ANALISA VARIASI KUAT ARUS ELEKTRODA E6013 TERHADAP SAMBUNGAN LAS PADA PELAT BAJA UNTUK TABUNG GAS 3 KG

The quality of the welding results is influenced by the qualified welder, the appropriate type of connection, the type of welding, and the electrode. Standard electrode AWS E 6013 with trademark Nikko Steel Welding Elektodes, NK 68 with φ 2.6 mm. The type of camp used is SNI standard 1452-2007 for 3 kg LPG tube. Specimens were subjected to tensile testing, impact toughness, hardness testing, curvature testing, microstructure with current variations of 50 A and 70 A of both types of electrodes used. Welding by SMAW method with circular welding at 3 kg of gas tube blank from JIS G 3116 SG 295 materials. From the test result will be known maximum tensile strength, impact toughness, hardness, curve strength, macro and microstructure. And by comparing the samples of SNI, non SNI and samples from both types of Nikko Steel and NK 68 electrodes, there are differences in mechanical and microstructure characteristics that will significantly affect the toughness of the welding results.

Food hardness and stone tool weight in wild primate nut-cracking

This study presents data on average stone tool weights and the hardness of foods processed by the three known stone-tool-using primate species: Burmese long-tailed macaques (Macaca fascicularis aurea), bearded capuchins (Sapajus libidinosus) and Western chimpanzees (Pan troglodytes verus). Each of these primates uses stone hammers to crack open nuts in the wild, making them suitable for inter-species behavioural comparison. This work draws on published results to identify a distinct difference in the tool weight/food hardness curve between chimpanzees and the two monkey taxa, with the latter reaching an asymptote in mean tool weight of just over 1 kg regardless of increasing food hardness. In contrast, chimpanzees rapidly increase their tool weight in response to increasing hardness, selecting average masses over 5 kg to process the hardest nuts. Species overlap in their preference for tools of 0.8-1 kg for opening foods of hardness 2-3 kN, suggesting that this conjunction may represent a primate stone-tool-use optimum.

Combined Effect of Cold-Rolling and Aging on Precipitation and Recrystallization Behavior of Al-Er-Zr Alloy

To investigate the effect of cold-rolling and aging on precipitation and recrystallization behavior of Al-0.04Er-0.08Zr (at. %) alloy, two thermo-mechanical processes containing peak aging + cold-rolling (A+CR) and cold-rolling + isochronal aging (CR+A) were studied. In A+CR process, the hardness of alloy under cold-rolled state was much higher than the maximum obtained during isochronal aging, due to the strong interaction between precipitates and dislocations or sub-grain boundaries. Furthermore, the recrystallization temperature was 475 °C as indicated by the hardness curve. The microstructure analysis revealed that the sample annealed at 525 °C for 1 h still don’t recrystallize fully. For CR+A, it turned out that the deformation play a small role in improving the maximum of hardness. But comparing with those without deformation, the existence of deformation accelerated the rate of precipitation process and obtained higher electrical conductivity.

CHANGE OF STRUCTURAL CONDITION OF WELDED JOINTS BETWEEN HIGH‐STRENGTH FINE‐GRAINED AND STRUCTURAL STEELS

First, the production process of fine‐grained structural steels was considered. The results from the thermal calculation, which is a part of the welding simulation, were compared with measurements and good concordance was achieved. A modification of the hardness was found during the analysis of the hardness curve, the so‐called local hardness drop. The reason was the transformation of the structure, caused by thermal factors. The available TTA (time‐temperature‐austenite) and available TTT (time‐temperature‐transformation) diagrams do not describe this tempering process, which results in tempering structural condition by means of constituents of the martensite and bainite. The method of solution was applied to an example of a mismatch‐joint and a good concordance was achieved.