METASTABLE STRUCTURE OF AUSTENITIC MANGANESE ALLOY AND PROSPECTS FOR CREATION OF PARTS BASED ON IT

Comparative microstructural studies and mechanical tests of an experimental austenic manganese alloy and typical structural materials have been carried out. As a result of the research, relative data have been revealed, indicating high mechanical properties of the experimental alloy, which makes it possible to recommend it for machine parts operating at high load-speed operating conditions and temperature exposure up to 700 0C.

Relationship between Thermal Diffusivity and Mechanical Properties of Wood

This paper describes an experimental study of the relationships between thermal diffusivity and mechanical characteristics including Brinell hardness, microhardness, and Young’s modulus of common pine (Pinus sylvestris L.), pedunculate oak (Quercus robur L.), and small-leaf lime (Tilia cordata Mill.) wood. A dependence of Brinell hardness and thermal diffusivity tensor components upon humidity for common pine wood is found. The results of the measurement of Brinell hardness, microhardness, Young’s modulus, and main components of thermal diffusivity tensor for three perpendicular cuts are found to be correlated. It is shown that the mechanical properties correlate better with the ratio of longitude to transversal thermal diffusivity coefficients than with the respective individual absolute values. The mechanical characteristics with the highest correlation with the abovementioned ratio are found to be the ratio of Young’s moduli in longitude and transversal directions. Our technique allows a comparative express assessment of wood mechanical properties by means of a contactless non-destructive measurement of its thermal properties using dynamic thermal imaging instead of laborious and material-consuming destructive mechanical tests.

Reconstruction of Regression Relationships for Determination of Strength Values for Alloys of Products in Diffusion Welding

The article deals with the problem of obtaining the dependence of the product strength parameter on the welding time, welding temperature and pressure during mechanical tests, leak tests. The relevance of this work is due to the complexity of carrying out field experiments to identify dependencies. In particular, the complexity arises from the duration of diffusion welding and the high cost. Application of the method of regression analysis based on a non-compositional plan of the second order for three factors will allow to restore the dependence of the product strength parameter on the time during which welding was carried out, the temperature at which diffusion welding was carried out or could be carried out and on the applied pressure at which mechanical tests were carried out. In the current study, a non-compositional design of the second order for three factors was used - allowing to restore the dependence of the missing values of the strength of the product. The aim of the research is to improve the quality of mathematical modeling. Application of the proposed approach will make it possible to obtain the strength distribution function depending on time, temperature and pressure using the example of a product made of VT14 titanium alloy and 12X18H10T stainless steel. This will make it possible to obtain optimal parameters for the diffusion welding mode and to improve the quality of the resulting products.

A new stiffness-sensing test to measure damage evolution in solids

We propose and assess a procedure to measure the damage evolution in solids as a function of the applied strain, by conducting stiffness-sensing mechanical tests. These tests consist in superimposing to a monotonically increasing applied strain numerous, low-amplitude unloading/reloading cycles, and extracting the current stiffness of the specimens from the slope of the stress–strain curve in each of the unloading/reloading cycles. The technique is applied to a set of polymeric and metallic solids with a wide range of stiffness, including CFRP laminates loaded through the thickness, epoxy resins, injection-moulded and 3D printed PLA and sintered Ti powders. The tests reveal that, for all the materials tested, damage starts developing at the very early stages of deformation, during what is commonly considered an elastic response. We show that the test method is effective and allows enriching the data extracted from conventional mechanical tests, for potential use in data-driven constitutive models. We also show that the measurements are consistent with the results of acoustic and resistive measurements, and that the method can be used to quantify the viscous response of the materials tested.

Effect of Fibrillated Cellulose on Lime Pastes and Mortars

The use of nanocellulose in traditional lime-based mortars is a promising solution for green buildings in the frame of limiting the CO2 emissions resulting from Portland Cement production. The influence of the fibrillated cellulose (FC) on lime pastes and lime-based mortars was studied incorporating FC at dosages of 0%, 0.1%, 0.2% and 0.3wt% by weight of binder. The lime pastes were subjected to thermal and nitrogen gas sorption analyses to understand if FC affects the formation of hydraulic compounds and the mesoporosities volume and distribution. The setting and early hydration of the mortars were studied with isothermal calorimetry. The mechanical performances were investigated with compressive and three-point-bending tests. Furthermore, fragments resulting from the mechanical tests were microscopically studied to understand the reinforcement mechanism of the fibres. It was found that 0.3wt% of FC enhances the flexural and compressive strengths respectively by 57% and 44% while the crack propagation after the material failure is not affected.

Numerical Study on Fragmentation Characteristics of Granite Under a Single Polycrystalline Diamond Compact Cutter in Rotary-Percussive Drilling

Fragmentation characteristics of granite in rotary-percussive drilling are studied using the distinct element method. We developed a model to investigate the interaction between the rock and a Polycrystalline Diamond Compact cutter. The micro contact parameters in the model are calibrated by conducting a series of simulated mechanical tests of the rock. Sensitivity analyses are then conducted according the drilling performances which are quantified as the penetration displacement, the fragmentation volume and the specific energy, as well as the lateral force and the particle size distribution. Results show that the model can well represent the typical fracture system under indentation of the cutter, the torque fluctuation phenomenon in drilling and the formation of lateral chips, which verify the reliability of the model. The cutter with a back rake angle of 55°and impact frequency of 30Hz has the best penetration performance in evaluated parameters. Increasing the frequency has a great effect on the rock breaking speed under the coupling effect of impact and cutting in the low frequency range. Considering crushing efficiency, 50 Hz is the recommended impact frequency. This paper provides a useful tool to represent the fragmentation performance of rotary-percussive drilling and sensitivity analyses shed light on the potential ways to improve the performance.

Mechanical Tests Performed on Rubber Plates Used on Railway Vehicles

In order to place a product on the market that is completely safe for users, the manufacturer must go through certain steps: design, prototyping, execution and prototype validation through experimental methods, obtaining documents that allow to sell the product from certain public or private companies (for example homologation certificate) and series production. One of the most important steps is the validation tests of the prototype because it will depend on them that the prototype corresponds to the design requirements.

Determining the Stages of Deformation and Destruction of Composite Materials in a Static Tensile Test by Acoustic Emission

Composite materials are used in many industries. They are construction materials that are being used more and more often, which makes it necessary to accurately identify the process of their destruction. Recent decades have resulted in an intensive increase in diagnostic tests of structures and mechanical elements. Non-destructive testing (NDT) represents a group of test methods (surface and volumetric) that provide information about the properties of the tested element without changing its structure. The method of acoustic emission (AE) is also being used more frequently. Thanks to the ability to detect and locate signal sources, as well as to perform tests during operation, it is a method that is increasingly used in industry. In this article, the acoustic emission was used to analyze the changes occurring in composite materials. Obtained parameters helped to determine the signals originating from fibre delamination, fibre cracking, etc., as well as the starting point of these changes and the stress values at which these changes occurred. The analysis of acoustic emission signals recorded during the tests helped to determine the values of amplitudes characteristic for the destruction mechanisms of considered composite materials. Signals with an amplitude in the range of 30–41 dB may indicate elastic–plastic deformation of the matrix. Signals with an amplitude in the range of 42–50 dB indicate matrix cracks with the accompanying phenomenon of fibre delamination. Signals with amplitudes greater than 50 dB indicate fibre breakage. Based on the test results, the permissible stress was determined; when exceeded, the mechanisms of damage to the structure of composite materials accumulate. This stress limit for the tested material is 70 MPa. The use of the acoustic emission method in mechanical tests may contribute to a greater knowledge of composite materials used as a construction material, as well as determine the stresses allowable for a given structure.

Characterization of the Composition, Structure, and Mechanical Properties of Endocarp Biomass

HighlightsEndocarps have higher lignin content, cellular and bulk density, and hardness than typical biomass feedstocks.The impacts of lignin content, bulk density, and mechanical properties on energy consumption are discussed.Endocarps can be a potential feedstock for a biorefinery coproducing biofuel and bioproducts.Abstract. Lignin is an abundant biopolymer and a promising source of feedstock for high-value chemicals and materials. This study aims to characterize the lignin-rich endocarp biomass and identify features of this unique feedstock that are relevant to feedstock preprocessing and logistics. The chemical composition and cellular structure of walnut and peach endocarps were characterized using HPLC and scanning electron microscopy (SEM) imaging. Mechanical properties of the endocarps were investigated using nanoindentation. Mechanical tests revealed hardness values of up to 0.48 and 0.40 GPa for walnut and peach endocarps, respectively. With screen sizes of 1 and 2 mm, the specific energy consumption was 9.21 and 1.86 MJ kg-1 for walnut and 12.6 and 2.72 MJ kg-1 for peach, respectively, as determined using a knife mill. Milling energy consumption was correlated to screen size, lignin content, bulk density, and mechanical properties. This study provides critical information on feedstock supply logistics necessary to implement a novel feedstock in biorefineries and evaluate the economic feasibility for coproduction of biofuels and lignin-derived products. Keywords: Biomass feedstock, Lignin, Mechanical properties, Nanoindentation, Size reduction.