Advanced Materials Research Vols. 189-193

Abstract: The main objective of this study is to generate new understanding and improve computational method for optimization design on the parameters of double ellipsoid welding heat source. On the basis of Infrared measurement (IR), two optimization design methods, the zero-order method and first-order method, were combined to confirm the heat source parameters. The simulated thermal cycles, the weld penetration and the weld width were consistent to the experimental results with such corrected parameters. The effects of the parameters were analyzed by gradient evaluation method. It presents that as each of the parameters increasing, the peak temperature in the thermal cycle declines. Of all the three parameters, the sensitivities of the weld penetration and width with parameter c are great.

Abstract: Limit bearing capacity analysis of structure system with different types of element (SSDE) is difficult to elastic modulus adjustment procedures. In this paper, elastic modulus reduction method (EMRM) is introduced for evaluation of the limit bearing capacity of SSDE, using the element bearing ratio (EBR) as the governing parameter. As a dimensionless quantity, the EBR can be used to measure the bearing state of every element, and the scheme of reducing elastic modulus can be expressed using a uniform equation for different types of element. When the structure system destroys, all elements will tend to reach their own strength. The algorithm is then extended to the plastic limit analysis of SSDE. Numerical examples are employed to demonstrate the applicability, accuracy and efficiency of the method.

Abstract: This article designed a coding system DJBM-1of parts based on structural similarity. According to Fuzzy theory, the relationship between parts was determined quantitatively by mathematical methods, and threshold value λ was obtained through calculation. Objective classification was realized after initial classification and verification, avoiding the deficiencies of traditional classification method of parts and implementing the classification of parts effectively.

Abstract: Fu Feng highway prestressed concrete bridge is located in Changchun City which is the capital and largest city of Jilin province and it located in the northeast of China. The strengthening of the bridge structural members can be attempted by replacing poor quality or defective materials by better quality materials, attaching additional load-bearing materials, and re-distribution of the loading actions through imposed deformation on the structure system. The objectives of this study are to explain the strengthening process of damaged structural members of Fu Feng bridge, and to evaluate the performance of the bridge structure by adopting static load test. The strengthening process of damaged structural members includes three stages. These stages include the strengthening of box girders floor by casting of 10cm of reinforced concrete in the floor of box girder within the location of positive bending moment in the mid-span and edge span, the strengthening of box girders web by pasting steel plates in the inside of the right and left of box girders, and the strengthening of the transverse beam of piers No. 18 and No. 19 by using carbon fiber sheet. The results of static load test show that the values of testing coefficient ( ) of stress range from 0.83 to 0.92 are less than allowable value 1.05. Therefore, these values satisfy the allowable value of standard, indicating that the structural member has a certain strength reserve and the working state of the bridge structure in good state. the ratio between the measured and theoretical deflection is 1.41 and 1.68 for condition 3 more than allowable value 0.8, indicating that the state of stiffness is not good and there are still a serious shortage in stiffness of structure. Therefore, this study recommended that the bridge structural members need to re-strengthen by using other effective technical and materials to increase the stiffness of structural members of the bridge.

Abstract: The objective of this study is to calculate and analyze the internal forces under designed dead and live loads to evaluate the structural performance of corbels and T-shaped cantilever structure of the main span of Jiamusi highway prestressed concrete bridge to evaluate the state of the structural members of the bridge. Two software are used in this analysis. The first software is Dr. Bridge Ver. 2.95 which is used to analyze the internal forces of T-shaped cantilever structure under different load combinations. The second software is Ansys Ver. 10 which is used to analyze the internal forces in the corbel. The results of analysis show that at the dead load stage, the maximum compressive stress at the upper and bottom edge of all sections of T-shaped cantilever structure satisfies the allowable values of standard. The tensile stress doesn’t appear. At the normal service stage, there is enough reserve of compressive stress in the all sections, and the compressive stress is smaller than the allowable value of the standard. There is no tensile stress for all the controlled sections. The maximum main compressive stress and maximum main tensile stress of all controlled sections is smaller than the allowable value of standard. The bending strength of all sections satisfies the allowable values of standard, and there is big reserve of strength. The steel settled in the oblique section of 45° in the web of the corbel has enough reserve for the tensile strength. If the prestressed steel in the corbel is inefficient, the resistance of the oblique section given by the ordinary steel in the corbel and it can be resisted the loads. The longitudinal positive stress of vertical section a-b, vertical shear stress, main tension stress and main tension stress of oblique section a-c of 45 satisfy the allowable values of standard.

Abstract: The viscous flow of the supersonic jet element was simulated numerically based on CFD technology, and many tests have been done to verify the numerical precision. The results show that the calculated data are good agreement with the experimental data. So the numerical simulation of the viscous flow for the supersonic jet element is accurate and reliable, and it can be applied to investigate the steady flow and unsteady flow in supersonic jet element.

Abstract: For the loess cave characteristics, such as the thin coverage soil layer at the hole top, the poor self-stabilizing capacity, the large disturbance deformation after excavation and the easy collapse, thus in this paper, the loess cave safety factor is obtained by the method of strength reduction. And the stability calculation analysis is much more perfect. The Northwest Area Lishi loess cave is used in this paper, and the idea of strength reduction finite element method is applied, based on the Drucker-Prager yield criterion, the loess cave static stability analysis is made by the software of ANSYS.The results show that the actual situation can be reflected by the method of finite element strength subtraction. And the obtained loess cave stability coefficient is much closer to the actual steady state, thus showing the certain advantages of stability analysis.The method is also adopted in this paper. And its feasibility can be applied to the engineering practice, also a theoretical basis of reference is provided for engineering application.

Abstract: Taking the plastic injection mould of the air conditioning panel for example, through the flow simulation and analysis of the filling mould process for three gating system design programs, the paper gets each program’s filling time, temperature, shearing rate, melting wiring and air pocket, injecting pressure and the distribution map of locking strength. Through comparing and analyzing, the paper draws the relatively good design program, and finds the shaping defect that may appear ahead of time, which improves the success rate of once-testing mould so as to realize shorten mould design cycle and reduce mould manufacturing cost.

Abstract: With the aid of commercial FE code MSC.SuperForm, the structural steel tube continuous rolling process of a typical hollow tube specification 152.5×12.5mm is simulated based on Bao Steel 152.5 main pass sequence of 140mm 8-stand mandrel mill, and the distribution characteristics of stress/strain, outline lateral spread, temperature changes of workpiece in continuous rolling process and distribution of stress/strain, friction of workpiece in deformation zone are analyzed. Analysis results indicate that deformation of workpiece along the width of the groove, especially at the top and the bottom of the groove is highly inhomogeneous due to the unequal draught and the longitudinal stress of special position (the top and the bottom of the groove) of workpiece is always an alternate state, in a tensile-compressive-tensile manner, and has a distinct rule. In the first stand, outline dimension of workpiece gradually increases during reducing process and early stage of wall thickness reduction, but it gradually decreases during middle-late stage of wall thickness reduction and tends towards stability at last. It is inhomogeneous that distribution of unit compressive stress and longitudinal strain of workpiece in deformation zone, and contact stress and total equivalent plastic strain are maximal in inner surface of workpiece contacting with mandrel. Temperature difference between the outer and the inner surfaces of workpiece is obvious.

Abstract: In continuous tube rolling process, wall thickness reduction per stand will be changed due to wall thickness fluctuation of pierced shell caused by piercing process, which results in changes in metal flow conditions and affects force parameters, deformation parameters, especially transverse wall thickness precision of rolled hollow tube. In this paper, with the aid of commercial FE code MSC.SuperForm, the high pressure boiler steel tube continuous rolling process of a typical hollow tube specification 133.0×4.0mm are simulated based on 133 main pass sequence of 89mm 6-stand semi-floating mandrel mill, and force parameters, equivalent plastic strain, transverse wall thickness precision, outline dimension and real roundness of rolled hollow tube are analyzed and compared on the condition of two different wall thicknesses of pierced shell. Analysis results indicate that force parameters increase with wall thickness of pierced shell, maximal rolling force, rolling moment and mandrel axial force increase 10% or so in the first three stands when rolling pierced shell of wall thickness 11.5mm compared to that of wall thickness 10.5mm. When rolling pierced shell of wall thickness 10.5mm, there exist front and back tensions among the third, the fourth and the fifth stands and outline dimension and real roundness of rolled hollow tube is slightly better. However, transverse wall thickness of rolled hollow tube at the bottom of groove is pulled thin obviously.