Готові списки джерел за темами / Preloads

Добірка наукової літератури з теми "Preloads"

Автор: Grafiati
Опубліковано: 10 грудня 2022
Оновлено: 28 січня 2023

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Статті в журналах з теми "Preloads"

1

Wu, Qing, Colin Cole, Maksym Spiryagin, and Weihua Ma. "Preload on draft gear in freight trains." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 232, no. 6 (October 31, 2017): 1615–24. http://dx.doi.org/10.1177/0954409717738849.

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Adjusting draft gear preloads requires minimum or no structural changes to the existing coupler systems. Better or optimal preloads are more promising to be implemented than modifying other parameters such as wedge angles and spring stiffness. This paper presents a method to model draft gear preloads and investigates the numerical step-size requirements for the simulations of draft gear preloads. The implications of preloads on the draft gear impact performance, longitudinal train dynamics performance and coupler fatigue damage were also investigated. The results show that step sizes of less than 2.5 and 0.2 ms (with the fourth Runge–Kutta solver) are recommended to simulate preloads during the simulations of longitudinal train dynamics and wagon impacts, respectively. Wagon impact simulations indicate that the increase of draft gear preloads can noticeably decrease the maximum draft gear deflection during wagon impacts. Longitudinal train dynamics simulations for a distributed power train with 214 vehicles on a 320 km long track were conducted. The longitudinal train dynamics simulations indicate that, when the preload is increased from 0 to 100 kN, the difference of maximum vehicle accelerations is insignificant. When the draft gear preload is further increased to 200 or 300 kN, maximum vehicle accelerations are evidently increased. Draft gear preloads do not noticeably influence the maximum tensile coupler forces. However, preloads have evident implications for maximum compressive coupler forces, especially for the second half of the train. Coupler fatigue damage calculations show that the sum of coupler fatigue damage evidently decreases with the increase of draft gear preload. The damage for the zero preload case is 8.7 times than that of the 300 kN preload case.
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2

Astbury, Nerys M., Emma J. Stevenson, Penelope Morris, Moira A. Taylor, and Ian A. Macdonald. "Dose–response effect of a whey protein preload on within-day energy intake in lean subjects." British Journal of Nutrition 104, no. 12 (September 28, 2010): 1858–67. http://dx.doi.org/10.1017/s000711451000293x.

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The effect of consuming different amounts of whey protein on appetite and energy intake was investigated in two separate studies using randomised, crossover designs. Healthy-weight men and women (range: BMI 19·0–25·0 kg/m2, age 19·4–40·4 years) consumed one of four 400 ml liquid preloads, followed by an ad libitum test meal 90 min later. In study 1, preloads were 1675 kJ with 12·5, 25 or 50 % of energy from protein, and in study 2, preloads were 1047 kJ with 10, 20 or 40 % energy from protein. Flavoured water was used as the control in both the studies. Appetite ratings were collected immediately before 30, 60 and 90 min after consuming the preloads; and immediately, 30 and 60 min after consuming the test meal. In study 1, energy intake following the control preload (4136 (sem 337) kJ) was significantly higher than each of the 12·5 % (3520 (sem 296) kJ), 25 % (3384 (sem 265) kJ) and 50 % (2853 (sem 244) kJ) protein preloads (P < 0·05). Intake after the 12·5 % preload was significantly higher than following 25 and 50 % preloads (P < 0·05). In study 2, energy intake following the control preload (4801 (sem 325) kJ) was higher than following the 10 % (4205 (sem 310) kJ), 20 % (3988 (sem 250) kJ) and 40 % (3801 (sem 245) kJ) protein preloads (P < 0·05). There were no differences in subjective appetite ratings between preloads in either study. These findings indicate a dose–response effect of protein content of the preload on energy intake at a subsequent meal.
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3

Szlosarek, Robert, and Matthias Kröger. "Fatigue behavior of bolted boreholes under various preloads." Materials Testing 64, no. 2 (February 1, 2022): 195–201. http://dx.doi.org/10.1515/mt-2021-2032.

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Abstract Bolted joints are one of the most used joining technologies in engineering. It is possible to join different kind of materials and to transmit heavy loads. Nevertheless, they are vulnerable to fatigue cracks. The present research investigates the dependency between the preload of the bolt and the initiation of a fatigue crack in the bolted sheet. Therefore, a representative bolt connection with a bolt of size M22 was selected in combination with a 5 mm thick sheet made of steel S355MC (1.0976). The bolted sheet was loaded by a fluctuating tension load and a load ratio of 0.1. The test results show a strong correlation of the preload and the number of load cycles to crack for preloads from 0 kN to 30 kN. The load cycles to crack are increased by about factor 20 by using a preload in contrast to the sheet without any preload. For higher preloads, the load cycles to crack does not change considerably. However, the crack initiation location changes by increasing the preload. For small preloads, the crack starts at the bolt hole, and for high preloads, the crack starts at the fretting zone.
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4

Hulshof, Toine, Cees De Graaf, and Jan A. Weststrate. "Short-term satiating effect of the fat replacer sucrose polyester (SPE) in man." British Journal of Nutrition 74, no. 4 (October 1995): 569–85. http://dx.doi.org/10.1079/bjn19950159.

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The effects of different amounts of the non-absorbable fat replacer sucrose polyester (SPE), water, and fat added to six warm preload lunches on feelings of appetite and food intake were investigated in two studies that were replicates of each other. In the first study thirty-nine subjects consumed rice preloads; in the second study thirty-five subjects consumed macaroni preloads. The six preloads were fixed on three energy levels: 1·8, 2·7, or 3·7MJ. At 2 h after preload consumption a test-meal buffet of thirty-one products was presented. Food intake was recorded on the study day, and the day after the study day. For women no energy compensation occurred in either study. Men showed a tendency to compensate for the energy differences between the preloads. However, when the fat of the preloads was replaced by SPE, energy compensation was less than 50% and non-significant. Statistically significant energy-compensation (66 %) was found when fat was replaced by water. No macronutrient-specific compensation occurred in men or women in either study. Lower total fat and energy intakes were found with the preloads where fat was replaced by SPE compared with the preloads containing fat. The appetite ratings were in line with the energy intake values, with no differences in women, and higher appetite ratings after the lower energy preloads in men. This short-term study indicates that SPE may be a useful aid to reduce fat and energy intakes.
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5

Wang, Zhi Gang, Ze Yu Weng, Qi Peng Cao, Jin Hu Mei, and Fu Hong Zhu. "Study on the Relation of Wheel Hub Bearing Preload and Natural Frequency by Dynamic Test." Key Engineering Materials 693 (May 2016): 1453–57. http://dx.doi.org/10.4028/www.scientific.net/kem.693.1453.

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Preloads have an important influence on working performance and service life of wheel hub bearing. In order to study the action mechanism, carrying out the study on the effect of wheel hub bearing preload on the natural frequency is particularly important. Aiming at a certain type of car wheel hub bearing, the wheel hub bearing swept-sine vibration test system is built, and the conclusion is got after testing on wheel hub bearings with different preloads. The conclusion is that the natural frequency of wheel hub bearing increases with preload increasing, but increasing trend tends to slow.
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6

PATEL, VIPULKUMAR ISHVARBHAI, QING QUAN LIANG, and MUHAMMAD N. S. HADI. "NUMERICAL ANALYSIS OF CIRCULAR CONCRETE-FILLED STEEL TUBULAR SLENDER BEAM-COLUMNS WITH PRELOAD EFFECTS." International Journal of Structural Stability and Dynamics 13, no. 03 (April 2013): 1250065. http://dx.doi.org/10.1142/s0219455412500654.

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This paper presents a new numerical model for the nonlinear analysis of circular concrete-filled steel tubular (CFST) slender beam-columns with preload effects, in which the initial geometric imperfections, deflections caused by preloads, concrete confinement and second order effects are incorporated. Computational algorithms are developed to solve the nonlinear equilibrium equations. Comparative studies are undertaken to validate the accuracy of computational algorithms developed. Also included is a parametric study for examining the effects of the preloads, column slenderness, diameter-to-thickness ratio, loading eccentricity, steel yield stress and concrete confinement on the behavior of circular CFST slender beam-columns under eccentric loadings. The numerical model is demonstrated to be capable of predicting accurately the behavior of circular CFST slender beam-columns with preloads. The preloads on the steel tubes can affect significantly the behavior of CFST slender beam-columns and must be taken into account in the design.
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7

Koller, Heiko, Michael Mayer, Juliane Zenner, Herbert Resch, Alfred Niederberger, Johann Fierlbeck, Wolfgang Hitzl, and Frank L. Acosta. "Implications of the center of rotation concept for the reconstruction of anterior column lordosis and axial preloads in spinal deformity surgery." Journal of Neurosurgery: Spine 17, no. 1 (July 2012): 43–56. http://dx.doi.org/10.3171/2012.4.spine11198.

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Object In thoracolumbar deformity surgery, anterior-only approaches are used for reconstruction of anterior column failures. It is generally advised that vertebral body replacements (VBRs) should be preloaded by compression. However, little is known regarding the impact of different techniques for generation of preloads and which surgical principle is best for restoration of lordosis. Therefore, the authors analyzed the effect of different surgical techniques to restore spinal alignment and lordosis as well as the ability to generate axial preloads on VBRs in anterior column reconstructions. Methods The authors performed a laboratory study using 7 fresh-frozen specimens (from T-3 to S-1) to assess the ability for lordosis reconstruction of 5 techniques and their potential for increasing preloads on a modified distractable VBR in a 1-level thoracolumbar corpectomy. The testing protocol was as follows: 1) Radiographs of specimens were obtained. 2) A 1-level corpectomy was performed. 3) In alternating order, lordosis was applied using 1 of the 5 techniques. Then, preloads during insertion and after relaxation using the modified distractable VBR were assessed using a miniature load-cell incorporated in the modified distractable VBR. The modified distractable VBR was inserted into the corpectomy defect after lordosis was applied using 1) a lamina spreader; 2) the modified distractable VBR only; 3) the ArcoFix System (an angular stable plate system enabling in situ reduction); 4) a lordosizer (a customized instrument enabling reduction while replicating the intervertebral center of rotation [COR] according to the COR method); and 5) a lordosizer and top-loading screws ([LZ+TLS], distraction with the lordosizer applied on a 5.5-mm rod linked to 2 top-loading pedicle screws inserted laterally into the vertebra). Changes in the regional kyphosis angle were assessed radiographically using the Cobb method. Results The bone mineral density of specimens was 0.72 ± 22.6 g/cm2. The maximum regional kyphosis angle reconstructed among the 5 techniques averaged 9.7°−16.1°, and maximum axial preloads averaged 123.7–179.7 N. Concerning correction, in decreasing order the LZ+TLS, lordosizer, and ArcoFix System outperformed the lamina spreader and modified distractable VBR. The order of median values for insertion peak load, from highest to lowest, were lordosizer, LZ+TLS, and ArcoFix, which outperformed the lamina spreader and modified distractable VBR. In decreasing order, the axial preload was highest with the lordosizer and LZ+TLS, which both outperformed the lamina spreader and the modified distractable VBR. The technique enabling the greatest lordosis achieved the highest preloads. With the ArcoFix System and LZ+TLS, compression loads could be applied and were 247.8 and 190.6 N, respectively, which is significantly higher than the insertion peak load and axial preload (p < 0.05). Conclusions Including the ability for replication of the COR in instruments designed for anterior column reconstructions, the ability for lordosis restoration of the anterior column and axial preloads can increase, which in turn might foster fusion.
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8

Paretkar, Dadhichi, Marleen Kamperman, David Martina, Jiahua Zhao, Costantino Creton, Anke Lindner, Anand Jagota, Robert McMeeking, and Eduard Arzt. "Preload-responsive adhesion: effects of aspect ratio, tip shape and alignment." Journal of The Royal Society Interface 10, no. 83 (June 6, 2013): 20130171. http://dx.doi.org/10.1098/rsif.2013.0171.

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We tested the adhesive response of polymer surfaces structured with arrays of cylindrical fibrils having diameters of 10–20 µm and aspect ratios 1–2.4. Fibrils had two different tip shapes of end-flaps and round edges. A preload-induced mechanical buckling instability of the fibrils was used to switch between the states of adhesion and non-adhesion. Non-adhesion in fibrils with round edges was reached at preloads that caused fibril buckling, whereas fibrils with end-flaps showed adhesion loss only at very high preloads. The round edge acted as a circumferential flaw prohibiting smooth tip contact recovery leading to an adhesion loss. In situ observations showed that, after reversal of buckling, the end-flaps unfold and re-form contact under prevailing compressive stress, retaining adhesion in spite of buckling. At very high preloads, however, end-flaps are unable to re-form contact resulting in adhesion loss. Additionally, the end-flaps showed varying contact adaptability as a function of the fibril–probe alignment, which further affects the preload for adhesion loss. The combined influence of preload, tip shape and alignment on adhesion can be used to switch adhesion in bioinspired fibrillar arrays.
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9

Melanson, Kathleen J., Margriet S. Westerterp-Plantenga, Wim H. M. Saris, Françoise J. Smith, and L. Arthur Campfield. "Blood glucose patterns and appetite in time-blinded humans: carbohydrate versus fat." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 277, no. 2 (August 1, 1999): R337—R345. http://dx.doi.org/10.1152/ajpregu.1999.277.2.r337.

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We assessed the extent to which a possible synchronization between transient blood glucose declines and spontaneous meal initiation would lend support to the interpretation of a preload study with isoenergetic (1 MJ) isovolumetric high-fat or simple carbohydrate (CHO) preload drinks. Ten men (18–30 yr) fasted overnight and then were time blinded and made aware that they could request meals anytime. At first meal requests, volunteers consumed a preload; ad libitum meals were offered at subsequent requests. Postabsorptively, transient declines in blood glucose were associated with meal requests (χ2 = 8.29). Subsequent meal requests occurred during “dynamic declines” in blood glucose after the peak induced by drink consumption (100%). These meal requests took twice as long to occur after high-fat than after CHO preloads (fat = 126 ± 21, CHO = 65 ± 15 min), consistent with differences in interpolated 65-min satiety scores (fat = 38 ± 8.2, CHO = 16 ± 4). Postprandially, transient blood glucose declines were associated with meal requests (χ2 = 4.30). Spontaneous meal initiations were synchronized with transient and dynamic blood glucose declines. Synchronization of intermeal interval and dynamic declines related to higher satiating efficiency from high-fat preloads than from simple CHO preloads.
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10

Fukuoka, Toshimichi, and Tomohiro Takaki. "Finite Element Simulation of Bolt-Up Process of Pipe Flange Connections." Journal of Pressure Vessel Technology 123, no. 3 (December 19, 2000): 282–87. http://dx.doi.org/10.1115/1.1358842.

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Achieving uniform bolt preload is difficult when tightening a pipe flange with a number of bolts. Several bolt-tightening strategies have been proposed so far for achieving uniform bolt preloads. It seems, however, that effective guidelines for tightening pipe flange connections have not been established. In this study, a numerical approach is presented for estimating the scatter in bolt preloads and achieving the uniform bolt preloads when tightening each bolt one by one in an arbitrary order. Numerical analyses are conducted using three-dimensional FEM as an elastic contact problem. The analytical objects are pipe flanges specified in JIS B 2238 with an aluminum gasket inserted. The validity of the numerical procedures proposed here is ascertained by experiment.
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Дисертації з теми "Preloads"

1

Woodend, Dianne. "The effect of sucrose and safflower oil preloads on satiety, mood and memory." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0021/MQ49777.pdf.

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2

Nettles, A. T. "The effects of tensile preloads on the impact response of carbon/epoxy laminates." Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-06062008-154902/.

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3

Regan, Paula J. "Influence of macronutrient preloads on appetite and metabolic parameters in liver and renal transplant recipients." Thesis, Queen Margaret University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271521.

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4

Jakel, Roland. "Analyzing a bolted, conical hub-shaft-connection with finite friction contact in Creo Simulate 3.0: Best practices for working with large displacement analysis, bolt preloads and finite friction contact." Technische Universität Chemnitz, 2018. https://monarch.qucosa.de/id/qucosa%3A21441.

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Анотація:
Der Vortrag beschreibt, wie mittels des Kontaktmodells mit endlicher Reibung in Creo Simulate 3.0 ein Schwungrad mit axial verschraubtem mit Kegel-Presssitz berechnet werden kann. Da in Creo Simulate 3.0 des Softwareentwicklers PTC das Kontaktmodell mit endlicher Reibung nur für die Theorie großer Verformungen implementiert ist, nicht jedoch für einfache Analysen mit kleinen Deformationen, muss der Anwender einige softwareseitige Einschränkungen geschickt umgehen. Es werden Vorgehensweisen vorgeschlagen, wie der Anwender dies bewerkstelligen kann. Ein besonderer Schwerpunkt liegt dabei auf der Modellierung von Schrauben sowie der Einstellung der Schraubenvorspannung. Rechenergebnisse des Programms werden mit analytischen Lösungen verglichen.
The presentation describes how to analyze a flywheel with axially bolted hub-shaft- connection using a conical press fit with help of the finite friction contact model in Creo Simulate 3.0. Since Creo Simulate 3.0 from PTC offers a finite friction contact model implementation just for large displacement analysis, but not for simple analyses with small displacements, the user has to work around a couple of code specific limitations. Best practices are proposed how to do this. Special attention is paid on bolt modeling and preload adjustment. Analysis results are compared with analytical solutions.
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5

Xu, Weiwei. "Effect of Bolted Joint Preload on Structural Damping." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4794.

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Bolted joints are integral parts of mechanical systems, and bolt preload loss is one of the major failure modes for bolted joint structures. Understanding the damping and frequency response to a varying preload in a single-bolted lap-joint structure can be very helpful in predicting and analyzing more complicated structures connected by these joints. In this thesis, the relationship between the bolt preload and the natural frequency, and the relationship between the bolt preload and the structural damping, have both been investigated through impact hammer testing on a single-bolted lap-joint structure. The test data revealed that the bolt preload has nonlinear effects on the structural damping and on the natural frequency of the structure. The damping ratios of the test structure were determined to increase with decreasing preload. An increase in structural damping is beneficial in most engineering circumstances, for it will reduce the vibrational response and noise subjected to external excitations. It was also observed that the modal frequency increased with increasing preload, but remained approximately constant for preload larger than 30% in the bolt yield strength. One application for studying the preload effect is the detection for loose bolts in structures. The possibility of using impact testing for estimating preload loss has been confirmed, and the modal damping was determined to be a more sensitive indicator than the natural frequency in a single-bolted lap-joint structure.
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6

Lundin, Malin. "Left atrial functions: effects of increased and decreased preload." Thesis, Örebro universitet, Institutionen för hälsovetenskap och medicin, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-44928.

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7

Thomas, Anthony H. 1981. "Strain based preload measurement in drive axle pinion bearings." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30322.

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Анотація:
Thesis (S.M. and S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
Includes bibliographical references (leaf 44).
Bearing setting has a significant impact on bearing life and system performance. A strain based load measurement technique that has been previously developed and patented will be used to measure preload in automotive drive axle pinion bearings. This technique utilizes strain gages placed in notches that have been machined into the outer diameter of a bearing cup. The performance of two gage types, semiconductor and metal foil, are compared. Preload in the pinion bearings is simulated in a machine by applying an axial load to a bearing assembly. The bearing assembly is rotated at various speeds and temperatures for each set of axial loads. Two notch geometries are compared for each set of tests conducted. An effort has been made to develop a finite element model that can be used to verify the results of the gage calibration. The results of the calibration reveal that metal foil and semiconductor gages can provide preload measurements that are accurate to within 3.7% and 7.7% of the full scale input load (73 lbs. and 155 lbs.) respectively.
by Anthony H. Thomas, II.
S.M.and S.B.
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8

Jacobs, Nicholas R. "Displacement of Screw-Retained Single Crowns into New Generation Narrow Diameter Implants with Conical and Conical/Hex Internal Connections and their Performance when Cyclically Loaded." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1566144926275455.

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9

Preuss, Jason Lee. "Design and analysis of a composite flywheel preload loss test rig." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/100.

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Flywheel energy storage units have become a viable alternative to electrochemical batteries in applications such as satellites, uninterrupted power supplies, and hybrid vehicles. However, this performance is contingent upon safe operation since these flywheels can release their stored energy almost instantaneously upon failure. The research presented here investigates a health monitoring technology that may give an early indication of degraded material properties in a concentric ring composite flywheel. The existence of degraded material properties is manifested as a change in mass eccentricity due to asymmetric growth of the outermost flywheel ring. A test rig concept to investigate the technology is developed in detail using a systems engineering design process. Successful detection of the change in mass eccentricity was verified analytically through dynamic modeling of the flywheel rotor and magnetic suspension system. During steady state operation detection was determined to be feasible via measurements of the magnetic bearing currents and shaft position provided by the magnetic suspension feedback sensors. A rotordynamic analysis was also conducted and predicts successful operation to the maximum operating speed of 50,000 Rpm.
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10

Åkerblom, Mats. "Gearbox noise : Correlation with transmission error and influence of bearing preload." Doctoral thesis, KTH, Maskinkonstruktion (Inst.), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9899.

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Анотація:
The five appended papers all deal with gearbox noise and vibration. The first paper presents a review of previously published literature on gearbox noise and vibration. The second paper describes a test rig that was specially designed and built for noise testing of gears. Finite element analysis was used to predict the dynamic properties of the test rig, and experimental modal analysis of the gearbox housing was used to verify the theoretical predictions of natural frequencies. In the third paper, the influence of gear finishing method and gear deviations on gearbox noise is investigated in what is primarily an experimental study. Eleven test gear pairs were manufactured using three different finishing methods. Transmission error, which is considered to be an important excitation mechanism for gear noise, was measured as well as predicted. The test rig was used to measure gearbox noise and vibration for the different test gear pairs. The measured noise and vibration levels were compared with the predicted and measured transmission error. Most of the experimental results can be interpreted in terms of measured and predicted transmission error. However, it does not seem possible to identify one single parameter, such as measured peak-to-peak transmission error, that can be directly related to measured noise and vibration. The measurements also show that disassembly and reassembly of the gearbox with the same gear pair can change the levels of measured noise and vibration considerably. This finding indicates that other factors besides the gears affect gear noise. In the fourth paper, the influence of bearing endplay or preload on gearbox noise and vibration is investigated. Vibration measurements were carried out at torque levels of 140 Nm and 400 Nm, with 0.15 mm and 0 mm bearing endplay, and with 0.15 mm bearing preload. The results show that the bearing endplay and preload influence the gearbox vibrations. With preloaded bearings, the vibrations increase at speeds over 2000 rpm and decrease at speeds below 2000 rpm, compared with bearings with endplay. Finite element simulations show the same tendencies as the measurements. The fifth paper describes how gearbox noise is reduced by optimizing the gear geometry for decreased transmission error. Robustness with respect to gear deviations and varying torque is considered in order to find a gear geometry giving low noise in an appropriate torque range despite deviations from the nominal geometry due to manufacturing tolerances. Static and dynamic transmission error, noise, and housing vibrations were measured. The correlation between dynamic transmission error, housing vibrations and noise was investigated in speed sweeps from 500 to 2500 rpm at constant torque. No correlation was found between dynamic transmission error and noise. Static loaded transmission error seems to be correlated with the ability of the gear pair to excite vibration in the gearbox dynamic system.
QC 20100923
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Книги з теми "Preloads"

1

Woodend, Dianne. The effect of sucrose and safflower oil preloads on satiety, mood and memory. Ottawa: National Library of Canada, 2000.

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2

Bell, K. The effects of multiple preloads on subsequent low temperature fracture of a pressure vessel steel. Cambridge: TWI, 1997.

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3

Zeggeren, Alexandra Van. 5-hydroxytryptamine metabolism and feeding behavior in lean and obese Zucker rats after intragastric carbohydrate preloads. Ottawa: National Library of Canada, 1990.

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4

Crawford, James MacKenzie. Multiple boundary condition testing for preloaded membrane structures. [Toronto, Ont]: Graduate Dept. of Aerospace Science and Engineering, University of Toronto, 1994.

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5

Zhong, Cai, and United States. National Aeronautics and Space Administration., eds. Development of hypersonic engine seals: Flow effects of preload and engine pressures. [Washington, DC: National Aeronautics and Space Administration, 1993.

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6

Crombie, Carrie Anne. Effect of a sucrose preload on food intake subjective measures of appetite in 9 and 10 year old healthy children. Ottawa: National Library of Canada, 1992.

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7

Laine, Daniel Petri. Effect of axial preloads on confined concrete. 2004.

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8

Vince, Daniel, Branscomb Caleb, and United States. National Aeronautics and Space Administration., eds. The effects of tensile preloads on the impact response of carbon/epoxy laminates. [Washington, D.C: National Aeronautics and Space Administration, 1995.

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The effects of tensile preloads on the impact response of carbon/epoxy laminates. [Washington, D.C: National Aeronautics and Space Administration, 1995.

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United States. National Aeronautics and Space Administration., ed. The effects of compressive preloads on the compression-after-impact strength of carbon/epoxy. [Washington, D.C: National Aeronautics and Space Administration, 1994.

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Частини книг з теми "Preloads"

1

Kolev, Nikolai, Günter Huemer, and Michael Zimpfer. "On-line and off-line determinations of ventricular preloads and volumes." In Transesophageal Echocardiography, 36–49. Vienna: Springer Vienna, 1995. http://dx.doi.org/10.1007/978-3-7091-7676-4_4.

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2

On, JeongSeok, JaeHyun Kim, Jaiyong Lee, Yeonsoo Kim, and Hakjin Chong. "A MAC Protocol with Adaptive Preloads Considering Low Duty-Cycle in WSNs." In Mobile Ad-Hoc and Sensor Networks, 269–80. Berlin, Heidelberg: Springer Berlin Heidelberg, 2007. http://dx.doi.org/10.1007/978-3-540-77024-4_26.

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3

Vest, Amanda R., and Frederick Heupler. "Preload." In Cardiovascular Hemodynamics, 3–27. Totowa, NJ: Humana Press, 2012. http://dx.doi.org/10.1007/978-1-60761-195-0_1.

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Lefebvre, Cedric W., Jay P. Babich, James H. Grendell, James H. Grendell, John E. Heffner, Ronan Thibault, Claude Pichard, et al. "Preload." In Encyclopedia of Intensive Care Medicine, 1833–36. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-00418-6_229.

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Vest, Amanda R. "Preload." In Contemporary Cardiology, 3–22. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-19131-3_1.

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6

Sills, Joel, Arya Majed, and Edwin Henkel. "A Deformed Geometry Synthesis Technique for Determining Stacking and Cryogenically Induced Preloads for the Space Launch System." In Sensors and Instrumentation, Aircraft/Aerospace, Energy Harvesting & Dynamic Environments Testing, Volume 7, 17–26. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-47713-4_3.

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Lefebvre, Cedric W., Jay P. Babich, James H. Grendell, James H. Grendell, John E. Heffner, Ronan Thibault, Claude Pichard, et al. "Preload Responsiveness." In Encyclopedia of Intensive Care Medicine, 1836. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-00418-6_3263.

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Ogundele, Olufunmilayo, and Michael R. Pinsky. "Preload-Dependent Monitoring." In Monitoring Technologies in Acute Care Environments, 117–26. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-8557-5_14.

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9

Piriou, V., B. Gostoli, and D. Jacques. "Assessment of preload." In Anaesthesia, Pain, Intensive Care and Emergency Medicine — A.P.I.C.E., 661–77. Milano: Springer Milan, 2003. http://dx.doi.org/10.1007/978-88-470-2215-7_5.

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10

Aylward, Pete, Ken Jokol, Jamie Macdonald, Paul Prudence, Glen Rhodes, Robbie Shepherd, and Todd Yard. "Designing Preloaders." In Flash MX Application & Interface Design, 1–24. Berkeley, CA: Apress, 2002. http://dx.doi.org/10.1007/978-1-4302-5217-7_1.

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Тези доповідей конференцій з теми "Preloads"

1

Shah, Vikram N. "Uncertainty of Preloads in Closure Bolts for Transportation Casks for Hazardous and Radioactive Materials." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61360.

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Maintaining closure bolting integrity under normal and accident conditions is essential for the safe transportation of shipping casks bearing hazardous and radioactive materials. Bolt preload introduces a clamping force in the joint that plays a critical role in ensuring a less-than-specified rates of leakage from such casks. Precise control over bolt preload is essential to introduce adequate clamping force in the joint. Uncertainty is introduced in the closure bolt preloads when an individual bolt is tightened and then when the other bolts are tightened in a specified sequence. Tightening an individual bolt can introduce uncertainty as high as ±35% mainly because of the variation in the coefficient of friction. Tightening the subsequent bolts in a specified sequence introduces uncertainty because the elastic interactions between bolts reduce the preloads already installed. This paper reviews the literature related to the methods employed for installing the preloads, factors introducing uncertainty in the preloads, methods for reducing the uncertainty, and the techniques available for measuring the preloads. It is concluded that the use of an elastic interaction matrix has a potential for providing the specified preload in the bolted joint and that ultrasonic measurements can be used to monitor the preload with ±10% or less uncertainty.
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2

Du, Michael, Fei Song, Haoming Li, and Ke Li. "Preload Assurance in Bolted Flanges With a Model and Test Based Optimized Assembly Procedure." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21688.

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Abstract Bolted flanges are widely used to connect pipelines in many industries. To assure sealability of a flange, generation of proper preloads in the bolts during the assembly process is critical. However, in the existing standard practice, identical torques are typically applied to all bolts to assemble the flange. Due to elastic interactions between the bolts, tightening one bolt can alter the tensile loads in the other bolts. Hence, the resultant preloads can vary significantly. Even with an improved makeup sequence, the variation in the bolt preloads can be still substantial, as high as 60%. This could pose a risk of leakage. When the bolted flange works under non-benign conditions, such as vibration, pressure and temperature variation, the risk could become even higher. This paper introduces a new methodology to greatly enhance the preload assurance in bolted flanges with an optimized assembly procedure, which is enabled with advanced numerical modeling. A significantly improved uniform distribution of bolt preloads is achieved by optimizing the makeup torques, which is implemented by using physical test data as input and uniformly distributed preloads as the target function. The complexity of the elastic interactions between the flange, the sealing gasket, and the bolts presents uncertainties for the numerical model for quantitative prediction of the torque distribution that is required to yield uniform resultant bolt preloads. This paper resolves this modeling limitation through iterations between modeling and testing. These iterations calibrate and finally validate the model to generate the optimized makeup torque distribution which then leads to improved bolt preload uniformity. Based on the tests conducted on two different sizes of API flanges, 3-API-15K and 5-API-10K, the final preload distribution variation has been reduced to around 30% by utilizing the optimized makeup torque distributions.
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3

Fukuoka, Toshimichi, Masataka Nomura, Yuutaro Uemori, and Koji Sato. "Bolt Preload Reduction of Pipe Flange Connections After Plant Shutdown." In ASME 2012 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/pvp2012-78054.

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When pipe flange connections clamped with sheet gaskets are subjected to thermal load, the bolt preloads that tighten a pair of pipe flanges tend to decrease. It has been studied in the previous paper why and how the bolt preloads decrease, in which the loading and unloading curves of sheet gaskets at elevated temperature are expressed by means of simple equations. Meanwhile, it is also known that the bolt preloads are likely to decrease when the plant is shut down. In this paper, a numerical procedure, which can predict the amounts of bolt preload reduction occurred in the shutdown process, is proposed using axi-symmetric finite element method (FEM). The analytical objects are pipe flange connections tightened with aramid sheet gaskets. In the finite element formulation, stress-strain curves of the gaskets after plant shutdown are approximated by simple curves, considering that the hysteresis appeared in the curves is considerably small, comparing to that between the loading and unloading curves in the running condition. It is shown that the bolt preloads are decreased by as much as from 40% to 50% of those in the running condition. The validity of the proposed numerical method is confirmed by comparing the numerical results of the bolt preload reduction to experimental ones.
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Fukuoka, Toshimichi, and Nobukuni Sugano. "Measurement of Bolt Clamping Forces by Electromagnetic Vibration Method Without Disassembling Bolted Joints." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93166.

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The integrity and safety of a bolted joint can be greatly guaranteed by applying and maintaining an appropriate amount of bolt preloads. However, the variation of bolt preloads inevitably occurs in the service condition due to various reasons, even if the initial bolt preloads are properly applied. Accordingly, the monitoring of bolt forces in the service condition is significantly important. From the practical point of view, it is preferably conducted without disassembling the objective bolted joint. In this paper, Electromagnetic Vibration Method is introduced for monitoring the variation of bolt preloads in the service condition, and its performance is examined by experiments using bolted joints with various geometric configurations. Electromagnetic Vibration Method estimates the magnitude of bolt preload by measuring the resonant frequencies of the bolted joint, which vary in accordance with the contact pressure of the joint interface. From the experimental studies, Electromagnetic Vibration Method was found to be effective to evaluate the bolt force with a reasonable accuracy, except for the bolted joint whose plate interface being under very high contact pressure.
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Fukuoka, Toshimichi, Masataka Nomura, and Takashi Nishikawa. "Analysis of the Mechanical Behavior of Pipe Flange Connections by Taking Account of Gasket Compression Characteristics at Elevated Temperature." In ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77596.

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Sealing of contained fluids is the primary performance required for pipe flange connections. It is well known that the leakage is likely to occur when contained fluids at high temperature are concerned. Due to the differential thermal expansion of each part, bolt preloads that tighten a pair of pipe flanges tend to decrease. Therefore, it is significantly important for the joint safety to estimate the amount of bolt preload reduction at the design stage. In this paper, a finite element approach is proposed to analyze thermal and mechanical behavior of pipe flange connections at elevated temperature, by incorporating the stress-strain curves of sheet gaskets measured in the previous paper. Then, the reduction rate of bolt preloads at elevated temperature is systematically evaluated. The analytical objects are pipe flange connections tightened with aramid sheet gaskets. When a pipe flange connection is subjected to thermal load, the gasket stress usually decreases along unloading curves. The temperature dependency of gasket stiffness is considered by defining Young’s modulus in unloading E*, which can be introduced into FE formulation using ordinary solid elements. Numerical results show that bolt preloads are decreased by as much as 30% of the initial value when using aramid sheet gaskets of 3mm thickness. The effectiveness of the proposed numerical method has been confirmed by comparing the numerical results of bolt preload reduction to experimental ones.
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Fukuoka, Toshimichi, and Keisuke Nakano. "Improvement of Tightening Accuracy of Torque Control Method by Taking Account Geometric Errors in Threaded Fasteners." In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63083.

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Torque control method is commonly used when tightening bolted joints because of its easy operation. However, the method involves an essential problem of fairly large scatter in bolt preloads. It has been reported that even if the same torque is applied, bolt preloads show a considerable scatter, e.g., ranging from 25% to 35%. A scatter in coefficients of friction on nut bearing surface and thread pressure flank is a primary source of bolt preload scatter. Meanwhile, the effect of Equivalent Friction Diameter at the bearing surfaces of nut and bolt head cannot be ignored. The scatter in Equivalent Friction Diameter is caused by imperfect geometry, i.e., the flatness deviation at the bearing surfaces. In this paper, the magnitudes of Equivalent Friction Diameter are quantitatively evaluated by FEA, using the experimental data of flatness deviation measured for a number of commercial nuts and bolts. It is shown that the bolt preload is likely to be scattered by as much as plus minus 10% of the target value, owing to the flatness deviation. Based on the comprehensive calculations by considering the imperfect geometry, a strategy to effectively suppress the bolt preload scatter is proposed.
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Geng, Phil, Robert R. Martinson, Richard L. Williams, Michael Mello, and Steve Cho. "Shadow Moire´ Evaluation of Motherboard Warpage Under Preload CPU Thermal Solutions." In ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems collocated with the ASME 2005 Heat Transfer Summer Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/ipack2005-73046.

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This work investigated the motherboard coplanarity and preload correlation using the shadow moire´ interferometry. Motherboards under three different preloads in the CPU area were examined at room temperature and elevated temperature. Both the global board warpage and the local board warpage around the CPU area were measured for preload and temperature correlations. The measured board coplanarity was correlated to the board preload successfully. The results clearly identified a failure mode from the outlier, which has totally different warpage shape and corresponds to the uneven preload case. Also, the creep effect under preload during heating stage was observed and quantified.
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Zhang, Yanfei, Xiaohu Li, Jun Hong, Sun’an Wang, Baotong Li, Yanhui Sun, and Shuai Zheng. "Rotation Accuracy Analysis of Spindle Under Variable Preload." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71264.

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Variable preload technology is used to achieve appropriate preload applied on spindle bearing based on machining conditions. However, the bearing temperature rise will be directly affected by bearing preload as well as bearing rotation accuracy. So, the main objective of this paper is to propose a method to determine the rotation accuracy of the spindle affected by the thermal expensive due to heat generation under variable preloads. Five degrees of freedom (5-DOF) quasi-static model of angular contact ball bearing was established to investigate the internal load distribution of the contact areas between the race way and balls. Then local contact heat generation of the bearing is calculated based on hertz contact theory. Finally, an experimental platform equipped with hydraulic system is designed and fabricated, which is preloaded by a hydraulic chamber. Studies have shown that the rotation accuracy presents drastically with the spindle rotational speed. Moreover, the influence of the bearing preload has a secondary importance. Comparative analysis about the rotation accuracy between starting running state and stable running state after a few hours under the same preload has been investigated. Results show that the accuracy of rotation spindle present no obviously difference when the uneven thermal deformation of parts occurs in the spindle system.
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PARAMBIL, NITHIN K., BRANNDON R. CHEN, JOSEPH M. DEITZEL, JOHN W. GILLESPIE, JR., LOAN T. VO, and PETER SAROSI. "PREDICTING PROCESSING INDUCED RESIDUAL- STRESSES IN CARBON FIBER-THERMOPLASTIC MICRO-COMPOSITES." In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35843.

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A computational model of residual stress is developed for AS4/polypropylene composites and implemented via user material subroutine (UMAT) in ABAQUS. The main factors included in the model are the cooling-rate dependent crystallinity, temperature-dependent elastic modulus, and temperature-dependent coefficient of thermal expansion (CTE) of the matrix, and the temperature-independent transversely isotropic properties of the carbon fiber. Numerical results are generated for the case of a single fiber embedded in a thin film of polypropylene sample to replicate the process history and test configuration. During single fiber composite processing, a precalculated weight (tensile preload) is applied at the fiber ends to eliminate buckling/waviness of the carbon fiber induced by matrix shrinkage in the axial direction of the fiber. Experiments and Finite element (FE) analysis have been conducted with different preloads (1g, 4g, and 8g) at 25°C. Micro-Raman spectroscopy is utilized to validate the residual strain with different preloads at the bulk. The measured strain values show a good correlation with the predicted residual strain for various preload conditions.
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Vulpe, Cristina, and Susan Gourvenec. "Effect of Preloading on the Response of a Shallow Skirted Foundation." In ASME 2014 33rd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/omae2014-23440.

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The effect of preloading on the vertical settlement and bearing capacity of a circular skirted foundation was investigated as a function of relative preload and degree of consolidation by means of small strain finite element analyses. Significant gain in bearing capacity was observed for practical levels of preloads and duration of consolidation, offering an insight into potential efficiencies in foundation design.
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Звіти організацій з теми "Preloads"

1

Mosby, Matthew, Michael Tupek, and Johnathan Vo. A simple levelset contact algorithm for large overlap removal and robust preloads. Office of Scientific and Technical Information (OSTI), September 2021. http://dx.doi.org/10.2172/1819813.

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2

Roberts, Thomas Phillip, Scott Anthony Ouellette, and Adam Joseph Wachtor. Dynamic Effects of Preload in Hyperelastic Foam Models. Office of Scientific and Technical Information (OSTI), August 2019. http://dx.doi.org/10.2172/1557171.

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3

NUMERICAL STUDY OF THE PRELOAD FORCE LOSS OF CORRODED HIGH- STRENGTH BOLTS. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.338.

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Corrosion significantly affects the structural behavior of members in a connection (i.e., the preload force of bolts, the thickness of steel plates, and the anti-sliding friction of steel plates). The preload force of bolts is a key factor affecting the bearing capacity of high-strength bolts shear connections, and it will be significantly influenced by corrosion. In this study, the preload force loss of high-strength bolts shear connections after corrosion is studied. A finite element model validated by previous experiment is developed for estimating the preload force loss of high-strength bolts after corrosion. The value of the preload force loss of corroded highstrength bolts increases as the corrosion rate, but the effect of steel grade on the preload force loss is not obvious. Based on the results of finite element analysis, a degradation model for predicting the preload force loss of corroded high-strength bolts is suggested, and the degradation model agrees well with various test data. The results of this study can provide a reference for safety assessment of corroded high-strength bolted shear connections.
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4

TENSILE BEHAVIOR OF T-STUB SUBJECTED TO STATIC AND DYNAMIC LOADS. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.313.

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Анотація:
To study the tensile behavior of T-stubs with various design parameters under different loading scenarios, uniaxial static and dynamic tensile tests were carried out. The effects of flange thickness, bolt preload, bolt strength and loading conditions were discussed. The failure modes observed under different conditions were presented. Besides, the load-displacement response was analyzed in detail. The experimental results showed that the bolt preload only affected the initial stiffness of the specimens, and smaller flange thickness and lower bolt strength would result in unfavorable performance of T-stubs. Under dynamic loading scenarios, the test specimens showed greater resistance but limited deformation capacity compared to the static ones. Furthermore, it was observed that the ductility would be seriously reduced if brittle failure, such as bolt or weld fracture occurred which is recommended to be avoided in structural design.
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RESEARCH PROGRESS ON FATIGUE PROPERTIES OF THE HIGHPERFORMANCE STEEL AND CONNECTION FORMS. The Hong Kong Institute of Steel Construction, August 2022. http://dx.doi.org/10.18057/icass2020.p.196.

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This paper reviews the current research status of fatigue performance of high-strength steels, introduces the basic theory of fatigue life and current design methods, the fatigue test data of a large number of high-strength steels are statistically collected, and the fatigue properties of high-strength steel base material and different connection structures are analyzed and evaluated. The research results show that high-strength steels with yield strength greater than 420MPa show better fatigue resistance, and the fatigue strength is significantly higher than the calculated value. The design curve of the code is conservative, which underestimates the fatigue resistance of the steel. The fatigue strength of the highstrength steel weld joints is increased by a small margin, and it is in good agreement with the AISC360 and EC3 code curves. Due to the influence of welding quality and welding process, the data is more discrete and requires more test data to support. Fatigue strength of bolted connections is affected by many factors such as bolt preload, friction surface treatment process, and hole formation methods. Studies have shown that AISC360 and BS7608 design curves are suitable for fatigue life analysis of Q460 bolted connections, and for fatigue performance calculations for Q690 steel bolted connections, the normative approach is conservative. With the increasing application of high-strength steels, the current code needs to be supplemented with the latest research results and engineering experience of new materials in a timely manner.
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Tire Experimental Characterization Using Contactless Measurement Methods. SAE International, August 2021. http://dx.doi.org/10.4271/2021-01-1114.

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In the frame of automotive Noise Vibration and Harshness (NVH) evaluation, inner cabin noise is among the most important indicators. The main noise contributors can be identified in engine, suspensions, tires, powertrain, brake system, etc. With the advent of E-vehicles and the consequent absence of the Internal Combustion Engine (ICE), tire/road noise has gained more importance, particularly at mid-speed driving and in the spectrum up to 300 Hz. At the state of the art, the identification and characterization of Noise and Vibration sources rely on pointwise sensors (microphones, accelerometers, strain gauges). Optical methods such as Digital Image Correlation (DIC) and Laser Doppler Vibrometer (LDV) have recently received special attention in the NVH field because they can be used to obtain full-field measurements. Moreover, these same techniques could also allow to characterize the tire behavior in operating conditions, which would be practically impossible to derive with standard techniques. In this paper we will demonstrate how non-contact full-field measurement techniques can be used to reliably and robustly characterize the tire behavior up to 300 Hz, focusing on static conditions. Experimental modal analysis will extract the modal characteristic of the tire in both free-free and statically preloaded boundary conditions, using both DIC and LDV. The extracted natural frequencies, damping ratios and full-field mode shapes will be used on one side to improve the accuracy of tire models (either by deriving FRF based models or updating FE ones) but also as a reference for future investigation on the tire behavior characterization in rotating conditions.
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