Innovative Production Machines and Systems Conference

The stress limit of machine parts is usually determined by the criterion of linear elastic behaviour of the part and the material. The quite usable material behaviour in plastic stress regions is usually disregarded in calculations and treated as “extra safety”. The foil shows by an example of a bolt to link plate connection that the true cause of part failure, the full plastification, holds an increase of load carrying capacity to 145% of the value determined by elastic calculation. The cause of this is that the plasticising area of the part has little effect on the stiffness of the connection. The interaction of stress distribution and material behaviour leads to stress distributions that show the possible increase of load bearing capacity by using a combination of two materials – one with ideal elastic and one with ideal plastic behaviour - if the distribution of bending stress allows such an equalisation. Fields of solution for elastic and semi-plastic deformations due o different combinations of bending and tension/strain loads (e.g. by bolt to link plate connections or bended beams). IEaE = elastic inside and outside, iZaE = semi-plastic tension inside and elastic outside, iDaE = semi-plastic strain inside and elastic outside, iDaD = semi-plasti strain inside and outside etc.; 0P = no plastic deformation, 1P = plastic deformation onto one bending side, 2P = plastic deformation of the bending zone in the area of tension and strain load. Pkt. 1: borderline of the elastic area; Pkt. 2: plastic hinge (full plastification) by given combination of tension and bending [8, 9]