Using Rotational Motions to understand material damage in Civil Engineering structure

Fundamental mode shape and its derivatives in structural damage localization

We report a piezoelectric actuator having a single stator with rotary and linear motions (RLPA). The stator is fabricated as a single metallic cube with a through-hole. The surface of the inner circle of the hole generates elliptical motions at each natural frequency, transferring the energy to an output shaft, when AC voltages at the appropriate resonant frequency are applied to the piezoelectric elements. This study clarifies the principle of rotary and linear motions and uses finite element methods (FEM) to show how the elliptical motions are generated. Modal analysis illustrated the shapes of the vibration modes and the natural frequencies, and the shape of the stator was designed accordingly. A dynamic analysis of the stator showed the generation of elliptical motion in the directions of the rotary and linear motions. The prototype RLPA was successfully actuated at the resonant frequencies, consistent with the dynamic analysis. The speed of the rotary and linear motions was obtained.

Precision measurement of segmental motion from flexion—extension radiographs of the lumbar spine

BackgroundDuring prostate stereotactic body radiation therapy (SBRT), prostate tumor translational motion may deteriorate the planned dose distribution. Most of the major advances in motion management to date have focused on correcting this one aspect of the tumor motion, translation. However, large prostate rotation up to 30° has been measured. As the technological innovation evolves toward delivering increasingly precise radiotherapy, it is important to quantify the clinical benefit of translational and rotational motion correction over translational motion correction alone.PurposeThe purpose of this work was to quantify the dosimetric impact of intrafractional dynamic rotation of the prostate measured with a six degrees‐of‐freedom tumor motion monitoring technology.MethodsThe delivered dose was reconstructed including (a) translational and rotational motion and (b) only translational motion of the tumor for 32 prostate cancer patients recruited on a 5‐fraction prostate SBRT clinical trial. Patients on the trial received 7.25 Gy in a treatment fraction. A 5 mm clinical target volume (CTV) to planning target volume (PTV) margin was applied in all directions except the posterior direction where a 3 mm expansion was used. Prostate intrafractional translational motion was managed using a gating strategy, and any translation above the gating threshold was corrected by applying an equivalent couch shift. The residual translational motion is denoted as Tres. Prostate intrafractional rotational motion Runcorr was recorded but not corrected. The dose differences from the planned dose due to Tres + Runcorr, ΔD(Tres + Runcorr) and due to Tres alone, ΔD(Tres), were then determined for CTV D98, PTV D95, bladder V6Gy, and rectum V6Gy. The residual dose error due to uncorrected rotation, Runcorr was then quantified: ΔDResidual = ΔD(Tres + Runcorr) ‐ ΔD(Tres).ResultsFractional data analysis shows that the dose differences from the plan (both ΔD(Tres + Runcorr) and ΔD(Tres)) for CTV D98 was less than 5% in all treatment fractions. ΔD(Tres + Runcorr) was larger than 5% in one fraction for PTV D95, in one fraction for bladder V6Gy, and in five fractions for rectum V6Gy. Uncorrected rotation, Runcorr induced residual dose error, ΔDResidual, resulted in less dose to CTV and PTV in 43% and 59% treatment fractions, respectively, and more dose to bladder and rectum in 51% and 53% treatment fractions, respectively. The cumulative dose over five fractions, ∑D(Tres + Runcorr) and ∑D(Tres), was always within 5% of the planned dose for all four structures for every patient.ConclusionsThe dosimetric impact of tumor rotation on a large prostate cancer patient cohort was quantified in this study. These results suggest that the standard 3–5 mm CTV‐PTV margin was sufficient to account for the intrafraction prostate rotation observed for this cohort of patients, provided an appropriate gating threshold was applied to correct for translational motion. Residual dose errors due to uncorrected prostate rotation were small in magnitude, which may be corrected using different treatment adaptation strategies to further improve the dosimetric accuracy.

When whole-body is exposed to vertical vibration, asymmetry shape of human body affects the response on the translational(fore-aft, lateral, vertical) and rotational(roll, pitch, yaw) motion. While the translational motion has been studied with various titles, it has been rare to study the rotational motion of human body exposed to vertical excitation because of lack of experimental equipment. This study was performed by using a 6-axis force plate installing strain gage type sensors for the rotational response. Sixteen male subjects were exposed to vertical vibration on rigid seat in order to investigate apparent mass of three translational motion and apparent eccentric mass of three rotational motion. Random signal was generated to make excitation vibration which was on an effective frequency range of 3~40 Hz, and magnitude of 0.224 m/<TEX>$s^2$</TEX> r.m.s. The frequency range and magnitude used was selected for the vibration of passenger vehicle on idling condition. As the result, cross-axis apparent masses of fore-and-aft and lateral direction were not significant showing 20 % and 3 % of vertical apparent mass relatively. And apparent eccentric mass of pitch motion was dominant when compared to that of roll and yaw motion, which is reasoned by asymmetry direction of human body sitting on a seat.

Cable driven parallel robot (CDPR) possesses large workspace, outstanding dynamic performance and high load capacity. However, due to the actuation method of CDPR, only limited motion modes can be achieved, and its rotational and translational motions are usually coupled. This letter presents a novel design of CDPR, through applying winch-integrated driving method and wrapping driving cables around the moving platform, the positions of driving cables' attach points on moving platform adaptively vary with the movement. The proposed CDPR design naturally enables a novel planar one-translational and one-rotational (1R1T) motion mode with decoupled control of translation and rotation. The performance of the design is validated through simulation and experiment, confirming that there are no other motions generated and the translational and rotational motions can be controlled independently. The proposed configuration further expands the motion mode as well as operational capabilities of CDPR.

A video containing multiple objects undergoing independent translational and rotational motions is analyzed through a combination of spatial- and frequency-domain representations. The Fourier transform of the sequence is used to estimate the multiple translations and rotations in a computationally efficient manner, which is also robust to local inaccuracies and global illumination changes. A novel algorithm is presented for the simultaneous extraction of all objects undergoing translation and the background via a least squares technique that takes place entirely in the Fourier domain. Spatial information is combined with the frequency domain object extraction results, to further refine them. For the case of rotational or combined, rotational and translational motions, the moving objects are segmented using purely spatial information. We show that the combined analysis takes advantage of the strengths of both representations, by providing reliable and computationally efficient motion estimates and object segmentation. The proposed algorithm is shown to be robust to local noise and occlusion, because of its global nature. Experiments are performed on synthetic and real video sequences to demonstrate the capabilities of our approach.

We study the Stokes-Einstein (SE) and the Stokes-Einstein-Debye (SED) relations, Dt=kBT/6pietaR and Dr=kBT/8pietaR3, where Dt and Dr are the translational and rotational diffusivity, respectively, T is the temperature, eta the viscosity, kB the Boltzmann constant, and R the "molecular" radius. Our results are based on molecular dynamics simulations of the extended simple point charge model of water. We find that both the SE and SED relations break down at low temperature. To explore the relationship between these breakdowns and dynamical heterogeneities (DHs), we also calculate the SE and SED relations for subsets of the 7% "fastest" and 7% "slowest" molecules. We find that the SE and SED relations break down in both subsets, and that the breakdowns occur on all scales of mobility. Thus these breakdowns appear to be generalized phenomena, in contrast with a view where only the most mobile molecules are the origin of the breakdown of the SE and SED relations, embedded in an inactive background where these relations hold. At low temperature, the SE and SED relations in both subsets of molecules are replaced with "fractional" SE and SED relations, Dt approximately (tau/T)-xit and Dr approximately (tau/T)-xir, where xit approximately 0.84(<1) and xir approximately 0.75(<1). We also find that there is a decoupling between rotational and translational motion, and that this decoupling occurs in both the fastest and slowest subsets of molecules. Further, we find that, the decoupling increases upon cooling, but that the probability of a molecule being classified as both translationally and rotationally fastest also increases. To study the effect of time scale for SE and SED breakdown and decoupling, we introduce a time-dependent version of the SE and SED relations, and a time-dependent function that measures the extent of decoupling. Our results suggest that both the decoupling and SE and SED breakdowns originate at a time scale corresponding to the end of the cage regime, when diffusion starts. This is also the time scale when the DHs are more relevant. Our work also demonstrates that selecting DHs on the basis of translational or rotational motion more strongly biases the calculation of diffusion constants than other dynamical properties such as relaxation times.

Molecular dynamics studies of two generalized forms of the rough sphere model are reported. The generalization permits us to vary the coupling between rotational and translational motion through a stick parameter λ. The autocorrelation functions show deviations from the Enskog theory for all values of λ studied—indicating that collective effects are involved. It appears that the angular velocity correlation function is the sum of two exponentials. A simulation of a mixture of disparate sized rough spheres was also performed. It is found that the rotational motion of the small particle is not significantly altered upon introduction of the large particles, but the linear velocity correlation function of the small particle differes considerably from that of the neat fluid (in the time regime from 5–15 mean collision time units).

In this work, it was studied the process of interaction between the Apocynin Dimer (DiApocynin -DiApo) and , or Cyclodextrin (CD). All processes were described considering the translational and rotational movements. The translational movement was considered along the z-axis followed by simultaneous rotational (circular) movements (from 0 to 360 o in intervals of 1.0 o ) of the Apocynin Dimer around its center of mass. It were generated molecular stru tures i these pro esses a d the al ulatio s o er i g the o for atio al a al sis of , and -CD DiApo were carried out using the PM3 semiempirical methodology. To the most sta le ole ular stru tures to , , -CD, a ordi g to statisti al ther od a i a al sis, were obtained the interaction energies of -5,251; -63,012 e -65,637 kJ.mol -at ONIOM2(B3LYP/6-31G(d):PM3) level of theory, respectively.

SUMMARYA multidimensional positioning mechanism, along with high speed and high accuracy, is essential for an industrial machine. A positioning machine operates precisely in both vertical linear motion (z‐axis) and rotary motion (θ‐axis). A ball screw mechanism is used for thez‐axis whereas a servo motor is used for the θ‐axis. We developed a direct drive θ‐z motor for rotary and linear motion. Torque and thrust are generated directly by the mover. Thus, high speed and high accuracy as well as miniaturization are achieved without using machine elements such as a ball screw and belt. In this paper, we describe the structure and operating principle of the θ‐Z motor, and the sensor that can detect the θ‐axis and thez‐axis position. In addition, we consider a design method that minimizes copper loss by taking advantage of the shape of the permanent magnet and coil. Furthermore, using a prototype we evaluated the characteristics of torque, thrust, and repeatability.

Two explosions were set off on 4 March 2008 at the N3 explosion site in northeastern Taiwan. The code name for the first shot with 3000 kg explosives is N3P and that for the second shot with 750 kg explosives is N3. To record these two explosions, 8 triaxial rotational sensors, 13 triaxial accelerometers, and 12 six-channel, 24 bit dataloggers with Global Positioning System receivers were deployed to continuously record several hours before and after the explosions. These instruments were installed at about 250 m (1 station), 500 m (11 stations), and 600 m (1 station) from the explosions. The 11 stations form a center array with station spacing of about 5 m. Except for one rotational sensor, onscale records were obtained. Although the N3P shot used four times larger amounts of explosives than those used for the N3 shot, the peak ground translational acceleration and rotational velocity at the 13 station sites from the N3P shot are only about 1.5 times larger than those for the N3 shot. We also observed large variations (by tens of percent) of translational accelerations and rotational velocities at the center array with station spacing of about 5 m. The largest peak rotational velocity was observed for the x component: 2.74 and 1.75 mrad/sec at a distance of 254 m from the N3P and N3 shots, respectively. The main purpose of this article is to document our recordings of rotational and translation motions from two explosions in Taiwan and to release the data online for open access. The translational acceleration data from this experiment have been analyzed by Langston et al. (2009), and we plan to submit an article with analysis of the rotational velocity data in the future.

Geometrically non-linear free vibrations of clamped simply supported rectangular plates. Part I: the effects of large vibration amplitudes on the fundamental mode shape

Methods to quantification of precursor damage in carbon fiber reinforced polymer (CFRP) composite structures are reported herein. These techniques include coda wave interferometry (CWI) and nonlinear ultrasonics (NLU). Since low-frequency Lamb wave propagation is insensitive to the early-stage material degradation, it is shown that decoding the information in coda wave can overcome this well-known limitation. To conclude this possibility, CWI technique is cross verified with a traditional high-frequency ultrasound method. To achieve this goal, a tensile–tensile fatigue experiment was designed for CFRP composite specimens. By inducing controlled fatigue damage in these structures, material states are assessed using low-frequency (&amp;lt;500 kHz) ultrasonic guided wave and high-frequency (&amp;gt;10 MHz) P-wave. Stretching guided coda wave is utilized to quantify the precursor damage as a unique approach in this article. However, such method could be illuded by the changes in the signals due to bonds and contacts. To verify if the CWI is successful, and to evaluate the precursor damage in composite structures, additional nonlinear analysis of ultrasonic signals from both guided waves and P-waves is performed. Higher order nonlinearities in both low-frequency guided wave and high-frequency P-wave propagation demonstrate the growth of precursor damage in CFRP composite structures. So does the CWI of low-frequency guided wave data. Accuracy of these ultrasonic techniques is validated with experimentally obtained remaining strengths of the fatigue specimens. With this verification it is envisioned that both CWI and NLU together could quantify the precursor damage in composite structures.

Vibration tailoring of inhomogeneous rod that possesses a trigonometric fundamental mode shape