Machine Elements As A Subject 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