Papers by Keyword: Boundary Condition

Abstract: In irrigation structures, seepage through the body wall and foundation play a major role for the assessment of failures in the structures. To design any kind of structure for the proper irrigation, the effect due to seepage should be considered widely. Many methods have been suggested for the prediction of seepage. Seepage analysis of irrigation structures works mainly on the basis of two dimensional Laplace equation. The Partial Differential Equation Toolbox in MATLAB provides a powerful and flexible environment for the study and solution of partial differential equations in two space dimensions and time. The equations are discretized by the Finite Element Method (FEM). Fluid flow through porous media particularly in the case of irrigation and hydraulic structures like dams and weirs is the focus of the current study and here flaws or cracks which occur in the domain cause variations and need remedial ones to improve or bring back to the original flow pattern. Since flaws in terms of fissures are very small injecting nanomaterial mixed mortar can provide significant improvements and modifications. Here in a rectangular domain the flow is studied throw finite element modeling with and without different sizes and location of flaws. Later these flaws are filled with nanomaterial mortars whose properties are based on test results and the flow is again studied to bring out the changes and improvements. Results are given for different nanomaterial mortars with different flaw sizes.

Abstract: At the moment a problem of fracture and lifetime estimation for piezoelectric materials is not completely solved. The paper considers fundamentals of linear fracture electromechanics, fracture parameters and fracture criteria. The main difference from linear mechanics is crack face boundary conditions taking into account relative permeability of media inside the crack gap and coulomb traction. Different types of crack face boundary conditions and their numerical implementation are described. The paper presents results of finite element modeling of fracture toughness experiments on the compact tension specimens under combined electromechanical loading. Different types of crack face boundary conditions were tested and comparison of fracture parameters and fracture criteria was carried out.

Abstract: The low voltage supply system’s reliability play an important role on improving equipment’s operation level and standards of management, this paper proposed a method to evaluate the reliability of low voltage supply system .The method was composed of four parts: statistical index system, definition of every index’s meaning and statistical formulas, confirming the statistical boundary conditions. In order to test the effective and practicability of the method, this paper evaluated the low voltage power supply’s reliability of BinZhou and the results are satisfactory.

Abstract: In this paper, an improved wolf colony algorithm (WCA), named as efficient adaptive wolf pack search (EAWPS) algorithm was proposed. EAWPS adopts population manager strategy, adaptive sharing factor and boundary condition to avoid falling into the local minimum and to significantly improve the efficiency of WCA. The efficacy of EAWPS is compared with the original WCA and the standard PSO on six benchmark functions, the experimental results demonstrate that the proposed algorithm has a superior performance in both speed and accuracy.

Abstract: The stress distribution properties in a single lap-jointed cantilevered adhesive beam have been investigated using three dimensional finite element methods. Finite element solutions of the stress distributions in the adhesive layer have been obtained for three typical boundary conditions. It was found that the stress concentrations are confined to a very small region near the free ends of interfaces between the adherend and the adhesive layer while the centre region of the adhesive layer is mostly stress-free. This suggests that the first failure may be expected at the free ends of interfaces between the adherend and the adhesive layer. This also implies that the adhesive material near the free ends of the adhesive layer is mainly bearing the load being transferred through the adhesive joint. The analysis results show that by choosing suitable boundary condition, the bending effect can be reduced and the strength, fatigue life and reliability of the bond can be improved.

Abstract: Fire resistance performance of structural members has been evaluated from each singular section and standard fire curve since the beginning of fire tests. However, the need of the exact fire resistance of H-section columns applied in the steel buildings has increased. The main reason for this is there is a difference between the conditions being conducted during the fire test and that from real situation. In this paper, the structural stability of H-section column made of an ordinary strength grade structural steels, SS 400, SM 400, and SM 490 at high temperature were evaluated and compared with boundary conditions and column’s length. This was done in order to suggest a new guideline for the application of fire protective materials in steel column in which the boundary conditions and column lengths are different from that tested with hinge to hinge and 3500 mm. The findings from this study showed hinge to hinge boundary condition was more conservative. And fire resistance performance of longer columns in the case of hinge to fixed and fixed to fixed boundary condition than from 3500 mm and hinge to hinge boundary condition can sustain at high temperature without adding fire protective materials.

Abstract: A proper setting of boundary conditions is a standard upon which simulation results are justified. This study is specifically designed to simulate airflow over a repeating unit of simplified urban models with the application of periodic boundary condition. Similar setting of boundary conditions is used for all models which are of square layout with 25% packing density. The models are constructed with such that the initial velocity field is uniform throughout its internal domain. The results show that different domain heights of 4h and 5h (h as the building height) do not affect the spatial averaging of velocity profiles. In terms of the number of grids per building height, a finer meshing of 32 grids produce more accurate results of velocities and turbulence intensities compared with those of 25 grids when validated against the previous direct numerical simulation (DNS) data. Nevertheless, these criteria depend upon longer averaging period for better estimation of flow statistics. The boundary condition setting used in this preliminary study is nevertheless capable of producing current results comparable to past data although future works should focus on optimizing the important criteria in a simulation such as domain height, grid numbers, and averaging time.

Abstract: High-rise building is one of solution for lack of houses and offices in downtown. And high-rise buildings can be built by application of high strength materials such as structural steels and concrete. Particularly, high strength structural steels have much efficient properties in not only design phase but construction one. Therefore, the use of the high strength structural steels has been increased every year. However, the H-section made of the high strength structural steels can be designed and constructed with longer height than that was evaluated for fire resistance by fire test to satisfy the fire regulation. In this study, to suggest an exact fire performance at high temperature of H-section made of high strength structural steels, a fire engineering technique was used. The derived facts showed that SM 570 revealed better structural stability at high temperature and as longer length of H-section was used, the more fire protection materials requited.

Abstract: Finite element method is widely used in every field, in which ABAQUS is a typical product. For engineers and researchers, SHAKE91 is a good choice for seismic safety evaluation. For developing seismic response analysis for complicated cases, finite element method approach should be explored. An elastic layered model is built, which is calculated in SHAKE91 and ABAQUS respectively. The results of the two programs fitted well, which implies the correctness of the ABAQUS model. In the elastic model, simple boundary condition works well. In the future, more complex boundaries and dynamic constitutive models should be studied.

Abstract: Based on the traditional piezoelectric effect theory, the process of multi-piezoelectric effects generation is analyzed and the theory of the secondary and tertiary piezoelectric effect is deduced by four kinds of piezoelectric equations. Experimental research is performed through the PZT-5 piezoelectric ceramics stack, the existence of multi-piezoelectric effects is verified and experimental data is obtained under certain boundary conditions. The experimental data results show that if an external force which is applied to the positive piezoelectric effect is 400, the displacement generated by the secondary converse piezoelectric effect is 0.16. Therefore, starting from the first positive piezoelectric effect of the piezoelectric ceramics under applied force, the displacement generated by the secondary converse piezoelectric effect and the voltage generated by the tertiary positive piezoelectric effect are all linear with the applied force.