Shear strength of clinched connections in light gauge steel

The report reviews the results on shear strength of press joined connections manufactured and tested in the Finnish research project Connection Technologies for Thin Walled Steel Structures where the 'standard' round and rectangular clinches in hot-dip galvanised light-gauge steel were studied. The basic principles of the behaviour of clinches in shear are discussed and the difference between round and rectangular is demonstrated highlighting the importance of the internal geometry. Simple models based on the failure mode to estimate shear strength are presented for a round clinch and for a rectangular clinch with a load parallel or perpendicular to it. The models were tested using the experimental data available. A good correlation was achieved for rectangular clinches with standard materials of equal thickness. The model for the case where the force is perpendicular to a rectangular clinch can be readily used but for the parallel case the internal geometry of clinch should be known. The model for round clinches cannot be readily used in the practice because it requires knowledge of the internal geometry and the material strength after forming of clinch. The tests showed that neither corrosion exposure nor low cycle fatigue had no influence on shear strength. The tests with multiple clinches in row indicated slight or no decrease in strength compared to single clinches depending on the clinch. The tests with very high strength heavily cold- worked steel showed that it can be clinched but the relative strength remains low compared to standard materials. The methods of quality control are discussed and the accuracy of the common practice to measure two control dimension is considered to be doubtful. The deformation capacity of a clinch is considered to be insufficient for load bearing connections because of the brittle nature. A margin of extra safety is proposed in the design of force transferring clinched connections.