@article{21949,
  abstract     = {{This paper presents the results of an interlaboratory study of the rheological properties of cement paste and ultrasound gel as reference substance. The goal was to quantify the comparability and reproducibility of measurements of the Bingham parameters yield stress and plastic viscosity when measured on one specific paste composition and one particular ultrasound gel in different laboratories using different rheometers and measurement geometries. The procedures for both in preparing the cement paste and carrying out the rheological measurements on cement paste and ultrasound gel were carefully defined for all of the study’s participants. Different conversion schemes for comparing the results obtained with the different measurement setups are presented here and critically discussed. The procedure proposed in this paper ensured a reasonable comparability of the results with a coefficient of variation for the yield stress of 27% and for the plastic viscosity of 24%, despite the individual measurement series’ having been performed in different labs with different rheometers and measurement geometries.}},
  author       = {{Haist, Michael and Link, Julian and Nicia, David and Leinitz, Sarah and Baumert, Christian and von Bronk, Tabea and Cotardo, Dario and Eslami Pirharati, Mahmoud and Fataei, Shirin and Garrecht, Harald and Gehlen, Christoph and Hauschildt, Inga and Ivanova, Irina and Jesinghausen, Steffen and Klein, Christopher and Krauss, Hans-W. and Lohaus, Ludger and Lowke, Dirk and Mazanec, Oliver and Pawelczyk, Sebastian and Pott, Ursula and Radebe, Nonkululeko W. and Riedmiller, Joachim Jürgen and Schmid, Hans-Joachim and Schmidt, Wolfram and Secrieru, Egor and Stephan, Dietmar and Thiedeitz, Mareike and Wilhelm, Manfred and Mechtcherine, Viktor}},
  issn         = {{1359-5997}},
  journal      = {{Materials and Structures}},
  keywords     = {{Rheology, Wall Slip, Slip, apparent slip, suspension, cement, concrete}},
  title        = {{{Interlaboratory study on rheological properties of cement pastes and reference substances: comparability of measurements performed with different rheometers and measurement geometries}}},
  doi          = {{10.1617/s11527-020-01477-w}},
  year         = {{2020}},
}

@article{21948,
  abstract     = {{<jats:p>Since suspensions (e.g., in food, cement, or cosmetics industries) tend to show wall slip, the application of structured measuring surfaces in rheometers is widespread. Usually, for parallel-plate geometries, the tip-to-tip distance is used for calculation of absolute rheological values, which implies that there is no flow behind this distance. However, several studies show that this is not true. Therefore, the measuring gap needs to be corrected by adding the effective gap extension    δ    to the prescribed gap height    H    in order to obtain absolute rheological properties. In this paper, we determine the effective gap extension    δ    for different structures and fluids (Newtonian, shear thinning, and model suspensions that can be adjusted to the behavior of real fluids) and compare the corrected values to reference data. We observe that for Newtonian fluids a gap- and material-independent correction function can be derived for every measuring system, which is also applicable to suspensions, but not to shear thinning fluids. Since this relation appears to be mainly dependent on the characteristics of flow behaviour, we show that the calibration of structured measuring systems is possible with Newtonian fluids and then can be transferred to suspensions up to a certain particle content.</jats:p>}},
  author       = {{Pawelczyk, Sebastian and Kniepkamp, Marieluise and Jesinghausen, Steffen and Schmid, Hans-Joachim}},
  issn         = {{1996-1944}},
  journal      = {{Materials}},
  keywords     = {{wall slip prevention, effective gap height, parallel-plate system, structured surfaces, model suspensions, cement paste, fresh concrete}},
  title        = {{{Absolute Rheological Measurements of Model Suspensions: Influence and Correction of Wall Slip Prevention Measures}}},
  doi          = {{10.3390/ma13020467}},
  year         = {{2020}},
}

@article{21947,
  abstract     = {{Wall slip is a long-known phenomenon in the field of rheology. Nevertheless, the origin and the evolution are not completely clear yet. Regarding suspensions, the effect becomes even more complicated, because different mechanisms like pure slip or slip due to particle migration have to be taken into account. Furthermore, suspensions themselves show many flow anomalies and the isolation of slip is complicated. In order to develop working physical models, further insight is necessary. In this work, we measured experimentally the wall slip velocities of different highly filled suspensions in a rectangular slit die directly with respect to the particle concentration and the particle size. The slip velocities were obtained using a particle image velocimetry (PIV) system. The suspensions consisting of a castor oil–cinnamon oil blend and PMMA particles were matched in terms of refractive indexes to appear transparent. Hereby, possible optical path lengths larger than 15 mm were achieved. The slip velocities were found to be in a quadratic relation to the wall shear stress. Furthermore, the overall flow rate as well as the particle concentration has a direct influence on the slip. Concerning the shear stress, there seem to be two regions of slip with different physical characteristics. Furthermore, we estimated the slip layer thickness directly from the velocity profiles and propose a new interpretation. The PIV technique is used to investigate the viscosity and implicit the concentration profile in the slit die. It is shown that the particle migration process is quite fast.}},
  author       = {{Jesinghausen, Steffen and Weiffen, Rene and Schmid, Hans-Joachim}},
  issn         = {{0723-4864}},
  journal      = {{Experiments in Fluids}},
  keywords     = {{Rheology, Wall Slip, Slip, apparent slip, suspension}},
  title        = {{{Direct measurement of wall slip and slip layer thickness of non-Brownian hard-sphere suspensions in rectangular channel flows}}},
  doi          = {{10.1007/s00348-016-2241-6}},
  year         = {{2016}},
}

@article{9876,
  abstract     = {{Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. It has been shown previously in theoretical investigations that higher velocities and smoother movements can be obtained if these steps do not contain phases of stiction (''stick-slip`` operation), but use sliding friction only (''slip-slip`` operation). One very promising driving option for such motors is the superposition of multiple sinusoidal signals or harmonics. In this contribution, the theoretical results are validated experimentally. In this context, a quick and reliable identification process for parameters describing the friction contact is proposed. Additionally, the force generation potential of inertia motors is investigated theoretically and experimentally. The experimental results confirm the theoretical result that for a given maximum frequency, a signal with a high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion, while the maximum motor force is obtained with signals containing more harmonics. These results are of fundamental importance for the further development of high-velocity piezoelectric inertia motors.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  issn         = {{0939-1533}},
  journal      = {{Archive of Applied Mechanics}},
  keywords     = {{Inertia motor, High velocity, Stick-slip motor, Slip-slip operation, Friction parameter identification}},
  pages        = {{1--9}},
  publisher    = {{Springer Berlin Heidelberg}},
  title        = {{{High-velocity operation of piezoelectric inertia motors: experimental validation}}},
  doi          = {{10.1007/s00419-014-0940-0}},
  year         = {{2014}},
}

@inproceedings{9802,
  abstract     = {{It has been shown previously that ``slip-slip'' operation of piezoelectric inertia motors allows higher velocities and smoother movements than classic ``stick-slip'' operation. One very promising driving option is to use a superposition of multiple sinusoidal signals. In this contribution, previous theoretical results are validated experimentally. The results confirm the theoretical result that for a given maximum frequency, usually defined by the actuator characteristics, a signal with high fundamental frequency and consisting of two superposed sine waves leads to the highest velocity and the smoothest motion. This result is of fundamental importance for the further development of high-velocity piezoelectric inertia motors.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  booktitle    = {{Proceedings of 10th International Workshop on Piezoelectric Materials and Applications and 8th Energy Harvesting Workshop}},
  keywords     = {{Piezoelectric inertia motor, stick-slip motor, driving signal, velocity, smoothness}},
  pages        = {{16--18}},
  title        = {{{High-Velocity Slip-Slip Operation of Piezoelectric Inertia Motors - Experimental Validation}}},
  year         = {{2013}},
}

@article{9805,
  abstract     = {{Piezoelectric inertia motors, also known as ``stick--slip drives'', use the inertia of a body to drive it in small steps by means of a friction contact. While these steps are classically assumed to involve stiction and sliding, the motors can also operate in ``slip--slip'' mode without any phase of static friction. This contribution provides a systematic investigation and performance comparison of different stick--slip and slip--slip modes of operation. Different criteria for comparing the motional performance of inertia motors are defined: Steady state velocity, smoothness of motion, and start-up time. Using the example of a translational inertia motor excited by an ideal displacement signal, it is found that the maximum velocity reachable in stick--slip operation is limited principally, while continuous slip--slip operation allows very high velocities. For the investigated driving signals, the motor velocity is proportional to the square root of the actuator stroke. The motor performance with these ideal signals defines an upper boundary for the performance of real motors.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  journal      = {{Sensors and Actuators A: Physical}},
  keywords     = {{Inertia motor, Stick--slip drive, Mode of operation, Performance indicator, Velocity maximization, Actuator stroke}},
  pages        = {{90 -- 100}},
  title        = {{{Stick-slip and slip-slip operation of piezoelectric inertia drives - Part I: Ideal Excitation.}}},
  doi          = {{10.1016/j.sna.2012.11.012}},
  volume       = {{200}},
  year         = {{2013}},
}

@inproceedings{9784,
  abstract     = {{Piezoelectric inertia motors use the inertia of a body to drive it by means of a friction contact in a series of small steps. These motors can operate in ``stick-slip'' or ``slip-slip'' mode, with the fundamental frequency of the driving signal ranging from several Hertz to more than 100 kHz. To predict the motor characteristics, a Coulomb friction model is sufficient in many cases, but numerical simulation requires microscopic time steps. This contribution proposes a much faster simulation technique using one evaluation per period of the excitation signal. The proposed technique produces results very close to those of timestep simulation for ultrasonics inertia motors and allows direct determination of the steady-state velocity of an inertia motor from the motion profile of the driving part. Thus it is a useful simulation technique which can be applied in both analysis and design of inertia motors, especially for parameter studies and optimisation.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  booktitle    = {{Ultrasonics Symposium (IUS), 2012 IEEE International}},
  issn         = {{1948-5719}},
  keywords     = {{friction, ultrasonic motors, Coulomb friction model, efficient simulation technique, friction contact, high-frequency piezoelectric inertia motor, motor characteristics prediction, numerical simulation, slip-slip mode, stick-slip mode, time-step simulation, ultrasonic inertia motor, Acceleration, Acoustics, Actuators, Computational modeling, Friction, Numerical models, Steady-state}},
  pages        = {{277--280}},
  title        = {{{An efficient simulation technique for high-frequency piezoelectric inertia motors}}},
  doi          = {{10.1109/ULTSYM.2012.0068}},
  year         = {{2012}},
}

@article{9806,
  abstract     = {{Piezoelectric inertia motors, also known as ``stick-slip-drives'', use the inertia of a body to drive it by means of a friction contact in small steps. While these steps normally involve stiction and sliding, the motors can also operate in ``slip-slip'' mode without any phase of static friction. In this contribution, a one degree of freedom model of an inertia motor driven by an ideal actuator is analysed. Start-up and constant velocity operation of the motor are investigated and appropriate quantities to compare ``stick-slip'' and ``slip-slip'' operation are determined. Different aspects such as velocity, uniformity of motion, load capacity, robustness, efficiency, and wear are considered. The analysis allows both modes to be applied advantageously in different applications and can widen the field of application of piezoelectric inertia motors. Motor designers are enabled to choose the appropriate mode of operation and the best drive parameters for their individual applications.}},
  author       = {{Hunstig, Matthias and Hemsel, Tobias and Sextro, Walter}},
  journal      = {{ACTUATOR 2012 Conference Proceedings}},
  keywords     = {{Piezoelectric Inertia Motors, Drive Signals, Stick-slip, Slip-slip}},
  pages        = {{761--764}},
  title        = {{{Analysis of different operation modes for inertia motors}}},
  year         = {{2012}},
}