Study on the surface quality of 60vol% SiCp/Al2024 composites with large-grained

In this paper, the finite element cutting simulation model with irregular distribution of multiple particles is established, the stress and strain distribution of SiC particles in the process of machining, as well as the material removal mechanism are analyzed. The effects of cutting velocity and feed per tooth on the surface quality of the material are also analyzed. The effect of feed per tooth on subsurface damage is revealed. The results show that in the micro-milling of SiCp/Al2024 composites, the particle removal form is mainly crushing and extraction. The surface defects of the workpiece mainly include pits, scratches, cracks, and extrusion damage. When the cutting velocity increases, the surface defects gradually change to crack, which can improve the surface quality of the workpiece. Increasing the feed per tooth will increase the surface defects of the workpiece and lead to poor surface quality. When the feed per tooth increased from 0.428 µm to 0.714 µm, the subsurface damage thickness increased from 35.2 µm to 47.3 µm.

Using Plane Strain Compression Test to Evaluate the Mechanical Behavior of Magnesium Processed by HPT

There is a great interest in improving mechanical testing of small samples produced in the laboratory. Plane strain compression is an effective test in which the workpiece is a thin sheet. This provides great potential for testing samples produced by high-pressure torsion. Thus, a custom tool was designed with the aim to test 10 mm diameter discs processed by this technique. Finite element analysis is used to evaluate the deformation zone, stress and strain distribution, and the accuracy in the estimation of stress–strain curves. Pure magnesium and a magnesium alloy processed by high-pressure torsion are tested using this custom-made tool. The trends observed in strength and ductility agree with trends reported in the literature for these materials.

Iterative Methods for the Biomechanical Evaluation of Corneal Response. A Case Study in the Measurement Phase

the number of corneal surgeries steadily grew in recent years and boosted the development of corneal biomechanical models. These models can contribute to simulating surgery by reducing associated risks and the need for secondary interventions due to ectasias or other problems related to correcting other diseases. Biomechanical models are based on the geometry obtained with corneal topography, which is affected by intraocular pressure and material properties. Knowledge of stress distribution in the measurement phase is a key factor for improving the accuracy of in silico mechanical models. In this work, the results obtained by two different methods: prestress method and displacements method were compared to evaluate the stress and strain distribution in a general geometric model based on the Navarro eye geometry and two real corneal geometries. The results show that both methods are equivalent for the achievement of the stress distribution in the measurement phase. Stress distribution over the corneal geometry in the measurement phase is a key factor for accurate biomechanical simulations, and these simulations could help to develop patient-specific models and reduce the number of secondary interventions in clinical practice.

The role of the fiber ply configurations on the biomechanics of the hip prosthesis

The total hip replacement is the only approved procedure for restoring a degenerated hip joint through operation. The life span of a prosthesis could depend on the geometry and material properties of the implant. This study aims to analyze the biomechanics of the carbon/polyetheretherketone (PEEK) composite prosthesis having three different fiber ply configurations compared to traditional stainless steel (SS) ones. The implant-bone system was established and subjected to a load from the head of the femur and abductor muscle sides. The stresses and strains in the implant-bone systems were calculated and compared. The results revealed lower stresses and strains in composite prostheses compared to SS ones. The fiber ply orientation of the carbon/PEEK composite prosthesis is shown to be a key asset in stress and strain distribution of the 13 implant-bone systems. The fiber plies which orientated multidirectionally with −45 and +45 degrees exhibited uniform stress and strain distributions. The results suggested the advantage of using composite prostheses in implant designs as they not only invoke lower stresses and strains in the implant-bone system but also amplify the life span of implants in the body.

Features of device cooling in wiggler synchrotron workstations

The construction of the «Siberian Photon Ring Source», the SKIF synchrotron, in Novosibirsk is underway. At the first stage, six research workstations will be created, most of the devices of which work in a high vacuum. Synchrotron radiation is generated by superconducting Wigglers for two stations. The total radiation power is approaching 49 kW, and the power density on the axis is 92 kW/mrad2. The high energy density of the beam creates quite difficult conditions for the thermal management of optical elements at the workstations. The article presents specific requirements for cooling devices, an overview of the used and promising cooling systems is made, an example of calculating the temperature, stress and strain distribution in a diamond filter with a thickness of 300 microns using the ANSYS Fluent software package is given.

The ephemeral development of C' shear bands

<p>C' shear bands are common structures in ductile shear zones but their development is poorly understood. They occur in rocks with a high mechanical strength contrast so we used numerical models of viscoplastic deformation to study the effect of the proportion of weak phase and the phase strength contrast on C' shear band development. We employed simple shear to a finite strain of 18 in 900 steps and recorded the microstructure, stress and strain distribution at each step. We found that C' shear bands form in models with ≥5% weak phase when there is a moderate or high phase strength contrast, and they occur in all models with weak phase proportions ≥15%. Contrary to previous research, we find that C' shear bands form when layers of weak phase parallel to the shear zone boundary rotate forwards. This occurs due to mechanical instabilities that are a result of heterogeneous distributions of stress and strain rate. C' shear bands form on planes of low strain rate and stress, not in sites of maximum strain rate as has previously been suggested. C' shear bands are ephemeral and they either rotate backwards to the C plane once they are inactive or rotate into the field of shortening and thicken to form X- and triangle- shaped structures.</p>

Stability of Embankments Resting on Foundation Soils with a Weak Layer

The presence of weak layers in geotechnical systems, including soil or rock masses, both natural and man-made, is more frequent than is normally believed. Weak layers can affect both failure mechanisms, in drained and in undrained conditions, as well as in static and seismic conditions, and the safety factor. In the present study, conducted numerically using the finite-element method (FEM) Plaxis 2D code, the influence of a horizontal thin weak layer on stress and strain distribution, on failure mechanisms and on the overall stability of an embankment was evaluated. The results obtained prove that when the weak layer is located at a significant depth from the foundation plane, the failure mechanisms are normally mixtilinear in shape because the shear strains largely develop on the weak layer. As a result, the safety factor highly decreases compared to the same case without a weak layer. Then, in the presence of weak layers, even embankments that, if founded on homogeneous soils, would have very high global safety factors (higher than 2) can become unstable, i.e., the safety factor can become unitary. So particular attention must be paid during detail ground investigations to finding thin weak layers.

Voxel-based finite element modelling of wood elements based on spatial density and geometry data using computed tomography

In this paper, voxel-based finite element modelling based on spatial geometry and density data is applied to simulate the detailed stress and strain distribution in a large wood element. As example, a moulded wooden tube with a length of 3 m and a diameter of 0.3 m is examined. Gamma-ray computed tomography is used to obtain both, its actual geometric shape and spatial density distribution. Correlation functions (R2 ≈ 0.6) between density and elastic material properties are experimentally determined and serve as link for defining the non-uniform distribution of the material properties in the finite element model. Considering the geometric imperfections and spatial variation of the material properties, a detailed analysis of the stress and strain distribution of a wood element is performed. Additionally, a non-destructive axial compression test is applied on the wooden tube to analyse the load-bearing behaviour. By means of digital image correlation, the deformation of the surface is obtained, which also serves for validation of the finite element model in terms of strain distributions.

Stress and Strain Distribution in the Upsetting Process

Numerical simulation of metal flow behaviour was studied using DeformTM3D software. The simulation process was done on X20 steel taken from the software database at 1073-1273K temperature, 10mm/s die speed, and 67% height reduction. From the simulation results, forging load, damage, and stress/strain distributions were obtained. The results show that the forging load increased with a decrease in temperature or decreased with an increase in temperature. The maximum damage values increased as the temperature increased. The obtained maximum damage values were 0.42 (1073K), 0.43 (1173K), and 0.45 (1273K). The damage distribution was inhomogeneous in the deformed cylinder. The stress/strain distributions were inhomogeneous in the deformed cylinder. The location of the maximum strain was at the centre of the deformed cylinder while the maximum stress occurred at the die-cylinder contact surfaces. The study showed that flow stress behaviour can be predicted using finite element method. This shows the feasibility of applying the finite element analysis to analyse the forging process.