Cetim Cobra : Bolted joint design

The strength of the world leader for bolted joint design and failure analysis

 V6 version of Cetim’s Cobra software provides you with a French - English bilingual solution.

INDUSTRIAL REQUIREMENTS

Bolted joints analysis, review, verification and dimensioning, with controlled torque pre-tightening, following VDI 2230 recommendation (and extensions to standards NF E 25030-1, NF E 25030-2):

• Benefit from Cetim's expertise in bolted joint design and verification in the analysis of your assembly
• Improve your understanding of complex assemblies with the best validated software on the market
• Deliver reliable documentation with your validation report including design options
• Reduce verification and design time of complex assemblies
• Perform strength analysis beyond VDI 2230 recommendation

APPLICATION DOMAINS

Cetim Cobra is used in the industry to address complex bolted and screwed joints with critical safety and security issues

• Major companies of the transportation industry (automotive, rail, air, defense and space) use Cobra to analyse dynamic assemblies
• Cobra is widely used across the industry (gas, petroleum, agriculture, construction) for the design and analysis of heavy duty assemblies

UNIQUE FEATURES

Cetim has a unique experience in bolted and screwed joints verification and failure analysis. From this experience, Cetim has developed design and analysis functions beyond those of VDI 2230

• Improved computation of alternate stress for dynamic loading, accountable for 80% of failures in bolted joints
• Unique computation of geometry and tolérances, thread tolérances and material properties dispersion, tightening tool and friction coefficient dispersion for static loading validation
• Selection of appropriate torque level to support the design of complex bolted joints

SCOPE OF APPLICATIONS

• Mechanical and/or thermal stresses
• Fastener geometry (screw, stud, threaded rod, nut, washers...) and its mechanical properties. Threads ISO, UN, UNR
• Clamped part geometry
• Tightening conditions, method, friction coefficients, limitations etc...

The software can determine the optimum tightening conditions taking into account:

• The dispersion of the tightening process (material + Tools + operators)
• The friction coefficients (Under head or nut and in the thread)
• The risk of surface embedding
• The mechanical stress in the screw (tensile + torsion + bending)
• The failure load of the threads
• The presence of self-locking elements or prevailing torque (locknuts, tight fitting parts)

Once the calculation is performed, the software provides the following information:

• Load factor
• Dynamic stress range
• Stress distribution in the assemby
• Tightening method (torque, torque + angle, tensioning...)
• Minimum thread engagement

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WHY SELECT COBRA 

Benefit from the experience of a world leader in bolted joint verification and failure analysis

• 30 minutes design and verification time for a complex assembly --> Hand calculations or verification with other Tools usually take days
• 100% focused on operational data and production --> takes into account installation error and data dispersion
• 100% validated: continuous verification of data compliance / validation --> Cetim is the only software editor with laboratory testing facilities
• 100% dedicated to the industry --> Cetim is the only software editor "managed" by the industry
• 450 experts able to provide support sessions in addition to onsite training --> Cetim is the only editor with recognized field expertise

EXPERIENCE RETURN 

Specific data bases are provided:

• Materials (Re, Rm, E, Thermal influence)
• Screws, nuts, washers (diameter, length, property class, screw head size)
• Standard holes (fine series, medium, large)
• Standard torque

COMPUTATION RESULTS

• Resilience (or stiffness) of the fastener and the clamped parts
• Dynamic stress (fatigue resistance)
• Minimum tightening force to prevent opening and/or sliding
• Maximum allowable preload
• Minimum and maximum achieved preload
• Minimum required properties of fastener, when quality class not defined
• Elogation of the fastener after tightening
• Maximum stresses in the elastic washers
• Bearing pressure on contact surfaces (risk of embendding)
• Minimum threaded length (risk of stripping)
• Tightening settings determination (torque, angle, tension etc...)
  • tension in the screw
  • bearing pressure on the different contact surfaces
  • failure load of threads
  • required and/or a prevailing torque (on first tightening)

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For more information, contact your sales representative: Anouar OKADI

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Training to bolted joint dimensioning

Cetim offers various training sessions to better suit your needs:

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Training session in your premises: Optimisation and dimensioning of bolted joints with COBRA V6 software

•  duration: 4.5 days on site,
•  personnel concerned: training for technical advisors and design office or process engineers,
•  content:
  •  knowledge of standards,
  •  characteristics of a bolt,
  •  behaviour of bolted joint,
  •  presentation of Cobra V6 software,
  •  practical work with Cobra V6,
  •  study of a concrete case with Cobra V6.

Inter-company training: Dimensioning of bolted joints and use of the Cobra V6 software

• duration: 3 days in Cetim’s premises,
• personnel concerned: training for design office or process technicians and engineers,
• content:
  •  static and dynamic characteristics of attachment parts,
  •  design of a bolted joint,
  •  determination of the tightening torque,
  •  presentation of Cobra V6 software,
  •  practical work with Cobra V6,
  •  loosening, off-centred forces,
  •  Cobra V6 database.

Inter-company training: Use of the V6 Cobra software

• duration: 1 day in Cetim’s premises or on site,
• personnel concerned: design office or process technicians and engineers involved in the calculation of bolted joints and the implementation of the tightening torque,
• content:
  •  introduction to bolted joints,
  •  presentation of Cobra V6,
  •  practical work with Cobra V6,
  •  loosening, off-centred forces,
  •  Cobra V6 database.