STATISTICAL SUBSTANTIATION OF OPERABILITY OF WELDED BUTT JOINT WITH NON-CRACK-LIKE DEFECTS (PORES) EXCEEDING REGULATORY REQUIREMENTS OF THE RULES OF THE RUSSIAN MARITIME REGISTER OF SHIPPING

The paper presents the research and analysis of the structure of non-crack-like defects (NCD) detected by X-Ray Inspection (X-RI) method in the welded joint of the plate made of D36 steel in compliance with the quality requirements imposed by the Rules of the Russian Maritime register of shipping (RMRS). Defects (pores) identified by X-RI method are analyzed and subjected to statistical processing in order to obtain the mathematical model “base metal - weld with NCD - base metal”, which helps to analyze the degree of weld imperfection using X-RI photo and offer a theoretical model of losing production quality (reliability) of the welded butt joint. Using X-RI method for detection of NCD in the weld allows to find the relationship between the defect of the seam and operational reliability (performance) on the basis of the data obtained. Justification of saving operation qualities of a welded seam with NCD at a stage of mounting and maintenance of the ship hulls is today an important task. There are presented the parameters of steel plate No.3 for studying NCD influence on the strength of a multi-layer weld. The X-RI results of welded plate No.3 with NCD are shown for studying the size and degree of defects in the form of single pores and accumulation of pores. A design model for assessing statistical signs of a defective weld, a general scheme of computer processing of a X-RI picture with NCD (pores) in the weld of plate No. 3, an example of computer processing and analysis of defects of bar No.18 identified by X-RI are considered. Histograms and distribution of density of the sizes of the defected area for the plates are shown on the graph.