| 摘要 |
Fracture formation of components such as connecting rods used in automotive engines is known. Material with sufficient strength is used to form the component and then through providing a notch and appropriate loading a brittle fracture is achieved. Prior systems have utilised broaching tools or drilling in order to create a notch to initiate fracture. By providing a continuous laser incident upon a base component in order to melt a proportion of the surface of the component a notch is created in accordance with aspects to the present invention. The melting process and heat sink effect of the bulk of the component results in phase transformations which provide an embrittled notch and therefore acts as a fracture initiation site. By appropriate choice of laser power, incident area and drill time in association with material type and base component dimensions particular transformations can occur in the notch (2). With regard to steel these features are intergranular cracking at columnar grain boundaries in the re-solidified zone, intergranula-cracking of coarse grains at locations where the austenitising temperature was high and solid state transformations to martensite. |
