Simulasi Pembebanan Komponen Bender pada Desain Mesin Begel Fabricator Menggunakan Software Autodesk Inventor 2020

Stress analysis of the bender components in the design of the begel fabricator machine was carried out using FEA (Finite Element Analysis) with three variations of the constituent material parameters, namely 6061 aluminum, mild steel, and cast iron with a modulus of elasticity of 68.9 GPa, 220 GPa, 120.5 GPa, respectively. The test is carried out by a loading parameter 2520 MPa and fixed constraint. The maximum von misses stress and displacement obtained for each material parameter components using aluminum, mild steel, and cast iron are 17.78 MPa; 0.00765, 17.49 MPa; 0.00229, 17.62 MPa; 0.00427 respectively.

Keratoconus Diagnosis: Validation of a Novel Parameter Set Derived from IOP-Matched Scenario

Purpose. Considering that intraocular pressure (IOP) is an important confounding factor in corneal biomechanical evaluation, the notion of matching IOP should be introduced to eliminate any potential bias. This study aimed to assess the capability of a novel parameter set (NPS) derived from IOP-matched scenario to diagnose keratoconus. Methods. Seventy samples (training set; 35 keratoconus and 35 normal corneas; pairwise matching for IOP) were used to determine NPS by forward logistic regression. A large validation dataset comprising 62 matching samples (31 keratoconus and 31 normal corneas) and 203 unmatching samples (112 keratoconus and 91 normal corneas) was used to evaluate its clinical significance. To further assess its diagnosis capability, NPS was compared with the other two prior biomechanical indexes. Results. NPS was comprised of three biomechanical parameters, namely, DA Ratio Max 1 mm (DRM1), the first applanation time (AT1), and an energy loading parameter (Eload). NPS was successfully applied to the validation dataset, with a higher accuracy of 96.8% and 95.6% in the IOP-matched and -unmatched scenarios, respectively. More surprisingly, accuracy of NPS was 95.5% in the combined validation, an improvement compared to the two prior biomechanical indexes. Conclusions. This is the first study taking IOP bias into consideration to determine a biomechanical parameter set. Our study shows that NPS indeed offers comparable performance in keratoconus diagnosis. Translational Relevance. Determining a parameter set after eliminating the influence from IOP is useful in revealing the essential differences between keratoconus and normal corneas and possibly facilitating further progress in keratoconus diagnosis.

Stretching and Inflating the Nonlinear Elastic Inhomogeneous Hollow Cylinder

The influence of the inhomogeneity of material properties on the process of three-dimensional stability loss of a hollow cylinder stretched by axial force and loaded by uniform pressure on the outer or inner side surface is investigated. We used two standard models describing the compressible nonlinearly elastic material's mechanical properties, namely the three-constant Blatz and Ko model, as well as the five-constant Mournaghan model. Usage of the semi-inverse method allows the reduction of a three-dimensional cylinder equilibrium problem to the study of a non-linear boundary-value problem for an ordinary second-order differential equation. Stability analysis was carried out based on the linearization of the equilibrium equations in the vicinity of the constructed solution. The value of a de-formation characteristic for which there were nontrivial solutions of a homogeneous boundary-value problem for the equations of neutral equilibrium obtained in the linearization process was identified with the critical value of the loading parameter, i.e., the value at which the system loses stability. The coefficients of the cylinder's stretching or radial expansion and the dimensionless characteristic of the applied pressure served as such parameters. On the plane of the loading parameters, stability regions are determined. The influence of heterogeneity on the size and shape of these regions is analyzed.

Development of methods for calculating rod elements of steel structures under multi-parameter loading

In order to reduce the volume of calculation operations, a reverse course of the study of the strength and stability of the rod elements of steel structures in the general case of loading is proposed. For a given limit state in the cross section of the elastic rod element corresponding to the ultimate strain , using the elastic solution method and the «Section» algorithm, the real ultimate state in strength is established. The results obtained in this way are more reliable, since the development of plastic deformations (and for thin-walled elements - section reductions), are determined by the combined action of efforts. The stability of rod elements is known to be characterized by a violation of the equilibrium deformed state. Therefore, following the solutions of the strength problems, at the same loads, a number of stress states are considered in the most loaded section with various values ( ),according to which the «deformation» forces and the corresponding working cross-sectional area and the rod stiffness are determined. Using the latter, the inverse analytical solution of deformation problems determines the largest general loading parameter corresponding to the buckling coefficient.

«Reverse» method of calculating steel structure rod elements reinforced under load by increasing cross sections

To develop practical recommendations for strength and stability analysis in the general case of steel structure rod elements reinforced under load, there is proposed a «reverse» numerical-analytical calculation method, which allows reducing the calculation time by several orders of magnitude if compared with the currently used methods. For a given «elastic» limit state in the cross section corresponding to the criterion of maximum plastic deformation numerically, using the «Section» algorithm , the real limiting state of strength is established, namely, the general loading parameter and its relative eccentricities и . The results obtained in this way are more reliable than those according to SP 16.13330.2017, since the development of plastic deformations is determined by the joint action of forces. The stability of rod elements beyond the elastic limit is known to be characterized by a violation of the equilibrium deformed state. Therefore, following the technique of solving strength problems at a number of ultimate deformations by the «reverse» analytical method for the given flexibilities of the rod compressed with equal end uniaxial or biaxial eccentricities, the corresponding parameters of the total loading and its non-deformational eccentricities и are determined. In this case, the buckling factor will correspond to at and . Analytical solutions of such problems have sufficient accuracy for design practice and provide for all possible forms of buckling, namely, lateral, lateral-torsional and spatial ones.

A new time scale for turbulence modulation by particles

A new time scale for turbulence modulation by particles is introduced. This time scale is inversely proportional to the number density and the radius of particles, and can be regarded as a counterpart of the phase relaxation time, an important time scale in cloud physics, which characterizes the interaction between turbulence and cloud droplets by condensation–evaporation. Scaling analysis and direct numerical simulations of dilute inertial particles in homogeneous isotropic turbulence suggest that turbulence modulation by particles with a fixed mass-loading parameter can be expressed as a function of the Damköhler number, which is defined as the ratio of the turbulence large-eddy turnover time to the new time scale.

Strength analysis of composite rotor helicopter blade, having percussive damage, by limit equilibrium theory

Authors model the limiting state of the helicopter «ANSAT» rotor blade at different flight modes, taking into account the possible damage to the blade in the butt section. The method of variation of elastic constants, based on the limit equilibrium theory and allowing to obtain both upper and lower limits of the limit load, is used to estimate the strength. The stresses in the layers determined in accordance with the deformation law of the associated limit yield surface of these layers, are expressed in terms of the six-dimensional vector of generalized forces. Analysis of the limit stress state is reduced to the analysis of the limit state in the space of the generalized forces. The safety factors of the blade’s butt section depending on the azimuth angle of rotation of the blade are determined for the case when all the generalized forces are proportional to one loading parameter. The possibility of making internal diagnostics of damage areas using x-ray computer tomography is announced. It is proposed to use medical Siemens x-ray tomograph to perform such diagnostics.

Effect of Underloads on Plasticity-Induced Crack Closure: A Numerical Analysis

The effect of underloads is mostly quantified by the averaged effect on the fatigue crack growth rate, and the transient behavior is rarely investigated. The objective of this paper is to study the mechanisms behind the effect of underloads, periodic underloads, and underloads combined with overloads. A single underload smashes the material around the crack tip, producing a depression on crack flank and a local reduction of contact forces at the minimum load. The reduction of plastic elongation behind the crack tip has an immediate effect on crack opening level, which rapidly disappears with crack propagation. The smashing associated with the compressive force occurs mainly behind the crack tip position where the underload was applied. The effect of the underload is intimately linked to reversed plastic deformation, which explains its enhanced effect for kinematic hardening. The decrease of load below the minimum baseline load is the main loading parameter. The application of periodic underloads extends the effect of a single underload. The effect of the underload is enhanced by the presence of obstacles in the form of residual plastic deformation, which explains the great effect of underloads applied after overloads.

An elastic harmonic inclusion near a rigid harmonic inclusion loaded by a couple

We use conformal mapping techniques to solve the inverse problem concerned with an elastic non-elliptical harmonic inclusion in the vicinity of a rigid non-elliptical harmonic inclusion loaded by a couple when the surrounding matrix is subjected to remote uniform stresses. Both a size-independent complex loading parameter and a size-dependent real loading parameter are introduced as part of the solution procedure. The stress field inside the elastic inclusion is uniform and hydrostatic; the interfacial normal and tangential stresses as well as the hoop stress on the matrix side are uniform along each one of the two inclusion–matrix interfaces. The tangential stress along the interface of the elastic inclusion (free of external loading) vanishes, whereas that along the interface of the rigid inclusion (loaded by the couple) does not. A novel method is proposed to determine the area of the rigid inclusion.

STABILITY OF A CYLINDER FROM MURNAGHAN MATERIAL UNDER STRETCHING, COMPRESSION AND INFLATION

The problem of equilibrium and stability of a hollow cylinder subjected to simultaneous uniaxial tension/compression and inflation is considered within the framework of the three-dimensional nonlinear theory of elasticity. To describe the mechanical properties of the material of the cylinder five-constant Murnaghan model is used. By the semi-inverse method the three-dimensional problem is reduced to the study of a nonlinear boundary value problem for an ordinary second-order differential equation. For most sets of material parameters known from the literature, the presence of a falling section in the stretching/inflation diagram, indicating the possible existence of instability zones even in the area of tensile stresses, has been found numerically. The stability analysis was carried out using a bifurcation approach based on linearization of the equilibrium equations in the neighborhood of the constructed solution by means of the method of imposing a small strain on a finite one. The value of a particular deformation characteristic, for which non-trivial solutions of a homogeneous boundary-value problem exist for the equations of neutral equilibrium obtained in the linearization process, was identified with the critical value of the loading parameter, i.e. value at which the system loses stability. As a rule, the coefficient of stretching/shortening of the cylinder and the coefficient of increase/decrease of its internal or external radius were chosen as such parameters. On the plane of the above-mentioned deformation characteristics the areas of stability under tension and compression, as well as under compression by external force and inflation by internal pressure, are constructed. The forms of possible of stability loss depending on the type of stress state are constructed, and the effect on the stability of material and geometric parameters is studied.