Average strain rate in the Italian crust inferred from a permanent GPS network - II. Strain rate versus seismicity and structural geology

The effects of LWR water environments on fatigue life reduction of LWR component materials have been evaluated quantitatively. The environmental correction factor Fen, which is determined by strain rate, temperature and dissolved oxygen content has been proposed for assessing this reduction in the case of carbon, low alloy and austenitic stainless steels. Equations to calculate Fen have been established based on fatigue data derived under constant test conditions but strain rate and temperature in actual transients are usually not constant. A method for calculating Fen under conditions of continuously changing strain rate and temperature was established in this study for use in assessing fatigue damage on actual transients, with due consideration to the effects of LWR water environments. The method should be found applicable to Class 1 vessels. It should be possible to determine the stress cycle and fatigue usage factor in air in accordance with the ASME B&PV Code Section III NB-3200. Fatigue damage in LWR water may be found by linear summation of the products of Fen and partial fatigue usage factor in stress cycles. The method is consisted of simple and detailed methods. The evaluation of Fen must be applied for the strain range in which the strain increases continuously. In the simple method, the entire range of stain increasing is used as one segment and the average strain rate and the highest temperature in it are used for computing Fen. In the detailed method, the strain increasing range should be divided into small segments and average strain rate and highest temperature in it are used for finding Fen and Fens in all segments are subsequently averaged by weighting with strain increment in it. The Fen by this latter procedure was found much less than with the former under a condition of considerable temperature change.

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Surface strain accumulation and the seismic moment tensor

Bulletin of the Seismological Society of America ◽

10.1785/bssa0870051345 ◽

1997 ◽

Vol 87 (5) ◽

pp. 1345-1353

Author(s):

J. C. Savage ◽

R. W. Simpson

Keyword(s):

Strain Rate ◽

Accumulation Rate ◽

Moment Tensor ◽

Surface Strain ◽

Seismogenic Zone ◽

Strain Accumulation ◽

Average Strain ◽

Average Strain Rate ◽

Double Couple ◽

Scalar Moment

Abstract Although the scalar moment accumulation rate within the seismogenic zone beneath a given area is sometimes deduced from the observed average surface strain accumulation rate over that same area (e.g., Working Group on California Earthquake Probabilities, 1995), the correspondence between the two is very uncertain. The equivalence between surface strain accumulation and scalar moment accumulation is based on Kostrov's (1974) relation between the average strain rate over a volume and the moment-rate tensor for that volume. The average strain rate over the volume is replaced by the average strain rate measured at the free surface to deduce an approximate moment-rate tensor. Only in exceptional circumstances will that moment-rate tensor correspond to a double-couple mechanism, a mechanism that can be represented by a scalar moment accumulation rate. More generally, the moment tensor must be resolved into the superposition of two or more double-couple mechanisms, and that resolution can be done in many ways, each with its own scalar moment rate. Thus the resolution is not unique. This is demonstrated by deducing scalar moment accumulation rates for a GPS network that covers most of California south of San Francisco. It is shown that resolutions into different double-couple mechanisms lead to scalar moment accumulation rates differing by factors of ∼2. We suggest that the minimum scalar moment rate equivalent to principal surface strain rates ɛ1 and ɛ2 acting over the area A is M0(min) = 2μHA Max (¦ɛ1¦, ¦ɛ2¦, ¦ɛ1 + ɛ2¦), where μ is the rigidity and H the depth of seismogenic zone, and the function Max is equal to the largest of its arguments. Within the uncertainites of measurement, the scalar moment accumulation rate in southern California based on that approximation is in balance with the average historic seismic moment release rate so that no current earthquake deficit need be accumulating.

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The Influence of Strain Rate on the Passive and Stimulated Engineering Stress–Large Strain Behavior of the Rabbit Tibialis Anterior Muscle

Journal of Biomechanical Engineering ◽

10.1115/1.2834292 ◽

1998 ◽

Vol 120 (1) ◽

pp. 126-132 ◽

Cited By ~ 45

Author(s):

B. S. Myers ◽

C. T. Woolley ◽

T. L. Slotter ◽

W. E. Garrett ◽

T. M. Best

Keyword(s):

Strain Rate ◽

Tibialis Anterior ◽

High Speed ◽

Large Strain ◽

Strain Rates ◽

Average Strain ◽

Stress Strain ◽

Engineering Stress ◽

Average Strain Rate ◽

Strain Responses

The passive and stimulated engineering stress–large strain mechanical properties of skeletal muscle were measured at the midbelly of the rabbit tibialis anterior. The purpose of these experiments was to provide previously unavailable constitutive information based on the true geometry of the muscle and to determine the effect of strain rate on these responses. An apparatus including an ultrasound imager, high-speed digital imager, and a servohydraulic linear actuator was used to apply constant velocity deformations to the tibialis anterior of an anesthetized neurovascularly intact rabbit. The average isometric tetanic stress prior to elongation was 0.44 ± 0.15 MPa. During elongation the average stimulated modulus was 0.97 ± 0.34 MPa and was insensitive to rate of loading. The passive stress–strain responses showed a nonlinear stiffening response typical of biologic soft tissue. Both the passive and stimulated stress–strain responses were sensitive to strain rate over the range of strain rates (1 to 25 s−1). Smaller changes in average strain rate (1 to 10, and 10 to 25 s−1) did not produce statistically significant changes in these responses, particularly in the stimulated responses, which were less sensitive to average strain rate than the passive responses. This relative insensitivity to strain rate suggests that pseudoelastic functions generated from an appropriate strain rate test may be suitable for the characterization of the responses of muscle over a narrow range of strain rates, particularly in stimulated muscle.

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Comparative Study of Element Formulation on Simulation of Superplastic Forming

Materials Science Forum ◽

10.4028/www.scientific.net/msf.551-552.281 ◽

2007 ◽

Vol 551-552 ◽

pp. 281-286 ◽

Cited By ~ 1

Author(s):

X.F. Xu ◽

L.M. Tang ◽

G.Q. Tong

Keyword(s):

Finite Element ◽

Comparative Study ◽

Strain Rate ◽

Rate Control ◽

Superplastic Forming ◽

Control Algorithms ◽

Average Strain ◽

Pressure Time ◽

Average Strain Rate ◽

Forming Characteristics

A comparative study of different element formulations in simulating superplastic forming with the MARC finite element code is performed in the paper. Simulations were accomplished with solid, shell, membrane elements to predict forming characteristics and pressure-time curves. Finite element analysis (FEA) predictions of SPF pressure-time curves were found to be greatly affected by the element type and the strain rate control algorithms. Two strain rate control algorithms were applied in the present study: an algorithm based on limiting the rate of deformation with the average strain rate of all the elements, i.e. the build-in method in MARC, and a second algorithm which limits the rate of deformation based on the average strain rate of the elements with the 20 highest strain rates. The resulting pressure-time curves for each of these formulations were compared with respect to each type of element. Under the guide of the analysis, the die was fabricated and the AA5083 bracket was successfully manufactured. Good agreement was obtained between predicted and measured thickness in the part.

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Research on the Mechanical Behavior of Styropor Concrete at High Strain Rates

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.168-170.2086 ◽

2010 ◽

Vol 168-170 ◽

pp. 2086-2091

Author(s):

Ze Bin Hu ◽

Jin Yu Xu ◽

Jie Zhu ◽

Qiang He ◽

Gang Li ◽

...

Keyword(s):

Elastic Modulus ◽

Strain Rate ◽

Mechanical Behavior ◽

High Strain ◽

Dynamic Strength ◽

Strain Rates ◽

Average Strain ◽

High Strain Rates ◽

Average Strain Rate ◽

The Impact

Mechanical behavior of Styropor concrete(EPSC) added with various volumetric fractions of EPS subjected to high strain rates were studied by using the Large-Diameter-SHPB. The infection of volumetric fractions and average strain rate to dynamic properties of EPSC were investigated. The experimental results show that under high strain rate condition, the dynamic strength, dynamic strength increase factor(DIF) and limit strain of EPSC are strain rate dependent, the strain rate effect can be expressed by linear approximations, and the relationship between elastic modulus and average strain rate is independent.With the addition of volumetric fractions of EPS, the impact compressive strength and elastic modulus of EPSC declines, and the toughness of EPSC is reinforced.

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Measurement of the average strain rate of thin aluminum deformation under laser shock

Optical Engineering ◽

10.1117/1.oe.52.5.054302 ◽

2013 ◽

Vol 52 (5) ◽

pp. 054302

Author(s):

Hongbing Yao ◽

Zhusheng Zhou ◽

Yanqun Tong ◽

Jie Ping ◽

Liangwan Li ◽

...

Keyword(s):

Strain Rate ◽

Laser Shock ◽

Average Strain ◽

Thin Aluminum ◽

Average Strain Rate

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Use of Average Temperature in Fen Calculations

Volume 1: Codes and Standards ◽

10.1115/pvp2020-21009 ◽

2020 ◽

Author(s):

W. F. Weitze

Keyword(s):

Strain Rate ◽

Rise Time ◽

Water Environment ◽

Constant Strain Rate ◽

Temperature Response ◽

Threshold Temperature ◽

Average Strain ◽

Linear Temperature ◽

Average Temperature ◽

Average Strain Rate

Abstract The effect of the light reactor water environment on fatigue damage is referred to as environmentally assisted fatigue (EAF). This effect is accounted for by applying an environmental fatigue correction factor, Fen, to calculated fatigue usage. In providing guidelines for calculation of Fen, Revision 0 of NUREG/CR-6909 [1] permits temperature averaging for the case of a constant strain rate and linear temperature response, and permits it in other cases as well, but only if the average temperature used produces results that are consistent with the modified rate approach [1, p. A.5]. Revision 1 of NUREG/CR-6909 [2] modifies this slightly, requiring that the threshold temperature be used in averaging instead of the minimum if the minimum is below the threshold [2, p. A-6]. In both cases, the benchmark for accuracy is the modified rate approach [2, Section 4.4]. In this paper, we use real world examples to compare Fen values based on the modified rate approach with those using average strain rate and temperature. We also examine how to select the rise time used to calculate average strain rate in those cases where it is not obvious. We find that temperature averaging is conservative if rise time and other parameters are correctly selected.

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Coupled Static-Dynamic Tensile Mechanical Properties and Energy Dissipation Characteristic of Limestone Specimen in SHPB Tests

Advances in Civil Engineering ◽

10.1155/2020/7172928 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11 ◽

Cited By ~ 1

Author(s):

Qi Ping ◽

Zhaohui Fang ◽

Dongdong Ma ◽

Hao Zhang

Keyword(s):

Mechanical Property ◽

Tensile Strength ◽

Strain Rate ◽

Dynamic State ◽

Average Strain ◽

Absorbed Energy ◽

Dynamic Tensile Strength ◽

One Dimensional ◽

Average Strain Rate ◽

Dissipation Characteristic

To investigate the dynamic splitting tensile mechanical property of limestone under coupled static and dynamic state, the dynamic split tensile tests of limestone under one-dimensional coupled static and dynamic load with different strain rates were performed with the help of modified split Hopkinson pressure bar (SHPB) equipment. The dynamic splitting tensile mechanical property and energy dissipation characteristic under two stress states were also compared in this research. Test results indicated that the dynamic tensile strength of the limestone specimen increased with the increase of average strain rate, exhibiting an obvious strain rate effect. In addition, dynamic tensile strength under uniaxial state was higher than that under one-dimensional coupled static and dynamic load state under the same test condition. Moreover, the deformation modulus increased with increasing average strain rate under uniaxial state, while it decreased with increasing average strain rate under coupled static and dynamic state. Both the reflected energy and absorbed energy linearly increased with increasing incident energy. The preload in the radial direction could increase the reflected energy and decrease the absorbed energy. Moreover, the transmitted energy with preload state was slightly lower than that under uniaxial state. Finally, the dynamic tensile strength of limestone specimen increased as a power function with increasing absorbed energy.

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Estimation of Average Strain Rate during Equal-Channel Angular Pressing

Materials Science Forum ◽

10.4028/www.scientific.net/msf.850.419 ◽

2016 ◽

Vol 850 ◽

pp. 419-425 ◽

Cited By ~ 1

Author(s):

Fan Liu ◽

Ying Liu ◽

Jing Tao Wang

Keyword(s):

Plastic Deformation ◽

Strain Rate ◽

Equal Channel Angular Pressing ◽

Present Model ◽

Volume Flow Rate ◽

Average Strain ◽

Channel Angle ◽

Corner Angle ◽

Angular Pressing ◽

Average Strain Rate

In plastic deformation, the strain rate is a crucial factor to influence the constitutive behavior of materials such as the flow stress evolution, dislocation slipping, and deformation heat generation. In the present work, a formula based on the volume flow rate rule in plastic deformation was proposed to estimate the average strain rate of materials during equal-channel angular pressing (ECAP). It has been found that both the deformation parameters (channel angle Φ, corner angle Ψ, channel width d, and pressing speed v) and material characteristics (strain hardening behavior) can influence the average strain rate during ECAP. The present model was compared with two other models for estimating the strain rate and numerical values calculated by four different finite element methods (FEM). The result of the present model is in good agreement with the numerical strain rate values by FEM at various values for channel angle Φ and corner angle Ψ.

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