Compression Tests Of Cylinders Research Articles

Role of Carbon, Nickel and Iron Impurities on the Properties of the U-0.2% V Alloys

After reviewing briefly the influence of the incorporation of vanadium in the uranium matrix (for contents between 0.0 and 0.5), we will examine the effect of major impurities, mainly carbon, nickel and iron, on the properties of the uranium-0.2% vanadium alloys. Tensile tests at both ambient and elevated temperatures were conducted, together with some compression tests of cylinders in isothermal conditions, under primary vacuum. The results of these tests will be discussed in connection with metallurgical observations : viz, the growth of the grain boundaries and the recrystallization phenomena will be briefly examined and compared with the mechanical results.

Failure of three sedimentary rocks in triaxial and hollow cylinder compression tests : Santarelli F.J.; Brown E.T. Int J Rock Mech Min Sci V26, N5, Sept 1989, P401–413

Failure of three sedimentary rocks in triaxial and hollow cylinder compression tests : Santarelli F.J.; Brown E.T. Int J Rock Mech Min Sci V26, N5, Sept 1989, P401–413

Failure of three sedimentary rocks in triaxial and hollow cylinder compression tests

Results are presented of a laboratory study designed to examine the possibility of predicting the behaviour of rocks around model underground excavations from the results of triaxial compression tests. Series of triaxial and hollow cylinder compression tests were performed on three British sedimentary rocks with the emphasis being placed on macroscopic failure development. Measurements of strain localization were made to determine the point of failure surface initiation during triaxial tests. Studies of the failed specimens showed that failure can manifest itself in different ways depending on the microstructure of the rock. A qualitative model based on the concept of microcrack development in heterogeneous media is shown to be able to describe the failure patterns of all three rocks in both uniaxial and hollow cylinder compression tests. It is shown that, qualitatively, a parallel can be drawn between uniaxial and hollow cylinder tests in terms of both pre- and post-failure behaviour. However, the results cast doubt on the quantitative prediction of failure development around circular underground excavations using conventional approaches.

Strength pattern of cancellous bone at the ankle joint.

The strength pattern of cancellous bone was examined in 17 ankles by a cylinder compression test and in eight distal tibial specimens by an osteopenetration test. With the compression test, 6 mm levels were examined, five levels at the tibia and three levels at the talus. Cylinders were obtained from all levels from corresponding locations. The cylinders were tested at a constant deformation rate of 5 mm/min until failure. From the load deformation curves ultimate strength, yield strength, yield strain, ultimate strain and elastic modulus were calculated. The penetration test involves resection of the joint surface just above the subchondral bone plate at the distal tibia. Measuring force and displacement, a 2.5 mm conical needle was pushed into the bone at 25 locations in a 5 × 5 matrix. The force-displacement curves were integrated at intervals of 2 mm. Three levels were evaluated, corresponding approximately to the first level in the compression test. The study indicates the presence of a strong antero-lateral part and a slightly weaker postero-medial part at all levels in the tibial and talar bone. The compression test at level 1 and the penetration test at levels 1, 2, and 3 in the distal tibia revealed a high strength area crossing the central part, in contrast to the proximal levels of the tibia where the central parts were very weak. At the talus, a high strength area ran along the lateral and posterior border. There were no significant differences in the profiles of ultimate strength, yield strength, and elastic modulus.

Barreling of Solid Cylinders Under Axial Compression

Axisymmetric compression tests of solid aluminum cylinders, over a wide range of “aspect ratios” (length/diameter) and both under dry as well as lubricated conditions, suggest that the resulting curvature of the “barrel” formed fits closely a circular arc and its radius follows a power law with the true axial compressive stress. The true compressive stress-strain curve, extrapolated from the experimental data in each test, shows that within the variety of lubricants used the Specific Forming Energy is minimum with teflon sheets as dry lubricant, and increases successively with silicon spray, motor oil, and dry friction.

The effect of material properties on growth rates of folding and boudinage: Experiments with wax models

The growth of unstable structures was studied experimentally in layered wax models. The rheological properties of the two wax types were determined independently by a series of cylinder compression tests. Both waxes enhibited (1) a non-Newtonian stress vs strain-rate relationship (2) strain softening and (3) temperature-dependent viscosity. The stress-strain-rate relationships approximated a power-law, with stress exponents of 5 for the microcrystalline wax and 1.8 for paraffin wax. Blocks of paraffin with a single embedded layer of microcrystalline wax were deformed in two-dimensional pure shear with the layer oriented either parallel to the compressive strain axis so that it shortened and folded, or perpendicular to that axis so that it would stretch and boundinage would form. The growth rates of tiny initial disturbances were measured. The growth rates for folding and boudinage were much higher than could be accounted for by theories assuming Newtonian material properties. Theories taking non-Newtonian behaviour into account (Smith, R. B. 1975. Bull. geol. Soc. Am. 86, 1601–1609; Fletcher, R. C. 1974. Am. J. Sci. 274, 1029–1043) better describe the folding growth rates. Boudinage, however, grew almost three times faster than would be predicted even by existing non-Newtonian theory. A possible reason for this discrepancy is that the waxes do not exhibit steady-state creep as assumed in the theory. We, therefore, extend the theory to include strain-softening. The crucial step in this theory is the use of a scalar measure of the deformation as a state variable in the constitutive law. In this way the isotropic manifestation of strain-softening can be taken into account. The analysis shows that strain-softening can lead to greatly increased boudinage growth rates while having little influence on the growth rates of folds, which is in agreement with the experiments.

The compression and bearing capacity of cohesive layers

A theoretical study of the compression of blocks and cylinders of purely cohesive material between rough plates shows that the yield pressure of the blocks and cylinders increases with the roughness of the plates and with decreasing height of the specimen. Compression tests of blocks and cylinders of Plasticine and clay between perfectly rough plates are found to be in good agreement with the theory. The above analysis has been extended to obtain an estimate of the yield pressure of footings on cohesive layers: theoretically the bearing capacity should increase with the adhesion of the material on the footing and base and with decreasing thickness of the layer. The results of some loading tests on circular and strip model footings on Plasticine layers with a perfectly rough base conform with the theory.

Mechanism of Fracture of Concrete

H. J. COWAN'S1 hypotheses for the fracture of concrete are very similar to those already proposed by Prof. M. Roš2. Such hypotheses usually rely mainly on the observations of failing loads of specimens for their justification, and proceed from the assumption that concrete may be regarded as a homogeneous isotropic material. In the Division of Building Research of the Commonwealth Scientific and Industrial Research Organization, an extensive experimental study has been made of the strain distribution in various types of concrete specimen, using one concrete mix throughout. The results suggest that in all specimens the first failures occur when the tensile strain is about 10−4. In compression tests of cylinders, this strain occurs when the load is about fifty per cent of the ultimate, tand in unreinforced flexural specimens at about ninety per cent of the ultimate. The measurements made here also show how widely the concrete strains may vary in a region in which they are theoretically uniform.

4) コンクリートの壓縮強度時の歪度を超える範圍まで取扱つた應力歪度曲線に就いて

The stress-strain curve of the concrete beyond its maximum strss is necessary to get theoretically the real ultimate load which can be sustaind by reinforced concrete beam or column. The authers showed these curves by compression tests of concrete cylinders, using the martens, mirror apparatus. The strss-strain curves of the concrete beyond the maximum stresses vary even in the same concrete. Some of them are very unstable, namely the curves descend rapidly beyond their maximum stresses. But most of them are stable and descend very slowly for the relatively wide ranges of the strains which reach to the several times of the strain corresponding to the compressive strength. Considering the fact above, the concrete in the compressive domein of the concrete member is supposed very stable ior wide range beyond the maximum, stress in the compression test.

直徑方向の丸孔を有する軟鋼丸棒の引張、圧縮及び捩り實驗

直徑方向の丸孔を有する軟鋼丸棒の引張、圧縮及び捩り實驗

相異る2つの直径を有する軟鋼丸棒の引張、圧縮及び捩り實験

第1図の如く平行部ABの中央に直径の小なる部分を有する軟鋼丸棒に於て、兩直径d_0とd_1との比をほゞ一定とし、直径小なる部分の長さl_1を變化せしめ、引張、圧縮及び捩り試験を行ひ、その弾性變形、塑性變形及び破損の模様を考察した。引張試験に於ては、細部を含む標點距離lに就て測定したヤング率は細部及び太部が完全な弾性變形をなすものと假定して計算した値よりは稍小さい値を有する事を知つた。又直径小なる部分に就て算出した引張の強さ、破断の強さ及び延び率は細部の長さl_1とその直径d_1との比が小なる時は通常の値より大なる値を有し、l_1/d_1が大となるに従つて減少して通常の引張試験の結果に近づく事を認めたのでこれ等の値とl_1/d_1との問の関係式を誘導した。又断面収縮率はl_1/d_1が1より大なるものに就てはほゞ一定である事及び降伏點はl_1/d_1の値に依つて著しく變化する事を認めた。圧縮試験に於てはヤング率の變化の傾向は引張試験の場合と同様である事及び彎曲の状態はl_1/d_1の値に依り異る事を認めた。捩り試験に於ては細部を含む標點距離に就て求めた横弾性係數は、細部及び太部が完全に弾性變形をなすものと假定して計算した値と一致する事及び直径小なる部分に就て算出した剪断の降伏内力及び最大剪断内力は細部を有せざる通常の丸棒より求めた値と一致する事を認めた。