Shear-based deformation processing of age-hardened aluminum alloy for single-step sheet production

Shear-based deformation processing by hybrid cutting-extrusion and free machining are used to make continuous strip, of thickness up to one millimeter, from low-workability AA6013-T6 in a single deformation step. The intense shear can impose effective strains as large as 2 in the strip without pre-heating of the workpiece. The creation of strip in a single step is facilitated by three factors inherent to the cutting deformation zone: highly confined shear deformation, in situ plastic deformation-induced heating and high hydrostatic pressure. The hybrid cutting-extrusion, which employs a second die located across from the primary cutting tool to constrain the chip geometry, is found to produce strip with smooth surfaces (Sa < 0.4 μm) that is similar to cold-rolled strip. The strips show an elongated grain microstructure that is inclined to the strip surfaces – a shear texture – that is quite different from rolled sheet. This shear texture (inclination) angle is determined by the deformation path. Through control of the deformation parameters such as strain and temperature, a range of microstructures and strengths could be achieved in the strip. When the cutting-based deformation was done at room temperature, without workpiece pre-heating, the starting T6 material was further strengthened by as much as 30% in a single step. In elevated-temperature cutting-extrusion, dynamic recrystallization was observed, resulting in a refined grain size in the strip. Implications for deformation processing of age-hardenable Al alloys into sheet form, and microstructure control therein, are discussed.

Status Konservasi Vegetasi Pohon di Lahan Bera Womnowi Sidey Manokwari (Sebuah Catatan Kecil Inventarisasi Vegetasi di Hutan Sekunder Papua Barat)

Studi konservasi di hutan sekunder khususnya di lahan bera penting di masa mendatang. Penelitian ini bertujuan membuat sebuah catatan kecil inventarisasi vegetasi pohon di lahan bera Womnowi Sidey Manokwari berdasarkan data Union for Conservation of Nature Resources (IUCN). Penelitian ini menggunakan metode analisis vegetasi―sebuah teknik continuous strip sampling, 10 x 10 meter untuk fase tiang dan 20 x 20 meter untuk fase pohon yang dilakukan pada awal bulan Mei 2018. Total individu jenis yang diinventarisasi pada luas satu hektar adalah 378 individu terdiri dari 65 jenis tiang dan pohon. Hasil menunjukkan vegetasi pohon didominasi oleh status LC. Dua jenis telah teridentifikasi sebagai NT dan V pada fase tiang: Aglaia odorata Lour. (NT) and Intsia bijuga (Colebr.) Kuntze. (V). Indeks nilai penting (INP) jenis yang tergolong dalam IUCN adalah 76.05% pada fase tiang dan 83.53% pada fase pohon. Jenis dominan mungkin berpengaruh pada status konservasinya, penelitian lanjutan yang komprehensif perlu dilakukan dibeberapa tipe lahan bera di Papua Barat.Kata kunci: bera, konservasi, vegetasi pohon, analisis vegetasi, Manokwari

DISCUSSION ON HEIGHT SYSTEMS IN STEREOSCOPIC MAPPING USING THE ZY-3 SATELLITE IMAGES

The ZY-3 is the civil high-resolution optical stereoscopic mapping satellite independently developed by China. It is mainly used for 1&amp;thinsp;:&amp;thinsp;50,000 scale topographic mapping. One of the distinguishing features of the ZY-3 is that the panchromatic triplet camera can obtain thousands of kilometers of continuous strip stereo data. The working mode is suitable for wide-range stereoscopic mapping, in particular global DEM extraction. The ZY-3 constellation is operated in a sun-synchronous at an altitude 505&amp;thinsp;km, with a 10:30&amp;thinsp;AM equator crossing time and a 29-day revisiting period. The panchromatic triplet sensors have excellent base-to-height ratio, which is advantageous for obtaining good mapping accuracy.<br> In this paper the China quasi-geoid, EGM2008 and the height conversion method are discussed. It is pointed out that according to the current surveying and mapping specifications, almost all maps and charts use mean sea level for elevation. Experiments on bundle adjustment and DEM extraction with different height systems have been carried out in Liaoning Province of China. The results show that the similar accuracy can be obtained using different elevation system. According to the principle of geodesy and photogrammetry, it is recommended to use ellipsoidal height for satellite photogrammetric calculation and use the orthometric height in mapping production.