bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flutter Control of Straight/Swept Aircraft Wings Using Combined Feedback Control Laws
Authors: Karpouzian Gabriel , Librescu Liviu 
Published: July 2023

Abstract
The flutter feedback control of straight/swept aircraft wings operating in incompressible/compressible flight speed regimes is investigated. The stabilizing feedback control is produced via the action of bending moments which are applied at the tip of the wing. Relating the feedback bending moment acting at the wing tip with the kinematic response variables adequately selected and solving the resulting complex eigenvalue problem yields the closed loop speed and frequency of flutter. The numerical results reveal the power of this feedback control methodology to enhance the aeroelastic dynamic instability of aircraft wings, this enabling one to extend the operational envelope of flight vehicles without weight penalties.
Closed-Form Higher-Order Asymptotic Solutions for Plane Strain Elastic-Plastic Crack Growth
Authors: Drugan W. J. 
Published: July 2023

Abstract
A fundamental understanding and characterization of ductile crack growth, and a rigorous basis for predicting final fracture (as opposed to crack growth initiation), are only possible from incremental elastic-plastic solutions of crack growth. Previous analytical investigations have provided leading-order (in distance, r, from the crack tip) asymptotic solutions for the near-tip stress and deformation fields. Such solutions have a limited range of validity. Here we review our recent work which derives plane strain tensile elastic-ideally plastic stress and deformation solutions valid through second order in r. We explain how the higher-order solution structure is derived, and we show with specific examples how these second-order solutions can be used to estimate the radius of validity, as a function of angle about the crack tip, of previous leading-order solutions. Comparisons with full-field numerical solutions demonstrate that the new second-order solutions substantially extend the leading-order solutions’ range of validity. Such quantitative estimates of solutions’ regions of validity seem essential for determining when ductile crack growth characterization based on homogeneous-continuum-mechanical asymptotic solutions is applicable to actual polycrystalline or composite materials with their finite-sized microstructures.
Strain Distribution Surrounding a Growing Crack in Power Law Material
Authors: Chiang F. P. , Li S. 
Published: July 2023

Abstract
In general the problem of crack growth in an elastic-plastic material has to be treated by the flow theory of plasticity because unproportional deformation will exist at the crack tip. During crack extension part of the material surrounding the crack will relax while plastic deformation in other region may keep increasing and the previously relaxed region may be reloaded. The problem is much more complicated than a stationary crack and brings a great deal of difficulties in the asymptotic derivations.
Mixed-Mode Fracture of Cracks: Transition From Tensile to Shear Type
Authors: Chao Yuh J. , Liu Shu 
Published: July 2023

Abstract
Fracture of plates containing a crack under mixed-mode, I and II, loading conditions is investigated. Fracture mechanisms are first examined from the fracture surface morphology of a ductile material to correlate with the macroscopic fracture behavior. Two distinct features are observed, i.e. a shear type and a tensile type of failure. From this correlation, a fracture criterion based on the competition of the attainment of a tensile fracturing stress σc and a shear fracturing stress τc at a fixed distance around the crack tip is proposed. Material ductility is incorporated using τc/σc determined from classical material failure theories. The prediction of the fracture type is determined by comparing τmax/σmax at r = rc for a given mixed-mode loading to the material ductility τc/σc i.e. (τmax/σmax) &lt; (τc/σc) for tensile type of fracture and (τmax/σmax) &gt; (τc/σc) for shear type of fracture. The theory compares well with the available test data.
Crack-Tip Fields in Elastic-Plastic Material Under Plane Stress Mode I Loading
Authors: Yang S. , Yuan F. G. 
Published: July 2023

Abstract
Crack-tip fields in an elastic power-law hardening material under plane stress mode I loading are presented. Using a generalized asymptotic expansion of the stress function, the higher-order terms are found, and a series solution is obtained for the elastic-plastic crack-tip fields. Comparing the results with that for the plane strain mode I loading shows that (1) the effect of higher-order solutions on the crack-tip fields is much smaller, (2) the path-independent integral J also controls the second-order or third-order term in the asymptotic solutions of the crack-tip fields for most of the engineering materials (1 &lt; n &lt; 11) in plane stress, while J does not control the second and the third-order terms for plane strain mode I case for n ≥ 3. This theoretical results imply that the crack-tip fields can be well characterized by J-integral, and can be used as a criterion for fracture initiation in the plane stress state. This is in agreement with existing full-field solutions and experiments that J at crack growth initiation is essentially independent of specimen geometry. The comparison confirms the theoretical asymptotic solutions developed in this study.
Real Forcing Functions for Turbomachine Forced Response Analysis
Authors: Fleeter Sanford 
Published: July 2023

Abstract
Accurate design predictions of blade row HCF can not be made because important unsteady aerodynamic phenomena are not modeled in current aerodynamic analyses. Experimental results are examined to indicate the issues to be addressed in advanced HCF design analyses. The immediate industry need is advanced wake correlation models. Next, three dimensional vortical and potential forcing function components must be addressed. Also, the time-average wake may not be the only key variable for multistage turbomachines, with passage-to-passage variability important. Multiple harmonics are required to describe potential forcing functions to a centrifugal impeller. However, the impeller responds primarily to the first harmonic. However, this may not be the case for axial machines.
Coupled Diffusion-Reaction Models for Predicting the Distribution of Degradation in Polymer Matrix Composites
Authors: Cunningham Ronan A. , McManus Hugh L. 
Published: July 2023

Abstract
A quantitatively accurate model of the chemical degradation of the matrix in PMR-15 polymer matrix composites is presented. A brief review of the empirical understanding of this degradation is given. A mathematical model of oxygen diffusion coupled with oxidative and non-oxidative reactions is presented. The model is used in a preliminary form to replicate existing test data and to design experiments to isolate the presumed mechanisms. An experimental program, in which PMR-15 resin material is used in thermogravimetric analysis (TGA) tests under a variety of heating rates and atmospheres, is performed. The data is presented and reduced. The reduced data yields a more sophisticated and accurate degradation model.
Performance Simulation of High-Temperature Polymeric Composite Materials Using MRLife
Authors: Case Scott , Caliskan Ari , Iyengar Nirmal , Reifsnider Kenneth 
Published: July 2023

Abstract
The long-term performance of polymer matrix composites at elevated temperatures generally involves a complex combination of time- and cycle-dependent behavior, such as fatigue, creep, stress rupture, micro-cracking, and aging. The present paper discusses how methods of representing composite strength are used in the MRLife performance simulation code to create a predictive capability that enables the user to estimate the remaining strength and life of composites based upon the properties, geometry, arrangement, and performance of the constituents. A micromechanical model of tensile strength is combined with the damage accumulation concepts in the MRLife code to represent the behavior of a graphite reinforced composite under thermo-mechanical loading conditions in air.
On the Use of Continuous Wave-Like Geometric Fiber Patterns in Composite Structures to Improve Structural Damping
Authors: Pratt William F. , Rotz Christopher A. , Jensen C. Greg 
Published: July 2023

Abstract
The use of continuous wave-like geometric fiber oriented patterns in carbon fiber reinforced plastics to improve damping is investigated. Previous work showed the superiority of stress coupled, co-cured interlaminar viscoelastic materials, where layers of viscoelastic materials are interleaved with layers of carbon fiber reinforced plastics in unique chevron like patterns. Results revealed structural damping several orders of magnitude higher than conventional methods. Continuous wave-like geometric oriented patterns induced in fiber composites further improve the dynamics of stress-coupled co-cured viscoelastic structures. Numerical studies on the influence of wave shape in optimizing interlaminar damping are reported. The degree of stress coupling and damping is shown to be heavily influenced by the shape and period of the composite layers.
A Summary of Darpa’s Embedded Sensors for Submarine Structures Program
Authors: Belk John H. , Kelly James J. , Crane Roger M. 
Published: July 2023

Abstract
Composite material usage in structural applications have increased rapidly as the material and fabrication technology have matured. The majority of these applications are weight critical and are therefore manufactured with thin sections. Naval applications are typically significantly larger, requiring much thicker sections to react to the design loadings. As part of the Defense Advanced Research Project Agency’s (DARPA) Manufacture of Advanced Composite Submarine Structures (MACSS) program, the fabrication of thick section graphite epoxy composites to a part quality comparable to the autoclave cured thin section structures is being addressed; both thermoset and thermoplastic materials are being investigated. This paper discusses the impact of DARPA’s Embedded Sensors for Submarine Structures (ES3) program which used the MACSS material systems and MACSS-specified processes as a starting point for hosting compatible sensor systems for smart structures and health monitoring applications. Most of these systems were based on optical fiber sensors.
The Impact of Amplification on Efficiency and Energy Density of Induced Strain Actuators
Authors: Paine Jeffrey S. N. , Chaudhry Zaffir 
Published: July 2023

Abstract
To some degree, stroke amplification of solid-state electroceramic driven actuators is necessary in all engineering applications. Accompanying stroke amplification, however, are the penalties of loss of output displacement and loss of energy delivered to the load per unit actuator weight. The penalties can be significant when the actuator is used to drive an external stiffness-type load. Using a model which describes a very commonly used lever-type amplification mechanism, the impact of the stiffness and the attendant weight of various members in the amplification mechanism on energy transfer and energy density of the actuator material (under static conditions) is discussed. The significant finding of the study is that on average, after amplification, the energy density of the actuator is about 20 to 35% of the inherent energy density of the active material alone. In other words, only 20 to 35% percent of the energy density that can be delivered by the electroceramic alone when directly driving an external spring load, is available when the active material is used in a displacement amplified actuator device such as the type depicted in the study. The study also demonstrates that the highest stiffness of the amplification members is not desirable, as it significantly increases weight and thereby reduces the energy density. An active material stiffness to amplification structure stiffness ratio of 0.2 to 0.3 provides the highest overall energy density. The impact of using a variety of materials in the amplification mechanisms, is presented. In addition, the advantage of using high stiffness-to-weight composites and other novel materials is also presented.
The Thermal Compressive Behavior of a NiTi Fiber 6082-T6 Aluminum Alloy Matrix Composite
Authors: Armstrong William D. , Lorentzen Torben 
Published: July 2023

Abstract
A basic study was conducted of the constitutive response of a 20.5 volume percent, 50.7 at% NiTi shape memory alloy fiber reinforced 6082-T6 aluminum alloy matrix composite (SMA-MMC). The test materials were initially subjected to a 4% tensile prestrain at 19°C. The later stages of the prestrain process resulted in the strong growth of the martensite (001) diffraction peak. During a subsequent 19°C to 120°C unconstrained heating process, the SMA-MMC exhibited a nonlinear thermal contraction, and a strong decrease in the NiTi martensite (001) neutron diffraction intensity. Both experimental effects resulted from a powerful martensite to austenite shape memory transformation in the NiTi reinforcement. The experimental results are analyzed by a nonlinear Eshelby model, which describes the SMA-MMC phase state, external strain, and internal stress during the unconstrained heating process.
Actuator Placement and Selection in Static Deflection Control of Adaptive Structures
Authors: Baerwald Jeff E. , Gerwe Caroline E. , Utku Senol 
Published: July 2023

Abstract
Recently, in many branches of engineering, adaptive structures have received increased attention. An adaptive structure is an intelligent system that uses deformation inducing actuators for its adaptability. The potential uses of such structures stretch beyond civil engineering into the fields of mechanical engineering, aerospace engineering and robotics. With the ability to control in real time some of the critical response quantities, adaptive structures can be constructed more economically than their non-adaptive counterparts which are often over-designed in order to compensate for the large uncertainties in the loads. Although in most of the deflection control problems the number of actuators, q, is at least as great as the number of observed response components, p, the majority of the previous literature has studied actuator placement problems where q &lt; p. The higher level of interest of the q &lt; p case stems from the facts that (i) the difficulty in implementing multi-input multi-output control increases with increasing q, (ii) the cost of actuators increases with q, (iii) the proposed algorithms for this purpose can keep many large computers busy for a long time and end up with a mathematically unverifiable best placement when q is large. In this work, some of the algorithms for the actuator placement problem for controllable adaptive structures are reviewed for q = p and q &gt; p cases, and extensions proposed. When q &gt; p it is shown that the problem of actuator selection arises for economical operation of adaptive structures. The actuator selection problem is also an optimization problem that needs solutions in real-time.
Development of Mesoscale Actuation Device
Authors: Zhu Jinghui , Wang Donny , Kim Chang-Jin , Carman Greg P. 
Published: July 2023

Abstract
We propose to incorporate the micrometer-scale machining capability of Microelectromechanical Systems (MEMS) into millimeter-scale inchworm actuators to achieve large translational force as well as large displacement. The sliding surfaces of the inchworm device is micromachined from silicon wafers, while the PZT actuators are off-the-shelf. Large force becomes possible since the microscopic ridge patterns on the surfaces of inchworm and stator interlock each other as opposed to the smooth surfaces of existing inch-worm devices. Initial results toward the development of Mesoscale Actuation Devices (MAD) is reported in this paper. The fabrication process for the surface with microridges is described. An experimental setup has been developed to visualize and study the engagement and disengagement of a pair of microridged surfaces under the microscope. With further development, continuous inchworm motion by repeated stepping of the microridges is demonstrated. Current status for the development of load-bearing actuators is also discussed.
Photodeformation and Light-Temperature-Piezoelectric Coupling of Optical Actuators: Part 1 — Parameter Calibrations
Authors: Liu B. , Tzou H. S. 
Published: July 2023

Abstract
Conventional hard-wired sensor/actuator systems are sensitive to strong electromagnetic fields. The metallic signal busses act like antennas attracting electric noises. Non-contact optical actuators are driven by high-energy lights which do not require hard-wire connections. These optical actuators can operate in hostile and extreme environments with strong magnetic and/or electric disturbances.
In this study, detailed photostricition, pyroelectricity, thermoelasticity and photodeformation of 2-D optical actuators are analyzed. A servo control system is proposed and its governing system equation is derived. System parameters are calibrated with experimental data. Light intensities, induced strain levels, and the maximal actuation frequencies are investigated (Part–1). Photodeformation and distributed actuation are investigated and compared with the experimental results.
The optical actuators are then used in vibration control of rectangular plates (Part–2). Control effectiveness is evaluated.
New Fabrication Process for Active Micro-Sized Metal/Ceramic Devices
Authors: Ervin James D. , Brei Diann , Van Hoy Charles A. , Mawdsley Jennifer R. , Halloran John W. 
Published: July 2023

Abstract
A novel co-extrusion process was investigated as a means of fabricating active micro-sized metal/ceramic devices with high aspect ratios. This process involves mixing ceramic and metal powders with a thermoplastic and forming elements of a device at a scale many times larger than the final device size. These elements are assembled and co-extruded through a reducing die to achieve the desired size and then co-fired to produce the final micro-device. To evaluate the potential of this process for producing micro-scaled ceramic sensors and actuators, devices of various shapes were assembled, co-extruded, and co-fired using alumina, PZT, and PMN-PT. Features as small as 5 microns were achieved using this process. In addition, a PMN-PT/AgPd composite laminate was co-extruded and co-fired to demonstrate the ability to fabricate micro-devices with electrodes. Results of a shape retention study and metal/ceramic co-fire study are described in this paper.
Realizing Systems With MEMS
Authors: Gabriel Kaigham J. , McMichael James M. 
Published: July 2023

Abstract
As computers increasingly leave fixed locations and appear in the pockets and palms of users, they are getting closer to the physical world, creating new opportunities for perceiving and controlling the physical environment. To exploit these opportunities, computers will need to sense and act as well as compute. Filling this need is the driving force for the development of microelectromechanical systems (MEMS).
Ultrasonic MEMS Device for Fluid Pumping and Mixing
Authors: White Richard M. 
Published: July 2023

Abstract
Silicon-based micromachined devices that were originally made for ultrasonic sensing have been shown to pump and mix both gases and liquids. These devices employ megahertz ultrasonic plate waves, generated in piezoelectric films on a microns-thick membrane, to produce an evanescent disturbance in an adjoining fluid. Because of the high acoustic intensity near the membrane, the nonlinear phenomenon of acoustic streaming can occur, producing a steady force in the direction of propagation of the time-harmonic plate wave. Vorticity near the surface also stirs the fluid. We will present measured and (videotaped) experimental results, and describe some applications of this distributed pump and mixer.
Silicon Bulk Micromachining in Tohoku University
Authors: Minami Kazuyuki , Esashi Masayoshi 
Published: July 2023

Abstract
Micro systems which are small sized but relatively complicated intelligent systems were fabricated based on bulk silicon micromachining. Extremely sensitive sensors with thin beam structure, packaged micromechanical sensors for inertia measurement, microactuators as microvalve and optical scanner and active catheter which moves flexibly like a snake in a blood vessel were developed. Silicon nano-wire growth by electric field evaporation using UHV STM and novel three-dimensional micromachining as deep RIE were developed for the fabrication of the microsystems.
Damage in Unidirectional Graphite/Epoxy Laminates Containing a Circular Hole
Authors: Yang Fan , Chow C. L. , Fang H. Eliot 
Published: July 2023

Abstract
In this paper, a damage mechanics model is described for determining progressive damage process of unidirectional graphite/epoxy composite plates containing a central hole subjected to off-axis uniaxial tension. The inelastic behavior of these composite materials is attributed to the irreversible thermodynamics processes involving energy dissipation and stiffness variation caused by damage initiation and accumulation. The mechanical response of the composites is investigated by using a nonlinear finite element procedure formulated with a set of damage coupled constitutive equations. Separate damage criteria are derived for fiber failure and for matrix or fiber/matrix interaction failure in unidirectional composites. Validation of the damage model is achieved by comparing the numerical prediction and experimental data obtained from Moiré interferometry technique. It has been found that failure of the composite material near the hole region takes the form of an extensive damage zone. The macrocrack initiates at the material point near the hole boundary with high damage value and propagates along the direction of damage zone extension. Preliminary results indicate that the proposed damage model is an effective method of studying progressive failure behavior of unidirectional composite laminates containing a circular hole and can be readily extended to examine the damage response of composite structures.
Fire Emergency Ventilation Analysis of a Transit Station Using Computational Fluid Dynamics
Authors: Kumar Kiran , Abu-Zaid Sameer , Overstreet Jamahl , McCleery Jerry E. , Harris Kenneth J. 
Published: July 2023

Abstract
Computational Fluid Dynamics (CFD) is used in this study to evaluate evacuation and possible egress routes during a fire emergency in the proposed San Bruno station of the Bay Area Rapid Transit (BART) system. Three modes of ventilation, namely natural (no fans), push-pull (fans operating in supply-exhaust mode), and exhaust-exhaust (fans operating in exhaust-exhaust mode) are investigated. The methodology adopted for fire and smoke modeling is explained. The modeled geometry of the station includes its various geometrical features such as mezzanine floor, staircases, and exits. Steady-state simulation results for temperature distribution and velocity field for the three ventilation modes are presented and discussed for various sections of the station.
“Appropriate Equivalent Methodology” for Pressure Relief System PHAs
Authors: Berwanger Patrick C. , Kreder Robert A. 
Published: July 2023

Abstract
This article presents the “Berwanger Method”, a step by step process for designing or analyzing a pressure relief system to meet OSHA 1910.119 Process Safety Information (PSI) and Process Hazard Analysis (PHA) mandates. The author demonstrates that, to ensure safe operation and regulatory compliance, the pressure relief design information management system must be based on an equipment list. The previously common practice of using a relief device list as the basis of “verifying” the design is now recognized as incomplete because this method cannot ensure and document that all equipment is in fact protected.
The author also shows how an electronic relational database can be used to maintain the design information.