Optimal design method for middle cross beam of ROPS framework and cab for engineering machines

A method of manufacturing a rollover protective structure (ROPS) framework, comprising:

• determining, from a structure of the ROPS framework, a length dimension W of a middle cross beam, a length dimension L of corresponding pillars, and a height dimension Ld of the middle cross beam, and establishing a portal hyperstatic structural mechanics model;
• selecting the height dimension Ld as a structural design parameter and a profile sectional inertia moment I as a profile design parameter;
• analyzing bending stress of the portal hyperstatic structural mechanics model to determine:
• (i) a ratio n1 of the height dimension Ld of the middle cross beam to the length dimension L of the corresponding pillars when a maximum bending moment of the pillars is minimized;
• and
• (ii) a ratio n2 of a sectional inertia moment of the middle cross beam to a sectional inertia moment of the corresponding pillars when the height dimension Ld is optimal and a maximum bending stress of the middle cross beam is equal to a maximum bending stress of the corresponding pillars, wherein n2 ranges from 1.15 to 1.45;
• determining a height position of the middle cross beam according to the ratio n1 and selecting profiles of the middle cross beam and the corresponding pillars according to the ratio n2;
• providing two A-pillars, two B-pillars, two D-pillars, top cross beams, bottom cross beams, top longitudinal beams, bottom longitudinal beams, and the middle cross beam;
• forming a closed rectangular A-ring by connecting the two A-pillars with a first top cross beam and a first bottom cross beam;
• forming a closed rectangular B-ring by connecting the two B-pillars with a second top cross beam and a second bottom cross beam;
• forming a closed rectangular D-ring by connecting the two D-pillars with a third top cross beam and a third bottom cross beam;
• connecting corresponding corners of the A-ring and the B-ring with a first pair of top and bottom longitudinal beams;
• connecting corresponding corners of the B-ring and the D-ring with a second pair of top and bottom longitudinal beams;
• and
• mounting and joining the middle cross beam to inner sides of middle portions of the two D-pillars at the determined height position, such that Ld/L is from 0.45 to 0.55 and the sectional inertia moment of the middle cross beam is from 1.15 to 1.45 times the sectional inertia moment of each corresponding pillar.