A Consideration on the Behavior of Hydraulic Pressure Ripples in Relation to Hydraulic Oil Temperature

2015 ◽  
Author(s):  
Shuichi Nakagawa ◽  
Takayoshi Ichiyanagi ◽  
Takao Nishiumi
Keyword(s):  
Thermal Properties ◽  
Physical Properties ◽  
Mathematical Models ◽  
Bulk Modulus ◽  
Temperature Change ◽  
Speed Of Sound ◽  
Thermal Characteristics ◽  
Hydraulic Pressure ◽  
Hydraulic Oil ◽  
Pressure Ripples

It is well known that hydraulic noise can change as a system warms up. That change can be a factor for misperception of mechanical failure, because noise can play an important role as a signal that indicates abnormal operation. It is therefore important to understand the behavior of hydraulic pressure ripples that are a source of hydraulic noise in operating conditions, and how they change in relation to the temperature of the hydraulic oil. This study has investigated the ripple behavior that results from temperature change in simple hydraulic systems, using mathematical models that took thermal properties into account. Physical properties of the oil and the speed of sound in the oil have been defined as temperature-related variables in the mathematical models. The physical properties that should be used in the mathematical models have been obtained directly from the oil manufacturer. In contrast, the speed of sound in the oil has to be obtained from the isentropic tangent bulk modulus of the oil in an actual operating condition. That has been determined from the specific volume ratio of entrained air to the oil and the isentropic tangent bulk modulus of the only oil. The thermal properties of the speed of sound in the oil have been determined from the thermal characteristics of these variables, and it has been found that the speed of sound in the oil decreases with a rise in the oil temperature. The mathematical models of pressure ripples have shown that there were three distinct phenomena resulting from the temperature change of the oil. The first is the change of wavelength. The second is the spatial dependence of the thermal characteristics of the pressure ripples. The third is the difference of the thermal characteristics of the pressure amplitude at the peak in spatial modes. These changes that result from the temperature variation tend to be large at higher frequency.

Pore Structure and Thermal Characteristics of Clay Bricks

2014 ◽  
Vol 982 ◽  
pp. 104-107 ◽  
Author(s):  
Monika Čáchová ◽  
Dana Koňáková ◽  
Eva Vejmelková ◽  
Martin Keppert ◽  
Kirill Polozhiy ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Structural Material ◽  
Physical Properties ◽  
Thermal Characteristics ◽  
Clay Brick ◽  
Pore System ◽  
Clay Bricks ◽  
Vacuum Saturation ◽  
The Difference ◽  
System Characteristics

Clay brick was perhaps to be the first artificial structural material. First bricks were dried by sun; later people had started to burn bricks by fire and in that time further enhancements appeared. This article deals with two kinds of fired clay bricks; basic physical properties, pore system characteristics and thermal properties are studied. The values of basic physical properties by water vacuum saturation vary slightly; bulk density shows values around 1880 kg/m3 and in the case of open porosity it is around 27%. Regarding thermal properties the difference is higher, obtained results of thermal conductivities in dried state vary by about 33%.

Influence of Moisture Content on the Thermal Properties of Concrete Containing Agricultural Waste Materials

2016 ◽  
Vol 677 ◽  
pp. 241-245
Author(s):  
Dana Koňáková ◽  
Monika Čáchová ◽  
Eva Vejmelková
Keyword(s):  
Thermal Properties ◽  
Moisture Content ◽  
Physical Properties ◽  
Agricultural Waste ◽  
Thermal Characteristics ◽  
Waste Materials ◽  
Experimental Measurements ◽  
Transport Parameters ◽  
Cement Replacement ◽  
Coir Pith

This article deals with concrete containing waste material originating in a coir fibres extraction from outer protective peel of a coconut. Coir pith is used as cement replacement in amount of 5% and 10%. The influence of moisture content on the thermal properties of studied concrete is determined by means of experimental measurements of basic physical properties, hygric transport parameters and thermal characteristics. From achieved results it can be concluded, that the higher amount of coir pith is used, the better values of thermal characteristics material show. But at the same time thermal characteristics are more influenced by moisture content.

Experimental Investigation on Effective Bulk Modulus and Effective Volume in an External Gear Pump

2016 ◽  
Author(s):  
Shuichi Nakagawa ◽  
Takayoshi Ichiyanagi ◽  
Takao Nishiumi
Keyword(s):  
Bulk Modulus ◽  
Gear Pump ◽  
Hydraulic Systems ◽  
Hydraulic Oil ◽  
Positive Displacement ◽  
Effective Bulk Modulus ◽  
Source Impedance ◽  
Displacement Pump ◽  
External Gear Pump ◽  
Pressure Ripples

Pressure ripples generated by a positive displacement pump in a hydraulic system can lead to severe noise and vibration problems. The source impedance of a positive displacement pump has a considerable impact on the generation of pressure ripples. It is, therefore, important to be able to predict the source impedance in order to design quiet hydraulic systems. The source impedance of a positive displacement pump depends, amongst other things, on bulk modulus and volume. However, it is known that the mathematical model that takes into account the bulk modulus of hydraulic oil and the volume of a discharge room in the pump results in an estimated value of the source impedance that is greater than the measured value. In this study, the factors which affect the source impedance of an external gear pump for an agricultural tractor have been investigated. In particular, the effect of the following factors has been investigated experimentally: the effective bulk modulus as determined by the components of the pump: leakage in the pump: the specific volume ratio of entrained air to hydraulic oil: and the volume of the tooth space of the pump. In addition, the effect of volumetric change of the discharge room by pumping action has been investigated using CFD with moving mesh technique.

Effect of the number of arms on the mechanical properties of a star-shaped cyclic olefin copolymer

2019 ◽  
Vol 10 (41) ◽  
pp. 5578-5583 ◽  
Author(s):  
Takumitsu Kida ◽  
Ryo Tanaka ◽  
Koh-hei Nitta ◽  
Takeshi Shiono
Keyword(s):  
Mechanical Properties ◽  
Thermal Properties ◽  
Physical Properties ◽  
Secondary Amine ◽  
Aggregation Number ◽  
Drastic Change ◽  
Cyclic Olefin Copolymer ◽  
Cyclic Olefin

The increase of aggregation number in a star-shaped cyclic olefin copolymer was succeeded by using a triazine-based secondary amine, which caused a drastic change in physical properties without changing the thermal properties.

Modeling and Experimental Validation of the Effective Bulk Modulus of a Mixture of Hydraulic Oil and Air

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Hossein Gholizadeh ◽  
Doug Bitner ◽  
Richard Burton ◽  
Greg Schoenau
Keyword(s):  
Experimental Data ◽  
Bulk Modulus ◽  
Theoretical Models ◽  
Operating Conditions ◽  
Air Bubbles ◽  
Pressure Sensitivity ◽  
Hydraulic Oil ◽  
Effective Bulk Modulus ◽  
Experimental Apparatus ◽  
Major Factors

It is well known that the presence of entrained air bubbles in hydraulic oil can significantly reduce the effective bulk modulus of hydraulic oil. The effective bulk modulus of a mixture of oil and air as pressure changes is considerably different than when the oil and air are not mixed. Theoretical models have been proposed in the literature to simulate the pressure sensitivity of the effective bulk modulus of this mixture. However, limited amounts of experimental data are available to prove the validity of the models under various operating conditions. The major factors that affect pressure sensitivity of the effective bulk modulus of the mixture are the amount of air bubbles, their size and the distribution, and rate of compression of the mixture. An experimental apparatus was designed to investigate the effect of these variables on the effective bulk modulus of the mixture. The experimental results were compared with existing theoretical models, and it was found that the theoretical models only matched the experimental data under specific conditions. The purpose of this paper is to specify the conditions in which the current theoretical models can be used to represent the real behavior of the pressure sensitivity of the effective bulk modulus of the mixture. Additionally, a new theoretical model is proposed for situations where the current models fail to truly represent the experimental data.

scholarly journals Brazilian gutta-percha points. Part II: thermal properties

2007 ◽  
Vol 21 (1) ◽  
pp. 29-34 ◽  
Author(s):  
Cláudio Maniglia-Ferreira ◽  
Eduardo Diogo Gurgel-Filho ◽  
João Batista Araújo Silva Jr ◽  
Regina Célia Monteiro de Paula ◽  
Judith Pessoa Andrade Feitosa ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Thermal Properties ◽  
Physical Properties ◽  
Ambient Temperature ◽  
Amorphous Phase ◽  
Thermal Behaviour ◽  
Chemical Structure ◽  
Scanning Calorimetry ◽  
Gutta Percha ◽  
Thermal Manipulation

This study was undertaken to explore the effect of heating on gutta-percha, analyzing the occurrence of endothermic peaks corresponding to the transformation that occurs in the crystalline structure of the polymer during thermal manipulation. This study also seeked to determine the temperature at which these peaks occur, causing a transformation from the beta- to the alpha-form, and from the alpha- to the amorphous phase. Eight nonstandardized gutta-percha points commercially available in Brazil (Konne, Tanari, Endopoint, Odous, Dentsply 0.04, Dentsply 0.06, Dentsply TP, Dentsply FM) and pure gutta-percha (control) were analysed using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The transition temperatures were determined and analysed. With the exception of Dentsply 0.04 and Dentsply 0.06, the majority of the products showed thermal behaviour typical of beta-gutta-percha, with two endothermic peaks, exhibiting two crystalline transformations upon heating from ambient temperature to 130°. Upon cooling and reheating, few samples presented two endothermic peaks. It was concluded that heating dental gutta-percha to 130°C causes changes to its chemical structure which permanently alter its physical properties.

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