Catalogue of NIMS fatigue data sheets

Abstract

This paper summarizes the NIMS fatigue data sheets and makes a new gateway available to access them. The NIMS fatigue data sheets are a huge database of the fatigue properties of structural materials. This project covers fundamental fatigue properties at room temperature and at high temperatures, and the fatigue properties of welded joints. The fundamental fatigue properties recorded include high-cycle, low-cycle and gigacycle fatigue test results for steels, aluminium alloys, titanium alloys and so on. The high-cycle fatigue test results determine the fatigue limits. The low-cycle fatigue test results reveal not only the fatigue lives but also cyclic stress-strain curves. The gigacycle fatigue tests were conducted at 100 Hz for three years up to 1010 cycles, as well as at 20 kHz for a week. The fatigue properties at high temperatures were evaluated chiefly for steels, via low and high-cycle fatigue tests. The low-cycle fatigue tests were conducted by employing various strain rates and waveforms. The fatigue properties of welded joints were evaluated using thick plates of steels and aluminium alloys, conducting high-cycle fatigue and crack propagation tests employing large specimens in as-welded condition. The high-cycle fatigue tests were conducted using various specimen sizes, welding procedures, stress ratios and so on. The crack propagation tests were conducted for the base metal, the weld metal and the heat-affected zone. Many new findings were obtained with these fatigue data as reviewed in this paper.

Effect of microstructure of simulated heat‐affected zone on low‐ to high‐cycle fatigue properties of low‐carbon steels

“…Cyclic yield stresses were estimated by fitting the peak stresses of the hysteresis curves to a Ramberg‐Osgood type equation by linear regression: where E is Young modulus, C is the cyclic strain hardening coefficient, n is the cyclic hardening strain exponent, ε a is strain amplitude, ε el is elastic strain amplitude, ε pl is plastic strain amplitude, and σ a is stress amplitude. In the following figures, previously reported data on HAZ 11 and existing data 4 on steels and aluminium alloys, measured using incremental step fatigue tests, 25 were also plotted. Similar to the previous conclusion, 11 cyclic yielding stresses were comparable to data for existing steels regardless of changes in microstructure and were approximately proportional to monotonic tensile strength.…”

“…Unlike existing data, quench‐tempered carbon and low‐alloy steels, the HAZ microstructure does not clearly show cyclic softening. This is somewhat similar to SUS630 and A7075‐T6 aluminium alloys, which are precipitation‐hardened materials 4 …”

“…Because the fatigue crack growth rate is generally governed by the cyclic J integral, plastic strain amplitude has a greater impact than stress amplitude, especially in the low‐cycle fatigue region 26 . On the other hand, because the fatigue limit is usually proportional to tensile strength, 4 the high‐cycle fatigue region tends to be sensitive to tensile stress. Therefore, the data variation in Figures 8 and 9 is narrower than in Figure 7.…”

“…The effects of microstructure changes on fatigue property have been widely investigated and discussed based on a large fatigue database 4–6 . For example, it is well known that the fatigue limit is normally proportional to the monotonic tensile strength of the microstructure 4 . However, these previous investigations were mostly conducted on the “normal” microstructure of base metals such as quench‐tempered martensite or ferrite‐pearlite microstructure.…”

Experimental Study on Forged TC4 Titanium Alloy Fatigue Properties under Three-Point Bending and Life Prediction

“…With the continuous improvement of aviation equipment reliability and life index, the ultra-high-cycle-fatigue (10 7 ~10 12 cycles) problem has attracted increasingly more attention, and has become the focus of fatigue research [ 1 , 2 , 3 , 4 , 5 ]. Ultra-high-cycle fatigue belongs to micro-scale fatigue, which differs from traditional high-cycle fatigue (10 5 ~10 7 cycles) not only in the life length, but also in the more complex crack initiation and initial propagation mechanism, and also in the great difference due to different materials [ 6 , 7 , 8 ]. Titanium alloys have become the most widely used metal materials in the modern aviation industry because of their high specific strength, low density, excellent corrosion resistance, and good heat resistance, and the ultra-high-cycle fatigue problems are also the most prominent.…”