Fatigue strength test of casting material GS-20Mn5V
The Small-sample up and down fatigue test method was used to test the fatigue limit of casting GS-20Mn5V which is the most popular casting material in civil engineering. The symmetric tension-compression fatigue test was on the high frequency fatigue tester. Ten useful test values were obtained through twelve tests with standard specimens. The mean value of fatigue limit of GS-20Mn5V is 202.8MPa after a statistic of the test results. The test provides the available data for engineering application.
Elastoplastic analysis and experimental study on spherical cast-steel joint of reticulated shells
Elastoplastic analysis and full scale experiment of a spherical cast steel joint used in steel reticulated shells of Chongqing Olympic Stadium was carried out. By forming finite element model and performing elastoplastic analysis, the stress and strain distribution of the cast steel joint were obtained. The stresses on test points in the surface of the cast steel joint were gained from prototype experiment. Combining theoretical analysis with the prototype experiment, static behavior and stress transfer pathway of the cast steel joint are analyzed, and the‘high low high low’variation regularity of stress distribution from pipe shaft to surface of spherical joint are pointed out. Based on the Von Mises strength criterion, the security and load bearing capacity of the joint are evaluated. In addition, the ratio of stresses on pipe shaft and pipe foot, as a main factor to measure the degree of the stress concentration, is also analyzed. It is indicated that the distribution of stresses on large spherical cast steel joint can be improved by controlling the ratio of stresses.
Application of resource allocation optimisation to provide profitable options for dairy production systems
A linear program (LP) model analysed resource use on a 100 ha dairy farm. A single optimum-profit combination was established for resources which were either optimised or constrained. It was found that, with a fixed herd of 320 milking cows, when production increased from 305 kg milksolids per cow (kg MS/cow) to 415 kg MS/cow, cash profit increased by 65%. This required additional supplements. If, however, feed demand and supply were optimised at 415 kg MS/cow, the LP reduced milking cow number rather than buy in feed to meet the increased feed demand from higher production per cow. At all production levels chosen between 305 and 415 kgMS/cow, it was most economic to dry off and cull cows early in dry summers to optimise feed demand vs. feed grown; use nitrogen (N) fertiliser to avoid a feed deficit only when response rates of better than 10 kgDM to 1 kg N could be expected; not use N for growing supplements to harvest. Pasture cover, within defined constraint levels, provided a buffer for feed demand and supply fluctuations. The study highlights the importance of assessing production, income and cost in an integrated framework to identify the point at which individual resources become limiting.