Dynamic Characteristics Optimization of Joint Interface of Machine Tool Based on Porous Oily Materials

2014 ◽  
Vol 709 ◽  
pp. 63-67
Author(s):  
Jian Feng Ma ◽  
Qiang Li ◽  
Ji Kun Feng ◽  
Liang Sheng Wu
Keyword(s):  
Porous Material ◽  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Unit Area ◽  
Test System ◽  
Joint Interface ◽  
Characteristic Parameters ◽  
Damping Characteristics ◽  
Stiffness And Damping

The joint interface plays a significant role in machine tools and other machineries. A novel type of joint which consists of oily porous material was proposed in the paper. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces were represented. The stiffness and damping parameters were compare to the conversional structures. The result showed that the joint which contains an oil film interlayer formed by porous and steel was superior to the joint with non-media formed by steel in stiffness and damping characteristics. In the case of the same preload, the former’s stiffness is increased by about 50 %, and the damping is increased about five to six times.

Research on the Static and Dynamic Characteristics of the Sliding Rail Joint Surfaces of the Fe-Based Porous Oily Material

2014 ◽  
Vol 607 ◽  
pp. 422-426
Author(s):  
Jian Feng Ma ◽  
Qiang Li ◽  
Liang Sheng Wu ◽  
Chong Nian Qu
Keyword(s):  
Dynamic Characteristics ◽  
Unit Area ◽  
Test System ◽  
Joint Interface ◽  
Equivalent Stiffness ◽  
Characteristic Parameters ◽  
Single Degree Of Freedom ◽  
Joint Surfaces ◽  
Machine Tool Structures ◽  
Stiffness And Damping

The dynamic characteristics of joint interfaces have significant effect on both static and dynamic behaviors of the whole machine tool structures. A test system for identifying the unit area dynamic characteristic parameters of Fe-based joint interfaces in still and motion states were represented based on Equivalent Single Degree Of Freedom (ESDOF) system theory. Compared with the stiffness and damping parameters in stationary state, the stiffness is reduced and the damping is increased in motion. When the velocity increased, the equivalent stiffness and damping parameters of joint interface are both increased.

Research on Stiffness and Damping Characteristics of Fixed Oily Porous Materials Joint Interface

2011 ◽  
Vol 422 ◽  
pp. 575-579
Author(s):  
Chong Nian Qu ◽  
Liang Sheng Wu ◽  
Jian Feng Ma ◽  
Yi Chuan Xiao
Keyword(s):  
Porous Material ◽  
Porous Materials ◽  
Parallel Plate ◽  
Joint Interface ◽  
Force Model ◽  
Equivalent Stiffness ◽  
Contact State ◽  
Damping Characteristics ◽  
Stiffness And Damping ◽  
Damping Model

In this document, using the anti-squeezed force model in the narrow parallel plate when fluid is squeezed, the equivalent stiffness and damping model is derived. It is further verified that it can increase the stiffness and damping while there are oil between the joint interfaces theoretically. Because the contact state of oily porous material can divide into liquid and solid parts, the document supposes that it is correct and effective to think the stiffness and damping of the two parts as shunt connection.

The Effects of the Damping Characteristics of Slideways on the Dynamic Characteristics of Workpiece Fixtures Mounted on Machine Tool Tables

1994 ◽  
Vol 208 (4) ◽  
pp. 245-251
Author(s):  
T Kobayashi ◽  
M Burdekin
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Design Criterion ◽  
Damping Characteristics ◽  
Machine Tool Structures ◽  
Dynamic Rigidity ◽  
Cutting Point

Not only dynamic characteristics of machine tool structures but also those of workpiece fixtures are important in machine tools as they directly influence the dynamic rigidity at a cutting point. In this paper, the effects of damping characteristics of slideways on the dynamic characteristics of workpiece fixtures mounted on machine tool tables have been clarified both theoretically and experimentally. Furthermore, a design criterion of workpiece fixtures has been suggested.

Dynamic Characteristics of a Machine Tool at Working Positions in Operating Test

2011 ◽  
Author(s):  
Huimin Dong ◽  
Yang Tan ◽  
Delun Wang ◽  
Yali Ma
Keyword(s):  
Machine Tool ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Dynamic Properties ◽  
Vibration Energy ◽  
Testing Method ◽  
Spring Element ◽  
Machining Center ◽  
Brick Element ◽  
Stiffness And Damping

A machine tool is an assembly structure fitted by some moveable substructures, which the relative motion between the substructures creates normal and limit operating positions. Along with the substructures moving, the distributions of masses, stiffness and damping of the machine in space vary, leading to variety of structure distributions and dynamic properties. For exploring the dynamic properties distributions of machine tools, this paper presents a testing method under practical operational excitations, which is under operating excitations from remaining unbalanced value in the spindle, and collecting vibration signals of time and frequency at the spindle foreside at working positions. To identify resonance characteristics, a judging matrix is established by comparing vibration energy and vibration amplitude at 1st octave. By this method, MDH50 active pole horizontal machining center is tested, and the dynamic characteristics is determined. It reveals that dynamic characteristics of resonance come from the substructure independent resonance and their superposition in operating excitation. For verifying this result, FEA is conducted, in which 20 nodes brick element and spring element are applied to build the model entities and interfaces. The analysis result by FEM is consistent to the testing results. The research provides foundation for how setting up machining programs to avoid the resonance vibration of the machine in the operating.

Dynamic Characteristics of Aerostatic Porous Journal Bearings With a Surface-Restricted Layer

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Yuta Otsu ◽  
Masaaki Miyatake ◽  
Shigeka Yoshimoto
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Dynamic Stiffness ◽  
Porous Metal ◽  
Journal Bearings ◽  
Low Permeability ◽  
Bearing Surface ◽  
Permeability Surface ◽  
Stiffness And Damping

Aerostatic porous bearings have been successfully applied to various precision devices such as machine tools and measuring equipment to achieve a higher accuracy of motion. However, aerostatic porous bearings have a disadvantage in that they are prone to cause pneumatic hammer instability. Therefore, to avoid this instability, a surface-restricted layer that has permeability smaller than the bulk of the porous material is usually formed on the bearing surface. In this paper, the dynamic characteristics of aerostatic porous journal bearings that have a surface-restricted layer are investigated numerically and experimentally. The effects of permeability in bulk porous materials and of a surface-restricted layer on the bearing characteristics are discussed using two kinds of porous material: graphite and metal. It was confirmed that aerostatic porous metal bearings with relatively large permeability could achieve large values of dynamic stiffness and damping coefficients using a low permeability, surface-restricted layer.

Rotordynamic Performance of a Rotor Supported on Bump Type Foil Gas Bearings: Experiments and Predictions

2006 ◽  
Vol 129 (3) ◽  
pp. 850-857 ◽  
Author(s):  
Luis San Andrés ◽  
Dario Rubio ◽  
Tae Ho Kim
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Load Capacity ◽  
Test System ◽  
Foil Bearings ◽  
Rotor Imbalance ◽  
Synchronous Motion ◽  
Damping Characteristics ◽  
Rotor Surface ◽  
Stiffness And Damping

Gas foil bearings (GFBs) satisfy the requirements for oil-free turbomachinery, i.e., simple construction and ensuring low drag friction and reliable high speed operation. However, GFBs have a limited load capacity and minimal damping, as well as frequency and amplitude dependent stiffness and damping characteristics. This paper provides experimental results of the rotordynamic performance of a small rotor supported on two bump-type GFBs of length and diameter equal to 38.10mm. Coast down rotor responses from 25krpm to rest are recorded for various imbalance conditions and increasing air feed pressures. The peak amplitudes of rotor synchronous motion at the system critical speed are not proportional to the imbalance introduced. Furthermore, for the largest imbalance, the test system shows subsynchronous motions from 20.5krpm to 15krpm with a whirl frequency at ∼50% of shaft speed. Rotor imbalance exacerbates the severity of subsynchronous motions, thus denoting a forced nonlinearity in the GFBs. The rotor dynamic analysis with calculated GFB force coefficients predicts a critical speed at 8.5krpm, as in the experiments; and importantly enough, unstable operation in the same speed range as the test results for the largest imbalance. Predicted imbalance responses do not agree with the rotor measurements while crossing the critical speed, except for the lowest imbalance case. Gas pressurization through the bearings’ side ameliorates rotor subsynchronous motions and reduces the peak amplitudes at the critical speed. Posttest inspection reveal wear spots on the top foils and rotor surface.

An Efficient Technique for Design of Hydraulic Engine Mount via Design Variable-Embedded Damping Modeling

2005 ◽  
Vol 127 (1) ◽  
pp. 93-99 ◽  
Author(s):  
Jun-Hwa Lee ◽  
Kwang-Joon Kim
Keyword(s):  
Dynamic Characteristics ◽  
Low Frequency ◽  
High Amplitude ◽  
Nonlinear Damping ◽  
Efficient Design ◽  
Equivalent Viscous Damping ◽  
Damping Characteristics ◽  
Design Variables ◽  
Engine Mount ◽  
Stiffness And Damping

For an efficient design of hydraulic mounts, it is most important to have a good mathematical model available, which must be simple yet capable of representing dynamic characteristics of the hydraulic mounts accurately. Under high amplitude excitations in the low-frequency range, the hydraulic mounts show strongly frequency-dependent stiffness and damping characteristics, which are related with so-called inertia track dynamics. Since nonlinear damping models based on fluid mechanics are typically used to predict the dynamic characteristics of the hydraulic mounts, relations between various design variables, such as geometry of the inertia track, and resultant stiffness and damping characteristics are understood only by tedious numerical computations. In this paper, the use of an equivalent viscous damping model—derived from a nonlinear model and represented in terms of design variables in an explicit manner—is proposed and, based on the equivalent linear model, are presented simple as well as very useful formulas for an efficient design of the hydraulic mounts.

Dynamic Modelling and Analysis of Rectangle-Shaped Plastic-Coated Slideways in Machine Tools

2011 ◽  
Vol 50-51 ◽  
pp. 37-41
Author(s):  
Jian Fu Zhang ◽  
Zhi Jun Wu ◽  
Ping Fa Feng ◽  
Ding Wen Yu
Keyword(s):  
Mathematical Model ◽  
Machine Tools ◽  
Vibration Mode ◽  
Dynamic Modelling ◽  
Rigid Bodies ◽  
Theoretical Research ◽  
Damping Characteristics ◽  
Vibration Properties ◽  
Stiffness And Damping ◽  
The Mathematical Model

The plastic-coated slideways have been widely used for form-generating movement in machine tools. Its dynamic behavior plays an important role in the vibration properties of the whole machine. In this work, according to the situation that researches on this subject were rather insufficient, a theoretical research was analyzed concerning the stiffness and damping characteristics of rectangle-shaped plastic-coated slideways. The mathematical model was firstly suggested especially based on the assembly of the saddle and worktable. Both stiffness and damping characteristics on vertical and horizontal directions were theoretically determined. To derive the governing motion equation of the slideway system, the carriage and rail were considered as rigid bodies and connected with a series of spring and damping elements at the joint face. Moreover, through the Lagrange’s approach, the frequencies of the carriage at vertical, pitching, yawing and rolling vibration mode were identified.

Design Optimization of Machine-Tool Structures With Respect to Dynamic Characteristics

1983 ◽  
Vol 105 (1) ◽  
pp. 88-96 ◽  
Author(s):  
M. Yoshimura ◽  
T. Hamada ◽  
K. Yura ◽  
K. Hitomi
Keyword(s):  
Machine Tool ◽  
Design Optimization ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Structural Model ◽  
Optimization Method ◽  
Practical Applications ◽  
Design Variables ◽  
Design Changes ◽  
Machine Tool Structures

This paper proposes a design optimization method in which simplified structural models and standard mathematical programming methods are employed in order to optimize the dynamic characteristics of machine-tool structures in practical applications. This method is composed of three phases: (1) simplification, (2) optimization, and (3) realization. As design variables employed in this optimization are greatly reduced, machine-tool structures are optimized effectively in practice. With large design changes being conducted through this multiphase procedure, dynamic characteristics of machine tools can be greatly improved. This method is demonstrated on a structural model of a vertical lathe.

Numerical Investigation of Static and Dynamic Characteristics of Water Hydrostatic Porous Thrust Bearings

2011 ◽  
Vol 5 (6) ◽  
pp. 773-779 ◽  
Author(s):  
Yuki Nishitani ◽  
◽  
Shigeka Yoshimoto ◽  
Kei Somaya
Keyword(s):  
Porous Material ◽  
Dynamic Characteristics ◽  
Machine Tools ◽  
Measuring Equipment ◽  
Load Capacity ◽  
Damping Coefficient ◽  
Static And Dynamic Characteristics ◽  
Thrust Bearings ◽  
Hydrostatic Bearings ◽  
Aerostatic Bearings

A moving table supported by aerostatic bearings can achieve excellent accuracy of motion because of its noncontact support and, hence, it is used in various precision machine tools and measuring equipment. However, because of low viscosity of air, the damping coefficient of aerostatic bearings is not very high, causing vibration with nanometer-order amplitudes. The accuracy of machine tools and measuring equipment could deteriorate because of this vibration. It is expected that water hydrostatic bearings would have a higher damping coefficient than aerostatic bearings due to the higher viscosity of water. In addition, water, like air, does not pollute the environment. In this paper, the static and dynamic characteristics of water hydrostatic thrust bearings using porous material were numerically investigated and comparedwith conventional pocket hydrostatic bearings with a capillary restrictor. Hydrostatic porous bearings can be easily constructed because the porous material becomes a viscous restrictor itself. It was consequently found that water hydrostatic porous thrust bearings have higher maximum load capacity and slightly lower stiffness than water bearings with a capillary restrictor.

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