Papers by Keyword: Master Curve

Abstract: The low temperature tensile properties, Charpy-V notch impact performance and fracture toughness of SA738Gr.B steel plate for domestic CAP1400 containment vessel were tested. On this basis, the reference temperature T₀ of the master curve method was obtained. The fracture toughness distribution of the steel in the whole ductile-brittle transition zone is predicted and its applicability is verified by the theoretical basis of the master curve method. The results show that the reference temperature of SA738Gr.B steel master curve method is-123.6 °C. The master curve method is appropriate for SA738Gr.B steel with domestic nuclear containment vessel.

Abstract: The behaviour of the materials in ductile-brittle transition region must be known when performing structural integrity assessments of nuclear reactor vessels working under the effects of neutron irradiation. The characterisation of this region has been usually carried out by means of Charpy impact tests. Just during last few years new approaches based on direct fracture mechanics tests have begun to be used. In most of these cases, the Master Curve methodology, which allows the transition region to be characterised using only one parameter (T₀ reference temperature), has been employed. In this paper the transition region of two materials –one vessel steel and one common structural steel-has been characterised by means of Small Punch Tests. First of all, this zone has been characterised using conventional specimens and the results were compared with those of Charpy impact tests. Finally a new approach based on the use of notched Small Punch samples together with Master Curve methodology has been proposed.

Abstract: Beam welded joints made from fine grain steels show martensitic micro structure, high weld hardness and thus low toughness in the weld seams. At the same time there is a risk for these welds to have crack-like defects that cannot be detected during the production and which grow due to cyclic loading. If such structures are used in areas with low ambient temperatures, it may come to brittle failure of the component. To secure components against such failure, fracture mechanic tests were carried out on electron beam welded SE(B)-samples made from S690QL and S960QL and the J-integral was determined. In order to describe the scattering of the results in the temperature transition region the results were evaluated by means of the Master Curve concept in accordance with ASTM E 1921. Afterwards the reference temperature in the transition range, T₀, was determined and correlated with the T_27J- temperature of Charpy V-notch tests.

Abstract: This paper presents the reliability analysis of the creep rupture strength and long-term life of a directionally solidified nickel-base superalloy, DZ125, which is widely used for manufacturing turbine blades of advanced aeroengines. A number of creep rupture experiments of DZ125 alloy are carried out at 760^oC, 850^oC, 980^oC and 1040^oC. Larson-Miller (L-M for short) parameter is used to predict the long-term creep life and a master curve in the L-M parameter is obtained. A “Z-parameter” model is employed to characterize the magnitude of the deviation of the creep rupture data to a master curve. The “Z-parameter” of DZ125 alloy followed Gaussian distribution which is verified by Chi-square testing. Based on the “Z-parameter” model, the curves of Stress-TTP (i.e. Time-temperature parameter)-Reliability, Stress-Life-Reliability and Allowable Stress-Temperature-Reliability are obtained to predict the creep rupture strength and life for DZ125 alloy.

Abstract: The effect of styrene-ethylene/buthylene-styrene triblock copolymer (SEBS) on the thermal and rheological properties of thermoplastic polyurethane/polypropylene (TPU/PP) blends was investigated. For the selection of polymer materials and polymer blends for various fields of applications the stability of materials under constant deformation are very important. The blends were therefore characterized by measuring secondary viscoelastic functions creep, recovery and creep modulus using dynamic mechanical analysis (DMA) in the creep fatigue regime. The master curves at the reference temperature of 25°C were created by time-temperature correspondence (TTC) principle. The correlation of the creep modulus with time, temperature and addition of compatibilizer was discussed. The differential scanning calorimetry (DSC) results indicated that the addition of SEBS as a compatibilizer in TPU/PP blends increases glass transition temperature (T_g) and decreases crystallinity (χ_c). SEBS block copolymer acts as an efficient compatibilizer for TPU/PP blends.

Abstract: In order to realize effective detection of the splitting strength of shallow asphalt pavement, using the self-researched and developed Strength Detector of Shallow Pavement, researched deep into the change regulation between shallow pavement strength and temperature by laboratory and spot penetrating experiments in multiple temperatures. First of all, the splitting strength is found to be a linear function of the average penetrating depth; Secondly, on the basis of temperature and average penetrating depth equivalence principle, obtained the master curve of the splitting strength by translation and fitting. Established a unified and practical test standard for the Strength Detector of Shallow Pavement; At last, analyzed the spot penetrating experiments data of three different types of asphalt pavement in Harbin district. The results show that the splitting strength curve of asphalt pavement in Harbin district appear a deep V-shaped character from April to October. The differentials between splitting strength of the three different types of asphalt pavement maximize in July.

Abstract: The polymer-based propellant is a typical viscoelastic material. Better understanding of the relaxation properties of the propellant in the storage conditions is of great importance for predicting the lifetime. Due to the component complexity of the composite propellants, the transformation relation between the relaxation modulus and the complex modulus may not be suitable for all kinds of propellants. In the present work, we focused on the transformation of the relaxation modulus and complex modulus for the HTPB propellant. The master curves for the relaxation modulus and the storage modulus of the aged/unaged HTPB propellants were obtained by performing the stress relaxation tests and DMA tests, respectively. It was found that there existed a great difference in the double logarithmic plot between relaxation modulus and storage modulus master curves. Moreover, the testing results for the relaxation modulus and the storage modulus were well fitted by an empirical transformation relation with three segment-related coefficients. These three coefficients were determined by using the unaged samples, and then were applied to estimate the relaxation modulus of the aged samples. A good agreement between the calculation and the experimental results was also found, revealing that the three coefficients were insensitive to the aging time.

Abstract: In order to analyze the characteristics of high modulus asphalt mixture dynamic modulus, Universal Testing Machine (UTM-25) was used for dynamic modulus test of three kinds of mixtures, which were PR Module modified asphalt mixture and PR PLAST.S modified asphalt mixture and virgin asphalt mixture, to investigate dynamic modulus and phase angle at different temperatures and frequencies. The results indicate that: the dynamic modulus order of the three asphalt mixtures is PR MODULE > PR PLAST.S > Virgin. PR MODULE asphalt mixture dynamic modulus is much larger than the other two.

Abstract: In the paper, the master curve for the high-strength steel S960-QC is derived. It turns out that the mathematical form of the classical master curve can be preserved. However, some coefficients must be changed. The new formula does not contain the influence of the specimen thickness on fracture toughness. The explanation of this observation is proposed.

Abstract: The stress relaxation modulus E(t) is one of the most important properties of viscoelastic materials such as solid propellant, and it is used to define the viscoelastic behavior based on the influence of time and temperature. In this paper, stress relaxation tests are conducted under constant strain 2% for 600 seconds in the range of temperature 60°C to-60°C and tensile tests are performed for solid propellants under constant cross head rate 5 mm/min in the same temperatures as stress relaxation tests. Based on the results, time-temperature shift factors are obtainedby shifting the relaxation modulus curves horizontally and the master curve of relaxation modulus is generated. The master curve of relaxation modulus according to classical method and Williams-Landel-Ferry (WLF) method are discussed. Also, the master curve of tensile properties are drawn using predetermined shift factor and the results are discussed.