Determination of the optimum ball radius for researching materials using ball indenting

The article discusses the study of the effect of a change in the radius of the ball in the injecting of the sample on the curve in the coordinates «load – indentation depth», the deviation of the indentation depth during elastoplastic indentation from the indentation depth with the elastic indentation and the amount of the axial deformation of the ball. The study was conducted using the Ansys Mechanical APDL program implementing the fenite element method. In the process of the study, it was found that with a change in the radius of the ball, there is no obvious change in the behavior of the sample material, and the deviation of the indentation depth during the elastoplastic indulgence from the indentation depth during the elastic indentation is not dependent on the size of the ball radius. There was also an effect of changing the radius of the ball on the size of the axial deformation of the ball and proposed a formula for determining the size of the axial deformation of the ball for the ball of any diameter, which will determine the actual depth of the ball into the ball when using the balls of different radius.

Influence of multiple load indentation on the mechanical and material behaviour of steel cone-cylinder under axial compression

The first set of test data on axial collapse of cone-cylinder assembly having multiple load indentation (MLI) and its accompanying numerical studies is presented in this paper. Two perfect and two imperfect steel cone-cylinders were prepared in pairs. The cone-cylinder models have the following geometric parameters: cone radius of 40 mm, cylinder radius of 70 mm,wall thickness of 0.5 mm and cone angle of 16.7°. Cone and cylinder part were combined using Metal Inert Gas (MIG) welding technique. Results show that the repeatability of the experiment was good (3% for the perfect and 7% for the imperfect). Also, numerical prediction tends to reproduce the test data with good accuracy. The error between both approches ranges from 1% to -8%. Furthermore, the influence of geometric parameters are also significant in determining the collapse load of this type of structure. Finally, the worst multiple load indentation (WMLI) was explored for steel cone-cylinders assembly using different number of load indentations. Results indicate that as the number of indents increases, the sensitivity of the cone-cylinder models to imperfection also increases. However, at different imperfection amplitude, A, two regions were observed; (i) the region where cone-cylinder with N = 8 is more sensitive (A < 1.5), and (ii) the region where N = 4 produce the worst imperfection (1.5 < A ≤ 1.68).

Accidental impact by ships in the updated EN 1991-1-7

<p>Ship collision is still one of the risk-prone expositions for bridges crossing navigable inland and mar- itime waterways. Within the preparation of the 2nd generation of the Eurocodes a 3rd (final) draft of an updated EN 1991-1-7 is edited [2]. Rules and background information for the Eurocode impact rules concerning inland and maritime waterway traffic are given. The rules and recommendations cover aspects like impact dynamics, load-indentation-functions, collision angles, collision probabili- ties and reliability criteria. For seagoing vessels new impact mechanics have been included. Infor- mation from some National Annexes and open questions are mentioned. Examples with determined ship impact forces are presented.</p>

Determination of stress–strain curves of materials at high strain rates using dynamic indentation technique

Determination of dynamic behaviour of materials is a serious challenge in mechanics of materials. In this investigation, a new approach is proposed to obtain stress–strain curves of metals from dynamic indentation test. This approach is based on a combined experiment, simulation, and optimization techniques. In the experiment side, a conical penetrator is shot against the material as the target. The load–indentation depth curve is obtained from the dynamic indentation test. The indentation test is simulated using Ls-dyna and the numerical load–indentation depth is obtained from the simulation. The stress–strain curves are defined by Johnson–Cook material model. From optimization of the difference between the experimental and numerical load–indentation depth curves, the constants of the material model are identified. The material model is validated also by stress–strain curves obtained from quasi-static test conducted using Instron and dynamic tests conducted using Split Hopkinson Bar. The results show a close agreement between the model prediction and the experimental stress–strain curves for different strain rates.

Calibration of a Constitutive Model from Tension and Nanoindentation for Lead-Free Solder

It is challenging to evaluate constitutive behaviour by using conventional uniaxial tests for materials with limited sizes, considering the miniaturization trend of integrated circuits in electronic devices. An instrumented nanoindentation approach is appealing to obtain local properties as the function of penetration depth. In this paper, both conventional tensile and nanoindentation experiments are performed on samples of a lead-free Sn–3.0Ag–0.5Cu (SAC305) solder alloy. In order to align the material behaviour, thermal treatments were performed at different temperatures and durations for all specimens, for both tensile experiments and nanoindentation experiments. Based on the self-similarity of the used Berkovich indenter, a power-law model is adopted to describe the stress–strain relationship by means of analytical dimensionless analysis on the applied load-penetration depth responses from nanoindentation experiments. In light of the significant difference of applied strain rates in the tensile and nanoindentation experiments, two “rate factors” are proposed by multiplying the representative stress and stress exponent in the adopted analytical model, and the corresponding values are determined for the best predictions of nanoindentation responses in the form of an applied load–indentation depth relationship. Eventually, good agreement is achieved when comparing the stress–strain responses measured from tensile experiments and estimated from the applied load–indentation depth responses of nanoindentation experiments. The rate factors ψ σ and ψ n are calibrated to be about 0.52 and 0.10, respectively, which facilitate the conversion of constitutive behaviour from nanoindentation experiments for material sample with a limited size.

Impact of Different Boundary Conditions on the Response of Glare Fiber-Metal Laminates under Lateral Indentation

In this paper, a finite element modelling procedure is implemented in order to predict the static load-indentation curves and the defection shape of simply supported circular GLARE fibre-metal laminates subjected to lateral indentation by a hemispherical indentor. ANSYS software is used and a non-linear analysis is employed with geometric and material non-linearities for FEM calculations. The finite element modelling procedure is applied to GLARE 2–2/1–0.3 and to GLARE 3–3/2–0.4 simply supported circular plates with various diameters. It is found that the simply supported circular GLARE plates deform axisymmetrically from the beginning of the indentation process up to the point of their first failure due to glass-epoxy tensile fracture. By comparison of the obtained load-indentation curves to corresponding previously published load-indentation curves of clamped circular GLARE plates, the effect of the different boundary conditions on their lateral indentation response is studied. Furthermore, the strain energy-indentation curves of the considered circular GLARE 2 and GLARE 3 plates with simply supported and clamped boundaries are calculated and compared. It is found that the simply supported GLARE plates have reduced stiffness and demonstrate an increased first failure defection due to glass-epoxy tensile fracture versus the clamped GLARE plates, whereas the first failure load is not significantly affected by the different boundary conditions. It is also found that for the same lateral indentation, simply supported GLARE plates absorb lower strain energy levels than clamped GLARE plates. Referring to a specific lateral indentation level, the influence of the different boundary support on the corresponding indentation load and the absorbed strain energy is strong and can reach a deviation level of 45 % between the two support types. To our knowledge, a research concerning the response of simply supported GLARE plates under lateral indentation has not been published elsewhere.