Papers by Keyword: Bending Stress

Abstract: The force transferred from the NiTi arch wire to the tooth during orthodontic treatment is strongly dependent on the geometry of the wire and brackets used by the orthodontist. This study investigated the effect of orthodontic bracket geometry on the bending behaviour of superelastic NiTi arch wire. A three-dimensional finite element models of wire bending in three-brackets configuration was developed by employing superelastic user material subroutine and contact interaction. The finite element model was used to anticipate the bending forces and stresses of NiTi wires as they were engaged in various slot width dental brackets. Four different bracket widths were considered, ranging from 1.5 mm to 4.5 mm. Throughout the bending course, the superelastic NiTi wire bent in the 4.5 mm width bracket continuously demonstrated the highest bending force in comparison to the other bracket widths. As the bracket width was raised from 1.5 mm to 4.5 mm, the wire unloading force measured at 2.5 mm deflection increased gradually from 0.40 N to 1.7 N. The bending stress of the wire deformed in the 1.5 mm width bracket was 543 MPa, band it increased to 1051 MPa when the 4.5 mm width bracket was used. The proportion of complete martensite structure at the wire curvature gradually increased as the width of the bracket slot was increased.

Abstract: The 7020-aluminum alloy is a lightweight and high strength material which is widely used in aerospace industries where the damage tolerance, the factor of safety and environmental induced fatigue is very high. The low density and better mechanical properties enable its applications in industries over conventional engineering materials. In the present work, the fatigue crack growth (FCG) behavior of the pre-corroded 7020-aluminum alloy was investigated. The samples were subjected to an aqueous solution of sodium chloride; the micro-hardness was optimized and the significance of corrosion on FCG was studied in the context of bending stress, the number of cycles (N) to failure/fatigue life and microstructure. The solution treated samples at a temperature of 520°C for 3 hours provided the maximum hardness. However, the hardness of samples was optimum for 3 hours of solution heat treatment and minimum for 2 hours of solution heat treatment. It is suggested that the precipitation of the metastable phase affected the hardness. In the initial stage, the fatigue life of pre-corroded samples was significantly lower as compared to as-received samples. However, at the later stage, it became less significant but still, the pre-corroded sample showed lower fatigue life. Both types (pre-corroded and as-received) of samples showed a similar trend as fatigue life decreases with increasing bending stress. The fractured microstructure of the pre-corroded sample showed scratches on the surface which were produced during mechanical rubbing of the specimen pieces during plastic deformation under load. However, the microstructure at the edge of the notch showed "volcano-mouth" features" which indicated the phenomena of galvanic corrosion. The galvanic corrosion envisages due to deposition on the 7020-aluminum alloy and the impurities in the alloy. The elements Fe, Si, C and Mn existed as impurities that induced the galvanic corrosion and an elliptical corrosion pit was observed.

Abstract: This study investigated bending stress distribution on involute spur gear tooth profiles with pressure angle of 20 ̊ but different modules 2.5, 4.0 and 6.0 mm, using a finite-element-based simulation package - AutoFEA JL Analyzer. The drafting of the geometry for the three gear tooth profiles were implemented on the platform of VB-AutoCAD customized environment, before importing to the package. These were separately subjected to analysis for bending stresses for a point at the tooth fillet region with appropriate settings of material property, load and boundary conditions. With the same settings, the bending stresses were computed analytically using American Gear Manufacturers Association (AGMA) established equation. The results of the two approaches were in good agreement, with maximum relative deviation of 4.38%. This informed the confidence in the implementation of the package to investigate the variation of bending stress within the gear tooth profile. The simulation revealed decrease in the bending stresses at the investigated regions with increase in the module of the involute spur-gear. The study confirms that Finite element simulation of stresses on gear tooth can be obtained accurately and quickly with the AutoFEA JL Analyzer.

Abstract: The present work concerns the nonlinear dynamic behaviour of fully clamped skew plates at large vibration amplitudes. A model based on Hamilton’s principle and spectral analysis has been used to study the large amplitude free vibration problem, reducing the non linear problem to solution of a set of non-linear algebraic equations. Two methods of solution have been adopted, the first method uses an improved version of the Newton-Raphson method, and the second leads to explicit analytical expressions for the higher mode contribution coefficients to the first non-linear mode shape of the skew plate examined. The amplitude dependent fundamental mode shape and the associated non-linear frequencies have been obtained by the two methods and a good convergence has been found. It was found that the non-linear frequencies increase with increasing the amplitude of vibration, which corresponds to the hardening type effect, expected in similar cases, due to the membrane forces induced by the large vibration amplitudes. The non-linear mode exhibits a higher bending stress near to the clamps at large deflections, compared with that predicted by linear theory. Numerical details are presented and the comparison made between the results obtained and previous ones available in the literature shows a satisfactory agreement. Tables of numerical results are given, corresponding to the linear and nonlinear cases for various values of the skew angle θ and various values of the vibration amplitude. These results, similar to those previously published for other plates, are expected to be useful to designers in the need of accurate estimates of the non-linear frequencies, the non linear strains and stresses induced by large vibration amplitudes of skew plates.

Abstract: The damage experiments of reinforced concrete (RC) samples under synergistic effects of cyclic freeze-thaw, deicing-salt attack, rebar corrosion and bending stress were investigated using a comprehensive experimental method. Synergistic effects of these factors on the damage evolvement of RC were studied by measuring the change of dynamic modulus of concrete, rebar strain and concrete strain. Experimental results showed similar rule in damage evolvement but different damage rate between the normal-strength concrete (C45, the 28-day compressive strength of 52 MPa) and the high-strength concrete (C70, the 28-day compressive strength of 77 MPa). The dynamic modulus of the reinforced concrete degraded with increasing effecting factors.

Abstract: The aim of this paper is to determine the effect on direct design asymmetric high contact ratio spur gear based on tooth load sharing. A unique Ansys parametric design language code is developed for this study. The load sharing based bending and contact stresses are determined for different drive side contact ratios. In addition to that the location of critical loading point is determined. Because the critical loading point for high contact ratio spur gear not lies on fixed point like normal contact ratio spur gears namely highest point of single tooth contact. In conclusion an increase in drive side contact ratio leads to increase in the load sharing based bending stress and decrease in the contact stress at the critical loading point.

Abstract: This work mainly aims to explore the actual load, fillet and contact stresses induced during a mesh cycle in a spur gear tooth. As the mesh stiffness differs at different contact points along the path of contact, it significantly affects the load sharing between the simultaneously meshed contact pairs hence stresses. Comparative study has been made between existing symmetric spur gear pair used in light motor vehicle gear box and asymmetric spur gear. Finite element multi pair contact model has been used to explore the load sharing behavior and related stresses in this work.

Abstract: The loaded specimens were put in fresh water, 3.5%NaCl solution, 5.0%Na₂SO₄ solution, and simulated sea water with different concentrations respectively, and then the damage process under wetting and drying cycle was investigated. The ultrasonic non-metal testing technology, X-CT scanned image, free chloride and sulfate ions chemical titration were used to investigate the degradation of the marine concrete under the coupling effect of Chemistry and Mechanics. The effect of solutions, wetting and drying cycle and bending stress to the durability of marine concrete were further studied. The results indicate that different salt solution affects marine concrete at different degrees: sulfate salt is more corrosive than chloride salt, simulated seawater is similar to 5.0%Na₂SO₄ solution, while five-time simulated seawater is the most corrosive; wetting and drying cycle remarkably accelerates the penetration of corrosive ions, which results in the concrete damage, compared to the corrosive environment, concrete is damaged violently under the coupling effect of Chemistry-Mechanics and tensile stress has greater influence on the damage.

Abstract: Spur gears are widely used in industry where the power transmission is required at heavy loads with smoother and noiseless operation. The study in this paper shows that the complex design problem of spur gear requires superior software skills for modeling and analysis. The problem been has solved using Pro/E and ANSYS software which provides equivalent results to that of AGMA. In this paper, spur gear was modeled using Pro/Engineer wildfire 4.0 and stress analysis was carried out using ANSYS 11.0. The results obtained from both AGMA and FEM were compared and found to be approximately similar.

Abstract: The double-circular-arc gear bearing capacity is the key problems for realizing the low speed and high torque work demands of small-diameter deep-well turbodrill reducer. Double double-arc gear shaft structure is adopted for improving the gear bearing capacity Based on the 2K-H-NGW type planetary gear transmission. Increase modulus and decrease teeth number properly can improve the double-circular-arc gear capacity on the premise of limited radial size. This article analyze the gear bending stress based on ANSYS and simulation results show that stress mainly concentrated on tooth root and tooth waist area and maximum loading is at tooth waist area. The simulation maximum bending stress is 289N/mm2 and the theoretical bending stress is 277.50N/mm2.The two results are basically identical. It is consistent with the actual work situation.