Original scientific paper The joints made by fusion of materials are exposed to the influence of residual stresses induced by welding thermal cycles. Residual stresses were measured on butt welded plates made of NIOMOL 490K, before and after reparation. The objective of this paper is to compare three methods of residual stress measurement (hole-drilling method, x-ray diffraction and directional...

This paper analyses the non linear properties exhibited by a drill string system under various un balanced mass conditions. The drill string is affected by continuous friction in the form of drill bit and well bore hole interactions. This paper proves the origin of limit cycling and increase of non linearity with increase in speed of the drilling in the presence of friction. The spectrum of the...

In this paper, we implement the combined method of drilling stop hole and FRP reinforcement to repair cracked steel plates subjected cyclic tension. The crack initiation growth are experimentally investigated. stress distribution at residual fatigue life evaluated by FEM. effects on prolonging analyzed. results show that effectiveness only using is limited, while has dramatically prolonged life...

Many failures of supporting structures or machines are not caused only by stresses that are invoked by loading, but they often result due to residual stresses. Time needed for reparation of equipment and production losses are important factors, but much more serious are possible injuries or death of people. Residual stresses occur also in the structures without loadings. They arise mostly due t...

The distinctive characteristics of carbon fibre reinforced plastics, like low weight or high specific strength, had broadened their use to new fields. Due to the need of assembly to structures, machining operations like drilling are frequent. In result of composites inhomogeneity, this operation can lead to different damages that reduce mechanical strength of the parts in the connection area. F...

Optical and medical devices require microdrilling of holes on glass. Brittle fracture occurs during the drilling. Cone and radial cracks are generated due to impact load and walking when a drill hit a glass to make a hole. To produce good holes without cracks and fracture, a condition monitoring of glass drilling processes is required. In this paper, to develop a costeffective direct monitoring...

In this paper we present an algorithm suitable for the condition monitoring of a manufacturing drilling process that will be able to detect tool wear and impending failure. The algorithm is based around a Hidden Markov Model (HMM) [5] which is trained on “normal” data obtained from the early stages of the lifetime of a drill operating under a particular drilling condition (defined by rotation s...

The change from steerable motor to rotary steerable system has been both technically and commercially successful in Lybia. Through these case histories the paper will demonstrate benefits resulting from the use of rotary steerable systems that have led to a step change in overall drilling performance in the Middle East. This paper describes the successful introduction and application of a rotar...