Aging behaviors of extruded and rolled AZ80 and AZ31 Mg alloys were investigated under conditions similar to the paint-bake cycle currently used in automotive industry.Artificial aging at 170℃ from 0.5 to 12 h was co...Aging behaviors of extruded and rolled AZ80 and AZ31 Mg alloys were investigated under conditions similar to the paint-bake cycle currently used in automotive industry.Artificial aging at 170℃ from 0.5 to 12 h was conducted on solution-treated specimens to study the effects of aging on mechanical properties.SEM observations and EDS data show thatβ-phase of Al12Mg17 precipitates continuously or discontinuously fromα-Mg matrix and distributes along grain boundaries of the AZ80 alloy during artificial aging.Data of tensile tests and Vickers hardness tests show that an optimum mechanical property is achieved after baking at 170℃ for 6-8 h when Vickers hardness,tensile strength,and elongation are increased by 6.35%,15.30%,and 7.88%,respectively, while the AZ31 alloy does not exhibit significant hardening behavior over the aging period.展开更多
In a manufacturing industry, mixed model assembly line(MMAL) is preferred in order to meet the variety in product demand. MMAL balancing helps in assembling products with similar characteristics in a random fashion. T...In a manufacturing industry, mixed model assembly line(MMAL) is preferred in order to meet the variety in product demand. MMAL balancing helps in assembling products with similar characteristics in a random fashion. The objective of this work aims in reducing the number of workstations, work load index between stations and within each station. As manual contribution of workers in final assembly line is more, ergonomics is taken as an additional objective function. Ergonomic risk level of a workstation is evaluated using a parameter called accumulated risk posture(ARP), which is calculated using rapid upper limb assessment(RULA) check sheet. This work is based on the case study of an MMAL problem in Rane(Madras) Ltd.(India), in which a problem based genetic algorithm(GA) has been proposed to minimize the mentioned objectives. The working of the genetic operators such as selection, crossover and mutation has been modified with respect to the addressed MMAL problem. The results show that there is a significant impact over productivity and the process time of the final assembled product, i.e., the rate of production is increased by 39.5% and the assembly time for one particular model is reduced to 13 min from existing 18 min. Also, the space required using the proposed assembly line is only 200 m2 against existing 350 m2. Further, the algorithm helps in reducing workers fatigue(i.e., ergonomic friendly).展开更多
The swelling behavior of argillaceous rocks is a complex phenomenon and has been determined using a lot of indexes in the literature. Determining the required modeling indexes that need to be performed requires expens...The swelling behavior of argillaceous rocks is a complex phenomenon and has been determined using a lot of indexes in the literature. Determining the required modeling indexes that need to be performed requires expensive tests and extensive time in different laboratories. In some of the cases, it is too diffi- cult to find a relation between the effective variables and swelling potential. This paper suggests a method for modeling the time dependent swelling pressure of argillaceous rocks. The trend of short term swelling potential during the first 3 days of the swelling pressure testing is used for modeling the long term swelling pressure of mudstone that is recorded during months. The artificial neural network (ANN) as a power tool is used for modeling this nonlinear and complex behavior. This method enables predicting the swelling potential of argillaceous rocks when the required indexes and also correlation between them is unattainable. This method facilitates the model of all studied samples under a unique formulation.展开更多
基金Project(50801034)supported by the National Natural Science Foundation of ChinaProject(20060425)supported by the Scientific and Technological Research Key Laboratory Foundation of Liaoning Education Department,China
文摘Aging behaviors of extruded and rolled AZ80 and AZ31 Mg alloys were investigated under conditions similar to the paint-bake cycle currently used in automotive industry.Artificial aging at 170℃ from 0.5 to 12 h was conducted on solution-treated specimens to study the effects of aging on mechanical properties.SEM observations and EDS data show thatβ-phase of Al12Mg17 precipitates continuously or discontinuously fromα-Mg matrix and distributes along grain boundaries of the AZ80 alloy during artificial aging.Data of tensile tests and Vickers hardness tests show that an optimum mechanical property is achieved after baking at 170℃ for 6-8 h when Vickers hardness,tensile strength,and elongation are increased by 6.35%,15.30%,and 7.88%,respectively, while the AZ31 alloy does not exhibit significant hardening behavior over the aging period.
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文摘In a manufacturing industry, mixed model assembly line(MMAL) is preferred in order to meet the variety in product demand. MMAL balancing helps in assembling products with similar characteristics in a random fashion. The objective of this work aims in reducing the number of workstations, work load index between stations and within each station. As manual contribution of workers in final assembly line is more, ergonomics is taken as an additional objective function. Ergonomic risk level of a workstation is evaluated using a parameter called accumulated risk posture(ARP), which is calculated using rapid upper limb assessment(RULA) check sheet. This work is based on the case study of an MMAL problem in Rane(Madras) Ltd.(India), in which a problem based genetic algorithm(GA) has been proposed to minimize the mentioned objectives. The working of the genetic operators such as selection, crossover and mutation has been modified with respect to the addressed MMAL problem. The results show that there is a significant impact over productivity and the process time of the final assembled product, i.e., the rate of production is increased by 39.5% and the assembly time for one particular model is reduced to 13 min from existing 18 min. Also, the space required using the proposed assembly line is only 200 m2 against existing 350 m2. Further, the algorithm helps in reducing workers fatigue(i.e., ergonomic friendly).
文摘The swelling behavior of argillaceous rocks is a complex phenomenon and has been determined using a lot of indexes in the literature. Determining the required modeling indexes that need to be performed requires expensive tests and extensive time in different laboratories. In some of the cases, it is too diffi- cult to find a relation between the effective variables and swelling potential. This paper suggests a method for modeling the time dependent swelling pressure of argillaceous rocks. The trend of short term swelling potential during the first 3 days of the swelling pressure testing is used for modeling the long term swelling pressure of mudstone that is recorded during months. The artificial neural network (ANN) as a power tool is used for modeling this nonlinear and complex behavior. This method enables predicting the swelling potential of argillaceous rocks when the required indexes and also correlation between them is unattainable. This method facilitates the model of all studied samples under a unique formulation.
