Dynamic response and failure mechanisms of high-strength built-up columns subjected to axial impact loading

Recent models of piano string excitation suggest that string motion is proportional to hammer velocity. Preliminary to measuring dynamics in piano performance, the relationship between radiated piano sound and hammer velocities was studied. A computer-monitored piano allowed reproduction of a range of hammer velocities, and a microphone placed near a pianist's head location recorded radiated sound. The first eperiment indicated that peak amplitude of the waveform was directly proportional to the hammer velocity of individual notes for a wide range of frequencies and hammer velocities. A second experiment investigated the waveforms of notes struck simultaneously and compared these with the waveforms of the individual component notes. The peak amplitude of the dyads was directly proportional (with proportionality close to 1) to the sum of the individual peak amplitudes. A third experiment extended these findings to a wider range of dyadic pitch intervals. These findings suggest linear relationships between hammer velocity, amplitude of string motion, bridge motion, and amplitude of the soundboard vibration for single notes. The additivity of dyads indicates that the principle of superposition is obeyed with a small energy loss. [Work supported by MIT Media Lab, Ohio State University Small Research Grant, and a Wellesley College Brachman Hoffman Fellowship.]

Based on the dynamic analysis method and central difference explicit algorithm, a dynamic explicit finite element code is developed for modeling the hammering deformation processes, in which hammer velocity is calculated by the energy balance principle. The dynamic upsetting processes of copper block under different hammer velocities are simulated using the developed code, and the deformed configuration, the displacement and the equivalent plastic strain distribution are investigated. Then, the calculated results are compared with that obtained by the static implicit program, and the comparison shows that the results obtained by the developed code are nearly identical to that obtained by the static implicit program under a low hammer velocity, and that there is a great difference between them under a high hammer velocity, which can be explained from the viewpoint of inertial effect and stress wave propagation effect. The research results indicate that the developed code adequately considers the dynamic characteristic under drop hammer impact, and can be used to analyze the effect of hammer velocity on the deformation during the hammering deformation process.

The relationship between final hammer velocity and maximum amplitude of radiated piano sound was investigated. Piano tones with varying hammer velocities were produced by a computer-monitored acoustic piano containing optical sensors and solenoids, and the sounded tones were recorded and digitized for analysis. Maximum amplitudes over the duration of the sounded tones were linearly proportional to piano hammer velocities for a range of frequencies and hammer velocities. Changes in room acoustics did not alter the linear relationship. Measurements of maximum amplitudes of individual tones and combined tones (dyads) also indicated a linear relationship between the sum of the maximum amplitudes of the individual tones and the maximum amplitude of the dyads. These findings indicate that the principle of superposition holds for peak amplitudes of sounded piano tones. Findings are discussed with regard to production and perception of musical dynamics.

Interacted buckling failure of thin-walled irregular-shaped aluminum alloy column under axial compression

Effect of the deformation temperature, hammer velocity, height reduction and shear factor on the equivalent stress, strain and temperature rise has been studied in forging process of a TC6 titanium alloy disc with deformation temperatures of 1153–1213 K, hammer velocities of 1·2–12 000 mm min−1 and shear factors of 0·1–0·4. The calculated results show that the deformation temperature, hammer velocity and height reduction have a significant effect on the equivalent stress and temperature rise, but have a slight effect on the equivalent strain. The predicted load–displacement curves are found to be in a good agreement with the experimental results.

Preliminary to an attempt at measuring the relative intensities of overlapping tones in acoustically recorded piano music, this study investigated whether the relative peak sound levels of recorded piano tones can be reliably inferred from the levels of their two lowest harmonics, measured in the spectrum near tone onset. Acoustic recordings of single tones were obtained from two computer-controlled mechanical pianos, one upright (Yamaha MX100A Disclavier) and one concert grand (Bösendorfer 290SE), at a range of pitches and hammer velocities. Electronic recordings from a digital piano (Roland RD250S), which were free of mechanical and sound transmission factors, were included for comparison. It was found that, on all three instruments, the levels of the lowest two harmonics (in dB) near tone onset generally increased linearly with the peak root-mean-square (rms) level (in dB) as hammer velocity was varied for any given pitch. The slope of this linear function was fairly constant across midrange pitches (C2 to C6) for the first harmonic (the fundamental), but increased with pitch for the second harmonic. However, there were two sources of unpredictable variability: On the two mechanical pianos, peak rms level varied considerably across pitches, even though the strings were struck at nominally equal hammer velocities; this was probably due to the combined effects of unevenness in hammer-string interaction, soundboard response, and room acoustics. Moreover, for different pitches at equal peak rms levels, the levels of the two lowest harmonics varied substantially, even on the electronic instrument.(ABSTRACT TRUNCATED AT 250 WORDS)

The interaction between the deformation behaviour and the microstructure evolution is the main characteristic in the forging process of titanium alloy and this interaction is researched using finite element (FE) simulation. Coupled simulation of deformation behaviour with microstructure evolution has been carried out by means of a new constitutive equation presented by Li et al. (Mater. Sci. Technol., 2004, 20, 1256–1260). The effect of deformation temperature, hammer velocity,height reduction and shear factor on the microstructure variables, including grain size and volume fraction, has been studied in the forging process of the TC6 titanium alloy disc with deformation temperatures of 880–940°C, hammer velocities of 1·2–12 000 mm min−1 and shear factor (m) of the friction of 0·1–0·4. The simulated results show that deformation temperature, hammer velocity and height reduction have a significant effect on themicrostructure evolution and this effect is more significant on the microstructure evolution in hot forging than that in isothermal forging. The simulated results are in good agreement with the experimental results.

Dynamic local and global buckling of cylindrical shells under axial impact

First applications of a novel unified model for global and local buckling of sandwich columns

Local and global buckling prevention design of corrugated steel plate shear walls

Fiber element simulation of interaction behavior of local and global buckling in axially loaded rectangular concrete-filled steel tubular slender columns under fire exposure

Little research has been reported that investigates the effects of plate local buckling and postbuckling on the in-plane behavior and strength of steel arches, and hitherto there has been no corresponding design guidance available. This paper presents a numerical investigation of the structural behavior of steel arches, and proposes a strength design method against their in-plane failure by considering plate local elastic-plastic buckling and postbuckling coupled with global elastic-plastic buckling. The failure modes of pin-ended steel circular arches having a box section under a uniformly distributed radial load are analyzed by using a large deformation elastic-plastic finite-element formulation. It is found that plate local buckling significantly influences the in-plane failure mode and strength of a steel arch. The arch may fail owing to local elastic-plastic buckling of its plates, global elastic-plastic buckling of the arch, or coupled local and global elastic-plastic buckling. The failure m...

Cross-sectional optimization of cold-formed steel channels to Eurocode 3

Design methods of high strength steel welded H-sections under compression accounting for local–global buckling

Numerical investigations on elastic buckling and hysteretic behavior of steel angles assembled buckling-restrained braces