TY - JOUR A1 - Qiao, Linan A1 - Nagelschmidt, Sven A1 - Herbrich, Uwe T1 - Application of a Modified Arrhenius Equation to Describe the Time-Temperature Equivalence in Relaxation Analysis of Metal Seals N2 - For the application of the time-temperature superposition principle a suitable relation is needed to describe the time-temperature shift factor α. Therefore, the Arrhenius equation is widely used due to its simple form and often leads to suitable results. Where, the Arrhenius equation presents a linear relation for the temperature-dependent shift factor in logarithmic scale ln(α) with the absolute inverse temperature (1/ϑ). However, in cases with a large temperature range which eventually include more complex reaction processes, the functional relation between ln(α) and (1/ϑ) is nonlinear in the ‘Arrhenius plot’. In those cases, the monotone change of the nonlinear range in the ‘Arrhenius plot’ can be interpreted as a transient range between two approximately linear or constant regions. An extended application of the modified Arrhenius equation from Nakamura (1989) is presented in this study for this transient range. The introduced method was applied to describe the time-temperature equivalence in the relaxation analysis of restoring seal force of metal seals, which are used in lid-systems of transport and interim storage casks for radioactive materials. But, the method is widely valid and can be used for different objectives which are characterized by thermorheologically simple behavior with nonlinear sensitivity to inverse temperature. KW - Metal seals KW - TTS principle KW - Arrhenius equation KW - Non-linear Arrhenius behavior KW - Relaxation analysis KW - Seal force PY - 2017 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-446759 UR - http://www.davidpublisher.org/index.php/Home/Article/index?id=33931.html DO - https://doi.org/10.17265/1934-7359/2017.09.004 SN - 1934-7359 VL - 11 IS - 9 SP - 853 EP - 861 PB - David Publishing Company CY - USA, NY 10989, Valley Cottage AN - OPUS4-44675 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qiao, Linan A1 - Herbrich, Uwe A1 - Nagelschmidt, Sven T1 - Describing Relaxation Behavior of Metal Seals Using Time-Temperature Superposition Principle N2 - In order to study the time- and temperature-dependent long-term behavior of metal seals, experimental investigations on special metal seals have been carried out at five different temperatures in a temperature range between 20 and 150°C for more than 7 years. Experimental results indicate a noticeable change of relevant sealing properties like seal force and usable resilience depending on time and temperature. In this study, the metal seals are treated as a homogeneous material block so that the identified decrease in seal force can be treated as a material relaxation effect. For the time-dependent behavior of seal force, an enhanced power-law model is introduced for the first time and is compared with the currently used power-law model. Additionally, regarding the influence of temperature, the timetemperature superposition principle is applied to metal seals for the first time with a clearly defined process. Thus, possible mistakes in the application of principle could be avoided. The introduced method is widely available for different applications regarding effects the principle with time and temperature. KW - Metal seals KW - Relaxation KW - Thermo-viscoplasticity KW - Time-temperature superposition PY - 2018 UR - https://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EM.1943-7889.0001424 DO - https://doi.org/10.1061/(ASCE)EM.1943-7889.0001424 SN - 0733-9399 VL - 144 IS - 4 SP - 04018016-1 EP - 04018016-8 PB - American Society of Civil Engineers AN - OPUS4-44676 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Qiao, Linan A1 - Nagelschmidt, Sven A1 - Herbrich, Uwe A1 - Keller, Christian T1 - Introduction of a Power Law Time-Temperature Equivalent Formulation for the Description of Thermorheologically Simple and Complex Behavior N2 - Abstract: In this work, a conceptual framework is suggested for analyzing thermorheologically simple and complex behavior by using just one approach. Therefore, the linear relation between master time and real time which is required in terms of the time-temperature superposition principle was enhanced to a nonlinear equivalent relation. Furthermore, we evaluate whether there is any relation among well-known existing time-temperature equivalent formulations which makes it possible to generalize different existing formulations. For this purpose, as an example, the power law formulation was used for the definition of the master time. The method introduced here also contributes a further framework for a unification of established time-temperature equivalent formulations, for example the time-temperature superposition principle and time-temperature parameter models. Results show, with additional normalization conditions, most of the developed time-temperature parameter models can be treated as special cases of the new formulation. In the aspect of the arrow of time, the new defined master time is a bended arrow of time, which can help to understand the corresponding physical meaning of the suggested method. KW - bended arrow of time KW - time-temperature superposition principle KW - time-temperature equivalent formulation PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-543800 DO - https://doi.org/10.3390/ma15030726 VL - 15 IS - 3 SP - 1 EP - 11 PB - MDPI AN - OPUS4-54380 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Völzke, Holger A1 - Wolff, Dietmar A1 - Probst, Ulrich A1 - Nagelschmidt, Sven A1 - Schulz, Sebastian T1 - Long term performance of metal seals for transport and storage casks N2 - Dual purpose casks for the transportation and storage of spent nuclear fuel and other radioactive materials require very high leak tightness of lid closure systems under accident conditions as well as in the long term to prevent activity release. For that purpose metal seals of specific types with an inner helical spring and outer metal liners are widely used and have shown their excellent performance if certain quality assurance requirements for fabrication and assembling are satisfied. Well defined surface roughness, clean and dry inert conditions are therefore essential. No seal failure in a loaded cask happened under these conditions until today. Nevertheless, the considered and licensed operation period is limited and all safety assessments have been performed and approved for this period of time which is 40 years in Germany so far. However, in the meantime longer storage periods might be necessary for the future and therefore additional material data will be required. BAM is involved in the qualification and evaluation procedures of those seals from the early beginning. Because long term tests are always time consuming BAM has early decided to perform additional tests with specific test seal configurations to gain a better understanding of the long term behaviour with regard to seal pressure force, leakage rate and useable resilience which is safety relevant mainly in case of accidental mechanical loads inside a storage facility or during a subsequent transport. Main test parameters are the material of the outer seal jacket (silver or aluminium) and the temperature. This paper presents the BAM test program including an innovative test mock-up and most recent test results. Based on these data extrapolation models to extended time periods are discussed, and also future plans to continue tests and to investigate seal behaviour for additional test parameters are explained. KW - Metal Seal KW - Spent Fuel KW - Storage KW - Ageing KW - Cask KW - Leak tightness PY - 2014 DO - https://doi.org/10.1179/1746510914Y.0000000057 SN - 1746-5095 SN - 1746-5109 SN - 0957-476X VL - 25 IS - 1 SP - 8 EP - 15 PB - Ramtrans Publ. CY - Ashford AN - OPUS4-32327 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Nagelschmidt, Sven A1 - Herbrich, Uwe A1 - Keller, Christian A1 - Qiao, Linan T1 - Re-evaluation of tensile and creep rupture data of metals using a modified Larson–Miller approach N2 - More than 70 years ago, in 1952 Larson and Miller adapted an existing relationship whichevaluates the relative effects of time and temperature on creep rupture behavior of various alloys by using existing data and by constructing so-called master curves. Since that time, the formulated Larson–Miller relation, commonly known as Larson–Miller parameter, is a widely used time–temperature parameter for various applications, e.g. for rupture life, creep and relaxation analyses of metals and some other materials such as polymers, concrete and ceramics.Nevertheless, the physical meaning of this parameter as well as the determination of master curves are still the subject of major criticism. In this work, both aspects are reviewed and analyzed with data originally considered in thepaper of Larson and Miller based on the following approach: (a) the parameter was modifiedregarding a reference time and a reference temperature according to the time–temperature superposition principle; (b) master curves were generated for five materials investigated originally by Larson and Miller, based on a stretched exponential function type. It has been shown, that: (1) With normalized time and temperature, the Larson–Miller parameter corresponds to real logarithmic rupture time. (2) For the relationship between Creep rupture stress and the modified Larson–Miller parameter, the stretched exponential function is a good choice as a master function. (3) Corresponding model parameters have physical meaning and can be easily determined based on data from creep test data. The investigations provide a better understanding and applicability of Larson–Miller approach. KW - Larson–Miller parameter KW - Creep rupture time KW - Time–temperature equivalence KW - Stretched exponential function KW - Extrapolation of short-term data PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-644486 DO - https://doi.org/10.1016/j.engfracmech.2025.111582 SN - 0013-7944 VL - 329 SP - 1 EP - 16 PB - Elsevier Ltd. AN - OPUS4-64448 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -