# What is Joints: Definition and 68 Discussions

A joint or articulation (or articular surface) is the connection made between bones in the body which link the skeletal system into a functional whole. They are constructed to allow for different degrees and types of movement. Some joints, such as the knee, elbow, and shoulder, are self-lubricating, almost frictionless, and are able to withstand compression and maintain heavy loads while still executing smooth and precise movements. Other joints such as sutures between the bones of the skull permit very little movement (only during birth) in order to protect the brain and the sense organs. The connection between a tooth and the jawbone is also called a joint, and is described as a fibrous joint known as a gomphosis. Joints are classified both structurally and functionally.

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1. ### JavaScript Physics engine with "angular stiffness" at joints

I have been experimenting with a minimal "toy" physics engine for JavaScript, called verlet.js but now I want to switch to a more versatile and feature rich engine. One feature I would like to use is the ability to assign a reference angle to a pair of segments (i.e. links, i.e. distance...
2. ### The Stewart Platform (why the joints?)

Good Morning As I have understood, the standard Stewart platform has six legs. Each leg consists of a lower and upper body, connected by a translational joint (TJ) (that enables extension and contraction) The bottom body of a leg, connects to the base plate via a UNIVERSAL JOINT (UJ) The top...
3. ### Engineering Structure Mechanics-Three Pinned/Hinged Arches

The Example 2 at this site ' http://ocw.ump.edu.my/pluginfile.php/1435/mod_resource/content/2/Chapter%205%20%E2%80%93%20Three%20Pinned%20Arch.pdf ' (page 14): It is parabolic hence the equation is y = (x^2)/10. I used the section method between A-D and applied equilibrium of moment to find a...
4. ### What do the numbers in the method of joints analysis for trusses represent?

Hello all I am trying to analyse a truss using the method of joint process i.e I am trying to determine whether each member is in tension or compression. I have the following truss that I want to analyse using the method of sections. Just focusing on joint A, I have created a FDB and...
5. ### Why weld joints are stronger than the base material itself?

I wonder it for a long time and still couldn't find a reliable source. I've seen some posts on the internet saying that welds are mostly stronger than the base material but at first glance it contradicts with my intuition. I'm working on a bicycle frame for myself and the welds are important for...
6. ### Type of Joints in portal frame

I was told that for building portal frame, the beam to column connection must be rigid , which means, it has to be fixed , while the column to foundation connection can be either fixed or pinned, am I right ? I couldn't find anything about this online . Pls help
7. ### Static Analysis Of Bolted Joints

Greetings, I'm an Undergraduate Mechanical Engineering student. I want to design bolted joints on Figure 1, I'm trying to perform a basic static analysis of the structure to understand the forces acting on its members and its current stress state. I've included dimensions and position of its...
8. ### Truss Method of Joints: Solving Unequal Member Forces

Homework Statement The load is known. Just 2 reactions needed to describe all external forces. Homework Equations method of joings The Attempt at a Solution I'm working on a pretty simple truss for work and want to check some of the elements for buckling. The strange thing is I am not...
9. ### Automotive How to Calculate maximum torque a riveted joint can stand

A plate is riveted with a rivet having small rod like projection over the head and the point as shown in drawing.Considering we fix the plate to a vise,and then giving torque to the Rivet Rod;What will be the Maximum Torque the rivet can withstand without getting loosened and how to calculate...
10. ### Statics: Method of Joints (Truss)

Can someone explain to me why that highlighted force is 0? Homework Equations ∑Fx = 0 The Attempt at a Solution I found FDC to be 780lb and I am still trying to solve for FDE
11. ### Solving Truss Equations: Find Force in Members EA, EF and EG

Homework Statement Find force in members EA, EF and EG given the loads shown. A and G are pinned supports. Homework Equations Three equations of equilibrium for sections (method of sections) 2 equations for any node (method of joints). I also used the dimensions to decompose member forces. The...
12. ### Joint Calculation for Truss Reactions: r, m, and j in Truss Members

Homework Statement in the notes, r =number of reactions, m = number of truss members , j = number of joints i suspect that the j for d and e are wrong... Homework EquationsThe Attempt at a Solution I have circled the joints and calculated them, for d , j= 9, for part e , it should be j= 14, Am...
13. ### Method of Joints Query: Shedding Light On Truss Calculations

Hello all, I have recently been attempting to refresh my memory in regards to method of joints and have been making some reasonable progress, however I have ran into a stumbling block that has left me quite puzzled. I have been using the Skyciv truss calculator to verify my work and for the...
14. ### Method of joints for bridge truss

Homework Statement Calculate the forces for each member. Homework Equations Sum of forces in x=0 Sum of forces in y=0 Sumof moments about D=0The Attempt at a Solution Work is on attached image of problem. I'm having trouble solving for support reactions. At D there is [/B] a hinge. At A...
15. ### What is the reasoning behind the different forms of F in bolted joint equations?

I am having trouble understanding the F used in these equations. Is it supposed to be the force F shown on the left, or is it F/2 or F/4?

Homework Statement Homework Equations M = 3(L – 1) – 2J L= number of links, J = number of joints The Attempt at a Solution As far as I can see, using the above L and J values for each linkage yields the correct M value. However, the L and J values lead me to think I'm missing something...
17. ### Mechanics, degree of freedom question

Homework Statement Calculate the DoF (mobility) of the following system: Homework Equations [/B] M = 3(L-1) - 2J1 - J2 (where L = number of links, J1 is the number of full binary joints and J2 is the number of half joints. The Attempt at a Solution I am very confident about there being...
18. ### Solve Truss Joints Using Method of Joints

Homework Statement Determine the axial forces in the members of the truss and indicate whether they are in tension or compression. Homework Equations Fx = 0 Fy = 0 Mp = 0 The Attempt at a Solution I attempted to find the reactions at the supports first. So: Fx = 0 = Bx + 800cos(250)N Fy...
19. ### Truss Analysis : Method of Joints only (Picture provided)

Hello, In my statics course, we had to design a bridge, and now, I have to calculate the internal forces in every member of the truss. At first, I have found Ay and Oy with the moment of force, but then, I am stuck since the truss is not perfectly aligned. Sadly, I can't use the method of...
20. ### Understanding Bolted Joints: Basics & Forces Explained

Hello I really struggle with understand how and why bolted jonts actually works: The following figure copied from http://ocw.mit.edu/courses/mechanical-engineering/2-72-elements-of-mechanical-design-spring-2009/lecture-notes/MIT2_72s09_lec10.pdf shows a bolted joint: After the bolt is...
21. ### Truss Homework: Solving for Joint Forces using Method of Joints

Homework Statement http://oi59.tinypic.com/2h65cm1.jpg[/B]Homework EquationsThe Attempt at a Solution [/B] All triangles: angles A = B = 53.13 degrees, angle C = 73.74 degrees from cosine law and the 180 degree ruleBut it looks like all of the joints in the bridge have more than 2...
22. ### Method of Joints, Virtual Load

Hi I was hoping someone could clear something up for me, I've been set an virtual load (unit load method) question at University, that part of the question I can do however its the calculating the force on the members part that I am struggling with. The question asks for all the forces in the...
23. ### Understanding Method of Joints for Solving Statics Problems

Homework Statement So this is more of a general question as I'm trying to follow the book's way of solving the problems and it's not working. This is what the book says: Always assume the unknown member forces acting on the joint’s free-body diagram to be in tension ; i.e., the forces “pull”...
24. ### Truss Analysis using joints method 2D analysis

Given a warren truss, where the load is 2kN/m so the weight per joint is 10kN, since the ends are supported by ground not truss, can anyone please verify my way of solving for the tension and compression at point B. See attachment Your help is greatly appreciated. So I figured out that AB is...
25. ### Load carrying expansion joints

Are there any expansion joints (for example between two beams) which can carry a shear force?
26. ### Engineering Statics 3D equilibrium (sleeves and ball joints)

Homework Statement Ends A and B of the 5-kg rigid bar are attached by lightweight collars that may slide over the smooth fixed rods shown in the figure. The center of mass of the bar is at its midpoint. The length of the bar is 1.5 m. Determine the horizontal force F applied to...
27. ### Solving a Truss: Methodial of Joints

Homework Statement The truss is suspended by two pin joints. Each segment is 3 m wide and 4 m high. The applied force is F = 6 N. What is the force in member 10? Include the sign for tension (positive) or compression (negative). Homework Equations T=rf sum of forces = 0 The...
28. ### Truss Analysis - Method of Joints

Ok so first I considered the entire structure (which is in equilbrium) and resolved to find out that HA = -4.8 kN, VA= -0.9 kN and VE=0.9 kN. (these answers were correct according to mark scheme) Then I considered each joint separately (in order to find the forces in each of the members). I...
29. M

### Method of Joints Truss Analysis

Hello, I was curious, for the method of joints truss analysis, when considering a joint, is it assumed that all forces at that joint are radiating away from the joint (meaning tension), even if it was already found from a previous joint that the member is acting in compression? I'm not sure if...
30. ### Statics: Forces in a truss, method of joints

Homework Statement Using the method of joints, determine the force in each member of the truss shown. State whether each member is in tension or compression. Homework Equations ƩFx=0 ƩFy=0 ƩM=0 The Attempt at a Solution I got the forces at C and D by using the equilibrium...
31. ### Gap in Joints of Large Steel Constructions

Hello, I'm a very curious EPE student (electrical power engineer) who is trying to figure out why there are variable gaps between joints of large steel structures. Because of this gap the stress seems to be distributed with peak force at the intersection of the bottom plate, why is this...
32. ### Why welded joints rust faster?

Hey , Earlier today, I discovered that on a metal frame in my house, rust was accumulating on the weld whereas other parts seemed ok. Some ppl told me that it was because the welded region was hotter and hence, it rusts faster. But I don't get it... The welded joint has been cool and at the...
33. ### Method of joints & forces between joints

Part of my assignment is to find the stresses in each member of a truss bridge, but unlike the problems I have been taught before, this involves a load between the joints of the bridge. Me and my group are using the method of joints to find the forces acting through each member, the problem is...
34. ### Converting Uniform Load to Point Forces on Truss Pin Joints

If there is a uniformly distributed load due to gravity on a truss, how do I convert this into point forces on the three pin joints on the truss? I am having trouble trying to work it out as I'm pretty sure there will be both forces in the x and in the y for each of the joints, but I can't...
35. ### What is the Relationship Between Input Shaft Angle and Torque in U-Joints?

Hello, I need to select an appropriate electric motor for a drive mechanism which includes a U-Joint. It's understood that rotational variances occur in U Joints as the angle of the input shaft increases relative to the output shaft. Can someone refresh my memory as this relates to torque? In...
36. ### Constant velocity joints vs. universal joint.

i have to design an actuation system which will change the angle with which the power is transmitted through a motor,the range of angle is about,--35 to +35,w.r.t to the vertical,what should i use,a u joint or a velocity joint?there is a predefined load on the shaft(bending + torsional),what...
37. ### Method of Joints: Solving for Fab in a Truss Structure

Homework Statement Everything is in the PDF Homework Equations The Attempt at a Solution So once I get to the last 2 joints Then all I have left to solve for is Fab. I get different numbers each way i try to figure it out. So I know I'm doing something wrong. Any ideas?
38. ### Truss - Method of Joints in terms of load P

Hello guys. I would like someone to check that I am doing this problem correctly. The answer given in the book is 0.577(P) for FAB and FAE which differs from the answer I get. Homework Statement Determine the force in each member of the truss in terms of the load P and state if the members...
39. ### The Method of Joints (support reactions)

So, I have a question regarding the method of joints used to solve force members in a truss. I am just starting the question and I am stuck on determining the moment in the support reactions. So my questions are: (1) For the moment around support reaction E do I include Force Dx in my...
40. ### What is the reason for using electrically insulating joints in a water system?

I'm living in France and have just replaced my "chauffe eau" - a 200 litre hot water tank with built in 2.4kW electrical heater and thermostat. The instructions say that it should be installed with an electrically insulating joint where the hot water outlet pipe is attached. I bought a pair...
41. ### Deflection - difference between pin and fixed joints

Deflection -- difference between pin and fixed joints Hello all I have a question regarding deflection. What is the difference between pin and fixed joint in frame l(first picture fixed the second pin), I can summarize my question in points: 1.fixed connection introduces equal theta as...
42. ### Tension and Compression in Truss Joints

Statics - Forces in a Truss Homework Statement http://i.imgur.com/NbZlc.png Homework Equations Equations of equilibrium (sum of the forces in all directions = 0, sum of the moments about an point = 0) The Attempt at a Solution My attempt: http://i.imgur.com/qlLCY.jpg Hopefully...
43. ### Truss analysis using method of joints

The question is to calculate the forces ina ll members of the trussnby method of joints. First i have calculated the reaction forces for A and B by taking the moment from both these points. These came too: Ay=25N and By=25N I do not know where to go from here, what point should i analyse...
44. ### Truss Analysis: Method of Joints

I'm doing this truss analysis by method of joints and I have determined the forces at "A" and "G" and have moved on to determine the loads at each joint. I have determined the angle to be 63.34 for the 10' and 53.13 for the 15'(I took the inverse tangent of 20/10=63.34 and I took the inverse...
45. ### How to protect poor solder joints

I have tried and tried to make a decent joint, but the wire keeps falling off! the joint is very small, and my tools are limited, so I need suggestions on rigging it up somehow. I'm thinking a drop of two-part epoxy? thanks! picture...
46. ### Strength reduction factors for welded edge joints

I've looked everywhere and can't seem to find any information. Would someone be kind enough to point me to some literature?
47. ### How to calculate strength of welds (welded joints)?

I need to calculate strengths of welds / welded joints. Could you point me to a handbook or website? I will be a bit more specific. The welds are fusion welding w/o any filler materials and the materials to be welded are thin strips of stainless steel (thickness 5/1000 in)
48. ### Method O' Joints, question about the Method itself, semi-

Method O' Joints, question about the Method itself, semi-urgent! Homework Statement Hi everyone, my first post! :D This is more of a general question about the method rather than a specific example. I have a problem with substitution while I'm doing the method of joints for a loaded...
49. ### Method of joints, force in each member

Homework Statement Using method of joints, determine the force in each member of the truss. State whether each member is in compression or tension. Homework Equations joint method, I'm not sure how to describe it.The Attempt at a Solution The answer is of course Fab = 261.8 lb T Fbc =...
50. ### Medical What Is the Ideal Knee Joint Implant Design for Osteoarthritis Patients?

Any ideas of what's the best type of knee joints structure implant to help patients with osteoarthritis and other disease?