Finite Element Analysis of a Spur Gear Considering Mass Relief Strategies

This paper deals with analyzing the structural influence of mass reliefs in spur gears. For this purpose, a system composed of pinion and a gear was designed, such that for gear several geometries were designed with different reliefs shapes and soul thicknesses. From the proposed geometries, finite element analysis (FEA) was performed, and the tooth stresses of each model were compared with the solid gear. From the results, it was observed that the tooth stresses are reduced in some cases. Besides, from the aforementioned cases, it is possible to observe that the maximum stresses may take place in its core instead of the teeth (rim area). On the other hand, based on other cases, the core thickness plays an important role as a criterion that defines the local stress.

Morphing Winglet Design for Aerodynamic Performance Optimization of the CRJ-700 Aircraft. Part 1 – Structural Design

This study aims to design a morphing winglet structure for the CRJ-700 regional transport aircraft. The morphing technology is applied on winglets to demonstrate a significant increase of the aerodynamic performance of aircraft. From the aerodynamic data of the LARCASE Virtual Research Simulator VRESIM, the aerodynamic benefits in the cruising phase were obtained through a study on the ParaView software. The morphing winglet design was drawn using CATIA V5; this new concept included several structural components, as well as a simple and light mechanism allowing to orientate the winglet angles between 90° and -90° of inclination. The structural model was exported to HyperMesh structural analysis software. Maximum stresses were obtained, and the model demonstrated its resistance to maximum aerodynamic loads as well as load factors of -2G to 7G.

Analysis of a Replaceable Cutting Tooth of Bucket Chain Excavator

This paper briefly outlines the design of replaceable cutting teeth of bucket chain excavator, which are attached to a holder with a detachable joint. The description of the rock cutting process is very complex, so the investigation of the effect of lateral forces is complicated through cutting tests. We use accordingly numerical analysis to examine some segments of the cutting process. Our main objective is to present the finite element analysis of cutting teeth in which the linear increase of the lateral force is taken into consideration. The finite element analysis is a powerful technique, which is enabled to compute the stress and displacement distribution in cutting teeth. The simulation results have shown that the maximum stresses decrease if the lateral force increases. The geometry of the optimized cutting teeth will be safe under the given loading conditions.

Selection Methodology of Femoral Stems According to the Cross Section and the Maximum Stresses

The maximum stresses on a femoral stem must be known for selecting the right size and shape of the shaft cross-sectional area for reducing the stress shielding effect generated after the total hip arthroplasty (THA) surgical procedure. The methodology proposed in this study provides the tools to the designers of femoral stems and orthopedic surgeons to select the adequate femoral stem cross section, decreasing the stiffness of the stem, thus reducing the stress shielding effect in the patient bones. The first contribution is the theoretical development of the maximum static stress calculation for 12 different femoral stem models with the beam theory, followed by the comparison with the static finite element analysis (FEA) simulations and finally the experimental corroboration of one femoral stem model measuring the strain with linear strain gages and transform it to stresses, the three different approaches provide comparable results, with a maximum average error of less than 8.5%. The second contribution is the formulation of a new selection methodology based on maximum stresses in the femoral stem and the cross-section area for decreasing the stress shielding effect, optimizing the area needed for withstand the loads and decreasing the overall stiffens of the stem.

Concentration of stresses near the hole in contact with rigid cylinder in composite plate, taking into account lateral clearances

Problems. When designing bolted joints (BJ), it is necessary, in particular, to carry out their verification calculations for strength. At the same time, it is desirable to use express analysis: calculations by simple formulas of sufficient accuracy. For BJ of plates made of layered polymer composite materials (PCM), the problem has not yet been solved. The aim of the study. The task is to test the accuracy of three known formulas for quick calculation of the value of the stress concentration factor (SCF) in zone of contact of bolt-hole with a rigid cylinder (bolt). The study was carried out on contrasting examples of materials and schemes of reinforcement of plates made of PСM, taking into account possible clearance between bolt and hole in the real range: from zero to 1% of diameter. Methodology of implementation. Numerical calculations were made using the finite element method (contact problem) for the BJ of plates made of layered PCM. 3D orthotropy of each monolayer was provided. Three simple formulas of express analysis were tested. The results are summarized in the tables and many illustrations are given. Research results. Numerical estimates of depending of the SCF in zone of the surface of the bolt-hole from considered factors are obtained. The factors are the material characteristics, the schemes of reinforcement of plates made of layered PСM and the values of the clearance between bolt and hole in the plates, as well as the accuracy of the considered formulas. Conclusions. Changing the material and the scheme of reinforcement of plate made of layered PСM leads to a significant change in the values ​​of maximum stresses and SCF in zone of the bolt-loaded hole in the weakened by hole cross section of a plate. Considered formulas of the express analysis have insufficient accuracy for consideration of contrast properties of materials and schemes of reinforcement of a plate. Changing size of clearance between bolt and hole in the range from zero to 1% of the diameter leads to relatively small changes in SCF: up to 10% maximum. Additional research is needed.

Gripping of Anchor Fiber of Ukrainian Production with Fine- Grain Concrete

The results of tests for drawing anchor fibers with a length of 50 mm and a diameter of 1 mm, laid at the end of concrete prisms 50x50x100 mm made of fine-grained concrete of classes C 20/25, C25/30 and C 30/35 are presented. From the tests of 50 fibers, the average value of tensile strength was determined, which is equal to 1242 MPa with a coefficient of variation of 2.1%. Prisms were made of fine-grained concrete, which included cement with an activity of 41.2 MPa for concrete class C 20/25 and an activity of 50.8 MPa for concrete classes C 25/30 and C 30/35. Sand with a modulus of size 2.1 was used as a filler. The concrete mixture was prepared in a forced concrete mixer, and the concrete was compacted on a vibrating platform. Simultaneously with these prisms, cubes with dimensions of 150x150x150 mm and prisms with dimensions of 100x100x400 mm were made to determine the bottom and prism strength of concrete. The length of laying fibers into concrete was 10,15 and 25 mm. It is shown that the forces perceived by the end anchors and the smooth part of the fibers rise with increasing strength of concrete. The results of tests for drawing fibers from concrete prisms are given in tables 1 - 3. For the length of laying fiber 10 mm into prisms with strength fcm,cube = 29.31MPa and fcm,prism = 23.15MPa the maximum stresses during drawing were 515.30 - 549.04 MPa (average value - 532.10 MPa). At the same length of laying fiber into concrete prisms with strength fcm,cube = 34.76MPa and fcm,prism = 27.11MPa, these stresses were equal to 554.47 - 588.54 MPa (average value - 569.70 MPa). For the length of laying the fiber 10 mm into prisms with strength fcm,cube = 38.96MPa and fcm,prism = 31.14MPa, the maximum tensile stresses were 590.51 - 621.72 MPa (average value - 606.81MPa). At the specified strengths of the prism concrete, the maximum values of the average stresses for fiber drawing were on average 13.37 MPa for concrete of class C20/25, 14.34 MPa for concrete of class C25/30 and 15.27 MPa for concrete of class C30/35. With a fiber laying length of 15 mm into prisms with concrete strength corresponding to class C20/25, the maximum tensile stresses were 575.80 - 607.64 MPa (average value - 587.10 MPa). With such a length of laying fiber into prisms made of concrete class C25/30, these stresses were equal to 614.44 - 680.25 MPa (average value - 638.95 MPa). At the length of laying the fiber 15 mm into the prisms of concrete class C30/35, the maximum stresses during drawing were 681.14 - 692.99 MPa (average value - 685.44 MPa). The maximum values of average stresses for fiber drawing were on average 9.87 MPa for concrete of class C20/25, 10.70 MPa for concrete of class C25/30 and 11.52 MPa for concrete of class C30/35. At a fiber laying length of 25 mm into prisms with concrete strength corresponding to class C20/25, the maximum tensile stresses were 645.44 - 735.03 MPa (average value - 692.76 MPa). With such a length of laying fiber into prisms made of concrete class C25/30, these stresses were equal to 736.58 - 773.25 MPa (average value - 752.37 MPa). With the length of laying fiber 25 mm into prisms made of concrete class C30/35, maximum stresses during drawing were equal to 780.27 - 839.49 MPa (average value - 809.12 MPa). The maximum values of the average stresses during fiber drawing were on average 6.97 MPa for concrete of class C20/25, 7.57 MPa for concrete of class C25/30 and 8.12 MPa for concrete of class C30/35. The coefficient of anchoring capacity η, which under Ukrainian standards of fibroconcrete structures designing is equal to 0.9, as shown by the data of our experiments, is not constant, so it is necessary to take this into account in the formula for determining the tensile strength of fibroconcrete.

FRP pipeline performance in tensional and torsional S-lay installation loads

The loading conditions of a composite pipeline is the main factor for its dimensioning. During S-lay offshore installation of multilayered FRP pipelines, severe tensional and torsional loads take place in the above sea part of the pipeline. Since the wall pipe is multilayered and the material properties of the laminae and the laminate is anisotropic, the maximum stresses depend on the stacking sequence. In the present work, an analytical model is proposed for calculating the capacity of multilayered FRP pipelines to carry axial and torsional loads. Numerical results for typical multilayered filament wound E-Glass/Epoxy pipelines under axial tension and torsion are provided and discussed.

Fracture Areas Quantitative Investigating of Bending–Torsion Fatigued Low-Alloy High-Strength Steel

In this study, the impact of pseudo-random non-proportional bending-torsion fatigue loadings proportion on the fatigue life and the fracture surface topography was analyzed. Investigation was carried out for 24 specimens made of S355J2 steel with 11 different ratios of maximum stresses λ. For these cases, after the fatigue tests, the surface topography measurements were carried out using an optical profilometer, using the focus variation method. Three fracture zones were analyzed for each specimen: (1) total; (2) propagation; (3) rupture, taking into account the root average square height Sq and void volume Vv parameters. The results pointed that ratio of maximum stresses λ is the most influenced on volume surface parameters represented by void volume at a given height Vv, in the rupture area. A new fatigue loading parameter P was used, depending on fatigue life T and ratio of maximum stresses λ, which shows very good correlation in 4th degree type of fit, to void volume Vv parameter for the rupture area.

Analysis of the Frequency of Acoustic Emission Events in Terms of the Assessment of the Reduction of Mechanical Parameters of Cellulose–Cement Composites

The article proposes the application of the acoustic emission method as a technique for the evaluation of mechanical parameters of cellulose–cement composites. The analysis focused on frequency values in a time series analysis of elements subject to three-point flexural stress. In the course of a statistic analysis, it has been demonstrated that a significant reduction of the recorded frequency values is associated with a considerable reduction in strength. This allowed the authors to determine the range of frequencies related to the depreciation in the strength of an element. The tests were carried out on elements cut from a full-size cellulose–cement board. Samples exposed to potential operational factors (environmental and exceptional) were analysed. It was shown that the frequencies recorded before reaching the maximum load during bending of samples exposed to environmental factors (water and low temperature) were significantly different (were much lower) from the sounds emitted by elements subjected to exceptional factors (fire and high temperature). Considering the fact that the analysed frequencies of acoustic emission events occur before the maximum stresses in the material are reached and the elements are destroyed, this provides the basis for the use of the acoustic emission method to assess the condition of cellulose–cement composites in terms of lowering mechanical parameters by observing the frequency of events generated by the material during load action. It was found that generating by material frequencies above 300 kHz during bending does not result in a significant decrease in mechanical parameters. The emission of signals with frequencies ranging from 200 to 300 kHz indicate that there was a decline in strength exceeding 25% but less than 50%. The registration of signals with frequencies below 200 kHz indicates that the reduction in mechanical parameters was greater than 50%.

Impact of Load Retention on Aircraft Engine Parts Under Real Flight Cycle Conditions in Service Life Monitoring

One of the major problems in the development of algorithms for monitoring the life of aircraft gas turbine engines is that the character of loading in real flight cycles is crucially different from the character of the static and dynamic loading during the testing of samples. This paper proposes a method for taking into account the effect of retentions at maximum stresses and cycle temperatures on the low-cycle fatigue (LCF) of the heat-resistant alloys used in engine parts. Regularities in repeated-static loading (RSL) are used in combination with the method of linear accumulation of damage due to the LCF and RSL, with retentions of a variable length. A non-linear equation is derived for the summation of these damages, the solution of which determines the durability (life) of the part while taking into account the retention duration. The theoretical results were verified by using the experimental characteristics of the GS-6K and EI-437B nickel-based alloys, previously reported by other researchers.