Fabrication of Conically Shaped CuCr1 Chrome Bronze Products by Wire-Feed Electron Beam Additive Manufacturing

The structure and properties of conically shaped products made of CuCr1 chrome bronze obtained by wire-feed electron beam additive technology have been investigated. The studies show that the organization of the structure in the samples fully corresponds to the peculiarities of the printing process and heat removal from the samples. The structure is represented by large grains elongated in the direction of heat removal. Chromium in the samples is mainly localized in the form of particles located between the dendrite arms. Near the substrate, intense mixing of the bronze with the substrate material (steel 321) is observed. The mechanical properties of the conical and cylindrical sample parts material are at a fairly close level. The samples are characterized by low values of yield strength, low values of tensile strength and high plasticity. Near the substrate, the mechanical properties of the specimens increase.

Hot deformation behavior of 60NiTi shape-memory alloy fabricated by hot isostatic pressing

The 60NiTi (Ni60wt%–Ti40wt%) intermetallic is a hard-to-process material. Understanding of hot deformation behavior is crucial for the hot working of 60NiTi. This work studied hot deformation behavior and corresponding microstructure of the hot isostatic pressed 60NiTi in the temperature range of 900 °C–1050 °C and at strain rates of 0.1, 0.01, and 0.001 s-1 through a hot compression test. The flow stress and microstructure were susceptible to the hot deformation parameters. The flow stress decreased with the increase in deformation temperature and decrease in strain rate. Work hardening occurred at a small strain, then followed by softening; finally, near-dynamic equilibrium was achieved between work hardening and softening. A constitutive equation was developed to describe the effects of strain rate and temperature on flow stress. Simulation of hot deformation via the finite element method revealed the workpiece’s inhomogeneous deformation. The deformation occurred mainly in the center area of the cylindrical sample, resulting in high stress and strain concentrations in this region and causing the equiaxial grains to be compressed into prolate grains. This work can provide guidance for the hot working, such as forging and hot rolling, of 60NiTi.

Experimental Study of Hardened Young’s Modulus for 3D Printed Mortar

Few studies have focused on determining the Young’s modulus of 3D printed structures. This study presents the results of experimental investigations of Young’s modulus of a 3D printed mortar. Specimens were prepared in four different ways to investigate possible application of different methods for 3D printed structures. Study determines the influence of the number of layers on mechanical properties of printed samples. Results have shown a strong statistical correlation between the number of layers and value of Young’s modulus. The compressive strength and Young’s modulus reduction compared to standard cylindrical sample were up to 43.1% and 19.8%, respectively. Results of the study shed light on the differences between the current standard specimen used for determination of Young’s modulus and the specimen prepared by 3D printing. The community should discuss the problem of standardization of test methods in view of visible differences between different types of specimens.

Domain discretizations for numerical solution of fracture problems

В работе для численного моделирования хрупкого разрушения с целью повышения эффективности громоздких расчетов предлагается использовать двухуровневую процедуру построения сетки дискретизации. На верхнем уровне генерируется сетка фрагментов - локусов задаваемых размеров и произвольной случайной формы, по границам которых может происходить разрушение. На нижнем уровне каждый локус разбивается на сетку конечных элементов. Разрыв связей между конечными элементами по траектории разрушение между локусами реализуется с помощью процедуры сцепляющей среды. Для построения сетки дискретизации верхнего уровня использована диаграмма Воронова. Разработан алгоритм процедуры создания локусов на телах произвольной формы в двумерной и трехмерной постановках. Процедура реализована на языке APDL, для использования в программном комплексе ANSYS. Алгоритм протестирован при различных значениях задаваемых параметров и на объектах разнообразной формы. Численное решение задачи о разрушении цилиндрического образца из хрупкого материала по бразильскому тесту определения прочностных характеристик материала на растяжение продемонстрировало хорошее согласование полученной картины разрушения с реальной. In this paper, for numerical modeling of brittle fracture in order to increase the efficiency of complex calculations, it is proposed to use a two-level procedure for generating a discretization network. At the upper level, a network of fragments – locus’s, of specified sizes and arbitrary random shape, is generated. At the lower level, each locus is meshed by FE. The breaking of connections between finite elements along the trajectory of destruction between locus is realized using the cohesive zone procedure. The properties of the Voronov diagram are used to generate the upper-level discretization network. The algorithm of the procedure for creating locus on bodies of arbitrary shape in two-dimensional and three-dimensional formulations is developed. The procedure is implemented in the APDL, for use in the ANSYS. The algorithm is tested at various values of the specified parameters and on objects of various shapes. The numerical solution of the problem of the destruction of a cylindrical sample made of brittle material according to the Brazilian test for determining the tensile strength characteristics of the material demonstrated a good agreement of the obtained fracture pattern with the real one.

Temperature distribution in a cylindrical lengthy workpiece under plasma electrolytic heating

The article focuses on developing a model of a stationary temperature field inside a semi-infinite cylindrical sample partly immersed in electrolyte. Temperature calculation is carried out by solving a heat transfer equation separately for the immersed and protruding parts of the sample. The heat flux is set on the outer area boundaries; meanwhile heat flux density for the immersed part is linearly dependent on the vertical coordinate. Within the framework of the model, vertical and radial temperature gradients are worked out both in protruding and immersed parts of the anode. It has been established that the vertical coordinate of the sign reversal point of the heat flux density in the immersed part depends on heat exchange conditions in the protruding part.

High-accuracy absolute magnetometry with application to the Fermilab Muon g-2 experiment

We present details of a high-accuracy absolute scalar magnetometer based on pulsed proton NMR. The B-field magnitude is determined from the precession frequency of proton spins in a cylindrical sample of water after accounting for field perturbations from probe materials, sample shape, and other corrections. Features of the design, testing procedures, and corrections necessary for qualification as an absolute scalar magnetometer are described. The device was tested at B = 1.45 T but can be modified for a range exceeding 1–3 T. The magnetometer was used to calibrate other NMR magnetometers and measure absolute magnetic field magnitudes to an accuracy of 19 parts per billion as part of a measurement of the muon magnetic moment anomaly at Fermilab.

A Novel Classification Method for Pores in Laser Powder Bed Fusion

Nowadays, additive manufacturing (AM) using laser powder bed fusion (LPBF) is acknowledged for its ability to generate near-net-shape components for various industries such as aerospace, automotive, and health industries. However, internal defects seem to be the inevitable concomitant in the current state of laser powder bed fusion of Al alloys. Hence, knowledge of the formation, different types, and morphologies of pores and their suppression is an essential element for successful future AM applications. The purpose of this research is to qualify a new approach of defect classification using X-ray tomography. In this framework, this research examined the influence of size, shape, and location of pores on crack initiation for AlSi10Mg parts produced by LPBF. For this reason, a total number of 39,228 pores detected in a cylindrical sample were categorised. Additionally, 26 selected pores of different morphology from the X-ray scan were analysed by means of finite element analysis (FEA). Moreover, fracture mechanics determinations were carried out to examine the correlations between pore characteristics and degree of stress concentration. The result is an evaluated novel pore classification method that can be used for process adjustments, quality assurance, as well as further research.

Theoretical and Experimental Analysis of Inter-Layer Stresses in Filament-Wound Cylindrical Composite Structures

This paper analyses the issues relative to the modelling of tubular (cylindrical) composite structures. This paper aims to describe the design of a multi-layer structure of filament-wound composite pipes where, after loading, the hoop-stress distribution would be as uniform as possible. That would allow the mass of the composite to decrease while maintaining the proper mechanical strength. This publication presents the development of a calculation model dedicated to mono- and multi-layered tubular composite structures. The equations describing the stress pattern were based on the Lamé Problem, whereas to describe the modelled structures, an anisotropy coefficient was introduced and interlayer pressures values were determined. To verify the calculations, experimental studies were performed. The test specimens were fabricated by winding fibre bundles around a steel core (as rings with an internal diameter of 113 mm and a height of 30 mm). For the test, the method of pressing a conical ring into a split ring, which acts on the internal surface of the tested cylindrical sample, was selected. The operation of the test rig (test stand) was simulated using the Finite Element Method (FEM). Measurements with strain gauges were conducted during the experiments.

Syn-shearing deformation mechanisms of minerals in partially molten metapelites

We investigated an experimentally sheared (γ = 15, γ ̇ = 3 x 10-4s-1, 300 MPa, 750°C) quartz-muscovite aggregate to understand the deformation of parent and new crystals in partially molten rocks. The SEM and EBSD analyses along the longitudinal axial section of the cylindrical sample suggest that quartz and muscovite melted partially and later produced K-feldspar, ilmenite, biotite, mullite, and cordierite. Quartz grains became finer, and muscovite was almost entirely consumed in the process. With increasing , melt and crystal fractions decreased and increased, respectively. Amongst the new minerals, K-feldspar grains (highest area fraction and coarsest) nucleated first, whereas cordierite and mullite grains, finest and least in number, respectively, nucleated last. Fine grain size, weak CPOs, low intragranular deformation, and equant shapes suggest both initial and new minerals deformed dominantly by melt-assisted grain boundary sliding, which is further substantiated by higher misorientations between adjacent grains of quartz, K-feldspar, and ilmenite.