Cause of damage

TB 9-2510-242-40

then adding a reinforcing plate. The original strength of the member cannot be restored by welding the crack/break

alone. The reinforcing plate can be internal, external, or a combination of both on a frame channel member (see

(1) Cause of damage. The type of repair for a cracked or broken weld depends on whether the damage

resulted from normal service or from a single accident (collision or explosion). Damage resulting from normal service

(fatigue through normal wear and tear) indicates an inadequate weld joint/component design. In such cases the repair

must add a reinforcement for greater strength. On the other hand, to repair accident-related damage the weld joint/frame

member must be restored to its original strength.

(2) Critical areas. Critical areas of semitrailer frames include king pin supports and upper coupler plate,

gooseneck and adjacent areas, and suspension mou nting brackets and adjacent areas, lunette and draw bars (lunette

trailers). If the crack is in a critical area, do not repair by welding and reinforcing. The ends of the reinforcement plates

are typical stress concentration areas, and will cause additional cracking. If cost effective, cracks in critical areas should

be eliminated by replacing the entire cracked segment. If a suspension mount or another component cannot be installed

after adding the reinforcing plate, consider replacement of the segment or the entire member.

(3) Beam size. SEMITRAILERS frequently have main longitudinal beams, which are relatively large, and minor

rails, which are of smaller cross section. Smaller cross section beams can often be completely replaced.

c. Multiple Cracks. Multiple cracks in close proximity may indicate a frame which cannot be safely repaired.

Similar cracks on the right and left side of the vehicle are also suspect. It may be more cost effective to replace the

entire rail when multiple cracks are present in a single rail.

d. Corrosion. Deterioration caused by corrosion of the metal frame structure is probably the most common single

defect in any frame. It can be the result of a single or a combination of causes such as age, inadequate maintenance,

electrolysis, improper design, or a lack of protective finish. In some cases, such as deep pitting and scrapes,

deterioration is easy to detect and measure. In other cases, such as corrosion with age, it is impossible to establish the

degree of deterioration without a thorough examination. Measure the thickness of corroded members and compare it

with the thickness of similar undamaged members. After detecting deterioration and determining its degree, evaluate

and determine to what extent repairs are necessary.

(1) Overall frame corrosion deterioration is an indication of inadequate maintenance or improper application of

the protective coating system. The extent (area) of corrosion deterioration and loss of material thickness must be

measured. A 10 percent loss of frame material thickness is approximately a 10 percent loss of frame strength. Strength

losses of up to 15 percent can be tolerated as long as not located.at the high stress areas: suspension support points,

mounting brackets, or points for carried loads. When overall loss of material thickness