has a lower shear modulus, one would expect it to deform more easily. Using a new technique to quasistatically push the sand through a tube with an enforced parabolic (Poiseuille-like) profile, we minimize the effect of avalanches and shear localization. We observe that the resistance against deformation of the wet (partially saturated) sand is much smaller than that of the dry sand, and that the latter dissipates more energy under flow. This is also observed in large-amplitude oscillatory shear measurements using a rotational rheometer, showing that the effect is robust and holds for different types of flow.
Drift wave test particle transport in reversed shear profile
International Nuclear Information System (INIS)
Drift wave maps, area preserving maps that describe the motion of charged particles in drift waves, are derived. The maps allow the integration of particle orbits on the long time scale needed to describe transport. Calculations using the drift wave maps show that dramatic improvement in the particle confinement, in the presence of a given level and spectrum E x B turbulence, can occur for q(r)-profiles with reversed shear. A similar reduction in the transport, i.e., one that is independent of the turbulence, is observed in the presence of an equilibrium radial electric field with shear. The transport reduction, caused by the combined effects of radial electric field shear and both monotonic and reversed shear magnetic q-profiles, is also investigated
Signatures of granular microstructure in dense shear flows
Müth, D M; Karczmar, G S; Eng, P J; Nagel, S R; Jäger, H M; Müth, Daniel M.; Debregeas, Georges F.; Karczmar, Greg S.; Eng, Peter J.; Nagel, Sidney R.; Jaeger, Heinrich M.
2000-01-01
Granular materials react to shear stresses differently than do ordinary fluids. Rather than deforming uniformly, materials such as dry sand or cohesionless powders develop shear bands: narrow zones containing large relative particle motion leaving adjacent regions essentially rigid[1,2,3,4,5]. Since shear bands mark areas of flow, material failure and energy dissipation, they play a crucial role for many industrial, civil engineering and geophysical processes[6]. They also appear in related contexts, such as in lubricating fluids confined to ultra-thin molecular layers[7]. Detailed information on motion within a shear band in a three-dimensional geometry, including the degree of particle rotation and inter-particle slip, is lacking. Similarly, only little is known about how properties of the individual grains - their microstructure - affect movement in densely packed material[5]. Combining magnetic resonance imaging, x-ray tomography, and high-speed video particle tracking, we obtain the local steady-state pa...
Finite element analyses for Seismic Shear Wall International Standard Problem
International Nuclear Information System (INIS)
In the seismic design of shear wall structures, e.g., nuclear reactor buildings, a linear FEM analysis is frequently used to quantify the stresses under the design loading condition. The final design decisions, however, are still based on empirical design rules established over decades from accumulated laboratory test data. This paper presents an overview of the state-of-the-art on the application of nonlinear FEM analysis to reinforced concrete (RC) shear wall structures under severe earthquake loadings based on the findings obtained during the Seismic Shear Wall International Standard Problem (SSWISP) Workshop in 1996. Also, BNL's analysis results of the International Standard Problem (ISP) shear walls under monotonic static, cyclic static and dynamic loading conditions are described
Influence of Grain Size Coarse Soil on Shear Strength
Directory of Open Access Journals (Sweden)
Moulay smaîne Ghembaza
2014-04-01
Full Text Available The geo- mechanical behavior of coarse soils is difficult to grasp by geotechnical methods , mainly due to the presence of large elements that disrupt or prevent the tests . Our work presents a study of the mechanical behavior of two coarse soils of different types namely Tuff MEKKEDRA and crushed gravel SIDI ALI- Benyoub west of Algeria by observing the effect of the size of diameters of the grains on the shear strength. Two aspects are considered. The first relates to a state of the art parameters which have a direct influence on the shear strength of coarse material . The second part concerns a presentation and analysis of the results of direct shear tests of materials prepared for Optimum Proctor. It is noted that the grain size affects in a significant way the properties of the shear strength. The bigger the diameter, the greater the angle of friction is important. However, the cohesion decreases with increasing grain size.
Shear strength measurements at high temperatures and pressures
International Nuclear Information System (INIS)
A method for measuring the shear strength of materials at high pressures and temperatures up to 500degC is described. Two different experimental techniques are evaluated. The method is subsequently applied to pyrophyllite, boron nitride, and aluminium. (author)
Shearing Strength and Reliability of Recycled Concrete Beams
Bin Lei; Yusong Yan; Hui Wu
2013-01-01
The shearing behaviour of recycled concrete beams is studied here, by putting forward the formula for calculating shearing strength of recycled concrete beams and then assessing their reliability therefore. Based on the comparison between the experimental data by domestic and overseas researchers and the calculated results by formula from the code for design of concrete structures (GB 50010-2010) (CDCS), the applicability of the CDCS for the recycled concrete beams is validated statistically....
Harmonic morphisms, conformal foliations and shear-free ray congruences
Baird, P.; Wood, J. C.
1996-01-01
Equivalences between conformal foliations on Euclidean $3$-space, Hermitian structures on Euclidean $4$-space, shear-free ray congruences on Minkowski $4$-space, and holomorphic foliations on complex $4$-space are explained geometrically and twistorially; these are used to show that 1) any real-analytic complex-valued harmonic morphism without critical points defined on an open subset of Minkowski space is conformally equivalent to the direction vector field of a shear-free ...
Shear Instabilities in Granular Flows down on Inclined Plane
Dou, Hua-Shu; Khoo, Boo Cheong; Phan-Thien, Nhan
2005-01-01
Instabilities at interface of two stream granular flows have been reported in recent experiment [1] that breaking waves can form at the interface between two streams of identical grains flowing on an inclined plane downstream of a splitter plate. In this report, the theory of hydrodynamic instability is used to analyze the shear flow of granular materials. It is shown that the shear instability in two-stream granular flows actually comes from the competition between the ener...
Aging and effective delays in colloidal glasses under shear
Viasnoff, Virgile; Lequeux, Francois
2003-01-01
In this paper we analyze the changes in the microscopic dynamics of a colloidal glass submitted to an oscillatory shear. We use Multispeckle diffusing Wave Spectroscopy to monitor the transient dynamical regimes following a shear application. We show that the system displays a spontaneous aging that is amplified by a low amplitude oscillation (overaging) but stopped by a high amplitude one (rejuvenation). Intermediate amplitudes drive the system into a dynamical state that c...
The rheology and processing of “edge sheared” colloidal polymer opals
Energy Technology Data Exchange (ETDEWEB)
Wong, Hon Sum; Mackley, Malcolm, E-mail: mrm5@cam.ac.uk; Butler, Simon [Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge CB2 3RA (United Kingdom); Baumberg, Jeremy; Snoswell, David; Finlayson, Chris; Zhao, Qibin [Cavendish Laboratory, NanoPhotonics Centre, University of Cambridge, Cambridge CB3 OHE (United Kingdom)
2014-03-15
This paper is concerned with the rheology and processing of solvent-free core shell “polymer opals” that consist of a soft outer shell grafted to hard colloidal polymer core particles. Strong iridescent colors can be produced by shearing the material in a certain way that causes the initially disordered spheres to rearrange into ordered crystalline structures and produce colors by diffraction and interference of multiple light scattering, similar to gemstone opals. The basic linear viscoelastic rheology of a polymer opal sample was determined as a function of temperature, and the material was found to be highly viscoelastic at all tested temperatures. A Cambridge multipass rheometer was specifically modified in order to make controlled mechanical measurements of initially disordered polymer opal tapes that were sandwiched between protective polyethylene terephthalate sheets. Axial extension, simple shear, and a novel “edge shearing” geometry were all evaluated, and multiple successive experiments of the edge shearing test were carried out at different temperatures. The optical development of colloidal ordering, measured as optical opalescence, was quantified by spectroscopy using visible backscattered light. The development of opalescence was found to be sensitive to the geometry of deformation and a number of process variables suggesting a complex interaction of parameters that caused the opalescence. In order to identify aspects of the deformation mechanism of the edge shearing experiment, a separate series of in situ optical experiments were carried out and this helped indicate the extent of simple shear generated with each edge shear deformation. The results show that strong ordering can be induced by successive edge shearing deformation. The results are relevant to polymer opal rheology, processing, and mechanisms relating to ordering within complex viscoelastic fluids.
Schematic models for dynamic yielding of sheared colloidal glasses
Fuchs, Matthias; Cates, Michael E.
2003-01-01
The nonlinear rheological properties of dense suspensions are discussed within simplified models, suggested by a recent first principles approach to the model of Brownian particles in a constant-velocity-gradient solvent flow. Shear thinning of colloidal fluids and dynamical yielding of colloidal glasses arise from a competition between a slowing down of structural relaxation, because of particle interactions, and enhanced decorrelation of fluctuations, caused by the shear a...
Midbroken Reinforced Concrete Shear Frames Due to Earthquakes
DEFF Research Database (Denmark)
Köylüoglu, H. U.; Cakmak, A. S.; Nielsen, Søren R. K.
1996-01-01
A non-linear hysteretic model for the response and local damage analyses of reinforced concrete shear frames subject to earthquake excitation is proposed, and, the model is applied to analyse midbroken reinforced concrete (RC) structures due to earthquake loads. Each storey of the shear frame is represented by a Clough and Johnston hysteretic oscillator with degrading elastic fraction of the restoring force. The local damage is numerically quantified in the domain [0,1] using the maximum softeni...
Shear Capacity of Steel and Polymer Fibre Reinforced Concrete Beams
DEFF Research Database (Denmark)
Kragh-Poulsen, Jens C.; Hoang, Cao Linh; Goltermann, Per
2011-01-01
This paper deals with the application of a plasticity model for shear strength estimation of fibre reinforced concrete beams without stirrups. When using plastic theory to shear problems in structural concrete, the so-called effective strengths are introduced, usually determined by calibrating the plastic solutions with tests. This approach is, however, problematic when dealing with fibre reinforced concrete (FRC), as the effective strengths depend also on the type and the amount of fibres. In t...
Yielding shear panel device for passive energy dissipation
Chan, RWK; Albermani, F; Williams, MS
2007-01-01
This paper summarizes a series of experimental investigations of a yielding shear panel device (YSPD) developed as a passive energy device for seismic protection of frame structures. Belonging to the family of metallic dampers, the device is to be incorporated into K-braced moment-resisting frames. It consists of a short length square hollow section (SHS) with a diaphragm plate welded inside it. Under moderate earthquake loading, the device deforms plastically under applied shear forces, whil...
Conditions for Shear Band Formation in Tungsten Alloys
H. Couque; Eches, N.
1997-01-01
Local loading conditions associated with shear banding formation in laboratory tungsten alloy specimens are examined. The specimens consist of compression specimens of large length to diameter ratio made of 91W-6Ni-3Co swaged tungsten alloys tested with the Hopkinson pressure bar and symmetric Taylor techniques. Experimental and numerical results provide insights on the effect of the hydrostatic pressure on shear band formation in tungsten alloys.
The rheology and processing of “edge sheared” colloidal polymer opals
International Nuclear Information System (INIS)
This paper is concerned with the rheology and processing of solvent-free core shell “polymer opals” that consist of a soft outer shell grafted to hard colloidal polymer core particles. Strong iridescent colors can be produced by shearing the material in a certain way that causes the initially disordered spheres to rearrange into ordered crystalline structures and produce colors by diffraction and interference of multiple light scattering, similar to gemstone opals. The basic linear viscoelastic rheology of a polymer opal sample was determined as a function of temperature, and the material was found to be highly viscoelastic at all tested temperatures. A Cambridge multipass rheometer was specifically modified in order to make controlled mechanical measurements of initially disordered polymer opal tapes that were sandwiched between protective polyethylene terephthalate sheets. Axial extension, simple shear, and a novel “edge shearing” geometry were all evaluated, and multiple successive experiments of the edge shearing test were carried out at different temperatures. The optical development of colloidal ordering, measured as optical opalescence, was quantified by spectroscopy using visible backscattered light. The development of opalescence was found to be sensitive to the geometry of deformation and a number of process variables suggesting a complex interaction of parameters that caused the opalescence. In order to identify aspects of the deformation mechanism of the edge shearing experiment, a separate series of in situ optical experiments were carried out and this helped indicate the extent of simple shear generated with each edge shear deformation. The results show that strong ordering can be induced by successive edge shearing deformation. The results are relevant to polymer opal rheology, processing, and mechanisms relating to ordering within complex viscoelastic fluids
Shear-induced platelet aggregation in aspirin-treated patients
DEFF Research Database (Denmark)
Würtz, Morten; Hvas, Anne-Mette; Wulff, Lise Nielsen; Kristensen, Steen D; Grove, Erik L
2012-01-01
Whole blood platelet function testing is widely used to evaluate the effect of antiplatelet agents. Most platelet function tests employ agonists to evaluate drug-specific platelet-activating pathways. Shear-based tests may better reflect physiological conditions in vivo compared with agonist-based tests. The novel PlaCor PRT provides a global platelet reactivity test based on shear-induced platelet aggregation. We evaluated the PlaCor PRT and its agreement with two widely used platelet function ...
Mechanical Behavior of Knitted Fabrics under Bending and Shear Deformation
UÇAR, Mehmet
2003-01-01
It is very important to understand the mechanical response of fabrics under deformation since their aesthetic properties and performance are directly related to their mechanical properties, such as tensile, bending and shear. During use, fabric is always stressed by these kinds of deformations. Fabric properties such as drape, handle, and bagging are also affected by the bending and shear characteristics of the fabric. Thus, this study was carried out to gain a better understanding ...
Shockwave determination of the shear velocity at very high pressures.
Anderson, O. L.
1972-01-01
Description of a proposed shockwave experiment that may provide some understanding on the behavior of planet core materials in the presence of high temperatures and pressures. Shockwave experimentation is shown to offer promise of revealing some information on shear velocity behavior at high pressures, and its relevance to properties of planet interiors consists in that abrupt changes in shear velocities at boundary layers could be experimentally confirmed where abrupt changes in density are suspected from seismic interpretation.
Coupling of sound and internal waves in shear flows
International Nuclear Information System (INIS)
Gravity waves in the parallel shear flow of a continuously stratified compressible fluid are considered. It is demonstrated that the shear induces a coupling between the sound waves and the internal gravity waves. The conditions for the effectiveness of the coupling are defined and a corresponding linear mechanism of wave transformation and energy transfer between the modes is described. It is also shown that, under suitable conditions, beat waves can be generated. (author). 28 refs, 5 figs
A Model of Barchan Dunes Including Lateral Shear Stress
Schwaemmle, V.; Herrmann, H
2003-01-01
Barchan dunes are found where sand availability is low and wind direction quite constant. The two dimensional shear stress of the wind field and the sand movement by saltation and avalanches over a barchan dune are simulated. The resulting final shape is compared to the results of a model with a one dimensional shear stress. A characteristic edge at the center of the windward side is discovered which is also observed for big barchans. Diffusion effects reduce this effect for...
Phenomenological model for ordered onions under shear flow
Odagiri, Kenta; Kudo, Kazue
2010-01-01
We propose a phenomenological model for the multi-lamellar vesicles (onions) formation induced by shear flow. In a nonionic surfactant (C$_{12}$E$_4$) system, onion phases under a fixed shear flow within a certain range show the order-disorder transition accompanied with a size jump by changing temperature. Our model can simulate ordered and disordered onion phases with different onion sizes. We show numerical results of the onion formation simulated by the model and also di...
The performance of soil reinforcement in bending and shear
Pedley, Martin John; Milligan, G. W. E.
1990-01-01
Previous experimental studies of soil-reinforcement interaction have generally concentrated on the effect of reinforcement working in axial tension; this study looks at reinforcement working in bending and shear. The experimental programme was carried out in a large scale direct shear apparatus able to contain a cubic soil sample of side 1m. A previous study showed that the apparatus required improvements to its boundaries. Modifications to the apparatus resulted in a significant improvem...
On Howard's Conjecture in Heterogeneous Shear Flow Problem
Indian Academy of Sciences (India)
R G Shandil; Jagjit Singh
2003-11-01
Howard's conjecture, which states that in the linear instability problem of inviscid heterogeneous parallel shear flow growth rate of an arbitrary unstable wave must approach zero as the wave length decreases to zero, is established in a mathematically rigorous fashion for plane parallel heterogeneous shear flows with negligible buoyancy force $g\\beta \\ll 1$ (Miles J W, J. Fluid Mech. 10 (1961) 496–508), where is the basic heterogeneity distribution function).
Experimental investigation of reinforced concrete slabs with punching shear reinforcement
Lips, Stefan; Muttoni, Aurelio
2010-01-01
Over the past century, the use of flat slabs in buildings and especially in parking garages has been growing as it is an economic and efficient solution. Flat slabs are easy to build and have, through their smaller depth, an economical and architectural advantage compared to slabs on girders. Because of their limited depth, flat slabs are especially sensitive to deflections and to punching shear, which are their main design criteria. Furthermore, flat slabs without punching shear reinforcemen...
Parametric excitation of drift wave in a sheared slab geometry
International Nuclear Information System (INIS)
The threshold for parametric excitation of drift waves in a sheared slab geometry is calculated for a drift-wave pump which has a standing wave structure along the magnetic field, and the coupling is achieved by the Hasegawa-Mima vector product-type nonlinearity. The usual shear damping is counteracted by the parametric interaction and the eigenvalue problem is solved analytically using Taylor's strong coupling approximation. (11 refs.)
Shear thinning and thixotropy of HMHEC and HEC water solutions
Maestro Garriga, Alicia; González García, Ma. Concepción; Gutiérrez González, José María, 1953-
2002-01-01
Steady state viscosity and thixotropy of hydrophobically modified hydroxyethyl cellulose HMHEC and nonassociative cellulose water solutions are studied. Although all the samples are shear thinning, only the HMHEC is thixotropic, since the migration of hydrophobes to micelles is controlled by diffusion. The Cross model fits steady state curves. The Mewis model, a phenomenological model that proposes that the rate of change of viscosity when the shear rate is suddenly changed is related to the ...
Quantifying shear-induced wave transformations in the solar wind
Gogoberidze, Grigol; Rogava, Andria; Poedts, Stefaan
2007-01-01
The possibility of velocity shear-induced linear transformations of different magnetohydrodynamic waves in the solar wind is studied both analytically and numerically. A quantitative analysis of the wave transformation processes for all possible plasma-$\\beta$ regimes is performed. By applying the obtained criteria for effective wave coupling to the solar wind parameters, we show that velocity shear-induced linear transformations of Alfv\\'en waves into magneto-acoustic waves...
Seismic behavior of lightly reinforced concrete squat shear walls
Greifenhagen, Christian
2006-01-01
This thesis addresses the seismic evaluation of existing buildings. In particular, it focuses on the seismic behavior of lightly reinforced shear walls that are not designed to withstand earthquake actions. A shear strength envelope for the assessment of deformation capacity of these non-ductile walls is presented. The approach is the result of experimental investigations and analytical modeling. Existing models for plastic hinges in beams are enhanced in order to determine drift capacity of ...
Aspect ratio dependence in magnetorotational instability shearing box simulations
Bodo, G.; Mignone, A.; Cattaneo, F.; Rossi, P.; Ferrari, A.
2008-01-01
Aims: We study the changes in the properties of turbulence driven by the magnetorotational instability in a shearing box, as the computational domain size in the radial direction is varied relative to the height Methods: We perform 3D simulations in the shearing box approximation, with a net magnetic flux, and we consider computational domains with different aspect ratios Results: We find that in boxes of aspect ratio unity the transport of angular momentum is strongly inter...
Aspect ratio dependence in magnetorotational instability shearing box simulations
FERRARI, Attilio; Mignone, Andrea
2008-01-01
Aims. We study the changes in the properties of turbulence driven by the magnetorotational instability in a shearing box, as the computational domain size in the radial direction is varied relative to the height. Methods: We perform 3D simulations in the shearing box approximation, with a net magnetic flux, and we consider computational domains with different aspect ratios. Results: We find that in boxes of aspect ratio unity the transport of angular momentum is strongly intermittent and domi...
Thermonuclear Fusion with the Sheared Flow Stabilized Z-Pinch
Winterberg, F.; Wanex, L. F.
2008-01-01
Two basic approaches to producing thermonuclear fusion with a sheared flow stabilized z-pinch are considered. One consists of heating the entire length of the z-pinch column to the required temperatures. The other basic approach considered here involves the concept of fast ignition. A localized "hot-spot" is produced under the proper conditions to ignite a thermonuclear burn wave in the z-pinch plasma. Here we demonstrate that sheared flow stabilization is more efficient in ...
On shear flow stabilization concepts for the dense z pinch
Winterberg, F.
2009-01-01
Different ways to achieve the stabilization of a linear z-pinch by a superimposed shear flow are analyzed. They are: 1) Axial shear flow proposed by Arber and Howell with the pinch discharge in its center, and experimentally tested by Shumlak et al. 2) Spiral flow of a dense low temperature plasma surrounding a dense pinch discharge. 3) A thin metallic projectile shot at a high velocity through the center of the pinch discharge. 4) The replacement of the high velocity projec...
Simple shear behaviour of palm biodiesel contaminated soil
Chew S. J.; Lee, C. Y.
2010-01-01
Palm biodiesel contaminations may bring adverse effect on basic geotechnical properties of foundation soils. This paper presents the results of an experimental study on shear behaviour of palm biodiesel contaminated sandy soil. A comprehensive set of laboratory experiments have been undertaken in a direct simple shear device on samples of palm biodiesel contaminated sandy soil. In the experiments the soil samples were prepared by mixing the sandy soil with B20 palm biodiesel ranging from 0% t...
Correlation of Shear to Compression for Progressive Fracture Obliquity
Lowenberg, David W.; Nork, Sean; Abruzzo, Frederick M.
2008-01-01
The accompanying shear force at the point of bone opposition is an important factor inherent to tibial fracture stability during axial loading. We determined at which angle of fracture obliquity shearing becomes a dominant force after stabilization with circular external fixation, and how modifications to the external fixator can reduce this effect. We constructed tibial fracture models with a successively increasing fracture angle obliquely (from 0° to 60°) to determine the stability in the ...
Observation of neoclassical transport in reverse shear plasmas on TFTR
Efthimion, P. C.; Von Goeler, S.; Houlberg, W. A.; Synakowski, E. J.; Zarnstorff, M. C.; Batha, S. H.; Bell, R. E.; Bitter, M.; Bush, C. E.; Levinton, F. M.; Mazzucato, E.; McCune, D. C.; Mueller, D.; Park, H. K.; Ramsey, A. T.; Roquemore, A. L.; Taylor, G.
1999-11-01
Perturbative experiments on TFTR have investigated the transport of multiple ion species in reverse shear (RS) plasmas. The profile evolutions of trace tritium and helium and intrinsic carbon indicate the formation of core particle transport barriers in enhanced reverse shear (ERS) plasmas. There is an order of magnitude reduction in the particle diffusivity inside the RS region. The diffusivities for these species in ERS plasmas agree with neoclassical theory.
Reflection and Exclusion of Shear Zones in Inhomogeneous Granular Materials
Borzsonyi, Tamas; Unger, Tamas; Szabo, Balazs; Wegner, Sandra; Angenstein, Frank; Stannarius, Ralf
2011-01-01
Shear localization in granular materials is studied experimentally and numerically. The system consists of two material layers with different effective frictions. The presence of the material interface leads to a special type of "total internal reflection" of the shear zone. In a wide range of configurations the reflection is characterized by a fixed angle which is analogous to the critical angle of refraction in optics. The zone leaves and reenters the high friction region ...
Waves in geomaterials with negative Cosserat shear modulus
Dyskin, Arcady; Pasternak, Elena
2015-04-01
Materials with negative moduli cannot exist on its own as they break the positive definiteness of the elastic energy making such materials unstable. They can however be statically stable as a part of an encompassing system that is stiff enough to stabilise the negative stiffness material. There indeed exist mechanisms that produce reversible descending branch giving rise to negative elastic stiffness (modulus). One such mechanism is rotation of non-spherical grains under shear stress in the presence of high compressive load. This mechanism creates an effect of negative Cosserat shear modulus that relates the non-symmetric part of the shear stress with the rotation. While the negative shear modulus makes the potential energy non-positive, there still exists a range of values of this negative modulus at which the wave propagation is possible. All four types of travelling waves known in isotropic Cosserat continuum (p-wave, two shear waves and a twist wave) exist. Furthermore, while in the conventional isotropic Cosserat continuum the twist wave and one of the shear waves exist only at high frequencies, higher than a certain threshold frequency, the presence of formally negative Cosserat shear modulus removes this threshold and makes all four waves exist in all frequencies. In general, negative values of the Cosserat shear modulus break isotropy making the corresponding Cosserat continuum orthotropic. This means that the properties of the travelling waves depend on the direction of travel. We investigate this dependence analyse the method to used the directional observations (measurements) of these waves can provide a method of detecting the presence of the negative modulus.
Feedback Control of Turbulent Shear Flows by Genetic Programming
Duriez, Thomas; Parezanovi?, Vladimir; von Krbek, Kai; Bonnet, Jean-Paul; Cordier, Laurent; Noack, Bernd R.; Segond, Marc; Abel, Markus; Gautier, Nicolas; Aider, Jean-Luc; Raibaudo, Cedric; Cuvier, Christophe; Stanislas, Michel; Debien, Antoine; Mazellier, Nicolas
2015-01-01
Turbulent shear flows have triggered fundamental research in nonlinear dynamics, like transition scenarios, pattern formation and dynamical modeling. In particular, the control of nonlinear dynamics is subject of research since decades. In this publication, actuated turbulent shear flows serve as test-bed for a nonlinear feedback control strategy which can optimize an arbitrary cost function in an automatic self-learning manner. This is facilitated by genetic programming pro...
Structural studies of lamellar surfactant systems under shear
DEFF Research Database (Denmark)
Mortensen, K.
2001-01-01
Recent experimental studies on concentrated surfactant systems are reviewed. Particular attention is focused on the transformation from planar lamellar sheets to multilamellar vesicles. It is discussed whether both of these states are thermodynamic stable, or if the MLV is an artifact of shear induced factors. Recent studies includes the dependence on shear, and dependence on salt and cosurfactants, and thereby related lamellar defects. The review include moreover the demonstration that polymeri...
An experimental investigation for external RC shear wall applications
Directory of Open Access Journals (Sweden)
M. Y. Kaltakci
2010-09-01
Full Text Available The strength and rigidity of most reinforced concrete (RC buildings in Turkey, which are frequently hit by destructive earthquakes, is not at a sufficient level. Therefore, the result of earthquakes is a significant loss of life and property. The strengthening method most commonly preferred for these type of RC buildings is the application of RC infilled walls (shear walls in the frame openings of the building. However, since the whole building has to be emptied and additional heavy costs arise during this type of strengthening, users prefer not to strengthen their buildings despite the heavy risk they are exposed to. Therefore, it is necessary to develop easier-to-apply and more effective methods for the rapid strengthening of housing and the heavily-used public buildings which cannot be emptied during the strengthening process (such as hospitals and schools. This study empirically analyses the different methods of a new system which can meet this need. In this new system, named "external shear wall application", RC shear walls are applied on the external surface of the building, along the frame plane rather than in the building. To this end, 7 test samples in 1/2 and 1/3 geometrical scale were designed to analyse the efficiency of the strengthening technique where the shear wall leans on the frame from outside of the building (external shear wall application and of the strengthening technique where a specific space is left between the frame and the external shear wall by using a coupling beam to connect elements (application of external shear wall with coupling beam. Test results showed that the maximum lateral load capacity, initial rigidity and energy dissipation behaviours of the samples strengthened with external shear wall were much better than those of the bare frames.
Dynamic light scattering at low rates of shear
Ackerson, B. J.; Clark, N. A.
1981-01-01
Dynamic light scattering as a probe of fluctuations for systems undergoing steady linear shear is examined. Several approximations are made to calculate the intensity correlation function for a dense system of independent particles or fluctuations at low rates of shear. In this limit the intensity correlation function is similar in structure to the equilibrium intensity correlation function ; however, the signal to background factor becomes correlation time dependent. The result is tested exp...
Study of the behavior of GFRP – RC beams under shear
Directory of Open Access Journals (Sweden)
Mettu Bhaskara Rao 1 , P.J. Rao2 , M.V.S. Rao3 , K.J. Rao
2013-07-01
Full Text Available The present paper reviews the study of Glass Fiber Reinforced Polymer (GFRP flats under shear in reinforced concrete beams. Many failures in concrete structures in particular bridges are due to corrosion of reinforcement, particularly in aggressive environments. This has prompted researcher’s world over to look for an alternative non corrosive and non metallic reinforcement for strengthening the reinforced concrete structures both in flexure and shear.
Shear strengthening of reinforced concrete beams with CFRP
Bukhari, IA; Vollum, RL; Ahmad, S.; Sagaseta, J
2010-01-01
The current paper reviews existing design guidelines for strengthening beams in shear with carbon fibre reinforced polymer (CFRP) sheets and proposes a modification to Concrete Society Technical Report TR55. It goes on to present the results of an experimental programme which evaluated the contribution of CFRP sheets towards the shear strength of continuous reinforced concrete (RC) beams. A total of seven, two-span concrete continuous beams with rectangular cross-sections were tested. The con...
Study of the behavior of GFRP – RC beams under shear
Mettu Bhaskara Rao 1 , P.J. Rao2 , M.V.S. Rao3 , K.J. Rao
2013-01-01
The present paper reviews the study of Glass Fiber Reinforced Polymer (GFRP) flats under shear in reinforced concrete beams. Many failures in concrete structures in particular bridges are due to corrosion of reinforcement, particularly in aggressive environments. This has prompted researcher’s world over to look for an alternative non corrosive and non metallic reinforcement for strengthening the reinforced concrete structures both in flexure and shear.
Shear zones between rock units with no relative movement
DEFF Research Database (Denmark)
Koyi, H.; Schmeling, H.; Burchardt, S.; Talbot, C.J.; Mukherkjee, S.; Sjöström, H.; Chemia, Zurab
2012-01-01
Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such zones, which we call wakes in this study, form due to the movement of exotic blocks within a viscous medium (denser blocks sinking within a salt structure, boudin tracks), melt in a partially molten surr...
Shear zones between rock units with no relative movement
DEFF Research Database (Denmark)
Koyi, Hemin; Schmeling, Harro; Burchardt, Steffi; Talbot, Christoffer; Mukherjee, Soumyajit; Sjöström, Håkan; Chemia, Zurab
2013-01-01
Shear zones are normally viewed as relatively narrow deformation zones that accommodate relative displacement between two "blocks" that have moved past each other in opposite directions. This study reports localized zones of shear between adjacent blocks that have not moved past each other. Such deformation zones, which we call wakes, form due to the movement of exotic blocks within a viscous medium (denser blocks sinking within a salt structure, (the paths) between separated boudins), melt in p...
Interfacial shear stress measurement using high spatial resolution multiphase PIV
André, Matthieu A.; Bardet, Philippe M.
2015-06-01
In multiphase flows, form drag and viscous shear stress transfer momentum between phases. For numerous environmental and man-made flows, it is of primary importance to predict this transfer at a liquid-gas interface. In its general expression, interfacial shear stress involves local velocity gradients as well as surface velocity, curvature, and surface tension gradients. It is therefore a challenging quantity to measure experimentally or compute numerically. In fact, no experimental work to date has been able to directly resolve all the terms contributing to the shear stress in the case of curved and moving surfaces. In an attempt to fully resolve the interface shear stress when surface tension gradients are negligible, high-resolution particle image velocimetry (PIV) data are acquired simultaneously on both sides of a water-air interface. The flow consists of a well-conditioned uniform and homogeneous water jet discharging in quiescent air, which exhibits two-dimensional surface waves as a result of a shear layer instability below the surface. PIV provides velocity fields in both phases, while planar laser-induced fluorescence is used to track the interface and obtain its curvature. To compute the interfacial shear stress from the data, several processing schemes are proposed and compared, using liquid and/or gas phase data. Vorticity at the surface, which relates to the shear stress through the dynamic boundary condition at the surface, is also computed and provides additional strategies for estimating the shear. The various schemes are in agreement within the experimental uncertainties, validating the methodology for experimentally resolving this demanding quantity.
Effect of shear patterns and EPS on fouling in microfiltration
Pongpairoj, Pharima; Field, R. W.; Cui, Zhanfeng
2013-01-01
Concentration polarisation and fouling reduce performance as well as increase costs. In order to mitigate these effects, understanding the cause and effects of these phenomena is crucial. It has been hypothesized, and to a certain extent shown, that amelioration of fouling can be achieved through the use of time varying shear for example use of air-sparging or sharp changes in crossflow velocity. Nevertheless the effect of shear on membrane fouling, in particular its effect on the foulant dep...
Dynamics of Vesicle Suspensions in Shear Flow Between Walls
Podgorski, Thomas; Natacha, Callens; Christophe, Minetti; Coupier, Gwennou; Frank, Dubois; Misbah, Chaouqi
2011-01-01
The behaviour of a vesicle suspension in a simple shear flow between plates (Couette flow) was investigated experimentally in parabolic flight and sounding rocket experiments by Digital Holographic Microscopy. The lift force which pushes deformable vesicles away from walls was quantitatively investigated and is found to be rather well described by a theoretical model by Olla (J Phys II (France) 7:1533, 1997). At longer shearing times, vesicles reach a steady distrib- ution about the center pl...
Boundary shear stress distribution and flow structures in trapezoidal channels
Ansari, Kamran
2011-01-01
The commercially available Computational Fluid Dynamics (CFD) software ANSYS-CFX version 11 (2008) is employed to predict the distribution of the bed and sidewall shear stresses in trapezoidal open channels. The investigation includes computation of wall shear stress (1) directly, using CFD for a range of channels layouts (straight, turning, with ridges), and (2), building on the division line concept initially formulated by Leighly in 1932 and later by Einstein in 1942, through the evaluatio...
Investigation of sheared liquids by neutron backscattering and reflectivity
Wolff, M; Hock, R; Frick, B; Zabel, H
2002-01-01
We have investigated by neutron scattering structural and dynamical properties of water solutions of the triblock copolymer P85 under shear. To this end a shear cell that suits the requirements for neutron backscattering and another for reflectivity experiments have been built. In reflectivity measurements we find the polymer concentration (nominal concentration of 33% by weight) to vary right at the surface between 12% and 52% for hydrophilic or hydrophobic coated silicon wavers, for temperatures between 18 C and 73 C and for shear rates up to 2500 s sup - sup 1. Additional structural changes deeper in the bulk are also observed. On the backscattering instrument (IN10 at ILL) we find that the liquid appears to stick to the plates of the shear cell, implying an unusual macroscopic velocity distribution that differs from that found earlier for lubrication oils. We report further on changes of the quasielastic line width in the direction of the shear gradient for different temperatures and shear rates. (orig.)
Traction Forces of Endothelial Cells under Slow Shear Flow.
Perrault, Cecile M; Brugues, Agusti; Bazellieres, Elsa; Ricco, Pierre; Lacroix, Damien; Trepat, Xavier
2015-10-20
Endothelial cells are constantly exposed to fluid shear stresses that regulate vascular morphogenesis, homeostasis, and disease. The mechanical responses of endothelial cells to relatively high shear flow such as that characteristic of arterial circulation has been extensively studied. Much less is known about the responses of endothelial cells to slow shear flow such as that characteristic of venous circulation, early angiogenesis, atherosclerosis, intracranial aneurysm, or interstitial flow. Here we used a novel, to our knowledge, microfluidic technique to measure traction forces exerted by confluent vascular endothelial cell monolayers under slow shear flow. We found that cells respond to flow with rapid and pronounced increases in traction forces and cell-cell stresses. These responses are reversible in time and do not involve reorientation of the cell body. Traction maps reveal that local cell responses to slow shear flow are highly heterogeneous in magnitude and sign. Our findings unveil a low-flow regime in which endothelial cell mechanics is acutely responsive to shear stress. PMID:26488643
Shear-induced structure in polymer-clay nanocomposite solutions.
Lin-Gibson, S; Kim, H; Schmidt, G; Han, C C; Hobbie, E K
2004-06-15
The equilibrium structure and shear response of model polymer-clay nanocomposite gels are measured using X-ray scattering, light scattering, optical microscopy, and rheometry. The suspensions form physical gels via the "bridging" of neighboring colloidal clay platelets by the polymer, with reversible adsorption of polymer segments onto the clay surface providing a short-range attractive force. As the flow disrupts this transient network, coupling between composition and stress leads to the formation of a macroscopic domain pattern, while the clay platelets orient with their surface normal parallel to the direction of vorticity. We discuss the shear-induced structure, steady-shear rheology, and oscillatory-shear response of these dynamic networks, and we offer a physical explanation for the mesoscale shear response. In contrast to flow-induced "banding" transitions, no stress plateau is observed in the region where macroscopic phase separation occurs. The observed platelet orientation is different from that reported for polymer-melt clay nanocomposites, which we attribute to effects associated with macroscopic phase separation under shear flow. PMID:15144824
Measurements and scaling of wall shear stress fluctuations
Colella, K. J.; Keith, W. L.
2003-02-01
Measurements of velocity and wall shear stress fluctuations were made in an external turbulent boundary layer developed over a towed surface-piercing flat plate. An array of eight flush-mounted wall shear stress sensors was used to compute the space-time correlation function. A methodology for in situ calibration of the sensors for ship hydrodynamic applications is presented. The intensity of the wall shear stress fluctuations, ? rms/ ? avg was measured as 0.25 and 0.36 for R ? =3,150 and 2,160 respectively. The probability density is shown to exhibit positive skewness, and lack of flow reversals at the wall. Correlations between velocity and wall shear stress fluctuations are shown to collapse with outer boundary layer length and velocity scales, verifying the existence of large-scale coherent structures which convect and decay along the wall at an angle of inclination varying from 10 to 13° over the range of Reynolds numbers investigated. The wall shear stress convection velocity determined from narrow band correlation measurements is shown to scale with outer variables. The space-time correlation of the wall shear is shown to exhibit a well-defined convective ridge, and to decay 80% over approximately 3? for R ? =3,150.
E. coli in a wall bounded shear flow
Molaei, Mehdi; Sheng, Jian
2012-11-01
Understanding bacteria motility over a wall in a shear flow is critical to determine those crucial biophysical processes involved in the biofilm formation and the shear erosion. Using digital holographic microscopy combined with microfluidics we capture three-dimensional swimming patterns of wild-type E. coli bacteria in a straight micro-channel subjecting to a carefully controlled flow shear. Three-dimensional locations and orientations of bacterial are extracted with a resolution of 0.185 ?m in lateral directions and 0.5 ?m in the wall normal direction. Robust statistics based on thousands of trajectories allow us to characterize bacteria swimming over a surface under flow shear. These characteristics, including swimming velocity, tumbling frequencies, cellular attachment, and suspension dispersion, will be used to elucidate the cell wall interactions in shear flows. Current analysis will focus on the hydrodynamic mechanisms other than near field interfacial forces on cell migration and orientation near a sheared surface. Preliminary data on bacteria over a chemically modified surface will also be presented. National Institution of Health.
Three-dimensional brittle shear fracturing by tensile crack interaction.
Healy, David; Jones, Richard R; Holdsworth, Robert E
2006-01-01
Faults in brittle rock are shear fractures formed through the interaction and coalescence of many tensile microcracks. The geometry of these microcracks and their surrounding elastic stress fields control the orientation of the final shear fracture surfaces. The classic Coulomb-Mohr failure criterion predicts the development of two conjugate (bimodal) shear planes that are inclined at an acute angle to the axis of maximum compressive stress. This criterion, however, is incapable of explaining the three-dimensional polymodal fault patterns that are widely observed in rocks. Here we show that the elastic stress around tensile microcracks in three dimensions promotes a mutual interaction that produces brittle shear planes oriented obliquely to the remote principal stresses, and can therefore account for observed polymodal fault patterns. Our microcrack interaction model is based on the three-dimensional solution of Eshelby, unlike previous models that employed two-dimensional approximations. Our model predicts that shear fractures formed by the coalescence of interacting mode I cracks will be inclined at a maximum of 26 degrees to the axes of remote maximum and intermediate compression. An improved understanding of brittle shear failure in three dimensions has important implications for earthquake seismology and rock-mass stability, as well as fluid migration in fractured rocks. PMID:16397496
Shear layer characteristics of supersonic free and impinging jets
Davis, T. B.; Kumar, R.
2015-09-01
The initial shear layer characteristics of a jet play an important role in the initiation and development of instabilities and hence radiated noise. Particle image velocimetry has been utilized to study the initial shear layer development of supersonic free and impinging jets. Microjet control employed to reduce flow unsteadiness and jet noise appears to affect the development of the shear layer, particularly near the nozzle exit. Velocity field measurements near the nozzle exit show that the initially thin, uncontrolled shear layer develops at a constant rate while microjet control is characterized by a rapid nonlinear thickening that asymptotes downstream. The shear layer linear growth rate with microjet control, in both the free and the impinging jet, is diminished. In addition, the thickened shear layer with control leads to a reduction in azimuthal vorticity for both free and impinging jets. Linear stability theory is used to compute unstable growth rates and convection velocities of the resultant velocity profiles. The results show that while the convection velocity is largely unaffected, the unstable growth rates are significantly reduced over all frequencies with microjet injection. For the case of the impinging jet, microjet control leads to near elimination of the impingement tones and an appreciable reduction in broadband levels. Similarly, for the free jet, significant reduction in overall sound pressure levels in the peak radiation direction is observed.
Effect of Particle Size on Shear Stress of Magnetorheological Fluids
Directory of Open Access Journals (Sweden)
Chiranjit Sarkar
2015-05-01
Full Text Available Magnetorheological fluids (MRF, known for their variable shear stress contain magnetisable micrometer-sized particles (few micrometer to 200 micrometers in a nonmagnetic carrier liquid. To avoid settling of particles, smaller sized (3-10 micrometers particles are preferred, while larger sized particles can be used in MR brakes, MR clutches, etc. as mechanical stirring action in those mechanisms does not allow particles to settle down. Ideally larger sized particles provide higher shear stress compared to smaller sized particles. However there is need to explore the effect of particle sizes on the shear stress. In the current paper, a comparison of different particle sizes on MR effect has been presented. Particle size distributions of iron particles were measured using HORIBA Laser Scattering Particle Size Distribution Analyser. The particle size distribution, mean sizes and standard deviations have been presented. The nature of particle shapes has been observed using scanning electron microscopy. To explore the effect of particle sizes, nine MR fluids containing small, large and mixed sized carbonyl iron particles have been synthesized. Three concentrations (9%, 18% and 36% by volume for each size of particles have been used. The shear stresses of those MRF samples have been measured using ANTON PAAR MCR-102 Rheometer. With increase in volume fraction of iron particles, the MR fluids synthesized using “mixed sized particles” show better shear stress compared to the MR fluids containing “smaller sized spherical shaped particles” and “larger sized flaked shaped particles” at higher shear rate.