bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stress Analysis of Bolted Joints With Plain Washers
Authors: Sawa Toshiyuki , Yasui Hajime 
Published: January 2022

Abstract
Bolted joints have been widely used in many kind of industries, being used commonly. Recently, the bolt strength has been improved and high strength bolts are usually used. As the bolt strength increases, bolt preload increases. In reliable design standpoint of bolted joints, the contact stress at the bearing surfaces between a bolt head and a clamped part must be examined in order to prevent the permanent set due to over stress at the bearing surfaces. Thus, flat washers have been used in bolted joints in order to enlarge the bearing area. In this paper, the contact stress at the bearing surfaces between a plain washer and a clamped part is analyzed using the axisymmetric theory of elasticity as a contact problem, where clamped parts are finite hollow cylinders. In the analysis, a bolt head and bolt shaft are replaced by finite solid cylinders and a plain washer and the clamped parts by finite hollow cylinders. In the numerical calculations, the effects of the stiffness, the thickness and the outer diameter of plain washers on the contact stress distribution are examined. Furthermore, it is important to know the mechanical behaviors of bolted joints with plain washers subjected to external loads. When, an external load W is applied to a bolted joint with a plain washer, an increment of axial bolt force Ft occurs in the bolt and the contact stress between the clamped parts is decreased. The ratio Ft/W is known as the load factor and it is necessary to know the load factor in designing bolted joints with plain washers. The analysis of the load factor is also done. In addition, the effects of plain washers on the load factor are examined in the numerical calculations. The experiments to measure the load factor of bolted joints with plain washers are carried out. The results of the analysis are compared with the experimental results.
Effect of Interface Configuration on the Mechanical Behaviors of Bolted Joints
Authors: Kudo Atsushi , Sawa Toshiyuki 
Published: January 2022

Abstract
In designing a bolted joint, it is important to examine the sealing performance and to estimate the load factor, that is the ratio of an additional axial bolt force to a load. In order to improve the sealing performance raised faces of the interface have been used. But these interfaces in bolted joints have been designed empirically and the theoretical grounds are not made clear. In the present paper, in the case of T-shaped flanges with raised faces the sealing performance (clamping effect) is analyzed by a two-dimensional theory of elasticity and the point matching method. Then, the load factor is analyzed. Moreover, with the application of the load a bending moment is created in bolts and the stress is added due to this bending moment. The bending moment in the bolt is also analyzed. In order to verify these analysis experiments were carried out to measure the load factor and the maximum bolt stress. The analytical results are in a fairly good agreement with the experimental ones.
A Three Dimensional Finite Volume Method in Curvilinear Coordinates for Complex Geometries: Formulation and Analysis
Authors: Banerjee Sibashis S. , Hassan Y. A. 
Published: January 2022

Abstract
A strongly conservative finite volume formulation for complex geometries in three-dimensions using a complete transformation of the governing equations on a nonstaggered grid is presented. This method retains its conservative character at the scalar discretization level. The use of physical contravariant components as dependent variables eliminates the need for any transformation to calculate the cell face mass fluxes. A partially implicit treatment of the nonorthogonal diffusion terms is used to enhance the diagonal dominance of the scheme. This is an extension of the method proposed by Sharatchandra (1994). The method is then tested for two test problems for which analytical solutions are available and an error analysis is performed.
Reliability HCF Design of Gas Turbine Blades Using Probabilistic Goodman Diagram
Authors: Shen M.-H. Herman 
Published: January 2022

Abstract
A probability-based procedure has been developed to predict reliability of gas turbine engine blades subjected to high cycle fatigue. The procedures provides a systemic approach for predicting and designing turbomachinery blading reliability against various potential fatigue problems for all relevant vibratory modes and taking into account variability in geometry (e.g. dimensional variation, mistuning, etc.), unsteady aerodynamics, structural damping, and thermal loading. The variability in materials (e.g. damage, cracks, degradation, etc.) can be also considered in this approach. A reliability prediction was performed on gas turbine blades at high frequency modes (e.g. third strip modes) using a probabilistic vibratory stress distribution in conjunction with the Haigh or modified Goodman Diagrams. The cumulative reliability and risk assessment are then calculated using the fast probability integration (FPI) technique to construct a novel probabilistic Goodman (or Haigh) diagram which provides blade’s lifetime design guide line and an optimal maintenance strategy in management in decisionmaking relating to the PM/inspection scheduling, replacement, spare parts requirements.
Adhesion, Adhesion Hysteresis and Friction in MEMS Under Controlled Humidity Ambients
Authors: de Boer M. P. , Knapp J. A. , Redmond J. M. , Michalske T. A. , Maboudian R. 
Published: January 2022

Abstract
In surface micromachining, compliant structures and high surface to volume ratios render surface properties such as adhesion and friction critical parameters in system reliability. The adhesion and friction of polycrystalline silicon (polysilicon) MEMS structures depends strongly on the ambient to which they are subjected. This dependence is reduced, but not eliminated, when molecular coatings are applied to their surfaces. From measured adhesion energy (Γ, J/m2) for uncoated beams, we demonstrate that capillary condensation produces an exponential dependence of adhesion on relative humidity (RH). For coated beams, we demonstrate that after substantial exposure to high RH ambients, adhesion begins to vary along the length of the beam. This implies a localized breakdown mechanism of the molecular coating. Finally, we present data on a new structure to measure friction in MEMS. With this structure, we can infer slip on a nanometer length scale.
Load Transfer Characteristics in the Vicinity of Fiber Breakage
Authors: Tandon G. P. , Pagano N. J. , McCartney L. N. 
Published: January 2022

Abstract
The single fiber, axisymmetric concentric cylinder model is widely used for analyzing the thermo-elastic stress field in a composite representative volume element. In this study, the concentric cylinder model has been utilized to evaluate the load transfer characteristics in the immediate vicinity of a broken fiber in a unidirectional composite. A number of researchers have studied the stress distributions around discontinuous fibers. The so-called shear lag analysis is frequently used for analysis of stress transfer between fiber and the matrix. However, this simplified approach leads to inaccurate predictions of shear stresses and energy release rates [1]. By developing sets of recurrence relations, McCartney [2] has extended the two cylinder stress transfer model to multiple cylinders and used the technique to study the stress transfer behavior when fiber fracture occurs. Using Reissner’s variational principle, Pagano [3] has developed the axisymmetric damage model to approximate the elastic stress field and energy release rates of bodies composed of concentric cylinders containing damaged regions either as annular or penny-shaped cracks in the constituents and/or debonds between them. This variational model of a concentric cylinder [3] can be easily employed to simulate fiber breakage.
The prediction of micro-mechanical damage initiation and growth in composite materials requires accurate stress and deformation analyses. For the fiber fracture stress transfer problem, singularities are encountered for the axial stress in the matrix in the plane of fiber fracture. In this work, the detailed stress and displacement fields in the neighborhood of fiber break are analyzed using the recursive [2] and variational [3] methods, and compared with the asymptotic stresses around the crack tip [4] and with other numerical methods such as FEM using mesh refinement in the regions of singularity. In this study a comparison of the different solutions is presented highlighting the distance at which leading terms of asymptotic analysis are dominant and the ability of the approximate elasticity solutions to capture the local radial and angular distributions near the crack tip. Also, the assumptions of the more commonly used shear-lag analyses will be critically assessed.
A Novel Eigenfunction Expansion Solution for a Three-Dimensional Crack Problem
Authors: Chaudhuri Reaz A. , Xie Minsheng 
Published: January 2022

Abstract
A new eigenfunction expansion method is developed to obtain hitherto unavailable explicit expressions for three-dimensional asymptotic singular stress fields in the vicinity of (a) an interior point (edge), (b) the surface corner point (vertex) and (c) the transition region located at the front of a a semi-infinite crack. In comparison with the existing asymptotic methods valid for the interior region, the present method is considerably easier to implement, and is also computationally more efficient in the sense that it does not need to resort to iterative schemes to solve the system of three coupled partial differential equations of three-dimensional elasticity theory.
At the crack front, the edge or the interior solution is valid at all points except the two vertices or the surface corner points, which Me in the closure of the edge. The edge or interior point singularity Si is understood in the context of a dihedron emerging radially (in the sense of the cylindrical polar coordinate system) from the edge and distributed over the crack front except the vertex. The vertex or the surface corner point singularity is, on the contrary, to be understood in the context of a cone emerging radially (in the sense of the spherical coordinate system) from the vertex. For the surface corner point, the present asymptotic analysis yields that the singular stresses are proportional to ρ−ss fij(q, f) as ρ → 0, ρ, θ, ϕ being the spherical coordinate system, where σs is the surface corner point singularity. For this special case of a crack, both si and ss are found to be equal to 0.5, although for other problems, e. g., a re-entrant corner of arbitrary interior angle, these are not equal. In the transition region, where both the edge and vertex solutions are superposed, a renormalization type approach is used to keep the crack front displacement finite, which, in turn, satisfies the locally finite strain energy condition for uniqueness.
Finally, the relationship between the strain energy release rate and the stress intensity factor is also investigated from a three-dimensional standpoint. Furthermore, numerical results pertaining to development of plastic yield zone ahead of the front of a semi-infinite crack are also obtained. The latter results are consistent with experimentally observed yield zones.
Interaction of Two Circular Cylindrical Inhomogeneities Under Antiplane Shear
Authors: Linzhi Wu 
Published: January 2022

Abstract
For the inhomogeneous medium with inclusions or inhomogeneities including fibers, whiskers, particles, cracks, etc. (see Mura, 1987), the interaction between inclusions or inhomogeneities is very important in analyzing and investigating the following problems: the stress concentration near inclusions or inhomogeneities, the effective properties, the damage mechanism and failure mode, etc. For this purpose, the elastic field of the infinite homogeneous isotropic medium with two circular cylindrical inhomogeneities under the antiplane shear stress is investigated. The corresponding analytical solution is obtained by using the conformal mapping and the theorem of analytic continuation. Here, two circular cylindrical inhomogeneities are parallel to each other, infinitely long along the direction perpendicular to xy-plane and have the radii rl and r2, respectively. When the matrix, assumed to be infinite in all directions, is subjected to the uniform antiplane shear stress, the present problem is the antiplane one.
From the results obtained, it can be found that the elastic field depends on the shear moduli of individual phases, the geometric parameters of the system and the applied shear stresses at infinity. When one of two circular cylindrical inhomogeneities has the same shear moduli with matrix, the present expressions can degenerate into the results of Gong and Meguid (1992). In addition, numerical results show that the shear moduli of two circular cylindrical inhomogeneities and the geometric parameters of the system have the important effect on the shear stress distribution. The presence of two circular cylindrical inhomogeneities makes the stress field between these two inhomogeneities to have sharper changing tendencies. When two circular cylindrical inhomogeneities approach each other, the interaction between these two inhomogeneities is more prominent.
Transient Elastic Wave Propagation and Local Dynamic Stress Concentration in Woven Fabric Composites
Authors: Chou Tsu-Wei , Chen Baoxing 
Published: January 2022

Abstract
Investigations of the response of composites to time-dependent loadings are of considerable importance in structural analysis of many engineering fields, including aerospace, aeronautic, naval and automotive applications. Wave propagation in woven fabric composites poses major theoretical and experimental challenges. The mathematical modeling of dynamic stress concentrations in woven fabric composites is a fairly difficult task due to the great number of wave interactions between the fiber and the matrix. When composite structures composed of woven fabric preforms are loaded impulsively, stress waves propagate in different constituent phases at different speeds, which results in dynamic normal and shearing stresses at the interfacial bond region as well as at the yarn cross-over points. The concentration of these stresses may initiate unstable delamination and eventually failure of the laminated structure. This paper presents a theoretical study on the elastic wave propagation and local dynamic stress concentration in woven fabric composites. The analysis focuses on the unit cell of an orthogonal woven fabric composite, which is composed of two sets of mutually orthogonal yarns of either the same fiber (non-hybrid fabric) or different fibers (hybrid fabric) in a matrix material. Using the mosaic model for simplifying woven fabric composites and a shear lag approach to take into account the inter-yarn deformation, a one-dimensional analysis has been developed to predict the local elastodynamic and elastostatic behavior. The initial and boundary value problems are formulated and then solved using Laplace transforms. Closed form solutions of the dynamic displacements and stresses in each yarn, and the bond shearing stresses at the interfaces between adjacent yarns, are obtained in the time domain for in-plane, as well as out-of-plane impact loadings. When time tends to infinity, the dynamic solutions approach to their corresponding static solutions, which are also developed in this article. Solutions of certain special cases are identical to those reported in the literature. Lastly, the dynamic stresses and bond shearing stresses of plain weave composites subjected to step uniform impacts are presented and discussed as an example of the general analytical model.
Comparison of Elastic Properties for Unidirectional and Woven Laminates
Authors: Schoeppner G. A. , Roy A. K. 
Published: January 2022

Abstract
An experimental program to examine the relationship between the material constants of laminates made of unidirectional pües and laminates made of woven fabric composites including plain weave (PW) and eight harness satin (8HS) weave has been conducted. All of the unidirectional and woven composite tension, compression and shear test coupons were fabricated with the same carbon fiber and toughened epoxy resin system. The test specimens were instrumented with back-to-back rosette strain gages and monitored throughout the test. The PW and 8HS woven fabric specimens were tested in both the warp and fill directions. The stress-strain curves of the woven fabric specimens reveal a knee (change in slope) at about 70 ksi, indicating the failure initiation process. The stress field of the weave geometry will be analyzed to understand the failure initiation process.
Interlaminar Phenomenon in Composite Materials: 1969–1999
Authors: Pipes R. Byron 
Published: January 2022

Abstract
The development of multiaxial laminates consisting of layers of collimated, high performance fibers in a polymer matrix provided the opportunity to design material properties for each application. The earliest analytical methods for determining stresses in the individual laminae assumed linear strain variation through the laminate thickness (Kirchhoff assumption). For much of the design work with composite laminates this simplification was both appropriate and convenient. Yet in 1969 it was postulated by the leading engineers and scientists (such as Dr. N.J. Pagano and Dr. J. E. Ashton) that a planar state of stress within each laminae could not exist near a laminate free-edge. The argument rested on the fact that inplane shearing stresses, induced in the angle-ply laminae of a laminate under normal external loads, could not exist at the free-edge.
Numerous investigators began analyses of the three-dimensional stress state in finite-width laminates including Pagano, Pipes, Puppo and Evenson. Several important developments came for this early work. First, the interlaminar load transfer mechanism between laminae in finite-width laminates was fully articulated as a boundary-layer phenomenon and the influence of stacking sequence on the sign of the interlaminar normal stress for bidirectional laminates was discovered. The roles of laminate material anisotropy and geometric variables such as laminae-to-laminate thickness and laminae-to-laminate width were clarified. A singularity in the interlaminar normal stress at the free-edge was postulated in this early work.
The development of three-dimensional and anisotropic finite-element methods and increases in computation power lead to the further investigation of the afore mentioned phenomenon and to the ability to analyse the three-dimensional state of stress occurring at numerous geometric discountinuities typically found in composite structure. These analyses have confirmed many of the findings of the earlier work and provide powerful tools for investigations required in the future.
Ultrasonic NDE of Transverse Cracks in Laminated Composites
Authors: Maslov K. , Kim R. , Kinra V. K. , Pagano N. 
Published: January 2022

Abstract
Detection of transverse cracks in laminated composites is important for the development and verification of damage-growth models. Historically, it has been assumed that the matrix cracks propagate all the way across the width of a test coupon. When this happens, the dye-penetrant technique works well for the detection of cracks. However, when a crack starts at one edge but does not run all the way across (a partial crack) or when the crack is totally internal, the dye-penetrant method does not give satisfactory results. Moreover, the dye-penetrant technique cannot be used for in-situ testing. The objective of this paper is to report the development of an ultrasonic method for in-situ detection of partial or internal across-the-width cracks.
In the transmission mode, a pair of 20-MHz focused transducers was used in the pitch-catch arrangement. The angle of incidence was chosen to exceed the critical angle for the excitation of a longitudinal wave. This results in the excitation of a shear wave which is more sensitive for the detection of transverse cracks.
Sometimes access is limited to only one side of the plate. To cover these situations, a reflection technique was also developed. Here, higher-order Lamb-wave modes were used (Modes 1 and 3; frequency range 4 MHz – 11 MHz). The advantage here is that in the absence of a crack, there is no reflection, i.e., the wave “sees” a crack against a “dark background”. Moreover, the inspection can be done at a lower frequency where wave propagation is less sensitive to plate surface roughness. A disadvantage is that the spatial resolution of the reflection mode is not as good as that of the transmission mode.
The technique was used to examine a number of graphite/epoxy [0,90,0] coupons, 0.5mm–1mm thick, which had been subjected to monotonic tensile loading prior to the ultrasonic test. A large number of transverse cracks were detected. As expected, a majority of the cracks ran all the way across the width of the test coupon. Some of the cracks started at one edge but were arrested in the middle. Occasionally a crack that started and stopped in the interior was detected. The cracks were also recorded by an examination of the edges using an optical microscope; an excellent correlation between the optical and the ultrasonic images was observed.
It is well known that a closed crack cannot be detected by the use of ultrasound. It is considered possible that what is ultrasonically perceived as a partial crack may, in fact, be an across-the-width crack with a part of its length closed (due, for example, to residual stresses). In order to guard against this possibility the following experiments were conducted. A plate was subjected to a significant bending moment, guaranteeing that at least one half of the crack (the half that occupies the tensile half of the plate) is open. No difference in the ultrasonic images with or without bending was observed. It is concluded that the technique is suitable for the detection of partial and internal cracks.
Rayleigh Waves Propagating Along an Oblique Cut Surface of Directional Fiber Reinforced Composites
Authors: Ohyoshi Tadashi 
Published: January 2022

Abstract
It is well known that the major contribution to an impact response of solid material is the surface waves propagating along a free edges of the plate materials. Then, the subject is focused to the characteristic waves relating to a fiber reinforced composite material. The stress free surface is the cross section generated in mechanical production process by cutting at off-angle to a material symmetric axis. The analytical results show that the cutting angle and fiber volume fraction of composite materials affect the path and direction of particle motion considerably as well as the phase velocity. In the analysis, classical effective modulus theory was used because the wave length is quite large comparing with the geometrical dimensions of composites in most practical cases. The elastic constants are set under the plane stress condition. Numerical calculation was carried out for a glass fiber reinforced epoxy resin matrix composite; Young’s modulus Ef = 73.1[GPa], Em = 3.45[GPa], Poisson ratio vf = 0.22, vm = 0.35, density Df = 2.6[g/m3], Dm = 1.15[g/m3], and miss-alignment factor k = 0.95. The graphs have been made by selecting the parameters of off-angle and volume fraction of fiber. The numerical results show us the some interesting phenomena. For example, the characteristic Rayleigh waves studied are the different ones from the conventional ones. The Rayleigh wave propagating along the oblique cut surface, is composed of two different body waves, quasi-longitudinal P-wave and quasitransverse S-wave. Furthermore, phase plane directions of the body waves are different each other, and they are not orthogonal to the free surface any more. These characteristic results provide important information for analyses of dynamic response of a fiber reinforced composite material.