scholarly journals ЭКСПЕРИМЕНТАЛЬНОЕ ОПРЕДЕЛЕНИЕ ОСТАТОЧНОЙ ПРОЧНОСТИ ЭЛЕМЕНТОВ КОНСТРУКЦИЙ ПАРАШЮТОВ, ИСЧЕРПАВШИХ ЗАДАННЫЙ СРОК ЭКСПЛУАТАЦИИ

2019 ◽  
pp. 80-87
Author(s):  
Кирило Вікторович Миронов ◽  
Євген Федорович Кучерявий
Keyword(s):  
Compressive Force ◽  
High Strength ◽  
Technical Condition ◽  
Suspension System ◽  
Structural Elements ◽  
Design Elements ◽  
Textile Materials ◽  
Wide Range ◽  
Speed Up ◽  
Working Section

To make a decision on determining the periods of safe operation of parachute systems that have exhausted a given resource, it is necessary to know the parameters of their actual technical condition. Experimental destructive methods for determining the parameters of residual strength are considered: breaking strength and relative deformations during the breaking of the standard specimens.Parachute design elements to be examined include parachute dome fabrics, carcass reinforcement ribbons, strops, and suspension system belts. In order to ensure that all requirements set forth by regulatory documents for conducting an experiment with textiles, specialized devices have been developed, designed, manufactured and tested experimentally. These devices provide strength experiments on a universal tensile machine designed to work with samples of metallic materials.The need to create specialized devices is caused by a very wide range of braking forces (from tens to several thousand newtons), as well as by the specifics of synthetic textile materials of the parachute design elements. A set of devices has been developed that provide the required conditions for conducting rupture experiments on samples of textile materials. The created devices provide sufficient compressive force of the sample in the clips without slip-page and without violating the integrity of the contact surface of the studied synthetic textile materials. Ensuring that the sample is sufficiently compressed in the clamping devices of the tearing machine is ensured by special transitional gaskets and methods for creating a compressing force on the sample. Compressing devices and devices for conducting experiments with low-strength specimens of the dome fabric, with medium-strong reinforcing skeleton tapes, strops and high-strength straps of the suspension system are created. In order to speed up the preparation of samples for the experiment, methodologies have been created that ensure the required length of the working part of the sample and its fixation without warps. A universal strain gauge was developed to determine the change in the length of the working section of the specimen in 100 mm. Installing the meter on the sample under study allows you to measure displacements up to rupture. The meter is fastened to the specimen using spring clips. The developed devices were tested during the experiment with hundreds of samples of the structural elements of 3 parachutes.

scholarly journals Fatigue Resistance Models of Structural for Risk Based Inspection

2020 ◽  
Vol 6 (2) ◽  
pp. 375-383
Author(s):  
Sergei Belodedenko ◽  
V. Hanush ◽  
A. Baglay ◽  
О. Hrechanyі
Keyword(s):  
Fatigue Resistance ◽  
Influence Factors ◽  
High Strength ◽  
Technical Condition ◽  
Damage Function ◽  
Fatigue Tests ◽  
Structural Elements ◽  
Model Combining ◽  
Safety Margins ◽  
Complex Indicators

The current stage of civil engineering is characterized by special attention to the safety of structures with a long service life. Such objects were designed several decades ago and their safe operation was ensured by significant safety margins. Now this approach to safety has been replaced by the concept of acceptable risk. It forms the basis of a risk based inspection (RBI) maintenance strategy. The transition from preventive maintenance strategies to a technical condition maintenance is substantiated. Complex indicators of technical condition, suitable for RBI- maintenance, are considered. The methodology of the resource safety index (RSI) is proposed. The latter is used as an indicator of risk. Special models of fatigue resistance is required for its control. The purpose of this paper is to build fatigue models for critical structural elements that are serviced according to the RBI concept. Instead of the traditional S-N curve, the lifetime general equation (first model) be used, where by the arguments are the main influence factors. Along with this, a modified ε - N equation is proposed for deformation criteria. The novelty of this equation is that it uses the rate of S-N- curve (slope) obtained in the first model with high cycle fatigue. The second model, combining the results of fatigue tests, is the equation for the dispersion of durability. The third model is the accumulated damage function under overloads. The efficiency of the RSI method is demonstrated by the example of the reliability assessment of the high strength bolts. Thanks to RSI method forecasting, during RBI-maintenance, parts can be used 3-5 times longer than with traditional methods.

scholarly journals Determination of parameters of plastic deformation of elliptic membranes

2019 ◽  
Vol 15 (2) ◽  
pp. 90-95
Author(s):  
Nail K Galimov ◽  
Samat N Yakupov
Keyword(s):  
Plastic Deformation ◽  
High Strength ◽  
Middle Surface ◽  
Membrane Thickness ◽  
Structural Elements ◽  
Algebraic Equations ◽  
Design Elements ◽  
Calculation Results ◽  
Thin Walled ◽  
Determination Of Parameters

Introduction. Thin-walled structural elements, combining lightness with high strength, are widely used in all industries. Widespread round design elements. However, based on the functional purpose, thin-walled structural elements of various shapes in plan are becoming more and more common. Methods. A technique has been developed for the study of thin elliptic membranes for the case of plastic deformation under the action of uniform pressure. The deflections of the membranes in the experiment are more than ten thicknesses. In this regard, to solve the problem, the following are used: geometric nonlinear relations for the deformations of the middle surface (according to Kh.M. Mushtari and K. Z. Galimov), relations for finite displacements and deformations for curvature expressions (according to K.Z. Galimov), physical relations (according to the theory of plasticity A.A. Ilyushin). Due to the smallness of the membrane thickness, only tensile membrane strains and forces are taken into account. The problem is solved by the Bubnov - Galerkin method and reduced to solving a nonlinear system of three algebraic equations. The “shooting” algorithm for solving the resulting system of equations is described. Results. The work on the assessment of the reliability of the results. To estimate the error, the comparison of the calculation results with the experimental results of G.D. Golovlev was also performed. An example of the calculation of an elliptical membrane is considered.

scholarly journals Improving safety and reliability of Gazelle series vehicles by upgrading frame structures

2020 ◽  
pp. 39-44
Author(s):  
M. S. Dolmatov ◽  
◽  
S. A. Ivanov ◽  
A. G. Isaev ◽  
◽  
...  
Keyword(s):  
Load Capacity ◽  
High Strength ◽  
Technical Condition ◽  
The Body ◽  
High Tech ◽  
Passenger Cars ◽  
Load Bearing ◽  
Light Duty ◽  
Wide Range ◽  
Lap Welding

Introduction. The cargo frame is a load-bearing element of the car, since the body and chassis are installed on it. Therefore, high strength requirements are imposed on this node. For safe and reliable operation of the truck, the frame must be adjusted and balanced, since even minor changes in the geometry can negatively affect the overall condition and safe operation of the equipment. This article discusses methods for lengthening the load-bearing elements of trucks on the example of a light-duty car "GAZelle". Problem Statement. Car frame extension is a high-tech process that requires high precision, knowledge, and the use of a wide range of equipment. The extended frame adds a number of advantages to the car, which in turn makes it possible to transport cargo with larger dimensions. The main goal of this work is to enable the car to transport bulky cargo. Also, in the process of extending the frame, it is checked for cracks, breaks and corrosion foci and, if necessary, repairs are made, which increases the reliability, safety and service life of the entire structure as a whole. Theoretical Part. When extending the standard support, all attachments are removed from the car: fuel tanks, body, transmission, drive shaft. All that remains is the cab, the bridge, and the engine. Then the frame is cut in three places. Two cuts are made at a distance of 80 cm in the direction from the cab to the rear bridge, and the last one is made at a distance of 40 cm from the rear bridge in the direction of the rear overhang. Then a longer channel is installed on the frame. It is secured with rivets, bolts, or lap welding. After that, the structure is assembled back. This takes into account the redistribution of loads and the need for high-quality performance of all types of work. Conclusion. The frame is an integral part of not only trucks, but also an important component of passenger cars, as well as light-duty vehicles. Its technical condition is just as important as the condition of, for example, the braking system, as it also ensures the safety of both the driver and pedestrians. The lengthening of the frame in the conditions of repair and mechanical enterprises allows you to increase the load capacity of serial cars of the GAZelle series while ensuring their reliability and safety.

Theoretical study of the prestressing strand's stress by computer modeling methods

2020 ◽  
Vol 76 (11) ◽  
pp. 1139-1148
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
E. M. Golubchik
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Steel Microstructure ◽  
Compressive Stresses ◽  
Wide Range ◽  
Prestressing Strands ◽  
Increasing Temperature ◽  
Wire Strand

The modern construction industry widely uses reinforced concrete structures, where high-strength prestressing strands are used. Key parameters determining strength and relaxation resistance are a steel microstructure and internal stresses. The aim of the work was a computer research of a stage-by-stage formation of internal stresses during production of prestressing strands of structure 1х7(1+6), 12.5 mm diameter, 1770 MPa strength grade, made of pearlitic steel, as well as study of various modes of mechanical and thermal treatment (MTT) influence on their distribution. To study the effect of every strand manufacturing operation on internal stresses of its wires, the authors developed three models: stranding and reducing a 7-wire strand; straightening of a laid strand, stranding and MTT of a 7-wire strand. It was shown that absolute values of residual stresses and their distribution in a wire used for strands of a specified structure significantly influence performance properties of strands. The use of MTT makes it possible to control in a wide range a redistribution of residual stresses in steel resulting from drawing and strand laying processes. It was established that during drawing of up to 80% degree, compressive stresses of 1100-1200 MPa degree are generated in the central layers of wire. The residual stresses on the wire surface accounted for 450-500 MPa and were tension in nature. The tension within a range of 70 kN to 82 kN combined with a temperature range of 360-380°С contributes to a two-fold decrease in residual stresses both in the central and surface layers of wire. When increasing temperature up to 400°С and maintaining the tension, it is possible to achieve maximum balance of residual stresses. Stranding stresses, whose high values entail failure of lay length and geometry of the studied strand may be fully eliminated only at tension of 82 kN and temperature of 400°С. Otherwise, stranding stresses result in opening of strands.

SP 700

Alloy Digest ◽  
1995 ◽  
Vol 44 (6) ◽  
Keyword(s):  
High Strength ◽  
Heat Treating ◽  
Bend Strength ◽  
Beta Titanium Alloy ◽  
Superplastic Behavior ◽  
Temperature Performance ◽  
Beta Titanium ◽  
Wide Range ◽  
Alpha Beta ◽  
Cold Workability

Abstract SP 700 is a high strength, beta-rich alpha-beta titanium alloy. It was developed with the following attributes: (1) excellent hot- and cold-workability; (2) enhanced hardenability with a wide range of mechanical properties that can be obtained by heat treatment; and (3) superior superplastic behavior at low temperature (around 1050 K). This datasheet provides information on composition, physical properties, microstructure, elasticity, tensile properties, and bend strength. It also includes information on high temperature performance as well as heat treating. Filing Code: TI-107. Producer or source: NKK Corporation.

ALMAR 300 ALLOY

Alloy Digest ◽  
1978 ◽  
Vol 27 (7) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Elevated Temperature ◽  
Cold Working ◽  
High Strength ◽  
Heat Treating ◽  
Age Hardening ◽  
Ultra High Strength Steel ◽  
Wide Range ◽  
Iron Nickel ◽  
Useful Yield

Abstract ALMAR 300 Alloy is a vacuum-melted ultra-high-strength steel. The annealed structure of this alloy is essentially a carbon-free, iron-nickel martensite (a relatively soft Rockwell C 28) that can be strengthened by cold working and elevated-temperature (900-950 F) age hardening to useful yield strengths as high as 300,000 psi. The unique properties of this alloy make it suitable for a wide range of section sizes. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SA-349. Producer or source: Allegheny Ludlum Corporation.

USS TENELON

Alloy Digest ◽  
1975 ◽  
Vol 24 (5) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Elevated Temperatures ◽  
Stress Rupture ◽  
High Strength ◽  
Heat Treating ◽  
Creep Properties ◽  
United States Steel Corporation ◽  
Excellent Corrosion Resistance ◽  
Wide Range ◽  
Mild Acid

Abstract USS TENELON is a completely austenitic, nickel-free stainless steel with exceptionally high strength which is retained at elevated temperatures. It has excellent corrosion resistance in atmospheric and mild acid exposures and maintains nonmagnetic characteristics even when 60% cold reduced. It also has good stress-rupture and creep properties in the range 1200-1500 F. It has a wide range of applications. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness, creep, and fatigue. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SS-311. Producer or source: United States Steel Corporation.

SAE 8642

Alloy Digest ◽  
1981 ◽  
Vol 30 (7) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Physical Properties ◽  
Surface Treatment ◽  
Tensile Properties ◽  
Alloy Steel ◽  
High Strength ◽  
Heat Treating ◽  
Steel Mills ◽  
Wide Range ◽  
Strength And Toughness

Abstract SAE 8642 is a triple-alloy steel that can be hardened by austenitizing and quenching in oil. This steel has moderate hardenability with relative high strength and toughness, especially in the quenched-and-tempered condition. It is used in a wide range of components, parts and tools; examples are bolts, shafts, gears, wrenches, axles and housings. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: SA-382. Producer or source: Alloy steel mills and foundries.

DOMEX 550MC

Alloy Digest ◽  
2009 ◽  
Vol 58 (3) ◽  
Keyword(s):  
Physical Properties ◽  
Hsla Steel ◽  
Steel Structures ◽  
High Strength ◽  
Heat Treating ◽  
Bend Strength ◽  
Cold Forming ◽  
Wide Range ◽  
Hot Rolled ◽  
Earthmoving Machines

Abstract Domex 550MC is a hot-rolled, high-strength low-alloy (HSLA) steel for cold forming operations. It is available in thicknesses of 2.00-12.80 mm. The alloy meets or exceeds the requirements of S550MC in EN 10149-2. Applications include a wide range of fabricated components and steel structures, including truck chassis, crane booms, and earthmoving machines. This datasheet provides information on composition, physical properties, tensile properties, and bend strength as well as fatigue. It also includes information on forming, heat treating, and joining. Filing Code: SA-594. Producer or source: SSAB Swedish Steel Inc.

scholarly journals Temporal concatenation for Markov decision processes

2021 ◽  
pp. 1-28
Author(s):  
Ruiyang Song ◽  
Kuang Xu
Keyword(s):  
Markov Decision Processes ◽  
Large Scale ◽  
Optimal Solution ◽  
Upper Bounds ◽  
Black Box ◽  
Decision Processes ◽  
Optimal Solutions ◽  
Wide Range ◽  
Markov Decision ◽  
Speed Up

We propose and analyze a temporal concatenation heuristic for solving large-scale finite-horizon Markov decision processes (MDP), which divides the MDP into smaller sub-problems along the time horizon and generates an overall solution by simply concatenating the optimal solutions from these sub-problems. As a “black box” architecture, temporal concatenation works with a wide range of existing MDP algorithms. Our main results characterize the regret of temporal concatenation compared to the optimal solution. We provide upper bounds for general MDP instances, as well as a family of MDP instances in which the upper bounds are shown to be tight. Together, our results demonstrate temporal concatenation's potential of substantial speed-up at the expense of some performance degradation.

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