Abstract: The aim of this research was to investigate the effects of longitudinal position (stem height) and heart-sapwood on density, modulus of elasticity (MOE) and modulus of rupture (MOR) in bending for Persian silk wood (Albizzia julibrissin). Five normal trees were selected from the Guilan region, Iran. Samples for testing were prepared at four stem height levels (5%, 25%, 50% and 75% of total stem height) in both positions along radial direction (heartwood and sapwood). Analysis of variance results (Anova) indicated that the effects of longitudinal position (stem height) and heartwood-sapwood on the wood density, MOE and MOR were significant. The mean of wood density, MOE and MOR along longitudinal position from base to top decreased with height. The mean of wood density, MOR and MOE in sapwood are lower compared to the corresponding values for heartwood. The relationship between wood density and mechanical strength properties were analyzed by regression models. A positive correlation was found between wood density with MOE and MOR in both heartwood and sapwood.

Resumen: El objeto de esta onvestigación fue estudiar los efectos de la posición en dirección longitudinal (altura del tronco) y del duramen y la albura sobre la densidad, el módulo de elasticidad (MOE) y el módulo de ruptura (MOR) en flexión para la madera de 'seda' persa (Albizzia julibrissin). Se recolectaron cinco árboles representativos de la región de Guilan, Irán. Se elaboraron especímenes para prueba a cuatro niveles de la altura del árbol (5%, 25%, 50% y 75% de la altura total del tronco) en ambos tipos de madera en la dirección radial (duramen y albura). Los resultados de los análisis de varianza (Andeva) indicaron que los efectos de la ubicación longitudinal (altura del árbol) y duramen y albura sobre la densidad de la madera, el MOE y el MOR fueron significativos. Los valores promedio de la densidad, MOE y MOR a lo largo de la posición longitudinal de la base a la copa disminuyeron con la altura. Los valores promedio de la densidad, MOR y MOE en albura son menores comparados con los del duramen. La relación entre la densidad de la madera y las propiedades mecánicas se analizaron por medio de modelos de regresión. Se encontró una correlación positive entre la densidad de la madera con MOE y MOR tanto en duramen como en albura.

Persian Ironwood (Parrotia persica (DC) CA Meyer) is native species from Iran and covers 10,54% of the commercial volume. Its wood structure and its chemical composition are affected by growth conditions. The aim of the study was to assess the variation of mineral content (Ni, Fe, Cu, Zn, Pb, Cd), wood density and chemical properties (cellulose, lignin, ash and extractive) of ironwood in relation to altitude above sea level (100, 500 and 700 meter) and pith distance within stem (near to pith and bark and middle point). In addition was investigate the relationship between mineral content with oven-dried density and chemical properties. Results showed that Cd, Cu, Fe, Ni and Zn content (except Pb concentration) increased by increasing of altitude and decreased along radial position within stem from the pith to the bark. Lignin, ash and extractive content increased by increasing altitudes from 100 to 700 meter while cellulose decreased. Radial position had not significant impact on the chemical properties. There are significant relationships between mineral content-chemical properties and between mineral content-wood density (except Cu - density). Forward stepwise regression showed that ash and lignin content had important role on the variation of all of mineral content except on Cd.

Recently, the Smoothed Particle Hydrodynamics (SPH) method has been utilized as an effective tool for capturing details of the fluid flows. The Lagrangian nature of the SPH method facilitates the modeling of the free surface flows. In the present article, different numerical features of 3D-SPH are probed to find a set of options that can be used to achieve an accurate numerical simulation of the dam break problem. Several numerical techniques such as time stepping algorithm, filter density and viscosity treatment are considered as compiling options. Twelve sets of mentioned schemes are also chosen and the elevation of free surface flow is captured. The obtained results are compared against the experimental data existing in the literature. Finally, it is concluded that the Symplectic algorithm in conjunction with density filter and SPS turbulence model can be used to achieve the desired accurate numerical results.

Sheet metal bending is one of the most widely applied sheet metal operations. The bending operations present several technical problems in production, such as prediction of spring-back and the punch load. In this paper, the value of the spring-back and bending forces are investigated for a low carbon steel material. Two thicknesses of material (0.95 and 0.75 mm) are applied. Sheet metal components, which are used in the experiments, have oblong holes on their bending surfaces. The influence of the area of the holes, die angles, die widths and punch radius on the value of the spring-back and the bending forces in V-die bending is studied. It is found that all these parameters affect the spring-back and the bending forces, but not in the same way. A new equation is suggested in this paper to predict the bending forces in V-shaped dies for parts with holes on the bending surfaces.