Normalized Ratcheting Diagram Under Sinusoidal Vibration Waves

2021 ◽  
Author(s):  
Jinqi Lyu ◽  
Naoto Kasahara ◽  
Masakazu Ichimiya ◽  
Ryunosuke Sasaki
Keyword(s):  
Thermal Stress ◽  
Mechanical Stress ◽  
Natural Frequency ◽  
Frequency Ratio ◽  
Inelastic Deformation ◽  
General Mechanism ◽  
Seismic Loads ◽  
Sinusoidal Vibration ◽  
Acceleration Waves ◽  
The Difference

Abstract Ratcheting is a progressive incremental inelastic deformation or strain which can occur in a component that is subjected to variations of mechanical stress, thermal stress, or both. This study concentrated on the ratcheting occurrence of the piping model under the combined effect of constant external force and dynamic cyclic vibrations. Bent solid bars represented piping models, and sinusoidal acceleration waves were loaded. Characteristics of seismic loads between load-controlled and displacement-controlled properties were studied from the viewpoint of the frequency ratio of the forcing frequency to the natural frequency of the piping model. Besides, the ratcheting occurrence conditions of the beam and the piping model were compared in one normalized diagram to display the general mechanism of ratcheting with the consideration of the effect from the difference of shape and material. Results show that ratcheting occurs easily with a lower frequency ratio in both beam and piping models. In addition, it is meaningful to use beam models to understand the ratcheting mechanism of piping models. Describing the occurrence of ratcheting using the normalized ratcheting diagram for different components is feasible.

scholarly journals Measurement and Isolation of Thermal Stress in Silicon-On-Glass MEMS Structures

Sensors ◽  
2018 ◽  
Vol 18 (8) ◽  
pp. 2603 ◽  
Author(s):  
Zhiyong Chen ◽  
Meifeng Guo ◽  
Rong Zhang ◽  
Bin Zhou ◽  
Qi Wei
Keyword(s):  
Thermal Stress ◽  
Natural Frequency ◽  
Frequency Conversion ◽  
Thermal Stresses ◽  
Sensors And Actuators ◽  
Stress Variation ◽  
Rigid Frame ◽  
Measured Stress ◽  
Stress Isolation ◽  
Frequency Variations

The mechanical stress in silicon-on-glass MEMS structures and a stress isolation scheme were studied by analysis and experimentation. Double-ended tuning forks (DETFs) were used to measure the stress based on the stress-frequency conversion effect. Considering the coefficients of thermal expansion (CTEs) of silicon and glass and the temperature coefficient of the Young’s modulus of silicon, the sensitivity of the natural frequency to temperature change was analyzed. A stress isolation mechanism composed of annular isolators and a rigid frame is proposed to prevent the structure inside the frame from being subjected to thermal stresses. DETFs without and with one- or two-stage isolation frames with the orientations <110> and <100> were designed, the stress and natural frequency variations with temperature were simulated and measured. The experimental results show that in the temperature range of −50 °C to 85 °C, the stress varied from −18 MPa to 10 MPa in the orientation <110> and −11 MPa to 5 MPa in the orientation <100>. For the 1-stage isolated DETF of <110> orientation, the measured stress variation was only 0.082 MPa. The thermal stress can be mostly rejected by a stress isolation structure, which is applicable in the design of stress-sensitive MEMS sensors and actuators.

Scaling Behavior of Dynamic Hysteresis in Hard PZT Bulk Ceramics under Influence of Compressive Stress

2008 ◽  
Vol 55-57 ◽  
pp. 281-284 ◽  
Author(s):  
N. Wongdamnern ◽  
Athipong Ngamjarurojana ◽  
Supon Ananta ◽  
Yongyut Laosiritaworn ◽  
Rattikorn Yimnirun
Keyword(s):  
Energy Dissipation ◽  
Electric Field ◽  
Mechanical Stress ◽  
Compressive Stress ◽  
Power Law ◽  
Field Amplitude ◽  
Electric Field Amplitude ◽  
Bulk Ceramic ◽  
Compressive Stresses ◽  
The Difference

Effects of electric field-amplitude and mechanical stress on hysteresis area were investigated in partially depoled hard PZT bulk ceramic. At any compressive stress, the hysteresis area was found to depend on the field-amplitude with a same set of exponents to the power-law scaling. Consequently, inclusion of compressive stresses into the power-law was also obtained in the form of < A – Aσ=0 > α E05.1σ1.19 which indicated the difference of the energy dissipation between the under-stress and stress-free conditions.

Analysis of Stress Distribution for Powder Compression Molding by Finite Element Method

2019 ◽  
Vol 891 ◽  
pp. 269-274 ◽  
Author(s):  
Prakorb Chartpuk ◽  
Chaiwat Chaimahapuk
Keyword(s):  
Stress Distribution ◽  
Natural Frequency ◽  
Ceramic Powder ◽  
Bearing Steel ◽  
Outer Diameter ◽  
Maximum Compression ◽  
Aisi 52100 ◽  
Steel Aisi ◽  
The Difference ◽  
Powder Compression

The ultrasonic mold was designed for the ceramic powder compression. CAD and CAE were used in the design to analyze the mold strength and its natural frequency. The study of stress distribution and compression in upper and lower punch, mold body and waveguide comparison of stresses was analyzed by FEA experiments under maximum compression at 50,000 N to validate the results of both methods and the mold natural frequency. The difference between FEA and experimental analysis was 3-7%, acceptable. The redesign results in a cylindrical mold body with the outer diameter of 80 mm, the height of 100 mm, and the upper punch of 125 mm in length. The six sides are 26 mm of the high waveguide with 100 mm height. The internal and external diameters are 80 and 110 mm, respectively. The mold has been redesigned and can support the maximum compression force of 1,500 kN. with the bearing steel, AISI 52100, obtainable hardness 65 HRC, the stress concentration occurs at the neck of the upper punch using the ultrasonic at 12.00 to 12.45 kHz.

Freezing of Cells: Role of Ice and Solutes in Cell Damage

2007 ◽  
Author(s):  
Hiroshi Takamatsu
Keyword(s):  
Mechanical Stress ◽  
Cell Damage ◽  
Cellular Damage ◽  
Elevated Concentration ◽  
Cellular Injury ◽  
Extracellular Solution ◽  
Different Types ◽  
A Cell ◽  
The Difference

The mechanism of cellular damage associated with freezing of biological cells is discussed by summarizing the author’s recent studies that consists of four different types of experiments. The “solution effects” that designate the influence of elevated concentration of electrolytes during freezing is examined first by a nonfreezing experiment that exposes cells to hypertonic solutions using a perfusion microscope. The cell damage due to the solution effect is evaluated directly from a pseudo-freezing experiment, where cells were subjected to the milieu that simulated a freeze-thaw process in the absence of ice. Contribution of ice formed in the extracellular solution is then estimated from the difference in cell survival between the pseudo-freezing experiment and a corresponding freezing experiment. The cellular injury by the mechanical stress is also examined independently by a cell deformation experiment, which mimicked the situation that cells are compressed and deformed between ice crystals. This experiment was designed to examine a complex effect of mechanical stress from ice and elevated concentration of electrolytes. Based on all these experiments, the role of concentrated solutes and ice is revealed as a function of freezing conditions.

Effects of natural frequency ratio on vortex-induced vibration of a cylindrical structure

2015 ◽  
Vol 110 ◽  
pp. 62-76 ◽  
Author(s):  
Xiangxi Han ◽  
Wei Lin ◽  
Youhong Tang ◽  
Chengbi Zhao ◽  
Karl Sammut
Keyword(s):  
Natural Frequency ◽  
Frequency Ratio ◽  
Vortex Induced Vibration ◽  
Cylindrical Structure

Comparison of evolutionary techniques for the optimization of machining fixture layout under dynamic conditions

2017 ◽  
Vol 232 (12) ◽  
pp. 2145-2158 ◽  
Author(s):  
M Sabareeswaran ◽  
KP Padmanaban ◽  
KA Sundararaman
Keyword(s):  
Genetic Algorithm ◽  
Particle Swarm Optimization ◽  
Natural Frequency ◽  
End Milling ◽  
Excitation Frequency ◽  
Particle Swarm ◽  
Machining Accuracy ◽  
Swarm Optimization ◽  
Fixture Layout ◽  
The Difference

Modern manufacturing industries are striving to improve the machining accuracy and productivity to reduce the rejection rate and unit cost of the machined parts. The properly designed fixture layout enables the designer to minimize the vibration so that the requisite machining accuracy can be achieved. During machining, especially in end milling, the intermittent engagement of multitooth cutter induces vibration on the workpiece. When the excitation frequency of multitooth cutter coincides with any one of the natural frequencies of the fixtured workpiece, it leads to the condition of resonance. The vibration increases under these circumstances, which degrades the machining accuracy and surface finish of the machined workpiece. Hence, the issues related to the design of fixture layout are to be addressed by recognizing the dynamic behavior of the fixture–workpiece system. In this research paper, finite element method is utilized to simulate the end milling operation and to determine the natural frequency of the workpiece. The main focus is to maximize the difference between natural frequency of the fixtured workpiece and excitation frequency of the cutter to minimize the vibration on the workpiece. Two different evolutionary techniques genetic algorithm and particle swarm optimization are employed to maximize the difference between these frequencies by optimizing the machining fixture layout. The performance of genetic algorithm and particle swarm optimization on the fixture layout optimization is compared. The comparison of results concludes that particle swarm optimization is the most appropriate approach than the genetic algorithm in achieving the better results.

A note on the relationship between induced mechanical stress and thermal stress in recumbent pigs

1984 ◽  
Vol 38 (2) ◽  
pp. 309-311 ◽  
Author(s):  
J. M. Bruce ◽  
C. R. Boon
Keyword(s):  
Thermal Stress ◽  
Mechanical Stress ◽  
Floor Area ◽  
The Relationship

ABSTRACTThe hypothesis is proposed that pigs will induce a mechanical stress, by huddling and over-lying, that is related to the degree of thermal stress experienced. Measurements of the floor area covered by groups of 12 pigs have been used to validate the hypothesis.

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