The stiffness of unidirectionally reinforced CFRP as a function of strain rate, strain magnitude and temperature

Composites ◽  
1985 ◽  
Vol 16 (1) ◽  
pp. 19-22 ◽  
Author(s):  
H. Vangerko ◽  
A.J. Barker
Keyword(s):  
Strain Rate ◽  
Strain Magnitude

scholarly journals Bone strain magnitude is correlated with bone strain rate in tetrapods: implications for models of mechanotransduction

2015 ◽  
Vol 282 (1810) ◽  
pp. 20150321 ◽  
Author(s):  
B. R. Aiello ◽  
J. Iriarte-Diaz ◽  
R. W. Blob ◽  
M. T. Butcher ◽  
M. T. Carrano ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Strain Rate ◽  
Flow Rate ◽  
Structural Integrity ◽  
Tissue Level ◽  
Bone Adaptation ◽  
Bone Strain ◽  
Mechanical Stimuli ◽  
Fluid Flow Rate ◽  
Strain Magnitude

Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone strain magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level strain magnitude and rate have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar–canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow rate, a product of bone strain rate and gradient, but does not provide a mechanism for detection of strain magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because strain magnitude is an important determinant of skeletal fracture. Using strain gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between strain rate and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone strain magnitude is encoded in strain rate at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow rate at the cellular level, facilitating bone adaptation via mechanotransduction.

The Influence of Strain Rate on the Springback of Commercially Pure Titanium in a Stretch Forming Operation

2015 ◽  
Vol 639 ◽  
pp. 107-114 ◽  
Author(s):  
Alan G. Leacock ◽  
Shane Quinn ◽  
Gregor Volk ◽  
David McCracken ◽  
Desmond Brown
Keyword(s):  
Stress State ◽  
Strain Rate ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Stretch Forming ◽  
Commercially Pure ◽  
Strain And Strain Rate ◽  
Strain Magnitude ◽  
Cp Ti ◽  
Processing Stress

A common processing stress state used in the construction of sheet metal components is that of uniaxial tension/stretching. This work examines the stretching of CP-Ti over a rigid form tool using varying degrees of strain and strain rate. The degree of springback is shown to be influenced by the interaction of strain rate, strain magnitude and time following forming.

The Strain Rate- and Temperature-Dependent Mechanical Behavior of Veriflex-E in Tension

2010 ◽  
Author(s):  
A. J. W. McClung ◽  
G. P. Tandon ◽  
J. W. Baur
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Monotonic Loading ◽  
Poisson's Ratio ◽  
Strain Magnitude

In this study, the inelastic deformation behavior of Veriflex-E, a thermally-triggered shape memory polymer resin, was investigated. The experimental program was designed to explore the influence of strain rate on monotonic loading at various temperatures. In addition, the creep behavior of specimens at various temperatures was evaluated. The time-dependent mechanical behavior of the Veriflex-E resin is strongly influenced by the temperature as well as the deformation rate. Thermally-actuated shape memory polymers can be thought of as having two phases separated by the glass transition temperature (Tg). At temperatures well below the Tg (room temperature), the Veriflex-E exhibits a high elastic modulus and positive, nonlinear strain rate sensitivity in monotonic loading. Likewise, the room temperature creep response is significantly influenced by the prior strain rate. The Poisson’s ratio at room temperature is independent of the strain rate, but dependent upon the strain magnitude. As the temperature is increased, the strain rate sensitivity in monotonic loading decreases. Well above the Tg, the elastic modulus drops by several orders of magnitude, and strong strain rate sensitivity is no longer observed in the path of the stress-strain curve. In this high temperature region, the material achieves strain levels well above 100% and the Poisson’s ratio is constant at 0.5 regardless of strain rate or strain magnitude. The creep strain, on the other hand, is significantly influenced by the prior strain rate at the elevated temperature. A slight hysteresis is observed during unloading, while recovery following unloading shows a permanent strain.

scholarly journals Do mechanical strain magnitude and rate drive bone adaptation in adult women? A 12-month prospective randomized trial

2018 ◽  
Author(s):  
Karen L. Troy ◽  
Megan E. Mancuso ◽  
Joshua E. Johnson ◽  
Zheyang Wu ◽  
Thomas J. Schnitzer ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Healthy Adult ◽  
High Strain ◽  
Mechanical Strain ◽  
Bone Adaptation ◽  
Adult Women ◽  
Loading Dose ◽  
Osteoporosis Prevention ◽  
Strain Magnitude

AbstractAlthough there is strong evidence that certain activities can increase bone density and structure in some individuals, it is unclear what specific mechanical factors govern the response. This is important because understanding the effect of mechanical signals on bone could contribute to more effective osteoporosis prevention methods and efficient clinical trial design. The degree to which strain rate and magnitude govern bone adaptation in humans has never been prospectively tested. Here, we studied the effects of a voluntary upper extremity compressive loading task in healthy adult women during a twelve month prospective period. One hundred and two women age 21-40 participated in one of two experiments. (1): low (n=21) and high (n=24) strain magnitude. (2): low (n=21) and high (n=20) strain rate. Control: (n=16): no intervention. Strains were assigned using subject-specific finite element models. Load cycles were recorded digitally. The primary outcome was change in ultradistal integral bone mineral content (iBMC), assessed with QCT. Interim timepoints and secondary outcomes were assessed with high resolution pQCT (HRpQCT). Sixty-six subjects completed the intervention, and interim data were analyzed for 77 subjects. Both the low and high strain rate groups had significant 12-month increases to ultradistal iBMC (change in control: -1.3±2.7%, low strain rate: 2.7±2.1%, high strain rate: 3.4±2.2%), total iBMC, and other measures. “Loading dose” was positively related to 12-month change in ultradistal iBMC, and interim changes to total BMD, cortical thickness and inner trabecular BMD. Subjects who gained the most bone completed, on average, 130 loading bouts of (mean strain) 550 με at 1805 με/s. Those with the greatest gains had the highest loading dose. We conclude that signals related to strain magnitude, rate, and number of loading bouts contribute to bone adaptation in healthy adult women, but only explain a small amount of variance in bone changes.

Dislocation Substructures Produced During Tensile, Creep, and Fatigue Deformation of Ti3Al at 700°C

1977 ◽  
Vol 35 ◽  
pp. 272-273
Author(s):  
S. M. L. Sastry
Keyword(s):  
Intermetallic Compound ◽  
Strain Rate ◽  
Tensile Creep ◽  
Slip Systems ◽  
Slip Vector ◽  
Superlattice Structure ◽  
Slip Activity ◽  
Dislocation Arrangement ◽  
Ordered Intermetallic ◽  
Tangled Dislocation

Ti3Al is an ordered intermetallic compound having the DO19-type superlattice structure. The compound exhibits very limited ductility in tension below 700°C because of a pronounced planarity of slip and the absence of a sufficient number of independent slip systems. Significant differences in slip behavior in the compound as a result of differences in strain rate and mode of deformation are reported here.Figure 1 is a comparison of dislocation substructures in polycrystalline Ti3Al specimens deformed in tension, creep, and fatigue. Slip activity on both the basal and prism planes is observed for each mode of deformation. The dominant slip vector in unidirectional deformation is the a-type (b) = <1120>) (Fig. la). The dislocations are straight, occur for the most part in a screw orientation, and are arranged in planar bands. In contrast, the dislocation distribution in specimens crept at 700°C (Fig. lb) is characterized by a much reduced planarity of slip, a tangled dislocation arrangement instead of planar bands, and an increased incidence of nonbasal slip vectors.

Quantitative analysis of in situ straining experiments in the case of strong frictional forces

1978 ◽  
Vol 36 (1) ◽  
pp. 570-571
Author(s):  
F. Louchet ◽  
L.P. Kubin
Keyword(s):  
Strain Rate ◽  
Radiation Effects ◽  
Dislocation Line ◽  
Critical Length ◽  
Local Strain ◽  
Local Flow ◽  
Double Kink ◽  
Dislocation Densities ◽  
Frictional Forces ◽  
Local Strain Rate

Investigation of frictional forces -Experimental techniques and working conditions in the high voltage electron microscope have already been described (1). Care has been taken in order to minimize both surface and radiation effects under deformation conditions.Dislocation densities and velocities are measured on the records of the deformation. It can be noticed that mobile dislocation densities can be far below the total dislocation density in the operative system. The local strain-rate can be deduced from these measurements. The local flow stresses are deduced from the curvature radii of the dislocations when the local strain-rate reaches the values of ∿ 10-4 s-1.For a straight screw segment of length L moving by double-kink nucleation between two pinning points, the velocity is :where ΔG(τ) is the activation energy and lc the critical length for double-kink nucleation. The term L/lc takes into account the number of simultaneous attempts for double-kink nucleation on the dislocation line.

Observations of dislocation interactions with recrystallized grain boundaries

1988 ◽  
Vol 46 ◽  
pp. 628-629
Author(s):  
C. W. Price
Keyword(s):  
Dislocation Density ◽  
Grain Boundary ◽  
Strain Rate ◽  
Grain Boundaries ◽  
Dislocation Structure ◽  
Hot Deformation ◽  
Static Recrystallization ◽  
High Dislocation Density ◽  
High Angle ◽  
Dislocation Interactions

Little evidence exists on the interaction of individual dislocations with recrystallized grain boundaries, primarily because of the severely overlapping contrast of the high dislocation density usually present during recrystallization. Interesting evidence of such interaction, Fig. 1, was discovered during examination of some old work on the hot deformation of Al-4.64 Cu. The specimen was deformed in a programmable thermomechanical instrument at 527 C and a strain rate of 25 cm/cm/s to a strain of 0.7. Static recrystallization occurred during a post anneal of 23 s also at 527 C. The figure shows evidence of dissociation of a subboundary at an intersection with a recrystallized high-angle grain boundary. At least one set of dislocations appears to be out of contrast in Fig. 1, and a grainboundary precipitate also is visible. Unfortunately, only subgrain sizes were of interest at the time the micrograph was recorded, and no attempt was made to analyze the dislocation structure.

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