Automotive Supply Chain Insights: Fastener Selection Guide for Body and Chassis of EVs-Zhejiang Zhongrui Auto Parts Co., Ltd.

This article will focus on the critical fasteners in the body and chassis of EVs, providing an in-depth analysis of their property parameters and offering specific selection guidance to help engineers build safer and more reliable EVs.

Functional Analysis of Fasteners in Key Areas

Battery Pack Fixation Fasteners: As the core component of an EV, the battery pack must be fixed securely and reliably to withstand vibrations, impacts, and potential collisions during vehicle operation. Fasteners need to possess high strength, fatigue resistance, and excellent corrosion protection to ensure the battery pack's safety under all operating conditions.

Motor/E-drive System Mounting Fasteners: The motor and e-drive system are the vehicle's power source, and their mounting fasteners must withstand the torque and vibrations generated during motor operation, ensuring stable power output. High strength and resistance to loosening are critical requirements for these fasteners.

Suspension Connection Fasteners: The suspension system directly affects the vehicle's handling and ride comfort, and its connection fasteners must endure complex dynamic loads, including tension, compression, shear, and bending. High fatigue strength and reliable locking performance are essential.

Steering Mechanism Fastening Fasteners: The reliability of the steering system is directly related to driving safety, and its fastening fasteners must ensure the precise positioning and secure connection of the steering mechanism, withstanding the torque and impacts during steering operations. High strength and resistance to loosening are fundamental requirements.

Braking System Connection Fasteners: The braking system is a critical safety guarantee for the vehicle, and its connection fasteners bear immense braking forces during vehicle deceleration. They must possess extremely high strength and reliability to prevent brake failure due to fastener malfunction.

Body Structural Component Joining Fasteners: The connection strength of body structural components directly impacts the vehicle's overall rigidity and crash safety. Depending on the different stress characteristics of the connection points, fasteners with appropriate strength and joining methods, such as high-strength bolts, self-tapping screws, and rivets, need to be selected.

Specific Fastener Selection Guidance for Key EV Systems

Battery Pack Fixation: It is recommended to use high-strength alloy steel bolts (grade 10.9 or higher) with Dacromet or zinc-nickel alloy coating, combined with high-reliability locking nuts or bolts with anti-loosening coatings, to ensure the battery pack does not detach in the event of a vehicle collision.

Motor/E-drive System Mounting: Select high-strength alloy steel bolts (grade 10.9 or higher) and implement effective anti-loosening measures (such as locking nuts or thread-locking adhesives) to withstand the torque and vibrations generated during motor operation.

Suspension Connections: Use high-fatigue strength alloy steel bolts (grade 10.9 or higher) combined with self-locking nuts or locking washers to ensure the reliability of the connections under complex dynamic loads.

Braking System Connections: Choose high-strength alloy steel bolts (grade 12.9) with high-grade anti-corrosion treatment to ensure they can withstand the immense braking forces and safeguard driving safety.

Key properties
Strength Grade:

Definition: Indicates tensile failure resistance of bolts/studs (e.g., 8.8, 10.9, 12.9). Example: 8.8 grade has R m ≥ 800 MPa and R e l ≥ 640 MPa.
Selection: High-Stress Areas (suspension, brakes, battery): Use high grades (≥10.9). General Structure: Select based on actual stress (e.g., 8.8).

Material:

Common Types: Carbon steel, alloy steel, stainless steel (304, 316).
Selection: High Strength: Alloy steel with heat treatment. Corrosion Resistance (chassis, exposed): Stainless steel or treated carbon steel. Lightweighting: Consider lightweight, high-strength alloys if strength allows.

Surface Treatment:

Common Treatments: Zinc plating, hot-dip galvanizing, Dacromet, phosphating, black oxide.
Selection: General Rust Prevention (indoor): Zinc plating. Higher Rust Prevention (outdoor, humid): Hot-dip galvanizing or Dacromet (typically >500h salt spray). Severe Corrosion (coastal, chemical): Stainless steel or special treatments. Friction: Consider treatment impact on friction coefficient.

Anti-loosening Performance:

Common Methods: Spring washers, locking nuts (nylon insert, all-metal), locking washers, thread-locking adhesives.
Selection: General Vibration: Spring washers. Medium/High Vibration (motor mount, suspension): Locking nuts or thread-locking adhesives. Locking torque should meet standards. Special Cases: Mechanical locking washers.
Data: Refer to supplier vibration test data for locking nuts.

Dimensions and Specifications:

Definition: Thread diameter, pitch, length, head shape, etc.
Selection: Match installation space and load needs. Ensure correct thread engagement.
Standards: Relevant national or industry standards.

Preload:

Definition: Axial force applied during tightening, crucial for joint reliability.
Selection: Calculate and apply appropriate preload based on connection importance, load, and fastener strength. Use torque wrenches for control.
Reference: Engineering handbooks and standards for calculation.

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