A required finite element method（FEM） model applicable for narrow gap CMT and CMT＋P MIX welding was established based on the interactions between arc,base metal and filler metal.A novel method of simplifying wire f...A required finite element method（FEM） model applicable for narrow gap CMT and CMT＋P MIX welding was established based on the interactions between arc,base metal and filler metal.A novel method of simplifying wire feeding pulses and heat input pulses was supposed under the conduction of equivalent input.The method together with composed double-ellipse heat sources was included in the model.The model was employed in the investigation of thermal cycling and the identification of the softened zone of AA7A52 base plates.Low-frequency behavior emerged in the form of low-cooling rate sects,which were not expected under experimental conditions.The softened zone including the quenched zone and averaging zone of the base plate was much wider internal the base plate than that close to the surfaces.The reliability of the predictions in thermal cycling was supported by infrared imaging test results of the thermal cycle process.展开更多
Undercut is one kind of important spaces to place the mining blocks in the mass underground mining. This structure is also used as a compensation space during blasting. In the process of underground mining in the frag...Undercut is one kind of important spaces to place the mining blocks in the mass underground mining. This structure is also used as a compensation space during blasting. In the process of underground mining in the fragment orebody, it is important and critical to analyze the stability and blockage of the three-dimensional wedges created around the undercut space. The wedge stability is mainly controlled by factors including geometry （i.e., the size, shape and spatial location of the wedge and undercut）, the strength （shear and tensile） of the discontinuities that created the wedge, and the stress distribution within the rock mass. The Unwedge software was used to conduct the orthogonal simulation tests （three factors and five levels） that considered different cross sections, trends, and plunges of the undercut space. The results demonstrate that the control value of the safety factor of wedge is set to be 1.2. The optimal parameters are determined in the undercut space, such as the blasting fragmentation, orientation of the fluid flow, and the equipment gradeability;the wedge stability can be evaluated in the light of the block images and continuous falling;the stability of the key block meets the needs of the undercut space, the parameters gained are reasonable and optimal. Cross section is 27°, trend is from 315°to 325°（it is 320°at in-suit test） and plunge is 5°.展开更多
基金Project (9140C850205120C8501) supported by the Major Program of National Key Laboratory of Remanufacturing and the Army Foundation Project of China
文摘A required finite element method（FEM） model applicable for narrow gap CMT and CMT＋P MIX welding was established based on the interactions between arc,base metal and filler metal.A novel method of simplifying wire feeding pulses and heat input pulses was supposed under the conduction of equivalent input.The method together with composed double-ellipse heat sources was included in the model.The model was employed in the investigation of thermal cycling and the identification of the softened zone of AA7A52 base plates.Low-frequency behavior emerged in the form of low-cooling rate sects,which were not expected under experimental conditions.The softened zone including the quenched zone and averaging zone of the base plate was much wider internal the base plate than that close to the surfaces.The reliability of the predictions in thermal cycling was supported by infrared imaging test results of the thermal cycle process.
基金Project(2015CX005)supported by Innovation Driven Plan of Central South University,ChinaProject(2016zzts451)supported by the Graduate Innovation Fund of Central South University,China+1 种基金Project(2016JJ21)supported by the Fundamental Research Funds for the Hunan Province,ChinaProject(2012BAB14B01)supported by the National Science and Technology Pillar Program during the 12th Five-year Plan Period of China
文摘Undercut is one kind of important spaces to place the mining blocks in the mass underground mining. This structure is also used as a compensation space during blasting. In the process of underground mining in the fragment orebody, it is important and critical to analyze the stability and blockage of the three-dimensional wedges created around the undercut space. The wedge stability is mainly controlled by factors including geometry （i.e., the size, shape and spatial location of the wedge and undercut）, the strength （shear and tensile） of the discontinuities that created the wedge, and the stress distribution within the rock mass. The Unwedge software was used to conduct the orthogonal simulation tests （three factors and five levels） that considered different cross sections, trends, and plunges of the undercut space. The results demonstrate that the control value of the safety factor of wedge is set to be 1.2. The optimal parameters are determined in the undercut space, such as the blasting fragmentation, orientation of the fluid flow, and the equipment gradeability;the wedge stability can be evaluated in the light of the block images and continuous falling;the stability of the key block meets the needs of the undercut space, the parameters gained are reasonable and optimal. Cross section is 27°, trend is from 315°to 325°（it is 320°at in-suit test） and plunge is 5°.
