Determination of the plastic characteristics of materials with a tendency to local strain development

1981 ◽  
Vol 13 (12) ◽  
pp. 1497-1500
Author(s):  
V. V. Vasil'ev ◽  
L. S. Gol'braikh ◽  
P. G. Zykin ◽  
L. D. Rapoport ◽  
I. Kh. Fakhrutdinov
Keyword(s):  
Local Strain ◽  
Strain Development

Basic set of experiments for determination of mechanical properties of sand

2014 ◽  
Vol 62 (1) ◽  
pp. 129-137
Author(s):  
A. Sawicki ◽  
J. Mierczyński
Keyword(s):  
Mechanical Properties ◽  
Soil Mechanics ◽  
Physical And Mechanical Properties ◽  
Local Strain ◽  
Initial State ◽  
Laboratory Equipment ◽  
Additional Information ◽  
Basic Set ◽  
Initial Anisotropy

Abstract A basic set of experiments for the determination of mechanical properties of sands is described. This includes the determination of basic physical and mechanical properties, as conventionally applied in soil mechanics, as well as some additional experiments, which provide further information on mechanical properties of granular soils. These additional experiments allow for determination of steady state and instability lines, stress-strain relations for isotropic loading and pure shearing, and simple cyclic shearing tests. Unconventional oedometric experiments are also presented. Necessary laboratory equipment is described, which includes a triaxial apparatus equipped with local strain gauges, an oedometer capable of measuring lateral stresses and a simple cyclic shearing apparatus. The above experiments provide additional information on soil’s properties, which is useful in studying the following phenomena: pre-failure deformations of sand including cyclic loading compaction, pore-pressure generation and liquefaction, both static and caused by cyclic loadings, the effect of sand initial anisotropy and various instabilities. An important feature of the experiments described is that they make it possible to determine the initial state of sand, defined as either contractive or dilative. Experimental results for the “Gdynia” model sand are shown.

Determination of the Mechanical Response of Thin Films with X-Rays

1993 ◽  
Vol 308 ◽  
Author(s):  
I. C. Noyan ◽  
G. Sheikh
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Mechanical Response ◽  
Strain Analysis ◽  
Local Strain ◽  
X Rays ◽  
Stress Strain ◽  
X Ray ◽  
The Individual

ABSTRACTThe mechanical response of a specimen incorporating thin films is dictated by a combination of fundamental mechanical parameters such as Young's moduli of the individual layers, and by configurational parameters such as adhesion strength at the interface(s), residual stress distribution and other process dependent factors. In most systems, the overall response will be dominated by the properties of the (much thicker) substrate. Failure within the individual layers, on the other hand, is dependent on the local strain distributions and can not be predicted from the substrate values alone. To better understand the mechanical response of these systems, the strain within the individual layers of the thin film system must be measured and correlated with applied stresses. Phase selectivity of X-ray stress/strain analysis techniques is well suited for this purpose. In this paper, we will review the use of the traditional x-ray stress/strain analysis methods for the determination of the mechanical properties of thin film systems.

scholarly journals Strain resolution of scanning electron microscopy based Kossel microdiffraction

2014 ◽  
Vol 47 (5) ◽  
pp. 1699-1707 ◽  
Author(s):  
D. Bouscaud ◽  
A. Morawiec ◽  
R. Pesci ◽  
S. Berveiller ◽  
E. Patoor
Keyword(s):  
Strain Tensor ◽  
Ccd Camera ◽  
Local Strain ◽  
X Ray Diffraction ◽  
Determination Process ◽  
Ni Alloy ◽  
Kossel Technique ◽  
Strain Determination ◽  
Scanning Electron

Kossel microdiffraction in a scanning electron microscope enables determination of local elastic strains. With Kossel patterns recorded by a CCD camera and some automation of the strain determination process, this technique may become a convenient tool for analysis of strains. As for all strain determination methods, critical for the applicability of the Kossel technique is its strain resolution. The resolution was estimated in a number of ways: from the simplest tests based on simulated patterns (of an Ni alloy), through analysis of sharp experimental patterns of Ge, to estimates obtained byin situtensile straining of single crystals of the Ni-based superalloy. In the latter case, the results were compared with those of conventional X-ray diffraction and synchrotron-based Kossel diffraction. In the case of high-quality Ge patterns, a resolution of 1 × 10−4was reached for all strain tensor components; this corresponds to a stress of about 10 MPa. With relatively diffuse patterns from the strained Ni-based superalloy, under the assumption of plane stress, the strain and stress resolutions were 3 × 10−4and 60 MPa, respectively. Experimental and computational conditions for achieving these resolutions are described. The study shows potential perspectives and limits of the applicability of semiautomatic Kossel microdiffraction as a method of local strain determination.

scholarly journals Determination of Local Stresses and Strains within the Notch Strain Approach: Efficient Implementation of Notch Root Approximations

2021 ◽  
Vol 11 (21) ◽  
pp. 10339
Author(s):  
Ralf Burghardt ◽  
Lukas Masendorf ◽  
Michael Wächter ◽  
Alfons Esderts
Keyword(s):  
Service Life ◽  
Newton’S Method ◽  
Newton's Method ◽  
Notch Root ◽  
Local Strain ◽  
Computational Accuracy ◽  
Life Estimation ◽  
Computational Performance ◽  
Service Life Estimation

An estimation of the elastic-plastic stress state using elasticity-theoretical input data is an essential part of the service life estimation with the local strain approach in general and a German guideline based on it, in particular. This guideline uses two different notch root approximations (an extended version of Neuber’s rule and an approach according to Seeger and Beste) for this estimation. Both require the implementation of Newton’s method to be iteratively solved. However, many options are left open to the user concerning implementation in program code. This paper discusses ways in which notch root approximation methods can be implemented efficiently for use in software systems and elaborates an application recommendation. The following aspects and their influence on the computational accuracy and performance of Newton’s method are considered in detail: influence of the formulation of the root finding problem, determination of the derivative required for Newton’s method and influence of the termination criterion. The investigation shows that the advice given in the abovementioned guideline indeed leads to a conservative implementation. By carefully considering the investigated aspects, however, the computational performance can be increased by approximately a factor of 2–3 without influencing the accuracy of the service life estimation.

High-Speed Wave-Piercing Catamaran Global Loads Determined by FEA and Sea Trials

2019 ◽  
Vol 161 (A2) ◽  
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Local Strain ◽  
Element Model ◽  
Sensor Data ◽  
Design Stage ◽  
High Speeds ◽  
Design Loads ◽  
Hull Forms

Wave-piercing catamaran hull forms are widely used for high-speed ferry applications due to the hull slenderness, suitable for achieving high speeds. The global loads acting on these craft are of great interest as there is limited knowledge on determining the magnitude of the loads, in particular when operating in random sea conditions. Longitudinal and transverse bending moments as well as pitch connecting moments and hull torsion loads act on the hull simultaneously. This paper investigates the estimation of these global loads from full-scale catamaran sea trials strain gauge data using finite element methods. Det Norske Veritas (DNV) load cases are applied to a finite element model in order to determine the conversion between local strain values observed during sea trials and prevailing global loads. Comparisons are thus made of global loads determined from strain data collected from sea trials with DNV global load cases. The results show that this method is relatively reliable for the prediction of hull global loads in the absence of slamming. Comparisons have been made for different heading angles. The quasi-static design loads are important during the ship design stage, as they are good proxies in wavelengths comparable to the hull length for rationally determined loads obtained from a first-principles dynamic analysis. The broad aims here are to demonstrate the use of strain sensor data obtained during sea trials for determination of global sea loads, to reconcile the loads thus determined with DNV load cases and thereby to improve the accuracy of the predicted loads used in design to increase the structural efficiency of vessel design.

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