Showing papers on "Charpy impact test published in 1992"

Effects of particle size on mechanical and impact properties of epoxy resin filled with spherical silica

Abstract: Effects of particle size on the mechanical and impact properties of cured epoxy resins are studied. This resin was filled with spherical silica particles prepared by hydrolysis of silicon tetrachloride. Particles were sorted into five kinds of different mean sizes in the range from 6–42 μm. A static flexural and tensile tests and an instrumented Charpy type impact test were carried out. Flexural strength, tensile strength, and impact-absorbed energy increased with a decrease in the particle size. Fractured surfaces were observed using a scanning electron microscope to clarify the initiation point of fracture.

Small-punch and TEM-disc testing techniques and their application to characterization of radiation damage

Abstract: The present paper summarizes the development of miniaturized small-punch (SP) and TEM-disc (TD) testing techniques and shows their applicability in characterizing the mechanical properties of irradiated materials. The yield strength, ductility and fracture toughness,J lc, were empirically estimated by analysing the deformation and fracture behaviour observed in the miniaturized specimen tests. The ductile-brittle transition temperature (DBTT) was determined from the variation of the SP or TD fracture energy with temperature. A linear correlation between the DBTT obtained from the SP and Charpy V-notched specimen tests has been theoretically and experimentally established. The problems of cracking detection and data scattering often observed in the SP or TD specimen tests are discussed in terms of heterogeneous embrittlement behaviour of materials. It has been demonstrated that these miniaturized testing techniques are capable of evaluating hardening, DBTT shifts andJ lc decreases caused by neutron irradiation.

Grain-boundary segregation and precipitation of boron in 0.2 percent carbon steels

Abstract: The segregation and precipitation of boron have been studied in two 0.2C−0.6Mn0.−5Mo steels containing (nominally) 10 and 50 ppm B. After heating to 1260 δC, samples were air-cooled to 870 °C and then held for times between 0 and 5000 seconds. Additional samples were heated to 1260 °C, air-cooled to 900 °C, reduced in thickness by 50 pct, and then held for various times at 870 °C, as above. The distributions of boron under these various conditions were investigated qualitatively by an autoradiographic technique. In both steels, segregation and/or precipitation of boron at austenite grain boundaries was detected under all conditions examined. Precipitation of iron borocarbide particles occurred along austenite grain boundaries in the 50 ppm B steel during cooling to the holding temperature of 870 °C, while in the 10 ppm B steel, such precipitation occurred only after long times at 870 °C. Mechanical properties of single-pass-rolled samples were measured after tempering to assess the effects of borocarbide precipitation on notch toughness. Such precipitation lowered the Charpy upper shelf energy and increased the transition temperature.

High strength low alloy steel

Abstract: A high strength low alloy steel having a yield strength of at least 100 ksi and a Charpy V-notch impact strength of at least 35 ft-lbs. at minus 84° C. (minus 120° F.) at thickness of up to 6 inches is provided wherein the steel consists essentially of an effective amount up to 0.036% carbon, for low temperature toughness up to 5% manganese, up to 1% silicon, up to 0.015% sulfur, 2 to 4% nickel, up to 2% copper, up to 0.1% niobium, and up to 0.1% aluminum, up to 4.% molybdenum, up to 4% chromium and the balance iron and incidental impurities and is characterized by low carbon bainite microstructure in the as-quenched condition.

Influence of sulfide inclusion on ductility and fracture behavior of resulfurized HY-80 steel

Abstract: The influence of sulfide inclusions on the ductile fracture process of experimental HY-80 steels having graded sulfur levels from 50 to 500 ppm and heat-treated to different strength levels was studied with respect to mechanical properties, namely, tensile ductility and Charpy impact en-ergy. Sulfide inclusions are found to have deleterious effect on both axisymmetric ductility and Charpy impact properties, whereas the plane strain ductility was found to be less sensitive to sulfide inclusions. The effect of interaction between the inclusion and the matrix and the as-sociated stress strain distribution at the void nucleating sites, which control the fracture process by microvoid coalescence, were discussed in the light of various models to suggest a micro-mechanism of fracture. Other toughness parameters obtained from instrumented impact tests were evaluated and discussed as a function of sulfur content.

Effects of Heat Treatment and Chemistry on the Long-Term Phase Stability of a High Strength Nickel-Based Superalloy

Abstract: Phase stability of UDIMET@ alloy 720 (U720), a high strength, hot corrosion resistant alloy was studied as a function of chemistry, processing, heat treatment, and service temperature. U720 is relatively stable with respect to sigma phase when given a supersolvus heat treatment which results in a coarse grain creep resistant microstructure. When U720 is given a subsolvus heat treatment to preserve a fine grain high strength microstructure rapid precipitation of a globular grain boundary sigma phase occurs during 760°C exposure. This precipitation is associated with a degradation in tensile ductility, creep resistance and toughness. As much as a 60% reduction in initial tensile ductility was observed after 1000 hours of exposure while room temperature charpy v-notch impact strengths were reduced from 22 to 6 ft. lb. A modified version of UDIMET alloy 720LI (U72OLI) was found to be substantially less prone to precipitation of sigma phase in fine grain product. U72OLI maintains tensile properties and only suffers minor degradation in ductility after 1000 hours exposure at 760°C.

Low temperature mechanical properties of Fe28Mn5Al1C alloy

Abstract: The mechanical properties from 300 to 77 K of an Fe28.3Mn5.38Al1.04C0.24Si alloy were studied. It was found that this alloy possesses high strength, good ductility and high impact toughness. At 77 K, this alloy has 1112 MPa yield stress, 1536 MPa ultimate tensile strength, 28% total elongation and 72 J Charpy V-notch impact energy. After aging, the Charpy V-notch impact energy.at 300 K is much reduced, and also falls continuously with decreasing temperature. The impact energy is less than 10 J and the fracture surface becomes mainly intergranular at temperatures below 183 K.

J-integral analysis of fibre-reinforced injection-moulded thermoplastics

Abstract: The instrumented Charpy impact test was used to detemine the toughness properties of fibre-reinforced thermoplastics. The fracture process of short fibre-reinforced thermoplastic matrix was determined by energy dssipative processes

A comparison of toughness of

Abstract: The low-temperature toughness of C-Mn weld steel with different grain sizes was investigated with notched and precracked specimens. The results indicated that the fine grain steel, evaluated by notched specimens (Charpy V-notch and 4 point bending specimens), is tougher than that of the coarse grain steel over a temperature range from -196 °C to -30 °C. On the other hand, the coarse grain steel, evaluated with precracked specimens, has a remarkably greater plane strain fracture toughness compared to the fine grain steel. The microstructural analysis revealed that the fracture toughness of both the fine grain and the coarse grain steel is not directly related to the distance of the fracture initiation site from the precrack tip or the size of the ferrite grain. The behavioral discrepancy can be explained in terms of the ratio of local fracture stress to yield stress,i.e., σ f f/σ y. The fine grain steel had a higher σ f f/σ y in the notched specimens but a lower value in the precracked specimens compared to the coarse grain steel. The scatter of toughness data can be mainly attributed to the probabilistic distribution of the weakest particle. We suggested that σ f f/σ y may be a useful parameter for the engineering evaluation of toughness.

Mechanical Properties of Incoloy 908 — An Update

Abstract: Incoloy 908 is a nickel-iron base superalloy with its coefficient of thermal expansion and mechanical properties optimized for use in Nb3Sn superconducting magnets. Thermoelastic, tensile, fatigue crack growth, fracture toughness,and Charpy impact properties, and the results of conduit pressurization tests are summarized for base and weld metal.A limited number of stress rupture tests were also performed in air. The average yield strength (0.2% offset) for the solution annealed and aged base metal is 1200 MPa at 4.2 K. The fracture toughness,KIC, is greater than 230 MPa√m at 4.2 K. The fatigue behavior at 4.2K is comparable to austenitic stainless steels. Fatigue crack growth rates are a factor of three lower at 4.2 K than 298 K and are independent of heat treatment. At 4.2 K, the 20% cold-work-then-aged material has a 20% higher yield strength and a 10% higher ultimate tensile strength. Gas tungsten arc weld (GTAW) metal with or without Incoloy 908 filler metal exhibited comparable yield and about 10% lower tensile strength when compared with that of the base metal after a 200 hour age at 650°C. Fracture toughness, tensile elongation and Charpy absorbed energy were about 40% of those of the base metal. Leak-before-break behavior was observed in an internal pressurization test at room temperature for a geometry identical to that of the US-Demonstration Poloidal Coil conduit. The stress rupture performance is better than other low COE alloys of a similar type to that of Incoloy 908.

High Temperature Degradation of Alloy 718 after Longtime Exposures

Abstract: An isothermal aging study was carried out on alloy 718 for up to 50,000 hours in a temperature range of 593 C to 704OC. Large structural transitions occurred as the material was aged for 25,000 hours at 649°C and in 5,000 hours at 704°C. As the matrix f coalesced, f, delta, and aCr precipitated and grew in the grain boundaries. The drop in yield strength with increasing time of exposure or at higher temperatures was attributed to the overaging of the y phase, while much earlier drops in Charpy impact energies was more related to the grain boundary changes. Structures found in a stress-rupture sample which had been tested at 732OC for 5,400 hours at 69 MPa and structures found in the outer rim of 28,000 hour service turbine disk showed the same overaged structures as isothermally aged alloy 718 which had 25,000 hours aging at 649OC. The stress that can be applied to alloy 7 18 depends on the degree of overaging of the 1/’ phase and subsequent f, delta, and aCr formed at the grain boundaries. Suoerallovs 1992 Edited by S.D. AntoloGch, Rk. Stusrud, R.A. Ma&Cay, D.L. Anton, T. Khan, R.D. Kissinger, D.L. Klarstrom The Minerals, Metals & Materials Society, 1992

Charpy Absorbed Energy and JIc as Measures of Cryogenic Fracture Toughness

Abstract: In this paper, we present experimental comparisons between the critical energy line integral (JIc) and Charpy absorbed energy (Cv) at 4 and 77 K for materials ranging from fully austenitic steels to ferritic steels. At 4 K the correlation between JIc and Cv is weak, indicating that Cv is a poor indicator of static fracture roughness at this temperature. At 77 K, a good correlation exists between JIc and Cv. A good correlation is also observed between JIc at 77 K and Cv at 4 K. The results are explained by the large temperature rise during the Charpy rest. Further evidence of the temperature rise is the marginal change in Cv between 4 and 77 K and the disparity in fracture modes between Charpy and fracture mechanics specimens. For c stainless steels, Cv changed little from 4 to 77 K whereas JIc increased significantly. For ferritic steels, Cv increased in proportion to JIc from 4 to 77 K. Especially in steels with low nickel contents, fracture surfaces of Charpy specimens revealed higher ductility than those of fracture mechanics test specimens. The results qualitatively support the predicted temperature rises to 130 and 150 K for crack initiation during Charpy tests at 4 and 77 K, respectively. Due to a wide variation in roughness response to temperature rise, the Cv-based regulatory criteria developed for one group of alloys will have no validity when applied to another group. Therefore the Charpy test near absolute zero should not be regarded as a measure of the static fracture resistance. Alternative simplified methods of cryogenic fracture toughness are suggested.

Hyperbolic distributions and fractal character of fracture surfaces.

Abstract: The fractal character of fracture surfaces of thick-walled pressure vessels produced in the final fast fracture that terminates low-cycle-fatigue tests is compared with that of fracture surfaces produced in Charpy impact tests in samples of the same high-strength and -toughness steel (ASTM A723) alloy. Slit island analysis yielded fractal dimensions near 1.25 for the Charpy specimens, which is typical of high-strength steel alloys previously studied; however, extremely high fractal dimensions near 1.40 were determined for the low-cycle-fatigue specimens. The distributions of island and lake areas and of island and lake perimeters on random sections exhibit hyperbolic distributions analogous to those found for geographic islands and lakes.

Prediction of weld metal Charpy V notch toughness

Abstract: In the present investigation a series of empirical equations has been developed which relates the toughness to the weld metal microstructure and tensile strength. A comparison between predictions and experiments shows that the best agreement is achieved by the use of measured values for the ultimate tensile strength and the acicular ferrite content. The results are presented in the form of novel process diagrams which summarize the effect of important metallurgical variables in a systematic and illustrative manner. These diagrams can, in turn, serve as a basis for proper selection of consumables for welded steel structures.

Determination of Ductile-Brittle Transition Temperature (DBTT) in Dynamic Small Punch Test

Abstract: A dynamic small punch test technique is demonstrated for measuring the ductile-brittle transition temperature (DBTT) of aged Cr-Mo-V turbine rotor steels. Based on fracture energy measurements and fracture surface observations it is shown that the dynamic small punch test specimens exhibit a clear ductile-brittle transition behavior. The DBTT can be determined reliably by statistically analyzing the scatter in the fracture energy data and by defining the fracture appearance transition temperature. The measured values of DBTT are compared with those obtained from Charpy impact tests.

Effect of silicon content on microstructure and toughness of simulated heat affected zone in titanium killed steels

Abstract: hree steels having different silicon contents were prepared to study the microstructure and toughness of the thermally simulated heat affected zone (HAZ) in titanium killed steels. For a low silicon addition, the oxygen content in the molten steels decreased remarkably. This in turn caused a change in the inclusion phase from predominantly titanium oxide to titanium nitride (TiN), the change being accompanied by two major microstructural modifications. The austenite grain size became refined and the quantity of intragranularly nucleated acicular ferrite decreased. The microstructural change was found to cause coarsening of Charpy fracture surfaces and deterioration of HAZ toughness of the steels. The minor change of silicon content therefore has a profound influence on the properties of titanium killed steels.MST/1503

Instrumented impact testing of a glass swirl mat‐reinforced reaction injection‐molded polyamide block copolymer (NBC)

Abstract: The fracture behavior of a reaction injection-molded (RIM) polyamide block copolymer (NBC) reinforced with a continuous glass strand mat (swirl mat) was studied in instrumented high-speed impact-bending tests. Investigations were carried out on Charpy and Izod specimens of different size and notching direction to elucidate specimens' size effects. From the tests performed at ambient temperature and −40°C, fracture mechanical parameters (fracture toughness, fracture energy) and E-modulus were derived. Changes observed in the above parameters of the matrix were attributed to a molding-induced skin-core morphology. Both fracture toughness and energy of the composites depended strongly on the type, i.e., on the ligament width (W) and length-to-span ratio (L0/L) of the specimens. Reliable fracture mechanics data can be determined in three-point bending when W > 12 mm and L0/L > 1.7 for the specimens. The fracture toughness and E-modulus increased monotonously, whereas the fracture energy reached a plateau as a function of fiber mat content. Their values were only slightly influenced by the temperature. It was also shown how molding-and machining-induced flaw size can be defined. The failure mode of the materials was studied by fractography and the failure events were summarized in a model and discussed.

Fracture behavior of stainless steel-toughened NiAl composite plate

Abstract: Analysis of the tensile and fracture behavior of a composite system consisting of boron carbide particulate-reinforced NiAl with continuous 304 stainless steel toughening regions was performed. The composite was fabricated by extrusion, with the toughening regions extending along the length of the plate in the extrusion direction. Mechanical properties were determined as a function of orientation. Tensile testing revealed that the composite modulus varied only slightly as a function of testing direction, the strength was approximately 25 pct greater in the longitudinal relative to the transverse orientation, and the transverse failure strain was only 0.3 pct compared to values in excess of 10 pct for longitudinal testing. Notched Charpy impact testing indicated that the energy absorption values varied significantly as a function of specimen location and crack growth direction, ranging from 2 to 40 Joules. In addition,K IC values measured on subsize compact tension samples were found to range from 17 to 27 MPa ⋅ m1/2. It was also established that theK max values determined from the maximum load measured during compact tension testing were similar to theK Q values calculated from instrumented notched Charpy impact testing. Finally, the fatigue crack growth characteristics of the composite were determined as a function of orientation.

Statistical Analyses of Fracture Toughness Results for Two Irradiated High-Copper Welds

Abstract: The objectives of the Heavy-Section Steel Irradiation Program Fifth Irradiation Series were to determine the effects of neutron irradiation on the transition temperature shift and the shape of the K{sub Ic} curve described in Sect. 6 of the ASME Boiler and Pressure Vessel Code. Two submerged-arc welds with copper contents of 0.23 and 0.31% were commercially fabricated in 215-mm-thick plates. Charpy V-notch (CVN) impact, tensile, drop-weight, and compact specimens up to 203.2 mm thick (1T, 2T, 4T, 6T, and 8T C(T)) were tested to provide a large data base for unirradiated material. Similar specimens with compacts up to 4T were irradiated at about 288{degrees}C to a mean fluence of about 1.5 {times} 10{sup 19} neutrons/cm{sup 2} (>1 MeV) in the Oak Ridge Research Reactor. Both linear-elastic and elastic-plastic fracture mechanics methods were used to analyze all cleavage fracture results and local cleavage instabilities (pop-ins). Evaluation of the results showed that the cleavage fracture toughness values determined at initial pop-ins fall within the same scatter band as the values from failed specimens; thus, they were included in the data base for analysis (all data are designated K{sub Jc}).

Synthesis and structure–property relationships of a new class of rubber-toughened PMMA

Abstract: In the present work, blends between poly(methyl methacrylate) (PMMA) and poly(ethylene-co-vinyl acetate) (EVA) rubbers obtained by in situ polymerization of the acrylic monomer in the presence of the rubber have been investigated by linear elastic fracture mechanics (LEFM), by Charpy impact tests, and by scanning electron microscopy (SEM). Particularly, a correlation among molecular weight and composition of the EVA rubbers, phase structure development, and, consequently, mechanical impact properties of the resulting blends has been drawn.

Irradiation effects on fracture toughness of two high-copper submerged-arc welds, HSSI series 5. Volume 2, Appendices E and F

Abstract: The Fifth Irradiation Series in the Heavy-Section Steel irradiation (HSSI) Program was aimed at obtaining a statistically significant fracture toughness data base on two weldments with high-copper contents to determine the shift and shape of the K{sub lc} curve as a consequence of irradiation The program included irradiated Charpy V-notch impact, tensile, and drop-weight specimens in addition to compact fracture toughness specimens Compact specimens with thicknesses of 254, 508, and 1016 mm [1T C(T), 2T C(T), and 4T C(T), respectively] were irradiated Additionally, unirradiated 6T C(T) and 8T C(T) specimens with the same K{sub lc} measuring capacity as the irradiated specimens were tested The materials for this irradiation series were two weldments fabricated from special heats of weld wire with copper added to the melt One lot of Linde 0124 flux was used for all the welds Copper levels for the two welds are 023 and 031 wt %, while the nickel contents for both welds are 060 wt % Twelve capsules of specimens were irradiated in the pool-side facility of the Oak Ridge Research Reactor at a nominal temperature of 288{degree}C and an average fluence of about 15 {times} 10{sup 19} neutrons/cm{sup 2} (> 1 MeV) This volume, Appendices more » E and F, contains the load-displacement curves and photographs of the fracture toughness specimens from the 72W weld (023 wt % Cu) and the 73 W weld (031 wt % Cu), respectively « less