JIS SS400 Research Articles

Tensile strengths of super high-strength steel strand wire ropes and wire rope open swaged socket connections at fire and post fire

PurposeThe main purpose of this study was to evaluate the tensile strengths of JIS G3549 super high-strength steel strand wire ropes (1,570 MPa-class high-carbon steels) and wire rope open swaged socket connections at fire and post fire.Design/methodology/approachSteady-state tests from ambient temperature (20 °C) to 800 °C, transient-state tests under the allowable design tensile force and tensile tests in an ambient temperature environment after heating (heating temperatures of 200–800 °C) were conducted.FindingsThe tensile strengths of the wire rope and end-connection specimens at both fire and post fire were obtained. The steel wire rope specimens possessed larger reduction factors than general hot-rolled mild steels (JIS SS400) and high-strength steel bolts (JIS F10T). The end-connection specimens with sufficient socket lengths exhibited ductile fracture of the wire rope part at both fire and post fire; however, those with short socket lengths experienced a pull-out fracture at the socket.Originality/valueThe fundamental and important tensile test results of the super high-strength steel strand wire ropes (1,570 MPa-class high-carbon steels) and wire rope open swaged socket connections were accumulated at fire and post fire, and the fracture modes were clarified. The obtained test results contribute to fire resistance performance-based design of cable steel structures at fire and fire-damage investigations to consider their reusability post fire.

MICROSTRUCTURE AND HARDNESS PROFILE OF DISSIMILAR LAP JOINT OF TYPE 304 STAINLESS STEEL TO SS400 CARBON STEEL

Dissimilar metal welds between austenitic stainless steel and carbon steel are commonly used in oil and gas industries for certain reasons. The objective of this research is to asses the effect of filler metal and shielding gas on the microstructure and hardness of dissimilar lap joint of type 304 austenitic stainless steel to JIS SS400 low carbon steel. For the purpose of this investigation, the weldments were produced using flux-cored arc welding (FCAW). Three types of filler metals (E316L, E309L and E308L) and two different gas compositions (100%CO2 and 90%Ar+10%CO2) were selected to be used. Each of the weldments were analyzed on the microstructure characteristic and hardness profile of base metal (BM), heat affected zone (HAZ) and weld metal (WM) using optical microscope and microhardness Vickers. The metallographic examination revealed HAZ-SS400 contains martensites. Both HAZ-304 and WM show austenitic microstructure, with columnar and cellular sub-structures present at WM. The hardness profile of HAZ-304 is higher than BM-304, it may be attributed to the presence of the fine grains in HAZ-304 due to high temperature during welding. The hardness profile of WM-E309L exhibited the hardness from HAZ to WM tend to decrease linearly, while WM-E316L and WM-E308L showed the hardness from HAZ to WM also decreased but drastically dropped at fusion line (FL). The welds using E309L offer the best result in the point of view homogeneity of the hardness profile.

Effect of Gap Size on Galvanic Corrosion between AA5052 Aluminum-Magnesium Alloy and SS400 Carbon Steel in Aqueous NaCl Solutions

Recently, aluminum alloys (AAs) have been utilized to automobile body parts in order to reduce the weight of the body and improve fuel consumption efficiency. Although some aluminum alloys such as 5000 and 6000 series have relatively good corrosion resistance in atmospheric environments, galvanic corrosion between aluminum alloys and other electroconductive materials is one of the critical issues on automotive application of the aluminum alloys. So far, we have investigated galvanic corrosion between AA5052 aluminum-magnesium alloy and SS400 carbon steel in aqueous NaCl solutions and reported that the galvanic corrosion behavior changes depending on the concentration of NaCl solutions [1]. In this study, effect of gap size between aluminum alloys and steel on galvanic corrosion behavior was investigated in aqueous NaCl solutions. A galvanic couple used in this study was almost the same as that reported before, which was made of AA5052 Al-Mg alloy (Mg: 2.65, Si: 0. 08, Fe: 0.27, Cu: 0.01, Cr: 0.17, Zn: 0.01, Al: bal. (mass%)) and carbon steel (JIS SS400). The plate of both materials was 10-mm width and 15-mm length and 5-mm thickness. After lead wires were connected to each plate, both plates were embedded together in an epoxy resin. In this study, both plates were placed separately along the surface with gap sizes from 500 um to 10 mm so that a coplaner galvanic couple was prepared. The surface of the galvanic couple was ground with SiC papers up to JIS 2000 grit and rinsed in EtOH. Galvanic corrosion experiments were done for 72 h in aqueous NaCl solutions of various concentrations ranging from 5 mM to 2 M. Galvanic current and corrosion potential of the couple were measured during the immersion in the solutions. It was found from the results of corrosion potential, galvanic current, and surface observation that galvanic corrosion behavior changes depending on the gap size between AA5052 and SS400 in the NaCl solutions. When the gap size was 10 mm, no corrosion occurred on the SS400 side in all of the test solutions, suggesting that anodic dissolution reaction was dominant on the AA5052 side. However, when the gap size was decreased, the corrosion of the steel occurred in the solutions at lower concentrations, although the aluminum alloy also showed localized corrosion. These results indicated that anodic dissolution reaction was generated on both materials in the smaller gap-size condition with decreasing the NaCl concentrations. In this study, the change in the galvanic corrosion behavior with the gap size was also discussed from the results of change in the solution chemistry and polarization behavior of the materials. 1. K. Ota, E. Tada, A. Ooi, A. Nishikata, ECS meeting abstracts, MA2018-02, 574, 2018.

Effects of Deep Rolling on Surface Residual Stress and Microhardness of JIS SS400 MIG Welding

Metal Inert Gas (MIG) welding process is a common welding process for carbon steels. During the cooling after welding, non-uniform cooling cause tensile residual stress on the surface of welded joint and, in most cases, in Heat Affected Zone (HAZ) also. The tensile residual stress is undesirable because it affects the strength and shorten the workpiece fatigue life. In order to convert the tensile residual stresses to desirable compressive residual stresses, the mechanical surface treatment like deep rolling process was used in this research. The surface residual stresses were measured by XRD machine with the sin2ψ method. For statistical analysis of significant factors used in deep rolling process, there are three factors each factor has two levels: rolling pressure, rolling speed and number of passes. Taguchi experimental design was used in conjunction with a deep rolling process to determine factors affected the surface residual stresses and surface microhardness. The results of the research showed that the most significant factors that affect the surface residual stress and surface microhardness were the number of passes, followed by the rolling pressure and the rolling speed, respectively. The maximum compressive residual stress measured at the welded joint was -521.5 MPa. The highest measured surface microhardness was 266.2 HV at the welded joint. The appropriated factors of deep rolling process for JIS SS400 MIG welding were rolling pressure 270 MPa, rolling speed 1,500 mm/min and number of passes 3 times.

Galvanic Corrosion between AA5052 Aluminum-Magnesium Alloy and SS400 Carbon Steel in Aqueous NaCl Solutions

Aluminum alloys (AAs) such as 5000 and 6000 series have relatively good corrosion resistance and plastic workability. The use of these alloys for automobile body parts have been increased significantly because of reducing the weight of the body and improvement of fuel consumption. Although aluminum alloys themselves have relatively good corrosion resistance in atmospheric environments, galvanic corrosion between aluminum alloys and other materials should be taken into consideration in automotive application. This is because the body parts made of Al alloys should be jointed with other materials such as steel parts by welding or other methods and because the jointed parts can be exposed to atmospheric corrosion environments. In this study, galvanic corrosion between AA5052 aluminum-magnesium alloy and SS400 carbon steel is investigated in aqueous NaCl solutions. A galvanic couple used in this study was made of AA5052 Al-Mg alloy (Mg: 2.65, Si: 0. 08, Fe: 0.27, Cu: 0.01, Cr: 0.17, Zn: 0.01, Al: bal. (mass%)) and carbon steel (JIS SS400). The plate of both materials was 10-mm width and 15-mm length and 3-mm thickness. After lead wire was connected on the surface of the plates, they were embedded in an epoxy resin. At this time, both materials were separated with a 500-um gap. The surface of the galvanic couple was polished with SiC papers up to JIS 2000 grit and rinsed in EtOH. Galvanic corrosion experiments were performed for 2 hours in aqueous NaCl solutions at various concentrations ranging from 5 mM to 500 mM. Galvanic current and corrosion potential of the couple were measured during the immersion in the solutions. Corrosion potentials measured during the immersion in various concentrations of NaCl were almost constant for 2 h. The corrosion potentials changed in the less noble direction with increasing NaCl concentrations. Galvanic currents between AA5052 and SS400 showed positive values during the immersion in the solutions, indicating that aluminum-alloy side was basically an anode. However, the galvanic currents were almost the same independent of NaCl concentrations. From the results of polarization behaviors for AA5052 and SS400, a significant anodic current increase due to the propagation of localized corrosion on aluminum alloy and a diffusion-limiting current for the reduction of dissolved oxygen on steel were observed at the corrosion potentials of the galvanic corrosion tests. These results indicated that galvanic corrosion between AA5052 and SS400 in the early stage of immersion progressed under a diffusion-limiting condition for the reduction of dissolved oxygen on steel.

DIFFERENT BEHAVIORS OF ZINC RICH PAINT AGAINST CORROSION IN ATMOSPHERIC ZONE AND TIDAL ZONE OF INDUSTRIAL PORT ENVIRONMENT

A study on zinc rich paint (ZRP) and its behaviors of protecting JIS SS400 constructional steel against impacts of industrial port environment at Phu My port (Ba Ria - Vung Tau Province, Vietnam) was started in January 2014. After three years of investigation, thickness of ZRP decreased slowly and the reduction reached to 38 µm and 31 µm in atmospheric and tidal zone, respectively. Moreover, in accelerated environmental conditioning tests, separation and failures of ZRP from steel substrate were responsible for blistering. By comparison of field exposure test and accelerating test, growth of blistering on ZRP is caused by high temperature and time of wetness.

Galvanic Corrosion of AA5052 Aluminum-Magnesium Alloy and Carbon Steel in NaCl Solutions

Aluminum alloys (AAs) such as 5000 and 6000 series, which show relatively good corrosion resistance and plastic workability, have been utilized to automobile body parts for reducing the weight of the body and for the improvement of fuel consumption. However, since the body parts made of Al alloys should be joined with steel parts by welding or other methods and the joined parts can be exposed to atmospheric corrosion environments, there has been a concern about degradation of the parts due to galvanic corrosion between Al alloy and steel. In this study, galvanic corrosion behavior of AA5052 aluminum-magnesium alloy and SS400 carbon steel is investigated in NaCl solutions. A galvanic couple used in this study consisted of AA5052 Al-Mg alloy (Mg: 2.65, Si: 0. 08, Fe: 0.27, Cu: 0.01, Cr: 0.17, Zn:0.01, Al: bal. (mass%)) and carbon steel (JIS SS400). Both materials were 15-mm-square plates of 3 mm in thickness. After lead wire was connected on the surface of the plates, they were embedded in an epoxy resin. At this time, both materials were separated with a 500-um gap. The surface of the galvanic couple was polished with SiC papers down to JIS 2000 grit and rinsed in EtOH. Galvanic corrosion experiments were done in aqueous NaCl solutions of various concentrations ranging from 5 mM to 500 mM. Galvanic current and corrosion potential of the couple were measured during the immersion in the solutions. When a galvanic couple was immersed in a NaCl solution, galvanic current decreased gradually with immersion time and reached almost a constant value. On the other hand, corrosion potential for the galvanic couple showed complex behavior with immersion time. Just after immersion, the corrosion potential decreased in the less noble direction, which may be due to the initiation of corrosion of AA5052, and then after reaching the minimum value, the corrosion potential started to increase to a noble potential. Although the corrosion potential and the magnitude of the galvanic current were different depending on the concentration of the NaCl solutions, they did not change in a regular manner as a function of the NaCl concentrations. The changes in the corrosion potential and the galvanic current may be related to the transition of anodic dissolution behavior of AA5052 in the NaCl solutions of different concentrations.

Material strength of long-term used penstock of a hydroelectric power plant

In this study, the material strength of a carbon steel (JIS SS400), which has been used for the penstock of a hydroelectric power plant for about 50 years, is examined. A series of data were obtained and analyzed by measuring the chemical compositions, observing the macro- and micro-structure and conducting tensile tests. The present study revealed that the material strength (0.2% proof strength and ultimate tensile strength) measured at one site can not be regarded as a reliable representative of the entire structure. On the other hand, strong and positive correlation between equivalent carbon content and material strength indicates that measuring the former is an effective and reasonably accurate estimate of the latter. In addition, potential use of nondestructive evaluations, including the Vickers hardness, and their reliability is discussed. In practice, a series of statistical analysis with those valuable field data provides us with the insight on the material strength of long-term used penstock.

Effect of welding sequence of a multi-pass temper bead in gas-shielded flux-cored arc welding process: hardness, microstructure, and impact toughness analysis

Welding is used in ships, military, buildings, industrial machinery, automobiles, and many other industries. Problems associated with welding are common issues encountered in these fields. This paper investigated the weld profile, impact toughness, microhardness, and microstructure of a JIS SS400 structural multi-layer welding joint using gas-shielded flux-cored arc welding (FCAW-G). It further examined the effects of temper bead welding (TBW) made with two different welding processes, namely with 4 Layers 4 Passes (4L4P) and 4 Layers 10 Passes (4L10P). Thermocouples were fixed to measure the thermal cycles, and the temperature distribution curves along the weld seams were measured by infrared radiation (IR) images. All welded samples were checked using nondestructive phased array ultrasonic testing (PAUT) to ensure defect-free samples before the experiments commenced. The Charpy impact tests were finished at 20 and −20 °C, respectively. Vickers microhardness measurement was carried out at room temperature. The 4L4P welding process was found to improve the impact toughness of the welding joints. Ferrite (F) and acicular ferrite (AF) were observed via an optical microscope (OM) analysis of the 4L4P welding process, which was more effective in tempering the heat-affected zone (HAZ). In addition, it was found that the 4L4P welding process produced an overall lower hardness than the 4L10P welding process. The microstructure of the welding joints as well as the mechanical properties including impact toughness and microhardness were studied by using a scanning electron microscope (SEM) attached with an energy-dispersive spectrometer (EDS) and an OM.

Groove configurations of a flux-cored arc welding process used in critical structures of precision mechanical presses—mechanical and metallurgical studies

This paper utilized a flux-cored arc welding (FCAW) technique and investigated various groove configurations as well as multi-pass welding sequences to create welding specifications in the precision mechanical press industry. Experimental investigations were conducted to examine the influence of three different groove configurations of 40-mm-thick JIS SS400 structural steel welded joints on mechanical and metallurgical properties. Mechanical properties of the welded joints were evaluated by uniaxial tensile testing and Charpy V-notch (CVN) impact testing at room temperature. Simultaneously after a multi-pass welding sequence, various degrees of thermal treatments such as tempering or normalization inevitably occur in the heat-affected zone (HAZ). The unfavorable microstructures in the HAZ and reheated zones can be intentionally modified via the above procedure such that the toughness and microhardness of the HAZ improve. The experimental results revealed that of the three types of groove configurations (C1, C, and F), groove type C1 possessed the maximum yield strength (YS) and ultimate tensile strength (UTS) while groove type F possessed the highest CVN values tested at room temperature. The fundamental reason may be attributed to heat dissipation characteristics of each groove configuration and associated exertion of the multi-pass welding sequence. Microstructural and morphological features as revealed through an optical microscope also indicate a significant influential factor of these joints among the different groove configurations. Therefore, grain refinement of varying degrees can be obtained due to the variation of thermal characteristics of heat input/dissipation; thus, various mechanical and CVN impact properties can be obtained.

An investigation of organic mixed coolant (Palm Olein) for green machining

Purpose – The purpose of this paper is to investigate and contribute to a better understanding of cutting process characteristics using the proposed RBD Palm Olein-based organic mixed coolant. Design/methodology/approach – In this research, refined, bleached and deodorized (RBD) Palm Olein is selected as the base oil for organic coolant and mixed coolant (base oil mixed with chemicals) to compare with the cutting performance of industrial water-soluble chemical (inorganic) coolant. Using coated carbide tool, JIS SS400 Mild Steel was tested in milling process. At fixed spindle speed, the relations between feed rate and depth of cut (DOC) on cutting temperature and surface roughness were investigated. Also, the dynamic viscosity, specific heat capacity and pH level for each coolant are taken into consideration. Findings – As predicted, cutting fluid with lower viscosity removes more heat. The cutting temperature increased with increasing feed rate and DOC. However, surface roughness increased with increasing feed rate but decreased with increasing DOC. From the data gathered, the proposed RBD Palm Olein-based organic mixed coolant showed better heat removal properties than organic coolant and it produced a far better machined surface than inorganic coolant. Originality/value – Overall, the proposed organic mixed coolant has shown great potential to be a good cutting fluid when balance between cooling properties and lubricity, and consistent quality of cutting fluids are sought to produce environmental friendly quality workpiece.

Three-dimensional magnetic microscopy of early stage fatigue in WMZ of low carbon steel plates (JIS-SS400)

Cyclic stresses around welding joint part affect the strength of mechanical components. In order to understand the fatigue phenomena caused by the cyclic stresses, non-destructive methods that can be related to number of stress cycles are necessary. In the present work, we used a newly developed scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor and observed three-dimensional magnetic fields of the specimen before and after four-point fatigue testing at room temperature in air. Low carbon steel plates (JIS SS400) were used in the experiments. It was found that the intensity of the magnet field in a direction perpendicular to the specimen surface was strongly affected by the fatigue cycles. This result means that we can evaluate the fatigue in welding joint area using quantitative magnetic field measurements. Furthermore, it was discovered that the key factor to evaluate the fatigue is the range between ‘S’ and ‘N’ (‘peak to bottom’ values) of the magnetic fields. The three-dimensional magnetic fields decrease before the dislocation does not accumulate enough to generate a small crack at the early stage of the fatigue.

Experimental Study on Enhancement of Steel Mechanical Properties by High Pressure Jet Quenching

The purpose of this study is to enhance the strength of steel by increasing the percentage of martensite microstructure with a high pressure water jet quenching. JIS SS400 carbon steel was chosen as a test sample. The cooling rate of surface and center reached approximately 180oC/sec and 65oC/sec, respectively. After this quenching process, the metallographic analysis showed that the steel turned into martensite structure. Furthermore, the tensile strength of sample increased from 363MPa to 543MPa; the yielding strength increased from 284MPa to 420Mpa. In general, the overall enhancement of mechanical strength was about 140%.

Biofouling of Cr-Nickel Spray Coated Films on Steel Surfaces

Nowadays, corrosion of metals brings us serious economic loss and it often reaches several percentage of GNP. Particularly the marine corrosion was serious and the counter measure was very hard to be established, since the number of factors is huge and complicated. One of the complicated factors in marine corrosion is biofouling. Biofouling was classified into two main categories, microfouling and macrofouling. The former is composed of biofilm formation mainly. Marine bacteria are attached to material surfaces, seeking for nutrition in oligotrophic environment and they excrete polysaccharide to form biofilm on metal surfaces. Then larger living matters are attached on the biofilms to develop biofouling on metal surfaces, which often lead loss and failures of metals in marine environments. From the viewpoint of corrosion protection and maintenance of marine structures, biofouling should be mitigated as much as possible. In this study, we applied spray coating to steels and investigated if chromium-nickel spray coating could mitigate the biofouling, being compared with the conventional aluminium-zinc spray coating in marine environments. The specimens used for this investigation are aluminium, zinc, aluminium-zinc, stacked chromium/nickel and those films were formed on carbon steel (JIS SS400). And the pores formed by spray coating were sealed by a commercial reagent for some specimens. All of those specimens were immersed into sea water located at Marina Kawage (854–3, Chisato, Tsu, Mie Prefecture) in Ise Bay for two weeks. The depth of the specimen was two meter from sea water surface and the distance was always kept constant, since they were suspended from the floating pier. The temperature in sea water changed from 10 to 15 degrees Celsius during the immersion test. The biofouling behavior was investigated by low vacuum SEM (Hitachi Miniscope TM1000) and X-ray fluorescent analysis. When the spray coated specimens with and without sealing agents were compared, the former showed higher antifouling properties generally. Aluminium-zinc alloy spray coated films had higher antifouling property. And the anti-property decreased in this order: Al-Zn alloy spray coating > Zinc spray coating > Aluminium spray coating > Stacked chromium/nickel spray coating. Aluminium and zinc spray coating has been evaluated high conventionally for anti-biofouling in marine environment. However, the Cr/Ni spray coating showed pretty high anti-fouling property.

BaO<sub>2</sub>-BaO中におけるSS400およびSUS304鋼の高温腐食挙動

BaO2塩中におけるSS400鋼およびSUS304鋼の高温腐食挙動が質量減量の測定および腐食形態の観察，腐食生成物の分析により調べられた．固体BaO2は723 Kで溶融し，1073 K以上の高温域で酸素ガスと固相のBaOに解離することから，このような環境変化に伴う腐食挙動の変化がとくに注目された．973 K以下の溶融BaO2中おいて，SS400鋼は内層スケールとしてFeOおよびFe3O4から成る酸化物スケールを生成した．一方，同じ環境でSUS304鋼は主にBaFe2O4から成る厚いスケールを生成した．溶融BaO2中では，SUS304鋼は773 Kで腐食減量の極大値を示した．この温度でのSUS304鋼の腐食減量はSS400鋼よりも約9倍大きかった．1073 K以上の固相BaO中では，SS400鋼の腐食速度は温度の上昇と共に著しく増加した．この場合，この鋼はFeOおよびFe3O4から成る内層スケールとBaOとBaFe2O4から成る外層スケールを生成した．一方，この環境でのSUS304鋼の腐食速度はSS400鋼に比べ大きく低下した．このときこの鋼は，内層スケールとしてCr2O3･FeOから成るスケールを含む，薄いスケールを生成した．

Wavelet Package for the In-Process Monitoring of Gas Metal Arc Welding Mild Steel

The acoustic signals were strongly related to the behavior of the arc column, the molten pool and droplet transfer in gas metal arc welding(GMAW).In this study, all the work pieces (JIS SS400) were welded at the same speed with different currents using a gas metal arc; the purpose was to observe the relationship between these factors. Using a sound capture card and microphone we collected the audio signals generated by the welding. In this paper, wavelet package transformation (WPT) decomposes the sounds signals into 128 channels within the frequency domain. The properties of the audio signals were analyzed by the wavelet-based channel energy. The ROC (Receiver Operating Characteristic) parameters, (Ac, Se, Sp, ppv, and npv), were used for classification performance evaluation. Experimental results also show that acoustic emissions are useful in the quality control of plasma arc welding.

An Investigation on Green Machining: Cutting Process Characteristics of Organic Metalworking Fluid

This paper compares the cutting process characteristics of organic and inorganic coolant for milling process. RBD(refined, bleached & deodorized) palm olein, refined canola and soy bean oil were selected as based oil for soluble mixture(organic) while Jetkool SC95 as inorganic metalworking fluid (MWF). Throughout the research, carbide coated cutting tool and JIS SS400 mild steel are used with various feed rate, depth of cut and fixed spindle speed to determine the cutting temperature, forces and also surface roughness. Heat capacity, pH and tool wear assessment are carried out as well with same material. From the research, cutting temperature, cutting force and surface roughness are proportional to the feed rate and depth of cut. The MWFs pH level also drops after cutting process. Each MWFs showing their different strength on different assessments, overall from the results obtained, palm oil has a high potential to be marketed as organic MWF.

Evaluation of Residual Stress for Plasma Sprayed Member Using Inherent Strain Method

Residual stresses and the resulting dimensional changes due to thermal spraying can be a major factor in affecting the performance of fabricated parts and components. In this study, the residual stress and deformation behaviors of square plate due to blasting treatment and thermal spraying was clarified by based on an inherent strain method... It was found that the inherent strain of blasted surface, that was calculated by the deflection measurement of substrate (JIS SS400, 150×150×1 tmm), was +0.026% in x-direction of square substrate and +0.082% in y-direction of square substrate. Also, it was found that the inherent strain of titanium plasma sprayed layer on the blasted substrate that was calculated by the deflection measurement of the blasted plate was -0.061% in x-direction of substrate and -0.16% in y-direction of substrate. It was also confirmed that the inherent strain method due to deflection measurement was applicable to estimate the residual stress distribution in case of the titanium plasma sprayed steel plate with blasting treatment. As a result, it was found that the residual stress at the surface of plasma sprayed steel plate was 7.60 MPa in x-direction of substrate and 20.4 MPa in y-direction of substrate.

炭素鋼／ＰＭＭＡ異種材料接着継手強度に及ぼす継手形状の影響

The adhered joint composed of polymer and metal is a useful and practical method to take advantage of the both material properties. However, there are some basic problems for the material mismatch due to the different Young's modulus. Inthis study, the stress singularity at the intersection between the free surface and the interface betweenpoly-methyl-methacrylate (PMMA) and structural carbon steel (JIS SS400) was analyzed to clarify the joint strength using a finite element method. As a result, the stress singularity was found above 130 degree of PMMA apex angle and between 35 and 41 degree of PMMA apex angle. In this experiment, it was confirmed that the no free-edge stress singularity was useful conditions to insure the reliability of bending strength for the adhered joint composed of SS400 and PMMA.

金属組織の伸び変形の測定に基づいた破断ひずみの推定

A quantitative metallographic study was performed on JIS SS400 steel to estimate the fracture strain from the measurement of aspect ratio for ferrite grains. The circumferentially notched round bar tensile specimens with the notch root radius of 6, 3, 1, 0.5mm were employed to obtain a wide range of fracture strain.The relationship between plastic strain and aspect ratio for ferrite grains was obtained from the detailed metallographic observations on the polished and etched longitudinal midsection through the fractured half of smooth round bar tensile specimen. A large number of ferrite grains, plastically deformed to various strains, were examined carefully to determine the dependence of aspect ratio on plastic strain.The aspect ratio was well expressed by an exponential equation as a function of plastic strain. It was then possible to provide an appropriate estimate of the fracture strain of notched specimens from the above relation. The average aspect ratio of 9 views immediately underneath the fracture surface was used to deduce the fracture strain. The estimated values were found to be in reasonably good agreement with the measured values within an error of about 1 to 8pct.