Cyclic stress

About: Cyclic stress is a research topic. Over the lifetime, 3259 publications have been published within this topic receiving 42855 citations.

Motor interface for parallel drive shafts within an independently rotating member

Abstract: Mechanisms, assemblies, systems, tools, and methods incorporating the use of an offset drive shaft within an independently rotating member are provided. An example mechanism includes a base and a main shaft mounted to rotate relative to the base, a first drive shaft mounted inside the main shaft, and a first drive feature engaged with the first drive shaft. The main shaft includes a proximal end, a distal end, and a main shaft rotational axis defined therebetween. The first drive shaft is offset from the main shaft rotational axis. A first drive feature rotational axis is defined for the first drive feature and is fixed relative to the base as the main shaft rotates. The first drive feature rotates the first drive shaft.

Mechanical behavior of additive manufactured, powder-bed laser-fused materials

Abstract: Mechanical behavior of four metallic alloys fabricated with layered, laser-heated methods of additive manufacturing (AM) was compared to that of similar alloys produced with conventional methods (wrought and machined). AM materials were produced by a leading commercial service provider, as opposed to incorporating material specimens produced by unique or specially-adapted equipment. The elastic moduli were measured in flexure, stress–strain characteristics were measured in tensile deformation, and fatigue strengths were measured in fully reversed bending. The effects of fabrication orientation, surface polishing, and hot isostatic pressing upon mechanical behavior were studied. The fatigue strengths exhibited by SLM AlSi10Mg and DMLS Ti6Al4V in the as-fabricated condition proved to be significantly inferior to that of conventional material. These lower fatigue strengths are a consequence of multiple fatigue cracks initiating at surface defects, internal voids and microcracks, and growing simultaneously during cyclic loading. Measured fatigue strengths of DMLS 316L and 17-4PH approached those of corresponding wrought materials when subjected to principal stresses aligned with the build planes. When cyclic stresses were applied across the build planes of the DMLS stainless steels, fatigue fractures often developed prematurely by separation of material. Post-processing the DMLS Ti6Al4V and SS316L with hot isostatic pressure elevated the fatigue strength significantly. Measurements of surface roughness with an optical profilometer, examinations of the material microstructures, and fractography contribute to an understanding of the mechanical behavior of the additive materials.