Lorenzen, C L; Calkins, C R; Green, M D; Miller, R K; Morgan, J B; Wasser, B E
2010-08-01
The ability to perform Warner-Bratzler and slice shear force on the same beef top loin steak was investigated. Three, 2.54-cm steaks from top loins (n=99) were allotted to either Warner-Bratzler only (WBS), slice shear force only (SSF), or Warner-Bratzler and slice shear force (WBS/SSF). Steaks were thawed at 2 degrees C for 48h prior to cooking. Steaks were cooked to 71 degrees C using a conveyor convection oven and allowed to cool at room temperature for a minimum of 4h. Steaks allotted to WBS used six 1.27-cm cores and steaks allotted for WBS/SSF used four cores. Steaks allotted to SSF and WBS/SSF used one, 1 cm x 5 cm slice. Correlations among WBS and SSF for all steaks ranged from 0.49 to 0.69 (P<0.0001). When correlations were generated for steak location within the top loin, the relationships among WBS and SSF performed in the same steak ranged from 0.53 to 0.70 (P<0.05). These results indicate that it may be feasible to conduct WBS and SSF on the same top loin steak, and that the steak taken 2.54 cm from the 13th rib is the optimal location for this combination of procedures. PMID:20416791
Pork tenderness estimation by taste panel, Warner-Bratzler shear force and on-line methods.
Van Oeckel, M J; Warnants, N; Boucqué, C V
1999-12-01
The extent to which modification of Warner-Bratzler shear force (WBSF) determinations, relating to storage and preparation of the meat, aperture of the V-shaped cutting blade and shearing velocity, improve the relationship with sensory tenderness perception of pork was studied. Additionally four on-line methods: pH1, FOP1 (light scattering), PQM1 (conductivity) and DDLT (Double Density Light Transmission), were evaluated for their ability to predict tenderness. Sensory tenderness evaluation was conducted on 120 frozen (at -18°C for several months) samples of m. longissimus thoracis et lumborum. After overnight thawing, the meat was grilled to an internal temperature of 74°C and scored on an eight-point scale, from extremely tough to extremely tender. The standard WBSF procedure (protocol A) consisted of heating fresh meat samples (stored for 48 h at 4°C post slaughter) at 75°C for 50 min, cooling in cold tap water for 40 min, taking cylindrical cores parallel to the fibre direction, and shearing at a velocity of 200 mm/min with a blade aperture of 60°. For the prediction of sensory tenderness, the WBSF standard procedure (protocol A) showed the lowest variance (R(2)=15%) and the highest standard error of the estimate (SEE=0.97 N) compared to the other WBSF protocols. A decrease in shearing velocity, from 200 to 100 mm/min and, a replacement of the cutting blade with an aperture of 60° by one with an aperture of 30° led to improvements of R(2) (respectively, 19% vs. 13% and 47% vs. 23%) and SEE (respectively, 0.93 N vs. 0.97 N and 0.80 N vs. 0.97 N) and thus were better predictors of tenderness. A blade aperture of 30° instead of 60° also led to considerably lower WBSF values (22.1 N vs. 30.0 N). Freezing, frozen storage and thawing of the meat, prior to WBSF measurement, resulted in higher shear force values (32.7 N vs. 28.7 N) and a better prediction of tenderness, R(2) (25% vs. 15%) and SEE (0.94 N vs. 1.00 N). Furthermore, preparing the frozen stored meat for WBSF determination in the same way as for the sensory evaluation, namely grilling instead of boiling, led to higher WBSF values (35.5 N vs. 32.7 N) and a further improvement in the prediction of tenderness (R(2)=31% vs. 25% and SEE=0.90 N vs. 0.94 N). From the on-line instruments: pH, FOP and PQM, pH was best in predicting tenderness. Linear regression with tenderness as dependent variable and the on-line techniques as independent variables revealed the following R(2): 16, 8, 8 and 10% and SEE: 0.96, 1.01, 1.01 and 1.00 N for, respectively, pH1, FOP1, PQM1 and DDLT. Thus, the classical instruments and the DDLT technique, which is analogous to the CGM (Capteur Gras/Maigre), an officially accepted carcass grading apparatus in France and Belgium, are not good predictors of tenderness. PMID:22063468
Yancey, E J; Dikeman, M E; Addist, P B; Katsanidis, E; Pullen, M
2002-07-01
Three groups of 12 high percentage Charolais steers were slaughtered on three dates. Steers (n = 27) were infused immediately after exsanguination at 10% of BW with a solution containing saccharides, NaCl, and phosphates (MPSC solution; MPSC, Inc., St. Paul, MN) plus either 500 ppm vitamin C (MPSC+C), 500 ppm vitamin E (MPSC+E), or 500 ppm vitamin C plus 500 ppm vitamin E (MPSC+C+E). Noninfused controls (CON) were 9 steers. The longissimus thoracis (LT), semitendinosus (ST), and quadriceps femoris muscles were removed at 48-h postmortem, vacuum-packaged, and aged until 14-d postmortem. Steaks 2.54-cm thick were cut from the LT and ST. The quadriceps was utilized for ground-beef production. Infused steers had higher dressing percentages and heavier heart and liver weights (P infusion with vitamins C, E, or C plus E had no effect (P > 0.05) on USDA yield and quality-grade traits, LT and ST Warner-Bratzler shear force, descriptive-attribute traits, and freshly cooked steak flavor-profile traits. Vascular infusion had little effect on the flavor-profile traits of warmed-over steaks. Therefore, the results of our study indicate that vascular infusion with vitamins C, E, or C plus E can increase dressing percentage and organ weights, but have minimal effects on descriptive-attribute and flavor-profile sensory panel ratings. PMID:12162658
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 padronizao da textura um dos principais problemas relacionados qualidade da carne bovina. Por isso, a avaliao objetiva da maciez, por mtodos mecnicos, vem sendo estudada h muitos anos. Para que a avaliao instrumental da textura seja uma ferramenta efetiva nos estudos envolvendo a maciez da carne, necessrio minimizar as causas de variao envolvidas na anlise. Atualmente, a fora de cisalhamento Warner-Bratzler o mtodo mais amplamente empregado para essa finalidade. O protocolo padro dessa tcnica analtica preconiza a utilizao de uma lmina de cisalhamento de 1,016mm de espessura. Neste trabalho, foram comparados dados de textura de carne bovina obtidos com a lmina de cisalhamento padro Warner-Bratzler, de 1,016mm de espessura, e uma lmina mais grossa, de 3,05mm de espessura. Aps o abate, amostras de msculo Longissimus dorsi, semelhantes em relao aos teores de umidade, lipdeos e protenas, foram submetidas a duas diferentes temperaturas de resfriamento, atingindo diferentes velocidades de queda de temperatura e, consequentemente, diferentes graus de contrao do tecido muscular, o que foi confirmado pela determinao do comprimento dos sarcmeros. Os resultados demonstraram uma maior sensibilidade da lmina padro Warner-Bratzler na deteco de variaes da textura da carne, em funo 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...
Assessment of three devices used in shear tests of cooked breast meat.
Lyon, B G; Lyon, C E
1998-10-01
Methods that increase processing efficiency to save energy costs and to improve yield and volume must be evaluated in terms of maintaining or improving final product quality. Shear tests measure the force to cut through fibers of cooked samples. They are the simplest and most common tests used to document cooked meat texture. However, information obtained from shearing devices that perform in a similar way may not be interchangeable. In this study, three shearing devices were assessed. Eight treatments were imposed on broiler breasts processed under commercial conditions to represent ranges of texture characteristics. Treatments included electrical stimulation (S), or no stimulation (NS) of carcasses; postchill deboning at 2 or 6 h; and marination (M), or no marination (NM). Shear force values of cooked breasts were obtained from the benchtop Warner-Bratzler (BT-WB) machine, the Warner-Bratzler blade attachment (TA-WB) and a 45 degrees chisel-end blade attachment (TA-WD). The TA-WB and TA-WD were attached to Model TA.XT2 texture analyzer. For each device, shear value differences were significant (P < 0.05) for deboning time. Marination effects were significant (P < 0.05) for BT-WB and TA-WB. Stimulation by debone interactions were significant (P < 0.05) for BT-WB and TA-WD. The TA-WD values varied the greatest over all treatments (SD = 5.52; SE = 0.65). Variations of BT-WB and TA-WB shear values were similar (SD = 3.25, 2.97, respectively; SE = 0.38, 0.35). PMID:9776069
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...
Scientific Electronic Library Online (English)
C., Gomes; L.B., Karam; R.E.F., Macedo.
2013-04-01
Full Text Available Avaliaram-se as caractersticas sensoriais e determinou-se a fora de cisalhamento de cortes de carne de paca (Agouti paca). As anlises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por coco at a temperatura interna de 70C. A avaliao de aspecto, co [...] r, sabor, odor e maciez foi realizada pela aplicao de teste afetivo a 146 provadores, utilizando-se escala hednica, e a fora de cisalhamento foi determinada pela tcnica Warner Bratzler. Na avaliao sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferena significativa (p0,05) entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante carne suna e com boa aceitao pelos consumidores. O estudo evidenciou o potencial da paca como uma espcie silvestre para a produo comercial de carne para o mercado de carnes vermelhas ou exticas. 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 70C. 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 caractersticas sensoriais e determinou-se a fora de cisalhamento de cortes de carne de paca (Agouti paca. As anlises foram realizadas nos cortes desossados de paleta, lombo e pernil de nove pacas, preparados por coco at a temperatura interna de 70C. A avaliao de aspecto, cor, sabor, odor e maciez foi realizada pela aplicao de teste afetivo a 146 provadores, utilizando-se escala hednica, e a fora de cisalhamento foi determinada pela tcnica Warner Bratzler. Na avaliao sensorial, os cortes de paleta, lombo e pernil de paca mostraram diferena significativa (p0,05 entre os cortes, que se mostraram igualmente macios. A carne de paca apresentou-se sensorialmente semelhante carne suna e com boa aceitao pelos consumidores. O estudo evidenciou o potencial da paca como uma espcie silvestre para a produo comercial de carne para o mercado de carnes vermelhas ou exticas.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 70C. 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.
High-angular Resolution Laser Threat Warner
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Sushil Kumar
2007-07-01
Full Text Available In this paper, the design and development aspects of a high-angular resolution laser-threat Warner developed at the Laser Science & Technology Centre (LASTEC, Delhi are presented. It describes a high-angular resolution laser-threat warner capable of giving warning with a resolution of i 3" when it is exposed to laser radiation from visible and near-IR pulsed solid-state laser source. It has a field of view of 90' in the azimuth direction, whereas the elevation coverage is between -5" and + 25". It is capable of handling multiple types of laser threats covering wavelength from 400 nm to 1100 nm and has an operational range of 4 km for a Q-switched laser source energy (10 ns of 10 mJ/pulse and output beam divergence of 1 mrad. The paper also describes its simulated evaluation process and field-testing which it has undergone. The result of field-testing confirms that it meets all its performance specifications mentioned above.
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 mghead(-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
Morfologa de Neochetina eichhorniae (Warner (Coleoptera: Curculionidae
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Oscar Martnez-Morales
2014-01-01
Full Text Available En este trabajo se describen e ilustran caractersticas morfolgicas de Neochetina eichhorniae (Warner, 1970. Esta especie se ha utilizado para el control biolgico del lirio acutico (Eichhornia crassipes (Mart. Solms-Laubach, 1883. En el huevo, el aspecto cambiante del corion es dado por el desarrollo embrionario. En la larva se realiz una descripcin de la quetotaxia de la cpsula ceflica y se identificaron tres nstares larvales con la medicin de su anchura; tambin se revis la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en trax y abdomen, tambin se observaron dos tipos de espirculos; el ms caracterstico es el espirculo abdominal por su posicin dorsal, que adems de ser esclerosado, posee rganos sensoriales en su pice. La morfologa externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Adems se proporciona una descripcin de las alas, proventrculo y genitalia, estructuras importantes en la taxonoma. Las caractersticas morfolgicas de N. eichhorniae encontradas en ste trabajo pueden ser tiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926, la cual ha sido liberada en muchos pases. Es el primer trabajo de morfologa N. eichhorniae en Mxico.
2012-06-12
... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Employment and Training Administration Pfizer Therapeutic Research, Formerly Known as Warner Lambert Company... known as Warner Lambert Company, Pfizer Worldwide Research & Development Division,...
Scientific Electronic Library Online (English)
Oscar, Martnez-Morales; Edith G., Estrada-Venegas; Armando, Equihua-Martnez; Jorge, Valdez-Carrasco.
Full Text Available En este trabajo se describen e ilustran caractersticas morfolgicas de Neochetina eichhorniae (Warner, 1970). Esta especie se ha utilizado para el control biolgico del lirio acutico (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 realiz una descripcin de la quetotaxia de la cpsula ceflica y se identificaron tres nstares larvales con la medicin de su anchura; tambin se revis la microescultura del cuerpo de la larva, sobresaliendo unas microespinas, cuyo arreglo es diferente en trax y abdomen, tambin se observaron dos tipos de espirculos; el ms caracterstico es el espirculo abdominal por su posicin dorsal, que adems de ser esclerosado, posee rganos sensoriales en su pice. La morfologa externa de los adultos de N. eichorniae es muy parecida en ambos sexos; su principal diferencia se encuentra en el rostrum. Adems se proporciona una descripcin de las alas, proventrculo y genitalia, estructuras importantes en la taxonoma. Las caractersticas morfolgicas de N. eichhorniae encontradas en ste trabajo pueden ser tiles para diferenciar a esta especie de Neochetina bruchi (Hustache, 1926), la cual ha sido liberada en muchos pases. Es el primer trabajo de morfologa N. eichhorniae en Mxico. 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.
Community Connections. Time Warner Community Responsibility Report, 1998-2000.
Owens, Jane; Stein, Carol
This report highlights efforts by Time Warner personnel to strengthen community connections through various programs and services aimed at supporting: education, the arts, volunteerism, diversity, and business-community action. The report is divided into sections focusing on each of these areas. The first section, Education, describes programs
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
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.
Walter Warner (ca.1557-1643) and his notes on Animal Organisms
Prins, Johannes Lambertus Maria
1992-01-01
As opposed to most of his contemporaries, Thomas Hobbes (1588-1679) assumed that all phenomena could be explained in terms of matter in motion. All the more intriguing is his suggestion that what he wrote came out of his own head. Yet, already during his lifetime he was accused of having taken his natural philosophy from the mathematician and natural philosopher Walter Warner (ca. 1557-1643). Warners posthumous notes were said to suggest that he worked on the development of a ...
Time Warner veab aktsionäriga vägikaigast / Peeter Teder
Teder, Peeter
2005-01-01
Meediafirma Time Warner juhid tõrjuvad aktsionär Carl Icahni süüdistusi firma juhtkonna tegevusetuses ja halvas majandamises. Diagramm: Time Warneri aktsia. Vt. samas: Kes on miljardär Carl Icahn
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.
PRINCIPAL COMPONENT REGRESSION OF NEAR-INFRARED REFLECTANCE SPECTRA FOR BEEF TENDERNESS PREDICTION
Tenderness is the most important factor affecting consumer perception of eating quality of meat. In this paper, the development of the principal component regression (PCR) models to relate near-infrared (NIR) reflectance spectra of raw meat to Warner-Bratzler (WB) shear force measurement of cooked m...
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...
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
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...
Directory of Open Access Journals (Sweden)
Thomas Bonnici
2003-06-01
Full Text Available Durante os ltimos quarenta anos, investigou-se e discutiu-se o aspecto ps-colonial da pea A tempestade, de Shakespeare. O romance Indigo, de Marina Warner, publicado em 1992, a reescrita da pea, na qual os papis femininos so realados e analisados numa narrativa mltipla que compreende a invaso de uma ilha caribenha no sculo XVII e a fortuna dos descendentes desses invasores no sculo XX. Enquanto a ideologia dos colonizadores ingleses se baseava na construo de imprio, as duas personagens femininas, Scorax e Serafine, se esforam na construo de comunidades. Nessa verso feminina de A tempestade, Warner apresenta uma alternativa para suplantar o patriarcalismo e fundar princpios bsicos para uma sociedade mais douradora e mais igualitriaDuring the last four decades the postcoloniality in Shakespeares The Tempest has been investigated and discussed. Marina Warners novel Indigo, published in 1992, is a reworking of the play in which feminine roles are enhanced and analysed in a multiple narrative comprehending the 17th century invasion of a Caribbean island and the fortune of the invaders descendents in the 20th century. In contrast to the English colonizers stance of empire building, the two female characters of the novel, Sycorax and Serafine, endeavour to build communities. In this feminine version of The Tempest, Warner shows an alternative way to replace patriarchy and establish the basic tenets of a more-enduring and equalitarian society
International Nuclear Information System (INIS)
A shear machine for irradiated nuclear fuel elements has a replaceable shear assembly comprising a fuel element support block, a shear blade support and a clamp assembly which hold the fuel element to be sheared in contact with the support block. A first clamp member contacts the fuel element remote from the shear blade and a second clamp member contacts the fuel element adjacent the shear blade and is advanced towards the support block during shearing to compensate for any compression of the fuel element caused by the shear blade (U.K.)
Physical and sensory characterization and consumer preference of corn and barley-fed beef.
Wismer, W V; Okine, E K; Stein, A; Seibel, M R; Goonewardene, L A
2008-11-01
Steaks from corn-fed and barley-fed beef were characterized by a trained panel, which rated corn-fed beef higher (p0.05) for either type of finished beef. Japanese consumers showed a preference (p0.05) were observed for Warner-Bratzler shear, marbling scores, cooking losses or Hunter colorimeter values. There was a trend for higher concentrations (p0.10) in mono or polyunsaturated fatty acids. PMID:22063608
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...
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.
Application of exogenous enzymes to beef muscle of high and low-connective tissue.
Sullivan, G A; Calkins, C R
2010-08-01
Exogenous enzymes tenderize meat through proteolysis. Triceps brachii and Supraspinatus were randomly assigned to the seven enzyme treatments, papain, ficin, bromelain, homogenized fresh ginger, Bacillus subtilis protease, and two Aspergillus oryzae proteases or control to determine the extent of tenderization (Warner-Bratzler shear and sensory evaluation) and mode of action (myofibrillar or collagen degradation). Sensory evaluation showed improvement (Pficin for water soluble (P=0.0002) and A. oryzae concentrate for salt soluble proteins (P=0.0148). All enzyme treatments can increase tenderness via myofibrillar and collagenous protein degradation with no difference among high and low-connective tissue muscles. PMID:20416788
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.
Bainy, Eduarda Molardi; Bertan, Larissa Canhadas; Corazza, Marcos Lucio; Lenzi, Marcelo Kaminski
2015-08-01
The influence of two common cooking methods, grilling and baking, on chemical composition, water retention, fat retention, cooking yield, diameter reduction, expressible water, color and mechanical texture of tilapia (Oreochromis niloticus) fish burgers was investigated. Texture analyses were performed using a Warner-Bratzler test. The fish burger had a softer texture with a lower shear force than other meat products reported in the literature. There were no significant differences in proximate composition, diameter reduction, fat retention and expressible water between the grilled and oven-baked fish burgers. Cooking methods did not affect the cooking times and cooking rates. Warner-Bratzler parameters and color were significantly influenced by the cooking method. Grilling contributed to a shear force and work of shearing increase due to the lower cooking yield and water retention. Raw burgers had the highest L* (69.13??0.96) and lowest b* (17.50??0.75) values. Results indicated that baking yielded a product with better cooking characteristics, such as a desired softer texture with lower shear values (4.01??0.54) and increased water retention (95.82??0.77). Additionally, the baked fish burgers were lighter (higher L*) and less red (lower a*) than the grilled ones. PMID:26243932
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.
Directory of Open Access Journals (Sweden)
Mrcia Arocha Gularte
2000-06-01
Full Text Available A maciez da carne geralmente o atributo mais importante para o consumidor. Vrios so os fatores que influem sobre esSe aspecto no animal, como por exemplo: gentipo, idade, sexo, entre outros. Neste estudo, verificou-se a influncia da idade e do sexo na maciez do msculo Longissimus dorsi de ovinos da raa Corriedale, atravs de mtodos sensoriais e instrumentais. Aps o abate, realizou-se a avaliao visual da textura do msculo pela granulao da superfcie do mesmo. As amostras foram congeladas por 5 meses. Aps a coco, foi analisada a maciez da carne pelo equipamento Warner-Bratzler shear medindo a fora de cisalhamento, e por avaliao sensorial realizada por uma equipe treinada de julgadores. Resultados obtidos pela avaliao sensorial e instrumental indicaram que o msculo Longissimus dorsi de fmeas e de animais de menor idade foram mais macios.The meat tenderness is the most important atribute to the consumer. Several factors have influence in this aspect, for exemple: genotype, age, sex and others. The objective of this work was to study the influence of age and sex on Longissimus dorsi muscle tenderness of Corriedale lineage lamb, through sensory and instrumental methods. After slaughter Longissimus dorsi, texture was evaluated by granites surface method. The samples were frozen for five months. After thawing and cooking, meat tenderness was evaluated by Warner-Bratzler shear and sensory evaluation by a group of trained judges. The results indicated that female and younger animals produced more tender meat.
Ohira, Yutaka
2013-01-01
We consider particle acceleration by large-scale incompressible turbulence with a lengthscale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation which 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...
Maiti, Moumita; Vinutha, H. A.; Sastry, Srikanth; Heussinger, Claus
2015-01-01
Using an athermal quasistatic simulation protocol, we study the distribution of free volumes in sheared hard-particle packings close to, but below, the random-close packing threshold. We show that under shear, and independent of volume fraction, the free volumes develop features similar to close-packed systems -- particles self-organize in a manner as to mimick the isotropically jammed state. We compare athermally sheared packings with thermalized packings and show that thermalization leads t...
Bergm Robert F.; Moldover, Michael R.; Yao, Minwu; Zimmerli, Gregory A.
2009-01-01
We measured shear thinning, a viscosity decrease ordinarily associated with complex liquids such as molten plastics or ketchup, near the critical point of xenon. The data span a wide range of dimensionless shear rate: the product of the shear rate and the relaxation time of critical fluctuations was greater than 0.001 and was less than 700. As predicted by theory, shear thinning occurred when this product was greater than 1. The measurements were conducted aboard the Space Shuttle Columbia to avoid the density stratification caused by Earth's gravity.
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...
Magnetohydrodynamic Shearing Waves
Johnson, B M
2006-01-01
I consider the nonaxisymmetric linear theory of an isothermal magnetohydrodynamic (MHD) shear flow. The analysis is performed in the shearing box, a local model appropriate for a thin disk geometry. Linear perturbations in this model can be decomposed in terms of shearing waves (shwaves), which appear spatially as plane waves in a frame comoving with the shear. The time dependence of these waves cannot in general be expressed in terms of a frequency eigenvalue as in a normal mode decomposition, and numerical integration of a set of first-order amplitude equations is required for a complete characterization of their behavior. Their generic time dependence, however, is oscillatory with slowly-varying frequency and amplitude, and one can construct accurate analytic solutions by applying the Wentzel-Kramers-Brillouin method to the full set of amplitude equations. For the bulk of wavenumber space, therefore, the shwaves are well-approximated as modes with time-dependent frequencies and amplitudes. The incompressiv...
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.
Scientific Electronic Library Online (English)
Lindon W, Mamani-Linares; Carmen, Gallo.
2011-12-01
Full Text Available Se compar la composicin qumica 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 estndares de Chile. Las canales fueron refrigeradas durante 24 horas a 4 C. En el msculo [...] Longissimus lumborum (LL) se determin la composicin proximal, contenido de colesterol y colgeno, pH, color (L*, a*, b*, H*, C*), capacidad de retencin de agua (WHC), prdida de coccin, prdida del descongelado y fuerza de corte Warner-Bratzler (WBSF). La carne de llama present mayores niveles de protena y colgenos 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 [...] C). 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
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.
Baek, Hyung M.; Mix, Adam W.; Giacomin, A. Jeffrey
2014-05-01
For highly viscous fluids that slip in parallel sliding plate rheometers, we want to use a slightly converging flow to suppress this wall slip. In this work, we first attack the steady shear flow of a highly viscous Newtonian fluid between two gently converging plates with no slip boundaries using the equation of motion in cylindrical coordinates, which yields no analytical solution. Then we treat the same problem using the lubrication approximation in Cartesian coordinates to yield exact, explicit solutions for dimensionless velocity, pressure and shear stress. This work deepens our understanding of a drag flow through a gently converging slit of arbitrary convergence angle. We also employ the corotational Maxwell model to explore the role of viscoelasticity in this converging shear flow. We then compare these analytical solutions to finite element calculations for both Newtonian and corotational Maxwell cases. A worked example for determining the Newtonian viscosity using a converging shear rheometer is also included. With this work, we provide the framework for exploring other constitutive equations or other boundary conditions in future work. Our results can also be used to design the linear bearings used for the parallel sliding plate rheometer (SPR). This work can also be used to evaluate the error in the shear stress that is caused by bearing misalignment and specify the parallelism tolerance for the linear bearings incorporated into a SPR.
Shear thickening of cornstarch suspensions
Fall, Abdoulaye; Bertrand, Franois; 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.
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...
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.
Indian Academy of Sciences (India)
Akira Onuki; Akira Furukawa; Akihiko Minami
2005-05-01
We present a time-dependent GinzburgLandau 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.
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.
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
Vacuum skin pack of beef--a consumer friendly alternative.
Lagerstedt, sa; Ahnstrm, Maria L; Lundstrm, Kerstin
2011-07-01
The aim of this study was to assess how beef quality traits are affected by skin packaging compared with vacuum and high-oxygen modified atmosphere packaging (MAP; 80% O(2) and 20% CO(2)). Both M. longissimus dorsi from 6 young bulls were cut and aged in vacuum for 7 days and then cut into 3.5-cm steaks, thereafter either frozen directly day 7 or stored in skin pack, vacuum pack or MAP for an additional 7 or 14 days and then frozen. Warner-Bratzler shear force, loss and colour were measured and sensory analysis was performed. The results showed no differences in shear force, sensory analysis and total loss between steaks packed in skin pack or vacuum, but skin packed steaks had lower purge loss. MAP steaks had lower sensory scores than the other treatments at days 14 and 21. Raw MAP-steaks were bright red, but showed signs of premature browning when cooked. PMID:21316869
Scientific Electronic Library Online (English)
Wesley Oliveira de, Sousa; Germano Henrique, Rosado-Neto; Marinz Isaac, Marques.
2012-09-01
Full Text Available A teoria plastro foi testada em adultos de Neochetina eichhorniae Warner, 1970, por meio da anlise da estrutura que reveste o tegumento destes insetos e em experimentos laboratoriais de submerso. Os processos tegumentares foram reconhecidos em trs tipos: escamas aglutinadas e com perfuraes lar [...] gas; escamas plumosas de tamanhos e formas variadas; e plos. Os experimentos realizados com 264 indivduos adultos os quais permaneciam submersos por diferentes intervalos de tempo (n = 11) e em dois tratamentos, gua natural no aerada e gua previamente fervida, com quatro repeties para cada tratamento, revelaram uma mortalidade mxima aps 24 horas de mergulho no tratamento gua previamente fervida. A sobrevivncia dos adultos foi negativa e significativamente correlacionada com os tratamentos empregados e entre os diferentes intervalos de tempo. Os valores de oxignio dissolvido (mg/l) na gua diferiram significativamente entre os tratamentos aplicados, sendo positivamente correlacionado com a sobrevivncia dos adultos nos dois tratamentos, embora mais acentuadamente no tratamento com gua previamente fervida. A mortalidade dos adultos aps 24 horas de mergulho no tratamento com gua previamente fervida pode estar associada s condies fsico-qumicas da gua no testadas neste estudo, como, por exemplo, baixa tenso superficial e concentrao de solutos. Estes resultados sugerem uma funcionalidade do plastro nos adultos desta espcie. 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.
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
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.
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 literature. A good agreement has been found.A simplified method to calculate the shear capacity of T......-beams is presented....
Shear viscosity of nuclear matter
Xu, Jun
2013-01-01
In this talk I report my recent study on the shear viscosity of neutron-rich nuclear matter from a relaxation time approach. An isospin- and momentum-dependent interaction is used in the study. Effects of density, temperature, and isospin asymmetry of nuclear matter on its shear viscosity have been discussed. Similar to the symmetry energy, the symmetry shear viscosity is defined and its density and temperature dependence are studied.
Shear behaviour of ferrocement plates
MADHURI N.SAVALE; PROF. P. M.ALANDKAR
2013-01-01
Ferrocement members can be used in the form of plates Such as for walling unit, marine structures etc. Such plates are subjected to shear buckling hence shear resistance capacity of plate need to be verified. Various authors have studied shear behaviour on different specimens such as box beams, panels, and plates. The ansys software used for finite element analysis (FEM) of plates. In the present study an attempt is made to observe behaviour of ferrocement plate with various mesh patterns. Th...
Jiang, Weifeng; Xuan, Shouhu; Gong, Xinglong
2015-04-01
Dense non-Brownian suspension has rich rheology and is hard to understand, especially for distinguishing continuous shear thickening (CST) from discontinuous shear thickening (DST). By studying the shear stress dependent rheology of a well-known DST suspension of cornstarch in water, we find that the transition from CST to DST could occur not only by increasing the volume fraction ? but also by increasing the shear stress ?. For the recovery process of jammed suspension, we observe that the shear activates the time-dependent nature of particle rearrangement. DST can then be interpreted as the consequence of shear-induced jamming. Based on the test data, we plot the schematic phase diagram in the ?-? plane and find out that ? and ? perform almost the same effect on flow-state transition.
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
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
Comparison of textural atributes of selected meat sausages using instrumental analysis
Directory of Open Access Journals (Sweden)
Vladimr 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
Miller, M F; Kerth, C R; Wise, J W; Lansdell, J L; Stowell, J E; Ramsey, C B
1997-03-01
A boneless beef strip loin (IMPS #180) was fabricated from each of 320 carcasses to study the effects of slaughter plant location, quality grade, fat thickness, and aging time on beef tenderness and palatability. Carcasses were selected for fat thickness ( or = .5 cm fat thickness) and USDA quality grade (Select or Low Choice) from two slaughter facilities (IBP, Inc., Garden City, KS or Excel Inc., Plainview, TX), and the strips were aged for either 7 or 14 d. Aging steaks 14 d improved all sensory traits and Warner-Bratzler shear (WBS) values regardless of all other main effects (P .05). Therefore, aging beef strip loin steaks for 14 compared with 7 d improved sensory score and decreased WBS values, but fat thickness had no effect on the palatability of loin strip steaks processed under these conditions. PMID:9078481
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.
Schmidt, J R; Miller, M C; Andrae, J G; Ellis, S E; Duckett, S K
2013-09-01
Angus-cross steers (n = 60) were used to assess the effect of forage species [alfalfa (AL; Medicago sativa L.), bermudagrass (BG; Cynodon dactylon), chicory (CH; Cichorium intybus L.), cowpea (CO; Vigna unguiculata L.), and pearl millet (PM; Pennisetum glaucum (L. R Br.)] in replicated 2-ha paddocks for finishing on cattle performance, carcass quality, and meat quality in a 2-yr study. Steers were blocked by BW and assigned randomly to finishing-forage treatments before the start of the experiment. Steers grazing AL and CH had greater (P 1 kg/d). Finishing on legumes (AL and CO) increased dressing percentage, reduced Warner-Bratzler shear force values, and increased consumers preference, whereas finishing on grasses (BG and PM) enhanced anticarcinogenic fatty acid concentrations. PMID:23825343
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.
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\
Tempo de cozimento e textura de razes 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 adequao de medidas instrumentais de textura como ndice de qualidade de razes da mandioca de mesa e sua correlao com o tempo de cozimento. Quinze razes de mandioca foram colhidas no 11. ms de cultivo na regio noroeste fluminense. Pedaos de razes for [...] am cozidos em gua, sendo o tempo de cozimento determinado, em triplicata, quando se observou pouca resistncia penetrao do garfo. A resistncia ao corte foi realizada nas polpas cruas e cozidas, em cinco a nove repeties, operando o texturmetro TA. XT Plus Texture Analyser com probe Warner-Bratzler Blade HDP/BSW, velocidades de pr-teste de 0,2 cm/s, de ps-teste e de teste de 0,5 cm/s, e distncia de 5 cm. Os dados foram analisados por ANOVA e teste de mdia Tukey (tempo de cozimento); GLM, LSMEANS e PDIFF (resistncia ao corte) e anlise de correlao 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
Macroscopic Discontinuous Shear Thickening versus Local Shear Jamming in Cornstarch
Fall, A.; Bertrand, F.; Hautemayou, D.; Mezire, C.; Moucheront, P.; Lematre, 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.
SEDflume - High Shear Stress Flume
Federal Laboratory Consortium — The U.S. Army Corps of Engineers High Shear Stress flume (SEDflume) is designed for estimating erosion rates of fine-grained and mixed fine/coarse grained sediments...
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 behaviour of ferrocement plates
Directory of Open Access Journals (Sweden)
MADHURI N.SAVALE
2013-03-01
Full Text Available Ferrocement members can be used in the form of plates Such as for walling unit, marine structures etc. Such plates are subjected to shear buckling hence shear resistance capacity of plate need to be verified. Various authors have studied shear behaviour on different specimens such as box beams, panels, and plates. The ansys software used for finite element analysis (FEM of plates. In the present study an attempt is made to observe behaviour of ferrocement plate with various mesh patterns. The results gives that Increasing the volume fraction (VF of the wire mesh layer subsequently increases the shear carrying capacity of the plate To attain this advantage, supports and loading points should be design and strengthened to prevent local failure, Shear behaviour of ferrocement plates (SBFP.The stress intensity is determined using FEM (Ansys and compared with the available results. it is observed that stress intensity as well as cracking shear strength of plate depends upon volume fraction. the available equations from literature can be used for analysis of mesh plate.
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...
Shear strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
based upon the hypothesis that cracks can be transformed into yield lines, which have lower sliding resistance than yield lines formed in uncracked concrete.Proposals have been made on how the derived standard solutions may be applied to more complicated cases, such as continuous beams, beams with......The report deals with the shear strength of statically indeterminate reinforced concrete beams without shear reinforcement. Solutions for a number of beams with different load and support conditions have been derived by means of the crack sliding model developed by Jin- Ping Zhang.This model is...... combined loading, prestressed beams and beams with different reinforcement area at top and bottom....
Cosmic Shear at Cosmological Distances
Ratnatunga, Kavan
2001-07-01
Weak gravitational lensing has become an important probe of the geometry and large-scale structure of the universe. Galaxy-galaxy lensing is a well established result, and the focus has now shifted to the measurement of `cosmic shear', i.e. the weak gravitational lensing of galaxy images caused by the large scale distribution of dark matter. A number of ground based programs have announced the presence of this shear and using the HST Medium Deep Survey database we have tentatively detected such a shear at smaller angular scales, corresponding to larger cosmological distances. Confirmation and reduction of errors in the detection of this elusive effect has however, been complicated by various systematics in the observational data which can masquerade the true signal. The MDS database was optimized for galaxy morphology ignoring several second order effects which could not be addressed a few years ago. Recent reconstruction by ST-ECF of the jitter files for all HST WFPC2 observations, and the detailed models for the HST focus position has set the stage for a more rigorous reanalysis as required for a more confident measurement of cosmic shear. Well characterized WFPC2 observations from the rigorously monitored HST provide the best hope for the robust measurement of cosmic shear in the near future and will set the stage for more precise measurements with the Advanced Camera.
Scientific Electronic Library Online (English)
Lindon W., Mamani-Linares; Faustina, Cayo; Carmen, Gallo.
2013-04-01
Full Text Available Se compararon las caractersticas tecnolgicas de doce msculos de llamas que fueron criadas al pastoreo. Las llamas (n=10) fueron faenadas bajo procedimientos estndares de Bolivia. Las canales fueron refrigeradas durante 24 horas a 4 C. Los msculos fueron removidos de cada canal despus del desp [...] oste. Cinco bifes de 2.54 cm de espesor fueron cortados de cada msculo. En cada msculo se determin el pH24, color (L*, a*, b*), capacidad de retencin de agua y fuerza de corte Warner-Bratzler (WBSF). No se observaron diferencias estadsticas en el pH entre los msculos. Los valores de L* (luminosidad) y b* (tenor de amarrillo) de los msculos 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 C). 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
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.
Hypermixing in linear shear flow
Bolster, Diogo; Dentz, Marco; Le Borgne, Tanguy
2011-01-01
[1] In this technical note we study mixing in a two?dimensional linear shear flow. We derive analytical expressions for the concentration field for an arbitrary initial condition in an unbounded two?dimensional shear flow. We focus on the solution for a point initial condition and study the evolution of (1) the second centered moments as a measure for the plume dispersion, (2) the dilution index as a measure of the mixing state, and (3) the scalar dissipation rate as a measure for the rate of...
International Nuclear Information System (INIS)
Experiments at RHIC suggest that the quark-gluon plasma created in heavy-ion collisions is an almost-perfect fluid. Furthermore, the ?/s ratio (shear viscosity per entropy density) turns out to be minimal at the phase transition. We discuss the formalism which connects quantum field theory at finite temperature and the macroscopic transport coefficients for dissipative hydrodynamical systems. Within the framework of ChPT we compute the shear viscosity of an interacting pion gas in the confined phase. The results are compared to the AdS/CFT bound of 1/4?.
Unexpected shear strength change in magnetorheological fluids
Directory of Open Access Journals (Sweden)
Yu Tian
2014-09-01
Full Text Available Smart materials of magnetorheological (MR fluids could be turned from a liquid state into a solid state, which solidification extent or shear strength often increases monotonically with the applied magnetic field. In this study, the shear stress of a dilute MR fluid decreased with increasing applied magnetic field at a constant shear rate. The dynamic shear stress was significantly higher than the stable counterpart at medium magnetic fields. They are ascribed to the slow particle structure transformation. A higher shear rate and particle volume fraction could reduce the transient time and the shear strength difference.
Shear jamming in granular materials
Zhang, Jie
2013-11-01
For frictionless particles with purely repulsive interactions, there is a critical packing fraction ?J below which no jammed states exist. Recent experiments have shown that applying shear to a stress-free initial state can generate states which are either fragile or shear jammed depending on the way the force-network is percolated (Bi et al. Nature 2011). The nature of the jamming transition however is obscured because the existence of friction between the system and the third dimension. A new apparatus at SJTU has been designed to completely eliminate this friction by letting the particles float on the surface of a shallow water layer, which allows a study of the more detailed nature of the shear-jammed states and the transition from an unjammed state to a shear-jammed state. In this study, we also use high-precision force sensors to monitor the dynamical changes near the jamming transition. We further combine numerical simulations with the experiments to diagnose the nature of this jamming transition and its possible dependence on certain particle properties. The work at SJTU is in collaboration with Ling Zhang and Jie Zheng. The numerical simulations are in collaboration with Maobin Hu at Univ. of Sci. & Tech. of China.
Grouted Connections with Shear Keys
DEFF Research Database (Denmark)
Pedersen, Ronnie; Jrgensen, M. B.; Damkilde, Lars; Clausen, H. B.; Andersen, K.
2012-01-01
This paper presents a finite element model in the software package ABAQUS in which a reliable analysis of grouted pile-to-sleeve connections with shear keys is the particular purpose. The model is calibrated to experimental results and a consistent set of input parameters is estimated so that...
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 viscosity of the quark matter
Iwasaki, Masaharu; Ohnishi, Hiromasa; Fukutome, Takahiko
2007-01-01
We discuss shear viscosity of the quark matter by using Kubo formula. The shear viscosity is calculated in the framework of the quasi-particle RPA for the Nambu-Jona-Lasinio model. We obtain a formula that the shear viscosity is expressed by the quadratic form of the quark spectral function in the chiral symmetric phase. The magnitude of the shear viscosity is discussed assuming the Breit-Wigner type for the spectral function.
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...
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 properties of the temporomandibular joint disc in relation to compressive and shear strain.
Tanaka, E; Kawai, N; Hanaoka, K; Van Eijden, T; Sasaki, A; Aoyama, J; Tanaka, M; Tanne, K
2004-06-01
Shear stress can result in fatigue, damage, and irreversible deformation of the temporomandibular joint disc. Insight into the dynamic shear properties of the disc may give insight into the mechanism inducing tissue failure due to shear. We tested the hypothesis that the dynamic shear properties of the disc depend on the amount of shear and compressive strain. Twenty-four porcine discs were used for dynamic shear tests. The specimens were clamped between the plates of a loading apparatus under compressive strains of 5%, 10%, and 15%. Dynamic shear was applied to the specimen by a sinusoidal strain of, respectively, 0.5%, 1.0%, and 1.5%. Both the dynamic elasticity and viscosity were proportional to compressive strain and inversely proportional to shear strain. These shear characteristics suggest a significant role of compressive and shear strain on the internal friction of the disc. PMID:15153455
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
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)
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 strength of non-shear reinforced concrete elements
DEFF Research Database (Denmark)
Hoang, Cao linh
1997-01-01
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...
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.
Magnetorheological Shear Flow Near Jamming
Vgberg, Daniel; Tighe, Brian
2015-03-01
Flow in magnetorheological (MR) fluids and systems near jamming both display hallmarks of complex fluid rheology, including yield stresses and shear thinning viscosities. They are also tunable, which means that both phenomena can be used as a switching mechanism in ``smart'' fluids, i.e. fluids where properties can be tuned rapidly and reversibly by changing external parameters. We use numerical simulations to investigate the rheological properties of MR fluids close to the jamming transition as a function of the applied field and volume fraction. We are especially interested in the crossover region where both phenomena are needed to describe the observed dynamics. Funded by the Dutch Organization for Scientific Research (NWO).
Martin, Stefan; Szwaykowski, Piotr
2007-01-01
A technique for measuring optical beam shear is based on collecting light from the four quadrants of the beam and comparing the optical power collected from each quadrant with that from the other three quadrants. As used here, "shear" signifies lateral displacement of a beam of light from a nominal optical axis. A sensor for implementing this technique consists of a modified focusing lens and a quad-cell photodetector, both centered on the nominal optical axis. The modification of the lens consists in cutting the lens into four sectors (corresponding to the four quadrants) by sawing along two orthogonal diameters, then reassembling the lens following either of two approaches described next. In one approach, the lens is reassembled by gluing the sectors back together. In the simplest variant of this approach, the kerf of the saw matches the spacing of the photodetector cells, so that the focus of each sector crosses the axis of symmetry to fall on the opposite photodetector cell (see figure). In another variant of this approach, the lens sectors are spaced apart to make their individual foci to fall on separate photodetector cells, without crossing the optical axis. In the case of a sufficiently wide beam, the modified lens could be replaced with four independent lenses placed in a square array, each focusing onto an independent photodetector
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-Induced Reactive Gelation.
Brand, Bastian; Morbidelli, Massimo; Soos, Miroslav
2015-11-24
In this work, we describe a method for the production of porous polymer materials in the form of particles characterized by narrow pore size distribution using the principle of shear-induced reactive gelation. Poly(styrene-co-divinylbenzene) primary particles with diameter ranging from 80 to 200 nm are used as building blocks, which are assembled into fractal-like clusters when exposed to high shear rates generated in a microchannel. It was found that independent of the primary particle size, it is possible to modulate the internal structure of formed fractal-like aggregates having fractal dimension ranging from 2.4 to 2.7 by varying the residence time in the microchannel. Thermally induced postpolymerization was used to increase the mechanical resilience of such formed clusters. Primary particle interpenetration was observed by SEM and confirmed by light scattering resulting in an increase of fractal dimension. Nitrogen sorption measurements and mercury porosimetry confirmed formation of a porous material with surface area ranging from 20 to 40 m(2)/g characterized by porosity of 70% and narrow pore size distribution with an average diameter around 700 nm without the presence of any micropores. The strong perfusive character of the synthesized material was confirmed by the existence of a plateau of the height equivalent to a theoretical plate measured at high reduced velocities using a chromatographic column packed with the synthesized microclusters. PMID:26488233
Hierarchical Cosmic Shear Power Spectrum Inference
Alsing, Justin; Jaffe, Andrew H; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2016-01-01
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; Lematre, Anal; Bertrand, Franois; 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.
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.)
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.
Shear strength properties of wet granular materials
Richefeu, V; Radja"i, F; Richefeu, Vincent; Youssoufi, Moulay Sa\\"{i}d El; Radja\\"{i}, Farhang
2006-01-01
We investigate shear strength properties of wet granular materials in the pendular state (i.e. the state where the liquid phase is discontinuous) as a function of water content. Sand and glass beads were wetted and tested in a direct shear cell and under various confining pressures. In parallel, we carried out three-dimensional molecular dynamics simulations by using an explicit equation expressing capillary force as a function of interparticle distance, water bridge volume and surface tension. We show that, due to the peculiar features of capillary interactions, the major influence of water content over the shear strength stems from the distribution of liquid bonds. This property results in shear strength saturation as a function of water content. We arrive at the same conclusion by a microscopic analysis of the shear strength. We propose a model that accounts for the capillary force, the granular texture and particle size polydispersity. We find fairly good agreement of the theoretical estimate of the shear...
Confined Cubic Blue Phases under Shear
Henrich, O.; Stratford, K.; Marenduzzo, D.; Coveney, P. V.; Cates, M. E.
2011-01-01
We study the behaviour of confined cubic blue phases under shear flow via lattice Boltzmann simulations. We focus on the two experimentally observed phases, blue phase I and blue phase II. The disinclination network of blue phase II continuously breaks and reforms under shear, leading to an oscillatory stress response in time. The oscillations are only regular for very thin samples. For thicker samples, the shear leads to a "stick-slip" motion of part of the network along the vorticity direct...
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.
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...
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 910C, 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.
Shear bands in aluminium-lithium alloys
International Nuclear Information System (INIS)
The formation of shear bands in Al-Li alloys in cold rolling and their influence on mechanical properties of rolled and heat treated sheets are under consideration. It is shown that shear bands as well as the network of recrystallized grains along previous bands are undesirable structural constituents in aluminum alloy sheets as they decrease processing and operational properties of alloys. In further metal forming the localization of strain is observed along shear bands or zones of recrystallized grains. To avoid failure due to shear band formation it is recommended to roll alloys in as-annealed state and properly regulate reduction degree
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
Arch generated shear bands in granular systems
Bordignon, A. L.; Sigaud, L.; Tavares, G.; Lopes, H.; Lewiner, T.; Morgado, W. A. M.
2009-06-01
We propose an arch based model, on cubic and square lattices, to simulate the internal mobility of grains, in a dense granular system under shear. In this model, the role of the arches in granular transport presents a non-linear dependence on the local values of the stress components that can be modeled geometrically. This non-linearity is very important since a linear dependence on the stress will make the models behave similarly to viscous fluids, which will not reproduce highly interesting properties of the sheared systems such as shear bands. In particular, we study a modified Couette flow and find the appearance of shear bands in accordance with the literature.
Low-rise shear wall failure modes
Energy Technology Data Exchange (ETDEWEB)
Farrar, C.R. (Los Alamos National Lab., NM (USA)); Hashimoto, P.S. (EQE Engineering, Inc., Costa Mesa, CA (USA)); Reed, J.W. (Benjamin (J.R.) and Associates, Inc., Mountain View, CA (USA))
1991-01-01
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 strength in one- and two-way slabs according to the critical shear crack theory
Muttoni, Aurelio; Fernndez 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...
Quadruple Lap Shear Processing Evaluation
Thornton, Tony N.; McCool, A. (Technical Monitor)
2000-01-01
The Thiokol, Science and Engineering Huntsville Operations (SEHO) Laboratory has previously experienced significant levels of variation in testing Quadruple Lap Shear (QLS) specimens. The QLS test is used at Thiokol / Utah for the qualification of Reusable Solid Rocket Motor (RSRM) nozzle flex bearing materials. A test was conducted to verify that process changes instituted by SEHO personnel effectively reduced variability, even with normal processing variables introduced. A test matrix was designed to progress in a series of steps; the first establishing a baseline, then introducing additional solvents or other variables. Variables included normal test plan delay times, pre-bond solvent hand-wipes and contaminants. Each condition tested utilized standard QLS hardware bonded with natural rubber, two separate technicians and three replicates. This paper will report the results and conclusions of this investigation.
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
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
Finite element modelling of fabric shear
International Nuclear Information System (INIS)
In this study, a finite element model to predict shear force versus shear angle for woven fabrics is developed. The model is based on the TexGen geometric modelling schema, developed at University of Nottingham and orthotropic constitutive models for yarn behaviour, coupled with a unified displacement-difference periodic boundary condition. A major distinction from prior modelling of fabric shear is that the details of picture frame kinematics are included in the model, which allows the mechanisms of fabric shear to be represented more accurately. Meso- and micro-mechanisms of deformation are modelled to determine their contributions to energy dissipation during shear. The model is evaluated using results obtained for a glass fibre plain woven fabric, and the importance of boundary conditions in the analysis of deformation mechanisms is highlighted. The simulation results show that the simple rotation boundary condition is adequate for predicting shear force at large deformations, with most of the energy being dissipated at higher shear angles due to yarn compaction. For small deformations, a detailed kinematic analysis is needed, enabling the yarn shear and rotation deformation mechanisms to be modelled accurately
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.
Shear buckling of square perforated plates
Grosskurth, J. F., Jr.; White, R. N.; Gallagher, R. H.; Thomas, G. R.
1974-01-01
The behavior of thin square perforated plates under the action of uniform shear deformation is studied experimentally and analytically using finite element analysis. Elastic Shear buckling strength is established as a function of the diameter of a round, centrally located hole in the plate. Post buckling behavior and the behavior of perforated plates with various ring stiffeners are also studied experimentally.
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.
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.
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...
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
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 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.
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.
Reversible shear thickening at low shear rates of electrorheological fluids under electric fields.
Tian, Yu; Zhang, Minliang; Jiang, Jile; Pesika, Noshir; Zeng, Hongbo; Israelachvili, Jacob; Meng, Yonggang; Wen, Shizhu
2011-01-01
By shearing electrorheological (ER) fluids between two concentric cylinders, we show a reversible shear thickening of ER fluids above a low critical shear rate (100 V/mm), which can be characterized by a critical apparent viscosity. Shear thickening and electrostatic particle interaction-induced interparticle friction forces are considered to play an important role in the origin of lateral shear resistance of ER fluids, while the applied electric field controls the extent of shear thickening. The electric-field-controlled reversible shear thickening has implications for high-performance electrorheological-magnetorheological fluid design, clutch fluids with high friction forces triggered by applying a local electric field, other field-responsive materials, and intelligent systems. PMID:21405692
Transient dynamics in dense colloidal suspensions under shear: shear rate dependence
International Nuclear Information System (INIS)
A combination of confocal microscopy and rheology experiments, Brownian dynamics (BD) and molecular dynamics (MD) simulations and mode coupling theory (MCT) have been applied in order to investigate the effect of shear rate on the transient dynamics and stress-strain relations in supercooled and glassy systems under shear. Immediately after shear is switched on, the microscopic dynamics display super-diffusion and the macroscopic rheology a stress overshoot, which become more pronounced with increasing shear rate. MCT relates both to negative sections of the generalized shear modulus, which grow with increasing shear rate. When the inverse shear rate becomes much smaller than the structural relaxation time of the quiescent system, relaxation through Brownian motion becomes less important. In this regime, larger stresses are accumulated before the system yields and the transition from localization to flow occurs earlier and more abruptly.
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.
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 WarnerBratzler (WB shear force, cooking loss and sarcomere length. The LVES had no significant effect on WB shear force, cooking loss and sarcomere length. There wasnt 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.
Wind shear and turbulence simulation
Bowles, Roland L.
1987-01-01
The aviation community is increasing its reliance on flight simulators. This is true both in pilot training and in research and development. In moving research concepts through the development pipeline, there is a sequence of events which take place: analysis, ground based simulation, inflight simulation, and flight testing. Increasing fidelity as progress toward the flight testing arena is accompanied by increasing cost. The question that seems to be posed in relation to the meteorological aspects of flight simulation is, How much fidelity is enough and can it be quantified. As a part of the Langley Simulation Technology Program, there are three principal areas of focus, one being improved simulation of weather hazards. A close liaison with the JAWS project was established because of the Langley Simulation Technology interests regarding reliable simulation of severe convective weather phenomena and their impact on aviation systems. Simulation offers the only feasible approach for examining the utility of new technology and new procedures for coping with severe convective weather phenomena such as wind shear. These simulation concepts are discussed in detail.
Hierarchical cosmic shear power spectrum inference
Alsing, Justin; Heavens, Alan; Jaffe, Andrew H.; Kiessling, Alina; Wandelt, Benjamin; Hoffmann, Till
2016-02-01
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 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-mode, B-mode and EB-cross power spectra from a simulated galaxy shear catalogue with a number of important features; galaxies distributed on the sky and in redshift with photometric redshift uncertainties, realistic random ellipticity noise for every galaxy and a complicated survey mask. The obtained posterior distributions for the tomographic power spectrum coefficients recover the underlying simulated power spectra for both E- and B-modes.
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.
New combined shear and compression test method
International Nuclear Information System (INIS)
A new test method was developed to determine shear/compression properties of composite insulation systems used in superconducting magnets. It was developed specifically to enable in-situ testing (without warm-up) of insulation systems in a high flux neutron radiation and cryogenic (4 K) temperature environment at the Munich Research Reactor (FRM - Forschungsreaktor Munchen). The new shear/compression specimen consists of two sections of composite insulation bonded at a specific angle between three pieces of 316 stainless steel. During the test, the specimen is compressed between two loading platens. By varying the angle of the test specimen, different shear/compression ratios can be evaluated and a shear/compression envelope for various materials can be produced. This test method produces the same shear and compressive strengths found in other shear/compression tests, but the test fixture is smaller, and multiple test specimens are not required. The composite insulation systems were tested at 45 degrees to demonstrate the feasibility of the test. Specimens were produced from a vacuum pressure impregnation (VPI) resin system and a prepreg resin system. Design and fabrication of the test specimens and their shear and compressive properties are presented
Method for shearing spent nuclear fuel assemblies
International Nuclear Information System (INIS)
A method is disclosed for shearing spent nuclear fuel assemblies of the type wherein a plurality of long metal tubes packed with ceramic fuel are supported in a spaced apart relationship within an outer metal shell or shroud which provides structural support to the assembly. Spent nuclear fuel assemblies are first compacted in a stepwise manner between specially designed gag-compactors and then sheared into short segments amenable to chemical processing by shear blades contoured to mate with the compacted surface of the fuel assembly
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 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)
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.
Reactively driven drift modes in sheared flow
Energy Technology Data Exchange (ETDEWEB)
Vranjes, J.; Jovanovic, D. [Institute of Physics, Belgrade (Yugoslavia); Shukla, P.K. [Institut fuer Theoretische Physik, Fakultaet fueur Physik und Astronomie, Ruhr Universitaet Bochum, Bochum (Germany)
2000-07-01
Equations describing drift waves in strongly inhomogeneous plasma with a sheared flow and a sheared magnetic field are derived. New stabilization criteria are obtained in the linear regime. In the nonlinear regime, it is found that the governing equations admit stationary solutions in the form of tri polar vortex and vortex chains that are driven by the equilibrium plasma flow and magnetic shear. The tri polar vortex obtained in this paper is surprisingly similar to corresponding structures in two-dimensional flows in ordinary fluids. (author)
Two-fluid tokamak equilibria with reversed magnetic shear and sheared flow
Poulipoulis, G; Tasso, H
2005-01-01
The aim of the present work is to investigate tokamak equilibria with reversed magnetic shear and sheared flow, which may play a role in the formation of internal transport barriers (ITBs), within the framework of two-fluid model. The study is based on exact self-consistent solutions in cylindrical geometry by means of which the impact of the magnetic shear, s, and the "toroidal" (axial) and "poloidal" (azimuthal) ion velocity components on the radial electric field, its shear and the shear of the ExB velocity is examined. For a wide parametric regime of experimental concern it turns out that the contributions of the toroidal and poloidal velocity and pressure gradient terms to the electric field, its shear and ExB velocity shear are of the same order of magnitude. The impact of s on ExB velocity shear through the pressure gradient term is stronger than that through the velocity terms. The results indicate that, alike MHD, the magnetic shear and the sheared toroidal and poloidal velocities act synergetically ...
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
Scaling and intermittency in incoherent ?-shear dynamo
Mitra, Dhrubaditya; Brandenburg, Axel
2012-03-01
We consider mean-field dynamo models with fluctuating ? effect, both with and without large-scale shear. The ? effect is chosen to be Gaussian white noise with zero mean and a given covariance. In the presence of shear, we show analytically that (in infinitely large domains) the mean-squared magnetic field shows exponential growth. The growth rate of the fastest growing mode is proportional to the shear rate. This result agrees with earlier numerical results of Yousef et al. and the recent analytical treatment by Heinemann, McWilliams & Schekochihin who use a method different from ours. In the absence of shear, an incoherent ?2 dynamo may also be possible. We further show by explicit calculation of the growth rate of third- and fourth-order moments of the magnetic field that the probability density function of the mean magnetic field generated by this dynamo is non-Gaussian.
Acoustic waves in unbounded shear flows
International Nuclear Information System (INIS)
The linear evolution of acoustic waves in fluid flow with constant density and uniform shear of velocity is investigated. The process of the mean flow energy extraction by the three-dimensional acoustic waves which is due to the non-normality of linear dynamics in shear flows is analyzed. The thorough examination of the dynamics of different physical quantities, specifying the wave evolution, is outlined. The revealing of the behaviour becomes possible owing to the nonmodal approach that has been extensively used in the study of the perturbations evolution in shear flows since the beginning of the nineties. In addition, a detailed analyses of the physics of shear energy gain by vortex and acoustic perturbations is presented. (author). 28 refs, 7 figs
Recent progress in shear punch testing
International Nuclear Information System (INIS)
The shear punch test was developed in response to the needs of the materials development community for small-scale mechanical properties tests. Such tests will be of great importance when a fusion neutron simulation device is built, since such a device is expected to have a limited irradiation volume. The shear punch test blanks a circular disk from a fixed sheet metal specimen, specifically a TEM disk. Load-displacement data generated during the test can be related to uniaxial tensile properties such as yield and ultimate strength. Shear punch and tensile tests were performed at room temperature on a number of unirradiated aluminum, copper, vanadium, and stainless steel alloys and on several irradiated aluminum alloys. Recent results discussed here suggest that the relationship between shear punch strength and tensile strength varies with alloy class, although the relationship determined for the unirradiated condition remains valid for the irradiated aluminum alloys
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.
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...
Turbulence evolution in plasma shear flows
International Nuclear Information System (INIS)
The renormalized nonlinear analysis of the temporal evolution of drift-type modes in plasma shear flows is developed. The theory accounts for the effect of the turbulent motions of plasma on the saturation of the resistive drift instability. The nonlinear balance equation, which determines the saturation level of the resistive drift instability in shear flow is obtained. It was prowed that the nonlinear effect of the enhanced decorrelation by shear flow has nothing in common with process of the saturation. The same conclusion is applicable to all fluid models of plasma, obtained in drift approximation, in which all nonlinearities, other than EB are ignored. The linear non-modal kinetic theory to the Vlasov-Poisson system is developed. This theory reveals the velocity shear in a non-modal time-dependent effect of the finite Larmor radius. (author)
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.
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...
Nucleation and initial propagation of shear cracks
Directory of Open Access Journals (Sweden)
F. MULARGIA
1977-06-01
Full Text Available SUMMARY. - By means of the dislocation theory, an explanation is found
for the antientropic process of microcracking-macrocracking transition in the
shear fracture initial propagation.
Stress analysis of shear/compression test
International Nuclear Information System (INIS)
Stress analysis has been made on the glass fiber reinforced plastics (GFRP) subjected to the combined shear and compression stresses by means of finite element method. The two types of experimental set up were analyzed, that is parallel and series method where the specimen were compressed by tilted jigs which enable to apply the combined stresses, to the specimen. Modified Tsai-Hill criterion was employed to judge the failure under the combined stresses that is the shear strength under the compressive stress. The different failure envelopes were obtained between the two set ups. In the parallel system the shear strength once increased with compressive stress then decreased. On the contrary in the series system the shear strength decreased monotonicly with compressive stress. The difference is caused by the different stress distribution due to the different constraint conditions. The basic parameters which control the failure under the combined stresses will be discussed
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.
Particle acceleration in astrophysical shear flows
Rieger, Frank M.; Duffy, Peter
2005-01-01
We consider the acceleration of particles due to a velocity shear in relativistic astrophysical flows. The basic physical picture and the formation of power law momentum spectra is discussed for a non-relativistic velocity field using a microscopic approach. We identify possible sites for shear acceleration in relativistic astrophysical jets and analyze their associated acceleration timescales. It is shown in particular that for a mean scattering time $\\tau$ scaling with the gyro-radius, the ...
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...
Critical packing in granular shear bands
Fazekas, S.; Trk, J.; Kertsz, 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...
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 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
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 collisions to the pr...
Liquid migration in sheared unsaturated granular media
Mani, Roman; Herrmann, Hans J
2012-01-01
We show how liquid migrates in sheared unsaturated granular media using a grain scale model for capillary bridges. Liquid is redistributed to neighboring contacts after rupture of individual capillary bridges leading to redistribution of liquid on large scales. The liquid profile evolution coincides with a recently developed continuum description for liquid migration in shear bands. The velocity profiles which are linked to the migration of liquid as well as the density profiles of wet and dry granular media are studied.
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 Poznań, 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
Avalanches in anisotropic sheared granular media
Pea, Andrs 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...
Velocity Profiles in Slowly Sheared Bubble Rafts
Lauridsen, John; Chanan, Greg; Dennin, Michael
2003-01-01
Measurements of average velocity profiles in a bubble raft subjected to slow, steady-shear demonstrate the coexistence between a flowing state and a jammed state similar to that observed for three-dimensional foams and emulsions [Coussot {\\it et al,}, Phys. Rev. Lett. {\\bf 88}, 218301 (2002)]. For sufficiently slow shear, the flow is generated by nonlinear topological rearrangements. We report on the connection between this short-time motion of the bubbles and the long-time averages. We find ...
Critical packing in granular shear bands
Fazekas, S; Kertsz, 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 instability of a gyroid diblock copolymer
DEFF Research Database (Denmark)
Eskimergen, Rya; 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 ...
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.
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...
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.
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.
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.
Influence of Shear on Rotation Capacity of Reinforced Concrete Members Without Shear Reinforcement
Vaz Rodrigues, Rui; Muttoni, Aurelio; Fernndez 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...
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.
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 ...
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.
How to create mylonitic shear zones in the presence of shear heating
Thielmann, Marcel; Rozel, Antoine; Kaus, Boris; Ricard, Yanick
2013-04-01
Lithospheric-scale shear zones are commonly defined as regions inhomogeneous and localized deformation. Strain softening has been demonstrated to be necessary for localization in those shear zones, but there is still debate about the physical cause of this softening. Here, we investigate the interplay between two mechanisms that have been suggested to have a significant impact on lithospheric localization: shear heating and grain size reduction. Shear heating has been suggested to play an important role in i) creating deep focus as well as intermediate-depth earthquakes (Ogawa (1987), Kelemen and Hirth (2007)) and ii) creating lithospheric-scale shear zones, thus creating a weak decoupling interface that enables subsequent subduction initiation (Kaus and Podlatchikov (2006), Crameri and Kaus (2010)). As natural shear zones typically have a significantly reduced grain size, it has been put forward that grain size reduction provides the necessary strain softening to localize deformation. As grain size reduces, the dominant deformation mechanism switches from dislocation to diffusion creep, thus requiring less stress to deform the rock. Usually, the equilibrium grain size is thought to follow a piezometric relationship, thus indicating the stress under which a shear zone deformed. Recent work (Austin and Evans (2007), Rozel et al. (2011)) suggests that the equilibrium grain size is not dependent on stress, but rather on the deformational work. In our study, we employ the grain size evolution law of Rozel et al. and use 1D viscoelastic numerical models of simple shear deformation to investigate the influence of both weakening mechanisms and their interaction for a variety of boundary conditions. We find that grain size reduction in pure olivine does not localize very efficiently, as grain size very rapidly reaches a steady state. Even when a fraction of the deformational work is used by grain size reduction processes, shear heating is found to localize very efficiently (Kaus & Podlatchikov (2005), Braeck et al. (2009)) and the significant temperature increase induced by shear heating severely affects the grain size in the shear zone. Generally, we find that the elevated temperature inside the shear zone results in a larger grain size inside the shear zone compared to the surrounding rock matrix. This finding is not compatible with field observations, where shear zones are usually characterized by small grain sizes. This indicates that further mechanisms are needed to keep either the grain size small (e.g. pinning by secondary phases (Herwegh et. al (2011), Bercovici and Ricard (2012) ) or to limit the temperature increase inside the shear zone.
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
Punching shear capacity of reinforced concrete slabs with headed shear studs
DEFF Research Database (Denmark)
Hoang, Linh Cao; Pop, Anamaria
2015-01-01
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...
Repeated buckling of composite shear panels
Singer, Josef; Weller, Tanchum
1990-01-01
Failures in service of aerospace structures and research at the Technion Aircraft Structures Laboratory have revealed that repeatedly buckled stiffened shear panels might be susceptible to premature fatigue failures. Extensive experimental and analytical studies have been performed at Technion on repeated buckling, far in excess of initial buckling, for both metal and composite shear panels with focus on the influence of the surrounding structure. The core of the experimental investigation consisted of repeated buckling and postbuckling tests on Wagner beams in a three-point loading system under realistic test conditions. The effects of varying sizes of stiffeners, of the magnitude of initial buckling loads, of the panel aspect ratio and of the cyclic shearing force, V sub cyc, were studied. The cyclic to critical shear buckling ratios, (V sub cyc/V sub cr) were on the high side, as needed for efficient panel design, yet all within possible flight envelopes. The experiments were supplemented by analytical and numerical analyses. For the metal shear panels the test and numerical results were synthesized into prediction formulas, which relate the life of the metal shear panels to two cyclic load parameters. The composite shear panels studied were hybrid beams with graphite/epoxy webs bonded to aluminum alloy frames. The test results demonstrated that composite panels were less fatigue sensitive than comparable metal ones, and that repeated buckling, even when causing extensive damage, did not reduce the residual strength by more than 20 percent. All the composite panels sustained the specified fatigue life of 250,000 cycles. The effect of local unstiffened holes on the durability of repeatedly buckled shear panels was studied for one series of the metal panels. Tests on 2024 T3 aluminum panels with relatively small unstiffened holes in the center of the panels demonstrated premature fatigue failure, compared to panels without holes. Preliminary tests on two graphite epoxy shear panels with small holes in the center showed no similar fatigue life degradation and no shift in failure mode. Further tests on the effect of holes are in progress.
Extreme model reduction of shear layers
Qawasmeh, Bashar Rafee
The aim of this research is to develop nonlinear low-dimensional models (LDMs) to describe vortex dynamics in shear layers. A modified Proper Orthogonal Decomposition (POD)/Galerkin projection method is developed to obtain models at extremely low dimension for shear layers. The idea is to dynamically scale the shear layer along y direction to factor out the shear layer growth and capture the dynamics by only a couple of modes. The models are developed for two flows, incompressible spatially developing and weakly compressible temporally developing shear layers, respectively. To capture basic dynamics, the low-dimensional models require only two POD modes for each wavenumber/frequency. Thus, a two-mode model is capable of representing single-wavenumber/frequency dynamics such as vortex roll-up, and a four-mode model is capable of representing the nonlinear dynamics involving a fundamental wavenumber/frequency and its subharmonic, such as vortex pairing/merging. Most of the energy is captured by the first mode of each wavenumber/frequency, the second POD mode, however, plays a critical role and needs to be included. In the thesis, we first apply the approach on temporally developing weakly compressible shear layers. In compressible flows, the thermodynamic variables are dynamically important, and must be considered. We choose isentropic Navier-Stokes equations for simplicity, and choose a proper inner product to present both kinetic energy and thermal energy. Two cases of convective Mach numbers are studied for low compressibility and moderate compressibility. Moreover, we study the sensitivity of the compressible four-mode model to several flow parameters: Mach number, the strength of initial perturbations of the fundamental and its subharmonic, and Reynolds number. Secondly we apply the approach on spatially developing incompressible shear layers with periodicity in time. We consider a streamwise parabolic form of the Navier-Stokes equations. When we add arbitrary excitation at different harmonics to the model, we observe the promoting or delaying/eliminating of vortex merging events as a result of mode competition. To study coherent structures in shear layers, we solve the Direct Lyapunov Exponents (DLEs) to identify the Lagrangian coherent structures (LCS). The negative-time LCS provide structures similar to the ones shown by flow visualization in experiments. The positive-time LCS are also important in describing the dynamics. Both negative and positive LCS are plotted together to give a complete picture of dynamics in shear layers.
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...
Shear-enhanced adhesion of Pseudomonas aeruginosa
Lecuyer, Sigolene; Rusconi, Roberto; Shen, Yi; Forsyth, Alison; Stone, Howard
2010-03-01
Bacterial adhesion is the first step in the development of surface-associated communities known as biofilms, which are the cause of many problems in medical devices and industrial water systems. However the underlying mechanisms of initial bacterial attachment are not fully understood. We have investigated the effects of hydrodynamics on the probability of adsorption and detachment of Pseudomonas aeruginosa strain PA14 on model surfaces under flow, in straight microfluidic channels, and measured the distribution of bacteria residence time as a function of the shear rate. Our main discovery is a counter-intuitive enhanced adhesion as the shear stress is increased over a wide range of shear rates. In order to identify the origin of this phenomenon, we have performed experiments with several mutant strains. Our results show that shear-enhanced adhesion is not regulated by primary surface organelles, and that this process is not specific to a certain type of surface, but rather appears a general feature of the adhesive behavior of P. aeruginosa. These results suggest that shear-induced adhesion could be a very widespread strategy in nature.
Nonmonotonic flow curves of shear thickening suspensions
Mari, Romain; Seto, Ryohei; Morris, Jeffrey F.; Denn, Morton M.
2015-05-01
The discontinuous shear thickening (DST) of dense suspensions is a remarkable phenomenon in which the viscosity can increase by several orders of magnitude at a critical shear rate. It has the appearance of a first-order phase transition between two hypothetical "states" that we have recently identified as Stokes flows with lubricated or frictional contacts, respectively. Here we extend the analogy further by means of stress-controlled simulations and show the existence of a nonmonotonic steady-state flow curve analogous to a nonmonotonic equation of state. While we associate DST with an S -shaped flow curve, at volume fractions above the shear jamming transition the frictional state loses flowability and the flow curve reduces to an arch, permitting the system to flow only at small stresses. Whereas a thermodynamic transition leads to phase separation in the coexistence region, we observe a uniform shear flow all along the thickening transition. A stability analysis suggests that uniform shear may be mechanically stable for the small Reynolds numbers and system sizes in a rheometer.
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.
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.
Viscoelasticity and shear thinning of nanoconfined water
Kapoor, Karan; Amandeep, Patil, Shivprasad
2014-01-01
Understanding flow properties and phase behavior of water confined to nanometer-sized pores and slits is central to a wide range of problems in science, such as percolation in geology, lubrication of future nano-machines, self-assembly and interactions of biomolecules, and transport through porous media in filtration processes. Experiments with different techniques in the past have reported that viscosity of nanoconfined water increases, decreases, or remains close to bulk water. Here we show that water confined to less than 20-nm-thick films exhibits both viscoelasticity and shear thinning. Typically viscoelasticity and shear thinning appear due to shearing of complex non-Newtonian mixtures possessing a slowly relaxing microstructure. The shear response of nanoconfined water in a range of shear frequencies (5 to 25 KHz) reveals that relaxation time diverges with reducing film thickness. It suggests that slow relaxation under confinement possibly arises due to existence of a critical point with respect to slit width. This criticality is similar to the capillary condensation in porous media.
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 ...
COMPUTATIONAL APPROACH TO PREDICT SOIL SHEAR STRENGTH
Directory of Open Access Journals (Sweden)
Rajeev Jain,
2010-08-01
Full Text Available The paper presents an artificial neural network technique to predict the shear strength parameters of medium compressibility soil, which influenced by basic properties of soil in unconsolidated undrained conditions. Obviously obtained the undisturbed samples of soil to determination of shear strength parameters is a tedious work. Commercial softwares MATLAB-7 was used for this study. Triaxial shear tests were conducted to obtain these parameters at different water contents and densities. The results were used to predict the strength parameters. A set of 198 experimental results were used to construct the ANN model out of which 120 for training , 39 for validation and 39 for testing or prediction of shear strength parameters ( Cohesion & Angle of internal friction were used. The correlation between the basic properties and shear strength parameters were obtained from the trained neural network. For trained the feed forward ANN models: multilayer perceptrons and radial basis function neural network, followings parameters were considered as input data the compaction energy, degree of saturation, dry density and C & ? were output parameter. The regression coefficient and MSEwere 0.94, 0.76 and 0.0642, 0.253 respectively. In addition, the experimental results were compared to MLPN and RBF networks predicted results. It was concluded that the performance of the multilayer perceptron feed forward neural network model with three hidden layers is better than radial basis function neural network model.
Parametric Study of Multi-Spot Welded Lap Shear Specimen for Shear Strength
Directory of Open Access Journals (Sweden)
Raghunath T Bandgar
2015-09-01
Full Text Available The effect of number of spots, spot spacing, squeezing force, welding current, weld time , overlapping length and sheet thicknesson the shear strength of two similar galvanized steel sheets are investigated through experiments using RSM method. Similar sheets of galvanized steel sheets are made by resistance spot welding at different processing conditions and these joint populations were tested under lap-shear loading conditions. Specially fabricated fixture is used to load the lap shear specimen in the universal testing machine Regression analysis is done to obtain relationship between shear strength and selected parameters. The experimental results indicate that the failure loads of spot welds in lap-shear specimens increase when number of spot, squeezing force, welding current and sheet thickness increase for the given ranges.
Shear viscosity in magnetized neutron star crust
Ofengeim, D. D.; Yakovlev, D. G.
2015-12-01
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.
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.
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 of a hot pion gas
International Nuclear Information System (INIS)
The shear viscosity of an interacting pion gas is studied using the Kubo formalism as a microscopic description of thermal systems close to global equilibrium. We implement the skeleton expansion in order to approximate the retarded correlator of the viscous part of the energy-momentum tensor. After exploring this in g?4 theory we show how the skeleton expansion can be consistently applied to pions in chiral perturbation theory. The shear viscosity ? is determined by the spectral width, or equivalently, the mean free path of pions in the heat bath. We derive a new analytical result for the mean free path which is well conditioned for numerical evaluation and discuss the temperature and pion-mass dependence of the mean free path and the shear viscosity. The ratio ?/s of the interacting pion gas exceeds the lower bound 1/4? from AdS/CFT correspondence. (orig.)
The many faces of shear Alfven waves
International Nuclear Information System (INIS)
One of the fundamental waves in magnetized plasmas is the shear Alfven wave. This wave is responsible for rearranging current systems and, in fact all low frequency currents in magnetized plasmas are shear waves. It has become apparent that Alfven waves are important in a wide variety of physical environments. Shear waves of various forms have been a topic of experimental research for more than fifteen years in the large plasma device (LAPD) at UCLA. The waves were first studied in both the kinetic and inertial regimes when excited by fluctuating currents with transverse dimension on the order of the collisionless skin depth. Theory and experiment on wave propagation in these regimes is presented, and the morphology of the wave is illustrated to be dependent on the generation mechanism. Three-dimensional currents associated with the waves have been mapped. The ion motion, which closes the current across the magnetic field, has been studied using laser induced fluorescence. The wave propagation in inhomogeneous magnetic fields and density gradients is presented as well as effects of collisions and reflections from boundaries. Reflections may result in Alfvenic field line resonances and in the right conditions maser action. The waves occur spontaneously on temperature and density gradients as hybrids with drift waves. These have been seen to affect cross-field heat and plasma transport. Although the waves are easily launched with antennas, they may also be generated by secondary processes, such as Cherenkov radiation. This is the case when intense shear Alfven waves in a background magnetoplasma are produced by an exploding laser-produced plasma. Time varying magnetic flux ropes can be considered to be low frequency shear waves. Studies of the interaction of multiple ropes and the link between magnetic field line reconnection and rope dynamics are revealed. This manuscript gives us an overview of the major results from these experiments and provides a modern prospective for the earlier studies of shear Alfven waves.
Shear reinforced beams in autoclaved aerated concrete
DEFF Research Database (Denmark)
Cornelius, Thomas
. Recently developed formulas covering these areas will be presented and analyzed. The results presented show very consistent conformity with theory, both when considering mechanical anchorage of the reinforcement and when assuming pure bond for transferring initial forces between reinforcement and aircrete...... 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 reinforced aircrete is highly dependent on the anchorage and bond behaviour of the shear reinforcement....... Codes for designing prefabricated reinforced components of aircrete structures have adopted these recently developed approaches....
Enhancing Rotational Diffusion Using Oscillatory Shear
Leahy, Brian D.
2013-05-29
Taylor dispersion - shear-induced enhancement of translational diffusion - is an important phenomenon with applications ranging from pharmacology to geology. Through experiments and simulations, we show that rotational diffusion is also enhanced for anisotropic particles in oscillatory shear. This enhancement arises from variations in the particle\\'s rotation (Jeffery orbit) and depends on the strain amplitude, rate, and particle aspect ratio in a manner that is distinct from the translational diffusion. This separate tunability of translational and rotational diffusion opens the door to new techniques for controlling positions and orientations of suspended anisotropic colloids. 2013 American Physical Society.
Halo abundances and shear in void models
DEFF Research Database (Denmark)
Alonso, David; Garca-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.
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 independent measurements of the frequency-dependent shear modulus of the equilibrium liquid....
Shear and Compression Bioreactor for Cartilage Synthesis.
Shahin, Kifah; Doran, Pauline M
2015-01-01
Mechanical forces, including hydrodynamic shear, hydrostatic pressure, compression, tension, and friction, can have stimulatory effects on cartilage synthesis in tissue engineering systems. Bioreactors capable of exerting forces on cells and tissue constructs within a controlled culture environment are needed to provide appropriate mechanical stimuli. In this chapter, we describe the construction, assembly, and operation of a mechanobioreactor providing simultaneous dynamic shear and compressive loading on developing cartilage tissues to mimic the rolling and squeezing action of articular joints. The device is suitable for studying the effects of mechanical treatment on stem cells and chondrocytes seeded into three-dimensional scaffolds. PMID:26445842
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.
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
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
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.
Velocity Profiles in Slowly Sheared Bubble Rafts
Lauridsen, J; Dennin, M; Lauridsen, John; Chanan, Greg; Dennin, Michael
2004-01-01
Measurements of average velocity profiles in a bubble raft subjected to slow, steady-shear demonstrate the coexistence between a flowing state and a jammed state similar to that observed for three-dimensional foams and emulsions [Coussot {\\it et al,}, Phys. Rev. Lett. {\\bf 88}, 218301 (2002)]. For sufficiently slow shear, the flow is generated by nonlinear topological rearrangements. We report on the connection between this short-time motion of the bubbles and the long-time averages. We find that a smooth, average velocity is reached after averaging over only a relatively few number of rearrangement events.
Shears Mechanism in the A ? 110 Region
International Nuclear Information System (INIS)
Lifetimes of states in a rotational-like M1 band in 110Cd have been determined through a Doppler-shift attenuation method measurement performed with the Gammasphere array. The deduced B(M1) values, which agree well with the predictions of the tilted axis cranking model, clearly confirm that it has the character of a shears band. Using a semiclassical scheme of the coupling of two long j vectors we deduce information on the strength and form of the effective interaction between the constituent nucleons. These results are the first definitive evidence of the shears mechanism and magnetic rotation' in this mass region. copyright 1999 The American Physical Society
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...
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.
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.
International Nuclear Information System (INIS)
The non-potentiality of solar magnetic fields is traditionally measured in terms of a magnetic shear angle, i.e., the angle between the observed and potential field azimuths. Here, we introduce another measure of the shear that has not been previously studied in solar active regions, i.e., the one that is associated with the inclination angle of the magnetic field. This form of the shear, which we call 'dip shear', can be calculated by taking the difference between the observed and the potential field inclination. In this Letter, we study the evolution of the dip shear as well as the conventional twist shear in a ?-sunspot using high-resolution vector magnetograms from the Hinode space mission. We monitor these shears in a penumbral region located close to a flaring site during 2006 December 12 and 13. It is found that (1) the penumbral area close to the flaring site shows a high value of the twist shear and dip shear as compared with other parts of the penumbra, (2) after the flare, the value of the dip shear drops in this region while the twist shear tends to increase, (3) the dip shear and twist shear are correlated such that pixels with a large twist shear also tend to exhibit a large dip shear, and (4) the correlation between the twist shear and dip shear is tighter after the flare. The present study suggests that monitoring the twist shear alone during the flare is not sufficient, but we need to monitor it together with the dip shear.
Zhao, Ji-Song; Scholz, Peter; Gu, Liang-Xian
2012-10-01
The global wall shear stress measurement technique using shear-sensitive liquid crystal (SSLC) is extended to wind tunnel measurements. Simple and common everyday equipment is used in the measurement; in particular a tungsten-halogen light bulb provides illumination and a saturation of SSLC coating color change with time is found. Spatial wall shear stress distributions of several typical flows are obtained using this technique, including wall-jet flow, vortex flow generated by a delta wing and junction flow behind a thin cylinder, although the magnitudes are not fully calibrated. The results demonstrate that SSLC technique can be extended to wind tunnel measurements with no complicated facilities used.
Computer simulation of three dimensional shearing of granular materials: Formation of shear bands
Fazekas, S; Kertsz, 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.
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 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 ...... descriptions of shear crack opening, sliding and subsequent failure are presented....... 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...
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
Two-Phase Shear Band Structures at Uniform Stress
Britton, Melanie M.; Callaghan, Paul T.
1997-06-01
Using NMR microscopy we measure the velocity distribution for a wormlike surfactant solution in the gap of a small angle cone-and-plate rheometer. This system, cetylpyridinium chloride/sodium salicylate 100 mM/60 mM, exhibits biphasic shear band structure when the applied shear rate exceeds the critical rate of strain beyond which a plateau is observed in the shear stress. The structure is characterized by two low/high shear interfaces and the region of high shear evolves by increasing width as the average gap shear is increased.
Shear buckling analysis of a hat-stiffened panel
Ko, William L.; Jackson, Raymond H.
1994-01-01
A buckling analysis was performed on a hat-stiffened panel subjected to shear loading. Both local buckling and global buckling were analyzed. The global shear buckling load was found to be several times higher than the local shear buckling load. The classical shear buckling theory for a flat plate was found to be useful in predicting the local shear buckling load of the hat-stiffened panel, and the predicted local shear buckling loads thus obtained compare favorably with the results of finite element analysis.
Granular dynamics under shear with deformable boundaries
Geller, Drew; Backhaus, Scott; Ecke, Robert
2015-03-01
Granular materials under shear develop complex patterns of stress as the result of granular positional rearrangements under an applied load. We consider the simple planar shear of a quasi two-dimensional granular material consisting of bi-dispersed nylon cylinders confined between deformable boundaries. The aspect ratio of the gap width to total system length is 50, and the ratio of particle diameter to gap width is about 10. This system, designed to model a long earthquake fault with long range elastic coupling through the plates, is an interesting model system for understanding effective granular friction because it essentially self tunes to the jamming condition owing to the hardness of the grains relative to that of the boundary material, a ratio of more than 1000 in elastic moduli. We measure the differential strain displacements of the plates, the inhomogeneous stress distribution in the plates, the positions and angular orientations of the individual grains, and the shear force, all as functions of the applied normal stress. There is significant stick-slip motion in this system that we quantify through our quantitative measurements of both the boundary and the grain motion, resulting in a good characterization of this sheared 2D hard sphere system.
Shear bands as bottlenecks in force transmission
Tordesillas, Antoinette; Pucilowski, Sebastian; Tobin, Steven; Kuhn, Matthew R.; And, 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.)
MHD stability of reversed shear configurations
International Nuclear Information System (INIS)
We present a review of MHD stability issues in reversed shear configurations. This work will focus on identifying issues relevant to existing and proposed devices. The aim is to provide a framework for assessing the value of different designs. We will use available experimental data to support our conclusions where it is possible
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
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.
Equilibrium states of homogeneous sheared compressible turbulence
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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.
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.; Garca, L.; Calvo, I.; de Pablos, J.L.; Stckel, Jan
Varava, 2007. -. [EPS Conference on Plasma Physics/34th./. 02.07.2007-06.07.2007, Varava] 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
Shear strength of aluminum fillet welds
Lovoy, C. V.
1980-01-01
Shear-strength tests on aluminum fillet welds are documented in report. Test were made on aluminum alloy 2219 to aid designers in specifying sizes and lengths of fillet welds necessary to sustain expected loads in this material. Report discusses fillet-weld size and geometry, including root penetration and surface contour.
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.
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.
International Nuclear Information System (INIS)
The experimental data from RHIC, especially the measured elliptic flow indicate that the matter produced in Au+Au collisions exhibit properties which are more like a strongly interacting liquid than a weakly interacting gas. The shear viscosity ? or the internal friction of the fluid symbolizes the ability to transfer momentum over a distance of ? mean free path. Therefore, in a system where the constituents interact strongly the transfer of momentum is performed easily - resulting in lower values of ?. Consequently such a system may be characterized by a small value of ?/s. The importance of viscosity also lies in the fact that it damps out the variation in the velocity and make the fluid flow laminar. A very small viscosity (large Reynold number) may make the flow turbulent. Although a large amount of work has been done on shear viscosity in QGP phase, the shear viscosity in hadronic matter has received much less attention so far. In the present work shear viscosity has been evaluated in a kinetic theory approach by solving Boltzmann transport equation using the relaxation time approximation
Herle, V.; Manneville, S.; Fischer, P.
2008-05-01
We carried out pointwise local velocity measurements on 40mM cetylpyridinium chloride-sodium salicylate (CPyCl-NaSal) wormlike micellar solution using high-frequency ultrasound velocimetry in a Couette shear cell. The studied wormlike solution exhibits Newtonian, shear-thinning and shear-thickening rheological behavior in a stress-controlled environment. Previous rheology, flow visualization and small-angle light/neutron scattering experiments in the shear-thickening regime of this system showed the presence of stress-driven alternating transparent and turbid rings or vorticity bands along the axis of the Couette geometry. Through local velocity measurements we observe a homogeneous flow inside the 1mm gap of the Couette cell in the shear-thinning (stress-plateau) region. Only when the solution is sheared beyond the critical shear stress (shear-thickening regime) in a stress-controlled experiment, we observe inhomogeneous flow characterized by radial or velocity gradient shear bands with a highly sheared band near the rotor and a weakly sheared band near the stator of the Couette geometry. Furthermore, fast measurements performed in the shear-thickening regime to capture the temporal evolution of local velocities indicate coexistence of both radial and vorticity shear bands. However the same measurements carried out in shear rate controlled mode of the rheometer do not show such rheological complexity.
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.
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.
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.
Gap size and shear history dependencies in shear thickening of a suspension ordered at rest
International Nuclear Information System (INIS)
An investigation is made of the flow properties of a suspension of uniform 197 nm diameter spheres at a volume fraction of 0.50 dialyzed to equilibrium against 10-3 M KCl which displayed long-range orientational order at rest. In wide gap rheometers (i.e., tool gaps ?0.5 mm), microstructures and flow properties are similar to those seen in many suspensions which are ordered at rest. Low shear rate response is found to be independent of rheometer tool gap down to 4.5 ?m. However, the shear rate marking the onset of thickening is a decreasing function of rheometer tool gap for gaps smaller than 15 ?m. These results are consistent with abrupt shear thickening seen in dense suspensions containing uniform particles arising from the formation of percolating clusters produced during shear melting
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.
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 ...
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...
Parametric Study of Multi-Spot Welded Lap Shear Specimen for Shear Strength
Raghunath T Bandgar; Pravin.A Dhawale
2015-01-01
The effect of number of spots, spot spacing, squeezing force, welding current, weld time , overlapping length and sheet thicknesson the shear strength of two similar galvanized steel sheets are investigated through experiments using RSM method. Similar sheets of galvanized steel sheets are made by resistance spot welding at different processing conditions and these joint populations were tested under lap-shear loading conditions. Specially fabricated fixture is used to load the la...
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.
Lpez-Barrn, 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.
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
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.
Turbulent transport in tokamak plasmas with rotational shear.
Barnes, M; Parra, F I; Highcock, E G; Schekochihin, A A; Cowley, S C; Roach, C M
2011-04-29
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E×B shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcations in the E×B shear. The critical temperature gradient for the onset of turbulence increases with flow shear at low flow shears; at higher flow shears, the dependence of heat flux on temperature gradient becomes less stiff. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity. PMID:21635042
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
Interfacial Shear Strength Evaluation of Jute/Poly(Lactic Acid)
Kobayashi, Satoshi; Yamamoto, Tatsuro; Nakai, Asami
In order to evaluate the interfacial shear strength between fiber bundle and matrix of jute/poly(lactic acid) (PLA), a fiber bundle pull-out test method is proposed. Shear stress distribution was calculated based on the parabolic shear-lag analysis. Fiber bundle pull-out tests were conducted to evaluate the effects of molding condition on the interfacial shear strength. The interfacial shear strength increased with increasing molding temperature up to 185C. Then gradual decrease in the interfacial shear strength with molding temperature was observed. Similar tendency was also observed in the effect of molding time, whereas the interfacial shear strength decreased with increasing molding pressure. Comparing the result of the tensile tests in the previous study, interfacial shear strength has corelations with tensile strength.
Variational bounds for the shear viscosity of gelling melts
K"ohler, C H; Mller, 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 Viscosity from the Effective Coupling of Gravitons
Cai, Rong-gen; Nie, Zhang-Yu; Sun, Ya-Wen
2010-01-01
We review the progress in the holographic calculation of shear viscosity for strongly coupled field theories. We focus on the calculation of shear viscosity from the effective coupling of transverse gravitons and present some explicit examples.
Adaptive Estimation of Intravascular Shear Rate Based on Parameter Optimization
Nitta, Naotaka; Takeda, Naoto
2008-05-01
The relationships between the intravascular wall shear stress, controlled by flow dynamics, and the progress of arteriosclerosis plaque have been clarified by various studies. Since the shear stress is determined by the viscosity coefficient and shear rate, both factors must be estimated accurately. In this paper, an adaptive method for improving the accuracy of quantitative shear rate estimation was investigated. First, the parameter dependence of the estimated shear rate was investigated in terms of the differential window width and the number of averaged velocity profiles based on simulation and experimental data, and then the shear rate calculation was optimized. The optimized result revealed that the proposed adaptive method of shear rate estimation was effective for improving the accuracy of shear rate calculation.
Turbulent Transport in Tokamak Plasmas with Rotational Shear
International Nuclear Information System (INIS)
Nonlinear gyrokinetic simulations are conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal ExB shear value for plasma confinement. Local maxima in the momentum fluxes are observed, implying the possibility of bifurcations in the ExB shear. The critical temperature gradient for the onset of turbulence increases with flow shear at low flow shears; at higher flow shears, the dependence of heat flux on temperature gradient becomes less stiff. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity.
Scientific Electronic Library Online (English)
Gaspar Manuel, Parra-Bracamonte; Ana Mara, Sifuentes-Rincn; Williams, Arellano-Vera; Juan Gabriel, Magaa-Monforte; Jos Alberto, Ramrez-De Len; Gonzalo, Velzquez.
2014-04-01
Full Text Available La suavidad de la carne bovina es un rasgo importante para la satisfaccin del consumidor y es la principal caracterstica asociada a su palatabilidad, por lo que es importante evaluar su variabilidad en diferentes razas bovinas. Un experimento fue diseado 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; adems, se realiz una evaluacin de preferencia de consumo para estimar cuantitativamente la suavidad, jugosidad, sabor, trmino y aceptacin general de los cortes evaluados. La media de la FCWB fue 5.03 kg 0.93 kg, lo que tericamente representa una carne dura. En la distribucin de las muestras se registraron 21 % y 11 % de cortes, respectivamente, de carne moderadamente suave y suave. La condicin de los animales (toros o novillos) no fue significativa para la FCWB (p > 0.5). Todas las caractersticas evaluadas en la evaluacin hednica tuvieron alrededor de 6 puntos de un total de 8 (8 era mejor). La suavidad, jugosidad y sabor mostraron una correlacin 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
Anisotropy of force distributions in sheared soft particle systems
Boberski, Jens; Shaebani, M. Reza; Wolf, Dietrich E.
2014-01-01
In this numerical study, measurements of the contact forces inside a periodic two-dimensional sheared system of soft frictional particles are reported. The distribution of normalized normal forces exhibits a gradual broadening with increasing the pure shear deformation, leading to a slower decay for large forces. The process however slows down and the distribution approaches an invariant shape at high shear deformations. By introducing the joint probability distribution in sheared configurati...
Shear viscosity for a moderately dense granular binary mixture
Garzo, Vicente; Montanero, Jose Maria
2003-01-01
The shear viscosity for a moderately dense granular binary mixture of smooth hard spheres undergoing uniform shear flow is determined. The basis for the analysis is the Enskog kinetic equation, solved first analytically by the Chapman-Enskog method up to first order in the shear rate for unforced systems as well as for systems driven by a Gaussian thermostat. As in the elastic case, practical evaluation requires a Sonine polynomial approximation. In the leading order, we determine the shear v...
Reda, Daniel C.; Wilder, Michael C.; Nixon, David (Technical Monitor)
1998-01-01
The shear-sensitive liquid crystal coating (SSLCC) method is an image-based technique for both visualizing dynamic surface-flow phenomena, such as transition and separation, and for measuring the continuous shear-stress vector distribution acting on an aerodynamic surface. Under proper lighting and viewing conditions (discussed below), the coating changes color in response to an applied aerodynamic shear. This color-change response is continuous and reversible, with a response time of milliseconds, and is a function of both the shear magnitude and the shear vector orientation relative to the observer. The liquid crystal phase of matter is a weakly-ordered, viscous, non-Newtonian fluid state that exists between the nonuniform liquid phase and the ordered solid phase of certain organic compounds. Cholesteric liquid crystal compounds possess a helical molecular arrangement that selectively scatters white light, incident along the helical axis, as a three-dimensional spectrum. This property is linked to the helical pitch length, which is within the range of wavelengths in the visible spectrum. The pitch length, and hence the wavelength of the scattered light, is influenced by shear stress normal to the helical axis. This unique optical property produces a measurable color change in response to an applied shearing force. The full-surface shear stress vector measurement method, developed at NASA-Ames, is schematically illustrated. As with the visualization method, the coated test surface is illuminated from the normal direction with white light and the camera is positioned at an above-plane view angle of approximately 30 deg. Experiments have been initiated at NASA Ames to begin the process of quantifying surface-inclination (surface-curvature) effects on shear vector measurement accuracy. In preliminary experiments, surface-inclination angles theta(sub x), theta(sub y) of 0, +/-5, +/-10, and +/-15 deg were employed. In this arrangement, white-light illumination was positioned normal to the untilted test surface, and the camera above-plane view angle was set at 30 deg relative to the untilted test surface. As can be seen, vector-aligned lambda(sub d) values showed no dependence on theta(sub x) or theta(sub y) for absolute values of these tilt angles is less than or equal to 15 deg. Acquisition and analyses of full-surface color images are presently underway to definitively document the insensitivity limits of the shear vector measurement methodology to surface-slope variations.
Seismic behavior of semi-supported steel shear walls
DEFF Research Database (Denmark)
Jahanpour, A.; Jnsson, 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...
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.
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, γ ˙ , are used to define a diffusion coefficient, D ∝ / γ ˙ , 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.
Plasticity Approach to HSC Shear Wall Design
DEFF Research Database (Denmark)
Liu, Lunying; Nielsen, Mogens Peter
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...... 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 tests cover 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....
Shear viscosity, cavitation and hydrodynamics at LHC
International Nuclear Information System (INIS)
We study evolution of quark-gluon matter in the ultrarelativistic heavy-ion collisions within the frame work of relativistic second-order viscous hydrodynamics. In particular, by using the various prescriptions of a temperature-dependent shear viscosity to the entropy ratio, we show that the hydrodynamic description of the relativistic fluid becomes invalid due to the phenomenon of cavitation. For most of the initial conditions relevant for LHC, the cavitation sets in very early stage. The cavitation in this case is entirely driven by the large values of shear viscosity. Moreover we also demonstrate that the conformal terms used in equations of the relativistic dissipative hydrodynamic can influence the cavitation time.
Influence of particle elasticity in shear testers
Kadau, D; Theuerkauf, J; Wolf, D E; Kadau, Dirk; Schwesig, Dominik; Theuerkauf, Joerg; Wolf, Dietrich E.
2005-01-01
Two dimensional simulations of non-cohesive granular matter in a biaxial shear tester are discussed. The effect of particle elasticity on the mechanical behavior is investigated using two complementary distinct element methods (DEM): Soft particle molecular dynamics simulations (Particle Flow Code, PFC) for elastic particles and contact dynamics simulations (CD) for the limit of perfectly rigid particles. As soon as the system dilates to form shear bands, it relaxes the elastic strains so that one finds the same stresses for rigid respectively elastic particles in steady state ow. The principal stresses in steady state ow are determined. They are proportional to each other, giving rise to an effective macroscopic friction coefficient which is about 10 % smaller than the microscopic friction coefficient between the grains.
Hierarchical probabilistic inference of cosmic shear
Schneider, Michael D; Marshall, Philip J; Dawson, William A; Meyers, Joshua; Bard, Deborah J; Lang, Dustin
2014-01-01
Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the glo...
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)
Thixotropy of MR shear-thickening fluids
International Nuclear Information System (INIS)
Particle sedimentation is a key issue of conventional magnetorheological (MR) fluids. We recently fabricated MR shear-thickening fluids (MRSTF), which can work as novel MR fluids without particle settling. This merit of the material against particle settling is attributed to the thixotropy property. By using shear-thickening fluids as a base medium, a series of MRSTF samples was prepared and their rheological properties were tested. It was found that when the weight fraction of the STF base is above a threshold value of 15%, the MRSTF exhibits a significant thixotropy phenomenon, which greatly reduces the settling problem of MR fluids and consequently increases the stability of MR fluids. A theoretical approach was proposed to verify the experimental studies
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...
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.
Direct measurement of shear properties of microfibers
International Nuclear Information System (INIS)
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 119, were also characterized with this system and were found to have G = 16.5 2.1 and 2.42 0.32 GPa, respectively
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.
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).
Drop impact of shear thickening liquids
Boyer, Francois; Dijksman, J Frits; Lohse, Detlef
2013-01-01
The impact of drops of concentrated non-Brownian suspensions (cornstarch and polystyrene spheres) onto a solid surface is investigated experimentally. The spreading dynamics and maxi- mal deformation of the droplet of such shear thickening liquids are found to be markedly different from the impact of Newtonian drops. A particularly striking observation is that the maximal de- formation is independent of the drop velocity and that the deformation suddenly stops during the impact phase. Both observations are due to the shear-thickening rheology of the suspensions, as is theoretically explained from a balance between the kinetic energy and the viscously-dissipated en- ergy, from which we establish a scaling relation between drop maximal deformation and rheological parameters of concentrated suspensions.
Velocity Profiles in Slowly Sheared Bubble Rafts
Lauridsen, John; Chanan, Gregory; Dennin, Michael
2004-07-01
Measurements of average velocity profiles in a bubble raft subjected to slow, steady shear demonstrate the coexistence between a flowing state and a jammed state similar to that observed for three-dimensional foams and emulsions [P. Coussot et al., Phys. Rev. Lett.PRLTAO0031-9007 88, 218301 (2002)10.1103/PhysRevLett.88.218301]. For sufficiently slow shear, the flow is generated by nonlinear topological rearrangements. We report on the connection between this short-time motion of the bubbles and the long-time averages. We find that velocity profiles for individual rearrangement events fluctuate, but a smooth, average velocity is reached after averaging over only a relatively few events.
Shear instabilities in shallow-water magnetohydrodynamics
Mak, Julian; Hughes, D W
2016-01-01
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 ...
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...
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...
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.
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.
Testing modified gravity with cosmic shear
Harnois-Draps, 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.
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
Study of Shear Viscosity of Amorphous Materials
Y. Hiki; Kobayashi, H.; Takahashi, H.
1996-01-01
Viscoelastic properties of amorphous solids deformed under uniform shear stress were studied using a kind of sandwich method with utilizing a sensitive optical technique. Time-dependent deformation data were analyzed on the basis of a mechanical model of anelasticity plus viscosity. Experiments were performed to determine the temperature dependence of viscosity for several kinds of inorganic glasses and an amorphous polymer below their glass transition temperatures. Activation energies contro...
Shear rheological characterization of motor oils
Bair, Scott; Winer, Ward O.
1988-01-01
Measurements of high pressure viscosity, traction coefficient, and EHD film thickness were performed on twelve commercial automotive engine oils, a reference oil, two unformulated base oils and two unformated base oil and polymer blends. An effective high shear rate inlet viscosity was calculated from film thickness and pressure viscosity coefficient. The difference between measured and effective viscosity is a function of the polymer type and concentration. Traction measurements did not discriminate mileage formulated oils from those not so designated.
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...
A wall-shear stress predictive model
Energy Technology Data Exchange (ETDEWEB)
Marusic, Ivan; Mathis, Romain; Hutchins, Nicholas, E-mail: imarusic@unimelb.edu.au [Department of Mechanical Engineering, University of Melbourne, Victoria 3010 (Australia)
2011-12-22
Following the approach of Marusic et al. (2010b), here we develop a predictive model for the fluctuating wall-shear stress, where the only required input is large-scale information of the streamwise velocity at a location in the outer, logarithmic region of the flow. The model consists of two components, incorporating a superposition and modulation effect of outer region motions that interact with the flow field in the viscous sublayer. The model is seen to capture Reynolds number trends reliably.
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...
Motional Effect on Wall Shear Stresses
DEFF Research Database (Denmark)
Kock, Samuel Alberg; Torben Frnd, Ernst; Yong Kim, Won
Atherosclerosis is the leading cause of death and severe disability. Wall Shear Stress (WSS), the stress exerted on vessel walls by the flowing blood is a key factor in the development of atherosclerosis. Computational Fluid Dynamics (CFD) is widely used for WSS estimations. Most CFD simulations...... are based on static models to ease computational burden leading to inaccurate estimations. The aim of this work was to estimate the effect of vessel wall deformations (expansion and bending) on WSS levels....
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.
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...
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.
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 stress, arterial identity and atherosclerosis.
Lehoux, Stephanie; Jones, Elizabeth A
2016-02-29
In the developing embryo, the vasculature first takes the form of a web-like network called the vascular plexus. Arterial and venous differentiation is subsequently guided by the specific expression of genes in the endothelial cells that provide spatial and temporal cues for development. Notch1/4, Notch ligand delta-like 4 (Dll4), and Notch downstream effectors are typically expressed in arterial cells along with EphrinB2, whereas chicken ovalbumin upstream promoter transcription factor II (COUP-TFII) and EphB4 characterise vein endothelial cells. Haemodynamic forces (blood pressure and blood flow) also contribute importantly to vascular remodelling. Early arteriovenous differentiation and local blood flow may hold the key to future inflammatory diseases. Indeed, despite the fact that atherosclerosis risk factors such as smoking, hypertension, hypercholesterolaemia, and diabetes all induce endothelial cell dysfunction throughout the vasculature, plaques develop only in arteries, and they localise essentially in vessel branch points, curvatures and bifurcations, where blood flow (and consequently shear stress) is low or oscillatory. Arterial segments exposed to high blood flow (and high laminar shear stress) tend to remain plaque-free. These observations have led many to investigate what particular properties of arterial or venous endothelial cells confer susceptibility or protection from plaque formation, and how that might interact with a particular shear stress environment. PMID:26676959
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.
A comparison between magnetic shear and flare shear in a well-observed M-class flare
International Nuclear Information System (INIS)
We give an extensive multi-wavelength analysis of an eruptive M1.0/1N class solar flare, which occurred in the active region NOAA 10044 on 2002 July 26. Our emphasis is on the relationship between magnetic shear and flare shear. Flare shear is defined as the angle formed between the line connecting the centroids of the two ribbons of the flare and the line perpendicular to the magnetic neutral line. The magnetic shear is computed from vector magnetograms observed at Big Bear Solar Observatory (BBSO), while the flare shear is computed from Transition Region and Coronal Explorer (TRACE) 1700 A images. By a detailed comparison, we find that: 1) The magnetic shear and the flare shear of this event are basically consistent, as judged from the directions of the transverse magnetic field and the line connecting the two ribbons' centroids. 2) During the period of the enhancement of magnetic shear, flare shear had a fast increase followed by a fluctuated decrease. 3) When the magnetic shear stopped its enhancement, the fluctuated decreasing behavior of the flare shear became very smooth. 4) Hard X-ray (HXR) spikes are well correlated with the unshearing peaks on the time profile of the rate of change of the flare shear. We give a discussion of the above phenomena. (invited reviews)
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.
Velocity Profiles in Shear-Banding Wormlike Micelles
Salmon, Jean-Baptiste; Colin, Annie; Manneville, Sbastien; Molino, Franois
2003-06-01
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 the complex, non-Newtonian nature of the flow in the highly sheared band.
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.
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 ...
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
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 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.
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...
Drift waves in a quadrupole with sheared field configuration
International Nuclear Information System (INIS)
We develop the linear theory of drift waves in a sheared quadrupole magnetic field configuration, with a view to applying the theory to the UMIST quadrupole GOLUX; shear can be introduced into this system by imposing a uniform longitudinal field. An eigenvalue equation is obtained, and appropriate sets of boundary conditions are proposed. The basic instability is due to the 'dissipative trapped electron' mechanism in both the simple and sheared quadrupole configurations, but the mode structure changes with shear; at sufficiently large values the mode adopts the Pearlstein-Berk (1969) form and may then be stabilized by shear damping. A novel prediction of the theory is that the 'private flux' region of the quadrupole, which without shear is completely stable, is destabilized at very small values of longitudinal field. We propose that the sheared quadrupole will form an excellent laboratory system for testing theories of drift waves developed for tokamak configurations. (Author)
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 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.
Pereira, Fabola Manhas Verbi; Bertelli Pflanzer, Srgio; Gomig, Thasa; Lugnani Gomes, Carolina; de Felcio, 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
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)
Hilton, G G; Montgomery, J L; Krehbiel, C R; Yates, D A; Hutcheson, J P; Nichols, W T; Streeter, M N; Blanton, J R; Miller, M F
2009-04-01
An experiment was conducted using 200 beef carcasses to evaluate the effects of feeding zilpaterol hydrochloride with or without monensin and tylosin on carcass cutability and meat sensory variables. The experiment was conducted using a randomized complete block design with treatments arranged as a 2 (no zilpaterol vs. zilpaterol) x 2 (monensin and tylosin withdrawn vs. monensin and tylosin fed) factorial. Cattle (n=3,757) were fed zilpaterol hydrochloride, a beta(2)-adrenergic agonist, for 30 d at the end of the finishing period and withdrawn from zilpaterol hydrochloride for the last 5 d on feed. Five carcasses (weighing between 305 and 421 kg and free of slaughter defects) were selected from each of 40 feedlot treatment pens. Strip loins from the left sides were collected for sensory analysis and Warner-Bratzler shear force (WBSF) testing, and the rib was collected for 9th, 10th, 11th-rib dissections. A subsample of 3 carcass right sides per pen was fabricated into boneless subprimals according to Institutional Meat Purchase Specifications. Carcasses from zilpaterol-fed steers had greater (P or= 0.26). For the main effect of monensin and tylosin, withdrawal of monensin and tylosin decreased (P=0.01) consumer juiciness scores, although other yield and compositional measurements were not affected (P >or= 0.07). Zilpaterol is a strong repartitioning agent that increases meat yield through increased protein and decreased fat deposition. PMID:19028853
Physicochemical Characteristics of Beef Jerky Cured with Salted-fermented Anchovy and Shrimp.
Kim, Gap-Don; Go, Gwang-Woong; Lim, Hyun-Jung; Jung, Eun-Young; Seo, Hyun-Woo; Jeong, Jin-Yeon; Joo, Seon-Tea; Yang, Han-Sul
2014-01-01
The aim of this study is to evaluate the availability of salted and fermented fish (SFF) including salted and fermented anchovy (SFA) and shrimp (SFS) as a marinade of beef jerky. In curing solutions, half (SFA 1 and SFS 1) or whole (SFA 2 and SFS 2) salt-water was replaced with SFF juices. Higher water activity (aw) was found in the beef jerky cured with SFFs than the control (C) (p< 0.05). The SFFs had the effect of causing a decrease in hardness and an increase in cohesiveness (p<0.05). Among the treatment samples, springiness was the highest in SFA2 and SFS2 (p<0.05) and the lowest values of Warner-Bratzler shear force were found in SFA1 and SFA2 (p<0.05). The SFFs also had the effect of increasing the flavor of the sensory properties; however, color measurements from both the instrumental surface color (L*, a*, b*, chroma, and hue angle) and color of sensory evaluation were decreased by addition of SFFs (p<0.05). Therefore, we conclude the SFFs can improve the texture and sensory properties of the beef jerky. In particular, the SFS is a good ingredient for the curing solution. However, studies are still needed on improving the aw, pH, and surface color of the beef jerky to apply the SFFs for making beef jerky. PMID:26760751
Directory of Open Access Journals (Sweden)
ALINA NARCISA POSTOLACHE
2014-11-01
Full Text Available This research is subscribed of an extensive project that has as main objective the production of crossbred specialized beef hybrids from reformed Romanian Black Spotted cattle's with bulls from breeds specialized for meat production (Blue Blanch Belgique, Aberdeen-Angus and Limousin. Averaged biochemical indicators analyzed showed a normal state of animal's health. The obtained half-breeds products (bulls were raised under semi-intensively conditions and slaughtered at 12 months of age. Live weight, back-fat thickness and carcass traits were significantly influenced by breed, all fat parameters being lower at this age than at standard minimum age of slaughter for meat production (18 months. Drip loss and chemical composition were similar for the breeds. The meat was lighter and pH24 values of longissimus muscle were between 5.57 and 5.64. Sensory panel tenderness and Warner-Bratzler shear force values indicated tougher meat at RBSxAA than at RBSxL1 or RBSxBBB. Differences in meat quality were probably due to the combined effects of brute chemical composition and pH dynamic during ripening. It is concluded that slaughtering steers at younger ages may require supplementary feeding, being recommended a slaughter age between 18 and 25 months old.
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.
Relationship between temperament with performance and meat quality of feedlot steers with predominantly Charolais or Nellore breed
Scientific Electronic Library Online (English)
Isabella Dias Barbosa, Silveira; Vivian, Fischer; Luis Henrique Ebling, Farinatti; Joo, Restle; Dari Celestino, Alves Filho; Lus 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.
Selani, Miriam M; Shirado, Giovanna A N; Margiotta, Gregrio B; Saldaa, Erick; Spada, Fernanda P; Piedade, Sonia M S; Contreras-Castillo, Carmen J; Canniatti-Brazaca, Solange G
2016-02-01
Pineapple byproduct and canola oil were evaluated as fat replacers on physicochemical and sensory characteristics of low-fat burgers. Five treatments were performed: conventional (CN, 20% fat) and four low-fat formulations (10% fat): control (CT), pineapple byproduct (PA), canola oil (CO), pineapple byproduct and canola oil (PC). Higher water and fat retention and lower cooking loss and diameter reduction were found in burgers with byproduct addition. In raw burgers, byproduct incorporation reduced L*, a*, and C* values, but these alterations were masked after cooking, leading to products similar to CN. Low-fat treatments were harder, chewier, and more cohesive than full-fat burgers. However, in Warner Bratzler shear measurements, PA and PC were as tender as CN. In QDA, no difference was found between CN and PC. Pineapple byproducts along with canola oil are promising fat replacers in beef burgers. In order to increase the feasibility of use of pineapple byproduct in the meat industry, alternative processes of byproduct preparation should be evaluated in future studies. PMID:26562792
Gonzlez-Rios, H; Pea-Ramos, A; Valenzuela, M; Zamorano-Garca, L; Cumplido-Barbeitia, G; Gonzlez-Mndez, 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
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 12.07 g digestible lysine/kg) were fed either with (10mg/kg) or without ractopamine (RAC) for the last 28 days of growth. Vaccination of C occurred at 16 and 20 weeks and slaughtering at 24 weeks 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
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 3109 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 -120C. 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
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.
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
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.
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
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...
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)
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)
Flow and segregation in sheared granular slurries
Barentin, C.; Azanza, E.; Pouligny, B.
2004-04-01
We study the behaviour of a granular slurry, i.e., a very concentrated suspension of heavy (denser than the fluid) and polydisperse particles sheared between two parallel-plane circular disks. For small gaps, the slurry behaves as a 2d system with a characteristic radial size segregation of particles. For large gaps, the slurry responds as a 3d system, with considerable vertical segregation and a concomitant 2-phase (fluid, solid) flow structure. The thickness ? of the fluid phase is the 2d-3d gap crossover. Surprisingly, ? is found to be nearly unaffected by very large changes in the particle size distribution.
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.
Nonequilibrium steady states in sheared binary fluids
Stansell, P.; Stratford, K.; Desplat, J. -C.; Adhikari, R.; Cates, M. E.
2005-01-01
We simulate by lattice Boltzmann the steady shearing of a binary fluid mixture undergoing phase separation with full hydrodynamics in two dimensions. Contrary to some theoretical scenarios, a dynamical steady state is attained with finite domain lengths $L_{x,y}$ in the directions ($x,y)$ of velocity and velocity gradient. Apparent scaling exponents are estimated as $L_{x}\\sim\\dot{\\gamma}^{-2/3}$ and $L_{y}\\sim\\dot{\\gamma}^{-3/4}$. We discuss the relative roles of diffusivity and hydrodynamic...
On nonlinear physics of shear Alfvn 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 Alfvn 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 Alfvnic 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.
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
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.
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.
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 $\\Omega_m^{0.7}\\sigma_8 = 0.276^{+0.036}_{-0.050}$.
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.
Transient growth in a shearing stratified atmosphere
Brandenburg, A; Brandenburg, Axel; Dintrans, Boris
2001-01-01
The stability of fully compressible isothermal shear flows is studied in response to recent claims that such flows could be locally unstable to a linear instability. The behavior of the solution is characterized by the time-dependent Rayleigh quotient, which lies between the smallest and the largest eigenvalue. The imaginary part of the Rayleigh quotient (corresponding to a growth rate) is, for different initial conditions, always found to approach zero provided the flow is Rayleigh stable (angular momentum increasing outwards). The real part (corresponding to frequency) is usually growing linearly in time, which reflects the progressive increase in wavenumber for horizontally propagating sound waves.
Pure and shear-enhanced compaction bands in Aztec Sandstone
Eichhubl, Peter; Hooker, John N.; Laubach, Stephen E.
2010-12-01
We report on the occurrence of deformation bands in Jurassic eolian Aztec Sandstone at Valley of Fire, Nevada, that accommodated roughly equal amounts of shear and band-perpendicular compaction by grain rearrangement and porosity collapse. These bands, referred to as shear-enhanced compaction bands, differ in orientation, structural arrangement, and microtexture from pure compaction bands that form perpendicular to the shortening direction. Shear-enhanced compaction bands are planar over tens of meters, and commonly composed of multiple parallel thinner strands. Pure compaction bands are less commonly planar, typically wavy or chevron in geometry, and composed of single strands. Shear-enhanced compaction bands are inferred to form at 38-53 relative to the maximum compressive principal stress, and thus differ from compactive shear bands that form at distinctly lower angles. While shear offsets along shear-enhanced compaction bands are only about 1/10th of the band thickness, by contrast, shear offsets may be large for compactive shear bands with formation of slip surfaces. Based on inferred timing and burial conditions, we interpret that the formation of shear-enhanced and pure compaction bands requires large initial porosity close to the loose packing porosity, good sorting, and high effective maximum compressive principal stress of about 20 MPa.
Lin, Neil Y. C.
2013-12-01
Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large-amplitude oscillatory shear. Using the particle positions, we quantify the in situ anisotropy of the pair-correlation function, a measure of the Brownian stress. From these data we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small-amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations. 2013 American Physical Society.
Reynolds stress and shear flow generation
International Nuclear Information System (INIS)
The so-called Reynolds stress may give a measure of the self-consistent flow generation in turbulent fluids and plasmas by the small-scale turbulent fluctuations. A measurement of the Reynolds stress can thus help to predict flows, e.g. shear flows in plasmas. This may assist the understanding of improved confinement scenarios such as H-mode confinement regimes. However, the determination of the Reynolds stress requires measurements of the plasma potential, a task that is difficult in general and nearly impossible in hot plasmas in large devices. In this work we investigate an alternative method, based on density measurements, to estimate the Reynolds stress, and demonstrate the validity range of this quantity, which we term the pseudo-Reynolds stress. The advantage of such a quantity is that accurate measurements of density fluctuations are much easier to obtain experimentally. Prior to the treatment of the pseudo-Reynolds stress, we present analytical and numerical results which demonstrate that the Reynolds stress in a plasma, indeed, generates a poloidal shear flow. The numerical simulations are performed both in a drift wave turbulence regime and a resistive interchange turbulence regime. Finally, the implications of misaligned probe arrays on the determination of Reynolds stresses are investigated, and alignment is found to be important but not severe. (author)
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.
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.)
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
Cosmic Shear - with ACS Pure Parallel Observations
Ratnatunga, Kavan
2002-07-01
The ACS, with greater sensitivity and sky coverage, will extend our ability to measure the weak gravitational lensing of galaxy images caused by the large scale distribution of dark matter. We propose to use the ACS in pure parallel {non- proprietary} mode, following the guidelines of the ACS Default Pure Parallel Program. Using the HST Medium Deep Survey WFPC2 database we have measured cosmic shear at arc-min angular scales. The MDS image parameters, in particular the galaxy orientations and axis ratios, are such that any residual corrections due to errors in the PSF or jitter are much smaller than the measured signal. This situation is in stark contrast with ground-based observations. We have also developed a statistical analysis procedure to derive unbiased estimates of cosmic shear from a large number of fields, each of which has a very small number of galaxies. We have therefore set the stage for measurements with the ACS at fainter apparent magnitudes and smaller, 10 arc-second scales corresponding to larger cosmological distances. We will adapt existing MDS WFPC2 maximum likelihood galaxy image analysis algorithms to work with the ACS. The analysis would also yield an online database similar to that in archive.stsci.edu/mds/
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
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.
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.
Shear-induced instabilities in layered liquids
Auernhammer, Gnter 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.
Sheares? Method of Vaginoplasty - Our Experience
Directory of Open Access Journals (Sweden)
Somajita Chakrabarty
2011-01-01
Full Text Available Introduction: The Mayer-Rokitansky-Kuster-Hauser (MRKH syndrome is one of the most common causes of primary amenorrhoea and is associated with vaginal atresia and absent uterus despite the presence of normal ovaries and external genitalia. Various techniques have been used, with many disadvantages, to create a neovagina. Aims and Objectives: Our aim is to create a neovagina with a simple and safe method. Materials and Methods: We have operated 18 cases of MRKH syndrome with the Sheares? method of vaginoplasty, in which the space between the two labia is dilated with a Hegar?s dilator along the vestigial Mullerian ducts. Thus, two tunnels are created and the central septum is excised to form a single vagina. A mould covered with amnion is placed in the neovagina. All cases are followed up for six months. They have all had a good length of vagina with regular manual dilatation. Conclusions: The Sheares? method of vaginoplasty is an easy and safe method to create a neovagina with least complications, like injury to urinary bladder, rectum or bleeding.
Shear and shear friction of ultra-high performance concrete bridge girders
Crane, Charles Kennan
Ultra-High Performance Concrete (UHPC) is a new class of concrete characterized by no coarse aggregate, steel fiber reinforcement, low w/c, low permeability, compressive strength exceeding 29,000 psi (200 MPa), tensile strength ranging from 1,200 to 2,500 psi (8 to 17 MPa), and very high toughness. These properties make prestressed precast UHPC bridge girders a very attractive replacement material for steel bridge girders, particularly when site demands require a comparable beam depth to steel and a 100+ year life span is desired. In order to efficiently utilize UHPC in bridge construction, it is necessary to create new design recommendations for its use. The interface between precast UHPC girder and cast-in-place concrete decks must be characterized in order to safely use composite design methods with this new material. Due to the lack of reinforcing bars, all shear forces in UHPC girders have to be carried by the concrete and steel fibers. Current U.S. codes do not consider fiber reinforcement in calculating shear capacity. Fiber contribution must be accurately accounted for in shear equations in order to use UHPC. Casting of UHPC may cause fibers to orient in the direction of casting. If fibers are preferentially oriented, physical properties of the concrete may also become anisotropic, which must be considered in design. The current research provides new understanding of shear and shear friction phenomena in UHPC including: (1) Current AASHTO codes provide a non-conservative estimate of interface shear performance of smooth UHPC interfaces with and without interface steel. (2) Fluted interfaces can be created by impressing formliners into the surface of plastic UHPC. AASHTO and ACI codes for roughened interfaces are conservative for design of fluted UHPC interfaces.(3) A new equation for the calculation of shear capacity of UHPC girders is presented which takes into account the contribution of steel fiber reinforcement. (4) Fibers are shown to preferentially align in the direction of casting, which significantly affects compressive behavior of the UHPC.
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.
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; Kertsz, 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.
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 rheology of lipid monolayers and insights on membrane fluidity
Espinosa, Gabriel; Lpez-Montero, Ivn; 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 knowledge is still lacking as measurements of membrane shear properties have remained incomplete so far. In the present contribution we report a surface shear rheology study of different lipid monolayers that model distinct biologically relevant situations. The results evidence a large variety of mechanical behavior under lateral shear flow. PMID:21444777
Understanding critical levels of sheared flow on microinstabilities
Newton, Sarah L; Loureiro, Nuno F
2010-01-01
The competition between the drive and stabilization of plasma microinstabilities by sheared flow is investigated, focusing on the ion temperature gradient mode. Using a twisting mode representation in sheared slab geometry, the characteristic equations have been formulated for a dissipative fluid model, developed rigorously from the gyrokinetic equation. They clearly show that perpendicular flow shear convects perturbations along the field at a speed we denote by $Mc_s$ (where $c_s$ is the sound speed), whilst parallel flow shear enters as an instability driving term analogous to the usual temperature and density gradient effects. For sufficiently strong perpendicular flow shear, $M >1$, the propagation of the system characteristics is unidirectional and no unstable eigenmodes may form. Perturbations are swept along the field, to be ultimately dissipated as they are sheared ever more strongly. Numerical studies of the equations also reveal the existence of stable regions when $M < 1$, where the driving ter...
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.
Transport Bifurcation Induced by Sheared Toroidal Flow in Tokamak Plasmas
Highcock, E G; Parra, F I; Schekochihin, A A; Roach, C M; Cowley, S C
2011-01-01
First-principles numerical simulations are used to describe a transport bifurcation in a differentially rotating tokamak plasma. Such a bifurcation is more probable in a region of zero magnetic shear, where the component of the sheared toroidal flow that is perpendicular to the magnetic field has the strongest suppressing effect on the turbulence, than one of finite magnetic shear. Where the magnetic shear is zero, there are no growing linear eigenmodes at any finite value of flow shear. However, subcritical turbulence can be sustained, owing to the transient growth of modes driven by the ion temperature gradient (ITG) and the parallel velocity gradient (PVG). Nonetheless, in a parameter space containing a wide range of temperature gradients and velocity shears, there is a sizeable window where all turbulence is suppressed. Combined with the relatively low transport of momentum by collisional (neoclassical) mechanisms, this produces the conditions for a bifurcation from low to high temperature and velocity gr...
The dynamics of internal transport barrier formation in reverse shear and weak shear discharges
International Nuclear Information System (INIS)
The experimental regime with reversed central magnetic shear and a coincident enhanced confinement region has opened an operating window which provides the confinement benefits of VH-mode discharges without the difficulties of coupling to the edge physics. A theoretical challenge is to model the dynamics of the transition to the enhanced confinement regime. This requires incorporating the linear effects of the reversed shear profiles in a nonlinear model to capture the bifurcation dynamics. A simple first principles model incorporating the nonlinear coupling between the turbulent fluctuations and the sheared radial electric field is used to investigate the dynamics of the transition to an enhanced confinement mode in the reversed shear/weak shear discharges. From this simple version of the model it is found that by incorporating both growth rate profiles and particle/power deposition profiles a rich variety of transition dynamics exist. The power threshold for the transition is found to depend on the local growth rate and the local gradient in the deposition profile. The size of the enhanced confinement region is predicted to depend on the growth rate profile and the total deposition inside the reversal region. The transition itself can take the form of a propagating front like transition. After the transition the transport in the enhanced regime is neoclassical with the performance limits determined by MHD stability which is not included in the model presented. The simple model can predict the evolution of the transition, scaling of the threshold levels and the optimal deposition profiles. In order to allow an increasingly reasonable investigation of power thresholds and hysteresis effects a more complete transport model is needed. This transport model is coupled to the simple dynamical model allowing the transition dynamics to be self-consistently evolved
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...
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 ...
Dissipative instabilities of magnetic neutral layers with velocity shear
International Nuclear Information System (INIS)
The general problem of instability of magnetic neutral sheets in the presence of velocity shear is considered. Both resistivity and viscosity are included in the treatment. It is shown that velocity shear and/or viscosity introduce different orderings with respect to resistive tearing modes and that the classical tearing modes represent a singular case. Possible orderings for growth rates are discussed and a specific example containing the effect of velocity shear is treated in detail. (author)
Shear-Sensitive Monomer/Polymer Liquid Crystal System
Singh, Jag J.; Eftekhari, Abe; Parmar, D. S.
1993-01-01
Report describes preliminary investigation of new monomer/polymer liquid crystal system, thin film of shear-sensitive cholesteric monomer liquid crystal (TI 511) on Xydar (STR800) (or equivalent) liquid crystal polymer substrate. Monomer/polymer liquid crystal films applied to surfaces provide quantitative indications of shear stresses caused by winds blowing along surfaces. Effects of shear stresses reversible in new coating system. System provides quantitative data on flows in wind tunnels.
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.
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 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...
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.
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.
Nonhelical mean-field dynamos in a sheared turbulence
I. Rogachevskii; Kleeorin, N.
2008-01-01
Mechanisms of nonhelical large-scale dynamos (shear-current dynamo and effect of homogeneous kinetic helicity fluctuations with zero mean) in a homogeneous turbulence with large-scale shear are discussed. We have found that the shear-current dynamo can act even in random flows with small Reynolds numbers. However, in this case mean-field dynamo requires small magnetic Prandtl numbers (i.e., ${\\rm Pm} < {\\rm Pm}^{\\rm cr}
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...
Shear rheology of lipid monolayers and insights on membrane fluidity
Espinosa, Gabriel; Lpez-Montero, Ivn; 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...
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...
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)
Shear viscosity and spectral function of the quark matter
Iwasaki, Masaharu; Ohnishi, Hiromasa; Fukutome, Takahiko
2006-01-01
We discuss the shear viscosity of the quark matter by using the Kubo-Mori formula. It is found that the shear viscosity is expressed in terms of the quark spectral function. If the spectral function is approximated by a modified Bright-Wigner type, the viscosity decreases as the width of the spectral function increases. We also discuss dependence of the shear viscosity on the temperature and the density.
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
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...
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...
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 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-Induced Collapse in a Lyotropic Lamellar Phase
Porcar, L.; Warr, G. G.; Hamilton, W. A.; Butler, P. D.
2005-08-01
An entropically stabilized cetylpyridinium chloride, hexanol, and heavy brine lyotropic lamellar phase subjected to shear flow has been observed here by small angle neutron scattering to undergo collapse of smectic order above a threshold shear rate. The results are compared with theories predicting that such a lamellar phase sheared above a critical rate should lose its stability by a loss of resistance to compression due to the suppression of membrane fluctuations.
Shear-Induced Collapse in a Lyotropic Lamellar Phase
International Nuclear Information System (INIS)
An entropically stabilized cetylpyridinium chloride, hexanol, and heavy brine lyotropic lamellar phase subjected to shear flow has been observed here by small angle neutron scattering to undergo collapse of smectic order above a threshold shear rate. The results are compared with theories predicting that such a lamellar phase sheared above a critical rate should lose its stability by a loss of resistance to compression due to the suppression of membrane fluctuations
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 ...
Shear Viscosity of a Superfluid Dipolar Gas at Low Temperatures
M. Khademi Dehkordi
2014-01-01
We compute the shear viscosity of superfluid Bose and Fermi gases on the base of Boltzmann equation and relaxation times. We show that, in the low temperature limit, the shear viscosities of Bose and Fermi gases are proportional to T-1evp0/T and T-4, respectively. For the superfluid Bose gas at low temperature limit, only splitting processes contribute to the shear viscosity.
Lee, Ji-Seok; Song, Ki-Won
2015-11-01
The objective of the present study is to systematically elucidate the time-dependent rheological behavior of concentrated xanthan gum systems in complicated step-shear flow fields. Using a strain-controlled rheometer (ARES), step-shear flow behaviors of a concentrated xanthan gum model solution have been experimentally investigated in interrupted shear flow fields with a various combination of different shear rates, shearing times and rest times, and step-incremental and step-reductional shear flow fields with various shearing times. The main findings obtained from this study are summarized as follows. (i) In interrupted shear flow fields, the shear stress is sharply increased until reaching the maximum stress at an initial stage of shearing times, and then a stress decay towards a steady state is observed as the shearing time is increased in both start-up shear flow fields. The shear stress is suddenly decreased immediately after the imposed shear rate is stopped, and then slowly decayed during the period of a rest time. (ii) As an increase in rest time, the difference in the maximum stress values between the two start-up shear flow fields is decreased whereas the shearing time exerts a slight influence on this behavior. (iii) In step-incremental shear flow fields, after passing through the maximum stress, structural destruction causes a stress decay behavior towards a steady state as an increase in shearing time in each step shear flow region. The time needed to reach the maximum stress value is shortened as an increase in step-increased shear rate. (iv) In step-reductional shear flow fields, after passing through the minimum stress, structural recovery induces a stress growth behavior towards an equilibrium state as an increase in shearing time in each step shear flow region. The time needed to reach the minimum stress value is lengthened as a decrease in step-decreased shear rate.
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
Nonlinear Brownian dynamics of interfacial fluctuations in a shear flow
International Nuclear Information System (INIS)
Using Brownian dynamics simulations, we investigate the effect of an external flow on the fluctuations of a liquid–liquid interface for a wide range of shear rates. Although the statistics is Gaussian at low shear, we observe a transition to a nonlinear phenomenology above a critical shear rate. In particular, we show that statistical properties at high forcing share striking similarities with Burgers turbulence. An energy criterion allows us to predict the onset of non-Gaussian statistics. It also provides a simple explanation for the development of shock singularities through the exchange of kinetic energy from regions with positive to negative gradients in the shear direction. (paper)
Shear tests for characterization of bituminous mixtures stiffness
Pereira, Paulo A. A.; Pais, Jorge C.; Azevedo, M. C. M.
1997-01-01
This paper presents the results of a study where the shear stiffness and the shear phase angle of bituminous mixtures, with two different air-void contents and three different bitumen contents were measured using shear strain controlled tests. The shear tests were carried out at three temperatures, 4, 20 and 40 C, and 10, 5, 2, 1, 0.5, 0.2 and 0.1 Hz frequencies were used, in agreement with SHRP M-003 specification. The specified strain level of 0.0001 mm/mm was used beside two more strain l...
Diagonal Cracking and Shear Strength of Reinforced Concrete Beams
DEFF Research Database (Denmark)
Zhang, Jin-Ping
1997-01-01
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......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...
Re-entrant phenomena in a lamellar phase under shear
International Nuclear Information System (INIS)
The influence of shear on an defective lamellar phase of the ternary mixture sodium dodecyl sulphate/decanol/D2O was studied using small-angle neutron scattering at D11. Shear-flow leads to an alignment of lamellae along the flow direction but we found, in addition, a re-orientation of the layer normal at increasing shear-rates from perpendicular to the velocity gradient direction to parallel to it. This behaviour could be interesting for industrial engineering of layered systems because shear deformation is involved in the processing of such materials. (authors)
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 behavior of reinforced Engineered Cementitious Composites (ECC) beams
DEFF Research Database (Denmark)
Paegle, Ieva; Fischer, Gregor
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...
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.
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.
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
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
Simple average expression for shear-stress relaxation modulus
Wittmer, J. P.; Xu, H.; Baschnagel, J.
2016-01-01
Focusing on isotropic elastic networks we propose a simple-average expression G (t ) =?A-h (t ) for the computational determination of the shear-stress relaxation modulus G (t ) of a classical elastic solid or fluid. Here, ?A=G (0 ) characterizes the shear transformation of the system at t =0 and h (t ) the (rescaled) mean-square displacement of the instantaneous shear stress ? ?(t ) as a function of time t . We discuss sampling time and ensemble effects and emphasize possible pitfalls of alternative expressions using the shear-stress autocorrelation function. We argue finally that our key relation may be readily adapted for more general linear response functions.
Morphologies of three-dimensional shear bands in granular media
Fazekas, S; Kertsz, 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 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
Helfenstein-Didier, C.; Andrade, R. J.; Brum, J.; Hug, F.; Tanter, M.; Nordez, A.; Gennisson, J.-L.
2016-03-01
The shear wave velocity dispersion was analyzed in the Achilles tendon (AT) during passive dorsiflexion using a phase velocity method in order to obtain the tendon shear modulus (C 55). Based on this analysis, the aims of the present study were (i) to assess the reproducibility of the shear modulus for different ankle angles, (ii) to assess the effect of the probe locations, and (iii) to compare results with elasticity values obtained with the supersonic shear imaging (SSI) technique. The AT shear modulus (C 55) consistently increased with the ankle dorsiflexion (N = 10, p wave elastography technique (SSI technique) can be used to compare tendon mechanical properties across populations. Future studies should determine the clinical relevance of the shear wave dispersion analysis, for instance in the case of tendinopathy or tendon tear.
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...
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...
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.
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.
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.
Near-surface shear layer dynamics
Brandenburg, A
2007-01-01
The outer surface layers of the sun show a clear deceleration at low latitudes. This is generally thought to be the result of a strong dominance of vertical turbulent motions associated with strong downdrafts. This strong negative radial shear should not only contribute to amplifying the toroidal field locally and to expelling magnetic helicity, but it may also be responsible for producing a strong prograde pattern speed in the supergranulation layer. Using simulations of rotating stratified convection in cartesian boxes located at low latitudes around the equator it is shown that in the surface layers patterns move in the prograde direction on top of a retrograde mean background flow. These patterns may also be associated with magnetic tracers and even sunspot proper motions that are known to be prograde relative to the much slower surface plasma.
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
Machalick, K.; Hor?i?kov, I.; Eliov, 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.
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.
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.
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
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
Unsteady distributed wall shear stress measurements in fluid flows
Gnanamanickam, Ebenezer P.
Wall-bounded flows are amongst the most common flows encountered in fluid mechanics. Wall shear stress on the walls of these flow fields is an important engineering quantity as it is responsible for skin friction drag, which is a significant portion of the drag on bodies ranging from airplanes to flow in biological systems. Measuring, understanding and eventually controlling the wall shear stress has implicit financial significance. In general there is limited literature reporting unsteady, distributed wall shear stress measurements, especially in air, due to the lack of sensors to carry out such measurements. This work is a small step in the direction of filling this gap in the literature. A wall shear stress sensor, referred to as the micro-pillar wall shear stress sensor is presented from concept to actual measurements in a wall jet flow field. The micro-pillar shear stress sensor is based on the principle that a micro-pillar on the wall of a wall-bounded flow deflects an amount proportional to the drag force experienced by it. This drag force in turn is proportional to the wall shear stress. Hence, tracking the tip deflection of an array of micro-pillars provides a means to measure the unsteady, distributed wall shear stress. The sensor from design to manufacture along with static and dynamic characterization is presented. It's ability to measure unsteady, distributed wall shear stress is studied using demonstrative experiments. Finally, wall shear stress measurements are carried out on the wall of a three-dimensional turbulent wall jet. The wall jet is subsequently excited and the effect of excitation on the wall shear stress in the near jet exit flow field is studied.
Shear degradation in fiber reinforced laminates due to matrix damage
Salavatian, Mohammedmahdi
The objective of this study was to develop and implement a shear modulus degradation model to improve the failure analysis of the fiber reinforced composite structures. Matrix damage, involving transverse and shear cracks, is a common failure mode for composite structures, yet little is known concerning their interaction. To understand the material behavior after matrix failure, the nonlinear response of the composite laminate was studied using pressure vessels made from a [+/-o] bias orientation, which tend to exhibit a matrix dominated failure. The result of this work showed laminate matrix hardening in shear and softening in the transverse direction. A modified Iosipescu coupon was proposed to study the evolution of shear and transverse damage and their mutual effects. The proposed method showed good agreement with tubular results and has advantages of simplified specimen fabrication using standard test fixtures. The proposed method was extended by introducing a novel experimental technique to study the shear degradation model under biaxial loading. Experimental results of the transverse modulus reduction were in good agreement with material degradation models, while the predicted shear modulus reduction was higher than experiment. The discrepancy between available models and observations was due to the presence of a traction between the crack surfaces. Accordingly, a closed form solution was proposed for the shear stress-strain field of a cracked laminate by replacing the cracks with cohesive zones. The constitutive equations of the crack laminate were derived including the effects of internal tractions and transverse stress on the shear modulus. The proposed analytical model was shown to be the most comprehensive model for shear modulus degradation reduction of the fiber reinforced laminates. A numerical implementation of the shear degradation model was done using continuum damage mechanics. Through this work it was shown the common assumption of a linear relation between matrix damage variables do not sufficiently describe shear response. Therefore, a modified damage model for matrix failure was developed and implemented in ABAQUS using a UMAT subroutine.
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
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.
Strengthening of flat slabs against punching shear using post-installed shear reinforcement
Fernndez 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...
Dimensionless critical shear stress in gravel-bed rivers
Petit, Franois; Houbrechts, Geoffrey; Peeters, Alexandre; Hallot, Eric; Van Campenhout, Jean; Denis, Anne-Ccile
2015-12-01
This paper first compiles critical shear stress values from 26 studies of gravel-bed rivers (GBRs) worldwide. The most frequently proposed value of the Shields criterion (?c) is 0.045, but three major groups with ?c values ranging from 0.100 were identified. Second, dimensionless critical shear stresses (the Shields criterion) were evaluated for 14 GBRs (18 sites) with watershed areas ranging from 12 to 3000 km2. Different approaches were used to identify the initial movement of the bed material: painted and PIT-tag pebbles, sediment traps, and bedload samplers. The Shields criterion (?c) was estimated using the total shear stress (?) and the grain shear stress (??). Several shear stresses were also estimated using shear velocities. For bedload transport, we obtained an average Shields criterion (?c) of 0.040. The values were higher in small rivers (> 0.050) than larger rivers (< 0.030) because of more significant bedform shear stresses. The Shields criterion (??c) was lower when the grain shear stress (??) was used and only reached 0.019. Different values are also proposed in relation to the type of mobilization: the ?c value for partial transport was ~ 0.025 and exceeded 0.040 for full transport (usually reached in association with discharges with a 10-year return period). The values based on the results of sediment traps and a bedload sampler were greater than those obtained using tracers, but these differences are smaller than those usually reported in the literature.
Micromechanics of sea ice gouge in shear zones
Sammonds, Peter; Scourfield, Sally; Lishman, Ben
2015-04-01
The deformation of sea ice is a key control on the Arctic Ocean dynamics. Shear displacement on all scales is an important deformation process in the sea cover. Shear deformation is a dominant mechanism from the scale of basin-scale shear lineaments, through floe-floe interaction and block sliding in ice ridges through to the micro-scale mechanics. Shear deformation will not only depend on the speed of movement of ice surfaces but also the degree that the surfaces have bonded during thermal consolidation and compaction. Recent observations made during fieldwork in the Barents Sea show that shear produces a gouge similar to a fault gouge in a shear zone in the crust. A range of sizes of gouge are exhibited. The consolidation of these fragments has a profound influence on the shear strength and the rate of the processes involved. We review experimental results in sea ice mechanics from mid-scale experiments, conducted in the Hamburg model ship ice tank, simulating sea ice floe motion and interaction and compare these with laboratory experiments on ice friction done in direct shear, and upscale to field measurement of sea ice friction and gouge deformation made during experiments off Svalbard. We find that consolidation, fragmentation and bridging play important roles in the overall dynamics and fit the model of Sammis and Ben-Zion, developed for understanding the micro-mechanics of rock fault gouge, to the sea ice problem.
Constant rate shearing on two dimensional cohesive disks
Olivi-Tran, N; Fraysse, N
2005-01-01
We performed two-dimensional Molecular Dynamics simulations of cohesive disks under shear. The cohesion between the disks is added by the action of springs between very next neighbouring disks, modelling capillary forces. The geometry of the cell allows disk-disk shearing and not disk-cell wall shearing as it is commonly found in literature. Does a stick-slip phenomenon happen though the upper cover moves at a constant velocity, i.e. with an infinite shearing force? We measured the forces acted by the disks on the upper cover for different shearing rates, as well as the disk velocities as a function of the distance to the bottom of the cell. It appears that the forces measured versus time present a periodic behavior,very close to a stick slip phenomenon, for shearing rates larger than a given threshold. The disks' collective displacements in the shearing cell (back and ahead) is the counterpart of the constant velocity of the upper cover leading to a periodic behavior of the shear stress.
Constant rate shearing on two-dimensional cohesive discs
International Nuclear Information System (INIS)
We performed two-dimensional molecular dynamics simulations of cohesive discs under shear. The cohesion between the discs is added by the action of springs between very next neighbouring discs, modelling capillary forces. The geometry of the cell allows disc-disc shearing and not disc-cell wall shearing as is commonly found in the literature. Does a stick-slip phenomenon happen though the upper cover moves at a constant velocity, i.e. with an infinite shearing force? We measured the forces with which the discs acted on the upper cover for different shearing rates, as well as the disc velocities as a function of the distance to the bottom of the cell. It appears that the forces measured versus time present a periodic behaviour, very close to a stick-slip phenomenon, for shearing rates larger than a given threshold. The discs' collective displacements in the shearing cell (back and ahead) are the counterpart of the constant velocity of the upper cover, leading to a periodic behaviour of the shear stress
Rotation shear induced fluctuation decorrelation in a toroidal plasma
International Nuclear Information System (INIS)
The enhanced decorrelation of fluctuations by the combined effects of the E x B flow (VE) shear, the parallel flow (Vparallel) shear, and the magnetic shear is studied in toroidal geometry. A two-point nonlinear analysis previously utilized in a cylindrical model shows that the reduction of the radial correlation length below its ambient turbulence value (?r0) is characterized by the ratio between the shearing rate ?s and the ambient turbulence scattering rate ??T. The derived shearing rate is given by ?s2 = (?r0)2[1/??2{?/?r(qVE/r)}2 + 1/??2{?/?r(V parallel/qR)}2], where ?? and ?? are the correlation angles of the ambient turbulence along the toroidal and parallel directions. This result deviates significantly from the cylindrical result for high magnetic shear or for ballooning-like fluctuations. For suppression of flute-like fluctuations, only the radial shear of qVE/r contributes, and the radial shear of V parallel/qR is irrelevant regardless of the plasma rotation direction
Midbroken Reinforced Concrete Shear Frames Due to Earthquakes
DEFF Research Database (Denmark)
Kyloglu, H. U.; Cakmak, A. S.; Nielsen, Sren R. K.
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...
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.
Domino boudinage under layer-parallel simple shear
Dabrowski, Marcin; Grasemann, Bernhard
2014-11-01
The boudin segments of a torn competent layer experience synthetic rotation in layer-parallel simple shear. As long as the individual segments in a boudin train are constrained by their neighbors, even a highly viscous boudin deforms internally to create the necessary space for rotation. The rotation rate is then much smaller compared to the case of an isolated segment. Hence, a small tilt of boudin segments is not indicative of low strain. The rotation rate at this stage largely depends on the aspect ratio of the boudin segments and the scaled gap width. Once the tilted boudins are no longer constrained by their neighbors, the rotation rate greatly accelerates. In the case of a low viscosity ratio between the boudins and the host, the boudin segments develop complex shapes, which may give an impression of shear-band boudins forming under the opposite shear sense. We furthermore investigate the behavior of boudin trains of finite length. The terminal segments are displaced out of the shear plane, deforming into isoclinal folds, and separate into groups of boudin segments that rotate into the shear direction and eventually lead to an overall chaotic appearance of the structure. Natural examples of domino boudinage from a high shear -strain detachment zone in the Western Cyclades (Greece) show many similarities with the modeled structures suggesting that, under simple shear deformation, the rotation and separation of boudin segments is an indicator for high shear strain.
Cold versus hot shear banding in bulk metallic glass
Cheng, Y. Q.; Han, Z.; Li, Y.; Ma, E.
2009-10-01
We present an analysis of the shear-banding dynamics in a bulk metallic glass (BMG), including the temperature rise in the band, the sliding speed of the band, and the time elapsed as well as the step size of the shear offset growth in a stop-and-go cycle. This model analysis quantitatively demonstrates that the major shear band can remain cold and slide in a stick-slip manner. We predict that the shear step (distance covered by a stop-and-go cycle) scales with the sample size and machine stiffness. We also illustrate the conditions when such serrated shear is unsustainable and a hot shear band directly develops in a runaway instability (catastrophe). These findings provide physical insight into the shear-instability processes and offer useful information for improving the plasticity of BMGs. The calculation results are used to explain several intriguing recent experimental observations, including the stick slip of the dominant shear-band and the sample-size effects on the plastic-flow behavior of BMGs.
Effect of linear shear flow on interchange modes
Energy Technology Data Exchange (ETDEWEB)
Tatsuno, T.; Volponi, F.; Yoshida, Z. [Graduate School of Frontier Sciences, Tokyo Univ., Tokyo (Japan)
2000-06-01
Effect of the linear shear flow on linear interchange modes in incompressible neutral fluid, and linear two-dimensional electromagnetic interchange instabilities in incompressible plasmas are investigated. Although the transient growth may occur in a short period, background shear flow overcomes the interchange instability and makes it damped away in a long term due to phase mixing. (author)
Effect of linear shear flow on interchange modes
International Nuclear Information System (INIS)
Effect of the linear shear flow on linear interchange modes in incompressible neutral fluid, and linear two-dimensional electromagnetic interchange instabilities in incompressible plasmas are investigated. Although the transient growth may occur in a short period, background shear flow overcomes the interchange instability and makes it damped away in a long term due to phase mixing. (author)
Conductivity measurements in a shear-banding wormlike micellar system
Photinos, Panos J.; Lpez-Gonzlez, M. R.; Hoven, Corey V.; Callaghan, Paul T.
2010-07-01
Shear banding in the cetylpyridinium chloride/sodium salicylate micellar system is investigated using electrical conductivity measurements parallel to the velocity and parallel to the vorticity in a cylindrical Couette cell. The measurements show that the conductivity parallel to the velocity (vorticity) increases (decreases) monotonically with applied shear rate. The shear-induced anisotropy is over one order of magnitude lower than the anisotropy of the Nc nematic phase. The steady-state conductivity measurements indicate that the anisotropy of the shear induced low-viscosity (high shear rate) phase is not significantly larger than the anisotropy of the high viscosity (low shear rate) phase. We estimate that the micelles in the shear induced low viscosity band are relatively short, with a characteristic length to diameter ratio of 5-15. The relaxation behavior following the onset of shear is markedly different above and below the first critical value ??1 , in agreement with results obtained by other methods. The transient measurements show that the overall anisotropy of the sample decreases as the steady state is approached, i.e., the micellar length/the degree of order decrease.
Kamal, A.; Giurgiutiu, V.
2014-08-01
This article discusses shear horizontal (SH) guided-waves that can be excited with shear type piezoelectric wafer active sensor (SH-PWAS). The paper starts with a review of state of the art SH waves modelling and their importance in non-destructive evaluation (NDE) and structural health monitoring (SHM). The basic piezoelectric sensing and actuation equations for the case of shear horizontal piezoelectric wafer active sensor (SH-PWAS) with electro-mechanical coupling coefficient {{d}_{35}} are reviewed. Multiphysics finite element modelling (MP-FEM) was performed on a free SH-PWAS to show its resonance modeshapes. The actuation mechanism of the SH-PWAS is predicted by MP-FEM, and modeshapes of excited structure are presented. The structural resonances are compared with experimental measurements and showed good agreement. Analytical prediction of SH waves was performed. SH wave propagation experimental study was conducted between different combinations of SH-PWAS and regular in-plane PWAS transducers. Experimental results were compared with analytical predictions for aluminium plates and showed good agreement. 2D wave propagation effects were studied by MP-FEM. An analytical model was developed for SH wave power and energy. The normal mode expansion (NME) method was used to account for superpositioning multimodal SH waves. Modal participation factors were presented to show the contribution of every mode. Power and energy transfer between SH-PWAS and the structure was analyzed. Finally, we present simulations of our developed wave power and energy analytical models.
Shear Stress Measurements of Non-Spherical Particles in High Shear Rate Flows
Koos, Erin; Hunt, Melany L.; Brennen, Christopher E.
2007-11-01
The behavior of liquid-solid flows varies greatly depending on fluid viscosity, particle and liquid inertia, and collisions and near-collisions between particles. An initial investigation by Bagnold found two different flow regimes [1]. In an examination of that work, Hunt et al. found that Bagnold's experiments were marred by secondary flows in the fluid [2]. The current experiment addresses this rheology further. Shear stress measurements used a coaxial rheometer with a height to gap ratio (h/b) of 11.7 and gap to outer radius ratio (b/ro) of 0.166 that was specially designed to minimize effects of secondary flows. Experiments were performed for a range of Reynolds numbers, solid fractions and ratio of particle to fluid densities. With neutrally buoyant particles, the dimensional shear stress exhibits a linear dependence on Reynolds Number: the slope is monotonic but a non-linear function of the solid fraction. Though non-neutrally buoyant particles exhibit a similar linear dependence at higher Reynolds numbers, at lower values the shear stress exhibits a non-linear behavior in which the stress increases with decreasing Reynolds number due to particle settling. [1] R.A. Bagnold, Proc. R. Soc. Lond. Ser. A, 225, p.49 (1954). [2] M.L. Hunt etc., J. Fluid Mech., 452, p.1 (2002).
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.
The Skin Acts to Maintain Muscle Shear Modulus.
Yoshitake, Yasuhide; Miyamoto, Naokazu; Taniguchi, Keigo; Katayose, Masaki; Kanehisa, Hiroaki
2016-03-01
It is not clear how the tissues covering the skeletal muscles affect the muscles' mechanical properties. The main purpose of this study was to examine changes in muscle shear modulus as a representative mechanical property of muscle with and without the covering tissues of skin and epimysium (fascia). Shear modulus of the medial gastrocnemius (MG) muscle was determined using ultrasound shear-wave elastography in the Thiel's embalmed cadavers under three different conditions: original (intact cadavers), removal of the skin on the MG and subsequent removal of the epimysium. Muscle shear modulus significantly decreased by 50% after removal of the skin, whereas no additional changes in shear modulus were observed after subsequent removal of the epimysium. This study suggests that the skin is a main contributor for maintaining the muscle mechanical properties among tissues covering the skeletal muscle. PMID:26738629
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)
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; Snchez, C; Suchyta, E; Troxel, M A; Vikram, V; Abbott, T; Abdalla, F B; Allam, S; Annis, J; Benoit-Lvy, 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.
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.
Shear induced phase transitions induced in edible fats
Mazzanti, Gianfranco; Welch, Sarah E.; Marangoni, Alejandro G.; Sirota, Eric B.; Idziak, Stefan H. J.
2003-03-01
The food industry crystallizes fats under different conditions of temperature and shear to obtain products with desired crystalline phases. Milk fat, palm oil, cocoa butter and chocolate were crystallized from the melt in a temperature controlled Couette cell. Synchrotron x-ray diffraction studies were conducted to examine the role of shear on the phase transitions seen in edible fats. The shear forces on the crystals induced acceleration of the alpha to beta-prime phase transition with increasing shear rate in milk fat and palm oil. The increase was slow at low shear rates and became very strong above 360 s-1. In cocoa butter the acceleration between beta-prime-III and beta-V phase transition increased until a maximum of at 360 s-1, and then decreased, showing competition between enhanced heat transfer and viscous heat generation.
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.
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
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.
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.
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.
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/.
Directory of Open Access Journals (Sweden)
Mara C. Miquel
2009-01-01
Full Text Available The objective of this paper was to determine the association of a SNP in the -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 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.
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.
Thielmann, M.; Rozel, A.; Kaus, B. J.; Ricard, Y. R.
2012-12-01
Lithospheric-scale shear zones are commonly defined as regions inhomogeneous and localized deformation. Strain softening has been demonstrated to be necessary for localization in those shear zones, but there is still debate about the physical cause of this softening. Here, we investigate the interplay between two mechanisms that have been suggested to have a significant impact on lithospheric localization: shear heating and grain size reduction. Shear heating has been suggested to play an important role in i) creating deep focus as well as intermediate-depth earthquakes (Ogawa (1987), Kelemen and Hirth (2007)) and ii) creating lithospheric-scale shear zones, thus creating a weak decoupling interface that enables subsequent subduction initiation (Kaus and Podlatchikov (2006), Crameri and Kaus (2010)). As natural shear zones typically have a significantly reduced grain size, it has been put forward that grain size reduction provides the necessary strain softening to localize deformation. As grain size reduces, the dominant deformation mechanism switches from dislocation to diffusion creep, thus requiring less stress to deform the rock. Usually, the equilibrium grain size is thought to follow a piezometric relationship, thus indicating the stress under which a shear zone deformed. Recent work (Austin and Evans (2007), Rozel et al. (2011)) suggests that the equilibrium grain size is not dependent on stress, but rather on the deformational work. In our study, we employ the grain size evolution law of Rozel et al. and use 1D viscoelastic numerical models of simple shear deformation to investigate the influence of both weakening mechanisms and their interaction for a variety of boundary conditions. We find that grain size reduction in pure olivine does not localize very efficiently, as grain size very rapidly reaches a steady state. Even when a fraction of the deformational work is used by grain size reduction processes, shear heating is found to localize very efficiently (Kaus & Podlatchikov (2005), Braeck et al. (2009)) and the significant temperature increase induced by shear heating severely affects the grain size in the shear zone. Generally, we find that the elevated temperature inside the shear zone results in a larger grain size compared to the surrounding rock matrix. This finding is not compatible with field observations, where shear zones are usually characterized by small grain sizes. This indicates that further mechanisms are needed to either keep the grain size small (e.g. pinning by secondary phases (Herwegh et. al (2011), Bercovici and Ricard (2012) ) or to limit the temperature increase inside the shear zone.
International Nuclear Information System (INIS)
This paper presents a new constitutive model of cracked RC plates subjected to combined axial and shear stress. First, we carried out reversed cyclic shear load test where reinforcement ratio of RC plates and axial stress values were set as parameters. Pre-cracks were generated by tensile stress, and reversed cyclic shear loads were applied under the specified axial stress. Then, based on the test results, we obtained the constitutive model for smeared crack model, where shear stiffness of the plate varied depending on shear strain and axial strain. By adopting proposed model into nonlinear FEM (Finite Element Method) analysis program, analysis results were improved and the efficiency of the model was validated. (author)
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.
Meza, Daphne; Abejar, Louie; Rubenstein, David A; Yin, Wei
2016-03-01
Endothelial cell (EC) morphology and functions can be highly impacted by the mechanical stresses that the cells experience in vivo. In most areas in the vasculature, ECs are continuously exposed to unsteady blood flow-induced shear stress and vasodilation-contraction-induced tensile stress/strain simultaneously. Investigations on how ECs respond to combined shear stress and tensile strain will help us to better understand how an altered mechanical environment affects EC mechanotransduction, dysfunction, and associated cardiovascular disease development. In the present study, a programmable shearing and stretching device that can apply dynamic fluid shear stress and cyclic tensile strain simultaneously to cultured ECs was developed. Flow and stress/strain conditions in the device were simulated using a fluid structure interaction (FSI) model. To characterize the performance of this device and the effect of combined shear stress-tensile strain on EC morphology, human coronary artery ECs (HCAECs) were exposed to concurrent shear stress and cyclic tensile strain in the device. Changes in EC morphology were evaluated through cell elongation, cell alignment, and cell junctional actin accumulation. Results obtained from the numerical simulation indicated that in the "in-plane" area of the device, both fluid shear stress and biaxial tensile strain were uniform. Results obtained from the in vitro experiments demonstrated that shear stress, alone or combined with cyclic tensile strain, induced significant cell elongation. While biaxial tensile strain alone did not induce any appreciable change in EC elongation. Fluid shear stress and cyclic tensile strain had different effects on EC actin filament alignment and accumulation. By combining various fluid shear stress and cyclic tensile strain conditions, this device can provide a physiologically relevant mechanical environment to study EC responses to physiological and pathological mechanical stimulation. PMID:26810848
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
Shear rheology of a cell monolayer
Energy Technology Data Exchange (ETDEWEB)
Fernandez, Pablo [Experimentalphysik I, Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Heymann, Lutz [Technische Mechanik und Stroemungsmechanik, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Ott, Albrecht [Experimentalphysik I, Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Aksel, Nuri [Technische Mechanik und Stroemungsmechanik, Universitaet Bayreuth, D-95440 Bayreuth (Germany); Pullarkat, Pramod A [Experimentalphysik I, Physikalisches Institut, Universitaet Bayreuth, D-95440 Bayreuth (Germany)
2007-11-15
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 {approx}10{sup 6} 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.
Symmetry related dynamics in parallel shear flows
Kreilos, Tobias
2013-01-01
Parallel shear flows come with continuous symmetries of translation in the downstream and spanwise direction. Flow states that differ in their spanwise or downstream location but are otherwise identical are dynamically equivalent. In the case of travelling waves, this trivial degree of freedom can be removed by going to a frame of reference that moves with the state, thereby turning the travelling wave in the laboratory frame to a fixed point in the co-moving frame of reference. Further exploration of the symmetry suggests a general method by which the translational displacements can be removed also for more complicated and dynamically active states. We will describe the method and discuss its relation to general symmetry reductions and to the Taylor frozen flow hypothesis. We will demonstrate the method for the case of the asymptotic suction boundary layer. When applied to the oscillatory edge state with its long period, the method allows to find local phase speeds which remove the fast oscillations so that ...
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 RC300) 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.
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.
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 DeltaTron 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).
Extreme shearing interferometry: theoretical limits with practical consequences.
Servin, M; Cywiak, M; Dvila, 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
Dynamic shear properties of the temporomandibular joint disc.
Tanaka, E; Hanaoka, K; van Eijden, T; Tanaka, M; Watanabe, M; Nishi, M; Kawai, N; Murata, H; Hamada, T; Tanne, K
2003-03-01
Shear stress might be an important factor associated with fatigue failure and damage of the temporomandibular joint disc. Little information, however, is available on the dynamic behavior of the disc in shear. Since the disc is an anisotropic and viscoelastic structure, in the present study the dependency of the dynamic shear behavior on the direction and frequency of loading was examined. Ten porcine discs were used for dynamic shear tests. Shear stress was applied in both anteroposterior (A-P test) and mediolateral (M-L test) directions. The dynamic moduli increased as the loading frequency increased. The dynamic elasticity was significantly larger in the A-P test than in the M-L test, although the dynamic viscosity was similar in both tests. The present results suggest that non-linearities, compression/shear coupling, and intrinsic viscoelasticity affect the shear material behavior of the disc, which might have important implications for the transmission of load in the temporomandibular joint. PMID:12598554
Estimated strength of shear keys in concrete dams
Energy Technology Data Exchange (ETDEWEB)
Curtis, D.D. [Hatch Energy, Niagara Falls, ON (Canada); Lum, K.K.Y. [BC Hydro, Burnaby, BC (Canada)
2008-07-01
BC Hydro requested that Hatch Energy review the seismic stability of Ruskin Dam which was constructed in 1930 at Hayward Lake in British Columbia. The concrete gravity dam is founded nearly entirely on rock in a narrow valley. The vertical joints between blocks are keyed and grouted. The strength of the shear keys was assessed when a non-linear finite element model found that significant forces were being transferred laterally to the abutments during an earthquake. The lateral transfer of loads to the abutment relies on the strength of the shear keys. The dynamic finite element analysis was used to determine the stability of the dam. A review of the shear strength measurements reported in literature showed that the measurements compared well to those obtained by BC Hydro from cores taken from Ruskin Dam. The cohesive strength obtained using the Griffith failure criteria was also in good agreement with both sets of measurements. A simple ultimate shear strength equation was developed using the Mohr-Coulomb failure criteria to determine combined cohesive and frictional strength of shear keys. Safety factors of 2.0 for static loads and 1.5 for seismic loads were proposed to reduce the ultimate strength to allowable values. It was concluded that given the relatively high shear strength established for the shear keys, the abutment rock or dam/abutment contact will control the amount of load which can arch to the abutments. 8 refs., 4 tabs., 5 figs.
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
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 Alfvn wave, driven by the parallel flow shear.
Electromagnetic effects in the stabilization of turbulence by sheared flow
International Nuclear Information System (INIS)
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>1/?? 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<1/?? 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 Alfvn wave, driven by the parallel flow shear. (paper)
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 ΔGc, 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 ΔGc, 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.
Je?bek, Petr; Bukovsk, 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.
Shear Capacity and Failure Behavior of Steel-Reinforced High Ductile Concrete Beams
Mingke Deng; Jie Dai; Huasong Lu; Xingwen Liang
2015-01-01
The shear behavior of six high ductile fiber reinforced concrete (HDC) beams is studied to investigate the influence of shear-span ratio and HDC mechanical property on the improvement of the shear failure mode and shear capacity of short beams. Four steel-reinforced high ductile concrete beams (SHDC) beams with different shear span ratios are tested under concentrated load at midspan. To study the effect of stirrups and steel on the shear capacity of short beams, two additional specimens with...
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
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.
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.
Shear wave heterogeneity in the lower mantle from seismic tomography
Robertson, Graham Scott.; Woodhouse, J. H.
1994-01-01
?To date, most shear velocity heterogeneity models in the lower mantle have been derived using long period data. Comparatively little use has been made of the vast ISC database of shear wave arrival times, which covers the years 1964 to 1991. The aim of this study is to use this database to construct global models of shear wave heterogeneity in the lower mantle and compare it with existing P models using similar period data in order to evaluate the hypothesis that P and S heteroge...
Performance testing of a Savonius windmill rotor in shear flows
Mojola, O. O.; Onasanya, O. E.
The effects of flow shear and/or unsteady behavior on the power generation capability of a Savonius wind turbine rotor are assessed in view of measurements conducted, both in two statistically steady shear flows and in the wind, of rotor tip speed and torque at a number of streamwise stations for each of four values of the rotor bucket overlap ratio. It is found that, even in the absence of shear, the power coefficient of a Savonius wind turbine rotor is most strongly dependent on tip speed ratio.
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
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)
Piezoelectric shear wave resonator and method of making same
Wang, Jin S. (Harbor City, CA); Lakin, Kenneth M. (Ames, IA); Landin, Allen R. (Ames, IA)
1988-01-01
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/.degree.C.
Influence of microfluidic shear on keratin networks in living cells
Nolting, Jens-Friedrich; Kster, 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.
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.
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.
Shear waves in a ﬂuid 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 ﬂuid 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 signiﬁcantly in comparison to that in isotropic elastic media.
Adapting a commercial shear rheometer for applications in cartilage research
Boettcher, K.; Grumbein, S.; Winkler, U.; Nachtsheim, J.; Lieleg, O.
2014-09-01
Cartilage research typically requires a broad range of experimental characterization techniques and thus various testing setups. Here, we describe how several of those tests can be performed with a single experimental platform, i.e. a commercial shear rheometer. Although primarily designed for shear experiments, such a rheometer can be equipped with different adapters to perform indentation and creep measurements, quantify alterations in the sample thickness, and conduct friction measurements in addition to shear rheology. Beyond combining four distinct experimental methods into one setup, the modified rheometer allows for performing material characterizations over a broad range of time scales, frequencies, and normal loads.
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.
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.
Aggregates relaxation in a jamming colloidal suspension after shear cessation
Ianni, F; Sarcia, R; Hbraud, 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.
Impact of a shear flow on double tearing nonlinear dynamics
International Nuclear Information System (INIS)
The dynamics of global reconnection in the presence of a poloidal shear flow located in between magnetic islands is investigated. Different linear and nonlinear regimes are identified depending on the resistivity, the equilibrium velocity amplitude, and the distance between the low-order resonant surfaces. It is found that nonlinearly, the shear flow can significantly delay DTM generation and global reconnection. It is shown that this delay is linked to a symmetry breaking imposed by the shear flow and the generation of mean poloidal flows in the resistive layers. It is also found that turbulence can be generated by Kelvin-Helmholtz instability in between the resonance layers and enhance magnetic reconnection processes.
The Palomares brittleductile Shear Zone of southern Spain
Weijermars, Ruud
The Palomares Shear Zone is a major Neogene-Quaternary strikeslip 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 straindistance 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.
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)
Wall shear stress hot film sensor for use in gases
International Nuclear Information System (INIS)
The purpose of this work is to present the construction and characterization of a wall shear stress hot film sensor for use in gases made with MEMS technology. For this purpose, several associated devices were used, including a constant temperature feedback bridge and a shear stress calibration device that allows the sensor performance evaluation. The sensor design adopted here is simple, economical and is manufactured on a flexible substrate allowing its application to curved surfaces. Stationary and transient wall shear stress tests were carried on by means of the calibration device, determining its performance for different conditions.
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