Contact damping massachusetts institute of technology. If b 0, then viscous damping is only proportional to the mass distribution of the model, and eq. Suitability for an incremental approach to numerical solution merits its use. During formulation, the damping matrix is assumed to be proportional to the mass and stiffness matrices as follows. Abaqusbased verification of the rayleigh damping matrix in.
Modal analysis of mdof systems with proportional damping. An extended rayleigh damping matrix, called caughey damping 1,2. It should be mentioned that mass proportional damping can be applied by the abaqus directly. The concept of proportional damping is critically examined and a generalized.
Due to limitation imposed by the stable time increment, the stiffness proportional damping is usually neglected in abaqus explicit, and only a simplified mass proportional damping is used, which. For a damped harmonic oscillator with mass m, damping coefficient c, and spring constant k, it can be defined as the ratio of the damping coefficient in the systems differential equation to the critical damping. Threedimensional finite element models were developed for the constrained damping layer using the finite element package, abaqus. Data lines to define temperature andor field variabledependent mass proportional damping alphatabular in abaqusexplicit. This method is much faster than the direct method, but it has to ignore the damping effect of the dashpota. Several studies showed that by using appropriate parameters for the rayleigh damping, favorable results can be achieved in site response analysis e. To avoid a dramatic drop in the stable time increment, the stiffness proportional damping factor, should be less than or of the same order of magnitude as the initial stable time increment without damping. Rayleigh damping in abaqusexplicit dynamic analysis. The three damping models investigated were mass proportional, stiffness proportional, and viscoelastic. Rayleigh damping is defined by a damping matrix formed as a linear combination of the mass and the stiffness matrices. Currently the stiffness proportional damping is not working in abaqus. Jan 21, 2017 creating the spring mass system for studying wave propagation, using abaqus. The coefficients a 2p, b 0 were used to create a proportional.
Proportional damping an overview sciencedirect topics. Jun 22, 2014 viscous proportional damping is used for directintegration timehistory analysis. Damping coefficients technical knowledge base computers. Damping technical knowledge base computers and structures. On the use of materialdependent damping in ansys for mode. Damping mznual mass scaling can also be used with an anisotropic mass. A new form of mass proportional damping has been formulated in form of multi. Timedomain pml formulation for modeling viscoelastic waves. However, mass proportional damping can significantly affect rigid body motion, so large is often undesirable.
Abaqus users using stiffness proportional damping in a umat. Nonetheless the approximation of proportional damping is. In abaqus explicit the damping coefficient will remain at the specified constant value while the surfaces are in contact and at zero otherwise. Proportional damping is a widely used approach to model dissipative forces in complex engineering structures and it has been used in various dynamic problems for more than ten decades. A proportional damping model is the first analytical model used to study damping for an mdof system. Classical damping, nonclassical damping and complex modes. The damping ratio provides a mathematical means of expressing the level of damping in a system relative to critical damping.
How to set a special amount of damping in abaqusexplicit. When the materials, vibration control devices or vibration isolators in a structure have different damping ratios, elements with different damping ratios can be. Rayleigh damping in abaqusexplicit dynamic analysis scientific. This product is a complete abaqus environment that provides a simple, consistent interface for creating, submitting, monitoring, and evaluating results from abaqus simulations. Unlike mass and stiffness properties, damping cannot usually be modelled. Learn more abaqus create contact damping object in python script. If the element contains more than one material in abaqus standard, the volume average value of is used to multiply the elements mass matrix to define the damping contribution from this term. It is shown that a massproportional damping model gives a decay with distance. Viscous damping with the rayleigh damping approximation is commonly used for the linear and nonlinear site response analyses to model soil damping at small strains. The explicit dynamics procedure performs a large number of small time increments efficiently. Enter the stiffness proportional damping term to be used. This property is proportional to mass and stiffness.
Damping models for structural vibration university of cambridge. If the mass is pulled down an additional 3 in and then given an initial velocity downward of 4 insec. To define rayleigh damping, you specify two rayleigh damping factors. The parameters used in the theoretical results can be calculated as 25. Abaqus spring mass vibration system dynamic analysis with. This damping factor defines mass proportional damping, in the sense that it gives a damping contribution proportional to the mass matrix for an element. In the nonlinear timehistory analysis for highrise building, different damping models may lead to results with great difference. Hi, in an explicit model i d like to enter a mass proportional damping with parameter alpha r. Model calibration and validation for material damping using.
This became a stumbling block to the analysis of a damped mdof system. Limited by the stable time increment, the stiffness proportional damping is usually neglected in abaqus explicit, and only a simplified mass proportional damping is used, which can be derived from the fundamental frequency and the critical damping factor, hi this. The effect of damping on dynamic stress intensity factors in. Java project tutorial make login and register form step by step using netbeans and mysql database duration. Then, the effects of different damping ratios on dsifs in a plane strain plate with a center crack, and also a plane stress beam with an edge crack, assuming homogeneous and. So if you have trouble in setting the correct damping, you might need to look into the theory mannual to see what algorithm abaqus uses to compute the result. You can specify mass proportional loads such as gravitation on an anisotropic mass. To this end, the mass of the concrete slab is supported on spring elements see fig. I method of direct integration of equations of motion of the structuresoil system.
Many examples are provided to help you develop your own scripts. Data lines to define temperature andor field variable dependent mass proportional damping alphatabular in abaqusexplicit. It provides a convenient abstraction to damp lower massdependent and higher stiffnessdependent. Abaqusbased verification of the rayleigh damping matrix. If the proportional damping matrix coefficients are. Abaqus based verification of the rayleigh damping matrix in dynamic analyses for npp civil structures. Alpha and beta are constants used to set the amount of damping. Hysteretic proportional damping, also mass and stiffness proportional, is used for steadystate and powerspectraldensity analyses. In the nonlinear timehistory analysis for highrise building, different damping. May 16, 2014 rayleigh damping was utilized to consider the structural damping mechanisms in the dynamic analysis of the bridge. For example, to model the damping of an aircraft fuselage one could fit generalized proportional damping models for all the ribs and panels by testing them separately and then combine the element or substructure damping matrices in a way similar to the assembly of the mass and stiffness matrices in the standard finite element method. Stack overflow for teams is a private, secure spot for you and your coworkers to find and share information. The damping coefficient can be defined as a proportionality constant with units of pressure divided by velocity or as a unitless fraction of critical damping. Lab 2c driven mass spring system with damping objective warning.
And the only way to apply the damping is to use modal damping. Mar 31, 2012 this research explored the relationship between physical damping and its implementation in abaqus, with a focus on investigating the different effects of different damping models. Rayleigh damping came out of linear theory mass springdashpot systems where it is easy to view each mode independently. Proportional damping is rather unique, since only one or two parameters at most. If the element contains more than one material in abaqus standard, the volume average value of. The viscous, mass, andor stiffness proportional damping matrix will include the. For abaqus standard the default value for the tangent fraction is 0. Hence, proportional damping is not a rule but rather the exception.
Finite element modeling of the dynamic response of a. Displacement of the free bridge edge in response to a random excitation 2. In abaqus, the damping can be defined at a materialelement level and global level in the analysis. An important parameter to describe the properties of the damping is damping ratio. This manual describes the abaqus scripting interface, which is an application 6. Damping devices may also be modeled as a structural subsystem, as described. An example of adding a gui plug in to the plugins menu. Damping modelling using generalized proportional damping. By this artifice damping dependent on mass only can be attained 7 viscous damping. You can define the fraction of critical damping to be used with the mass elements when calculating composite damping factors for the modes when used in modal dynamic analysis.
The umat was verified to consider the stiffness proportional damping correctly. Damping is a function of velocity, so if there is no motion then there will be no damping. Modeling technique of material damping properties in ansys. Material damping massachusetts institute of technology. I use abaqus for dynamic analysis of composite structures. Mass proportional damping ratios decrease inversely with.
Mass and stiffness proportional damping, normally referred to as rayleigh damping, is commonly used in nonlineardynamic analysis. With these factors specified, the damping matrix cis added to the system. Hello i have a umat and i need to add stiffness proportional damping to it by writing codes inside it because abaqus only allows defining mass proportional damping for umats. Mass proportional damping in nonlinear timehistory. Then determine the first time the maximum magnitude will occur. R is used to multiply the elements mass matrix to define the damping contribution from this term.
Abaqus offers several methods for performing dynamic analysis of problems in. As stated previously, damping in the tangential direction in abaqus explicit is proportional to the elastic slip rate see frictional behavior rather than the total rate of relative sliding. Determine the position ut of the mass at any time t. To measure and investigate the dynamic characteristics of a driven spring mass damper system. The hyperelastic and viscoelastic behaviour were considered to represent the material properties of the rubber layer. Abaqus create contact damping object in python script. Abaqus provides rayleigh damping for these situations.