Name: lifting tong force analysis
Uploaded: 2023-09-22T11:49:25.000Z
Duration: 1 min 30 s
Channel: JoVE

考虑一个提升夹具承载 100 kg 的载荷。该夹具由可动部分 DAF 和 CBG 组成，二者通过构件 AB 连接在一起。
假设该结构关于点 E 对称，则构件 AB 上所受的力是多少？
绘制出表示作用在点 E 的力的受力图。
缆绳的张力与负载的重力相平衡，并沿竖直方向向上作用。
ED 和 EC 为二力杆件，因此力 FED 和 FEC 分别指向铰接点 D 和 C。
这些力被分解为水平和垂直分量，并结合结构的几何形状来确定杆件 ED 与水平力分量之间的夹角。
根据水平方向的力平衡条件，可确保 FED 等于 FEC。
类似地，竖直方向的力平衡条件可得出杆件 ED 上的力。
现在，考虑截面 DAF 的受力分析图。可对节点 F 应用力矩平衡条件。
将所有已知数值代入方程，可得到沿构件 AB 的力。

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	<li>比尔，F.P.;约翰斯顿，ER;马祖克，DF;克伦威尔，PJ 和塞尔夫，BP（2019 年）。工程师的矢量力学 \u2012 静力学和动力学。纽约:麦格劳-希尔。第 348 页</li>
	<li>Meriam， JL、Kraige， LG 和 Bolton， JN （2020）。工程力学 \u2012 静力学。新泽西州霍博肯:约翰·威利。页码 200</li>
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机械：问题求解ii

Machines: Problem Solving II

机械是由可移动、由销进行连接的多力构件所组成的复杂结构，通过这些构件的共同作用来对力进行传递。假设有一个承载100公斤负荷的起重钳。它是由连接在一起的可移动部分DAF和CBG以及构件AB所组成的。 <img alt="Figure 1" src="/files/ftp_upload/14295/14295_PT_Fig_1v2.svg" style="text-align: center; height: 350px;"> 假设结构在E点处具有对称性，那么则可以计算作用在构件AB上的力。 首先，考虑在E点处产生作用力的受力分析图。其负荷的重量等于质量乘以其重力加速度，可以通过计算来得出其中的力为981N。电缆的张力能够平衡负载的重量并使其产生垂直向上的作用。ED和EC都是双力构件。因此，力FED和FEC能够分别指向接头D和C。 接下来，将力FED和FEC分解为水平方向和垂直方向的分量。通过结构的几何性质可以计算出构件ED和水平力分量之间的夹角为30.96度。 力的平衡条件可以应用到关节E中。 <img alt="Equation 1" src="/files/ftp_upload/14295/14295_PT_Equation_1v2.svg" style="text-align: center; height: 13px;"> <img alt="Equation 2" src="/files/ftp_upload/14295/14295_PT_Equation_2v2.svg" style="text-align: center; height: 13px;"> 沿水平方向应用力的平衡条件可以确保FED等于FEC。类似地，垂直力的平衡条件得到了构件ED上的力为953.46牛顿。 现在，绘制部分DAF的受力分析图。可以得出力矩的平衡条件将会应用到关节F中。 <img alt="Equation 3" src="/files/ftp_upload/14295/14295_PT_Equation_3v2.svg" style="text-align: center; height: 13px;"> 可以得出构件AB上的力为2423.76牛顿。 了解承载钳系统中每个构件所受的力对于确保安全操作和设计高效的起重机至关重要。通过对力进行分析并应用平衡条件，工程师可以优化其结构并确保其在各种条件下能够安全的承载负荷。

机械：问题求解II

机器是由可移动的、通过销钉连接的多力构件组成的复杂结构，这些构件协同工作以传递力。以吊装夹钳为例……

Education

教育

JoVE Core

Mechanical Engineering

机械工程

Unit 1

第一单元

Structural Analysis

结构分析

KEY TERMS AND CONCEPTS

关键术语与概念

lifting tong force analysis

Lifting tong force analysis shows how forces move through a pin-connected machine. The structure uses movable sections DAF and CBG with member AB linking them together. Because these parts work as connected members, the load can be studied with equilibrium methods.

The example starts with a 100 kg load at point E. The load weight is found by multiplying mass by gravity, which gives 981 N. The cable tension acts upward and balances that weight. Since the structure is symmetrical at E, the forces on the two sides can be compared.

Members ED and EC are two-force members, so their forces act along the members toward joints D and C. Their forces are then split into horizontal and vertical parts. Using the geometry of the tong, the angle between member ED and the horizontal is 30.96 degrees. Force equilibrium at joint E shows that F ED equals F EC, and the vertical balance gives the force in member ED as 953.46 N.

After that, a free-body diagram for section DAF is used. The moment equilibrium condition is applied at joint F. This step gives the force in member AB as 2423.76 N. This kind of analysis helps engineers check the forces in each member so lifting systems can work safely and efficiently under load.

Lifting Tong Force Analysis

introduction to structures

Structure Types and Force Paths

Structures are systems of interconnected members that support or transfer forces and handle the loads placed on them. Engineers can find the internal forces in a structure by breaking it apart and drawing free-body diagrams for individual members or groups of members. This helps show how structural elements behave and how the whole system stays stable under load. There are three main categories of structures: trusses, frames, and machines. Trusses are stationary structures that stay rigid when...

simple trusses

Simple Trusses and Triangular Frames

Simple trusses are planar trusses built from slender members joined at points in one flat plane. They are designed to carry external loads while using less material and keeping weight low. A truss is a structural framework, and the simple truss is one of its most basic forms. The most basic simple truss uses three members arranged in a triangle. That triangular shape is naturally stable and rigid because of its geometry. It gives students a clear starting point for understanding how larger...

method of joints

Truss Forces Using the Method of Joints

The method of joints is used to find the forces in structural trusses. It relies on equilibrium, which means the forces at a joint must balance. In this model, the truss members are connected by frictionless pins. For a plane truss, the members lie in the same plane. That means each joint has a coplanar and concurrent force system. The analysis begins by identifying and labeling all the joints in the truss. Next, each joint is isolated and shown in a free-body diagram. This diagram includes...

method of joints: problem solving i

Truss Joint Force Analysis by Equilibrium

The method of joints uses equilibrium to find forces in structural trusses. It treats the truss members as being joined by frictionless pins. For each joint, the forces acting there must balance. That balance makes it possible to solve for the member forces one joint at a time. Here, a truss has 20 N acting at joint C and 10 N acting at joint D. The method of joints is used to find FCB, FDC, FDB, and FAD. The analysis starts with a free-body diagram of joint C. Free-body diagram means drawing...

method of joints: problem solving ii

Truss Force Analysis at Joints A to E

Truss force analysis at joints A to E uses the method of joints to find the force in each member. The truss has frictionless joints, a wall support, and a roller support. A 150 N force is applied at joint A, and the member forces are solved from joint to joint. First, the angle between members AC and AB is found using the inverse tangent of the ratio of BC to AB. This gives an angle of 67.38°. A free-body diagram of joint A is then drawn, and each unknown force is split into vertical and...

zero-force member

Finding Zero-Force Members in Trusses

Trusses are frameworks made of slender members that connect at their ends by joints. Engineers and architects use them to stabilize and strengthen structures such as bridges, roofs, and towers. Truss members carry loads through tension and compression so the structure can handle external forces. A key part of truss analysis is spotting zero-force members. A zero-force member is a truss member that carries no stress under loading conditions. During analysis, some members may show zero force,...

method of sections

Truss Member Force Analysis by Sections

Truss member force analysis by sections finds the force in selected members of a truss. In this problem, forces F1 and F2 act at joints B and D. The goal is to determine the forces in members EF, DC, and DF. The method uses the idea that a truss in equilibrium also has each of its sections in equilibrium. A free-body diagram of the whole truss is drawn first. The moment equation about joint A is then used to estimate the support reaction at point E. Next, a cut is made along a sectional plane...

method of sections: problem solving i

Truss Member Force Calculation by Sections

Truss member forces can be found with the method of sections in a symmetrical roof truss. The structure here includes vertical, diagonal, and horizontal members. Each horizontal member is 4 m long. The vertical members FB and HD are 4 m long, and member GC is 6 m long. The roof truss carries loads at several joints. Joints F, G, and H each have a 2 kN load. Joints A and E each have a 1 kN load. To start the analysis, moment equilibrium is used at point A. The force and distance values are...

method of sections: problem solving ii

Truss member force analysis by sections finds the forces in selected members of a wall-mounted truss. The structure here includes diagonal, vertical, and horizontal members. The known loads and member lengths are used to solve for the forces in CB, GB, and GH. A cut is made through members CB, GB, and GH. The right side of the truss is then isolated as a free-body diagram. Next, the moment equilibrium equation is taken about point G. This step gives the force in member CB as 4 kN, and the...

space trusses

Space Truss Forces and Stability

A space truss is a three-dimensional truss made from members joined at their ends. It is the 3D version of a planar truss. These frameworks often use ball-and-socket joints, which help the structure stay stable and flexible under load. Space trusses are used in many construction projects because they can adapt to complex forces. Their basic building block is the tetrahedron. A tetrahedron has six members and four triangular faces. Engineers can build larger space trusses by adding one joint...

space trusses: problem solving

3D Truss Force Analysis with Joint Equilibrium

A space truss is a three-dimensional truss structure made of members connected at their ends. It often uses ball-and-socket joints to form a stable and versatile framework. Because it can handle complex loads, this type of structure is used in many construction projects. The example begins with a tripod made from a tetrahedral space truss. A ball-and-socket joint is located at C. The height and the lengths of the horizontal and vertical members are known. A tensile force is applied at joint D.

frames

Frame Analysis in Structural Systems

Frames are important parts of many mechanical and structural systems used every day. They are valued for stability and for their ability to bear heavy loads. A frame is built from two-force members and multi-force members, and the parts are connected with pin joints. Trusses are different because they are made entirely of two-force members. Frames appear in many practical settings. They can support beams and columns in buildings. They are also used in automobile chassis construction. In the...

frames: problem solving i

Jib Crane Reaction Forces in Frames

Jib crane reaction forces in frames are found by analyzing the pin joints, the cable tension, and the load carried by the pulley. The structure in this problem has an external load suspended from the pulley, and the member sizes are shown in the figure. Because the pulleys are frictionless, the force balance can be worked out step by step. The frame has two main parts. Member BD is a two-force member, which means it is a straight part loaded only at its two ends, D and B. Those end forces are...

frames: problem solving ii

Hydraulic Hoist Force Analysis

Hydraulic hoist force analysis shows how to find the forces in key members of a simple frame. The load is 1 kN, and the structure is represented with known member dimensions. In this setup, BF and BD act as two-force members. EFG and EDC are multi-force members, so each one is analyzed with a free-body diagram. The first step is to study member EFG. The inclined force in BF is split into vertical and horizontal parts. Then the moment equilibrium condition is applied at joint E. Using this...

machines

Cutting Pliers as a Force-Multiplying Machine

Cutting pliers are a machine that helps transmit force through movable, pin-connected members. In this example, the handles and cutting edges work together to cut wire by turning an input force into a larger output force at the jaws. When equal and opposite forces are applied to the handles, the cutting edges move toward each other. They then apply equal and opposite reaction forces to the wire. These reaction forces are greater than the forces applied to the handles, which is why the wire can...

machines: problem solving i

Toggle Clamp Force Analysis

A toggle clamp can be analyzed to find its clamping force from a known handle force. In this example, a 200 N force is applied at the handle. The clamp is used in holding and clamping tasks in woodworking, metalworking, and assembly operations. The toggle clamp is a machine structure made of movable, pin-connected multi-force members. These members form a stabilized system that transmits force. Member CD is a two-force member, which means the forces at its ends are equal in magnitude and...

machines: problem solving ii

Lifting tong force analysis shows how forces move through a pin-connected machine. The structure uses movable sections DAF and CBG with member AB linking them together. Because these parts work as connected members, the load can be studied with equilibrium methods. The example starts with a 100 kg load at point E. The load weight is found by multiplying mass by gravity, which gives 981 N. The cable tension acts upward and balances that weight. Since the structure is symmetrical at E, the...

key terms and concepts

Analyze a lifting tong with pin-connected members, symmetry, and equilibrium. See how force, tension, and moments determine the load on member AB.

Lifting Tong Force Analysis | JoVE K12

JoVE Core Mechanical Engineering offers concise, easy-to-understand animated videos covering key topics such as equilibrium, forces, truss analysis, and structural mechanics. Explore their real-world applications, and witness these concepts in action through scientist-led experiments.

mechanical engineering

Lifting Tong Force Analysis

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