The use of metallic foams as a filler in thin-walled structures can enhance their crashworthiness characteristics. It is believed that, tailoring the properties of the foam filler would enhance the effectiveness of these characteristics. This view is also supported by recent works in the literature. It is the objective of this study to examine the crush behaviour of functionally graded foam-filled tubes and evaluate the effect of discretely graded density upon the specific energy absorbed. Nonlinear parametric finite element simulations of the foam-filled tube were developed to estimate the most favourable foam density gradient in the lateral and axial directions. The effect of various design parameters such as density grading, number of grading layers, and thickness of the interactive layer upon the resulting specific energy absorption was investigated. The results show that the specific energy absorption of a tube filled with functionally graded foam is better than uniform density foam.

The use of metallic foams as a filler in thin-walled structures can enhance their crashworthiness characteristics. It is believed that, tailoring the properties of the foam filler would enhance the effectiveness of these characteristics. This view is also supported by recent works in the literature. It is the objective of this study to examine the crush behaviour of functionally graded foam-filled tubes and evaluate the effect of discretely graded density upon the specific energy absorbed. Nonlinear parametric finite element simulations of the foam-filled tube were developed to estimate the most favourable foam density gradient in the lateral and axial directions. The effect of various design parameters such as density grading, number of grading layers, and thickness of the interactive layer upon the resulting specific energy absorption was investigated. The results show that the specific energy absorption of a tube filled with functionally graded foam is better than uniform density foam.

Consumers often have to wait during the process of acquiring and consuming many products and services. These waiting experiences are typically negative and have been known to affect customers¡¦ overall satisfaction with the product or service. To better manage these waiting experiences, many firms have instituted a variety of programs to reduce the actual duration of the wait. However, consumers are influenced by their perceptions of the waiting duration, not the actual one. Therefore, understanding how consumers perceive their waiting time is particularly important in the marketing of service. In this paper, I use laboratory experiment method and examine the impact of mood, distance to the goal state, and filled mechanism on consumers¡¦ perceptions of waiting time and their affective responses. A total of 206 students recruited at the university participated in the study. The results demonstrate that people in a positive mood tend to perceive shorter duration of the wait than those in a negative mood. Further, the distance to the goal state, i.e. the stage at which the delay occurs during the service encounter, has the impacts on consumers¡¦ time perception and affective responses. The delay produced longer time estimates and stronger affective responses at further from the goal state than at closer to the goal state. And filling time resulted in shorter time perception and less negative emotions. However, the relevance to the service of filled mechanism will not affect consumers¡¦ time estimates but only consumers¡¦ positive affective responses. The distance to the goal and different kind of filled mechanism have an interactive effect only on the time perceptions. Moreover, consumers¡¦ involvements toward service and time style have moderating effects. The higher the involvement, the longer the time estimates and the more negative responses. Qualitative subjects perceived longer waiting time, and quantitative ones have more positive affective responses.

Thesis (Ph. D.)--University of Florida, 1984. / Description based on print version record. Typescript. Vita. Includes bibliographical references.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2003. / Bibliography: leaves 182-188.

Master thesis deals with highly filled particulate composite materials for dental applications. In the practical part, the dimetacrylate matrix was filled with a mixture of particles of different types and different sizes to achieve the maximum possible packing. Moreover, filler content and the influence of filler on composite material was studied. Hydrolytic stability was also tested on composite materials. The methods used to characterize composite materials were bending test, thermogravimetric analysis (TGA), differential scanning photocalorimetry (DPC), dynamic-mechanical analysis (DMA) and scanning electron microscopy (SEM). Curing of the matrix was characterized by the degree of conversion, the heat of polymerization and the polymerization rate. Furthermore the polymerization shrinkage was measured. The glass transition temperature, the dynamic modulus at 40 °C and 100 °C, the modulus of elasticity, the strength, the critical value of the stress factor and the critical energy release rate were found in the tested samples.

No description available.

Yes / This paper presents the behaviour of circular concrete-filled double-skin steel tubular (CFDST) stub columns compressed under concentric axial loads. To predict the performance of such columns, a finite element analysis is conducted. Herein, for the accurate modelling of the double-skin specimens, the identification of suitable material properties for both the concrete infill and steel tubes is crucial. The applied methodology is validated through comparisons of the results obtained from the finite element analysis with those from past experiments. Aiming to examine the effect of various diameter-to-thickness (D/t) ratios, concrete cube strengths and steel yield strengths on the overall behaviour and ultimate resistance of the double-skin columns, a total of twenty-five models are created to conduct the parametric study. In addition, four circular concrete-filled steel tubes (CFST) are included to check the dissimilarities, in terms of their behaviour and weight, when compared with identical double-skin tubes. A new formula based on Eurocode 4 is proposed to evaluate the strength of the double-skin specimens. Based on the comparison between the results derived from the analysis, the proposed formulae for the concrete filled double-skin would appear to be satisfactory.

<p>The laminar natural convection in air-filled rectangular cavities with and without a partition on the wall was experimentally investigated. Temperature measurements and flow visualizations were performed for cases with heated and cooled vertical walls (corresponding to global Grashof numbers GrH of approximately 1.4 x 10^8 to 1.8 x 10^8) and non-dimensional top wall temperatures θT of 0.52 (insulated) to 2.3. In the rectangular cavities without the partition and with aspect ratios of 0.5, 1.0 and 2.0, the heated top wall caused the natural convection boundary layer flow to separate from either the top wall (for the cases with Or ;S 1.2) or the heated vertical wall (for the cases with θT >~ 1.2) due to the negative buoyancy force. For the cases with θT >~ 1.2, there is an anti-clockwise recirculating flow in the upper left corner region. The extent of the recirculating flow decreased with an increase of the aspect ratio. The temperature gradient in the core region, dθ∞ /d(y/H), increased with an increase of θT. For a given aspect ratio, dθ∞/d(y/H) changed more rapidly with the change in θT for the cases with θT <~ 1.2 compared to the cases with θT >~ 1.2. The increase in dθ∞/ d(y/H) was more significant for the smaller aspect ratio cavity. The temperature profiles predicted from the similarity solutions proposed by Kulkarni et al. [1] and from the non-similarity model developed by Chen and Eichhorn [2] for natural convection on an isothermal vertical wall in a stratified environment were compared to the measurements in the current cases. These models were not able to accurately describe the characteristics of the natural convection flow in the rectangular cavities.</p> <p>An aluminium partition with non-dimensional heights Hp/H of 0.0625 and 0.125 was attached either to the heated vertical wall or top wall at y/H = 0.65, 0.95 and x/H = 0.1, 0.2, 0.4 and 0.6 to study the effect of the partition on the laminar natural convection flow in a square cavity. The blockage and thermal effects of the partition resulted in changes in the temperature and flow fields, but were mainly limited in the vicinity of the partition. The effect of the partition changed with the height and location of the partition. When the partition was attached to the heated top wall, a recirculating flow was formed between the partition and the heated vertical wall. For a given partition height, the structure of this recirculating flow was dependent on the partition location and θT. A thermal boundary layer developed along the rear surface of the partition due to the thermal effect of the partition. The ambient temperature outside the boundary layer and Nu near the corner region were affected by the partition height due to the changes in the recirculating flow and the rear surface of the partition.</p> / Thesis / Doctor of Philosophy (PhD)

No / This paper presents the buckling behaviour and design of axially loaded concrete filled steel elliptical hollow sections. The experimental investigation was conducted using normal and high strength concrete of 30, 60 and 100 MPa. The current study includes both the stub and slender column tests. Based on the existing design guidance in Eurocode 4 for composite columns, the proposed design equations were found to provide an accurate and consistent prediction of the cross section and buckling capacity of the composite concrete filled steel elliptical hollow sections in axial compression.