Showing papers on "Spot welding published in 1983"

A Review of the Fatigue Properties of Spot-Welded Sheet Steels

Abstract: Over the past several years, the automotive industry has used increasing amounts of high-strength sheet steels to reduce vehicle weight for improved fuel economy. It is important that these high strength steels exhibit spot-weld fatigue characteristics at least equal to those of previous lower strength low-carbon steels. This study reviews the spot-weld fatique performance of uncoated sheet steels with respect to material strength, spot-weld diameter, sheet thickness, and the number and array of spot welds. Models used to describe the state of stress around the spot weld are also reviewed. Selected results contained in the literature are reevaluated using fracture-mechanics concepts. Comments are given regarding fatigue-crack growth in spot welds with respect to the cyclic-stress ratio and threshold-fatigue limit. Limitations of current theories used to evaluate fatigue performance of spot welds are discussed, and an alternative approach to interpreting such data is recommended.

An empirical method for estimating the fatigue resistance of tensile-shear spot-welds

Abstract: An empirical method which is based principally on estimates of the fatigue crack initiation life (N sub I) has been developed which predicts the fatigue resistance of tensile-shear spot welds in the long life regime. The method uses Basquin's law and Peterson's equation to estimate N sub I and thus is founded on the fatigue behavior of smooth specimens and modelling of the fatigue notch size effect. The fatigue notch factor (K sub f) required in this analysis was obtained from Pook's relationships for the stress intensity factors of tensile-shear spot welds. Estimates of N sub I are added to estimates of the fatigue crack propagation life N sub P to obtain the total fatigue life (N sub T) but in the long life regime N sub P can usually be neglected. The improvement of tensile-shear spot weld fatigue resistance through manipulation of geometry and material property variables are discussed with the aid of the model. The model predicts that nugget diameter, sheet thickness, and residual stress control offer the best possibilities for fatigue life improvement.

Progressive ultrasonic welding system

Abstract: A method of progressively ultrasonically welding together workpieces is provided wherein the spot welds effected are initiated as small points and then progressively grow to full size. The method employs an ultrasonic welding apparatus of the type having a welding tip and a complimentary anvil between which the workpieces to be welded may be inserted. The workpieces are first clamped together and the workpieces "presqueezed" to disperse any adhesives which may be used between the workpieces. Initial pressure and energy levels are then introduced to "scrub" the workpieces. Pressure and energy are then synchronously ramped in phase to maximum levels to effect a weld between the workpieces. The welding operation is controlled by control means which permit automatic synchronization of the operation.

Instrumented spot welding electrode

Abstract: An instrumented spot welding electrode significantly improves the weld quality available from production resistance spot welding machines by providing real time measurements of key multivariable resistance welding parameters. The real time data provided may be used as inputs to adaptively control welding machines and dynamically adjust welding system operation responsive to the sensed variables. A number of sensors are positioned within a cavity specially formed into a water cooled electrode tip to obtain the desired measurements while being protected against physical damage. The sensors are advantageously placed in good thermal and electrical contact with a plug element which bears directly on the workpieces being welded to enhance the accuracy of the sensed variables. This specially configured and instrumented sensor cavity is ideally suited for use with all end types of electrodes including spherical, truncated, offset, flat and the like.

Adaptive schedule selective weld control

Abstract: @ A spot weld control senses differences in welding current required to produce an optimum weld by determining the time rate of change of resistance during the increasing resistance portion of the weld cycle. The weld control can reduce the welding current if the time rate of resistance change exceeds a maximum value and increase the current if the resistance change is less than a minimum value. The weld current may be terminated when a decrease in resistance from the peak resistance value has reached a predetermined percentage of the peak resistance value or terminated after a predetermined number of current cycles.

Acoustic wave spot welder adaptive control

Abstract: The thickness of the molten weld nugget is continuously monitored during resistance spot welding, and when proper penetration is achieved the applied current is turned off. An ultrasonic transducer housed in the water cooled lower welding electrode transmits ultrasonic pulses into the workpiece and receives waves reflected at each solid/solid and liquid/solid interface. The position of the latter is tracked by pulse time discrimination of reflected signals; weld nugget penetration is computed using a ratio of times or a pulse time difference.

A new mechanical joining technique for steel compared with spot welding

Abstract: Two mechanical joining techniques were compared with spot welding in a number of plain carbon and high-strength steels with or without various metallic and painted coatings. Spot welds had higher static strength than mechanical joints, but the new button-type (crack-free) joint had equivalent fatigue strength at long lives. Relationships were developed to estimate the strength of the button-type mechanical joint given base metal strength properties and the geometry of the joint.

Spot weld quality monitoring system

Abstract: Adjusted voltage measurements of monitored AC electrical energy supplied during a welding operation are evaluated by integration with respect to time during half cycles to develop a variable criterion each half cycle that is compared with adjusted limits to electronically make weld quality judgements. The generation of a fail signal during two consecutive half cycles as a result of such judgements, is operative through logic gating to produce a reject signal to control the marking of defective welds, interrupt the supply of energy to the welding electrodes and effect timely operation of an ejector removing articles with defective welds from a production line.

Method and apparatus for detecting the onset of melting in a resistance spot weld

Abstract: During a weld period the weld parameters are monitored and data representing the weld resistance curve and the power curve are acquired and stored for analysis by a suitably programmed computer. The derivative of R, R is calculated and stored and the function is divided by power P to obtain R/P. The resistance curve is searched to obtain the maximum value Rm which occurs during the heating phase and the function R/P is searched prior to the time of Rm to find the maximum of that curve representing the highest rate of resistance increase. Then the R/P curve is searched subsequent to its maximum to determine when the function reaches a specified percentage of the maximum. That value occurs at the knee of the resistance curve and approximates the onset of melting in the weld. A prediction of whether a weld is a nugget or a sticker is made by calculating the ratio of weld energy after the onset of melting to the total weld energy, the ratio of the resistance drop after the resistance peak to the peak resistance, and then a weighted sum of the energy ratio and resistance drop ratio. An edge weld geometry is detected by calculating from the resistance and power curves the weld energy during the period of expulsion, if any, divided by the cumulative energy between the onset of melting and the end of expulsion, a measure of expulsion intensity based on the maximum degree of resistance inflection, and then a weighted sum of the energy value and the inflection value.

Stabilized ultrasonic welding apparatus

Abstract: Ultrasonic spot welding apparatus is provided including a welding tip and a complimentary anvil, both mounted on a stationary welding frame and between which workpieces may be inserted for welding. The welding tip includes a vibratory reed adapted to introduce into and through the workpieces high frequency vibratory energy in order to effect a weld between the workpieces. The apparatus includes a reed stabilizer for clamping about and stabilizing the vibratory reed at its nodal point and clamping means for clamping the workpieces. The clamping means are mounted on a clamping frame which is pivotably mounted to the stationary welding frame.

Composite resistance spot welding electrode

Abstract: A composite electrode configuration prevents mushrooming of resistance spot welding electrodes due to local high contact pressure and current densities. For a truncated electrode, an outer sleeve of high strength and high electrical resistivity material is attached to the end of the electrode and takes the high contact stress at the edge of the flat end face. A spherical end electrode has a plug of higher strength material in the center where the highest contact stress exists, and the outer sleeve reduces the joule heating effect. A transverse insulating spacer is a thermal and electrical barrier.

Arc spot welding equipment

Abstract: An arc spot welding equipment wherein a hand having a positioning and clamping device for a work and a welding torch is attached to an arm of an industrial robot. The small work is clamped in a predetermined positional relation to the welding torch and is moved by the arm of the robot to an object to which said work is to be welded, thereby realizing an automatic positioning of the work to the object and eliminating the need to prepare a large-scale jig for positioning and clamping work to reduce the cost of the equipment.

Method and apparatus for preventing tip sticking during welding operation

Abstract: A method is provided for preventing tip sticking during the spot welding of workpieces including ultrasonic vibratory spot welding. The welding apparatus includes a welding tip and a complimentary anvil between which the workpieces to be welded may be inserted. The welding tip is adapted to introduce into and through the workpieces sufficient amounts of energy to effect a weld between the workpieces. Shim material is inserted between the welding tip and the workpieces and/or between the anvil and the workpieces, said shim material having a hardness greater than the hardness of the workpieces. After insertion of the shim material, welding energy is then introduced through the shim material and the workpieces and welds are effected therebetween. The shim material is then torn away and discarded. Apparatus for effecting this method is further provided.

Self-piercing rivets for aluminum components

Abstract: Recent trends in the automotive industry toward improving fuel economy have led to the conversion of many steel applications to aluminum. The use of aluminum reduces vehicle weight while allowing the automaker to continue to use traditional fabricating methods. The primary joining technique used for steel sheet components has been resistance spot welding. While this technique is currently used to join many aluminum components, automakers are reluctant to specify this joining technique due to capital equipment cost, electrode tip life, or reliability concerns. Several alternate joining techniques have been investigated and used. These include adhesive bonding, weld bonding, resistance welding with arc cleaning, GMA spot welding, clinching, and riveting. Recently, a method of riveting components without prepunching or predrilling holes has generated a large amount of interest. This paper is a review of this riveting technique. Data is included for comparisons to resistance spot welded joints.

Assessment of Resistance Spot Welds in Low Carbon and High Strength Steel Sheet

Abstract: The introduction of high strength steels has highlighted the lack of knowledge regarding the properties required of resistance spot welds, particularly in the vehicle industry. The laboratory static and dynamic tests currently employed cannot be used to predict performance under service conditions, and there is a further complication because of lack of standardisation of test techniques. Specimen dimensions strongly influence the results when the properties of welds in low carbon and high strength steels are compared. The suitability of routine shop floor tests used in mass production industries has been questioned with regard to the necessity of generating plug failure. This cannot be resolved until the significance of plug failure in high strength steels is established. If plug failure is not essential, weld size can be determined by employing high speed metallurgical techniques for steels giving interface failure. Resistance welding is the most widely used technique for assembling transport vehicles and similar structures but despite this there is a lack of realistic data which adequately define the properties and likely service behaviour of such joints. This article describes the various test methods for resistance welds and summarises observations of the influence of test technique on the results obtained for welds in low carbon and high strength steels.

A Microprocessor-Based Control System for Resistance Spot Welding Process

Abstract: Due to the large number of interrelated variables associated with the process, weld quality of the resistance spot welding is extremely operation-dependent and thus requires on-line monitoring and control of appropriate process variables that can reflect weld quality. One of such variables is instantaneous resistance variation curve during the weld formation. In this paper the dynamic resistance variation is monitored and utilized for a microprocessor-based welding process control. The control objective is to track a desired resistance variation curve (reference dynamic resistance) during the welding process to assure uniform quality of the weld joint regardless of variation of welding conditions. For this purpose a current controller is designed to generate the welding control current, and two types of control algorithms are implemented and tested through a microcomputer: (1) proportional control (P) (2) proportional plus integral control (PI). Tracking performance of these controllers is evaluated through a series of experiments conducted under various welding conditions.

Spot welding gun

Abstract: A spot welding gun adapted for use in robotic welding in which the electrode holding arms of the gun are each turnably journalled on an attachment means. One of the electrode holding arms or an operating lever thereof supports a cam member with a cam surface thereon. A pressure roller acts against said cam surface during transport of the welding gun between welding points and thereby holds each electrode holding arm in a respective fixed position relative to the attachment means.

Studies on the ultrasonic metal welding – on the limit of ultrasonic spot welding and on the trial of ultrasonic butt welding –

Abstract: To determine the maximum efficacy of ultrasonic spot welding of metal plates, the ultrasonic spot welding with two vibration systems of 0.1 mm to 10.0 mm thick aluminum plates is studied, and the static pressure distributions of weldments are measured by pressure sensitive film units. As the thickness of specimens increases over 8 mm, it becomes very difficult to weld specimens successfully. An ultrasonic butt welding equipment is designed and the ultrasonic butt welding of aluminum plates is studied under various welding conditions. It is shown that the weld strength of 6 mm thick and 15 mm width aluminum plates obtained is over 800 kg, i.e. the weld strength per unit area is about 9 kg/mm2. The ultrasonic butt welding to join specimen plates edge to edge is very effective to weld thick specimen plates.

Welded joint for automobile-body sheets

Abstract: Welded joint for automobile-body sheets in which the adjacent body sheets (1, 2) have flanged edge strips (3, 4) which bear against one another and are joined to one another by a row of resistance spot welds (5). At least one edge strip (3, 4) has cut-outs (6, 6a) extending right into the area between the row of resistance spot welds (5) and the flanged edge (9). The two edge strips (3, 4) are in each case welded to one another at the root (7) of the cut-out by means of at least one fusion weld spot (8). The joint is given adequate dimensional stability, and cracking of the paint in the joint-groove area of the sheets is prevented.

Spot welding method

Abstract: PURPOSE:To prevent generation of a strain or flaw on the surface of plates to be welded in the stage of superposing plural sheets of said plates and subjecting the same to spot welding by disposing a welding electrode on one surface thereof and disposing a bearing member made of ceramics on the other suface. CONSTITUTION:The end part of bodies 3 to be welded which are formed into three layers is inserted between a welding electrode 5a of a spot welding machine and a bearing member 8 made of ceramics in indirect spot welding of a door hem part, etc. of an automobile. The parts of the bodies 3 where the thin steel sheet 2 and thin steel sheet 1 thereof are spaced parallel are inserted between the other electrode 5b and a back electrode 4b. A pressure is exerted on the end part of the bodies 3 via the electrode 5a and the member 8, and welding current is conducted between the electrodes 5a and 5b to spot-weld the contact parts of the sheets 1, 2 in the end part of the bodies 3. The generation of a strain and flaw on the surface of the sheet 1 is prevented without wearing of the member 8 in continuous welding by the above-mentioned method.

Removal of a first metal sheet secured to a second metal sheet by spot welding

Abstract: A first metal sheet secured to a second metal sheet by spot welding, for example in motor vehicle bodies, can be removed by drilling through the first sheet in the region of the welded spot around the latter until the second sheet is reached. First of all the middle of the welded spot can be drilled with a corresponding tip (2) of a drill (1) and during further drilling the external region of the area of sheet to be removed can be cut. When the outer cutting region meets the second sheet, the drill tip can already have penetrated the latter so that the drill is centred and guided also in this phase. When the first sheet has been cut through with the outer cutting region, the remainder of the sheet can be removed. In this case it is sufficient for the drill tip (2) to project beyond the lateral cutting edges (4) of the drill (1) by roughly the thickness of the sheet to be removed.

Butt welding method

Abstract: PURPOSE:To prevent the cracking of deposited metal and to increase the rate of deposition in butt welding of dissimilar materials of different m p by spot welding the thin metallic plate which is the same as the welding material used for welding on a low m p material side and arc welding the materials CONSTITUTION:After mating of the groove face 1a of a base material 1 on a low m p side such as carbon steel and the groove face 2a of a base material 2 on a high m p side such as stainless steel is completed, a thin metallic sheet 4 having the chemical components and mechanical properties which are the same as or similar to those of an electrode wire 3 is adhered by spot welding 5 to the face 1a, after which both materials are arc welded Since the material 1 on the low m p side is not exposed to right under the arc 6 generated by the wire 3, the excessive penetration of the material 1 by arc heat is suppressed, and since the sheet 4 melts and forms deposited metal together with the deposited metal 7 of the wire 3, the welding is made possible at a high rate of deposition

Contact device for resistance spot welder

Abstract: Means for making electrical contact with a pair of spot welding electrodes and workpieces engaged by the electrodes. The means includes two rigid insulating blocks for mounting on each electrode of an electrode pair. Each block has a first electrical conductor for physically engaging the electrode upon which it is mounted and a second electrical conductor for physically engaging an exposed surface of the workpiece the electrode will engage in a welding process. The electrical conductors extend in a direction substantially perpendicular to the electrodes when the blocks are mounted thereon. In addition, means integral with the blocks and conductors for respectively electrically connecting the conductors to a device for measuring the voltage drop between electrodes and between the exposed surfaces of the workpieces when welding current is applied to the workpieces by the electrodes.

Welding method of metallic material having insulating layer

Abstract: PURPOSE: To perform easily, stably and beautifully welding of a metallic material by heating electrodes to the temp. or more at which insulating layers are softened, superposing metallic materials having the insulating layers and bringing the electrodes into press contact with the materials to break down the insulating layers thereby welding said materials. CONSTITUTION: Electrode tips 18, 19 are first heated by heaters 27, 29 to the temp. or more at which insulating layers 23, 25 are softened and in this state the electrode tips are brought into press contact with superposed metallic materials 18, 19 from above and below in the stage of welding the laminated metallic materials 18, 19 consisting of metallic layers 21a, 21b and 24a, 24b as well as the insulating layers 23, 25 by the electrode tips 26, 28 of a spot welding machine. The heat from the tips 26, 28 is transmitted via the layers 21a, 24b to the layers 23, 25 by which the insulating layers are successively softened and fluidized. The softened and fluidized layers 23, 25 are thereby forced sideways and finally the metallic layers 21a, 21b, 24a, 24b come into direct contact with each other. The layers 23, 25 rise around the welding spot. If a welding part 30 is welded, the weld zone having beautiful appearance is formed. COPYRIGHT: (C)1985,JPO&Japio

Fatigue of Automotive High Strength Steel Sheets and Their Welded Joints

Abstract: Fatigue properties in various types of high strength steel sheets for automotive use and their spot and arc welded joints were investigated. In steel sheets and strain-aged sheets, fatigue limit stresses and notch sensitivities depend on not only the tensile strength but also the yield strength. Two methods for improving fatigue strength of spot welded high strength steel joints were found. One is to generate moderate expulsion during welding with a current just above the upper lobe curve and another is to conduct a controlled tempering treatment during the welding schedule. By these methods, fatigue strengths at 10 to the 7th power cycles of spot welded high strength steel joints increase by about twice as compared with those by the conventional welding method.

Weldable sealants for metal and method of use

Abstract: A weldable sealant composition is made by adding ferrous metal particles to a sealant having a viscosity of at least 6 million centipoises. The sealant composition is placed between two metal plates and permits resistance welding, i.e. spot welding, to take place.

Concrete product and its manufacture

Abstract: PURPOSE:To obtain PC piles having excellent impact resistance by a method in which high-tensile iron bars ade of martensitic steel wires subjected to tempering process are welded to a spiral iron bar as a cross beam, the welded portions are tempered, and the iron bars in tensed state are buried in concrete. CONSTITUTION:High-tensile iron bars 1, obtained by subjecting wire materials containing 0.4% or less carbon and a martensite structure formed by cooling controlled from a temperature below 700 deg.C after hot rolling to a tempering process without passing through drawing process, are arranged on the circumferential side of a concrete product form. Then, an iron bar 2 is spirally wound around the periphery of the high-tensile iron bars 1 and spot-welded by flowing about 2,500-3,250A of current in the spot welding electrode of movable electrode in about 2-4 cycles. The welded portions are tempered by flowing about 2,750-3,500A of current in the tempering electrode in about 2-4 cycles. The iron bars in tensed state are buried in concrete to bring the elongation at breakage of the high-tensile iron bars 1 to 8.1% or more.

Manufacture of semiconductor device

Abstract: PURPOSE:To unnecessitate the gold plating to be performed on the external connection terminal of the titled semiconductor device by a method wherein, when the electrode and the wire of a semiconductor element are joined together by performing a thermo-press welding, said wire and the external connection terminal are connected by performing an electric welding. CONSTITUTION:A gold wire 3 is led out through the intermediary of the capillary 6, the inner part of insulating material 1 such as ceramic and the like and the external part made of conductive material 2 such as tungsten and the like. The electrode and the gold wire 3 of the semiconductor element 4 are bonded by performing a thermo-press welding, but the external connection terminal 5 and the gold wire 3 are bonded by performing an electric spot welding by running the current I on the conductive material 2 of the capillary 6. Consequently, as the external connection terminal and the gold wire 3 are bonded using no thermo-press welding, the gold plating on the bonding surface of the external connection terminal 5 can be unnecessitated.

Reinforcing structure of spot welding zone

Abstract: PURPOSE:To increase the strength in a spot welding zone of a flange part to be spot welded by providing a bead near the spot welding zone. CONSTITUTION:Flange parts 11a, 12b are formed at the bottom ends of a side sill outer panel 11 and a side sill inner panel 12. Said flange parts are joined and are spot welded 13 by a proper interval. Beads 14 for reinforcement are provided near both sides in the spot welding zone 13 of the panel 12 so as to be located straightforward approximately with a polygonal line 12b. The flange part 11b is formed to the top end of the panel 11 and is joined to the flange part 15 of a floor panel (b) of a vehicle body. Both flange parts are fixed by spot welding 16 by a proper interval. Beads 17 are provided near both sides in the spot welds 16 in the flange part 15 on the panel 6 side in the direction approximately at a right angle to a polygonal line 15a. The force for stripping is received in the bead parts even if said force acts; therefore, the strength in the weld zones is increased.

Resistance seam welding

Abstract: The invention relates to a combined method of seam and projection welding for coated, in particular galvanized, sheet. During the welding, the non-uniform pick-up of zinc at the rollers to carry current is troublesome and leads to the formation of small irregular prominences on the rollers. These prominences are levelled by means of blades rubbing on the rollers, as a result of which their troublesome effect on the welding current feed is removed.