Advanced Materials Research Vols. 652-654

Abstract: The single-directional and single-pass compression test were conducted on SA516GR70 vessel steel by a Gleeble-3500 thermal-mechanical simulator with the parameters of 800-1100 oC and 0.01-5 s-1. The influence of deformation temperatures and strain rates on the flow stress and the evolution of dynamic recrystallization of the observed steel were investigated. The results showed that the work hardening, dynamic recovery and dynamic recrystallization softening processes might be occurred successively or simultaneously with the strain increasing. The flow stress-strain curves for the compressed steel can be divided into work hardening stage, transition stage, softening stage and steady-state stage. The dynamic recrystallization occurred in the deformation samples when the observed steel was compressed at above temperatures and strain rates. At a certain deformation temperature, increasing the strain rates was helpful to increase the volume fraction of the dynamic recrystallization and to refine the grains. At a certain strain rate, decreasing the deformation temperatures was helpful to refine and homogenize the macrostructures. The deformation activation energy was 377 kJ/mol and the equation of hot deformation was built by analysing stress-strain curve of SA516GR70 steel.

Abstract: Focus on the problems in thickness design of shells with multi-holes, an optimized design method based on theory of finite element method is presented. In this method, mathematical model of optimized design is built up based on theory of finite element method and theory of plates and shells, and realized method of optimized design of thickness based on ANSYS software is established. Additionally, the influence factors of optimized design of thickness are analyzed, including load forms, constraint types. In the end, an example about cellular board design shows this method is a good way and available in engineering projects.

Abstract: In order to utilize Overlay Tester to evaluate the crack resistance of Hot Mixture Asphalt (HMA) of steel deck pavement, three-dimensional finite element (FE) models of local steel deck pavement, composite beam and Overlay Tester specimen were established by Abaqus Software. The results show that the characteristic tensile stress in three FE models are similar, and the tensile stress of composite beam’s steel plate is much larger than that of composite beam’s HMA layer, hence the steel plate undergoes the major external force in the composite beam fatigue test, while the HMA layer seems not to be tested. To reduce this problem, FE models of Overlay Tester in three different displacements: 0.63mm, 0.063mm and 0.01mm, were analyzed. The results indicate that the stress in the 0.63mm displacement condition is much larger so that the asphalt mixture will be broken, and the stress in the 0.01mm displacement condition is similar to that of local steel deck pavement. In consideration of testing cycles and other factors, the 0.063mm displacement is recommended to test the HMA of steel deck pavement.

Abstract: As there was no precise theoretical model for predicting the stress of deformation zone while straightening thin-walled tube, some technological parameters depended mostly on the experience of workers and on the results of trials, therefore by means of the membrane shell theory the equilibrium differential equations of stress is obtained firstly, then we analyze the strain of deformation zone, finally lead to a new theoretical model for predicting the stress in the elastic and plastic zone. Subsequently the simulated experiments have been done, the results show that the theoretical calculations coincide well with the simulated results, the errors are within 1％of the calculations, it is testified that the model is correct and efficient for the thin-walled tube straightening.

Abstract: Aluminum alloy goal crossbar (crossbar for short) as an essential part of soccer goals, according to practical needs, needs to be designed in other ways. So the segmented optimization design of crossbar has been proposed.This paper proposes that cut off crossbar from the middle first, then use an iron core turning the segmented crossbar into a whole part again when used. By means of parametric modeling in AutoCAD and SolidWorks and finite element analysis in MARC, the feasibility of the optimization design has been demonstrated. Finally, the paper comes to a conclusion via the way of experimental test.

Abstract: This study examines the effects of twisted steel fiber obtained by changing the shape of the fiber in order to improve the toughness of the conventional straight steel fiber. Three types of twisted fiber with different lengths (l) and diameters (d) are considered while maintaining the aspect ratio (l/d) to 100. Flexural tensile test is performed on the K-UHPC paste mixed with 1%, 1.5% and 2% of fiber relative to the volume of the matrix to analyze the flexural tensile performance, deflection capacity and energy absorption performance. The results show that the use of twisted fiber increases significantly the flexural toughness of K-UHPC compared to the use of the traditional straight fiber. Especially, the adoption of a quantity of twisted fiber reduced by 0.5% is seen to secure identical performances. The reduction of this quantity by 1% develops slightly lower flexural strength but provides remarkable deflection capacity. Accordingly, since the adoption of twisted fiber enables to reduce the mix ratio of fiber by 0.5 to 1% according to the intended purpose, such fiber is expected to allow further reduction of the fabrication cost of K-UHPC.

Abstract: Stress and fatigue analysis of welded case shell on aeroengine under combined internal pressure and axial loads using elastic-plastic finite element has been performed. The results show that the largest stress concentration appears on the mutational cross section of the fixture seat and fixture fringe structure some distance from the weld toe. The positions with the weakest fatigue life locate at the fixture fringe close to the weld toe of girth joint, and also appear at the ring closed weld of the case shell middle.

Abstract: An experimental investigation was conducted to determine the bearing stress of single-lap double bolted composite joints. The bearing stress of a group of specimen was presented and the relationship between the stress and strain was obtained. The experimental results show that the damage of the bolted joints was a progressive process; and the ultimate bearing stress depends not only on the laminates’ strength but also on the bolt strength. A finite element model was created based on the bolted joint specimen to simulate the loading – displacement response. The numerical results verified the experiment results qualitatively.

Abstract: Due to the complex structure and nonuniform material of unbonded flexible pipes, an elastic thin-walled cylinder model and a helical steel strip model were established respectively to simulate different layers based on the specific structure form and parameters. Quasi-static incremental load was adopted to identify the structural parameters which had significant effects on the axial, radial and bending behavior of the pipes during the complex deformation. Sensitivity of these parameters were also analysed. The conclusion in this paper could provide guaidance for the design of unbonded flexible pipe.

Abstract: This paper discussed how we can do to design gem stones cut in accordance with their physical properties. Thickening or thinning can be used for the colored gemstones to improve their color. Orienting the table facet is necessary for the star gem stones, cat's eye gem stones and tiger's eye gem stones. It is very important for a pleochroic stone to be cut in proper orienting to show off the different colors. It is desirable to choose cabochon for an opaque gemstone and facet for a transparent gemstone. And a well-crafted geometrical arrangement of facets is key technique to maximize the brilliance and fire of the stones, such as diamond. Do with these skills and get your ideal gems.