scholarly journals Friction Damping in Compressor Blade Dovetail Attachments

1986 ◽  
Author(s):  
J. M. Allen
Keyword(s):  
Normal Force ◽  
Tangential Force ◽  
Resonant Response ◽  
Endurance Test ◽  
Friction Damping ◽  
Free Standing ◽  
Force Coefficient ◽  
Compressor Blades ◽  
Force Ratio ◽  
Cyclic Slip

An empirical model is presented for predicting the fundamental mode resonant response of friction damped, free standing compressor blades from the cyclic slip that can occur in its dovetail attachment. The model is an extension of the conventional approach in that it includes the microslip regime of slip by assuming that the tangential force coefficient (tangential force to normal force ratio when slip occurs) depends on the magnitude of slip but, like friction coefficient, is independent of normal force. Experimental data obtained from bench damping tests are presented relating these quantities for plain and coated [copper-nickel indium (Cu-Ni-In) plus molydisulphide (MoS2)] dovetail attachments. The results demonstrate that substantial friction damping can be obtained at low compressor speeds, where aerodynamic excitation is often most severe, and that such damping is dominated by the microslip properties of the dovetail interface. The dovetail coating significantly increased friction damping and proved to be durable in an endurance test, as it has in service.

scholarly journals Numerical Investigation the Effect of the Different Tip Vanes on the Loading of an H-VAWT

2018 ◽  
Vol 53 ◽  
pp. 03041 ◽  
Author(s):  
Li Shoutu ◽  
Wang Yin ◽  
Yang Congxin ◽  
Li Ye
Keyword(s):  
Normal Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Simulation Method ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Force Coefficient ◽  
Average Value ◽  
Unsteady Numerical Simulation

In this paper, the effect of the three typical tip vanes on the loading of an H-VAWT is investigated by employing the three-dimensional unsteady numerical simulation method. The results show that the both transient tangential force coefficient (CT) and normal force coefficient (Cn) have obvious change when the winglet and the V type vane is used at the blade's tip, respectively. However, in three tip vanes, the CT average value is the lowest and the CT fluctuation characteristic is the highest when the winglet is used. Although the winglet and V type vane contribute to change the transient CT and Cn, the normal force is increased too, it results in increasing fatigue loading and decreasing lifetime for H-VAWT. By comparison, the effect of the plate vane on the loading is weaker. Additionally, the winglet is advantage to improve power coefficient in the low tip speed ratio.

Experimental Verification of Friction Behaviors Under Periodically-Varied Normal Force by Developing a Two-Directional Friction Test System

2015 ◽  
Author(s):  
Kunio Asai ◽  
Muzio M. Gola
Keyword(s):  
Contact Pressure ◽  
Contact Area ◽  
Normal Force ◽  
Contact Stiffness ◽  
Tangential Force ◽  
Test System ◽  
Dissipated Energy ◽  
Friction Test ◽  
Force Coefficient ◽  
Tangential Contact

In order to achieve more accurate friction damping of turbine blades equipped with shroud covers and under-platform dampers, it is necessary to clarify such friction behaviors as tangential contact stiffness, micro-slips, and dissipated energy, under periodically varied normal force instead of constant normal force. Although some analytical studies were reported on the contact mechanics under alternating normal force, only minimal research has been conducted on the experimental verification of such behaviors, as friction tests were commonly done under constant normal force. In this study, we developed an original two-directional friction test system that can apply any combination of alternating normal and tangential forces by changing the displacement-controlled loading direction. In this system, relative displacement and contact force were measured simultaneously by using a laser Doppler displacement sensor and force transducers of the strain gage type. By using our original test system, we examined the dissipated energy under constant normal force and periodically-varied normal force whose amplitude is the same as that of tangential force with no phase difference. We then obtained a new finding that dissipated energy depends on alternating normal force under the same mean normal force and alternating tangential force. More specifically, when the tangential force coefficient, defined as the ratio of the amplitude of alternating tangential force to mean normal force, is large enough to cause a macro-slip, dissipated energy under variable normal force is smaller than that under constant normal force. Conversely, when tangential force coefficient is small in the micro-slip region, dissipated energy under variable normal force is larger than that under constant normal force. This behavior was successfully reproduced by FE analysis based on a macro-slip model, where an array of macro-slip elements was used to describe micro-slip behavior. It was found that alternating normal force makes it easier to cause a micro-slip in a certain area of the contact surface under variable normal force, resulting in higher dissipated energy than at constant normal force when tangential force coefficient is small. In this study, basic friction data were also obtained regarding the tangential contact stiffness with variations in contact pressure, as well as the relation between a micro-slip and the tangential force coefficient. Tangential contact stiffness increases as contact pressure increases. In addition, tangential contact stiffness increases with the nominal contact area, but is not proportional to the area. The non-dimensional slip range (corresponding to the ratio of slip range to stick displacement) was confirmed as being described in a unified form against different contact area (6 and 18 mm2) and contact pressure ranging from 3 to 40 MPa.

Grinding at Very Low Speed

2008 ◽  
Vol 53-54 ◽  
pp. 231-235 ◽  
Author(s):  
Bao Fu Feng ◽  
Lei Zheng ◽  
P. Wang ◽  
Quan Fang Gai ◽  
D. Li ◽  
...  
Keyword(s):  
Normal Force ◽  
Tangential Force ◽  
Grinding Force ◽  
Machining Process ◽  
Grinding Forces ◽  
Low Speed ◽  
Section Area ◽  
Force Ratio ◽  
Single Grain ◽  
Depth Increase

Grinding is a very complex machining process. Single grain grinding methods are useful to study complex grinding action. Very low speed single-grain grinding tests were carried out for 45 steel and 20Cr alloy with 14# ZA grain. The grinding groove width and depth, the grinding force ratio, specific grinding forces, and grain wear and fracture are studied. The plowing decreases with the grinding section area or grinding depth increase. The average tangential force at grain fracture in the experiments is 54.4N; the average normal force at grain fracture is 949.6N. The ratio of tangential-to-normal force varies suddenly when grain fracture.

scholarly journals Effect of Water-Based Nanolubricants in Ultrasonic Vibration Assisted Grinding

2018 ◽  
Vol 2 (4) ◽  
pp. 80 ◽  
Author(s):  
Mir Molaie ◽  
Ali Zahedi ◽  
Javad Akbari
Keyword(s):  
Surface Roughness ◽  
Specific Energy ◽  
Material Removal ◽  
Normal Force ◽  
Tangential Force ◽  
Process Efficiency ◽  
Multiwall Carbon Nanotube ◽  
Ultrasonic Vibrations ◽  
Mql Grinding ◽  
Water Based

Currently, because of stricter environmental standards and highly competitive markets, machining operations, as the main part of the manufacturing cycle, need to be rigorously optimized. In order to simultaneously maximize the production quality and minimize the environmental issues related to the grinding process, this research study evaluates the performance of minimum quantity lubrication (MQL) grinding using water-based nanofluids in the presence of horizontal ultrasonic vibrations (UV). In spite of the positive impacts of MQL using nanofluids and UV which are extensively reported in the literature, there is only a handful of studies on concurrent utilization of these two techniques. To this end, for this paper, five kinds of water-based nanofluids including multiwall carbon nanotube (MWCNT), graphite, Al2O3, graphene oxide (GO) nanoparticles, and hybrid Al2O3/graphite were employed as MQL coolants, and the workpiece was oscillated along the feed direction with 21.9 kHz frequency and 10 µm amplitude. Machining forces, specific energy, and surface quality were measured for determining the process efficiency. As specified by experimental results, the variation in the material removal nature made by ultrasonic vibrations resulted in a drastic reduction of the grinding normal force and surface roughness. In addition, the type of nanoparticles dispersed in water had a strong effect on the grinding tangential force. Hybrid Al2O3/graphite nanofluid through two different kinds of lubrication mechanisms—third body and slider layers—generated better lubrication than the other coolants, thereby having the lowest grinding forces and specific energy (40.13 J/mm3). It was also found that chemically exfoliating the graphene layers via oxidation and then purification prior to dispersion in water promoted their effectiveness. In conclusion, UV assisted MQL grinding increases operation efficiency by facilitating the material removal and reducing the use of coolants, frictional losses, and energy consumption in the grinding zone. Improvements up to 52%, 47%, and 61%, respectively, can be achieved in grinding normal force, specific energy, and surface roughness compared with conventional dry grinding.

A New Model of Local Elastic Deflections in Grinding

1984 ◽  
Vol 106 (1) ◽  
pp. 154-163 ◽  
Author(s):  
D. P. Saini
Keyword(s):  
Plastic Deformation ◽  
Mild Steel ◽  
Mathematical Models ◽  
Normal Force ◽  
Tangential Force ◽  
Force Component ◽  
Workpiece Material ◽  
Direct Function ◽  
New Model ◽  
Single Grain

Mathematical models describing the deflection behavior of the wheel-work contact presented so far are based on the assumption that contact deflections are a direct function of the normal force on the wheel or the grains during grinding. This paper presents experimental results showing the evidence of a new mechanism of contact deflections due to the rotation of grain as a result of the tangential force component. In this perspective, a new model which considers the deflections due to both the normal and the tangential force is proposed and developed with the assumption of elasto-plastic deformation of the workpiece material around the grain during cutting. The model is shown to be consistent with experimental deflections obtained from single grain cutting on mild steel and EN25 steel specimens.

Experimental Study of the Plastic Interaction of Model Surface Asperities during Sliding

1968 ◽  
Vol 10 (2) ◽  
pp. 121-132 ◽  
Author(s):  
C. M. Edwards ◽  
J. Halling
Keyword(s):  
Experimental Study ◽  
Friction And Wear ◽  
Normal Force ◽  
Tangential Force ◽  
Experimental Results ◽  
Interfacial Conditions ◽  
High Adhesion ◽  
Theoretical Predictions ◽  
Very High ◽  
Low Shear

The paper describes an experimental study of the plastic interaction of triangular shaped lead model asperities deformed under conditions of plane strain. The investigation yields values of the normal and tangential force variations throughout the junction interaction and details of the plastic deformation particularly in relation to junction growth. A number of asperity interfacial conditions are considered ranging from complete adhesion to very low shear strengths achieved using p.t.f.e. strip. The experimental results are compared with an earlier theoretical solution to this problem and show reasonable agreement with the theoretical predictions. In particular it is shown that the normal force, which is usually compressive, may become tensile for conditions of high adhesion between the asperities. This leads to very high values of the macroscopic friction coefficient such as occur in hard vacuum situations. The experimental results for the various surface conditions show sufficient agreement with theoretical predictions to justify the use of this type of theoretical approach for the wider study of the friction and wear of mating surfaces.

Investigation of Grinding Force and Surface Integrity of IC10 in Creep Feed Grinding

2020 ◽  
Author(s):  
Jun-chen Li ◽  
Wen-hu Wang ◽  
Rui-song Jiang ◽  
Xiao-fen Liu ◽  
Huang Bo ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Tool Wear ◽  
Material Removal ◽  
Normal Force ◽  
Removal Rate ◽  
Tangential Force ◽  
Grinding Force ◽  
Wheel Speed ◽  
Creep Feed Grinding ◽  
Creep Feed

Abstract The IC10 superalloy material is one of the most important materials for aero-engine turbine blade due to its excellent performances. However, it is difficult to be machined because of its special properties such as terrible tool wear and low machined efficiency. The creep feed grinding is widely used in machining IC10 superalloy due to the advance in reducing tool wear, improving material removal rate and surface quality. The creep feed grinding is a promising machining process with the advantages of high material removal rate due to large cutting depth, long cutting arc and very slow workpiece, and its predominant features might have significant influence on the grinding force and surface quality for the workpiece. Hence, it is of great importance to study the grinding force and surface integrity in creep feed grinding IC10 superalloy. In this paper, a series of orthogonal experiments have been carried out and the effects of grinding parameters on the grinding force and the surface roughness are analyzed. The topographies and defects of the machined surface were observed and analyzed using SEM. The results of the experiments show that the tangential force is decreased with the workpiece speed increasing. However, there is no significant change in tangential force with the increasing of grinding depth and wheel speed. The normal force is decreased with the workpiece speed increasing when the workpiece speed is less than 150 mm/min, but when the workpiece speed is more than 150 mm/min the normal force is increased tardily. Moreover, the normal force is increased sharply with the increase of grinding depth and is increased slowly with the increase of wheel speed. In general, the surface roughness is increased with workpiece speed and grinding depth increasing, while the trend of increase corresponding that of workpiece speed is more evident. The value of the surface roughness is decreased with wheel speed increasing. And it is found out that the main defect is burning of the IC10 superalloy material in creep feed grinding by energy spectrum analysis of some typical topography in this study.

scholarly journals A Technique to Determine Friction at the Fingertips

2008 ◽  
Vol 24 (1) ◽  
pp. 43-50 ◽  
Author(s):  
Adriana V. Savescu ◽  
Mark L. Latash ◽  
Vladimir M. Zatsiorsky
Keyword(s):  
Coefficient Of Friction ◽  
Normal Force ◽  
Tangential Force ◽  
Vertical Direction ◽  
Force Sensor ◽  
Displacement Method ◽  
Significant Difference ◽  
The Coefficient Of Friction ◽  
Slip Method ◽  
Slip Force

This article proposes a technique to calculate the coefficient of friction for the fingertip– object interface. Twelve subjects (6 males and 6 females) participated in two experiments. During the first experiment (the imposed displacement method), a 3-D force sensor was moved horizontally while the subjects applied a specified normal force (4 N, 8 N, 12 N) on the surface of a sensor covered with different materials (sandpaper, cotton, rayon, polyester, and silk).Thenormal forceand thetangential force(i.e., the force due to the sensor motion) were recorded. Thecoefficient of friction(µd) was calculated as the ratio between the tangential force and the normal force. In the second experiment (the beginning slip method), a small instrumented object was gripped between the index finger and the thumb, held stationary in the air, and then allowed to drop. The weight (200 g, 500 g, and 1,000 g) and the surface (sandpaper, cotton, rayon, polyester, and silk) in contact with the digits varied across trials. The same sensor as in the first experiment was used to record thenormal force(in a horizontal direction) and thetangential force(in the vertical direction). Theslip force(i.e., the minimal normal force or grip force necessary to prevent slipping) was estimated as the force at the moment when the object just began to slip. The coefficient of friction was calculated as the ratio between the tangential force and the slip force. The results show that (1) the imposed displacement method is reliable; (2) except sandpaper, for all other materials the coefficient of friction did not depend on the normal force; (3) theskin–sandpapercoefficient of friction was the highest µd= 0.96 ± 0.09 (for 4-N normal force) and theskin–rayonrayon coefficient of friction was the smallest µd= 0.36 ± 0.10; (4) no significant difference between the coefficients of friction determined with the imposed displacement method and the beginning slip method was observed. We view the imposed displacement technique as having an advantage as compared with the beginning slip method, which is more cumbersome (e.g., dropped object should be protected from impacts) and prone to subjective errors owing to the uncertainty in determining the instance of the slip initiation (i.e., impeding sliding).

scholarly journals Shape optimization of turbine blades with the integration of aerodynamics and heat transfer

1998 ◽  
Vol 4 (1) ◽  
pp. 21-42 ◽  
Author(s):  
J. N. Rajadas ◽  
A. Chattopadhyay ◽  
N. Pagaldipti ◽  
S. Zhang
Keyword(s):  
Heat Transfer ◽  
Shape Optimization ◽  
Tangential Force ◽  
Turbine Blades ◽  
Leading Edge ◽  
Optimization Techniques ◽  
Multidisciplinary Optimization ◽  
Heat Transfer Analysis ◽  
Maximum Temperature ◽  
Force Coefficient

A multidisciplinary optimization procedure, with the integration of aerodynamic and heat transfer criteria, has been developed for the design of gas turbine blades. Two different optimization formulations have been used. In the first formulation, the maximum temperature in the blade section is chosen as the objective function to be minimized. An upper bound constraint is imposed on the blade average temperature and a lower bound constraint is imposed on the blade tangential force coefficient. In the second formulation, the blade average and maximum temperatures are chosen as objective functions. In both formulations, bounds are imposed on the velocity gradients at several points along the surface of the airfoil to eliminate leading edge velocity spikes which deteriorate aerodynamic performance. Shape optimization is performed using the blade external and coolant path geometric parameters as design variables. Aerodynamic analysis is performed using a panel code. Heat transfer analysis is performed using the finite element method. A gradient based procedure in conjunction with an approximate analysis technique is used for optimization. The results obtained using both optimization techniques are compared with a reference geometry. Both techniques yield significant improvements with the multiobjective formulation resulting in slightly superior design.

Cutting performance comparison of two different diamond segments used in frame saw for granite

2020 ◽  
Author(s):  
Qin Sun ◽  
Jinsheng Zhang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Production Rate ◽  
Cutting Forces ◽  
Normal Force ◽  
Performance Comparison ◽  
Horizontal Force ◽  
Force Ratio ◽  
Wear Tool ◽  
Scanning Electron

A concave segment and a multi-layered segment were employed to cut large granite (size > 2000 mm × 2000 mm × 2000 mm) using diamond frame saw, which can mount 80 – 120 blades (size: 4000 mm × 180 mm × 3.5 mm). Cutting forces were determined by Kistler dynamometer and diamond segments wear was examined by Scanning Electron Microscopy and Keyence microscopy. Sawing performance of segments was evaluated by slab quality, radial wear, cutting force (force ratio) and slab production rate. Compared with multi-layered segments, experimental results showed that concave segments have better slab quality, lower cutting forces and force ratio (normal force/horizontal force), lower radial wear (tool consumption) and higher slab production rate. Experiments indicate that the concave diamond segments are more suitable for diamond frame saw to cut granite.

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