Özgür Cebeci ,030060158,11th Week

Holonomic Motion

As used in robotics , the term motion controll or motion control system refers to the lower-level controll functions . Depending on the number of DOF available for motion planning system are catagorized.

Holonomic System : There have enough DOF for an arbitrary motion . The minimum number of those is equal to dimensionality of the corresponding C-space: For example 6 is the minimum number of DOF a 3D arm manipülatör needs to realize an arbitrary motion in space without obstacle.

(Sensing, intelligence, motion ; Vladimir Lumelsky ; pg:20 , 2006)

Surface Remelting

Laser surface melting is the variety of convention coating techniques with which manufacturers are generally more familiar. The integrity of surface produced by laser melting is high. The melted region exhibits low porosity and few imperfections , and has a sound metallurgical bond with the substrate. The energy input is low , causing littel distosion to a component , which reduces or eleminates the need for post-melt finishing operations. Melting promotes homogenization of the surface composition , which means that materials such as nodular cast iron may be hardended , and surface properties improvedmarkedly over those of the parent material. High cooling rate results şn fine solidified microstructure , which may contain non –equilibrium phases , novel precipitates and exteded solid solubility.

(Laser processing of engineering materials ; John C. Ion , pg: 265 , 2005)

Fatigue Wear

Another mechanism for generating wear particles or losing material from solid surface in solid-state contact is associated with fatiqu process where there are repeated applications of stress. Under such conditions , the generation of cracks , both surface and subsurface , leads to the formation of wear particles and the loss of the material form solid surface.

The process can ocur in such elements as Rolling element bearings where a ball or roller repeatedly rolls over the same surface and after some time , a crack is observed to initiate either subsurface or in the surface region. The subsurface crack gradually progresses to the surface and liberates a wear particle ; however , the surface crack moves downward into the bulk , connects with other cracks , and generates wear particles.

(Surface effects in adhesion, friction, wear, and lubrication ; Donald H. Buckley ; pg: 500 , 1981)

Shot Peening

Shot peening is a very common method for increasing the fatigue strength and har frequently been used for aero engile applications for mnay years . Aero engine components are characterized by high-strengh material , high cyclic loads and high service temperature. In the past shot peening has been used for safety-critical parts mainly as a measure to increase safety margins rather than for extending service lives. However , with increasing understanding of the mechanisms of shot peening and increasing predictive capabilites , the opportunities of increasing service live by shot peening or other surface treatments are expected to grow in the future.

(Shot peening ; Lothar Wagner ; pg: 13 , 2003)