Effect of electrohydropulsed treatment on the characteristics of the fine structure of 30KhN2MFA steel

Translated from Fiziko-Khimicheskaya Meckhanika Materialov, No. 6, pp. 77–80, November–December, 1989.     

Effect of the shock-wave treatment on the dynamic strength of 38KhN3MFA steel

Effect of the shock-wave treatment on the dynamic strength of a 38KhN3MFA grade steel was studied in two different regimes—shock wave propagation and superdeep incorporation of ultrafine powder. In the first case, an increase in the dynamic strength is observed, related primarily to a decrease in the proportion of hard and brittle domains in the material as a result of the shock-wave action. The superdeep ultrafine powder incorporation produced no significant effects on the dynamic properties of steel.     

Behavior of particle-filled polymer composite under static and dynamic loading

Experimental results of quasi-static and dynamic fracture of particle-filled polymer composite (PFPCM) “ALTUGLAS EI CH25” with a matrix of polymethylmethacrylate (PMMA) are reported in this paper. PMMA matrix is filled with rubber particles, as result a shock-resistant transparent composite is produced. The main task was to investigate experimentally and theoretically the fracture toughness of this composite under static and dynamic loading. A high-rate loading has been created by impulse magnetic field. Analysis of fracture process and its relation with the load parameters and material microstructure have been established. Application of the original testing method enabled determination of fracture toughness at very short loading times and comparison of the results with material dynamic properties. Theoretical analyses are based in general on the notion of delayed fracture. More specifically, the theoretical analysis is based on experimental results and on the hypothesis of fracture incubation time, or delay time.     

Mechanical properties of 304L stainless steel SMAW joints under dynamic impact loading

The impact properties of 304L Stainless Steel Shielded Metal Arc Welded (SMAW) joints are studied at strain rates between 10^{− 3} and 7.5× 10³ s^{− 1} using a compressive split-Hopkinson bar. The effects of strain rate on the flow response and fracture characteristics are fully evaluated. The results show that the tested weldments exhibit a pronounced strain rate sensitivity, and that changes in the strain rate result in a difference in the flow stress, fracture strain, and work hardening rate. Furthermore, it is noted that the strain rate sensitivity and activation volume vary with the magnitude of the strain rate, and are related to different work hardening stress levels. At all values of strain rate, the tested weldments fail as a result of adiabatic shearing, in which cracks initiate within the shear band and then propagate along this shear band until failure occurs. Observation of the fractured specimens reveals that the fracture surfaces of the fusion zone and base metal regions are characterized by the presence of elongated dimples. The variation in the observed dimple features with strain rate is consistent with the results of the impact stress-strain curves.     

Bearing strength of carbon epoxy laminates under static and dynamic loading

An experimental study has been carried out to investigate both the static and dynamic bearing strengths of a pinned-joint carbon epoxy composite plate with [0°/45°/−45°/90°]_S and [90°/45°/−45°/0°]_S stacking configurations. The static and dynamic experiments have been carried out according to the ASTM D953 standards and ASTM STP 749, respectively [ASTM D 953-D, Standard Test method for Bearing Strength of Plastics, ASTM Designation. 342; Joining of Composite Materials, ASTM STP 749, American Society for Testing and Materials (1981) 131]. The ratio of the edge distance to the pin diameter (E/D), and that of the width to the pin diameter (W/D) of the specimens were varied to obtain the static bearing strength and the S–N fatigue curve. The experiments show that the static bearing strengths reach their upper limit when E/D and W/D ratios are equal to or greater than 4 for both [0°/45°/−45°/90°]_S and [90°/45°/−45°/0°]_S stacking sequences. The fatigue strength, on the other hand, reduces by up to 65% as E/D and W/D ratios increase for both stacking configurations.     

Crack propagation velocities in bi-phase plates under static and dynamic loading

An investigation of the dependence of the crack-propagation velocity in complex bimaterial plates at different loading rates was undertaken. The specimens were fractured under the influence of both static and dynamic loadings and the crack-propagation velocities were detected by high speed photography with the optical method of caustics.The investigation was concentrated in detecting the influence that the different loading rates have on the fracture velocities in both phases of the plates and how this influence interferes—counteracting or superimposing—with the other factors that determine the crack propagation process in bi-material specimens. These factors are the effect of interface, the influence of the mechanical characteristics of each phase on the crack-propagation velocity etc.The results show that for constant and given material characteristics of the bi-phase plate the crack propagation velocity in the first (notched) phase tends to increase with increasing strain rates.The same is valid for the crack propagation velocity in the second phase, but only for the case when fracture occurs under the influence of a dynamic load. A significant discrepancy of the latter statement occurs, however, in the case of fracture under a continuously-increasing static load. In this case the crack-propagation velocity in the second phase reaches some remarkably high values, which are of the order of high strain-rate dynamic crack propagation velocities.In this way, the crack-arrest effect on the crack propagation velocity appears to be more significant in the case of a static loading than it is for the case of dynamic loading.     

一维动静组合加载下深部石英片岩破坏研究

为研究锡铁山铅锌矿深部石英片岩的力学特性,利用分离式霍普金森杆(SHPB)对埋深863¹ 264m的试样进行25、30、35MPa轴压下的一维动静加载实验,和采用LS-DYNA软件模拟了25、30、35、40、45、50 MPa轴压情况下的冲击实验。研究结果表明:在冲击作用下,试样的一维动态抗压强度和破坏所需的入射能随着埋深的增加而增加,并呈现出常见的压剪破坏模式;当轴压40MPa左右,埋深1 428m的岩石动态抗压值达到最大;当轴压低于40 MPa时,轴压的增大能加强试样的抗压能力;当轴压大于40MPa时,轴压的增加反而减弱了试样的抗压能力。     

Effect of welding thermal cycles and cold working on fracture toughness of SN490 steel under static and dynamic loading

Abstract

The static fracture toughness K _IC and dynamic fracture toughness K _Id of SN490, its pre-strained steel, and its welding heat affected zone were measured. K _IC tests were conducted according to the ASTM standard, and K _Id tests were carried out on an instrumented Charpy impacting machine. The experimental results were used to determine the effects of welding thermal cycle and cold working. It was found that both welding heat input and cold working are harmful to the fracture toughness of SN490 steel under both static and dynamic loading. The deleterious effects are serious under static loading. The detrimental effect of welding heat input during submerged arc welding was found to be more significant than that of the 10% plastic prestrain.     

Variation of the mechanical properties and fine structure of 12KhN10T steel after hydrogen charging

Translated from Fiziko-Khimicheskaya Mekhanika Materialov, No. 1, pp. 74–77, January–February, 1989.     

Fatigue of bonded steel interfaces under cyclic shear loading and static normal stress

Hybrid joints that combine mechanical fastening and bonding provide potential joining alternatives for high strength steel structures. An experimental and analytical research program has been initiated to assess the static and cyclic Mode II shear strength of epoxy bonded steel interfaces subjected to static normal (Mode I) pre-stress. During cyclic loading, shear stress vs. interface displacement could be divided into elastic and inelastic regions with a power law equation describing the inelastic curve. Hysteresis loop shape varied with normal stress, shear stress and accumulated fatigue cycles. A shear stress amplitude threshold equal to about 50% of the fracture shear stress was observed.     

Fracture behavior of ultra-fine grained steel bar under dynamic loading

Ultra-fine grained steel bars were recently developed by thermo-mechanical controlled rolling with rapid cooling for increasing the strength of low carbon and low alloy steels. The developed steels are characterized by fine ferrite grains of less than 1 m and high strength as a result of grain refinement. However, their correlations between tensile properties and impact behavior are not well understood. In this paper, impact absorbed energy (E _p) and dynamic fracture toughness (J _Id) were used to evaluate the dynamic fracture behavior of the ultra-fine grained steels, and the fracture mechanisms were also investigated. For the ultra-fine grained steels, tensile stress-strain curve was shown to be correlated with the impact curve of load vs. time, and to be related to the dynamic fracture toughness. The steel with large ferrite grains, small ferrite grain colony and martensite was found to have a good combination of strength and toughness.     

Fracture behaviour of selective laser sintered Rapidsteel 2.0 under static and dynamic loading

Abstract

Selective laser sintered Rapidsteel parts were sintered and infiltrated with Cu-10 at.-%Sn, in two different atmospheres (e.g. 30%H₂-70%N₂ and vacuum with a partial pressure of 200 mbar of Ar). The processing atmospherehada significant effect on the mechanical properties of the infiltrated parts. The parts intered/infiltrated in a 30%H₂-70%N₂ atmosphere, exhibited a tensile strength of 780 MPa and a ductility of 4.45%. However, the tensile strength was reduced moderately to 650 MPa while the ductility was increased significantly to 11.7% by changing the sintering/infiltration atmosphere from 30%H₂-70%N₂ to vacuum + Ar. Furthermore, the parts processed in a vacuum + Ar atmosphere exhibited a better fracture resistance than parts processed in 30%H₂- 70%N₂. The improvement in ductility and fracture resistance for parts processed in vacuum + Ar atmosphere was primarily due to the elimination of nitrides. For both cases, ductile fracture occurred in stainless steel particulate and striation was found in the bronze infiltrant.