Stress-strain Simulation Research Articles

The spindle of remaining lifetime predicted in the failure machine tool

ABSTRACTThis paper mainly carries out researches on the small part samples of the spindles. Through the Weibull distribution and least squares,the mathematical analysis has made on the lifetime of the spindle parts of the retired machine tool. Through using MATLAB simulation, the theoretical life of the spindle parts is obtained. Then, the motion analysis was made on the old and retired machine tool spindle. At the same time,the finite element model of the spindle is set up with the support of the software ABAQUS. Besides, the static analysis and meshing are conducted to obtain the corresponding stress strain simulation results. Also,the analysis data are imported into the fatigue analysis software NCODE to make the life prediction.Through loading on the old machine tool, the corresponding cloud lifetime chart and damage cloud chart are obtained. The readings of the cloud chart are calculated to obtain the life expectancy which the spindle lifetime can reach and the spindle can be re-manufactured, conforming to the theory analysis results of the Weibull distribution as well as the method of least square.It proves that the method is feasible.

Вычислительная модель алюмоматричного композита В95/SiC и ее применение для расчета напряженно-деформированного состояния при растяжении, сжатии и сдвиге

Вычислительная модель алюмоматричного композита В95/SiC и ее применение для расчета напряженно-деформированного состояния при растяжении, сжатии и сдвиге

An efficiently dynamic stress strain simulation method on digital rock

The dynamic stress strain simulation is one of the several digital rock physics methods that calculate elastic property of digital rocks. Simulations for calculating P- and S-wave property of one digital rock includes one compressional simulation and three shear simulations. Moreover, the simulation frequency must be low enough to meet the long wavelength assumption. Hence, heavy computational burden is unavoidable. To improve the computational efficiency, in addition to parallel computation, one possible way is to optimize the boundary condition applied on the digital rocks. The idea is to integrate the four kinds of boundary condition which correspond to the four separated simulations in the existed method into one boundary condition, accordingly the number of simulation reduces to one. The computational efficiency of the new simulation method improves approximately four times, and the numerical accuracy is proved to be unaltered.

Integrated Approach for Steam Turbine Thermostructural Analysis and Lifetime Prediction at Transient Operations

In order to achieve the highest power plant efficiency, original equipment manufacturers continuously increase turbine working parameters (steam temperatures and pressures), improve components design, and modify start-up cycles to reduce time while providing more frequent start-up events. All these actions result in much higher levels of thermostresses, a lifetime consumption of primary components and an increased demand for accurate thermostructural and low cycle fatigue (LCF) simulations. In this study, some aspects of methodological improvement are analyzed and proposed in the frame of an integrated approach for steam turbine components thermostructural analysis, reliability, and lifetime prediction. The full scope of the engineering tasks includes aero/thermodynamic flow path and secondary flows analysis to determine thermal boundary conditions (BCs), detailed thermal/structural two-dimensional and three-dimensional (3D) finite element (FE) models preparation, components thermal and stress–strain simulation, rotor–casing differential expansion and clearances analysis, and finally, turbine unit lifetime estimation. Special attention is paid to some of the key factors influencing the accuracy of thermal stresses prediction, specifically, the effect of “steam condensation” on thermal BC, the level of detailing for thermal zones definition, thermal contacts, and mesh quality in mechanical models. These aspects have been studied and validated against test data, obtained via a 30 MW steam turbine for combined cycle application based on actual start-up data measured from the power plant. The casing temperatures and rotor–stator differential expansion, measured during the commissioning phase of the turbine, were used for methodology validation. Finally, the evaluation of the steam turbine HPIP rotor lifetime by means of a LCF approach is performed.

Modeling effective elastic properties of digital rocks using a new dynamic stress-strain simulation method

We have developed a dynamic stress-strain simulation methodology to compute effective elasticity on digital rocks in a wide range of frequency based on the rotated staggered grid finite-difference method. The primary advantage of this simulator lies in characterizing the anisotropic behavior of complex porous rocks by setting specified boundary conditions along specified directions: The edges perpendicular to the propagating wave are applied with a strain boundary condition, and the edges parallel to the propagating wave are applied with a periodic boundary condition. The accuracy of the simulator is validated by comparing the simulating results in microinhomogeneous porous media containing randomly distributed inclusions and aligned oriented cracks, with that obtained by effective medium theories of self-consistent approximation in isotropic and anisotropic domains. This dynamic simulator can successfully capture anisotropic magnitude of rocks containing needle-like inclusions with different degrees of alignment. For real digital rock saturated with viscoelastic fluids, it is able to predict the dependence of velocities and attenuating factors on the frequency. We found that the magnitude of dispersion increases with the increase of pore fluid viscosity. Therefore, this method offers a robust and effective tool to compute effective elastic properties and anisotropy for real complex porous rocks.

Novel Long Stroke Reciprocating Compressor for Energy Efficient Jaggery Making

Novel Long Stroke Reciprocating Compressor is analysed for jaggery making while avoiding burning of bagasse for concentrating juice. Heat of evaporated water vapour along with small compressor work is recycled to enable boiling of juice. Condensate formed during heating of juice is pure water, as oil-less compressor is used. Superheat of compressor is suppressed by flow of superheated vapours through condensate. It limits heating surface temperature and avoids caramelization of sugar. Thereby improves quality of jaggery and eliminates need to use chemicals for colour improvement. Stroke to bore ratio is 0.6 to 1.2 in conventional reciprocating drives. Long stroke in reciprocating compressors enhances heat dissipation to surrounding by providing large surface area and increases isentropic efficiency by reducing compressor outlet temperature. Longer stroke increases inlet and exit valve operation timings, which reduces inertial effects substantially. Thereby allowing use of sturdier valves. This enables handling liquid along with vapour in compressors. Thereby supressing the superheat and reducing compressor power input. Longer stroke increases stroke to clearance ratios which increases volumetric efficiency and ability of compressor to compress through higher pressure ratios efficiently. Stress-strain simulation is performed in SolidWorks for gear drive. Long Stroke Reciprocating Compressor is developed at Heat Pump Laboratory, stroke/bore 292 mm/32 mm. It is operated and tested successfully at different speeds for operational stability of components. Theoretical volumetric efficiency is 93.9% at pressure ratio 2.0. Specific energy consumption is 108.3 kWhe/m3 separated water, considering free run power.

Modeling and simulation of the debonding process of composite solid propellants

In order to study the damage evolution law of composite solid propellants, the molecular dynamics particle filled algorithm was used to establish the mesoscopic structure model of HTPB(Hydroxyl-terminated polybutadiene) propellants. The cohesive element method was employed for the adhesion interface between AP(Ammonium perchlorate) particle and HTPB matrix and the bilinear cohesive zone model was used to describe the mechanical response of the interface elements. The inversion analysis method based on Hooke-Jeeves optimization algorithm was employed to identify the parameters of cohesive zone model(CZM) of the particle/binder interface. Then, the optimized parameters were applied to the commercial finite element software ABAQUS to simulate the damage evolution process for AP particle and HTPB matrix, including the initiation, development, gathering and macroscopic crack. Finally, the stress-strain simulation curve was compared with the experiment curves. The result shows that the bilinear cohesive zone model can accurately describe the debonding and fracture process between the AP particles and HTPB matrix under the uniaxial tension loading.

Development and implementation of bottom ash crushing system in Submerged Scrapper Conveyor (SSC) for Coal-fired Power Plant

The existence of Submerged Scrapper Conveyor (SSC) in coal-fired power plant is to handle the by-product of bottom ash. However, soot-blowing will be performed sometimes, in order to remove slag formed at the boiler furnace wall. Thence, this lead to a sudden loading of large amount of slags and bottom ash at SSC after soot-blowing, causing SSC conveying system to jam and conveying chain breakage. In this paper, a new SSC design with additional crushing system is proposed. By implementing the new design proposed, it is expected to improve the overall current performances, and to reduce the trip issue of SSC in coal-fired power plant. The new 3D model of SSC is designed, and stress-strain simulation of the model is analysed by using software of PTC Creo Parametric. Final cost and safety factor analysis of model is made to prove its validation.

Material Properties from Air Puff Corneal Deformation by Numerical Simulations on Model Corneas

ObjectiveTo validate a new method for reconstructing corneal biomechanical properties from air puff corneal deformation images using hydrogel polymer model corneas and porcine corneas.MethodsAir puff deformation imaging was performed on model eyes with artificial corneas made out of three different hydrogel materials with three different thicknesses and on porcine eyes, at constant intraocular pressure of 15 mmHg. The cornea air puff deformation was modeled using finite elements, and hyperelastic material parameters were determined through inverse modeling, minimizing the difference between the simulated and the measured central deformation amplitude and central-peripheral deformation ratio parameters. Uniaxial tensile tests were performed on the model cornea materials as well as on corneal strips, and the results were compared to stress-strain simulations assuming the reconstructed material parameters.ResultsThe measured and simulated spatial and temporal profiles of the air puff deformation tests were in good agreement (< 7% average discrepancy). The simulated stress-strain curves of the studied hydrogel corneal materials fitted well the experimental stress-strain curves from uniaxial extensiometry, particularly in the 0–0.4 range. Equivalent Young´s moduli of the reconstructed material properties from air-puff were 0.31, 0.58 and 0.48 MPa for the three polymer materials respectively which differed < 1% from those obtained from extensiometry. The simulations of the same material but different thickness resulted in similar reconstructed material properties. The air-puff reconstructed average equivalent Young´s modulus of the porcine corneas was 1.3 MPa, within 18% of that obtained from extensiometry.ConclusionsAir puff corneal deformation imaging with inverse finite element modeling can retrieve material properties of model hydrogel polymer corneas and real corneas, which are in good correspondence with those obtained from uniaxial extensiometry, suggesting that this is a promising technique to retrieve quantitative corneal biomechanical properties.

Flexural Capability of Patterned Transparent Conductive Substrate by Performing Electrical Measurements and Stress Simulations.

The suitability of stacked thin films for next-generation display technology was analyzed based on their properties and geometrical designs to evaluate the mechanical reliability of transparent conducting thin films utilized in flexural displays. In general, the high bending stress induced by various operation conditions is a major concern regarding the mechanical reliability of indium–tin–oxide (ITO) films deposited on polyethylene terephthalate (PET) substrates; mechanical reliability is commonly used to estimate the flexibility of displays. However, the pattern effect is rarely investigated to estimate the mechanical reliability of ITO/PET films. Thus, this study examined the flexible content of patterned ITO/PET films with two different line widths by conducting bending tests and sheet resistance measurements. Moreover, a stress–strain simulation enabled by finite element analysis was performed on the patterned ITO/PET to explore the stress impact of stacked film structures under various levels of flexural load. Results show that the design of the ITO/PET film can be applied in developing mechanically reliable flexible electronics.

Investigations on the influence of substrate temperature in developing enhanced response ZnO nano generators on flexible polyimide using spray pyrolysis technique

Zinc oxide was deposited on flexible substrate over a large area to demonstrate nano charge generation capability using spray pyrolysis technique for the first time. The influence of growth substrate temperature towards piezoelectric property has been investigated. It is observed that the samples deposited at 300°C showed best output peak voltage of 1.91V. A direct relation between piezoelectric output and intrinsic defects from photoluminescence spectra is observed. A load v/s voltage output along with capacitance-voltage analysis is performed to investigate the effect of loading on the polarization of ZnO. The enhanced piezoelectric response of ZnO compared to previous reports is due to very low intrinsic defects, smooth morphology and pre-strained behavior of substrate. The curved profile nano generator harvests electricity by d31 mode. ANSYS stress-strain simulation of arched shape film is performed, in which large stress due to large strain even at very low load is observed.

3D connectivity of eutectic Si as a key property defining strength of Al–Si alloys

The relationship between microstructure and mechanical behavior of the eutectic phase in hypoeutectic Al–Si alloys is analyzed empirically using two experimental and thirteen synthetic microstructures. For all microstructures, a morphological analysis is combined with mechanical stress–strain simulations performed via finite element method (FEM). The synthetic microstructures are generated by a stochastic microstructure model that gives a realistic description of the eutectic Si in Al–Si alloys. The stochastic model was developed on the basis of a 3D image of a real Sr-modified Al–Si alloy and is used to generate a large variety of virtual 3D structures of eutectic Si that differ from each other by the number of Si particles, their degree of branching, and connectivity. In the simulation study, it is shown that highly connected and branched morphologies of Si are beneficial to the strength of the material. Besides, when the connectivity of Si is low, i.e. when an Al matrix is reinforced by discrete (disconnected) particles of Si, the strength of the material increases with the number of those particles. The Euler number is shown to be highly effective in characterizing the connectivity and is closely related to the strength of the material.

Stress-Strain Analysis and Simulation for Estimation of Cutting Forces on the Skin

In order to control correctly robot-assisted surgeries and to avoid compromising the patient's vital organs, the forces exerted over the tissues of the human body must be calculated, monitored and adjusted. In a skin incision, the magnitude of the force depends on the incision’s depth and on the biomechanical properties of skin itself. In this paper, a finite element analysis of the incision and puncture when using a scalpel is presented; its purpose is to calculate the range of forces that can safely be applied with it during a surgery. First, a tension evaluation of puncturing with a scalpel until it completely cuts across the skin was carried out. Then, the stress of performing a 10 mm incision with a surgical scalpel was assessed. The results of these analyses demonstrate that the range of forces that could be applied depends on skin's biomechanical properties and on the condition of the skin sample. In order to perform the puncture, the force should be among the ranges of 0.840 to 8.598 N, while for cutting the skin, the force range is from 0.93 to 10.32 N. This work makes an important contribution for the field of “Computational Analysis of Materials” and “Modeling of Skin Characteristics”.

Closed Chain Simulations of a Cast Aluminium Component - Incorporating Casting Process Simulation and Local Material Characterization into Stress-strain Simulations

The coupling between simulations of solidification, microstructure and local mechanical behaviour and simulation of stress-strain behaviour is studied by applying a recently developed simulation strategy to a high pressure die cast aluminium component. In the simulation strategy, named a closed chain of simulations for cast components, the mechanical behaviour throughout the component is determined locally by a casting process simulation. The entire casting process, including mould filling and solidification, is simulated to predict the formation of microstructure and residual stresses throughout the component, and material characterization models are applied to relate microstructural features to local elastic and plastic mechanical material behaviour. The local material behaviour is incorporated into a finite element method (FEM) stress-strain simulation of a realistic load case of the component in service.In the current contribution the influences of local variations in mechanical behaviour and residual stresses on the component behaviour are investigated. The simulation results for local microstructure and mechanical behaviour are compared to experimental results, and the predicted local mechanical behaviour is incorporated on an element level into the FEM simulation. The numerical effect of the variations in mechanical behaviour is quantified by comparing the results achieved using local behaviour and homogeneous behaviour. The influence of residual stresses predicted by the casting process simulation on the component behaviour is also studied.The casting process simulation is found to accurately predict the local variations in microstructure throughout the component, and the local variations in mechanical behaviour are well described. The numerical results show that casting process simulation and modelling of microstructure formation, material behaviour and residual stresses are important contributions to correctly predict the behaviour of a cast aluminium component in service. This motivates the use of the proposed simulation strategy, and show the importance of incorporating materials science and casting process simulations into structural analyses of cast components. It is discussed that integration of these areas, e.g. using the closed chain of simulations, is important in order to increase the accuracy of FEM simulations and the product development efficiency in the future.

Computational analysis on plug-in hybrid electric motorcycle chassis

Plug-in hybrid electric motorcycle (PHEM) is an alternative to promote sustainability lower emissions. However, the PHEM overall system packaging is constrained by limited space in a motorcycle chassis. In this paper, a chassis applying the concept of a Chopper is analysed to apply in PHEM. The chassis 3dimensional (3D) modelling is built with CAD software. The PHEM power-train components and drive-train mechanisms are intergraded into the 3D modelling to ensure the chassis provides sufficient space. Besides that, a human dummy model is built into the 3D modelling to ensure the rider?s ergonomics and comfort. The chassis 3D model then undergoes stress-strain simulation. The simulation predicts the stress distribution, displacement and factor of safety (FOS). The data are used to identify the critical point, thus suggesting the chassis design is applicable or need to redesign/ modify to meet the require strength. Critical points mean highest stress which might cause the chassis to fail. This point occurs at the joints at triple tree and bracket rear absorber for a motorcycle chassis. As a conclusion, computational analysis predicts the stress distribution and guideline to develop a safe prototype chassis.

Research on the Finite Element Method of Reinforced Concrete Member in Bending Oblique Section Bearing Capacity

With the development of computer science and technology, computer hardware and software conditions have been improved greatly, which can make the finite element analysis of complex structure possible. Reinforced concrete is one of the most commonly used components in building structure, the study of reinforced concrete mechanics is mainly compared through the experiment, however finite element analysis of oblique section stress is not much, based on the theory of combining elastic-plastic mechanics, using ANSYS structure analysis software carries out the analysis of numerical simulation for the oblique section stress of reinforced concrete. Through the stress-strain numerical simulation curve, this paper can get the maximum load of oblique section without corrosion reinforced concrete frame that is0.03N/mm2, finally this paper will choose three different corrosion degree of the reinforced concrete members are to carry on the analysis of numerical simulation, and compared with experimental results, the results prove the reliability of numerical simulation, to provide a reliable basis for the mechanical study of reinforced concrete inclined section.

Damage mechanisms evolution of ductile cast irons under thermomechanical loadings

In this work, tensile and compression tests were carried out on ferritic cast iron samples in order to understand the influence of the stress state for temperatures until 800°C. Results show an asymmetric behaviour of ductile cast iron (DCI). The damage created during hardening was evaluated using local microstructural quantifications. Several damage differences are highlighted at room temperature. Therefore, when temperature increases, differences between damage mechanisms under tension and under compression are amplified. A relation between nodules deformation experimentally determined at different stress-strain stages and numerical simulation is proposed. The numerical predictions are in good agreement with the distribution of the aspect ratio (the ratio between major and minor axis of nodules) obtained experimentally. It was noted that nodules deformation can represent the total material strain at room temperature. In addition, it was shown that graphite nodules in cast iron cannot always be assimilated to voids during the strain.

Constitutive Model Based on the Multiplicative Decomposition of Deformation Gradient in Arbitrary Orthogonal Coordinate System

According to general crystallographic slip constitutive laws, the stress-strain analysis of nickel based single crystal superalloy (NBSCS) in arbitrary coordinate system were based on material coordinate system (SRCS method). Ignoring the other symmetry of NBSCS, only the symmetry of plane families {001} were considered, which bring considerable errors into the stress-strain analysis. In this paper, the variation regulation of micro-physical systematical property about this alloy in arbitrary directions was investigated. From the arrangement of atoms in different crystal planes, NBSCS has four symmetry plane families, {001}, {110}, {112} and {111}. According to these symmetry planes, three reference orthogonal coordinate systems were established. Based on these coordinate systems and the coordinate rotation method (TRCS method), the stress-strain relationship of crystallographic slip constitutive model in arbitrary coordinate system was established. Meanwhile elastic constants in arbitrary directions were obtained. Comparing the results of the tensile stress-strain curves obtained from TRCS method with that from SRCS method, it is found that by the TRCS method the elastoplastic stress-strain simulation error of the NBSCS could be effectively reduced.

Casting and stress-strain simulations of a cast ductile iron component using microstructure based mechanical behavior

The industrial demand for increased component performance with concurrent reductions in component weight, development times and verifications using physical prototypes drives the need to use the full potential of casting and Finite Element Method (FEM) simulations to correctly predict the mechanical behavior of cast components in service. The mechanical behavior of the component is determined by the casting process, and factors as component geometry and casting process parameters are known to affect solidification and microstructure formation throughout the component and cause local variations in mechanical behavior as well as residual stresses. Though residual stresses are known to be an important factor in the mechanical behavior of the component, the importance of local mechanical behavior is not well established and the material is typically considered homogeneous throughout the component. This paper deals with the influence of solidification and solid state transformation on microstructure formation and the effect of local microstructure variations on the mechanical behavior of the cast component in service. The current work aims to investigate the coupling between simulation of solidification, microstructure and local variations in mechanical behavior and stress-strain simulation. This is done by performing several simulations of a ductile iron component using a recently developed simulation strategy, a closed chain of simulations for cast components, able to predict and describe the local variations in not only elastic but also plastic behavior throughout the component by using microstructural parameters determined by simulations of microstructural evolution in the component during the casting process. In addition the residual stresses are considered. The results show that the FEM simulation results are significantly affected by including microstructure based mechanical behavior. When the applied load is low and the component is subjected to stress levels well below the yield strength of the material, the residual stresses highly affect the simulation results while the effect of local material behavior is low. As the applied load increases and the stress level in the component approaches and passes the yield strength, the effect of residual stresses diminishes while the effect of local mechanical behavior increases. In particular the predicted strain level is heavily affected by the use of local mechanical behavior. It is proposed that it is important to include both local mechanical behavior and residual stresses in stress-strain simulations to predict the true mechanical behavior of the component.

Development of a ReaxFF Reactive Force Field for Ettringite and Study of its Mechanical Failure Modes from Reactive Dynamics Simulations

Ettringite is a hexacalcium aluminate trisulfate hydrate mineral that forms during Portland cement hydration. Its presence plays an important role in controlling the setting rate of the highly reactive aluminate phases in cement paste and has also been associated with severe cracking in cured hardened cement. To understand how it forms and how its properties influence those of hardened cement and concrete, we have developed a first-principles-based ReaxFF reactive force field for Ca/Al/H/O/S. Here, we report on the development of this ReaxFF force field and on its validation and application using reactive molecular dynamics (RMD) simulations to characterize and understand the elastic, plastic, and failure response of ettringite at the atomic scale. The ReaxFF force field was validated by comparing the lattice parameters, pairwise distribution functions, and elastic constants of an ettringite crystal model obtained from RMD simulations with those from experiments. The predicted results are in close agreement with published experimental data. To characterize the atomistic failure modes of ettringite, we performed stress-strain simulations to find that Ca-O bonds are responsible for failure of the calcium sulfate and tricalcium aluminate (C3A) column in ettringite during uniaxial compression and tension and that hydrogen bond re-formation during compression induces an increase in plastic strain beyond the material's stress-strain proportionality limit. These results provide essential insight into understanding the mechanistic role of this mineral in cement and concrete degradation, and the ReaxFF potential developed in this work serves as a fundamental tool to further study the kinetics of hydration in cement and concrete.