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901.
The performance of vacuum arc remelting (VAR) ingot depends largely on ingot structure and chemical uniformity, which are
strongly influenced by molten pool profile that is influenced by VAR process. To better understand the effect of remelting
current on molten pool profile of titanium alloy ingot during VAR process, a 3D finite element model is developed by the ANSYS
software. The results show that there are three remelting stages during VAR process when the remelting current is 2.0 kA.
The molten pool depth increases gradually from 30 to 320 s, then the change of molten pool depth is very small during the
steady state stage from 320 to 386 s, and lastly the molten pool depth becomes shallow after 386 s. The melting rate and temperature
of superheat increase with the remelting current increasing, which leads to the augment of molten pool volume. In the end,
the total remelting time and steady state molten pool time decrease with the melting current from 1.6 to 2.8 kA. 相似文献
902.
The quenching of a metal component with a channel section in a water tank is numerically simulated. Computational fluid dynamics
(CFD) is used to model the multiphase flow and the heat transfer in film boiling, nucleate boiling and convective cooling
processes to calculate the difference in heat transfer rate around the component and then combining with the thermal simulation
and structure analysis of the component to study the effect of heat transfer rate on the distortion of the U-channel component.
A model is also established to calculate the residual stress produced by quenching. The coupling fluid-thermal-structural
simulation provides an insight into the deformation of the component and can be used to perform parameter analysis to reduce
the distortion of the component. 相似文献
903.
In this paper, the effects of hardening exponent, yield strength and elastic modulus on the deformability of near hemispherical
shells are investigated by means of finite element method and orthogonal experiment design. The largest eccentric angle during
the deformation process and thickness reduction after the deformation are introduced to estimate the deformability quantitatively
according to the deformation characteristics of near hemispherical shells. The results indicate that the hardening exponent
is the most influential parameter, followed by elastic modulus and yield strength. The shell exhibits good deformability when
the hardening exponent and elastic modulus are in the range of 0.1–0.125 and 70–108 GPa, respectively. 相似文献
904.
In this paper, we consider a floating raft isolation system with elastic limiters. The limiters might be “contact” or “no
contact”, thus forming a unilateral system generating possible contacts. In order to avoid the large displacement of the floating
raft under shock, limiters might be adopted but good limiters design requires the values of the gaps. Based on the contact
dynamics, the multi-degree-freedom dynamic model of floating raft isolation system with elastic limiters is established. The
artificial neural network has been developed to dingtinguish the contact state of elastic limiters at each step. The example
analysis shows that the algorithm of neural network for contact can shorten the time of caclaution. From the example analysis,
we get some interesting results that may be useful to the ship engineering. 相似文献
905.
A biomechanical musculo-skeletal model of upper limb is presented in this paper, which can provide accurate representations
of muscles and joints, and capture important interactions between joints. The upper limb model is made up of seven segments:
ribs, sternum, clavicle, scapular, humerus, radius and ulna, considered as a single rigid body respectively and includes 22
muscles. The individual muscle forces can be calculated by using an electromyography (EMG) assisted method, which is verified
by comparing the simulation results with other researches of an elbow flexion motion. These comparisons show that the muscle
forces and the estimated joint moment match well with previous literatures. 相似文献
906.
The feasibility of electromagnetically stimulated thermography non-destructive testing (NDT) for the detection of defects
in metallic conductive materials has been carried out by finite element analysis. Aluminum plates with defects of different
diameters, depths, locations, shapes and orientation with respect to eddy current are numerically investigated. ANSYS software
is used to solve the coupled electromagnetic and temperature field equations. The peak temperatures on the top surface of
circular defects with different diameters and depths are calculated at varying excitation frequencies. It is demonstrated
that the obtained temperature inreases with increase of the defect diameter and decrease of its depth. The dependence of the
temperature over the top surface of the defect on its location and orientation is also presented. The results indicate that
we can detect the subsurface defect and estimate its depth and location by choosing a suitable coil-specimen configuration. 相似文献
907.
Solar energy is considered as one of the best alternative energy in the future. Multicrystalline silicon ingot casting is
the main production process for major supply of solar cell. However, the casting process cannot be understood clearly because
of some difficulties, such as enclosed furnace, long cycle time of production and so on. In this paper, an integrated model,
including casting process analysis, quality prediction and production parameters optimization, is proposed and the preliminary
results are acquired. The framework of the proposed model is introduced and the numerical simulation results on the temperature
field and grain growth process are also given out and discussed. 相似文献
908.
Secret sharing schemes are multi-party protocols related to key establishment. They also facilitate distributed trust or shared
control for critical activities (e.g., signing corporate cheques and opening bank vaults), by gating the critical action on
cooperation from t(t ∈ Z
+) of n(n ∈ Z
+) users. A (t, n) threshold scheme (t < n) is a method by which a trusted party computes secret shares Γ
i
(1 ⩽ i ⩽ n) from an initial secret Γ
0 and securely distributes Γ
i
to user. Any t or more users who pool their shares may easily recover Γ
0, but any group knowing only t−1 or fewer shares may not. By the ElGamal public key cryptophytes and the Schnorr’s signature scheme, this paper proposes
a new (t, n) threshold signature scheme with (k,m) (k,m ∈ Z
+) threshold verification based on the multivariate linear polynomial. 相似文献
909.
In an identity based proxy signature (IBPS) scheme, a designated proxy signer can generate the signature on behalf of an original
signer. Traditional IBPS schemes normally rely on the assumption that private keys are kept perfectly secure. However, due
to viruses, worms or other break-ins allowed by operating-system holes, key exposure seems inevitable. To minimize the damage
caused by key exposure in IBPS, we propose an identity-based key-insulated proxy signature (IBKIPS) scheme in the standard
model, i.e. without random oracles. 相似文献
910.
Giles Thomas Stefan Winkler Michael Davis Damien Holloway Shinsuke Matsubara Jason Lavroff Ben French 《Journal of Marine Science and Technology》2011,16(1):8-21
Slam events experienced by high-speed catamarans in irregular waves were characterised through experiments using a hydroelastic
segmented model. The model was designed to represent the dynamic behaviour of the full-scale Incat 112 m vessel and to allow
the measurement of the slam load on the centrebow and wet deck. It was tested in irregular head seas at two speeds relating
to Froude numbers of 0.32 and 0.60. Nearly 300 slams were identified in the test data and analysed with respect to kinematic
parameters. Slams were found to have a large range of magnitudes, with the largest equivalent to 1785 tonnes full scale (approximately
70% of vessel displacement); however, the majority of events were of relatively low severity. Differences in slam characteristics
were found for the two model speeds tested; slams at the slower speed generally occurred further forward on the hull, prior
to the wave crest and with a bow down pitch angle. Immersion of the centrebow to the two-dimensional filling height of the
cross-section between the centrebow and demihulls is shown to be a better indicator of slam occurrence than immersion to the
top of the archway. 相似文献