Identification and Modeling of Process Damping in Milling

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
L. T. Tunc ◽  
E. Budak
Keyword(s):  
Energy Balance ◽  
Time Domain ◽  
Stability Limit ◽  
Process Damping ◽  
Damping Coefficients ◽  
Tool Geometries ◽  
Different Types ◽  
Stability Limits ◽  
Milling Tools ◽  
Cutting Speeds

In this study, a practical identification method for process damping is presented for milling, and the information obtained from identification is used for modeling purposes. In the proposed approach, the process-damping coefficients in x and y directions are identified directly from the experimental stability limits. Then, they are used in identification of the indentation constant through energy balance formulation. The identified indentation constant is further used in modeling of process damping and estimation of stability limit for different cutting conditions and tool geometries. Milling tools with two different types of flank geometries, namely, planar and cylindrical, are considered in this study. The predictions are verified by time-domain simulations and experimental results. It is shown that the presented method can be used for identification and modeling of process damping in milling to determine chatter-free cutting depths at relatively low cutting speeds.

A New Method for Identification and Modeling of Process Damping in Machining

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
E. Budak ◽  
L. T. Tunc
Keyword(s):  
Stability Limit ◽  
Damping Coefficient ◽  
Test Results ◽  
Limited Data ◽  
Damping Force ◽  
Process Damping ◽  
Analytical Stability ◽  
Practical Model ◽  
The Stability ◽  
Stability Limits

Although process damping has a strong effect on cutting dynamics and stability, it has been mostly ignored in chatter analysis as there is no practical model for estimation of the damping coefficient and very limited data are available. This is mainly because of the fact that complicated test setups were used in order to measure the damping force in the past. In this study, a practical identification and modeling method for the process damping is presented. In this approach, the process damping is identified directly from the chatter tests using experimental and analytical stability limits. Once the process damping coefficient is identified, it is related to the instantaneous indentation volume by a coefficient which can be used for different cutting conditions and tool geometries. In determining the indentation coefficient, chatter test results, energy, and tool indentation geometry analyses are used. The determined coefficients are then used for the stability limit and process damping prediction in different cases, and verified using time-domain simulations and experimental results. The presented method can be used to determine chatter-free cutting depths under the influence of process damping for increased productivity.

The Study on the Influence of Pipe-Soil Interaction on VIV for Different Free Span Types

2017 ◽  
Author(s):  
Chongyao Zhou ◽  
Gang Xu ◽  
Zhiming Huang ◽  
Dagang Zhang ◽  
Naiquan Ye ◽  
...  
Keyword(s):  
Time Domain ◽  
Cross Flow ◽  
Sensitivity Study ◽  
Structural Damping ◽  
Flexible Pipe ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Different Types ◽  
Main Factors ◽  
Parameter Influence

Subsea pipeline laid on the seabed will experience free span when the lay path is long and seabed is rugged. Hydrodynamic loads caused by the currents around the pipeline can induce oscillations in both cross-flow and in-line directions. This phenomenon is called vortex-induced vibration (VIV) which is the most common case that could induce serious fatigue problems. The pipe-soil interaction is one of the main factors that influence the vibration. In this paper, a study focusing on the effect of pipe-soil interaction on VIV for different types of free span is presented. The Milan wake oscillator is applied to calculate the dynamic response induced by VIV in Orcaflex, and the results are compared with experimental data to identify its validity. A sensitivity study is also performed to study the parameter influence of the Milan wake oscillator model. Four types of free span (including the multiple free spans) are modeled in Orcaflex and time domain VIV analysis is carried out to study the influence of pipe-soil interaction. Comparison among different types of free span is discussed. The influence of structural damping is studied for flexible pipe only because its influence on steel pipe is negligible. The influence of structural damping on flexible pipe is studied by means of a predefined moment-curvature curve. In addition, several cases are studied to investigate the influence of tension on VIV by Milan wake oscillator.

Mechanism of Variable Helix Tools in Suppressing Chatter Using Process Damping for Machining Titanium Alloys at Low Cutting Speed

2013 ◽  
Vol 773-774 ◽  
pp. 370-376
Author(s):  
Muhammad Adib Shaharun ◽  
Ahmad Razlan Yusoff ◽  
Mohammad S. Reza
Keyword(s):  
Titanium Alloy ◽  
Cutting Speed ◽  
Milling Process ◽  
Cutting Process ◽  
Chatter Vibration ◽  
Process Damping ◽  
High Cutting Speed ◽  
Titanium Machining ◽  
Different Types ◽  
Variable Helix

Titanium is difficult-to-cut materials due to its poor machinability and thermal conductivity when machining at high cutting speed. To overcome this machining titanium alloy problem, this study in interaction between machining structural system and the cutting process are very important. One of the main problems in the cutting process is chatter vibration. Due to chatter problem, the mechanism to suppress chatter named, process damping is a useful method can be manipulated to improve the limited productivity of titanium machining at low speed machining in milling process. In the present study, experiment are conducted to evaluate and study the process damping mechanism in milling using different types of variable tools geometries. These tools are variable he-lix/uniform pitch, variable pitch/uniform helix and variable helix and pitch and uniform helix/pitch. The result showed that the variable helix and pitch tools is very significantly improve process damping performance in machining titanium alloy compare to traditional of regular tools and other irregular tools.

scholarly journals Characteristics of Functional Stability in Young Adolescent Female Artistic Gymnasts

2021 ◽  
Vol 77 (1) ◽  
pp. 51-59
Author(s):  
Agnieszka Opala-Berdzik ◽  
Magdalena Głowacka ◽  
Kajetan J. Słomka
Keyword(s):  
Postural Control ◽  
Center Of Pressure ◽  
National Level ◽  
Stability Limit ◽  
Young Adolescent ◽  
Quiet Standing ◽  
Adolescent Female ◽  
Functional Stability ◽  
Postural Control System ◽  
Stability Limits

Abstract The aim of this study was to determine whether young adolescent female artistic gymnasts demonstrate better functional stability than age- and sex-matched non-athletes. Different characteristics of the gymnasts’ postural control were expected to be observed. Twenty-two 10- to 13-year-old healthy females (ten national-level artistic gymnasts and twelve non-athletes) participated in the study. To assess their forward functional stability, the 30-s limit of stability test was performed on a force plate. The test consisted of three phases: quiet standing, transition to maximal forward leaning, and standing in the maximal forward leaning position. Between-group comparisons of the directional subcomponents of the root mean squares and mean velocities of the center of pressure and rambling-trembling displacements in two phases (quiet standing and standing in maximal leaning) were conducted. Moreover, anterior stability limits were compared. During standing in maximal forward leaning, there were no differences in the center of pressure and rambling measures between gymnasts and non-athletes (p > 0.05). The values of trembling measures in both anterior-posterior and medial-lateral directions were significantly lower in gymnasts (p < 0.05). Both groups presented similar values for anterior stability limits (p > 0.05). The comparisons of rambling components may suggest a similar supraspinal control of standing in the maximal leaning position between gymnasts and healthy non-athletes. However, decreased trembling in gymnasts may indicate reduced noise in their postural control system possibly due to superior control processes at the spinal level. The anterior stability limit was not influenced by gymnastics training in female adolescents.

An improved semi-analytical approach for modeling of process damping in orthogonal cutting considering cutting edge radius

2019 ◽  
Vol 234 (3) ◽  
pp. 641-653 ◽  
Author(s):  
Chang Cao ◽  
Xiao-Ming Zhang ◽  
Tao Huang ◽  
Han Ding
Keyword(s):  
Computational Efficiency ◽  
Orthogonal Cutting ◽  
Finite Amplitude ◽  
Cutting Edge ◽  
Workpiece Surface ◽  
Process Damping ◽  
Flank Face ◽  
The Stability ◽  
The Time Domain ◽  
Stability Limits

Process damping generated between the tool flank face and the wavy finish workpiece surface has a non-negligible effect on cutting dynamics and chatter stability, especially at low cutting speeds, resulting in higher stability limits. In modeling of process damping, the calculation of extruded volume is one of the most critical challenges, especially in machining with honed tools due to the complex and time-variable contact condition between the arc cutting edge and the finite amplitude wave surface. In this study, a semi-analytical method with high computational efficiency is proposed to calculate the extruded volume in cutting with honed tools. Based on this method, we construct the stability lobes under the condition of finite vibration amplitude accurately and efficiently, which overcomes the limitation of analytical methods based on the assumption of small amplitude vibrations and the low computational efficiency of numerical method. The predicted cutting stability is verified against both the experimental results and the time-domain simulation results.

scholarly journals Thermal Time Constant of PV Roof Tiles Working under Different Conditions

2019 ◽  
Vol 9 (8) ◽  
pp. 1626 ◽  
Author(s):  
Kurz ◽  
Nawrowski
Keyword(s):  
Energy Balance ◽  
Thermal Resistance ◽  
Temperature Change ◽  
Environmental Parameters ◽  
Thermal Capacity ◽  
Electrical Characteristics ◽  
Legal Regulations ◽  
Temperature Changes ◽  
Different Types ◽  
The Relationship

This paper presents different types of photovoltaic (PV) roof tiles integrating PV cells with roof covering. Selected elastic photovoltaic roof tiles were characterised for their material and electrical characteristics. Practical aspects of using PV roof tiles are discussed, alongside the benefits and drawbacks of their installation on the roof. Thermal resistance, heat transfer coefficient and thermal capacity were identified for elastic PV roof tiles and roof construction built of boards and PV roof tiles, according to valid standards and legal regulations. The resistance–capacity (RC) models of PV roof tiles and roofs are proposed according to the time constants identified for the analysed systems. The energy balance of the studied systems (PV roof tiles alone and the roof as a whole) is presented, based on which temperature changes in the PV cells of the roof tiles working under different environmental conditions were identified. The timing of PV cells’ temperature change obtained by material data and energy balance analyses were compared. The relationship between the temperature change times of PV cells and the thermal resistance and heat capacity of the whole system are demonstrated, alongside environmental parameters.

The Electric Arc Furnace—A Useful Teaching System

1980 ◽  
Vol 17 (1) ◽  
pp. 51-57
Author(s):  
R. Armstrong
Keyword(s):  
Magnetic Fields ◽  
Frequency Domain ◽  
Time Domain ◽  
Stability Limit ◽  
Electric Arc Furnace ◽  
Electric Arc ◽  
Arc Furnace ◽  
Rotating Magnetic Fields ◽  
Teaching System

A simplified study of problems relating to an electric arc furnace system is presented as a means of illustrating a variety of principles required to produce a meaningful solution. Features discussed in the article are: Rotating magnetic fields; Linearisation technique; Time domain solution; Frequency domain solution; Locus diagram; Stability limit.

Unified integro-differential equation for efficient dispersive FDTD simulations

2017 ◽  
Vol 36 (4) ◽  
pp. 1089-1105 ◽  
Author(s):  
Omar Ramadan
Keyword(s):  
Differential Equation ◽  
Time Domain ◽  
Stability Limit ◽  
Model Parameters ◽  
Time Step ◽  
Content Type ◽  
Integro Differential Equation ◽  
Dispersive Model ◽  
Fdtd Simulations ◽  
Dispersive Models

Purpose The purpose of this paper is to derive a unified formulation for incorporating different dispersive models into the explicit and implicit finite difference time domain (FDTD) simulations. Design/methodology/approach In this paper, dispersive integro-differential equation (IDE) FDTD formulation is presented. The resultant IDE is written in the discrete time domain by applying the trapezoidal recursive convolution and central finite differences schemes. In addition, unconditionally stable implicit split-step (SS) FDTD implementation is also discussed. Findings It is found that the time step stability limit of the explicit IDE-FDTD formulation maintains the conventional Courant–Friedrichs–Lewy (CFL) constraint but with additional stability limits related to the dispersive model parameters. In addition, the CFL stability limit can be removed by incorporating the implicit SS scheme into the IDE-FDTD formulation, but this is traded for degradation in the accuracy of the formulation. Research limitations/implications The stability of the explicit FDTD scheme is bounded not only by the CFL limit but also by additional condition related to the dispersive material parameters. In addition, it is observed that implicit JE-IDE FDTD implementation decreases as the time step exceeds the CFL limit. Practical implications Based on the presented formulation, a single dispersive FDTD code can be written for implementing different dispersive models such as Debye, Drude, Lorentz, critical point and the quadratic complex rational function. Originality/value The proposed formulation not only unifies the FDTD implementation of the frequently used dispersive models with the minimal storage requirements but also can be incorporated with the implicit SS scheme to remove the CFL time step stability constraint.

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