New soluble polyimides with inherent viscosities of 0.25–0.62 dl g−1 were synthesized from 3,6-diamino-9-alkylcarbazole and various aromatic tetracarboxylic dianhydrides by the conventional two-step method, including ring-opening polyaddition and subsequent thermally cyclodehydration. Most of the polyimides having hexyl alkyl chains were soluble in N-methylpyrrolidinone and m-cresol, while the polymers having ethyl chains were not soluble in organic solvents. The glass transition temperatures and 10% weight loss temperatures under argon of the polyimides having hexyl chains were in the ranges 232–269 °C and 485–518 °C, respectively.

In order to investigate very high cycle fatigue characteristics of the Zr 55 Al 10 Ni 5 Cu 30 (in at.%) bulk amorphous alloy, fatigue tests were performed in rotating bending at a frequency of 52.5 Hz with a stress ratio of R=-1. The test environment was in room atmosphere without any control of temperature nor humidity. The fatigue endurance limit σ w of the bulk amorphous alloy was about 700 MPa and the fatigue strength ratio σ w /σ B (fatigue endurance limit divided by the ultimate tensile strength) was found to be 0.38. Fracture surfaces of failed specimens were observed by scanning electron microscope (SEM). The fracture surface was separated into three typical regions; (1) multi-facet region, (2) stable crack propagation region and (3) instantaneous fracture region. The cracks took place on the specimen surface and fatigue striations were clearly formed in the stable crack propagation region on the fracture surface. A distinct boundary was observed between the stable crack propagation region and instantaneous fracture region. The instantaneous fracture region was covered by the dimple-type morphology. Vein-like patterns peculiar to the static fracture surface of amorphous alloys were also found in the edge region of the fracture surface. The fatigue fracture toughness of this bulk amorphous alloy was in the range of 20-29 MPa·m 1/2 .

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Fatigue property in gigacycle regime is focused as an important subject in recent years. In such a long-life region, a tremendous long period is required to perform the fatigue tests. In order to overcome this difficulty, special types of fatigue testing machines in rotating bending whose loading type is cantilever bending has been developed. It is known that this type of fatigue machine can be performed much quickly comparing with the tension and compression fatigue testing machines. And these experimental results are consistent with much data obtained by using traditional testing machines like tension and compression fatigue testing machines and the rotating bending fatigue test machines whose loading type is uniform bending named as Ono type, though it is unclear that much data of an ultrasonic fatigue testing machine are consistent with them. Although it prefers to perform the fatigue tests as fast as possible, but the maximum frequency of a rotating bending fatigue test are limited because of the possibility of temperature rise in specimen caused by the cyclic plastic work and the heat transfer from fatigue testing machine. Such local temperature rise might affect the fatigue property. However, the appropriate loading frequency limit is unclear because of the difficulty of the temperature measurement in the fracture portion of a specimen precisely during the rotating bending fatigue test. An in-situ temperature measuring technique is proposed to measure the temperature at the fracture portion of the specimen in real time during the fatigue testing, and the validity to determine the loading frequency of a rotating bending fatigue testing machine is discussed in this study.

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