An analytical method for selecting the optimal nozzle external geometry for fluid dynamic gauging

Fluid dynamic gauging (FDG) was developed to measure, in situ and in real time, the thickness of a soft deposit layer immersed in a liquid without contacting the surface of the layer. An analysis based on the lubrication assumption for the flow patterns in the space between the nozzle and the surface being gauged yielded analytical expressions for the relationships between the main flow variables and system parameters. Nozzle shapes for particular pressure, pressure gradient and shear stress profiles could then be identified. The effect of flow rate, nozzle geometry and nozzle position on the pressure beneath the nozzle and shear stress on the gauged surface showed very good agreement with computational fluid dynamics (CFD) simulations. Case studies presented include nozzle shapes for uniform pressure and shear stress profiles, which are useful for measuring the strength of soft deposit layers.     

Development of a qualitative test method for the cleanability of polymer woven filter media

In this paper a new method for cleaning of filter media is presented, and the cleanability with different textures and surface finishes is compared. With the method described, it is possible to evaluate the quality of the cleaning process. According to the German VDMA standard cleaning test, riboflavin and malt extract are applied as model contaminants for evaluation of the cleaning results. To compare the cleanability of filter media with different properties and geometries the results are adapted to the law of mass transfer and to the Sherwood number, a dimensionless parameter describing the quality of a cleaning process.     

Adherence of elastomers: Fracture mechanics aspects

Application of fracture mechanics concepts to adherence of elastic and viscoelastic solids is examined. It is shown that the Dugdale-Barenblatt model could be applied both for explaining the transition from Johnson-Kendall-Roberts to Deryagin-Muller-Toporov solution in adherence of spheres, and for liquid bridges. The problem of the threshold energy release rate G₀ for elastomers is considered. It is proposed to add to the viscoelastic losses a supplementary friction term when polymeric chains strongly held at the interface by primary bonds are pulled out.     

WHEN LESS IS MORE: EXPERIMENTAL EVIDENCE FOR TENACITY ENHANCEMENT BY DIVISION OF CONTACT AREA

Most recent data on hairy systems demonstrated their excellent adhesion and high reliability of contact. In contrast to smooth systems, some hairy systems seem to operate with dry adhesion and do not require supplementary fluids in the contact area. Contacting surfaces in such devices are subdivided into patterns of micro- or nanostructures with a high aspect ratio (setae, hairs, pins). The size of single points gets smaller and their density gets higher as the body mass increases. Previous authors explained this general trend by applying the JKR theory, according to which splitting up the contact into finer subcontacts increases adhesion. Fundamental importance of contact splitting for adhesion on smooth and rough substrata has been previously explained by a very small effective elastic modulus of the fibre array. This article provides the first experimental evidence of adhesion enhancement by division of contact area. A patterned surface made out of polyvinylsiloxane (PVS) has significantly higher adhesion on a glass surface than a smooth sample made out of the same material. This effect is even more pronounced on curved substrata. An additional advantage of patterned surfaces is the reliability of contact on various surface profiles and the increased tolerance to defects of individual contacts.     

具有溶解气影响的油井不稳定IPR理论曲线的几种计算方法及对比

以不稳定渗爱理论为基础，结合Ｓｔａｎｄｉｎｇ、Ｈａｒｒｉｓｏｎ、Ｋｌｉａｓ等方法给出了无质、双孔、复合油藏等多种模型的不稳定ＩＰＲ曲线及定流压条件下的油井产量计算方法。通过３口井实际资料对比分析，认为不稳定渗透理论与Ｋｌｉａｓ方法结合计算的理论产量与实际产量吻合程度较高，适用范围广，而Ｓｔａｎｄｉｎｇ、Ｈａｒｒｉｓｏｎ方法在表皮系数较大或流压值较高的井中应用效果好。     

3D/2D hybrid model for ribbon impellers operating in laminar regime

In the study a 3D/2D hybrid model for ribbon mixers, for a laminar range of mixing was verified. Distributions of the experimental and model values of velocity components and the experimental and model values of mixing power for this type of mixers were compared. Further on, based on the model solutions the optimum parameters of ribbon agitators due to the time of homogenization were established.     

Modelling and fatigue life assessment of complex structures

This paper presents some of the motivations and main conclusions from a series of joint Nordic research initiatives in which an integrated research approach to the development of future generations of advanced fabricated structures have been employed. The integrated research approach includes coordinated efforts in several key technologies: high‐speed welding processes, high strength materials, cost‐effective NDE, post‐weld treatments and FE‐based design assessment tools. Traditionally, fatigue assessment methods for welded structures have been developed based on small‐scale test specimens and verification studies for large structures are rarely published. Applications on complex structures have led to several new assessment concepts and areas for future work. A modified structural stress method that proposes a multi‐linear stress distribution through the plate thickness is introduced. Also, a crack growth assessment method in which the constraint equations of a sub‐model are linked to the global model is presented. Both these new methods are promising for complex structures. The crucial role of boundary conditions for complex structures is highlighted as is the future challenge of understanding and making use of the residual stress state for welded structures.     

3D adaptive finite element modeling of non-planar curved crack growth using the weighted superconvergent patch recovery method

In this paper, an adaptive finite element analysis is presented for 3D modeling of non-planar curved crack growth. The fracture mechanical evaluation is performed based on a general technique for non-planar curved cracks. The Schollmann’s crack kinking criterion is used for the process of crack propagation in 3D problems. The Zienkiewicz-Zhu error estimator is employed in conjunction with a weighted SPR technique at each patch to improve the accuracy of error estimation. Applying the proposed technique to 3D non-planar curved crack growth problems shows significant improvements particularly at the boundaries and near crack tip regions. Several numerical examples are presented to illustrate the robustness of the proposed technique.     

机织人工气管的性能分析

采用多层和多重结构设计思路,研制出一种纬二重结构机织人工气管.通过径向压缩、径向拉伸等力学性能测试,并以针织人工气管为参照,分析机织人工气管的特性,为进一步试验应用莫定基础.     

杨庄煤矿煤物理力学性质研究与相关性分析

系统地测试了杨庄煤矿 5、6煤层煤岩物理力学性质指标 ,详细地分析了煤的物理力学性质特征 ,探讨了各指标之间的相关关系 ,揭示了它们之间的内在联系 ,为煤矿设计提供了科学依据