bluuebunny/crossref_metadata_2025 huggingface dataset:
Fuel Pump Vibration Measurements Using Laser Transducers
Authors: Wu Sean F. , Li Li , Rivin Eugene
Published: July 2023

This paper presents the results of vibration and noise measurements of Bosch fuel pumps by using laser transducers. Vibration of the pump consisted primarily of three components: radial, axial, and torsional. Results showed that radial vibration was predominant in the low frequency regime, torsional vibration in the mid to high frequency regime, and axial vibration in the high frequency regime. Pump noises were produced primarily by axial vibration, followed by torsional vibration. At high speeds, however, the tonal sound pressure levels of the harmonics due to torsional vibration became close to those of axial vibration, indicating that the two components of vibration were equally important. Contribution from radial vibration to the overall noise was negligible. Nevertheless, the amplitude of radial vibration was the highest and the vibration pattern of the pump housing was predominated by the first breathing mode of radial vibration. The causes of radial vibration could be attributable to the radial component of the force exerted on the pump housing by the fluid as it was sucked into the pump, and to the unbalancing forces of the shaft and impellers. The frequencies of the radial modes confirmed these assertions. The cause of axial vibration could be attributable to fluid/impeller interaction, which was also confirmed in the axial velocity spectrum. The causes of torsional vibration needed to be investigated further. The present hypothesis is that torsional vibration is due to moter-related excitations.
Case Study on Reducing Automotive Blower Rumble Noise
Authors: Humbad Niranjan G. , Hall Tim J. , Terry Joe , Hess Graham , Sohaney Rich C.
Published: July 2023

The climate control system is one of the major contributors to automobile interior noise, especially when the climate control blower operates at full speed. The air rush noise from the blower operated at high speed can be very annoying due to high noise levels and or due to discrete frequency tones or low frequency rumble. Every attempt is made to reduce the annoyance to improve customer satisfaction. This paper presents results of a case study related to source identification and resolution of low frequency rumble noise in a newly developed climate control system. Flow visualization, sound intensity and noise measurements were used to identify the noise source and subsequent changes to blower scroll in reducing the rumble noise in the bench study. Bench test noise reductions were verified on the vehicle. Subjective rating improvements of 2 (0–10 scale) were obtained on a new design compared to the baseline design.
Noise Reduction System for Telephones
Authors: Birman Chaim , Nasar Alan S. , Raichel Daniel R.
Published: July 2023

The goal of this project is to design a system that increases the intelligibility of voice transmission through a telephone or similar device when used in a noisy environment. The designed system incorporates an auxiliary microphone into the transmitter portion of an ordinary telephone handset. This microphone, strategically located so that it receives the ambient noise and virtually no speech from the user, develops a signal that becomes phase-inverted by the system.. The resultant signal is mixed with the signal from the primary microphone to produce a final signal that contains significantly less background noise than the original signal. The amended signal is then relayed to the telephone receiver in the same manner as in an ordinary telephone. This system has many applications in the design of telephones and two-way radios for use in noisy environments such as subway stations, city streets, aircraft cabins, truck cabs, construction sites, etc.
A Software for Acoustical Study and Design of Architectural Spaces
Authors: Narasimhan Mukundan , Raju P. K.
Published: July 2023

The study of architectural spaces and their acoustical characteristics is needed for a better understanding of the functional performance of an auditorium. Some of the methods used to analyze these spaces and their characteristics are scale model studies, wave analysis techniques and statistical methods. Computer aided analysis has become an important means for studying the propagation of sound and the distribution of acoustical energy. Keeping these aspects in view, a computer model using geometric ray analysis has been developed to study the temporal response of the reflection patterns of transient sound inside listening halls. The software has been implemented in C-Language. The program has built-in modules, which models both specular and diffuse reflections at the boundary. In the last module of the program, attempts have been made to design the reflectors inside the hall to avoid echoes. Using the developed software the change in the reflection pattern due to the presence of special reflectors has been studied with reference to the number of echo points, delay time and the Sound Pressure Level (SPL) difference between the straight ray and the reflected ray. Also, the variation in the difference of SPL and delaytime has been studied graphically with reference to the distance from the source. Experiments were conducted at an existing hall, and echograms obtained from these experiments are compared to the modelled results. Thus this software will be a very useful tool for acousticians designing auditorium.
Ultra High Speed Hydraulic Turbo Motor
Authors: Maeda Teruyuki
Published: July 2023

This paper describes an ultra high speed hydraulic turbo motor utilizing a negative damping flow force. The negative damping flow force is the main cause of the self-excited oscillation of a valve. The disk which was attached to the motor shaft was rotated with different loads which were determined by “ Eddy current method”. Rotational speed of the disk was measured by a non-contact revolution counter, and frequency characteristics of the sound pressure level were measured by a sound pressure level meter. We found that this ultra high speed improved hydraulic turbo motor had a 5 % higher rotational speed than the conventional one and it achieved 40,000 rpm under no load, 10 MPa, and 60 degree in C conditions. An theoretical analysis was conducted to explain these experimental results.
Study on the Dynamics of a Load Sensing System
Authors: Sakurai Yasuo , Takahashi Koji , Ikeo Shigeru
Published: July 2023

This paper deals with the dynamics of a load sensing system. The load sensing system is one of the most effective means to save energy. This kind of system, however, has an inherent demerit that it often falls into instability, which may be caused by the interaction between the load sensing mechanism and the load. It is important, therefore, to investigate the dynamic characteristics of a load sensing system. In the present paper, both experimental and simulation studies are performed. By making use of experimental results, a suitable mathematical model of the whole system is obtained. The effects of system parameters on the stability of the system are investigated using this model.
A Modified Orifice Flow Formula for Numerical Simulation of Fluid Power Systems
Authors: Ellman Asko , Piché Robert
Published: July 2023

The conventional turbulent orifice flow formula has an infinite derivative when the pressure drop is zero. This can cause ODE solvers to crash during numerical simulation of fluid power circuits. A two-regime orifice flow formula is proposed in which an empirical polynomial laminar flow formula is used for small pressure differences. The proposed formula has a smooth transition between laminar and turbulent regimes and does not have a singular derivative, and so is well-suited for accurate and trouble-free simulation.
Mapping of Large Scale Fluid Power System Simulations on a Distributed Memory Parallel Computer Using Genetic Algorithms
Authors: Pollmeier K. , Burrows C. R. , Edge K. A.
Published: July 2023

Parallel simulation of fluid power systems using the transmission-line modeling method offers the benefit of increased speed of execution, but requires the system model to be partitioned on to individual processors [Burton, 1994].

In this paper we address the automatic placement of component models on processors of a distributed memory parallel machine. A genetic algorithm is used to map the different processes onto several processors. The objective is to minimise the total processing time in order to achieve real time performance. For fine grained computation problems the communication time cannot be neglected, i.e. we consider the computation and the communication time of each task.

This mapping problem is a combinatorial optimization problem which can be reduced to the graph partitioning problem which is shown to be NP-complete. Combining genetic algorithms with heuristics leads to optimal or very good sub-optimal solutions. A hydraulic example circuit is partitioned in four and eight subsystems, respectively, and the simulation is implemented on a Transputer based platform. Using eight processors a speed up of 3.7 was achieved.
A Neuro-Fuzzy Control of an Electro-Hydraulic Fin Position Servo System
Authors: Lee Sang Yeal , Park Young Jun , Cho Hyung Suck
Published: July 2023

The electro-hydraulic servo systems have been frequently used in the fin position servo system of a missile because of their high power and good positioning capabilities. This paper presents a neuro-fuzzy control scheme for an electro-hydraulic fin position servo system. In this paper, we have explained a fuzzy control scheme which has multidimensional and asymmetrical membership functions, and we have designed a neuro-fuzzy controller which include parameters of the fuzzy logic controller. The effectiveness of this control scheme is verified by comparison with the conventional control algorithm through a series of simulation studies.
Weight Saving Plastic Design of Pressure Vessels
Authors: Porowski Janek S. , O’Donnell William J. , Reid Robert H.
Published: July 2023

Within the last two decades the use of elastic finite element analyses to demonstrate design compliance with the rules of the ASME Code has become a generally accepted engineering practice. Linearized stresses from these analyses are commonly used to evaluate Primary stresses. For redundant structures or complex structural details, the use of such analyses, instead of simple equilibrium models, often results in significant overconservatism. Direct use of finite element results is often preferred because equilibrium solutions are not unique and effective equilibrium models are not easily constructed for complex three-dimensional structures. However, finite element analyses include Secondary stresses, even for pressure, mechanical and shock loading.

For Primary stress evaluation the ASME Code allows the use of inelastic methods based on lower bound solutions and plastic analysis. For Primary stresses the Code requires equilibrium to be satisfied without violating the yield strength of the material. The use of finite element inelastic analysis to partition mechanically induced stresses into the Primary and Secondary categories was introduced by Porowski, O’Donnell et al. (1993). The latter provides a detailed discussion of the technical approach and the results for the axisymmetric junction between the plate and shell in a pressure vessel. This example was selected by the Session Organizer as a benchmark case to compare the efficiency of various analytical approaches presented at the Session. The authors have since used this approach to design more efficient structures. The practical application of this method to reduce the weight of complex redundant structures designed to meet Primary stress limits is described herein for a more complex three dimensional case. Plastic design utilizes the ability of actual materials to find the most efficient load distribution. A heat exchanger subjected to pressure, accelerations and nozzle external loads is evaluated as a practical example. The results of elastic analyses are compared with those obtained by inelastic analyses. It is shown that inelastic analyses can be used effectively to reduce the weight of structures using only modern PC’s for the engineering computations, as illustrated in this paper.
Benchmarking of Finite Element Codes for Radioactive Material Transportation Packages
Authors: Ammerman Douglas J.
Published: July 2023

The increased power of computers and computer codes makes the use of nonlinear dynamic finite element analyses attractive for use as a tool used in the design and certification of radioactive material transportation packages. For this analysis technique to be acceptable it must be demonstrated the technique has the ability to accurately capture the response of the packages to accident environments required by the regulations. The best method of demonstrating this ability is via a series of benchmark analyses. In this paper three benchmark problems involving significant inelastic deformations will be discussed. One of the problems has been analyzed using many different finite element codes. The other two problems involve comparison of finite element calculations to the results from physical tests. The ability of the finite element method to accurately capture the response in these three problems indicates the method should be acceptable for radioactive material transportation package design and certification.
Equivalent In-Plane Shear Elastic-Plastic Properties of Thick Tubesheets
Authors: McClellan Grant H. , Kizhatil Revi K.
Published: July 2023

In the design of tubesheets, using elastic-plastic analysis methods, inaccuracy in the equivalent in-plane shear properties will have little effect on the final analysis results. For the pressure loading involved in the design of tubesheets, the effects of anti-plane shear will be much more significant. However, when thermal effects of the no-tube-lane are to be taken into account, the accuracy of the in-plane shear properties may have a significant effect on results. In such a case, special care in modelling the anisotropy may be necessary in order to obtain accurate elastic-plastic solutions. Previous investigation (Slot and Branca, 1974) of the equivalent properties for perforated plates with a triangular pitch utilizes a finite element model that is a symmetric portion of a single ligament in order to limit computer run-times. The boundary conditions utilized in this investigation are, therefore, somewhat approximate because they do not represent the true repetitive symmetry of an infinite perforated plate. In addition, the previous work on in-plane shear properties does not take into account the variation in the equivalent properties resulting from hole pattern orientation with respect to the in-plane shear forces loading the ligaments. The purpose of this investigation is to study the effect of the extent of the model on the computed equivalent in-plane shear elastic-plastic properties for a thick perforated plate with a triangular pitch. In addition, a method is proposed for determining an integrated average equivalent in-plane shear property to allow a more accurate elastic-plastic analysis.
Inelastic Constitutive Equations Including Strain Rate Effects
Authors: Maresca Giuseppe , Pino Giovanni
Published: July 2023

Inelastic analysis can be applied to assess safety margins against explosions or impact loading sustained by confinement structures. To this purpose constitutive equations including strain rate effects must be managed in large displacement problems.

In this paper a finite strain generalization of the Hoenemser Prager and Perzyna models, allowing for work hardening and coupled to elastic equations, is presented. Related problems, like determination of physical parameters, response computation and model validation are briefly discussed.

Finally, the possibility to adopt, in the framework of this model, failure criteria allowing for large deformations is considered. To the purpose of testing this aspect of the model, an experimental campaign on cruciform specimens dynamically loaded is in progress at the Ispra European Joint Research Center on behalf of ANPA.
Inelastic Response of Foundations and Piping to High Dynamic Loads
Authors: Scavuzzo R. J. , Lam P. C. , Gau J. S.
Published: July 2023

This paper is a review of the authors’ work on the inelastic response of foundations and pipes subjected to dynamic loading into the plastic regime. A test in which foundations were subjected to high impact shock loading is summarized along with design calculations that bound plastic deformations. A second program in which pressurized piping was subjected to high impact loading is also summarized. Some of the analytical work associated with this program is reported. Lastly, ratcheting of pressurized piping in dynamic tests and quasi-static tests as well as the comparison of these data to analyses are briefly reviewed.
Crashworthiness of the AT-400A Shipping Container
Authors: Gruda Jeffrey D. , York Allen R.
Published: July 2023

Shipping containers used for transporting radioactive material must be certified to federal regulations. These regulations require containers be tested or evaluated in severe mechanical and thermal environments which represent hypothetical accident scenarios. The containers can only be certified if the containment vessel remains leaktight. This paper presents results from finite element accident simulations which include subjecting an AT-400A to a 30-foot (9.1 m) drop onto an unyielding target and crushing the container with an 1100 lb (500 kg) steel plate dropped from 30 feet (9.1 m). The simulations were done using PRONTO3D, an explicit, transient dynamics code developed at Sandia National Laboratories. The finite element predictions were supported using test results. The simulations of various impacts and crushes identified trends, worst-case orientations, and also showed that there is a significant margin of safety based on the failure of the containment vessel.
Asymmetric, Fully Plastic Crack Growth Mechanics and Tests for Structures and Piping
Authors: McClintock F. A. , Kenney K. L. , Jung S. , Reuter W. G. , Parks D. M.
Published: July 2023

Many structures damaged in recent earthquakes had cracks from welds that broke the flanges of beams, broke flanges from columns, or veered off, sometimes through columns. At least some structures were fully plastic during crack growth..

A complete asymmetric, plane strain, non-hardening, isotropic, rigid-plastic fracture mechanics is developed to predict such asymmetric crack growth from small specimen tests. For short cantilever specimens with an EDM slot across from an offset shoulder, slip line fields give the three crack tip driving parameters: a slip direction 58° to 77° from the transverse (loading) direction, a moderate mean normal stress, and a slip of about half the applied displacement. Tests on A710 steel, TS = 630 MPa, gave the crack tip growth responses at that mean normal stress: cracking within 4° of the observed slip direction and growth per unit slip of 3 to 5, somewhat low compared to other configurations and materials.
Scale Effects in Fracture of Pipelines
Authors: Mineev Vladimir Nikolaevith
Published: July 2023

The sudden failures of forty three gas pipelines are discussed. The lengths of the cracks and the intervals from the beginning of the pipe operation until the instance of the accidents as a function of the pipeline diameters can described by the energetic scale effect: the difference in the reserves of the elastic energy in the pipelines of the different diameters.
A Consistent Inelastic Formulation Analogous to Elastic Problems With Variable Coefficients
Authors: Jahed H. , Dubey R. N.
Published: July 2023

A technique for solving boundary value problems for inelastic solids based on their elastic solution is presented. For this purpose, a constitutive equation for inelastic materials is proposed in terms of variable parameters, similar in form to linear elastic equation. A method of obtaining these parameters based on energy consideration is presented. The technique is applied to predict the elastic-plastic analysis of a flat plate with circular notch subjected to uniform all around tension. It is also used to obtain the residual stress field induced by cold work expansion of fastener holes. Results of this method are compared to those obtained from finite element analysis and experimental data.
General Nonlinear Analyses Using a Co-Rotational Finite Element Formulation
Authors: Jiang Lei
Published: July 2023

In this paper, we describe the development of nonlinear analysis capabilities in our general-purpose finite element program, VAST, for combined geometrically and materially nonlinear analyses of shell and beam structures. This development is based on a co-rotational formulation, in which the total displacement field is divided into two parts. The first part corresponds to the rigid body motion and fully characterizes the geometric nonlinearity in the problem, whereas the second part represents the pure relative deformation and is solely involved in the constitutive relations. Because the co-rotational strain and stress measures adopted in this formulation meet the requirement of computational objectivity, the inclusion of nonlinear material models becomes relatively easy. In this study, the commonly used J2-flow theory of plasticity is considered. Various numerical integration algorithms for integrating the rate-type constitutive relations have been included along with the corresponding consistent tangent moduli. Mixed isotropic and kinematic strain hardening can also be characterized. To handle structural instabilities in general nonlinear analyses, a group of advanced solution strategies for nonlinear finite element systems have been implemented. Extensive numerical experiments have been conducted for verification purposes, and the accuracy and robustness of the current approach have been demonstrated.
A Probabilistic Model for Inelastic Deformation
Authors: Whaley Paul W.
Published: July 2023

A probabilistic model for inelastic deformation is described based on three scale domains to relate properties of the crystalline structure to mechanical response. The microdomain is the scale of the grain structure. Each microelement is composed of a strain-rate sensitive element, a strain-hardening element and a plastic slip element with the yield point modeled as a random variable. The mesodomain is the population of microelements, and the macrodomain is the scale of expected value calculations. The Rayleigh probability distribution function was used to model random yielding in a nickel based super-alloy. Isothermal results at several temperatures are presented. The model is capable of accurately predicting strain-rate history effects, reversed loading, nonproportional loading and creep.
Algorithms for Iterative Solution of Coupled Contact Constraints
Authors: Mello Frank J. , Heinstein Martin W.
Published: July 2023

Transient dynamic simulations of many manufacturing and forming problems are computationally dominated by contact detection and enforcement. This paper presents algorithms developed to predict correct contact conditions, improve the accuracy of the contact force calculation, and iteratively solve coupled contact constraints. An augmented predicted configuration is used to prevent contacts jumping between surfaces prematurely. An impedance-based kinematic partitioning factor is presented, which more accurately enforces the contact rate constraint. Finally, ghost nodes are introduced to allow an individual node to accumulate multiple contacts. Ghost nodes have unambiguous normals and their contact forces assemble in a straightforward way. An iterative scheme is required to properly account for constraint coupling. An illustrative numerical example is presented.
Adhesive Yielding in Single Lap Joints With Voids
Authors: Rossettos John. N. , Sturtevant Samuel. C.
Published: July 2023

The shear stresses in the adhesive and the loads in the adherends are obtained for a single lap joint with an elastic-perfectly plastic adhesive. Using a shear lag model, the adhesive is divided into yielded, elastic and void regions and appropriate continuity conditions are utilized. Two non dimensional parameters are identified and involve the overlap length of the joint together with the material and geometric properties of the adherends and the adhesive. The post yield response is determined by calculating the ratio P0 / P0L, where P0 is the current non dimensional post yield load, and P0L is the corresponding load which starts adhesive yielding. This ratio is shown to be sensitive to the parameters, clearly indicating how values of these parameters and void size influence the post yield load carrying capacity of the joint, and how they can be valuable components in design.
Progress in Railway Mechanical Engineering: 1995–1996 Survey — Locomotives
Authors: Bieber A. C.
Published: July 2023

This survey reports on motive power developments for the previous year ending August 1996. Invitations to participate were sent to a large number of locomotive builders throughout the world. The response this year was limited, possibly due to the many organizational changes that the locomotive manufacturing industry has undergone in recent years. Railway industry trade journals and other rail magazines provided additional input, however.

General information is presented on 4 diesel locomotives and 7 electric locomotives. For further details on any given design, the reader is urged to contact the builders.
Improvements and Tests of Slackfree Drawbar
Authors: McKeown Frank S. , Spencer Charles P. , Kaufhold Horst T.
Published: July 2023

American Steel Foundries introduced the Slackfree® Drawbar System to the North American Railroads in 1983. The system operated without significant problems until early 1993 when a series of yard derailments was reported on the CP Rail System. Derailments reportedly took place under empty or lightly loaded three platform container well cars. These cars were equipped with a shorter length drawbar system, developed in 1991, during facing point moves (in buff) through number 9 turnouts.

A series of yard tests conducted by the CP Rail in 1993 concluded that a sufficient lateral load applied to the car at the striker casting height would initiate near wheel lift on the truck ahead of the drawbar system under an empty platform as the car negotiated the number 9 turnouts. Yard tests also showed that the steel components inside the drawbar assembly could interact with the car geometry in a way that inhibits free lateral angling of the drawbar as the car advanced through certain curves.

ASF initiated a series of laboratory tests to determine the behavior of the system under conditions simulating the CP Rail Yard experiences. Tests were designed specifically to determine what might contribute to higher than intended lateral forces on the system including: (1) Component manufacture (tolerance, etc.), (2) Effect of non-lubrication, (3) Dynamic component behavior and (4) The mechanics of binding or jamming.

The results of the extensive laboratory investigation revealed that heavy draft loads on the system caused deflections that allowed the slack adjusting wedge to over-adjust, which, in turn, tended to inhibit free lateral angling of the drawbar. A solution was developed which allows the wedge to take up slack due to wear within the system without over-adjusting when the system is heavily stretched.
Effects of Service on Residual Stresses in Sub-Critically Quenched Rail Car Axles
Authors: Woodbury Clifford A. , Pearson John B. , Downs William E. , Brandimarte Glenn
Published: July 2023

Sub-critically quenched axles have been used in passenger rail cars for many years to obtain improved fatigue resistance. While the formation of axial compressive residual stresses by sub-critical quenching is well documented, it has been theorized that bending from service loads and high forces from mounting and demounting pressed-on axle components could possibly relax or relieve some or all of the beneficial stresses from the sub-critical quench. To test this theory, an axle with 11 years and an estimated 660,000 miles (1,056,000 km) of service was obtained for residual-stress measurements. A section of this axle was re-sub-critically quenched by the same procedure as when new. Residual stresses in this comparison section and the service axle were measured by both X-ray diffraction and ASTM E837 hole drilling methods. Axial compressive stresses found at the surface of the service axle were 15 to 18 percent lower than those on the surface of the re-heat treated section, and residual stresses levels tapered off with depth. After making an allowance for final machining of the service axle when it was manufactured, it is concluded that the 11 years of service and maintenance operations caused no significant reduction in axial residual compressive stresses.
Progress in Railway Mechanical Engineering: 1995–1996 Report of Survey Committee — Passenger and Commuter Rail Vehicles and Components
Authors: Smith Charles M.
Published: July 2023

This annual ASME committee report covers major worldwide developments in rail passenger and commuter vehicle equipment. The information contained herein was obtained from the responses to survey letters sent to the manufacturers of passenger rail vehicles and components, and from a review of the trade and technical publications.
Three-Piece Truck Development and Testing
Authors: Hawthorne V. Terrey , Wronkiewicz Robert D. , Moehling Charles , Pitchford Terry L. , McKeown Frank S.
Published: July 2023

A light weight carbody/truck system has been developed jointly by Johnstown America Corporation and American Steel Foundries. Johnstown America developed a light weight aluminum “bathtub” gondola and American Steel Foundries developed a new design freight car truck which has been designated as the ASF-2001™ truck. This carbody/truck system has been subjected to an extensive evaluation test program including the various AAR Chapter XI test regimes.

This report describes the design effort to reduce the weight of three-piece trucks by eliminating a portion of the redundant load path between the carbody bolster and truck bolster.

The goal, to reduce the carbody bolster and the truck bolster weights while maintaining acceptable dynamic stability and truck turning resistance, is realized by proper optimization of these parameters. The design approach to select the bolster support location is described.

In the process of developing this truck using NUCARS and Chapter XI testing, a unique variable-damped, dual-rate, load-coil spring group was developed. In conjunction with this load-coil system, a dual-rate, control-spring system was designed to permit this truck to satisfactorily pass the difficult bunched spiral test.

A revised truck bolster fatigue test to evaluate a side support bolster is proposed.
Strategies for Analysis of Textile Composites
Authors: Whitcomb John D. , Noh Jae , Chapman Clinton
Published: July 2023

Textile composites can take many forms (eg. weaves, braids, knits, etc.), but in each case there is interlacing of the fiber bundles. This interlacing offers the potential for increased damage growth resistance. It also introduces waviness in the fibers and complicates prediction of composite properties. Figure 1 shows schematics which illustrate the complex microstructure for weaves. A variety of analyses for analyzing the textile composites have been proposed in recent years. These range from modified laminated plate theory (eg. Ishikawa and Chou (1982, 1983), and Naik (1992)) to fully three-dimensional models (eg. Whitcomb (1991), Dasgupta (1994)). In some cases there has been “verification” of an analysis by comparison with experiments. While such comparisons are essential, they do not provide a complete story. Because of uncertainties in the actual tow architecture, variation of fiber fraction, and in situ constituent properties, it is quite possible for analytical predictions and experimental observations to agree, but for the wrong reasons. A useful compliment to comparison of a single analysis to experimental results is a comparison of several analyses which are based on a wide range of simplifying assumptions. Since the “virtual specimen” is known with much greater accuracy than a real one, it is possible to identify with much greater certainty the validity (or error) of various approximations. Of course, this procedure has its own weaknesses. The main weakness is that the various approximations are being evaluated for an idealized geometric model of the composite (since the real geometry is too complex). Conclusions based on an idealized geometry do not necessarily hold for the “real thing”. In spite of this risk, it is proposed that significant insight can be obtained.
In Situ Damage and Failure Observation in Model Carbon-Carbon Laminates Containing Planar Yarn Crimping
Authors: Roy Ajit K. , Anderson David P.
Published: July 2023

The two-dimensional carbon-carbon composite is an emerging class of material for high temperature applications. However, the structural application of two-dimensional carbon-carbon composites is currently very limited due to lack of understanding of failure mechanism under mechanical loading. The fiber reinforcement in two-dimensional carbon-carbon composites is normally in fabric form, mostly in satin weave. Failure in woven composites, in general, occurs in the vicinity of yarn crimping (due to two perpendicular yarns crimping over and under to each other, Figure 1) where the stress in known to be three-dimensional (Whitcomb, 1991). Due to the presence of two perpendicular yarns crimping at the failure location, there exists a difficulty in identifying experimentally the influence of the stress components on the failure of two-dimensional carbon-carbon composites.
Durability and Damage Tolerance Certification of Composite Structures
Authors: Deo R. B.
Published: July 2023

Several recent applications of polymer matrix, graphite fiber composites to operational aircraft structures have illustrated a need for well defined approaches or methodologies to demonstrate compliance with airworthiness certification requirements. This paper presents a review of the currently used compliance criteria, substantiating data required, and the methodologies available to address durability and damage tolerance certification of aircraft composite primary structures.
Use of Stacking Model of the Linear Inhomogeneous Layer Elements
Authors: Ohyoshi Tadashi , Sui Guangjun , Miura Kimihisa
Published: July 2023

Various numerical results of backscatter from an inhomogeneous stacking layer are obtained by the use of the linear inhomogeneous layer element, LILE. The stacking of LILE provides us an excellent analytical model for wave motion in inhomogeneous materials. Extensive numerical calculation of the reflecting energy to a wide frequency range by using the model is very important to inspect the effective use of the model. Reflectance curves developed as a function of the incident wave number, are therefore presented in a wide frequency range and discussed on the relation between layered structure of a composite and the backscatter intensity. And further, numerical results of backscatter from a defected layer inside a composite are developed in graph. Examinations of the relative error in the computational reflectance to white noise incidence, are also made to know the required number of stacking elements. When the backscatter calculation to a complex composite is made with comparatively high frequency waves, the superiority of the LILE stacking model is recognized.
Flutter Control of Straight/Swept Aircraft Wings Using Combined Feedback Control Laws
Authors: Karpouzian Gabriel , Librescu Liviu
Published: July 2023

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

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

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

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) < (τc/σc) for tensile type of fracture and (τmax/σmax) > (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

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 < n < 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

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

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

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

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

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

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.