Steel Test Pieces Research Articles

Thermal contact conductance of nominaly flat surfaces

The variation of thermal conductance of contact has been investigated as a function of apparent contact pressure experimentally. Experimental data has been obtained for steel, brass, copper and aluminum test pieces having different surface roughness over a wide range of contact pressures. Experimental results are compared with the theoretical predictions of an existing theory. Comparison revealed good agreement of trend with the experimental data, however, numerical values vary widely. Theory can predict the experimental results within an over-all error of less than 35%.

Miniature wideband ultrasonic transducers to measure compression and shear waves in solid

This paper reports on the characterisation of specially developed miniature ultrasonic transducers as receivers directly-coupled to a solid surface, to make field point measurements of the ultrasonic waves propagating from a pulsed transducer. The emitting transducer is water-coupled at various angles to steel test pieces, the miniature receiving transducer being coupled to an opposite surface. The receiver is fabricated as a needle-like probe using a lead metaniobate disc of diameter 0.3mm as the active element. The 6dB bandwidth of the miniature probe ranges from around 0.5 to 7MHz, which is wide enough not significantly to change the shape of the ultrasonic pulses investigated. To a reasonable approximation, the probe responds to the normal component of the particle velocity of the incoming wave, and can be used to measure both the longitudinal (compression) and transverse (shear) waves. The measurement results obtained compare well to the results of calculations made using theoretical models recently developed by the authors.

Numerical simulation of deformation and fracture in low-carbon steel coated by diffusion borating

Numerical simulation of tensile mechanical behavior of low-carbon steel test piece surface-hardened by diffusion borating is performed to investigate the effect of stress concentration on the mesoscale plastic-deformation pattern. The computer simulations under review employ low-carbon steel as a substrate material with FeB 2 serving as a surface-hardened layer. The computations are performed for representative mesovolumes based on real experimentally revealed structure with an intermediate layer of different configurations. A model taking into account crack formation is applied to investigate coating fracture. The results obtained are presented and discussed.

An exercise in cold ironing as the post-forging operation for net-shape manufacture

Cold ironing of thick-walled cylinders has been examined to study the process as a potential post-forging operation for net-shape manufacture practice. Steel test-pieces with different sizes were reduced in diameter in a single or double ironing process. The surface finish and geometry were examined for various initial and process conditions. The use of lubricant in the process was also studied, with emphasis on the surface topography. Finally the application of the cold ironing process to case hardening test-pieces was investigated. It was concluded that ironing had beneficial effects upon the final dimensions and surface finish of the test-pieces. Finite element modelling of the process has also been carried out to analyse the process, the FE model being validated for further parametric study.

The effect of environmental and meteorological variables on atmospheric corrosion of carbon steel, copper, zinc and aluminium in a limited geographic zone with different types of environment

Carbon steel, copper, zinc and aluminium test pieces were exposed to a large variety of environmental conditions in a reduced geographic area close to the coastline in order to ascertain the degree of deterioration of the same due to environmental corrosion. Calculations of corrosion rates were made via loss of weight (in the case of carbon steel, zinc and copper) and analysis of surface deterioration (in the case of aluminium) together with X-ray diffraction analyses. The levels of chlorides, SO 2 and time of wetness were also registered in order to be able to correlate the data with respect to corrosion rate with the environmental and meteorological parameters, using the potential law and a modified version of the same.

PLASMA SPECIES ANALYSIS FOR INSITU ASSESSMENT OF SURFACE TREATMENTS

In order to gain the maximum potential from plasma technology in surface engineering, knowledge is required about the influence of particular plasma phase species on the treatment response. In this study, optical emission spectroscopy (OES) is used in situ, without disturbing the treatment environment, to monitor the active species observed in three different types of nitriding plasma: direct current (dc), active screen, and plasma immersion ion implantation (PI3). The spectral information obtained is considered in conjunction with metallurgical characterisation of nitrided steel samples, using optical microscopy, glow discharge optical emission spectroscopy, X-ray diffraction, and microhardness testing. Active screen and dc nitriding have a similar nitriding effect in low alloy steel testpieces. OES evidence shows that both ions and neutrals are involved in the plasma reactions and a multistage theory is the model of best fit for nitrogen mass transfer in these dc powered plasma nitriding techniques. OES analysis can be used for in situ monitoring of treatment quality in PI3 nitriding.

Precise and direct determination of the elastic constants of a cylinder with a length equal to its diameter

A cylinder made of a homogeneous isotropic material and with a length equal to its diameter is excited by axial percussion. Its axial displacement is detected by speckle interferometry. The two lowest frequencies, the first symmetric mode and first antisymmetric mode, are compared with the corresponding nondimensional natural frequencies, calculated to six significant figures using the Ritz method for 51 values of Poisson’s ratio. The values of both dynamic elastic constants (shear modulus and Poisson’s ratio) are found based on the quotient of the measured frequencies by using a table that is given. The method requires only one experiment and a simple calculator. The origin of the uncertainties is analyzed to improve the method’s precision. The systematic uncertainty of the results shows relative values of 0.23% for shear modulus and 0.59% for Poisson’s ratio. The values of the elastic constants calculated for a stainless steel test piece are compared with the values obtained by other methods.

Embrittlement due to hydrogen in ferritic and martensitic structural steels

AISI 420 steel test-pieces were submitted to hydrogen discharge by electrolyzation at a constant current density (8 mA cm −2) under a constant load (14 daN mm −2), with different charging times (from 3600 to 450,000 s). Two test-pieces were hydrogenated simultaneously, then one was tensioned by a tensile machine, while the other was tested by a hydrogen analyzer. Tensile tests results have shown that as the charging time increases, the material toughness (obtained by the value of reduction in area) decreases, passes through a minimum value and then later tends to recover its original value. Hydrogen-analyzer results have highlighted that, in parallel with the decrease and the recovery in material toughness, there is an increase and a decrease in the amount of hydrogen extractable at 400 °C, respectively, while at 600 °C and 800 °C respectively, it remains practically constant and subsequently increases. This phenomenon has been confirmed by fractographic analysis.

A simulated plasma disruption experiment using a magneto-plasma-dynamic arcjet

If a melt layer is expelled by a strong electromagnetic force from some plasma during a plasma disruption, the wall thickness is reduced there remarkably. Although this phenomenon is considered as a very important issue, it has not been studied so far because of its difficulty and complexity. In this study, the phenomenon was simulated using a magneto-plasmic dynamic (MPD) arcjet. The MPD arcjet was used as both a heat source and an electric current source. The current flowed radially in a stainless steel test piece installed in a transverse magnetic field. The circumferential electromagnetic force generated a swirl flow in the melt layer, causing a centrifugal force, which thinned the central part of the round region and formed a circular embankment on the fringe. A numerical code was developed which could calculate the melting, the evaporation and the melt layer movement by the centrifugal force and the beam pressure. The calculational results on the melting depth and the thickness reduction in the central part were compared with experiment.

A quantitative analysis of pulsed video thermography

Abstract The defect imaging capability of a pulsed video thermography system is assessed by detailed quantitative analysis of its performance in imaging a set of well characterized artificial defects in a steel test-piece. An analytical model is presented which provides an understanding of the imaging process. A method is proposed for the determination of defect depth by exploiting the temporal dependences of images.

Adsorption on various leach container materials of plutonium and curium leached from nuclear waste glasses

The adsorption tendency of leached-out 238Pu and 244 Cm on the wall of leach containers, during the leaching of waste glasses, was studied. The test pieces of quartz glass, PFA Teflon, gold and stainless steel, which are candidates for a leach container, were immersed in deionized water with the waste glass containing 238Pu or 244 Cm in a Pyrex glass container at 100°C, and then they were decontaminated with dilute nitric acid. The quartz glass was found to have the smallest contamination of 238Pu and 244CM. The adsorption amounts of 244Cm on the PFA Teflon and quartz glass were approximately the same, and for 238Pu the Teflon showed about twice the amount of adsorption as that measured on the quartz glass. The gold and stainless steel showed 30–40 times the adsorption amount of 238Pu as that on the quartz glass. Adsorption and desorption of curium and plutonium were discussed in relation with difference of materials, time dependence and acidity of leachate. Curium, which has been previously leached out from waste glasses, showed a relatively simple adsorption and desorption behavior. In the case of plutonium, the colloidal species would take a large part in the adsorption and desorption processes. The relationship between the ratio of the colloidal to the ionic species of plutonium and the adsorption-desorption behavior was discussed. The observation of alpha autoradiographs elucidated that the ionic adsorption was desorbed more easily than the colloidal one.

New epoxy‐imide resins cured with bis(hydroxyphthalimide)s

AbstractNew epoxy‐imide resins were synthesized using bis(hydroxyphthalimide)s (BHPIs). Among these resins, that cured with BHPI(DDS), synthesized from 4,4′‐diaminodiphenylsulfone, exhibits the best thermal resistance, reaching a tan δ maximum temperature of 230°C. This resin also features a tensile lap shear adhesive strength of 320 kgf/cm2 when applied to steel test pieces. The cure reaction was followed by infrared spectroscopy and dynamic mechanical analysis. The ring‐opening reaction between the phenolic hydroxyl group of BHPI and the epoxy group is observed, and accelerated by a tertiary amine catalyst, triethylamine.

ステンレス鋼のマルテンサイト変態を利用した接触応力測定法

The stress distribution at the contact area of a machine element has a large effect on the total performance of the machine. It is one of the important factors that closely relate to the performance of the element as a gear pair, a set of bolt and nut and so on. Many theoretical studies for estimating the contact stress were published. However, their validity has not been proved by experiments, because the known measuring methods are insufficient in accuracy or resolving power. The measuring method using martensite transformation is offered in this paper. If the stress is applied to the test piece made of 18-8 stainless steel at a temperature of 198 K, the stressed part of the test piece changes its structure from austenite to martensite. The martensite structure has the nature of ferromagnetism. Therefore, the contact stress distribution in the test piece can be obtained by measuring the distribution of remaining magnetism. For confirming the practical use of the method some experiments have been done using the block type (10 mm in thickness) and the film type (5 μm in thickness) test pieces of stainless steel. It has been confirmed that at the more stressed part, the more martensite transformation is induced in the test pieces, and that the test pieces have sensitivity for the measurement of the stress distribution. A homogeneous structure in the test piece is needed for the purpose of measurement.

プラズマＣＶＤ法による鉄基板上へのＳｉ３Ｎ４の析出について

Conditions favorable to the deposition of Si3N4 on pure steel substrates by means of an inductively coupled, externally heated plasma discharge were determined, and comparisons made with reducedpressure CVD. A push-pull Hartley RF (13.56MHz) oscillator with a maximum output of 70W was designed using a triode. The reactive gases-NH3 and SiN4-were diluted with Ar to a prescribed concentration. Test pieces of pure steel measuring 5×5×0.5mm were prepared, their surfaces were polished using diamond paste, and the Si3N4 was deposited onto the surfaces.It was found that the optimum distance between the test pieces and the oscillator electrode was 25cm, and the optimum ratio of NH3 and SiH4 gases was 1:2.5. Investigating the effect of reaction temperature and deposition time under these conditions, it was found that in the case of plasma CVD, 800°C was a boundary value above which film thickness decreased, while the rate of film growth varied with deposition time depending on whether the reaction temperature was below or above 750°C. Comparison with reduced-pressure CVD indicated that this was due to the effect of Coulomb discharge, and it was found by differential thermal analysis and X-ray diffraction that in Si3N4 at 746°C or less, deposits were amorphous.Further, at 800°C, film growth proceeded rapidly, reaching 12.5μm after 30min but thereafter decreased and was only 15μm after 240min. In reduced-pressure CVD, film growth proceeded linearly for 60min and thereafter almost linearly although with a decreased slope, reaching 12.5μm after 240min at 800°C.Investigation of the apparent activation energy of the growth of the Si3N4 including a diffusion layer in the initial reaction period gave a value of 20kcal/mol at 750°C or less for plasma CVD, and 12 kcal/mol at 700-800°C for reduced pressure CVD.

0.45 mass%C鋼のころがり接触疲れにおよぼす接線力の影響

Rolling contact fatigue of cylindrical carbon steel test pieces was studied in the presence of a tangential force. The test was carried out under the conditions in which the contact stress was varied from 588 MPa to 1176 MPa and the tangential force was varied from 3.92 N to 205.8 N.The structural change of the rolling contact fatigue surface was examined by X-ray diffraction, and the microhardness and microstructure at the rolling contact surface were also measured.From the experiment, the following results are obtained.(1) The tangential force acting on the contact surface reduces the rolling contact fatigue life.(2) Effective strain and microhardness at the contact surface increase a little with the increase of the number of revolutions, and when these exceed certain values, surface cracks are observed at the surface.(3) The cracks observed consist of main-cracks and branched sub-cracks, and these play as a whole major roles in producing pitting phenomena.

New aspects on the appraisal of the cooling process during hardening of steel

It has been difficult to judge, in actual practice, the cooling capacity of a quenching medium based on cooling curves recorded from silver test pieces. This is partly because silver has a much greater heat conductivity than steel and partly due to the fact that certain quenching media, such as oil emulsions and polymer quenching media, give rise to cooling curves that are not readily capable of interpretation. A number of such examples illustrating these difficulties are given in the paper.Even when the cooling curves are recorded from steel test pieces (both austenitic and martensitic), misjudgments do occur, in many instances, because of a lack of understanding of the transformations taking place in the temperature ranges that are inherent in the various stages of the cooling curve.When steel is being hardened, it is necessary to take into consideration the occurrence of nucleation and growth, which affect the diffusion-dependent transformation products. The realization of this concept is fundamental to the new application of the cooling curves.From investigations using dilatometer techniques and actual hardening tests, it has been possible to prove that, contrary to current consensus of opinion, a protraction of the vapor-blanket stage in the upper metastable austenite range is beneficial to the hardenability of the steels under investigation. There is no lack of references in the earlier literature testifying to this observation, but they have been ignored since no acceptable explanations were advanced.If, after hardening, an insufficient amount of martensite results and a large amount is required, it is most essential that there shall be a high cooling rate through those temperature ranges in which the main part of the diffusion-dependent transformations take place. Investigation results that definitely prove this fact will be reported in this article.The temperature location of the convection stage is also of importance to the hardenability and the dimensional stability of the hardened steel.The investigations carried out have also shown that such CCT-diagrams as are constructed from the linear cooling and from cooling conditions that differ markedly from those prevailing in steel during hardening present a faulty picture of the true state of affairs. Nor are such diagrams of much practical value, except when used to compare in a general fashion the hardenability of various steels. Moreover, such comparisons may be made by using much simpler aids.Hence, a completely new type of CCT-diagrams has been developed. These diagrams are in much better agreement with the conditions existing during hardening.

衝撃をうける接触面のすべり摩擦(第1報)

In this paper, a coefficient of statical friction on the interfaces is named a coefficient of impulsive friction μi, and its measuring method is presented. The apparatus is symmetrically set to the axis of a vertical hexagonal pillar (test piece), and the opposite sides of the pillar are holizontally pressed by the end of two similar rectangular plates (test pieces; both with a slit which vertically reflects the shearing stress waves to change them into the compressive stress waves). The μi is theoretically calculated by using the stresses produced in Hopkinson bars which are screwed up on the test pieces. A gained μi is proved to be realizable when η is nearly unity. The η is the ratio of applied impact energy to propagated energy, calculated from stresses in each part of apparatus which are obtained experimentally and theoretically. By the measurement of μi about the ground test pieces of steel, it is shown that the proposed method is reliable and that the μi is smaller than the ordinary coefficient of kinetic friction.

Characterization of Atmospheric Corrosion Products on Weathering Steels

Abstract Microalloyed steels show a greater atmospheric corrosion resistance than plain carbon steels through the formation of protective films, designated as patinas. During the development of these films, they present a continuous double layer structure. The inner phase is the only one left after long exposure periods and is determinant of the low atmospheric corrosion rates observed. In the present work a new technique was applied for the separation of phases. Characterization of both phased film and inner phase alone was performed by IR analysis, electrochemical reduction, and scanning electron microscopy. Test pieces of a weathering steel (C, 0.11; Mn, 0.38; Si, 0.23; P, 0.9; Cr, 0.69; Ni, 0.11; and Cu, 0.38) were exposed for 9 and 22 months at a semi-industrial atmosphere. Characterization techniques applied to samples of both phases and inner phase of patinas showed little difference in composition, noticeable morphological differences suggesting on the contrary greater barrier effect due to the in...

Corrosion of welds in seawater

Some preliminary results are presented from a study of the corrosion of welds involving mild steel and stainless steel. In aerated seawater at 60°C, welded samples of mild steel undergo general corrosion but with particularly severe attack on the weld metal. There is evidence that post-weld heat treatments, involving heating into the austenitic temperature range, produce more uniform corrosion on the specimens but do not eliminate completely the accelerated attack at the weld. There appears to be no significant corrosive effects associated with the welds either between stainless steel testpieces or between mild steel and stainless steel although, in the latter case, severe wastage of the mild steel part of the sample occurs as expected.

Effect of the nature of the stressed state on ductility and failure in structural steels

1. Formation and development of plastic strain zones inductile steel testpieces with circular notches markedly depend on the stressed state of the material. 2. During transition from the elastic to plastic regions (up to 3%) the nature of the distribution of the stressed state stiffness coefficient Π in the minimum cross section of the testpiece does not vary, which distinguishes it from the stress concentration coefficient, since with increasing plastic strain the region of stress concentration is displaced within the testpiece. 3. The sensitivity of material ductility to changes in the stressed state (inclination of the curves eψ-П and β-Π to the Π axis) depends on the supply of initial, ductility eψ and the stressed state range under consideration; Sec. I is strongly sensitive with П>Пcr, Sec. II is weakly sensitive with П>Пcr. 4. The point of failure in structural steels, and also the type of fracture, depend not only on absolute values of active normal stresses, but on the overall nature of the stress state, i.e., on the values of II, since the latter determine the ratio of normal to tangential stresses, the ratio of specific energy consumed in changing the shape and volume of the body, and naturally, on the state of crack initiation and growth.