Tensile creep testing

Type of stress. A uniaxial tensile creep test would not be expected to give the required data if the designer was concerned with torsional or compressive creep. 

Such tests, while they constitute an adequate basis for routine evaluation of plasticizers, furnish only a rudimentary picture of the elastic properties of the plasticized resin. More complete studies supply valuable information. For example, tensile creep tests have shown that polyvinyl chlonde resin plasticized with uioctyl phosphate will deform more in response to stresses of short duration than will resin plasticized with tncresyl phosphate the reverse is true for stresses of long duration. 

S. M. Wiederhom, R. Krause, and D. C. Cranmer, Tensile Creep Testing of Structural Ceramics, in Proceedings of the Annual Automotive Technology Development Contractors Coordination Meeting 1991, (P-256, Dearborn, MI, October 28-31,1991), Society of Automotive Engineers, Warren-dale, PA, 1992, pp. 273-280. 

M. Giirtler and G. Grathwohl, Tensile Creep Testing of Sintered Silicon Nitride, in Proceedings of the Fourth International Conference on Creep and Fracture of Engineering Materials and Structures, Institute of Metals, London, U.K., 1990, pp. 39 408. 

The thermal and UV stabilising action of linear, low molec.wt. unsaturated polyesters and epoxy resins in PVC was investigated using short-term tensile and long-term tensile creep testing and calculations of isochronous creep... 

A constant tensile-stress method is outlined in ISO 6252, in which a test specimen is exposed to a constant tensile force while immersed in a stress cracking agent so as to determine the time to rupture under a specified stress. This uniaxial test leads to the determination of the lifetime of the specimen with accuracy, but it is time consuming and requires complex equipment. Variations of this test include a tensile creep test that monitors the strain and a monotonic creep test that uses a constant stress rate instead of a fixed stress [1]. 

The first quantitative study of deformation mechanisms in ABS polymers was made by Bucknall and Drinkwater, who used accurate exten-someters to make simultaneous measurements of longitudinal and lateral strains during tensile creep tests (4). Volume strains calculated from these data were used to determine the extent of craze formation, and lateral strains were used to follow shear processes. Thus the tensile deformation was analyzed in terms of the two mechanisms, and the kinetics of each mechanism were studied separately. Bucknall and Drinkwater showed that both crazing and shear processes contribute significantly to the creep of Cycolac T—an ABS emulsion polymer—at room temperature and at relatively low stresses and strain rates. 

Flat tensile creep specimens were machined from the blocks so that the longitudinal specimen axes were either parallel to the plane containing the majority of the long axes of the fibres for the squeeze-cast composites or parallel to the extrusion direction for powder metallurgy materials. Constant stress tensile creep tests were carried out at temperatures from 423 to 523 K. The applied stresses ranged from 10 to 200 MPa. Creep tests were performed in purified argon in tensile creep testing machines with the nominal stress maintained constant to within 0.1% up to a true strain of about 0.35. Almost all of the specimens were run to final fracture. 

Therefore, substituting v = 0.4, the creep hoop strain will be smaller than that in a tensile creep test by a factor (1 — v ), if the hoop and tensile stresses are equal. Examining Fig. 7.6, the tensile stress to cause a creep strain of 3/0.84 = 3.6% after 50 years is approximately 4 MPa. For a 4 bar pressure to cause a hoop stress of 4 MPa, the pipe SDR = 21 by Eq. (14.2). This is the maximum SDR allowed. 

Fig. 4.132 Principle of tensile creep test (a) and stress relaxation test (b) under uniaxial loading.

The valid and mostly used standard for the tensile creep test of rigid plastics is the ISO 899-1 Plastics -Determination of creep behaviour - Part 1 Tensile creep. The specimens used for this preferred standard are frequently in accordance to ISO 527 or ISO 293 up to ISO 294. If the specimens prepared from semifinished products or moulded parts by milling or cutting standard ISO 2818 should be applied. The data... 

Fig. 4.133 Evaluation of tensile creep tests on polymers according to ISO 899-1.

Testing of plastics - Tensile creep test (withdrawn)... 

Technical Rule, Beiblatt 1 Testing of welded joints of thermoplastic sheets and pipes - Tensile creep test - Testing of socket joints... 

Testing of fused joints on liners of polymer materials - Tensile creep test on PE... 

Several tensile creep tests were carried out on SCS-6[o]/MoSiz-50Si3N4 composite specimens between 1273 and 1473 K in vacuum. Test durations of-1000 hr were achieved and some idea of long term durability was obtained. Specimens tested at these temperatures exhibited a short primary creep stage and an extended secondary stage. The minimum creep rates ranged from 1.0 x 10 to 2.0 x 10 at 70 MPa between 1373 and 1473 K. 

SiOC-Nextel 312 BN 2D Composites (5X) Specimen A-7 Tensile Creep Test at 566C... 

Tensile creep tests were conducted at 1000 and 1100 °C in air and in steam. Results are summarized in Table II, where creep strain accumulation and rupture time are shown for each creep stress ievel, test temperature and environment. Creep-rupture results from prior work obtained at 1200 °C are included in Table 11 for comparison. Creep curves obtained at 1000 and 1100 °C ate shown in Figs. 3 and 4, respectively. Creep curves from prior work obtained at 1200 °C are shown in Fig. 5. Note that at each temperature creep tests were conducted both in air and in steam. The time scale in Fig. 5(b) is reduced to clearly show the creep curves obtained at stress levels > 125 MPa. 

This superplastically deformed silicon nitride also showed substantially improved creep resistance at high temperatures, when the stress was applied along the extruding direction. For example, the creep rates of the deformed body in tensile creep tests conducted at 1200 °C was found to be about one order of magnitude lower... 

Testing of Fused Joints on Liners Made of Polymer Materials - Testing Proeedure, Requirements Testing of Fused Joints on Liners Made of Polymer Materials - Lap Shear Test Testing of Fusion on PE-Liner - Peel Testing Testing of Joints on Liners Made of Polymer Materials -Tensile Creep Test... 

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