Advanced Materials Research Vols. 217-218

Abstract: In this work, two SAE 52100 grades with different oxygen contents were repeatedly quenched and the influence of this cyclic heat treatment as well as the role of the oxygen content level on the mechanical properties of the material were investigated by rolling contact fatigue tests. The repeated quenching process increased the retained austenite content and had little influence on the material’s hardness. The prior austenite grain size was decreased and consequently, refinement of the martensitic phase in both types of materials occurred. The higher content of the retained austenite (higher fracture toughness) and the refinement of the microstructure accounted for the higher fatigue properties of the repeatedly quenched material. Flaking failure was present in the material quenched only once, after 4.3x107 cycles (higher oxygen content) and 108 cycles (lower oxygen content). Flaking failure did not occur in the samples treated by repeated quenching. The results show the importance of both optimized heat treatment and alloy cleanness for the lifetime of bearing steel.

Abstract: The influence of gas nitriding of commercial pure titanium and Ti-6Al-4V (Ti64) alloy by using a Q-sw laser on the wear loss during rolling contact fatigue is investigated. Despite very good biocompatibility, high strength to weight ratio and corrosion resistance, the tribological properties of titanium alloys are inferior to those of other metal alloys, such as steel. Fretting and wear related aspects become important issues when titanium alloys are used in rolling contact applications. Titanium bearings are employed in applications requiring high strength, light weight, and minimum maintenance (for example, aerospace and defense industries). In this work, a Q-sw laser was used to coat pure commercial titanium and Ti-6Al-4V bearings with TiN in a closed chamber in nitrogen atmosphere. The samples were tested under water by using a thrust-type rolling contact fatigue machine. The microstructure, morphology and crystallographic texture of the layers were observed by laser confocal microscope, scanning electron microscope and electron backscatter diffraction (EBSD). By optimizing the laser processing parameters, such as laser scanning speed, power and beam diameter, thin TiN coats of 1 to 3 m were produced. The wear loss of the coated samples was at least ten times lower than that of the uncoated bearings.

Abstract: A secure multi-party computation problem deals with computing a function on any input, in a distributed network, ensuring that no more information is revealed to a player in the computation. New protocols are developed for the following interesting variation on a typical problem of secure multi-party computation: Given secrets shared among a group of players, compute the function value of basic computations, such as interpolation, addition, multiplication or inversion, in the exponent. The protocols can be proven robust and secure in standard computation models.

Abstract: Base on the finite element method, the effect of interface damage on macroscopic constitutive behavior of composite materials subjected to uniaxial tension was studied. A bilinear cohesive law, which relates the traction and displacement jumps, was adopted to model the debonding of particle/matrix interface. Stress-strain curves for a material with different interface properties, particle size and volume fraction were discussed in detail. The results show that the damage due to debonding of particle/matrix interfaces can significantly affect the macroscopic response of composite materials, and that the interaction of particles is innegligible in multi-particle structure.

Abstract: An ideal bone graft material should have osteocondutive, osteroindurctive, and osteogenic features. Scientists and doctors have been trying to develop this kind of material for over one century. However, all the features of few materials used in clinic now have been qualified. Recently, COLLOSS, as the new generation bone graft material of demineralized bone matrix, almost achieved this height. The paper presents a general survey of COLLOSS including its extraction processes, biological characteristics, and application prospects.

Abstract: The existences of traditional water propulsion promote low efficiency. Used by biological propulsion, after the last million years of evolution, the maximum utilization of its power, the best way. Bionic propulsion system designed in this paper consists of two large travel umbrella wing plate in reciprocating linear travel agencies, led by the reciprocating motion along the vertical, in the water under the influence of backward movement of the wing disk automatically open, resulting in the pull forward, the forward movement of the wing disk automatically shut down to reduce water resistance. This paper designs a bionic propulsion and efficiency measurement tests carried out.

Abstract: With elaborating the research evolvement of equipment support resource verification, this paper demonstrated the significance of operational mission to this research. It decomposed Equipment Support System (ESS) into three subsystems: operational mission system, support object system and support resources system. According to the theories of Integrated Logistics Support, the overall parameter model was established to depict the relationship and impact mechanism of ESS’s components. Focusing on the key parameter: mean logistic delay time (MLDT), this paper proposed a transformation model to convert operational mission requirements to equipment support requirements.Transformation model can predict and ascertain all support resources needed to accomplish operational mission scientifically.

Abstract: Considering the requirement of testing on ship powering performance, and the actual situation of the towing tank, a system, which contains the testing module of resistance performance, propeller on open water, self-propulsion and calibration, was designed. And a system software used for measuring ,controlling and analyzing date was written as well. Every modules’ main functions, test requirements and the realization forms were also put forward in this paper. Considering it not only meets the need of the model test mentioned already, but also fits the function expanding in the future, this system was designed to be modularized and scalable. I hope that it could give technical support to the researchers in ship performance and ship construction enterprises.

Abstract: In this paper an improved algorithm of BP neural network --- Levenberg-Marquardt (LM) algorithm is introduced, and the simulation predictions of oilfield cementing quality is done by using this method. Finally, a practical example verified the feasibility of the presented method.

Abstract: This paper presents a method to calibrate pipe friction factor in oilfield water injection pipeline based on genetic algorithm. For the shortcoming, of basic genetic algorithms, genetic algorithm is made the corresponding improvements, this algorithm is improved global searching capability. Finally, a practical example verified the feasibility of the presented method.