Worth collecting! Aviation fastener knowledge

On June 5, 2022, Beijing time, the Shenzhou XIV manned spacecraft was successfully launched. This mission will also achieve many firsts. For the first time, two manned spacecraft will be in orbit at the same time, and the astronauts will rotate in orbit for the first time. In recent years, China's aerospace industry has developed vigorously and achieved remarkable achievements. With the development of aerospace industry, our demand for aviation fasteners has correspondingly increased. Because the fasteners used in aerospace are used under high temperature, high pressure and high strength, their quality requirements are particularly high. At present, aerospace fastener manufacturers are mainly concentrated in Europe, the United States and other countries and regions worldwide. Next, the editor in chief of Aozhan will talk about aviation fasteners to help you understand the important link in Aerospace - fasteners.

Fasteners are a kind of mechanical parts that fasten and connect more than two parts. They are widely used and are called the "rice of industry". Aerospace fasteners refer to the fasteners used in aerospace, processed with special materials, with special properties or uses, and can meet the special technical requirements of aerospace. Aerospace fasteners are generally used in aircraft, satellites, rockets and other aerospace vehicles. They are a typical high-end fastener and a necessary basic part of aerospace vehicles. Their performance requirements are much higher than those of fasteners in other fields. Aviation fasteners can be divided into many categories according to their different classification standards. Each category also contains many different specifications and types to meet the diverse needs of different materials and structures.

There are many classification standards for aviation fasteners. The following Aozhan Xiaobian will introduce some common classifications: ① according to whether the fasteners can be disassembled, they are divided into detachable fasteners and permanent fasteners, of which detachable fasteners include bolts, screws and nuts; Permanent fasteners include high lock nuts, ordinary rivets, etc; ② According to the product type, it is divided into bolts (screws), nuts, single-sided fasteners, special fasteners, etc; ③ According to the materials used for fasteners, they are divided into carbon structural steel fasteners, alloy structural steel fasteners, stainless steel fasteners, high-temperature alloy fasteners, aluminum alloy fasteners, titanium alloy fasteners, titanium niobium alloy fasteners and non-metallic fasteners; ④ According to the difference of assembly operation requirements, it is divided into single-sided connection fasteners and double-sided connection fasteners; ⑤ According to the nature of the working load, fasteners are divided into two types: tensile type and shear type.

航空紧固件按产品种类进行分类较为普遍，接下来奥展小编将详细介绍一下铆钉类紧固件、螺栓类紧固件、螺母类紧固件、单面紧固件和特种紧固件：

（1）铆钉类紧固件：用在航空航天上的紧固件，质量的保障和轻便是最为重要的选择因素。铆钉类紧固件就是飞机上使用量最大的紧固件之一，其材料有铝合金、不锈钢、耐热合金、钛合金等，目前大多数铆钉主要用于铝合金、钛合金复合材料较薄结构的连接，使用直径一般在Φ4mm以下，同时为了满足飞机结构高寿命的要求，大都采用自动钻铆机和柔性装配系统进行装配，随着铆钉材料强度的不断提高，还开发出了相应的重要部位使用的承力铆钉，如双金属铆钉和高抗剪铆钉，其强度均可达到抗剪型钛合金高锁螺栓的强度。

(2) Bolt fasteners: the most commonly used fasteners on aircraft with large load are bolt fasteners, among which bolts mainly include ordinary bolts, high lock bolts, tapered bolts, etc. High lock bolt is a kind of threaded fastener that can be used on one side. It is a type of bolt that is widely used in the aviation industry. For aircraft design, weight reduction is an important index. The use of high specific strength materials can replace large-scale fasteners with low comparative strength. Therefore, 1100mp TC4 titanium alloy fasteners are widely used in the aircraft body structure. In addition to specific strength, fatigue resistance, corrosion resistance, rigidity, brittleness, compatibility, heat resistance and other properties should also be considered in the design.

(3) Nut fasteners: nut fasteners are used together with bolts, and have various structural forms to meet the needs of different occasions, including hexagon nuts, hexagon nuts, spline nuts, bracket nuts, barrel nuts, high lock nuts, etc. Most nuts adopt self-locking structural forms. Bracket nuts include nuts with ear plates, nuts without ear plates, traveling bracket nuts and group traveling bracket nuts, which have two sealing forms: sealed and unsealed. Nuts without ear plates can improve the structural life; Hexagon nuts are widely used in aircraft; Dodecagonal nuts are widely used in engines and high-strength bolts; High lock nuts are used together with high lock bolts in large quantities, including shear type high lock nuts and tensile type high lock nuts. They have common high lock nuts, self-aligning high lock nuts, sealed high lock nuts and upsetting high lock nuts.

(4) Single side fasteners: the fasteners used in the non open parts of the aircraft mainly have two structural forms, one is the pallet nuts / bolts and quick release fasteners used in the removable parts such as the hatch cover and the cabin door, and the other is the single side pull nails widely used in the permanent connection parts. Among them, the pull-out screws can be mainly divided into two categories: one is the pull-out screw, which can be divided into single-sided rivets and single-sided bolts; the other is the screw pull-out screw, which can be divided into gap type, interference type and main bearing structure type. Among them, the large foot titanium alloy single-sided screw pull-out screw is specially designed for the structural assembly of composite materials. The interference single-sided screw pull-out screw fastening system can improve the sealing and fatigue resistance properties, The high-strength nail pulling fastening system can be used for the main bearing structure.

(5) Special fasteners: including ring groove nails and ring groove nail fastening system, quick release lock fasteners and composite fasteners. Ring groove nail and ring groove nail fastening system are permanent fasteners installed on both sides and riveted on one side. They are widely used in Boeing and Airbus aircraft. They can be divided into gap type and interference type according to the fitting form, and pull riveting type and upsetting riveting type according to the installation form. At present, most of them use titanium alloy ring groove nail fastening systems with uniform load, such as titanium alloy ring groove nail and ring groove nail fastening system. Quick release lock fasteners are mainly used for the connection of the hatch cover and the compartment door. They have various structural forms and can realize the function of fast loading and unloading. They have high reliability requirements and need to meet the index requirements of 1500 reliable disassembly. Composite fasteners are fasteners made of composite materials, including rivets, bolts, screws and nuts. They are ideal fasteners for solving weight, strength, corrosion, lightning strikes, radar images and other problems. At present, their strength can reach the highest shear strength of high-strength aluminum rivets, and can only be used in aircraft secondary bearing structures.

At present, the number of aerospace fastener manufacturers in China is still small. In the future, manufacturers with aerospace fastener production technology will have more competitive advantages. Enterprises can increase their independent research and development efforts and break through existing technical and financial barriers.