Peak Compressive Stress Research Articles

Dynamic unloading behavior of soda lime glass

An experimental study was conducted to see if the reverberation plate technique, using commercial manganin stress gauges, could be used to determine the dynamic unloading behavior of brittle materials. Using a 50-mm powder gun, plate impact experiments were conducted on soda lime glass, providing unloading data from stress states from below the Hugoniot elastic limit to 17.0 GPa. The slopes of the unloading paths were found to increase as the peak compressive stress was increased. Such unloading behavior is similar to that of quartz, suggesting that the technique is viable.

THE EFFECTS OF STRESS RATIO, COMPRESSIVE PEAK STRESS AND MAXIMUM STRESS LEVEL ON FATIGUE BEHAVIOUR OF 2024‐T3 ALUMINIUM ALLOY

Abstract— Fatigue crack growth behaviour of 2024‐T3 aluminium alloy is investigated as a function of stress ratio, compressive peak stress and maximum stress level. It is found that as the stress ratio and the magnitude of the compressive peak stress are increased, the threshold stress intensity range decreased linearly. Intermediate and near threshold growth rate data are analysed with different formulae for effective stress intensity range. The data covered different values of stress ratio, compressive peak stress and maximum stress level. A formula for the crack opening stress level is introduced as a function of stress ratio, compressive peak stress and maximum stress level. The formula permitted a good correlation between crack growth data for both positive stress ratio and negative compressive peak stress values. Using the new formula, intermediate and near threshold crack growth data for the 2024‐T3 aluminium alloy yielded a unique crack growth rate vs effective stress intensity range curve for all stress ratio and compressive peak stress values investigated. This suggests that for the 2024‐T3 aluminium alloy the crack growth rate vs effective stress intensity range curve does not depend on stress ratio, compressive peak stress, or maximum stress level. The significance of the new equation and the crack growth rate versus effective stress intensity range curve is that they allow a designer to find crack growth rate vs stress intensity range data for the 2024‐T3 aluminium alloy in both intermediate and near threshold regions for the particular stress ratio, compressive peak stress and maximum stress level conditions of the component under investigation.

A modified dual-mass amplifier for high-strain-rate testing of SIFCON in uniaxial compression

An experimental procedure is described for obtaining compressive strength data at high rates of strain for slurry-infiltrated fiber concrete (SIFCON). A Monterey Research Laboratory dual-mass shock amplifier was modified to apply short-duration compressive loads to cylindrical test samples at rates of strain from 14 to 35/s. The data obtained are compared to data from static compressive strength tests and reveal increased peak compressive stresses at lower peak strains as compared to static strength values.

Thermoelastoplasticity simulation of a large-scaled low-alloy steel shaft material. (2nd report. On the circumferentially grooved cylinder loaded in the two defferent coolings).

The thermoelastoplastic stresses caused within a large-scaled low-alloy steel shaft material, which has a circumferential groove in the longitudinal center of its axis, are dynamically simulated by FEM based on the incremental strain theory under the two different cooling conditions, i. e. water and air. An inner tensile peak stress zone and compression stress concentration areas along the groove move through the cooling process because both the plastic deformation at the surface and the non-similarity of volumetic expansion due to transformation are compounded. As a result, characterizing the residual distributions on principal stresses, σ1 and σ2 are close with the inner in the air cooled zone compared with the water cooled, and σ3 shows high compression stress concentrations at the fillets of the groove.

Fatigue Crack Growth Threshold and Crack Opening of a Mild Steel

Abstract The effects of stress ratio, compressive peak stress, and cold rolling on the threshold stress intensity and crack closure level of a mild steel (SAE 1010) were investigated. As the stress ratio and the magnitude of the compressive peak stress were increased, the threshold level decreased linearly. The threshold stress intensity also decreased linearly as the yield strength was increased by cold rolling. Crack opening measurements showed that the measured threshold is composed of two parts: an intrinsic threshold stress intensity range, ΔKin, and an opening stress intensity, ΔKop. The opening stress intensity decreased with increasing magnitude of the compressive peak stress. The intrinsic threshold stress intensity range was not significantly affected by the compressive peak stress. Severe cold rolling decreased the opening stress in the near threshold region to near zero. In a constant amplitude load-controlled test, the ratio of the opening stress intensity to the maximum stress intensity decreased as the maximum stress intensity (crack length) increased, and no crack closure could be observed when the net stress approached the yield strength of the material.

The effect of compressive peak stress on fatigue behaviour

The effect of compressive peak stress on the maximum stress at the endurance limit, crack propagation rate, threshold stress intensity and crack closure was studied in a laboratory environment using two steels (SAE1045 and SAE1010) and two aluminium alloys (2024-T351 and 7075-T651). As the compressive peak stress, Scp, was increased in magnitude, the maximum stress at the endurance limit, Sfa, decreased linearly. Compression-compression cycling did not initiate any cracks in a centre-notched SAE1010 steel specimen but initiated cracks, which gradually became non-propagating, in the notched 2024-T351 aluminium alloy specimens. In compression-tension tests, the crack propagation rate increased, and the threshold and the crack opening stress intensities decreased linearly with increasing compressive peak stress. During compression-compression cycling the load/displacement curves were not linear, indicating that the crack was not fully closed.

Locomotory stresses in the limb bones of two small mammals: the ground squirrel and chipmunk.

Peak stresses acting in limb bones should increase with increasing size if the forces acting on the bones increase in direct proportion to the animal's body weight. This is a direct consequence of the scaling of limb bone geometry over a wide range in size in mammals. In addition, recent work has shown that the material strength of bone is similar in large and small animals. If the assumptions in this analysis are correct, large animals would have a lower safety factor to failure than small animals. The purpose of this study was to measure peak stresses acting in the limb bones of small animals during locomotion and compare the results with similar measurements available for larger animals. Locomotory stresses acting in the fore and hindlimb bones of two rodents, the ground squirrel (Spermophilus tridecemlineatus) and chipmunk (Tamais striatus), were calculated using ground force recordings and measurements of limb position taken from high speed x-ray cine films. Peak (compressive) stresses calculated to act in the bones of these animals (-31 to -86 MN/m2) are similar in magnitude to those determined for much larger mammals. The more proximal bones of the fore and hindlimb, the humerus and femur, were found to develop stresses (-31 to -42 MN/m2) significantly lower than those acting in the more distal bones of each limb: the radius, ulna and tibia (-58 to -86 MN/m2). All of the long bones from both species, except their femora, were found to be loaded principally in bending. The caudal cortices of each bone developed a peak compressive stress, whereas the cranial cortices were loaded in tension. Various features of the musculo-skeletal organization and manner of locomotion of these rodents are considered to explain how animals of different size maintain a uniform safety factor to failure.

Stress Amplification in a Ring Caused by Dynamic Instability

An analysis is presented for stress amplification in a ring caused by the dynamic instability of symmetric in-and-out breathing oscillations, which results in energy transfer to flexural modes. Stress amplification is shown to depend on a ring stability parameter p that is proportional to the unperturbed hoop strain and inversely proportional to the thickness-to-radius ratio. The analysis is a generalization of earlier work by Goodier and McIvor. They showed that, with p tacity assumed small, stress is amplified by approximately the factor 6, independent of the wave number of the flexural mode into which the breathing energy is transferred. The present analysis shows that for large p (increased instability), higher-order nonlinear terms must be included in the differential equations in order to give bounded solutions. With these terms included, stress amplification departs from 6 as p is increased, the peak compressive stress becoming larger and the peak tensile stress becoming smaller. With damping also included, the amplification approaches unity (no amplification) as p approaches zero, and passes through a maximum as p is increased. An experimental example of flexural fracture caused by such amplification is given.

Effects of shock pressures from a nuclear explosion on mechanical and optical properties of granodiorite

The Hardhat shot, fired February 15, 1962, was a 5.0±1.0 kt nuclear detonation 286 meters underground in granodiorite at the Nevada test site. Postshot exploration included drilling four holes approximately radially into the cavity region. Core samples were examined for variations in microfractures, plastic deformation, and physical properties, i.e., strengths, sonic velocities, permeability, as functions of shock pressures in the 2- to 110-kb region over preshot distances of three cavity radii. Cavity radius was 19 meters. A fracture index, defined as the average fracture frequency per thin section, shows the degree of microfracturing. Fracturing gradually increases from a preshot index of 3.0 to 7.5 over a 36-meter interval subjected to pressures that reached 50 kb at 18 meters from the shot point. Nearer the cavity, the index increases to 16.2 at the 100-kb point. Extension fractures in quartz show preferred orientations close to the cavity but become random, farther outward. Quartz grains in granodiorite experiencing peak compressive stresses above 50 kb (estimated) contain two to five sets of parallel planar surfaces per grain. These appear to develop by plastic adjustments in intensely shocked rock. Biotite displays intense kink banding in granodiorite shocked above 30 kb. These petrofabric features allow estimates of pressures and interpretation of transient states of stress during the explosion.