Joints Of Sheets Research Articles

Improved self-pierce rivet performance through intentional decarburization

Two significant self-pierce rivet (SPR) performance metrics are column strength, to be able to pierce materials without buckling, and the ability of the rivet to flare without the formation of fractures. The ability to flare is required to facilitate interlock, which provides joint strength. A test method to evaluate these properties through mechanical flaring of the rivet over a conical die was developed. The test method was utilized to assess performance improvements gained through the incorporation of a decarburized ferrite surface layer that was produced through a modified quench and temper process. Mechanical flaring studies performed using digital image correlation techniques indicated a significant improvement in flaring performance with minimal compromise in column strength when the modified heat treatment process was applied to the current SPR alloy, 10B37. The improvements in flaring capability, while retaining sufficient column strength to pierce the material, have been evaluated in riveting trials for cases where the mechanical properties of the rivet have limited the joint development and joint commonization. Intentionally decarburized rivets were used to join two demanding joint configurations: press-hardened steel to AA6111 and a joint of aluminum sheets with a longer than optimal rivet. In each case, rivets were free of cracking and buckling, and the rivet interlock exceeded the minimum to qualify the joints for application.

The Investigation on the Dissimilar Material Overlapping Region via Friction Stir Lap Welding of Copper and Titanium

The technological innovation of joint method for dissimilar metals of titanium (Ti) and copper (Cu) still stays in demand. The promising joining method of friction stir lap welding was successfully introduced to produce the defect-free and high-performance lap joints of dissimilar Cu and Ti sheets. After process parameter optimization, the macro/micro-structures, and mechanical tensile properties of the lap joints were carefully analyzed. The formation mechanisms of the Cu/Ti alternate band structure were discussed in detail, as the results of utilizing a special Cutting Pin for promoting Cu/Ti mixing and transferring and limiting the evident formation of Cu-Ti inter-metallic compound phases in the overlapping region, with the composite-like structure playing a so-called mechanical locking effect on the Cu/Ti lap joints. The strengthening effect was also provided by the metallurgical bonding at the Cu/Ti band interfaces without cracking in micro scale. The fracture resistant strength of the joint reached 95% of that of the used parent copper.

Influence of the Parameters of Electrodynamic Actions on the Stressed State of Welded Joints of Sheets of AMg6 Alloy

We study the influence of the parameters responsible for different durations of the electrodynamic actions on the decrease in residual stresses in welded joints of the sheets made of AMg6 aluminum alloy after electrodynamic treatment. It is discovered that as the time of electrodynamic action increases as a result of the increase in the inductance of the discharge contour in the course of electrodynamic treatment performed for constant amplitude values of impulsive electric currents, the period of decay of impulsive electric current is longer than the period of its growth. In this case, the efficiency of electrodynamic treatment increases. It is established that, for the duration of electrodynamic treatment t Σ ≥ 4.5 msec, the decrease in residual stresses is determined both by the intensity of the electrodynamic influence and by the local heat treatment as a result of the Joule heating of the surface of the plate.

Mechanical properties of the welded joints of 1565ch alloy sheets at low temperatures

The effect of the method of welding on the mechanical properties of the welded joints of the 1565chM alloy is studied at room, high, and low temperatures.

Characterization and quality assessment of granitic building stone deposits: A case study of two different Portuguese granites

Several factors determine building stone exploration in order to maximize the extraction, processing and application of these natural materials. Some factors are intrinsic to stones, such as their physical-mechanical properties, while others are related to their exploitability, such as quarry reserves or fracturing density. During an exploration campaign, these factors are not always considered or properly weighed in terms of the negative consequences on quarry activities or rock behaviour under particular conditions. In this study, two well-known Portuguese granites are assessed to highlight the main factors. These granites have different characteristics, weathered and sound, and are exploited in quarries with different joint densities. The most relevant physical-mechanical properties were evaluated and related to the specific petrophysical features of each granite. The fracture patterns were identified in the quarries and then modelled in order to compute the quarry yield. The weathered granite shows an important microcrack network and a general alteration of the rock-forming minerals, which has an important impact on its physical-mechanical properties and on the resistance to environmental factors. Moreover, the extreme differences in the degree of weathering require careful choices for the possible applications. In both quarries, the joint sets are similar to the regional faulting, but some random joints can be found and, consequently, diminish the quarry yield. The development of horizontal sheet joints during the exploitation process could have a great influence on the quarry productivity if they are not used do delimitate the extracted blocks. The modelling of the natural fracture pattern allows us to determine the potential volume of blocks that could be exploited. However, the quality of the information gathered could lead to an over-estimation of the quarry production.This example shows the importance of the exhaustive researches during a building stone assessment campaign.

Defect features, texture and mechanical properties of friction stir welded lap joints of 2A97 Al-Li alloy thin sheets

1.4mm 2A97 Al-Li alloy thin sheets were welded by friction stir lap welding using the stirring tools with different pin length at different rotational speeds. The influence of pin length and rotational speed on the defect features and mechanical properties of lap joints were investigated in detail. Microstructure observation shows that the hook defect geometry and size mainly varies with the pin length instead of the rotational speed. The size of hook defects on both the advancing side (AS) and the retreating side (RS) increased with increasing the pin length, leading to the effective sheet thickness decreased accordingly. Electron backscatter diffraction analysis reveals that the weld zones, especially the nugget zone (NZ), have the much lower texture intensity than the base metal. Some new texture components are formed in the thermo-mechanical affected zone (TMAZ) and the NZ of joint. Lap shear test results show that the failure load of joints generally decreases with increasing the pin length and the rotational speed. The joints failed during the lap shear tests at three locations: the lap interface, the RS of the top sheet and the AS of the bottom sheet. The fracture locations are mainly determined by the hook defects.

Influence of heat treatment on mechanical properties of clinched joints in titanium alloy sheets

Clinching is a widely used sheet material connection technology in different industrial fields. The effects of annealing and quenching on the mechanical performances of clinched titanium alloy joints were investigated in this research. Tensile–shear tests were carried out to study the join ability, load-bearing capacity, energy absorption, and failure modes of different clinched titanium alloy joints. The F–N curves were obtained from fatigue tests to characterize the fatigue properties of different types of clinched joints. The typical fracture interfaces were analyzed by scanning electron microscopy. Results show that the tensile–shear strength of the clinched titanium alloy joints was severely decreased by quenching, but both tensile–shear strength and energy absorption were improved by annealing. For all types of joints tested, fatigue cracks always appeared near the indentation of the upper sheet. Analysis of the microstructure suggested that the plasticity of the titanium was improved by annealing.

Investigation of Joint Strength for Dissimilar Joint of CFRP and Aluminium Alloy Sheets by Punching Rivet Method

Investigation of Joint Strength for Dissimilar Joint of CFRP and Aluminium Alloy Sheets by Punching Rivet Method

SPR Characteristics Curve and Distribution of Residual Stress in Self-Piercing Riveted Joints of Steel Sheets

Neutron diffraction was used to describe the residual stress distributions in self-piercing riveted (SPR) joints. The sheet material displayed a compressive residual stress near the joint, and the stress gradually became tensile in the sheet material far away from the joint. The stress in the rivet leg was lower in the thick joint of the softer steel sheet than in the thin joint of the harder steel sheet. This lower magnitude was attributed to the lower force gradient during the rivet flaring stage of the SPR process curve. This study shows how the residual stress results may be related to the physical occurrences that happened during joining, using the characteristics curve. The study also shows that neutron diffraction technique enabled a crack in the rivet tip to be detected which was not apparent from a cross-section.

Optimization of electrical parameters in Resistance Spot Welding of dissimilar joints of micro-alloyed steels TRIP sheets

The Resistance Spot Welding (RSW) process in dissimilar joints of micro-alloyed steels TRIP (Transformation Induced Plasticity) sheets was herein optimizing. The welding electrical parameters (time and current intensity) had an important effect in the final Shear Tensile Resistance of these kind of joints. Taguchi Design of Experiments was employed in order to optimize the process by the signal-to-noise ratio. Furthermore ANOVA analysis determined the relevance of each parameter in the final mechanical resistance of the welds. The optimum welding conditions were established inside the lobe curve that maximize the response of the experiment.

Sustainability Analysis of Friction Stir Welding of AA5754 Sheets

The environmental impact of friction stir welding process vs. welding parameters was evaluated and analysed in detail. To this purpose, butt joints in AA5754 aluminum alloy sheets were obtained at different rotational and welding speeds. All input and output data, in terms of materials, energies and emissions, were collected and analyzed using a life cycle assessment software in order to evaluate the environmental impact index. Sound weld was used as functional unit and all energy and material flows were based on it. The results given by the life cycle assessment analysis has shown that the environmental impact of friction stir welding is strongly affected by rotational and welding speeds. The environmental impact was also related to the mechanical properties of joints, expressed as ultimate tensile strength and ultimate elongation.

Measurement of residual stress in arc welded lap joints by cosα X-ray diffraction method

The welding residual stress of lap joints of thin steel sheets was measured by the cosα X-ray diffraction method and compared with the numerical simulation. The longitudinal residual stress in the region near the weld is close to the yield strength of the base metal. The welding residual stress distribution is asymmetrical on the two plates and two sides of the weld because of the asymmetrical geometry of the lap joint. A higher residual stress was observed on the lower plate of lap joints. The longitudinal residual stress has almost the uniform distribution along the weld line except near two ends. The influencing length near two ends of the weld line is about 20–30mm. The maximum tensile value of the longitudinal residual stress of the lap joint of the high strength steel TS590 is higher than that of the mild steel TS270.

Characteristics of the mechanically fastened joints of one-layer bitumen sheets

The system of mechanic fastening is one of the most frequently used variants of roof membrane stabilization against the impacts of wind sucking. With the growing number of applications of mechanically fastened roofs the number of defects is also growing. We particularly see them in the joints of waterproofing membranes. The contribution is thus dedicated to examination of mutual dependence between the type of the carrier and the strength characteristics of mechanically fastened joints of these sheets. Bitumen sheets with different types of carrier used for onelayer mechanically fastened waterproofing membranes of flat roofs were chosen as samples. The above mentioned dependence is frequently stated in the practice, but is not explicitly documented. The aim of the contribution is to confirm or refute a hypothesis that a relation between the bitumen sheet carrier type and the strength of their joints exists. The results were arranged on the base of statistic evaluation of data obtained by laboratory measurement.

Characteristics of the mechanically fastened joints of one-layer bitumen sheets

The system of mechanic fastening is one of the most frequently used variants of roof membrane stabilization against the impacts of wind sucking. With the growing number of applications of mechanically fastened roofs the number of defects is also growing. We particularly see them in the joints of waterproofing membranes. The contribution is thus dedicated to examination of mutual dependence between the type of the carrier and the strength characteristics of mechanically fastened joints of these sheets. Bitumen sheets with different types of carrier used for onelayer mechanically fastened waterproofing membranes of flat roofs were chosen as samples. The above mentioned dependence is frequently stated in the practice, but is not explicitly documented. The aim of the contribution is to confirm or refute a hypothesis that a relation between the bitumen sheet carrier type and the strength of their joints exists. The results were arranged on the base of statistic evaluation of data obtained by laboratory measurement.

The analysis of implementation options of transverse joints of bitumen sheets

One of the most frequent sources of faults on flat roofs is a violation of the waterproof layers along the transverse joints between bitumen sheets. This fault is caused by a failure to adhere to the technological methodologies. This paper presents current solutions, as well as a new solution, for creating such joints. The new solutions are experimentally compared with existing solutions.

The analysis of implementation options of transverse joints of bitumen sheets

The analysis of implementation options of transverse joints of bitumen sheets

The problem of the compatibility of bitumen sheets for the reconstruction and ehabilitation of roofs

During the renovation of flat roofs, the waterproofing layer is often repaired locally rather than completely replaced. When making such repairs, it is very important to know whether the proposed bitumen sheets are compatible in order to prevent delamination and the release of the joints. This paper deals with the determination of the resistance of bitumen sheet joints against peeling when combined with different bitumen materials. On the basis of the described test methodology it was possible to determine whether the selected bitumen materials were compatible with bitumen sheets. As part of the experiments, modified bitumen sheets with plastomers (PO), oxidized bitumen (OX), and elastomers (SBS), were tested.

Influence of Shunting Current on the Metallurgical and Mechanical Behaviour of Resistance Spot-welded Joints in AA2219 Joints

The effects of shunting current on metallurgical and mechanical behavior of resistance spot-welded (RSW) joints in AA2219 sheets are analysed experimentally via the investigation of mechanical and metallurgical properties, while numerical results predicted by the finite element method (FEM) are used to check the thermal aspects of the phenomenon and its effect on experimental results. Welding distance is chosen as the main variable for two consecutive nuggets. Predicted temperature distribution and cooling rates of FEM are verified by checking the nuggets and heat-affected zone (HAZ) dimensions, the SEM investigation of cracks, and performing a tensile-shear test. Experimental results have been in agreement with the predicted results, since HAZ development, the presence of cracks, interfacial failure, and poor mechanical strength of shunted nugget with shorter welding distance are all predicted in the form of temperature distribution and cooling rates of shunted nugget in finite element analysis (FEA). The temperature dependence of material properties and coupling between all aspects of the solution are respected in the FEA model while experimental tests are performed according to a three-factor design of experiment (DOE) to set the levels of factors based on their significance.

Hybrid friction diffusion bonding of 316L stainless steel tube-to-tube sheet joints for coil-wound heat exchangers

Hybrid friction diffusion bonding (HFDB) is a solid-state bonding process first introduced by Helmholtz-Zentrum Geesthacht to join aluminum tube-to-tube sheet joints of Coil-wound heat exchangers (CWHE). This study describes how HFDB was successfully used to manufacture 316L test samples simulating tube-to-tube sheet joints of stainless steel CWHE for molten salt coolants as foreseen in several advanced nuclear- and thermal solar power plants. Engineering parameters of the test sample fabrication are presented and results from subsequent non-destructive vacuum decay leak testing and destructive tensile pull-out testing are discussed. The bonded areas of successfully fabricated samples as characterized by tube rupture during pull-out tensile testing, were further investigated using optical microscopy and scanning electron microscopy including electron backscatter diffraction.

Prediction of Spot Welding Parameters for Dissimilar Weld Joints

Development of manufacturing systems are needed to invent new kind of methodology for joining process in current research and development. Spot welding technologies are widely applied in non-conventional joining process. In this investigation predicted the mechanical properties like tensile strength and Hardness. The hardness evaluated in different regions of the spot welded Stainless steel sheet and Mild steel sheet joints such as welded zone, heat affected zone and parent material subjected to different Welding Parameters. The Experimental procedures are developed by factorial design and the regression model developed from the experimental results through Response surface methodology. The variable parameters are Electrode force, Weld Current and the Weld time. The measurable parameters are Tensile strength and hardness. The optimization process is carried out by Response surface methodology and the optimized parameters are defined the quality of the welded steel joints. The optimized welded parameters are expressed the effective joining and improve the quality of the welded member. stainless steel .The phase transformation which occur during the weld thermal cycle were analyzed which shows that fusion zone exhibited a carbide precipitates with small amount of martensite the HTHAZ exhibited a martensite, the MTHAZ exhibiting the higher hardness, the LTHAZ exhibited Cr- carbide. The grain growth which occurred in FZ and HTHAZ is a major problem accompanied with fusion welding of FSSs. It shows that the peak load and energy absorption of the welds were improved as the welding current increases due to the formation of larger FZ size at higher heat input. (2) In their research, the effects of electrode force, weld nugget, and hardness of spot welded steel joints are examined based on observed values of the experiment. Mechanical properties and the microstructure of the welded joints are having significant impact on weld nudge. The significant values of difference are identified in the hardness due to the changes presence in weld nudge. The mechanical properties and the microstructure on the heat affected zone is preserve higher value compare with welded zone. (3) Weld nudges and weld time are investigated through Finite element methods by two dimensional models in resistant spot welding. This analysis defined the effect of nugget size and weld time on AISI304L stainless steel sheet.