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Failure of a lancing system was investigated. A local company produces bridge slot screen filter pipes. Specific cutting tools, part of the lancing system, brake down repeatedly. The parts were manufactured from AISI D2 steel. A systematic investigation consisting of on site inspection, visual examination, dimensional verification, hardness measurements and chemical analysis was carried out. Samples were selected and prepared for destructive testing. The fracture surfaces and the cross section of the tools were analyzed by light and SEM microscopy. The tools failed due to high shear stresses, unevenly developed on the surface of the parts. Their breakage is mainly attributed to poor design. The cutting-forming system should be redesigned and some aspects regarding the machine use and maintenance should be specified. Additionally, alternatives regarding the material selection of the tools are provided in order to ensure efficiency and to improve operational reliability.

The failure of a motorbike fuel tank was investigated. Leakage of fuel was detected on the stabilizing subassembly at the front side of the base. The main container was replaced. The new container ended up leaking as well after only four months of use, proving that the failure was not a random incident. The study comprises visual examination, non-destructive testing by penetrant liquids, microhardness measurements and chemical analysis. Welded samples of the leakage area were investigated from macroscopic and microscopic perspective. The microstructure was analyzed by optical and scanning electron microscopy. Welding defects were found on the failure area. Most of them could be associated to inappropriate welding parameters. Hairline cracks were detected on resistance spot welding points. The cracks originated approximately at the center of the weld nugget, propagated through the weld zone, pierced the welding interface and reached the opposite sheet surface. Findings indicated interfacial failure mode. Poor welding process is considered the main cause of the failure and the specific sequence should be improved. Detailed practice recommendations and rigorous inspection are required to assure tank integrity. The tank tightness is of pivotal importance for the safe operation of the engine, the safety of passengers and protection of the environment.

Cooling towers are important heat exchangers in power generation industry comprising of centrifugal fans which are used for cooling purposes. The present research investigates the failure occurred on the fan blade supporting system, installed on the cooling tower of a power plant. Τhe tower is consisted of twenty fans. Their blades are supported onto a hub by “U” shaped holders. These specific fitments frequently undergo damages increasing plant downtimes as well as the risk of accidents. The study comprises of historical data recording, macroscopic examination, hardness measurements and chemical analysis of three failed components. Moreover, the microstructure and fracture surface morphology of failed components are thoroughly analyzed. Conclusions are presented regarding the failure mechanism and its propagation mode. Holders were totally break by low cycle fatigue. Improper material selection and poor design are mainly responsible for the repeated damage. Practical recommendations were delivered to avoid similar failures.

A company produces truck wheel covers as spare parts for the local market. The production of these parts is based on a progressive die performing consecutive forming and selective cutting stages throughout the initial circular steel sheet. The failure occurred to the final stage of manufacturing, as the die marks, by mold-printing, the assembly configuration of the wheel cover onto the wheel rim. The paper presents a thorough failure analysis of the broken tool. The investigation includes preliminary examination, hardness measurements and chemical analysis. In depth microscopic examination was carried out using stereoscope and optical and electron microscopy. The failure mechanism was investigated from macroscopic and microscopic perspective and conclusions regarding the crack initiation and propagation were conducted and analyzed. The causes that led to the total fracture were discussed. The design of the tool and improper surface roughness are considered to be the main causes of the failure. Some complementary recommendations were proposed so to enhance the production rate of the specific tool.

A company produces prefabricated stirrup cages for the reinforcement of concrete. The process consists of straightening, cutting and twin bending of coiled steel re-bars, in a custom produced machine. The punch of the cutting system failed repeatedly. Its cutting edges lose their functionality much earlier than expected. Two representative pieces were analyzed. The study included visual inspection, chemical analysis, hardness and micro-hardness measurements. Optical metallographic examination on representative samples was carried out. The fracture areas were analyzed using a scanning electron microscope (SEM) and the crack initiation and propagation were discussed. The punches failed by chipping wear mechanism due to low-cycle fatigue. Their repeating failures provoked by faulty machine design. Problem solving suggestions are proposed. In addition, alternatives related to material selection are provided in order to reduce crack susceptibility, in an economical way. Moreover, conclusions and recommendations can be useful, resulting in higher productivity of prefabricated stirrup cages.

The usual failure of an anchor hoisting assembly was investigated. The anchor ensures stability in cases of ship mooring in a harbor, anchorage or bay and provides adequate safety combined with convenient and easy handling. For the anchor hoisting a hydraulic motor is used consisting of a main two-speed crankshaft, the oldham’s coupling and a valve spool. The oldham’s coupling of a specific oil-tanker frequently fails during the anchor descent and blocks the whole hoisting system. Three pieces used to the same anchor were examined. Two of them exhibited total fracture while the third one had been plastically deformed. The study involved chemical analysis, hardness measurements and in-depth examination of microstructures and fracture morphologies of specimens derived from the failed parts. The paper presents conclusions related to the fracture mechanism and the type of fractures respectively. It was found that poor design and wrong material selection were the main causes of failure.

The present study is focused on the failure of a die used in plastic injection moulding. The die was made from AISI H13 steel and was intended for the production of plastic cups used for the outer closure of cylindrical aluminium cans in coffee packaging. The appearance of the die provides a clear picture of degradations. Extended corrosion damage on various areas of the metallic part and a wide crack can be observed by the naked eye. Hardness measurements and chemical analysis eliminated the probability of faulty material selection or improper heat treatment. Visual inspection, macro-examination and microscopic observations of representative failed parts revealed that the failure was caused by corrosion that led to the total cracking of the die. The design deficiency and improper cooling conditions generated a complex fatigue-corrosion cracking mechanism that lead to the damage of the die after half of it’s predicted service life.

Tire recycling includes three steps: cutting strips, turning strips into small pieces, and shredding pieces into powder. The bases of the first stage machine’s cutting blades usually broke down provoking extensive down times. The paper is focused on the microscopic examination of the failed part. Historical data were collected, hardness measurements were carried out and chemical analysis was performed. The fracture surfaces and the cross section structure of the tool were in depth investigated by light and scanning electron microscopy. The fracture mechanism and the type of the fractures were discussed. The principal causes that led to the premature failure of the base are exposed. Considering the absence of similar failure analysis case studies in bibliography, the study may be useful for industries using similar cutting machinery.

The paper studies the fracture surfaces of a rotary cold working die that broke down during the setup process on the machine it was designed for. The die was manufactured using AISI D2 tool steel and was intended for cutting paper at room temperature. The tool failed during the setup process on the machine. Initially, historical data were collected: operating conditions, lifetime, restitution of sound operation, collection of recorded service history. This was followed by measurement of temperatures, hardness control, optical inspection and selection and preparation of samples. The cutting edges, fracture surfaces and the structure, not affected by the failure, were investigated by optical microscopy. The quality of the nitrated layers were inspected. Additional information concerning the fracture was obtained by examining the fracture surfaces using a scanning electron microscope. Local chemical analysis of the material was made using an EDX spectrometer. Fracture mechanism, the type of the fractures, and the principal causes that led to the premature failure of the die are discussed. Justification of these causes facilitates the prevention of future failures and sometimes contributes to an increased service life of the tools.

The failure of a cutting tool intended for the production of car racks was investigated. The tool consisted of two parts, the mould and the counter-die. The die, made of AISI O1 steel and designed for cutting metal sheets up to 2 mm thick, failed during the final grinding process, before performing any production service. Recorded history was collected, with data concerning the material selection, the manufacturing conditions and the final heat treatment. The die was inspected visually and than photographed. Hardness measurements and chemical analysis were performed in order to identification the tool material. A representative sample was subjected to magnetic-particle inspection for the emergence of surface cracks. Specimens were examinated by optical and electron microscopy (SEM). The type of failure and the principal factors that caused it are studied, and some suggestions are presented, in order to avoid similar failures.