Luboš Kaščák

The Experimental Analysis of Forming and Strength of Clinch Riveting Sheet Metal Joint Made of Different Materials

The paper presents the pressed joint technology using forming process with or without additional fastener. The capabilities for increasing the load-carrying ability of mechanical joints by applying special rivets and dies were presented. The experimental research focused on joining steel sheet metal made of different materials. The joint forming was performed with the solid round die and rectangular split die for riveted joint forming. The load-carrying ability of joints was evaluated by measuring the maximum load force in the shearing test in the tensile testing machine. The effect of joint forming process on joined material strain was compared by measuring the microhardness of the joints.

FEM Analysis of Clinching Tool Load in a Joint of Dual-Phase Steels

The clinching tool with a die of 5 mm diameter with a specially formed gap and a punch of 3.6 mm diameter were used for mechanical joining of dual-phase steel sheets DP600 with the pressing force of 30 kN. The punch and die were deposited by PVD coating of CrN type with LARC technology. The coating state of each 50th manufactured joint was evaluated by SEM. Cracks in the area of punch’s radius were detected. The finite element method was applied for the assessment of punch load in the joining process.

Wear Study of Mechanical Clinching Dies During Joining of Advanced High-Strength Steel Sheets

This study is focused on the wear of the die cavity of the mechanical clinching tool used for joining microalloyed hot-dip galvanized advanced high-strength steel sheets H220PD+Z. Steel sheets were joined using round, single stroke clinching with rigid die with no flexible elements. The joint forming process takes place within the specially formed cavity of the die. Dies and punches for the mechanical clinching were made of tool steel (1.3343 grade) and subsequently covered by three types of PVD coatings: ZrN, CrN, and TiCN ones. The individual die wear was evaluated during the operation period, which means that 300 joints were produced by each die covered with the corresponding coating. The experimental data obtained were compared with the results of FEA numerical simulation, which substantiated the fact that the dominant part of wear is localized in the radius area surrounding the die cavity.

Clinching - An Innovative Trend in Joining of Combined Materials in Car Body Production

Various ferrous and non-ferrous materials and their combinations are used in car body production in automotive industry. The most commonly used method for joining the materials is resistance spot welding. Some materials or combinations of materials are very difficult or impossible to join by resistance spot welding. Therefore, car producers are seeking for alternative joining methods. One of the innovative joining alternatives is clinching. The paper presents the results of evaluation of clinched joint properties. The high-strength dual-phase steel sheet DP600 in combination with the drawing grade steel sheets DC06, DX53D+Z and DX51D+Z were used for experiments. The influence of position of the sheets relative to the punch and die of the tool on the carrying capacities of the clinched joints was observed as well. The tension test and metallographical analysis were used for the evaluation of clinched joint properties.

Surface Finish Techniques for FDM Parts

Additive manufacturing technologies decrease production time and costs in engineering industry but also in other industries. Parts produced with Fused Deposition Modeling (FDM) have typical low surface finish quality. This paper is aimed on research of surface finishing technologies applicable to improve the quality of FDM prototypes surface finish. Pretreated samples were blasted with sodium bicarbonate and glass beads. The values of Ra and Rz were measured on the samples and compared the impact of selected pre-treatment, blasting medium and blasting conditions on surface finish quality of FDM prototypes.

Analysis of Cutting Surface During Cutting of Electric Sheets

The contribution evaluates the influence of the size of the cutting gap on the quality of the cutting surface during the cutting process. Four types of electrical sheets were evaluated. Examined sheet types have the nominal thickness of 0.65 and 0.5 mm. Sheets differ in mechanical properties (yield strength, ultimate tensile strength, and elongation). For the impact analysis, four values of the 0.02, 0.05, 0.1, and 0.2 mm cutting gap were used.

ANALYSIS OF WELDABILITY OF DUAL-PHASE STEEL SHEETS USED IN CAR BODY PRODUCTION

Materials used in car body production are joined by resistance spot welding as the dominant method of joining. Significant changes occur in mechanical and metallurgical properties of the weld nugget and heat affected zone during welding process. The research into these changes is very important for estimation of optimal welding parameters to ensure the required quality of welded joints. The paper deals with the problems of weldability of high strength dual-phase steel sheets used in the car body production. Dual-phase steel was developed specifically for automotive industry to benefit from its formability and crash absorption ability in comparison with conventional advanced high-strength steels. Weldability of dual-phase steel is one of the key factors governing its application in automotive industry. The influence of the resistance spot welding parameters, mainly welding current and welding time, on the weld quality was investigated by visual control, static tension test, and structural analysis of the joints and microhardness measurements.

Evaluation of Corrosion Resistance of Galvanized Steel Sheets Used in Automotive Production

The steel sheets used for the car body production are protected against corrosion by zinc coating. Resistance spot welding is used mainly for joining these sheets, because of its high speed and adaptability for automation in high-rate production. However, resistance spot welding has a negative influence on the corrosion resistance of joints. The paper focuses on the analysis of quality of welds on galvanized steel sheets and their corrosive properties. Tensile test and accelerated corrosion test in corrosive environment were used for evaluation of the welds’ quality. Protective efficiency of zinc coatings for automobile sheets was evaluated as well, based on the determination of their electrochemical characteristics in passivated and non-passivated state, as well as their corrosion resistance in simulated corrosion environments. Two types of DX54D+Z material were used for experiments: non-passivated and passivated with Cr3+.

Analysis of Welds Made by Delta Spot Method

Resistance spot welding has been widely used in sheet fabrication for several decades. Development of new materials leads to innovation of welding processes. The paper describes the principle of innovative welding method known as Delta Spot and evaluates the properties of Delta Spot joints made by combination of galvanized steel sheets H220PD (a0 = 0.9 mm) and TRIP 40/70+Z100MBO (a0 = 0.77 mm). The quality of welded joints was evaluated by tensile test and metallographic analysis. The influence of the welding parameters on the structure of welded joint was observed too. The properties of Delta Spot joint were compared to the properties of standard resistance spot welds.