Crashworthiness of Side Facing Seating Positions in Aircrafts, Biodynamic Stresses and Maximum Strain Criterion

1997 ◽  
Author(s):  
Martin Sperber ◽  
Erich Schuller ◽  
Carl Jürgen Schroth
Keyword(s):  
Maximum Strain ◽  
Strain Criterion

A Further Examination on the Application of the Strain Energy Density Theory to the Angled Crack Problem

1982 ◽  
Vol 49 (2) ◽  
pp. 377-382 ◽  
Author(s):  
K. J. Chang
Keyword(s):  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Material Parameter ◽  
Biaxial Tension ◽  
Crack Problem ◽  
Core Region ◽  
Maximum Strain ◽  
Strain Criterion ◽  
Strain Energy Density Theory

The strain energy density theory (the S-theory) has been examined. Two points that may lead to confusion have been discussed when the S-theory is employed in the study of the angled crack problem. Predictions for the biaxial tension configuration based on the S-theory compared with one based on the maximum strain criterion are presented. Use of the ratio of core region radius as a material parameter in the S-theory is also questioned.

A theoretical analysis on the failure of unpressurized and pressurized pipelines

2002 ◽  
Vol 216 (3) ◽  
pp. 151-165 ◽  
Author(s):  
W Q Shen ◽  
D W Shu
Keyword(s):  
Theoretical Analysis ◽  
Impact Energy ◽  
Empirical Formula ◽  
Plastic Hinge ◽  
Threshold Value ◽  
Maximum Strain ◽  
Strain Criterion ◽  
Pressurized Pipelines ◽  
Global Deformation ◽  
The Impact

A theoretical quasi-static analysis is proposed to predict the response and the onset of failure for pipelines. The maximum strain criterion, the effect of strain rate and an empirical formula for estimating the length of a plastic hinge are employed in the analysis. This theoretical study allows the local or denting deformation to continue during the global deformation phase. A good agreement has been achieved between the theoretical predictions and the corresponding experimental results for the threshold value of the impact energy and the maximum permanent transverse deflection for both unpressurized and pressurized pipelines. It transpires that both the maximum strain criterion and the empirical formula for the hinge length are applicable in the theoretical analysis. With a simple computer program, the theory can be used to predict the failure of pipelines. Discussions are made for the influence of internal pressure on the shape of the indentation and the threshold value of the impact energy.

scholarly journals The Maximum Stress Failure Criterion and the Maximum Strain Failure Criterion: Their Unification and Rationalization

2020 ◽  
Vol 4 (4) ◽  
pp. 157
Author(s):  
Shuguang Li
Keyword(s):  
Shear Stress ◽  
Failure Criterion ◽  
Maximum Stress ◽  
Uniaxial Stress ◽  
Longitudinal Shear ◽  
Maximum Strain ◽  
Poisson Effect ◽  
Stress Strain ◽  
Strain Criterion ◽  
Stress Criterion

The maximum strain failure criterion is unified with the maximum stress failure criterion, after exploring the implications of two considerations responsible for this: (1) the failure strains for the direct strain components employed in the maximum strain criterion are all defined under uniaxial stress states, not uniaxial strain states, and (2) the contributions to the strain in a direction as a result of the Poisson effect do not contribute to the failure of the material in that direction. Incorporating these considerations into the maximum strain criterion, the maximum stress criterion is reproduced. For 3D stress/strain state applications primarily, the unified maximum stress/strain criterion is then subjected to further rationalization in the context of transversely isotropic materials by eliminating the treatments that undermine the objectivity of the failure criterion. The criterion is then applied based on the maximum and minimum direct stresses, the maximum transverse shear stress and the maximum longitudinal shear stress as the invariants of the stress state, instead of the conventional stress components directly.

On the nominal transverse shear strain to characterize the severity of creasing

TAPPI Journal ◽  
2018 ◽  
Vol 17 (04) ◽  
pp. 231-240
Author(s):  
Douglas Coffin ◽  
Joel Panek
Keyword(s):  
Shear Strain ◽  
Transverse Shear ◽  
Elastic Limit ◽  
Experimental Results ◽  
Transverse Shear Strain ◽  
Maximum Strain ◽  
Machine Direction ◽  
Engineering Approach ◽  
Wide Range ◽  
Analytic Expression

A transverse shear strain was utilized to characterize the severity of creasing for a wide range of tooling configurations. An analytic expression of transverse shear strain, which accounts for tooling geometry, correlated well with relative crease strength and springback as determined from 90° fold tests. The experimental results show a minimum strain (elastic limit) that needs to be exceeded for the relative crease strength to be reduced. The theory predicts a maximum achievable transverse shear strain, which is further limited if the tooling clearance is negative. The elastic limit and maximum strain thus describe the range of interest for effective creasing. In this range, cross direction (CD)-creased samples were more sensitive to creasing than machine direction (MD)-creased samples, but the differences were reduced as the shear strain approached the maximum. The presented development provides the foundation for a quantitative engineering approach to creasing and folding operations.

scholarly journals An Extension Strain Type Mohr–Coulomb Criterion

2021 ◽  
Author(s):  
Manfred Staat
Keyword(s):  
Failure Modes ◽  
Peak Stress ◽  
Fracture Initiation ◽  
Failure Surface ◽  
Confining Pressure ◽  
Biaxial Compression ◽  
Simple Extension ◽  
Strain Criterion ◽  
Shear Component ◽  
Extension Strain

AbstractExtension fractures are typical for the deformation under low or no confining pressure. They can be explained by a phenomenological extension strain failure criterion. In the past, a simple empirical criterion for fracture initiation in brittle rock has been developed. In this article, it is shown that the simple extension strain criterion makes unrealistic strength predictions in biaxial compression and tension. To overcome this major limitation, a new extension strain criterion is proposed by adding a weighted principal shear component to the simple criterion. The shear weight is chosen, such that the enriched extension strain criterion represents the same failure surface as the Mohr–Coulomb (MC) criterion. Thus, the MC criterion has been derived as an extension strain criterion predicting extension failure modes, which are unexpected in the classical understanding of the failure of cohesive-frictional materials. In progressive damage of rock, the most likely fracture direction is orthogonal to the maximum extension strain leading to dilatancy. The enriched extension strain criterion is proposed as a threshold surface for crack initiation CI and crack damage CD and as a failure surface at peak stress CP. Different from compressive loading, tensile loading requires only a limited number of critical cracks to cause failure. Therefore, for tensile stresses, the failure criteria must be modified somehow, possibly by a cut-off corresponding to the CI stress. Examples show that the enriched extension strain criterion predicts much lower volumes of damaged rock mass compared to the simple extension strain criterion.

scholarly journals Chemistry of collagen cross-links: glucose-mediated covalent cross-linking of type-IV collagen in lens capsules

1993 ◽  
Vol 296 (2) ◽  
pp. 489-496 ◽  
Author(s):  
A J Bailey ◽  
T J Sims ◽  
N C Avery ◽  
C A Miles
Keyword(s):  
Type Iv Collagen ◽  
Cross Linking ◽  
Mechanical And Thermal Properties ◽  
Maximum Strain ◽  
Scanning Calorimetry ◽  
Melting Temperatures ◽  
Type Iv ◽  
Collagen Molecules ◽  
Cross Links

The incubation of lens capsules with glucose in vitro resulted in changes in the mechanical and thermal properties of type-IV collagen consistent with increased cross-linking. Differential scanning calorimetry (d.s.c.) of fresh lens capsules showed two major peaks at melting temperatures Tm 1 and Tm 2 at approx. 54 degrees C and 90 degrees C, which can be attributed to the denaturation of the triple helix and 7S domains respectively. Glycosylation of lens capsules in vitro for 24 weeks caused an increase in Tm 1 from 54 degrees C to 61 degrees C, while non-glycosylated, control incubated capsules increased to a Tm 1 of 57 degrees C. The higher temperature required to denature the type-IV collagen after incubation in vitro suggested increased intermolecular cross-linking. Glycosylated lens capsules were more brittle than fresh samples, breaking at a maximum strain of 36.8 +/- 1.8% compared with 75.6 +/- 6.3% for the fresh samples. The stress at maximum strain (or ‘strength’) was dramatically reduced from 12.0 to 4.7 N.mm.mg-1 after glycosylation in vitro. The increased constraints within the system leading to loss of strength and increased brittleness suggested not only the presence of more cross-links but a difference in the location of these cross-links compared with the natural lysyl-aldehyde-derived cross-links. The chemical nature of the fluorescent glucose-derived cross-link following glycosylation was determined as pentosidine, at a concentration of 1 pentosidine molecule per 600 collagen molecules after 24 weeks incubation. Pentosidine was also determined in the lens capsules obtained from uncontrolled diabetics at a level of about 1 per 100 collagen molecules. The concentration of these pentosidine cross-links is far too small to account for the observed changes in the thermal and mechanical properties following incubation in vitro, clearly indicating that another as yet undefined, but apparently more important cross-linking mechanism mediated by glucose is taking place.

Sign in / Sign up

Export Citation Format

Share Document