Types of Materials

Wind turbines are useful for generating electricity, but they need to be robustly anchored. This article will explain the choices of materials used in anchor bolts for wind turbine towers, describe their properties, and assess any risks associated with them. The choice of material used in anchor bolts depends on environmental conditions at the point where the tower is sited, particularly the wind speed. The tower itself will be made from one of the conventional materials used in construction (steel or concrete) and the anchor bolts must transmit this high structural loading to the foundation. Clearly, it is not possible to use a material with insufficient strength or resistance to fatigue failure.

A range of steels is typically used for the manufacture of anchor bolts. Carbon steel is a cheap option but has poor resistance to corrosion, particularly in more aggressive coastal or wet conditions, while weathering steel provides good corrosion resistance but is an expensive alloy. Monel and Inconel are two nickel-based alloys both with high corrosion resistance which also have excellent fatigue properties and resistance to stress relaxation.

The choice of foundation will depend on many factors such as soil or rock conditions and is beyond the scope of this article, but it is usual for a pile to be used which will require an anchor bolt. This again typically uses steel with good fatigue properties. If the ground conditions are uncertain then polypropylene or glass-fiber-reinforced plastic (GFRP) piles are also available. So, the material selected for an anchor bolt will depend on its intended location and should be chosen accordingly.

Wind Turbine Bolt Torque, Tension Tools and Solutions

Wind turbines are tall and heavy structures that require a lot of torque to stay in position. When the turbine reaches its final height, it has to withstand high winds and corrosion which can cause damage if precautions aren’t taken. The foundation bolts keep the wind turbine bolted to the base and provide an adequate connection to prevent any unwanted movement or damage.

All wind turbines need to have bolts that are tightened to ensure that it does not fall off. Wind turbines are complex machines with parts that need to be carefully placed. The bolts which are attached to the turbine shaft help maintain the position of these parts by increasing or decreasing the torque of the turbine. The bolt torque is one of the most important aspects of a wind turbine because it affects many other parts and pieces of the machine.

Both the foundation bolts and turbine bolts need to be treated with care. Foundation bolts can corrode by themselves due to the nature of their environment, while turbine bolts require an anti-seize treatment for them to last longer. The two go hand in hand when it comes to keeping your wind turbine safe.  Let’s take a look at some of the reasons why you should use anti-seize lubricant on your wind turbine bolts and how to protect wind turbine foundation bolts.

Bolt Tensioning for Wind Turbines

Bolt Tensioning Technology for Wind Turbines is a system that allows each rotor blade to be tensioned independently, which reduces or eliminates blade flutter, a phenomenon present in all turbines.

Bolt Tensioning Technology for Wind Turbines is an efficient and reliable system that permits each rotor blade to be tensioned independently. This reduces or eliminates blade flutter, a phenomenon present in all turbines. The bolts on a wind turbine have been traditionally tightened in a certain order to ensure the rotor blade is tensioned evenly. Bolt Tensioning Technology for Wind Turbines utilizes an independent bolt tensioning system. This system reduces the risk of fatigue on the blades by having each bolt tightened independently.

What is the Purpose of Tension Tools in Wind Turbines?

Tension tools in wind turbines are designed to create a tight connection between the blade and the vane. They play a vital role in wind turbine design and function. The tension tool is manufactured from high-quality steel with a strength of more than 250 MPa. The size of the tool has to be determined by calculating the torque and rpm of the rotor, which will vary depending on where it is installed on the wind turbine.

There are many types of tension tools for wind turbines and it is important to be familiar with each. A compressive type of tension tool is designed to compress the blade in the hub and uses a compressive force to transfer load. They use a compressive force to transfer load and work in a similar way as an internal clamping force. The advantage of this type of tool is that they can generate high forces when needed, they are easy to install, and the quality of the interaction between blade and hub can be improved by using steel pads on both surfaces. Compression tools also require less torque than ratchet wrenches when loading blades. One disadvantage is that these tools do not provide any restraint against the sliding movement, so high loads may result in bending or buckling of blade/hub interfaces.

Tension Tools in Wind Turbines

There are four different types of tension tools used in this type of turbine: the spiral wedge torque device, clamped bolt torque device, bolt spring torque device, and the tensioning lever.

To know more about Wind turbine Foundation Bolts, Click here.

In choosing the steel used for wind turbine fasteners, material selection is critical. Material selection often depends on several factors. Wind turbines come in all shapes and sizes. The blades of a wind turbine produce power by pumping air in a circular motion. The turbine blades are secured to a rotating shaft or hub, which rotates a generator to produce electrical power. The materials used to manufacture the wind turbine’s blades directly impact the performance of the turbine. In industrial wind turbines, most blades are made out of high-strength low-alloy, or stainless steel.

The most commonly used grades of steel in wind turbine fasteners are 304, 310, 316, and 316L stainless steel. The grades chosen for wind turbine fasteners will be influenced by a number of factors, including:

Wind Turbine Fasteners Material Selection Criteria:

When it comes to designing fasteners, the material selection criteria are quite simple because there are only three basic factors that must be considered when selecting any material for this application. These are its strength, elongation range, and cost. Due to these properties, steel is the most widely used material for the production of fasteners, and it has three distinct advantages.

Firstly, steel is available in high strengths compared to other materials such as aluminum and brass. Therefore, it can be used for making bolts that will withstand higher amounts of load which is important in applications where there are heavy loads like offshore wind turbines.

Secondly, steel has a wide range of elongation from about 12% for A36 grade to around 20% for some grades of stainless steel. This means it can be used in different applications where there are long or short bolts needed which is important because these applications span a wide range of sizes and design requirements.

Thirdly, steel bolts are inexpensive compared to other materials like titanium, aluminum, and stainless steel. Generally, the low cost of steel fasteners makes them more reliable because it often leads to their longer life which is directly linked to improved productivity in most applications.

Material Properties:

The correct material for a certain application is selected according to the particular demands of the situation. If we consider the steel grades, there are many different grades with various material properties like strength, corrosion resistance, toughness, and weldability (which can be important in some applications such as offshore), etc.

However, for this article, we will only consider the basic properties of the material grades since they are already mentioned in some articles on wind turbines on ENGINEERING.com. These are Yield strength (ultimate strength), Tensile strength, Modulus of elasticity, Poisson’s ratio, and Density. The first three properties are broadly defined as Material Strength Properties whereas the last two define material stiffness (density) and deformation (Poisson’s ratio). These properties can also be compared with those of aluminum.

It is important to mention that steel has different strength levels depending on whether it is cold drawn, annealed or hot rolled. Cold drawn steel is stronger than annealed and hot rolled steel is stronger than both of them. However, the material must be designed properly so that it can bear different types of loads and also minimize structural weight.

Material Structure and Composition:

The next important factor is the structure or composition of the material used in the fastener. For example, alloyed grades like A286 with Carbon-Manganese-Silicon alloy are commonly used in the oil industry. These alloys have good resistance to abrasion and corrosion, but they lose strength when heated above 350oC. However, non-alloyed grades like A36 steel (the most common grade of structural steel) can also be used depending on design requirements and the type of loads.

Abrasion Resistance:

When it comes to high-strength bolts, abrasion resistance is very important. This is because failure caused by wear may result in catastrophic failure. For example, this can be clearly seen in bolts used for offshore wind turbines where bolts are directly exposed to sand particles moving at high velocity and under high pressure. As a result, it is important to use the right material and surface treatment like heat treatments (especially for bolts under high stress), additives, and coatings.

Surface Treatment:

Surface treatment should also be considered when designing fasteners because this property not only affects their efficiency but also their aesthetics (looks). For example, in certain applications galvanization is required to protect the material from corrosion. However, it may not be aesthetically desirable in wind turbines even though at small thicknesses its effect may be negligible.

Aesthetic Quality:

This is another property that should also be considered depending on the application. For example, in certain applications, the bolts are exposed to harsh weather conditions, and the fasteners may corrode due to this exposure. In such applications, materials with good corrosion resistance should be selected for making the bolts.

Material Strength:

The bolt’s strength should be matched to its application so as not to experience large deformations and fail before other parts which will cause catastrophic damage. For example, if we consider the shear strength of a bolt, then we will see that it is an important material property because it governs the way in which components such as turbines, gearboxes, and generators are connected. Therefore, to securely attach these components to each other, bolts with high shear strength should be used.

One of the most important factors when selecting a material for a certain application is its strength. For example, if we consider common structural steel grades like A36 and M24, the ultimate strength of A36 is 36 KSI (250 MPa) while that of M24 is 24 KSI (170 MPa). However, in high-strength bolts used for offshore applications, yield strengths of about 90 psi (620 MPa) are common. This shows how important the material’s properties are when making fasteners for offshore applications. They need to be strong enough for the application.

Elongation:

Elongation is another important material property that should be considered during the design of fasteners. For example, in certain applications, there may be welding on the bolt which will lead to high-stress concentrations at the weld bead interface. If the elongation is too low for this particular application, then there could be micro-cracking in the bolt which can lead to catastrophic failure.

The elongation of a steel bolt is directly related to its ductility. Therefore, the higher the elongation value, the more ductile it becomes which means it can experience larger deformations before failure occurs. This property should be carefully considered because not only are bolts affected by cyclic stress of vibration frequency but also high levels of shock during an impact which will cause large deformation and failure.

Processing:

The processing of fasteners also affects their performance. For example, increasing shot peening increases the fatigue life of bolts by reducing some problems like internal microcracking.

Surface Coating:

Surface coatings also affect the performance of bolts, and these are applied for different applications depending on their requirements. For example, wind turbine fasteners are used to protect against corrosion given that they are exposed to harsh weather conditions.

Flexibility:

The bolt should be flexible enough such that it can undergo high levels of shock during an impact. Furthermore, different applications require bolts with different flexibility such as vibration-proofing applications where maximum flexibility is required. These are important because these types of applications that have high levels of shock can have a higher probability of experiencing fatigue failure due to the fact that repeated shocks lead to an increase in cyclic stress.

Stiffness:

The structural stiffness of the bolt is critical to its performance because it is linked to four critical factors. First, it will influence how much load can be transmitted by the fasteners. Secondly, it will also affect the bolts’ fatigue life since if they are more flexible, high cyclic stress of vibration frequency can occur which will lead to increased repeated loading of the bolt until it fails. Thirdly, it will affect the bolts’ ability to resist high levels of shock and finally, it will influence how much force can be transmitted through the bolt before deformation occurs. Therefore, if we consider a bolt with high stiffness, then more load can be transmitted and distributed among connected components.

Toughness:

It is not necessary that all high toughness bolts will be tough, but it’s just a factor to consider when choosing the right bolt for an application because they rate higher than normal steel bolts and due to this they tend to be more expensive which means they should only be used in specific applications where this factor is necessary.

A bolt is a machine element that can be in the form of a fastener, and its main purpose in most applications is to provide load-carrying ability through rotational or translational movement. Fasteners are used for connecting together two objects called components such as turbines, gearboxes, and generators, etc., they consist of bolts and nuts where the former can be described as a rod with a head on one end and thread(s) on the other. Bolts are cylindrical in shape but they may have non-cylindrical shapes such as square or hexagon, and their dimensions vary depending on how thick the bolt is and the size of its thread pitch.

The bolt’s dimensions also depend on the following factor:

Application:

Bolts are manufactured in different shapes and sizes according to their intended application, for example; hexagonal bolts which can be used as a pivot point such as a hinge or they can be used as a fastening component of screws. Furthermore, if we consider the shear strength of a bolt, then it is an important material property because it governs the way in which components such as turbines, gearboxes, and generators are connected. Therefore, to securely attach these components to each other, bolts with high shear strength should be used.

Bolts can be classified into three main categories according to their application:

Structural bolts:

Structural bolts are non-threaded fasteners that mainly consist of hexagonal or square heads. They can be used in different applications where tension, shear, and bearing loads occur. This implies that they are used to connect together the components of a structure like beams, struts, and panels, etc., but there is no rotational movement involved.

Machine bolts:

Machine bolts are also non-threaded fasteners with hexagonal or square heads which can be used in the same way as structural bolts, but they differ because in addition to connecting together components of a structure; they can provide rotational movement.

Threaded fasteners:

These are the most versatile bolts as they consist of an external thread and ahead with a specific shape. They can be used for different applications where tension, shear, and rotational loads occur.

Different types of steels have different chemical compositions, which means that they possess different properties and can be used for different applications as shown below:

  • Low carbon (< 0.25%) mild steel is used for structural applications where tensile load occurs. This implies that the steel is not very hard, so it is easy to shape and form using conventional methods such as cold-working or hot-working.
  • Medium carbon (0.25% – 0.75%) mild steels are much harder than low-carbon steels; they are used for applications where shear force occurs.
  • High carbon (0.75% – 2%) medium steels are hard and strong, but they can only be shaped using hot-working methods; therefore, these types of steel are mainly used to produce machine parts that require high strength and hardness such as cutting tools.
  • Stainless steel is a medium carbon grade alloy steel, but it also contains Chromium in its chemical composition which can form a passive surface oxide layer that avoids further oxidation of the metal. This type of steel has many applications because it is corrosion-resistant and easy to shape and form compared with other types of alloy steel.
  • Structural steel contains a range of different alloying elements such as Mn, Cr, Ni, etc., it can be formed into various shapes and forms by hot-working or cold-working the molten metal, but this type of steel is not corrosion-resistant therefore it requires a protective coating to avoid oxidation.
  • High-tensile structural steel contains a range of different alloying elements such as Mn, Cr, Ni, etc., it can be formed into various shapes and forms by hot-working or cold-working the molten metal. As well as being strong, this type of steel is also ductile meaning that it can undergo extensive plastic deformation without fracturing, so it is commonly used in the automotive industry to produce vehicle chassis and doors. some car manufacturers even use high-tensile structural steel to produce the entire body of their cars.
  • Alloy steel contains a range of different alloying elements such as Mn, Cr, Ni, etc., it can be formed into various shapes and forms by hot-working or cold-working the molten metal. As well as being strong, this type of steel is also hard and therefore it can only be shaped using hot-working methods. Due to these properties, this type of steel is mainly used to produce machine parts that require high strength and hardness such as gears.
  • Cast iron contains a range of different alloying elements such as Mn, Cr, Ni, etc., it can be formed into various shapes and forms by hot-working or cold-working the molten metal, but this type of steel is not corrosion-resistant therefore it requires a protective coating to avoid oxidation. This makes cast iron brittle with poor wear resistance; therefore, it is mainly used to produce machine parts that require high strength such as crankshafts and brake drums. Another advantage is that it has a low melting point, which means that the molten metal can be poured into molds to produce different shapes and forms.
  • Copper is a soft metal which means that it cannot be shaped or formed easily by cold-working, so hot-working methods are used to shape the molten metal in order to make products such as household appliances and pipes; one advantage of copper is that it has excellent thermal and electrical conductivity and because of this, copper is used to making electrical wiring and cooking utensils.
  • Aluminum has a very high strength to weight ratio therefore its lightweight properties are widely used in many applications such as aerospace engineering and motorsports. Another advantage of aluminum is that it has excellent corrosion resistance properties; this makes aluminum suitable for applications where the metal will be exposed to seawater, making it an ideal choice to produce storage tanks for transporting liquid fuels such as gasoline and diesel oil.