Induced Bending Stresses Research Articles

Experimental and analytical stress analysis of spur gear

Gears are most powerful machine element to transmit the motion between rotating shaft. It acts as a dominating transmission system from many years ago. In this work, a spur gear from stone crusher machine is analysed using theoretical Lewis equation and Finite element analysis method. Here, the bending stress on the spur gear is analysed since these stresses induced play a vital role in gear life. The analysis presented the effect of gear material on induced bending stress. The material C15 steel/CI 30 is replaced by C45 steel/CI 30.The C45 steel material has better mechanical properties than C15 material. The result explains that C45/CI30gives lower value of bending stress as compare to the existing material. Module is important parameter during modelling of spur gear. The parameter is varied and proportionally the bending stress are determined theoretically for both new and existing materials. Finally the results of both gear are compared and concluded with the American gear manufacturer association data. The results shows that the bending stress reduces with increase in module. The future work is to find the bending stress induced on spur gear by varying the module using FEA and varying the shape of meshing structure.

Effect of module variation on a 100watt horizontal axis wind turbine spur gear drive

Spur gears are simple to design and construct to actualize their usage in power transmission as well as for speed reduction or increase. The aim of this research work is to determine the effect of module variation on a 100Watt horizontal axis wind turbine (HAWT) spur gear drive. The solution is to determine and appropriately select gear parameter values based on design considerations and the significance is for enhanced machine reliability and balance with economic production. The method used involved the application of gear design principles, modelling the gears with AutoCAD, module variation and evaluation of induced bending stress at the gears root; gear diameter, tooth thickness and face width become bigger with choosing higher modules for cutting tooth size, with the largest diameter of 168.4mm and 80mm for driver and driven gear respectively and face width of 60mm from using a module of 6mm. Although, the total torque exerted remains constant at 7.9Nm and 3.8Nm for a 100W HAWT. The tangential force in meshed operation of the gears and induced bending stress kept reducing as module increased. The highest tangential force is 282.4N and corresponding induced bending stress is 26.1N/mm2 based on American Gear Manufacturers Association (AGMA) standard and the range of data analyzed, at the lowest module of 2mm. Selecting lower modules means that higher bending stresses will be induced at the gears root, but smaller production cost and more compact system with less space requirement. The lower bending stresses with increasing module will support higher load capacity of the gears due to the increasing face width and enhance the reliability of the HAWT in respect of its performance.
 Keywords: Module, Spur Gear, Power Transmission, Bending Stress, Wind Turbine

Diverse maize hybrids are structurally inefficient at resisting wind induced bending forces that cause stalk lodging

BackgroundStalk lodging (breaking of agricultural plant stalks prior to harvest) results in millions of dollars in lost revenue each year. Despite a growing body of literature on the topic of stalk lodging, the structural efficiency of maize stalks has not been investigated previously. In this study, we investigate the morphology of mature maize stalks to determine if rind tissues, which are the major load bearing component of corn stalks, are efficiently organized to withstand wind induced bending stresses that cause stalk lodging.Results945 fully mature, dried commercial hybrid maize stem specimens (48 hybrids, ~ 2 replicates, ~ 10 samples per plot) were subjected to: (1) three-point-bending tests to measure their bending strength and (2) rind penetration tests to measure the cross-sectional morphology at each internode. The data were analyzed through an engineering optimization algorithm to determine the structural efficiency of the specimens.ConclusionsHybrids with higher average bending strengths were found to allocate rind tissue more efficiently than weaker hybrids. However, even strong hybrids were structurally suboptimal. There remains significant room for improving the structural efficiency of maize stalks. Results also indicated that stalks are morphologically organized to resist wind loading that occurs primarily above the ear. Results are applicable to selective breeding and crop management studies seeking to reduce stalk lodging rates.

Factors governing the dimensional accuracy and fracture modes under compression of regular and shifted orthogonal scaffolds

Direct ink writing allows controlling the structure of tissue engineering scaffolds. The aim of this work was to study the effects of the in silico pattern design on the dimensional accuracy of tricalcium phosphate scaffolds and of the loading direction on the compressive strength and fracture modes. Regular and shifted scaffolds showed anisotropic shrinkage during drying and isotropic shrinkage during sintering. Shifted layers induced bending stresses when compressed longitudinally, resulting in lower compressive strength. The transverse Young’s modulus and compressive strength were higher than the longitudinal ones for both regular and shifted structures. Strand deflections were more pronounced in shifted structures. Finite element modelling suggested that such deflections considerably increased the effective transverse modulus of the shifted scaffolds, thus increasing the related compressive strength. In conclusion, shifted scaffolds performed similarly to regular ones in the transverse direction but were less mechanically reliable under the longitudinal direction.

Bond strength measurement for additively manufactured Inconel 718- GRCop84 copper alloy bimetallic joints

To benefit from the fascinating properties of multi-material structures, the interfacial joint should exhibit good mechanical strength. Evaluating the shear strength of a bimetallic joint via conventional methods is usually complex, and in most cases produces unreliable data due to induced bending stress among others. In this work, a novel single-shear test device was designed and fabricated to measure shear strength of bimetallic joints. The device was first standardized by shearing standard materials, and the results were in good agreement with published data. Subsequently, the shear strength of Inconel 718/copper alloy (GRCop-84) bimetallic joint built via laser engineered net shaping (LENS™) was evaluated. Compression test on the bimetallic joint was carried out as well for more mechanical characterization. Both shear and compressive yield strengths of the bimetallic joints were compared with the base materials in addition to influence of thermal cycling on the joint strength. Inconel 718/GRCop-84 bimetallic-joint shear strength was 220 ± 18 MPa and 231 ± 27 MPa for as-printed sample and after thermal cycling, respectively. Likewise, the bimetallic yield strength after compression test was 232 ± 3 MPa and 337 ± 15 MPa. No cracking through or along the interface was observed even after thermal cycling, which indicates no thermal degradation at the bimetallic interfacial joint. Increase in compressive yield strength after thermal cycling could be attributed to precipitation of Cr2Nb particles in GRCop-84 matrix along with strengthening due to gamma phases in Inconel 718. Scanning electron microscopy (SEM) and backscatter electron imaging were used to examine the interfacial microstructures and failure modes. EDS was used as well to analyze the interface elemental composition. The development of the single-shear test device can provide an added opportunity to effectively evaluate mechanical behavior, reliability and performance of additively manufactured multi-material structures through bond strength analysis.

Technical Guidance Note (Level 2, No. 18): Design of unreinforced masonry retaining walls

This Technical Guidance Note is intended to act as an aide to those seeking to design an unreinforced masonry retaining wall. Following this guidance will prevent cracking and ensure that the wall performs as originally intended. The note will not cover the design of reinforced masonry retaining walls and variants of that form. Such reinforcement typically strengthens the wall itself against induced bending stresses and the wall’s geometry will therefore be somewhat different to that of an unreinforced retaining wall. The note will also not discuss the applied actions that a retaining wall will be subjected to, nor the construction of retaining walls. These subjects have previously been covered in the following Technical Guidance Notes: Level 1, No. 8: Derivation of loading to retaining structures and Level 1, No. 33: Retaining wall construction. It is assumed that the reader is familiar with the content of both these notes.

Potential of energy harvesting in barium titanate based laminates from room temperature to cryogenic/high temperatures: measurements and linking phase field and finite element simulations

This paper studies the energy harvesting characteristics of piezoelectric laminates consisting of barium titanate (BaTiO3) and copper (Cu) from room temperature to cryogenic/high temperatures both experimentally and numerically. First, the output voltages of the piezoelectric BaTiO3/Cu laminates were measured from room temperature to a cryogenic temperature (77 K). The output power was evaluated for various values of load resistance. The results showed that the maximum output power density is approximately 2240 nW cm−3. The output voltages of the BaTiO3/Cu laminates were also measured from room temperature to a higher temperature (333 K). To discuss the output voltages of the BaTiO3/Cu laminates due to temperature changes, phase field and finite element simulations were combined. A phase field model for grain growth was used to generate grain structures. The phase field model was then employed for BaTiO3 polycrystals, coupled with the time-dependent Ginzburg–Landau theory and the oxygen vacancies diffusion, to calculate the temperature-dependent piezoelectric coefficient and permittivity. Using these properties, the output voltages of the BaTiO3/Cu laminates from room temperature to both 77 K and 333 K were analyzed by three dimensional finite element methods, and the results are presented for several grain sizes and oxygen vacancy densities. It was found that electricity in the BaTiO3 ceramic layer is generated not only through the piezoelectric effect caused by a thermally induced bending stress but also by the temperature dependence of the BaTiO3 piezoelectric coefficient and permittivity.

A finite element analysis of an elastic contact between a layered cylindrical hollow roller and flat contact

PurposeThe purpose of this paper is to present a finite element analysis (FEA) which shows the comparison between a layered cylindrical hollow roller bearing and hollow roller bearing.Design/methodology/approachIn this work, FEA is carried out to solve the elastic contact between a layered cylindrical hollow roller and flat contact for different hollowness percentages ranging from 10 to 80 per cent. Graphical solution is developed to determine the optimum hollowness of a cylindrical roller bearing for which induced bending stress should be within endurance limit of the material.FindingsDifferent parameters such as von Mises stress, contact pressure, contact width and deformation are shown here.Originality/valueThe value of this research work is the calculation of contact width and other parameters using FEA for layered cylindrical hollow roller bearing.

Influence of Secondary Fillers on the Behavior of Translaminar Failure in Glass-Epoxy Composites

The results of the experimental analysis carried out on the Glass-Epoxy composites with secondary fillers in particular emphasis on critical stress intensity factor have been reported. The silicon carbide particles and Graphite have been used as the secondary fillers. The experiments were carried out according to ASTM E 1922 standards. The results have revealed that the addition of graphite as the secondary filler has increased the critical stress intensity factor in comparison with the SiCp. The influence of applied tensile stress and the induced bending stress during eccentric loading have been evaluated separately. From the macroscopic analysis it has been identified that the induced bending stress plays a vital role in the failure mechanism of these filled composites.

Flip-Flop-Induced Relaxation of Bending Energy: Implications for Membrane Remodeling

Cellular and organellar membranes are dynamic materials that underlie many aspects of cell biology. Biological membranes have long been thought of as elastic materials with respect to bending deformations. A wealth of theory and experimentation on pure phospholipid membranes provides abundant support for this idea. However, biological membranes are not composed solely of phospholipids—they also incorporate a variety of amphiphilic molecules that undergo rapid transbilayer flip-flop. Here we describe several experimental systems that demonstrate deformation-induced molecular flip-flop. First we use a fluorescence assay to track osmotically controlled membrane deformation in single component fatty acid vesicles, and show that the relaxation of the induced bending stress is mediated by fatty acid flip-flop. We then look at two-component phospholipid/cholesterol composite vesicles. We use NMR to show that the steady-state rate of interleaflet diffusion of cholesterol is fast relative to biological membrane remodeling. We then use a Förster resonance energy transfer assay to detect the transbilayer movement of cholesterol upon deformation. We suggest that our results can be interpreted by modifying the area difference elasticity model to account for the time-dependent relaxation of bending energy. Our findings suggest that rapid interleaflet diffusion of cholesterol may play a role in membrane remodeling in vivo. We suggest that the molecular characteristics of sterols make them evolutionarily preferred mediators of stress relaxation, and that the universal presence of sterols in the membranes of eukaryotes, even at low concentrations, reflects the importance of membrane remodeling in eukaryotic cells.

Modeling and experimental verification of the 300 mm Ar anneal process

We demonstrate a new model for simulating thermal and gravitational induced stress appearing in state of the art 300 mm argon annealing processes. Purpose of this work is to predict the allowable ramp rates in a vertical batch furnace system. The gravitational induced bending stress is modeled by using methods from structural mechanics like common finite element modeling. Calculation of the important specular reflecting radiation component – transporting extra radiation energy to the wafer center between the spacing of two horizontally oriented wafers – was achieved by using finite volume methods known from fluid dynamics. A reduction of the total resolved shear stress could be determined from our model if specular reflection is taken into account and thus allowing higher ramp rates. We furthermore demonstrate new experimental data for the upper yield stress of 300 mm Si-ingots with different boron and nitrogen co-doping levels. Especially at high temperatures, the upper yield stress of high ohmic material drops down significantly thus making it necessary to use planar support geometries to diminish the gravitational induced bending stress.

EXPERIMENTAL AND THEORETICAL INVESTIGATION OF THE LINEAR AND NON-LINEAR DYNAMIC BEHAVIOUR OF A GLARE 3 HYBRID COMPOSITE PANEL

A theoretical model based on Hamilton's principle and spectral analysis is used to study the non-linear free vibration of hybrid composite plates made of Glare 3, a new aircraft structural material. It consists of alternating layers of metal- and fibre-reinforced composites. In previous work, the theoretical model has been used to calculate the first non-linear mode of fully clamped rectangular composite fibre-reinforced plastic (CFRP) laminated plates. This study concerns determination of the linear dynamic properties of the Glare 3 hybrid composite rectangular panel (G3HCRP) such as natural frequencies and mode shapes. The theoretical model is used to calculate the fundamental non-linear mode shape and associated flexural behaviour of the fully clamped G3HCRP. A series of experimental investigations have been conducted using a G3HCRP in order to determine linear dynamic properties. The response due to random excitation was investigated and the experimental measurements are analyzed and discussed. Comparisons are made with finite element predictions and response estimates given by the ESDU method, the latter being a “design guide” approach used by industry. Concerning the non-linear analysis, the results are given for various plate aspect ratios and vibration amplitudes, showing a higher increase of the induced bending stress near the clamps at large deflections. Comparisons between the dynamic behaviour of an isotropic plate and G3HCRP at large vibration amplitudes are presented and good results are obtained.

Sorptive Stress Estimation: An Important Key to the Mechano-Sorptive Effect in Wood

The mechano-sorptive effect (MSE) can be classified as a veryinteresting, but not yet completely explained phenomenon of woodbehaviour. We therefore decided to try to discover its most relevantmechanisms, by conducting two independent series of measurements:accurate measurements of bending deflections on small, clear specimensof spruce wood in changeable climate conditions; and average moisturecontent (MC) in three parts of the cross-section of unloaded dummysamples. The paper emphasises on the sorptive part of MSE. A computersimulation of the wetting experiment is done to determine the space andtime-dependent MC field in the cross-section of the sample. Using aso-called inverse problem identification method, where the equivalenceof the computed and measured responses of the numerical model and realsample is imposed, we identified unknown material properties. Thesolution of the inverse problem enabled us simultaneously to estimatethe moisture diffusion coefficients and to determine the MC field. Twokinds of boundary conditions were used in simulations. To estimate themagnitude of sorption stresses a numerical analysis using Finite ElementMethod (FEM) was done. The sorptive stresses resulting from thenonhomogeneous MC distribution in the sample were obtained. The decisivefactor is the gradient of moisture content and resulting sorptivestresses must be taken into account because their magnitude is of thesame order as the load induced bending stresses. Our experiments and thecalculations following enabled us to conclude that the reason for MSbehaviour could be the simultaneous action of permanent load stressesand the transient triaxial sorptive stress state.

Calculation of forces and bending stresses in centrally struck circular plates

A method is described for solving the Volterra integral equation of the 2nd kind, which models normal impact between a falling hemispherically surfaced impactor and a thin circular plate. The model includes the vibration induced in the plate as the result of forcing by a time-dependent Hertzian pressure distribution. Calculations are performed which model experimental impacts of various polycrystalline graphite discs, in which the impactor velocity was chosen so that each disc just failed after a single impact. The maximum impact induced bending stresses calculated were compared with the experimentally determined three point bend strengths of each graphite material.

Monte Carlo simulation of weldment fatigue strength

Abstract The fatigue strength of constructional steel weldments is predicted using a Monte Carlo simulation which estimates the mean fatigue strength and its expected uncertainty at long lives. The underlying analytical model is at present solely based on fatigue crack initiation and early crack growth and is restricted to long-life applications. Several different kinds of fatigue variables are considered: applied or induced bending stresses, notch severity, notch-root residual stresses, and notch-root mechanical properties. Each of the fatigue variables is treated as a random variable, and its uncertainty is modeled by an appropriate probability distribution function based on laboratory observations. Simulations of constructional steel weldment fatigue strength are compared with laboratory test results on cruciform weldments and similar recent fatigue data reported in the literature. The Monte Carlo simulation also permits one to estimate the contribution of each fatigue variable to the overall uncertainty in fatigue strength and thus determine the economic merits of reducing the uncertainty in any one of the fatigue variables to improve the design fatigue strength.

The elastic analysis of a dent on pressurised pipe

The elastic analysis of a dent on a pressurised cylinder is investigated. The predetermined shapes of the dent are grouped into three categories according to the physical geometry of the dent width, namely the local dent, the short dent, and the long dent. The induced bending stresses associated with the dent are evaluated using Sanders's non-linear shell theory. The geometry of the dent is treated as an initial geometric imperfection and incorporated in the expressions of strain. The non-linear cylindrical shell equations thus obtained are linearised and then solved by a Fourier series expansion technique. Comparison of theoretical results with the finite element approach is made for a pipe of assumed dimensions and pressure. Good agreement of the results is observed. The analytical approach of this paper is suitable for pipe or cylinder with a dent depth of up to five times the wall thickness.

Fatigue strength of structural members with high stress concentration of a fast container ship in rough seas

It has recently been recognized that structural failures of large ocean-going vessels are essentially related to the dynamic stresses induced by bottom and bow-flare slamming in rough seas. Bottom slamming may cause an excessive vertical bending moment in a hull girder which may lead buckling of the upper deck, while bow-flare slamming may cause an excessive torsional moment in the fore-body of high speed ships in oblique waves. Local dents and cracking failures due to slamming are also observed in the fore body of large ships, they might be accelerated by severe corrosion.In high speed ocean-going ships, cracking failures are sometimes observed in middle and aft parts of the hull girders after passing through a rough sea. Since this type of failure is not necessarily exceptional to newly build ships, it may be caused by low cylce fatigue due to repeated whipping stresses induced by bow-flare slams. In the present paper, fatigue strength is investigated for structural members with high stress concentration factors in the neighbourhood of the front end of the superstructure of a container ship, where the applied stress is composed of a wave induced bending stress including non-linear effects, whipping components of stresses, and possibly coupled vibratory stresses of the superstructure.Having calculated the dynamic stress components among regular waves in head seas, the fatigue strength of highly stressed portions are examined by using appropriate S-N curves, in which effects of ship speeds and wave heights are taken into considerations. When a high speed vessel passes through very rough seas, the fatigue strength may be reduced due to the significant elevation of the repeated stress range caused by the whipping components of stresses superposed on the wave induced bending stress.

Experimental determination of mechanical shear stress about an anastomotic junction

The present study is undertaken to determine whether the elastic tube model originally developed by Kuchar and Ostrach ( Biomedical Fluid Mechanics Symposium, pp. 45–69, 1966) accurately provides a first approximation of the biomechanics of the anastomotic junction. The experimental protocol involves the use of canine carotid arteries as the host vessel and several graft materials including autogenous and prosthetic substitutes. The host artery-graft combinations are perfused in vitro in a pulsatile perfusion apparatus which simulates the natural hemodynamic environment. This apparatus provides accurate dynamic measurements of radial wall motion (measured at various longitudinal increments), associated pressures and rates of fluid flow. These data are then applied to the theoretical model for calculation of anastomotic induced bending stresses. The results indicate that the predictions derived from the elastic model consistently overestimate the measured radial change adjacent to the anastomotic junction. As a result shear stresses based on elastic theory deviate from values derived from a numerical curve fit to the experimental data.