Numerical evaluation of expansion loops for pipe subjected to thermal displacements

The thermal expansion can lead to the high stress on the pipe. The problem can be overcome using expansion loops in a certain length depending on the material’s elastic modulus, diameter, the amount of expansion, and the pipe’s allowable stresses. Currently, there is no exact definition for the dimension of expansion loops design both for loop width (W) and loop footing height (H) sizes. In this study, expansion loops were investigated with using ratio of width and height (W/H) variations to understand pipe stress occurring on the expansion loops and the expansion loops’ safety factor. Relationship between non dimensional stress on the expansion loop pipe was studied numerically by finite element software on several working temperatures of 400oF, 500oF, 600oF, and 700oF. It can be found that stress occurring on the pipes increases as the increases of W/H of the expansion loops and results in a lower safety factor. The safety factor of the expansion loops pipe has a value of 1 when the ratio of loop width and loop footing height (W/H) value was 1.2 for a 16-inch diameter pipe. Stress occurring on the pipe increases with the increase of the working temperature. Expansion loops pipe designed for 400oF can still work well to handle thermal extension pipe occurring on 500oF.

How to estimate fatigue strength of wood material

When wood materials are used for a mechanical structure, the fatigue strength should be estimated due to repeated loads they receive. This paper reveals that the methods to calculate allowable stresses along with American Society for Testing and Materials (ASTM) and Architectural Institute of Japan (AIJ) can take the strength reduction due to fatigue into account because the ASTM/AIJ allowable stresses against the static strength closely resemble the fatigue limit against the wood static strength.

Theoretical foundations of design optimization ship's control, decision-making systems and information processing

Problem setting. The problems of optimizing the protection parameters of REA structures operating under complex mechanical influences, their diagnostics of quality, reliability and strength, as well as structural and parametric synthesis in the last decade are devoted to the work [1 9]. However, these works do not consider the issues of optimisation of vibration prote ction parameters and strength of structures on the basis of determination of functional dependencies of forces against deformation and damping against deformation rate for vibration insulation systems and structural elements included in the instrument. The main results given in these works relate to the determination, at best, of resonant frequencies, which is insufficient to optimize vibration protection parameters and diagnose the reliability of devices. The aim. Develop a methodological basis for the use of quality and durability control and diagnostics methods to improve the reliability of the operation of ship information and control systems in extreme operating conditions by optimizing their vibration protection. Results. The basics of modeling the designs of radio-electronic equipment devices for various mechanical influencing factors are described. Description of models and mathematical peculiarities of organization of initial data for modeling is given. When comparing design stresses and allowable stresses, the strength of the product is determined. Allowable stresses are obtained using endurance curves for each material of the device design. Simulation of the panel instrument design under vibration impact is considered and processing of its results is presented. When creating a typical product operation model, the main operating modes and levels of external influencing factors and loads of each mode are determined. The example of the console instrument shows the procedure for modeling strength and determining the value of failure-free operation. It has been found that for a given console device the most complex effect is vibration, since it creates a multi-cycle loading of the structure, which affects the strength of the product as a whole. Practical significance. The proposed approach to determination of structural strength makes it possible to find the number of loading cycles under vibration impact for each element and time operating time, as well as the calculated value of failure-free operation of the console device. This simulation can be performed at any stage of the instrument design.

Research and development of a car body assembly structure using CAD/CAE systems

In the studies, a 3D assembly of a car body strut, and for express analysis, a module of the KOMPAS-3D APM FEM system are used. It is found, that the unit under investigation is equally effective in torsion of the body both to the left and to the right. The weakest structural elements are determined in terms of allowable stresses. Keywords: CAD/CAE systems, strength analysis, finite element model, stress state. [email protected], [email protected]

Allowable Stress Development of Diffusion Bonded Alloy 800H for Section III

There is increased interest in the application of compact heat exchangers (CHXs) for nuclear service given their high thermal efficiency and compactness. CHXs are fabricated by joining a stack of etched plates with dense microchannels through diffusion bonding. Diffusion bonding material has basic mechanical properties that differ from a base material, requiring appropriate mechanical properties and allowable stresses for design. Existing nuclear code ASME Section III, Division 5 does not address diffusion bonded materials . Hence, there is a need to develop material properties and allowable stresses of diffusion bonded materials and weldments. In this paper, one candidate material, Alloy 800H, was selected for diffusion bonding trials. Preliminary results obtained from a series of tensile and creep tests suggest that the diffusion bonded material is weaker than the base metal 800H. These experimental data are used in determining recommended allowable stresses of the diffusion bonded 800H material. In this paper, tables of the strength reduction factors for various allowable stresses which includes Smt, So, St, Sy and Su for diffusion bonded Alloy 800H are presented. These reduction factors are applicable to CHX design. The Larson Miller Parameter (LMP) is used to extrapolate short term creep tests to longer creep life and lower temperatures, and estimate the onset of tertiary creep strain.

Safety of Eurocode Model for Prediction of Shear Strength of Bridge Deck Slabs

Deck slabs of box girder bridges designed according to the theory of allowable stresses are mostly without shear reinforcement. In the case of new bridges, designed according to Eurocodes, significantly increases an application of shear reinforcement. This raises a question: are bridges built before implementation of the Eurocodes safe? The paper deals with safety analysis of the models for prediction of the shear capacity using results of more than 40 tests carried out on clamped slabs subjected to concentrated load. The analyses have shown that methods based on an effective shear width provide unsafe results for shear span to effective depth ratio larger than 3. A significant improvement of the model's safety has been attained by limiting the distance of critical section from the inner edge of the loaded area.

RESERVE CAPACITY OF LONGITUDINAL BEAM OF WAGON TRUCK UNDER THE ACTION OF UNIFORMLY DISTRIBUTED LOADING

Priority directions and measures among the main branches of urban electric transport are resource saving in the subway transportation system during its operation. First of all, this problem must be solved by scientific support, that is, at the stage of designing parts and components of vehicles. One of the main tasks that are solved at the design stage is to increase the load-bearing capacity of the parts by analyzing their stress-strain state. The article is devoted to the calculation of the load capacity reserve of the longitudinal beam of the front subway trolley under the action of evenly distributed over the entire length of the load without taking into account the transverse forces. The priority of the research topic is substantiated, the purpose and tasks are formulated. Two approaches to the power calculation of the bearing capacity of the longitudinal beam are introduced: the calculation of the permissible stresses and the limit state. In both cases elastic models of beams are considered. In the case of calculation on the limit state, the mechanics of the occurrence of plastic hinges at the places of rigid fixing of the ends of the beam are first substantiated. The beam still retains its load capacity. With the further growth of the external load, the emergence of a plastic hinge is justified even in the middle of the beam with the simultaneous loss of the beam of the bearing capacity. To simulate the behavior of the beam according to its characteristics, including the stress and the degradation condition of its load capacity, the mathematical formulation of the problem of calculating the load capacity of the longitudinal beam when calculating the permissible stresses and the limit state without taking into account the transverse force. The load-bearing capacity of the longitudinal beam in the calculation of permissible stresses and the limit state is analyzed. The analysis of the obtained results allows us to judge the effectiveness of the proposed mathematical model as a whole. The obtained equations for the maximum allowable load when calculating the limit state and the allowable stresses allow us to reliably estimate the bearing capacity of the longitudinal beam in both cases. The increase in the bearing capacity of the beam in the case of calculation on the limit is three times. The conclusions about the adequacy of the analysis of the bearing capacity of the longitudinal beam bearing capacity were made. Keywords: resource saving, beam, bearing capacity, allowable stresses, limit state.

Strengthening the existing connection of steel beams with a column

The paper presents a solution that includes strengthening the connection of a support column with beams from both sides, placed in a vertical plane together with the pole. All the bar elements connected in the analyzed node were made of hot-rolled steel I-sections. Due to the need to increase the load on the joined beams to the pole, load-bearing capacity of the primary connection is lost, which necessitates the reinforcement of the existing connection. The analysis carried out in this paper shown exceeding the allowable stresses in the column web at the place of joining the beams. The calculations made in this paper showed the possibilities of restoring the safe operation of the connection node in question, by introducing elements increasing its load-bearing capacity. In addition to analytical calculations, numerical analysis was also performed using the ADINA program.

Increasing the Overlap Factor in the Elastic Model of a Modified Gear

Coupled and approximate gears are considered in this article. Methods of localization of the contact patch and the elimination of edge impact are analyzed. Based on the solution of the Hertz problem, mathematical models of gearing in the MathCAD program are constructed, with the help of which the overlap ratio of the gearing is calculated taking into account contact deformations. Circular and parabolic modifications for cylindrical spur gears are proposed. The allowed values of the modification parameters are determined. Contact stresses are equal to the allowable stresses when calculating multi-cycle fatigue. The influence of contact deformation on the load capacity of non-conjugate gears is analyzed.