Ingenieurwissenschaften und zugeordnete Tätigkeiten
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For many sealing applications low temperature performance is required. The overall understanding of the relevant influences on low temperature performance of rubber seals are summarized and the currently running investigations described.
The correlation of the physical material properties with seal performance is studied. This includes as well purely static sealing applications as the performance during/after fast partial relief of seals at low temperatures.
For many sealing applications rubbers are applied due to their special material properties and easy use. In many applications as e.g. in aviation, traffic or process technology the material can be exposed to low temperatures during operation. Therefore, it is important to know the material behaviour at those low temperatures to determine the temperature range that allows a safe operation of the seal.
In this work, we focus on the behaviour of elastomer seals at low temperatures with regard to potential decrease of leak-tightness or catastrophic seal failure of O-ring rubber seals. This is required as material properties of rubbers are strongly temperature dependent but their temperature application range is not always clearly defined.
Based on previous investigations which considered the physical material properties and the seal behaviour under purely static conditions we widen the focus on the sealing performance after a fast partial relief of compressed seals and additional materials.
For the investigations, different typical rubber seal materials were used as e.g. fluorocarbon (FKM), ethylene propylene diene (EPDM) and hydrogenated acrylonitrile-butadiene (HNBR) rubber.
The correlation of the physical material properties with seal performance is studied. This includes as well purely static sealing applications as the Performance during/after fast partial relief of seals at low temperatures.
Shrinkage measurement of miniaturized low temperature co-fired
ceramics (LTCC) samples under load typically leads to a collapsing of
the sample due to the softening of the glassy phase, which hampers
the characterization of shrinkage up to full densification. In practical
sintering processes in contrast, LTCC panels are sintered under axial
loads of up to 1 MPa without lateral shrinkage or collapsing of the
structure. To characterize the shrinkage behavior during such
processes, a measurement setup was developed, which allows for in-situ
thickness shrinkage measurements of practical, large LTCC panels
during pressure-assisted sintering in a sintering press. Using this setup,
the shrinkage behavior of two commercial LTCC tapes (GreenTape 951
and Ceramtape GC) has been measured under loads of up to 1 MPa.
No crushing of the specimens was observed and reproducible
characterization of shrinkage up to full densification has been
performed. Based on comparisons to thermomechanical analyzer
measurements in this and other studies, it is concluded that the in-situ
approach is much better suited for shrinkage characterization of LTCC
under load.
Shrinkage measurements of miniaturized low temperature co-fired ceramics (LTCC) samples under load typically lead to collapsing of the samples, which hampers the characterization of shrinkage up to full densification. In this paper, a measurement setup is presented, which allows for in situ shrinkage measurements of practical, large LTCC panels during pressure-assisted sintering in a sintering press. The shrinkage behavior of two commercial LTCC systems (GreenTape 951 and Ceramtape GC) has been measured under loads of up to 1 MPa. No crushing of the specimens was observed and reproducible characterization of shrinkage up to full densification has been performed. Based on comparisons to thermomechanical analyzer measurements in this and other studies, it was found that the in situ approach is much better suited for shrinkage characterization of LTCC under load.
Reproducibility and accuracy of the method are discussed and practical as well as more academic applications are proposed.