Influence Of Loading Conditions Research Articles

Welding residual stress behavior under mechanical loading

For an accurate estimation of the fatigue performance of welded joints, not only the initial residual stress field but also its variation under load is decisive. The portion of residual stress which stays stable can shift the load stress range much the same way as the mean stresses do in fatigue loading. The relaxation of residual stresses during fatigue loading however reduces this hazard to the structural health. That is, before considering the influence of residual stresses in fatigue, the effect of fatigue on residual stresses should be understood. In this work, the influence of the quasi-static and cyclic loading on the relaxation of welding residual stresses in small specimens and large components out of different steels namely S235JRG2, S355J2G3, P460NL, S690QL, S960QL, and S1100QL has been investigated experimentally. X-ray diffraction analysis as a reliable method has been used for the determination of residual stress profiles in surface layers. For residual stress analysis in deeper layers, synchrotron and neutron diffraction techniques were applied as complementary methods. A clear recognition of the difference between initial welding residual stresses in small- and large-scale specimens was observed. Tensile residual stresses as high as the yield strength could appear in large-scale welded specimens. That was not the case for small-scale welds due to the low grade of restraint. Nevertheless, in both types of samples, the highest residual stresses were obtained in the weld centerline. At the weld toe which is critical regarding fatigue crack initiation, the magnitude of the residual stresses is lower. Beside of that, it was observed that in the case of relaxation, the first load cycles especially in components out of low-strength steels are decisive. The influence of loading conditions and local mechanical properties on the relaxation of welding residual stresses was investigated based on principles of solid mechanics. The von Mises failure criterion was able to describe the relaxation behavior.

載荷状態が漁船の漂流運動に及ぼす影響の推定に関する研究

It is known that a loading condition of fishing vessel changes frequently by fish catching and fuel oil consumption. This paper describes the study on influence of loading condition on drifting motion of fishing vessel in a regular wave. In previous paper, model experiments were carried out and it was shown that the trim condition of vessel affects the beginning of drifting motion. In this paper, the characteristics of steady drifting motion in a regular wave were examined by numerical simulation based on experimental data of forces acting on a hull. As the results, it was found that the trim condition of vessel affects the speed and direction of drifting motion. Especially, according to the incident angle of wave, the direction differs significantly. Therefore, it is important to consider the trim condition of vessel for the prediction of drifting motion.

Torque Analysis of Permanent-Magnet Flux Switching Machines With Rotor Step Skewing

This paper investigates the torque characteristics of permanent-magnet flux switching (PMFS) machines with rotor step skewing. The cogging torque, torque ripple, and average output torque of a PMFS machine with a common stator and different rotor pole widths and rotor pole numbers are first established using two-dimensional (2-D) finite element analysis (FEA). A cost-effective rotor step skewing technique is then proposed to reduce the cogging torque and torque ripple of the machine with two different rotors. The results have revealed that the least step number and angle for optimal torque ripple mitigation of the PMFS machine are determined by the harmonic contents of the torque pulsation and the rotor pole number. The influences of load conditions on the machine torque characteristics are carried out by varying current excitations. The corresponding three-dimensional (3-D) FEA models are constructed and experimental prototypes are built for validations.

Safety assessment of pipes with multiple local wall thinning defects under pressure and bending moment

The safety assessment of pipes with local wall thinning defects is highly important in engineering. Most attention has been paid on the safety assessment of pipe with single local wall thinning defect, while the studies about multiple local wall thinning defects are not nearly enough. However, the interaction of multiple local wall thinning defects in some conditions is great, and may have a great impact on the safety assessment. In the present standard API 579/ASME FFS, the safety assessment of pipes with multiple local wall thinning defects is given, while as well as the influence of load condition, the influences of arrangement and relative depth of defects are ignored, which may influence the safety assessment considerably. In this paper, the influence of the interaction between multiple local wall thinning defects on the remaining strength of pipes at different arrangements and depths of defects under different load conditions (pressure, tension-bending moment and compression-bending moment) are studied. A quantified index is defined to describe the interaction between defects quantitatively. For different arrangements and relative depths of defects, based on a limit value 0.05 of the quantified index of the interaction between defects, a relatively systematic safety assessment of pipes with multiple local wall thinning defects under different load conditions has been proposed.

Influence of loading conditions on the measurement of mode I critical stress intensity factor for wood and medium-density fiberboard by the single-edge-notched tension test

AbstractThe mode I critical stress intensity factorKIcfor wood and medium-density fiberboard (MDF) was obtained by conducting the single-edge-notched tension (SENT) test, designed for isotropic materials, under various loading conditions, and performing subsequent numerical analysis on the test data. The validity of the SENT test for this purpose was examined by conducting double cantilever beam (DCB) tests and comparing test data with those of the SENT tests. The best values ofKIcare obtained by conducting the SENT test under pin loading and introducing an additional crack length into the equations used for analyzing the test data.

Contact models of repaired articular surfaces: influence of loading conditions and the superficial tangential zone

The superficial tangential zone (STZ) plays a significant role in normal articular cartilage's ability to support loads and retain fluids. To date, tissue engineering efforts have not replicated normal STZ function in cartilage repairs. This finite element study examined the STZ's role in normal and repaired articular surfaces under different contact conditions. Contact area and pressure distributions were allowed to change with time, tension-compression nonlinearity modeled collagen behavior in the STZ, and nonlinear geometry was incorporated to accommodate finite deformation. Responses to loading via impermeable and permeable rigid surfaces were compared to loading via normal cartilage, a more physiologic condition, anticipating the two rigid loading surfaces would bracket that of normal. For models loaded by normal cartilage, an STZ placed over the inferior repair region reduced the short-term axial compression of the articular surface by 15%, when compared to a repair without an STZ. Covering the repair with a normal STZ shifted the flow patterns and strain levels back toward that of normal cartilage. Additionally, reductions in von Mises stress (21%) and an increase in fluid pressure (13%) occurred in repair tissue under the STZ. This continues to show that STZ properties of sufficient quality are likely critical for the survival of transplanted constructs in vivo. However, response to loading via normal cartilage did not always fall within ranges predicted by the rigid surfaces. Use of more physiologic contact models is recommended for more accurate investigations into properties critical to the success of repair tissues.

Numerical simulations of void growth in aluminum alloy AA5083 during elevated temperature deformation

Finite element computations are used to simulate void growth during elevated temperature deformation of polycrystalline aluminum alloy AA5083. The model accounts rigorously for the coupling between dislocation creep, grain boundary diffusion and grain boundary sliding; and considers a realistic 2D grain structure. The simulations are used to predict the influence of loading conditions, material properties and microstructure on void growth rates. The predictions are shown to be in good agreement with experimental observations of cavitation in aluminum. In addition, the simulations show that the rate of void growth is strongly sensitive to the detailed grain structure near the void. Consequently, the void growth rates in a realistic microstructure differ substantially from the predictions of models that idealize the grain structure as a periodic array.

Analysis of bone–prosthesis interface micromotion for cementless tibial prosthesis fixation and the influence of loading conditions

A lack of initial stability of the fixation is associated with aseptic loosening of the tibial components of cementless knee prostheses. With sufficient stability after surgery, minimal relative motion between the prosthesis and bone interfaces allows osseointegation to occur thereby providing a strong prosthesis-to-bone biological attachment. Finite element modelling was used to investigate the bone–prosthesis interface micromotion and the relative risk of aseptic loosening. It was anticipated that by prescribing different joint loads representing gait and other activities, and the consideration of varying tibial–femoral contact points during knee flexion, it would influence the computational prediction of the interface micromotion. In this study, three-dimensional finite element models were set up with applied loads representing walking and stair climbing, and the relative micromotions were predicted. These results were correlated to in-vitro measurements and to the results of prior retrieval studies. Two load conditions, (i) a generic vertical joint load of 3×body weight with 70%/30% M/L load share and antero-posterior/medial-lateral shear forces, acted at the centres of the medial and lateral compartments of the tibial tray, and (ii) a peak vertical joint load at 25% of the stair climbing cycle with corresponding antero-posterior shear force applied at the tibial–femoral contact points of the specific knee flexion angle, were found to generate interface micromotion responses which corresponded to in-vivo observations. The study also found that different loads altered the interface micromotion predicted, so caution is needed when comparing the fixation performance of various reported cementless tibial prosthetic designs if each design was evaluated with a different loading condition.

Fatigue of biomaterials: Hard tissues

The fatigue and fracture behavior of hard tissues are topics of considerable interest today. This special group of organic materials comprises the mineralized (roughly 50% mineral by volume or greater) and load-bearing tissues of the human body; it includes bone, cementum, dentin and enamel. An understanding of their fatigue behavior and the influence of loading conditions and physiological factors (e.g. aging and disease) on the mechanisms of degradation are essential for achieving lifelong health. But there is much more to this topic than the immediate medical issues. There are many challenges to characterizing the fatigue behavior of hard tissues, much of which is attributed to size constraints and the complexity of their microstructure. The relative importance of the constituents on the type and distribution of defects, rate of coalescence, and their contributions to the initiation and growth of cracks, are formidable topics that have not reached maturity. Hard tissues also provide a medium for learning and a source of inspiration in the design of new microstructures for engineering materials. This article briefly reviews fatigue of hard tissues with shared emphasis on current understanding, the challenges and the unanswered questions.

Influence of Loading Condition and Size–Effect on the K R –Curve Based on the Cohesive Stress in Concrete

Studies of the influence of specimen geometry and size–effect on the K R –curves and the related fracture parameters were carried out by the authors (Kumar and Barai 2008b). The present paper is a supplementary contribution and reports interesting results related to the effect of the loading condition and size–effect studies on the K R –curves associated with the cohesive stress distribution for complete fracture process, the double–K fracture parameters, the CTOD–curves and the process zone length using two different loading conditions (i.e., three–point bending test and four–point bending test). The laboratory size specimen with initial–notch length/depth ratios 0.3 and 0.5 are considered in the work. The load–crack opening displacement curves for these loading conditions are obtained using well known version of fictitious crack model.

Experimental study of the influence of loading conditions on the stability of rotating cylindrical shells

The effect of the loading conditions on the stability of rotating cylindrical shells is examined experimentally. It is established that the critical loads of axially compressed rotating shells substantially decrease with increasing speed of rotation

406 骨粗鬆症脊椎の衝撃解析における荷重条件の影響(OS4-2,オーガナイズドセッション4:生体のモデリング・シミュレーション・計測,学術講演)

406 骨粗鬆症脊椎の衝撃解析における荷重条件の影響(OS4-2,オーガナイズドセッション4:生体のモデリング・シミュレーション・計測,学術講演)

Influence of loading conditions on the impact damage resistance of composite panels

In this paper the onset of impact induced delaminations in stiffened composite panels is analysed by using an approach based on a threshold critical impact force. This approach is adopted in combination with geometrically non-linear finite element analyses in order to investigate the influence of the in-service loading conditions on the impact damage resistance of the composite panels. An application to a stiffened composite panel under compression is presented in order to point out the sensitivity of the impact damage resistance to the level of load. Finally, indications on a novel approach, able to take into account the non-linearity of the composite stiffened panels’ response, are given.

Statistical Methods in Genetic Epidemiology

Advances in speckle-tracking echocardiography allowed the rise of deformation imaging as a feasible, robust, and valuable tool for clinical routine. The global or segmental measurement of strain can objectively quantify myocardial deformation and can characterize myocardial function in a novel way. However, the proper interpretation of deformation measurements requires understanding of cardiac mechanics and the influence of loading conditions, ventricular geometry, conduction delays, and myocardial tissue characteristics on the measured values. The purpose of this manuscript is to review the basic concepts of deformation imaging, briefly describe imaging modalities for strain assessment, and discuss in depth the underlying physical and pathophysiological mechanisms which lead to the respective findings in a specific disease.

Influence of loading condition and reinforcement size on the concrete/reinforcement bond strength

The paper reports on a study of bond strength between reduced-water-content concrete and tensile reinforcement in spliced mode. Three different diameters (12, 16 and 22 mm) of tensile steel were spliced in the constant moment zone, where there were two bars of same size in tension. For each diameter of reinforcement, a total of nine beams (<TEX>$1900{\times}270{\times}180mm$</TEX>) were tested, of which three beams were with no axial force (positive bending) and the other six beams were with axial force (combined bending). The splice length was selected so that bars would fail in bond, splitting the concrete cover in the splice region, before reaching the yield point. It was found that there was a considerable size effect in the experimental results, i.e., as the diameter of the reinforcement reduced the bond strength and the deflection recorded at the midspan increased significantly, whilst the stiffness of the beams reduced. It was also found for all reinforcement sizes that higher bond strength and stiffness were obtained for beams tested in combined bending than that of the beams tested in positive bending only.

Influence of Loading Condition on the Behavior of a Moored Liquefied Natural Gas Ship

In a recent paper, a verification study was presented of the time-domain mooring simulation program TERMSIM. In that paper, the verification was restricted to the behavior of loaded ships. Extension to the verification of the model for different loading conditions is made in this technical note. For the downtime analysis of a new liquefied natural gas (LNG) terminal, the influence of the loading condition is often neglected and the analysis is only carried out for the loaded ship. This assumption seems valid, because the draft difference between laden and ballast is small for LNG ships. However, prototype measurements of line forces showed quite large increase of mooring forces during the loading process of the ship. This strong dependence also follows from computer simulations presented in this technical note. Large differences in moored ship behavior in swell waves between the loaded and ballasted condition can occur because of a different roll period and ratio between the wave frequency and stiffness of the mooring system.

Adaptive mechanisms of left ventricular diastolic function to the physiologic load of pregnancy.

Pregnancy is associated with marked alteration in cardiovascular hemodynamics. Recent reports have characterized the effects on cardiac systolic function. Little has been written on the influences of loading conditions on Doppler measures of diastolic function during pregnancy. Stage of pregnancy has an impact on Doppler indices of diastolic function independent of loading conditions, systolic function, and heart rate. Thirty healthy women were prospectively evaluated by serial echocardiography and Doppler examinations at six time periods: 10-12, 18-20, 28-30, 36-38 weeks gestation, 2-4 and 12-14 weeks postpartum. The related effects on indices of diastolic function and its interaction with load, heart rate, mass, and systolic function were determined. Compared with the nonpregnant state, early (E) velocity increased (0.7+/-0.1-0.9+/-0.1 m/s, p = 0.0001), peaking at 18 weeks and returning to normal levels during late pregnancy. Atrial phase (A) velocity peaked at 18 weeks (0.48+/-0.12-0.60+/-0.13 m/s, p = 0.0001), remaining high throughout the rest of pregnancy. Consequently, the EWA ratio fell significantly during late pregnancy, from 1.9+/-0.4 to 1.4+/-0.3 (p = 0.02). In addition, mean acceleration was significantly increased in early pregnancy with a peak at 18 weeks (7.4+/-1.3 m/s2), returning to nonpregnant level at term (5.7+/-1.4 m/s2, p = 0.0001). Generalized estimating equation using multivariate regression analysis demonstrated that rising heart rate and stroke volume index had an independent effect on A velocity, and that contractility and preload had an independent effect on E velocity. Pregnancy itself had an independent influence on early filling, not explained by the other parameters. During normal pregnancy, there is a reversible shift in transmitral flow velocities from early to late filling with a decrease in acceleration, consistent with an increase in ventricular compliance. Changes in heart rate, preload, and contractility, as well as stage of pregnancy influence this alteration.

On the Influence of Loading Condition on Characteristics of Hydrodynamic Forces in Steering Motion

On the Influence of Loading Condition on Characteristics of Hydrodynamic Forces in Steering Motion

Effect of Hydrostatic Pressure on the Rate Dependence of the Fracture Toughness of High-Filled Polymeric Materials

The paper presents results of an experimental investigation of the effect of hydrostatic pressure on the fracture toughness of high-filled polymeric materials. It has been shown that the critical value of the stress intensity factor and hence the crack propagation rate increase with increasing hydrostatic pressure of the medium. To take into account the effect of pressure on the fracture toughness characteristics of the materials under investigation, it is proposed to employ the pressure-time analogy method. The method makes it possible to represent experimental plots of fracture toughness against crack propagation rate, obtained at various levels of hydrostatic pressure, as a generalized pressure-time plot that defines the influence of loading conditions on fracture characteristics of the material. Simple empirical relations are proposed for the approximation of the experimental data obtained.

111 ラット尾椎の力覚応答における荷重負荷量の影響(OS4-2 生体材料)(OS4 生体材料力学の新展開)

111 ラット尾椎の力覚応答における荷重負荷量の影響(OS4-2 生体材料)(OS4 生体材料力学の新展開)