Technical information
Elastomeric bearings have been used in structural engineering for more than half a century. In a technical article in the journal "Der Bauingenieur 39" (published in 1964), a Theory of elasticity for reinforced rubber bearings as bridge bearings. The author, Dr.-Ing. Boris Topaloff, was the first to provide theoretical calculation approaches for this complex construction product. The first approval for elastomeric bearings in the construction industry was granted in 1963.
Previously, components were stored using e.g. fixed mechanical connections, a mortar joint or a double layer of roofing felt as a separating or sliding layer, which often led to sometimes considerable component damage. Since then, however, much has changed for the better and there are now excellent technical solutions for all conceivable challenges in the field of component storage!
Elastomeric bearings enable the designer to support components without constraints and thus allow movements in the building structure. In addition, elastomeric bearings can significantly increase the assembly speed of precast elements. Furthermore, elastomeric bearings can be used to compensate for so-called "support imperfections" (unevenness and skewness of components) and reduce compressive stress concentrations.
The main raw material of elastomeric bearings is rubber in various variations. Together with fillers, such as carbon black, rubbers form the main component of an elastomer compound (mass proportion between 25-60 %). Vulcanization of the elastomer raw compound initiates chemical crosslinking processes. The resulting physical and mechanical properties of an elastomeric bearing are determined on the one hand by the composition of the mixture and on the other hand by the type and duration of vulcanization.
Extensive details on the different types of rubber and other raw material components in an elastomer compound can be found in the chapter "What is rubber".
The term "rubber" is used in technology to describe vulcanizates made from naturalor synthetic rubber..
Natural rubber is a rubbery substance in the milky sap (latex) obtained from many different rubber plants.
Synthetic rubbers are purely industrially manufactured rubber grades produced on the basis of petrochemical raw materials.
The particular advantage of rubber is primarily its elasticity. After mechanical tensile stress (stretching), rubber can return to its original state when the load is removed, and can do so repeatedly. Likewise, depending on the type, rubber can also deform back under compressive stress, sometimes more and sometimes less.
Rubber-like materials are approximately incompressible. This means that the volume of the body (almost) does not change during deformation and the resistance to volumetric deformation is correspondingly high, resulting in lower reaction forces. Properties that have a positive effect on their use as elastomeric bearings.
Natural rubber (NR)
NR is characterized by high strength, even in the unfilled state, combined with high elasticity. Thermal application range: from -50 °C to +70 °C (continuous temperature). Special NR materials can also be used up to +100 °C permanently or for short periods (a few hours to days) up to 120 °C. NR is not oil-resistant and must be protected by certain additives when exposed to ozone. NR has the lowest damping of all elastomers and exhibits the lowest creep at temperatures up to +50 °C. Therefore, the NR material is ideal as a rubber spring and generally suitable for vibration damping. Other applications include: mechanically highly stressed parts such as truck tires, conveyor belts, etc.. The properties of NR materials can be varied within wide limits. NR is therefore an ideal all-purpose rubber
Synthetic rubber types
Chloroprene rubber (CR)
CR is a synthetic rubber with significantly better aging resistance than NR, IR, BR and SBR. Thermal application range: from -40 °C to +120 °C, briefly up to +130 °C. If CR vulcanizates are exposed to temperatures below 0 °C for a longer period of time, hardening occurs as a result of crystallization. However, this process is reversible. CR has a certain resistance to mineral oils and greases. The CR material is used in applications such as: cooling water hoses, conveyor belts, axle boots, sealing profiles for outdoor applications, cable sector, flame-retardant elastomer parts.
Ethylene-propylene-diene copolymer (EPDM)
EPDM is resistant to very high temperatures, but not resistant to mineral oil. Thermal application range: from -40 °C to +140 °C, briefly up to +170 °C. Due to its good resistance to ozone and light cracking, EPDM is particularly suitable for outdoor applications. EPDM has a very low DVR (compression set) at high temperatures and excellent water resistance. Applications of EPDM material include: Seals, O-rings, molded parts for the washing machine and cable sector.
Styrene butadiene rubber (SBR)
SBR is the starting material for the most commonly produced variant of synthetic rubber and is used in particular in the manufacture of tires, seals and conveyor belts. SBR is characterized by high strength and good wear properties combined with improved heat resistance compared to NR. Thermal application range: -40 °C to +110 °C, briefly up to +120 °C. SBR is not resistant to mineral oils.
Nitrile Butadiene Rubber (NBR)
NBR has very good resistance to mineral oils and greases. The higher the acrylonitrile content, the better the oil resistance but the poorer the cold properties. Can be used from -30 °C to +120 °C, briefly up to 150 °C. NBR is an important sealing material, especially for automotive and mechanical engineering, O-rings, shaft seals, hydraulic seals and hoses.
Other ingredients of rubber compounds and background information
Blends of the above-mentioned rubber types with affinity to each other are also possible (even more than 2 rubber types) and are available on the market. In these blends, the proportions of the rubber types used can be varied or combined, as can the total proportion of rubber in the compound (see above). Due to the rubber types used alone, an infinite number of different elastomer compounds are conceivable whose end products - even with otherwise identical compounds - exhibit different material properties.
Compounds
Fillers, such as carbon blacks, particularly influence the tensile strength of an elastomeric material.
Abrasion, wear, compression set or aging resistance are particularly influenced by "light fillers". Fillers account for a considerable proportion of the mass of an elastomer compound (approx. 20-50%).
A distinction is made between active and passive fillers. Active fillers are characterized by a small particle size combined with a large (fissured) particle surface. Active fillers lead to an improvement in the physical properties of an elastomer, since the tensile strength of the molecular chains - up to a certain saturation point - is increased.
With the use of passive fillers (e.g. carbon blacks) of different activity and different mass fractions in the compound, the physical properties of a finished rubber are significantly influenced. In "low-cost" compounds, a more or less large proportion of passive fillers is often added to reduce the production costs.
The number of fillers offered on the market is high. For example, carbon blacks are produced according to a total of seven different manufacturing processes, and there are 10 particle diameter categories for carbon blacks. Bright reinforcing fillers are produced from four different material groups: Silica (active), Aluminum Silicate, Calcium Silicate and Calcium Carbonate (passive filler).
A high filler content in an elastomer compound can therefore indicate both high quality (if active fillers are used) and lower quality (if passive fillers are used).
Thus, by using different fillers, the vulcanizates of otherwise identically structured elastomer compounds can exhibit significantly different physical properties.
Anti-aging agent
Aging processes occur at all temperatures, with higher temperatures accelerating these processes, which can lead to a reduction in component life. In addition, oxidation, media, dynamic stresses, high-energy light, etc. can also can initiate or accelerate aging processes. The aging resistance of materials is improved by appropriate selection of suitable rubber grades, fillers and crosslinking systems, as well as addition of further chemicals (waxes, coatings on the surface, anti-aging agents in the compound).
More than 100 different chemical substances are now available on the market as antioxidants. However, the proportion of antioxidants in an elastomer compound is very small (usually less than 1% by mass). The influence on the physical properties of the elastomers is therefore rather insignificant. However, the use of waxes means that these, together with other antioxidants and antiozonants used, are transported to the surface of the finished products - intentionally - for protection. This fact can then significantly influence the frictional behavior to the adjacent components; an effect that must be taken into account for the use of elastomer products as bearings in building construction
Plasticizer
As a rule, this group of substances is of greatest importance in rubber compounds in terms of mass fraction, along with rubber and fillers. As the proportion of plasticizer increases, the Shore hardness of an elastomer material generally decreases. Plasticizers are used to increase the flowability of a rubber compound (processability), to change the thermal application limits of an elastomer material, to influence the media-dependent swelling behavior, to improve the extensibility and elasticity of a material or to improve the electrical conductivity and fire behavior of a compound.
Plasticizers act like hinges between the molecular chains. Unlike a door, the connection is relatively loose. But if a hinge is now forced out of its position, this point in the elastomer becomes stiffer. If this happens too often, an elastomer becomes brittle.
It is therefore in the interest of a high-quality compound to use plasticizers that show a high chemical similarity to the molecular chains of the rubber. As a result, they are literally "absorbed" by the rubber. This molecular affinity results in a permanent encapsulation of the plasticizers in the overall structure and an improvement in the mobility of the molecular chains within themselves.
Nevertheless, less specially formulated, cheaper plasticizers are often added (mostly for cost reasons) (reducing the Shore hardness) and at the same time "cheap" carbon black is added (increasing the Shore hardness), which in total keeps the Shore hardness the same. However, these cheap ingredients are then added at the expense of the (relatively expensive) rubber content, which on the one hand leads to a lower compound price, but on the other hand seriously reduces the crosslinking density and consequently the product performance.
The same applies to the group of plasticizers: there is a large variety of different plasticizers, resulting from three groups (mineral oil plasticizers, pure and modified natural substances and synthetic plasticizers) with a large number of subgroups and a whole range of commercial products for the respective types. Plasticizers are necessarily present in a rubber compound. Not only the type, but also the plasticizer content significantly influences all relevant physical material properties of the vulcanizates in an otherwise identical compound.
Processing aids
These serve to further improve the flowability of compounds (similar to plasticizers), especially for the manufacturing process of injection molding. Since this process is used practically exclusively for molded parts, which is of no significance in the manufacture of bearings, it will not be discussed further here.
Special additives
Special additives are required for special applications. Conceivable for bearings are, for example, additives for flame retardancy or blowing agents for foamed materials, which, however, can also have an influence on physical properties of the compound and the behavior of the finished product. However, no meaningful experience is (yet) available on this subject, but there are scientific studies and research projects on this topic, in which the company ESZ Becker is also involved with commitment.
Vulcanization activators
This refers to all chemicals required for the vulcanization of the elastomer: vulcanization coagents, accelerators and retarders. The absolute mass proportion of these chemicals in the total compound is small (significantly less than 10 %).
The selection of the crosslinking system (sulfur, peroxide or radiation crosslinking) is also important, in addition to the appropriate composition of the chemicals, and at the same time is also decisive for the physical properties of the end product.
Vulcanization gives the components, which have already been mixed as homogeneously as possible by the mixing process, the necessary elasticity through the formation of chemical bonds. The loose, tangled polymer chains are irreversibly bonded and acquire a permanent conformation (a spatial arrangement that resembles a spaghetti ball in this case). Vulcanization usually takes place under pressure and at elevated temperature in special molds. At the same time, vulcanization gives the material dimensional stability.
Networking density
The goal is the achieving an optimal networking densitywhich is decisive for the physical property profile of the elastomer material. The optimum crosslinking density is defined by the number of network nodes (among the polymer chains) and the structure of the network node system.
The influence of the crosslink density on selected physical properties of the vulcanizate is shown in the following figure:
An elastomer blend consists of about 15-30 ingredients from about 11 groups of ingredients.
Each group of ingredients contains a variety of different material types, each of which is marketed by different producers in different grades. Different ingredients from a group can be combined with each other. In addition to the horizontal combinability (within the groups), the ingredients can also be combined vertically (ingredients from the different groups).
This results in an infinite spectrum of different rubber compounds with corresponding differences in the physical properties of the vulcanizates manufactured from them. The possible physical properties of vulcanizates - even when using a single (arbitrary) rubber type - sometimes differ greatly from one another.
These differences are reflected in the different calculation models for viscoelastic materials reflected. Depending on the size of the deformation, different elastic and plastic proportions occur. Furthermore, the elastomer characteristics are Relaxation (stress reduction with constant deformation) and retadation (so-called "creep"; delayed deformation response at constant load) vary in degree.
These characteristics can be represented by a combination of "spring and damper elements":
The DIBt (Deutsches Institut für Bautechnik), as the approval body for construction products and types of construction, provides the following information on the question of whether elastomeric bearings can be assigned to an independent fire resistance class.
Elastomeric bearings cannot be assigned to an independent fire resistance class. Fire resistance classes refer to building components, such as walls, ceilings, columns, etc. (see e.g. DIN 4102-2, section 1). (see e.g. DIN 4102-2, section 1), but not to individual building materials.
According to building regulations, building materials, including those for joints and bearings, are considered in terms of fire resistance. In this respect, it is not necessary under building regulations to assign a building material, e.g. for joints and bearings, to a fire resistance class.
However, according to building regulations, proof of fire behavior is required. Elastomeric bearings must therefore be at least normally flammable (see § 26 of the model building code or the corresponding § of the respective state building code). Higher requirements for the fire behavior of the building material can result from special uses (in components, e.g. fire walls).
Here you will find a detailed explanation on the subject of fire protection and fire behavior of ESZ deformation bearings.
DIN 4141
The DIN 4141 series of standards "Bearings in construction" was superseded with the introduction of the European follow-up series of standards DIN EN 1337 and has therefore no longer been valid since 2005. This standard had differentiated between the so-called bearing classes 1 and 2.
DIN EN 1337
DIN EN 1337 (parts 1 to 11) currently regulates "bearings in construction" at European level.
Part 3, which is relevant for elastomeric bearings, limits the load-bearing capacity for reinforced and unreinforced bearings to 7 N/mm². However, this value is significantly below the maximum compressive stress capacity of the elastomeric bearings available on the market and is definitely too low for practical construction applications. The maximum permissible (format-dependent) surface pressure for the ESZ Type 200, for example, is 28 N/mm²; after technical clarification with ESZ, even higher pressures may be possible. Thus, this standard does not cover elastomeric bearings with a performance capacity above 7 N/mm².
In addition, only CR- and NR-based products are regulated in this standard. In the meantime, EPDM-based elastomeric bearings have also proven themselves very well in practice.
General technical approvals / European technical assessments / General type approvals
If a construction product cannot be assigned to a harmonized EU standard, it is possible to provide evidence of the usability of construction products either by means of a general technical approval (abZ) or a European Technical Assessment (ETA). Applications can be submitted to Deutsches Institut für Bautechnik (DIBt).
The DIBt issues general design approvals (aBG) for designs with bearings that are not subject to final technical regulation.
Load assumptions
Depending on the safety relevance of the limit state under consideration, the design should be carried out for the serviceability limit state or for the ultimate limit state. According to the current approval principles, the design for serviceability must be determined by verifying the use in the ultimate limit state - in accordance with the so-called semi-probabilistic partial safety factor concept. The verification concept according to DIN EN 1990:2010-12 with National Annex applies. The bearings may only be used for statically or quasi-statically loaded components.
The basic requirements for the bearing thus result for the support areas from the structural analysis of the components or the supporting structure. In addition, when elastomeric bearings are used as supports, the following actions must be taken into account in the design of the bearings:
Deviation from plane parallelism
Deviations from the plane-parallelism of contact surfaces of abutting structural members must be taken into account for the verification of the bearings and considered mathematically like planar rotations. Geometric imperfections and deviations from the plane-parallelism of reinforced concrete contact surfaces must be assumed to be at least 0.01 [rad] (equivalent to 10 ‰ or 0.57 °) and added to the calculated value of the bearing twist from the component deformations. If no more precise verification is provided, unevenness of precast concrete elements must be taken into account at 0.625 / a [rad] and considered mathematically in the same way as planned twisting. If the overlying component is made of in-situ concrete or steel, this value can be reduced by half.
Temperature and climatic effects
In the interior of high-rise buildings with insulated building envelope, compared to an installation temperature T0 = +10°C, temperature variations ΔTN,k = ± 10 °K, provided that the components are not exposed to direct solar radiation. In individual cases, it must be checked whether more unfavorable conditions must be taken into account due to the structural conditions or due to use or building conditions. In the case of building components to which the outside air has frequent or constant free access and which are exposed to solar radiation, the temperature effects must be taken into account. If no more precise proof is provided, the temperature effects can be applied on the basis of DIN EN 1991 (see Part 1 and Part 5).
Bearing proof
The bearing verification is usually carried out on a product-specific basis or in accordance with the applicable standard. Elastomeric bearings are generally used as deformation bearings and are not considered as locating bearings in the sense of DIN EN 1337-1. Thus, they should be considered as static single-value thrust bearings (main load in compression and in one direction).
Compressive load
Bearings are individually limited in their maximum load capacity, depending on the proof of use. Due to the large number of products available on the market and their different product properties, there is also no generally applicable definition for the maximum compressive load capacity.
Therefore, the valid regulations and approvals apply in addition to the corresponding product specifications and information provided by the manufacturer for their products.
Torsion due to component deformation
The rotatability of a bearing is limited. The max. permissible twists α can be found in the respective product approvals.
The twisting of a bearing has several reactions as a result:
The component edges move out of your scheduled position. An edge contact must be avoided at all costs. The distance between the component edges should be calculated ≥ 3mm at least.
The twisting causes a Load eccentricity respectively a restoring torque. This must be taken into account.
In general, the harder and thinner a bearing is, the greater the eccentricity or restoring torque will be.
Unless otherwise specified, we believe that the restoring torque for rectangular bearings can be determined as follows:
Unless otherwise specified, the eccentricity for rectangular bearings can be determined as follows:
Angular torsion at the support can cause significant shear deformation of the bearing, depending on the component geometry.
Shear deformation
Parallel to the bearing plane, bearings should only be subjected to loads as a result of constraint and variable actions. Actions from permanent external loads, including earth pressure, are not permissible. The shear deformation of the bearing as a result of relative displacements in the bearing joint or forces acting parallel to the bearing plane must be limited so that neither the bearing is damaged nor edge contact of the components occurs. Unless otherwise specified, the shear deformation of the bearing can be limited as follows:
The shear deformation is calculated by vectorial addition of tanγx and tanyy .
with
 |  |
ux & uy Horizontal displacement in X and Y direction
Fx,q & Fy,q variable horizontal loads in X and Y direction
Slipping, sliding and bearing creep
If the adhesion between the bearing and the adjacent components is overcome by actions parallel to the bearing plane, the bearing may slip. This is permissible if a possible failure of the bearing due to slippage is prevented by design measures. If the bearing must not slip or external variable forces must be transmitted through the bearing, the following condition must be met unless otherwise specified:
 |  |
| σz min, d | the to Fx,y q associated smallest design value of the bearing pressure |
| A = a x b | Base area of unloaded rectangular bearing |
| A = π x d2/4 | Base area of an unloaded round bearing |
with
Fx,y q is the sum of the shear deformation acting on the bearing from variable loads and the vector sum of the design values of the variable actions parallel to the bearing plane.
If less than 75% of the load is permanent - in the rare combination according to DIN EN 1990 - the bearing must be secured against bearing movement.
Condition:
For a proportion of more than 25% variable load in the frequent combination according to DIN EN 1990, bearings with general approval or standardized bearings must be used.
Condition:
Adjacent components
The value of the permissible bearing resistance zul σ must form the basis for the verification of the adjacent components (i.e. if, for example, the bearing can support a maximum of 20 N/mm² as a material, the adjacent components must also be able to support this). The eccentricity e resulting from torsion and shear distortion of the bearing must be taken into account, if necessary, in the design of the adjacent components. The load center may be determined as follows, unless a more accurate verification is provided:
| a | Bearing side a or diameter in [mm] |
| αa | Rated value of bearing torsion over the bearing side a |
| ua | Design value of horizontal displacement of the bearing in direction a. |
Remark: Two-dimensional actions have to be captured analogously by vectorial addition.
The transverse tensile force T arising in the adjacent structural members as a result of the expansion restraint of unreinforced elastomeric bearings T must be verified and absorbed by appropriate measures: [reinforced concrete construction: e.g. by reinforcement close to the surface / timber construction: e.g. by steel plate / masonry construction: e.g. by reinforced mortar joints].
The transverse tensile force due to transverse elongation can be determined as follows for elastomeric bearings, unless otherwise specified (as in the case of approved products, for example).
| Tk | characteristic value of the transverse tensile force |
| c | largest bearing side a, b or bearing diameter d in [mm]. |
Position safety and bearing creep
The mechanical relationships can be found in simplified form in the "response" of an elastomer bearing to load changes.
Elastomeric bearings tend to be subject to an "effect" of bearing migration under frequently changing loads. For less than 75% permanent loads, positional restraint should therefore be considered. In the withdrawn old standard 4141-15 for unreinforced elastomeric bearings, this had to be taken into account when differentiating between bearing classes 1 and 2.
Elastomeric bearings expand laterally under compressive stress. This leads, among other things, to transverse tensile forces in the bearing joint, which must be taken into account when dimensioning the adjacent components. If the (partial) load on the bearing is too great, in an unfavorable case it will not deform centrically but eccentrically - i.e. not back to its original position. With frequent repetitions, this can lead to a bearing moving out of its original position under such alternating stress with live loads > 25 % ("bearing wandering").
Bearing creep due to frequent load changes can be prevented, for example, by providing design cleats or a chamber (cleat).
There are other various causes that promote bearing creep.
The lower the physical characteristics (softer) of a bearing, the more it tends to spread out under pressure, the more it tends to creep.
The more uneven the condition of the contact surfaces, the more likely a bearing is to creep.
Alternating shear stress and alternating loads can lead to a temporary overcoming of the frictional connection between bearing and component. The less friction the greater the spreading and the greater the risk that the bearing will contract unevenly and promote bearing creep.
Notes on bearing forms and bearing behavior:
A round bearing behaves optimally, since an absolutely uniform stress distribution is formed in the bearing material.
Square bearings behave slightly worse than round bearings, but comparatively more favorable than rectangular bearings.
Strip-shaped bearings behave less favorably than rectangular bearings
(always related to deformation at a given load, based on area, with more deformation being
Based on these mechanical relationships, you can:
prove a parallelogram with an equal-area rectangular bearing with an aspect ratio of 1:1.5 (A:B).
prove a circular bearing over an area-equivalent rectangular bearing, where the bearing side b corresponds to the diameter of the circle and the twist must be chosen perpendicular to the bearing side b.
The ESZ Type 200 bearing can support up to 96.90 N/mm² as a round bearing (depending on form factor) in accordance with the approval.
The bearing areas must be designed in accordance with the design-specific technical specifications and standards. In general, sufficient edge distances must be provided. The elastomeric bearing must be located within the reinforcement, also under load action with consideration of the spreading dimension.
The bearing width depends on the geometry and material. This means that the planner must have product-specific information on this, which must be taken into account in the planning.
As a general rule, preference should be given to materials (products) that are stable under long-term pressure.
When using bearings with steel contact surfaces, the steel surfaces
should be at least
be at least 25 mm larger than the bearing.
If elastomeric bearings have to be tamped under due to the structural situation, special attention must be paid to a mortar quality suitable for this purpose.
The lateral surfaces of the bearings must not be impeded in their planned deformation under any circumstances.
Each component must be separated horizontally and vertically from the
from the adjoining components in such a way that the intended support (statics) can be effective.
It should be noted that deformability can be impaired by joint fillings, such as joint compounds, profiles made of foam or boards made of mineral wool or foam materials. In the case of in-situ concrete execution, the proper production of the bearing joint must be ensured.
In the case of horizontally displaceable components, it must be checked whether fixed points or fixed zones must be arranged by which the zero point of movement of the component to be stored is determined. It should be noted that unintentional fixed points can have a detrimental effect on component storage.
The enivronmental influences must be checked with regard to possible damage to the bearings.
Elastomeric bearings and support surfaces must be and remain free of contamination.
Loose particles are generally not permitted.
The bearing surfaces must be free of ice and snow, grease, solvents, oils or separating agents. This must be ensured by suitable measures.
For a quick and convenient bearing dimensioning of the approved ESZ products, the calculation tools created by ESZ Becker can be accessed.
Here you can find our calculalting program
A short tutorial on how to use the online calculating program can be found here: ESZ online calculating program help
Alternatively, you can get the current calculation tools as an Excel file. Please feel free to ask for them if you are interested. We will also be happy to explain how to use the programs.
The calculation bases of the programs are based on the respective specifications in the product approvals and are also in line with the respective product performance, which we as a supplier can assure on the basis of our decades of experience with these materials.
The calculating programs are to be regarded as an aid to the approvals. You can obtain concrete results on the usability of a bearing type using the calculation tools, since all the effects that occur (compressive stress and torsion) can be taken into account in combination.
If no usable bearing can be determined during dimensioning with the help of the calculation tools, please contact us. We will find a solution for the task with you.
Explanation will follow
Explanation will follow
A | B
Bearing
Bearing describes the totality of all structural measures that serve to transfer the internal forces (forces, moments) resulting from the static calculation from one component to another and at the same time to enable the planned component deformation at these points. Components are supported by point, line or surface supports.
Bearings and bearing designations (here in the sense of elastomeric bearings)
A bearing is a separately manufactured component to realize intermediate conditions in building structures. The type designations are related to function, shape and material.
Bulging of the bearing
The spreading dimension describes the lateral spreading of the bearing under compressive stress. The spreading dimension depends on the nominal bearing thickness and the permissible design compressive stress.
C
Coefficient of friction μ The friction coefficient has no unit and determines how strong the frictional forceRis. It arises when bodies move against each other, and it always acts against the direction of motion. A distinction is made between different types of friction. If, for example, a body is to be set in motion on the floor, the static frictional force must first be overcome. During the subsequent movement, the smaller sliding friction force or rolling friction force then takes effect. In addition to the type of movement, the coefficient of friction is different depending on the material surfaces, lubrication and temperature. Therefore, there are whole tables of friction coefficients, which are mostly determined by tests. In addition to the friction coefficient μ, the normal force FN is also requiredN to calculate a specific friction force. This is the portion of the weight force that is perpendicular to the surface: FR = μ⋅FN For the friction work, this force must be multiplied by the distance s traveled: WR= μ⋅FN⋅s The friction force is smaller the smoother the surfaces and the better they are lubricated. Compact bearings Bearing made of a homogeneous elastomer sheet or extrudate without surface profiling or other geometric features. Creep Creep (also retardation) describes the time- and temperature-dependent deformation of materials under constant stress. The creep test is an important indicator of the long-term behavior of elastomeric bearings.
D | E
Elastomeric bearings
The spring characteristic describes the load of the spring (here material "rubber") on its way.
Deformation bearings are bearings that allow the movements (torsion and displacements) not by mechanical construction, but by deformation of the bearing material (here always elastomer). Other designations are: Elastomeric bearing, rubber bearing. Deformation bearings can be reinforced and unreinforced.
F | G | H | I | J | K | L | M | N | O | P
Profiled bearings
Bearing made of a homogeneous elastomer sheet or extrudate with surface profiling or special geometric shaping.
Q | R
Kompakte Lager
Lager aus einer homogenen Elastomerplatte oder einem Extrudat ohne Oberflächenprofilierung oder sonstigen geometrischen Besonderheiten.
...
S
Sliding bearings
Sliding bearings are bearings in which the movements are effected by sliding two surfaces against each other. Plain bearings can be reinforced and unreinforced.
Spring characteristic (here as compression characteristic)
The spring characteristic describes the load of the spring (here material "rubber") on its way.
The test can be displacement-controlled or force-controlled. In displacement-controlled testing of the spring characteristic, a specific deflection distance (e.g. 40 % deformation) is approached and the force response is determined. In the force-controlled test, a previously defined force is applied to the material (spring) and the distance covered is determined.
The results are usually displayed in a force-displacement diagram.
...
T | U P
Unreinforced bearing
Bearing made of a/ a homogeneous elastomer sheet or extrudate without metallic or textile reinforcements.
V | W | X | Y | Z
Elastomeric bearings
Lager im Bauwesen | Eggert, Kauschke
Vorlesungen über Lager im Bauwesen | Eggert
Elastomere Federung, elastische Lagerung | Battermann, Köhler
Kautschuk Technologie | Sommer Röthemeyer
Technische Elastomerwerkstoffe | Freudenberg
Polymer Engineering | Eyerer, Hirth, Elsner
Werkstoffe | Hornbogen
Normen
DIN 4141 | DIN EN 1337 | Eurocode 0, | Eurocode 1, | Eurocode 2
DAfStb Heft 339
Simply arrange an appointment with us. Our team will be happy to provide you with advice. By telephone or by email.
DE