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# Technical calculation

Oct 13, 2020 | Blog

The Machine product family of Rejlers Industry employs about twenty experts in technical calculation around Finland, serving our customers in various different sectors.

Technical calculation allows the simulation of real-life events by loading the item under inspection with different external or internal loads. The threshold values used in the simulations for loads, approval thresholds and other boundary conditions are often based on the requirements of norms and standards.

#### Calculation is more cost effective than practical testing

The objective of technical calculation is to ensure the strength, safety and functionality of the item in question. Ideally, calculation is included in the process from the early stages of research and development activities, making it possible to optimise the rigidity and shape of the product and the use of materials. Calculation results help visualise the parts of a structure that need improvement or can even be eliminated. This allows for flexible comparison of different structure variants. In comparison to practical testing, calculation is often faster, easier and cheaper, i.e. more cost effective.

#### The interpretation of calculation results requires strong, practical expertise

Traditional manual calculation has largely given way to FEM calculation that utilises the element method. Preparing a three-dimensional calculation model, implementing structural support, stresses and joints between elements and particularly the interpretation of the results require solid practical knowhow that Rejlers’s FEM calculation team boasts. In the early stages of research and development activities in particular, calculation models can be simplified to establish the scale of the main structural elements quickly. At later stages, smaller details can be addressed using more detailed models. The structure under inspection can be made from steel or other metals, plastic, composite materials or combinations of the above. The parts can be assembled using screw, rivet, welded or glued joints, and their properties and strength are included in the analysis.

#### Based on calculation principles and goals, technical calculation can be divided into different types of applications

In its most traditional form, FEM calculation is static and linear. In this form, the method is used for the determination of transitions and tensions of statically stressed structures, usually without exceeding the material-specific yield values. The results obtained can be used in fatigue analysis, for example, which focuses on the effects of repetitive loading. Typical objects of calculation include different steel structures, engine components and hoisting accessories.

Nonlinear analysis is required when the stress on a material becomes so high that its yield values are exceeded, which results in permanent or significant deformations, or when the joints between elements require it. Possible applications include the ROPS and FOPS simulations according to safety requirements, which ensure a protective space for the pilot in the case of an accident.

Transient calculation aims to find the specific frequencies and forms that a structure tends to vibrate at and the transitions, accelerations and tensions that external dynamic loads cause in the structure.

Stability analysis is used in studying a structure’s susceptibility to the loss of load-bearing capacity due to buckling. Typical applications include various framework structures, silos and containers, booms and other items that are exposed to bending or compressive stress.

Heat transfer analysis focuses on heat conduction, radiation or convection in structures. Most frequently, the cases are related to refrigeration or thermal insulation.

Pressure equipment and piping design calculation focuses on the dimensioning of equipment that complies with applicable standards and is often subject to approvals by the authorities.

Explicit calculation is applied to the analysis of extremely rapid or highly nonlinear events. These include collision control and explosions.

Computational Fluid Dynamics (CFD) concentrates on the flow of liquids or gases in or around devices, channels and pipelines. The objective is to investigate the influence of obstructions in the flow path to the flow process. The CFD tools can help establish information on the operation of equipment that would be extremely challenging to measure in practice.

#### Our customer base mostly consists of companies in the mechanical engineering, process industry and energy sectors.

Rejlers employs about 20 experts in technical calculation who work at different offices around Finland. Our customer base mostly consists of companies in the mechanical engineering, process industry and energy sectors. Customer projects that involve technical calculation may be related to other engineering projects Rejlers works on, or they may be separate assignments.

Below, you find a list of a few applications of FEM calculation that we master:

• Paper machines (machine frames, components)
• Cranes (port, bridge, boom cranes)
• Hoisting accessories
• Windmill structures and generators
• Steel structures
• Vehicles (trains, ships, cars, working machines)
• Piping and pressure equipment

Calculation projects are always carried out according to valid standards in close collaboration with the customer. At the customer’s request, we can suggest changes to the structure to comply with the requirements set. We can also modify the geometry as needed and deliver a 3D model of a compliant structure to the customer. Calculation results are reported to the scope desired by the customer or required by the authorities. The FEM calculation software we use includes Ansys, Femap/Nastran, Solid Works Simulation, FINNSAP and VVD.