Did you know that the fastener weight reduction method can reduce hundreds of kilograms of an aircraft?

Did you know that the fastener weight reduction method can reduce hundreds of kilograms of an aircraft?

For an aircraft, weight is significant. Reducing weight can save costs and increase the load of passengers. The use of #fasteners to reduce weight can achieve the effect of hundreds of kilograms or more. Do you believe it? Of course. Below, Hongnai shares some methods of weight reduction of fasteners. See how much weight fasteners can go to when reducing weight on an aircraft?

1. Use materials with high specific strength

For the materials of bolt standard parts commonly used in aircraft and engines, the figure lists different materials and their corresponding strength grades and specific strengths.

For aircraft design, using high-strength materials can replace low-strength larger diameter fasteners to achieve a weight reduction effect. The higher the specific strength of the material, can achieve the more weight reduction effect. From the figure can be seen TC4 titanium alloy has the highest specific power, coupled with its fatigue resistance, corrosion resistance, and other excellent comprehensive properties. So it has become the most used fastener material in the aircraft body structure. The body uses threaded fasteners in the aircraft, and more than 90% of the pins are titanium alloy fasteners. At present, titanium alloy fasteners have been used on the aircraft body to replace 1100MPa grade alloy steel fasteners, and 1240~1300MPa higher strength #titanium alloy has been developed.

Higher-strength materials over 1500MPa in the figure, such as high-strength INCONEL718, H-11, Aermet 100, etc., are used in critical load-bearing joints of aircraft. For strength, it can widely use not the higher the power of the material, the selection process must consider various performance requirements. In addition to the specific strength, consider fatigue resistance, corrosion resistance, rigidity, brittleness, compatibility, heat resistance, and other properties.

2. Different structural sizes are adopted according to the force situation

Fastener weight reduction using high-performance materials, improve strength and specific strength, can achieve a high weight reduction effect. Still, when the material and its stability are determined, further weight reduction will be handed over to the fastener structure size designer to complete. To meet the aircraft structure on the force and weight reduction requirements, the fastener structure size design using a variety of measures, mainly:

The use of different stress states of fasteners.

Fasteners with different lengths and short #threads .

Optimized design of combined #pins , etc.

·1) Choose fasteners with different head shapes according to the stress state

The body structure of modern aircraft mainly adopts the form of a shear structure. Hence, many shear fasteners have 100 ° countersunk heads, flat heads, and other head types. In the thick sandwich using tensile fasteners, the shear titanium high lock bolt than tensile titanium high lock bolt head height reduction is more remarkable, so it has a significant weight reduction effect. After calculation, the head of the shear titanium high lock #bolt is 57% lighter than the head of the tensile titanium high lock bolt. For the tensile fastener head, weight reduction measures are also adopted, such as the weight reduction socket of the #hexagonal head and the weight reduction socket of the twelve-pointed head.

2) Change of thread size

To further reduce the weight of the fasteners, a lightweight titanium high-lock bolt with a short closing thread was developed based on the ordinary titanium high-lock bolt of the original 2P closing thread (finishing and strengthening technology), using patented technology (finishing and strengthening technology), with a finishing line of 1.5P and 1P thread. Compared with the first generation of ordinary titanium high-lock bolts, the length of the high-lock nut used is also shortened due to the shortened closing thread, which reduces the overall structure by 10%. Compared with standard titanium bolted connections, the weight reduction effect is more evident due to the shorter thread length.

In addition, most of the aircraft assemblies in the past used long thread connections, while most modern aircraft have been refined in design. In the anti-shear part or small force part, the bolt adopts a short thread and short nut fit, which can further reduce the weight.

3) Combination connection optimization

The complex fastening system uses high-strength titanium alloy and other high-specific strength materials, such as titanium alloy brushed nails. The jacket is made of high-strength α titanium alloy. The core rod is made of β titanium #alloy with higher strength than TC4, and the overall strength is consistent with the power of single-sided thread nails designed for composite materials. Still, its weight is more than 30% lighter than the latter.

Aviation fasteners mainly through the use of high strength, high specific strength materials in the shear structure and less bearing parts of the use of anti-shear head fasteners, in the thick sandwich and tensile #parts of the use of tensile fasteners. The use of short-end thread fasteners and other methods to achieve a weight reduction effect, in addition, to the use of weight reduction sockets and weight reduction holes. The use of high specific strength titanium alloy fasteners and structural optimization design of a complex fastening system to replace the traditional steel fasteners can also obtain a better weight reduction effect only after all pins are designed and manufactured lightly, to achieve a significant weight reduction effect of the whole machine.