Murat Inalpolat

University of Massachusetts Lowell | UML · Department of Mechanical Engineering

In this study, a dynamic model of a spur gear pair is employed to investigate the influence of gear tooth indexing errors on the dynamic response. This transverse-torsional dynamic model includes periodically-time varying gear mesh stiffness and nonlinearities caused by tooth separations in resonance regions. With quasi-static transmission error ti...

In this study, a two-dimensional, steady-state, discrete dynamic model of a double-planet planetary gearset is proposed. The dynamic model is generalized such that it can consist of N number of planet branches and can operate under any operating conditions (load and speed). The contact between each external to external and external to internal gear...

Wind turbine blades undergo high operational loads, experience variable environmental conditions, and are susceptible to failure due to defects, fatigue, and weather-induced damage. These large-scale composite structures are fundamentally enclosed acoustic cavities and currently have limited, if any, structural health monitoring (SHM) in place. A n...

A novel structural damage detection methodology that relies on the detectability of the changes in acoustic transmissibility across boundaries of structural cavities is investigated. The approach focuses on active damage detection by leveraging the acoustic pressure responses measured external to structural cavities while exposed to internal acoust...

This paper proposes a new in-situ damage detection approach for wind turbine blades, which leverages blade-internal non-stationary acoustic pressure fluctuations caused by the mechanical loading as the main source of excitation. This acoustic excitation was leveraged for the detection of fatigue-related damage modes on a full-scale wind turbine bla...

Explosive Ordnance Disposal (EOD) suits are widely used to protect human operators to execute emergency tasks such as bomb disposal and neutralization. Current suit designs still need to be improved in terms of wearer comfort, which can be assessed based on the interaction forces at the human-suit contact regions. This paper introduces a simulation...

A wind turbine blade monitoring system would provide significant benefit to wind farm owners and operators by reducing operation and maintenance costs and increasing energy production by limiting turbine downtime. Previous work has demonstrated potential success of a system based on monitoring the flow-generated sound with blade internal cavity mic...

This paper details an analytical investigation on free and forced vibration response sensitivity of centrifugal pendulum vibration absorbers (CPVA) to symmetry-breaking absorber imperfections. Minor variations in the absorbers’ design due to manufacturing tolerances, errors as well as operational wear and tear tend to break cyclic-symmetry and lead...

Existing passive acoustics-based techniques for wind turbine blade damage detection lack the robustness and adaptability necessary for an operational implementation due to their physics- and model-based dependency. In contrast, this study develops an entirely unsupervised, data-driven damage detection technique. The novelty of the technique lies in...

This paper details the development of a generalized computational approach that enables prediction of cavity-internal sound pressure distribution due to flow-generated noise at high frequencies. The outcomes of this research is of particular interest for development of an acoustics-based structural health monitoring system for wind turbine blades....

Soldiers working in the field of explosive ordnance disposal (EOD) wear cumbersome personal protective equipment (PPE) that may affect their performance in the field, limit their mobility, and cause discomfort. The objective of this study was to develop a test methodology to identify the relationship between EOD suit interface loads and mission-cri...

Noise generated by turbulent boundary layer over the trailing edge of a wind turbine blade under various flow conditions is predicted and analyzed for structural health monitoring purposes. Wind turbine blade monitoring presents a challenge to wind farm operators, and an in-blade structural health monitoring system would significantly reduce O&M co...

In this paper, a generalized nonlinear time-varying multibody dynamic model of dual clutch transmissions (DCT) is presented. The model consists of clutches, shafts, gears and synchronizers, and can be used to model any DCT architecture. A nonlinear clutch model is used to determine the transmitted power to the transmission at any speed and clutch t...

In this paper, a generalized dynamic model of a shell structure has been developed and utilized for diagnostics purposes. The dynamic model is three-dimensional, includes the effects of rotary inertia and shear deformation, and can handle moving loads in radial, tangential and axial directions. The model is utilized to determine in-plane radial dis...

Switch reluctance motors (SRM) have become a prominent alternative for electric vehicles in recent years due to their simple, high power density architecture and cost-effective manufacturability. Despite its potential, NVH problems have been one of the biggest challenges for SRM's implementation. Vibration and noise generated by the SRM are mainly...

A finite element based computational model simulating the standard drop tower test for military helmets was created and used in conjunction with a multi-output Gaussian process surrogate to seek different designs of helmets for improved blunt impact performance. Experimental drop test results were used for the validation of the model’s ability to s...

The development of a viable structural health monitoring (SHM) technology for the operational condition monitoring of wind turbine blades is of great interest to the wind industry. In order for any SHM technology to achieve the technical readiness and performance required for an operational implementation, advanced signal processing algorithms need...

Foams are used in a variety of impact energy absorption applications because of their ability to engage in large deformations under steady load transfer during the cell collapse. Quantification of the energy absorption capabilities of foams, including those resulting from repeated loading and unloading, is critical to both modeling and prototype de...

This article details the implementation of a novel passive structural health monitoring approach for damage detection in wind turbine blades using airborne sound. The approach utilizes blade-internal microphones to detect trends, shifts, or spikes in the sound pressure level of the blade cavity using a limited network of internally distributed airb...

This paper presents a general overview of the different aspects of a novel structural health monitoring technique developed for wind turbine blades. The proposed technique is based upon detecting the changes in acoustic transmission loss due to structural deformation and damage incurred. This acoustics-based damage detection technique consists of t...

A generalized computational methodology for reduced order acoustic‐structural coupled modeling of the aeroacoustics of a wind turbine blade is presented. This methodology is used to investigate the acoustic pressure distribution in and around airfoils to guide the development of a passive damage detection approach for structural health monitoring o...

This study employs an analytical model of a gear pair with transverse-torsional dynamics that allows analysis of single-sided, double-sided, and random rattle situations to contrast rattle characteristics of isotropic PM gears with a baseline steel gearset. This model utilizes time-varying gear mesh stiffness and transmission error as the internal...

A generalized nonlinear time-varying, planar dynamic model of bifilar centrifugal pendulum vibration absorbers (CPVA) is proposed. This dynamic model enables fast prediction of vibration reduction performance of any CPVA design considering the impact of absorber rollers, gravity, end stops and translational motion of the system. The modeling framew...

As the use of wind power continues to increase globally, the need for improved structural health monitoring systems for wind turbine blades increases as well. Acoustics-based methods are deemed promising in this endeavor, as they are non-contact, nondestructive and enabling distributed sensing. To systematically design an acoustics-based blade heal...

Cavities with different geometries represent the internal volumes of various engineering applications such as cabins of passenger cars, fuselages and wings of aircraft, and internal compartments of wind turbine blades. Transmissibility of acoustic excitation to and from these cavities is affected by material and cross-sectional properties of the st...

A new acoustic wave resonance device induced by coupling micropillars with a quartz crystal microbalance (QCM-P) was developed for potential use in a wide range of applications such as drug discovery and development. The effect of wetting states of liquid on the micropillars of the QCM-P devices becomes essential in understanding the frequency sign...

This paper reports the outcomes of a series of two Concussion Research Workshops held in Lowell, MA, USA. The workshop examined the state-of-the-art in concussion research, research challenges and the future directions of research within the following three core topic areas: (A) Concussion Prevention Techniques & Technology, (B) Concussion Diagnosi...

A computational model of a planetary gearset is developed to investigate the influence of gear tooth pitting on the dynamic response from transmissions that consist of planetary gearsets. The computational model is capable of simulating the system response due to pitting damage under static, quasi-static, and dynamic conditions. Both off-resonant a...

Enclosures with different geometries constitute the internal sections of various engineering applications including cabins of passenger cars, fuselages of aircraft wings, and internal compartments of wind turbine blades. Acoustic insertion loss from and to these enclosures affect certain objective and subjective acoustic measures along with the abi...

This article proposes a non-contacting measurement technique based on acoustic monitoring to detect cracks or damage within a structure by observing sound radiation using a single microphone or a beamforming array. The technique works by mounting an audio speaker inside a hollow structure, such as a wind turbine blade, and observing the sound radia...

Wind turbine blades undergo high operational loads, experience variable environmental conditions, and are susceptible to failures due to defects, fatigue, and weather induced damage. These large-scale composite structures are essentially enclosed acoustic cavities and currently have limited, if any, structural health monitoring in practice. A novel...

This work reports a novel Quartz Crystal Microbalance (QCM) based method to analyze the droplet-micropillar surface interaction quantitatively during dropwise condensation. A combined nanoimprinting lithography and chemical surface treatment approach was utilized to directly fabricate the micropillar based superhydrophobic surface on the QCM substr...

Double planet planetary gear sets have significantly more design options than their single planetary counterparts as the addition of the second planet set allows for greater flexibility in sizing and synthesizing transmission kinematic chains. Generally, the primary design constraints for these systems are based on transmitted load, speed ratio, an...

Wind turbine blades are exposed to continuously-varying aerodynamic forces, gravitational loads, lightning strikes, and weather conditions that lead the blade damage such as leading and trailing edge splits, cracks and holes. In this study, actively-controlled acoustic sources were utilized in order to excite the blade’s cavity structure from inter...

Double planet planetary gear sets have significantly more design options than their single planetary counterparts as the addition of the second planet set allows for greater flexibility in sizing and synthesizing transmission kinematic chains. Generally, the primary design constraints for these systems are based on transmitted load, speed ratio, an...

In this study, a two-dimensional, steady-state, discrete dynamic model of a double-planet planetary gearset is proposed. The dynamic model is generalized such that it can consist of number of planet branches and can operate under any operating conditions (load and speed). The contact between each external to external and external to internal gear p...

In this study, a two-dimensional, steady-state, discrete dynamic model of a double-planet planetary gearset is proposed. The dynamic model is generalized such that it can consist of number of planet branches and can operate under any operating conditions (load and speed). The contact between each external to external and external to internal gear p...

A transverse-torsional dynamic model of a spur gear pair is employed to investigate the influence of gear tooth indexing errors on the dynamic response. This model includes periodically-time varying gear mesh stiffness and nonlinearities caused by tooth separations in resonance regions. With measured long-period quasi-static transmission error time...

This paper proposes a non-contact measurement technique for health monitoring of wind turbine blades using acoustic beamforming techniques. The technique works by mounting an audio speaker inside a wind turbine blade and observing the sound radiated from the blade to identify damage within the structure. The main hypothesis for the structural damag...

In this paper, a computational model is developed to investigate the influence of tooth spacing errors on the dynamics of spur gear pairs. This finite element based computational model implicitly includes periodically-time varying gear mesh stiffness and nonlinearities caused by tooth separations in resonance regions. The model can simulate the lon...

A planetary gear set introduces complicated gear vibration frequency structures, especially in sequentially phased planetary gear sets. Frequency components from a fixed sensor can be enhanced and/or canceled with different planets and ring gear configurations. In this study, an amplitude modulation based formula and simple trigonometric function m...

Near field radiation behavior of an unbaffled square plate with free edges, which is excited by a harmonic force at its midpoint, is analytically, computationally and experimentally studied. Emphasis is on the applicability of simplified analytical models to predict the near field sound pressures and spatially-averaged surface and acoustic intensit...

In this study, a nonlinear time-varying dynamic model is proposed to predict modulation sidebands of planetary gear sets. This discrete dynamic model includes periodically time-varying gear mesh stiffnesses and the nonlinearities associated with tooth separations. The model uses forms of gear mesh interface excitations that are amplitude and freque...

In this paper, a simplified mathematical model is proposed to describe the mechanisms leading to modulation sidebands of planetary gear sets. The model includes key system parameters such as number of planets, planet position angles, and planet phasing relationships defined by the position angles and the number of teeth of the gears. The model is u...

In this paper, a generalized dynamic model for multi-stage planetary gear trains of automotive automatic transmissions is proposed. The planetary gear train is formed by N number of planetary gear sets of different types (single-planet, double-planet, or complex-compound), connected to each other in any given kinematic configuration. In addition, e...