Machine Elements 1 PDF

Gépelemek 1. MACHINE ELEMENTS AS A SUBJECT Authors: Dr. Kerényi György Molnár László, Dr. Marosfalvi János, Dr. Horák Péter, & Dr. Baka Ernő Gépelemek bevezetés| GÉPELEMEK 1. előadás 1 Mechanical systems Gépelemek 1. environment Plants, factories Machines Machine parts Macnine elements...

Gépelemek 1. MACHINE ELEMENTS AS A SUBJECT Authors: Dr. Kerényi György Molnár László, Dr. Marosfalvi János, Dr. Horák Péter, & Dr. Baka Ernő Gépelemek bevezetés| GÉPELEMEK 1. előadás 1 Mechanical systems Gépelemek 1. environment Plants, factories Machines Machine parts Macnine elements Gépelemek bevezetés| GÉPELEMEK 1. előadás 2 Machine, machine elements Gépelemek 1. Machine: those kind of equippment, which consumes or transmits power or energy and its operation principle is mechanical. (in case of no mechanical motion then no machine.) Machines are made up of machine elements, which are individual parts of the machine that move and impact other parts to make the machine work. Although a machine element may consist of smaller structural parts, the entire setup that performs the function is considered the element. General-purpose machine elements can be used in any application, and include items such as gears, bearings, and shafts. Gears are rotating parts with interlocking teeth that turn against other gears, causing them to turn and transmit rotational force, or torque. Bearings are used to carry force — an example is the ball bearing, which allows for reduced friction as it rolls freely beneath a moving part. Shafts and couplings, like gears, also transmit torque and are used to connect parts, especially in vehicles such as cars and motorcycles. Although many variations and other types of general-purpose elements exist, they all work based on the same principles of force and motion and can be incorporated into almost any machine as necessary. Gépelemek bevezetés| GÉPELEMEK 1. előadás 3 Basic types of machine elements Gépelemek 1. − joints: force, form, material closing; function: force and/or torques transfer; − plumbing elements: pipes, fittings, taps, pressure vessels, seals & gaskets, function: liquids, gases etc. storing, transfering, and stream regulation. − springs, spring systems: various metal or rubber constructions (polimer springs); function: energy storing, damping, tuning of dynamic systems − arrangements: sliding & rolling bearings & linear guideways; function: force transferring by mechanical movement; − drives, drive systems: shafts, clutces, couplings, gear elements, belts, chains, friction drives, function: transfer or convert power (torque). Gépelemek bevezetés| GÉPELEMEK 1. előadás 4 Complete assemblies Gépelemek 1. Gépelemek bevezetés| GÉPELEMEK 1. előadás 5 Almost all types of machine elements in one assembly Gépelemek 1. Gépelemek bevezetés| GÉPELEMEK 1. előadás 6 Task of an engineer Gépelemek 1. Aim of an engineer, can be to find a solution of a technical problem at certain given boundary conditions: ...and optimize them from the – – – – – the material, the structure, the manufacturing, the product-human interface, the quality, timing, costs side. Gépelemek bevezetés| GÉPELEMEK 1. előadás 7 Assignment of an engineer Gépelemek 1. The task: − non determined, − thorough & wide-range activity, − based on many sciences as, mathematics, mechanics, materials, manufacturing, streams, heat, economy, etc. − and also deals with, ergonomics, aestethics, shape design, marketing, and other social sciences as well. Gépelemek bevezetés| GÉPELEMEK 1. előadás 8 A possible way of product design Gépelemek 1. According Pahl-Beitz design process Gépelemek bevezetés| GÉPELEMEK 1. előadás 9 Who is an engineer? Gépelemek 1. An engineer applies scientific and mathematical principles to develop solutions for various problems faced by society. Engineers use their creativity and expertise to design, develop, and optimize systems, structures, machines, and processes that are safe, efficient, and costeffective. They work to improve the quality of life by providing innovative solutions to complex problems, ranging from designing sustainable infrastructure to developing cutting-edge technologies. Engineers are often required to work in interdisciplinary teams and collaborate with other professionals to bring their ideas to fruition. They use their analytical skills to evaluate data, assess risks, and find ways to improve existing systems. Engineers may work in various fields, such as aerospace, civil, mechanical, electrical, chemical, and software engineering, among others. They often specialize in specific areas within their field, such as materials science, robotics, or environmental engineering. Gépelemek bevezetés| GÉPELEMEK 1. előadás 10 The 3 focus of an engineer Gépelemek 1. The 3 focus of an engineer (we always need to be able to...) DETERMINE THE LOAD CASE IDENTIFY THE STRESS, THEN DETERMINE TRESHOLD VALUES CALCULATIONS AND CREATE DIMENSIONS tasks are... As engineers we always need to have analytical results as first run, than we can use FEM methods to achieve accurate targets. During our development process we always balance between the 3 following factors. We need to have a some kind of optimal solution, but this does not happen all the time. Quality START Timing FINISH Cost Gépelemek bevezetés| GÉPELEMEK 1. előadás 11 The engineer is always part of a quality system Gépelemek 1. The goal is to meet customer requirements efficiently and effectively. What You Should Know When Preparing for IATF 16949® Certification. Gépelemek bevezetés| GÉPELEMEK 1. előadás 12 Expenditures (costs, time) Gépelemek 1. Manufacturing processes versus number of products Costs Universal machining & general tools Special machining & special tools Critical number of pieces Manufactured pieces The chosen manufacturing process to be based on the number of pieces! Gépelemek bevezetés| GÉPELEMEK 1. előadás 13 Costs at tolerances Gépelemek 1. Close tolerances may necessitate additional steps in processing and inspection or even render a part completely impractical to produce economically. Tolerances cover dimensional variation and surface-roughness range and also the variation in mechanical properties resulting from heat treatment and other processing operations. Gépelemek bevezetés| GÉPELEMEK 1. előadás 14 Design & development is a process Gépelemek 1. Design & development is also a technology: • manpower: help of the creative/thinking men is the computer; • methodology: pl. CAD, CAE, FEM, FMEA, etc. We can say that: teamwork gives us the possiblity getting more & more knowledge during design & development therefore the best is when all specialists sits at the same table and speak the same language and are on the „same page” from engineering point of view. Gépelemek bevezetés| GÉPELEMEK 1. előadás 15 The engineering teamwork Gépelemek 1. We need to work in effective teams, in teams we need to know about: marketing design manufacturing preparation manufacturing purchasing supplier development management customer • methodology (eg. brain-storming, FAST, 8D, QFD, DFMEA, etc.) • ethics. Better in teams Gépelemek bevezetés| GÉPELEMEK 1. előadás 16 The 3 step design phase of an engineer Gépelemek 1. In the beginning the designer faces a 3 step development process which is: • Load case of the structure element, • The state of stress and stress limits • Geometrical structure and dimensions. Gépelemek bevezetés| GÉPELEMEK 1. előadás 17 Design steps of the engineer Gépelemek 1. First step of the designer: To determine the load case of the structure. Load case means: all the external loads which have any effect on our product. Task: the load-modell creation. Base: theory & practice of product analysis the engineer generally designs products for a certain period of time (planned obsolecence), therefore the load, as a function of time is the most important factor. Gépelemek bevezetés| GÉPELEMEK 1. előadás 18 Different time-dependent load case modells Gépelemek 1. M(t) Terhelés mint idõfüggv. Application examples (for polymer elements): M(t) Idõben változó Idõben állandó t M(t) Folyamatosan Változó Szakaszosan változó t -interference fitted ring on a shaft, -reading lamp,clamped -(bolt joints), -intermittent operation of an impeller, M(t) Változó ampl. Állandó amplitúdó t M(t) Rendszertelen Rendszerezett t -rollers, -gears. -programmed, eperimental fatigue test M(t) Stacionér t M(t) -real load case, Instacionér [by ...Matolcsy Mátyás] Gépelemek bevezetés| GÉPELEMEK 1. előadás 19 Design steps of the engineer Gépelemek 1. Second step of the designer: For optimal operation: to determine the maximum allowable stresses & endurance limits of structures & assemblies. To determine in advance!! All possible effects & failure modes, fatigue & fracture causes Methodology: e.g. DFMEA (Design Failure Mode and Effect Analysis) Gépelemek bevezetés| GÉPELEMEK 1. előadás 20 Failures & causes Gépelemek 1. Possible reasons: • On loaded mating surfaces it is wear therefore (eg.: heating, wear, scoring, scuffing), • Temperature field effects (eg.: material property change, heat expansion, heat stress), • Non-allowable motions ( eg.: vibration, swing), • Different substrate, radiation (eg.: corrosion, expansion, aging), • Electrical, optical, various property change, • Biological degradation, • etc. Gépelemek bevezetés| GÉPELEMEK 1. előadás 21 The failure process Gépelemek 1. The failure process can lead us to: • Usage value decrease, • Needed refurbishment, maintenance, • Most dangerous method, the fracture. The fracture is related to stress- and strain state (plastic, ductile, creep, relaxation, stb.) of the material. Remark: in further investigations we use the Hooke’s law as a material modell, but in some cases we can also study the elasto-plastic transition as a boundary condition and also the modells of the fatigue&fracture. Gépelemek bevezetés| GÉPELEMEK 1. előadás 22 Design steps of the engineer Gépelemek 1. The third step of the designer: stress analysis. He designs the structure with dimensions and calculates the stress state from the load case and then compare it to endurance limit of given elements and determine whether the construction is good or wrong. endurance limit of structure safety (factor) = stress state of structure safety (factor) = ultimate strenght working stress brittle, rigid materials safety (factor) = yield strenght working stress ductile materials Endurance limit can mean uselessness for products. eg. Bigger deflection than expected, buckling, indentation, wear, etc. Gépelemek bevezetés| GÉPELEMEK 1. előadás 23 Design steps of the engineer Gépelemek 1. Nowadays we have more & more interests to have reality close models and describe more & more reality effects in engineering models.. e.g.: • cumulative failure theories, • operational solidness, • mathemathical statistics, e.g. calculation for a so called surviveing possibility function, • calculation for fracture, and checking, • calculation for elasto-plastic boundary conditions, • and further different theories & methods... Gépelemek bevezetés| GÉPELEMEK 1. előadás 24 Gépelemek 1. Base of the design for materials & manufacturing Gépelemek bevezetés| GÉPELEMEK 1. előadás 25 Methods for design for manufacturing (DFM) Gépelemek 1. ...is the process of designing parts, components or products for ease of manufacturing with an end goal of making a better product at a lower cost. This is done by simplifying, optimizing and refining the product design. Gépelemek bevezetés| GÉPELEMEK 1. előadás 26 Engineering tasks Gépelemek 1. Engineering tasks: to select material according to the requirements list. Materials can be chosen: − cast iron, − steel , − aluminium, − bronze, − polymer, − glass, porcelain, − ceramics, − wood, paper etc. At first approach: our brain-storming can be guided by the ratio different material properties. (modulus, stress, strain) Gépelemek bevezetés| GÉPELEMEK 1. előadás 27 Structural material properties Gépelemek 1. Let’s take a look at... − − − − − − mechanical, termical, electrical, optical, tribological, And other, specific properties. The engineer: to explore the advance material properties and reduce the disadvantageuos effects. Gépelemek bevezetés| GÉPELEMEK 1. előadás 28 Comparison metals & polymers Gépelemek 1. Polymers are... Mechanical properties: Termical properties: − density (ρ): app. 1/7, − operation temperature: <100 oC, − young modulus (E): 1/10, − heat elongation coefficient (α): 510 x bigger, − Tensile strenght (σB): 1/10, − strain (ε): 10-20 x bigger, − damping (tgδ): 10 x bigger, − Heat conduction coefficient (λ): 100-200 x worse − heat capacity (cp): 2-3 x bigger. ...compared to steels Gépelemek bevezetés| GÉPELEMEK 1. előadás 29 Comparison metals & polymers Gépelemek 1. Polymers are... Electrical properties: Optical properties (to glass): − Resistance (ρ): in the range of dielectric materials, − bigger fracture strenght, − Relative dielectric constant (ε): in the range of capacitor materials. − lower density& surface skratch resistance, − Good reflective index; good tranlucent properties. Tribological properties: − low friction coefficients, − good embedding capacity, − good mating properties. ...compared to steels Gépelemek bevezetés| GÉPELEMEK 1. előadás 30 Generally about design for manufacturing (DFM) Gépelemek 1. DFM can be used to shorten product development cycles. A good DFM will help identify and get rid of design flaws. This avoids issues and costly re-design changes. A rough design will often turn out to be more difficult to apply. This leads to higher costs and slower product development. Simplifying the processes involved in each of the stages can shorten product development cycles. A good DFM will help calculate costs upfront and lower the total cost of ownership. Via DFM, expenses can be managed in the design stage itself. With DFM, designs can be discussed, and more cost-effective solutions can be applied. That being said, quality control is the most important aspect of any product. Each part and process needs to be tested to check that quality meets industry standards. DFM can add value to product designs across industries. Different designs options can be explored, and processes can be optimized to lower costs at higher quality Gépelemek bevezetés| GÉPELEMEK 1. előadás 31 Engineering guidelines at steel & cast iron Gépelemek 1. Advantages of different castings: − Casting is the shortest way from raw material to ready product, − instead of different machine elements casting can summarize them in one intergrated part, − weight of castings can vary from some gramms to several tonnes, − manufacturing costs are lower than machining from solid materials, − difficult and sculpture surfaces are also possible. Gépelemek bevezetés| GÉPELEMEK 1. előadás 32 Engineering guidelines at steel & cast iron Gépelemek 1. Advantages of cast irons: – – – – – less sensitiveness against external notches, good damping properties, good wear resistance, applicable for machining processes better resistance to pressure then tension. Steel casting (not alloyed, light alloyed, specific alloys): – high heat resistance, – corrosion resistance – etc. Gépelemek bevezetés| GÉPELEMEK 1. előadás 33 Split line at sand casting Gépelemek 1. Gépelemek bevezetés| GÉPELEMEK 1. előadás 34 Reconsidering & review of a cast iron or steel Gépelemek 1. Pattern Production 1. − Simple geometrical shapes, − Simple production, − Undivided modell, possibly without a core, − Simple easy fixed cores. Mould Production 2. − 1:20…1:50 draft angles, − Avoid undercutting, − proper radius at transitions. Casting process 3. − Smooth transition of wall thickness, − Orientate the increase of wall thickness. Cooling&solidifying (shrinkage) 4. − Regulate cooling process, − Avoid materilal junction (lunkers), − Avoid steps in wall thickness (possible cracks), − Try to have symmetrical details (avoid warpage and/or eigen stresses) Gépelemek bevezetés| GÉPELEMEK 1. előadás 35 Reconsidering & review of a cast iron or steel Gépelemek 1. 1. Example: fulfilling the production requirements of patterning Gépelemek bevezetés| GÉPELEMEK 1. előadás 36 Reconsidering & review of a cast iron or steel Gépelemek 1. 2. Example: fulfiling the drafting and moulding requirements Gépelemek bevezetés| GÉPELEMEK 1. előadás 37 Reconsidering & review of a cast iron or steel Gépelemek 1. 3. Example: for fulfiling the casting requirements Gépelemek bevezetés| GÉPELEMEK 1. előadás 38 Reconsidering & review of a cast iron or steel Gépelemek 1. Estimating of wall thickness based on cast dimensions 50 45 Wall thickness [mm] 40 35 30 L – lenght of cast [m] 25 B – width of cast [m] 20 H – height of cast [m] 15 10 5 0 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 [The International Meehanite Metal Co. Ltd.] Gépelemek bevezetés| GÉPELEMEK 1. előadás 39 Reconsidering & review of a cast iron or steel Gépelemek 1. 4. Example: fulfiling the cooling & solidifying requirements Gépelemek bevezetés| GÉPELEMEK 1. előadás 40 Engineering guidelines (examples) Gépelemek 1. Pahl - Beitz: Engineering design, 1989 Casting guidelines Gépelemek bevezetés| GÉPELEMEK 1. előadás 41 Engineering guidelines (examples) Gépelemek 1. Pahl - Beitz: Engineering design, 1989 Impact extrusion guidelines Gépelemek bevezetés| GÉPELEMEK 1. előadás 42 Engineering guidelines (examples) Gépelemek 1. Pahl - Beitz: Engineering design, 1989 Sheet metalling guidelines Gépelemek bevezetés| GÉPELEMEK 1. előadás 43 Engineering guidelines (examples) Gépelemek 1. Pahl - Beitz: Engineering design, 1989 Assembly & tolerancing guidelines Gépelemek bevezetés| GÉPELEMEK 1. előadás 44 NSPE National Society of Professional Engineers Gépelemek 1. Gépelemek bevezetés| GÉPELEMEK 1. előadás 45 Gépelemek 1. FASTENERS, EFFECTS ▬ BOLT JOINTS Authors: Dr. Kerényi György Molnár László, Dr. Marosfalvi János, Dr. Horák Péter, & Dr. Baka Ernő Kötések, csavarkötés | GÉPELEMEK 1. előadás 1 Joints Gépelemek 1. A connection where a joint fixes or limits the relative movement between machine elements or boundary parts. The joint task (function): fixing & limiting the relative motion of machine elements in certain directions while transffering power or force. Kötések, csavarkötés | GÉPELEMEK 1. előadás 2 Grouping of joints Gépelemek 1. By phisical principle: – Force closing (friction force) – Form closing – Material closing (welding, soldering, glueing) By assembly: – Detachable – Un-detachable By elements: – Direct connection – Traction (in-between) element connection Kötések, csavarkötés | GÉPELEMEK 1. előadás 3 Design of joints Gépelemek 1. 1. 2. Definition of load case & constraints Definition of mating surfaces (force transition surfaces: pressured surface, weakest cross section) according to the flow of flux. 3. Calculation the load per unit area (average pressure, stress) 4. Comparison to ultimate strenght (allowable stresses) → n = … (safety factor) 5. Analysis of extraordinaries – E.g..: stress calculation in useful section; calculation of ring stress; etc- Kötések, csavarkötés | GÉPELEMEK 1. előadás 4 Elements of bolted joints Gépelemek 1. Hexagon head bolt Hexagon nut Hexagon head bolt Stud bolt Hexagon nut Spring washer Spring washer Spring washer + connected parts Kötések, csavarkötés | GÉPELEMEK 1. előadás 5 Materials of bolts Gépelemek 1. The most common bolt ISO standards are: ISO 898-1:2013 - This standard specifies the mechanical and material properties of bolts, screws and studs made of carbon steel and alloy steel used in bolting assemblies. It also specifies the methods for verifying these properties. ISO 898-2:2009 - This standard applies to bolts, screws and studs made of austenitic or austenitic-ferritic stainless steel used in bolting assemblies. It specifies the mechanical and material properties of these fasteners, as well as the methods for verifying these properties. ISO 3506-1:1997 - This standard applies to stainless steel bolts, screws and studs used in bolting assemblies. It specifies the mechanical and material properties of these fasteners, as well as the methods for verifying these properties. ISO 3506-2: Corrosion-resistant stainless steel fasteners ISO 965-1: General table of tolerances ISO 1042: Chemical analysis of steels Kötések, csavarkötés | GÉPELEMEK 1. előadás 6 Some types of bolts Gépelemek 1. Kötések, csavarkötés | GÉPELEMEK 1. előadás 7 Materials of bolts Gépelemek 1. • The bolts are made from the following materials: 3.6; 4.6; 4.8; 5.6; 5.8; 6.8; 8.8; 10.9; 12.9 és 14.9. first number is 100-fold of the tensile strenght in MPa, second number is 10-fold of the quotient of yield strenght/tensile strenght. (e.g. In 5.6 group the material has a minimum of 500 Mpa tensile strenght, and yield strenght is 300 MPa.) • The nut strenght groups are the following: 5; 6; 8; 10; 12; 14. The number represents the 100 fold investigated stress which requires a mnimum tensile strenght of the bolt in Mpa which can be paired with the nut. Kötések, csavarkötés | GÉPELEMEK 1. előadás 8 Materials of bolts Gépelemek 1. Kötések, csavarkötés | GÉPELEMEK 1. előadás 9 Manufacturing of bolts Gépelemek 1. The bolts are manufactured by plastic forming • upsetting the head & body • head forming • thread rolling Kötések, csavarkötés | GÉPELEMEK 1. előadás 10 Manufacturing of bolts Gépelemek 1. Kötések, csavarkötés | GÉPELEMEK 1. előadás 11 The bolt joint Gépelemek 1. This joint is simultaneously force & form closing The fastening procedure: Tightening torque (spanner torque) Bolt joint Clamping force (tension force) Kötések, csavarkötés | GÉPELEMEK 1. előadás 12 Types of threads (operation) Gépelemek 1. 1. Mounting thread 2. Transmission thread 3. Transport thread 1. Mounting (Fastening) thread is probably the type of thread that most of you think of first. They are tight threads, as we find in nuts and bolts. 2. Transmission (movement) threads, on the other hand, are thread types that convert rotary motion into linear motion. 3. Nowadays, we find Transport threads in agricultural machines and in water conveyance in the form of screws. Generally 2 major types mounting (sharp or vee) threads: ISO European & Whithworth (UK-US standard) Kötések, csavarkötés | GÉPELEMEK 1. előadás 13 Types of threads (geometry) Gépelemek 1. 1.Classification based on Gender 1. Internal Thread 2. External Thread 2.Classification based on Designation 1. Connection 2. Sealing 3. Fastening 4. Special 5. Motion 3.Classification based on Handedness 1. Right handed 2. Left handed 4.Classification based on Pitch 1. Coarse Pitch 2. Fine Pitch 5.Classification based on Profile 1. Trapezoidal 2. Round 3. Triangular 4. Scalene 5. Square 6.Classification based on Start 1. Single-Start 2. Multi-Start 7.Classification based on Surface Shape 1. Cylindrical 2. Conical 8.Classification based on Scope 1. Pipe thread 2. Workshop thread Kötések, csavarkötés | GÉPELEMEK 1. előadás 14 General nomenclature Gépelemek 1. Kötések, csavarkötés | GÉPELEMEK 1. előadás 15 General nomenclature Gépelemek 1. Kötések, csavarkötés | GÉPELEMEK 1. előadás 16 Forces on threads Gépelemek 1. I. the connection between the fastening torque & tension force Operational forces when tightening a sharp threaded nut: • Mv : tightening torque • Fv : tension force • Fk : tightening perimetral force • ρ : spatial friction cone half angle • β : thread angle • α : helix angle • d2 : pitch diameter Kötések, csavarkötés | GÉPELEMEK 1. előadás 17 Forces on threads during fastening Gépelemek 1. Thread angle: 𝑝 𝛼 = arctg 𝑑2 𝜋 Friction force which hinders motion: Because of wedge effect where p is the pitch 𝐹𝑆 = 𝜇𝐹𝑁 where 𝜇 = tg𝜌 𝐹𝑁 ′ 𝐹𝑁 = 𝛽 cos 2 Introducing apparent half cone angle: 𝜇 ′ ′ 𝜌 = 𝑎𝑟𝑐𝑡𝑔𝜇 = 𝑎𝑟𝑐𝑡𝑔 𝛽 cos 2 Essential perimetral force for nut tightening Fk 𝐹𝑘 = 𝐹𝑣𝑡𝑔(𝛼 + 𝜌′ ) Kötések, csavarkötés | GÉPELEMEK 1. előadás 18 Forces on threads during loosening Gépelemek 1. Calculation of loosening perimetral force: − If the joint is self-locking, is then the perimetral force: 𝛼 ≤ 𝜌′ 𝐹𝑘 = 𝐹𝑣𝑡𝑔(𝛼 − 𝜌′ ) − If the joint is not self-locking 𝛼 > 𝜌′ then the nut twists off the bolt on its own. Kötések, csavarkötés | GÉPELEMEK 1. előadás 19 Tightening torque Gépelemek 1. The tightening torque is calculated from the perimetral force on the thread: 𝑀𝑣 = 𝐹𝑣 𝑑2 𝑡𝑔(𝛼 ± 𝜌′ ) 2 The frictional torque derived from the friction on the bearing surface of the nut during tightening: 𝑑𝑎 𝑀𝑎 = 𝐹𝑣𝜇𝑎 2 where da : middle diameter of bearing surface of the nut μa : friction coefficient on bearing surface of the nut Total tightening torque of the nut: 𝑑2 𝑑𝑎 ′ 𝑀 = 𝐹𝑣 𝑡𝑔(𝛼 ± 𝜌 ) + 𝜇𝑎 2 2 Kötések, csavarkötés | GÉPELEMEK 1. előadás 20 Klein diagram Gépelemek 1. The figure shows the tightening torque versus tension force at the two boundary values of friction coefficient. The required torque can be achieved with a certain deviation (e.g.: ± 3 %) , therefore the minimum & maximum tension force can be calculated. Kötések, csavarkötés | GÉPELEMEK 1. előadás 21 Load carrying capacity of the joint Gépelemek 1. Bolt joint as a form closing joint Load capacity of bolt by tension force. (based on study of joints) Kötések, csavarkötés | GÉPELEMEK 1. előadás 22 Load carrying capacity of the joint Gépelemek 1. 1. Load case of the bolt: is Fv tension force 2. Mating surfaces: a. load transmission surface (Ap ) b. veakest cross section (Aτ ) 𝐷 2 − 𝑑32 𝐴𝑝 = 𝜋𝑖 4 𝐴𝜏 = 𝑑3 𝜋𝑚 where i : thread number of the nut m: height of the nut Kötések, csavarkötés | GÉPELEMEK 1. előadás 23 Load carrying capacity of the joint Gépelemek 1. 3. Determination of the load per unit area: 𝑝𝑎𝑣𝑒𝑟𝑎𝑔𝑒 = 𝐹𝑣 𝐴𝑝 𝜏𝑎𝑣𝑒𝑟𝑎𝑔𝑒 = 𝐹𝑣 𝐴𝜏 4. Comparing to boundary state (as a safety factor): 𝑝𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 𝑛= 𝑝𝑎𝑣𝑒𝑟𝑎𝑔𝑒 𝜏𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 𝑛= 𝜏𝑎𝑣𝑒𝑟𝑎𝑔𝑒 Kötések, csavarkötés | GÉPELEMEK 1. előadás 24 Load carrying capacity of the joint Gépelemek 1. 5. Analyzing extraordinaries: a. Load distribution on the thread Solutions for the load distribution smoothing Kötések, csavarkötés | GÉPELEMEK 1. előadás 25 Load carrying capacity of the joint Gépelemek 1. 5. Analyzing extraordinaries: b. Stress in the threaded bolt after tightening the nut Stress from tension force: 𝐹𝑣 𝜎= 𝐴𝜎 where 𝑑12 𝜋 𝐴𝜎 = 4 Stress on the threads from tightening torque: 𝑀𝑣 𝜏= 𝐾𝑝 where 𝑑13 𝜋 𝐾𝑝 = 16 The equivalent stress based on Mohr”s theory: 𝜎𝑟 = 𝜎 2 + 4𝜏 2 Kötések, csavarkötés | GÉPELEMEK 1. előadás 26 Gépelemek 1. DETACHABLE FASTENERS, LOOSENING, BOLT SECURING Authors: Dr. Kerényi György Molnár László, Dr. Marosfalvi János, Dr. Horák Péter, & Dr. Baka Ernő Kötések, csavarkötés | GÉPELEMEK 1. előadás 1 Engineering topics Gépelemek 1. − − − − Bolt joint modell Spring basics Pretensional triangle Load case modells − Non-rotational loosenings − External (force) − Internal (force) − Intermediate (force) − Diversion loosening − Energy loosening − Rotational loosenings (self-slacking) − Bolt securings − Design principles Kötések, csavarkötés | GÉPELEMEK 1. előadás 2 The bolt joint spring modell Gépelemek 1. Bolted connections are one of the most common elements in construction and mechanical design. It consists of an externally threaded fastener (such as a bolt) that captures and holds other parts together and is secured with a corresponding internal thread. There are two main types of bolted connection designs: tension and shear connections Kötések, csavarkötés | GÉPELEMEK 1. előadás 3 The bolt joint spring modell Gépelemek 1. In a tension joint, the bolt and the clamped components of the joint are designed so that the applied tensile load is transmitted through the clamped component through the joint by designing an appropriate balance of joint and bolt stiffness. As well as the deformation of both elements are elastic therefore the joint can be modelled by spring system. The lineary elastic elements can be described by HOOKE”s law: Material constants: E: Young”s modulus ν: Poisson”s ratio Kötések, csavarkötés | GÉPELEMEK 1. előadás 4 Spring fundamentals Gépelemek 1. Elongation of the l lenght beam loaded by F force f : f = Fl AE The F = f (f) function is called spring characteristic, which is at lineary elastic elements the so called stiffness. (s). F N tg  = = s   f  mm  At tensioned beam the stiffness is: AE s= l Kötések, csavarkötés | GÉPELEMEK 1. előadás 5 Pre-tensioned bolt & deformed members Gépelemek 1. Before tightening After tightening Elongation of the bolt & the compression of the members. (exagerrated) Kötések, csavarkötés | GÉPELEMEK 1. előadás 6 Pre-tensioning triangle Gépelemek 1. Characteristic of the bolt & members shown together: Fv: Preload force λ1 : elongation (strain) of bolt λ2 : compression of members Kötések, csavarkötés | GÉPELEMEK 1. előadás 7 Stiffness of bolt Gépelemek 1. The bolt stud has two kind of parts: • grip lenght (l1): Ø d ; • thread lenght (l2): Ø d3. ...then elongation of bolt: Fv l1 Fv l 2 1 = + A1 E1 A2 E1 Stiffness of bolt in general: where d i2 Ai = 4 Fv E1 s1 = = n li 1  i =1 Ai cross sections of i-th part. Kötések, csavarkötés | GÉPELEMEK 1. előadás 8 Stiffness of members Gépelemek 1. The stiffness of the grip is calculated based on a simplified pressure-cone method. This method predicts the pressure distribution throughout the thickness of the grip. The pressure cone for a joint can be visualized in the diagram right. ØD Od2 v h Od1 Bolt with nut Tapped joint ( ) E 2 D 2 − d12  s2 = = 2 h 4 Fv Kötések, csavarkötés | GÉPELEMEK 1. előadás 9 Load case modells Gépelemek 1. The modell is a function of the load case in operation: – Force loosening • external • internal • Interediate – Energy type loosening – Diversion loosening Kötések, csavarkötés | GÉPELEMEK 1. előadás 10 Non-rotational loosening (External force slackening) Gépelemek 1. At external loosening the loosening force is acting below the head of bolt.. The springs are in a parallel circuit in the modell. Kötések, csavarkötés | GÉPELEMEK 1. előadás 11 Non-rotational loosening (External force slackening) Gépelemek 1. Based on the similarity of triangles we can derive the increase of the preload of bolt. (F1) because of the loosening force. Fü s1 F1 = Fü s1 + s2 Reduced force in members: s2 F2 = Fü s1 + s2 The triangle diagram Kötések, csavarkötés | GÉPELEMEK 1. előadás 12 Critical force Gépelemek 1. The critical load at which the joint fully loosens, means... F2 = Fv : s2 Fv = Fkrit s1 + s 2 where Fkrit s1 + s 2 = Fv s2 Kötések, csavarkötés | GÉPELEMEK 1. előadás 13 Critical force Gépelemek 1. How the critical force can be increased??? Fkrit ? − stiffer bolt; − softer members. Kötések, csavarkötés | GÉPELEMEK 1. előadás 14 Critical force ‒ Gépelemek 1. the stiffness increase of the bolt can be achieved by increasing the dimensions of bolt; ‒ To „soften” the members we can have these options: Kötések, csavarkötés | GÉPELEMEK 1. előadás 15 Critical force Gépelemek 1. In case of repetative load on the bolt needs to be redused!, which can be achieved by „softening” the stud of bolt. (e.g.: bolt diameter turned to minor diameter or a drilled stud bolt. We reinforce the structures in the way that we cut-off material from it!! ☺ Kötések, csavarkötés | GÉPELEMEK 1. előadás 16 Non-rotational loosening (Internal force slackening) Gépelemek 1. Loosening force is acting between the members. The springs are in a series circuit in the modell. Kötések, csavarkötés | GÉPELEMEK 1. előadás 17 Critical force Gépelemek 1. In here the increase of the preload F1 = 0 because the operational Fü force is smaller than, the preload Fv force. The critical loosening force: Fkrit = Fv The triangle diagram Until the operational Fü force does not reach the Fv force (preload) NO movement in the joint. Kötések, csavarkötés | GÉPELEMEK 1. előadás 18 Non-rotational loosening (Intermediate force slackening) Gépelemek 1. Loosening force is acting at an interediate position of the members. The springs are in a parallel&series circuit in the modell. Kötések, csavarkötés | GÉPELEMEK 1. előadás 19 Non-rotational loosening (Force type slackenings) Gépelemek 1. Engineering guidelines: 1. The critical Fkrit force is the smallest at a clear internal loosening, and this is the most critical situation from slackening point of view. In this case the critical Fkrit force is independent from the stiffness of the members. 2. The critical Fkrit force increases by applying more stiff bolts & softer members. 3. The load increase in the bolt is the smallest in case of clear internal loosening situation. 4. The load increase in the bolt can be reduced by applying soft bolts & stiff members. Kötések, csavarkötés | GÉPELEMEK 1. előadás 20 Non-rotational loosening (Force type slackenings) Gépelemek 1. Built-in examples External loosening Internal loosening Intermediate loosening Kötések, csavarkötés | GÉPELEMEK 1. előadás 21 Non-rotational loosening (Environmental slackenings) Gépelemek 1. „Diverted” loosening happens if the preload force decreases because... − heat expansion between bolts & members; − relaxation, creep; − surface smoothenings − Corrosion − Etc... In this case we can have a proper construction if both stiffnesses (bolt&members) are little. Kötések, csavarkötés | GÉPELEMEK 1. előadás 22 Non-rotational loosening (Energy slackenings) Gépelemek 1. This type occurs when an external energy (impact) gets into the bolt system. The loosening energy is the below formula W... 𝐹ü = 2𝑊(𝑠1 + 𝑠2 ) Kötések, csavarkötés | GÉPELEMEK 1. előadás 23 Non-rotational loosening (Energy slackenings) Gépelemek 1. The total slackening happens when the external (impact) energy is equal/bigger than the joint energy. (kind of a force type loosening situation) In this case we can have a proper construction if both stiffnesses (bolt&members) are little. Kötések, csavarkötés | GÉPELEMEK 1. előadás 24 Bolt securing methods Gépelemek 1. There are three commonly used bolt locking methods, which include friction locking, mechanical locking and permanent locking. Permanent locking that is called non removable locking includes welding, riveting, bonding, etc, which usually destroys threaded fasteners during disassembly and can’t be reused. Common friction locking methods include washer, self-locking nut, double nut, etc. 1. Double nut When the double nut is locked, two friction surfaces are generated. The first friction surface is between the nut and the fastener, and the second friction surface is between the nut and the nut. 2. Self locking nut Self-locking nuts are generally self-locking by friction. 3. Wedge Nord lock washer Radial serrations on outer surface of the wedge lock washer engage with the surface of the workpiece it contacts. When the locking system is subjected to dynamic load, displacement can only occur on the inner surface of the washer. Kötések, csavarkötés | GÉPELEMEK 1. előadás 25 Bolt securing methods Gépelemek 1. 4. Cotter pin and slotted nut After the nut is tightened, insert the cotter pin into the nut slot and the bolt tail hole and pull open the split pin tail to prevent the relative rotation of the nut and bolt. Slotted nuts are used together with threaded rod bolts with holes and cotter pins to prevent the relative rotation between bolts and nuts. 5. Lock washer After the nut is tightened, bend and stick the lock washer to the side of the nut and the connector to lock the nut. If two bolts need to be tightened by double interlocking, double lock washers can be used. 6. Spring washer The anti loose principle of spring washer is that after the spring washer is pressed, the spring washer will produce a continuous elastic force, which will keep a friction force between the nut and the threaded connection of the bolt, generating a torque to prevent the nut from loosening. 7. Hot melt fastening technology The hot melt fastening technology does not require pre opening and connection can be realized by direct tapping under closed profiles, which is widely used in the automotive industry Kötések, csavarkötés | GÉPELEMEK 1. előadás 26 Bolt securing methods Gépelemek 1. Securing methods protect us from slackening of the nut. Based on effects we can have: ‒ form closing; ‒ force closing; ‒ material „closing” bolt securings. Form closing solutions Kötések, csavarkötés | GÉPELEMEK 1. előadás 27 Bolt securing methods Gépelemek 1. Securing by force closing methods Taper nut Notch nut Washers Tab washer nut Lock nut (Nylock nut) Nord-Lock Prevailing torque nuts Kötések, csavarkötés | GÉPELEMEK 1. előadás 28 Bolt securing methods (Nord-lock patent) Gépelemek 1. These wedge-locking washers use tension instead of friction to assure that bolted joints are steadfast when vibration and dynamic loads occur. Kötések, csavarkötés | GÉPELEMEK 1. előadás 29 Bolt securing methods (Nord-lock patent) Gépelemek 1. Kötések, csavarkötés | GÉPELEMEK 1. előadás 30 Bolt securing methods Gépelemek 1. Bolt securing with added material After tightening glue is applied on the bolted joint elements. Kötések, csavarkötés | GÉPELEMEK 1. előadás 31 Bolt securing methods Gépelemek 1. Pre-coated bolts is a processing technology in which a microcapsule compound containing an adhesive is specially applied to the threads of screws to provide sealing and locking functionality. Reaction initiates by tightening a screw Screws are coated with a dry resin film. When screwed in, their microcapsule breaks and the contained locking ingredients seep out, causing a curing reaction. The screw, lock agent, and sealant are integrated, and an excellent effect can be achieved simply by tightening the screw. PRECOTE system (Metrikont bolt & securing systems) Met Tech bolting techiques Kötések, csavarkötés | GÉPELEMEK 1. előadás 32 Bolt securing methods Gépelemek 1. Securing with 2 kind of threads. One coarse , one fine. Because of the different helix angles the nut does not slacken. Kötések, csavarkötés | GÉPELEMEK 1. előadás 33 Engineering guidelines Gépelemek 1. Thread run-out Internal thread in sheet metall d 1 = 1,15d d) R=0,5t good b) t wrong d h t a) e) c) f) Kötések, csavarkötés | GÉPELEMEK 1. előadás 34 Engineering guidelines Gépelemek 1. Screwing into plastic tubes (screw towers with inserts) a) b) 1,6d c) d wrong Plastic sheets fixing good a) b) 1 2 c) 1 1 wrong Kötések, csavarkötés | GÉPELEMEK 1. good előadás 35 Engineering guidelines Gépelemek 1. a) Parallelism of the mating surfaces is required. c) b) d) e) Kötések, csavarkötés | GÉPELEMEK 1. előadás 36 Engineering guidelines Gépelemek 1. Supporting principle (the crown wheel mating from the front) a) Fa wrong b) Fa good Kötések, csavarkötés | GÉPELEMEK 1. előadás 37 Gépelemek 1. SEMI-DETACHABLE FASTENERS Authors Dr. Kerényi György Molnár László, Dr. Marosfalvi János, Dr. Horák Péter, & Dr. Baka Ernő Alakkal záró kötések| GÉPELEMEK 1. előadás 1 Form closing principle Gépelemek 1. − Function of form closing joint, grouping: − Types − Riveting − process − types − calculation − Pins & dowel pins − calculation − Polymer form closing − Clipping features: cantilever beam, cylindrical joint − calculation Alakkal záró kötések| GÉPELEMEK 1. előadás 2 Form closing principle Gépelemek 1. Function: To maintain the flow of Flux on compressed & sheared surfaces Possible grouping: • Elements: – Lap joints – Butt joints. • Assembly: – In general riveted joint considered as a „semi-permanent” one. Alakkal záró kötések| GÉPELEMEK 1. előadás 3 Riveted joint Gépelemek 1. A bridge pillar An aeroplane body Alakkal záró kötések| GÉPELEMEK 1. előadás 4 Form closing principle (riveting process) Gépelemek 1. chuck Fejezõ szerszám k l Od2 Od die Ellentámasz l = k + ( 1,3 ... 1,75)d Rivet diameter [mm] 10 13 16 19 22 25 28 31 34 37 40 43 Recommended play [mm] 0,3 0,3 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1 1 1 Alakkal záró kötések| GÉPELEMEK 1. előadás 5 Form closing principle (riveting process) Gépelemek 1. Alakkal záró kötések| GÉPELEMEK 1. előadás 6 Various rivets Gépelemek 1. Félgömbfejû szegecs Süllyesztettfejû szegecs Lencsefejû szegecs Alcsony félgömbfejû szegecs Szíjszegecs Csõszegecs Csõszegecs gépkocsi fék- és tengelykapcsoló betétekhez Alakkal záró kötések| GÉPELEMEK 1. előadás 7 Oscar rivets Gépelemek 1. Robbanás explosion Húzás tension Nyomás compression Alakkal záró kötések| GÉPELEMEK 1. előadás 8 Blind (pop) rivets Gépelemek 1. Alakkal záró kötések| GÉPELEMEK 1. előadás 9 Upset rivets Gépelemek 1. Solid rivet Semitubular rivet Blind side upset Countersunk flush rivet Closed end break-mandrel blind rivet Alakkal záró kötések| GÉPELEMEK 1. előadás 10 Main state of stress of rivets (in construction) Gépelemek 1. wrong a) Helytelen Upper construction is wrong because of the load. The stress state in the rivet is tension. The lower construction is much better because the stress state in the rivet is SHEARING. F F good b) Jó F F Alakkal záró kötések| GÉPELEMEK 1. előadás 11 Riveting patterns Gépelemek 1. Behind one another Next to one another Zig-zag pattern Alakkal záró kötések| GÉPELEMEK 1. előadás 12 State of stress of rivets (shearing & bearing stress) Gépelemek 1. Shearing stress т Bearing stress p Alakkal záró kötések| GÉPELEMEK 1. előadás 13 Linear riveting pattern Gépelemek 1. The required minimum space for the rivets (D) & the die tool (Df) Fix pitch of rivets Alakkal záró kötések| GÉPELEMEK 1. előadás 14 Elastic „cushion” modell Gépelemek 1. As a result of F vertical load the rivet pattern twists as shown below under the T twisting torque. From the center of rotation: the rivets in (ri) distance twist a (λi) displacement. Accorning to the model: the acting force (Fi) on the rivet is proportional with dispacement. Alakkal záró kötések| GÉPELEMEK 1. előadás 15 Elastic „cushion” modell Gépelemek 1. From Twisting torque: 𝑇 = 𝐹𝑘 The force (Fi) on the rivet is normal to the radius. (ri) The further the rivet is from the rotational point the more force (Fi) is on it. From Vertical force: (Q) The loading (resultant) F force on the rivet is from: TWISTING & SHEARING 𝐹 = 𝐹𝑖 + 𝐹𝑄 Alakkal záró kötések| GÉPELEMEK 1. előadás 16 Construction improvement (assistance) Gépelemek 1. satisfactory a) Megfelelő M good b) Jó M Alakkal záró kötések| GÉPELEMEK 1. előadás 17 Pins & dowel pins Gépelemek 1. Detachable joints with functions: Attach elements, fix, guide, grip, centralize, secure, locate etc. Pin joints fix & locate, and in general do not allow any movement. Pins • • • are standardized: Cylindrical, taper pins, Groove pins, Dowel pins, spring dowel pins. Pin material is commonly steel. Can be normalized, hardened or annealed structural steel. Alakkal záró kötések| GÉPELEMEK 1. előadás 18 Pins & dowel pins Gépelemek 1. Dowel pins Clevis pins & cotter pins Alakkal záró kötések| GÉPELEMEK 1. előadás 19 Clevis pins Gépelemek 1. Clevis pins are usually built into rotational pivots, hinges. The pin is in interference fitment in on element and in clearance fitment in the other element. Clevis pins are standardized: • • • • standard dowel pin, clevis pin with cotter pin hole, headed clevis pin, threaded clevis pin. Securing with cotter pins, spring washers, retaining rings, nuts etc. Pin materials generally are structural steel, high strenght annealed & hardened steel. Alakkal záró kötések| GÉPELEMEK 1. előadás 20 Clevis pins Gépelemek 1. Clearance fit Clearance fit Interference fit Alakkal záró kötések| GÉPELEMEK 1. előadás 21 Clevis pins Gépelemek 1. State of stress of pins are shearing, bending & bearing pressure. At interference fitted pins shearing is major. At clearance fitted pins bending is major. The bearing stress to be also investigated. Alakkal záró kötések| GÉPELEMEK 1. előadás 22 Clevis pins (calculation) Gépelemek 1. 𝑀ℎ 𝜎= < 𝜎𝑚𝑒𝑔 𝐾 𝐹 𝜏 = < 𝜏𝑚𝑒𝑔 𝐴 𝐹 𝐹 𝑝= 𝑖𝑛 𝑝𝑖𝑛 , 𝑝 = (𝑖𝑛 𝑓𝑜𝑟𝑘) < 𝑝𝑚𝑒𝑔 𝑑𝑏 2𝑑𝑡 Alakkal záró kötések| GÉPELEMEK 1. előadás 23 Pin riveting Gépelemek 1. Before upsetting Zömítés előtt a) b) c) Zömítés After után upsetting Alakkal záró kötések| GÉPELEMEK 1. előadás 24 Polymer form closing joints Gépelemek 1. a: szonotróda Ultrasonic welding (normal & shallow head) Normal head Shallow head Alakkal záró kötések| GÉPELEMEK 1. előadás 25 Polymer fastener clips (automotive) Gépelemek 1. Rivet clips Groove clips Alakkal záró kötések| GÉPELEMEK 1. előadás 26 Polymer clip joints Gépelemek 1. Alakkal záró kötések| GÉPELEMEK 1. előadás 27 Polymer clip joints Gépelemek 1. Alakkal záró kötések| GÉPELEMEK 1. előadás 28 Polymer clip joints Gépelemek 1. Alakkal záró kötések| GÉPELEMEK 1. előadás 29 Polymer clip joints Gépelemek 1. Polymer clipping: Such a form closing joint when the connecting parts has interference during assembly, then the clips go to a non-strain standstill position Temporary strain 3-5 % as maximum Permanent strain 0-1 % as maximum Alakkal záró kötések| GÉPELEMEK 1. előadás 30 Calculation of clipping Gépelemek 1. General considerations: • mechanical load in joint • assembly disassembly forces Calculation of cantilever beams: • „f” calculation (sagging) Alakkal záró kötések| GÉPELEMEK 1. előadás 31 Calculation of clipping Gépelemek 1. Nomenclature: f= allowable sagging, ε= allowable strain, (megengedhető) kitérés l= beam lenght, h= beam height, b= beam width, e= neutral line, W= cross section factor E= Young”s modulus, Kitérítő erő Q= assembly force. Alakkal záró kötések| GÉPELEMEK 1. előadás 32 Allowable strain (assembly) values Gépelemek 1. In case of regular clipping back&forth the 60% of the values can be considered at calculations. POLYMER Allowable strain. ε% PE 8 PP 6 PA conditioned 6 PA just injected 4 PA with glass fibers 2 POM 6 % 6 PBT 5 % 5 PBT with glass fibers 1,5 PC 4 ABS 2,5 PS 1,8 PVC 2 Alakkal záró kötések| GÉPELEMEK 1. előadás 33 Calculation of clipping Gépelemek 1. Deflection of cantilever beam during assembly: Alakkal záró kötések| GÉPELEMEK 1. előadás 34 Calculation of clipping (modulus) Gépelemek 1. stress Secant modulus values of polymers versus strain Initial (tangent) & unloading secant modulus strain strain strain strain strain strain strain Determination of the secant modulus Alakkal záró kötések| GÉPELEMEK 1. előadás 35 Calculation of clipping (assembly&disassembly force) Gépelemek 1.  + tan  F = Q  tan( +  ) = Q  1 −  tan  Values of friction coefficient for various polymers: Alakkal záró kötések| GÉPELEMEK 1. előadás 36 Calculation of clipping (stress distribution) Gépelemek 1. Tangential stress Distribution of tangential (major) stress in tube during assembly Alakkal záró kötések| GÉPELEMEK 1. előadás 37 Calculation of clipping (pressure force) Gépelemek 1. Q is a function of... Q = f d E  X f = d X: geometrical factor Alakkal záró kötések| GÉPELEMEK 1. előadás 38 Calculation of clipping (deformation of parts) Gépelemek 1. During assembly: Other part Both parts Real acting force Acting force Acting force One part  + tan  F =Q 1 − tan  deflection deflection deflection deflection overlapping Alakkal záró kötések| GÉPELEMEK 1. előadás 39 Calculation of clipping (dimensioning example) Gépelemek 1. Material: Danamid 𝜀𝑚𝑒𝑔 = 2,5% 𝐸𝑠 = 1200 𝑀𝑃𝑎 𝜇 = 0,525 Dimensions l = 13 mm f = 2 mm  = 30o Width of clip b=5 mm. Determination the thickness of the clip (h) from deflection (sagging) f = 0,67  l2 h  h = 0,67  l2 f 0,025 132 = 0,67 = 1, 42 mm 2 Deflection force: 𝑏ℎ2 𝐸𝑠 ⋅ 𝜀 5 ⋅ 1, 42 1200 ⋅ 0,025 𝑄= ⋅ = ⋅ = 3,77 𝑁 6 𝑙 6 13 Assembly force: 𝜇 + 𝑡𝑔𝛼 0,525 + 𝑡𝑔30𝑜 𝐹=𝑄⋅ = 3,77 ⋅ = 5,96 𝑁 1 − 𝜇𝑡𝑔𝛼 1 − 0,525 ⋅ 𝑡𝑔30𝑜 Alakkal záró kötések| GÉPELEMEK 1. előadás 40 Gépelemek 1. UNDETACHABLE JOINTS Authors: Dr. Kerényi György Molnár László, Dr. Marosfalvi János, Dr. Horák Péter, & Dr. Baka Ernő Anyaggal záró kötések| GÉPELEMEK 1. előadás 1 Undetachable joints Gépelemek 1. − Welding − types − method − Calculation − Glueing − pros&cons − method − Calculation − Soldering − types − method Anyaggal záró kötések| GÉPELEMEK 1. előadás 2 Welded joints Gépelemek 1. In metalworking, a welding joint is a point or edge where two or more pieces of metal or plastic are joined together. (with same materials) They are formed by welding two or more workpieces according to a particular geometry. Advantages. • Big strenght (nearly same as the component strenght), • Indispensable for special manufacturing, • Maintenance for cracked & weared elements, • Productive, can be easily automated with robots, • Advantageous shapes can be designed from deflection & strenght point of view. Anyaggal záró kötések| GÉPELEMEK 1. előadás 3 Welded joints Gépelemek 1. Disadvantages: • Just for certain materials, • Warpage occurs because of the high local heat concentration, • After-welding process is needed, • No damping effect, • At quality welding the non-destructive control of the joint is cost effective. Welding techniques of metals: • MMA Metal manual Arc, • MIG Gas Metal Arc Welding, • TIG Gas Tungsten Arc Welding, • FCAW Flux Cored Arc Welding • SAW Submerged Arc Welding • SMAW Stick Shielded Metal Arc Welding, • Resistance welding, • Forge welding (e.g.: spot welding), • Friction welding, • Induction welding. Anyaggal záró kötések| GÉPELEMEK 1. előadás 4 Welded joints (Main Types) Gépelemek 1. Anyaggal záró kötések| GÉPELEMEK 1. előadás 5 Welded joints Gépelemek 1. Anyaggal záró kötések| GÉPELEMEK 1. előadás 6 Different Welded joints Gépelemek 1. Anyaggal záró kötések| GÉPELEMEK 1. előadás 7 Welded joints Gépelemek 1. (HAZ) Heat affected zones of welded joints 1) Weld metal (bead): In fusion welding, a portion of the base metals surrounding the junction is melted and re-solidified. The zone around the junction that melts and re-solidifies. 2) Heat affected zone: is a part of the base metal that is not melted during the fusion welding but is heated to an elevated temperature (below the melting temperature of the concerned material) before cooling down to room temperature 3) Base material: no chemical or mechanical material alteration. Anyaggal záró kötések| GÉPELEMEK 1. előadás 8 HAZ, Heat Affected Zones Gépelemek 1. Anyaggal záró kötések| GÉPELEMEK 1. előadás 9 Heat Affected Zones & Weld Metals (bead) Gépelemek 1. Weld Metal Heat Affected Zone (HAZ) Weld metal is usually treated as a separate part in the welded sample, rather than considering it as a part of the base metal. Weld metal region exists at the junction of two parent components. In fusion welding, weld metal undergoes phase change due to meting and subsequent solidification (solid to liquid and once again liquid to solid). HAZ is usually considered as an integrated part of the base metal. It contains significant portion of filler material (except in autogenous welding). Chemical composition of weld bead may differ from that of the parent metals. Properties of the weld metal can be improved during welding in several ways (such as appropriately selecting filler composition, shielding gas, etc.). It does not contain any filler material. It is purely a part of the base materials. Chemical composition of HAZ is mostly same with that of the parent metals. Properties of the HAZ cannot be improved favourably during welding (its width can only be controlled to some extent). HAZ exists within the parent components surrounding the weld bead. HAZ is never melted. It always remains solid. So no phase change occurs in HAZ. Weld bead produces in both fusion welding and solid HAZ is noticeable particularly in fusion welding state welding processes. However, it is narrow in processes. With solid state welding, HAZ is very solid state welding. narrow and is mostly not detectable. Geometry of the weld metal is characterised by three Only geometrical parameter of interest of the HAZ is parameters, namely (i) depth of penetration, (ii) weld its lateral width. bead width, and (iii) reinforcement height. Anyaggal záró kötések| GÉPELEMEK 1. előadás 10 Types of welded joints Gépelemek 1. Butt joint: One of the best joints: − big strenght, reliable, cheap; − at metal sheets it requires rework. Lap joint: Poor quality not the best: − double weld metal; − more material, − additional bending. Strap joint: Resembles to riveted joint: − big load capacity; − quadrant weld metal; − more material; − no additional bending. Anyaggal záró kötések| GÉPELEMEK 1. előadás 11 Types of welded joints Gépelemek 1. Corner joints a) Best corner joint, least material, biggest load capacity. At sheet metal it requires additional rework. b) Cheap , but less load capacity. c) Bigger load capacity than previous one but more expensive because of theneed of accurate fitment. d) Good strenght but more expensive than the previous ones. Anyaggal záró kötések| GÉPELEMEK 1. előadás 12 Construction of welded joints Gépelemek 1. General principles in the design of welded assemblies: Select the material with high weldability Use of a minimum number of welds Do not shape the parts based on casting or forging Use standard components Avoid straps, laps, and stiffeners Select the proper location of the weld Prescribe the correct sequence of the welding Anyaggal záró kötések| GÉPELEMEK 1. előadás 13 Construction of welded joints Gépelemek 1. The „best” solution is the butt joint because the flow of flux is not deflected. Átlapolt Lap kötés joint Hevederes Strap kötés joint Butt Tompa joint varrat 1:4 1:4 In order to achieve the smooth flow of flux the steps in cross sections must be avoided. 1:4 Anyaggal záró kötések| GÉPELEMEK 1. előadás 14 Construction of welded joints Gépelemek 1. Do not place a welded joint in the proximity of the peak of stress! Stress distributiona in sheet metal Feszültségeloszlás lemezben Helyes varratelhelyezés Good joint placement: A varrat a feszültséggyüjtő the joint is relatively far fromtávol the hatást okozó saroktól helyezkedik peak of stress! el. Hibás Wrongvarratelhelyezés joint placement: A varrat a csúcsfeszültségi the joint is placed helyen van. in the peak of stress! Anyaggal záró kötések| GÉPELEMEK 1. előadás 15 Construction of welded joints Gépelemek 1. Avoid the welding lines crossings! Helytelen elrendezés Incorrectvarrat joint placement Helyes joint varratplacement elrendezés Correct Rossz Wrong Megfelelő Appropriate JóGood The fewer joints are the better! Anyaggal záró kötések| GÉPELEMEK 1. előadás 16 Construction of welded joints Gépelemek 1. v 5v r 5v r Hibás! Incorrect! A hidegen hajlított The joint is at thelehet cold szakaszon nem bended section hegesztési varrat. Correct! Jó. A hidegen hajlított The joint is mért at least 5v szakasztól far away from the cold távolság legalább 5v. bended section. At cold worked sheet metals, especially at corners or at bending curves welded joints must NOT be placed because of aging or rigid fracture. Anyaggal záró kötések| GÉPELEMEK 1. előadás 17 Construction of welded joints Gépelemek 1. Welded joint on fitted surfaces to be avoided! Incorrect Rossz Wrong Elfogadható Appropriate Correct JóGood The corner joint to be welded as double, At dynamic loads to be concave. Anyaggal záró kötések| GÉPELEMEK 1. előadás 18 Construction of welded joints Gépelemek 1. t 1. The rib must not have an apex point because it melts down during welding. b c a 2. At corner 3 joints are connecting. (weld accumulation) e b Hibás Incorrect Megfelelő Correct Avoid skew connection! Anyaggal záró kötések| GÉPELEMEK 1. előadás 19 Construction of welded joints Gépelemek 1. Avoid the tension forces on root side. Erők Forces HelyesCorrect megoldás Incorrect Helytelen At spot welded joints: Avoid the tension the joint to be designed for shearing! t Od t F Od F Anyaggal záró kötések| GÉPELEMEK 1. előadás 20 Weld nomenclature Gépelemek 1. Anyaggal záró kötések| GÉPELEMEK 1. előadás 21 Calculation for static loads Gépelemek 1. I. Dimensions of the welded joint: 1) throat size „a" 2) Lenght of weld „l” Anyaggal záró kötések| GÉPELEMEK 1. előadás 22 Calculation for static loads Gépelemek 1. II. Calculation of stresses in the weld: • tension  = F a l • bending  = M K • shearing 𝐹 𝜏ҧ = 𝑎⋅𝑙 • torsion Bredt-form = K is cross section factor; M cs 2 A0 a A0 : section drawn by the middle line of the weld all along the way. Anyaggal záró kötések| GÉPELEMEK 1. előadás 23 Calculation for static loads Gépelemek 1. III. Determining the stress components in the normal & transverse plane. The followi