Fit Joint Research Articles

Joint Modeling of Longitudinal Change and Survival

Joint longitudinal-survival models are useful when repeated measures and event time data are available and possibly associated. The application of this joint model in aging research is relatively rare, albeit particularly useful, when there is the potential for nonrandom dropout. In this article we illustrate the method and discuss some issues that may arise when fitting joint models of this type. Using prose recall scores from the Swedish OCTO-Twin Longitudinal Study of Aging, we fitted a joint longitudinal-survival model to investigate the association between risk of mortality and individual differences in rates of change in memory. A model describing change in memory scores as following an accelerating decline trajectory and a Weibull survival model was identified as the best fitting. This model adjusted for random effects representing individual variation in initial memory performance and change in rate of decline as linking terms between the longitudinal and survival models. Memory performance and change in rate of memory decline were significant predictors of proximity to death. Joint longitudinal-survival models permit researchers to gain a better understanding of the association between change functions and risk of particular events, such as disease diagnosis or death. Careful consideration of computational issues may be required because of the complexities of joint modeling methodologies.

Groove design for form fit joints made by electromagnetic pulse crimping

The electromagnetic pulse process can be an alternative for many conventional productionprocesses. It can be used for perforating, cutting, welding, forming and crimping. In this thesis, the latter willbe investigated in detail, with the emphasis on tubular joints bearing axial tension and/or torsion loading.To get acquainted with the subject, first a literature study was performed concerning the general principlesof electromagnetic pulse crimping. Because a new field shaper had to be designed, literature on this topicwas also consulted. Finally, the design and use of grooves in crimp joints was studied. It has been reportedthat an inner piece (mandrel) with additional grooves in the joining zone significantly increases the strengthof a crimped joint [1]. However, the information on electromagnetic pulse crimping with a mandrel with morethan one groove is very limited. Therefore one of the main goals of this thesis is to determine an optimaldesign for a mandrel with two grooves used for axially loaded joints. A combination of finite elementsimulations and experiments was used to draw preliminary conclusions involving the double groove design.In a later stage torsional joints will be designed and suitable filler materials to realize leak proof joints will beevaluated.

Recommendations for the estimation of the strength of the railway wheel set press fit joint

Although press fit joints are very important in railway engineering, few authors have investigated the strength of press fit joints in terms of their application in railway vehicles. This study analyses the tribological parameters that influence the strength of press fit joints, especially the contact pressure and the static friction coefficient. This research was targeted towards the control of the friction coefficient value to obtain the required strength of a press fit joint in conditions close to the minimum contact pressure that results in less prestressed press fit joints. To estimate press fit joint strength, this study examines the use of minimum and maximum values of the friction coefficient as recommended in the literature considering wide tribological conditions, as well as the experimentally determined friction coefficient values for specific tribological conditions. The study also points out the discrepancy between current railway standards and engineering practice considering the inspection of wheel set press fit joint strength.

Torque Transmission Characteristics of the Press Fit Joint Between the Aluminum Shaft and Steel Ring with Small Teeth

Hybrid or aluminum tube structure requires reliable joining of the shaft to other components such as steel yoke and universal joint, which is often the most difficult task. Therefore, a reliable joining method between the aluminum tube and the steel yoke of a hybrid composite propeller shaft for automobile is required. In this work a press fitting method for joining of an aluminum tube to an aluminum yoke is devised by a steel ring with many small teeth to increase reliability as well as to reduce manufacturing cost of the hybrid propeller shaft rather than using other joining methods such as adhesively bonded or welded joints. The optimal shape and number of teeth of the steel ring were obtained experimentally for the maximum static torque capabilities and fatigue characteristics of the press fit joint, and was compared to the finite element analysis results. Finally, a design guideline for the press fit joint using a steel ring with many small teeth for joining the aluminum shaft to the steel ring was suggested. With the developed press fit joint, the static average shear strength of 70 MPa and fatigue strength of 21 MPa between the aluminum tube and the steel ring were realized, which were almost three times higher than that of the adhesively bonded joint.

A New Circular Distribution and Its Application to Wind Data

A new circular probability distribution which is based on GvM(generalization of the von Mises) is proposed. The newdistribution is used to construct a joint probability distributionwhich is applied to fit joint distribution of linear and circularvariables such as wind speed and wind direction. The results of several numerical experiments show that compared with the existing distribution models, the new circular distribution and the new constructed joint distribution in the paper can provide higher degree of the fit for the wind data under study.

Computational issues with fitting joint location/dispersion models in unreplicated [formula omitted] factorials

Maximum likelihood estimation for a joint location/dispersion model has been found occasionally to experience convergence problems when applied to experiments of the 2 k factorial series. We explore these problems and identify models for which the likelihood diverges or is multimodal. We derive the conditions under which this occurs and provide simple ways to check for problems both before and during computation.

313 冷媒用銅管フレア継手部内に生じる凍結膨張圧に関する研究 : 凍結膨張圧と過冷却現象の関係(大気・水環境評価技術)

The purpose of the present study is to clarify the mechanism that the internal pressure of the flare fitting joint increases by freezing of the dew condensation water. The experimental apparatus to be able to measure supercooling phenomenon in the model joint was built, and the experiments that cooled the model joint was carried out by changing the volume of water inside the joints. It was clarified that the expansion pressure was generated depending on the transition of supercooled water freezing, even if the inside of model joint was not filled with water.

The effect of adhesive type and bond line thickness on the strength of mortise and tenon joints

This study was carried out in order to determine the effects of adhesive type, bond line thickness and moisture content on the strength of mortise and tenon joints. The polyvinyl acetate (PVAc), urea-formaldehyde (UF) and animal adhesives were used, combined with three different bond line thicknesses. At the same time the effect of the moisture content of the wood was investigated by using wood material conditioned to 8%, 12%, 15% moisture contents. The results of the experiments showed that the strength difference between tight fitting and loose fitting joints was 28% if animal adhesive was used, 11% with UF adhesive and negligible with PVAc adhesive. The effect of the moisture content of the wood when the joints were assembled did not depend on the adhesive used. If 12% is taken as the standard moisture content, increasing it to 15% weakened joints by 15% and decreasing it to 8% strengthened them by 6%, irrespective of the adhesive. Test results indicate that strongest joints are obtained when a close tolerance is maintained between the tenon and mortise.

Torque transmission capability of composite–metal interference fit joints

In this paper the performance of an interference fit joint between a composite tube and a steel shaft under torsional load was investigated. Some important design parameters on the interference fit joint were presented and addressed based on the results from analytical and numerical models. The stress state of the joint under torsional load with contact elements was calculated by three dimensional finite element analysis. For the long term use of the interference joint the viscoelastic behavior of the composite tube was also considered through the analytical model. Finally the validity of analysis of the interference fit joint was experimentally examined.

Magnetic contactless detection of stress distribution and assembly defects in constructional steel element

The paper describes contactless stress measurement in a fit joint. The stress was investigated on the basis of changes in material's magnetisation. The level of magnetic leakage field changes due to mechanical stress is low. The stress measurements are determined by material's magnetoelastic sensitivity. This sensitivity must be ascertained. The magnetising field intensity is selected with high accuracy in the range where material's magnetoelastic sensitivity is greatest. The fit joint was executed with tolerance kept within planned limits. The elastic deformation of the ring's material at the lateral surface was measured with a strain gauge. At the last stage, the analytic and numerical calculations of the fit joint were compared to the magnetic field measurement results. The experiment has proven that it is possible to carry out contactless magnetic tests in constructional steel characterised by low magnetoelastic sensitivity.

An Analysis of the Riveting Process as 2-D Frictional Contact Problem

A frictional contact model is adopted for the analysis of conventional solid rivet setting. Material properties for the selected plates and rivets are obtained from analytical method using elastic constants and tensile strengths for each material. Rigid- and elasto-plastic models are selected for process analysis in this paper. Process variables are selected to investigate the effect of variables on the successful rivet setting and servicing in any structure as force transmitting member. Major variables in riveting process are material variables such as material properties and geometrical variables, which are dimensions of head, shank, and blank diameters. Analysis in this study is concentrated on the influence of variety of materials and of shank dimensions on the contact area after rivet setting, i.e. after forming process of rivet head. Soft and hard materials are selected as mother materials to investigate how the selection of material influences on the riveting process in quantitative manner. The geometry of head is closely investigated through simulation in terms of contact status, i.e. contact area between rivet head and mother material, which would affect the snap fit joint by riveting.

Optimal design of the press fit joint for a hybrid aluminum/composite drive shaft

In this work, a one-piece hybrid drive shaft composed of aluminum and carbon/epoxy composite was designed for a rear wheel drive automobile. The aluminum yoke was joined to the hybrid shaft by the press fit joining method using a steel ring which has many small teeth to increase reliability and to reduce manufacturing cost. To obtain high strength of the press fit joint, an optimal design method for the teeth was devised with respect to number and shape of the steel teeth. The developed optimal design method predicted well the static torque capability and failure mode of the press fit joint. Then, the prototype one-piece automotive hybrid aluminum/composite drive shaft was manufactured and tested. The one-piece automotive hybrid aluminum/composite drive shaft allowed 50% mass reduction compared with the conventional two-piece steel drive shaft.

Modeling stylized facts for financial time series

Multivariate probability density functions of returns are constructed in order to model the empirical behavior of returns in a financial time series. They describe the well-established deviations from the Gaussian random walk, such as an approximate scaling and heavy tails of the return distributions, long-ranged volatility–volatility correlations (volatility clustering) and return–volatility correlations (leverage effect). The model is tested successfully to fit joint distributions of the 100+ years of daily price returns of the Dow Jones 30 Industrial Average.

Stochastic model for joint wave and wind loads on offshore structures

The stochastic wave load environment of offshore structures is of such a complicated nature that any engineering analysis requires extensive simplifications. This concerns both the transformation of the wave field velocities and accelerations to forces on the structure and the probabilistic description of the wave field itself. In this paper the last issue is in focus. The modeling follows the traditional structure of subdividing the time development of the wind driven wave process into sea states within each of which the wave process is modeled as a stationary process. The wave process of each sea state is modeled as an affinity in height and time of a Gaussian process defined by a normalized dimensionless spectrum of Pierson-Moskowitz type. The affinity factors are the so-called significant wave height H s and the characteristic zero upcrossing time T z . Based on measured data of ( H s , T z ) from the North Sea a well fitting joint distribution of ( H s , T z ) is obtained as a so-called Nataf model. Since the wave field is wind driven, there is a correlation between the time averaged wind velocity pressure Q and the characteristic wave height in the stationary situation. Using the Poisson process model to concentrate on those load events that are of importance for the evaluation of the safety of the structure, that is, events with Q larger than some threshold q 0, available information about the wind velocity pressure distribution in high wind situations can be used to formulate a Nataf model for the joint conditional distribution of ( H s , T z , Q) given that Q> q 0. The distribution of the largest wave height during a sea state is of interest for designing the free space between the sea level and the top side. An approximation to this distribution is well known for a Gaussian process and by integration over all sea states given Q> q 0, the distribution is obtained that is relevant for the free space design. However, for the forces on the members of the structure also the wave period is essential. Within the linear wave theory (Airy waves) the drag term in the Morison force formula increases by the square of the ratio between the wave height and the wave length, and the mass force term increases proportional to the ratio of the wave height and the square of the period. For a strongly narrow band Gaussian process Longuet-Higgins has derived a joint distribution of the height and the period. However, simulations show that the Pierson–Moskowitz spectrum (or any other standard spectrum for wind driven sea waves of similar bandwidth such as the JONSWAP spectrum) does not provide a sufficiently narrow banded process for the distribution of Longuet-Higgins to make a good fit. Surprisingly it turns out that the random time L between two consecutive 0-upcrossings and the random wave height H observed between the two 0-upcrossings behave such that L and the ratio H/ L are practically uncorrelated and both normally distributed except for clipping the negative tails. This result is of global nature and is therefore very difficult if not impossible to obtain by analytical mathematical reasoning. Finally, by combining all the derived distributional models into a Rosenblatt transformation, a first order reliability analysis of a tubular offshore platform can be made with respect to static pushover. Correction for non-linear wave theory can be taken into account crudely by using the deterministic 5th order Stokes wave in the limit state formulation. A dynamic analysis will be more complicated, of course, but the provided distributional information and the demonstrated modeling principles are judged as generally applicable.

Machine Design: A CAD Approach

Machine Design: A CAD Approach

Analysis and design of metal-plate-connected joints subjected to buckling loads

A comprehensive analytic study has been conducted to investigate the instability problems of metal-plate-connected (MPC) joints in light frame trusses. The primary objective in this study is to determine the governing factors that constitute the buckling of the metal connectors and their effects on the structural response of joints. Another objective is to recommend design curves for the daily structural design of these joints. The numeric data presented in this paper has emerged from a broad base that was founded on over 350 advanced computer simulations, and was supported by available experimental results obtained by others. This basic-to-applied research includes practical engineering parameters such as size of gaps, shear lengths, gauge (plate thickness) of connectors, size of un-braced areas, failure modes, and progressive disintegration of joints. Square-end members have been emphasized though the results cover the custom-made fitted joints. The results indicate that chord shears cause and dominate the buckling of MPC joints, and the shear length has a more pronounced effect than the size of gaps. Further, large gauges and small un-braced areas improve the buckling response. Several practical recommendations have been suggested throughout the paper such as keeping the ratio of gap/shear length below 3/4 for improving the buckling strength. The study reveals that multi-area joints should not be simplified as single web-to-chord MPC joints such as keeping the ratio of gap/shear length below 3/4 for improving the buckling strength, even where one web is in tension and the other in compression. Finally, the results obtained from this study favorably agree with experimental data by others, and the classic buckling theories for other structural components.

Parametric investigation of the buckling performance of metal-plate-connected joints

A comprehensive analytic study has been conducted to investigate the instability problems of metal-plate-connected (MPC) joints in light frame trusses. The primary objective in this study is to determine the governing factors that constitute the buckling of the metal connectors and their effects on the structural response of joints. The numeric data presented in this paper has emerged from a broad base that was founded on over 350 advanced computer simulations, and was supported by available experimental results obtained by others. This basic-to-applied research includes practical engineering parameters such as size of gaps, shear lengths, gauge o connectors, size of unbraced areas, failure modes, and progressive disintegration of joints. Square-end members have been emphasized though the results cover the custom-made fitted joints. The results indicate that chord shears cause and dominate the buckling of MPC joints, and the shear length has a more pronounced effect than the size of gaps. Further, large gauges and small unbraced areas improve the buckling response. Several practical recommendations have been suggested throughout the paper. The study reveals that the engineering of single web-to-chord MPC joints should not be interpreted for multi-area joints, even where one web is in tension and the other in compression. Finally, the results obtained from this study favorably agree with experimental data by others, and the classic buckling theories for other structural components.

Finite Element Calculation of a Press Fit Joint between a Composite Materials Tube and an Aluminium Cylinder

This paper presents the design and calculation of a press fit joint between a fibre reinforced plastic tube and an aluminium cylinder. This joint is used for connecting the several tube portions that form a crane structure.

Behavior and Modeling of Wood-Pegged Timber Frames

Traditional timber connections with wood pegs are encountered in the renovation and rehabilitation of historic wood structures and in the construction of new structures where rustic appearance and traditional methods are desired. This study examined four types of traditional connections: mortise and tenon, mortise and tenon with a shoulder, mortise and tenon with a shoulder and a knee brace, and fork and tongue. A total of 60 specimens, primarily white oak and Douglas fir, were tested. About a quarter of the specimens were assembled and allowed to season under simulated in-service load. All specimens were tested under simulated gravity load up to failure or to about five times typical design load. Some knee-braced specimens were retested to simulate lateral loads. Test results showed that joint behavior is primarily linear. A tightly fitting joint carries load with less peg damage than a loose joint allows. A mortise and tenon with a shoulder performs better than a mortise and tenon or a fork and tongue. ...

Strength evaluation of axisymmetric bonded joints using anaerobic adhesives

Axisymmetric adhesive joints are increasingly used as alternative means of structural joining particularly in highly loaded powertrain components. The paper deals with the use of high strength single component adhesives which cure anaerobically, and the strength evaluation of joints produced using appropriate industrial assembly techniques. The paper provides relevant information on static and fatigue strength properties and gives through stress analysis a better understanding of the factors controlling joint strength when using interference fit joint assemblies.