Advanced Materials Research Vols. 1004-1005

Abstract: Intergranular stress corrosion cracking is one of important failure form of structural materials in nuclear power plants, and the initiation and development of crack at grain boundary are affected by the grain size of materials. The macroscopic model and mesoscopic model of crack propagation was established by using finite element method, and the effects of grain size on fracture parameters such as Mises stress, the maximum principal stress and equivalent plastic strain nearby crack tip were studied. The results indicate that the distribution of Mises stress and equivalent plastic strain are discontinuity at grain boundary, and the maximum principal stress locates at grain boundary. The Mises stress, maximum principal stress and equivalent plastic strain nearby crack tip increase with the increasing of grain size.

Abstract: Aiming at the problem that current CNC incremental forming technology can’t directly manufacture the sheet-metal part with non-horizontal end face, the method that can manufacture this kind of sheet-metal part by using the equidistant tool path parallel to the sheet metal was proposed in this paper, in which the support and sheet metal was made together and sheet metal was directly fixed on the support. In addition, the equidistant tool path parallel to the sheet metal was generated using UG software and the sheet-metal part was fabricated by using vertical CNC machining center.

Abstract: Turbine disc is the key component of aviation engine, its performance is important to ensure the reliability and safety of the whole aviation engine. In this paper, forging forming of GH4169 alloy turbine disks of certain type aero-engine are discsimulated by DEFORM-3D soft system,these forming methods include next three kinds: common hot die forging, isothermal forging and composite sheath hot die forging.The influences of various forging ways on turbine disk forging quality and the used die are analyzed in order to find the most suitable way of forging. The forging defects in the forging process are analyzed . For basically eliminating these defects, the forging process of superalloy turbine disk are optimized based on the most economical and simple principles and some useful methds are gained，which will provide a reference to actual superalloy turbine disk forging process.

Abstract: The traditional method has been used to the foundry technique for the melt block mobile plate. The pouring position,the parting face and some of the casting parameters were determined, such as the allowance for finish, stripping taper, the rate of shrinkage and soon on. The commercial casting simulation software was introduced into the casting process, the filling and solidification process were calculated by it. The results shown that there are some shrinkage exists in the original technique and the filling process were inordinate. The gating system was optimized and according to the simulation results, the shrinkages in the original technique were eliminated and the filling process is smoothly which could help the designer to make a correct determination.

Abstract: Based on the constitutive equation of the orthotropic material, the relation between elasticity parameter and crystal orientation was analyzed. Finite element computation were carried out for simulating the stress of body-centered cubic crystal under high cycle fatigue, and after the analysis of the crystal stress, variation of the shear stress and normal stress on the slip plane were discussed depending on the angles between the crystal principal axis and the loading direction. The results show that, under high cycle fatigue, to the body-centered cubic crystal metal, the resolved shear stress on the slip plane reaches a maximum when the crystal principal axis approaches to the macro loading direction, and the calculated normal stress on the slip plane gets the maximum when crystal principal axis and the macro loading direction are inclined to 54 deg.

Abstract: Cylinder block with different design structures will affect casting process and final product quality in various degrees. In this paper, mold filling and solidifying process of a cylinder block was simulated with Procast software and the results show that there are several casting defects caused by the self-structure. In order to improve such a situation, we adjusted the bottom structure and thick parts on the basis of original cylinder. After analyzing the results of simulation, the optimized cylinder has better mold filling process, less impacts on the sand core and less shrinkage porosity during the solidifying process.

Abstract: Studying Al particles reinforced composite lead-free solder by experiments of constant temperature thermal stress aging treatment. Scanning electron microscope was used to observe the micro-structure of composite solder. The results show that composite lead-free solder after constant 125°C aging treatment for 24 hours, Al particles has two types of morphologies: one is small amount of solid solution,another type is a large number of aluminum particles structure.The existence of Al particles slowed down the coarsening rate of the Bi Phase grain, and obtained uniform refined the Bi Phase grain.

Abstract: Electrical discharge grinding is one of the most widely used method to machine polycrystalline diamond compact cutting tool. Polycrystalline diamond compact samples with different crystal granularity are the research object. Peak current, pulse width and pulse interval are chosen as the main process parameters. The material removal volume and electrode loss set as the evaluation index of productive efficiency; workpiece surface roughness value sets as an evaluation standard of processing quality. With electrical discharge grinding experiments, combined with scanning electron microscopy observation and roughness tester, the influences of the main process parameters on electrical discharge grinding are analyzed, polycrystalline diamond compact electrical discharge grinding process are summarized.

Abstract: The development of standard simple of tin bronze for casting is presented,design of composition, selection melting temperature 1150 °C, put into 0.2m³/kg argon gas, stirring with 100rpm for 1min, keeping temperature for 30min as the optimum process conditions, coarse and fine tests of homogeneity with data analyses, determination of standard values and standard deviation. The homogeneity and standard values of samples meet the national standard GB/T15000 and YS/T409-1998. The standard sample series has ratification as National Reference Materials (GSB 04-2707-2011) by National Technical Commission on Reference Materials.

Abstract: In this paper, an integrated rolls system deformation calculation model is established based on the influence function method combining with pass schedule calculation, rolls wear and roll thermal deformation calculation, and the corresponding calculation procedure has been developed. Then the influence of work roll bending, work roll shifting and intermediate roll bending on transverse distribution of strip thickness, strip crown, quadratic flatness, and quartic flatness are analyzed with the procedure. According to the analysis result, flatness control strategy of the single-stand reversing cold rolling mill is determined. The flatness control strategy will provide the basis for flatness control presetting of the mill. The practical application shows that the flatness control strategy is suitable for flatness control of the single-stand reversing cold rolling mill.