Nominal Yield Strength Research Articles

Microstructural influences on fatigue crack propagation in Ti-10V-2Fe-3Al

Tensile properties and Fatigue Crack Propagation (FCP) rates have been measured in laboratory air for a wide variety of different Ti-10-2-3 microstructures, all having nominal yield strengths of 1240 MPa. These microstructural variations included both recrystallized and unrecrystallized conditions, as well as varying amounts of primary α, both α- and Ω-aged conditions, and also several hot forming histories. With one exception, microstructure was found to have very little or no influence on FCP. Not only was the rate of FCP unaffected, but moreover, the macroscopic fracture surface roughness was largely unaltered. The one exception was a notable one: the Ω-aged condition. Strengthening through the precipitation of Ω instead of α was found to retard FCP significantly; no significant change in macroscopic fracture surface roughness was found, however. The retardation was attributed to changes in slip character and reversibility.

Mechanical properties of manganese sulphides in the temperature range between room temperature and 1000.DEG.C.

Manganese sulphide powders, prepared by a sulphur deoxidation of MnSO4, were melted at 1700°C in a graphite crucible, and then solidified into buttons, about 20mm diameter and 15mm long. Several kinds of bulk manganese sulphide with additives were prepared from powder mixtures of MnS and one of Al2O3, SiO2, MnO, CaO, CaS, and FeS. In the temperature range from room temperature to about 1000°C, their microhardness and nominal yield strength were measured and the following results were obtained.(1) Purified MnS samples had almost the same hardness as those reported so far. Their nominal yield strength varied with temperature from about 9kgf/mm2 at room temperature to about 2kgf/mm2 around 1000°C.(2) Additions of impurities into MnS brought about increases in both hardness and nominal yield strength. The hardening is presumably caused by solid solution of oxygen and calcium. The nominal yield strength varied with temperature from about 11 to 12kgf/mm2 at room temperature, to about 2 to 5kgf/mm2 around 1000°C depending on kinds of additives.

Mechanical properties of aluminum-phosphorous brass in temperature-rate loading

1. A composite investigation of the hardness, strength, and plasticity of the brass made it possible to more throughly study the process of deformation of the alloy in heating. 2. Despite the generally similar character of change in the nominal yield strength and tensile strength in relation to temperature, the values obtained for a deformation rate of 10−4 sec−1 in the 290–900°K temperature range are higher than for a rate of more than 10−3 sec−1. 3. For all of the deformation rates considered with an increase in temperature the strength and hardness of the alloy are controlled by the same mechanisms and processes respon sible for plastic deformation and successively replacing one another as for other fcc and bcc materials [9, 10, 13]. 4. The alloy possesses the greatest plasticity and least strength at a deformation rate of 2·10−3 sec−1, which may be preferred in setting up the production operations for working of it.

Empirically derived equations for predicting springback in bending

(1) An empirical equation has been developed that predicts springback for a variety of die geometries on the basis of yield strength, thickness, and bend radius; and for some die conditions for bend angle, hold-down, plan view curvature, and punch-to-die clearance. Since an internally consistent rationalization of the predictive equation has also been developed, the predictive equation would appear to have some general validity. However, the extent of this validity cannot be established until it has been more thoroughly evaluated. (2) By using variation analysis of the predictive equation for springback, important insights have been established about the interrelationships between variation in springback; variation in yield strength; variation in thickness divided by the nominal thickness, (R/t); and nominal yield strength. This analysis indicates the importance of interactions between the causative variables on variations in springback.

Performance of lapped splices in reinforced concrete loaded beyond yielding of the steel

Eighteen beams designed to fail in the lap splice after reaching yield of the reinforcing steel were tested under either a single load application or low cycle repeated loading. Splice lengths were varied from well below code requirements up to approximately those required by current codes and design methods. Performance was studied on the basis of the ductility exhibited prior to failure and the influence of load cycling and stress–strain characteristics of the reinforcing steel. No confinement (stirrups or a spiral) was provided to the splice.Comparison is made with common lap splice design methods. These assume that the beam will respond adequately and the splice will not fail prematurely if the splice length is made long enough to withstand a steel stress 25% above the normal yield strength of the reinforcing steel. The detrimental effects on ductility of higher than nominal yield stress and of strain hardening at relatively low strains for the grade 60 (nominal yield stress = 60 ksi (414 MPa)) deformed reinforcing steel used are noted. The possible weakness of using nominal yield strengths for the reinforcing steel with current design methods is emphasized.

２Ｖシャルピ衝撃試験の破面遷移温度とＣＯＤ試験によるぜい性破壊発生温度との相関

The relationship between the fracture appearance transition temperature υTrs in the V-notch Charpy test and the brittle fracture initiation temperature in the COD test has been investigated. The obtained results can be summarized as follows:-(1) The relationship can be expressed by the equation, [Tδ]^σ=σ_c=c = (0.006121δy+0.4704)νTrs+8.26√t+0.608δy[{1n(c/40)(2σ/δy)2}+{c(2σ/δy)2-40}/100]-90.2(°K)where [Tδ]^σ=σ_c=c is the critical temperature at which the brittle fracture is initiated in an infinite plate with a crack of a length 2C and application of an uniform stress σ, δy is the nominal yield strength and t is the thickness of steel plates.(2) For preventing brittle fracture in welded structures made with HT60 or HT80, the required value of νTrs for the welds should be lowered with an increase in the strength and the thickness of steel plates, the design stress and the length of the crack in the welds. And the maximum acceptable crack length should be decreased with an increase in the strength and the thickness of steel plates, the design stress and νTrs.(3) The maximum acceptable crack length, for preventing brittle fracture in welds of HT60 or HT80 welded with the same heat input of 40-50 kj/cm, increases with the plate thickness up to the thickness of 40 mm and decreases with the plate thickness in a range of more than 40 mm.

Effect of Strain-Hardening Exponent and Strain Concentrations on the Bursting Behavior of Pressure Vessels

Studies by the Subcommittee for Effective Utilization of Yield Strength of the Pressure Vessel Research Committee of the Welding Research Council have provided a better understanding of the behavior of pressure vessels in the bursting mode of failure. Specifically, these studies have shown that high-strength steels can be more effectively utilized in pressure vessel applications, and with appropriate safety. However, before specific Code changes are recommended, the possible influence of undetected sharp flaws on the burst pressure, as predicted by the modified Svensson equation, should be established. Accordingly, a study of six notched pressure vessels was conducted to establish the limitations of the Svensson equation with respect to severe strain concentrations, namely, sharp longitudinal notches. Three steels (A517, A516, and 304SS) having a wide range of strain-hardening exponents (0.09, 0.19, and 0.59) were used to fabricate thin-walled pressure vessels (16-in. (406 mm) O.D., 1/2 in. (13 mm) wall thickness, 48-in. (1.22 m) length). Each vessel had a 15-in. (381 mm) long sharp machined notch with flaw depths ranging from 15 to 35 percent of the wall thickness. These vessels were tested hydrostatically to burst at room temperature. All failures were ductile. The results indicate that for pressure vessel steels having nominal yield strength up to 115 ksi (793 MN/m2) and normal ductility and toughness, the modified Svensson equation can be used to predict burst pressure very reliably as long as the flaw depths are less than 25 percent of the wall thickness. On the basis of these test results, as well as burst tests of vessels with moderate strain concentrations such as nozzles and flat end closures, it is recommended that the terms Fcyl and Fsph (factors that describe the effect of strain-hardening exponent on the bursting behavior of cylinders and spheres) be incorporated into the appropriate Code provisions. It is further recommended that the appropriate Code committee consider a possible reduction in the factor of safety against bursting on the basis of the results of this investigation.

Mechanical properties behavior of neutron irradiated 12Ni-5Cr-3Mo maraging steel plate and companion weld metal

Charpy-V notch ductility and tensile properties changes in neutron irradiated 12Ni-5Cr-3Mo maraging steel have been evaluated following low (<250°F) and elevated temperature (550 to 740°F) exposure. The study was performed with 1-in, thick plate material (six heats) aged at 900°F for 2 and 20 hr to nominal yield strengths of 160 and 180 ksi respectively. Long term thermal stability of both heat treatment conditions was investigated for the conditions of irradiation. The <250°F and 550°F irradiation performance of matching (12-5-3) and mismatching (17Ni-2Co-3Mo) TIG weld deposits maraged to 180 ksi yield strength was also assessed in this study.General properties changes of the 12-5-3 maraging steel plate and companion weld metals were found to be rather small with <250°F exposures, indicating good resistance to neutron-induced embrittlement. However, a marked deterioration of notch ductility properties with long term exposure at elevated was revealed and traced to a non-nuclear thermal instability. The observed instability instability is believed to be a continuation of aging processes at temperatures well below the initial maraging temperature. Extended time-at-temperature treatments indicate that service above 550°F may produce sufficient properties changes for failure by low energy tear. Aging treatments of 1900 to 3300 hours duration increased the yield and tensile strengths of the 12-5-3 alloy by as much as 52.0 and 53.3 ksi respectively while not altering appreciably percent elongation and reduction of area values.

MARVAC 18 and 18A

Abstract Marvac 18 and Marvac 18A are vacuum consumable electrode melted low carbon, iron base alloys capable of nominal yield strengths of 250,000 and 280,000 psi respectively, coupled with excellent toughness and ductility. Both of the alloys respond to a managing heat treatment. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-175. Producer or source: Latrobe Steel Company.

Fatigue Characteristics of Open-End Thick-Walled Cylinders Under Cyclic Internal Pressure

Thick-walled cylinder fatigue data due to cyclic internal pressure for open-end cylinders in the range of 103 to 105 cycles to failure and having a diameter ratio of 1.4 to 2.0 at a nominal yield strength of 160,000 pounds per square inch is presented. Discussed and also presented are the effects of autofrettage on the fatigue characteristics of thick-walled cylinders. Autofrettage substantially enhances fatigue characteristics at stress levels below the corresponding overstrain pressure, the degree of improvement increasing the decreasing stress levels. The rate of improvement in fatigue characteristics increases significantly with diameter ratio in autofrettaged cylinders up to a diameter ratio of 1.8–2.0 and to a much smaller degree in the nonautofrettaged condition. The rate of improvement of fatigue characteristics above 2.0 is the same for both the autofrettaged and nonautofrettaged cases. It is shown that thermal treatment of 675 F for 6 hours after autofrettage does not affect fatigue characteristics and that there is a correlation between the cyclic-stress level and the area and depth of the fatigue crack to the point of ductile rupture. The depth of the fatigue crack decreases with increasing cyclic-stress level. A means for using data from a unidirectional tensile fatigue test to predict the fatigue characteristics of thick-walled cylinders is discussed.