-
Design of the Hydrostatic Thrust Spherical Bearing with Restrictors (Fitted Type)
Ahmad Waguih Yacout Elescandarany
Issue:
Volume 7, Issue 2, April 2019
Pages:
34-45
Received:
1 March 2019
Accepted:
26 April 2019
Published:
29 May 2019
Abstract: The hydrostatic bearings are broadly observed in industrial applications owing to their potential characteristics of low running friction, high load-carrying capacity, high stiffness and small viscous dissipation. Spherical bearings have advantages over other configurations of bearings because of their self-aligning property and also their capacity to accept both radial and thrust loads. Operation of the spherical bearings is unaffected by angular miss-alignment. They are mainly used in machine tools, precision measuring instruments, hydraulic piston pumps and motors, gyroscope gimbals, telescopes, radar tracking units, air craft engines and rotary drum of centrifugal separator for enriched uranium. The main objective of this part of study is to handle the fitted bearing design taking into consideration the combined effects of rotational inertia, surface roughness and the fluid film viscosity variability. The mathematical expressions derived in part 2 for this type of bearings with its different configurations (with and without recess; hemispherical and partial hemispherical seats) have been used in the detailed bearing design. Improving the previous design through developing some mathematical expressions, a new conception is adopted to reveal the bearing consistency showing how the fluid flow rate pulsation or intermittent could be prevented. The detailed design procedures show the advantages of this method to get the central pressure ratio mathematically through maximizing the flow rate with minimizing the supply pressure which means minimum pump power to get maximum discharge. This design showed very high mean static stiffness of all the bearing configurations and an acceptable temperature rise for a heavy duty bearing without the need to a use a cooling system.
Abstract: The hydrostatic bearings are broadly observed in industrial applications owing to their potential characteristics of low running friction, high load-carrying capacity, high stiffness and small viscous dissipation. Spherical bearings have advantages over other configurations of bearings because of their self-aligning property and also their capacity...
Show More
-
Fracture Toughness Testing and Prediction for Ceramic Materials Using in Large-Flow-Rate Emulsion Pumps
Ran Li,
Wenshu Wei,
Shoubin Li,
Yinshui Liu,
Hao Liu,
Huigang Wu,
Wei Wang,
Jian Ye,
Chenjin Tian,
Dalong Wang,
Mengyu Wu,
Jiankai Zhang
Issue:
Volume 7, Issue 2, April 2019
Pages:
46-53
Received:
20 April 2019
Accepted:
28 May 2019
Published:
12 June 2019
Abstract: Fracture toughness (KIC) tests have been carried out on single edge precracked beam specimens with dimensions in accordance with ISO15732 requirements for two types of zirconia and one type of alumina, i.e. ZrO2 -1, ZrO2 -2 and Al2O3. Experimental determinations of KIC for the two zirconia and one alumina materials are 12.18 MPa•m1/2, 16.35 MPa•m1/2 and 4.99 MPa•m1/2, respectively. The median rank method is used to calculate the probability of fracture, F(KIC) of the three cermaic materials for representing the experimental results. The SEM analysis on fracture surfaces of ZrO2-1 materials is carried out, which indicates the fracture in ZrO2 -1 material occurred at the interior of the grain associated with interior stress distribution with principal components of ZrO2 and SiO2. Th extended finite element method (XFEM), based on the linear elastic fracture mechanics in conjuciton with a bilinear traction-separation damage law, is used to simulate the progressive crack growth process in the SEPB specimens. The XFEM predicted KIC results are compared with the corresponding experimental data. The XFEM approach overpredicts the KIC values, from 10.4% to 25.6%, for the three ceramic materials. The possible reasons, in the aspect of loading conditions and contact assumptions, for the difference between the predicted and tested results are also discussed.
Abstract: Fracture toughness (KIC) tests have been carried out on single edge precracked beam specimens with dimensions in accordance with ISO15732 requirements for two types of zirconia and one type of alumina, i.e. ZrO2 -1, ZrO2 -2 and Al2O3. Experimental determinations of KIC for the two zirconia and one alumina materials are 12.18 MPa•m1/2, 16.35 MPa•m1/...
Show More
-
A Study of Mechanical Properties Evaluation for Stainless Steel Under Low Temperature Region
Jung Soo Oh,
Sueng Hyun Cho,
Min Young Hong,
Bong Soo Lee
Issue:
Volume 7, Issue 2, April 2019
Pages:
54-57
Received:
15 April 2019
Published:
15 June 2019
Abstract: For equipment operated in extreme weather regions such as Eastern Europe, Northern Russia, and Canada, etc. (with average temperature is colder than –20°C during winter), measures against freezing are necessary for the materials that compose plant modules and metal materials for the components of automobiles. However, only a portion of research on the effects at high temperatures have been performed in the cases of high-speed tension tests for cryogenic materials until now with the effects at low temperature being confirmed only to the extent of the presence of differences at high and low speeds. In this study, characteristics of two universal materials for stainless steel, namely TP304 and TP316, at low temperature were examined by executing comparative tests on their mechanical characteristics at both ordinary temperature and low temperature. As a result, TP304 displayed a secondary stiffening phenomenon in the low temperature range. Meanwhile, TP316 displayed a reduction in the elongation ratio in the low temperature and it was confirmed that the maximum tensile strength increased more so than at ordinary temperature. Regarding temperature dependency, the maximum tensile strength and elongation ratio were higher for TP304, while the yield strength was higher for TP316.
Abstract: For equipment operated in extreme weather regions such as Eastern Europe, Northern Russia, and Canada, etc. (with average temperature is colder than –20°C during winter), measures against freezing are necessary for the materials that compose plant modules and metal materials for the components of automobiles. However, only a portion of research on ...
Show More
-
Design of Solar Powered and Fatigue Durable Quadcopter
Ying Xu,
Qianfeng Wan,
Mwanza Taipa Raymond,
Gang Lu,
Xianghu Zeng
Issue:
Volume 7, Issue 2, April 2019
Pages:
58-65
Received:
22 April 2019
Published:
15 June 2019
Abstract: This paper features a new concept design of mini-quadcopter consisting of two types of power source systems. The solar type of power source and rechargeable lithium battery type of power source systems. The quadcopter design introduced showcases the extensive usefulness of solar cells on aircrafts. The title is “SPFD quadcopter”, the SPFD stand for “solar powered fatigue durable” quadcopter. the quadcopter in question is designed to be powered by 40 solar thin film cells rated at 1.5v per panel. A fatigue analysis is conducted in its arm structures that offer support to the four mounted brushless motors responsible for driving the propellers that produce sufficient thrust to provide lift. By use of the “ANSYS” designing and simulating program, the carried out analysis shows the level of deformation in the arms due to the weight of the entire craft which tends to rest on the arms when the quadcopter is in flight. A fatigue structure analysis was considered necessary, to take appropriate precautions in both early stages of design and choice of material, to prevent premature structure failure in the field. Our objective of this paper is generally to show case the use of flexible solar cells as the source of power for providing power to the motors with the capability of charging the lithium battery during flight when being operated in battery mode. this new type of UAV can be used for military and civilian needs, surveillance and even space operations such as being set as a satellite to provide signal for internet back to earth.
Abstract: This paper features a new concept design of mini-quadcopter consisting of two types of power source systems. The solar type of power source and rechargeable lithium battery type of power source systems. The quadcopter design introduced showcases the extensive usefulness of solar cells on aircrafts. The title is “SPFD quadcopter”, the SPFD stand for...
Show More
