In technical publications and European Standards the development time (i.e. time of getting out of penetrant from a discontinuity to the material surface) in penetration testing is specified within the range of 10-30 minutes. In practice, however, it is seen , that it is closely connected with the material type and ranges from several minutes to 24 hours. In the literature, only interactions coming from the penetrant are described, whereas those from the material under testing, i.e. the influence of material factors on adhesion between penetrant and material, are not taken into consideration. In this connection, it has been described precisely in the paper the adhesion phenomenon and also it has been indicated the other factors affecting the development time. Recapitulating the adhesion theories presented in the paper, it can be formulated two fundamental circumstances which must occur that adhesion joint may be formed, namely: the approach of the particles of two solids to the distance less than 0,9 nm while the high attractive force occurring between molecules should be connected with possibly low potential energy of the bond formed in this way.

The paper is the continuation of the previous ones entitled "Material factors in relation to development time in liquid-penetrant inspection. Part 1. Material factors" and "Material factors in relation to development time in liquid-penetrant inspection. Part 2. Investigation programme and preliminary tests" in which material factors influencing essentially the development time in penetrant testing as well as the range of their values have been specified. These factors are: material kind, surface roughness and imperfection width.In the paper it has been described how far the development time in colour penetrant testing is influenced by an individual material factor. Moreover, it has been presented the equation being the function of material factors and development time.

MaterIal factors In relatIon to developMent tIMe In lIquId-penetrant InspectIon. part 2. InvestIgatIon prograMMe and prelIMInary testsThe paper is the continuation of the previous one entitled "Material factors in relation to development time in liquidpenetrant inspection. Part 1. Material factors" in which the material factors influencing essentially the development time in penetrant testing have been marked out. These are: type of material, surface roughness and imperfection width. In the paper it has been described how to prepare the factorial plan which will enable to test every factor with taking into account its different values. Moreover, it has been presented investigations on natural cracks, their width and roughness profile what will allow to assign suitable values of independent variables to the factorial plan. The purpose of the plan prepared in such a way will be the determination of the influence of the material kind , surface roughness and discontinuity width on the development time in penetrant testing.

Badania ultradźwiękowe osi pełnych The ultrasonic testing of full axles Mgr inż. Łukasz Rawicki; dr hab. inż. Jacek Słania, prof. IS; dr inż. Karol Kaczmarek; dr inż. Paweł Irek-Instytut Spawalnictwa, inż. Marcin Osiński-PKP CARGO.