Topology Optimization of Self-Supporting Structures for Additive Manufacturing with Adaptive Explicit Continuous Constraint

The integration of topology optimization(TO)and additive manufacturing(AM)technologies can create significant synergy benefits,while the lack of AM-friendly TO algorithms is a serious bottleneck for the application of TO in AM.In this paper,a TO method is proposed to design self-supporting structures with an explicit continuous self-supporting constraint,which can be adaptively activated and tightened during the optimization procedure.The TO procedure is suitable for various critical overhang angles(COA),which is integrated with build direction assignment to reduce performance loss.Besides,a triangular directional self-supporting constraint sensitivity filter is devised to promote the downward evolution of structures and maintain stability.Two numerical examples are presented;all the test cases have successfully converged and the optimized solutions demonstrate good manufacturability.In the meanwhile,a fully self-supporting design can be obtained with a slight cost in performance through combination with build direction assignment.

突变观与渐变观的较量——《新青年》的进化论思想实践及历史影响

在进化论思想已经获得广泛传播的条件下,《新青年》转向了进化论思想的实践,推动反封建的思想革命。在重大历史转折关头,新青年一派坚持进化论思想中以渐变为前提的突变观念。这表现为他们观念中的新旧思想对立和中西文化发展水平的时代差异,并试图以西方文明来革新中国传统文化。进化论思想中的渐变和突变观念,分别给激进主义和保守主义提供了思想工具。在实践中存在一种时机错位的现象,即特定时期的思想论争,其思维模式在事过境迁后它的应有有效性会发生逆转,好像历史又回到了原来的起点上;但激进或保守的历史作用,最终要接受历史的裁定。