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Non-destructive tests were conducted on welded fatigue specimens prepared using the same steel material and welding method as the one used in the manufacture and repair procedures of a KRUPP SchRs 600 bucket wheel excavator to reveal any defects present. The chemical composition, the mechanical properties, tendency to cracks and the microstructure of the bucket wheel material were determined using appropriate tests. The initiation of cracks and their subsequent growth during fatigue testing of the welded specimens was studied using ultrasound testing (UT) and a metallographic examination in order to investigate the causes of failure during service and predict fatigue life of the bucket wheel welded parts. It was found that the welding method used produces welds with numerous discontinuities that can only be detected using ultrasound techniques.

Coal or lignite thermal power stations are built next to the lignite mines and they are usually vast technological installations with a multitude of mechanical parts that need to be maintained and tested for life assessment. These include the excavating equipment, the ore crushers and belt conveyors, the furnace with its steam generating tubes and super heater coils, a steam drum and a steam turbine. Most of these are made of steel and other metal alloys and often fail due to normal service wear, bad maintenance, human error and poor material quality.The ability to extend the lifetime of a plant's power plant's mechanical system beyond the original design is of very important economic and technical significance. In recent years, various techniques have been developed for inspection and control methods to be applied so that residual life in mechanical systems of power plants and welded structures can be calculated in a timely and accurate manner. The control techniques include:• Various non-destructive tests to examine the state of a system and the possible mechanism that causes its wear and failure• Mechanical tests such as tensile, hardness, fatigue, impact and creep testing• Metallographic investigation using both optical and electron microscopy• Calculation of the operating stresses of the component, usually involving finite element analysis and a theoretical assessment of residual life depending on the wear mechanism found in the componentIn the present applied research work, the above techniques are employed in case studies on various mechanical parts from the thermal plants in the region of Western Macedonia, Greece.The purpose of the case studies was to determine the causes of mechanical failure, develop testing methods for the various parts, study the effect of material microstructure, property and processing method on part service performance and develop innovative construction methods. Case study 1Fatigue testing of reinforced-concrete steel bars to be used in the construction of the fifth power plant in the Region of Western MacedoniaThe fatigue characteristics of reinforced-concrete steel bars are usually studied with axial fatigue tests using conven tional testing machines and specimens in the as-delivered state, usually ribbed rods. The advantages of such tests include low costs and the possibility of defining test conditions precisely. However, there is a signifi cant disadvantage related to problems con nected with clamping bars in testing machines, where local stresses in bar clamping areas are responsible for the premature failure of the bars. A number of studies [1][2][3][4] con tain information about various methods to prepare the grip parts of specimens usually connected with us ing an added layer between a specimen and a testing machine jaw and/or slight machining of specimen ends. Little information is, however, available concerning the failure mechanism of untreated bars and the effectiveness of the measures mentioned.The study involves the fatigue testing of steel bars of various diamete...

Abstract.A test method for the peel resistance of the bonded rubber lining of large of large conveyor belt metal drums is presented that will assist engineer in designing conveyor systems with predetermined specifications. A simple specimen preparation method is developed and the peel strength of the liming is measured using a modified version of the Standard EN 28510-1:2014, 'Adhesives-Peel test for a flexible-bonded-to-rigid test specimen assembly' [1]. The method was applied to various types of samples and it was found that only metal drums where the rubber lining was bonded using hot-vulcanisation under pressure satisfied the condition of the peel force greater than 2 N/m.