Key Engineering Materials Vols. 353-358

Abstract: The crystal structure of a new compound NdFeSb3 has been determined by X-ray powder diffraction using the Rietveld method. The compound crystallizes in the orthorhombic, space group Pbcm (No.57) with the CeNiSb3 structure type and lattice parameters a=1.26828(2)nm, b=0.61666(2)nm, c=1.81867(4) nm, z=12 and Dcalc=7.917g/cm3.

Abstract: The DDA method parallels the finite element, which solves a finite element type of mesh where all the elements are bounded by discontinuities. In the current studies on the DDA method, the deformation of all the discontinuities is neglected, only the deformation of blocks is concerned with. The actual engineering indicates that the deformation of control discontinuity is often greater than that of block, and can not be neglected; but the deformation of the smaller discontinuities may be neglected. In this paper, the deformation of discontinuity is studied, and the result indicates that the displacement and stress of block element are affected by the deformation of discontinuity to a degree. Therefore, the deformation of control discontinuity can not be neglected in the study of the DDA method.

Abstract: In the present paper, TiB2/Al composite with 5% volume fraction of TiB2 was fabricated by LSM method. The effects of purification and degassing methods on TiB2/Al composite were examined by means of X-ray diffraction (XRD) and image analysis. Hydrogen contents in the molten composites were detected and compared among flux, inert gas and vacuum purification processes. The experimental results indicate that under general cast condition a majority of the TiB2 particles distribute on grain boundary, and only a few particles disperse within grains. The flux and vacuum purifications have no virtual impact on the distribution of TiB2 and the fraction of TiB2 remains the same after purification. However, degassing with inert gas will be detrimental; the TiB2 particles will be separated and removed from the matrix. The hydrogen contents for flux, inert gas and vacuum processes are 0.15ml/100g/Al, 0.12ml/100g/Al and 0.12ml/100g/Al respectively.

Abstract: A polyimide-epoxy blend has been prepared by reacting epoxy resin with imide compounds containing carboxyl groups at the ends of the molecular. When coated on the silicon steel sheets, the blend can be used as a kind of adhesive to bind together the silicon steel sheets of aerospace electrical machineries. Put pressure of 0.4-0.5MPa on a stack of coated silicon steel sheets, and cured at 200°C for 2 hours, binding course of 0.01- 0.02mm on the sheets was formed. Tensile shear strength of the binding course on stainless steal substrate is greater than 23MPa at room temperature, 8MPa at 200°C. After enduring in air at 300°C for 48 hours the tensile shear strength at room temperature remained 17MPa, dipping in aerospace lubricant at 250°C for 48 hours remained 18 MPa, steeping in dimathylacetamide at 160°C for 12 hours remained 12 MPa.

Abstract: In this paper, a new low-pressure die-casting with degassing function, casting under adjusted pressure (CAP), is proposed. The working principle of CAP process is introduced in details. This paper focuses on the influences of moisture of compressed air on the hydrogen content within the melt aluminum during the cyclic vacuum-pressurizing programs for CAP process. The experimental results indicate that degassing under vacuum acts positive in refining aluminum melt. The relative moisture of compressed air exerts a significant influence on the hydrogen content of aluminum melt. After the melt aluminum is exposed to the air with a relative moisture of 85% for 90 min, the hydrogen content of the melt aluminum can get to 0.4 ml/100g/Al; while under the circumstance of CAP process, the hydrogen content is maintained between 0.05 and 0.15 ml/100g/Al depending on the moisture capacity of the air, which virtually has no more influence on the casting qualities. Under the condition of dry compressed air, the hydrogen content can be kept at a level as low as 0.05ml/100g/Al, which facilitates to obtain high air-tightness castings.

Abstract: The influences of Sn addition of 3%-30% on the friction and thermal expansion properties of Al-Sn bearing alloys were investigated in this paper. The experiments were carried out on a specially designed friction testing machine and a dilatometer. It is shown by the experiments that the friction coefficient and hardness of the alloys decrease with the increasing of Sn content. The friction coefficient decreases dramatically when Sn content is higher than 6%. On the other hand, the friction coefficient is also dependent on the load. The friction coefficient increases as the load rises. The linear CTE is also a function of temperature and Sn contents. CTE increases when the temperature rises but has no obvious differences for the alloy system when the temperature is below 80°C. As the temperature rises, the differences become large among the alloy system. The higher the Sn content, the lower the CTE.

Abstract: Based on a large number of investigation and analysis for slag detection system (SDS), a kind of automatic SDS using vibration measurements had been put forward in this paper. After studying casting process from ladle to pouring box and protection casting supporting mechanical structure, vibration dynamics model of supporting structure was established, also variation of steel water impact force and influencing factors of inspecting spot vibration are analyzed. Theories of wavelet, wavelet package and their applications in signal processing are presented. Vibration signal of steel water was processed by the way of wavelet package, then its eigenvector and tolerance range were obtained, and that can realize effective identification for steel water status. Experimental results indicate that this system is very effective and achieves anticipated outcomes.

Abstract: In order to obtain the total cutting energy and the ratios of the three parts of the total energy during cutting off the rubber, a test method was proposed and a test apparatus was constructed to perform the rubber cutting experiment. In the test, the friction force and the cutting force were obtained. Through the analysis of the test results, the friction work, the deformation energy, the surface fracture energy in cutting different thickness of the rubber were calculated. This work originally proposed a test method to acquire the friction force, the friction work between the cutter and workpiece during punching process.

Abstract: Based on COMPASS forcefield, the relationship between microstructure and macroscopic properties of poly (propylene-co-γ-butyrolactone carbonate) (PPCG) was firstly investigated with ‘Materials Studio’ simulation soft successfully. The results of simulation showed that the molecular chain of PPCG was flexible. Degradable carbonic and carboxylic ester groups were distributed outside the PPCG cell. Furthermore the structure of micro-phase separation was observed in PPCG cell. The structure of micro-phase separation of PPCG can be applied to the self-assembly of drug molecule.

Abstract: Chemical components of the soil take an important role in the structure stability. It controls the soil structure under the normal water environment such as ordinary temperature, atmospheric pressure, and slowly changing hydro-chemical environment etc. It also has an important influence on the ground subsidence and the formation of soil caves as well as the collapse of dispersive soil. Scanning Electron Microscopy(SEM), CT technology and X diffraction were used to measure the chemical damage of water to the soil structure in the laboratory. Results indicate that under normal water environment, the change of the environmental parameters is not sufficient to cause damage to the internal crystal force of mineral intergranulars and to activate atoms in crystal lattice, which leads some defects and displacement of the crystal lattice. However, it can activate linking substance of clay grains be defined as “soil mini-structure”. As the greatest contributor of soil stability, the mini-structure is the "platform" and main place in which soil stability and instability will develop.