P 3.3 8 external mechanical impact. Insured event mechanical impact. External mechanical impact methods of confirming the resistance of electrical equipment

Let us consider the stability of instrumental equipment to mechanical stress using the example of aviation instruments and devices, since they operate under the most severe conditions of the complex action of all types of mechanical factors.

The main sources of external dynamic influences for aviation instrumentation (APA) are aircrafts (Aircraft) on which it is installed and the environment. Excitation of dynamic effects from an aircraft is called kinematic, and from internal devices LA - power. Force effects are most often a consequence of the operation of power supply units, air conditioning devices, hydraulic systems, fuel supply, etc. electromechanical devices with reciprocating moving masses or unbalanced rotating rotors.

Mechanical influences include: linear overload, vibration, shock.

During transmission from the source to the AUV and its elements, external mechanical influences are transformed - the amplitude-frequency characteristics of the oscillations, the amplitude and duration of the shock pulses change; there are transient oscillatory processes accompanying the effect of long-term linear loads.

Overload is the ratio of the effective acceleration to the acceleration of gravity. Linear overloads, except for short-term ones, cannot be eliminated or weakened. Therefore, the performance of the structures is ensured by increasing the rigidity and strength of the elements, which, as a rule, leads to an increase in the mass of the AUV structures.

AUV vibration is understood as mechanical vibrations of its elements or structure as a whole. The vibration can be intermittent or random. In turn, periodic vibration is subdivided into harmonic and polyharmonic, and random - into stationary, non-stationary, narrowband and broadband.

Vibration is usually characterized by vibration displacement, vibration velocity and vibration acceleration.

Vibration displacement with harmonic vibration is defined as

where Z - vibration displacement amplitude; - vibration frequency.

Vibration velocity and vibration acceleration are found as a result of differentiation (5.1):

Vibration acceleration with harmonic vibration is phase ahead of vibration displacement by an angle, vibration velocity by an angle.

Amplitudes of vibration displacement Z, vibration velocity , vibration acceleration and angular vibration frequency are the main characteristics of harmonic vibration. However, apart from them, harmonic vibration can be characterized by vibration overload

. (5.2)

If in (5.2) the amplitude of vibration displacement is expressed in mm, and the acceleration of gravity is in, then the relation for vibration overload can be written in the form where - circular vibration frequency.

Polyharmonic or complex periodic vibration can be represented as a sum of harmonic components.

For random vibration, it is characteristic that its parameters (vibration displacement amplitude, frequency, etc.) change over time by chance. It can be stationary and non-stationary. In the case of stationary random vibration, the mathematical expectation of vibration displacement is zero, the mathematical expectations of vibration velocity and vibration acceleration are constant. In the case of unsteady vibrations, the statistical characteristics are not constant.

In addition to vibration, the structure can be exposed to shock effects arising from operation, transportation, installation, etc. Upon impact, structural elements experience loads for a short period of time, accelerations reach high values \u200b\u200band can lead to damage to the elements. The intensity of the shock impact depends on the shape, amplitude and duration of the shock pulse.

The shape of the shock pulse is determined by the dependence of the shock acceleration on time (Fig. 5.1). When analyzing shock effects, the real shape of the shock pulse is replaced with a simpler one, for example, rectangular, triangular, half-sinusoidal.

The amplitude of the shock pulse is taken as the maximum acceleration upon impact. The duration of the impact is the time interval during which the impact pulse acts.

Damped vibrations occurring in the structural elements are a consequence of the impact. Therefore, in practice, it becomes necessary to protect AUV structures simultaneously from shocks and vibrations, since in real operating conditions, structures are often subjected to complex mechanical influences, which should be reflected

when designing protective equipment.

The structural elements of the AUV are characterized by their mechanical resonance frequencies, varying over a wide range depending on the mass and rigidity of fixing the component parts. In all cases, the formation of a mechanical oscillatory system in the load field should not be allowed - this applies to circuit boards, panels, housings, installation wires and other parts of the APU structure.

The field of loads is understood as the mechanical loads of the system caused by oscillations of various frequencies and amplitudes during testing, installation, transportation and operation.

As a result of mechanical influences, reversible and irreversible changes can occur in the AUV structural elements.

Reversible changes are characteristic of the electronic equipment of the APA, which leads to a violation of stability and deterioration in the quality of the equipment functioning. The factors causing reversible changes can be grouped into the following groups depending on the physics of the processes occurring in the design:

Deformations in active and passive components, leading to a change in their parameters;

Violations of electrical contacts in connectors and permanent connections, causing a change in the ohmic resistance of the contacts;

Changes in the parameters of electric, magnetic and electromagnetic fields, which can lead to a violation of the conditions of electromagnetic compatibility in the structure.

Irreversible changes are inherent in the structural elements of APA, are associated with violation of strength conditions and are manifested in mechanical destruction of elements. The elements that are pre-loaded during assembly and wiring (bolts,

screws, rivets, welds with residual thermal stresses, bulk conductors with excessive tension, etc.).

The irreversible changes occurring in the structural elements of the APU under mechanical stress include fatigue failure.

Fatigue is the process of gradual accumulation of damage in the material of a part under the influence of alternating stresses. The mechanism of this process is associated with the structural heterogeneity of the material (individual grains are not the same in shape and size, are oriented differently in space, have inclusions, structural defects). As a result of this inhomogeneity, in individual unfavorably oriented grains (crystals) at alternating stresses, shears arise, the boundaries of which expand with time, pass to other grains and, covering an ever wider region, develop into a fatigue crack. The fatigue strength of materials depends on the magnitude and nature of the change in stresses, on the number of loading cycles.

AUV structures operating under mechanical stress must meet the requirements of strength and stability. Strength (vibration and shock resistance) to the impact of mechanical factors means the ability of structures to perform functions and maintain the parameter values \u200b\u200bwithin the limits established by the standards, after exposure to mechanical factors.

Resistance (vibration and shock resistance) to mechanical factors is understood as the ability of a structure to perform specified functions and maintain its parameters within the limits established by standards during exposure to mechanical factors.

It is well known that the physical and mechanical properties of a material, including concrete, are largely determined by its structure. By the concept of concrete structure, we will agree to understand the totality of the “macrostructure” created by the arrangement of aggregates and the “microstructure” of the cement stone, including the “cement stone - aggregate” contact zone.

The structure of concrete is a complex function of the physical-chemical-mechanical factors attached to it.

The “MACROstructure” of concrete is formed as a result of external mechanical action on all its components during the preparation and compaction of the concrete mixture. By and large, the perfection of the macrostructure of concrete reflects the recipe proportions of concrete (the ratio between the binder, aggregates and water), as well as the degree of uniformity of their distribution among themselves (mixing efficiency).

At the same time, the “MICROstructure” of concrete is formed both under the influence of external mechanical action and under the influence of colloidal-chemical and physicochemical processes occurring in the binder (dispersion of cement grains, their dissolution, followed by coogulation and crystallization, etc.)

It is characteristic that the change in time of all the basic physical and mechanical properties of concrete (strength, elasticity, shrinkage, creep, density) is mainly due to the kinetics of changes in the characteristics of the “microstructure” of concrete. We can control it (with varying degrees of efficiency) both at the level of the initial structure formation of the cement stone, and in the process of the initial formation of contact fields between the binder and aggregates. In practical terms, “control” of the microstructure of cement stone is possible along the path of chemical (various types of additives and modifiers in concrete), mechanical (external mechanical action on the initial stages of cement hydration) and thermal (heat and moisture treatment).

As one of the most effective ways modification of concrete parameters both at the level of "microstructure" and at the level of "macrostructure" is a vibration effect on the concrete mixture at the stage of its preparation - vibration activation, vibration mixing. Even more effective is the mechanochemical control of the microstructure of cement stone, when solid-phase reactions (mechanical activation) and (or) direct chemical action of chemical modifiers (surfactants, electrolytes, polymers) are superimposed on the mechanical action.

10.2.4.1 Intensification of cement hydration processes in the process of vibration exposure.

If we consider microsections of a cement stone prepared by conventional mixing of components (Fig) and prepared in a vibrating mixer (Fig), the difference is clearly visible. In the latter case, the microstructure of the cement stone is more dispersed - the crystals of the neoplasms are much smaller. Accordingly, the structure of the cement stone is more homogeneous, there are less internal stresses and local microdefects, which significantly reduces the likelihood of the appearance of foci of destruction - as a result, the strength of such a cement stone will be higher.

Figure A micrograph of a cement stone preparation prepared by manual mixing of cement with water (dark zones - unreacted cement grains).

Figure A micrograph of a cement stone preparation prepared using vibro-mixing of cement with water (dark zones - unreacted cement grains).

Numerous experiments confirm that under the influence of external mechanical action (in this case, vibration), the processes of cement hydration are significantly accelerated (see Table)

Values \u200b\u200bof the degree of hydration and compressive strength during hardening of vibration-treated cement stone.

Characteristics of cement stone	Hydration degree (%)				Compressive strength (kg / cm2)
	1 day	3 days	7 days	28 days	1 day	3 days	7 days	28 days
Cement M-600, V / C \u003d 0.30, without vibration (control)				10.1	31.5	211.0
Cement M-600, V / C \u003d 0.30, vibration during laying - 6 minutes			10.2	12.6	56.0	298.0
Cement M-500, V / C \u003d 0.26, without vibration (control)		11.0	12.1	12.8	125.0	180.0
Cement M-500, V / C \u003d 0.26, vibration during installation - 6 minutes		11.1	12.5	13.3	132.0	255.0
Cement M-500, V / C \u003d 0.26, preliminary vibration activation - 10 minutes + vibration during installation - 6 minutes		12.2	13.4	13.6	216.0	450.0

Note: Cement from Brocno plant

10.2.4.2 Empirical prediction of the performance of vibroactivated concrete in comparison with conventional concrete.

When studying the influence of vibration effects on the process of concrete hardening, a characteristic phenomenon is observed: that absolute difference in strength between vibration-treated and control samples (prepared in a traditional way, without vibration exposure), which is formed at the beginning of the structure formation of the cement stone remains close to constant and during the further course of hardening.

As shown by numerous studies, the reason for the increased strength of concrete subjected to vibration is the compaction of coagulation structures. The reason for the constancy of the increase in strength in all time periods of concrete hardening is the same intensity of crystallization of both vibration-treated and control samples.

The fact of the constancy of the increase in strength opens up a wonderful opportunity to determine the absolute values \u200b\u200bof the strength of vibration-treated samples during hardening and, in connection with this, the effectiveness of vibration treatment, if there are data on changes in the strength of control samples and the initial difference in their strengths is known. From a practical point of view, an opportunity arises based on 12 - 24 hour test data. determine the final strength by recalculating the data of the control (not vibroactivated) composition hardening under similar conditions with a coefficient close to 1.08. (The increasing coefficient was determined experimentally - it reflects the fact that vibration treatment not only contributes to the improvement of coagulation structures and acceleration of the initial structure formation, but also is the reason for a certain increase and more complete development of structure formation processes at a later date.

The calculation can be carried out using the following simple formula:

Rvibro \u003d 1.08 * (Rcontrol + Rdelta)

Rvibro is the calculated strength of a vibration-activated sample for a given hardening duration

Rcontrol - experimental strength of a control non-vibration-activated sample for the same hardening period

Rdelta is the absolute difference in strength between vibration-treated and control samples at the age of 12 - 24 hours.

10.3 Activated and special cements as an alternative to high-strength, fast-setting and extra-fast-setting Portland cements.

10.3.1 Theoretical and practical features of the production of high-strength and fast-setting cements from special clinkers.

In accordance with the areas of application in concrete technology, it seems logical to divide Portland cement into the following classes: ordinary, high-strength, high-strength (HPTs), quick-hardening (BTTS), extra-quick-hardening (OBTC).

Portland cement of the M-400 brand is called ordinary. The class of high-strength cements includes M-500 cements. The high-strength class includes cements of the M-550 and M-600 grades (GOST 10178-76), and the fast-hardening class includes all cements with a compressive strength of at least 25.0 MPa after 3 days of hardening.

The first pilot batches of Portland cement in the USSR with an activity of about 55.0 MPa, according to modern estimates, were manufactured by VNIITs at the Volsk cement plants back in 1938.

Later, in the mid-50s, the first experimental batch of cement was produced at the Belgorod Cement Plant, corresponding in activity to the current M-600 grade. When producing pilot batches, very strict and difficult to achieve technological standards were used, which did not allow for the regular production of such cements.

To resolve these technological difficulties, a solution was proposed, the essence of which boiled down to a whole range of rather complex measures, which, nevertheless, made it possible to optimize all technological redistributions - from optimizing the mineralogical composition of special cements and ending with the features of their grinding and storage.

As a result, the teams of cement plants, together with narrowly applied research institutes, produced pilot and then industrial batches and began continuous industrial production of high-strength cement, first with an activity of 55.0 MPa (grade M-700 according to GOST 970 - 61) at the Bryansk, October ( Novorossiysk group), Zdolbunovsky. Subsequently, the production of cements with an activity of 60.0 MPa was also mastered at the plants Zdolbunovsky, Bolshevik (Volsk group), Belgorodsky, Bryansk, Abvrosievsky, Teplozersky.

The first experimental batches of fast-setting cement were produced in the USSR in the 1930s under the leadership of V.N. Jung and S.M. Royak. Its commercial production began in 1955 to meet the needs of the newly created precast concrete industry, and the original strength standards were lower than the current ones - about 10.0 - 12.0 MPa after 1 day of normal hardening and 20.0 MPa after 3 days of hardening with the current test methods.

The effectiveness of the use of high-strength and fast-hardening cements (VPC and BTC) in the construction and construction industry is due to the possibility of increasing the grade of concrete, reducing the material consumption of reinforced concrete products and structures, reducing the technological cycle of their manufacture, installation, installation under a working load, and, finally, an increase in the bearing capacity and reliability of structures, buildings and structures. These advantages sharply increase with an increase in the HCV activity up to 70.0 - 80.0 MPa.

In addition, entire areas of production of building materials are entirely dependent on the supply of special cements. So, for example, the production of foam concrete becomes economically feasible and highly profitable only when using fast-hardening cements of the M-500 and M-600 grades.

10.3.1.1 Mineralogical features of high-strength and fast-setting cements.

To obtain high-strength and fast-hardening cements, only raw mixtures with maximum reactivity are suitable, depending on the physicochemical nature of raw materials, the chemical composition and dispersion of the mixtures, The physicochemical nature of the raw materials is a combination of the geological and mineralogical characteristics of the main components - lime and silicate - determining their reactivity and resistance to grinding.

For the production of high-strength and fast-hardening cements, far from all raw materials used for the production of ordinary cements are suitable. In some regions, for example, Central Asia, the production of such cements is generally impossible - the raw materials do not allow.

In addition to the features of the selection of raw materials, high-strength and fast-setting cements are also distinguished by certain difficulties in their firing - special alite crystals (tricalcium silicate - C3S) of a strictly defined shape and size with a rhombohedral crystal structure should prevail in the clinker.

10.3.1.2 Influence of particle size distribution on the activity of HCV and BTZ.

Cement is produced by grinding specially fired raw materials - clinker. Like any fired product that has undergone melting-crystallization processes, cement clinker has a certain submicrostructure. Therefore, the granulometric composition of clinker after grinding in ball mills mainly depends on the nature of the internal crystal structure of the clinker - in the process of grinding, destruction primarily occurs along the least strong sections of the crystal structure of the clinker. This situation is due to the fact that our influence on the grain composition of the grinding products of drum mills with ball and cylinder loading can only be modifying.

Table 10.3.1.2-1

Granulometric composition of fast-setting, high-strength and high-strength cements

(C3S - 60-65%, C3A - 3-7%)

(modification of alite in clinker)	Type and brand of cement	Specific surface, cm2 / g
			less than 5 microns	5 - 30 microns
Zdolbunovsky (R-C3S)	BTTS-500	2500 – 3200	12 – 18	40 – 50
	BTTS-550	3200 – 3700	15 – 21	45 – 60
	OBTC-550	3500 – 3800	18 – 23	50 – 65
	VPC-600	4300 – 6100	25 – 40	55 – 70
	VPC-600	4000 – 4500	21 – 27	58 – 68
Novorossiysk (M-C3S)	VPC-550	3200 – 3700	17 – 20	40 – 45
	OBTC-550	3800 – 4000	19 – 23	42 – 55
	VPC-600	4500 – 4700	25 – 28	55 – 60
Bryansk (M-C3S)	VPC-550	3200 – 3700	8 – 12	65 – 71
	VPC-600	3600 – 4000	18 – 20	54 – 65
Volsky (M-C3S)	VPC-600	3900 — 4230	14 — 23	48 — 65

Note: All cements of the Zdolbunovsky plant were obtained by grinding in a closed cycle, the rest in an open cycle.

OBTC - extra-fast-hardening cement Rday \u003d 20.0 MPa

So, with fine grinding of clinker, it is impossible to avoid the formation of a fine fraction (less than 5 microns) in an amount of 12.5% \u200b\u200bof half the mass of the middle fraction (5 - 30 microns). In the absence of separation, a large fraction (more than 30 microns) will inevitably remain in the amount of 25 - 50% of the mass of the middle fraction. All other things being equal, the coarse fraction is 1.5 times less in cements from fine-crystalline clinkers than in cements from coarse-grained clinkers. The granulometric composition of high-strength cements (Table) is characterized by an increased content of fractions of 5 - 30 and less than 5 microns, and fast-hardening - fractions less than 5 microns. The linear correlation coefficient between the content of the fraction less than 5 μm and the strength of the cement after 1 day of hardening is 0.77 (therefore, this fraction is preferable in the BTC), and between the amount of the middle fraction and the activity of cement at 28 days of age - 0.68

The smaller size of alite crystalline blocks in comparison with belite is a likely reason for the concentration of alite in fine cement fractions. So, with 55% alite in the original clinker and a specific cement surface of 3000 cm2 / g, the fraction less than 5 microns contains on average 60% elite, and with an increase in the specific surface of cement to 5000 cm2 / g, already 75-80% alite. Thus, at the stage of grinding, there is a significant change in the chemical and mineralogical composition of cement, when different fractions of cement consist of, in fact, different minerals!

The depletion of the middle fraction in alite cannot be recognized as a positive factor. On the contrary, enrichment of the fine fraction with belite would help to activate its hardening. This is one of the most important problems in cement technology. Such a distribution of minerals is achieved in the cements of the Belgorod and Balakley plants (they have a similar raw material base in many respects) due to the dendritic structure of belite, which “reinforces” the intermediate clinker substance and increases its fragility. A large amount of belite is concentrated here in fine, and alite - in the middle fractions of cement, which explains the positive properties of the cement of the Belgorod and Balakley plants well known to builders - a rapid increase in strength, in particular during steaming, high crack resistance, reduced shrinkage and creep.

10.3.1.3 Relationship between the dynamics of hydration of cements from special clinkers and their grain size composition.

Studies have shown that with an increase in the fineness of cement grinding from 2000 cm2 / g to 6000 cm2 / g (with the optimal content of gypsum for each level of dispersion), the degree of hydration (by the content of non-evaporated water) and strength increase at 1 - 3 days of age, and at 28-day-olds increase only up to certain limits, and then decrease significantly. The optimal dispersion of cement grinding depends on the mineralogical features of the clinker, and primarily on the predominance of certain alite modifications in it.

In some cases, with an increase in the specific surface area of \u200b\u200bcement from 2000 to 3000 cm2 / g, the content of the fraction less than 5 μm generally decreases, which can cause a decrease in hydration and the absence of an increase in cement strength with a simultaneous increase in its dispersion.

The presence of a maximum dispersion of cement, exceeding which leads to a slowdown in hydration, is a relatively “young” discovery, which, nevertheless, explains many paradoxes encountered by modern researchers, who, in an attempt to obtain fast-hardening cements, are one-sidedly limited by its additional grinding.

This paradox can be explained by the influence of two oppositely acting factors - an increase in the reaction surface of cement particles interacting with water, and an increase in the shielding ability of hydrated neoplasms, which, surrounding the cement particles, prevent the access of water. At W / C \u003d 0.4, the degree of hydration of the fine fraction after 1 day is 100%, the middle fraction is 20%, the coarse fraction has practically not hydrated yet.

After 3 days, all small and already about half of all medium and large fractions will also be hydrated. And only after a month from 60 to 90 percent of all cement will hydrate.

Such a “stepwise” hydration of cement of various fractions forms a mechanism (first predicted at the tip of a feather by G. Kühl) that the contact zones between the hydration products of the medium and fine fractions “stick together” precisely the hydration products of the fine fraction (do not hit hard - as he was able to explain ).

All this points to the intensifying effect of the fine fraction on the hydration of the remaining cement fractions. Experiments on mixing cements of different fineness have shown that the optimal ratio of fine and medium fractions in HCV with rhombohedral alite is from 1: 4.8 to 1: 5.1. Without a small fraction, the HCV cannot be obtained in principle!

10.3.1.4 Basic technological schemes for the production of high-strength and fast-setting cements.

The main technological scheme for the production of high-strength and fast-hardening cements is based on the use of specially selected components of the raw material slurry for the clinker burning. Extraction of raw materials for BTC and VOC is a very troublesome and expensive undertaking, because its selection at the existing raw material pits of cement plants has to be carried out selectively. So at the Bryansk havod they discard the sandy part of the clay and chalk from the karst sinkholes. At the Zdolbunovsky plant - clay containing more than 20% quartz grains, at the Voskresensky plant - inclusions of silicified chalk (bruises), at the Novorossiysk plant - marls containing glauconite and phosphorites, etc.

The production of BTC and HCV very rigidly regulates the production of raw sludge - it requires a much more careful homogenization (this entails an increase in the capacity of the slurry pools) and finer grinding of the raw material to particles less than 40 microns. At one time in the USSR, only the Belgorod plant was able to fully meet the requirements of the technological regulations for the preparation of sludge for firing clinker for special cements.

There are no special technical difficulties at the stage of clinker firing in rotary kilns - the required thermal parameters of firing are well within the characteristics of modern kilns. And a number of domestic cement plants (in particular Balakleisky, Kamenets-Podolsky, Stary Oskolsky) at one time quite successfully brought their furnaces to modes that ensured the mass production of high-activity clinker from which cement grade M-600 and higher was subsequently obtained. But due to such an abnormal and undesigned operating mode (the furnaces were nevertheless designed for the production of ordinary cements), it was necessary to increase the fuel consumption for firing (increase the temperature in the sintering zone) and artificially reduce the productivity of the furnaces by 10-15% (to stabilize the zone sintering).

The peculiarities of the production technology of VPC and BTC also impose significant differences from the traditional production scheme for ordinary cements and at the grinding stage. The main feature of the grinding mode of the BTZ and, especially, the VPC is the use of the minimum possible average diameter of the balls in ball mills. This, in turn, makes it practically impossible to use powerful and high-performance drum mills of large diameter for grinding BTC and VPC (or significantly reduce their rotation speed from the design one).

All together this determines the fact that even modern mills operating in a closed cycle with separation, when grinding BTC and VPC, show productivity 40-50% less than when grinding ordinary cements.

Moreover, all the expensive tricks for the production of high-quality, fast-setting and high-strength cements can be completely leveled out in just a few months of storage. Even in bituminized five-layer bags, during storage, cement loses from 5 to 15 percent of its activity per month !!!

Therefore, all taken together (briefly given above) at all times caused an extremely “unfriendly” attitude of cement plants even to the very idea of \u200b\u200bestablishing a massive and constant production of BTC and VOC. And only when such high-quality cements were required for the most important objects, primarily military infrastructure and medium-sized machine-building, the “firm hand of the Party” could push cement plants to such achievements.

Is it any wonder that, in the absence of this “firm hand,” BTC and VOC also completely disappeared from the domestic cement market - objective economic prerequisites for their production have not yet emerged; it is cheaper to export such cements if the need arises.

(It is quite possible that the rise in cement prices in Russia will form a more favorable conjuncture, when the mass use of BTC and HCV becomes economically feasible - and then the domestic construction market again, like a quarter of a century ago, with enthusiastic breath and admiration will “savor” these charming any factory abbreviation technologist - BTTS, OBTC, VPC.)

(to be continued)

Case 1

Case 2

A- Primary action

B- Reaction without energy dissipation

C- Primary action

D- Reverse reaction with energy dissipation

In case 2, the connective tissue, due to the elastic element present in it, makes it possible to “absorb” the shock and spread it widely over the surface.

This property is called passive protection, extremely effective, even if it sometimes becomes a double-edged weapon. In cases of lashing due to the energy accumulated by the fluid masses of the body tissues, the damage manifests itself later.

"... and if this energy were not dissipated by its own fluid masses of fascial tissue and the consequences of a whip, push or injury would appear immediately, what damage would be done to the body?"

There is only one answer: of course, much more difficult!

Example: a knife blade tears tissue and creates a cut wound only when applied from the sharpened side; using the blunt side can lead to chafing, swelling, skin reactions, but not genuine organic damage; the only difference between these two situations is the area of \u200b\u200bthe affected surface. The larger the area covered by the injury, the less severe it will be biological damagecaused by trauma.

The second phase of the defensive role follows the first and consists in the propagation of the applied impact force through the continuous fascial system.

The force acting on the body leads to the concentration of kinetic energy at the point of impact, causing powerful damaging effects. The continuity of the connective tissue prevents a high concentration of kinetic energy; it is redistributed through tissue links and then dissipated by a number of factors associated with the resumption of movement and functional adaptation, both fascial and general organic, in which kinetic energy is converted into heat, electrical, etc., preventing the formation of a large amount of potential energy. This second phase is designated by the term active defense.

"Biological damage" is a strategy used by the fascial system to prevent the accumulation of kinetic energy, which has suddenly arrived in such a short time that the body is unable to endure and redistribute it (physics teaches that energy cannot be destroyed, but is transferred to other forms).

Osteopathy, with its fascial techniques, has been shown to be an effective weapon in neutralizing such situations, facilitating the redistribution of kinetic energy through ever-increasing dispersion and decreasing the potential for destructive power.

Role of fascia in coordination of movements

Fasciae and aponeuroses are involved in coordinating the movements of both muscles and viscera, separating the muscle structures with membranes and ensuring that the contractile groups targeting a similar (synergistic) role can work simultaneously to perform the same function.

Each membrane and muscle bed is assisted in the performance of their functions by the ability of the connective membrane to support a set of body parts. The nerve structures contained in each bed are in close mechanical relationship with the tissues that must be stimulated. The role of the nerves is carried out through the neuromuscular fibers, the Golgi tendon apparatus, Pacini's bodies and Ruffini's organs.

Ruffini endings

Are located in joint capsules and adjacent areas; are responsible for muscle contraction, which, together with subsequent movement, changes the tension of the capsule. Indefatigable structures are called upon during the movement so that it can be produced in a smooth manner, without jerking. In addition to allowing the position to be maintained, the direction of movement is noted.

Golgi endings

Slow adaptation structures, for a long time “Assimilate” the information directed to them. They are located in the ligaments attached to the joints and deliver information regardless of the level of muscle contraction in such a way as to inform the body about the position of the joints, moment by moment, regardless of muscle activity.

Pacini corpuscles

Found in supra-articular connective tissue; quickly adapt and inform the central nervous system about the degree of acceleration of the movement produced (acceleration receptor).

Muscle spindle

Regulates muscle tone. The location of the spindles as they attach to the skeletal muscle (tendon) parallel to the muscle fibers. While the spiral-circular ending responds quickly to the slightest change in muscle length, the colorful ending for balance only provides information after significant changes in muscle length. The muscle spindle is a “length comparison unit” that can provide information for a long time for each stimulation.

Inside the spindle there are thin inter-spindle fibers that change its sensitivity; they can change without any real variation in muscle length by means of a special y-gamma controlled by the fibers themselves.

Golgi tendon receptors

More reflects muscle tension than length. If an overload is found in an organ, it can with their help stop muscle activity and thereby avoid the risk of injury; this factor determines muscle relaxation.

Trigger points (trigger points, vibrators) are localized areas of great soreness and increased resistance; acupressure of these points often provokes muscle contraction / grouping, which, if held, causes pain in the targeted areas.

It is about signal posts that provide constant feedback with the central nervous system and higher centers regarding the instantaneous states of the tissue in which they are located. Their modulation can be caused by both psychic influence and changes in the chemical composition of the blood.

Chains

The neuromuscular system, contained in and in direct contact with connective tissue, enables direct synergistic participation when muscles attach to the aponeurosis and indirect synergistic participation when muscles attach to bone.

The concept of "muscle tension chain", introduced by osteopathy and then picked up and expanded by postural gymnastics, finds its application in the fascial concept.

The function of the guarantor of coordination of movements performed by the connective tissue arises from its connections with the nervous system (due to the purely mechanical action exerted on the nerve component and its sensitivity to tension); in addition to distinguishing between movement, intensity, strength, the spindle is able to activate the higher nervous system and develop new patterns of functioning. Often, this kind of adaptation goes beyond physiology in the compensations involved by the body, aimed at eliminating any kind of force that can cause pain.

If we consider our posture as a constant oscillation of establishing balance and its loss, aimed at maintaining an upright position of the body, it becomes understandable why, even in the presence of mild anomalies, our balancing system must perform corrections with great accuracy to maintain both a static posture (erect posture) and dynamic (movement).

When exposed to force, the fascial component of our body adapts to the situation, masking and “hushing up” the primary source of the problem in such a way as to cancel the nervous effect caused by the situation of discomfort or pain.

This fact allows only the last compensation produced by the body to manifest itself, and from here follows symptom of painwhich, if eliminated without suppressing the root cause of the dysfunction, will be persistently triggered again by the original problem.

The symptom of pain is the last signal of a series of adaptations introduced by the increasing compensatory capacity of the connective tissue, which changes the physiological pattern, which are “silent” until the very last adaptation in the chain can no longer be compensated.

Conflicting information

Korr (1976) re-emphasized the importance of the bone marrow, which contains a large number of muscle “patterns” of activity. The brain works by producing complex movements that depend on the activation of muscle chains rather than individual muscles. For this purpose, programmed models “stored in reserve” in the trunk and bone marrow are involved, which are modified into an infinite variety of models that are even more complex and enrich the “warehouse” with these new derivatives.

Thus, each type of activity is modified, improved and "corrected" by appropriate feedbacks constantly emanating from muscles, tendons, joints (their connective tissue component) participating in the movement.

GAS and LAS

The English abbreviation for General Adaptation Syndrome ( GAS) and local adaptation syndrome (LAS).

The syndrome of general adaptation, OSA, consists of an anxiety reaction, a phase of resistance (adaptation), a phase of exhaustion (unsuccessful adaptation) and covers the entire body. Local adaptation syndrome, SMA, manifests itself in much the same sequence, but in a limited area of \u200b\u200bthe body.

Seyle (1976) identified stress as a nonspecific contributor to illness. Describing the relationship between the syndrome of general and local adaptation, he emphasized the importance of connective tissue.

Stress contributes to the creation of models of adaptation, specific for each organism and for each type of force impact. In response to stress, homeostatic self-normalizing mechanisms are activated.

If the state of anxiety is prolonged and repeated, processes of defensive adaptation occur, leading to long-term changes that can become chronic.

Through palpation of neuromusculoskeletal changes, an idea is created of the attempts made by the body to adapt to the stresses accumulated over time; the result is a confusing picture of tense, compressed, compacted, overworked and finally fibrotic tissues (Chaitow, 1979).

It is important to understand that due to prolonged stresses of the postural type (due to the position of the body), physical and mechanical, some areas of the body apply so much compensatory and adaptive efforts that structural changes appear that can develop into pathology.

In most cases, the combination of physical and emotional stress alters the neuromusculoskeletal structures to the extent that it causes a number of identifiable physical abnormalities. The compensatory attempts of these structures will in turn generate new stressors; because of this, painful phenomena, articular restrictions, and general ailments, such as fatigue, may occur.

In the process of chronic adaptation to biomechanical and psychogenic stress, chain reactions develop, associated with compensatory modifications of soft tissues (Lewitt, 1992). These adaptations are always detrimental to the optimal functioning of the body and are the source of an ever-increasing functional disorder (physiological changes).

Sequence of responses to stress

In the case of a prolonged increase in muscle tone, there are:

n retention of catabolic products and edema

n local lack of oxygen (associated with tissue needs) and subsequent ischemia

n maintenance or increase of increased functional tone

n chronic inflammation or irritation

n stimulation of sensitizers of nerve structures and the development of increased reactivity (hyperreactivity)

n activation of macrophages for increased vascularization and fibroblast activity

n fibrosis with contraction / shortening of the connective tissue component.

Along continuous fasciae throughout the body, any local overstrain can reflect and negatively affect distant structures supported and attached by the fascia itself (nerves, muscles, lymphatic and blood vessels). As a result, the following may appear:

n changes in elastic tissues (muscles) with chronic reactive hypertension and subsequent fibrosis

n inhibition of antagonistic muscles

n chain reactions in which the postural muscles are shortened and the phasic muscles are weakened

n ischemia and pain caused by prolonged muscle tension

n biomechanical changes, impaired coordination of movements with articular limitation and imbalance, fascia retraction

n the appearance of areas with increased reactivity of neurological structures (areas of relief) in the back areas and inside the muscles (trigger points)

n energy expenditure on maintaining hypertension and, as a consequence, general fatigue

n constant feedback impulses from the central nervous system, psychogenic alarms with an inability to adequately relax areas with increased tone

n biologically non-replaceable functional patterns caused by chronic musculoskeletal problems and pain.

The effectiveness of osteopathy lies in the fact that it goes the other way in restoring the symptom of pain to identify the primary cause, the direct action on which opens the way to its elimination. Thus, there will be a return to the physiological norm of the stress parameters, which will also imply - but not only - the disappearance of the pain symptom.

The fascial technique makes it easier to find the root cause than the traditional one. With refined palpation, it is not difficult to follow the direction of the fascia tension and reach the true origin of the problem ... especially in cases where the doctor cannot prove the correctness of symptomatology on the basis of the patient's pain zone.

Avoid mechanical stress on electrical equipment in modern world practically impossible, therefore, an assessment of resistance to the influence of external mechanical factors must be carried out. There are several methods of such verification, which the authors of the material talk about.

EXTERNAL MECHANICAL IMPACT
METHODS FOR CONFIRMING THE RESISTANCE OF ELECTRICAL EQUIPMENT

Valentin Shishenin,
Doctor of Technical Sciences,
Vladimir Bakin,
Ph.D.,
Vladimir Pavlov,
Engineer, Scientific Research Center 26 Central Research Institute of the Ministry of Defense of the Russian Federation,
St. Petersburg

The scientific development of the problems of checking the factors of impact and vibration on various equipment was started back in the 50s and 60s of the last century. Research carried out in this area has made it possible to identify groups of equipment that are most critical to vibration and shock loads.
Electrical equipment belongs to the group most sensitive to vibration and shock (hereinafter referred to as mechanical) loads, since it has automatic switches (switches), electromagnetic starters, relays and circuit breakers in the structure of functional circuits different typesshowing control devices (ammeters, voltmeters, etc.). These conclusions are confirmed by foreign studies.
Mechanical effects on electrical equipment are largely due to dynamic phenomena arising from the rotation and reciprocating motion of unbalanced elements and parts. In turn, low-amplitude mechanical vibrations often cause resonant vibrations of other structural elements. An additional source of mechanical influences on electrical equipment are technogenic factors, as well as external natural factors, including earthquakes. The examples of recent years confirm that there are no places on earth now where earthquakes are impossible.
Even greater potential danger for the environment and the population is distinguished by cases of malfunction and failure from mechanical effects of electrical equipment installed at hazardous industries and nuclear power plants. Therefore, the resistance of electrical equipment at facilities increased danger higher requirements are imposed.

Test standards
According to GOST 17.516.1-90, electrical products are divided into groups of mechanical design, depending on the area of \u200b\u200bapplication and installation location. Based on this, requirements are imposed on them in terms of strength, stability and resistance to mechanical external influencing factors of various degrees of rigidity.
For hardware, instruments, devices and equipment for military purposes, the requirements for resistance to external factors are put forward in accordance with GOST RV 20.39.304-98. Tests of electrical equipment for compliance with the requirements of GOST 17.516.1-90 in terms of resistance to mechanical external influencing factors are carried out in accordance with test methods in accordance with GOST 20.57.406-81 and GOST 16962.2-90. Tests of electrical equipment for military purposes for compliance with the requirements of GOST RV 20.39.304-98 in terms of resistance to mechanical external factors are carried out in accordance with test methods in accordance with GOST 20.57.305-98.
In the general case, verification of the compliance of electrical equipment with the requirements put forward can be carried out by experimental, calculation and calculation-experimental methods. Each of them has its own characteristics, advantages and disadvantages.

Experimental method
The most complete and reliable data on the strength, stability and resistance of equipment to the mechanical effects of external factors can be obtained only experimentally. Analysis of the results of tests of electrical equipment for the effect of external mechanical factors, carried out over the past 10–20 years at NRC 26 Central Research Institute, made it possible to establish the most typical failures and shortcomings.
1. Breakage or destruction of attachment points caused by:

• by cutting the mounting bolts and studs;
• deformation of support units made of profile or sheet steel;
• the appearance of cracks and destruction of the cast-iron foundation frames at the base;
• the appearance of cracks in the welded seams of the support units of the units.

2. Deformation or destruction of the integrity of the body due to:

• deformation of the frame, covers and doors of rack-mount and cabinet-type equipment;
• deformation of the supporting nodes of the door pillars, preventing their further fixation in the closed position;
• destruction and spalling of flange protrusions on cast-iron covers of electric motors.

3. Deformation or breakage of internal assemblies and elements as a result of:

• displacement of roll-out carts;
• destruction of bushing and support insulators, getinax boards and textolite cases;
• falling out of arc chambers, electrical measuring instruments;
• destruction of the filament of lamps in lighting equipment and apparatus;
• destruction of bearings.

4. False actuation of contact elements.

Spontaneous closing and opening of the contact elements of the devices at the moment of exposure to the load can lead to the shutdown of important technical systems and disruption of technological processes.
For objective reasons, in Russia over the past fifteen years there has been a significant reduction in the number of functioning test laboratories and test centers and, as a result, the number of test facilities that reproduce mechanical, including seismic, effects.
It should also be noted that the park of testing facilities for mechanical stress is very worn out, the test benches are relatively small, and the lack of multicomponent installations.
In fact, there is no possibility of testing large-sized equipment with linear dimensions of more than 3 m and a mass of more than 3 tons for vibration and shock.
And as practice shows, unique large-sized and massive equipment, due to its inertial characteristics, tolerates mechanical stress worse and therefore needs mandatory testing for the effect of expected external mechanical factors. The same is the case with test facilities for testing for effects adequate to intense earthquakes. IN the former USSR five large programmed seismic platforms equipped with hydraulic drives functioned. In recent years, seismic platforms located on the territory of the Russian Federation practically did not work, and it remains unclear what the required allocations are for restoring their operability and modernization.

Calculation method
A significant disadvantage of using the experimental method is its dependence on the limited capabilities of the test equipment. Therefore, if it is necessary to assess the strength to mechanical stress of samples of electrical equipment made from materials with known characteristics, a calculation method is used. This is facilitated by the modern development of modeling and calculation methods, software tools and computing technology. The indisputable advantage of the calculated method for determining the strength lies in the fact that its application is not limited by the size and maximum mass of the calculated equipment. In addition, in comparison with the experimental method, the calculation has a fairly low cost.
Among the main disadvantages of this method for determining strength, the following can be emphasized:

• by calculation, it is practically impossible to assess the stability of the operation of electrical equipment during the influence of an external mechanical factor;
• it is practically impossible to confirm compliance with the established requirements for strength to the effect of external mechanical factors for equipment samples with nonlinear characteristics and complex systems of electrical equipment;
• the accuracy of determining the strength depends on the adopted design model, the qualifications of calculation specialists, the software products and methods used.

Calculation and experimental method
Considering technical capabilities of existing testing facilities, testing of a complex electrical system for resistance under the influence of mechanical factors may actually be unrealizable or require significant material costs, and the assessment of the resistance of the system as a whole by calculation is impossible. In this case, a computational and experimental method is used.
On a vibrodynamic stand, the cabinets were tested for resistance to sinusoidal vibration with the indicated amplitudes of vibration displacement and vibration acceleration in the range from 7 to 100 Hz. As you know, vibration tests in the range from 1 to 5 Hz are difficult due to the lack of vibrodynamic stands of the required carrying capacity. During the tests, the acceleration parameters were recorded with the help of three sensors installed in certain places of the cabinets. In parallel, design models of cabinets were developed and calculations for a similar effect were carried out.

Practical example
The task was to assess the resistance of a group of electrical equipment cabinets with a maximum dimensions of 600x800x2000 mm and a maximum mass of 250 kg to the effects of sinusoidal vibration in the range from 1 to 100 Hz, with an amplitude of vibration acceleration of 7 m / s2 from 1 to 35 Hz and with an amplitude of vibration acceleration of 10 m / s2 from 35 to 100 Hz.

After the tests, the calculated and experimental data were compared in the frequency range from 7 to 100 Hz, and a sufficient convergence of the calculation and test results was revealed. Tests have shown that the cabinets are resistant to test impacts in the range from 7 to 100 Hz. After the tests, the calculations of the cabinets were carried out on the proven design models for the effect of sinusoidal vibration in the range from 1 to 7 Hz. The kinematic parameters obtained by calculation at the set points did not exceed the motion parameters recorded at the same points during the tests. Therefore, according to the results of the computational and experimental evaluation, a positive conclusion was made about the resistance of the equipment in the range from 1 to 100 Hz when exposed to a given sinusoidal vibration.

Computational and experimental is the most versatile method for determining the resistance (strength, stability) of equipment samples and their systems to external mechanical factors. It combines the advantages and partially eliminates the disadvantages of the computational and experimental methods, but its application requires a sufficient amount of necessary initial and experimental data, the correctness of the methods and techniques used, and highly qualified specialists.

A few tips for manufacturers
Increasing the resistance of electrical equipment to external mechanical factors can be carried out by:

• the use of optimal circuit solutions;
• use of resistant components in equipment;
• reducing the size of products;
• rational layout and fastening of components, increasing the fill factor;
• the use of unified frames of the optimal profile;
• improvement of locking devices for doors and covers of cabinet equipment;
• devices for additional fastening at the top of the product;
• calculation of standard equipment attachment points;
• control during installation of the required tightening force of bolted connections.

Literature
1. Vibrations in technology. Reference book in 6 volumes. - T. 3. Oscillations of machines, structures and their elements. - M .: Mechanical Engineering, 1980.
2. Coloiaco A.P., Elsher E. G. Sine-beat tests verifies switchgear control equipment // IEEE Trans. Power Appar. and Syst. - 1973. - Vol. 93, N2. - P. 751-758.
3. Kirillov A.P., Ambriashvili Yu.K. Seismic resistance of nuclear power plants. - M .: Energoatomizdat, 1985.
4. GOST 17.516.1-90 “Electrical products. General requirements in terms of resistance to mechanical external factors ”.
5. GOST RV 20.39.304-98 "Requirements for resistance to external influencing factors". 6. GOST 20.57.406-81 "Electronic products, quantum electronics and electrical".
7. GOST 16962.2-90 “Electrical products. Test methods for resistance to mechanical external influencing factors ".
8. GOST RV 20.57.305-98 "Test methods for the impact of mechanical factors".
9. Bakin V.A., Belyaev V.S., Vinogradov V.V., Sirro V.A. Testing of building structures and large-sized equipment for seismic effects // Seismic construction. - M .: VNIINTPI, 1996. - Issue. 6. - P. 3-10.