Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
A.D. Bruin Herbeproeving van hijsgereedschappen.
Literature survey, Report 99.3.TT.5160, Transport Engineering and Logistics.
In 1997 the labour environment legislation (Arbowetgeving) has been changed. From that moment the tensile strength test was no longer compelled for the retesting of lifting appliances. In spite of this change the EKH (association of inspection companies for lifting appliances) still compels to her members the tensile strength test. The EKH now wants to know if this tensile strength test adds more accuracy to the judging of lifting appliances. This was the reason for this research project.
In the last century, the materials of lifting appliances have gone through major changes. Nowadays lifting appliances are made of alloys with extreme high strengths. In contrast with the materials from the past, the present materials are not negatively influenced by aging. Due to the high internal stresses, the material is considerably stronger. When these high-strengthened materials fail, the most probably cause is fatigue. This defect most frequently starts at the materials surfaces. Non Destructive Testing methods (NDO) like Visual Inspection, Liquid Penetrant Inspection and Magnetic Particle Inspection are useful for analyzing the state of the material.
Possible advantages of the tensile strength test are extra strengthening of the material by crack closure and the verification of the previous NDO-investigations. There have to be further investigations to verify this.
At this moment the advantages of the tensile strength test seem to be little but the real size of the advantages has to be further investigated. With this knowledge there can be decided whether the test has to be preserved in the future.
Reports on Transport Engineering and Logistics (in Dutch)
