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Baobab size class distributions were surveyed in the Limpopo National Park (LNP), Mozambique, and the Kruger National Park (KNP), South Africa. There are very few elephants in the LNP and the baobab population there had a reverse J-shaped size class distribution with many small baobabs. In contrast, the elephant-impacted baobab population of KNP displayed a mono-modal size-class distribution, with a lack in recruitment. Within KNP, elephant impact (percentage bark stripped up to the height of 3 m) decreased with increasing rockiness and slope steepness. We interpret this to suggest that steep rocky slopes are inaccessible to elephants and therefore these sites may act as a refuge for baobabs. In such inaccessible areas, the baobab population has a similar size-class distribution to that of the populations in the LNP. However, these baobab refugia are restricted in the northern KNP landscape and are therefore probably not large enough to sustain a viable baobab population. [ABSTRACT FROM AUTHOR]

The strength and deformation behavior of an Fe-Mn-Al-Ni shape memory alloy at different strain rates was studied. Furthermore, the effect of grain size was investigated. To this end, a batch with bamboo-like grain arrangement and a batch with smaller, nevertheless coarse, grains were analyzed. Tensile tests at quasi-static, intermediate, and dynamic loading rates were performed. Digital image correlation and microstructural analysis revealed the localized deformation and phase transformation in favorable oriented grains. At higher strain rates, a increased number of orientations was activated for the phase transformation. A higher strain rate resulted in an increased strength for the coarse-grained material while the bamboo-like material did not show this effect. The analysis of fracture surfaces revealed ductile fracture and cleavage fracture for all strain rates.

In this study, the effect of non-metallic inclusions on the material behavior of 42CrMo4 was investigated. By adding aluminum oxide particles to steel powder, different inclusion contents were simulated. The mechanical and fracture toughness properties were measured under dynamic loading. The damage was examined using the acoustic emissions. With an increasing inclusion content, a decreasing strength, deformability and fracture toughness were observed. The distribution of the inclusions along the surfaces of the prior steel particles lead to small distances between inclusions and favors the initiation of cracks at low stress. The early appearance of material damage was proven by acoustic emissions.

Examines performance, environment, and subjectivity in Theatre of the Homeless. Theater versus environment; Living Theatre's 1989 street action; Processions and `subsectors' dealing with fundamental survival issues; Living Theatre's site-specific spectators; Performance for the performers; Details.

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As the mechanical properties of honeycomb structures are influenced by several parameters, detailed analysis is necessary before their potential application in transportation industry components. Previous Finite Element Model (FEM)-based numerical analysis demonstrated that variation in cell geometry affects the achievable strength level and, thus, the energy absorption capability. According to this FEM study, the Kagome geometry – an ordered sequence of hexagons and triangles – exhibits properties that are particularly promising when compared to the square-celled structures investigated to date. When the load is applied parallel to the channel axis (the out-of-plane direction), the increment of strength is comparatively low, whereas in the in-plane direction (loading orthogonal to the channel axis), the dissipated specific energy can reach almost double that of the square-celled structure. In this study, the results of static and dynamic compression tests – performed in the out-of-plane and in-plane modes – are presented to examine the influence of strain rate and loading direction on the characteristic deformation stages of squarecelled and Kagome structures. Particular attention is paid to deformation induced martensite formation in the cell wall material, indicating the TRansformation Induced Plasticity (TRIP) effect as a function of applied cell geometry, strain rate and loading direction.

Abstract. The focus of this study is on the deformation mechanisms of high-alloy cast austenitic TRIP/TWIP steel with the nominal composition Fe-16Cr-6Mn-6Ni. Due to its chemical composition, the material exhibits a low stacking-fault energy of 17.5 mJ/m2 which facilitates the formation of the deformation-induced γ (fcc) → ε (hep) → α’ (bcc) transformation. Consequently, the steel exhibits a tensile strength of 800 MPa with fracture elongation of 55 % under quasi-static loading. The experiments presented demonstrate the response of this steel to flyer-plate impact (FPI) at room temperature using two different test setups. In the first setup, laser interferometry measurements of the sample free surface were used for determination of the dynamic mechanical properties (Hugoniot elastic limit / HEL. spall strength) after impact with aluminium plates accelerated up to 650 m/s. In the second setup, an experimental shock testing device developed at the Freiberg High-Pressure Research Centre was used for impacting large cylindrical samples without the occurrence of spallation. Subsequently, microstructural investigations were carried out by scanning electron microscopy (SEM) and transmission election microscopy (TEM) in combination with diffraction techniques and magnetic martensite measurements. Their results facilitate the representation of a complete image of deformation mechanisms during shock wave loading.

Dynamic crack initiation with crack tip loading rates K˙ of approximately 2 ‧ 106 MPa√ms− in high-strength 42CrMo4 steel was investigated. To this end, a recently developed split Hopkinson pressure bar with four-point bending was utilized. V-notched and precracked Charpy specimens were tested. The tests were performed at temperatures of –40 °C and 20 °C. The loading of the specimen was determined by analyzing the strain in the incident and transmission bars. Furthermore, strain gauges at the specimen’s surface were applied to measure the crack tip loading. High-speed photography complemented the analysis of the specimens loading and the detection of the crack initiation. Fracture surface analysis by means of scanning electron microscopy enabled the measurement of the fracture surface topography and, consequently, stretch zone height and width. Hence, the macroscopically measured dynamic crack initiation toughness was correlated with the toughness at microscopic scale. It was observed that the resistance against dynamic crack initiation decreased with decreasing temperature. Microscopically, a decrease in toughness was analogously observed. Non-metallic inclusions resulted in crack path deflection with localized shear zones. After a small stable crack extension, cleavage fracture was observed.