Ľuboš Kaščák

CLINCHRIVET AS AN ALTERNATIVE METHOD TO RESISTANCE SPOT WELDING

Abstract Various materials are used in car body production which are not always possible to join by conventional joining methods such as resistance spot welding. Therefore ClinchRivet method seem to be possible alternative. The paper deals with evaluation of properties of the joints made by mechanical joining method - ClinchRivet. The joint is made with the using of a special rivet, which is pushed into the joined materials by the flat punch. Following materials were used for joining of this method: DX51D+Z and H220PD steel sheets. The tensile test for observing the carrying capacities and metallographicall analysis were used for the evaluation of joint properties. Some results of the tests of ClinchRivet joints were compared to the properties of the joints made by resistance spot welding.

Flexural Properties of FDM Prototypes Made with Honeycomb and Sparse Structure

The rapid prototyping (RP) process is capable of building parts of any complicated geometry in least possible time without incurring extra cost due of absence of tooling. Fused deposition modeling (FDM) is a fast growing RP technology due to its ability to build functional parts having complex geometrical shape in reasonable time period. The quality of built parts depends on many process variables. The presented study focus on assessment of mechanical property flexural strength of part fabricated using fused deposition modeling (FDM) technology. The 3-point bending test was used, to determine flexural strength. Samples were made of polycarbonate on Fortus 400 mc machine from polycarbonate with slice height 0.127mm. The experiment was focused on influence of air-gap size between fibers and number of outline contours on selected mechanical properties of FDM prototypes determined 3-point bending test. The results show possibility to obtain weight reduction in printed parts with sparse structure with sufficient flexural strength and with reduced build time, compared to structure printed with default machine setting,. To obtain optimal processing parameters for 3D printing prototypes, it is necessary to execute further experiments, which could verify gathered results.

Effect of Welding Parameters on the Quality of Spot Welds Combining AHSS Steel and HSLA Steel

The resistance spot welding of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. Advanced high strength steels and high strength low alloy steels are utilized in automotive industry to reduce weight of the vehicle body and consequently lowering the fuel consumption to achieve the lowest possible fuel consumption, high active and passive safety of passengers while decreasing the amount of emission. The influence of the primary welding parameters, especially welding current, microhardness and tensile shear load bearing capacity of dissimilar welds between TRIP 40/70 as an Advanced High Strength Steel and H220PD as a High-Strength Low-Alloy steel has been investigated in this paper.

Failure of Physical Vapour Deposition Coating Zirconium Nitride on the Punch of Clinching Tool

Abstract A tool with a punch of ø5 mm and a die with a specially formed circular cavity and an annular gap was used for mechanical joining of thin hot-dip galvanized steel sheets. The active parts of punch and die were covered by PVD coating of ZrN type with LARC technology. The punches and the dies were tested in a complex tool by joining thin hot-dip galvanized steel sheets with the pressing force of 7,000 N. Decohesion of coating with width of 100 – 200 μm was observed in the perimeter of cylindrical part of ø5×4 mm in the in edge of punch radius R = 0.5 mm with deposited ZrN coating after the creation of 150 mechanical joints. The decohesion of PVD coating occurred mainly in the surroundings of the radius R = 0.5 mm on the front plane of ø15 mm part.

Optimization of resistance spot welding parameters for microalloyed steel sheets

Abstract The paper presents the results of resistance spot welding of hot-dip galvanized microalloyed steel sheets used in car body production. The spot welds were made with various welding currents and welding time values, but with a constant pressing force of welding electrodes. The welding current and welding time are the dominant characteristics in spot welding that affect the quality of spot welds, as well as their dimensions and load-bearing capacity. The load-bearing capacity of welded joints was evaluated by tensile test according to STN 05 1122 standard and dimensions and inner defects were evaluated by metallographic analysis by light optical microscope. Thewelding parameters of investigated microalloyed steel sheets were optimized for resistance spot welding on the pneumatic welding machine BPK 20.

Joining three car body steel sheets by clinching method

Abstract The optimization of a car body in terms of cost can be achieved by using different materials in various positions of the car in order to utilize specific properties of each different material. Resistance spot welding is the most used method of joining in car body production, but it is not always easy or even possible to join some combination of materials by this method. Clinching is an alternative method to spot welding, as a combination of drawing and forming. The research is focused on the evaluation of clinched joints’ properties using shearing test and metallographic observation of material structure.

Mechanical Joining of Various Materials by Clinching Method

Clinching is a simple, cheap and efficient method of joining that enables to join two or more sheets without any additional elements such as rivets, bolts or nuts. In addition, clinching does not require a surface preparation e.g. drilling (riveting), cleaning and roughening of the surface (adhesive boding) and other types of surface preparations (arc welding). Clinching is utilized in a wide range of applications and can be applied to different materials such as low carbon steel sheets, high-strength steel sheets, aluminium alloys, magnesium alloys. The paper presents the results of evaluation of clinched joint properties. The advanced high-strength steel sheet DP600 in combination with the drawing grade steel sheets DC06, DX51D+Z and high-strength low alloy steel sheet H220PD 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 microhardness test were used for the evaluation of clinched joint properties.

Influence of Welding Parameters on the Quality of Resistance Spot Welded Joints of DP600 Steels

Advanced high-strength dual-phase steel was developed specifically for automotive industry in order to benefit from its excellent formability and great crash absorption ability in comparison with conventional AHSS. Resistance spot welding is the dominant and effective method of joining metal sheets in automobile industry. After spot welding, important changes occur in mechanical and metallurgical properties of the spot welded areas and heat affected zones. The investigation into these changes is very important for safety, which depends on the strength of the welded joints. Weldability of the DP steel is one of the key factors governing its application in automotive industry. The influence of the primary welding parameters, especially welding current, on the weld quality was investigated by testing microhardness and tensile shear load bearing capacity of resistance spot welds of DP600 steel sheets.

Clinching of Dual-Phase Steels as an Alternative to Resistance Spot Welding

Resistance spot welding is the dominant method for joining the materials in the car body production. Progressive materials are being developed to improve the car’s fuel consumption and the safety of passengers as well. Advanced high strength dual-phase steels are such materials. Despite of the dominancy of resistance spot welding in car body production, innovative methods are being developed to reduce the joining time, process costs and improve the load-bearing capacity of a particular joint. Mechanical clinching is such process. The research focused on the evaluation of the possibility of clinching as an alternative method to the resistance spot welding. Experimental samples were prepared from dual-phase steel sheets DP600. The samples were tested by uniaxial tensile test, microhardness test and metallographic observations. Both joining methods have advantages and disadvantages which could destine them for specific utilization. Clinching joining is a progressive, fast and low-cost technique, but the joint’s load-bearing capacity is lower when compared to resistance spot weld.

Method of Evaluation of the Properties of Thin Steel Sheets by Springback Test

Production of thin packaging sheets has gone through significant changes in recent years. Thickness of thin packaging sheets has decreased from 0.24mm down to 0.14 – 0.18mm due to the material saving, and the thickness of tin coating layer has decreased as well. Thin packaging sheets with the thickness lower than 0.18mm are produced with so called double reduction. Materials produced with this method possess higher strength properties and lower plastic properties. There exist several tests for examination of strength and plastic properties. Requirements of the processors of these sheets are that these tests are simple, without a complicated production of specimens, and easily repeatable. Exactly because of these reasons, the springback test is used for evaluation of double reduced packaging sheets by many processors from various countries. This contribution compares properties of double reduced thin packaging sheets obtained with the springback test, uniaxial tensile test and biaxial tensile test. Goal of this comparison is to objectify mechanical and plastic properties of packaging sheets obtained with the individual tests.