Materials Science Forum Vol. 1084

Abstract: Use the devices for the implementation of the combined casting process and deformation of non-ferrous alloys is a relatively new direction in the technology of materials processing by pressure. For an adequate description of the shaping processes implemented in such devices on the basis of certain mathematical models, experimental data on the energy-force parameters of deformation are required, as well as data for the nature of the distribution and intensity of deformations arising in the process during cyclic deformation of a metal product. The cyclical nature of the process of forming a metal product, coupled with large plastic deformations, does not allow directly using the traditional methods of experimental research of its stress-strain state adopted in the theory of metalworking by pressure. This gap is partly intended to fill by this study. The paper proposes a complex technique based on the registration (according to the electrical characteristics of the drive motor) of the instantaneous power of irreversible deformation for the material of a metal product. Prone to strain hardening in a cold state, a method for directly establishing the components of plastic deformation of the workpiece based on the method of rolled dividing grids with subsequent calculations according to Siebel's method. Analysis of the experimental results allows us to establish a qualitative picture of the deformation mechanism. The obtained experimental values are necessary for the verification of mathematical models and software systems for calculating the stress-strain state of materials under complex loading and finite deformations.

Abstract: Since the end part of the valve of the gas distribution mechanism is subjected to not only wear but also fatigue painting during operation of the car, this article proposes to remove the worn out layer of cast iron in several ways to avoid problems of renovation of parts of the gas distribution mechanism.

Abstract: Atoms constituting a metal define its molecular crystal structure (atomic system) and interact in molecular dynamics simulations of nanometric cutting of the metal. The removal of the material (metal) at nanoscale and generation of high quality surface with a nanometric finish is largely influenced by the mechanical and physical properties of the metal as it associates with the metal lattice (atomistic) structure. Improved studies of the molecular modelling (behaviour of molecules) as it creates mathematical models of molecular properties and behaviour of atomistic systems are required for condition prediction of a nanometric surface finish. In this study, atomic system of rapidly solidified aluminium (RSA) alloy, grade RSA 431, with the use of its alloying elemental compositions by weight percentage is designed and constructed with cell geometry and atom positions that are written into a data file using AtomsK program. In addition, atomic concentration influencing the structural properties of the alloying elements were calculated. Obtained microstructure depicts the spread of the elemental compositions and the data file is suitable for a code performing simulations on classical particles like the large-scale atomic/molecular massively parallel simulator (LAMMPS) software. Understanding the computer simulations (molecular dynamics) for analyzing the physical movements of atoms and molecules, and the peculiar characteristic properties of the composing alloying elements of the RSA 431 determine how much influence each of them (elements) has on the nanometric cutting surface. Hence, the nanometric surface finish of the RSA 431.

Abstract: Forming a metallic sheet along with the consideration of computer simulation and experiment had benefited the milling industry for a long time. The ideal forming, without an error, is a concerning topic. So, the computer simulation had the advantage then direct forming. To observe the results before doing the real experiments simulation comes handy. Which helped to set the parameters for the milling process for the single point incremental forming (SPIF) process. For milling, a CAD design was converted into a 3D model. For this, a conical shape of 3D modeling was made in fusion 360. After onwards, it was simulated for finding the maximum depth for the cracking point. Next for the experimental part, the maximum forming depth was considered, and used lubricant grease for reducing friction. While forming with the grease, the impact of parameters was also changed. Throughout the process, an optimization approach was set to reduce the cracking areas for the G-code. Along with the lubricant use, smooth milling finished surface was observed. To reducing the depth forming errors, an optimization approach was introduced in this research.

Abstract: The single point incremental forming (SPIF) process is a high-trend method for forming a metal in a desirable shape. Forming parameters is an important part of deforming metal sheets. So, while reshaping a metal sheet parameters like tools, toolpath, material properties, sheet thickness, and lubricant were considered. Since the Aluminum sheet is used world widely for the body parts of machines for manufacturing parts. So, an A5052 metallic sheet was formed for the improvement of the depth deforming through the SPIF process. While forming an A5052 sheet lubricant was used constantly. After deforming through the SPIF process, further evaluations of the formed part were examined with the nanoprofiling machine to evaluate the deformed areas. Moreover, the deformed part was analyzed for the nana profiling for the deformation occurs on the surface. Likewise, before forming a part, the A5052 design was computer analysis. The simulation part was studied for fixing the maximum depth.

Abstract: Carburized-quenched steel has a hard layer on the surface and a soft layer in the core. Internal fatigue cracks are observed around the boundary between these two layers under cyclic stress. In this research, we investigated the microstructures (carbon content, prior austenite grains and retained austenite) in the carburized-quenched chromium molybdenum steel bar (JIS-SCM415, diameter = 10 mm) failed by rotating bending test (RBT) at nominal stress amplitude of 716 MPa. After the investigations, we obtained three conclusions: the carbon content in the area from the surface to 0.1 mm depth was higher than other area; the prior austenite grain (PAG) sizes at 0.1 mm depth from the surface was almost the same as that of 0.6 mm depth; and the retained austenite which was indicated from the ratio of γ to α in the cross section ranging from the surface to 0.1 mm depth was decreased by rotating bending fatigue.

Abstract: Under high cycle and very high cycle fatigue, high strength steels break as a result of internal fracture from inclusions. In order to understand this fracture, “Fisheye” crack has been investigated. In our previous work we found that cracks grew from the boundary between the hard surface and soft core of case-hardened S45C, SUJ2 and SCM415 steel bars under rotating bending fatigue. These cracks were called “Transition area origin (TRO)” cracks. In this study, we closely observed the fracture surface of TRO crack areas in carburized JIS SCM415 specimens (under 734, 776 and 865 MPa). We found three features of the TRO cracks: outside of the TRO cracks had asperities; the shapes of TRO cracks were almost circular, and were different from those in S45C and SUJ2 steels; and the HAZ-TRO area which was located at hardened layer had some ridges, and the Core-TRO area at unheat-treated layer was smooth and flat.

Abstract: In order to research the relation between fracture and texture conditions of PEEK thrust bearing in water, the rolling contact fatigue, RCF test was carried out. And then, the specimen after test was observed with a laser confocal microscope. Three types of surface damage: single crack, flaking and multiple crack: were ob-served. Arithmetic Average Roughness Height, AARH’s around single crack and no-damaged area were calculated. AARH’s in these two areas have no sig-nificantly different each other. This means the effect of cracks on roughness was negligible, and vice versa. The changing of AARH during the test was also dis-cussed. AARH’s both of failure and non-failure specimens were decreased dur-ing RCF tests. AARH Range of non-failure specimens after test included that of the failure specimen. It indicated AARH was not dominated the condition failure of PEEK bearing in water. On the other hands, the load had a clear threshold. This means the failure of PEEK bearing in water is strongly affected by load.

Abstract: In large-sized metal structures, various stress concentrators are often present, which affects the operation of the material. These are intermittent bonds, holes, welded joints, material defects, etc. As a result of overloads under the action of an external cyclic load on structures in the area of stress raisers, the cycle asymmetry, the level of maximum stresses and deformations increase. In this case, the determination of the limit values of the stress cycles can be performed using a diagram of the limit stress amplitudes. The paper presents an engineering method for calculating the limiting stress amplitudes and constructing Hay’s diagrams. It is based on the use of mathematical models of classical linear and structural-mechanical fracture mechanics. Analytically and by calculation, the validity of the method is shown, which consists in determining the endurance limits and limiting stress amplitudes under high-cycle loading in a wide range of variation of the cycle asymmetry coefficient for ferrite-pearlite steels with a yield strength of up to 400 MPa. Thus, a generalized calculation method has been developed for determining the endurance limits for high values of cycle asymmetry and cycle stresses. The error of the method is estimated in the area of low-cycle load. The influence of constant and average load in a cycle on the endurance limit has been investigated both for high-cycle and low-cycle loading. The proposed approach allows to construct Smith and Hay’s fatigue diagrams for the tensile region, taking into account the structural characteristics of the material and the error allowed for engineering calculations.

Abstract: Nowadays, our society has the responsibility of reducing the energy consumed in the building sector. A promising technology to achieve this goal is the implementation of thermal energy storage (TES) solutions in buildings envelopes. Phase change materials (PCM) which act as a thermal buffer, take advantage of the melting temperature of the material to change its state, improving building energy efficiency. This work explores and investigates how with a cheap PCM material, such as surf wax, high impact thermal results are obtained. To check and verify this condition, two concrete specimens were prepared with treated PCM aggregate and two without the PCM. The four test cubes were placed in an oven and using thermal sensors, the data about the temperature evolution during the process of heating and cooling was collected for further analysis. The results between the PCM concrete samples and the samples without PCM were compared, verifying the promising performance in terms of energy impact.