Stress Cracking Tests Research Articles

Estimation From Censored, Interval Data of the Median Breaking Point of Polyethylene Subjected to Stress-Cracking Tests: A Monte Carlo Study

A Monte Carlo study has been carried out in order to study the properties of various alternative estimators for median breaking point of polyethylene specimens subjected to an environmental stress cracking test. Tables of bias, variance, and mean square error have been derived for different sample sizes, interval sizes, and levels of censoring data with the lognormal distribution as a model. These tables will aid in the design of experiments for efficient estimation of median breaking point.

Rheological Study on Cold and Warm Processings of Polycarbonate

The retentivity of shape in uniaxial compression of polycarbonate resin when processing in the cold and warm processing temperature range was investigated experimentally. Iupilon, a polycarbonate resin manufactured by the solvent process, was used as the sample. Strain recovery of test specimens, which were processed by compression at various temperatures, was measured after free annealing by raising the temperature gradually to a temperature higher than the processing temperature. Polycarbonate has superior processability in the vicinity of room temperature and has good strain-freezing properties at temperatures below the glass transition temperature; however, strain is recovered completely at temperatures above the glass transition point. A new Erichsen testing apparatus was developed for measuring the temperature dependence of processability of sheet in the cold and warm temperature range. A punch is pushed into the sheet whose temperature has been made uniform in a constant temperature apparatus at a fixed stroke speed; the Erichsen depth at fracture at the various temperatures is measured. Results indicated that processability of polycarbonate sheet (thickness, 1 mm) improves gradually with temperature rise as high as the glass transition point. Experiments on strain recovery of an Erichsen test specimen were carried out in the same manner as in the case of uniaxial compression. The results for combined stresses, such as in Erichsen bulging, were similar to those of uniaxial compression. An attempt is being made to utilize such Erichsen bulging test specimens for environmental stress cracking tests of polycarbonate.

黄銅の時期割れについて

Ammonia stress-cracking tests upon slowly solidified coarse-grained 70 Cu-Zn brass were carried out. At first, fine parallel cracks {111} or {110} appear, next, the cracking direction is changed transverse to the stress direction, finally, fine parallels connecting together as if they were single cracks appear transverse to the stress direction.

銅合金の応力腐蝕割れ (第4報)

Aqua ammonia stress-cracking tests have been conducted on the high tensile strength brass as using for ship's propeller.The stress corrosion cracking resistance in aqua ammonia of these alloys could be explained in both relations of the α/β ratio of alloy and the film effect.

銅合金の応力腐蝕割れ (第1報)

Aqua ammonia stress-cracking tests have been conducted on the 65/35 and 60/40 cast brasses containing some other alloy elements.Tin, aluminum and manganese, as an alloy addition, improve stress corrosion cracking resistance on account of their film effect, while iron have little effect on aqua ammonia cracking.Alloys which have slightly introduced a second phase because of having been added the alloy elements, however, show the lower resistance to stress corrosion attack. In the above case, micrographic examination has shown the crack originat edat the two-phase-boundary.It was considered that micro-crack (Griffith's), as nucleus of cracking, was formed by dislocations which had been piled up at the phase boundary and then the crack propagated in reducing the surface energy by corrosive attack.