Fastener Load Research Articles

Stresses in plates containing fasteners under fastener load and any remote load

A method has been developed to calculate the stresses in a plate containing a hole filled with a fastener (interference fit or clearance fit) with applied bolt load (in any direction) and subjected to any remote load (σ∞x σ∞y and τ∞xy). The material of the fastener can be different from that of the plate. The results using this method have been compared with finite element results and existing analytical results which had been solved for some special cases. Very good accuracy has been achieved.

Optimal festener pattern design considering bearing loads

In many engineering structures, failure occurs either at the connection itself or in the component at the point of attachment of the connection. To extend the service life of the structure it is important to ensure that the loads borne by the connections are distributed as uniformly as possible. This would also minimize the possibility of localized high stress regions within the component. In this work a topology optimization based approach has been developed to incorporate fastener load constraints into a problem formulated for optimal location of fasteners. The computational results indicate that it is effective in reducing the maximum fastener loads without compromising on the overall stiffness of the structure.

Stresses Around a Biaxially Loaded Fastener Hole in a Laminate of Finite Geometry

The stress analysis of a biaxially loaded fastener hole in a laminate of finite width has been conducted using a complex variational approach developed at the Institute for Aerospace Research. The formulation of the complex variational approach developed is described in this paper. In this approach, an infinitely stiff fastener is assumed to be in contact with one half of the hole edge. The fastener load is in equilibrium with the applied loads along the exterior edges, and a cosine distribution over the contact region is assumed. The stresses around a single fastener hole under biaxial loading conditions were determined. Various anisotropic laminates were analyzed. The effects of the biaxial loading ratios on the joint performance were examined. Results from the analytical approach are presented and discussed in this paper.

Analysis of composite laminates with multiple fasteners

Fatigue- and fracture-related cracks are to be expected with the large number of fasteners present in aircraft structures. Therefore, contact stresses around the fastener holes and stress intensity factors associated with edge cracks are critical concerns in damage-tolerant designs. Mechanical joints consisting of many fasteners with a staggered pattern further complicate the already rather complex analysis for single-fastener joints. Load distribution among the fasteners significantly influences the failure load of multi-fastener joints. Most existing analyses are confined to single-fastener joints, and the data available for multi-fastener joints are rather limited. Very few experimental and/or analytical/numerical investigations of contact stresses for mechanical joints with staggered fasteners exist in the literature. Therefore, the accurate prediction of contact stresses (load distribution) and stress intensity factors associated with edge cracks is essential for the reliable design of such mechanical joints. This study concerns the development of an analytical methodology, based on the boundary collocation technique, to determine the contact stresses and stress intensity factors required for strength and life prediction of bolted joints with many fasteners. It provides an analytical capability for determining the contact stresses in mechanically fastened composite laminates while capturing the effects of finite geometry, presence of edge cracks, interaction among fasteners, material anisotropy, fastener flexibility, fastener-hole clearance, friction between the pin and the laminate, and by-pass loading. Also, it permits determination of the fastener load distribution, which significantly influences the failure load of a multi-fastener joint.

Contact analysis of mechanically fastened joints in composite laminates by linear complementarity problem formulation

The contact phenomena and stress distributions in the vicinity of the hole on mechanically fastened joints are investigated in composite laminates exhibiting nonlinear elastic behavior. The effects of fastener stiffness, friction force between the fastener and the composite laminates, geometrical nonlinearities due to concentrated fastener load around the hole edge for the snug and clearance-fit in the [0 °] S, [± 45 °] S, [0°/± 45 °] S and laminates are also considered. An efficient numerical procedure is developed for the solution of the contact problems with Coulomb friction between the fastener and the hole based on a linear complementarity problem (LCP) formulation in an incremental form. A nonlinear finite element code for stress analysis of laminated composites using Lemke's complementary pivoting algorithm is developed for solving the LCP. The nonlinear analysis is composed of the combination of updated Lagrangian formulation of the frictional contact problem and the nonlinear shear stress-strain relation in each ply. The accuracy, applicability and computational efficiency of the proposed method are confirmed by comparison with previous researches.

5607518 Methods of deblocking, extracting and cleaning polymeric articles with supercritical fluids: Hoffman Roger J; Terry Wilson L Cumming, GA, United States assigned to Ciba Geigy Corporation

The contact phenomena and stress distributions in the vicinity of the hole on mechanically fastened joints are investigated in composite laminates exhibiting nonlinear elastic behavior. The effects of fastener stiffness, friction force between the fastener and the composite laminates, geometrical nonlinearities due to concentrated fastener load around the hole edge for the snug and clearance-fit in the [0 °]S, [± 45 °]S, [0°/± 45 °]S and laminates are also considered. An efficient numerical procedure is developed for the solution of the contact problems with Coulomb friction between the fastener and the hole based on a linear complementarity problem (LCP) formulation in an incremental form. A nonlinear finite element code for stress analysis of laminated composites using Lemke's complementary pivoting algorithm is developed for solving the LCP. The nonlinear analysis is composed of the combination of updated Lagrangian formulation of the frictional contact problem and the nonlinear shear stress-strain relation in each ply. The accuracy, applicability and computational efficiency of the proposed method are confirmed by comparison with previous researches.

Multirow joint fastener load investigation

A multirow joint subjected to the mechanical and thermal loadings was investigated to determine the loads taken by the fasteners in each row. The hole clearance was considered and its effect on the thermal expansion was defined. The friction in the interface between two plates in contact was analyzed and its effect on the distribution of fastener loads was determined. The primary joint design parameters, such as the material and size of the plates and of the fasteners and the patterns of fastener arrangement were considered. The principle of complementary virtual work was employed to derive the general equations involving these parameters, and the analytical solutions were obtained by solving the matrix equations. A computer program was developed to obtain the numerical solutions through the use of FORTRAN IV System 370/165 computer techniques. The application of the computer program to the practical joint design problems is discussed.

Fatigue Analysis of Mechanically Fastened Joints Utilizing PSI) Loads

Multicomponent wing load and corresponding derived internal stress time histories are evaluated considering load transfer through mechanically fastened joints. These time histories are from both analytically derived and dynamic response test measured data considering flights through continuous turbulence of a heavy logistics aircraft. This evaluation is used as a basis to develop a rational fastener load transfer fatigue analysis methodology that includes gust loads in the power spectral density form. The technique developed includes the establishment of a matrix of axial-shear stress phasing relationships based on variations in operational flight parameters. The results of a durability assessment, utilizing the developed procedure, of specific structural joints subjected to two different load spectra are presented. Significant elements of this procedure are the aforementioned stress phasing relationships, joint geometric configuration data, fastener characteristics, and built-up S-N data. The results are compared to a fatigue assessment based on a uniaxial-stress fatigue analysis procedure. The potential applications of the developed load transfer analysis technique include structural joint design optimization and the durability evaluations of structural joints that have operating loads different from their design loads.

Computer analysis of fastener load distribution in a multi-row joint

The fastener load distribution in a multi-row joint was investigated and general equations were obtained. The effects of essential parameters considered in the joint design on the fastener load distribution were analyzed and computer solutions were obtained. The results indicated that the fastener load at the end rows can be adequately reduced when the effects of the parameters were jointly analyzed. The method of equal partition of load among rows of fasteners, including the effect of friction, was developed.