Advanced Materials Research Vols. 538-541

Abstract: In order to study effects of geometric parameters in fracture test, this paper used 3D modeling software Solidworks and finite element analysis software Deform to simulate the fracture process of rocket shear pin and study the effects on shear test while various geometric parameters change in the assembly of fixtures and shear pins. According the results we improved the fixtures of shear test. The new fixtures were used in the rocket shear pin fracture test.

Abstract: Inorganic polymer concrete（IPC） is a new building material, since it has abundant raw materials, inexpensive, and has little pollution to environment during its manufacturing process and needs little time to condense to high strength; these have caused the domestic and foreign material researchers of great interest. The flexural failure process of inorganic polymer concrete beam was studied based on the mechanical test, study the stiffness of inorganic polymer concrete beam,and fractal analysis were done of the crack pictures getting during the test process by using MATLAB program and the results show that: the tenacity of inorganic polymer concrete beam is better than portland cement concrete beam,the crack development of inorganic polymer concrete beam has fractal feature; The relationship between box dimension and deflection of the beam is analyzed and the quantitative relation curves of them were fitted.

Abstract: Fatigue damage degree of crankshaft remanufacturing core was studied based on Metal Magnetic Memory Testing. Bending fatigue test of crankshaft remanufacturing core was conducted on the resonant fatigue test rig and variations of two-dimensional magnetic memory signal distribution in crankshaft pin fillets were studied at different bending fatigue cycle. Experimental research shows that distributions of Hp(x) signals, namely, tangential component of spontaneous stray field and Hp(y) signals, namely, normal component of spontaneous stray field in crankshaft pin fillets have no obvious change with loading cycle when no crack initiation and propagation occur in crankshaft pin fillets. Characteristics of Hp(x) and Hp(y) signal both show dynamic variations when crack in crankshaft pin fillets initiates and extends at medium rate or high rate. Metal Magnetic Memory Testing is a dynamic method for monitoring fatigue crack propagation in crankshaft.

Abstract: The toughness of powder metal (PM) steel is always inferior due to the presence of pores. An alloying element is typically found to improve the tensile strength, while sacrificing toughness. These issues prohibit the development of high-strength PM steels with satisfactory toughness. To formulate high-strength PM steels with superior toughness, the effects of Cr and Mo on the impact toughness and fracture behaviors of Ni-containing PM steels were investigated. The results indicated that both 1.5wt% Cr and 1.5 wt% Mo additives can improve the microstructures and tensile strengths of Ni-containing PM steels. However, while 1.5 wt % Mo apparently impairs the toughness, 1.5 wt % Cr does not. The addition of 1.5 wt% Cr results in the formation of Ni-rich martensite, which is strong and tough, thereby improving the tensile strength by 150% without sacrificing toughness.

Abstract: The effects of Ce on the inclusions and the high temperature mechanical properties of 2Cr13 stainless steel were studied. The results show that the morphologies and sizes of inclusions in 2Cr13 stainless steel are changed, and Ce played a very good role of modifying inclusions. The high temperature strength of 2Cr13 stainless steel is improved obviously by Ce. In comparison with 2Cr13 stainless steel without Ce, the high temperature strength of 2Cr13 stainless steel with Ce is increased 18.18% at 1273K, respectively.

Abstract: The flow behavior of 2205 duplex stainless steel for ship sheet in the strain rate ranging from 0.001 s-1 to 0.1s-1 and temperature ranging from 473K to 1073 K is studied on AG-10TA universal material testing machine. The results show that the 2205 duplex stainless steel is a strain rate sensitive material, and the flow stress increases with the increase of strain rate and decreases with the increase of temperature. The average elongation of the 2205 duplex stainless steel is above 25% with the temperature ranging from 473K-873K, and the elongation is above 47% at 1073K; At last, the flow stress constitutive equation is established based on the Browman model, which describes the flow stress behavior of 2205 duplex stainless steel in the temperature ranging from 473K-873K. The curves predicted by the constitutive equation agreement with the experiment data well.

Abstract: Four types of Cu sheets, with average grain sizes of 200 nm, 90 nm, 33 nm and 11 nm respectively, were electrodeposited and tested by tension at both high and low strain rate. Typically, a higher strength with lower tensile ductility was obtained by increasing the strain rate or reducing the grain size till 33 nm. An inverse Hall-Petch result was found in 11 nm Cu, while 200 nm Cu exhibited an increase of both strength and plastic strain by the increment of strain rate. Tensile deformation mechanisms of the Cu sheets were also discussed with their microstructural features.

Abstract: The mechanical properties of a new-invented CrMnNiMo steel tempered at 200°C~650°C were studied. The results show that mechanical properties are affected by tempering temperature severely. Strengths drop rapidly with increasing tempering temperature, concomitant with gradually rise of elongation and reduction in area. Yet impact energy decreases stepwisely, reaching minimum value at around 450°C and then ascends fast. Comparatively, optimum mechanical properties are reached at about 550°C. Fracture surface of impact specimen, dominated by dimples with different sizes, shows failure by microvoid coalenscence. Large amounts of complex inclusions, mainly Rare Earth-oxysulfides and aluminum oxides, sphericity or ellipsoid with dimension less than 10μm, are observed, which have little influence on mechanical properties.

Abstract: Activated carbon fiber reinforced composites is a kind of new material in ceaseless development which is receiving more and more attention because of its excellent absorption and mechanical properties. This article mainly studies the influence of polyacrylonitrile based activated carbon fibers on the mechanical properties of medium density fiberboard (MDF); add the static bending strength and internal bonding strength (IB) of medium density fiberboard in the PAN-ACF through comparison test and get the result of the influence of polyacrylonitrile based activated carbon fibers on medium density fiberboard.

Abstract: The simulation of the delamination process in composite structures made from carbon fiber-reinforced polyetheretherketone (PEEK) is quite complex and requires advanced finite element modeling techniques. Failure analysis tools must be able to predict initiation, size and propagation of delamination process. The objective of the paper is to present modeling technique which is able to predict a delamination in a double-cantilever-beam (DCB) test. The approach is to use a fracture mechanics criterion, but to avoid the complex moving mesh technique. The modeling technique using coarse mesh adopts higher-order approximation (p-level=8) based on Lobatto shape functions. For fracture analysis, also, virtual crack closure technique (VCCT) is considered. Using moving nodal modes, the delamination analysis is implemented and then the performance of present analysis is demonstrated by comparing with the results of references.