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Some zinc coated advanced high strength steels (AHSS), under certain manufacturing conditions, are known to be prone to liquid metal embrittlement (LME) during resistance spot welding. LME is an undesired phenomenon, which can cause both surface and internal cracks in a spot weld, potentially influencing its strength. An effort is made to understand influencing factors of LME better, and evaluate geometry-material combinations regarding their LME susceptibility. Manufacturers benefit from such knowledge because it improves the processing security of the materials. The experimental procedure of welding under external load is performed with samples of multiple AHSS classes with strengths up to 1200 MPa, including dual phase, complex phase and TRIP steels. This way, externally applied tensile load values are determined, which cause liquid metal embrittlement in the samples to occur. In the future, finite element simulation of this procedure gives access to in-situ stress and strain values present during LME formation. The visualization improves the process understanding, while a quantification of local stresses and strains allows an assessment of specific welded geometries.
A 3D electro-thermomechanical model is established in order to investigate liquid metal embrittlement.
After calibration to a dual phase steel of the 1000 MPa tensile strength class, it is used to analyse the thermo-mechanical system of an experimental procedure to enforce liquid metal embrittlement during resistance spot welding. In this procedure, a tensile stress level is applied to zinc coated advanced high strength steel samples during welding. Thereby, liquid metal embrittlement formation is enforced, depending on the applied stress level and the selected material.
The model is suitable to determine and visualise the corresponding underlying stresses and strains responsible for the occurrence of liquid metal embrittlement. Simulated local stresses and strains show good conformity with experimentally observed surface crack locations.
The Laser-Induced Breakdown Spectroscopy (LIBS) is a laser spectroscopic method which allows a time efficient, minor-destructive, chemical analysis of materials. In principle all elements on the periodic table can be simultaneously analysed by using LIBS, regardless of the state of aggregation. LIBS offers numerous applications in the field of civil engineering; most importantly the analysis of building materials. This work will focus on the evaluation of concrete structures and harmful substances which can penetrate the concrete. A variety of information can be collected through LIBS. Determining the concentration of harmful substances like chloride, sodium or sulphur, the examination of the carbonation depth and the distinction between varying layers of materials (e.g. aggregates, cement paste, metals, etc.) are possible applications. All this information can be provided through one LIBS measurement in the form of a high resolution 2D element map, with resolutions up to 0.1 mm x 0.1 mm. To scan a concrete surface only an optical access is needed. To create a depth profile of an intruding substance the extraction of a drill core is necessary. Onsite measurements via LIBS can be conducted by using a mobile version of the LIBS system. Through using calibration curves LIBS allows not only the qualitative but also quantitative analysis of element concentrations. All those prospects make LIBS a trendsetting method to secure the integrity of infrastructures in a sustainable manner.
The Laser-Induced Breakdown Spectroscopy (LIBS) is a laser spectroscopic method which allows a time efficient, minor-destructive, chemical analysis of materials. In principle all elements on the periodic table can be simultaneously analysed by using LIBS, regardless of the state of aggregation. LIBS offers numerous applications in the field of civil engineering; most importantly the analysis of building materials. This work will focus on the evaluation of concrete structures and harmful substances which can penetrate the concrete. A variety of information can be collected through LIBS. Determining the concentration of harmful substances like chloride, sodium or sulphur, the examination of the carbonation depth and the distinction between varying layers of materials (e.g. aggregates, cement paste, metals, etc.) are possible applications. All this information can be provided through one LIBS measurement in the form of a high resolution 2D element map, with resolutions up to 0.1 mm x 0.1 mm. To scan a concrete surface only an optical access is needed. To create a depth profile of an intruding substance the extraction of a drill core is necessary. Onsite measurements via LIBS can be conducted by using a mobile version of the LIBS system. Through using calibration curves LIBS allows not only the qualitative but also quantitative analysis of element concentrations. All those prospects make LIBS a trendsetting method to secure the integrity of infrastructures in a sustainable manner. A variety of examples which show the performance and results of LIBS analysis will be presented.
The effect of bouncing strikes on crack extension in low blow tests has been investigated.
• Crack propagation sensor signals, force-displacement records and loading level have been analyzed.
• Additional crack extension in the specimen due to bouncing strikes of the hammer is not to be expected.
It can be seen as a major experimental advantage that the striker does not have to be catched after the low blow test.
• This has to be proved for the given conditions of test setup, material and loading.
The European biocides directive (98/8/EG) demand the control of emissions into the envi-ronment like soil, water and air. In this study a method for measuring the input of biocides into the indoor air from materials should be developed. The emission of two products containing biocides (plastic foil, wool carpet) and six different types of biocide containing formulations applied on wood or ceramic tiles were investigated in 20 or 23 l glass emission chambers. Each chamber test was performed over a period of 100 up to 200 days. SVOC show totally different emission curves in chamber tests compared to volatile organic com-pounds (VOC). They reach their maximum value after some days or weeks. Thus a period of 3 months is sometimes necessary for exact measurements. Area specific emission rates (SERa in µg/m²h) for permethrin (0.006), propiconazole (0.2), dichlofluanid (1.5), tolylfluanid (1.2), octylisothiazolinone (2.5) and for iodpropinylbutyl-carbamat (1.7) were determined.