The Importance Of Material Hardness And Durability In Gear Design EXCLUSIVE

The Importance Of Material Hardness And Durability In Gear Design EXCLUSIVE

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The content of carbon (C) is not specified for SS330 - SS490. Carbon is responsible for the strength of steel and also influences hardenability.Therefore, if you choose SS400 material which is frequently used for gears in Japan, you are selecting it for low-strength metal gears which are not hardened.

SPCC is commonly used for gear material as its content of carbon (C) is high and also has versatility. As the thickness is thin, SPCC is used for gears whose strength is lower than SS materials. Their surface cannot be cured by hardening because of the low carbon content, so you need to specify soft nitriding treatment to simply harden their surfaces.

The tensile strength of quenching and tempering of carbon (C) is not specified for S15C - S25C because hardness is not improved by heat treatment due to the lower carbon (C) content. Choose this material when you simply want to use metal. If you want to harden the tooth surface of such a low-carbon steel, select these materials after specifying carburizing and quenching that add carbon to the material.On the other hand, material S30C and below contain more carbon and therefore, are suitable for general hardening. If you want to harden the tooth surface with these materials, specify either quenching & tempering (entire body) or induction hardening (selective portion).

Resin material is used for gears for cutting cost, reducing weight, and rust-proofing.Nylon and POM (polyacetal) with self-lubricity are commonly used as materials.As for nylon-based materials, MC901 (machining) and M90 (injection molding) are used.As for polyacetals, Duracon® (product name of Polyplastics) is generally used.On the other hand, ABS, PC (polycarbonate) and acryl which are commonly used for resin molding products like covers are unsuitable for machine element parts like gears because they become fragile due to solvent cracking (chemical cracking) if oil such as grease adheres.You need to design peripheral parts carefully to prevent grease and oil on rotating resin gears from scattering and adhering on ABS, PC, or acryl parts which may result in cracking.

The purpose of writing this article was to educate the readers with the elementary level of gear technology.We hope that the actual design and manufacturing of gears and machinery utilizing gears are done with sufficient technical and specialized considerations under the user's full responsibility.We disavow any liability and will not compensate for any direct or indirect damages caused by the gears designed by the users who read this article.

Selection of materials systems for aerospace applications, such as airframes or propulsion systems, involves multiple and challenging requirements that go beyond essential performance attributes (strength, durability, damage tolerance, and low weight). Materials must exhibit a set of demanding properties, be producible in multiple product forms, and demonstrate consistent high quality. Furthermore, they must be both commercially available and affordable. The list of materials meeting these requirements is not long. Integration and transformation of such highly engineered materials into airframe structures is likewise complex. The Boeing 747, for instance, requires more than 6,000,000 components from numerous materials systems and suppliers worldwide. This necessitates that materials be stable and that material design and structure engineering close on effective solutions simultaneously. High-temperature turbine engines demand strong, lightweight, high-temperature materials balanced by high durability and reliability in a severe service environment. Such applications provide remarkable examples of how engineering imperatives influence materials research and development for metallic and composite materials in terms of material chemistry, fabrication, and microstructure.

Modern aircraft comprise three major components: airframe, propulsion, and systems. This article discusses materials and key design and manufacturing considerations for airframe and engine structures. The systems component, which provides power, control, and utilities, will not be addressed.

Similarly, the design of turbine engines emphasizes low operating costs, placing a premium on increasing fuel efficiency and extending the time that an engine can remain on-wing before extensive maintenance and repair. Airline operators often require long-term maintenance agreements, 10 years or longer, that guarantee such factors as maintenance costs and engine time on-wing. This requirement is driving common materials solutions across engine models, greater standardization of manufacturing methods, use of materials and coatings that enhance environmental resistance, and improved materials qualification testing that can better predict long-term performance from short-duration testing.

Each major part of an aircraft involves different considerations. For fuselage design, durability and damage tolerance are the primary drivers. Fatigue, both crack initiation and growth rate, and fracture toughness are the leading materials attributes. However, strength, stiffness, and corrosion are also key parameters.

The empennage includes both the vertical fin and horizontal stabilizers. The fin design is primarily influenced by static strength for engine-out conditions, when an engine shuts down. The design loads are compressive loads due to bending. As a consequence, for this section of the aircraft, the stiffness in compression and the yield strength are important material properties. The design drivers for the stabilizers are similar to those for the wings except that the loading is generally reversed.

Turning to other structures, the requirements for the propulsion structure are governed by strength, fatigue, and damage tolerance, whereas those for landing gears are determined by strength, fatigue, and corrosion. Table I shows the relationship between the design drivers and the critical materials properties.

In the past, many aerospace alloys were developed by empirical methods. In contrast, integrated computational materials engineering (ICME) allows researchers to optimize alloy compositions and thermal processing to achieve novel materials more quickly and at lower cost. Thus, ICME is being extensively pursued in research and manufacturing facilities worldwide. (See the article in this issue by Xiong and Olson for an example of the use of ICME in materials design.)

The success of this effort led Boeing to employ CFRP on the B767 aircraft using the concepts developed through the NASA program. The inboard ailerons, elevators, and rudders used the same material and design as the ACEE B727 elevator, which used a standard-modulus carbon fiber with an untoughened 175°C resin cocured with aramid paper honeycomb core to make panelized skins, spars, and ribs that were bolted together. The B737 spoilers and outboard ailerons fabricated within the NASA program were made from polyacrylonitrile-based standard-modulus (220 GPa) carbon fibers reinforced with 120°C- and 175°C-cure epoxy matrixes. This yielded a full-depth aluminum honeycomb core with precured skins bonded secondarily.

The selection of airframe materials and processes is a complex endeavor, requiring a balance among myriad design, reliability, and maintainability requirements. Materials quality and fabricability must be given close scrutiny by designers in partnership with fabricators and part manufacturers to ensure that the design is achievable at a reasonable cost. Ultimately, design and build quality and cost are critical factors in light of the tremendous global competition in the aviation industry.

There is a need for continuing improvement in materials to support both airframe and advanced engine designs, with the expectation that the materials community can significantly shorten the development and implementation time without increasing development risk by taking advantage of computational tools.

Material selection is based on Process such as forging, die-casting, machining, welding and injection moulding and application as type of load for Knife Edges and Pivots, to minimize Thermal Distortion, for Safe Pressure Vessels, Stiff, High Damping Materials, etc.In order for gears to achieve their intended performance, durability and reliability, the selection of a suitable gear material is very important. High load capacity requires a tough, hard material that is difficult to machine; whereas high precision favors materials that are easy to machine and therefore have lower strength and hardness ratings. Gears are made of variety of materials depending on the requirement of the machine. They are made of plastic, steel, wood, cast iron, aluminum, brass, powdered metal, magnetic alloys and many others. The gear designer and user face a myriad of choices. The final selection should be based upon an understanding of material properties and application requirements.This paper commences with a general overview of the methodologies of proper gear material selection to improve performance with optimize cost (including of design & process), weight and noise. We have materials such as SAE8620, 20MnCr5, 16MnCr5, Nylon, Aluminium, etc. used on Automobile gears. We have process such as Hot & cold forging, rolling, etc. This paper will also focus on uses of Nylon gears on Automobile as Speedo-gears and now moving towards the transmission gear by controlling the backlash. It also has strategy of gear material cost control.

The effective case depth (ECD) plays an important role in the meshing strength of internal gear transmissions. Carburizing quenching heat treatment is commonly used to enhance gear strength and wear resistance. However, the different ECDs in internal and external gears caused by heat treatment significantly affect the meshing strength, causing vibration, reducing gear service life, and hastening malfunction in internal gear transmission. In this study, we conducted an investigation of different ECDs by the heat treatment of carburized gear pairs by numerical simulation with the finite element method (FEM) and experiment tests. We analyzed three different carburized layer models, with the ECD in the internal gear being greater than, less than, and equal to the ECD in the external gear. In addition, we investigated the ability to distinguish between hardness gradients in gear teeth by dividing the carburized depth into seven layers to improve modeling accuracy. Results revealed that the meshing strength of internal gear transmission could be significantly enhanced by adopting the model with the ECD in the internal gear being less than the ECD in the external gear, and moreover, the shear stress of carburized gears initially increased and then decreased along with depth direction, and the maximum value appeared in the middle of the lower surface. 2b1af7f3a8