The flow of blasted ore during mining of moderately dipping medium-thick orebodies is a challenge.Selecting a suitable mining system for such ore bodies is difficult.This paper proposes a diamond layout sublevel open ...The flow of blasted ore during mining of moderately dipping medium-thick orebodies is a challenge.Selecting a suitable mining system for such ore bodies is difficult.This paper proposes a diamond layout sublevel open stoping system using fan blastholes with backfilling to mine such orebodies.To evaluate the performance of system the relationships between ore recovery and stope footwall dip angle,footwall surface roughness,drawpoint spacing and production blast ring burden were investigated.An ore recovery data set from 81 laboratory physical model experiments was established from combinations of the listed factors.Various modules in a back propagation neural network structure were compared,and an optimal network structure identified.An ore recovery backpropagation neural network(BPNN)forecast model was developed.Using the model and sensitivity analysis of the factors affecting the proposed open stope mining system,the significance of each factor on ore recovery was studied.The study results were applied to a case study at the Shandong Gold Group Jiaojia Gold Mine.The results showed that the application of a BPNN and sensitivity analysis models for ore recovery prediction in the proposed mining system and field experimental results confirm that the suggested mining method is feasible.展开更多
It is difficult to achieve Al/Cu dissimilar welds with good mechanical properties for medium-thick plates due to the inherent high heat generation rate at the shoulder-workpiece contact interface in conventional frict...It is difficult to achieve Al/Cu dissimilar welds with good mechanical properties for medium-thick plates due to the inherent high heat generation rate at the shoulder-workpiece contact interface in conventional friction stir welding.Thus,doubleside friction stir welding is innovatively applied to join 12-mm medium-thick 6061-T6 aluminum alloy and pure copper dissimilar plates,and the effect of welding speeds on the joint microstructure and mechanical properties of Al/Cu welds is systematically analyzed.It reveals that a sound Al/Cu joint without macroscopic defects can be achieved when the welding speed is lower than 180 mm/min,while a nonuniform relatively thick intermetallic compound(IMC)layer is formed at the Al/Cu interface,resulting in lots of local microcracks within the first-pass weld under the plunging force of the tool during friction stir welding of the second-pass,and seriously deteriorates the mechanical properties of the joint.With the increase of welding speed to more than 300 mm/min void defects appear in the joint,but the joint properties are still better than the welds performed at low welding speed conditions since a continuous uniform thin IMCs layer is formed at the Al/Cu interface.The maximum tensile strength and elongation of Al/Cu weld are,respectively,135.11 MPa and 6.06%,which is achieved at the welding speed of 400 mm/min.In addition,due to the influence of welding distortion of the first-pass weld,the secondpass weld is more prone to form void defects than the first-pass weld when the same plunge depth is applied on both sides.The double-side friction stir welding is proved to be a good method for dissimilar welding of medium-thick Al/Cu plates.展开更多
A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures meas...A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.展开更多
基金funded by the State Key Research Development Program of China(2018YFC0604400)the National Science Foundation of China(No.51874068)+2 种基金the Fundamental Research Funds for the Central Universities(N160107001,N180701016)the 111 Project(B17009)Nazarbayev University for the Faculty Development Competitive Research Grant(240919FD3920)。
文摘The flow of blasted ore during mining of moderately dipping medium-thick orebodies is a challenge.Selecting a suitable mining system for such ore bodies is difficult.This paper proposes a diamond layout sublevel open stoping system using fan blastholes with backfilling to mine such orebodies.To evaluate the performance of system the relationships between ore recovery and stope footwall dip angle,footwall surface roughness,drawpoint spacing and production blast ring burden were investigated.An ore recovery data set from 81 laboratory physical model experiments was established from combinations of the listed factors.Various modules in a back propagation neural network structure were compared,and an optimal network structure identified.An ore recovery backpropagation neural network(BPNN)forecast model was developed.Using the model and sensitivity analysis of the factors affecting the proposed open stope mining system,the significance of each factor on ore recovery was studied.The study results were applied to a case study at the Shandong Gold Group Jiaojia Gold Mine.The results showed that the application of a BPNN and sensitivity analysis models for ore recovery prediction in the proposed mining system and field experimental results confirm that the suggested mining method is feasible.
基金financially supported by the National Natural Science Foundation of China(No.51905309)the Science and Technology Planning Project of State Grid Henan Electric Power Company(No.52170220009Y)。
文摘It is difficult to achieve Al/Cu dissimilar welds with good mechanical properties for medium-thick plates due to the inherent high heat generation rate at the shoulder-workpiece contact interface in conventional friction stir welding.Thus,doubleside friction stir welding is innovatively applied to join 12-mm medium-thick 6061-T6 aluminum alloy and pure copper dissimilar plates,and the effect of welding speeds on the joint microstructure and mechanical properties of Al/Cu welds is systematically analyzed.It reveals that a sound Al/Cu joint without macroscopic defects can be achieved when the welding speed is lower than 180 mm/min,while a nonuniform relatively thick intermetallic compound(IMC)layer is formed at the Al/Cu interface,resulting in lots of local microcracks within the first-pass weld under the plunging force of the tool during friction stir welding of the second-pass,and seriously deteriorates the mechanical properties of the joint.With the increase of welding speed to more than 300 mm/min void defects appear in the joint,but the joint properties are still better than the welds performed at low welding speed conditions since a continuous uniform thin IMCs layer is formed at the Al/Cu interface.The maximum tensile strength and elongation of Al/Cu weld are,respectively,135.11 MPa and 6.06%,which is achieved at the welding speed of 400 mm/min.In addition,due to the influence of welding distortion of the first-pass weld,the secondpass weld is more prone to form void defects than the first-pass weld when the same plunge depth is applied on both sides.The double-side friction stir welding is proved to be a good method for dissimilar welding of medium-thick Al/Cu plates.
基金financially supported by the National Natural Science Foundation of China(Nos.51525401,51274054,U1332115,51401044)the Science and Technology Planning Project of Dalian(No.2013A16GX110)+1 种基金the China Postdoctoral Science Foundation(2015M581331)the Fundamental Research Funds for the Central Universities
文摘A three-dimensional finite-element model has been established to investigate the thermal behavior of the medium-thick slab copper casting mold with different cooling water slot designs. The mold wall temperatures measured using thermocouples buried in different positions of the mold with the original designed cooling system were analyzed to determine the corresponding heat flux profile. This profile was then used for simulation to predict the temperature distribution and the thermal stress distribution of the molds. The predicted temperatures during operation matched the plant measurements. The results showed that the maximum temperature, about 635 K in the wide hot surface, was found about 60 mm below the meniscus and 226 mm from the center of the mold. For the mold with the type I modified design, there was an insignificant decrease in temperature of about 5 K, and for the mold with the type II modified design, the maximum temperature was decreased by about 15 K and the temperature of the hot surface was distributed more uniformly along the length of the mold. The corresponding maximum thermal stress at the hot surface of the mold was reduced from 408 MPa to 386 MPa with the type II modified design. The results indicated that the modified design II is beneficial to the increase of mold life and the quality of casting slabs.
