What is the use of blanking force to calculate pressure center
Publish: 2021-04-26 19:48:08
1. The pressure center of blanking die must be calculated. The force of the press generally acts on one point. If the blanking center is far away from the center point of the press, it is easy to cause damage to the machine tool and wear to the guide rail. I have seen on site that the guide pillar of the press is only worn on one side, and all the guide pillars are scrapped in the end. It also does great harm to the guide device of the die. When designing the die, try not to be eccentric
2. The action point of the resultant force of blanking force is called the pressure center of the die. In the design of the stamping die, the pressure center of the die must coincide with the center of the slider of the press. Otherwise, the eccentric load will occur ring the stamping, which will lead to the sharp wear of the die, the slider and the guide rail of the press, rece the service life of the die and the press, and even damage the die and equipment, resulting in stamping accidents. Therefore, the accurate determination of die pressure center plays an important role in die design
3. The pressure center of the die is the action point of the resultant force of the punching force
4. The pressure center of the die is the action point of the resultant force. In order to ensure the normal operation of the press and the die, the pressure center of the die should coincide with the center line of the press slider. Otherwise, the slider will bear eccentric load ring stamping, which will lead to abnormal wear of slider guide rail and die guide part, and the reasonable gap can not be guaranteed, thus affecting the quality of parts and recing the life of the die, and even damaging the die. In actual proction, e to the special shape or layout of the stamping parts, it is not suitable to make the pressure center coincide with the center line of the die handle in consideration of die structure design and manufacturing. At this time, attention should be paid to make the deviation of the pressure center not exceed the allowable range of the selected press.
5. In the field theory, the pressure center in aerodynamics should be described by the gradient in mathematics, that is to say, it is like developing a mountain into a terrace, and the top of the mountain is the place with the highest gradient.
6. Punching force to calculate the punching area, as well as a thickness of the material and a coefficient K value
7. Question: how much pressure is required for the workpiece with a circumference of 327mm, a thickness of 8mm and a material of Q235?
answer: the upper limit of tensile strength of Q235 is 460Mpa,
F = Lt σ B = 327 * 8 * 460 = 1203360n
about 120.336t
take the safety factor of 0.7, take the press of more than 172t, according to the priority number system:
1, open press can buy 200t punch press, model: j21-200, but in fact, it is also capable on the machine tool of 160t, but it may cause bad influence on the machine tool
2. Closed single point press is 200 tons, model: j31-200,
3. Four column universal hydraulic press is 200 tons, namely y32-200
answer: the upper limit of tensile strength of Q235 is 460Mpa,
F = Lt σ B = 327 * 8 * 460 = 1203360n
about 120.336t
take the safety factor of 0.7, take the press of more than 172t, according to the priority number system:
1, open press can buy 200t punch press, model: j21-200, but in fact, it is also capable on the machine tool of 160t, but it may cause bad influence on the machine tool
2. Closed single point press is 200 tons, model: j31-200,
3. Four column universal hydraulic press is 200 tons, namely y32-200
8. The pressure center is the geometric center and the center of mass of the part. According to the center of mass, the origin of the stamping coordinate system is established. The Z axis is the central axis of the die handle. After that, the die parts are arranged and the building blocks are set up
now we don't need to calculate according to the book. General 3D software such as CATIA has the function of automatically finding the center of mass. If we calculate according to the formula in the book, the irregular surface parts will be half dead....
now we don't need to calculate according to the book. General 3D software such as CATIA has the function of automatically finding the center of mass. If we calculate according to the formula in the book, the irregular surface parts will be half dead....
9. In fact, both designs exist and work. The key point is that in the case of CG in front of CP, considering the static margin of the aircraft, in the case of civil aircraft, e to the stability of the aircraft&# 8203; It is preferred that the tail proces negative lift for sexual reasons
another point is that ring the flight, the mass of the aircraft will decline, and its CG will constantly change its position. When CP exceeds CG, CG will move between CP of wing and CP of tail ring the whole flight (the weight distribution of fuel makes CG move towards tail ring the flight). In this case, the tail's boom gets shorter and shorter over time. So, as time goes on, your tail becomes less and less. On the other hand, if CG is before CP, the moment arm will also decrease, but it is always larger than the other case. As a result, you can control the aircraft better through the elevator
the limitation of CG design before CP is to ensure that CG will not cross CP at any time ring flight. Imagine that the CG of your plane is earlier than CP. In this case, you can use a wing with a negative curvature for the tail, or set a symmetrical tail at a negative incidence angle. In order to have a stable aircraft throughout the flight, you should ensure that CG does not cross CP. Because if so, your tail will create an unstable moment around CG, and the aircraft will lift to the nose until stall
in short, both designs are effective. However, CG case before CP is more suitable for civil aircraft "structural design". For military aircraft, there is no civil design constraint, so both designs are applicable<
answer 2:
it is not "always" there, but if the aircraft needs a certain degree of internal stability to make it easy to control, it helps to put the center of mass in front of the aerodynamic center. This introces a slight nose down pitching force, which is easily compensated by the appropriate downward force on the elevator. The closer the center of mass is to the aerodynamic center from this forward position, the more sensitive the aircraft is to the pitch control input. If the center of mass is located at the rear of the aerodynamic center, the natural inclination of the aircraft will become unstable, and constant elevator input is required to keep it level. The aircraft will "pitch" and may even deviate completely from the controlled flight
aircraft that are intentionally inherently unstable are commonly used in the current era, and they are controlled by complex software - the mass center can be located at the rear of the aerodynamic center
the center of gravity is not necessarily in the same physical position as the center of gravity (CG). If the aircraft is horizontal, it will be in the same vertical plane as CG, but can be above or below CG. If the center of mass is higher in the fuselage, the CG will move backward with the nose up; On the contrary, if the center of mass is lower in the fuselage, the nose up position will make CG move forward
a similar situation occurs in the aerodynamics Center - it is not the same as CP, but in a horizontal plane, it is in the same vertical plane as CP
both Anas Mazz and Rajan bhavnani have useful and helpful answers<
answer 3:
horizontal stabilizer is the main surface to stabilize the aircraft on the longitudinal axis. Leaving CP behind CG can make the aircraft more stable. When the sudden gust attacks the aircraft, it will not only increase the angle of attack of the wing, but also increase the angle of attack of the horizontal stabilizer or tail. This means that both surfaces will generate pitch moment through CG, which makes the aircraft go into horizontal flight
in fact, you can keep CP before CG while still maintaining stability. In this case, the wing will proce a clockwise moment and the tail lift will proce a counterclockwise moment. The tail with a longer moment arm will proce a higher moment and a nose down pitch angle to guide the aircraft to the previous trim position. Compared with the main aircraft or wing, the tail design of many aircraft has a lower incidence angle. This has an effect on the percentage of lift on the rear panel. This is important because the tail receives air from the downwash of the wing, and downwash has a tendency to rece the angle of attack and tail lift
LW is the wing moment and lt is the tail moment. Note that the stronger moment arm of the tail proces a stabilizing moment
through reading so far, you will understand the importance of CG position. It determines the stability of the aircraft. It also affects stall, viscosity and even the effective range of the aircraft.
another point is that ring the flight, the mass of the aircraft will decline, and its CG will constantly change its position. When CP exceeds CG, CG will move between CP of wing and CP of tail ring the whole flight (the weight distribution of fuel makes CG move towards tail ring the flight). In this case, the tail's boom gets shorter and shorter over time. So, as time goes on, your tail becomes less and less. On the other hand, if CG is before CP, the moment arm will also decrease, but it is always larger than the other case. As a result, you can control the aircraft better through the elevator
the limitation of CG design before CP is to ensure that CG will not cross CP at any time ring flight. Imagine that the CG of your plane is earlier than CP. In this case, you can use a wing with a negative curvature for the tail, or set a symmetrical tail at a negative incidence angle. In order to have a stable aircraft throughout the flight, you should ensure that CG does not cross CP. Because if so, your tail will create an unstable moment around CG, and the aircraft will lift to the nose until stall
in short, both designs are effective. However, CG case before CP is more suitable for civil aircraft "structural design". For military aircraft, there is no civil design constraint, so both designs are applicable<
answer 2:
it is not "always" there, but if the aircraft needs a certain degree of internal stability to make it easy to control, it helps to put the center of mass in front of the aerodynamic center. This introces a slight nose down pitching force, which is easily compensated by the appropriate downward force on the elevator. The closer the center of mass is to the aerodynamic center from this forward position, the more sensitive the aircraft is to the pitch control input. If the center of mass is located at the rear of the aerodynamic center, the natural inclination of the aircraft will become unstable, and constant elevator input is required to keep it level. The aircraft will "pitch" and may even deviate completely from the controlled flight
aircraft that are intentionally inherently unstable are commonly used in the current era, and they are controlled by complex software - the mass center can be located at the rear of the aerodynamic center
the center of gravity is not necessarily in the same physical position as the center of gravity (CG). If the aircraft is horizontal, it will be in the same vertical plane as CG, but can be above or below CG. If the center of mass is higher in the fuselage, the CG will move backward with the nose up; On the contrary, if the center of mass is lower in the fuselage, the nose up position will make CG move forward
a similar situation occurs in the aerodynamics Center - it is not the same as CP, but in a horizontal plane, it is in the same vertical plane as CP
both Anas Mazz and Rajan bhavnani have useful and helpful answers<
answer 3:
horizontal stabilizer is the main surface to stabilize the aircraft on the longitudinal axis. Leaving CP behind CG can make the aircraft more stable. When the sudden gust attacks the aircraft, it will not only increase the angle of attack of the wing, but also increase the angle of attack of the horizontal stabilizer or tail. This means that both surfaces will generate pitch moment through CG, which makes the aircraft go into horizontal flight
in fact, you can keep CP before CG while still maintaining stability. In this case, the wing will proce a clockwise moment and the tail lift will proce a counterclockwise moment. The tail with a longer moment arm will proce a higher moment and a nose down pitch angle to guide the aircraft to the previous trim position. Compared with the main aircraft or wing, the tail design of many aircraft has a lower incidence angle. This has an effect on the percentage of lift on the rear panel. This is important because the tail receives air from the downwash of the wing, and downwash has a tendency to rece the angle of attack and tail lift
LW is the wing moment and lt is the tail moment. Note that the stronger moment arm of the tail proces a stabilizing moment
through reading so far, you will understand the importance of CG position. It determines the stability of the aircraft. It also affects stall, viscosity and even the effective range of the aircraft.
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