共查询到20条相似文献,搜索用时 343 毫秒
1.
In this study, a method was developed for distinguishing insertion and driving performance between different self-tapping
bone screw designs. To measure screw starting load, torque and displacements, a test apparatus was developed utilizing a modified
drill press with the capability to measure in-line torque, axial compression load, and axial displacement. Specimens were
inserted into cadaver bone to measure a baseline response and a bone analog was developed to mimic the bicortical application
of screws in the cadaver model. Recorded data could be used to measure a distinguishable screw starting load and the torque
for the insertion of bone screws. The results were similar between the cadaver bone and the bone analog. The average insertion
load ranged from 5.4 to 64.5 N in cadaver tests and 9.0–41.0 N in the construct tests. Average first cortex insertion torques
ranged from 0.53 to 0.66 N-m in the cadaver tests and 0.29–0.32 N-m in the construct test. Average second cortex insertion
torques ranged from 0.70 to 1.03 N-m in the cadaver tests and 0.60–0.63 N-m in the construct tests. This method successfully
illuminated differences between several different self-tapping screw designs and was also successfully employed to determine
the impact of design and manufacturing methods on screw performance. An interesting finding in this study is that axial starting
load is very sensitive to screw tip design whereas insertion torque is not. 相似文献
2.
Andréas Redl Marie Hélène Morel Joëlle Bonicel Stéphane Guilbert Bruno Vergnes 《Rheologica Acta》1999,38(4):311-320
The rheological behaviour of a gluten plasticized with glycerol has been studied in oscillatory shear. The mixing operation
in a Haake batch mixer leads to a maximum torque for a level of specific energy (500–600 kJ/kg) and temperature (50–60 °C)
quite independent of mixing conditions (rotor speed, mixing time, filling ratio). The gluten/glycerol dough behaves as a classical
gluten/water dough, with a storage modulus higher than the loss modulus over the frequency range under study. A temperature
increase induces a decrease of moduli, but the material is not thermorheologically simple. Glycerol has a plasticizing effect,
which can be classically described by an exponential dependence. Mixing conditions influence the viscoelastic properties of
the material, mainly through the specific mechanical energy input (to 2000 kJ/kg) and temperature increase (to 80 °C). Above
50 °C, specific mechanical energy highly increases the complex modulus. The aggregation of proteins, as evidenced by size-exclusion
chromatography measurements, occurs later as the dough temperature reaches 70 °C. The nature of network interactions and the
respective influence of hydrophobic and disulphide contribution is discussed. A general expression is proposed for describing
the viscous behaviour of a gluten/glycerol mix, which could seem simplistic for such a complex rheological behaviour, but
would remain sufficient for modelling the flow behaviour in a twin screw extruder.
Received: 24 November 1997 Accepted: 28 April 1999 相似文献
3.
P. Nithiarasu 《Heat and Mass Transfer》2002,38(3):243-250
An adaptive remeshing procedure based on interpolation error has been developed for solving laminar natural convection problems.
A simple relation between the Rayleigh number and the equilibration constant is introduced to increase the efficiency of the
method. Unstructured meshes have been regenerated based on an initial solution and used in the calculations. This avoids the
expensive mesh sensitivity study. Two typical natural convection problems are solved to demonstrate the present technique.
Excellent performance has been observed at moderate and high Rayleigh numbers although present method gives good results over
the whole range of Rayleigh numbers considered.
Received on 27 October 2000 / Published online: 29 November 2001 相似文献
4.
5.
M. Kamiński 《Archive of Applied Mechanics (Ingenieur Archiv)》2001,71(10):679-694
Summary The main goal of the paper is to present theoretical aspects and the finite element method (FEM) implementation of the sensitivity
analysis in homogenization of composite materials with linear elastic components, using effective modules approach. The deterministic
sensitivity analysis of effective material properties is presented in a general form for an n-components periodic composite, and is illustrated by the examples of 1D as well as of 2D heterogeneous structures. The results
of the sensitivity analysis presented in the paper confirm the usefulness of the homogenization method in computational analysis
of composite materials the method may be applied to computational optimization of engineering composites, to the shape-sensitivity
studies and, after some probabilistic extensions, to stochastic sensitivity analysis of random composites.
Received 10 November 2000; accepted for publication 24 April 2001 相似文献
6.
A method is proposed for calculation of the complex eigenvalues of a boundary-value problem that describes the rotation of
a long vertical partially compressed rod subject to the action of dead weight and torque. The solution of the problem is sought
for two sections of the rod in the form of asymptotic expansions in a small parameter, which are then joined at a certain
point. The results obtained are discussed and compared with the results of other studies. The method may be used for analysis
of the rotation of a long vertical pipe in deep-well drilling.
Central Scientific and Research Institute of Geological Exploration, Moscow, Russia. Translated from Prikladnaya Mekhanika,
Vol. 36, No. 3, pp. 137–143. March, 2000. 相似文献
7.
A new high-resolution laser Doppler anemometer (LDA) has been developed with a working distance of 350 mm, allowing operation
in lab-scale wind tunnels. The measurement volume size is 35 μm in diameter by 60 μm in length, allowing resolution of the
smallest turbulence scales even at fairly high Reynolds numbers. The controversial question of velocity and validation bias
in LDA data is resolved with an experimental method for measuring and removing those effects. Uncertainty estimates are also
derived for all the mean and Reynolds stress measurements.
Received: 27 June 1999/Accepted: 30 August 2000 相似文献
8.
This paper is a contribution to the development of an original technique for measuring the in-cylinder equivalence air–fuel
ratio. The main objective was to construct an instrument able to furnish instantaneous values of hydrocarbon concentration
for many consecutive cycles at a definite location, especially at the spark plug location. The probe is based on a hot-wire-like
apparatus, but involves catalytic oxidation on the wire surface in order to be sensitive to the hydrocarbon concentration.
In this paper, we present the different steps needed to develop and validate the probe. The first step focuses on the geometric
configuration to simplify as much as possible the mass transfer phenomena on the wire. The second step is a parametric study
to evaluate the sensitivity, confidence and lifetime of the wire. By physical analysis, we propose a relationship between
the electrical signal and the air–fuel equivalence ratio of the sampled gases. The third step is the application of the probe
to in-cylinder motored engine measurements, which confirms the ability of the technique to characterise, quantitatively, the
homogeneity of the air–fuel mixture, especially during the compression stroke. This work points out that the global sensitivity
is estimated at 4 V per unit of equivalence air–fuel ratio and the response time is estimated at about 400 μs. The equivalence
air–fuel ratio range is from pure air to 1.2. Experiments show that it is necessary to calibrate the system before use because
of the existence of multiple catalysis states. The probe presents advantages associated with its simplicity, its low cost
and its direct engine application without any modifications.
Received: 1 November 2000 / Accepted: 30 May 2001 相似文献
9.
Michael Günther Otto Müller Reinhard Blickhan 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(3):283-302
The single-inverted pendulum (SIP) model is still the paradigm describing dynamics and control of quiet human stance in the
sagittal plane. We used two methods to verify this paradigm. First, in an experimental approach we acquired kinematic data
of both legs of ten subjects at high spatial resolution while quietly standing on two force platforms. We calculated all leg
joint angles, the belonging joint torques using inverse dynamics and estimates of joint stiffnesses. Some linear correlations
and regressions of both local (joint) and global (COM, COP: centre of mass respectively pressure) variables predicted by the
SIP model were investigated. All three verification criteria applied to mean values extracted from experimental data revealed
that the SIP is not a valid model for quiet human stance. As a second method, we used computer synthesis to demonstrate that
a double-inverted pendulum (DIP) model enters a stable attractor when just the “hip” joint torque is regulated, whereas no
torque is applied to the “ankle” joint. Here, angle and torque fluctuations are necessary because such a DIP strategy is of
inevitable dynamic character. The two predicted eigenfrequencies of this regulated DIP model approximate the upper and lower
limits of the main part of measured power spectra of quiet human stance. We suggest this dynamic necessity to be representative
of the biological constraints under which a mechanically unstable inverted multi-segment chain must be stabilised. 相似文献
10.
A method to measure very small torques that subject micro-diameter copper wires to plasticity is developed for quasi-static
torsion experiment. Following the concept in the work by Fleck et al. (Acta Metall. Mater. 42:2, 1994), we employed a glass fiber filament as the torque cell. To calculate the small torques applied on the micro-diameter copper
wires, an additional rotation sensor is required to measure the rotation of the glass fiber torque cell. The rotation sensor
system is attached between the glass fiber and the copper wire specimen. It uses a laser extensometer to gauge the distance
between a helical and a horizontal reflection tapes on a foam cylinder, which is calibrated with the angle of rotation. A
new set of torsional experimental data for the copper wires with four different diameters, from 16–180 μm, are presented.
All copper wires exhibit a typical elastic-plastic response. The torsional properties of these copper wires were not found
to be significantly different. The uncertainties of the measurement and analysis are discussed. 相似文献
11.
Neglect of end effects in Couette rotational viscometry introduces a 10–30% error in the estimate of shear stress at the spindle
surface. Actual deviations depend on the shear-thinning level of a given sample. We tackle the end effect for the standard
sensor Z40 DIN according to the ISO 3219 by solving the related 2D boundary-value problem for a class of shear-thinning viscosity
functions. The pseudosimilarity method of treating the primary data leaves an error of about 0.5% in shear stresses. Further
reduction in the errors needs a full numerical simulation for each point of the primary data based on a suitable wide-range
representation of the viscosity function. To support a high accuracy of torque calibrations, the effect of inertia on torque
for Newtonian liquids in standard sensor Z40 DIN at Re < 500 is calculated using the FLUENT 6.2 commercial software.
Paper was presented at the 3rd Annual Rheology Conference, AERC 2006, April 27–29, 2006, Crete, Greece. 相似文献
12.
H. Rubinsztein-Dunlop B. Littleton P. Barker P. Ljungberg Y. Malmsten 《Experiments in fluids》2001,30(1):36-42
A flow tagging technique based upon ionic fluorescence in strontium is investigated for applications to velocity measurements
in gas flows. The method is based upon a combination of two laser based spectroscopic techniques, i.e. resonantly-enhanced
ionisation and laser-induced ionic fluorescence. Strontium is first ionised and then planar laser-induced fluorescence is
utilised to give 2D `bright images' of the ionised region of the flow at a given time delay. The results show that this method
can be used for velocity measurements. The velocities were measured in two types of air–acetylene flames – a slot burner and
a circular burner yielding velocities of 5.1 ± 0.1 m/s and 9.3 ± 0.2 m/s, respectively. The feasibility of the method for
the determination of velocities in faster flows than those investigated here is discussed.
Received: 5 November 1998/Accepted: 19 January 2000 相似文献
13.
The Cauchy’s theorem for balance laws is proved in a general context using a simpler and more natural method in comparison
to the one recently presented in Segev (Arch. Ration. Mech. Anal. 154:183–198, 2000). By “generality” we mean that the ambient space is considered to be an orientable smooth manifold, and not only the Euclidean
space. 相似文献
14.
M. Mori Y. Takeda T. Taishi N. Furuichi M. Aritomi H. Kikura 《Experiments in fluids》2002,32(2):153-160
A new flow metering system using an ultrasonic Doppler method has been developed. By this method, an instantaneous velocity
profile is measured and its integral is evaluated to give flow rate. Instead of making multidimensional flow mapping to evaluate
its performance, the method was assessed in laboratory experiments where single line measurements were used over the whole
pipe diameter or radius to determine the flow rate. The system shows a good capability of tracking transient flows. Its accuracy
was investigated using the National Institute of Standards and Technology (NIST) flow standards in Gaithersburg, MD, USA;
averaged results show its deviation from NIST results to be 0.18% for Re=400 K and 0.58% for Re=2.6 M. Good repeatability and reproducibility were also confirmed.
Received: 28 April 2000/Accepted: 1 November 2000 Published online: 29 November 2001 相似文献
15.
In this work a novel in-line non-invasive rheological measuring technique is developed and tested in pilot plant and industrial-scale
applications. The method is based on a combination of the ultrasonic pulsed echo Doppler technique (UVP) and pressure difference
method (PD). The rheological flow properties are derived from simultaneous recording and on-line analysis of the velocity
profiles across the tube channel and related radial shear stress profiles calculated from the pressure loss along the flow
channel. It is shown that the in-line UVP-PD technique allows for the non-invasive rheological flow behaviour characterization
of non-transparent and highly concentrated suspensions.
Received: 8 May 2000 / Accepted: 22 June 2001 Published online: 29 November 2001 相似文献
16.
The authors have carried out a study to investigate and clarify the characteristics of purely oscillating pipe flows over
the developing region. The main objective of this study is to establish the method of time-dependent velocity profiles obtained
by the ultrasonic velocity profile (UVP) measurement method. First, the relationship between the test fluids and the microparticles,
as reflectors of ultrasonic pulses, was investigated. In addition, the relationship between the sound speeds of the test fluids
and the wall materials was studied. Second, the UVP was used to obtain the instantaneous velocity profiles in oscillating
pipe flows, and the developing characteristics of the flows were analyzed. Finally, the “entrance length” (by analogy with
a unidirectional pipe flow) required for oscillating pipe flows was analyzed by examining the amplitude of the harmonic spectral
components of the oscillating frequency. A fast Fourier transform (FFT) is proposed as the applicable method to estimate the
“entrance length”. From the Fourier transform of the velocity on the centerline, nonlinear oscillation of fluid occurs in
the “entrance length” of the oscillating flows, and the viscous dissipation of the higher-order velocity harmoncis determines
the entrance region. The “entrance length” can be obtained from the dissipation length of the third-order harmonic. These
results prove that the UVP method is highly applicable to carry out the flow measurement in the “entrance length” of oscillating
pipe flow.
Received: 20 March 2000 / Accepted: 10 August 2001 相似文献
17.
The paper presents a new technique based on laser-induced fluorescence, allowing droplet temperature measurement of evaporating
and combusting droplets to be performed. The liquid spray is seeded with a low concentration of rhodamine B. The fluorescence,
induced by the green line of an argon laser, is measured on two separated color bands. It is demonstrated that two color bands
can be selected for their strong difference in the temperature sensitivity of the fluorescence quantum yield. The determination
of the fluorescence ratio between the fluorescence intensity corresponding to each color band allows the tracer concentration
and the droplet size dependences to be eliminated. The technique was applied on a monodisperse spray: the effect of a thermal
impulse on the distribution of the droplet temperature is studied and, the temperature of combusting droplets is investigated.
Received: 16 June 2000/Accepted: 10 November 2000 相似文献
18.
A three-dimensional photographic method for measurement of phase distribution in dilute bubble flow 总被引:2,自引:0,他引:2
A three-dimensional photographic method has been developed to measure phase distributions in bubbly flow in a pipe. In this
method a mirror was used to reflect a side view of the flow into the front-view direction, and then flow images in both views
were taken simultaneously by one camera. After three-dimensional position and size of each bubble in the flow field were determined
by matching the two bubble images in the side and front views, the phase distributions were obtained for the bubbly flow.
Received: 25 April 2000 / Accepted: 21 June 2001 Published online: 29 November 2001 相似文献
19.
R. Camussi 《Experiments in fluids》2002,32(1):76-86
A new technique based on wavelet transform is applied to bidimensional velocity fields obtained by particle image velocimetry
(PIV) measurements, in order to extract and characterize swirling motion associated with coherent structures. The proposed
technique is based on the selectivity property of the wavelet transform and permits the detection of regions of the flow field
associated with coherent structures and their spatial localization. Furthermore, being the method based on the analysis of
the local energy content at separated scales, it is possible to extract the typical wavenumber associated with structures
and therefore the typical length-scale. The procedure is validated by the application to velocity vector fields obtained from
PIV measurements in different flow conditions and turbulence levels. Results are compared with those obtained by other more
standard procedures, and the advantages and limitations of the proposed method are then discussed.
Received: 16 October 2000 / Accepted: 18 June 2001 Published online: 29 November 2001 相似文献
20.
The accuracy of turbulent kinetic energy (TKE) dissipation rate measured by PIV is studied. The critical issue for PIV-based
dissipation measurements is the strong dependency on the spatial resolution, Δx, as reported by Saarenrinne and Piirto (Exp Fluids Suppl:S300–S307, 2000). When the PIV spacing is larger than the Kolmogorov scale, η, the dissipation is underestimated because the small scale
fluctuations are filtered. For the case of Δx smaller than the Kolmogorov scale, the error rapidly increases due to noise. We introduce a correction method to eliminate
the dominant error for the small Δx case. The correction method is validated by using a novel PIV benchmark, random Oseen vortices synthetic image test (ROST),
in which quasi-turbulence is generated by randomly superposing multiple Oseen vortices. The error of the measured dissipation
can be more than 1,000% of the analytical dissipation for the small Δx case, while the dissipation rate is underestimated for the large Δx case. Though the correction method does not correct the underestimate due to the low resolution, the dissipation was accurately
obtained within a few percent of the true value by using the correction method for the optimal resolution of η/10 < Δx < η/2. 相似文献