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Shape memory alloy characteristics
In addition to the strength, stiffness, ductility, ductility, and conductivity of metals, shape memory alloys also have very peculiar shape memory effects, superelasticity, and high damping properties. The alloy is a thermoelastic martensitic transformation alloy, and its phase transformation is reversible. The shape memory effect of the alloy is produced during the martensitic transformation.
Typical shape memory alloys are nickel-titanium alloys, in addition to copper-zinc-aluminum and copper-aluminum-antimony. Nickel-titanium (Ti50Ni50) alloy is one of the most practical shape memory alloys. Its martensitic transformation point is about 40°C, and it is convenient to use. Adding the third element can make the martensite transformation point reach 100°C. Its tensile strength is 636 MPa, pseudoelastic deformation is 10%, and it is generally practical in the range of 2% 3%. And reflect the influence of reheat rate and pre-deformation on the restoring force of nickel-titanium alloy (force to restore the original shape). It can be seen that the higher the temperature and the higher the heating rate, the greater the initial deformation and the greater the restoring force.
Nickel-titanium alloy's recovery force and regenerative speed relationship 400 300 200 100 300 320 340 360 380 Temperature T/K 100 k/s 35 k/s 15 k/s Recovery pressure/MPa refers to the memory alloy with its high temperature mother Phase (A) (Cscl structure) shape characteristics, TiNi memory alloy SME characteristics: deformation in the low-temperature M state, the residual strain disappears after heating, the alloy returns to the shape of the pre-deformation A state can reverse the stress-strain effect, when the alloy is free In the state, this effect can be used to output strain to the outside. When the alloy is in the constraint state, the stress can be output to the outside. As shown.
Relationship between restoring force and pre-deformation of nickel-titanium alloy Shape memory SE refers to the phenomenon that the memory alloy in the A state produces a strain that is much larger than its elastic limit strain under external force, and the strain can be automatically recovered after unloading. If the alloy exceeds the elastic limit stress under the temperature condition above Af, a large amount of plastic deformation occurs in the shape of the alloy (the elongation rate thereof is up to 10% or more) and stress induced martensite is generated. It is stable under the action of stress. Once the stress is eliminated, the martensite reverse phase transformation occurs immediately, and it returns to the state of the mother phase. The macroscopic deformation under the action of stress also disappears completely with the reverse phase transformation and returns to its original state. The stress-strain relationship is nonlinear, which is the superelasticity of the alloy. As shown.
The use of shape memory alloys in the application of TiNi shape memory alloys mainly utilizes the shape memory effect (SME) and superelasticity (SE) of the shape memory alloy and its derived damping effect. TiNi shape memory alloys are wire, plate, and spring. Components such as tubes, tubes, nails, and rings are gradually used in aerospace vehicles, space structure platforms, nuclear reactors, building bridges, and marine structures to control the deformation or vibration of structures, and to monitor the stress, strain, temperature, and damage inside structures. Such conditions improve the safety and reliability of the engineering structure.
The automobile thermostat automatically adjusts the amount of water entering the radiator according to the level of the cooling water temperature and changes the circulation range of the water to adjust the cooling capacity of the cooling system to ensure that the engine operates within a suitable temperature range. In the prior art, automotive thermostats are controlled using thermal expansion and shrinkage of paraffin. When the water temperature is lower than 70°C, the thermostatic expansion tube is in a contracted state and the main valve is closed. When the water temperature is higher than 80°C, the expansion tube expands, the main valve gradually opens, and the circulating water in the radiator begins to flow. The thermostat must maintain a good technical state, otherwise it will seriously affect the normal operation of the engine. If the temperature controller's main valve is opened too late, it will cause the engine to overheat; if the main valve is opened too early, the engine warm-up time will be prolonged and the engine temperature will be too low.
Crane refers to a certain range of vertical lifting and horizontal lifting of heavy lifting machinery. Crane, also known as crane. The main characteristics of the tire crane is: the driving cab and lifting control room combined, is evolved from a crawler crane, crawler crane), will walk mechanism of tracks and walking part of the stent into the tire chassis, overcome the crawler crane, crawler crane) crawler board of pavement caused by the destruction the shortcoming and belongs to the material handling machinery. Some working characteristic of the heavy equipment is intermittent exercise to do that in a working cycle of materials, transport and unloading action of the corresponding institutions is to alternate work, crane in the market of the development and the use of more and more widely. Because no leg lifting and hanging heavy driving often appear some accident, speed also a crawler crane, crawler crane); stable operation, great weight, in a specific range hoisting walk, but must ensure that the formation of a solid road, tire pressure meet the requirements, hanging from the ground shall not be more than 50cm; it is forbidden to load walk long distances. In order to ensure the safety of operation, at present, there is basically no lifting operation of supporting legs. Supporting the use of crane wire rope varieties including phosphating coating steel wire rope, galvanized wire rope and plain steel wire rope.
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classification
In the construction of the bridge crane in use, according to the structure and properties of different, generally can be divided into
For the light small lifting equipment, bridge type crane and boom type crane, four types of cable crane. Light small lifting heavy equipments such as: Jack, air hoist, electric hoist, hoist (also known as balance crane), winches, etc.. A type of bridge crane such as beam crane etc.. Boom type crane, such as fixed crane, tower crane, truck crane, tire crane, crawler crane, etc.. Cable crane, such as lift, etc..
According to the weight of the nature of points: mobile cranes, tower cranes, mast cranes.
By the driving mode: a concentrated drive, which uses a motor to drive the long drive shaft drive on both sides of the driving wheels; on the other class is respectively driven, is on both sides of the driving wheels to the a motor drive. Brake, reducer and motor are combined into one "triple a" driven by a small bridge crane in more, the weight of general overhead traveling crane for ease of installation and adjustment, driving device often used universal coupling.
According to the structure of the form, crane is mainly divided into light small lifting equipment, bridge (bridge and Gantry cranes, jib (self-propelled, tower, gantry type, type railway, pontoon, mast type crane), cable type.
1. light small lifting equipment
Light small lifting equipment is characterized by light, compact structure, simple operation, the scope of the project to point, line based. Light, small lifting equipment, generally only a lifting mechanism, it can only make a single lift heavy. Belong to this category are: Jack, pulley, hand (gas, electric hoist, winch etc.). Electric hoist is often equipped with a running trolley and metal frame to expand the scope of operation.
Electric hoist
CD1, MD1 series wire rope electric hoist system in the original CD, MD based on the improved products. The device has the advantages of compact structure, light weight, safety, reliability, high degree of commonality of parts and components, strong compatibility, high lifting capacity, convenient maintenance, etc., and is widely used.
The gourd has two types of fixed and trolley type. Fixed fixed foot in the upper, lower, left and right positions are divided into A1, A2, A3, A4 four types, can be installed directly on the frame, the car has a running function, can be installed on the track to use.
2. bridge crane
Can be used in the rectangular space and its operations, more for the workshop, warehouse, open yard and other items of loading and unloading, there are beam cranes, bridge cranes, cable cranes, bridge, etc..
(1) beam type crane: beam type crane mainly includes single girder bridge crane and double girder bridge crane
The single beam bridge crane used in the composite section I-shaped steel or steel and steel plate. Lifting trolley is often used as a hand hoist, electric hoist or hoist as a lifting body parts assembly.
The bridge is divided into supporting and hanging two. The former bridge along the beam of the vehicle crane orbit; the latter bridge along the hanging in the factory building roof truss crane rail operation. Single beam bridge crane breaking up, electric two. Manual single girder bridge cranes agencies work speed is low, the weight is small, but its quality is small, easy to organize production, low cost, suitable for no power move after the volume is small, the high requirement of speed and productivity occasions. Manual single girder bridge crane using manual monorail car as the car running, hand pulling hoist as lifting mechanism. The bridge from the main beam and side beam composition. The commonly used single beam, end beam is welded with steel plate or steel bending forming into.
Electric single beam bridge crane work speed, productivity is higher than the manual, the weight is also large. Electric single beam bridge from the bridge crane, crane traveling mechanism
(2) bridge crane:
Bridge crane is a bridge type crane running on the elevated track, also known as crane. Bridge crane bridge laying along the elevated track in the vertical sides of runs, heavy cart along the laying on the bridge transverse running track, constitute a rectangular scope of work, you can make full use of space below the bridge lifting material, from the ground equipment hindered.
Bridge crane can enable hanging on hooks or other fetching device of heavy vertical lifting and horizontal movement in the space. Bridge crane, including: lifting mechanism, large and small car running mechanism. Depending on the coordination of the mechanism, the weight can be lifted and carried in a certain cubic space. Bridge cranes, loading and unloading bridge, bridge crane, cable crane and so on are such.
Bridge crane widely used in indoor and outdoor warehouses, factories, docks and open storage yard, etc.. Bridge crane can be divided into ordinary bridge crane, simple beam bridge crane and metallurgical special bridge crane three.
General by the general bridge crane lifting trolley and bridge operationorganization bridge metal structure. Lifting trolley is composed of three parts, the lifting mechanism, the trolley running mechanism and the small frame.
The hoisting mechanism comprises an electric motor, a brake, a speed reducer, a drum and a pulley block. The electric motor drives the drum to rotate through the speed reducer, so that the steel wire rope is wound on the drum or is dropped from the drum to lift the heavy object. Small frame is a support and installation of lifting bodies and car running institutions and other parts of the rack, usually for welding structure.
(3) the gantry crane gantry structure according to the general form, main form, form to classify the spreader. Generally used in port.
According to the door frame structure
(a) the whole gantry crane: the main beam without suspension, the car in the main span of the.
(b) semi portal crane: the legs are high or low, can be used in accordance with the requirements of the use of the site.
(c) double cantilever gantry crane: the most common form of structure, the structure of the force and the effective use of the site area are reasonable.
According to the structure of the main beam structure
(a) single girder gantry crane
Single girder cantilever gantry crane is simple in structure, easy to manufacture and installation, and its own quality is small. Compared with the double girder gantry crane, the overall stiffness is weaker. Therefore, when the weight is Q = 50t, S = 35m span, can use this form. Single beam gantry legs to C type and L type two forms of L type of convenient manufacture and installation, good stress condition, its smaller mass, but to lift goods through the legs of the space is relatively small. The C shaped support legs are bent or bent, and the purpose is to have a larger transverse space so as to enable the goods to pass through the supporting legs.
(b) double beam bridge crane
Double girder overhead traveling crane is composed of straight rail, crane girder, lifting trolley, power supply system and electrical control system, which is especially suitable for large scale suspension and large range of weight.
Double beam bridge crane bearing capacity is strong, span is big, the overall stability is good, many varieties, but its quality with the same play weight of single girder gantry crane compared to larger, the construction cost is also high. According to the different structure of the main beam, it can be divided into two types of box girder and truss. Generally use box structure.
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