How to calculate bending force
Publish: 2021-03-22 22:20:00
1. 1、 Lever
(1) basic concept of lever
a hard rod that can rotate around a fixed point under the action of force is called lever
there are five terms of lever: ① fulcrum: the point around which the lever rotates (o); ② Power: the force that makes the lever rotate (F1); ③ Resistance: the force that prevents the rotation of the lever (F2); ④ Power arm: distance from fulcrum to action line of power (L1); ⑤ Resistance arm: distance from fulcrum to resistance action line (L2)< (2) the condition of leverage balance × Power arm = resistance × The resistance arm, the equilibrium condition, is the lever principle discovered by Archimedes< (3) three levers:
1. Labor saving lever: L1 & gt; L2, F1 & lt; F2 The feature is labor saving, but it costs a lot of distance (e.g. iron scissors, guillotine, driver)
② lever: L1 & lt; L2, F1 & gt; F2 The characteristic is laborious, but saves the distance (e.g. fishing rod, barber scissors, etc.)
③ equal arm lever: L1 = L2, F1 = F2 when balancing. It is characterized by no effort and no effort Such as: balance)
2. Buoyancy
(1) buoyancy
the upward force of liquid or gas on an object immersed in liquid or gas is called buoyancy. The cause of buoyancy is: the object immersed in liquid (or gas) is subject to the upward and downward pressure difference of liquid (or gas). Buoyancy is applied to liquid (or gas), buoyancy belongs to elastic force
(2) Archimedes principle
an object immersed in liquid is subject to upward buoyancy, which is equal to the gravity of the liquid it displaces. Expression: F = g row= ρ Liquid V discharges g (Archimedes principle also applies to gas)
it can be concluded that the density of the liquid and the volume of the liquid displaced by the object are two factors that affect the buoyancy< (3) the calculation method of buoyancy
① Archimedes principle: F floating = g row= ρ Liquid V row g (also suitable for gas)
② two force balance: F floating = g object (suitable for floating and suspension)
③ multi force balance: F floating = G-F (this is the case of measuring buoyancy with a spring dynamometer)
④ pressure difference method: F floating = f up-f down (not commonly used)
(4) measurement of buoyancy
① common method: measure the gravity g of an object with a spring dynamometer, When an object is immersed in the liquid and the indication F of the spring dynamometer is read out, the buoyancy of the object immersed in the liquid is: F floating = G-F< (2) measuring v-row (measuring cylinder) method: measure v-row and use f = g-row= ρ The buoyancy of liquid V row G is calculated
(5) the buoyancy and sinking conditions of objects are determined by the relationship between gravity and buoyancy. ① When gravity is greater than buoyancy, the object sinks; ② When gravity equals buoyancy, the object floats; ③ When gravity is less than buoyancy, the object floats< (6) utilization of buoyancy
1. Ship: hollow method is used to increase the available buoyancy, so that the ship can float on the water. The size of a ship is expressed in terms of its displacement - the mass of boiled water discharged when it is fully loaded
② submarine: submarine floats and sinks by changing its own gravity
③ balloons and airships: both use the buoyancy of the air to work. Balloon and airship lift, mainly by changing the volume of the airbag to change their own buoyancy to achieve.
(1) basic concept of lever
a hard rod that can rotate around a fixed point under the action of force is called lever
there are five terms of lever: ① fulcrum: the point around which the lever rotates (o); ② Power: the force that makes the lever rotate (F1); ③ Resistance: the force that prevents the rotation of the lever (F2); ④ Power arm: distance from fulcrum to action line of power (L1); ⑤ Resistance arm: distance from fulcrum to resistance action line (L2)< (2) the condition of leverage balance × Power arm = resistance × The resistance arm, the equilibrium condition, is the lever principle discovered by Archimedes< (3) three levers:
1. Labor saving lever: L1 & gt; L2, F1 & lt; F2 The feature is labor saving, but it costs a lot of distance (e.g. iron scissors, guillotine, driver)
② lever: L1 & lt; L2, F1 & gt; F2 The characteristic is laborious, but saves the distance (e.g. fishing rod, barber scissors, etc.)
③ equal arm lever: L1 = L2, F1 = F2 when balancing. It is characterized by no effort and no effort Such as: balance)
2. Buoyancy
(1) buoyancy
the upward force of liquid or gas on an object immersed in liquid or gas is called buoyancy. The cause of buoyancy is: the object immersed in liquid (or gas) is subject to the upward and downward pressure difference of liquid (or gas). Buoyancy is applied to liquid (or gas), buoyancy belongs to elastic force
(2) Archimedes principle
an object immersed in liquid is subject to upward buoyancy, which is equal to the gravity of the liquid it displaces. Expression: F = g row= ρ Liquid V discharges g (Archimedes principle also applies to gas)
it can be concluded that the density of the liquid and the volume of the liquid displaced by the object are two factors that affect the buoyancy< (3) the calculation method of buoyancy
① Archimedes principle: F floating = g row= ρ Liquid V row g (also suitable for gas)
② two force balance: F floating = g object (suitable for floating and suspension)
③ multi force balance: F floating = G-F (this is the case of measuring buoyancy with a spring dynamometer)
④ pressure difference method: F floating = f up-f down (not commonly used)
(4) measurement of buoyancy
① common method: measure the gravity g of an object with a spring dynamometer, When an object is immersed in the liquid and the indication F of the spring dynamometer is read out, the buoyancy of the object immersed in the liquid is: F floating = G-F< (2) measuring v-row (measuring cylinder) method: measure v-row and use f = g-row= ρ The buoyancy of liquid V row G is calculated
(5) the buoyancy and sinking conditions of objects are determined by the relationship between gravity and buoyancy. ① When gravity is greater than buoyancy, the object sinks; ② When gravity equals buoyancy, the object floats; ③ When gravity is less than buoyancy, the object floats< (6) utilization of buoyancy
1. Ship: hollow method is used to increase the available buoyancy, so that the ship can float on the water. The size of a ship is expressed in terms of its displacement - the mass of boiled water discharged when it is fully loaded
② submarine: submarine floats and sinks by changing its own gravity
③ balloons and airships: both use the buoyancy of the air to work. Balloon and airship lift, mainly by changing the volume of the airbag to change their own buoyancy to achieve.
2.
When calculating the force, it has nothing to do with whether the lever is bent or not
because the arm of force is the distance from the fulcrum to the action line of the force, which has nothing to do with the shape of the lever. Finding out the arm of force can be calculated according to the lever balance condition. As shown in the figure below, the arm of force is the length of the dotted line, which has nothing to do with the shape of the rod
3. The maximum bending moment is: M = P (force) × A (distance)
section coefficient of rectangle w = a × b × b ÷ 6＝2 × eight × eight ÷ 6 = 21.33 (cm3)
allowable stress of material [ σ〕 Take 1550 (kgf / cm ^ 2) = M ÷ W＝P × A ÷ 21.33＝P × two hundred ÷ 21.33
P＝1550 ÷ two hundred × 21.33 = 165 (KGF)
note: from the microscopic point of view, as long as something is a little heavy, the steel plate will be bent and deformed. It's just a matter of the amount of bending deformation. Now I'll give you how much force the steel plate can bear, which is more in line with the reality.
section coefficient of rectangle w = a × b × b ÷ 6＝2 × eight × eight ÷ 6 = 21.33 (cm3)
allowable stress of material [ σ〕 Take 1550 (kgf / cm ^ 2) = M ÷ W＝P × A ÷ 21.33＝P × two hundred ÷ 21.33
P＝1550 ÷ two hundred × 21.33 = 165 (KGF)
note: from the microscopic point of view, as long as something is a little heavy, the steel plate will be bent and deformed. It's just a matter of the amount of bending deformation. Now I'll give you how much force the steel plate can bear, which is more in line with the reality.
4. The maximum bending moment is: M = P (force) × A (distance)
section coefficient of rectangle w = a × b × b ÷ 6＝2 × eight × eight ÷ 6 = 21.33 (cm3)
allowable stress of material [ σ〕 Take 1550 (kgf / cm ^ 2) = M ÷ W＝P × A ÷ 21.33＝P × two hundred ÷ 21.33
P＝1550 ÷ two hundred × 21.33 = 165 (KGF)
note: from the micro point of view, as long as the point of heavy things will make the steel plate bending deformation, it's just the amount of bending deformation. Now I give you the calculation of how much force the steel plate can bear, which is more in line with the reality
section coefficient of rectangle w = a × b × b ÷ 6＝2 × eight × eight ÷ 6 = 21.33 (cm3)
allowable stress of material [ σ〕 Take 1550 (kgf / cm ^ 2) = M ÷ W＝P × A ÷ 21.33＝P × two hundred ÷ 21.33
P＝1550 ÷ two hundred × 21.33 = 165 (KGF)
note: from the micro point of view, as long as the point of heavy things will make the steel plate bending deformation, it's just the amount of bending deformation. Now I give you the calculation of how much force the steel plate can bear, which is more in line with the reality
5. 1. Torque: cross proct (m) of force (f) and arm of force (L). In physics, it refers to the force that makes an object rotate multiplied by the distance to the axis of rotation
2. That is: M = L × F Where l is the vector from the axis of rotation to the point of force and F is the vector force; The moment is also a vector< The dimension of moment is distance × power; The same dimension as energy. But the moment is usually in Newton meters, not joules. The unit of moment is determined by the unit of force and arm of force
4. The physical quantity of the rotation effect of the force on the object. It can be divided into moment of force to axis and moment of force to point. The moment of a force on an axis is the physical quantity of a force on an object rotating around an axis. It is an algebraic quantity whose magnitude is equal to the proct of the component of the force in the plane perpendicular to the axis and the vertical distance from the line of action of the component to the axis; The sign is used to distinguish the different turns of torque. It is determined according to the right-hand screw rule: clench the fist with the four fingers of the right hand along the direction of component force and the palm facing the rotation axis, and take the positive sign when the thumb direction is consistent with the positive direction of the axis, otherwise take the negative sign. The moment of a force to a point is the physical quantity that the force rotates the object around a certain point. It is a vector, which is equal to the vector proct of the position vector r of the force acting point and the force vector F. For example, if an object fixed at point o with a spherical hinge is subjected to a force F, the position vector from point O to point a is represented by R, and the angle between R and F is a. Under the action of F, the object rotates around the plane perpendicular to R and F and through the axis of o point. The magnitude of rotation and the direction of rotation axis depend on the moment vector m of F to o point, M = R × F The size of M is rfsina and the direction is determined by the right hand rule. The projection of moment M on the rectangular coordinate axis passing through the moment center O is MX, my and MZ. It can be proved that MX, my and MZ are the moments of F on the X, y and Z axes. The dimension of moment is l2mt - 2, and its international unit is n · M
5. For example, the moment of 3 Newton force acting on the lever 2 meters away from the fulcrum is equal to the moment of 1 Newton force acting on the lever 6 meters away from the fulcrum. Here, it is assumed that the force is perpendicular to the lever. In general, the moment can be defined as the cross proct of vectors (Note: not the vector dot proct): where R is the vector from the axis of rotation to the force and F is the vector force.
2. That is: M = L × F Where l is the vector from the axis of rotation to the point of force and F is the vector force; The moment is also a vector< The dimension of moment is distance × power; The same dimension as energy. But the moment is usually in Newton meters, not joules. The unit of moment is determined by the unit of force and arm of force
4. The physical quantity of the rotation effect of the force on the object. It can be divided into moment of force to axis and moment of force to point. The moment of a force on an axis is the physical quantity of a force on an object rotating around an axis. It is an algebraic quantity whose magnitude is equal to the proct of the component of the force in the plane perpendicular to the axis and the vertical distance from the line of action of the component to the axis; The sign is used to distinguish the different turns of torque. It is determined according to the right-hand screw rule: clench the fist with the four fingers of the right hand along the direction of component force and the palm facing the rotation axis, and take the positive sign when the thumb direction is consistent with the positive direction of the axis, otherwise take the negative sign. The moment of a force to a point is the physical quantity that the force rotates the object around a certain point. It is a vector, which is equal to the vector proct of the position vector r of the force acting point and the force vector F. For example, if an object fixed at point o with a spherical hinge is subjected to a force F, the position vector from point O to point a is represented by R, and the angle between R and F is a. Under the action of F, the object rotates around the plane perpendicular to R and F and through the axis of o point. The magnitude of rotation and the direction of rotation axis depend on the moment vector m of F to o point, M = R × F The size of M is rfsina and the direction is determined by the right hand rule. The projection of moment M on the rectangular coordinate axis passing through the moment center O is MX, my and MZ. It can be proved that MX, my and MZ are the moments of F on the X, y and Z axes. The dimension of moment is l2mt - 2, and its international unit is n · M
5. For example, the moment of 3 Newton force acting on the lever 2 meters away from the fulcrum is equal to the moment of 1 Newton force acting on the lever 6 meters away from the fulcrum. Here, it is assumed that the force is perpendicular to the lever. In general, the moment can be defined as the cross proct of vectors (Note: not the vector dot proct): where R is the vector from the axis of rotation to the force and F is the vector force.
6.
Approximate calculation formula of bending machine pressure: P = 650ssl / V
P: bending machine pressure (KN)
L: plate width (m)
s: plate thickness (mm)
V: lower die opening (mm)
reference data: Bronze (soft): 0.5p stainless steel: 1.5p
Aluminum (soft): 0.5p chromium molybdenum steel: 2.0P
7. Look at the materials of the book, to see the steel plate material, pressing method
the width of the sheet is 500-1500 mm; The thickness is 600-3000 mm. According to the types of steel, there are ordinary steel, high-quality steel, alloy steel, spring steel, stainless steel, tool steel, heat-resistant steel, bearing steel, silicon steel and instrial pure iron sheet; According to professional use, there are oil barrel plate, enamel plate, bulletproof plate, etc; According to the surface coating, there are galvanized sheet, tinplate, lead plate, plastic composite steel plate, etc.
the width of the sheet is 500-1500 mm; The thickness is 600-3000 mm. According to the types of steel, there are ordinary steel, high-quality steel, alloy steel, spring steel, stainless steel, tool steel, heat-resistant steel, bearing steel, silicon steel and instrial pure iron sheet; According to professional use, there are oil barrel plate, enamel plate, bulletproof plate, etc; According to the surface coating, there are galvanized sheet, tinplate, lead plate, plastic composite steel plate, etc.
8.
Bending force calculation formula: P = 650 × S × S × L / V (tensile strength = 450N / mm ~ 2)
P -- bending force (KN)
s -- plate thickness (mm)
L -- plate width (m)
V -- lower die groove width (mm), generally 8 times of plate thickness. For more than 10 thick plates, V is usually 10 times the thickness of the plate
under the pressure of the upper die or the lower die of the bending machine, the sheet metal first goes through elastic deformation, and then enters into plastic deformation. At the beginning of plastic bending, the sheet metal is free bending
with the pressure of the upper die or lower die on the sheet metal, the sheet metal and the inner surface of the V-shaped groove of the lower die are graally close, and the curvature radius and bending arm are graally smaller. Continue to press until the end of the stroke, so that the upper and lower die and the sheet metal are close to each other at three points, and a V-shaped bending is completed
extended data:
large fillet should be made at sharp bend to prevent folding ring final forging. There should be two fulcrums on the lower die to support the blank before bending. The height of these two points should enable the blank to be placed horizontally
When the blank is bent in the die groove, the control position of the stop table should be made at the end of the bending die groove. Transverse arc pits should be made on the protruding part of the die groove for the positioning of the blank. The depth of the pits is HL ~ (0.1 ~ 02) H (H is the depth of the corresponding part of the die groove). The die groove should have a proper slope, so that the blank can be easily taken out from the die groove after bending and the operation is convenient9. ? don't get it.... If you are using the corresponding cutter and lower die of the bending machine on the bending machine, there is one in the manual of the bending machine; If it is your design of the die or other, then before the design of these data calculated, specific you refer to the mold design.
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