Types of Rivet Failure: Riveted Joints Failure and How to Avoid It
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Table of Contents
Rivet failure is bound to happen. So how do we go about avoiding rivet failure as much as possible? This guide will show you the common types and causes of rivet failure. Of course, you will also learn how to solve the different types of rivet failures.
Table of Contents
Riveted Joints are a form of permanent joint that utilizes rivets to join two or more members together. Riveted joints are formed by drilling holes in the parts to be joined and driving rivets through the holes and then striking or pulling the rivets at one or both ends to expand the heads of the rivets, creating a strong fastening effect. Because riveted joints are not removable, they are typically used in structures requiring high strength, durability, and resistance to vibration.
You will often see riveted joints in structural engineering, aerospace, ships, bridges, railroad vehicles, boilers and some mechanical equipment.
Types of Riveted Joints
- Lap Joint: Riveted joint where a portion of two members overlap. Commonly used for joining plates.
- Butt Joint: Two members with opposite ends are joined by a riveted plate, usually used for thicker materials.
Why Rivets Fail?
No matter what the fastener is, there is always the possibility of a connection failure. Rivets are no exception. So what about riveting as a permanent connection that can suffer from rivet failure? Actually, rivet failure is related to many factors, including material, installation, environment and design. The following are common causes of rivet failure and detailed explanations.
1. Excessive Load
Rivet failure occurs when the actual applied load exceeds the load that the rivet is designed to withstand. When a rivet is subjected to tension or shear forces in excess of its design strength, the rivet will fail due to overloading.
So what happens to the rivet when this rivet failure occurs? The rivet may pull out, shear, or form a crack in the joint.
2. Fatigue Failure
When rivets are subjected to repeated tensile or shear stresses over a long period of time, metal fatigue can result. This can cause the rivet to develop micro-cracks that gradually expand to complete fracture. This is common in vibration environments such as aviation, railroads and heavy machinery.
3. Poor Installation
Problems can occur if the operator does not properly secure the rivets during installation or if there is incomplete pulling of the rivets. For example, rivets are not aligned, rivets are over tensioned or not tightened in place. These conditions may cause the rivet to loosen, deform or fail to form a strong connection.
If you want to know how to install pop rivets properly, read this article.
4. Corrosion
If your project requires rivets to be exposed to moisture or corrosive environments for long periods of time, there is a good chance that the metal will oxidize, corrode, and reduce its strength and toughness. As a result, rust, hole corrosion, and even perforation occur on the surface of the rivet.
5. Incorrect Rivet Selection
If you are using height rivets that are not made of the right material, size or type for your business, there is a good chance that the rivets will fail. For example, using aluminum rivets in high-temperature environments and lightweight rivets in high-load environments. These situations can cause rivets to fail or even break.
6. Unreasonable Design
The number, spacing or arrangement of rivets needs to be designed according to the stress requirements of the structure. Rivets that are designed too closely together can create stress concentrations, while too much spacing can weaken the overall connection.
7. Environmental Stress Corrosion Cracking
Under the joint action of stress and corrosive environment, the rivet material will occur stress corrosion cracking. Cracks appear on the surface of the rivet and gradually expand to fracture the entire rivet.
8. Low Quality Material
Substandard materials used in the manufacture of rivets, such as those containing impurities, manufacturing defects or low hardness, are prone to failure under stress. This may result in early breakage, deformation, or failure of the rivet under small loads.
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Types of Rivet Failure and How to Avoid
There are many types of rivet failures. Here I will give examples of the four most common types of rivet failure and list the specific causes of rivet failure. In addition to this, you will learn how to avoid rivet failure in advance.
1. Rivet Shear Failure
What is rivet shear failure? When a rivet is subjected to a shear force that exceeds the shear strength of its material, the rivet will break or slide, resulting in shear failure.
This type of rivet failure type manifests itself in the form of the rivet breaking in the direction of the shear force, which engineers typically see occurring at the cross-section of the rivet. So what are the causes of this type of rivet failure?
- Undersized rivets
- Insufficient material strength
- Subjected to excessive transverse loads
- Poorly designed rivet layout
How to Avoid Rivet Shear Failure?
Before choosing the right rivets for your project, you need to understand the shear requirements of the project and select the eligible rivet material and size. And you need to rationally design the rivet layout to avoid excessive lateral forces.
2. Rivet Tensile Failure
Rivets can experience tensile failure when subjected to excessive tensile forces, resulting in the rivet pulling off or pulling out of the connection. Typically, when this occurs, the rivet will pull off in the axial direction, usually accompanied by tensile deformation. The causes of this phenomenon are listed below:
- The diameter of the rivet is too small
- Insufficient material tensile strength
- The rivet is not installed in the proper position, resulting in a concentration of tensile force on the rivet
How to Avoid Rivet Tensile Failure?
First, select rivets with sufficient tensile strength, and second, increase the number of rivets to spread the tension.
3. Stress Corrosion Cracking, SCC
Brittle cracking of rivets under a combination of tensile stress and corrosive environment is called stress corrosion cracking. This occurs when small cracks appear on the surface or inside the rivet and the cracks extend to failure, usually along grain boundaries. Why does this type of rivet failure occur? Mainly rivets in the combination of high tensile stress and corrosive environment, especially in the chloride, sulfide environment is more likely to occur.
How to avoid rivet stress corrosion cracking?
Reduce the working stress of rivets, avoid brittle materials in corrosive environments, and add anti-corrosion coatings.
4. Rivet Fatigue Failure
When the rivet in the repeated stress (such as vibration or cyclic loading) in the gradual formation of micro-cracks, cracks expand to a certain extent after the rivet will fracture, resulting in fatigue failure. In this case, the surface or interior of the rivet will produce small cracks, and gradually expand to the entire rivet fracture. The possible causes are as follows:
- Long-term vibration
- Frequent changes in load (common in aviation, railroad, automotive and other vibration environment)
How to avoid it?
Use materials with good fatigue resistance, minimize vibration, and design to ensure even load distribution.
Contact Our Engineers Today
We provide you with high quality rivets, including customized services.
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