Stress Safety Factor Research Articles

Feasibility of the tower crane jib made of composite material

The main purpose of this research is to design a jib of a tower crane using composite material and to compare the effects/performance on the whole machine due to this lightweight process. The research starts by sizing the jib with steel material. Many different load conditions were involved and different criteria were assumed; those are: stress safety factor, stiffness, dynamic performance (modal) and buckling phenomenon which is the most important parameter. Then other non-standard load conditions were applied to the tower crane: moving load and jib (rotation and elevating) and adopting wind variable in time. The results of these load conditions were assumed to design a new jib made of pultruded composite material. The next step involves the design of additional elements of the crane: ropes, counter boom, counterweight, electric motor, etc. The last step concerns the economic feasibility of the new solution. The results show that the weight of the jib made by composite material is about 25% of the one made by steel and the economic payout for making the composite arm can be equalized in about a year and a half of machine operation, making the proposed solution very worthwhile.

STRENGTH ANALYSIS OF A CYLINDER FROM CARBON-CARBON COMPOSITE MATERIAL AS A RESULT OF TEMPERATURE DEFORMATION AND SHRINKAGE

Using the solution of the Lame problem, we analyzed the stress-strain state (SSS) of a cylinder made of carbon forced carbon composite material (CFC) for the case of fixed ends. It is shown that the thermal stress safety factor is close to four. In addition, an engineering analysis of the strength of CFC cylinder due to possible shrinkage of the fibers was carried out in the work. It is shown that the safety factor is equal to 0.386 and can be the cause of the destruction of the CFC during manufacture and operation.

Multi-objective optimization of sandwich structures for reinforcing composite fuselages

This study introduces a simulation-based optimization approach that combines a multi-objective genetic algorithm and the finite element method to design sandwich structures to reinforce composite fuselages. The sandwich structure has been parametrized with a set of mixed integer-continuous variables representing the polymer core thickness, the number and weight of laminated fiberglass layers, and size and position of the structure. Automatic scripting builds the geometry of the structure, then mounts it in the fuselage, and finally creates a conformal mesh. During the optimization, each reinforced fuselage is subjected to several load cases specified by the CS-22 EASA design standard, determining the worst load condition. Two objectives were considered: increasing the reinforced fuselage’s minimum fiber stress safety factor for improved safety and reducing the number of layers of the sandwich structure to minimize manufacturing costs. Structural constraints were the mass of the sandwich structure and buckling and flexo-torsional deformation of the reinforced fuselage. Results show an efficient material arrangement due to the reduced number of layers in the sandwich structure and a stress safety factor surpassing that set by the standard. Finally, the reinforcement of a glider fuselage to incorporate a retractable electric propulsion system is presented as a real-world industrial application.

Оперативная оценка технического состояния стальных канатов по данным магнитной дефектоскопии

A combined approach to the prompt analysis of technical condition of steel wire ropes of various functions is proposed. It is based on the bearing capacity (strength) criterion and the magnetic testing results. The principals are stated related to the strength assessment of degraded rope with measured local wire breaks and loss of metallic area due to corrosion (abrasion). After processing the received diagnostic charts the strength analysis is performed by means of appropriate mechanical model in terms of weak element hypotheses used in structure mechanics. Stress analysis gives the conservative strength estimates which will be referred to reliability margin. The stress safety factor is evaluated regarding the steady and cyclic loading. Because the measured data are of random nature and do not account for the distribution of faults at cross-section the statistical modeling of wear location over wires is performed. The total strength decrease is determined by superposition of strength reduction due to metallic area loss, and due to the wire breaks. Thus, the stress safety factor is considered as a probabilistic indicator of the state of the rope strength. The rope in service should be discarded if its stress safety factor becomes less than the empirical allowable strength factor which defines the rope margin of survival capability as a partially worn-out structure. Adjusted for regulatory disposal rules, three categories of worn rope condition are considered: serviceable, with a limited service life, and inoperative. These categories are presented by the green-yellow-red ranges at so-called «rope status map» in specified coordinates «Number of wire breaks — Loss of metallic section». The rope bearing capacity is promptly assessed by placing two mentioned testing data in corresponding position at the status map. An example is given related to the assessment of the status map for the load-carrying cable rod of the well pumping unit. Based on the obtained results the recommendations are formulated for application of the rope status maps as the templates for service personnel concerning further operation.

Application of topology optimization method for the gothic greenhouse design

Purpose This research presents a design method for designing greenhouse structures based on topology optimization. Moreover, the structural design of a gothic greenhouse is proposed in which its structural strength has been improved by using this proposed method. In this method, the design of the structure is done mathematically; therefore, in the design process, more attention can be focused on the constraint space and boundary conditions. It was also shown how the static reliability and fatigue coefficients will change as a result of the design of the greenhouse structure with this method. Another purpose of this study is to find the weakest part of the greenhouse structure against lateral winds and other general loads on the greenhouse structure. Design/methodology/approach In the proposed method, the outer surface and the allowable volume as a constraint domain were considered. The desired loads can be located on the constraint domain. The topology optimization was used to minimize the mass and structural compliance as the objective function. The obtained volume was modified for simplifying the construction. The changes in the shape of the greenhouse structure were investigated by choosing three different penalty numbers for the topology optimization algorithm. The final design of the proposed structure was performed based on the total simultaneous critical loads on the structure. The results of the proposed method were compared in the order of different volume fractions. This showed that the volume fraction approach can significantly reduce the weight of the structure while maintaining its strength and stability. Findings Topology optimization results showed different strut and chords composition because of the changes in maximum mass limit and volume fraction. The results showed that the fatigue was more hazardous, and it decreased the strength of structure nearly three times more than a static analysis. Further, it was noticed that how the penalty numbers can affect topology optimization results. An optimal design based on topology optimization results was presented to improve the proposed greenhouse design against destruction and demolition. Furthermore, this study shows the most sensitive part of the greenhouse against the standard loads of wind, snow, and crop. Originality/value The obtained designs were compared with a conventional arch greenhouse, and then the structural performances were shown based on standard loads. The results showed that in designing the proposed structure, the optimized changes increased the structure strength against the standard loads compared to a simple arch greenhouse. Moreover, the stress safety factor and fatigue safety factor because of different designs of this structure were also compared with each other.

Development of a wind turbine using 3D printing: A prospection of electric power generation from daily commute by car

The design, construction, and development of micro-turbines using 3D printing has been an important advance in the wind energy field to explore the possibility of offering viable alternative for the electric power generation, reducing the pollution caused by fossil fuels. In this work, a five blade vertical axis wind turbine prototype was tested. The components were designed using CAD and the turbine was manufactured by additive technology in a 3D printer. The material employed for 3D printing was commercial polylactic acid. The mechanical properties of the material used were obtained by tensile tests under the ASTM D-638 standard. On the other hand, a static structural simulation was performed by finite element method. Maximum tensile stress safety factor, maximum principal stresses, and fatigue analyses of the main turbine components were computed. The turbine performance as function of rotational velocity and relative wind velocity was analyzed implementing an experimental set-up.

Strength analysis of motor shaft based on ABAQUS

Focusing on the situation of the motor shaft breaking in the work, using finite element software ABAQUS, considering the coupling effect of interference fit, working load, and eccentric load, the strength analysis of the motor shaft is carried out. The results show that the interference fit will cause the stress concentration of the motor shaft, and the stress safety factor of the motor shaft under the working load can meet the use demand, while the eccentric load will significantly change the stress distribution of the motor shaft and reduce its safety factor. The variation of assembly interference and eccentric load will significantly affect the stress distribution of motor shaft.

Effects of Heat Treatment on the Corrosion and Mechanical Properties of Stainless Steel 316L as Used in Biomedical Applications

This work examines the influence of heat treatment processes, using oil and water at various temperatures as quenching media, on the mechanical, corrosion, and microstructural properties of 316L austenitic stainless steel as used as a biomaterial for temporary and permanent bone repairs or grafts and as a plate bone fixation during periods of treatment. The results show that the highest microhardness rate is obtained using normal water as a cooling media; this sample reached 157.7 Hv, a 9.97% higher value than that obtained using oil media and an 18.66% higher value than that obtained using one-hour heating. The microstructure images for the quenched samples in oil displayed more evenly and uniformly distributed carbon particles, suggesting the formation of a more pearlite structure as compared with the water-quenched samples, however. The highest polarization resistance value was obtained when using water cooling media with two hours heating time; this reached 2.849 V/μA. Dec., while the minimum value, reached 0.185 V/μA. Dec., was obtained using the hot water cooling medium. The minimum corrosion rate value was obtained using the oil cooling media; this was 0.34 × 10-5 milli-in./year, while the maximum value reached 0.86x10-5 milli-in./year for the water cooling medium with a three-hour heating duration. The resulting equivalent von-Mises stress reached its maximum value at 285.24 MPa at 150 Kg patient weight and 5 mm plate thickness. The total deformation reached a minimum value of 0.0723 mm, while the stress safety factor reached a maximum value of 2.7 for a patient weight of 60 Kg when using 10 mm plate thickness. The equivalent elastic strain and the strain energy reached minimum values of 4.7 × 10-4 mm and 0.021 mJ for a patient weight of 60 Kg when using 5 mm plate thickness, respectively.

Seismic analysis and retrofitting countermeasure for 1315 kV capacitor with multi-column posts

A number of power substations and converter stations are inevitably built in high earthquake intensity regions. There are many types of electrical equipment with multi-column posts in power substations and converter stations. The PLC/RI capacitor with high seismic vulnerability is a typical electrical equipment with multi-column posts. A 1315 kV PLC/RI capacitor was modeled and analyzed using finite element technique. The modal analysis results show that the primary frequency of the capacitor is close to the earthquake dominant frequency. Additionally, the 2nd, 3rd and 4th order frequencies are within the range of the flat segment of the seismic response spectrum. After performing seismic analysis, the most fragile location was identified, that is the porcelain insulator at the bottom of the capacitor. The stress safety factor of the porcelain insulator is 0.71, which indicates the capacitor does not meet the seismic requirement for peak ground acceleration (PGA) = 0.3 g. To improve the seismic performance of capacitor with multi-column posts, enhancing connection stiffness of the structure is proposed. Based on this countermeasure, the thickness of the connecting plate between the upper hollow composite insulators and the porcelain insulators at the bottom of capacitor was increased from 20 mm to 50 mm. After the optimization, the 1315kV PLC/RI capacitor satisfies the seismic requirement for PGA value of 0.3 g.

3D Model of Bone Scaffolds Based on the Mechanical Behaviour for a Hybrid Nano Bio-composites

Ceramic/polymer Nano composites in the view of possessing design uniqueness and property combinations have gained a great attention and reported to be the materials of the 21st century that are not found in conventional composites. In the present work, an attempt has been made to study, develop and improve the bio-mechanic for a designed and fabricated Ceramic/polymer bio-composite for a human natural bone repair and replacement in the case of complex fracture and bone diseases by adding the Nano fillers ceramic particles to the Polymer Matrix Nano composites (PMNC) for fabricated a hybrid Titanium dioxide and yttria stabilized zirconia reinforced high density polyethylene (HDPE) matrix bio-composites properties. These bioactive composites have been investigated by using hot pressing technique at different compression pressures of (30, 60, and 90 MPa) at a compounding temperature of (180, 190, and 200 °C). The SOLIDWORKS 17.0 and the finite element ANSYS 15.7 software programs were used to the simulation, modelling and analysing of femur bone biomechanics that can withstand the highest stresses and strains. The response surface methodology (RSM) technique was used to improve and verify the results. For all the fabricated Nano bio-composites systems, the results showed that the obtained output parameters values were increased with increasing the process input parameters, also the vice versa for the strain energy and equivalent elastic strain values, also the Nano ceramic compositions represented the main factor influenced the results. The main investigates results of the current research deduced that for the increase of the Nano ceramic powder (TiO2) contain from 1% to 10%, the compression fracture strength and the micro-Vickers hardness values increased by 50% and by 8.45%, respectively, and when adding 2% of zirconia (ZrO2), an additional increase in the compression fracture strength and micro hardness by 28.21% and 40.19% achieved, respectively. When using 10% TiO2 + 2% ZrO2/HDPE bio-composite at highest compact temperature of 200 °C and compounding pressure of 90 MPa, the strain energy and the equivalent elastic strain reduced by 82.69% and 14.53% when compared with using of 1% TiO2 content. While when increasing the nano ceramic content from 1% to 10% without adding the ZrO2 nano filler, they reduced by 142.25% and 67.81%, respectively. The maximum equivalent von Misses stress obtained is equal to 39.957MPa and when increasing the nano ceramic content from 1% to 10%, the stress safety factors and fatigue live values increased by 58.38% and by 46.28%, respectively and when adding 2% of zirconia (ZrO2), the stress safety factor reached its maximum values, with an additional increase in its values by 21.42% and 69.40%, respectively. These results give great choices to use successful in vivo tests and for a better life performance with any age, patient status and degree of injury.

Experimental Mechanics Procedures for Applied Stress Analysis on U-bend Stainless Steel 304 by using Strain Gauges Technique

The industrial failed pressure vessel leakage was operating in various parameters such as temperature, pressure, grain size, applied stresses, residual stresses, stress discontinuities in pressure vessel nozzle and many more directly or indirectly factors which lead to stress corrosion cracking (SCC) case study. Laboratory experimental steps are shown in this research to roughly determine the applied stresses, although it is very difficult to find out the exact way to calculate the actual true stress and true strain applied on a bending austenitic stainless steel (SS) 304 during the pressure vessels fabrication process. The effect of strain rate method was used to calculate the external applied stress on SS 304 plate as per E8 standard test methods for tension testing of metallic materials. The stress-strain behavior of SS 304 plate on bending test as per the recommended practice for hot-rolled and cold-finished steel bars in accordance with Table A1.2 ASTM A 370-15 standard test methods and definitions for mechanical testing of steel products was investigated in the laboratory. The investigation was carried to evaluate the external applied stresses on 13 mm thickness of U-bend SS 304 plate. Strain gauges were used on U-bend samples to determine the external stress induced on bending SS 304 plate. The findings from this study suggest that, we should minimize the mechanical tensile stress concentrations due to both elongation and compression during the fabrication, welding and installation process which occurs at sharp edges and notches. Stress safety factor boundary imposed by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel code,Section VIII, Division 1, Part UG-23 maximum allowable stress value, and also the design and fabrication criteria should be followed by the engineers especially for the oil and gas industrial pressure vessels fabrications.

Seismic performance improvement of a slender composite ultra-high voltage bypass switch using assembled base isolation

Since the seismic performance of the bypass switch (BPS) cannot satisfy the stress safety factor requirement, an isolated combination of wire ropes with linear viscous dampers was employed. The assembled base isolation was designed using modal parameters, and the effectiveness of the isolation was validated numerically using finite element (FE) analysis and experimentally by the shaking table test. The numerical study shows that wire rope isolation can reduce the stress of a BPS considerably. Furthermore, the implementation of supplementary viscous dampers can further reduce the stress and, more importantly, displacement response, which is significant for UHV equipment. The middle section of BPS generates obvious high frequency vibration during test, although the root section still experiences the maximum stress response. Besides, testing verified the reliability of the FE model and confirmed that the stress safety factor requirement was satisfied. Therefore, the isolation comprised of wire ropes and a viscous damper is proposed to improve the seismic performance of the slender 800 kV composite BPS.

Modeling and simulation for mechanical behavior of modified biocomposite for scaffold application

Bones in the human body are a natural composite material that can be fractured due to impact stress and excessive loads. Human bones become less dense and strong when age increases, thereby they become more susceptible to fracture. The present work aims to study the effect of adding nano-ceramic particles on the mechanical properties to fabricate four types of hybrids of Titanium dioxide (TiO2) and Alumina (Al2O3) reinforced polyetheretherketone (PEEK) biocomposites. The objective of this study is to develop and improve the biomechanical properties of the fabricated biomaterials to withstand the loads of the daily human activities. Modeling and analysis of femur bone biomechanics were implemented by using the SOLIDWORKS 17.0 and the finite element ANSYS 15.0 software programs. The response surface methodology (RSM) technique and the Design Expert 11.0 software program were used to improve and verify the results of biomechanical performance of the fabricated biocomposites. From the current research results, it was deduce that the maximum equivalent (von- Misses) and shear stresses on the modeled femur bone are 120,93 and 60,80 MPa. The tensile for modeling the fabricated 20 vol. % TiO2/5 vol. % Al2O3/PEEK biocomposite material is higher than the one of natural femur bone by 10%. The maximum strain energy and the maximum equivalent elastic strain were reduced by 20% and 26,09 %, respectively. The stress safety factor values increased in 5,81%, and the fatigue life for the fabricated biocomposite is more than 40,43%, when compared with natural femur bone material.

저속차량 차동장치의 내구성능 해석

Low speed vehicle(LSV), golf carts have unique requirements to differential gear design. For double axle torque LSV differential loading conditions were determined with the help of analytical model and ANSYS finite element analysis. With stress safety factor 3.15, fatigue safety factor 1.08 and fatigue life 106 cycle ring gear teeth strength analysis is performed and structure design optimized. This allows reducing overall cost of differential unit.

Combined approach to damaged wire ropes life-time assessment based on NDT results and rope mechanics

Principles of strength assessment and life-time prediction of deteriorated wire ropes based on magnetic NDT technique are presented. The measured loss of metallic cross-section area due to abrasion, corrosion etc. and local wire breaks are treated as input data for mechanical model of rope structure. The rope is interpreted as a system with two degrees of freedom that enables to calculate the strains and stresses in each wire when the rope is subjected to tension, torsion and bending. Stress safety factor is considered as a generalized parameter that specifies the rope degradation and may be used for predicting the instant lifetimes during the rope operating history. The rope discard criterion refers to residual life-time calculated with respect to minimal allowable strength factor. Examples of integrity analysis of mine hoisting rope and jib crane rope under tension-bending fatigue loading are demonstrated. The residual strength estimates give the rope inspector further information that helps to make a valid decision on testing policy.

The Q-factor of flexure membranes

We report on the intrinsic or material quality factor (Q-factor)of a number of different materials, possible suited for the construction oflow loss flexures. Clamped foil flexure membranes made from titanium, a glassyalloy, Cusil and Havar (high strength non-magnetic alloy), as well asmonolithic flexure membranes made from titanium, niobium and Marval 18(maraging) steel, have been tested. The results show that the highestintrinsic Q-factor occurs for monolithic flexure membranes constructed fromniobium, with maraging steel also yielding a high intrinsic Q-factor. Othermaterials tested were shown to be significantly inferior. For a pendulum ofmass 10 kg, with a stress safety factor of δ = 0.3, we predict a maximumQ-factor of 3.1×107 for a niobium flexure, and 2.9×106 for amaraging steel flexure.