Effect Of Loading Type Research Articles

Effects of loading type, temperature and oxidation on mechanical hysteresis behavior of carbon fiber-reinforced ceramic-matrix composites

The effects of loading type, i.e., cyclic loading/unloading tensile, cumulative tensile fatigue loading, and tension-tension fatigue loading, temperature and oxidation on the mechanical hysteresis behavior of carbon fiber-reinforced ceramic-matrix composites (CMCs) have been investigated. Based on the damage mechanism of fiber sliding relative to the matrix in the interface debonded region, the stress-strain relationships upon unloading/reloading when the interface partially and completely debonded have been determined considering fibers fracture. The effects of material properties, damage mode and cycle number on the interface slip and hysteresis loops have been analyzed. The mechanical hysteresis behavior of different loading types of C/SiC at room temperature and 800°C in air have been predicted.

Multiaxial fatigue assessment of crankshafts by local stress and critical plane approach

ABSTRACT. For multiaxially-loaded parts several stress-based fatigue assessment concepts are applicable mostly taking uniaxial test results as basis. These approaches work well in case of proportional loading states, but on contrary, for non-proportional stress conditions, implying a change of the principal stress direction, deviations in the fatigue life estimation may occur. The aim of this study is to evaluate the cyclic multiaxial material behavior experimentally and to proof the applicability of stress-based methods to assess the fatigue strength. The investigated base materials incorporate the commonly applied crankshaft steels 50CrMo4 and 34CrNiMo6 without surface-layer post-treatments. Extensive fatigue tests with small-scale specimens are performed to evaluate the material behavior under cyclic loading. The experiments include basic uniaxial characterizations, such as notch stress sensitivity and effect of loading type, including tests under tension, rotating bending, and torsion loading. Additionally, combined loading tests with proportional and non-proportional situations are presented to reveal the fatigue resistance for multiaxial stress states. Significant loading conditions, such as proportional stress under rotating bending and torsion, and further on, non-proportional effects like phase shifts and varying frequency ratios are presented. The local fatigue strength assessment is performed on the basis of the critical plane approach, whereat the normal and shear stresses are transformed in numerous cutting planes. Equivalent stress hypotheses are applied and compared with the experiments showing that the Huber-Mises-Hencky criterion fits well to the test results in case of proportional rotating bending and torsion loading. KEYWORDS. Multiaxial fatigue assessment; Local stress concept; Critical plane approach; Crankshaft.

Nonsway Model for Lateral Torsional Buckling of Wooden Beams under Wind Uplift

AbstractSimply supported wooden beams nailed to deck boards subjected to wind uplift forces are subjected to compressive stresses at their bottom fibers. Because the restraining action provided by decking is at the top fibers, it is unclear to what extent such restraints are effective in controlling lateral torsional buckling as a possible mode of failure under wind uplift. Present design standards do not have provisions for such cases. Thus, the present study aims to quantify the effect of restraints provided by the deck boards on the lateral torsional buckling capacity of twin-beam-deck systems under wind uplift. Toward this goal, a series of analytical and numerical models were formulated. All models capture the continuous rigid lateral restraint and partial twisting restraint provided by the deck boards. The effects of load type and load position were investigated. The bending stiffness of deck boards was observed to have a significant influence on the lateral torsional buckling capacity of twin-beam-...

Numerical analysis of settlement and bearing behaviour of piled raft in Babol clay

Piled raft foundations are the composite construction of a spread foundation and a few number of piles that are usually used in soft soils to compensate the weakness of a raft in satisfying the design requirements. Due to the complex behaviour of piled raft, it is necessary to take into account a number of factors such as pile geometry and arrangement, raft thicknesses, soil properties and loading condition in the design. In this study, a parametric study has been conducted by a three-dimensional finite-element method considering the full interaction between the components of piled raft foundation. The underlying soil consists of Babol clay in drained condition with various stiffness and plasticity, determined from the results of a geotechnical investigation. The results of numerical analyses show that the bearing capacity of piled raft obviously increases with increasing pile length, pile spacing and raft thickness, especially in stiff clay. The effect of load type is more significant for the differential settlement and pile loads than other parameters. Finally, the advantages of using an optimum design method are examined in a special case of analyses and a case history.

Effect of loading type on the fatigue strength of asymmetric and symmetric transverse non‐load carrying attachments

AbstractThis study considers the effect of bending loading and the symmetry of joints on the fatigue strength of transverse non‐load carrying attachments. Conventionally, the fatigue strength of a welded joint has been determined without taking these factors into account. Experimental and finite element analyses were carried out and both methods showed that both loading type and symmetry have an influence on the fatigue resistance of a welded joint. Under tensile loading, the fatigue strength of asymmetric T‐joints was higher than that of symmetric X‐joints. Respectively, the fatigue resistance of tested joints improved explicitly when the external loading was bending. The finite element analysis was in good agreement with the test results in the joints subjected to tension but gave very conservative results in the joints subjected to bending.

Free edge stresses in composite laminates with imperfect interfaces under extension, bending and twisting loading

An accurate analytical three-dimensional elasticity solution is presented for the free edge stresses in composite laminates under extension, bending and twisting loading, accounting for possible bonding imperfections at the layer interfaces. The bonding imperfection is modeled using the linear spring-layer model. A mixed formulation with both displacements and stresses as primary variables is developed using the Reissner-type variational principle and the solution is obtained using the recently developed mixed-field multiterm extended Kantorovich method (MMEKM). The method ensures exact and point-wise satisfaction of the traction-free edge boundary conditions and interlaminar stress continuity conditions, which is key to the accurate solution of free edge stresses. A detailed numerical study established excellent convergence characteristics of iterative series solution. The presence of bonding imperfection at an interface leads to nonsingular free edge interlaminar stresses at that interface, in contrast with the singular stress field occurring at a classical perfect interface. The effect of loading type on the relative reduction of free edge stresses with the increase in imperfection compliance is investigated for cross-ply and angle-ply laminates. The effect of ply-angle of angle-ply laminates on the same is also ascertained.

Nonlinear thermo-electro-mechanical dynamic behaviour of FGPM beams

The nonlinear dynamic characteristics of Functionally Graded Piezoelectric Material (FGPM) beams under in-plane and out-of-plane mechanical, thermal, and electrical excitations are examined. Large deflection behaviour is accounted for in both vibration and dynamic stability analyses using a modified couple stress theory to account for size effects. Response under thermo-electro-mechanical loads demonstrates the complex vibration, dynamic buckling, and post-buckling of the structure. The effects of load type, microstructural dependency, boundary conditions, beam geometry, composition rule of the constituents, and the applied actuator voltage are examined. It is shown that the applied external electric voltage may significantly affect the nonlinear dynamic response of the structure under different types of thermomechanical loading. Hence, to achieve desirable sensing and actuating characteristics, it would be possible to control the vibration, critical dynamic buckling, and stability response of the beam by applying a suitable electric voltage. Moreover, it has been demonstrated that the nonlinear dynamic response of the actuator under thermal (deformation-controlled) loading is quite different from that of mechanical (load-controlled) excitations.

Compression Loading Induced Cellular Stress Response of Intervertebral Disc Cells in Organ Culture

Introduction Mechanical stress is often associated to interverterbal disc (IVD) degeneration and the effect of mechanical loading on IVD has been studied and reviewed.1,2 Previously, expression of heat shock proteins, HSP70 and HSP27 has been found in pathological discs.3 However, there is no direct evidence on whether IVD cells respond to the mechanical loading by expression of HSPs. The objective of this study is to investigate the stress response of IVD cells during compressive loading in an organ culture. Materials and Methods Fresh adult bovine caudal discs were cultured with compressive loading applied at physiological range. Effect of loading type (static and dynamic) and repeated loading (2 hours per day for 2 days) were studied. Nucleus pulposus (NP) and annulus fibrosus (AF) of the IVD were retrieved at different time points: right after loading and right after resting. Positive control discs were heat shocked (43°C). Cell activity was assessed and expression of stress response genes (HSP70 and HSF1) and matrix remodeling genes (ACAN, COL2, COL1, ADAMTS4, MMP3 and MMP13) were studied. Results Cell activity was maintained in all groups. Both NP and AF expressed high level of HSP70 in heat shock groups, confirming their expression in response to stress. In NP, expression of HSP70 was up-regulated after static loading and dynamic loading with higher fold change was observed after static loading. During repeated loading, HSP70 appeared to be upregulated right after loading and decreased after resting. Such trend was not observed in AF and HSF1 levels. Expressions of matrix remodeling genes did not change significantly with loading except ADAMTS4 decreased in AF during static loading. Conclusion This study demonstrated that NP cells upregulate expression of HSP70 in response to loading induced stress without changing cell activity and matrix remodeling significantly. Acknowledgments This project was funded by AO Spine (AOSPN) (grant number: SRN_2011_14) and a fellowship exchange award by AO Spine Scientific Research Network (SRN). References Chan SC, Ferguson SJ, Gantenbein-Ritter B. The effects of dynamic loading on the intervertebral disc. Eur Spine J 2011;20(11):1796–1812 Neidlinger-Wilke C, Galbusera F, Pratsinis H, et al. Mechanical loading of the intervertebral disc: from the macroscopic to the cellular level. Eur Spine J 2014;23(Suppl 3):S333–S343 Sharp CA, Roberts S, Evans H, Brown SJ. Disc cell clusters in pathological human intervertebral discs are associated with increased stress protein immunostaining. Eur Spine J 2009;18(11):1587–1594

Effect of load type on standalone micro grid fault performance

This paper studies the influence of the load type on the fault performance of the standalone Micro Grid (MG). Different load types (static and dynamic) are considered to show their effects on the standalone MG fault behavior. Specifically, the effects of constant power static loads, constant impedance static loads, and constant current static loads are analyzed. Also, effects of dynamic (rotating) loads are highlighted. Results show, that the rotating loads have dominant effects on the fault performance of the MG during the standalone (islanded) mode. Furthermore, rotating loads cause fault currents and touch voltages three times the values associated with the static loads. Consequently, the employed protective devices with the rotating loads MG must be rated three times larger than the employed protective devices with the static loads MG. Also, the time settings of the MG protection devices are highly influenced with the load type. For static load MG, it is equal to 250% of the rotating loads MG protection devices time settings. The three types of static load show different impacts on islanded MG fault performance. Constant power static load has the highest effect compared to the other two static load types (namely, constant impedance and constant current static loads). The results obtained in this study provide a guide for the MG protection designers and planners to consider the effects of load type on the MG protection devices rating and setting.

Effect of loading type on fatigue crack growth behavior of solder joint in electronic packaging

Fatigue cracking tests of a solder joint were carried out using in-situ scanning electron microscopy (SEM) technology under tensile and bending cyclic loadings. The method for predicting the fatigue life is provided based on the fatigue crack growth rate of the solder joint. The results show that the effect of the loading type on the fatigue crack growth behavior of a solder joint cannot be ignored. In addition, the finite element analysis results help quantitatively estimate the response relationship between solder joint structures. The fatigue crack initiation life of a solder joint is in good agreement with the fatigue life (N50%) of a totally electronic board with 36 solder joints.

Effect of load type on temperature rise of a disc brake

Purpose – The purpose of this paper is to reveal the temperature rise characteristics of the disc and pads under different load types. Design/methodology/approach – Evolutions of the disc and pads temperature under a stable, gradual changing and sine-wave contact pressures widely used at present are analyzed numerically by using ANSYS software. Findings – The results show that during the loading process, the temperature increases most rapidly under a stable contact pressure, most slowly under a gradual changing contact pressure; the disc temperature rise curves expose saw-shaped character, the closer it is to the friction surface, the more serious the fluctuations will be, the pads temperature rise curves are rather smooth; temperature gradient in the axial direction is higher than that in the other two directions under all of the three types of contact pressure and shows a sine-wave variation under a sine-wave contact pressure. Originality/value – It indicates that a gradual changing contact pressure should be adopted preferentially in practical application. The simulation results of this work provide theoretical basis for load simulation.

Effects of Loading Type and Temperature on Performance, Transient Operation, and Kinetics of n-Hexane Vapor Removal in a Biofilter

In this research, different inlet concentrations of n-hexane vapor (1–11 g m−3) corresponds to the inlet loading rates of 9–598 g m−3 h−1 at different temperatures (35–45 °C) were eliminated from air under continuous and intermittent loading (10-h feeding per day) in a biofilter packed with compost and lava rock. Loading type had minor effect on the n-hexane removal at 35 °C and the removal efficiency (RE) was in the range of 70 to 100 % at an inlet concentration of 11 gm−3. On the contrary, RE dropped significantly to 25 % at 40 °C under intermittent loading while it was 77 % under continuous loading with the inlet concentration of 9 g m−3 and empty bed residence time (EBRT) of 2 min. Increasing the temperature to 45 °C significantly reduced the RE at both types of loading at both EBRTs of 2 and 1.3 min; however, intermittent loading was led to a slightly greater removal. According to transient-state experiment under intermittent loading at EBRT of 2 min, the biochemical reaction became the dominant mechanism, after an initial short period, every day to remove n-hexane rather than adsorption on bed. Kinetic modeling showed that the biodegradation rates changed linearly with increase in the logarithmic mean n-hexane concentration during intermittent loading at different temperatures while the order of reaction was higher at continuous loading.

Nonlinear stability and vibration of pre/post-buckled microstructure-dependent FGPM actuators

The present study deals with the study of the nonlinear stability and small free vibration of microstructure-dependent functionally graded piezoelectric material (FGPM) beams in pre/post-buckling regimes. The Timoshenko beam theory with various inplane and out-of-plane boundary conditions are considered under different types of mechanical and thermal loads. The beam is assumed to be under inplane mechanical, thermal, and electrical excitations. Each thermo-electro-mechanical property of the beam is graded across the thickness (i.e., height) of the beam, based on a power law model. The von Karman type geometric nonlinearity is included to account for the large deflection behavior of the beam under inplane loads. The modified couple stress theory is included to account for the size effects. A weak-form, displacement-based, finite element formulation is developed to discretize the equations of motion. The resulting system of nonlinear algebraic equations is solved using Newton’s iterative method. The numerical results of frequencies and lateral deflections as a function of load parameters reveal the existence of bifurcation or critical states in some cases. The effects of load type, microstructural dependency, boundary conditions, beam geometry, composition rule of the constituents, and actuator voltage are discussed through the various parametric studies.

Surface cracks in finite thickness plates under thermal and displacement-controlled loads – Part 2: Crack propagation

Surface cracks in finite-thickness plates subjected to thermal or displacement-controlled loads are considered with a focus on crack propagation. Detailed crack propagation analyses are performed and the effect of loading type on crack propagation patterns and lives are systematically investigated. The results show that although there are some slight differences between the crack propagation patterns and lives for the uniform stress and displacement loading, there exist increasingly higher differences for the bending stress and displacement loads during crack growth. It is shown that propagation lives are higher in the case of displacement/thermal loading compared to those of mechanical/stress loads.

Plastic Hinge Rotation Capacity of Reinforced HPFRCC Beams

High performance fiber reinforced cementitious composite (HPFRCC) materials exhibit strain hardening behavior under tensile loading. This strain hardening response occurs after the first cracking of the material. In this paper, experimental and parametric studies were conducted to assess the influence of the compressive strength, loading type, and tension reinforcement ratio (ρ) on the ultimate deformation characteristics of reinforced HPFRCC beams. The analytical and numerical results for simply supported beams with different amounts of tension reinforcement ratios under three different loading conditions are presented and compared with each other and with the available experimental data. The plastic hinge rotation capacity increases as the loading condition changes from the concentrated load in the middle to the uniform load, and it reaches a maximum in the case of two-point loading. The effect of loading type on the plastic hinge rotation capacity of the reinforced beams with a high amount of ρ is not as significant as that of lightly reinforced beams. Based on the analytical results, new simple equations as a function of the tension reinforcement ratio and the loading type are proposed. Analytical results indicate that the proposed equations can be used with sufficient accuracy to calculate the plastic hinge rotation capacity of reinforced HPFRCC beams.

Non-local energy based fatigue life calculation method under multiaxial variable amplitude loadings

Reliable design of industrial components against high cycle multiaxial fatigue requires a model capable of predicting both stress gradient and load type effects. Indeed, taking into account gradient effects is of prior importance for the applicability of fatigue models to real structures. In this paper, a fatigue life assessment method is proposed for proportional and non-proportional multiaxial variable amplitude loadings in the range 104–107 cycles. This method derives from the fatigue criterion initially proposed by Palin-Luc and Lasserre (1998) [2] and revisited by Banvillet et al. (2003) [16] for multiaxial constant amplitude loading. The new proposal consists of a complete reformulation and extension of the previously cited energy based fatigue strength criteria. It includes two major improvements of the existing criteria. The first one consists in a fatigue criterion for multiaxial variable amplitude loadings while only constant amplitude loadings were considered in the above cited works. The second one is an extension to an incremental fatigue life assessment method for proportional and non-proportional multiaxial variable amplitude loadings. No cycle counting technique is needed whatever the variable amplitude loadings type considered (uniaxial or multiaxial). The predictions of the method for constant and variable amplitude multiaxial loadings are compared with experimental results on specimens from literature and from new experiments on a ferrito-perlitic steel. The above mentioned method has been implemented as a post-processor of a finite element software. An application to a railway wheel is finally presented.

Effects of Load Type on the Mechanical Properties of the JLU Series Lunar Soil Simulant

The pressure-sinkage characteristics and the shear-strength characteristics of lunar regolith are the important influence factors to the trafficability of lunar rover. The performance curves and parameters of JLU luanr soil simulant were obtained by pressure-sinkage tests and shear-strength tests in the ground gravity-environmental load (1g) and the lunar gravity-environmental load (1/6g). The results show that, for the pressure-sinkage characteristics, the compression-strength of the JLU-1 is strongest, followed by the JLU-3, and the JLU-2 is the weakest. In different load levels, the deformability index n increases as the bulk density increases. The kc increase as the state becoming more and more compact,The k of JLU-1 is the largest of all, followed by JLU-3 next, JLU-2 has the smallest.The load levels have no significant effect to the tendency of n, kc and k. For the shear-strength characteristics, the shear resistance of JLU-2 is the weakest. JLU-1 has the greatest cohesion c of the three lunar soil simulant, followed by JLU-3, the c of JLU-2 is the smallest.The c of the same lunar soil simulant in natural state is greater than it in soft state. Compared with JLU-1 and JLU-3, JLU-2 has the smallest internal friction angle .The influence of the load levels to the the cohesion c internal friction angel is not obvious. The  mesured in the lunar load is wider than it in the ground load. This study will supply fundamental reference and foundation on the research and optimization of the lunar rover traveling mechanism in the authentic lunar environment.

The effect of loading in mechanical response predictions of bone lengthening

Intramedullary (IM) distractor nails have become a viable alternative in bone-distraction operations. Upon stabilization of the fractured/dissected limb via the nail, the resulting construct accommodates the load bearing function of the otherwise healthy limb. In establishing design performance targets for these devices, in vitro test conditions are widely accepted leaving the in vivo conditions aside. However, in vivo device failures due to distraction forces necessitate novel modeling considerations. It is especially important to simulate the loads in limb distraction, as this brings the bone-implant construct to a totally different regime than the hip-joint contact force (Point-Force Model, PFM). In this work we used a simplified approach to incorporate ligament stretching due to limb distraction via self-equilibrating spring elements in a finite-element setting (spring-force model, SFM). We compared the effect of loading type on load transmission paths through the locking pins, for these two distinct loading modes, namely, SFM and PFM. The two modes illustrate entirely different load transfer regimes around the bone/nail interface region. In order to avoid high contact stresses between the nail and the bone segments, it is advisable to keep the osteotomy away from the mid-range between the pin connections. It was also seen for both loading modes that including an additional pin at a load transfer location does not significantly alter the load carried by a single pin (the additional pin rather acts as a geometric stabilizer).

Effects of Wind Turbine Starting Capability on Energy Yield

The purpose of this study was to investigate the effect of turbine starting capability on overall energy-production capacity. The investigation was performed through the development and validation of matlab/Simulink models of turbines. A novel aspect of this paper is that the effects of load types, namely resistive heating, battery charging, and grid connection were also investigated. It was shown that major contributors to improved starting performance are aerodynamic improvements, reduction of inertia, and simply changing the pitch angle of the blades. The first two contributors can be attained from an exploitation of a “mixed-airfoil” blade.The results indicate that starting ability has a direct effect on the duration that the turbine can operate and consequently its overall energy output. The overall behavior of the wind turbine system depends on the load type, these impose different torque characteristics for the turbine to overcome and lead to different power production characteristics.When a “mixed-airfoil” blade is used the annual energy production of the wind systems increases with the exception of resistive heating loads. Net changes in annual energy production were range of −4% to 40% depending on the load types and sites considered. The significant improvement in energy production strongly suggests that both the starting performance and load types should be considered together in the design process.

Buckling, Vibration, and Flutter Behavior of Laminated Composite Panels with Flaws Subjected to Nonuniform Follower Forces

The present work uses a finite-element approach to study vibration, buckling, and dynamic instability characteristics in damaged cross-ply and angle-ply curved panels. The panels are subjected to nonuniform, centrally, and edge-distributed follower loading. First order shear-deformation theory was used to model the doubly curved panels and was formulated in accordance with Sanders’ first approximation. An anisotropic damage formulation was used to model damage. An analysis was carried out on plate and shallow shells to obtain vibration, buckling, and static instability (i.e., divergence) and dynamic instability (i.e., flutter) behavior. The effects of load type, load width, damage, and damage location on natural frequency, buckling load, divergence load, flutter load and flutter frequency were studied. The effect of curvature to improve the stability characteristics of panels is discussed. The desirable position of damage on a panel is discussed on the basis of different stability behavior. Results indica...