Influence Of Preload Research Articles

Influence of Pre-Load on Corrosion Vulnerability of Reinforced Concrete

The present study investigates the relation between loading and corrosion of reinforcing steel in reinforced concrete elements. Beam specimens of size 100 mm × 150 mm × 1200 mm were cast using three different normal and high strength concrete mixes. After 45 days of moist curing, these beams were subjected to four point bending at different loading levels. Some specimens were also subjected to cyclic flexural loads. After load tests, ponds were constructed on the tension side of these beams, and the specimens were subjected to ponding using 5% NaCl solution. Half cell potential readings were taken to monitor the time taken for corrosion initiation. After corrosion initiation, an external current was applied to these specimens to accelerate the corrosion process. The residual loading capacity of the beams was found at the end of the durability exposure tests. The results indicate that loading history and loading levels have significant effects on both corrosion initiation and corrosion propagation. The results also show that both corrosion initiation and propagation rates also depend on the type of concrete used.

Effects of preloads on joints on dynamic stiffness of a whole machine tool structure

The machine tool joint is a very important factor in the overall machine tool dynamic analysis, and it has great effects on the machining performance of a machine tool. As a very important operation parameter, preload greatly influences the stiffness and the damping of a machine tool joint. This paper presents the effect of preload on the dynamic stiffness of the spindle nose of a horizontal machining center. By discussing types and distribution of machine tool joints, studies on the joints of ball screws, linear guides and bolts are carried out. The influence of preload on the axial stiffness of a ball screw is calculated based on Hertzian contact theory and the effect of pretightening moment on pressure of bolt joint is discussed, while the dynamic stiffness and the damping of a linear guide are identified by an optimum algorithm with the simulated and experimental results. A finite element model (FEM) of the whole machine tool structure considering the effects of different joints is created and verified against the test results, and then the influence of preloads on ball screws and linear guides is predicted. Results indicate that preloads on machine tool joints have significant effects on the dynamic stiffness of the spindle nose.

Analysis and Research of Piezoelectric Dynamic Weighing Sensor

The Kistler company has invented piezoelectric dynamic weighing sensors which are applied to determine dynamically axle load, speed and gross weight of the vehicle based on piezoelectric effect of quartz crystal. They mainly consist of load-carrying beams and sensitive elements. Focusing on the control of preload in design and fabrication, finite element method (FEM) is applied with ANSYS software to optimize structural sizes. The influence curve of the structural dimensions of load-carrying beam on the preload is analyzed. With the piezoelectric coupling analysis function, the preload influence on the sensor sensitivity is researched. FEM simulation results show that the critical dimensions of load-carrying beam as well as the deformation and wall thickness of cavity have significant impact on the preload. Further studies show that the sensor has the highest sensitivity with the reasonable deformation and wall thickness of the cavity. In this paper, a sensor with range of 150 kN has the highest sensitivity at the wall thickness of 2 mm and the deformation of 0.14 mm.

Decrease of Food Intake in Rats after Ingestion of Medium-Chain Triacylglycerol

Previous studies have demonstrated that fatty acid oxidation in the liver may affect food intake. This study examined the influence of preloading of medium-chain triacylglycerol (MCT) on food intake in comparison with long-chain triacylglycerol (LCT). Male rats were fasted for 18 h and then administered LCT or MCT emulsion orally. Each group of rats was allowed to rest for 30 min, and then food intake during 1 h was measured. Food intake in the MCT group was significantly lower than that in the LCT group. To examine the influence of hepatic oxidation, the MCT+MA group was injected intraperitoneally with mercaptoacetate (MA), an inhibitor of fatty acid oxidation, 2 h before ingestion of MCT emulsion. Then, 30 min after ingestion of LCT or MCT emulsion, food intake was measured for 1 h. Food intake in the MCT group was significantly lower than that in the LCT group, but there was no significant difference between the MCT+MA group and the LCT group. Food intake in the MCT+MA group was significantly higher than that in the MCT group. The hepatic ATP content after MCT ingestion was significantly higher than that after LCT ingestion, but there was no significant difference between the MCT+MA group and the LCT group. The hepatic ATP content after MCT+MA ingestion was significantly lower than that after MCT ingestion. These results suggest that ingestion of medium-chain fatty acid (MCFA) increases the liver ATP content in fasted rats, consequently decreasing food intake.

Some experimental results on yield condition in plane stress state

In the present paper, the determination of yield locus curves for deep drawing sheet metal is described. The experiments are based on the combination of biaxial tension tests on plane cross-shaped specimens with uniaxial tension and compression tests performed on conventional specimens. The influence of preloading (prestrain) on the hardening behaviour is discussed. The material coefficients are computed through the equalization of the test results by means of a quadratic formulation of the yield condition. Finally, the material coefficients are given as functions of the prestrain of specimens in the rolling direction.

Influence of length changes on myocardial metabolism in the cat papillary muscle.

HomeCirculation ResearchVol. 49, No. 2Influence of length changes on myocardial metabolism in the cat papillary muscle. Free AccessAbstractPDF/EPUBAboutView PDFSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessAbstractPDF/EPUBInfluence of length changes on myocardial metabolism in the cat papillary muscle. G Cooper4th G Cooper4thG Cooper4th Search for more papers by this author Originally published1 Aug 1981https://doi.org/10.1161/01.RES.49.2.423Circulation Research. 1981;49:423–433 Previous Back to top Next FiguresReferencesRelatedDetailsCited By LeWinter M, Higashiyama A, Yaku H and Watkins M (1995) Influence of Preload on Non-Mechanical VO2 Assessed with 2,3-Butanedione Monoxime Cardiac Energetics: From Emax to Pressure-Volume Area, 10.1007/978-1-4615-2021-4_10, (113-127), . Suga H and Goto Y (1991) Cardiac Oxygen Costs of Contractility (Emax) and Mechanical Energy (PVA): New Key Concepts in Cardiac Energetics Recent Progress in Failing Heart Syndrome, 10.1007/978-4-431-67955-4_4, (61-115), . ter Keurs H, Savage D, Lester W and McGee D (2009) New perspectives on left ventricular hypertrophy: Anatomy, physiology, and significance, Clinical Cardiology, 10.1002/clc.4960121310, 12:S4, (IV-36-IV-49) Hisano R and Cooper G (1987) Correlation of force-length area with oxygen consumption in ferret papillary muscle., Circulation Research, 61:3, (318-328), Online publication date: 1-Sep-1987.Kusuoka H, Weisfeldt M, Zweier J, Jacobus W and Marban E (1986) Mechanism of early contractile failure during hypoxia in intact ferret heart: evidence for modulation of maximal Ca2+-activated force by inorganic phosphate., Circulation Research, 59:3, (270-282), Online publication date: 1-Sep-1986.Bittl J and Ingwall J (1986) The energetics of myocardial stretch. Creatine kinase flux and oxygen consumption in the noncontracting rat heart., Circulation Research, 58:3, (378-383), Online publication date: 1-Mar-1986.Cooper G and Marino T (1984) Complete reversibility of cat right ventricular chronic progressive pressure overload., Circulation Research, 54:3, (323-331), Online publication date: 1-Mar-1984.Cooper G and Tomanek R (1982) Load regulation of the structure, composition, and function of mammalian myocardium., Circulation Research, 50:6, (788-798), Online publication date: 1-Jun-1982. August 1, 1981Vol 49, Issue 2 Advertisement Article InformationMetrics Copyright © 1981 by American Heart Associationhttps://doi.org/10.1161/01.RES.49.2.423 Originally publishedAugust 1, 1981 PDF download Advertisement

The Influence of Preload Measured as Diastolic Mural Force on Myocardial Contractility Indices

There have been reports in the recent literature citing the influence of ventricular preload on indices of myocardial contractility. Most of these reports used left ventricular end-diastolic pressure (LVEDP) as an indicator of preload (1-6), but few have used an indicator which incorporated a geometry factor. Since ventricular radius contributes to the force in the ventricular wall and, therefore to the load on the myocardial fiber, directly measured mural force (MF = PπR) should provide a more accurate indication of preload changes than pressure alone. Therefore, the purpose of this investigation was to examine the influence of preload changes as measured by either MF or LVEDP on five simultaneously recorded indices of contractility. These indices were peak rate of pressure rise of left ventricular pressure (dP/dt) (1, 2), maximum physiological velocity of the contractile elements (Vpm) (3-6), time from onset of contraction to VPM (t-Vpm) (3, 4), the ratio of dP/dt to instantaneous pressure at 5 mmHg developed pressure [(dP/dt)/K·5] (7), and the ratio of dP/dt to common peak isovolumic developed pressure [(dP/dt)/CPIF] (1,4). Method. Eighteen mongrel dogs weighing from 18 to 31 kg (mean = 21.4 kg) were anesthetized with 20 mg/kg pentobarbital sodium. After institution of positive pressure respiration with room air, each animal received a supplemental dose of barbital sodium (150 mg/kg) intraperitoneally to maintain a steady state of anesthesia. Polyethylene catheters were inserted in a femoral vein and artery. The tip of the arterial catheter was positioned in the ascending aorta for the measurement of aortic blood pressure with a Statham P23Dd pressure transducer. Through a ventral midline incision in the neck, both vagii were isolated and severed. A left lateral thoracotomy was performed and the pericardium widely incised.