ALWAYS STRIVING FOR A SAFER
ENVIRONMENT
FOR EVERYONE

Cetim Cobra : Bolted Joint Design

The world leader for bolted joint design and failure analysis

Contact: matcor@matcor.asia

Cobra is widely used in the industry to address complex bolted and screwed joints with critical safety and security issues. Many companies in the oil and gas, petro-chemical, agriculture, construction and transportation industry including automotive, rail, air, defence and space use Cobra software to design and analyse heavy duty and dynamic assemblies.

INDUSTRIAL REQUIREMENTS

Benefit from Cetim’s expertise in bolted joint for design, analysis, review, verification and dimensioning with controlled torque pre-tightening. COBRA is the best validated software in the market in line with VDI 2230 recommendation extended to NF E 25030-1 and NF E 25030-2 Standards.

  • Verification and detailed analysis of existing assembly
  • Improve your understanding of complex assemblies
  • Deliver reliable documentation with validation report including design options
  • Reduce verification and design time of complex assemblies
  • Perform strength analysis beyond VDI 2230 recommendation

UNIQUE FEATURES

With the unique experience in bolted and screwed joints verification and failure analysis, Cetim has developed design and analysis functions that is beyond those specified in VDI 2230.

  • Improved computation of alternate stress for dynamic loading, accountable for 80% of failures in bolted joints
  • Unique computation of geometry and tolerances, thread tolerances 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 be used to 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 assembly
  • Tightening method (torque, torque + angle, tensioning…)
  • Minimum thread engagement

WHY SELECT COBRA?

Cetim is the only software editor with full laboratory testing facilities. Benefit from the experience of a world leader in bolted joint verification and failure analysis:

  • Save time! 30 minutes for design and verification of a complex assembly. Manual calculations or verification with other tools usually take a number of days
  • 100% focused on operational data and production taking into account installation error and data dispersion
  • 100% validated with continuous verification of data compliance
  • 100% dedicated to address challenges faced by the industry
  • 450 experts able to provide support sessions in addition to onsite training

EXPERIENCE IN 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
  • Elongation of the fastener after tightening
  • Maximum stresses in the elastic washers
  • Bearing pressure on contact surfaces
  • 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)

CETIM ACADEMY:

Training for Cobra V6 Software on Bolted Joint Dimensioning:

Five (5) day training session suitable for technical advisors, design office or process engineers may be conducted at your premises. Training content covers:

  • Knowledge of standards
  • Characteristics of a bolt
  • Behaviour of bolted joint
  • Training on software usage
  • Case study

K72 Essential Rules for the design of bolted assemblies.

Three (3) day Training Program for Dimensioning of bolted joints and use of the Cobra V6 software with course content covering:

  • 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.