For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-p...For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.展开更多
锻炼行为促进是公共卫生领域的关键议题,但现有理论在预测和干预锻炼行为时仍存在局限性。基于锻炼行为发生的必要条件,提出了锻炼行为的MTMSP(motor competence,time,motivation,self-control and physical exertion,运动能力、时间、...锻炼行为促进是公共卫生领域的关键议题,但现有理论在预测和干预锻炼行为时仍存在局限性。基于锻炼行为发生的必要条件,提出了锻炼行为的MTMSP(motor competence,time,motivation,self-control and physical exertion,运动能力、时间、动机、自我控制和体力消耗)决定因素模型(以下简称“MTMSP决定因素模型”)。该模型从个体层面深入解析锻炼行为的发生机制,将运动能力、时间、动机、自我控制和体力消耗作为核心决定因素,并通过“前提条件-双过程动机-自我控制调节”三级结构揭示各因素的内在关联。研究认为,MTMSP决定因素模型为克服锻炼意向−行为差距和维持问题提供了新的理论视角。未来研究可基于该模型,诊断目标人群的初始状态,设计更具针对性的干预方案,促进锻炼行为的发生。展开更多
基金Project(51164030)supported by the National Natural Science Foundation of China
文摘For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.
文摘锻炼行为促进是公共卫生领域的关键议题,但现有理论在预测和干预锻炼行为时仍存在局限性。基于锻炼行为发生的必要条件,提出了锻炼行为的MTMSP(motor competence,time,motivation,self-control and physical exertion,运动能力、时间、动机、自我控制和体力消耗)决定因素模型(以下简称“MTMSP决定因素模型”)。该模型从个体层面深入解析锻炼行为的发生机制,将运动能力、时间、动机、自我控制和体力消耗作为核心决定因素,并通过“前提条件-双过程动机-自我控制调节”三级结构揭示各因素的内在关联。研究认为,MTMSP决定因素模型为克服锻炼意向−行为差距和维持问题提供了新的理论视角。未来研究可基于该模型,诊断目标人群的初始状态,设计更具针对性的干预方案,促进锻炼行为的发生。
