Comparison of continuous and pulsed wave lasers in keyhole welding of stainless-steel to aluminium

A continuous wave (CW) and a nanosecond pulsed wave (PW) lasers were used to join 1-mm thick sheets of SS304L (SS) austenitic stainless-steel to AA5251 (Al) aluminium alloy in an overlap joint configuration. The weld shape (penetration depth and width), intermetallic compounds concentration, weld quality (cracking and porosity) and mechanical strength were correlated with the process energy and compared between each laser temporal mode. Successful CW joints were produced with the SS sheet on top of the Al, but the opposite configuration revealed to be impossible for the range of parameters tested. The PW joints were successful with the Al sheet on top of SS, but all the joints cracked at the interface when the opposite configuration was used. The mechanical tests showed that even though it is possible to achieve higher tensile shear load in CW welds due to the larger bonding area, the tensile shear strength revealed to be almost 5 × higher for PW welds at similar applied energy.

Comparison of Continuous and Pulsed Wave Lasers in Keyhole Welding of Stainless-Steel to Aluminium

A continuous wave (CW) and a nanosecond pulsed wave (PW) lasers were used to join 1 mm thick sheets of SS304L (SS) austenitic stainless-steel to AA5251 (Al) aluminium alloy in an overlap joint configuration. The weld shape (penetration depth and width), intermetallic compounds concentration, weld quality (cracking and porosity) and mechanical strength were correlated with the process energy and compared between each laser temporal mode. Successful CW joints were produced with the SS sheet on top of the Al, but the opposite configuration revealed to be impossible for the range of parameters tested. The PW joints were successful with the Al sheet on top of SS, but all the joints cracked at the interface when the opposite configuration was used. The mechanical tests showed that even though it is possible to achieve higher tensile shear load in CW welds due to the larger bonding area, the load per unit of weld length revealed to be almost 5x higher for PW welds at similar applied energy.

Investigation of the Mechanical Properties of Overlap Joint Combined Crash Boxes Joint Area by the Cold Metal Transfer Method

Bu çalışmada, otomotiv sektöründe çarpışma sönümleyici görevini üstlenen çarpışma kutularının üretiminde kullanılan galvaniz kaplı 2 mm kalınlığındaki SCGA440 (Çift Faz) çelik levhalar birleştirilmiştir. Birleştirme işlemi CMT yöntemi uygulaması ile yapılmıştır. Bu uygulamada kaynak hızı 60 cm/dk’da sabit tutularak yapılan bindirme birleştirmeleri CuAl8, SG2 dolgu telleri ile gerçekleştirilmiştir. CMT birleştirme işlemleri yapıldıktan sonra, bağlantı bölgelerindeki çekme mukavemeti (Mpa), çentik darbe enerjisi (J), sertlik değerleri (HV) makro ve mikro testleri yapılarak incelenmiştir.

Investigation of Mechanical Properties of Overlap Joint Form in CMT-Brazed Joints of DP800 Thin Zinc Coated Steel Plates Using Different Torch Feed Rates

Bu çalışmada,1 mm kalınlığındaki DP800 (Çift Fazlı) çelik plakalar bakır esaslı (CuAl8) ilave tel kullanılarak CMT-lehimleme (Soğuk Metal Transferi) tekniği ile birleştirilmiştir. Numuneler bindirme birleştirme formunda hazırlanmıştır. CMT-lehimleme işlemi, torç ilerleme hızları 21, 24, 27, 34 ve 39 cm/dk olmak üzere 5 farklı değerde yapılmıştır. Dolgu metali olarak büyük oranda bakırdan oluşan CuAl8 teli kullanılmıştır. CMT-lehimleme işlemi gerçekleştirildikten sonra; numunelerin gerilme özellikleri saptanmış ve DP800 çelik sacının CMT-lehimleme tekniği ile birleştirilebilirliğini görmek için birleşme noktalarının mikro ve makro görüntüleri incelenmiştir.

Experimental analysis of zero-gap laser welding of zinccoated steels in a lap joint configuration

Automotive manufacturing requires high productive manufacturing technologies to ensure a high-volume efficient production. Joining metal sheets in an overlap joint configuration of zinc-coated steel is an important task for body-in-white production. This paper describes the influence of different spot sizes regarding process stability in laser beam welding. Therefore, welds were performed in an overlap joint configuration with fully penetrated welds. Relevant material combinations for automotive industry were investigated. A broad-based parameter study and the analysis of interaction between spot- and keyhole diameter state a higher process stability. Welds with a smaller spot diameter lead to a sufficient increase of joint quality by using a zero gap overlap configuration. It is shown that the amount of joint instabilities such as pores, pinholes, spatter and further defects can be minimized by using smaller spot diameters. This can be explained by different keyhole regimes. Moreover, the change of isothermal interaction in the interlayer zone caused by the adjusted spot diameter leads to high-quality joints.

Test and Numerical Study on Monotonic Behavior of Complex CFT Column Joints

This paper presents a test and numerical investigation into the monotonic behavior of three different complex steel trusses to concrete-filled tubular (CFT) column joints. Based on an engineering structure, 1 : 4 reduced-scale specimens are manufactured and the three-dimensional subassembly testing system is designed to apply the monotonic load. Test phenomena and load-stress curves show that all three types of joints have a considerable load-carrying capacity and joint rigidity. Finite element (FE) analysis is adopted, and the stress distribution shows good agreement with test data. Both test and FE results show that local buckling and yielding in the root region of steel truss are the main failure modes of test joints and the core area of the CFT column remains intact which are in accordance with the design conception of “strong column and weak beam.” Design conception of proposed overlap joint form is then investigated based on the FE model, and results show that the optimized overlap joint can effectively reduce the stress concentration in the adjacent steel tube and beam member when compared to the traditional N-type overlap joint. Finally, the influence of the outer diaphragm on the stiffness of joint is analyzed. By comparing the end-displacement of the beam member, conclusion can be obtained that the beam flange thickness is suggested to be chosen as the outer diaphragm thickness. The forms of three different proposed joints and their design conceptions can provide good guidance for designers and engineers.