Notched Tension Tests Research Articles

Computer simulation of the round notched tension test of cox and low

The stress and strain rate in a circumferentially notched tensile bar with an OD ten times the root radius was calculated using the HEMP computer program. The location of the maximum principal stress and mean stress shifts from near the notch toward the axis of symmetry as the specimen is strained. (FS)

Brittle Fracture Initiation in Conical Shell of Pressure Vessel

For better understanding of pressure vessel performance, it is necessary to clarify the effects of out-of-plane bending stress component and biaxial stresses on brittle fracture initiation. The authors carried out the burst tests of conical pressure vessel, the anticipated fracturing portion of which was subjected to biaxial stresses including an out-of-plane bending component. Every test vessel has a knuckled weld joint either convex or concave. A surface notch was provided circumferentially at the knuckled joint, in order that the tensile stress parallel to notch was not less than the perpendicular stress. Three-point bend tests and surface notched tension tests were also carried out and the results were compared with those of burst tests.The effect of parallel component of stresses on brittle fracture initiation was not observed by data analysis. So, it may be concluded that the mechanism of brittle fracture initiation established for uniaxial stress state is always applicable. As to the small scale testing, it must be noted that a sufficient acuity of notch or plastic constraint is required for the safe-side estimation of service performance.

Screening for fracture toughness using the sharp notch tension test

Correlations are shown between the plane strain fracture toughness, K Ic , and the notch tensile/yield strength ratios, NTS/YS, for 2124-T851 alloy. Over 100 data points were available in each of the three conventional testing directions. Results indicate that the sharp notch tension test could have reduced by 50% the more expensive K Ic testing with a high degree of confidence based on proposed minimum K Ic values. Little difference was shown in examining the toughness in various locations within a large 2219-T851 plate. However, specimen size effects are shown in these alloys.

Fracture toughness studies of fibre reinforced plastic laminates

The mode of fracture and the origins of fracture work have been investigated for several fibreglass laminate constructions. Crack propagation in woven fabric and cross-plied unidirectional ply laminates with fibres parallel and perpendicular to the load direction was resisted by splitting between the fibres in the load direction at the crack tip. Crack propagation occurred by successive split formation and failure of the region of fibres adjacent to the split. Although crack tip damage was often extensive, fracture was governed by the classical crack tip stress singularity in all cases. The fracture work determined from notched tension tests was quantitatively associated with the elastic strain energy decrease in the region of fibres adjacent to the split at the crack tip when the crack advanced. Variations of up to a factor of fifteen in longitudinal ply fracture work were realized by varying the ply configuration of Scotchply laminates. Predictable increases in fracture work with fibre volume fraction and woven fabric ply orientation were also achieved.

A Study on the Brittle Fracture Initiation in the Constrained Structural Member

Recent progress in fracture mechanics suggests the possibility of its practical application to the purpose of preventing the brittle fracture of steel structures constructed of ductile material such as ordinary structural steels.One of the problems in determining permissible defect size, allowable stress level and service temperature on the basis of laboratory tests is the fact that fracture toughness values such as Kc or Φc are not material constants in a strict sense but rather variables depending on the intensity of mechanical constraint of the defective region of the structure.When the deformation at the crack tip in plate thickness direction is highly constrained, multiaxial state of stress is developed, which is supposed to cause the decrease of fracture toughness and the increase of transition temperature.This paper describes the results of an investigation on the brittle fracture initiation characteristics of severely constrained structural member using model specimen with a defect coupled with stress concentration, mechanical constraint and welding residual stress.These three factors are considered to increase the susceptibility to brittle fracture initiation. Comparative experiments have been carried out using wide plate notched tension test (without three factors) and that with longitudinal welds (with residual stress) to clarify the effect of the three factors mentioned above.Further the effects of pre-loading and cyclic loading at room temperature were investigated using the constrained model specimens.COD concept was applied as the fracture criterion for the analysis of the test results.

Notch tensile properties of selected titanium alloys

Selected α, α-β, and β titanium alloys have been tested in the notch-tension test. The base alloys were variously contaminated with carbon, nitrogen, and/or oxygen, and the notch sensitivity of the resultant materials was determined in the temperature interval —320° ≦ T ≦ 75°F. From these results contamination limits to produce embrittlement at the testing temperatures examined have been established.

Notch Toughnessの見地よりみたる材料試験結果の判定

To specify the notch toughness of materials, so-called the “Transition Temperature” is used as a criterion with the general belief that the characteristics of notch toughness cannot be evaluated by ordinary mechanical tests such as tension test etc.In the factory, however, it will be very inconvenient that we cannot judge the notch toughness of materials from the ordinary mechanical test and must obtain the transition temperature of each material. From this point of view authors have carefully experimented the ordinary tension test and torsional test in addition to slow bending test, Charpy impact and side notched tension test from which the transition temperature of materials are obtained, using four kinds of rimmed steels.These test results at low temperatures are shown in Figs. 2-6, from which we can see that it is difficult to specify the notch toughness of materials from the customary values such as elongation, tensile strength etc.. Then φ, φ', Φ or Ψ is defined respectively at each test (see Fig. 7).As to the value of φ, φ', Φ or Ψ the following characteristics are notable:a) Each value is constant within the tamperature range of -80°C to +100°C; therefore, these values can be easily obtained only by room temperature test.b) The relations between transition temperature and the values of φ, φ', Φ and Ψ within the temperature range of -80°C to +100°C are shown respectively in Figs. 12, 13, 14 and 15. From them, it is clear that the material of which φ, φ', Φ or Ψ value is the smaller shows the lower transition temperature.Thus authors propose to adopt φ, φ', Φ or Ψ as an index of the notch toughuess of materials.