Papers by Keyword: Temperature Measurement

Abstract: Laser powder bed fusion (LPBF) is a frequently used manufacturing process due to its advantages in lightweight construction, design possibilities and functionalization of geometry. However, the printed parts will often have to undergo time and cost expensive non-destructive testing by sophisticated methods like X-CT. Thus, there is a strong demand to identify suitable online process monitoring techniques that allow to reduce or substitute post-process NDT effort. The temperature field reacts sensitively to deviations during processing, thus online temperature monitoring is a promising approach. In the present work a spatially resolved temperature measurement, based on 2-channel-pyrometry, is used for process monitoring in LPBF. The camera system is coaxially integrated into the beam guidance of the LPBF system. The coaxial observation enables a lateral resolution better than 10 μm over the whole build-up area of 250 x 250 mm2. Single tracks were welded with different parameters and observed by the camera system to identify thermal indicators. Metallographic cross-sections of the tracks were compared with the melt pool width measured by the online observation system. The deviation was ca. 3 %. In addition, cubes of 10 mm by 10 mm by 10 mm are built up. The melt pool area is identified as useful indicator for the process behavior and for the first time the assessment of part density is demonstrated in LPBF during process by the help of a thermal monitoring system.

Abstract: In the present study, Rolling Contact Fatigue (RCF) tests of Poly-phenylene-sulfide (PPS) thrust bearings under dry condition were carried out and the relationship between fatigue life of bearings and temperature was studied. Furthermore, in order to investigate maximum temperature of PPS thrust bearings in service, in order to obtain the calibration data, the temperatures of rolling contact element and Infrared (IR) temperature on the side of top race were measured and correlated. It is concluded that the contact temperature of failure PPS bearing was higher than the glass transition point but lower than a melting point of PPS.

Abstract: The heating temperature of the silicon carbide sublimation growth crucible is changed by adjusting the output power of the medium frequency induction coil, and the sintering experiments were carried out using NaCl and Al₂O₃ to observe the morphological changes after sintered under different output power, the corresponding temperature was determined, and the corresponding relationship between the output power and the heating temperature was obtained, the precise temperature control was realized. The results of temperature measurement were compared with that of the infrared photoelectric pyrometer. Based on this, the SiC grains were prepared according to the temperature measurement results. The Raman spectroscopy result shows that the SiC polytype was 6H, the SiC grains distributions are homogeneous, and the size of the SiC grains is uniform and dense.

Abstract: This presented article deals with two newly designed experimental walls with different measuring sections (5 for each lightweight wooden wall). All fragments meet the standards required for zero and energy-plus buildings, which would be mandatory in Slovakia from the year 2020. The experimental walls are located in central Europe (town Zilina, Slovakia). Description of individual test sections, the measuring technology, data collection, interior technical equipment and outdoor boundary conditions monitoring are introduced. In the future, the experimental research should progressively combine theoretical calculations with real measurement and computer HAM simulation. In this paper, the focus is aimed to the temperature profiles in wall fragments during seven days chosen from the spring period in the year 2017. The results were graphically presented and evaluated from a point of view of continuous temperature measurement in the structure, exterior boundary conditions, wall orientation and surface character (material, color). Also further intensions of research are drawn.

Abstract: Thermal load, especially vertical temperature gradient, is an important factor that should be considered during the bridge design procedure. In the world, several researches focusing on temperature gradient was made, mostly in USA and China, but only a few analyzed actual temperature gradients measuring at European bridges. In this paper, short overview of temperature loading of bridge structures is described. Then, the temperature measurement of prestressed concrete box girder bridge built by launching method is analyzed. Recorded temperature gradient has been compared with temperature gradients for the concrete box girder cross section recommended by Eurocode design specifications.

Abstract: The comprehensive characterization of the change in metallic materials’ microstructure due to an applied load is of prime importance for the understanding of basic fatigue mechanisms or more general damage evolution processes. If those mechanisms and processes are to be understood to a much greater extent, advanced fatigue life calculation methods being far away from linear damage accumulation models, have to be realized providing more than “classic fatigue data” only. Among others the PHYBAL (physically based fatigue life calculation) method including current enhancements and a thereon-based development named SteBLife (step-bar fatigue life approach) have been developed over the last 10 years. These methods allow the efforts in experimentation to be reduced by more than 90 % and therefore offer the possibility to take further fatigue relevant parameters into account. This therefore allows a variety of S,N-curves dependent on those fatigue relevant parameters to be generated with those methods easily establishing a multidimensional dataset. To just name a few examples of those parameters such as the influence of temperature, loading conditions, geometry as well as thermal and mechanical ageing processes on the fatigue behavior can now be calculated in accordance to a process being straightforward leading to an important step with regard to improving the efficiency of assessing structural components. Consequently, safety factors can be defined more in accordance to structural needs, being of highest interest with respect to the increasing number of ageing infrastructure such as highways, bridges or others. A lot of this ageing infrastructure has a strong need to be managed with respect to its structural integrity and the engineering community therefore tries the residual life of this infrastructure to be determined as appropriate as possible. In that context non-destructive testing parameters are increasingly considered to characterize a metallic material’s microstructure allowing more precise information to be obtained regarding the actual damage condition and the integrity of a component. The paper will address the high capability of non-destructive testing techniques for the evaluation of damage evolution processes also with respect to mechanism based fatigue as well as residual life calculations according to PHYBAL and SteBLife.

Abstract: Polymer bearings are attracting more and more attention due to the advantages on light weight, chemical and corrosion resistant, etc. PTFE owns the third-lowest friction coefficient within any known solid material, which makes it a considerable polymer material for bearing producing. In the present study, RCF tests under dry condition were carried out, and the relationship between failure and temperature of PTFE thrust bearings was investigated.

Abstract: Internal combustion engines are typically equipped with an exhaust muffler to suppress the acoustic pulse generated by the combustion process. The paper presents the procedure and the experimental setup for some functional parameters determination as the noise level, the pressure drop and the temperatures through investigating three different manufacturing solutions for mufflers. An algorithm and a dedicated method have been proposed in order to emphasize more direct the mufflers influence on the engines performances. The procedure equally includes particular cycles of the engine and it is highlighted the relation between the engine operating conditions and the functional parameters of the automotive mufflers.

Abstract: In order to make the dynamically tuned gyroscope of Strap-down North-seeking working on the best temperature environment, reduce errors caused by temperature changes, a high-precision temperature control system is built up on the base of control theory and engineering. This system is a two-stage temperature control system. In order to realize high precision temperature control at a predetermined temperature range, temperature measurement circuit is analyzed and calculated on a two-stage temperature control had different measurement circuit match. Experimental results show that the accuracy of can achieve ± 0.1 °Cwhen the environment temperature within the range of-40 °C ~ + 60 °C. It can meet the temperature requirements of Strap-down North-seeking system.

Abstract: In order to improve the accuracy, range and instantaneity of high temperature measurement, a CCD (Charge Coupled Device) image temperature measurement system was designed based on multi-sensor truncated mean weighed fusion. Firstly, CCD temperature measurement range was expanded by 6 light filters. Then 15 colorimetric-sensors calculated the surface temperature of experimental molten pool. Finally, the more accurate fusion estimate of temperature value was acquired by using truncated mean weighted factors. The experiment results demonstrate that system have faster processing speed in the measurement of 800°C. The errors were kept within ±2%. This method is effective in improvement of system accuracy and instantaneity.