Showing papers by "Southwest Wisconsin Technical College published in 2018"
TL;DR: Maps of Jupiter’s internal magnetic field at a range of depths reveal an unusual morphology, suggesting that Jupiter's dynamo does not operate in a thick, homogeneous shell and it is proposed that this unexpected field morphology arises from radial variations, possibly including layering, in density or electrical conductivity, or both.
Abstract: The Juno spacecraft, which is in a polar orbit around Jupiter, is providing direct measurements of the planet's magnetic field close to its surface1 A recent analysis of observations of Jupiter's magnetic field from eight (of the first nine) Juno orbits has provided a spherical-harmonic reference model (JRM09)2 of Jupiter's magnetic field outside the planet This model is of particular interest for understanding processes in Jupiter's magnetosphere, but to study the field within the planet and thus the dynamo mechanism that is responsible for generating Jupiter's main magnetic field, alternative models are preferred Here we report maps of the magnetic field at a range of depths within Jupiter We find that Jupiter's magnetic field is different from all other known planetary magnetic fields Within Jupiter, most of the flux emerges from the dynamo region in a narrow band in the northern hemisphere, some of which returns through an intense, isolated flux patch near the equator Elsewhere, the field is much weaker The non-dipolar part of the field is confined almost entirely to the northern hemisphere, so there the field is strongly non-dipolar and in the southern hemisphere it is predominantly dipolar We suggest that Jupiter's dynamo, unlike Earth's, does not operate in a thick, homogeneous shell, and we propose that this unexpected field morphology arises from radial variations, possibly including layering, in density or electrical conductivity, or both
69 citations
TL;DR: In this paper, a constitutive equation was established using experimental results to predict the flow stress of a high strength aluminum alloy under elevated temperature and strain rates, which can accurately predict flow behavior of the Al-Zn-Mg-Cu alloy.
47 citations
TL;DR: In this article, a continuous bending channel was introduced into an equal channel angular rolling apparatus and a new rolling technology was successfully developed to alter the texture components and enhance the stretch formability of rolled AZ31 sheets by developing the rolling technology.
46 citations
TL;DR: The effect of rolling speeds varying from 1 to 4m/s on texture modifications and mechanical properties of AZ31 magnesium alloy sheets processed by a combination of equal channel angular rolling and continuous bending (ECAR+CB) at high temperature (550°C) was investigated in this article.
38 citations
02 May 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effects of solution and subsequent aging treatment on the microstructures and mechanical properties of in-situ Al3Ti/2024Al composites were studied.
Abstract: In the present work, in-situ Al3Ti/2024Al composites with different amount of Al3Ti reinforcements were fabricated by ultrasonic casting method. The effects of solution and subsequent aging treatment on the microstructures and mechanical properties were studied. The results show that solution at 500 °C for 6 h is suitable for in-situ Al3Ti/2024Al composites with mass fractions of reinforcements between 4 wt% and 16 wt%. The aging kinetics of Al3Ti/2024Al composites was promoted by the Al3Ti reinforcements. When the mass fraction of Al3Ti is increased from 0% to 16%, the peak hardness is increased by 20.3%, and the time required to reach the peak hardness is shortened by 66.7%. The microstructures of peak-aged Al3Ti/2024Al composites consist of equiaxed α-Al grains and evenly distributed reinforcing particles. As the mass fraction of Al3Ti increasing, the compression and tensile strengths were both increased gradually at the sacrifice of plasticity.
31 citations
TL;DR: An improved reliability analysis method based on the accelerated aging test of rubber O-rings is proposed in this paper and the comparison with the traditional statistical method is conducted to prove the advantage of this method.
Abstract: The sealing performance of rubber O-rings plays an irreplaceable role in ensuring the high reliability and safety of mechanical systems. However, traditional statistical analysis may not consider the aging process of rubber O-rings at different temperatures and the time-varying characteristics of rubber material parameters. In view of these problems, an improved reliability analysis method based on the accelerated aging test of rubber O-rings is proposed in this paper. This method is featured by a combination with the traditional accelerated model and the Gamma stochastic process. This paper first adopts the stationary Gamma process to describe the degradation of compression set which is the performance degradation indicator of rubber O-rings. Then, the reliability model is derived from the Gamma degradation model. Next, the Arrhenius model is used to represent the shape parameter of Gamma degradation model and the approach of maximum likelihood estimation is adopted to solve the parameters. Finally, the rubber O-rings of gas steering engine were selected and a series of accelerated aging tests were conducted to obtain the reliability and the storage lifetime of rubber O-rings at different temperature stresses through our improved method. Besides, the comparison with the traditional statistical method is also conducted to prove the advantage of this method.
27 citations
TL;DR: In this paper, a back pressure thixoextruding method was proposed to control the liquid segregation during the thixoing process, where the back pressure was provided by disk springs which can apply an elastic force on the deformed alloy to make it in a three-dimensional compression stress state.
24 citations
TL;DR: A novel double quantum image encryption approach based on quantum Arnold transform (QAT) and qubit random rotation is proposed in this paper, in which QAT is used to scramble pixel positions and the gray information is changed by utilizing random qubit rotation.
Abstract: Quantum image encryption offers major advantages over its classical counterpart in terms of key space, computational complexity, and so on. A novel double quantum image encryption approach based on quantum Arnold transform (QAT) and qubit random rotation is proposed in this paper, in which QAT is used to scramble pixel positions and the gray information is changed by utilizing random qubit rotation. Actually, the independent random qubit rotation operates once, respectively, in spatial and frequency domains with the help of quantum Fourier transform (QFT). The encryption process accomplishes pixel confusion and diffusion, and finally the noise-like cipher image is obtained. Numerical simulation and theoretical analysis verify that the method is valid and it shows superior performance in security and computational complexity.
18 citations
TL;DR: In this article, a multidirectional forging (MDF) of Mg-Gd-Y-Nd-Zr alloy was performed under a decreasing temperature condition, and the grain refinement, microstructure and mechanical properties homogeneity of the alloy during MDF process were investigated.
Abstract: Multidirectional forging (MDF) of Mg-Gd-Y-Nd-Zr alloy was performed under decreasing temperature condition. The grain refinement, microstructure and mechanical properties homogeneity of Mg-Gd-Y-Nd-Zr alloy during MDF process were investigated. The results show that the grain refinement mechanism of Mg-Gd-Y-Nd-Zr alloy during MDF process was dynamic recrystallization. The dynamic precipitations were observed after MDF process, which were mainly located at the grain boundaries and had a significant influence on the grain refinement, and the amount of dynamic precipitations increased as the MDF passes increase. The microstructure of the billet was not homogeneous due to the deformation and temperature inhomogeneity during MDF process. Optimization MDF process has been proposed, which benefited the microstructure homogeneity and reduced the amount of the dynamic precipitations. Based on the optimization MDF process, the elongation to fracture significantly increased.
17 citations
21 Feb 2018-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the effect of different (0002) distributions (ND and ND together with BT texture) on strength of slip and twinning predominant deformations of a Mg AZ31 plate was systematically studied.
Abstract: In the present study, the effect of different (0002) distributions ( // ND (MT texture) and // ND together with // RD (BT texture)) on strength of slip and twinning predominant deformations of a Mg AZ31 plate was systematically studied. The results show that the tensile yield strengths along the TD are similar in the two textures, but yield strength in compression along the TD is obviously higher in BT texture than in MT texture. Here, TD, RD and ND refer to the transverse direction, rolling direction and normal direction of the AZ31 plate, respectively. An analysis on Schmid factors demonstrates that the different compression yield strengths in the two texture mainly results from their different boundary obstacle effect against { 10 1 2 } twinning. The mechanism was further analyzed by a compound use of the activation stress difference of slip/twinning (ΔStress) and geometrical compatibility factor ( m ′ ) between neighboring grains. A lower ΔStress or a higher m ′ mean a lower boundary obstacle effect. There is a similar ΔStress in the two texture under compression, but an obvious lower m ′ in BT texture than that in MT texture. The lower m ′ in BT texture than in MT texture leads to a higher boundary obstacle effect and the resultant higher compressive yield strength in BT texture. It is found that the presence of a large number of neighboring grains with a high angle between their c-axes in BT texture mainly accounts for the lower m ′ .
16 citations
TL;DR: In this paper, a wave-shaped interface rolling (WIR) was proposed to tailor the strong basal texture of a hot-rolled Mg AZ31 plate to obtain different inclination angles.
TL;DR: In this article, the optimal isothermal forging of a cast Mg-Zn-Y-Zr magnesium alloy tank cover with complete die fill and without fold defect was studied.
Abstract: The isothermal forging of a cast Mg-589 wt% Zn-079 wt% Y-032 wt% Zr magnesium alloy was carried out to form the tank cover The forming process of isothermal forming is studied by finite element model simulation and experiment Based on the optimum isothermal forging process, the isothermal forging experiments of the cast Mg–Zn–Y–Zr magnesium alloy tank cover were successfully conducted The results show that the experimental results such as forming load are in good agreement with the calculated ones The tank cover forging with complete die fill and without fold defect can be obtained by utilizing the optimum isothermal forging process The mechanical properties of the tank cover show a significant improvement over those of original materials, and the tank cover exhibits an ultimate tensile strength of 302 MPa, a yield strength of 209 MPa, and an elongation of 13%
TL;DR: In this paper, the effects of 1.5% Ag addition and solid solution + artificial ageing at 160°C on the microstructure and mechanical properties of a Mg-5Sn alloy have been studied.
Abstract: Effects of 1.5 wt.% Ag addition and solid solution + artificial ageing at 160 °C on the microstructure and mechanical properties of a Mg-5Sn alloy have been studied. The results show that Ag addition has significantly hardened the solution-treated Mg-5Sn alloy. During the ageing process, the hardness increase rate and the strength and ductility of the Mg-5Sn alloy at each state are also improved by Ag addition. The improved strengthening behavior is primarily attributed to the refinement distribution of the Mg2Sn precipitates, the enhanced precipitation process, and the synergistic strengthening effect of Mg2Sn and a metastable plate DO19 phase formed at lower ageing temperature. For each solution-treated alloy, the strength and ductility are higher than the corresponding cast ones. Ageing further enhances the yield strength, and the ductility of the Mg-5Sn-1.5Ag alloy is also increased after ageing. The fracture surfaces of the both peak-aged alloys exhibit the characteristic of a mixture of quasi-cleavage and ductile fracture.
TL;DR: The effect of recrystallization annealing on corrosion behavior of Ta-4%W alloy was studied, and it is found that the deformed sample contains high dense dislocations and dislocation boundaries.
Abstract: The effect of recrystallization annealing on corrosion behavior of Ta-4%W alloy was studied. It is found that the deformed sample contains high dense dislocations and dislocation boundaries. During annealing, these dislocations and dislocation boundaries are replaced by recrystallizing grains until the alloy is fully recrystallized. Both the anodic dissolution and the cathodic activity is much more blocked. The corrosion potential gradual shift towards negative values and corrosion current density decrease, while polarization resistance increases after annealing, indicating enhanced corrosion resistance of the alloy. Such an enhancement is caused by the increase of low-Σ coincide site lattice boundaries and decrease of dislocations and dislocation boundaries.
TL;DR: AISI H13 hot work steel with fatigue cracks was repaired by a biomimetic laser remelting (BLR) process in the form of lattice units with different sizes as discussed by the authors.
Abstract: AISI H13 hot work steel with fatigue cracks was repaired by a biomimetic laser remelting (BLR) process in the form of lattice units with different sizes. Detailed microstructural studies and microhardness tests were carried out on the units. Studies revealed a mixed microstructure containing martensite, retained austenite and carbide particles with ultrafine grain size in units. BLR samples with defect-free units exhibited superior thermal fatigue resistance due to microstructure strengthening, and mechanisms of crack tip blunting and blocking. In addition, effects of unit size on thermal fatigue resistance of BLR samples were discussed.
TL;DR: In this article, the effect of SiC nanoparticle contents on microstructures and mechanical properties of the composites is systematically investigated, and it is found that the strength and ductility of the composite increase first and then decrease as the increase of n-SiCp contents.
Abstract: Nanosize SiCp (n-SiCp) reinforced Mg–9Al matrix composites (Mg–9Al–xSiC, x = 2.5, 5, 7.5, 10 wt%) with nearly full densification are fabricated by the semisolid powder hot pressing technique assisted with ultrasonic. The effect of SiC nanoparticle contents on microstructures and mechanical properties of the composites is systematically investigated. Grain size and density of Mg–9Al–xSiC composites and morphology of bonding interfacial between the n-SiCp and matrix are found to be greatly dependent on the n-SiCp contents, resulting in the strength and ductility of the composites increase first and then decrease as the increase of n-SiCp contents. As the SiCp content increasing to 7.5 wt%, superior mechanical properties with the yield strength of 191 MPa, ultimate tensile strength of 248 MPa, and elongation to failure of 5.3% are achieved. The improved mechanical properties could be attributed to grain boundary strengthening, Orowan strengthening, and load transfer strengthening.
TL;DR: In this article, a long-term natural failure mechanism was studied for the sealing function of the original nitrile rubber O-ring, and the surface and interior of the packaging barrel was analyzed.
Abstract: Nitrile rubber O-rings seals for packaging barrel was stored in China tropical marine atmosphere environments for 10 years, and then the sealing function of nitrile rubber O-ring was failed. By comparing the molecular structure, cross-link density, thermal decomposition, content of elements and chemical functional groups of the original nitrile rubber seals, the surface and interior of nitrile rubber seals storage for 10 years, a long-term natural failure mechanism was studied. The results showed that: the surface content of dibutyl phthalate and dibutyl sebacate, the surface carbonyl peak height and the surface content of oxygen element were higher than that in internal; the surface cross-link density was lower than that in internal but still higher than in original sample; and surface carbon- to-oxygen ratio were lower than that in internal and original sample. After aging for 10 years, the weight loss of plasticizer decreased, and the main chain content increased. It can be inferred that nitrile rubber mainly undergoes oxygen-absorbing cross-linking reaction to form carboxylic acids and esters, which is accompanied by the migration and enrichment of two plasticizers to the surface, causing reductions in elasticity and elasticity. The residual permanent compression set was lower than the design critical value, and the sealing function for the packaging barrel was lost, and a leak occurred.
TL;DR: Simulation results with respect to the mesoscale VPSC modeling show that the affine and Neff = 10 linearization schemes provide the best predictions for NiTi shape memory alloy with cubic structure.
Abstract: A coupled macro-meso-scale numerical simulation is applied to investigate the friction effect on texture evolution during uniaxial compression of NiTi shape memory alloy at 400 °C. In this approach, macroscale finite element simulations in consideration of various friction coefficient are conducted and then the corresponding velocity gradients in various regions are extracted mainly based on the delivery deformation gradient in the user-defined material subroutine (UMAT) in ABAQUS code. These velocity gradients are regarded as the deformation conditions applied in the mesoscale VPSC model. Simulation results in terms of macroscale finite element modeling demonstrate that only within the region of minimum deformation zone which is close to the die, friction effect has a nonnegligible influence on the velocity gradient. Simulation results with respect to the mesoscale VPSC modeling show that the affine and Neff = 10 linearization schemes provide the best predictions for NiTi shape memory alloy with cubic structure. Furthermore, the friction effect does have an influence on the evolution of slip mode activities in various deformation zones and therefore results in the inhomogeneous texture evolution within the deformed sample during uniaxial compression.
01 Jan 2018
TL;DR: In this article, the hot pressure deformation tests were carried out by using Gleeble-2000 simulator at the temperature of 950°C ~ 1150 °C and strain rate of 0.001s −1 ~ 1s -1 for a kind of high strength construction steel 34CrNiMo6 for Crankshafts and the curve of its flow stress were obtained.
Abstract: The hot pressure deformation tests were carried out by using Gleeble-2000 simulator at the temperature of 950°C ~ 1150 °C and strain rate of 0.001s -1 ~ 1s -1 for a kind of high strength construction steel 34CrNiMo6 for Crankshafts and the curve of its flow stress were obtained. By studied the data, the flow stress constitutive equation, hot deforming active energy and the Z parameter were obtained. The curve of flow stress of 34CrNiMo6 steel indicated that the flow stress was increased with the decrease of temperature or increase of the strain rate. During the deformation, temperature and strain rate take important effect on dynamic recrystallization and dynamic recovery. It was propitious to dynamic recrystallization with raising temperature or reducing strain rate, and also made for the refinement of grain.
TL;DR: In this paper, the basic properties of point defect structures of B2-NiAl crystal were analyzed by the density functional theory, including the heat of formation, energies of formation and equilibrium concentration of point defects.