When conducting tensile tests the beginning of yield point is marked with decreasing of apparatus values or recording device. Yield point can be determined by observing and registration these type of stress decreasing. This method is called method of testing machine lever dropping, which indicates that subject sample reached elasticity limit.
Methods for materials properties evaluation at the stage of cracks origination and development.
Earlier it was considered, that both in basic material and in welded joint cracks existence is not acceptable, and their origination during product service signifies its almost instantaneous destruction.
However, in practical situation it was found, that it is almost impossible to manufacture the product without cracks and quite often the constructions have to Continue reading →
Methods of evaluation welded seams durability for cold cracks formation (Part 2).
Metallurgical processes, occurred during point fusing, in spite of short-term of their behavior, are reproduced, apparently, with the same completeness level, as during real production facing.
The symmetry of fused point allows to apply to it strains of two types: tearing-off, which causes normal stresses σ in fusion zone and torsion, which causes tangential Continue reading →
Origination of crystals in liquids (Part 3).
Surface tension (γ) on the surface of crystal and liquid influence on the critical size of the nucleus. The bigger is energy of interphase boundary, the more energy fluctuations are necessary and nucleuses origination is found more difficult. Melt capability for overcooling depends on similarity of packing of atoms short-range order in liquid and crystal state. If the similarity is small, the surface tension between crystals and liquid is big and bigger fluctuations energies will be necessary Continue reading →
Attestation of welding technology (Part 6).
General program of enterprise about technology attestation by tests conducting is:
– Welding parameters determination;
– Examination of equipment’s and materials’ aptitude;
– Assemblage for welding and execution of welding process observation with registration all significant parameters and results;