DLC Coated Piston Skirts Behavior at Initial IC Engine Start Up  

Oleh:

Rehman, Zahid ur ; Qasim, S. Adnan ; Malik, M. Afzaal

Jenis: Article from Books - E-Book
Dalam koleksi: Transactions on Engineering Technologies: Special Volume of the World Congress on Engineering 2013, page 195-212.
Topik: DLC coating; Dry contact; Elasticity; IC engine; Initial engine start-up; Piston skirt
Fulltext: 15_978-94-017-8831-1_Rehman_Qasim_Malik.pdf (932.37KB)

Isi artikel

The diamond-like carbon (DLC) based coating protects the lubricant-starved dry surface of the piston skirts against wear in a low-load and speed initial start-up of an internal combustion (IC) engine. Despite a relatively large radial clearance a physical contact between the skirts and the cylinder liner causes an elastic deformation of the DLC coated surface producing elastic stress and strains of noticeable amplitudes. The elastic stress accumulation may facilitate a subsequent de-lamination of the DLC coating. This study develops the numerical piston dynamics model by incorporating the secondary eccentric displacements of the piston skirts and their contact with the engine cylinder liner during the 720-degree crank rotation cycle. The contact zone in the boundary-value problem is discretized using the finite difference method. The elastic surface displacements, stresses and strains are determined by applying the theory of elasticity and solving the Navier’s or Lame’s equation numerically. The nature and extent of the displacements, stresses and strains produced at the interface of a fairly thin DLC coating with the substrate are analyzed. The results highlight the extent of the depth of the elastic surface displacements, the stresses and strains produced in the coating and the substrate materials. The simulation results show that the dry piston skirts establish a physical contact with the liner in the compression stroke that is maintained in the expansion and exhaust strokes. The stresses produced at the low engine start-up speed are significant, increase beneath the surface and accumulate at the interface between the coating and the substrate. The elastic displacements of a fairly thin DLC coating prevents the stress accumulation on the substrate and protects it from adhesive wear.

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