Applied Mechanics and Materials Vols. 395-396

Abstract: The fastening is an important part for fastening when laying the rails, which requires sufficient fastening pressure, strength, and durability. This article focuses on the fatigue fracture of the spring clip of a fastening and gets a result that the fracture accounts for alternating twist-bend load by examining macro-fracture. The crack origin is on the surface of the clip where significant decarburization and corrosion exists and its extension makes the clip break by examining metallographic structure and testing micro-hardness. The solution is to improve the heat treatment method and the surface quality avoiding corrosion.

Abstract: Numerical and experimental study on honeycomb sandwich structure with a rectangular cut-out were carried out in this paper. Two designs were presented, with using a U-shaped sandwich structure or a combination of two separate sandwiches. Finite element models were developed and calculated using MSC.NASTRAN code by means of linear analysis and non-linear incremental deformation analysis. Compared with linear analysis, non-linear analysis was more suitable to evaluate the ability of sandwich structure with cut-out to resist compressive load. The results obtained from non-linear solution were verified by the supporting mechanical tests.

Abstract: With the development of highway and railway, the construction technique of bridge is developing at a lighting speed. Because of the need to across the river and channel, which span getting more and more large, the foundation of the bridge piers should be more and more stable. Lead to raising the load capacity of the pier foundation. The technique cofferdam construction is an effective mean to solve large foundation problems in deep water. And comparing the empirical value to the simulating value, the results demonstrate FLUENT is a reliable program to simulate the water resistance. This paper gives a model for complete resistance calculation and stability analysis of floating steel cofferdam which will provide a template for similar analysis of engineering application.

Abstract: The tunnel sprayer with no drift, pesticide recycling as the main feature, reflected increasingly its superiority to improve the efficiency of spray in the hedge frame crop and reduce pesticide pollution. In this paper, it’s infrastructure to tunnel frame stress distribution and optimum design that is static analysis and experimental research on self-propelled tunnel sprayer frame in the ultimate torsion condition.

Abstract: With the increasingly widespread application of high-strength steel (HSS), tailored properties, namely different mechanical properties required in different regions of the same part, have been proposed, in order to achieve the matching between mechanical properties and safety performance of motor vehicle parts. In this paper, the influence of air gap on the final hardness and strength distribution is discussed in terms of two different HSS, namely LG1500HS and WHT1500HF. As for steel LG1500HS, regardless of the location of samples in the formed part, the final fracture area is in the vicinity of the air gap center, proving the lowest hardness and strength in transition zones. Compared to steel LG1500HS, steel WHT1500HF exhibits gradient hardness distribution from the cooling zone to the heating zone, with no minimal value discovered in transition zones.

Abstract: The paper establishes the forming limit diagrams (FLDs) for QSTE340 seamed tube hydroforming and the mother sheet metal forming by numerical approach and experimental approach. A novel experimental approach is proposed to evaluate the formability for tube hydroforming under biaxial stretching through elliptical bulging.Then the Nakazima and three types of tube hydroforming tests are simulated with finite element (FE) program LS-DYNA. The failure criterion of thickness gradient criterion (TGC) is introduced. The FLDs for seamed tube hydroforming and the mother sheet metal forming are constructed. The comparison of results based on TGC with experimental data shows the TGC is an appropriate one to determine the onset of localized necking. Finally, the differences and relationships between the FLDs for the seamed tube hydroforming and the mother sheet metal forming are discussed.

Abstract: Research device structure upon suppressing impress and wrinkling about three-dimensional numerical control bending machine.3D ship curved-surface outside plate automatic forming process is always the difficult part in the field of domestic and international shipbuilding. Analyzing the problems in existing processing methods ,for example, line heating technology has the defects of poor production conditions, large labor intensity, not environmental friendly and cold bending forming method may result in indentation, wrinkling or rebound phenomenon.Presents the forming process of a ship hull plate based on square head adjustable die curved surface forming device. By setting the non pressure and a plurality of planar head to replace the traditional integral die method, the paper will illustrate the composition and working principles of the process at the same time try to implement effective control of indentation and wrinkle phenomenon followed by verification through experiments.

Abstract: A 3D numerical model for heating distribution of bread mold in the oven is presented in this study. In the process of bread production, heat effect is influenced by the shape of the mold. Being consistent with the results of calculation, the shape of the mold imposes great influence on the heating distribution uniformity and maximum temperature difference. Because of even boundary curvature, circular mold behaves better than elliptical and rectangular mold. By utilizing the introduced theoretical model, we are able to get the spatial heating distribution of all kinds of mold. And taking three kinds of mold as example, we illustrate that the more uneven the boundary curvature is, the less uniform the heating distribution will be.

Abstract: In order to investigate the thermal forming behavior of as-cast 42CrMo steel, the isothermal compression tests were performed on a Gleeble-1500D thermal mechanical simulator in the deformation temperature ranging from 850 to 1150°C with an interval of 100°C, the strain rate ranging from 0.05 to 5s^-1 and the height reduction of 60%. On the basis of the flow stress data, dynamic materials model (DMM) and Prasad's instability criterion, the processing maps for as-cast 42CrMo steel were constructed at the strains of 0.4 and 0.6. The safe and unsafe areas and the corresponding deformation regimes were predicted during hot working, which are verified through the microstructure observation. The results indicate that the safe zones in the temperature range of 850~1150°C and strain rate of 0.05~0.35s^-1, which exhibit the dynamic recovery and recrystallization. However, the flow instability domains are in the domain of deformation temperatures 850~1150°C and strain rate higher than 0.35s^-1. Typical microstructure of instability is cracking, which should be avoided so as to obtain desired mechanical properties in hot processing. Finally, the forging parameters were predicted and optimized accurately by the processing maps, the temperature range of 1050~1150°C and strain rate of 0.05~0.1s^-1 were recommended as the optimum deformation conditions for hot processing of as-cast 42CrMo steel.

Abstract: In the twin-roll strip casting process, analyses of heat transfer and deformation for the casting roll sleeve are carried out by using the finite element program ANSYS to examine the the thermal crown. The effects of several factors such as molten pool temperature, heat flux onto the roll surface and roll edge, heat flux onto the cooling channels, and cooling water temperature on thermal crown are investigated. The results show that the thermal crown does not change sharply during the casting process, after the casting roll reaches thermal equilibrium.