Fabrication and Mechanical Testing of the Uniaxial Graded Auxetic Damper

Auxetic structures can be used as protective sacrificial solutions for impact protection with lightweight and excellent energy-dissipation characteristics. A recently published and patented shock-absorbing system, namely, Uniaxial Graded Auxetic Damper (UGAD), proved its efficiency through comprehensive analytical and computational analyses. However, the authors highlighted the necessity for experimental testing of this new damper. Hence, this paper aimed to fabricate the UGAD using a cost-effective method and determine its load–deformation properties and energy-absorption potential experimentally and computationally. The geometry of the UGAD, fabrication technique, experimental setup, and computational model are presented. A series of dog-bone samples were tested to determine the exact properties of aluminium alloy (AW-5754, T-111). A simplified (elastic, plastic with strain hardening) material model was proposed and validated for use in future computational simulations. Results showed that deformation pattern, progressive collapse, and force–displacement relationships of the manufactured UGAD are in excellent agreement with the computational predictions, thus validating the proposed computational and material models.

Effect of magnesium on some mechanical properties of 1200 Aluminium alloy

This paper investigated the effect of magnesium as a dispersion strengthening material on some mechanical properties of 1200-Aluminium (Al-Fe-Si) alloy, a typical commercial aluminium alloy used in the production of household utensils. 1200-Aluminium (Al-Fe-Si) alloy containing varying percentages of the dispersion hardening material (i.e. Magnesium) were produced and mechanical tests namely; hardness, tensile strength and impact strength were carried out. Also, the microstructures of the cast materials were studied. The results showed that increase in magnesium content, as dispersion hardening material improved the hardness, tensile strength and caused a slight decrease in impact strength of the 1200-Aluminium alloy. It is inferred from this work that using magnesium as a dispersion hardening material brings about corresponding improvement in some mechanical properties of 1200-Aluminium (Al-Fe-Si) alloy. Keywords: Magnesium, Aluminium alloy, dispersion strengthened, reinforced alloy, crystallographic formation Depth, Geothermal Energy

A Method for Determining the Workability Diagram by Varying Friction Conditions in the Upsetting of a Cylinder between Flat Dies

This paper aims to develop a method for determining the workability diagram by varying frictional conditions in the cylinder upsetting test. The method is based on a known theoretical relationship between the average stress triaxiality ratio and in-surface strains if the initiation of fracture occurs at a traction-free surface. This relationship is valid for any rigid/plastic strain hardening material obeying the Mises-type yield criterion and its associated flow rule, which shows the wide applicability of the method. The experimental input to the method is the strain path at the site of fracture initiation. Neither experimental nor numerical determination of stress components is required at this site, though the general ductile fracture criterion involves the linear and quadratic invariants of the stress tensor. The friction law’s formulation is neither required, though the friction stress is the agent for varying the state of stress and strain at the site of ductile fracture initiation. The upsetting tests are carried out on normalized medium-carbon steel C45E, for which the workability diagram is available from the literature. Comparison of the latter and the diagram found using the new method shows that the new method is reliable for determining a certain portion of the workability diagram.

Optimization of Clostridium tyrobutyricum encapsulation by extrusion method and characterization of the formulation

Purpose: To optimize the process parameters for the encapsulation of Clostridium tyrobutyricum (Ct) and to determine its in vitro characteristics.Methods: The process parameters, including the concentration of the wall and hardening material, Ct to gelatin ratio and hardening time, were studied by single factor analysis, while optimization was performed by orthogonal experimental design for the encapsulation rate of Ct.Results: Optimal conditions exhibited by orthogonal experimental design at a 92.17 % encapsulation rate with a viable count of 9.61 ± 0.06 lgCFU/g were: 6 % modified starch, 3 % sodium alginate, and 2 % CaCl2 at a Ct to gelatin ratio of 1:1 with a hardening time of 30 min. The survival rates of encapsulated Ct were higher than free Ct in simulated gastric (6.22 %) and intestinal juices (15.55 %). Reduction in viable counts of Ct at 90 °C were higher for free cells (44.76 %) than encapsulated cells (28.09 %) after 30 min of heat treatment. Correspondingly, encapsulation boosted the capacity of Ct to withstand the strong acidic conditions of the stomach and improved the storage properties of Ct.Conclusion: The results suggested that extrusion is a good technique for the encapsulation of Ct, as it enhances the viability of Ct during their transit through the gastrointestinal tract. Furthermore, encapsulation is favorable for Ct if planned for use in formulations where high temperature treatment is required.

Combined EXTRUSION OF GLASSES WITH A CONICAL BOTTOM. METHODOLOGY FOR CALCULATING TECHNOLOGICAL PARAMETERS OF CONSTRAINED EXTRUSION AT INITIAL DEFORMATION BY BENDING

The methodology for calculating the energy-power and deformation parameters of the process of constrained extrusion of glasses with a conical bottom part, starting with the bend of the workpiece. The extrusion of both non-hardening and hardening material is considered. In the latter case, the account of the hardening of the extruded material is described in detail. The above formulas allow us to determine such important parameters of the stamping process as total and specific deforming force, maximum pressure on the die wall, and an increase in the yield stress.

COMBINED EXTRUSION OF GLASSES WITH A CONICAL BOTTOM. METHODOLOGY FOR CALCULATING TECHNOLOGICAL PARAMETERS OF THE TRADITIONAL PROCESS OF CONSTRAINED EXTRUSION

The methodology for calculating the energy-power and deformation parameters of the traditional process of constrained extrusion of glasses with a conical bottom part, including preliminary obtaining by molding the outer conical section of the bottom part of the product and the subsequent reverse extrusion of the glass with an internal cavity of the required geometry, is presented. The extrusion of both non-hardening and hardening material is considered. In the latter case, the account of the hardening of the extruded material is described in detail. The above formulas allow us to determine such important parameters of the stamping process as total and specific deforming force, maximum pressure on the die wall, and an increase in the yield stress.

Research of stamping of unequal channel bars. Part 5. Methods for calculating the extrusion of channels. 3. Calculations of the extrusion of the hardening material

Experimental studies on the extrusion of channels from a hardening material have carried out. Comparison of the results with theoretical calculations showed the high accuracy of the obtained formulas. Keywords: die forging, extrusion, misalignment, punch, matrix, plane strain. [email protected]

COMBINED EXTRUSION OF GLASSES WITH A CONICAL BOTTOM. METHODOLOGY FOR CALCULATING TECHNOLOGICAL PARAMETERS OF THE TRADITIONAL FREE EXTRUSION PROCESS

The method of calculating the energy-power and deformation parameters of the traditional process of free extrusion of glasses with a conical bottom part, including preliminary formation of the outer conical section of the bottom part of the product by molding and the following reverse extrusion of the glass with an internal cavity of the required geometry. The extrusion of both non-hardening and hardening material is considered. In the latter case, the account of the hardening of the extruded material is described in detail. The above formulas allow us to determine such important parameters of the stamping process as total and specific deforming force, maximum pressure on the die wall, and an increase in the yield stress.

Development of a technology of gas-flame application of powders to increase wear resistance and adhesion strength

Every year, the world economy suffers enormous losses due to wear and corrosion of machine parts and equipment. With targeted preventive protection against wear and tear, these losses can be avoided. Along with the coating of new parts, this includes the restoration of worn parts. An effective method is the surfacing of materials with high performance properties. The quality of hardened parts depends on the properties of deposited material, so hardening material or alloy is selected taking into account the working environment of the part and the coating method. Today there are many self-fluxing surfacing powder alloys based on nickel, copper and others, obtained by different methods. The paper discusses the process of studying the gas-flame application of powders to increase wear resistance and adhesion strength. Experimental studies have been carried out to determine the optimal composition of the CrB2 master alloy introduced into the composition of the GP-Ir40 surfacing alloy. It has been found that to obtain the hardness of the deposited metal in the range of 450–600 HV, it is necessary to introduce CrB2 into the coating composition, within 10 % of the total mass. Thus, the strength of the alloy is increased by more than 54.41 HV. Tests for corrosion resistance in aggressive environments of hydrogen sulfide H2S, sulfuric acid H2SO4 were carried out. The wear resistance of ground pumps was evaluated, and the service life of wear-resistant ground pump parts made of the IChH28N2 alloy was determined. The new developed self-fluxing surfacing powder material based on iron with a hardening additive will be used to restore machine and equipment parts operating under conditions of abrasive wear, corrosion and elevated temperatures or corrosive environments