Subproblem Approximation Method Research Articles

Optimization of ER8 and 42CrMo4 Steel Rail Wheel for Road–Rail Vehicles

Railway track maintenance services aim to shorten the time of removing failures on the railways. One of the most important element that shorten the repair time is the quick access to the failure site with an appropriate equipment. The use of road-rail vehicles is becoming increasingly important in this field. In this type of constructions, it is possible to use proven road vehicles such as self-propelled machines or trucks running on wheels with tires. Equipping these vehicles with a parallel rail drive system allows for quick access to the failure site using both roads and railways. Steel rail wheels of road-rail vehicles are designed for specific applications. Since the total weight of vehicle is a crucial parameter for roadworthiness, the effort is made to minimize the mass of rail wheels. The wheel under consideration is mounted directly on the hydraulic motor. This method of assembly is structurally convenient, as no shafts or intermediate couplings are required. On the other hand, it results in strict requirements for the wheel geometry and can cause significant stress concentration. Therefore, the problem of wheel geometry optimization is discussed. Consideration is given to the use of ER8 steel for railway application and 42CrMo4 high-strength steel. Finite element analysis within Ansys software and various optimization tools and methods, such as random tool, subproblem approximation method and first-order method are applied. The obtained results allow to minimize the rail wheel mass with respect to the used material. Moreover, computational demands and methods leading to the best results are compared.

Determination of the Optimum Material Gradient for a Functionally Graded Endodontic Prefabricated Post Using a Sub-Problem Approximation Method

The treatment process of a tooth every short period has many disadvantages to the dental patient, for instance, wasting time, losing money, and tiring the dental patient. Therefore, selecting the suitable technique for treating the tooth, with increasing the lifetime of the tooth has become more necessary in the daily life of the dental scientists. In the present days, an Endodontic Prefabricated Post (EPP) plays an important vital role in the treatment process of the tooth. Comparisons among von Mises stress, shear stress, and deformation of homogenous cases were investigated in the present work through the finite element analysis (FEA). The effect of EPP material on von Mises stress, shear stress, and deformation components occurred on the dentin in cases of Functionally Graded Endodontic Prefabricated Post (FGEPP), and EPP-homogenous was carried out. After that, the sub-problem approximation method was adopted for determining the optimum material gradient for a FGEPP.

Beam-end stiffness identification for a structural health monitoring-oriented finite-element transmission tower model using effective optimization techniques

As an important issue for establishing structural health monitoring–oriented finite element models for large steel pylons, identification of beam-end stiffness draws the attention of the engineering circle. Since the methods adopted by other researchers for parameter identification are impracticable, a beam-end stiffness identification method which combines in situ measurements for the structure’s global dynamic properties with effective multi-variable optimization methods is utilized to improve the accuracy of established finite element models. A 131-m-high large transmission tower is employed as a case study to validate the method. In situ measurements for the tower’s global dynamic characteristics are performed, and identifications of Young’s modulus for 20 semi-rigid connections distributed along each of the tower’s four main chords are undertaken utilizing three multi-variable optimization methods, that is, the first-order method, the subproblem approximation method, and the response surface method. Static numerical simulations on two detailed connection models prove that multiple uncertain parameters can be correctly and simultaneously identified when appropriate optimization techniques are chosen. Finally, the influence of beam-end stiffness identification on the structural health monitoring–oriented structural safety assessment is revealed by calculating the wind-induced dynamic structural responses for the single tower and the transmission tower-line system, which indicates that identification of the correct beam-end stiffness and updating the structural health monitoring–oriented finite element model are indispensable procedures for reliable structural health monitoring.

Determination of the Optimum Material for an Endodontic Prefabricated Post Using a Sub-Problem Approximation Method

The success in the chewing process depends on the performance of the tooth used. Actually, taking care of the tooth and improving its performance can change our life. Therefore, the treatment process of the teeth has become more necessary in the life of a dental patient. Nowadays, a post plays an important vital role in this process. In the present work, analysis of the effect of the post material on the performances of the components of endodontically treated teeth (ETT) was carried out through the finite element analysis (FEA). The effects of post material on the von Mises stress component (Svon), shear stress, and displacement component (Usum) occurred on the all components of ETT were investigated. After that, the determination of the optimum material for an endodontic prefabricated post (EPP) was investigated through the sub-problem approximation method.

Dimensional Optimization of Helical Gear Pair Through Finite Element Analysis Using Subproblem Approximation Method

Traditional helical gear stress analysis techniques such as AGMA and ISO standards provides very often over-dimensioned gear pairs with bulky design. Therefore, it is required to optimize the gear pair design using latest techniques like finite element analysis. Stress analysis technique chosen to investigate the feasibility of dimensional optimization of a gear was Finite Element Analysis platform ANSYS 12.1. ISO 6336 standards and Hertz contact theory neglect friction between contact teeth. This work reflects coefficient of friction between contact teeth using FEA predicts more accurate results for contact stress. In this work, case hardened steel helical gear is optimised for optimum tooth root stress level subsequently to reduce the face width of gears with other geometrical parameters unaffected. Efforts has been carried out to verify contact stress value using Lagrange multiplier algorithm of optimised helical gear pair. Subproblem approximation method was implemented for searching of optimal solution of design variable. Optimized gear pair was manufactured and experimentally investigated for actual stresses and strains, as per loading condition mention in the rules of TED. Percentage saving in the material for optimised gear pair also been included in this work.

Damping characteristic analysis and application of a tubular stand-off-layer sandwiched structure

In the application, there are some situations where passive constrained layer damping structure (PCLDS) is not very ideal. This issue can be solved by using a kind of stand-off-layer damping treatment to some extent. A stand-off-layer is added between the base layer and the viscoelastic layer of PCLDS. This study applies the passive stand-off-layer damping treatment into a tubular structure. A motion equation of the tubular stand-off-layer sandwiched structure (TSSS) is established according to the first-order shear deformation theory. Based on the motion equation, the natural frequency and loss factor of the TSSS are obtained, and then the behaviors of stand-off- layer parameters are analyzed; some important parameters of TSSS are optimized using sub-problem approximation method. At last, the TSSS and the optimized results are used into a sprocket of the crawler construction vehicle. In order to perform the stand-off-layer damping treatment, the sprocket is changed from the existing monolithic structure into a separating-type one. The contrast tests are done between two kinds of sprocket, and the results show that this new separating-type sprocket with TSSS is effective for vibration-reducing. The research results of the study are useful to the further studies about various damping structure and the further application in more practical engineering structure.

Multi-variable H-β optimization approach for the lateral support design of a wide field survey telescope.

We have proposed a multi-variable H-β optimization approach (MHOA). Compared with the conventional push-pull-shear lateral support optimization (CPLSO), which has only one design variable, β, MHOA adds another design variable, H, which is the support position height. By contrast, the support position height of CPLSO is usually fixed at mid-thickness, Hm (or at H0, the height of the center of gravity for the mirror), on the outer rim of the mirror blank. In addition, hybrid optimization with the sub-problem approximation method and first order method is also applied in MHOA. To verify the feasibility and the advancement, the optimization of the lateral support of the 2.5 m-wide field survey telescope (WFST) is performed with MHOA in this paper. Three designs with different supporting points, including 18 supporting points, 24 supporting points, and 36 supporting points, are obtained, and the residual half path length errors are 23.71 nm, 19.60 nm, and 17.79 nm, respectively. Furthermore, other things being equal, CPLSO with H=H0 as well as CPLSO with H=Hm are used separately to validate the H-β design idea quantitatively. The results have suggested that limiting the value of the residual half path length error, obtained by MHOA, has improved almost 20 nm compared to that of CPLSO with H=H0, and almost 10 nm compared with that of CPLSO with H=Hm.

Determining the Optimum Material for an Endodontic Prefabricated Parallel Post Using a Sub-Problem Approximation Method

One of the most widely used techniques in present-day in order to save teeth is endodontic treatment (ET). Nowadays, a post or a dowel is widely used in the tooth treatment process. The aims of the current investigation are to: (1) evaluate the stress distribution surrounding the endodontic prefabricated parallel post (EPPP), gutta-percha, and dentin with six types of post materials, and (2) determine the optimum material of an EPPP. Six post materials: (1) carbon fibre post (CFP), (2) gold (G), (3) gold alloy (GA), (4) titanium (T), (5) titanium alloy (TA), and (6) stainless steel (SS) were selected in the present work. In order to evaluate the stress distribution surrounding the EPPP, gutta-percha, and dentin with different post materials, the finite element analysis (FEA) is adopted. After that, the sub-problem approximation method was used in order to investigate the optimum material of an EPPP. The results obtained indicate that the optimum elastic characteristics for the EPPP, elastic modulus (E), and Poisson’s ratio (υ) equal to 185 GPa and 0.245, respectively.

The Two-Level Method and its Application in Dynamic Optimization of a Truss

A two-level method is presented to improve dynamic characteristic of a truss and let it out of the resonance region. The does is as follow: selected the desired design variable by sensitivity analysis, used the optimum solution of the subproblem approximation method as initial solution of the simplex method, and improved the simplex method by introducing golden section method. While ensuring requirement of strength, stiffness and stability, the two-level method makes the truss less weight and avoids the resonance region. The improved simplex method searches the better point further by introducing golden section method on the path of the extending principle and the shrinking principle and reduces searching times.

복합재 압력용기의 스커트 치수 최적화 설계 연구

Key Words: Composite Pressure Vessel(복합재압력용기), Optimum Design(최적설계), Size Optimization(치수최적화), Sub-problem Approximation Method(부분문제근사법), Skirt Structure(스커트구조물)초록: 본연구의목적은최적화해석기법을이용하여복합재압력용기의스커트치수를도출하는것이다. 복합재압력용기스커트최적화해석은부분문제근사법을사용하였으며, APDL(ANSYS ParametricDesign Language)을이용하여해석의모든과정을일괄처리하였다. 설계변수로는압력용기스커트부위의두께와길이를선정하였으며, 내압에의해발생하는변위와무게를각각목적함수로하여최적화해석을통해최적의스커트치수를도출하였다. 그결과복합재압력용기의스커트무게를최대4.38% 절감할수있었다.Abstract: This study aims to find the optimal skirt dimensions for a composite pressure vessel with aseparated dome part. The size optimization for the skirt structure of the composite pressure vessel wasconducted using a sub-problem approximation method and batch processing codes programmed using ANSYSParametric Design Language (APDL). The thickness and length of the skirt part were selected as designvariables for the optimum analysis. The objective function and constraints were chosen as the weight and thedisplacement of the skirt part, respectively. The numerical results showed that the weight of the skirt of acomposite pressure vessel with a separated dome part could be reduced by a maximum of 4.38% throughsize optimization analysis of the skirt structure.

3D nonlinear finite element model for the volume optimization of a RC beam externally reinforced with a HFRP plate

In the present study, a numerical model is developed for the optimization of the external reinforcement of reinforced concrete beams by Hybrid Fiber Reinforced Polymer (HFRP) Plate. The model uses a finite element method adopted by ANSYS. To achieve this aim, a 3D nonlinear finite-element (FE) model is developed to study the behavior of concrete beams and plates with and without external reinforcement by FRP. Half of the full beam was used for modeling, taking advantage of the symmetry of the beam and loadings. Calibration and validation of the obtained results are compared to those given experimentally for different conditions from research. Comparisons made for load–deflection, load–strain and moment–curvature curves at mid-span show a good agreement between numerical and experimental results. The static nonlinear analysis is done to find the out ultimate capacity, formation of first crack, initiation of diagonal crack and its distance from the edges of HFRP plate. Parametric study is made to evaluate both effects of height and width of the HFRP plate on the retrofitted beam. Next, our model is used to optimize the volume of the HFRP plate which is bonded externally to the concrete beam. To obtain an optimal volume for our HFRP plate, two optimization methods, called the sub-problem approximation method and the first-order method, are proposed. For both methods, the program performs a series of analysis–evaluation–modification cycles: the design of the HFRP plate volume considered as the objective function is analyzed, the results are evaluated against specified design criteria, and the design is modified as necessary. The process is repeated until all specified design and state variables are met. The geometrical design variables are the height and width of the HFRP plate, and the state variables are the normal and shear stresses.

Optimization of Secondary Cooling on Rectangular Bloom Based on Subproblem Approximation Method

For understanding the surface and internal defects of Q195 steel of 150mm×220mm rectangular bloom, a solidification heat transfer mathematics model based on temperature measuring is established. Meanwhile, the secondary cooling water is optimized according to the metallurgical criteria by means of subproblem approximation method. The results showed that: after the optimizing result is applied in actual production, the water consumption is reduced 8.2~11.5%, the quality of bloom improved obviously, and the defects such as central pipe, center porosity and internal cracks are reduced respectively.

링 보강 원통셸의 고유진동수 최적화에 관한 연구

For the optimization of the fundamental natural frequency of stiffened cylindrical shells, simulations were performed for cylindrical shells that were stiffened with between one and five ring stiffeners. ANSYS 11.0 was used to simulate the optimization for the natural frequency. The Subproblem Approximation Method was applied as the optimization method. The design function of the optimization was the geometry of the T-shaped ring stiffener, and the constraint function was the maximum additional volume, constrained to a 10% increase. The objective function of the optimization was chosen to maximize the fundamental natural frequency. The performance index for optimal design was defined as the ratio of the natural frequency to the volume of the unstiffened and stiffened shells. The optimal performance index was obtained for the shell stiffened with three rings.

Optimized Design of the Horn of Ultrasonic Roll Welding

Previous studies on the amplitude horn only calculated sizes in consistent with the axial resonant mode frequency and disc bending resonant mode frequency without considering the overall stress and the amplitude of the disc’s outer ring. The resonant frequency of the amplitude horn cannot occur around 35 kHz. Such a design results in the inability to weld and may damage solar panels or lead to poor welding quality. Using the optimization method to address these problems, the proposed design process in this study is to conduct sensitivity analysis by the gradient method to understand the impact of design variables on the objective function for the selection of design variables. Then, this study applied the random search method to find out the feasible design of arrays to optimize the structure of two arrays closest to the design objective by the full factorial experiment method to ensure to get the global optimal solution rather than the local optimal solution. Finally, by design examples, this study used the sub-problem approximation method to search the optimized solution and compared the differences of the two methods, in order to confirm whether the objective of optimized design of amplitude horn had been achieved.

Optimum design on suspension joint parts of GFRP composite bogie frame with H-shaped side beams for urban railway trains

In order to optimize bolt locations for suspension joint parts of a GFRP composite bogie frame, the optimum design was done. The structural integrity of a composite bogie frame was evaluated under three main in-service loads according to JIS E 4207. The optimum design was conducted using a sub-modeling technique, a sub-problem approximation method, and batch processing codes programmed by ANSYS Parametric Design Language (APDL). The results showed that the optimum design using the sub-modeling technique was able to obtain more accurate results by the control of mesh density for the interesting parts, and reduce maximum Von-Mises stress in comparison with initial model.

Transient Dynamic Analysis and Optimization of Chamber

In order to make up the deficiency of traditional design theory, time-dependent load is loaded on chamber, and continuity assumption, homogenization assumption, isotropy assumption, small transmogrification assumption and plane section assumption are made, then transient dynamic analysis is adopted to analysis the chamber’s strength. Analysis result is according to the theoretical calculation perfectly. Based on the analysis result, using maximum compressive stress and the deformation of chamber as constraints, the chamber’s area is optimized. During optimization, the subproblem approximation method is adopted, while local stress concentration, strong charge are not taken into account in optimization process. Optimization result shows the chamber's thickness can be reduced to 1/3 of original. That means the chamber’s weight can be reduced to 1/9 of original. It’s a good base for the optimization of whole barrel to reduce naval gun’s weight.

서브모델링 기법을 이용한 철도차량 복합재 대차프레임의 금속재 체결부 볼트 위치 최적화 해석 연구

This paper describes the optimum design of bolt locations for metal joint parts of railway bogie frame made of glass fiber/epoxy 4-harness satin woven laminate composite and PVC foam core. The optimum design analysis was done by sub-problem approximation method using Ansys Parameter Design Language(APDL). The sub-modeling method was introduced to conduct the detailed recalculation for the only target parts and reduce calculating time. The structural analysis for composite bogie frame was performed according to JIS E 4207. The results showed that the optimum design analysis using sub-modeling method was able to obtain faster and more precise results than that of the entire model by the control of mesh size for the target parts, and the maximum Von-Mises stress has been reduced in comparison with its original dimensions due to the optimum design of bolt locations.

Combined finite element analysis and subproblem approximation method for the design of ultrasonic motors

This paper presents a design method of ultrasonic motors using finite element analysis and subproblem approximation method. It adopts the finite element method for modal analysis and harmonic analysis of the motor, and subproblem approximation method for searching the optimal solution of design variables. To verify the effectiveness of the design method, the proposed design method is applied to the design of a rod shape ultrasonic motor. The motor structure is determined using the proposed method. A prototype ultrasonic motor is manufactured using the design results and measured experimentally. The results demonstrate that the design method is effective and available for the design of ultrasonic motors.

Optimisation of continuous casting process parameters based on coupled heat and stress model

Based on a coupled heat and stress model, an artificial intelligence optimisation program was developed to optimise the process parameters in the continuous casting of steel. The program can be used to identify the key factors for the cracks of the strand and obtain the optimum process parameters of continuous casting. The optimisation program contains two models, one is the thermomechanical model developed using the finite difference method, and the other is the optimisation model developed using the subproblem approximation method. The whole program works by automatic iteration between the two models. This study has taken the stress constraint in the solidified shell into consideration when studying the metallurgical constraints. The application of the achieved optimum parameters would make it possible to run the caster at maximum productivity, with minimum cost and fewer defects. After manufacturing verification of this optimisation project, the incidence of cracks has reduced from 8% to 2%, and water consumption in the secondary cooling zone has been decreased by 25%.

Optimization for Secondary Cooling Parameters in Continuous Casting of High Carbon Chromium Bearing Steel

The high carbon chromium bearing steel, as a kind of special steel, entails high quality. The work aims to simulate the solidification process of continuous casting of high carbon chromium bearing steel, to find the cause for defect, and to optimize the secondary cooling parameters steel. A finite element model is developed to compute heat transfer and solidification in bearing continuous casting. By comparing the calculated data with the metallurgical constraints, the key factor caused the cracks on the strand can be found out. Then based on the subproblem approximation method, an optimization program is developed to search out the optimum cooling parameters. Those optimum parameters can meet all specified requirements but with a minimum expense of the operational and the design constraints and can make it possible to run the caster at its maximum productivity, minimum cost and to reduce the defects. Now, online verifying has been obtained with the cracks decreasing and the water consumption of secondary cooling zone saving.