Advanced Materials Research Vols. 472-475

Abstract: Fabrication of nanofibres has become a growing area of research because of their unique properties (i.e. smaller fibre diameter and higher surface area) and potential applications in various fields such as filtration, composites and biomedical applications. Although several processes exist for fabrication of nanofibres, electrospinning is considered to be the simplest. Most of the research in electrospinning is based on solution rather than melt. The feasibility of fabricating nanofibres of polypropylene (PP) by meltblowing and melt electrospinning has been investigated in this paper. In meltblowing different fluids such as air and water were fed at different inlets along the extrusion barrel for the fabrication of nanofibres whereas in melt electrospinning it was achieved by using different additives. The results obtained by using water in meltblowing were better with respect to the morphology and fibre uniformity compared to air. In melt electrospinning although all the additives (i.e. sodium oleate (SO), polyethylene glycol (PEG) and polydimethyl siloxane (PDMS)) helped in reducing the fibre diameter, only SO was effective to reduce the diameter down to nanoscale. It was concluded that both the solvent-free processes have the potential to substantially increase the production of nanofibres compared to solution electrospinning.

Abstract: Undercuts often exists in the surface at weld toe. Undercuts affects the capability of weld subjected to dynamic loading greatly and fatigue cracks usually initiate from these zones with undercuts. Combining with low-alloy middle strength steel 16Mn，study of increasing the fatigue strength and the fatigue life was carried out. Compared with specimen without defects, the fatigue strength of specimen with undercuts has been increased by 10~20%. Study also shows that comparing with as-welded specimen with defects, with TIG dressing treatment, fatigue strength of cruciform weld joint of steel 16Mn has been increased by 70%, fatigue life by 5~8 times. Compared with as-welded specimen without defects, fatigue strength has been increased by 34%, fatigue life by 3~4 times. Undercuts have no adverse effects on fatigue property of welded joints under TIG dressing.

Abstract: For the duplex stainless steel 2205 used to make into chemical ships in shipyards，TIG welding is used for the welding test of duplex stainless steel 2205. Residual stress on 2 mm thick welding specimen is tested with the slot-cuting method,and the distribution of longitudinal residual stress along weld cross-section has been found. Orthogonal test methods are also used in this paper to optimize welding parameters.

Abstract: Fe-Co based diamond-reinforced composites (D-MMCs) and diamond+SiC-reinforced composites (D+SiC-MMCs) were produced by cold pressing method. Investigation of the wear behaviors on two-body abrasive wear behavior of the composites were carried out under different conditions. 2k factorial designs of experiments were used to obtain the data in a controlled way. The wear parameters studied were sliding speed, load and sliding distance. An orthogonal array and analysis of variance (ANOVA) were employed to investigate the influence of process parameters on the wear resistance of these composites. The results indicated that the incorporation of SiC particles in the metal matrix as a secondary reinforcement increased the wear resistance. In addition to this, the applied load had the significant effect on the weight loss of both types of composites. Furthermore, a correlation was derived from the results of the experimental design by multiple regressions. Finally, confirmation of experiment was conducted to verify the predicted model.

Abstract: In metrology, a measurement process without uncertainty evaluation is incomplete. The same applies to nanoroughness metrology. In this paper, Scanning Electron Microscopy (SEM） measurement uncertainty of nanoroughness is studied based on ISO Geometric Product Specification and Verification (GPS). The uncertainty propagation model of SEM-based nanoroughness measurement is presented. The evaluation model of SEM-based standard measurement uncertainty is conducted. As a case study, the line edge roughness uncertainty produced by the JSM-6700F SEM is evaluated.

Abstract: The Titanium silicalite-1 (TS-1)/cordierite monolithic catalysts prepared by wash coating-method were investigated by means of experiments in which we discussed the effects of TS-1 mass fraction in slurry, coating times and solvent viscosity on loading amount and adhesiveness. The results of cyclohexanone ammonization in self-made recirculating reactor showed that the activity and stability of TS-1 monolithic catalysts supported on cordierite honeycomb were better than traditional TS-1 powder in slurry reactor.

Abstract: The threshold limit value of Takeya’s item relational structure theory is a fixed value, which is lacking of statistical meaning, in our previous paper, an improved threshold limit value by using the empirical distribution critical value was proposed, it was showed that the new theory is more sensitive and effective than the old one. However, for constructing the item relational structure, both of them can only be used for dichotomous items, not for polytomous items. In this paper, the empirical distribution critical value based polytomous item relational structure theory is proposed, it is a generalization of our previously improved theory. A calculus example was also provided in this paper to illustrate the advantages of the proposed method.

Abstract: Due to the increasing advancement in technology and limited resources as well as environment being polluted at the same time, the natural solar energy, which has the advantage of environmental protection and being the newly developed approach, will become the rushing field of study around the world in order to implement energy efficiency and reduce carbon pollution. In the meantime, the solar industry technology and new product development have become the considerations to the survival and competitiveness of enterprises. In this study, literature review and expert interviews are utilized to obtain five major key dimensions and 19 subordinate criteria regarding new product development. The Interpretive Structural Model (ISM) is employed to obtain the dimension-dimension and criterion-criterion dependence relationship, and used the Fuzzy Analytic Network Process (Fuzzy ANP) to determine the top priority weight for assessment improvement in the new product development solutions of the enterprises.

Abstract: One of the ways for determination of flow curves is the application of a ring test. Using this method, friction in the interface between the die and the specimen leads to a bulging of the sample and thereby to an inhomogeneous stress and strain state. The calculation of the flow stress from experimentally determined force–displacement curves implies a uniaxial stress state, but this will produce an error because of the above-mentioned bulging, when friction occurs. One method of avoiding these sources of error is to use the sigmoid curves, but the sigmoid curves are varied by the change of temperature and strain rate. Calculations of numerical sigmoid curves were done by the use of an iterative procedure, applying a corrective function. The paper presents a complete investigation of the AZ41 magnesium alloy sigmoid curves at temperature ranging between 473 K and 513 K and strain rates ranging between 0.025 s-1 and 0.00025 s-1 . Ring tests are used to determine the numerical sigmoid curves sensitivity to temperature and strain rate.

Abstract: Mathematical model of heat source in rotating arc welding (RAW) process was developed for investigating the heat and temperature distribution. The effect of rotating parameters on the temperature field in complex welding motion trajectory was studied. In this work, a transient three-dimensional (3D) model was established and computed by a finite element analysis computer program MARC as well as its subroutine. Comparing with non-rotating arc (NRAW) process, the width of temperature distribution enlarges, and the peak temperature of weld pool decreases. The effect of the rotating arc process becomes more and more significant with the increasing of rotating radius. In the weld center, the peak temperature increases with the rotating frequency. But in peripheral region of the weld, when rotating frequency is lower than 10 Hz, the peak temperature increases firstly and then decreases with the increasing of the rotating frequency. It is contradictory with the traditional view. Good agreement is shown between the computed results and experimental results of thermal circle in rotating arc welding process.