Use of Impact Penetrometer to Determine Changes in Soil Compactness After Entracon Sioux EH30 Timber Harvesting

Wood harvesting with the use of wheeled harvesters is now common in Polish and Czech forests. While moving in the forest, the wheels of these machines affect the forest soil and the extent of this impact is interesting. The paper presents the results of measurements of the changes that occur in the soil on the operational trails after the timber harvesting using the Entracon Sioux EH30 thinning harvester. The measurements were taken on fragments of three operational trails, in and between the ruts and at a distance of 1.0 m off the trail. An impact penetrometer was used to measure the penetration resistance, soil samples were collected to determine the bulk density and moisture content, and soil deformations on the trail were measured with a profile meter. Unit pressures exerted by harvester wheels on the ground were determined. It was shown that in the places where the harvester wheels pass, even of a small weight (5.73 tons, 8 wheels) and with unit pressures of the wheels on the ground <50 kPa, changes in soil parameters occurred. A statistically significant increase in penetration resistance in relation to the control occurred at a depth of up to 35 cm, while at a depth of up to 5 cm the increase was more than 2-fold. There was also a slight decrease in soil moisture content (up to 7.9%) and an increase (up to 8.4%) in bulk density in the ruts, while rut depths were small and reached 4 cm. As it was shown, the impact penetrometer, simple in design, which was assumed to be used for measurements, and which is not used in this type of research in forestry, despite its limitations, can be used to determine the compactness of the soil and its changes resulting from machine work

Strain Rate Contribution due to Dynamic Recovery of Ultrafine-Grained Cu−Zr as Evidenced by Load Reductions during Quasi-Stationary Deformation at 0.5 Tm

During quasi-stationary tensile deformation of ultrafine-grained Cu-0.2 mass%Zr at 673 K and a deformation rate of about 10−4 s−1 load changes were performed. Reductions of relative load by more than about 25% initiate anelastic back flow. Subsequently, the creep rate turns positive again and goes through a relative maximum. This is interpreted by a strain rate component ϵ˙− associated with dynamic recovery of dislocations. Back extrapolation indicates that ϵ˙− contributes the same fraction of (20±10)% to the quasi-stationary strain rate that has been reported for coarse-grained materials with high fraction of low-angle boundaries; this suggests that dynamic recovery of dislocations is generally mediated by boundaries. The influence of anelastic back flow on ϵ˙− is discussed. Comparison of ϵ˙− to the quasi-stationary rate points to enhancement of dynamic recovery by internal stresses. Subtraction of ϵ˙− from the total rate yields the rate component ϵ˙+ related with generation and storage of dislocations; its activation volume is in the order expected from the classical theory of thermal glide

Quasi-Stationary Strength of ECAP-Processed Cu-Zr at 0.5 Tm

The influence of the grain structure on the tensile deformation strength is studied for precipitation-strengthened Cu-0.2%Zr at 673K. Subgrains and grains are formed by equal channel angular pressing (ECAP) and annealing. The fraction of high-angle boundaries increases with prestrain. Subgrains and grains coarsen during deformation. This leads to softening in the quasi-stationary state. The initial quasi-stationary state of severely predeformed, ultrafine-grained material exhibits relatively high rate-sensitivity at relatively high stresses. This is interpreted as a result of the stress dependences of the quasi-stationary subgrain size and the volume fraction of subgrain-free grains

Quantitative Assessment of Retinal Vessels in Relation to Blood Pressure

In a random sample of 91 middle-aged men the retinal vascular pattern was quantitatively assessed by an unconventional method. Great variability of retinal vessels was found even between left and right eye in the same individual. Subjects having higher body mass and higher systolic blood pressure showed a tendency towards a greater average length of retinal vessels than ones with lower values. Among the variables the effect of increased systolic blood pressure proved to be significant for the elongation of retinal vessels

Quasi-Stationary Strength of ECAP-Processed Cu-Zr at 0.5 Tm

The influence of the grain structure on the tensile deformation strength is studied for precipitation-strengthened Cu-0.2%Zr at 673K. Subgrains and grains are formed by equal channel angular pressing (ECAP) and annealing. The fraction of high-angle boundaries increases with prestrain. Subgrains and grains coarsen during deformation. This leads to softening in the quasi-stationary state. The initial quasi-stationary state of severely predeformed, ultrafine-grained material exhibits relatively high rate-sensitivity at relatively high stresses. This is interpreted as a result of the stress dependences of the quasi-stationary subgrain size and the volume fraction of subgrain-free grains