Measurement of Impact Strains by a Carbon-Strip Extensometer

1940 ◽  
Vol 7 (1) ◽  
pp. A24-A28
Author(s):  
R. Fanning ◽  
W. V. Bassett
Keyword(s):  
High Speed ◽  
Longitudinal Strain ◽  
Sufficient Accuracy ◽  
Time Curve ◽  
Resistance Strain Gage ◽  
Strain Waves ◽  
Yield Information ◽  
Well Yield ◽  
Impact Problems ◽  
Actual Stress

Abstract This paper describes a method of experimentally ascertaining the actual stress-time curve in a mechanical part subjected to an impact blow. The apparatus consists of a resistance strain gage in conjunction with a high-speed recording oscillograph, the combination being sufficiently rapid in response to record strain variations occurring within a few microseconds. Consequently, the strains during impact are recorded with sufficient accuracy for detailed analysis. Longitudinal strain waves in long bars striking end to end have been subjected to theoretical analysis and have served as a subject for testing of the apparatus. The theory is reviewed in this paper, and computed results based thereon are compared with experimental data. The agreement is shown to be satisfactory, the form being as predicted and the magnitude within a few per cent of the computed value. The strain waves and reflections occurring in this simple case are surprisingly complex. An investigation of other impact problems by this method, such as the correlation of standard impact tests of materials, might well yield information of considerable value.

scholarly journals Fracture Initiation, Gas Ejection, and Strain Waves Measured on Specimen Surfaces in Model Rock Blasting

2020 ◽  
Author(s):  
Zong-Xian Zhang ◽  
Li Yuan Chi ◽  
Yang Qiao ◽  
De-Feng Hou
Keyword(s):  
High Speed ◽  
Fracture Initiation ◽  
Dynamic Strain ◽  
High Speed Photography ◽  
Surface Cracks ◽  
Rock Blasting ◽  
Measured Velocity ◽  
Strain Waves ◽  
Gas Penetration ◽  
Radial Cracks

AbstractCrack velocity, gas ejection, and stress waves play an important role in determining delay time, designing a blast and understanding the mechanism of rock fragmentation by blasting. In this paper, the emerging times of the earliest cracks and gas ejection on the lateral surfaces of cylindrical granite specimens with a diameter of 240 mm and a length of 300 mm were determined by high-speed photography, and the strain waves measured by an instrument of dynamic strain measurement during model blasting. The results showed that: (1) the measured velocity of gas penetration into the radial cracks was in a range of 196–279 m/s; (2) the measured velocity of a radial crack extending from the blasthole to the specimen surface varied from 489 to 652 m/s; (3) the length of strain waves measured was about 2800 µs, which is approximately 1000 times greater than the detonation time. At about 2850 µs after detonation was initiated, gases were still ejected from the surface cracks, and the specimens still stood at their initial places, although surface cracks had opened widely.

Experiment Study on the Dynamic Characteristics of the Abrasive Flow in Centrifugal Grinding

2006 ◽  
Vol 304-305 ◽  
pp. 369-373 ◽  
Author(s):  
Hao Cheng Wang ◽  
H.T. Zhang ◽  
Q. Wang ◽  
T.W. Chen
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Planetary Gear ◽  
Scientific Basis ◽  
Gear Ratio ◽  
Design And Technology ◽  
Time Curve ◽  
Perceptual Knowledge ◽  
Profound Impact ◽  
High Efficient

Being a high efficient technique for metal surface treatment , centrifugal grinding is widely applied in the field of polishing and burring for small-sized asymmetric parts. During the process of centrifugal grinding, the dynamic characteristics of the abrasive flow, which is determined by the planetary driver ratio of the instrument, has a profound impact on the quality and producing efficiency of the workpiece. Targeting on the massive abrasive, this paper investigates experimentally theinfluence of the planetary driver ratio of the instrument to the producing quality and efficiency. On one hand, a high-speed photograph is employed to record the movement of the abrasive flow in the processing of centrifugal grinding. The dynamic characteristics of the abrasive flow have been investigated for different planetary driver ratios. By qualitative analyzing the high-speed photographing results, the perceptual knowledge of the characteristics and the kinematic rules of the abrasive flow have been obtained. On the other hand, the surface roughness data at different planetary gear ratio and polishing time have been measured. The influence of planetary gear ratio on producing process have been illustrated by plotting the roughness-time curve combined with the high-speed photograph so as to provide a scientific basis for optimizing the parameters of design and technology.

Design of a Scaled Model for a High Rise, High Speed Elevator

2001 ◽  
Author(s):  
W. D. Zhu ◽  
L. J. Teppo
Keyword(s):  
High Speed ◽  
Scaling Laws ◽  
Sufficient Accuracy ◽  
Model Parameters ◽  
Minimal Effect ◽  
Model Design ◽  
Scaled Model ◽  
Lateral Dynamics ◽  
High Rise ◽  
Dimensionless Groups

Abstract A novel scaled model is developed to simulate the linear lateral dynamics of a hoist cable with variable length in a high rise, high speed elevator. The dimensionless groups used to formulate the scaling laws are derived through dimensional analysis. The model parameters are selected based on the scaling laws subject to space and hardware constraints. It is demonstrated that while it is almost impossible to obtain a fully scaled model unless the model is extremely tall, a reasonably sized model can be constructed with sufficient accuracy. The scaling laws that are not satisfied can be rendered to have a minimal effect on the scaling between the model and prototype. In conjunction with the model design, an analysis of model tension in a closed cable loop is developed. A new movement profile, which ensures a continuous jerk function during the entire period of motion, is derived. Practical considerations that occur in the design of the model are addressed. The methodology can be used to investigate the vibration of a very long cable in other applications.

scholarly journals Biomechanical assessment of various punching techniques

2020 ◽  
Author(s):  
Jiri Adamec ◽  
Peter Hofer ◽  
Stefan Pittner ◽  
Fabio Monticelli ◽  
Matthias Graw ◽  
...  
Keyword(s):  
High Speed ◽  
Vertical Wall ◽  
Force Plate ◽  
Physical Parameters ◽  
Time Curve ◽  
Biomechanical Assessment ◽  
Sports Science ◽  
General Terms ◽  
Force Time ◽  
The Impact

Abstract Punches without the use of instruments/objects are a common type of body violence and as such a frequent subject of medicolegal analyses. The assessment of the injuries occurred as well as of the potential of the assault to produce severe body harm is based on objective traces (especially the documented injuries of both parties involved) as well as the—often divergent—descriptions of the event. Quantitative data regarding the punching characteristics that could be used for the assessment are rare and originate mostly in sports science. The aim of this study was to provide physical data enabling/facilitating the assessment of various punching techniques. A total of 50 volunteers took part in our study (29 males and 21 females) and performed severe punches with the fist, with the small finger edge of the hand (karate chop), and with the open hand with both the dominant and the non-dominant hands in randomized order. The strikes were performed on a boxing pad attached to a KISTLER force plate (sampling frequency 10,000 Hz) mounted on a vertical wall. The punching velocity was defined as the hand velocity over the last 10 cm prior to the contact to the pad and ascertained by using a high-speed camera (2000 Hz). Apart from the strike velocity, the maximum force, the impulse (the integral of the force-time curve), the impact duration, and the effective mass of the punch (the ratio between the impulse and the strike velocity) were measured/calculated. The results show a various degree of dependence of the physical parameters of the strikes on the punching technique, gender, hand used, body weight, and other factors. On the other hand, a high degree of variability was observed that is likely attributable to individual punching capabilities. In a follow-up study, we plan to compare the “ordinary” persons with highly trained (boxers etc.) individuals. Even though the results must be interpreted with great caution and a direct transfer of the quantitative parameters to real-world situations is in general terms not possible, the study offers valuable insights and a solid basis for a qualified forensic medical/biomechanical assessment.

Waterhammer in Non-Rigid Pipes: Precursor Waves and Mechanical Damping

1977 ◽  
Vol 19 (6) ◽  
pp. 237-242 ◽  
Author(s):  
D. J. Williams
Keyword(s):  
Elastic Strain ◽  
Longitudinal Strain ◽  
Viscous Damping ◽  
Flexural Waves ◽  
Strain Waves ◽  
Fluid Theory ◽  
Mechanical Damping ◽  
Theory And Experiment

When a pipe can move, waterhammer effects are altered by the existence of precursor waves, i.e. longitudinal elastic strain waves in the pipe walls, modified by the presence of the fluid. Theory and experiment show that precursor waves cannot be ignored, if the effect of longitudinal strain is to be considered; conventional waterhammer theory is thus unsatisfactory. Flexural waves may also occur. It was found experimentally that pipe motion caused mechanical damping of the waterhammer–greater than the viscous damping. Viscoelastic piping also gave rise to strong mechanical damping, even without pipe motion.

Asymmetric Vessel Impact and Planing Hydrodynamics

1998 ◽  
Vol 42 (03) ◽  
pp. 187-198 ◽  
Author(s):  
Lixin Xu ◽  
Armin W. Troesch ◽  
William S. Vorus
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Initial Conditions ◽  
Singular Integral Equations ◽  
Two Dimensional ◽  
Nonlinear Boundary Value Problems ◽  
Flow Models ◽  
Large Asymmetry ◽  
Asymmetric Impact ◽  
Impact Problems

The paper proposes a two-dimensional theory for asymmetric impact problems of vessels with arbitrary geometry. The interaction of two body sides is incorporated into the hydrodynamic impact model. Following Vorus's (1996) flat-cylinder theory, two types of flow models are established for cases of small and large asymmetry. The distinguishing difference between the two types is whether the flow is attached or separates at the keel on the first instances of impact. General solutions for such nonlinear boundary value problems are determined by solving the singular integral equations, while free-vortex shedding (jet-spraying) is carried out through a time-marching procedure. Initial conditions are derived from basic solutions of flat-sided contours with constant impact velocity. The method of discrete vortices is then applied to the prediction of slamming loads (including both lifting force and restoring moment) on typical two-dimensional sections of vessels with flat or nearly flat bottoms. Calculated results of both flow types, i.e., small and large asymmetry, are presented for various hull contours with constant or variable impact velocity. This approach also provides the foundation for future work involving traverse dynamic stability analysis of high speed planing hulls

In Situ Analysis of Fluorinated Gases in Plasma Etching by Infrared Spectroscopy

1982 ◽  
Vol 36 (4) ◽  
pp. 445-451 ◽  
Author(s):  
H. U. Poll ◽  
D. Hinze ◽  
H. Schlemm
Keyword(s):  
Infrared Spectroscopy ◽  
Glow Discharge ◽  
Plasma Etching ◽  
Sufficient Accuracy ◽  
Actual State ◽  
Infrared Absorption Spectroscopy ◽  
Plasma Chemical ◽  
Partial Pressures ◽  
Yield Information

Infrared absorption spectroscopy proves to be a useful tool in the evaluation of plasma chemical conversions of etch gas mixtures during plasma etching for microelectronics. The partial pressures of the various perfluorinated gas components are obtained from infrared spectra with sufficient accuracy and may yield information about the actual state of the system. Methods of spectra recording and partial pressure computation are discussed. To demonstrate the applicability of the method, the conversions of CF4 + O2, and C2F4 in a glow discharge are investigated.

Development of Wireless Resistance Strain Gage Based on ATmega16

2010 ◽  
Vol 34-35 ◽  
pp. 859-863
Author(s):  
Cai Xia Liu ◽  
De Li Gong
Keyword(s):  
Strain Gage ◽  
High Speed ◽  
Resistance Strain ◽  
Work Piece ◽  
Single Chip ◽  
Single Chip Microcomputer ◽  
Contact Potential ◽  
Resistance Strain Gage ◽  
Signal Conversion ◽  
Measurement Signal

Measuring a large amount of parameters of work piece, resistance strain gage will have to use many resistive signal conversion boxes and long electric wires. Data acquisition becomes slow, inaccurate and discontinuous. Disorder and thermal of contact potential in the contacts affect the measurement signal and converting precision. In this paper, a wireless portable resistance strain gage is developed. ATmega16 is an 8-bit embedded and high-speed AVR single-chip microcomputer with 16k FlASH, and that is the core of system. Amplifier is designed to amplify and filter micro-voltage signals to improve measure accuracy. Wireless Bluetooth technology links ATmega16 and PC. Visual Basic software displays and processes data from ATmega16 in real time. This system is small in size and highly reliable, strong anti-interference ability and better economic performance.

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