Joseph C Slater

Tennessee Technological University | TTU · Department of Mechanical Engineering

Blade mounted strain gages are vital during rig and engine development to ensure safe engine operation. However, they also enable a change in dynamics of integrally bladed rotors (IBR). State-of-the-art IBR dynamic response predictions are accomplished using as-manufactured models (AMM) generated via optical measurements and mesh morphing. Two AMM...

Blade mounted strain gages are vital during rig and engine development to ensure safe engine operation. However, they also enable a change in dynamics of integrally bladed rotors (IBR). State-of-the-art IBR dynamic response predictions are accomplished using as-manufactured models (AMM) generated via optical topography measurements and mesh morphin...

As-manufactured rotors behave quite differently than nominal as-designed rotors due to small geometric and material property deviations in the rotor, referred to as mistuning. The mistuning of a 20 bladed, integrally bladed rotor (IBR) will be evaluated via analytical methods, benchtop testing, and using a rotating compressor research facility. Ana...

Safe engine operation is ensured by setting safety limits on rotor airfoil-mounted strain gauges that monitor the dynamic response of the component. Traditionally, strain gauge limits are generated using geometry obtained from an “as-designed” nominal model, in which finite element analysis is used to compute the static and modal stresses. Predicte...

As-manufactured rotors behave quite differently than nominal, as-designed rotors due to small geometric and material property deviations in the rotor, referred to as mistuning. The mistuning of a 20 bladed, integrally bladed rotor (IBR) will be evaluated via analytical methods, bench-top testing, and using a rotating compressor research facility. A...

Python -based harmonic balance solver.

You've spent days/months/years collecting/analyzing your research topic. You put the requested information into your paper/presentation, turn it in, and viola, you're done, right? Not really. What you've just generated is an electronic document of which the only remaining part may be a hard copy in a few years. Further, without all of the splendid...

The geometric mistuning problem is investigated for dual flow-path integrally bladed rotors (DFIBRs) by outlining two methods that explicitly account for blade geometry surface deviations. The methods result in reduced-order models (ROMs) that are a reduced form of a parent Craig-Bampton component mode synthesis (CB-CMS) model. This is accomplished...

Bending fatigue behaviour of direct metal laser sintering (DMLS), Nickel (Ni) Alloy 718 has been assessed as preliminary qualification to additively manufacture advanced gas turbine engine components. Motivation for this work comes from the possibility of using DMLS to improve functionality of hot-section components. By using DMLS, turbine blades a...

Fatigue damage is a critical problem for turbomachinery blisks. Although methods exist to manage the associated risks, they are slow, costly, and imperfect. An automated non- destructive evaluation (NDE) or structural health monitoring (SHM) method is therefore sought to not only improve current identification capabilities, but also to reduce assoc...

Two methods that explicitly model airfoil geometry surface deviations for mistuning prediction in integrally bladed rotors are developed by performing a modal analysis on different degrees of freedom of a parent reduced-order model. The parent reduced-order model is formulated with Craig-Bampton component-mode synthesis in cyclic symmetry coordinat...

A framework for creating a digital representation of physical structural components is investigated. A model updating scheme used with an artificial neural network to map updating parameters to the error observed between simulated experimental data and an analytical model of a turbine-engine fan blade. The simulated experimental airfoil has as-manu...

New turbine engine designs requiring secondary flow compression often look to dual flow- path integrally bladed rotors (DFIBRs) since these stages have the ability to perform work on the secondary, or bypassed, flow-field. While analogous to traditional integrally bladed rotor stages, these new DFIBR designs have many differences that result in uni...

Fatigue damage is a central concern for turbomachinery blisk safety, and inspection methods used to identify such damage are both too slow and too expensive. The high costs of implementation and higher costs for failure to detect fatigue damage demonstrate the need for an automated, offline structural health monitoring system capable of reducing co...

Two deterministic mistuning models utilizing component mode synthesis methods are used in a Monte Carlo simulation to generate mistuned response distributions for a geometrically perturbed integrally bladed rotor. The first method, a frequency-perturbation approach with a nominal mode approximation used widely in academia and industry, assumes airf...

Common vibration features such as natural frequencies and mode shapes as well as quantities derived from them are not very sensitive to crack-type damage until the damage is so large that it can become catastrophic. Several research groups have studied the effects of crack type damage on bladed disks. Fatigue cracks typically have very little, if a...

New geometric mistuning approaches for integrally bladed rotors (IBRs) are developed for incorporating geometric perturbations to a fundamental disk-blade sector, particularly the diskblade boundary, or connection. The developed Reduced Oder Models (ROMs) are formulated from a Craig-Bampton component mode synthesis (C-B CMS) framework that is furth...

Fatigue cracks pose significant risk to turbomachinery blisks, and current inspection methods are slow, costly and imperfect. Developing an automated structural health monitoring (SHM) system can help to reduce costs and improve detection probability, but a fast method for producing the necessary data libraries is prerequisite. In an effort to deve...

There is need for an automated Structural Health Monitoring (SHM) system capable of fatigue crack detection in bladed disks as current methods are slow, costly and imperfect. Prerequisite for such a system is a fast method for producing the necessary data libraries. In an effort to develop such a method for simulating nonlinear structural response,...

There is need for an automated Structural Health Monitoring (SHM) system capable of fatigue crack detection in bladed disks as current methods are slow, costly and imperfect. Prerequisite for such a system is a fast method for producing the necessary data libraries. In an effort to develop such a method for simulating nonlinear structural response,...

Large rigid body-like motions couple with potentially significant deections are com- monplace amongst ornithopters in both nature and laboratories. In the highly weight- constrained designs of ornithopters, accurate modeling of dynamic interplay between the control, actuation, mechanisms, and exible wing will be necessary for development of control...

Fatigue crack detection in aircraft engine bladed disk assemblies is slow, costly and imperfect, but developing an automated Structural Health Monitoring (SHM) system can help to reduce cost and improve detection probability. However, current methods for modeling nonlinear structural response are also too slow to generate suficiently large data lib...

Ballutes, balloon-parachutes, have been of considerable interest for atmospheric reentry for decades.7 While hyper- and super-sonic simulations are considered to be relatively reliable,6,9 the subsonic stability predictions of ballutes are not reliable. In this effort a ballute-like reentry vehicle was dropped into free fall from 98,000 ft. and 6 D...

The goal of this research is to further develop a Structural Health Monitoring (SHM) system for detection of fatigue cracks in blades and bladed disks using harmonic responses caused by crack nonlinearities. Driving weakly nonlinear systems, such as a cracked structure, results in the generation of harmonics. When these harmonics coincide with a re...

Damage in structural members usually causes stiffness changes that could be linear or nonlinear. Opening and closing fatigue cracks are usually represented by a bilinear stiffness characteristic. This work describes damage identification approach that is based on the changes in statistical properties of randomdec signatures caused by the onset of n...

Detection of fatigue cracks in turbomachinery components is an important and costly task. This work focuses on nonlinearities in the system dynamics resulting from the opening and closing of cracks that causes super-harmonic and sub-harmonic resonances due to harmonic excitations. Preliminary analytical results for a hypothetical compressor disk mo...

Identification of fatigue cracks in turbo-machinery components is a vital but costly effort. This work focuses on nonlinearities in the response behavior resulting from the opening and closing of cracks that results in super-harmonic resonances due to harmonic excitations. Experimental results for a cracked cantilever beam are presented as well as...

This article describes additional investigations on the detection of structural damage using randomdec signatures from experimental data. Previous application of the method to experimental data from the cracked beam showed that damage detection was possible, but it was not very reliable. It was found that some data from the intact baseline beam wou...

This article describes detection of structural damage using statistical properties of randomdec signatures. Proposed technique is model free and does not require input measurements. The technique is evaluated using acceleration data obtained from a finite element model of a frame-like structure. Damage in the model is represented by a structural me...

This article describes detection of structural damage using statistical properties of randomdec signatures. Proposed technique is model free and does not require input measurements. The technique is evaluated using acceleration data obtained from a finite element model of a frame‐like structure. Damage in the model is represented by a structural me...

The Wright State University Trebuchet Competition distinguishes itself from other STEM out- reach events in that it combines teamwork and a sporting event at the culmination of in-school educational activities. A moving average of approximately 20 local high schools participate in this event each year, with a total of 450 active participants in 200...

Mechanical joints are a primary source of variability in the dynamics of built-up structures. Physical phenomena in the joint are quite complex and therefore too impractical to model at the micro-scale. This motivates the development of lumped parameter joint models with discrete interfaces so that they can be easily implemented in finite element c...

This article describes detection of structural damage using statistical properties of ran-domdec signatures. Proposed technique is model-free and does not require input measurements. The technique is evaluated using acceleration data obtained from a finite element model of a frame-like structure. Damage in the model is represented by a structural m...

This work illustrates application of the minimum model error system identification method to obtain the nonlinear state space models of a fluttering panel. Identification using position and velocity data from forced response of the panel is presented here. The response was numerically simulated using two different discretization approaches: through...

The minimum model error method is applied to identify,models of a panel undergoing limit-cycle oscillations. This work is focused on identification using free-response position and velocity measurements. The response of the panel was obtained using two discretization approaches: through the use of finite differences and by Galerkin's method. Data f...

The majority of structural health monitoring techniques are based on detection of significant variation in vibration parameters. The random decrement technique allows estimation of modal parameters without having direct measurements of the inputs. The technique has been successfully applied for modal analysis and health monitoring of various struct...

The Minimum Model Error identification technique in conjunction with Proper Orthogonal Decomposition is used to obtain a reduced order nonlinear state space model of the fluttering panel. System identification is performed using the free response position and velocity data. Previous work on panel flutter identification with this identification tech...

The minimum model error method is applied to identify,models of a panel undergoing limit-cycle oscillations. This work is focused on identification using free-response position and velocity measurements. The response of the panel was obtained using two discretization approaches: through the use of finite differences and by Galerkin's method. Data f...

The nonlinear panel flutter problem solved by Dowell in 1966 is used to investigate the new application of the proper orthogonal decomposition model reduction technique to aeroelastic analysis. Emphasis is placed on the nonlinear structural dynamic equations with nonconservative forcing modeled assuming a supersonic, inviscid flow. Here the aeroela...

System identification is a valuable tool that can be used to create simplified mathematical models of complex aeroelastic systems. Linear system identification methods are very well developed. However, most dynamic systems are nonlinear, which limits the applicability of linear identification techniques. Minimum Model Error (MME) identification tec...

This paper investigates the effect of manufacturing variations on the blade-alone forced response of a transonic low aspect ratio fan. A simulated set of coordinate measurement machine measurements from a single rotor, representative of actual manufacturing variations, are used to investigate geometric effects. A reduced order model is developed to...

Proper orthogonal decomposition (POD) based reduced-order modelling is demonstrated to be a weighted residual technique similar to Galerkin's method. Estimates of weighted residuals of neglected modes are used to determine relative importance of neglected modes to the model. The cumulative effects of neglected modes can be used to estimate error in...

Development of proper orthogonal decomposition (POD) based reduced-order modelling as from of Galerkin's method is demonstrated. Neglected weighted residuals are used to evaluate the completeness of the simulation space defined by the POD analysis. This potentially allows the analyst to initiate further training when the reduced modes are no longer...

Proper orthogonal decomposition (POD) based reduced-order modelling is demonstrated to be a weighted residual technique similar to Galerkin's method. Estimates of weighted residuals of neglected modes are used to determine relative importance of neglected modes to the model. The cumulative effects of neglected modes can be used to estimate error in...

The fundamental challenge in identification of nonlinear dynamic systems is determining the appropriate form of the model. A robust technique which eliminates this problem is evaluated here. The technique is based on the Minimum Model Error (MME) optimal estimation approach. The method is applied to the identification of a nonlinear normal mode whi...

This work surveys methods for modeling and analyzing bladed disk assemblies common to gas turbine aircraft. An introduction to symmetric (tuned) bladed disk dynamics is presented, followed by a literature review of studies modeling bladed disks, blade mistuning, and the effect of mistuning forced response. A summary of results is given, and suggest...

Just like in any other L ATEX document, you begin the abstract, make the title, and define the author as shown in the example. Not that IMAC requires that the author names be in bold, so you have to do this yourself. In addition, I haven't yet hacked the style definition for the title. Maybe I will later, but that's a minor inconvenience.

In this paper two distinct methods, an impedance method and a "conventional" method, for modeling the dynamic interaction between the piezoelectric actuators/sensors and the substructures are summarized It is demonstrated that both methods yield equivalent models for the beam with piezoceramic actuation. The pros and cons of each technique are disc...

Convergence of finite element models is generally realized via observation of mesh independence. In linear systems invariance of linear modes to further mesh refinement is often used to assess mesh independence. These linear models are, however, often coupled with nonlinear elements such as CFD models, nonlinear control systems, or joint dynamics....

Many weakly non-linear structures exhibit normal modes that are analogous to linear modes of linear oscillatory systems. As in the testing of linear modal systems, optimal sensor and actuator placement is important for obtaining the best test results. Such optimal placement is also important in control. This paper addresses this issue by extending...

This paper examines a new approach for determining the nonlinear normal modes of undamped non-gyroscopic multiple degree-of-freedom systems. Unlike algebraic solutions that generally assume a solution in the form of a polynomial expansion, this method makes only the assumption of repetitive motion in numerically determining the mode shapes. The adv...

The inverse dynamic design technique presented herein tunes a structural model to achieve a prespecified frequency response at certain critical points of the structure. The technique can correct structural models based on vibration response test data and also can optimize structural design. The technique works by partitioning the second-order matri...

This work extends previous work on nonlinear normal modes to include the case of forced response. This allows the nonlinear normal mode method to be applied to the feedback control problem providing a new method of controlling nonlinear multiple-degree-of-freedom systems. The proposed method uses a transformation proposed earlier for homogeneous sy...

Comparisons are made between viscoelastic damping and certain types of feedback control. In situations where the sensors and actuators of a feedback control system are collocated, a designer can choose the parameters of the control law to mimic viscoelastic damping. This equivalence is illustrated for a simple mass-spring system and a more complica...

We consider a class of parameter estimation problems motivated by smart structures, i.e., structures with integrated piezoelectric actuators and sensors. Problems involving damped second order partial differential equations with unbounded input coefficients are discussed in the context of a variational formulation Theoretical, computational and exp...

This work formulates a method for the modeling of material damping characteristics in distributed parameter models which may be easily applied to models such as rod, plate, and beam equations. The general linear boundary value vibration equation is modified to incorporate hysteresis effects represented by complex stiffness using the transfer functi...

Many weakly nonlinear structures exhibit what are called nonlinear nomml modes which are analogous to linear modes of linear oscillatory systems. As in the testing of linear modal systems, optimal sensor and actuator placement is important for obtaining the best test results. This paper addresses this issue by extending the concepts of modal contro...

Modern finite element methods (FEM's) enable the precise modeling of mass and stiffness properties in what were in the past overwhelmingly large and complex structures. These models allow the accurate determination of natural frequencies and mode shapes. However, adequate methods for modeling highly damped and high frequency dependent structures di...

The authors consider parameter estimation problems in structures with piezoceramic actuators and sensors. The problems are discussed in the context of a variational formulation of damped second order partial differential equations with unbounded input coefficients. Approximation techniques are introduced and numerical results of parameter estimatio...

This work formulates a method for the modeling of material damping characteristics in plates. The Sophie German equation of classical plate theory is modified to incorporate hysteresis effects represented by complex stiffness using the transfer function approach proposed by Golla and Hughes, (1985). However, this procedure is not limited to this re...