0


RESEARCH PAPERS

J. Eng. Mater. Technol. 1986;108(4):279-284. doi:10.1115/1.3225883.

This paper describes the notch effect in low-cycle fatigue of an austenitic stainless steel SUS 304 at 873 K in air. Total strain range-controlled tests were carried out using a round unnotched and three round notched specimens. A prediction method for low-cycle fatigue lives of notched specimens was developed by predicting the crack initiation and propagation periods separately. To predict the former Neuber’s rule was applied and a nominal stress/strain criterion was developed to predict the latter. Failure lives, obtained by adding the two prediction lives, closely agree with observed failure lives.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):285-289. doi:10.1115/1.3225884.

Asymmetries like welds or shoulders, may eliminate one of the two shear zones of symmetrically fully plastic cracked parts and thus give crack propagation along the remaining active slip band through pre-strained material instead of through the relatively unstrained region between two shear bands of the symmetric case. One thus expects a reduced ductility in the single shear band asymmetric case. A macro-mechanical analysis provides a physical basis for explaining the development of deformation in both geometries, as observed from tests on several alloys. The asymmetric case is approximated as Mode II shearing, with the crack extension occurring by sliding off along a single slip plane and fracture. In the symmetric Mode I case, the crack is assumed to extend by alternating shear on two symmetric slip planes and fracture.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):290-295. doi:10.1115/1.3225885.

The delamination fracture toughness of graphite and aramid-epoxy composite laminates was determined as a function of loading rate for unidirectional and woven reinforcements. In addition, the in-situ fracture toughness of the epoxy matrix was obtained by determining the crack energy release rate during the delamination fracture of thin epoxy films. The fracture surfaces were investigated using scanning electron microscopy. The results show that increasing the loading rate and the use of woven reinforcements increase the fracture toughness. A model was used to estimate the relative contributions from the fiber-matrix interface and the matrix to the overall delamination crack energy release rate.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):296-302. doi:10.1115/1.3225886.

The damage caused by sand impingement can be severe and detrimental to canopies, radomes, wind screens, and structural components resulting in loss of transmittance, communications, and premature failure. Extensive parametric studies were conducted to characterize the optical transmittance characteristics of polymethyl methacrylate and polycarbonate surfaces as functions of (1) velocity of impact, (2) exposure time (3) distance of the nozzle (4) angle of impingement, and (5) mass flow rate of the erodent. Particle damage was caused by a jet of high speed spherical and (crushed glass and silicon carbide) angular particles. The relationship between the optical and surface characteristics are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):303-312. doi:10.1115/1.3225887.

A non-unified creep plasticity constitutive model and a unified creep-plasticity model have been considered. In the non-unified model, creep and plastic strains were added separately; in the unified model, they were treated in a unified manner. These models were used to predict cyclic hardening and mean stress relaxation for isothermal loading conditions. The results indicate that certain instabilities occured in unified creep-plasticity simulations at low temperatures. Material behavior for thermal loading was studied using the two-bar structure. Both constitutive models were modified to handle material behavior changes with temperature. The thermal loading response was predicted satisfactorily with both models for most cases. However, certain model limitations were encountered in the unified model. The capabilities of both models are outlined and discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):313-320. doi:10.1115/1.3225888.

The multiaxial yield behaviors of 1100-0 aluminum, 70:30 brass, and an overaged 2024 aluminum alloy (2024-T7) have been investigated for a variety of prestress histories involving combinations of normal and shear stresses. Von Mises effective prestrains were in the range of 1.2–32%. Prestress paths were chosen in order to investigate the roles of prestress and prestrain direction on the nature of small-strain offset (ε = 5 × 10−6 ) yield loci. Particular attention was paid to the directionality, i.e., translation and distortion, of the yield locus. A key result, which was observed in all three materials, was that the final direction of the prestrain path strongly influences the distortions of the yield loci. Differences in the yield locus behavior of the three materials were also observed: brass and the 2024-T7 alloy showed more severe distortions of the yield locus and a longer memory of their entire prestrain history than the 1100-0 aluminum. In addition, more “kinematic” translation of the subsequent yield loci was observed in brass and 2024-T7 than in 1100-0 aluminum. The 2024-T7 differed from the other materials, showing a yield locus which decreased in size subsequent to plastic straining. Finally, the implications of these observations for the constitutive modeling of multiaxial material behavior are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):321-327. doi:10.1115/1.3225889.

The development of a one-dimensional finite strain elasto-plastic shell model appropriate for use in modelling straight drawbeads is outlined. Numerical results obtained using a finite element technique are shown for practical bead designs. The sheet deformation is divided into two phases: that when the binder locks the sheet metal to form the bead, and that when the punch advances to form the panel, pulling the sheet and (possibly) drawing material through the bead. The effects of friction coefficient, bead geometry, and material properties are investigated, resulting in strain distribution diagrams and force-displacement curves for several bead designs.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):328-334. doi:10.1115/1.3225890.

For the measurement of axisymmetric three-dimensional residual stresses, Sachs’ method is often used. The accuracy of this method is not high when even small errors are contained in observed strains. In 1975, the authors presented a new approach for the measurement of residual stresses in which inherent strains (the source of residual stresses) are dealt with as parameters and formulated a basic theory using the finite element method. In this paper, based on the new approach, a basic theory for the measurement of axisymmetric three-dimensional residual stresses is developed and a practical procedure of measurement is presented. This method is applied to determine the residual stresses in a quenched shaft and its reliability and practicability are also demonstrated.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):335-339. doi:10.1115/1.3225891.

The freely expanding ring test (ERT) is a conceptually simple test for determining the stress-strain behavior of materials at large strains and at high strain rates. This test is conducted by placing a thin ring of test material in a state of uniform radial expansion and then measuring its subsequent velocity-time history. The ring is usually propelled by a high explosive driving system. The test has not become popular in the materials property community, however, because there has been some concern about how the launching of the ring sample with an explosively generated shock wave might affect the properties to be measured. To determine the suitability of the ERT for these fundamental investigations, a series of experiments was performed on a carefully controlled material—oxygen-free electronic fully annealed copper. Recovered ring samples were analyzed and the change in hardness determined. Comparisons of the ERT data with that from Hopkinson bar tests at strain rates of about 5 × 103 s−1 indicate that the shock-induced hardness is approximately equivalent to a strain hardening of 5 percent. ERT data on this material at strain rates up to 2.3 × 104 s−1 are presented.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):340-343. doi:10.1115/1.3225892.

The 4-K tensile and fracture toughess properties of a fully austenitic stainless steel weld are reported. One tensile and two compact tension fracture specimens were tested. The weld was produced by gas metal arc welding using an Fe-18Cr-20Ni-5Mn-0.16N electrode and a 98 percent argon-2 percent oxygen shielding gas mixture. The yield strength of 1015 MPa and average fracture toughness, KIc (J), of 203 MPa•m are higher than those of welds produced with 308L and 316L electrodes and compare favorably with base metal properties. Examination of the fracture surfaces of all samples by scanning electron microscopy showed ductile failure by microvoid coalescence. The suitability of this alloy for welding cryogenic structures is discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):344-353. doi:10.1115/1.3225893.

Sheet and rod stock of 304L stainless steel were tested in uniaxial tension and compression at strain rates between 10−4 s−1 and 104 s−1 . To evaluate the yield locus behavior of the sheet material, multiaxial experiments were performed at a strain rate of 10−3 s−1 . We have analyzed these results in terms of existing strain-rate sensitivity, work hardening, and yield locus models. Strain-rate sensitivity was found to follow a thermal activation law over the entire range of strain rates used in this investigation. The best description of strain hardening did depend on the strain range to which the data were fit. The Voce law was the most accurate at large strains (ε > 0.40), whereas at small strains, in the vicinity of yield, the laws of either Swift or Ludwik were the most accurate. A simple power law description of work hardening was inadequate over all levels of strain. We examined a number of yield criteria, both isotropic and anisotropic, with respect to the biaxial yield behavior. Bassani’s yield criterion gave the best fit to our experimental results. However, the simple von Mises yield function also gave an acceptable prediction of yield strength and direction of current plastic strain rate. The yield criteria of Hill, both the quadratic and nonquadratic versions, did not match the experimental data. We feel that these results have direct application to the selection of the proper constitutive laws for the finite element modeling of the deformation of 304L stainless steel.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):354-357. doi:10.1115/1.3225894.

A standard technique for finding the shear stress-strain relation of a material employs a torsion test on a solid circular cylinder. It is shown that the exact solution is easily obtained as a correction to the sometimes-used quasielastic approximation. The solution is extended to the case of hollow cylinders. The analysis is shown to be applicable also to the case where a constant axial stress is present, and to a special case of planar isotropic materials.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):358-364. doi:10.1115/1.3225895.

Precise understanding of thermal expansion behavior of flake graphite cast irons is essential to know the thermal fatigue resistance of these irons when used for elevated temperature application like diesel engine components, ingot moulds, hot mill rolls, glass moulds, dies, etc. Twenty-three pearlitic flake graphite irons having identical base compositions (levels of sulfur, manganese, phosphorus, dissolved gases, and trace elements) having two levels of carbon (3.93 percent and 3.00 percent) and alloyed with elements such as molybdenum, vanadium, chromium, tin, nickel, copper, antimony, and aluminum were produced by carburizing steel scrap in an electric melting furnace. Thermal expansion behavior of all these irons were studied with the help of a dilatometer to determine the influence of graphite morphology and chemical composition. It is seen from the results that thermal contraction of flake graphite irons follows a different path during cooling than the thermal expansion path followed during heating. Further increase in graphitic carbon and coarseness of graphite tend to lower the coefficient of thermal expansion. Additions like molybdenum/copper at high level help in reducing thermal expansion; higher content of tin/antimony/aluminum/silicon tend to increase it while chromium/nickel/copper at low level have no effect. The present investigation has thus provided information regarding thermal expansion/contraction behavior of twenty-three flake graphite irons having almost all commonly used alloying elements.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):365-373. doi:10.1115/1.3225896.

The roles of short range and long range internal stresses during nonelastic deformation have been postulated and explored using the MATMOD-4V deformation model. New microstructural variables have been introduced in MATMOD-4V which represent the effects of internal stresses upon deformation. Simulations for aluminum have been performed to demonstrate improved capability to represent small strain deformation behavior and dynamic recovery. Comparisons are made between experimental data and computer predictions of microplastic straining and cyclic deformation.

Commentary by Dr. Valentin Fuster

TECHNICAL BRIEFS

J. Eng. Mater. Technol. 1986;108(4):374-376. doi:10.1115/1.3225897.

Although thick walled cylinders subjected to both pressure difference and internal heat flow can be found in many engineering applications, optimizing for maximum material utilization is still needed. Hence, the present work presents a close insight into stress analysis and optimization of both thick walled impermeable and permeable cylinders under the combined effect of temperature and pressure gradients.

Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):376-377. doi:10.1115/1.3225898.
Abstract
Commentary by Dr. Valentin Fuster

BOOK REVIEWS

J. Eng. Mater. Technol. 1986;108(4):378. doi:10.1115/1.3225899.
FREE TO VIEW
Abstract
Topics: Soil
Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):378. doi:10.1115/1.3225900.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):378. doi:10.1115/1.3225901.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):378. doi:10.1115/1.3225902.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster
J. Eng. Mater. Technol. 1986;108(4):379. doi:10.1115/1.3225903.
FREE TO VIEW
Abstract
Commentary by Dr. Valentin Fuster

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In