RU2156448C1 - Process of manufacture of bourdon springs - Google Patents

Abstract

FIELD: instrumentation engineering. SUBSTANCE: process of manufacture of Bourdon springs is specifically related to manufacture of restoring sensitive elements which are primary converters employed to measure pressure of fluid media from units to tens of MPa. Tube before deformation during process is filled with fine-grained filling agent, for example, sodium bicarbonate. Tube with filling agent is rolled prior to heating. Spring is bent by revolving around roller. Filling agent is removed by chemical way, for instance, by boiling in solution of acetic acid. Bending of deformed tube around roller can be conducted by slow or fast revolving with application of force from outside. EFFECT: possibility of manufacture of Bourdon springs to measure pressure from one to tens of MPa with effective relation of strength, sensitivity and dimensions. 2 cl, 8 dwg

Description

 It relates to the field of instrumentation, in particular to the manufacture of elastic sensitive elements, which are the primary transducers in pressure measuring instruments of fluid media, namely: the manufacturing technology of tubular manometric springs used to measure pressure from units to tens of MPa.

The tubular manometric spring is a hollow pipe bent along an arc of a circle, under the influence of internal pressure or making free travel λ or developing traction force Q _t in the absence of travel. The most common are single-coil springs; when it is required to obtain a larger stroke, multi-coil springs are used (see Fig. 1).

 A known method of manufacturing tubular gauge springs, the so-called Nagatkin springs (the cross section of which is shown in Fig. 2), which uses bar material as a workpiece. To obtain a pipe, a rod is drilled along its axis, a flat is applied to the surface of the pipe along its length and in the bending of the resulting pipe (1).

 I also found application and a method of manufacturing a spring, slightly different from the specified one, namely: instead of drilling the bar along the axis and subsequent flat application, only one operation is performed - drilling the bar, but in a direction parallel and offset relative to the axis.

 However, such a manufacturing method is acceptable if the inner diameter of the pipe is several times smaller than the outer diameter and the length of the pipe is small. A manometric tubular spring made of such a pipe for measuring pressure ~ from one to several tens of megapascals will have very high rigidity and its work will be ineffective: the ratio of displacement to the pressure that caused it (sensitivity) is small, and the safety factor is too large. For this reason, such springs are used to measure pressures of hundreds or more MPa.

 Closest to the proposed one is a method of manufacturing gauge tubular springs using a pipe as a billet (see the Handbook of Instrument Engineering Technology, vol. 3, Book II, “Assembly Technology of Elements of Instruments and Automation Tools” edited by A. N. Gavrilov, Moscow , 1964, p. 222) (6).

 A method of manufacturing a tubular gauge spring, adopted as a prototype, includes a pipe segment, annealing it, flattening along one of the axes to obtain a given cross section, flattening one end of the pipe, filling the tube with sand, salt or rosin, bending the spring, cutting its ends and filler removal, flushing, heat treatment of the spring. After heat treatment of the spring, the pressure is marked and then stabilized.

 Depending on the wall thickness of the tube, flattening it along one of the axes is performed in one or more operations; in the latter case, after each operation, the preform is thermally processed to obtain the necessary plastic properties. Steel blanks are sometimes flattened and hot.

 Heat treatment after bending the springs is carried out to relieve residual stresses in order to obtain stable elastic properties.

 By marking the pressure value, we mean the determination of the maximum working pressure measured by a specific tubular manometric spring (or a specific standard size) with the provision of specified operating requirements.

Такой способ изготовления имеет преимущества, поскольку дает возможность использовать в качестве заготовки стандартные трубы из самых различных металлов и сплавов, имеющие широкий спектр величин диаметра, толщины и длины с гарантированным выполнением различных важных требований, например, изготовления и поставляемые по ГОСТ 9941-81 "Трубы бесшовные холодно- и теплодеформированные из коррозионно-стойкой стали. Технические условия".This method is used in the manufacture of tubular manometric springs of a plane oval cross-section (see Fig. 3), which are most widely used. This is explained by a favorable combination of manufacturability in manufacturing and good pressure sensitivity, provided by a large ratio of the half lengths of the oval axes

This manufacturing method has advantages, since it makes it possible to use standard pipes from a wide variety of metals and alloys as a workpiece, having a wide range of diameters, thicknesses and lengths with guaranteed fulfillment of various important requirements, for example, manufacturing and delivered in accordance with GOST 9941-81 "Pipes seamless cold and heat-deformed from corrosion-resistant steel. Technical conditions. "

 However, as practice has shown, the method adopted for the prototype can be successfully used in the manufacture of springs from thin-walled pipes only. But these gauge springs can measure pressure no more than a megapascal. At high pressures, unacceptably large stresses arise in them, which affects their performance.

 At the same time, there is a need for pressure meters of the order of units to several tens of MPa, which use tubular gauge springs having a small effective area as the primary pressure transducer.

 The simplest and most often used method of transition to the manufacture of manometer-shaped tubular springs operating at high pressures (including above the megapascal) is the use of pipes with a greater thickness and their bending with a smaller radius R. It is these two geometric parameters that greatly affect tension in springs (2). This decision is accompanied by a decrease in size, which is also an important circumstance.

 But the implementation of such a design in the manner adopted for the prototype is not always possible. Particular difficulties arise when using thick-walled pipes, when their thickness is commensurate with the length of the minor axis b and the ratio of the radius R to the length of the major axis a is several units (see Fig. 3).

 Let us dwell in more detail on the consideration of this issue by the example of a spring of a plane-oval cross-section.

Оно сопровождается лишь изгибными деформациями малой величины (фиг. 4а), что позволяет получить отношение

в большом диапазоне. При сплющивании же толстостенных труб возникают очень большие деформации, особенно на поверхности наружной - в области тора - и внутренней - в области плоского участка. Следствием этого является сначала стремление трубы к уменьшению деформаций, проявляющееся в эффекте "проседания" поперечного сечения в направлении малой оси (фиг. 4б), а затем разрушение ее в местах наибольших деформаций.When flattening thin-walled pipes, it is almost simple to change the cross section from a circle to a flat oval with a given ratio of axis lengths

It is accompanied only by small bending deformations (Fig. 4a), which allows one to obtain the ratio

in a large range. When flattening thick-walled pipes, very large deformations occur, especially on the surface of the outer - in the region of the torus - and the inner - in the region of the flat section. The consequence of this is first the pipe’s tendency to reduce deformations, which manifests itself in the effect of “subsidence” of the cross section in the direction of the minor axis (Fig. 4b), and then its destruction in the places of greatest deformations.

 What characterizes the moment preceding the deformation of the destruction of the pipe during its flattening? To clarify this circumstance, we use the dependence of the pipe height after flattening H on the diameter D and the thickness S of the pipe. This dependence is used to test pipes manufactured according to GOST 9941-81.

Принимая во внимание, что "признаком того, что образец выдержал испытания, служит отсутствие после сближения сжимающих поверхностей до величины H на внешней и внутренней поверхностях трубы трещин или надрывов", установленным ГОСТом 8692-75 (СТ СЭВ 486-77) "Трубы". Метод испытания на сплющивание", можно считать этот размер H предельным для сплющивания.In accordance with the technical requirements of this GOST, pipes made of all 14 grades of steel, including 12X18H10T, 12X18H12T, 12X18H9, must withstand tests for flattening to size H between flattening surfaces, determined by the empirical formula

Taking into account that “a sign that the sample has passed the test is the absence of cracks or tears on the external and internal surfaces of the pipe after the compression surfaces are close to H,” established by GOST 8692-75 (ST SEV 486-77) “Pipes”. Flattening test method, "this size H can be considered as the limit for flattening.

Полученная зависимость показывает, что предельный размер при сплющивании зависит лишь от отношения толщины трубы к ее диаметру S/D. Еще более важным является анализ предельного отношения

которое также является функцией отношения S/D (3). В графическом виде функции

приведены на фиг. 5. Графики показывают, что относительная толщина трубы S/D сильно влияет на возможность ее сплющивания. Практически, при способе изготовления пружин, принятом за прототип, при больших толщинах труб нельзя ожидать реализации отношения

Если же учесть, что в размер H_пр уже входит и возможность "проседания" поперечного сечения, то величина этого отношения для получения плоскоовального поперечного сечения способом, принятым за прототип, существенно меньше, но и для предельного перед разрушением и для предельного состояния перед "проседанием" существует вполне определенная величина

зависящая от отношения S/D.It is advisable to express the above dependence for H _pr in terms of relative values

The obtained dependence shows that the limiting size during flattening depends only on the ratio of the pipe thickness to its diameter S / D. Even more important is the analysis of the marginal relationship

which is also a function of the S / D ratio (3). Graphically Functions

are shown in FIG. 5. The graphs show that the relative thickness of the S / D pipe greatly affects the possibility of flattening it. In practice, with the method of manufacturing springs adopted as a prototype, with large thicknesses of pipes, one cannot expect the realization of the relation

If we take into account that the size of H _pr already includes the possibility of "subsidence" of the cross section, then the value of this ratio to obtain a flat oval cross section by the method adopted for the prototype is significantly less, but also for the limit before fracture and for the limit state before "subsidence "there is a well-defined quantity

S / D dependent.

то очевидно, что возможности гибки трубы также определяются отношением S/D.As for the radius

it is obvious that pipe bending capabilities are also determined by the S / D ratio.

Это означает, что для любого из отношений S/D существует вполне определенная величина безразмерного наибольшего эквивалентного напряжения

соответствующего предельным условиям формообразования как по сплющиванию -

так и по гибке -

Безразмерное наибольшее эквивалентное напряжение

вместе с величиной действующего давления P определяют величину наибольшего эквивалентного напряжения в пружине (1):

Поскольку для обеспечения работоспособности пружины под действием давления P должно выполняться соотношение

где σ_упр - предел упругости материала пружины,
n_з - коэффициент запаса, при ограничении величины

для каждого значения отношения S/D может быть обеспечено измерение давления, не превышающего

Проведенный анализ с помощью номограмм, построенных на основе численного решения для пружин плоскоовального сечения, показал, что изменение отношения

вдвое (от 4^х до 2^х), что соответствует изменению S/D втрое (от 0,04 до 0,12), из-за ограничения возможности в сплющивании может позволить увеличить давление всего лишь ~ в 4.0 раза как при свободном ходе, так и условиях силовой компенсации.Thus, for any of the S / D ratios, there are quite definite quantities

This means that for any of the S / D ratios there is a well-defined value of the dimensionless greatest equivalent voltage

corresponding to the extreme conditions of shaping as flattening -

and bending -

The dimensionless greatest equivalent voltage

together with the value of the effective pressure P determine the value of the largest equivalent stress in the spring (1):

Since in order to ensure the operability of the spring under the action of pressure P, the relation

where σ _yr is the elastic limit of the spring material,
n _s - safety factor, while limiting the value

for each value of the S / D ratio, a pressure measurement not exceeding

The analysis using nomograms constructed on the basis of a numerical solution for springs of flat oval section showed that the change in the ratio

twice (from 4 ^x to 2 ^x ), which corresponds to a threefold change in S / D (from 0.04 to 0.12), due to the limited possibility of flattening, it can only increase pressure by ~ 4.0 times as in a free run, and conditions of power compensation.

 But a value of this order cannot satisfy the requirement to increase the measured pressure from one MPa to 10 or more MPa.

 Further, in the manufacture of the tubular gauge spring, the issue of bending with a filler is very significant. When bending thin-walled flattened pipes by the method adopted for the prototype, a filler (sand, salt, rosin) is used. This is caused by the need to preserve the shape and dimensions of the cross section of the pipe, obtained even during flattening. The smaller the radius R, the greater the cross-sectional distortions that may occur during bending.

 When bending thick-walled pipes, the deformations of the material are so great that, when it is impossible to fully realize due to the presence of the filler, very great efforts are developed on it. With the coarse-grained structure of the filler, which sand and salt have, this leads to a very dense penetration of grains into the voids between them and strong pressure on each other, and in the boundary zone, the metal filler can also lead to partial penetration of grains into the metal. This makes it almost impossible to remove the filler from the spring after it is flexible, especially if it is multi-turn. The use of rosin does not change much, given that its removal also requires high temperature.

 Therefore, the manufacturing method adopted for the prototype, and in terms of the use of filler when bending a flattened pipe, cannot provide high-quality manufacturing of thick-walled tubular springs with a small radius.

 In connection with the need to switch to the manufacture of a tubular manometric spring from a thick-walled pipe with a small radius R, a serious question arises about the possibility of bending such a spring even in the presence of a filler. Since in such springs the semiminor axis is commensurate with the thickness of the pipe, during bending, large plastic deformations must pass through the entire thickness of the pipe.

 Otherwise, residual stresses appear in the material of a large magnitude, which appear in the finished spring (after removing the filler) in the form of a distortion in the shape of the cross section, which leads to a loss of sensitivity of the spring.

 So that plastic deformations during bending of the spring pass through the entire thickness, it could be carried out, like rolling the pipe, in several transitions. But the implementation of this reduces the manufacturability of the operation, because requires a large amount of equipment.

 Thus, the urgent problem remains the manufacture of manometric tubular springs for pressures from one to several tens of MPa with an effective ratio of strength, sensitivity and dimensions.

 In the proposed manufacturing method, this problem is solved by filling the pipe before deformation with a fine-grained filler, for example, baking soda; rolling a pipe with a filler before heating it; bending the rolled pipe with filler around the roller; chemical removal of the filler (for example, by boiling the spring with the filler after trimming its extreme clogged areas in the solution of acetic acid).

в зависимости от S/D при сплющивании трубы; на графике нанесены данные по

конкретной манометрической пружины, изготовленной прокаткой трубы по предлагаемому способу; на фиг. 6 представлен график изменения внутренней площади поперечного сечения

в зависимости от отношения наименьшего размера сечения H к диаметру трубы, из которой изготавливается пружина; на фиг. 7 представлен условный график изменения наибольших эквивалентных напряжений в трубчатой манометрической пружине плоскоовального сечения в зависимости от параметра

главного параметра; на фиг. 8 изображена форма поперечного сечения трубчатой пружины, получаемая предлагаемым способом по п. 3.In FIG. 1 depicts a single-coil tubular gauge spring; in FIG. 2 shows cross-sectional shapes of Nagatkin manometric tubular springs; in FIG. 3 shows a plano-oval cross-sectional shape; in FIG. 4 schematically shows the formation of a flat oval cross-section of a gauge tubular spring by flattening a thin-walled (a) and thick-walled (b) pipe, as well as when rolling a thick-walled pipe (b); in FIG. 5 shows graphs of changes in the limit values of relations

depending on S / D when flattening the pipe; data on

a specific gauge spring made by rolling the pipe according to the proposed method; in FIG. 6 is a graph of changes in the internal cross-sectional area

depending on the ratio of the smallest section size H to the diameter of the pipe from which the spring is made; in FIG. 7 is a conditional graph of the change in the largest equivalent stresses in a tubular manometric spring of a flat oval cross section depending on the parameter

main parameter; in FIG. 8 shows a cross-sectional shape of a tubular spring obtained by the proposed method according to p. 3.

до предельных величин, реализуемых предлагаемым способом изготовления.It turned out that a manometric tubular spring, which serves for the most effective pressure measurement with limit values from units to tens of MPa, can be obtained from the pipe by technological means due to the simultaneous action of two factors with the optimal implementation of each of them:
- giving the pipe material during the manufacturing process of the spring higher elastic properties (σ _control ) while preserving them in the finished tubular spring;
- reducing the magnitude of the largest dimensionless equivalent stress in the spring by simultaneously increasing the thickness of the pipe S, reducing the radius of the spring R, increasing the ratio of the axes of the cross section of the spring

to the limit values realized by the proposed manufacturing method.

 Let us demonstrate the possibility of implementing this on a gauge tubular spring of a flat oval profile.

Свойства материала пружины - σ_упр1. Предельная величина давления, которую она может измерять - P₁.Suppose that adopted for the prototype method of manufacturing a spring with the limit of technologically feasible geometric parameters S _CR1 , R _CR1 ,

Properties of the spring material - σ _upr1 . The limit value of pressure that it can measure is P ₁ .

Свойства материала пружины - σ_упр2. Предельная величина давления, которую может измерять такая пружина - P₂.When switching to another manufacturing method, it is possible to realize other values of the limiting values - S _CR2 , R _CR2 ,

Properties of the spring material - σ _upr2 . The maximum pressure that such a spring can measure is P ₂ .

используя формулу [1]. Для упрощения анализа будем считать условия работы и требования к этим двум пружинам одинаковыми, поэтому можно положить равными их коэффициенты запаса.Find the pressure ratio

using the formula [1]. To simplify the analysis, we consider the working conditions and requirements for these two springs to be the same, therefore, their safety factors can be set equal.

Если же нельзя считать равными коэффициенты запаса двух пружин, то к правой части этого выражения добавиться лишь постоянный коэффициент, который не может изменить хода дальнейших рассуждений.Then

If the safety factors of two springs cannot be considered equal, then only a constant coefficient will be added to the right side of this expression, which cannot change the course of further considerations.

Из формулы [4] следует, что если, как указывалось выше, недостаточно изменения (увеличения) толщины S и (уменьшения) радиуса R, чтобы обеспечить требуемое отношение

то для решения задачи можно дополнительно привлечь увеличение отношения

т.е. повысить упругие свойства пружины, а также увеличение отношения функций

представляющих собой безразмерные наибольшие эквивалентные напряжения, за счет изменения отношения осей поперечного сечения.As mentioned earlier, the simplest solution to the problem by changing only the thickness S and radius R does not provide the required increase in the ratio

From the formula [4] it follows that if, as mentioned above, a change (increase) in the thickness S and (decrease) in the radius R is not enough to provide the required ratio

then to solve the problem, you can additionally attract an increase in the ratio

those. to increase the elastic properties of the spring, as well as an increase in the ratio of functions

representing the dimensionless greatest equivalent stresses due to a change in the ratio of the axes of the cross section.

 Obviously, the solution of the problem due to the corresponding increase in these relations also has its limits, because each of them has a limitation in its implementation. When going beyond these boundaries, a transition should be made to another technology for manufacturing a tubular manometric spring or to another design.

пли повышение упругих свойств материалов в уже готовой пружине, может быть получено двумя способами: выбором другого материала с более высокими упругими свойствами, а также повышением свойств материала трубы-заготвоки в процессе изготовления пружины.Increase in attitude

or an increase in the elastic properties of materials in an already prepared spring can be obtained in two ways: by choosing another material with higher elastic properties, as well as by improving the properties of the material of the billet pipe in the process of manufacturing the spring.

 The use of the first method is very limited for the reason that the choice of material in the manufacture of a tubular manometric spring is dictated not only by its properties, but mainly by the ability to provide other requirements for the spring, for example, resistance in certain environments or conditions, as well as manufacturability, i.e. . the ability to make a spring from this material. So, for example, stainless steel 12X18H10T has been very widely used in the manufacture of an elastic sensitive element. (UCHE) and, in particular, tubular manometric springs due to good corrosion resistance and manufacturability, although its elastic properties are small.

 The second method is to improve the properties of the material of the original pipe (in particular, from 12X18H10T) in the process of its manufacture. There are many such methods. However, the choice of one of them should be based on the possibility of obtaining a given cross section of the spring and the implementation of its bending.

хотя величины в числителе и знаменателе этого отношения могут относиться к разным точкам сечения. Это дает возможность маневрировать в способах решения задачи.Due to the complex cross-sectional shape of the tubular manometric spring, it is difficult to improve the properties of the material at all points. And as it turned out, this is not mandatory. It is known that under the action of pressure on such a spring at different points of the cross-section, equivalent magnitudes of different magnitude arise. And this means that in order to ensure operability, it is necessary that, at each point, irrespective of the magnitude of the elastic limit of the material and the magnitude of the stresses in each of them, firstly, the condition for operability [1] is met, and secondly, the condition for increasing the ratio

although the values in the numerator and denominator of this ratio may refer to different points of the cross section. This makes it possible to maneuver in methods of solving the problem.

 Knowing the features of the manufacturing process of a tubular manometric spring and the features of its behavior during operation, the most simple and effective solution to the problem is to combine the process of obtaining the cross section of the spring with the process of increasing the elastic properties of the material. This should be done by rolling the pipe in the direction of the axis of the pipe. In this case, rolling must be carried out in several transitions, but without intermediate annealing of the material. For each transition, hardening of the material occurs by capturing more and more new and larger sections of the pipe surface and compression deformations of the material under the rollers, with each transition penetrating to a greater depth from the surface and creating a riveting of the material.

 Obviously, the greatest hardening of the material occurs along the minor axis. With an increase in the number of transitions and with a decrease in the size H during rolling, the hardening zone expands towards torus surfaces. In the same direction, the hardening intensity decreases. It is known that the hardening of a material during plastic deformation causes an increase in all the mechanical characteristics of the material that determine the resistance to deformation (the limit of proportionality, elasticity, yield, strength and hardness). In this case, the tensile strength by deformation with full hardening can be increased by two to three times (4).

 Thus, rolling the pipe allows you to obtain a significant increase in the mechanical properties of the material and to the greatest extent along the small axis of the cross section. Toward torus surfaces, the degree of increase in mechanical properties decreases.

 An important circumstance in favor of the proposed solution is that the direction of rolling coincides with the direction of the arc forming a circle, which undergoes bending deformations under pressure under pressure. The texture that arises during rolling of a pipe in a material, as it were, directs its direction to create “fibrousity”, which during spring operation will resist fracture to a much better degree than crystallite material that has not undergone plastic impact in the desired direction.

 All this characterizes the hardening of the material during pipe rolling.

 In order to exclude the phenomenon of “subsidence” of the cross section during rolling of the pipe, leading to distortion of the cross-section, and thereby also ensure hardening of the material over a larger area, and especially in the area around the small axis of the cross-section, the rolling operation of the pipe must be performed with a filler placed in pipe cavity. So that the filler cannot be squeezed out of the pipe during the spring manufacturing process, one end of the pipe is clogged before filling, and the other is filled after filling. Filling with filler should be carried out tightly, without voids, taking into account large deformations and efforts from the side of a thick pipe during rolling and bending.

 To avoid the drawbacks indicated in the analysis of the prototype for the removal of filler, one should use a filler with a fine-grained (or fine-crystalline) structure, which can be removed quite easily after bending and cutting off clogged pipe ends. Removal of the filler should be carried out without mechanical and high temperature influences so as not to cause undesirable changes in the geometric dimensions and properties of the spring material. This condition is fully consistent with the chemical method of acting on the filler with the formation of substances easily removed from the internal cavity of the spring, especially with the formation of gaseous compounds.

 Of course, the filler, the substance used for the chemical reaction with the filler, as well as the substances resulting from the reactions, should not cause corrosive effects on the spring material.

 As shown by studies conducted in the manufacture of a tubular manometric spring from a pipe of 12X18H10T material, baking soda (sodium bicarbonate) meets all these conditions, and its removal by boiling in acetic acid.

 It was found that after rolling a thick-walled pipe with a filler (drinking soda), the cross section practically does not change its length either along the midline, or on the outer or inner surface. This means that the filler, as it were, "holds" the inner surface, smoothing out all the deformations along it. Those. shaping during rolling of a thick-walled pipe with filler occurs in the same way as when flattening a thin-walled pipe without filler.

(см. фиг. 6). Это изменение тем больше, чем больше изменение высоты трубы при прокатке. В то же время прокатка сопровождается увеличением длины трубной заготовки.The calculation showed that when rolling a pipe from round to flat oval, taking into account the revealed features of shaping, a significant change in the internal cross-sectional area occurs

(see Fig. 6). This change is greater, the greater the change in pipe height during rolling. At the same time, rolling is accompanied by an increase in the length of the tube billet.

 All this is evidence that the filler, squeezed by the rolling force in the direction of the axis of the pipe, acts as an "inner roll", providing the necessary deformation along the entire inner surface of the cross section in the axial direction and in thickness. In this sense, the “soft flow” of baking soda creates favorable conditions for shaping and hardening (texture).

 Thus, the filler used during rolling with the above properties not only protects against the occurrence of "subsidence" of the spring section, but also provides the best conditions for its shaping and obtaining higher mechanical properties of the material of a thick-walled spring.

Вопрос о рациональной величине

возникает из-за противоречивости требований.We now turn to the question of obtaining a rational ratio of the axes of the cross section

Question of rational value

arises due to inconsistency of requirements.

Это же требование к поперечному сечению должно выполняться, если необходимо повысить чувствительность трубчатой манометрической пружины.In order to obtain the greatest hardening of the material and the largest zone of its distribution, it is necessary to obtain the smallest possible value of the minor semiaxis of the cross section b and the largest possible ratio of the axes

The same cross-sectional requirement must be met if it is necessary to increase the sensitivity of the tubular gauge spring.

опасная точка находится на большой оси сечения, то с уменьшением отношения

опасная точка перемещается в область малой оси; при некоторых же значениях главного параметра пружины

опасная точка находится на торовой поверхности, но смещена от большой оси в направлении к малой.At the same time, under the action of pressure on a tubular manometric spring, with an increase in the ratio of the axes of the cross section, the largest equivalent stresses increase and the location of the hazardous point changes. If for large values of the ratio

the danger point is on the major axis of the section, then with a decrease in the ratio

the danger point moves to the minor axis area; for some values of the main spring parameter

the danger point is on the torus surface, but is offset from the major axis in the direction of the minor.

при изготовлении пружины предлагаемым способом по сравнению со способом, принятым за прототип.Can all these requirements be correlated correctly and how?
Consider the possibilities of reducing the size of b and increasing the ratio

in the manufacture of the spring of the proposed method in comparison with the method adopted for the prototype.

 It is known that when plastic deformation increases, the metal goes through two stages: the first is the hardening stage, the second is the softening stage (4). If the first stage is accompanied by an increase in resistance to deformation, then softening processes are accompanied by a temperature effect, i.e. an increase in the temperature of the deformed body as a result of heat released during plastic deformation, and acceleration of deformation.

 The same phenomena were observed when rolling a 6x1 pipe made of stainless steel 12X18H10T. Therefore, the distinction between these stages can be performed without difficulty.

 Thus, in order to provide the greatest hardening of the spring material, the rolling process of the pipe should be suspended before the start of increasing its temperature. This can be fixed quite accurately.

представлены на фиг. 5 в виде точек. Оказалось, что предлагаемый способ позволяет уменьшить

на 15%, а

увеличить ~ в 1,5 раза.When rolling the pipe by the proposed method from the pipe with a diameter of 6 mm, a thickness of 1 mm from 12X18H10T, the following dimensions were obtained: a _ol = 3.25 mm; b _ol = 1.25 mm; H _ol = 3.5 mm. Data for

presented in FIG. 5 in the form of dots. It turned out that the proposed method allows to reduce

15%, and

increase ~ 1.5 times.

некоторое уменьшение ее практически не вызовет увеличения

(см. фиг. 5).An increase in thickness can only lead to a slight decrease in

its slight decrease will hardly cause an increase

(see Fig. 5).

что объясняется особенностями протекания процесса формообразования сечения.Therefore, by rolling a thick-walled pipe with a filler, the mechanical properties of the material can be simultaneously significantly increased and the ratio

which is explained by the peculiarities of the process of section forming.

?
Эпюры σ_экв показывают, что для трубки с отношением осей

опасные точки располагаются по концам малой оси сечения независимо от величины главного параметра пружины κ (5).Where is the dangerous cross-sectional point at these values?

?
The plots of σ _equiv show that for a tube with an axis ratio

Hazardous points are located at the ends of the minor axis of the section, regardless of the value of the main spring parameter κ (5).

Они приведены на фиг. 7. На этом графике выделена штриховкой область, в которой наибольшие напряжения возникают на малой оси поперечного сечения. Нанесем значение

которое можно реализовать предлагаемым способом. Чтобы определить наибольшее эквивалентное напряжение, нужно определить минимально возможную величину главного параметра κ, которая соответствует минимальной величине напряжения.For a more thorough analysis of the largest equivalent stresses and their location according to the diagrams (5), graphs of σ $\genfrac{}{}{0ex}{}{\text{max}}{\text{eq}}$ in arbitrary units depending on the ratio

They are shown in FIG. 7. On this graph, the region in which the highest stresses occur on the minor axis of the cross section is highlighted by shading. Put the value

which can be implemented by the proposed method. To determine the largest equivalent voltage, it is necessary to determine the minimum possible value of the main parameter κ, which corresponds to the minimum voltage value.

соответствует точка, нанесенная на график на фиг. 7. Оказывается, что она находится в области, соответствующей положению опасной точки на малой оси.In the manufacture of the same tubular gauge spring, the minimum possible value of R = 8.5 mm was obtained. It corresponds to the value of κ _CR = 0.8.
To these values

corresponds to the point plotted in FIG. 7. It turns out that it is in the area corresponding to the position of the danger point on the minor axis.

этой области от 2^х и 4^х, то оно вполне реализуется для толстостенных труб (см. фиг. 5). Это означает, что предлагаемым способом может быть реализовано соотношение [4] для толстостенных труб в части возможности увеличения отношения

Изменения

в интервале от 2^х до 4^х, как показал анализ, приводят к небольшим изменениям безразмерного эквивалентного напряжения. Т.е. изменение

(с соблюдением определенной величины R) служит только для перемещения опасной точки пружины к малой оси.Thus, the position of the danger point and the place of greatest hardening of the material are the same. They will match according to the graph in FIG. 7, for all springs falling into the shaded area. Regarding the ratio range

this area from 2 ^x and 4 ^x , then it is fully implemented for thick-walled pipes (see Fig. 5). This means that the proposed method can be implemented relationship [4] for thick-walled pipes in terms of the possibility of increasing the ratio

Changes

in the range from 2 ^x to 4 ^x , as shown by the analysis, lead to small changes in the dimensionless equivalent voltage. Those. change

(in compliance with a certain value of R) serves only to move the danger point of the spring to the minor axis.

практически будет определяться изменениями толщины S и радиуса R. Как это было показано выше, оно может быть доведено до ~ 4 единиц.Therefore, the ratio of functions

it will be practically determined by changes in thickness S and radius R. As shown above, it can be brought up to ~ 4 units.

 Given the combined effect of increasing the mechanical properties of the material and the rational change in geometric parameters, the pressure acting on the manometric tubular spring can be brought up to 8-12 MPa.

 2. It turned out that the residual stresses arising during the bending of the spring do not distort the cross-sectional shape obtained during rolling of the pipe by the proposed method, and thereby ensure the necessary sensitivity of the gauge tubular spring, it is sufficient to bend the flattened pipe by slow rolling around the roller. This allows you to minimize residual stresses. In this case, it may be useful, for example, to use a flat lining on the outside of the section with respect to the roller and to continuously tap on it, directing the force mainly in the direction of movement of the pipe during bending.

 As shown above, the method according to 1 and 2 can be used to produce gauge tubular springs with the best sensitivity, but at pressures of the order of one tens MPa.

 It turned out that in order to increase the potential of such a spring in increasing the effective pressure and bring it to tens of MPa, it is enough to use the residual stresses that arise when bending a flattened pipe. To do this, bending should be carried out around the roller by quick rolling. To do this, you can use the second roller.

 After trimming the clogged ends of the spring and removing the filler, the residual stresses in the material cause the profile to “subside” and acquire the shape shown in FIG. 8. The best opportunity for this is the material in the areas of the spring along the minor axis from the outside.

 Such an arch has increased strength, since it is supported by residual stresses throughout its existence. The magnitude of the subsidence is determined by the moment of reaching equilibrium in the action of residual stresses and elastic properties of the material.

 Under the action of internal pressure, the "sagging" side of the cross section works like an arch, which, as you know, has a strength many times greater than the strength of the original surface (for example, a plane of oval section). This means that such a spring can be used to work with pressures of several tens of MPa, which is confirmed by experimental data.

 All of the above indicates the indisputable advantages of the proposed method of manufacturing a tubular gauge spring, which serves to measure pressure from units to several tens of MPa.

Literature
1. L. E. Andreeva. Elastic elements of devices Moscow, "Engineering", 1981, p. 327.

 2. V.I. Feodosiev. Elastic elements of precision instrumentation publishing house of the defense industry, Moscow, 1949, p. 47, 49.

 3 I.N. Zhibareva. On the design of elastic sensors (gauge tubular spring). Herald of Mechanical Engineering, N 7, 1997.

 4. S.I. Gubkin. Plastic deformation of metals. Moscow, Metallurgizdat, 1961, Volume II, p. 69, p. 99.

 5. L.E. Andreeva. Elastic elements of devices. Moscow, Mashgiz, 1962, p. 398.

 6. Reference "Instrumentation Technology", vol. 3, book II "Technology of assembly of elements of devices and means of automation", Moscow, 1964, p. 222 - prototype.

Claims (3)

 1. A method of manufacturing manometric tubular springs, which consists in deforming the original pipe to obtain the desired cross section, bending it with a filler around the roller, followed by removing the filler, characterized in that the pipe is filled with a fine-grained filler before deformation, for example, baking soda, the deformation is carried out by rolling pipes with a filler, spring bending is carried out by rolling around the roller, after which the filler is removed chemically, for example by boiling the spring in a solution of acetic acid.  2. A method of manufacturing manometric tubular springs according to claim 1, characterized in that the bending of the deformed pipe around the roller is carried out by slow rolling with the application of force to its outer side mainly in the rolling direction.  3. A method of manufacturing a gauge tubular springs according to claim 1, characterized in that the bending of the deformed pipe around the roller is carried out by quick rolling with the application of force to its outer side mainly in the direction of the spring radius.

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