Fused deposition modeling (FDM) is one of the most accessible additive manufacturing (AM) technologies for processing polymeric materials. It allows processing most of thermoplastic polymers, with polyethylene terephthalate glycol-modified (PET-G) and polylactic acid (PLA). AM parts tend to display anisotropic behavior because of layer-by-layer fabrication and various technological parameters that can be set for 3D print, so it is hard to predict and analyze how the manufactured parts would behave under load. This research presents results of classic tensile strength tests performed on 57 PET-G specimens and 57 PLA specimens manufactured with varying technological parameters such as: printing temperature, print orientation, layer height, and infill percentage. Afterward, a comparative analysis is performed, proposing specific tensile strength (STS) as a benchmark to determine how 3D printed parts strength is varying due to beforementioned parameters, eliminating bias induced by varying weight of specimens. The biggest relative increase of UTS and the biggest relative decrease of STS was noted for variable infill percentage (increasing infill—PLA: 37.27% UTS increase and 30.41% STS decrease; PET-G: 24.42% UTS increase and 37.69% STS decrease). The biggest relative increase of STS between examined parameters was observed for both materials as the printing temperature was increased (27.53% for PLA and 12.69% for PET-G). Similar trends in STS changes were observed for both materials. Obtained data shows which FDM AM parameters are the most important to obtain the biggest UTS of manufactured parts, and those do not overlap with parameters needed to obtain optimal strength-to-weight ratio.
The large industrial cranes carry out transportation operations in the presence of a large impact load and mechanical stresses acting on the crane's structure. The safety and efficiency of crane operations can be improved through providing the continuous structural health monitoring of crane's equipment and components. Advanced nondestructive techniques can be employed for inspection of cranes during operation, that leads to reduce the down time costs and increase the safety confidence in the monitoring process. Magnetic flux leakage methods of non-destructive inspection are widely utilized in identification of damaged areas in steel structures. However, the traditional magnetic flux leakage techniques are more appropriate in detecting cracks, but not sensitive to the detection of micro-defects. Metal magnetic memory is a relatively novel method of detecting the micro-damage in ferro-magnets due to the stress concentration. This method proved its effectiveness in early identification of the possible defect location. However, the method is preferable to off-line inspection due to the presence of operational variations in on-line measurements that can cause false indications of damage. In this paper, the problem of continuous inspection of crane's frame using the metal magnetic memory method is considered. The influence of operational variations on the self-magnetic flux leakage signal is investigated and quantitatively analysed based on the experimental results obtained on a laboratoryscaled overhead travelling crane.
The safety and efficiency of material handling systems involve periodical inspections and evaluation of transportation device technical conditions. That is particularly important in case of industrial cranes, since they are subjected to a large impact load and mechanical stresses acting on the crane's structure and equipment. The paper considers the possibility of a crane structure inspection using the metal magnetic memory (MMM) method. As an advanced non-destructive technique, this method can be employed for inspection of crane structure during operation, which leads to reduce the down time costs and increase the safety confidence in the monitoring process. The MMM technique is effective for early identification of the possible defect location and detecting the micro-damage in ferromagnetic structures through detecting the stress concentration areas. The basic principle of MMM method is the self-magnetic flux leakage signal that correlates with the degree of stress concentration. This method allows detecting early damage of ferromagnetic material through performing measurement in the earth magnetic field, without the use of a special magnetizing device. The paper presents the experimental results carried out on the double-girder overhead travelling crane with hoisting capacity 1000 kg. The influence of the load variation and duration time on the intensity of the self-magnetic flux leakage signal is analysed and discussed.
With the passage of time of exploitation of means of technological transport, their degradation takes place and the threat to operational safety increases. The source of development of fatigue damages of gantry crane girders are areas of stress concentration caused by loads. The subject of the publication is to determine the possibility of diagnosing potential damage sites of the overhead travelling crane (girders) by magnetic metal memory (MPM). As a result of the test with the use of the TSC-7M-16 ferrite magnetometer, stress concentration areas were determined in which processes leading to the reduction of material strength or damage to the material structure may take place. Residual tangential magnetic field distributions and normal components of their gradients were determined. A magnetogram database for the needs of girder diagnostics was created.
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